JP7720775B2 - Foaming agent adding device, spray foaming machine, foaming agent adding method, and foam manufacturing method - Google Patents

Description

The present invention relates to a foaming agent addition device for adding a foaming agent to a liquid, a spray foaming machine, a foaming agent addition method, and a foam manufacturing method.

A widely known construction method involves mixing polyol and isocyanate on-site onto the roofs, walls, floors, etc. of buildings and structures, and then spraying and foaming the mixture to form polyurethane foam. One known method for enhancing the workability of polyurethane foam is to add a blowing agent as a third component when mixing two components, polyol and isocyanate (hereinafter referred to as the "froth method"). In the froth method, a blowing agent flow path is provided, connected to a liquid flow path for supplying polyol or isocyanate. A blowing agent addition device is commonly used, which adds a blowing agent, such as carbon dioxide, from a tank or the like to the polyol or isocyanate in the liquid flow path via the blowing agent flow path. The polyol or isocyanate to which a blowing agent, such as carbon dioxide, has been added in the blowing agent addition device is further mixed with the isocyanate or polyol and then discharged to the outside.

The liquid in the liquid flow path of the foaming agent addition device is generally supplied under pressure, and the foaming agent can be stably mixed with the liquid by being pressurized to a pressure higher than the liquid pressure in the liquid flow path and then added to the liquid flow path. Therefore, a device is used that measures the liquid pressure in the liquid flow path and the foaming agent pressure in the foaming agent flow path, and opens an on-off valve to add the foaming agent to the liquid when the foaming agent pressure is higher than the liquid pressure (see, for example, Patent Document 1).
Also disclosed is a device that heats a foaming agent container to increase the foaming agent pressure to a pressure higher than the liquid pressure in a liquid flow path without using a foaming agent pump, and controls the addition of the foaming agent to the liquid based on the differential pressure between the foaming agent pressure and the liquid pressure (see, for example, Patent Documents 2 and 3).

Patent No. 6395556 Patent No. 5255239 Patent No. 5255380

In conventional foaming agent addition devices, the foaming agent pressure must be higher than the liquid pressure as a condition for adding the foaming agent, and therefore the addition of the foaming agent is controlled while detecting the liquid pressure in the liquid flow path. However, in conventional foaming agent addition devices, the liquid flowing through the liquid flow path is supplied in a pulsating manner by a liquid pump, and therefore the liquid pressure in the liquid flow path is easily affected by the pulsation of the liquid pump, making it difficult to control the addition of the foaming agent using a control method that responds to the liquid pressure.
Furthermore, in conventional foaming agent adding devices, the amount of foaming agent added varies depending on the pressure difference between the liquid pressure and the foaming agent pressure when the on-off valve is opened to add the foaming agent to the liquid, and on the time the on-off valve is open, making it difficult to quantitatively determine the amount of foaming agent added and to adjust the amount of foaming agent added.
Furthermore, carbon dioxide is often used as the foaming agent to be added from the viewpoint of cost reduction. Carbon dioxide as an additive is easily vaporized, and the pressure of carbon dioxide in the foaming agent container tends to become higher than usual, especially under high temperatures such as in summer. In conventional foaming agent adding devices, a flow path is connected from the foaming agent container to an on-off valve that controls the amount of foaming agent added to the liquid. Therefore, when the pressure of the foaming agent in the foaming agent container becomes high, the pressure difference between the foaming agent and the liquid pressure in the liquid flow path increases, making it easy for excessive foaming agent to be added, and making it difficult to adjust the amount of foaming agent added.

Therefore, an object of the present invention is to provide a foaming agent addition device, a spray foaming machine, a foaming agent addition method, and a foam manufacturing method that are capable of stably supplying a foaming agent to a liquid flowing through a liquid flow path without being affected by the pulsation of the liquid pump by controlling the foaming agent in response to the drive of the liquid pump rather than the liquid pressure in the liquid flow path.
Another object of the present invention is to provide a foaming agent adding device, a spray foaming machine, a foaming agent adding method, and a foam manufacturing method that are capable of supplying a predetermined amount (predetermined volume) of foaming agent to a liquid flowing through a liquid flow path by utilizing a foaming agent metering pump that supplies a predetermined amount of foaming agent to the liquid flowing through the liquid flow path.
Another object of the present invention is to provide a foaming agent adding device, a spray foaming machine, a foaming agent adding method, and a foam manufacturing method that can prevent excessive foaming agent from being added to a liquid by providing a flow rate adjustment mechanism that adjusts the flow rate of the foaming agent in a flow path from a foaming agent container to an on-off valve that controls the amount of foaming agent added to the liquid.

The present invention is summarized as follows: [1] to [17]
[1] A foaming agent addition device for adding a foaming agent to a liquid supplied by a liquid pump and flowing through a liquid flow path, comprising: a pump operation detection unit that detects operation of the liquid pump; a foaming agent container that stores the foaming agent; a foaming agent flow path through which the foaming agent supplied from the foaming agent container flows; a foaming agent metering pump that supplies a predetermined amount of the foaming agent to the liquid flow path; an on-off valve that controls the addition of the foaming agent to the liquid by opening and closing; and an on-off valve control unit that controls the opening and closing of the on-off valve in accordance with the operation status of the liquid pump detected by the pump operation detection unit.
[2] The blowing agent addition device according to [1], wherein the on-off valve control unit opens the on-off valve when the drive position of the liquid pump reaches a predetermined position.
[3] The foaming agent addition device according to [1] or [2], wherein the on-off valve control unit controls the on-off valve to close when the predetermined amount of the foaming agent has been added to the liquid.
[4] The blowing agent adding device according to any one of [1] to [3], wherein the blowing agent metering pump is a positive displacement pump.
[5] The blowing agent adding device according to any one of [1] to [4], wherein the blowing agent metering pump is a reciprocating pump.
[6] The blowing agent addition device according to any one of [1] to [5], further comprising a blowing agent pressure pump, which is provided upstream of the blowing agent metering pump, for increasing the pressure of the blowing agent flowing through the blowing agent flow path to a predetermined pressure.
[7] The blowing agent adding device according to [6], wherein the blowing agent pressurizing pump is a pump that continuously pressurizes the blowing agent.
[8] The foaming agent adding device according to [6] or [7], wherein the foaming agent pressure pump is either an axial pump or a gear pump.
[9] The blowing agent addition device according to any one of [6] to [8], further comprising a blowing agent pressure gauge between the blowing agent pressure pump and the blowing agent metering pump, for measuring the pressure of the blowing agent flowing through the blowing agent flow path, and the blowing agent pressure pump pressurizes the blowing agent until the pressure value measured by the blowing agent pressure gauge reaches the predetermined pressure.
[10] The blowing agent adding device according to any one of [1] to [9], wherein the liquid contains polyol or polyisocyanate.
[11] The foaming agent adding device according to any one of [1] to [10], wherein the foaming agent contains carbon dioxide.
[12] The foaming agent addition device according to any one of [1] to [11], further comprising a liquid flow path pressure gauge that measures the pressure of the liquid flowing through the liquid flow path, and the on-off valve control unit controls the on-off valve not to open when the liquid pressure measured by the liquid flow path pressure gauge is lower than a predetermined value.
[13] The blowing agent addition device according to any one of [1] to [12], further comprising a flow rate adjusting mechanism for adjusting the flow rate of the blowing agent in the blowing agent flow path upstream of the on-off valve.
[14] The blowing agent addition device according to [13], wherein the flow rate adjustment mechanism is a second on-off valve that controls the flow rate of the blowing agent flowing in the blowing agent flow path upstream of the on-off valve by opening and closing.
[15] A foam spray machine equipped with the foaming agent addition device according to any one of [1] to [14].
[16] A foaming agent adding method for adding a foaming agent to a liquid supplied by a liquid pump and flowing through a liquid flow path, comprising the steps of: detecting the operation of the liquid pump with a pump operation detection unit; supplying a foaming agent contained in a foaming agent container to a foaming agent flow path; metering a predetermined amount of the foaming agent to be supplied to the liquid flow path with a foaming agent metering pump; and controlling the addition of the foaming agent to the liquid by opening and closing an on-off valve, wherein in the step of controlling the addition of the foaming agent by opening and closing the on-off valve, an on-off valve control unit controls the opening of the on-off valve in accordance with the operation status of the liquid pump detected by the liquid pump operation detection unit.
[17] The blowing agent adding method according to [16], comprising the step of increasing the pressure of the blowing agent flowing through the blowing agent flow path to a predetermined pressure with a blowing agent pressure pump, and adjusting the pressure in the blowing agent metering pump to the predetermined pressure, before the step of metering the blowing agent with the blowing agent metering pump.
[18] The method includes a step of measuring the pressure of the liquid flowing through the liquid flow path with a liquid pressure gauge,
The foaming agent adding method according to [16] or [17], wherein in the step of controlling the addition of the foaming agent by opening and closing an on-off valve, when the pressure measured by the liquid pressure gauge is lower than a predetermined value, the on-off valve is controlled not to open.
[19] A foam manufacturing method, comprising a step of adding a foaming agent to a liquid flowing through a liquid flow path by the foaming agent addition method according to any one of [16] to [18].

In the present invention, by controlling the blowing agent in accordance with the driving state of the liquid pump rather than the liquid pressure in the liquid flow path, it is possible to provide a blowing agent adding device, a spray foaming machine, a blowing agent adding method, and a foam manufacturing method that can stably supply a blowing agent to the liquid flowing through the liquid flow path without being affected by the pulsation of the liquid pump.
Furthermore, the present invention can provide a foaming agent adding device, a foaming machine for spraying, a foaming agent adding method, and a foam manufacturing method that are capable of supplying a predetermined amount (predetermined volume) of foaming agent to a liquid flowing through a liquid flow path by utilizing a foaming agent metering pump that supplies a predetermined amount of foaming agent to a liquid flowing through a liquid flow path.
Furthermore, the present invention provides a foaming agent adding device, a foaming machine for spraying, a foaming agent adding method, and a foam manufacturing method, which are capable of preventing excessive foaming agent from being added to a liquid by providing a flow rate adjusting mechanism for adjusting the flow rate of the foaming agent in a flow path from a foaming agent container to an on-off valve that controls the amount of foaming agent added to the liquid.

1 is a schematic diagram showing a foaming agent addition device according to a first embodiment of the present invention; 1 is a schematic diagram showing a foam spraying machine according to a first embodiment of the present invention. FIG. 1 is a flowchart showing a foaming agent addition method according to a first embodiment of the present invention. FIG. 4 is a schematic diagram showing a foaming agent adding device according to a second embodiment of the present invention. 4 is a flowchart showing a foaming agent addition method according to a second embodiment of the present invention. FIG. 10 is a schematic diagram (part 1) showing a foaming agent addition device according to a third embodiment of the present invention. FIG. 10 is a schematic diagram (part 2) showing a foaming agent addition device according to a third embodiment of the present invention. 10 is a flowchart (part 1) showing a foaming agent addition method according to a third embodiment of the present invention. 10 is a flowchart (part 2) showing a foaming agent adding method according to the third embodiment of the present invention. 4 is a flowchart illustrating a method for adding a foaming agent according to another embodiment of the present invention.

[First embodiment]
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
As shown in FIG. 1, the foaming agent adding device 10 according to the first embodiment is a device for mixing a foaming agent E into a liquid L1 flowing in a liquid flow path 30.

<Liquid>
The liquid L1 is not particularly limited, but is preferably a foam raw material, which is a raw material for foam. The blowing agent adding device 10 can produce a foam by mixing the foam raw material liquid L1 with a blowing agent E. Examples of foams include polyurethane foam, phenol foam, and polystyrene foam. Therefore, the liquid L1 can be any material that can be used as a raw material for these foams. Among the foams listed above, polyurethane foam is preferred from the viewpoints of ease of production, curing speed, and foamability. Furthermore, it is more preferable that the polyurethane foam is a rigid polyurethane foam. The use of a rigid polyurethane foam tends to improve self-adhesion, heat insulation, mechanical strength, and the like.

A urethane resin composition for forming polyurethane foam is generally prepared by mixing a first liquid containing a polyol with a second liquid containing a polyisocyanate. The urethane resin composition is foamed and cured by a blowing agent E mixed into the composition to form a polyurethane foam. The blowing agent E may be mixed into either the first liquid or the second liquid, but is preferably mixed into the first liquid from the standpoint of stability, etc. That is, the blowing agent adding device 10 preferably mixes the liquid blowing agent E into a liquid containing either a polyol or a polyisocyanate (first liquid or second liquid), but more preferably mixes the blowing agent E into a liquid containing a polyol (first liquid).
The liquid (first liquid) containing the polyol is preferably a polyol composition containing a catalyst and a foam stabilizer in addition to the polyol, and may further contain a blowing agent. The blowing agent previously contained in the first liquid (polyol composition) in this way is also called an "internal blowing agent" to distinguish it from the above-mentioned blowing agent E.

The urethane resin composition for forming the polyurethane foam may contain a filler. The inclusion of a filler in the urethane resin composition improves the flame retardancy of the resulting polyurethane foam. It is preferable to mix the filler with a liquid (one-component or two-component) containing either a polyol or a polyisocyanate, but it is more preferable to mix the filler with a liquid (one-component) containing a polyol.
The filler is contained as a solid component in the liquid raw material composition, and is generally a component present in the raw material composition in the form of particles or powder.
The filler may be any component that is solid at room temperature (23° C.) and atmospheric pressure (1 atmosphere) and does not dissolve in the liquid raw material composition.
Examples of the filler include solid flame retardants and anti-settling agents. Examples of the solid flame retardant include red phosphorus-based flame retardants, boron-containing flame retardants, bromine-containing flame retardants, phosphate-containing flame retardants, chlorine-containing flame retardants, antimony-containing flame retardants, metal hydroxides, and needle-shaped fillers, and the solid flame retardant is preferably at least one selected from the group consisting of red phosphorus-based flame retardants, boron-containing flame retardants, and bromine-containing flame retardants.

In addition to the curing catalyst, foam stabilizer, and filler, the polyol composition may also contain various additives such as flame retardants (solid flame retardants, liquid flame retardants), antioxidants, heat stabilizers, metal inhibitors, antistatic agents, crosslinking agents, lubricants, softeners, and pigments.

<Blowing Agent>
The internal blowing agent is not particularly limited, and examples thereof include hydrofluoroolefins (HFOs), hydrofluorocarbons (HFCs), hydrocarbons, and diethyl ether. Examples of the hydrofluoroolefins (HFOs) used as internal blowing agents include fluoroalkenes having approximately 3 to 6 carbon atoms, preferably 3 or 4 carbon atoms, and more preferably 3 carbon atoms. The hydrofluoroolefins may be hydrochlorofluoroolefins having chlorine atoms. Examples of hydrofluorocarbons (HFCs) include hydrofluorocarbons having approximately 1 to 4 carbon atoms, and the hydrofluorocarbons may have chlorine atoms. Examples of hydrocarbons include hydrocarbons having 2 to 5 carbon atoms. As hydrocarbons having 2 to 5 carbon atoms, hydrocarbons having 3 or 4 carbon atoms are preferred, and LPG containing propane and butanes as main components can also be used.

On the other hand, blowing agent E may be any blowing agent that can be used for foaming using the froth method, and may be a blowing agent that becomes a gas at room temperature (23°C) and normal pressure (1 atm), preferably one with a boiling point below 0°C at normal pressure. Blowing agent E is not particularly limited, but examples include hydrofluoroolefins (HFOs) and carbon dioxide. The froth method involves mixing blowing agent E, which becomes a gas at room temperature and normal pressure, with a foam raw material such as a liquid (one-component) containing polyol to cause foaming. Note that the liquid containing polyol may already contain a blowing agent (internal blowing agent), and in such cases, blowing agent E functions as a foaming aid to improve foaming properties and workability.

In the present invention, it is preferable to use carbon dioxide as the blowing agent E. Carbon dioxide can be mixed into the liquid L1 in a liquid state by pressurization, as described below, thereby improving the miscibility with the liquid L1. Furthermore, the use of carbon dioxide reduces the environmental load. However, carbon dioxide may be mixed into the liquid L1 in a supercritical or subcritical state.
When carbon dioxide is used as the blowing agent E, carbon dioxide may be used alone, or a mixed gas of hydrofluoroolefin (HFO) and carbon dioxide may be used.

(Foaming agent adding device)
The foaming agent addition device 10 will now be described in more detail.
The foaming agent addition device 10 includes a pump operation detection unit 41, a foaming agent container 11 that stores a foaming agent E, a foaming agent flow path 12, a foaming agent metering pump 50, an on-off valve 60, and an on-off valve control unit 61. The foaming agent addition device 10 is a device for adding the foaming agent E to the liquid L flowing through the liquid flow path 30.

A liquid pump 40 is connected to the liquid flow path 30, and the liquid L1 filled in a container (not shown) such as a drum is supplied to the liquid flow path 30 by the liquid pump 40 and delivered therefrom.
The liquid pump 40 may be either a positive displacement or non-positive displacement pump, but is preferably a positive displacement pump. Positive displacement pumps have large pulsations, but the present invention allows for stable supply of the foaming agent even with large pulsations. The positive displacement pump may be either a reciprocating or rotary pump, but reciprocating pumps such as syringe pumps with a sealing mechanism on the drive side and plunger pumps with a sealing mechanism on the cylinder side are preferred. The positive displacement pump may be either a variable displacement or a fixed displacement pump.
Depending on the type of pump, the liquid pump 40 periodically drives various drive parts such as a cylinder, gear, vane, and plunger by rotational or linear motion, thereby repeatedly discharging the fluid. For example, in a syringe pump, the cylinder repeatedly moves linearly between the bottom dead center and the top dead center.

The liquid L1 flowing through the liquid flow path 30 is pressurized to the discharge pressure. A liquid flow path pressure gauge 31 is connected to the liquid flow path 30, and the liquid pressure LP of the liquid L1 flowing through the liquid flow path 30 is measured by the liquid flow path pressure gauge 31. From the perspective of operational stability, the pressure of the liquid L1 flowing through the liquid flow path 30 is preferably 5 to 10 MPa.

The liquid pump 40 is provided with a pump operation detection unit 41. The pump operation detection unit 41 detects the operation of the liquid pump 40. The pump operation detection unit 41 transmits pump operation information DI relating to the detected operation of the liquid pump 40 to the on-off valve control unit 61.
As described above, the liquid pump 40 periodically drives the drive unit by reciprocating or rotating motion, and the pump drive detector 41 can detect the position to which the drive unit is driven during that period. For example, a reciprocating pump such as a syringe pump reciprocates between bottom dead center and top dead center, and the pump drive detector 41 can detect the position to which the pump's drive unit is driven during that reciprocating motion. Similarly, with a rotary pump, it is sufficient to detect the position to which the drive unit is driven during the rotational motion.
A sensor is used as pump drive detection unit 41. Specific examples of the sensor include a laser distance sensor that measures the drive position of the drive unit of liquid pump 40 as a distance, and a position sensor that detects that the drive unit of liquid pump 40 has reached a certain position (for example, top dead center or bottom dead center).

A pressure-resistant container, such as a known gas cylinder, is used as the foaming agent container 11. The foaming agent container 11 preferably contains the foaming agent E under pressure. The foaming agent container 11 may also be equipped with a heater (not shown). By heating the foaming agent container 11 with the heater, the internal pressure of the foaming agent container 11 increases, making it easier to deliver the foaming agent E to the foam flow path 12 under high pressure.

As described above, the foaming agent flow path 12 is a path for supplying the foaming agent E from the foaming agent container 11 to the liquid flow path 30. The foaming agent flow path 12 may be provided with a flow path cooling device (not shown) made of a coolant or the like, which can cool the foaming agent E flowing through the foaming agent flow path 12. By cooling the foaming agent E in the foaming agent flow path 12, the foaming agent E becomes less likely to vaporize in each foaming agent flow path, and the foaming agent E becomes more likely to mix in a liquid state with the liquid L.
The temperature inside the blowing agent flow path 12 is preferably maintained in the range of -20 to 20°C. The pressure inside the blowing agent flow path 12 is preferably adjusted so that the pressure of the blowing agent E sent to the liquid flow path 30 and the blowing agent metering pump 50 is in the range of 5 to 12 MPa. By adjusting the blowing agent E in the blowing agent flow path 12 to be within the above range, it is easily supplied in a liquid state to the liquid flow path 30. When the blowing agent E is supplied in a liquid state to the liquid flow path 30, it is easily mixed with the liquid L1.

A foaming agent metering pump 50 is provided midway along the foaming agent flow path 12. The foaming agent metering pump 50 receives the foaming agent E flowing through the foaming agent flow path 12 and meters it, thereby supplying a predetermined amount (predetermined volume) of foaming agent E to the liquid flow path 30.
The foaming agent metering pump 50 may be either a non-positive displacement or a positive displacement pump, but a positive displacement pump is preferred because it is easy to supply a constant amount of foaming agent and to vary the volume. As the positive displacement pump, a reciprocating pump such as a syringe pump or a plunger pump is preferred, and among them, a syringe pump is preferred because it has high metering accuracy for one shot amount and is also excellent for high-pressure transport.
The blowing agent metering pump 50 may be of a variable displacement type or a fixed displacement type, but a variable displacement type is preferred. By varying the volume, it is possible to vary the predetermined amount of blowing agent E to be supplied. The volume variable control of the blowing agent metering pump 50 may be implemented by a known control device equipped with a CPU (microprocessor), memory, input ports, output ports, etc., and may be implemented by a personal computer or may be manually variable.

An on-off valve 60 is provided in the foaming agent flow path 12 downstream of the foaming agent metering pump 50. The on-off valve 60 controls the addition of foaming agent E to liquid L1 by opening and closing. When the on-off valve 60 is open, the foaming agent E flowing through the foaming agent flow path 12 is supplied to liquid L1. When the on-off valve 60 is closed, the supply of foaming agent E to liquid L1 is stopped. The on-off valve 60 is configured, for example, as a solenoid valve.

An on-off valve control unit 61 is connected to the on-off valve 60, which controls the opening and closing of the on-off valve 60. The on-off valve control unit 61 receives pump drive information DI of the liquid pump 40 from the pump drive detection unit 41, and controls the on-off valve 60 to open in accordance with the drive status of the liquid pump 40. Specifically, the on-off valve control unit 61 controls the on-off valve 60 to open when the drive position of the liquid pump 40 reaches a predetermined position (predetermined position). By opening the on-off valve 60, a predetermined amount of foaming agent E is supplied to the liquid flow path 30, as described above.
The liquid pump 40 is driven periodically as described above, and when the position (drive position) of the drive part of the liquid pump 40 reaches a predetermined position and the on-off valve 60 opens, at the same timing in that period, the foaming agent E is supplied to the liquid L. Here, the liquid pump 40 supplies the liquid L to the flow path 30 with substantially the same behavior (i.e., substantially the same pressure and the same flow rate) at the same timing in the period, so when a predetermined amount (i.e., a constant amount) of foaming agent is supplied to the flow path 30 at that timing, the supply of the foaming agent E to the liquid L becomes stable.
In other words, in this embodiment, rather than controlling in response to the liquid pressure in the liquid flow path 30, the opening/closing valve 60 is controlled to open when the drive part of the liquid pump 40 reaches a predetermined position (specified position), thereby enabling a stable supply of foaming agent E to the liquid L.
Furthermore, by controlling the on-off valve 60 to open when the predetermined position is reached and then to close, the on-off valve is repeatedly opened and closed.

The predetermined position is not particularly limited, but when the liquid pump 40 is a reciprocating pump such as a syringe pump, it may be the top dead center, the bottom dead center, or a specific position therebetween, but is preferably either the top dead center or the bottom dead center. When the top dead center or the bottom dead center is reached, the pressure of the liquid L supplied to the liquid flow path 30 thereafter decreases. Therefore, if the predetermined position is the top dead center or the bottom dead center, the foaming agent E will be supplied at the timing when the pressure decreases, making it easier to mix the foaming agent E with the liquid L.
Furthermore, in a reciprocating pump, the predetermined position does not have to be one location during one cycle in which the drive unit moves from top dead center to bottom dead center and then moves from bottom dead center to top dead center, but may be two or more locations; for example, both the top dead center and the bottom dead center may be set as predetermined positions.
In addition, in the case of a rotary pump, the predetermined position may be set to, for example, a specific position n° (where n is any position from 0 to 360) within the rotation period (0 to 360°).

The on-off control unit 61 may control the on-off valve 60 to open once per cycle of the drive unit of the liquid pump 40, or may control the on-off valve 60 to open once per two cycles, or may control the on-off valve 60 to open once per n cycles (n is an integer of 3 or more). Furthermore, the on-off control unit 61 may control the on-off valve 60 to open multiple times per cycle of the drive unit of the liquid pump 40, for example, to open once per half cycle.
Note that opening the valve once per cycle means, for example, that if the top dead center is set to a predetermined position, the valve opens every time the top dead center is reached. The same applies to the bottom dead center.
Furthermore, for example, if the predetermined position is a specific position between top dead center and bottom dead center, there is no need to open the on-off valve 60 in any case where the drive unit is at the predetermined position, and it is preferable to control the valve to open either when the drive unit moves from top dead center to bottom dead center or from bottom dead center to top dead center.
Furthermore, in a double-acting pump having multiple drive units (e.g., a double-acting plunger pump), the on-off valve may be controlled based on the drive of any one of the drive units, or may be controlled based on the drive of multiple drive units. When controlled based on the drive of multiple drive units, for example, the valve may be opened each time the drive unit of each drive unit is positioned at a predetermined position.

The on-off valve control unit 61 controls to close the on-off valve 60 when a predetermined amount of foaming agent E has been added from the foaming agent metering pump 50 to the liquid L1 in the liquid flow path 30. In this way, by closing the on-off valve 60 when a predetermined amount of foaming agent E has been added from the foaming agent metering pump 50 to the liquid L1 in the liquid flow path 30, it is possible to stably supply a predetermined amount (predetermined volume) of foaming agent E without adding excess foaming agent E to the liquid L1 flowing through the liquid flow path 30.
Here, the on-off valve control unit 61 may measure the amount of foaming agent E delivered from the foaming agent metering pump 50, and when the delivered amount reaches a specified amount, determine that a predetermined amount of foaming agent E has been added to the liquid L1 and close the valve, or may close the valve after a certain time has elapsed since the valve was opened, thereby adding a predetermined amount of foaming agent E to the liquid L1. Moreover, the on-off valve control unit 61 may detect the operation of the foaming agent metering pump 50 and close the valve when it determines that the predetermined amount of foaming agent E metered by the foaming agent metering pump 50 has been added in its entirety.

The on-off valve control unit 61 also receives the liquid pressure LP of the liquid L1 flowing through the liquid flow path 30 measured by the liquid flow path pressure gauge 31, and controls the on-off valve 60 not to open if the measured pressure LP is lower than a predetermined value. By controlling the on-off valve control unit 61 not to open the on-off valve 60 when the measured pressure LP is lower than the predetermined value, it is possible to prevent the addition of foaming agent E when only a small amount of liquid L1 is flowing through the liquid flow path 30. Examples of when the measured pressure LP is lower than the predetermined value include when the foaming agent addition device 10 is started up or stopped, and when the liquid flow path 30 is clogged. The predetermined value of the measured pressure LP is preferably lower than the pulsating fluctuation of the liquid pump 40, and may be set to, for example, 3 MPa.

The amount of blowing agent E supplied to the liquid L1 flowing through the liquid flow path 30, expressed as a volume ratio of blowing agent E to liquid L1 at the time of addition, is preferably 0.05 to 5.0%, more preferably 0.1 to 4.5%, and even more preferably 0.15 to 4.0%. Keeping the amount of blowing agent E supplied within this range makes it possible to incorporate an appropriate amount of blowing agent into polyol, etc., and to properly foam the polyurethane foam. The amount of blowing agent E supplied to the liquid L1 flowing through the liquid flow path 30 is preferably adjusted depending on the blowing agent E used. For example, if the blowing agent E is carbon dioxide, the amount is preferably 0.2 to 2.0%, and if the blowing agent E is a mixed gas of hydrofluoroolefin and carbon dioxide, the amount is preferably 0.4 to 3.5%.

(Spray foaming machine)
As shown in Figure 2, the spray foaming machine 1 is equipped with the above-mentioned blowing agent adding device 10. The spray foaming machine 1 in this embodiment is an apparatus for forming polyurethane foam. However, in the present invention, the spray foaming machine is not limited to an apparatus for forming polyurethane foam, and may be an apparatus for forming other foams. As described above, the polyurethane foam is preferably a rigid polyurethane foam. Furthermore, the spray foaming machine 1 is an on-site spray foaming machine, and is an apparatus that is brought to a construction site where polyurethane foam is to be applied and forms polyurethane foam at the construction site.

In addition to the blowing agent addition device 10, the spray foaming machine 1 further comprises the above-mentioned liquid flow path 30 (hereinafter also referred to as the first liquid flow path 30) and liquid pump 40 (hereinafter also referred to as the first liquid pump 40). The spray foaming machine 1 also comprises a second liquid flow path 32 through which liquid L2, separate from the above-mentioned liquid L1, flows, and a liquid pump 42 (hereinafter also referred to as the second liquid pump 42) that delivers liquid L2 to the second liquid flow path 32. The first and second liquid pumps 40, 42 are connected to a liquid container (not shown) such as a drum, and deliver the liquids L1, L2 sucked from the liquid container to the first and second liquid flow paths 30, 32, respectively.

As described above, polyurethane foam can be formed by mixing a first liquid containing a polyol and a second liquid containing a polyisocyanate, followed by foaming and curing. Liquid L1 flowed through the first liquid flow path 30 is one of the first or second liquids, and liquid L2 flowed through the second liquid flow path 32 is the other of the first or second liquids. However, it is preferable that liquid L1 is a first liquid containing a polyol and liquid L2 is a second liquid containing a polyisocyanate.

The spray foam machine 1 includes a spray gun 70. The spray gun 70 includes a discharge section 70A and a mixing section 70B. The first and second liquid flow paths 30, 35 merge in the mixing section 70B. The first and second liquids flowing through the first and second liquid flow paths 30, 32 are mixed in the mixing section 70B, and the resulting mixture (urethane resin composition) is sprayed from the discharge section 70A. The urethane resin composition is preferably sprayed onto the target surface, such as the roof, walls, or floor of a building or structure. The sprayed urethane resin composition foams and hardens to form polyurethane foam. The polyurethane foam is used, for example, as a thermal insulation material.

The above-described spray foaming machine 1 uses liquid L1, which has been appropriately mixed with blowing agent E using the blowing agent addition device 10, as a raw material for polyurethane foam, allowing for the production of polyurethane foam with excellent foaming and sprayability.

[Method of adding foaming agent]
The method of adding the foaming agent E to the liquid L1 in the foaming agent addition device 10 in this embodiment will be described in detail with reference to the flowchart in Fig. 3. Note that the following description will be made of pressure, temperature, etc., taking the case where the foaming agent E is carbon dioxide as a specific example, but when the foaming agent E is another substance, the pressure, temperature, etc. may be set according to the properties of that substance.

First, in step S1, the operation of the liquid pump 40 is detected by the pump operation detection unit 41. Specifically, the operation position of the drive unit of the liquid pump 40, which pressurizes the liquid L1 flowing through the liquid flow path 30, is detected by the pump operation detection unit 41, and pump operation information DI related to the detected operation of the liquid pump 40 is obtained. The pump operation detection unit 41 is preferably a laser appli-sensor capable of continuously measuring the operation position of the drive unit of the liquid pump 40. The obtained pump operation information DI is sent to the on-off valve control unit 61.

Next, in step S2, the foaming agent E contained in the foaming agent container 11 is supplied to the foaming agent flow path 12. The temperature of the foaming agent E supplied to the foaming agent flow path 12 is preferably maintained in the range of -20 to 20°C. Furthermore, the pressure inside the foaming agent flow path 12 is preferably adjusted so that the pressure of the foaming agent E sent to the foaming agent metering pump 50 is in the range of 5 to 12 MPa.

Next, in step S3, a predetermined amount of foaming agent E to be supplied to the liquid flow path 30 is metered by the foaming agent metering pump 50.

Next, in step S4, the addition of the foaming agent E to the liquid L1 is controlled by opening and closing the on-off valve 60.
In the process of controlling the addition of foaming agent E by opening and closing on-off valve 60, on-off valve control unit 61 controls to open on-off valve 60 in accordance with the driving status of liquid pump 40 detected by pump drive detection unit 41. Specifically, on-off valve control unit 61 receives pump drive information DI of liquid pump 40 from pump drive detection unit 41, and controls to open on-off valve 60 when the driving position of the drive unit of liquid pump 40 reaches a predetermined position (predetermined position).

However, the above steps are merely an example of control, and may be performed in any order as long as it does not contradict the gist of the present invention. For example, step S1 may be performed simultaneously with step S2 or step S3, or may be performed after step S2 or step S3.

[Foam manufacturing method]
A foam can be formed by using the blowing agent addition device 10 according to the first embodiment of the present invention. The method for producing a polyurethane foam in this embodiment includes the above steps S1 to S4, and further includes a step of adding blowing agent E to liquid L1 flowing through liquid flow path 30 in blowing agent addition device 10, mixing liquid L1 and liquid L2 in spray foaming machine 1 to prepare a mixture, and discharging the mixture from the discharge device. Specifically, the method includes the following steps (1) to (5):
(1) A step of detecting the operation of the liquid pump 40 by the pump operation detection unit 41. (2) A step of supplying the foaming agent E contained in the foaming agent container 11 to the foaming agent flow path 12. (3) A step of metering a predetermined amount of foaming agent E to be supplied to the liquid flow path 30 by the foaming agent metering pump 50. (4) A step of controlling the addition of foaming agent E to the liquid L1 by opening and closing the on-off valve 60. (5) A step of mixing the liquid L1, which has been obtained by adding foaming agent E to the liquid L1 flowing through the liquid flow path 30 by the foaming agent addition device 10, with the liquid L2 in the spray foaming machine 1, and discharging the mixture prepared by the discharge device.

As described above, in this embodiment, by providing a pump operation detection unit 41 that detects the operation of liquid pump 40, the operation status of liquid pump 40 is detected and control is performed in accordance with the operation status of liquid pump 40. In this way, by performing control in accordance with the operation status of liquid pump 40 rather than control in accordance with the liquid pressure within liquid flow path 30, it is possible to stably supply foaming agent E to liquid L1 flowing through liquid flow path 30 without being affected by pulsation of liquid pump 40.
Furthermore, in this embodiment, by utilizing the foaming agent metering pump 50 that supplies a predetermined amount of foaming agent E to the liquid L1 flowing through the liquid flow path 30, a predetermined amount (predetermined volume) of foaming agent can be stably supplied to the liquid L1 flowing through the liquid flow path 30.

Second Embodiment
Next, a second embodiment of the present invention will be described in detail. The second embodiment differs from the first embodiment in that a blowing agent pressure pump 80 is provided in the blowing agent passage 12, as shown in FIG. 4. The differences between the first embodiment and the second embodiment will be described below. Parts for which description will be omitted are the same as those in the first embodiment. In the following description, the same reference numerals will be used to designate components having the same configuration as those in the first embodiment.

The blowing agent pressure pump 80 is provided upstream of the blowing agent metering pump 50 in the blowing agent flow path 12. The pressure of the blowing agent E flowing through the blowing agent flow path 12 is prone to change, such as being reduced by the suction of the blowing agent metering pump 50, and these pressure changes can cause the blowing agent E to vaporize or flow back. Therefore, the blowing agent pressure pump 80 pressurizes the blowing agent E flowing through the blowing agent flow path 12 to a predetermined pressure, making it possible to stably supply a constant amount of blowing agent E to the blowing agent metering pump 50 provided downstream.
From the viewpoint of preventing the vaporization and backflow of the foaming agent E, the predetermined pressure is preferably 5 to 12 MPa.
From the viewpoint of being able to supply the blowing agent E to the blowing agent metering pump 50 at a constant rate, the blowing agent pressure pump 80 is preferably a pump that can pressurize and supply the blowing agent E at a stable pressure, more preferably a pump that can continuously pressurize the blowing agent, and among these, it is preferably either an axial pump or a gear pump.

As shown in FIG. 4, the blowing agent addition device 10 of this embodiment may include a blowing agent pressure gauge 81 between the blowing agent pressure pump 80 and the blowing agent metering pump 50, for measuring the pressure of the blowing agent E flowing through the blowing agent flow path 12.
In this case, the foaming agent E supplied to the foaming agent metering pump 50 may be pressurized by the foaming agent pressure pump 80 until the pressure measured by the foaming agent pressure gauge 81 reaches a predetermined pressure.

The blowing agent pressure pump 80 is preferably controlled by a pump control unit (not shown). The pressure value measured by the blowing agent pressure gauge 81 is sent to the pump control unit, which controls the blowing agent pressure pump 80 to continue supplying the blowing agent E to the blowing agent metering pump 50 when the pressure value is less than a predetermined pressure. When the pressure value reaches the predetermined pressure, the pump control unit controls the blowing agent pressure pump 80 to stop supplying the blowing agent E to the blowing agent metering pump 50.
As described above, by controlling the pressure of the foaming agent E to be increased to a predetermined pressure using the foaming agent pressure gauge 81, it becomes possible to more stably supply the foaming agent E to the foaming agent metering pump 50 provided downstream.

As shown in the flowchart of FIG. 5 , the method for adding the foaming agent E to the liquid L1 in the foaming agent addition device 10 in this embodiment includes a step of pressurizing the foaming agent E flowing through the foaming agent flow path 12 to a predetermined pressure by the foaming agent pressure pump 80 before a step (step S3) of metering a predetermined amount of foaming agent E to be supplied to the liquid flow path 30 by the foaming agent metering pump 50.
In the step of pressurizing the foaming agent E to a predetermined pressure by the foaming agent pressure pump 80, the pressure of the foaming agent E flowing through the foaming agent flow path 12 may be measured by a foaming agent pressure gauge 81 provided between the foaming agent pressure pump 80 and the foaming agent metering pump 50. By measuring the pressure by the foaming agent pressure gauge 81, the accuracy of pressurizing the foaming agent E to a predetermined pressure by the foaming agent pressure pump 80 can be improved, and the foaming agent E can be supplied more stably to the foaming agent metering pump 50 provided downstream.

As described above, in this embodiment, by providing the foaming agent pressure pump 80, a stable, constant amount of foaming agent E can be supplied to the foaming agent metering pump 50, and the foaming agent metering pump 50 can stably supply a predetermined amount (predetermined volume) of foaming agent to the liquid L1 flowing through the liquid flow path 30.

However, the above steps are merely an example of control, and may be performed in any order as long as it does not contradict the gist of the present invention. For example, step S1 may be performed simultaneously with step S2, step S10, or step S3, or may be performed after step S2, step S10, or step S3.

[Third embodiment]
Next, a third embodiment of the present invention will be described in detail. The third embodiment differs from the first and second embodiments in that, as shown in Figures 6 and 7, a flow rate adjustment mechanism 90 for adjusting the flow rate of the foaming agent E is provided in the foaming agent flow path 12 upstream of the on-off valve 60. Differences between the first and second embodiments of the third embodiment will be described below. Furthermore, parts for which description will be omitted are the same as those of the first and second embodiments. Furthermore, in the following description, parts having the same configuration as those of the first and second embodiments will be denoted by the same reference numerals.

The flow rate adjustment mechanism 90 adjusts the flow rate of the blowing agent E to the blowing agent metering pump 50. The flow rate adjustment mechanism 90 can be a second on-off valve that controls the flow rate of the blowing agent E flowing in the blowing agent flow path 12 upstream of the on-off valve 60 by opening or closing it. When the second on-off valve opens, the flow rate adjustment mechanism 90 supplies the blowing agent E flowing in the blowing agent flow path 12 to the blowing agent metering pump 50. When the second on-off valve closes, the flow rate adjustment mechanism 90 stops the supply of the blowing agent E to the blowing agent metering pump 50. The second on-off valve is, for example, a solenoid valve.

An on-off valve control unit 61 is connected to the flow rate adjustment mechanism 90, which controls the opening and closing of the second on-off valve. The on-off valve control unit 61 controls the flow rate adjustment mechanism (second on-off valve) 90 depending on the open/close status of the on-off valve 60. Specifically, when the on-off valve 60 is open, the flow rate adjustment mechanism 90 is closed. When the on-off valve 60 is closed, the flow rate adjustment mechanism 90 is opened to supply foaming agent to the foaming agent metering pump 50, and then the flow rate adjustment mechanism 90 is closed before the on-off valve 60 is switched back to open, or at the same time as the on-off valve 60 is switched open. In this way, by controlling the open/close status of the flow rate adjustment mechanism 90, it is possible to control the flow path from the foaming agent container 11 to the on-off valve 60 to be prevented from being directly connected. In other words, by controlling the flow rate adjustment mechanism 90 to prevent the flow path from being directly connected from the foaming agent container 11 to the on-off valve 60, it is possible to prevent excessive addition of foaming agent E from the foaming agent container 11 to the liquid L1, even if the foaming agent pressure inside the foaming agent container 11 becomes high.

The method of adding the foaming agent E to the liquid L1 in the foaming agent addition device 10 shown in FIG. 6 of this embodiment is shown in the flowchart of FIG. 8, and the method of adding the foaming agent E to the liquid L1 in the foaming agent addition device 10 shown in FIG. 7 is shown in the flowchart of FIG. 9.
8 and 9, the method includes a step (step S30) of closing the on-off valve 60 and opening the flow rate adjustment mechanism 90 before a step (step S2) of supplying the foaming agent E contained in the foaming agent container 11 to the foaming agent flow path 12. Then, the method includes a step (step S31) of closing the flow rate adjustment mechanism 90 before a step (step S4) of controlling the addition of the foaming agent E by opening and closing the on-off valve 60.

However, the steps shown in the flowcharts of Figures 8 and 9 are merely examples of control, and may be performed in any order as long as it does not deviate from the spirit of the present invention. For example, in the steps shown in the flowchart of Figure 8, step S1 may be performed simultaneously with step S30, step S2, step S3, step S31, or step S4, or may be performed after step S30, step S2, step S3, step S31, or step S4. In the steps shown in the flowchart of Figure 9, step S1 may be performed simultaneously with step S30, step S2, step S10, step S3, step S31, or step S4, or may be performed after step S30, step S2, step S10, step S3, step S31, or step S4.

As described above, in this embodiment, the provision of the flow rate adjustment mechanism 90 makes it possible to control the connection of the flow path from the foaming agent container 11 to the on-off valve 60, and even when the foaming agent container 11 is pressurized, it is possible to adjust the differential pressure between the foaming agent E and the liquid pressure in the liquid flow path 30. Adjusting the differential pressure between the foaming agent E and the liquid pressure in the liquid flow path 30 allows the foaming agent metering pump 50 to stably supply a predetermined amount (predetermined volume) of foaming agent to the liquid L1 flowing through the liquid flow path 30. While the flow rate adjustment mechanism 90 in this embodiment is described as being a second on-off valve, other mechanisms may be used as long as they are capable of adjusting the flow rate of the foaming agent E.

[Other embodiments]
The foaming agent adding device, the spray foaming machine, the foaming agent adding method, and the foam manufacturing method described above in relation to the respective embodiments are merely examples of the present invention, and the present invention is not limited to the configurations of the above-described embodiments. Various improvements and modifications are possible within the scope of the spirit of the present invention, and components may be added as appropriate.
For example, as shown in FIG. 10 , the foaming agent addition method may include a step (step S20) of measuring the pressure of the liquid L1 flowing through the liquid flow path 30 with a liquid pressure gauge 31. When step S20 is included, in a step (step S4) of controlling the addition of foaming agent E to the liquid L1 by opening and closing an on-off valve 60, the on-off valve 60 may be controlled not to open if the measured pressure LP of the liquid pressure gauge 31 is lower than a predetermined value. By including step S20 in the foaming agent addition method, when the amount of liquid L1 flowing through the liquid flow path 30 is small, such as when the foaming agent addition device 10 is started or stopped, or when the liquid flow path 30 is clogged, foaming agent E is not added at a stable rate, and therefore control can be performed to prevent addition. The predetermined value of the measured pressure LP is preferably lower than the pulsation fluctuation of the liquid pump 40, and may be set to, for example, 3 MPa.

However, step S1 does not have to be performed in this order; for example, step S1 may be performed simultaneously with step S2, step S3, or step S20, or may be performed after step S2, step S3, or step S20.

Note that although the foaming agent addition device 10 in each embodiment is described as being equipped with a liquid pressure gauge 31, the liquid pressure gauge 31 may be omitted.

REFERENCE SIGNS LIST 1 spray foaming machine 10 foaming agent adding device 11 foaming agent container 12 foaming agent flow path 30 liquid flow path (first liquid flow path)
31 Liquid flow path pressure gauge 32 Second liquid flow path 40 Liquid pump (first liquid pump)
41 Pump operation detection unit 41
42 Liquid pump (second liquid pump)
50 Foaming agent metering pump 60 On-off valve 61 On-off valve control unit 70 Spray gun 70A Discharge unit 70B Mixing unit 80 Foaming agent pressure pump 81 Foaming agent pressure gauge 90 Flow rate adjustment mechanism E Foaming agent L1, L2 Liquid

Claims (17)

A foaming agent adding device for adding a foaming agent to a liquid supplied by a liquid pump and flowing through a liquid flow path, comprising:
a pump operation detection unit that detects operation of the liquid pump;
a foaming agent container for containing the foaming agent;
a foaming agent flow path through which the foaming agent supplied from the foaming agent container flows;
a blowing agent metering pump for supplying a predetermined amount of the blowing agent to the liquid flow path;
an on-off valve that controls the addition of the foaming agent to the liquid by opening and closing;
an on-off valve control unit that controls the on-off valve to open in accordance with the driving state of the liquid pump detected by the pump drive detection unit ;
a blowing agent pressure pump, located upstream of the blowing agent metering pump, for increasing the pressure of the blowing agent flowing through the blowing agent flow path to a predetermined pressure; 2. The blowing agent adding device according to claim 1 , wherein the blowing agent pressurizing pump is a pump that continuously pressurizes the blowing agent. 3. The blowing agent adding device according to claim 1 , wherein the blowing agent pressure pump is either an axial pump or a gear pump. a blowing agent pressure gauge for measuring the pressure of the blowing agent flowing through the blowing agent flow path is provided between the blowing agent pressure pump and the blowing agent metering pump;
4. The blowing agent adding device according to claim 1 , wherein the blowing agent pressure pump pressurizes the blowing agent until a pressure value measured by a blowing agent pressure gauge reaches the predetermined pressure. A foaming agent adding device for adding a foaming agent to a liquid supplied by a liquid pump and flowing through a liquid flow path, comprising:
a pump operation detection unit that detects operation of the liquid pump;
a foaming agent container for containing the foaming agent;
a foaming agent flow path through which the foaming agent supplied from the foaming agent container flows;
a blowing agent metering pump for supplying a predetermined amount of the blowing agent to the liquid flow path;
an on-off valve that controls the addition of the foaming agent to the liquid by opening and closing;
an on-off valve control unit that controls the on-off valve to open in accordance with the driving state of the liquid pump detected by the pump drive detection unit ;
a liquid flow path pressure gauge for measuring the pressure of the liquid flowing through the liquid flow path,
The blowing agent addition device , wherein the on-off valve control unit controls the on-off valve not to open when the pressure of the liquid measured by the liquid flow path pressure gauge is lower than a predetermined value. The foaming agent addition device according to claim 1 , wherein the on-off valve control unit opens the on-off valve when the drive position of the liquid pump reaches a predetermined position. The foaming agent adding device according to claim 1 , wherein the on-off valve control unit controls the on-off valve to close when the predetermined amount of the foaming agent has been added to the liquid. The blowing agent adding device according to any one of claims 1 to 7 , wherein the blowing agent metering pump is a positive displacement pump. The blowing agent adding device according to any one of claims 1 to 8 , wherein the blowing agent metering pump is a reciprocating pump. The blowing agent addition device according to any one of claims 1 to 9, wherein the liquid contains a polyol or a polyisocyanate. A foaming agent addition device according to any one of claims 1 to 10, wherein the foaming agent includes carbon dioxide. The blowing agent adding device according to any one of claims 1 to 11 , further comprising a flow rate adjusting mechanism for adjusting the flow rate of the blowing agent in the blowing agent flow path upstream of the on-off valve. The blowing agent adding device according to claim 12 , wherein the flow rate adjusting mechanism is a second on-off valve that controls, by opening and closing, the flow rate of the blowing agent flowing in the blowing agent flow path upstream of the on-off valve. A foam spray machine comprising the foaming agent adding device according to any one of claims 1 to 13 . A foaming agent adding method for adding a foaming agent to a liquid supplied by a liquid pump and flowing through a liquid flow path, comprising:
detecting the operation of the liquid pump with a pump operation detection unit;
supplying a foaming agent contained in a foaming agent container to a foaming agent flow path;
a step of metering a predetermined amount of the foaming agent to be supplied to the liquid flow path by a foaming agent metering pump;
a step of controlling the addition of the foaming agent to the liquid by opening and closing an on-off valve ;
and a step of increasing the pressure of the foaming agent flowing through the foaming agent flow path to a predetermined pressure by a foaming agent pressure pump, before the step of metering the foaming agent by the foaming agent metering pump, so that the pressure in the foaming agent metering pump becomes the predetermined pressure,
a blowing agent adding method, in which, in the step of controlling the addition of the blowing agent by opening and closing an on-off valve, an on-off valve control unit controls the on-off valve to open in accordance with the drive status of the liquid pump detected by the liquid pump drive detection unit. A foaming agent adding method for adding a foaming agent to a liquid supplied by a liquid pump and flowing through a liquid flow path, comprising:
detecting the operation of the liquid pump with a pump operation detection unit;
supplying a foaming agent contained in a foaming agent container to a foaming agent flow path;
a step of metering a predetermined amount of the foaming agent to be supplied to the liquid flow path by a foaming agent metering pump;
a step of controlling the addition of the foaming agent to the liquid by opening and closing an on-off valve ;
measuring the pressure of the liquid flowing through the liquid flow path with a liquid pressure gauge;
In the step of controlling the addition of the foaming agent by opening and closing an on-off valve, an on-off valve control unit controls the on-off valve to open in accordance with the drive status of the liquid pump detected by the liquid pump drive detection unit,
a step of controlling the addition of the blowing agent by opening and closing an on-off valve, the on-off valve being controlled not to open when the pressure measured by the liquid pressure gauge is lower than a predetermined value. A foam manufacturing method comprising the step of adding a foaming agent to a liquid flowing through a liquid flow path by the foaming agent adding method according to claim 15 or 16 .