JP7564745B2 - Material preheating device and injection device - Google Patents

Description

This invention relates to a material preheating device that preheats molding material before it is supplied to an injection device, and to the injection device.

When manufacturing molded products using an injection molding machine, dryers such as those described in Patent Documents 1 to 3 are used to heat the molding material before it is supplied to the injection device of the injection molding machine.

JP 2000-167840 A Special Publication No. 2012-521904 JP 2016-26919 A

By the way, when manufacturing molded products such as PET bottle caps, injection molding machines are sometimes used in high-cycle molding, where a series of processes from melting resin pellets or other molding materials and injecting them into a mold device to obtaining a molded product are repeated in a relatively short cycle. In such cases, the injection molding machine is required to have high production capacity.

The molding cycle of an injection molding machine can be shortened by increasing the rotation speed of the screw placed inside the cylinder of the injection device to complete the plasticization of the molding material in a short period of time, thereby shortening the time it takes for the molding material to accumulate at the tip of the cylinder.

On the other hand, when the screw is rotated at high speed, the molding material inside the cylinder is not sufficiently heated by the heater installed around the cylinder, and is sent rapidly to the tip of the cylinder. Even if the heating temperature of the heater is increased, the molding material may not be heated sufficiently because the residence time of the molding material inside the cylinder is short. In this case, the molten molding material injected from the tip of the cylinder into the mold device may contain unmelted molding material. The contamination of the molded product with unmelted molding material can cause defects such as a poor appearance or reduced strength of the molded product.

To address this issue, it is possible to preheat the molding material before supplying it to the injection device. However, in general dryers for drying molding materials such as those described in Patent Documents 1 to 3, the temperature of each molding material may not rise as quickly and sufficiently as required for the above-mentioned high-cycle molding.

Here, if a heater is designed that uses hot air to suspend the molding materials and create a fluidized layer in order to preheat the molding materials before they are supplied to the injection unit, it is expected that the heater will effectively raise the temperature of each molding material in a relatively short time. However, even with such a heater, it is estimated that it will be difficult to achieve rapid heating of each molding material with a single heater, taking into consideration the amount or speed of the molding material supplied to the injection unit, the blowing capacity of the equipment that supplies hot air to the heater, and other conditions.

The objective of this invention is to solve the problems described above, and to provide a material preheating device and an injection device that can effectively preheat the molding material before supplying it to the injection device.

One material preheating device that can solve the above problems preheats the molding material and supplies it to the injection device, and is equipped with multiple fluidized bed heaters that heat the molding material while forming a fluidized bed by supplying hot air.

In addition, one injection device has a cylinder for melting the molding material, and injects the molding material melted in the cylinder into the mold device, and is equipped with the material preheating device described above.

The material preheating device described above can effectively preheat the molding material before it is supplied to the injection device.

1 is a cross-sectional view showing a material preheating device according to an embodiment of the present invention together with an injection device. FIG. 2 is an enlarged cross-sectional view of the material preheating apparatus of FIG. 1. FIG. 4 is a cross-sectional view showing a material preheating device according to another embodiment. FIG. 11 is a cross-sectional view showing a material preheating device according to still another embodiment.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.
A material preheating device 21 according to an embodiment of the present invention is attached to an injection device 1 as shown in Fig. 1, and preheats the molding material before it is supplied to the injection device 1. The injection device 1, which constitutes a part of an injection molding machine, melts the molding material supplied from the material preheating device 21 and injects the molding material into a mold device (not shown). The illustrated injection device 1 is disposed on a slide base 101 of a moving device that moves the injection device 1 forward and backward, and includes a cylinder 11 that melts the molding material therein, a screw 12 that is driven to rotate inside the cylinder 11 to plasticize the molding material, a heater 13 that is provided around the cylinder 11 to heat the molding material inside the cylinder 11, and the like, but the detailed structure of the injection device 1 will be described later.

(Material preheating device)
The material preheating device 21 is attached to the rear end of the cylinder 11 on the opposite side to the tip end 14 from which the molding material is injected, in the direction of the rotation axis of the screw 12 (left and right direction in FIG. 1). More specifically, the material preheating device 21 is connected to a through-hole-shaped supply port 11a provided on a part of the circumference of the rear end of the cylinder 11, as shown in FIG. 2, and supplies molding material Mm, such as resin pellets having substantially spherical or cylindrical shapes or other shapes, to the supply port 11a.

The material preheating device 21 of this embodiment is equipped with two fluidized bed heaters 22, 23 that heat the molding material Mm by supplying hot air inside the fluidized bed heaters 22, 23 while forming a fluidized bed. In each of the fluidized bed heaters 22, 23, hot air from air or other heated gas is often supplied to the interior from below the molding material Mm contained therein. As a result, at least a portion of the molding material Mm is blown up and floated by the hot air from below as shown in the figure, forming a fluidized bed. At this time, the molding material Mm in a floating state in the fluidized bed heaters 22, 23 has a larger contact area with the hot air compared to when it is in a piled state, so it is effectively heated by the hot air. As a result, the fluidized bed heaters 22, 23 can sufficiently heat the molding material Mm in a relatively short time.

On the other hand, depending on the number or amount of molding material Mm supplied to the injection device 1 in high cycle molding, the supply speed, and other conditions, it may be necessary to heat a certain amount of molding material Mm in each preheating. In this case, in order to quickly heat each of the multiple molding materials Mm to a predetermined temperature in the fluidized bed, it is necessary to increase the flow rate of hot air sent to the molding material Mm, but it may not be practical to use a high-performance hot air generator capable of generating such a flow rate of hot air in an injection molding machine.

In contrast, in this embodiment, the material preheating device 21 is equipped with multiple, for example two, fluidized bed heaters 22, 23. In this way, the molding material Mm to be preheated is divided into small portions for the multiple fluidized bed heaters 22, 23, and heated in fluidized beds by each of the fluidized bed heaters 22, 23, allowing a relatively large amount of molding material Mm to be preheated quickly and effectively. This makes it possible to accommodate high-cycle molding without significantly increasing the capacity of the hot air generator.

In the illustrated embodiment, each of the fluidized bed heaters 22, 23 is, as an example, a container-shaped heater having a tip tube portion 22a, 23a located downstream (lower side in FIG. 2) in the supply direction of the molding material Mm to the injection device 1, a tapered portion 22b, 23b including a small-diameter end portion connected to the tip tube portion 22a, 23a, both of which have a tapered shape such as a truncated cone shape, a cylindrical main body portion 22c, 23c connected to the large-diameter end portion of the tapered portion 22b, 23b, and an annular portion 22d, 23d provided at the end portion of the cylindrical main body portion 22c, 23c on the opposite side (upper side in FIG. 2) from the tapered portion 22b, 23b side and extending from the end portion to the inner periphery. However, the specific shape and other configuration of the fluidized bed heater are not particularly important as long as it can heat the molding material while making it into a fluidized bed inside. Also, in this embodiment, the two fluidized bed heaters 22, 23 have approximately the same shape and size, but at least one of the multiple fluidized bed heaters may have a different shape and/or size from the other fluidized bed heaters.

Regarding the arrangement of the multiple fluidized bed heaters 22, 23, in the material preheating device 21 shown in FIG. 2, two fluidized bed heaters 22, 23 are arranged in series, substantially one above the other in the vertical direction, and a serial connection passage 24 is provided to connect the fluidized bed heaters 22, 23 to each other. In this example, the serial connection passage 24 is defined inside the tip tube portion 23a of the fluidized bed heater 23 located on the upper side in the vertical direction (upstream side in the supply direction of the molding material Mm). The tip tube portion 23a extends along the vertical direction that is approximately the same as the supply direction of the molding material Mm, and is connected to the annular portion 22d of the fluidized bed heater 22 located on the lower side in the vertical direction (downstream side in the supply direction of the molding material Mm).

2, when the material preheating device 21 is provided with a serial connection passage 24 that connects the fluidized bed heaters 22 and 23, when the molding material Mm is heated by the downstream fluidized bed heater 22, the molding material Mm can also be heated by the upstream fluidized bed heater 23. After the molding material Mm heated by the downstream fluidized bed heater 22 is supplied to the injection device 1, the molding material Mm heated by the upstream fluidized bed heater 23 is sent to the downstream fluidized bed heater 22 via the serial connection passage 24, and then heated by the downstream fluidized bed heater 22. By heating in multiple stages such as two stages, the molding material Mm is easily heated to a predetermined temperature by the fluidized bed heater 22 immediately before being supplied to the injection device 1. In order to realize multiple stages of heating by the fluidized bed heaters 22 and 23, the material preheating device 21 of this embodiment has the following specific configuration.

In each of the fluidized bed heaters 22, 23 of the material preheating device 21 shown in FIG. 2, the tip tube portion 22a, 23a serving as an outlet for the molding material Mm is provided with an air permeable opening/closing member 25a, 25b that is driven by a driving source (not shown) and opens and closes to pass or stop the passage of the molding material Mm at the outlet. When the air permeable opening/closing member 25a, 25b is closed, the hot air supplied to each of the fluidized bed heaters 22, 23 from the outlet side can pass through the air permeable opening/closing member 25a, 25b as described below, while the molding material Mm cannot pass through the air permeable opening/closing member 25a, 25b and is held on the air permeable opening/closing member 25a, 25b. Specific examples of such air permeable opening/closing members 25a, 25b include punching metal in which a plurality of through holes are formed by pressing or the like in a metal plate material, and mesh members having a mesh shape such as a square or other polygon when viewed from the front.

In addition, the material preheating device 21 includes a material supply passage 26 for the injection device 1 that connects the outlet of the downstream fluidized bed heater 22 to the supply port 11a of the injection device 1, a hot air feed passage 27a that connects the hot air generator 27 to the material supply passage 26, and a hot air return passage 27b that connects the annular portion 23d of the upstream fluidized bed heater 23 to the hot air generator 27. In the middle of the material supply passage 26, downstream of the connection point with the hot air feed passage 27a in the supply direction of the molding material Mm, a hot air blocking member 28 that is driven to open and close is provided. Although not shown, a hot air blocking member that can be opened and closed can also be provided in the hot air feed passage 27a, and when this hot air blocking member is closed, the flow of hot air from the hot air generator 27 to the fluidized bed heater 22 is blocked. In many cases, the material preheating device 21 further includes a hot air generator 27 that generates hot air to be supplied to the fluidized bed heaters 22 and 23, but the material preheating device 21 may not include the hot air generator 27, and the source of the hot air is not limited to the hot air generator 27.

Furthermore, as in the illustrated material preheating device 21, the upstream fluidized bed heater 23 preferably has a material inlet 23e, for example, provided in the annular portion 23d and used to feed the molding material Mm to the fluidized bed heater 23. The material inlet 23e can be provided with a hot air blocking member 23f that can be opened and closed. If the upstream fluidized bed heater 23 has a material inlet 23e, the molding material Mm can be fed from the material inlet 23e through the fluidized bed heater 23 and the serial connection passage 24 to the downstream fluidized bed heater 22. Therefore, it is not necessarily necessary to provide a material inlet in the downstream fluidized bed heater 22, but in this material preheating device 21, the downstream fluidized bed heater 22 is also provided with a material inlet 22e with a hot air blocking member 22f that can be opened and closed.

In the material preheating device 21 having the above-mentioned configuration, the hot air blocking member 23f is opened while the breathable opening/closing member 25b is open and the breathable opening/closing member 25a is closed, and the molding material Mm is fed from the material inlet 23e to the downstream fluidized bed heater 22. Thereafter, the breathable opening/closing member 25b is closed, and the molding material Mm is fed from the material inlet 23e to the upstream fluidized bed heater 23. Alternatively, when the material inlet 22e is also used, the hot air blocking members 22f and 23f are opened while both the breathable opening/closing members 25a and 25b are closed, and the molding material Mm is fed from the material inlets 22e and 23e to each of the fluidized bed heaters 22 and 23.

To heat the molding material Mm in the fluidized bed heaters 22 and 23, the air permeable opening/closing members 25a and 25b are closed, and the hot air blocking members 22f, 23f, and 28 are closed to supply hot air from the hot air generator 27 to the fluidized bed heaters 22 and 23. At this time, as shown by the arrow in FIG. 2, the hot air generated by the hot air generator 27 flows from the hot air delivery passage 27a to the material supply passage 26 through the air permeable opening/closing member 25a through which the hot air can pass, not to the injection device 1 side blocked by the hot air blocking member 28, but to the downstream fluidized bed heater 22. Then, the hot air heats the molding material Mm in the downstream fluidized bed heater 22 while floating it to form a fluidized layer, and flows through the air permeable opening/closing member 25b in the serial connection passage 24 to the upstream fluidized bed heater 23. In the upstream fluidized bed heater 23, similar fluidized bed heating of the molding material Mm is also performed by hot air. The hot air that passes through the upstream fluidized bed heater 23 returns to the hot air generator 27 through the hot air return flow path 27b.

This flow of hot air sufficiently heats the molding material Mm in the downstream fluidized bed heater 22 for a specified time, and when the preheating of the molding material Mm is completed, the hot air generator 27 is stopped and the breathable opening and closing member 25a and the hot air blocking member 28 are opened. As a result, the molding material Mm in the fluidized bed heater 22 falls by its own weight and is fed into the cylinder 11 from the supply port 11a. Then, the breathable opening and closing member 25a is closed and the breathable opening and closing member 25b is opened, so that the molding material Mm in the upstream fluidized bed heater 23 is sent to the downstream fluidized bed heater 22 through the serial connection passage 24. Then, the breathable opening and closing member 25b is closed and the hot air blocking member 23f is opened, and the molding material Mm is fed into the upstream fluidized bed heater 23 from the material feed port 23e.

Thereafter, the hot air blocking members 22f, 23f, and 28 are closed, and the molding material Mm is heated in the fluidized bed heaters 22 and 23 by supplying hot air as described above, and this heating of the molding material Mm and supplying it to the injection device 1 is repeated.

Although not shown in the figure, three or more fluidized bed heaters can be arranged in series. A serial connection passage is provided between each of the adjacent fluidized bed heaters arranged in series. In addition to fluidized bed heaters arranged in series, the material preheating device may also include fluidized bed heaters that are not arranged in series, such as fluidized bed heaters arranged in parallel as described below.

Figure 3 shows another embodiment of a material preheating device 121. This material preheating device 121 has a configuration similar to that of the material preheating device 21 shown in Figure 2, except that multiple fluidized bed heaters 122, 123 are arranged in parallel. That is, in the material preheating device 121 of Figure 3, two fluidized bed heaters 122, 123 are arranged side by side in a direction inclined or perpendicular to the vertical direction, typically in the horizontal direction. And between the fluidized bed heaters 122, 123 and the injection device 1, a parallel supply passage 126 is provided to send and supply the molding material Mm from each of the fluidized bed heaters 122 and 123 to the injection device 1.

More specifically, the parallel supply passage 126 has two branch passage sections 126a, 126b that connect to the respective tip tube sections 122a, 123a of the fluidized bed heaters 122, 123 connected to the parallel supply passage 126, and a junction passage section 126c where the branch passage sections 126a, 126b join together and reach the supply port 11a of the injection device 1. Although not shown, it is also possible to provide three or more fluidized bed heaters in a parallel arrangement, in which case the number of branch passage sections can be three or more depending on the number of the fluidized bed heaters.

Here, the fluidized bed heaters 122, 123 are arranged in parallel, and each of the fluidized bed heaters 122, 123 connected to the parallel supply passage 126 has a material inlet 122e, 123e equipped with a hot air blocking member 122f, 123f used to feed the molding material Mm to the respective fluidized bed heaters 122, 123.

In addition, in order to send hot air from the hot air generator 127 to each of the fluidized bed heaters 122 and 123, in addition to the hot air sending flow path 127a connecting the hot air generator 127 and the branch passage portion 126b on the fluidized bed heater 123 side located near the hot air generator 127, an extended feed flow path 127c is provided connecting the branch passage portion 126b and the branch passage portion 126a on the fluidized bed heater 122 side located away from the hot air generator 127. Hot air blocking members 128b and 128a are respectively arranged downstream of the connection point of the branch passage portion 126b with the hot air sending flow path 127a in the supply direction of the molding material Mm, and downstream of the connection point of the branch passage portion 126a with the extended feed flow path 127c in the supply direction of the molding material Mm. Although not shown in the figure, the hot air feed passage 127a and/or the extended feed passage 127c may be provided with a hot air blocking member capable of blocking the flow of hot air from the hot air generator 127 to the fluidized bed heaters 122 and 123.

In the material preheating device 121 illustrated in FIG. 3, the fluidized bed heater 123 is located near the hot air generator 127, and the fluidized bed heater 122 is located away from the hot air generator 127. However, multiple fluidized bed heaters may be located at approximately equal distances from the hot air generator. In this case, the hot air feed flow path from the hot air generator can be branched into two or more paths and connected to each fluidized bed heater. In the example shown in FIG. 3, instead of the extended feed flow path 127c, it is also possible to provide a branched hot air feed flow path that is connected to each fluidized bed heater 122, 123.

The hot air return flow path 127b is configured to include branch pipe flow path portions 127d, 127e connected to each of the fluidized bed heaters 122, 123 in order to return the hot air generated after heating the molding material Mm in each of the fluidized bed heaters 122, 123 to the hot air generator 127, and a main pipe flow path portion 127f to which the branch pipe flow path portions 127d, 127e are connected and which is connected to the hot air generator 127.

In the material preheating device 121 in Fig. 3, the molding material Mm is fed into the fluidized bed heaters 122, 123 from the material feed ports 122e, 123e, respectively, with the breathable opening and closing members 125a, 125b closed. When the molding material Mm in the fluidized bed heaters 122, 123 is heated, all the hot air blocking members 122f, 123f, 128a, and 128b are closed, and hot air is supplied from the hot air generator 127 to the fluidized bed heaters 122, 123. At this time, the hot air from the hot air generator 127 is sent to each of the fluidized bed heaters 122, 123 via the hot air feed path 127a and the extended feed path 127c, as shown by the arrows in Fig. 3. The hot air used to heat the molding material Mm in each of the fluidized bed heaters 122 and 123 passes through the branch pipe flow passage parts 127d and 127e and the main pipe flow passage part 127f of the hot air return flow passage 127b and returns to the hot air generator 127.

The molding material Mm heated by the fluidized bed heaters 122 and 123 can be supplied to the injection device 1 from the branch passage portions 126a and 126b and the junction passage portion 126c of the parallel supply passage 126 by stopping the hot air generator 127 and then opening the breathable opening/closing members 125a and 125b and the hot air blocking members 128a and 128b.

Here, in this material preheating device 121, the heated molding material Mm can be alternately supplied to the injection device 1 from each of the multiple fluidized bed heaters 122 and 123. For example, when heating of the molding material Mm is completed in one of the fluidized bed heaters 122, the molding material Mm in that fluidized bed heater 122 is supplied to the injection device 1. Next, the breathable opening and closing member 125a is closed, and the molding material Mm is input into one of the fluidized bed heaters 122 from the material input port 122e, and the molding material Mm is heated by the above-mentioned hot air. At this time, the molding material Mm remaining in the other fluidized bed heater 123 is also heated again by the hot air. After that, when heating in the other fluidized bed heater 123 is completed, the molding material Mm is left in one of the fluidized bed heaters 122, and the molding material Mm from the other fluidized bed heater 123 is supplied to the injection device 1. In this way, by alternately supplying molding material Mm to the injection device 1 from each of the multiple fluidized bed heaters 122, 123 arranged in parallel, the molding material Mm is heated multiple times with hot air in each fluidized bed heater 122, 123, making it possible to supply a predetermined high-temperature molding material Mm to the injection device 1 in a rapid cycle.

Alternatively, after the molding material Mm is heated by the hot air, the breathable opening and closing members 125a, 125b and the hot air blocking members 128a, 128b can all be opened almost simultaneously, and the molding material Mm in each of the multiple fluidized bed heaters 122, 123 can be supplied to the injection device 1 at once. This is advantageous when a large amount of molding material Mm is consumed in one melting and injection in the injection device 1, because the relatively large number of molding materials Mm supplied to the injection device 1 at once can be divided into small portions and sufficiently heated by each of the fluidized bed heaters 122, 123.

In yet another embodiment of the material preheating device 221 shown in FIG. 4, fluidized bed heaters 229 and 230 are connected in series to the upstream side of the fluidized bed heaters 222 and 223, which are arranged in parallel like the fluidized bed heaters 122 and 123 in FIG. 3, in the supply direction of the molding material Mm, via serial connection passages 224a and 224b. The rest of the configuration is substantially the same as the material preheating device 121 described above, and a repeated explanation will be omitted.

In this material preheating device 221, each fluidized bed heater 222, 223, 229, and 230 is provided with a material inlet 222e, 223e, 229e, 230e with a hot air blocking member 222f, 223f, 229f, 230f. If the fluidized bed heaters 229 and 230 on the upstream side in the supply direction of the molding material Mm have material inlets 229e and 230e, the molding material Mm can also be fed into the fluidized bed heaters 222 and 223 on the downstream side in the supply direction of the molding material Mm, so the material inlets 222e and 223e of the downstream fluidized bed heaters 222 and 223 may be omitted.

The molding material Mm in the fluidized bed heaters 222, 223, 229, and 230 can be heated by hot air generated by a hot air generator (not shown). Here, the hot air from the hot air generator is sent to the fluidized bed heaters 222 and 229, and the fluidized bed heaters 223 and 230, which are connected in series by the serial connection passages 224a and 224b, via the hot air sending flow path 227a or the extended sending flow path 227c, as shown by the arrows in FIG. 4. The hot air that has passed through the upstream fluidized bed heaters 229 and 230, respectively, reaches the main pipe flow path portion 227f from each branch pipe flow path portion 227d and 227e of the hot air return flow path 227b and is returned to the hot air generator.

The molding material Mm after heating in the downstream fluidized bed heaters 222 and 223 can be supplied alternately or simultaneously to the injection device 1. In this case, by opening the breathable opening/closing members 225a, 225b and the hot air blocking members 228a, 228b, the molding material Mm falls from the fluidized bed heaters 222 and 223, passes through the branch passage portion 226a or 226b and the junction passage portion 226c of the parallel supply passage 226, and reaches the injection device 1. After the molding material Mm is supplied from the downstream fluidized bed heaters 222, 223 to the injection device 1, the breathable opening and closing members 225a, 225b are closed and the breathable opening and closing members 225c, 225d are opened, so that the molding material Mm, which has been heated to a certain extent in the upstream fluidized bed heaters 229, 230, enters the downstream fluidized bed heaters 222, 223, and is heated again in the downstream fluidized bed heaters 222, 223 when hot air is subsequently supplied. Therefore, in this material preheating device 221, the molding material Mm can be heated quickly and supplied in a short cycle more effectively.

If necessary, a material pump can be provided between the material preheating device and the injection device 1, which sucks in and pumps the molding material Mm by introducing compressed gas from a compressor or the like. This is effective, for example, when the material preheating device is disposed around the cylinder 11 of the injection device 1, rather than directly above the supply port 11a of the cylinder 11, and the molding material cannot be supplied from the material preheating device to the injection device 1 due to its own weight. A material transport device such as a belt conveyor may be used instead of the material pump. Also, when there are fluidized bed heaters connected in series, a material pump such as the one described above can be provided in the series connection passage that connects them.

(Injection device)
An injection device 1 to which the above-mentioned material preheating device 21 and the like can be applied, as illustrated in FIG. 1 , mainly comprises a cylinder 11 for melting the molding material supplied from the material preheating device 21 therein, a screw 12 for plasticizing the molding material by being rotated inside the cylinder 11, a metering motor 31 arranged on the rear side in the direction of the rotation axis of the screw 12 (the right side in FIG. 1 ), and an injection motor 41 arranged further rearward of the metering motor 31.

A heater 13 is arranged around the cylinder 11 to heat the molding material supplied inside the cylinder 11. The cylinder 11 has a tip portion 14 where the inside and outside diameters become smaller at the tip side in the direction of the rotation axis (left side in FIG. 1), and heaters 13 are also arranged around the tip portion 14. In addition, a through-hole-shaped supply port 11a is provided at the rear end side in the direction of the rotation axis of the cylinder 11, and the material preheating device 21 described above is attached there.

The metering motor 31 and the injection motor 41 are fixed to the rear side of the two motor support plates 32, 42, which are arranged at a distance from each other in an upright position on the slide base 101, in the direction of the rotation axis. The screw 12 is driven to rotate by the metering motor 31 and driven to move forward and backward by the injection motor 41. The two motor support plates 32, 42 are connected to each other by rods 51, 52 at multiple points on the upper and lower sides separated by the metering motor 31.

The metering motor 31 mainly includes a rotor 33, a stator 34 arranged around the rotor 33, and a stator frame 35 that surrounds the rotor 33 and the stator 34 and has the stator 34 on its inner surface. The rotor 33 of the metering motor 31 is supported by bearings 33a inside the stator frame 35 at each end in the direction of its rotation axis. The rotor 33 is splined around the metering spline shaft 36, which is connected to a screw mounting portion 37 to which the screw 12 is attached. At the rear end in the direction of the rotation axis of the outer peripheral surface of the metering spline shaft 36, one or more keys 36a corresponding to the key grooves provided on the inner peripheral surface of the rotor 33 are formed. This allows the rotational driving force to be transmitted from the metering motor 31 to the screw 12, causing the screw 12 to rotate.

The injection motor 41 mainly includes a rotor 43, a stator 44 arranged around the rotor 43, and a stator frame 45 that is provided around the rotor 43 and the stator 44 and has the stator 44 on its inner surface. The rotor 43 is supported by bearings 43a inside the stator frame 45 at each end in the direction of its rotation axis. In the injection motor 41, the rotor 43 is connected to a drive shaft. More specifically, the drive shaft includes an injection spline shaft 46 splined at a groove 43b provided on the inner periphery of the cylindrical rotor 43, a threaded shaft 48 connected to the injection spline shaft 46, and a rotating shaft 50 rotatably attached to the inside of the metering spline shaft 36 via a bearing 49. A threaded nut 47 that screws onto the threaded shaft 48 is attached to the motor support plate 42 via a pressure detector 38 described later. With this structure, the rotational driving force of the injection motor 41 is converted into a linear driving force in the direction of the rotation axis of the screw 12 and transmitted to the screw 12 .

A pressure detector 38 is disposed between the stator frame 45 of the injection motor 41 and the motor support plate 42. The pressure detector 38 is attached to the motor support plate 42 and the screw nut 47, and detects the load acting on the pressure detector 38 in the transmission path of the driving force from the injection motor 41 to the screw 12. A cylindrical portion 39 is provided between the pressure detector 38 and the stator frame 45. An encoder 45a is provided on the rear end surface of the stator frame 45 of the injection motor 41, which is located on the opposite side of the drive shaft in the direction of the rotation axis, and is connected to the rotor 43 by a shaft portion 45b to detect the rotation of the rotor 43.

In one example of a molding process using an injection molding machine equipped with such an injection unit 1, a predetermined amount of molding material has already been measured and placed inside the cylinder 11 during the latter half of the previous molding process, and a mold clamping process is performed in which the mold unit (not shown) is closed to clamp the mold. Next, the screw 12 is advanced to inject the molding material into the mold unit, filling the cavity in the mold unit with the molding material, and the screw 12 is advanced further to maintain the molding material inside the tip 14 of the cylinder 11 at a predetermined pressure.

Then, a cooling process is carried out to cool and harden the molding material filled in the mold device to obtain a molded product. At this time, the molding material separately supplied from the material preheating device 21 to the cylinder 11 is melted while being sent toward the tip 14 of the cylinder 11 by the rotation of the screw 12 under heating by the heater 13, and a metering process is carried out to place a predetermined amount of molding material at the tip 14.

Here, in this embodiment, the molding material supplied into the cylinder 11 has already been heated to an appropriate temperature by the material preheating device 21. Therefore, even if the screw 12 is rotated at high speed and the molding material is sent to the tip 14 of the cylinder 11 in a short period of time, the molding material can be sufficiently plasticized. This shortens the time required for metering, and makes it possible to shorten the molding cycle.

After that, the mold device is opened to open the mold, and an ejection process is performed to remove the molded product from the mold device using an ejector device or the like.

REFERENCE SIGNS LIST 1 injection device 11 cylinder 11a supply port 12 screw 13 heater 14 tip portion 21, 121, 221 material preheating device 22, 23, 122, 123, 222, 223, 229, 230 fluidized bed heater 22a, 23a, 122a, 123a, 222a, 223a, 229a, 230a tip tube portion 22b, 23b, 122b, 123b, 222b, 223b, 229b, 230b tapered portion 22c, 23c, 122c, 123c, 222c, 223c, 229c, 230c cylindrical main body portion 22d, 23d, 122d, 123d, 222d, 223d, 229d, 230d Annular portion 22e, 23e, 122e, 123e, 222e, 223e, 229e, 230e Material inlet 22f, 23f, 28, 122f, 123f, 128a, 128b, 222f, 223f, 229f, 230f, 228a, 228b Hot air blocking member 24, 224a, 224b Serial connection passage 25a, 25b, 125a, 125b, 225a, 225b, 225c, 225d Breathable opening/closing member 26 Material supply passage 126, 226 Parallel supply passage 126a, 126b, 226a, 226b Branch passage portion 126c, 226c Junction passage portion 27, 127 Hot air generator 27a, 127a, 227a Hot air feed passage 27b, 127b, 227b Hot air return passage 127c, 227c Extended feed passage 127d, 127e, 227d, 227e Branch pipe passage portion 127f, 227f Main pipe passage portion 31 Metering motor 32 Motor support plate 33 Rotor 33a Bearing 34 Stator 35 Stator frame 36 Metering spline shaft 36a Key 37 Screw mounting portion 38 Pressure detector 39 Cylindrical portion 41 Injection motor 42 Motor support plate 43 Rotor 43a Bearing 43b Groove portion 44 Stator 45 Stator frame 45a Encoder 45b Shaft portion 46 Injection spline shaft 47 Screw nut 48 Screw shaft 49 Bearing 50 Rotating shaft 51 Rod 52 Rod 101 Slide base Mm Molding material

Claims (10)

A material preheating device that preheats a molding material and supplies the molding material to an injection device,
The apparatus is provided with a plurality of fluidized bed heaters that supply hot air to heat the molding material while forming it into a fluidized bed ,
A material preheating device which interconnects two of the plurality of fluidized bed heaters and is provided with a serial connection passage for conveying molding material from one of the fluidized bed heaters to the other fluidized bed heater . 2. The material preheating device according to claim 1, wherein, of the two fluidized bed heaters connected to each other by the serial connecting passage, at least the fluidized bed heater located upstream in the supply direction of the molding material to the injection device has a material inlet used for feeding the molding material to the fluidized bed heater. 3. The material preheating device according to claim 1, further comprising parallel supply passages for feeding and supplying molding material from at least two of the plurality of fluidized bed heaters to the injection device. A material preheating device that preheats a molding material and supplies the molding material to an injection device,
The apparatus is provided with a plurality of fluidized bed heaters that supply hot air to heat the molding material while forming it into a fluidized bed,
A material preheating device having parallel supply passages for feeding and supplying molding material from at least two of the plurality of fluidized bed heaters to the injection device. The parallel supply passages are
at least two branch passage portions each connected to one of the at least two fluidized bed heaters connected to the parallel supply passage;
5. The material preheating device according to claim 3, further comprising a confluence passage portion where the branch passage portion joins and leads to the injection device. The material preheating device according to any one of claims 3 to 5, wherein each of the at least two fluidized bed heaters connected to the parallel supply passages has a material inlet used for introducing a molding material into the fluidized bed heater. The material preheating device according to any one of claims 1 to 6, wherein each of the multiple fluidized bed heaters has an air permeable opening and closing member at the outlet of the molding material that passes the hot air and opens and closes to allow or stop the passage of the molding material at the outlet. A material preheating device that preheats a molding material and supplies the molding material to an injection device,
The apparatus is provided with a plurality of fluidized bed heaters that supply hot air to heat the molding material while forming it into a fluidized bed,
A material preheating device in which each of a plurality of fluidized bed heaters has an outlet for the molding material, the outlet having an air permeable opening and closing member which passes the hot air and opens and closes to allow or stop the passage of the molding material at the outlet. The material preheating device according to any one of claims 1 to 8 , further comprising a hot air generator for generating hot air to be supplied to the fluidized bed heater. An injection device that includes a cylinder for melting a molding material and injects the molding material molten in the cylinder into a mold device,
An injection device comprising the material pre-heating device according to any one of claims 1 to 9 .