JPH0214860B2 - - Google Patents

Description

[Detailed Description of the Invention] [Objective of the Invention] (Industrial Field of Application) The present invention relates to an automatic presser foot lifting device for a sewing machine, and is a method for controlling a solenoid in a sewing machine that sews extra-thick materials (for example, a stroke of 15 mm or more and a presser foot pressure of 15 kg or more). It is used in the presser foot lifting mechanism as an operating means.

(Prior Art) As a device of this type, a conventional technology disclosed in Japanese Utility Model Application Publication No. 40-39665 is known.

That is, as shown in FIG. 7, in a sewing machine equipped with a push-up bar 21 linked to a presser bar, the same operating shaft
A thrusting arm 23 that rotates around 2 and a pulling arm 24
The pull arm 24 is connected to an electromagnet device 26, and the lever 25 is provided with a knee switch 27 for controlling the electromagnet device 26.

(Problem to be solved by the invention) Conventionally, in this type of device using a general solenoid, the suction force is sufficiently higher than the presser pressure when the stroke is 6 mm or more, so there is no problem in presser operation, and the stroke When the pressure was less than 2 mm, there was a risk that the machine would not be able to operate because the suction force was lower than the pressure of the presser foot.

FIG. 5 is a diagram showing the relationship between the presser foot pressure of the sewing machine, W, and the suction force of the solenoid, T.

Conventionally, as a countermeasure to this problem, a large solenoid with a special high suction force was manufactured and used. Therefore,
It had many disadvantages, such as high cost, increased weight, and loss of compatibility with general models.

Also, for example, if the stroke is 6 mm or more,
It becomes a surplus suction power. Even taking this point into consideration, the state of use was inefficient.

The present invention aims to solve these problems mentioned above.

[Structure of the invention]

(Means for solving the problems) The means for solving the above problems in the present invention are as follows.

That is, an operating arm is slidably supported on the machine frame at one end, is operatively connected to the pressurizing device at the other end, and is formed with a cam surface; a connecting member that is pivotally supported in a swingable manner, one end of which is latched to the presser bar, and the other end of which faces the cam surface so as to be able to come into contact with the cam surface; and an adjustment member that partially corrects the inclination of the cam surface. It is.

(Operation) When the electromagnet is energized, the plunger is activated by the attraction force of the solenoid, causing the action arm to swing. This swinging of the working arm causes the contact point of the connecting member that contacts the cam surface to move, and the connecting member rotates in a take-up type on the shaft support while changing the lever ratio, and the other end that connects to the presser bar side. The operation of the presser foot acts as a force for lifting the presser foot.

(Example) In Fig. 1, 1 is a sewing machine frame, 2 is a spring fixed to the machine frame 1, and 3 is a presser bar that is pressed by the spring 2 and is slidable in the axial direction, and the presser bar is approximately It has an arm portion 3a protruding near the center at right angles to the axis, and a presser foot 4 is fixed to the lower end.

Reference numeral 5 denotes a linking member attached to the machine frame 1 with the base point 5a approximately at the center, one end of which is engaged with the lower surface of the arm 3a of the presser bar 3, and the other end of which is attached to the machine frame with one end fulcrum 6a. 1 and is engaged with a cam surface 6a formed near the other end of the rotatable working arm 6. Reference numeral 7 denotes an electromagnet fixed to the machine frame 1, and its plunger 7a abuts against the end of the working arm 6.

When the electromagnet 7 is energized, the plunger 7a moves downward, rotates the working arm 6 clockwise as seen in the figure, and the cam surface 6b of the working arm 6 causes the linking member 5 to move backwards around the fulcrum 5a. Rotate clockwise. Therefore, the end pushes the arm 3a of the presser bar 3 upward against the spring 2. Further, an adjusting member 28 is fixed to the end of the working arm 6 with a screw 29 so as to be adjustable from a position sunk below the cam surface 6b to a position protruding from the cam surface 6b.
contacts the connecting member 5 and increases the amount of lift of the presser bar 5.

As the electromagnet 7 in this embodiment, other pressurizing devices such as an air cylinder can also be used.

FIG. 3 shows another embodiment.

In FIG. 3, the configurations of the members numbered 1 to 4 in the figure are the same as those in the previous embodiment, and detailed description thereof will be omitted. 8 and 9 are rotatable L-shaped links whose respective fulcrums 8a and 9a are supported by the machine frame 1, and 10 is a rod connecting these links 8 and 9.

Reference numeral 11 denotes a push-up rod that is loosely fitted into the machine frame 1 so as to be movable upward, and 12 has a dish-shaped recess 12a at its upper end. This is a push-up rod whose portion 12b is loosely fitted into the machine frame 1 so as to be movable up and down. 13 is the fulcrum 13a
is an L-shaped link that is rotatably supported on the machine frame and has a dish-shaped recess 13b formed at one end thereof, and locks the lower end of the shaft of the push-up rod 12. Reference numeral 14 denotes an operating arm that has a cam surface 14a formed near its upper end and whose other end 14b is rotatably supported on the machine frame 1;
comes into contact with the arm portion 13b of the L-shaped link 13. 1
6 is a pressure device such as an electromagnet or an air cylinder, and a plunger portion 16a presses the end of the cam portion.

When the pressurizing device 16 acts, the working arm 14 becomes the fulcrum 1
The cam surface 1 is rotated counterclockwise around 4b.
4 presses the arm of the L-shaped link 13, and the fulcrum 13
Rotate clockwise around a. The dish-shaped recess 13b of the L-shaped link 13 includes the push-up rod 12, the push-up bar 11, the L-shaped link 9, the connecting rod 10, and the L-shaped link 13.
The presser bar 3 is pushed up against the pressure of the spring 2 via the letter-shaped link 8.

FIG. 4 shows another embodiment of the adjustment member.
The adjustment member 30 is fixed to the connecting member 5 so as to be adjustable with an inclined surface 30a facing the cam surface 6b, and the cam surface 6b and the connecting member 5 are in direct contact with each other at the position shown by the broken line, but at the position shown by the solid line. In this position, the cam surface 6b and the inclined surface 30a of the adjusting member 30 come into contact in the latter half of the action, so that the same effect as the structure shown in FIG. 2 is achieved.

〔Effect of the invention〕

With reference to FIGS. 1 to 5, the effects of the device of the present invention, including its operation, will be explained in relation to it.
That is, W: Pressure of the presser spring T: Attractive force of the electromagnet W': Force lifting the presser foot A: Distance from the fulcrum of the lever to the point of action B: Distance from the fulcrum of the lever to the point of contact with the cam surface of the working arm C: Distance from the fulcrum of the working arm to the point of action of the plunger D: Distance from the fulcrum of the working arm to the point of contact with the lever on the cam surface, W'=T×B/A×C/D. Assuming that the lever ratio when the presser foot lift amount is "0" is A:B:C:D: 1:1:2:1 respectively.The lever ratio when the presser foot lift amount is "15mm" is A:B:
When C:D are respectively 2:1:1:1, W'(0)=2TW'(15)=T/2.

In this way, the acting force is doubled by adjusting the lever ratio to compensate for the lack of attractive force of the electromagnet in the early stages of action, and in the range where there is surplus suction force in the latter half of the action arm, the acting force is halved, but the amount of action is On the contrary, it doubles.

The above action solves the problems of the prior art all at once, and the load on each connecting member is reduced by halving the excessive suction force at the final stage of action.
In addition to the cost reduction effect due to the smaller size and weighting of parts,
It is also advantageous in reducing vibration and noise. Also,
By the action of the adjustment member, it is possible to adjust the lift amount of the presser foot to an arbitrary value depending on the type of cloth, the number of layers, etc.

In order to solve the drawbacks of the prior art, it is possible to arrange two small solenoids in series in the pressurizing device as shown in Fig. 6, but in this implementation, when using a large solenoid, However, there are similar difficulties in terms of cost, weight, space, etc.

Another possible solution is to use an air cylinder as a pressurizing device, but in this case, a compressor, solenoid valve, pressure regulating valve, etc. are required, resulting in cost, space, operability, and pressure problems. Further undesirable problems arise, such as an increase in the load on each member due to the increase in pressure.

The present invention can eliminate all of the above-mentioned drawbacks by simply adding to the sewing machine a lever mechanism having a cam surface and an arm opposing the cam surface at the connecting portion between the solenoid and the presser bar.

[Brief explanation of drawings]

1 and 2 are configuration explanatory diagrams of an embodiment of the automatic presser foot lifting device of the present invention, FIGS. 3 and 4 are explanatory diagrams of another embodiment, and FIG. 5 is a related explanation line of each element in the device of the present invention. 6 is a diagram illustrating another countermeasure,
FIG. 7 is an explanatory diagram of a conventional device. DESCRIPTION OF SYMBOLS 1... Sewing machine frame, 3... Presser bar, 4... Fabric presser foot, 5... Connecting member, 6... Working arm, 6b... Cam surface, 7... Electromagnet, 7a... Plunger, 2
8... Adjustment member.

Claims (1)

[Scope of Claims] 1. A machine frame, a presser bar that is slidably held on the machine frame, is pressurized in the axial direction by the bias of a spring, and has a cloth presser fixed to its lower end, and A sewing machine having a pressurizing device that is fixed to the presser bar and raises the presser bar against the bias of the spring, one end of which is slidably supported on the machine frame and the other end of which is connected to the pressurizing device. an operating arm that is operatively connected and has a cam surface formed thereon; and a working arm that is pivotably supported on the machine frame at the center, one end of which is latched to the presser bar, and the other end of which is capable of contacting the cam surface. and an adjusting member that partially corrects the inclination of the cam surface, and the working arm swings under the action of the pressurizing device to adjust the contact point between the cam surface and the connecting member. An automatic presser foot lifting device for a sewing machine, which is configured to move to change a lever ratio of the connecting member.