JPH02959B2 - - Google Patents

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Field of Application) The present invention relates to an automatic presser foot lifting device for a sewing machine, and is suitable for sewing machines that sew extremely thick materials (for example, a presser foot lifting amount of 15 mm or more and a presser foot pressure of 15 kg or more). Used in the presser foot lifting mechanism using a solenoid as the operating means.

(Prior Art) As a device of this type, the conventional art disclosed in Japanese Utility Model Application Publication No. 49-39665 is known.

That is, as shown in FIG. 5, in a sewing machine equipped with a push-up bar 21 linked to a presser bar, the
A thrusting arm 23 that rotates around 2 and a pulling arm 24
A lever 25 is provided, an electromagnet device 26 is linked to the pull arm 24, and a knee switch 27 for controlling the electromagnet device 26 is provided to the lever 25.

(Problems to be Solved by the Invention) Conventionally, in this type of device using a general solenoid, for example, when the presser foot lifting amount is 6 mm or more, the solenoid output is sufficiently high due to the presser foot pressure, so there is no problem in the presser foot lifting operation. When the presser foot lifts less than 2 mm, the solenoid output is low due to the presser foot pressure, so there is a risk of malfunction.

FIG. 3 shows a diagram of the relationship between the presser foot pressure of the sewing machine, W, and the solenoid output, T.

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

Further, for example, in a range where the presser foot lifting amount exceeds 6 mm, even a general small solenoid has an output that is surplus to the presser foot pressure. 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, one end is rotatably supported on the sewing machine frame as a linking member between the presser bar and the pressure device that raises the presser bar, and a cam surface is formed near the other end, and the back side of the cam surface is connected to the pressurizing device. a cantilever lever member connected to the pressing device so as to face the pressing device; and a cantilever lever member connected to the presser bar at one end to raise the presser rod, and the cam so that the vicinity of the other end faces the cam surface. a lever-shaped lever member that is linked to the surface and whose center portion is rotatably supported on the sewing machine frame; The output of the pressurizing device is controlled to increase or decrease as appropriate by changing the lever ratio by shifting the connecting contact point with the vicinity of the other end of the lever member.

(Operation) When the electromagnet is energized, the plunger is operated by the attraction force of the solenoid, and the cantilever lever member rotates. The lever-shaped lever member that contacts the cam surface at one end while shifting its linkage contact point rotates in a scale-like manner at its fulcrum, and the operation near the other end that is linked to the presser bar side 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, approximately in the center thereof. It has an arm part 3a protruding perpendicularly to the axis near the lower end, and a presser foot 4 is fixed to the lower end.

Reference numeral 5 denotes a lever-like lever member rotatably attached to the machine frame 1 with the base point 5a approximately at the center thereof, one end of which is locked to the lower surface of the arm portion 3a of the presser bar 3, and the vicinity of the other end is attached to one end fulcrum. 6a is rotatably attached to the machine frame 1, and has an operating upper surface 5b that engages with the cam surface 6b of a cantilever lever member having a protruding curved cam surface 6b formed near the other end. Reference numeral 7 denotes an electromagnet fixed to the machine frame 1, and its plunger 7a faces and abuts against the back side of the cam surface 6bo of the cantilever lever member 6.

When the electromagnet 7 is energized, the plunger 7a moves downward, causing the cantilever lever member 6 to rotate clockwise as seen in the figure, and the cam surface 6b of the cantilever lever member 6 moves the point of action while moving the balance. shaped lever member 5
is rotated counterclockwise around the fulcrum 5a. Therefore, the end pushes the foot 3a of the presser bar 3 upward against the spring 2.

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

FIG. 2 shows another embodiment.

In the figure, the configurations of each member numbered 1 to 4 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 that connects these links 8 and 9.

Reference numeral 11 denotes a presser foot lifting rod which is loosely fitted into the machine frame 1 so as to be movable in the vertical direction, and 12 has a dish-shaped recess 12a formed at its upper end. This is a push-up rod whose shaft portion 12b is loosely fitted into the machine frame 1 so as to be movable up and down. 13 is the fulcrum 13
A is an L-shaped link (scale-shaped lever member) that is rotatably supported on the machine frame 1 and has a dish-shaped recess 1 at one end.
3b, and locks the lower end of the shaft of the push-up rod 12. Reference numeral 14 designates a cantilevered lever member having a cam surface 14a formed near its upper end and whose other end 14b is rotatably supported by the machine frame 1, and the cam surface 14a abuts against the arm portion 13c of the L-shaped link 13. . 16 is a pressure device such as an electromagnet or an air cylinder, and a plunger portion 16a presses the back side of the cam surface 14a.

When the pressure device 16 acts, the cantilever lever member 14
is rotated counterclockwise about the fulcrum 14b, and the cam surface 14a presses the arm portion 13c of the L-shaped link 13 while shifting its point of action, causing it to rotate clockwise about the fulcrum 13a. The dish-shaped recess 13b of the L-shaped link 13 pushes the presser bar 3 against the pressure of the spring 2 through the push-up rod 12, the push-up bar 11, the L-shaped link 9, the connecting rod 10, and the L-shaped link 8. Push up.

〔Effect of the invention〕

With reference to FIG. 1 and FIG. 3, the effects of the device of the present invention, including its operation, will be explained in relation to each other. That is, W: Pressure of the presser spring T: Output of the electromagnet W': Presser foot lifting force A: Distance from the fulcrum of the scale-shaped lever member to the point of action B: From the fulcrum of the scale-shaped lever member to the cam surface of the cantilever lever member C: Distance from the fulcrum of the cantilever lever member to the point of action of the plunger D: Distance from the fulcrum of the cantilever lever member to the contact point of the cam surface with the lever-shaped lever member, then W'=T× B/A×C/D.

If the presser foot lifting amount is “0”, the lever ratio is A:
B:C:D is 1:1:2:1 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)=2T W'(15)=T/2.

In this way, the acting force is doubled by adjusting the lever ratio to compensate for the lack of electromagnet output in the early stages of action, and in the latter half of action, in the range where there is surplus output power from the solenoid, the acting force is halved, but the amount of action is doubled. do.

The above action solves the problems of the conventional technology at once, and the excessive solenoid output at the final stage of action is halved, which reduces the load on each connecting member, resulting in a cost reduction effect due to the smaller size and lighter weight of the members. It is also advantageous in reducing vibration and noise.

In order to eliminate the drawbacks of the prior art, it is possible to arrange two small solenoids in series in the pressurizing device part as shown in Fig. 4, but in this implementation, a special large solenoid is used. There are similar difficulties in terms of case, 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 solves all of the above-mentioned drawbacks by simply adding to the sewing machine a cantilevered lever member that forms a cam surface at the connecting part of the presser bar of the solenoid, and a lever-like lever member whose other end faces the cam surface. can do.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram of the configuration of an embodiment of the automatic presser foot lifting device of the present invention, FIG. 2 is an explanatory diagram of another embodiment, FIG. A diagram illustrating a countermeasure, FIG. 5, is an explanatory diagram of a conventional device. 1... Sewing machine frame, 3... Presser bar, 4... Fabric presser foot, 5... Scale-shaped lever member, 6... Cantilever lever member, 6b... Cam surface, 7... Electromagnet, 7a... Plunger .

Claims (1)

[Claims] 1. A presser bar that is pressurized in the axial direction by the bias of a spring and fixes the presser foot at its lower end, and a pressurizing device that raises the presser bar against the bias of the spring. In the sewing machine, one end is rotatably supported on a sewing machine frame, a cam surface is formed near the other end, and the back side of the cam surface is connected to the pressure device so that it faces the pressure device. a holding lever member, one end of which is connected to the presser bar in order to raise the presser bar, the other end of which is connected to the cam surface so as to face the cam surface, and a central portion of which is rotatable to the sewing machine frame; and a lever-shaped lever member supported by the lever member, and by shifting a linking contact point between the cam surface of the cantilevered lever member and the vicinity of the other end of the lever-shaped lever member according to the amount of operation of the pressurizing device. An automatic presser foot lifting device for sewing machines that changes the lever ratio.