JPH0640917B2 - Sewing machine presser foot lifter - Google Patents

Description

Detailed Description of the Invention Technical Field: The present invention relates to a presser foot lifting device for a sewing machine, and more specifically to a presser foot lifting device for a sewing machine that can lift the presser foot, which presses down on a sewing object such as fabric against a needle plate, to any desired height with a small force.

BACKGROUND ART In the prior art, in this type of presser foot lifting device for sewing machines, as shown in Fig. 1, the presser foot 3, which is pressed against the needle plate 2 by the presser spring 1 made of a compression spring, is raised to a predetermined height by the solenoid 4 against the force of the presser spring. That is, in Fig. 1, when the knee actuating switch 6 embedded in the knee rest member 5 is switched on by the operator's knee, the solenoid 4 is excited and the knee lifting lever 7 is activated.
As shown by the arrow, the presser foot 3 rotates counterclockwise, lifting the presser rod 9, which is slidably mounted in the oil reservoir 8. When the presser rod rises, the rod 10 rises and rotates the lever 11 clockwise, as shown by the arrow, and the connecting rod 12 moves to the right, as shown by the arrow, and rotates the lever 13 clockwise. This clockwise rotation of the lever 13 pulls up the locking rod 15 fixed to the presser bar 14 attached to the lower end of the presser foot 3, lifting the presser bar against the force of the presser spring 1, and thus the presser foot is moved above the needle plate 2.

However, in such conventional presser foot lifting devices, the presser foot is raised by a solenoid, allowing the operator to raise it with little operating force, but the presser foot can only be positioned at two positions: the lowest position where it contacts the needle plate 2, and the highest position above the needle plate. This means that the presser foot cannot be raised slightly above the needle plate or to any height that is convenient for the operator. On the other hand, a technology for reducing the pressure of the presser spring when the presser foot is raised using a fluid pressure valve and a fluid cylinder is disclosed in Japanese Utility Model Publication No. 12605/1970. However, in such conventional technology, the pressure of the presser spring is controlled by a fluid, particularly air, which results in poor control response and unstable control.

DISCLOSURE OF THE INVENTION An object of the present invention is to provide a presser foot lifting device for a sewing machine which overcomes the drawbacks of the prior art as described above. That is, the present invention aims to raise the presser foot to any desired height with a small force.

To achieve this object, the presser foot lifting device of the present invention for a sewing machine includes a pressure relief mechanism that relieves the spring force of the spring means that urges the presser foot toward the needle plate, a presser foot drive mechanism that lifts the presser foot, and an operating mechanism operated by an operator. The pressure relief mechanism is operated by operating the operating mechanism to relieve the spring force of the spring means that urges the presser foot, and the presser foot drive mechanism is operated by operating the operating mechanism to drive the presser foot to a desired height position after the spring force has been relieved.

According to the presser foot lifting device of the present invention, the presser foot can be lifted with little force, which greatly reduces the fatigue of the operator, and since the presser foot can be lifted to any height, it can be used for sewing materials of various thicknesses, thereby achieving the effect of extremely good work efficiency.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a partial cross-sectional view of a presser foot lifting device for a conventional sewing machine;
FIG. 2 is a partial cross-sectional view showing one embodiment of a presser foot lifting device for a sewing machine according to the present invention, and FIGS. 3 and 4 are partial cross-sectional views of the presser foot portion showing other embodiments of the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION Preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

First, referring to FIG. 2, there is shown an embodiment of a presser foot lifting device for a sewing machine according to the present invention.
The presser foot includes a pressure reducing mechanism 200 that reduces the spring force of a spring means 102 that urges the presser foot 100 toward the needle plate 101, a presser foot drive mechanism 300 that lifts the presser foot 100, and an operating mechanism 400 that is operated by the operator.

The presser foot 100 is pivotally attached to the lower end of a presser bar 102. This presser bar is supported so as to be able to slide up and down in a bearing 104 fixed to a frame 103 of the sewing machine. A spring means 102 is disposed at the upper end of the presser bar, and the presser foot 100 is constantly pressed against the upper surface of a needle plate 101 with an appropriate force by this spring means. An item to be sewn (not shown) is held between the needle plate and the presser foot. In the embodiment shown in FIG. 2, the spring means 102 is a presser bar spring 102.
The pressure spring 105 is arranged around the guide rod 107, and the auxiliary spring 106 is arranged in a recess 108 provided at the upper end of the pressure rod 102. The upper end 107a of the guide rod is connected to an adjusting screw member 107 screwed into the frame 103.
The lower end 107b of the guide rod is inserted into and held in a recess 109a provided at the lower end of the presser rod 109, and the lower end 107b of the guide rod is held in a recess 108 of the presser rod 109.
The pressure spring 105 contacts the upper end surface of the pressure bar 102 and is disposed between the upper end 107a of the guide bar 107 and an annular plate 110 loosely fitted on the guide bar.

The pressure spring 105 and the auxiliary spring 106 each have an appropriate spring force, but the spring force of the pressure spring is set to be greater than the spring force of the auxiliary spring.

The pressure relief mechanism 200 comprises a drive means 201 and a link assembly 202 connected to the drive means to prevent the spring force of the pressure spring 105 from acting on the pressure bar 102. In the embodiment shown in Fig. 2, the drive means comprises a rotary solenoid with a drive shaft 203 that rotates. The drive means is connected to a main body 204.
is fixed to the frame 103.
The spring lifting rod 206 comprises a channel member 205 slidably attached to the presser bar, a spring lifting rod 206 engaged with the channel member and attached to the frame 103 so as to be movable up and down, a bell crank 207 connected to the spring lifting rod, and a connecting rod 208 connecting the bell crank to the drive shaft 203 of the solenoid. The channel member 205 has an upper arm 205a loosely fitted to the presser bar 102 and a lower arm 205b loosely fitted to the outer periphery of the bearing 104. The spring lifting rod 206 has a slot 209 extending in the vertical direction and an arm 210 extending in a substantially horizontal direction. A screw is inserted into the slot 209.
211 is inserted into the guide 210, and this screw is screwed into and fixed to the frame 103. Therefore, the spring lifting rod can move up and down along this slot. The tip of the guide 210 is located close to the underside of the upper arm 205a of the channel-shaped member 205. The bell crank 207 is rotatably attached to the frame 103 at its center by a screw 212. One arm 207a of the bell crank is pivotally attached to the upper end of the spring lifting rod 206, and one end of a connecting rod 208 is pivotally attached to the other arm 207b. The other end of this connecting rod is pivotally attached to the tip of the drive shaft 203.

In the illustrated embodiment, the presser foot drive mechanism 300 is composed of a link assembly. That is, the presser foot drive mechanism 300 includes a horizontal rod 301 fixed to the presser bar 102 and a presser bar lifting rod 302 which engages with the horizontal rod and is movable up and down.
2 and a first bell crank 3 connected to the presser bar lifting rod.
303, a second bell crank 304, a pressure rod 306 slidably provided on an oil pan 305, the first bell crank 303, and the second
The first connecting rod 307 and the second connecting rod 308 connect the bell crank 304 to each other.
The second lever 304 is interposed between the bell crank 304 and the pressure rod 306.
The presser bar lifting rod 302 is made up of a slot 309 extending vertically and an arm 310 extending horizontally.
The presser bar lifting rod is attached by the screw 211 that also attaches the spring lifting rod 206.
11 is inserted into the slot 309 of the presser bar lifting rod and the slot 209 of the spring lifting rod 206 and screwed into the frame. The arm 310 is disposed close to the underside of the horizontal rod 301.
The bell crank 303 is rotatably attached to the frame 103 by the screw 212 that attaches the bell crank 207 at its center, and the tip of one arm 303a is connected to the presser bar lifting rod 302.
The other arm 303b is pivotally attached to the upper end of the first connecting rod 30
The second bell crank 304 is pivotally attached to one end of the first connecting rod 307. The second bell crank 304 has its center rotatably attached to the frame by a screw 311 threaded into the frame 103. One arm 304a of the second bell crank is connected to the other end of the first connecting rod 307, and the other arm 304b is connected to the other end of the second connecting rod 308.
The other end of this second connecting rod is in contact with the head portion 306a of the pressing rod 306. This pressing rod 306 has a protruding rod 306b extending downward.

The operating mechanism 400 can be operated with the operator's knee. This operating mechanism includes an operating lever 401 that operates the presser foot drive mechanism 300 and a switch means 402 that operates the pressure relief mechanism 200. The operating lever 401 is generally L-shaped, and its center is rotatably attached to a bracket 404 by a screw 403. This bracket protrudes from the underside of the oil pan 305. The operating lever 401 is normally biased clockwise as viewed in FIG. 2 by a coil spring 405. One arm 401a of the operating lever is provided with a knee support member 406, and the other arm 401b is in contact with the protruding rod 306b of the presser rod 306. The switch means 402, which may be a limit switch, activates or deactivates the solenoid 204. This limit switch is fixed onto a protruding rod 407 extending from operating lever 401, and its movable contact piece 402a is constantly in contact with the underside of oil pan 305 by means of coil spring 405, thereby putting solenoid 204 into a non-operating state. When operating lever 401 is rotated counterclockwise against coil spring 405, this limit switch separates from the underside of the oil pan, putting solenoid 204 into an operating state. Note that a proximity switch, photo sensor, or other switch may be used instead of the limit switch.

The operation of the above device is as follows.

When the operator places his knee on the knee rest member 406 and pushes the knee rest member slightly, the operating lever 401 rotates slightly counterclockwise against the coil spring 405, and the limit switch 402
The movable contact piece 402a also rotates counterclockwise to
Then, the solenoid 201 is excited and its drive shaft 203 rotates clockwise as shown by the arrow, and the connecting rod 2
08 to the right and rotate the bell crank 207 clockwise.
The arm 210 moves upward and the upper arm 2
05a to move the channel member 205 upward, and the annular plate 110
102. The annular plate 110 is then lifted upward against the elastic force of the pressure spring 105 via the annular plate 110, causing the pressure spring to contract. As a result, the annular plate 110 is separated from the upper end of the pressure bar 102, and the elastic force of the pressure spring no longer acts on the pressure bar. As a result, only the force of the auxiliary spring 106 acts on the pressure bar.

Further, when operating lever 401 is rotated counterclockwise, presser bar 306 moves upward, moving second connecting bar 308 upward. This causes second bell crank 304 to rotate clockwise, moving first connecting bar 307 to the right and rotating first bell crank 303 clockwise. This rotation of the first bell crank moves presser bar lifting rod 302 upward, and its arm 310 engages with cross rod 301, pulling it upward. Consequently, presser bar 102, and therefore the presser foot, moves upward against the spring force of auxiliary spring 106.

The presser bar rises only against the relatively weak spring force of the auxiliary spring, and the elastic force of the presser bar spring is not applied to the presser bar at all, so that the presser foot can be raised from the throat plate with a relatively small operating force of the knee, and the presser foot can be raised and maintained at any height position.

Referring to FIG. 3, there is shown another embodiment of the present invention, in which a rotary solenoid, which is the driving means of the pressure reducing mechanism 200, is replaced by a reciprocating solenoid.
500 is used. In this embodiment, the spring means comprises an auxiliary spring 502 stretched between a recess 501 provided at the upper end of the presser bar and the inner wall of the frame 103, and a pressure spring 503 stronger than the auxiliary spring, positioned outside the auxiliary spring and stretched between the upper end of the presser bar and the frame. A cylinder 504 of the solenoid 500 is attached to the frame near the spring means. A substantially L-shaped member 506 is attached to the tip of a piston rod 505 of the solenoid, and one arm 506a of this member faces the lower end of the pressure spring 503.

In this embodiment, similar to the above embodiment, the knee pad member 406
When the operating lever 401 is rotated counterclockwise by pressing the solenoid 500, the solenoid 500 is excited and the piston rod 505 moves upward, thereby lifting the lower end of the pressure spring 503 via the L-shaped member 506, so that the pressure spring no longer acts on the presser bar 102. The presser foot drive mechanism then operates in the same manner as in the above-described embodiment.

Referring to FIG. 4, yet another embodiment of the present invention is shown.

In this embodiment, instead of the spring means being made up of two springs, a pressure spring and an auxiliary spring, it is made up of a single pressure spring 600. Also, a reciprocating solenoid 601 is used as the driving means for the pressure reducing mechanism. This solenoid has its cylinder 602 fixed to the outer wall of the frame 103,
A piston rod 603 penetrates the outer wall of the frame and extends into the frame, and at its tip is provided a spring holder 604. A pressure bar spring 600 is stretched between this spring holder 604 and the upper end of the pressure bar 102.

When the operating mechanism 400 is not operated, i.e., when the limit switch 4
When limit switch 402 is in contact with the underside of oil pan 305, solenoid 601 extends its piston rod 603 and holds pressure spring 600 as shown in FIG. 4. Therefore, the elastic force of the pressure spring presses presser foot 100 against throat plate 101. As in the above-described embodiment, when operating mechanism 400 is operated, limit switch 402 moves away from the underside of the oil pan, solenoid 601 is excited, and piston rod 603 moves upward, restoring the pressure spring by a predetermined amount and weakening its elastic force. Therefore, the urging force of presser foot 100 against throat plate 101 is weakened.

When the presser foot drive mechanism 300 is driven in this state, the presser foot can be raised to any desired height with a weak force.

The solenoid in the above embodiment may be replaced with an air cylinder or the like, and the operating lever may be foot operated.

As described above, it is clear that the present invention can achieve the above-mentioned objects.

According to the present invention, a pressure is always applied to the presser foot, and when it is desired to raise the presser foot, the pressure can be reduced by the pressure reduction mechanism, which has the advantages of significantly reducing the fatigue of the operator when raising the presser foot and allowing the presser foot to be maintained at any desired height to accommodate fabrics of various thicknesses. Furthermore, according to the present invention, the pressure of the presser spring is controlled by an auxiliary spring and a drive means for the presser spring, eliminating the drawbacks of the prior art disclosed in Japanese Utility Model Publication No. 12605/1970, namely, poor control response and instability, and realizing rapid control response and stable control. Furthermore, even after the pressure of the presser spring is reduced, the presser foot continues to press down on the fabric by the auxiliary spring, preventing unintended movement of the fabric. Another practical advantage is that the mechanism is simpler than conventional systems using a fluid system.

Claims (3)

[Claims] [Claim 1] A sewing machine comprising: a presser foot that is movable between a lowered position where it presses down on an object to be sewn and an elevated position where it is separated from the object to be sewn; spring means that urges the presser foot to press down on the object to be sewn at the lowered position; a pressure relief mechanism that relieves the spring force of the spring means; a presser foot drive mechanism that can be operated to raise the presser foot to the elevated position; and an operating mechanism that can operate the presser foot drive mechanism, wherein the spring means includes an auxiliary spring and a presser spring that urge the presser foot toward the object to be sewn; a pressure reducing mechanism for reducing the spring force of the spring means so that only the auxiliary spring acts on the presser foot by driving the presser spring so that the spring force of the presser spring does not act on the presser foot; and the presser foot drive mechanism is operated by operating the operating mechanism to move the presser foot to the raised position against the auxiliary spring after the spring force of the presser spring no longer acts on the presser foot. [Claim 2] The device of claim 1, wherein the pressure relief mechanism comprises a drive means and a link assembly connected to the drive means and engageable with the pressure spring, and the drive means operates the pressure spring via the link assembly so that the spring force of the pressure spring does not act on the presser foot. 3. Claim 1, wherein the drive means comprises a solenoid, the presser foot drive mechanism comprises a link assembly engageable with a presser bar extending from the presser foot, the operating mechanism comprises an operating lever operable by the knee of an operator and a switch means attached to the operating lever for controlling the activation and deactivation of the solenoid, and when the operating lever is operated, the switch means activates the solenoid and the presser bar, i.e., the presser foot, is raised via the link assembly.
Item 1 or 2.