US3696770A - Thread cutting attachment for a sewing machine - Google Patents

Abstract

The invention comprises a thread cutter for a sewing machine. The cutter comprises a block of material having a plurality of sides, each side providing a different cutting edge. This permits the cutter to be moved to another edge when the first edge becomes dull. In accordance with the present invention the block of material is mounted in a weighted holder which is in turn mounted at the end of a piston rod slidable in and out of an air cylinder. A backing plate is provided against which the cutter is forced by the air cylinder with a sudden burst of air. The optimum angle at which the particular cutting edge meets the backing plate is an angle of 19*. At this angle the cutter operates virtually without a miss. Experiment has indicated that the cutter will operate at a variance of plus or minus four degrees with reasonable efficiency. The cutter is operated by a conventional type of tripping circuit in which a piece of cloth entering the machine trips a sensing device which causes the cutter to operate in front of and at the rear of the cloth to trim the threads.

Description

United States Patent Dunne et al.

[ 51 Oct. 10,1972

1541 THREAD CUTTING ATTACHMENT FOR A SEWING MACHINE [72] Inventors: Owen F. Dunne, Tiverton; William E. Hebert, Portsmouth, both of R.I.;

Ronald Souza, North Westport; Ed-

. ward Wargat, Fall River, both of Mass.

[73] Assignee: Zalking Sewing Machine 8:. Supply Co., Fall River, Mass.

[22] Filed: July 24, 1969 211 Appl. No.: 844,451

[52] US. Cl ..112/252 [51] Int. Cl. ..D05b 65/00 [58] Field of Search ..112/252, 122, 129, 130; 83/697, 662, 694; 30/329, 334, 354, 169, 275

[56] References Cited UNITED STATES PATENTS 2,593,144 4/1952 l-lercik ..83/694 3,094,031 6/1963 Reeber et a1 ..112/252 X 3,250,237 5/1966 Myska. ..112/252 1,663,092 3/1928 Parys ..83/694 2,213,071 8/1940 Keller ..30/169 3,430,592 3/1969 Florczak ..112/252 Primary Examiner-James R. Boler Attorney-Cushman, Darby & Cushman ABSTRACT The invention comprises a thread cutter for a sewing machine. The cutter comprises a block of material having a plurality of sides, each side providing a different cutting edge. This permits the cutter to be moved to another edge when the first edge becomes dull. In accordance with the present invention the block of material is mounted in a weighted holder which is in turn mounted at the end of a piston rod slidable in and out of an air cylinder. A backing plate is provided against which the cutter is forced by the air cylinder with a sudden burst of air. The optimum angle at which the particular cutting edge meets the backing plate is an angle of 19. At this angle the cutter operates virtually without a miss. Experiment has indicated that the cutter will operate at a variance of plus or minus four degrees with reasonable efficiency. The cutter is operated by a conventional type of tripping circuit in which a piece of cloth entering the machine trips a sensing device which causes the cutter to operate in front of and at the rear of the cloth to trim the threads.

2 Claims, 6 Drawing Figures PKTENTED "B 10 I973 3.6 96 7 TO SHEET 1 OF 2 COMPRESSED AIR PRESSURE AIR FILTER REeu ATOR -fi 2 42 40 4/ PISTON 0 OT ENQI'ITROA-AIIEE L H SENSOR SENSOR AMPLIFIER VARIABLE 44 TIME DELAY MAKE 45 SOMS ELEgRI'RIC SEIIDECAI'ER PULSE SOLENOID PISTON3 vALvE 47 CLOTH ExIT VARIABLE TIME DELAY MAKE INVENTORS OWEN F. DUNNE WILLIAM E. HEBERT ESI'IIQRB vr F I G. 6 BY ATTORNEYS THREAD CUTTING ATTACHMENT FOR A SEWING MACHINE Our present invention relates to sewing machines and more particularly to a novel construction of a cutter attachment for a sewing machine.

The principal object of the present invention is to provide a cutting attachment for trimming threads hanging from work passing through the sewing machine both in front of and at the rear of the work.

Another object of the present invention is to provide a cutter which will operate witha maximum efficiency and practically no misses.

A further object of the present invention is to provide a cutting attachment in which the cutting element has a long life.

Another object of the present invention is to provide a cutting attachment in which the cutting element is provided with a plurality of cutting edges which are interchangeable as each wears out.

A further object of the present invention is to provide a cutting attachment for cutting thread on a sewing machine which is simple in construction and easy and economical to manufacture and assemble.

With the above and other objects and advantageous features in view our invention consists of a novel arrangement of parts more fully disclosed in the detailed description following in conjunction with the accompanying drawings and more particularly defined in the appended claims.

In the drawings,

FIG. 1 is a perspective view of a cutting attachment of the present invention mounted on a sewing machine head.

FIG. 2 is a side elevation thereof.

FIG. 3 is a view similar to FIG. 1 showing an alternate mounting of the device.

FIG. 4 is a side elevation of the mounting shown in FIG. 3.

,FIG. 5 is an exploded perspective view of the cutting element and its holder.

FIG. 6 is a block diagram of the hookup for operating the cutter of the present invention.

It has become desirable to provide certain types of sewing machines with thread cutting attachments. Certain machines, such as lock-stitch machines, over-lock machines, etc. use a considerable amount of thread. When the operator, frequently on piece work, feeds successive pieces of cloth through the machine the operator normally allows the thread to run between pieces so that the pieces of cloth are connected by chains of stitches which must be cut by hand. Accordingly cutting devices have been provided which automatically trim the cloth as it passes through the needle. A sensing device is provided of various forms which is tripped by the cloth. The cutter then cuts the thread in front of the cloth and at the rear of the cloth to provide a complete trimming action. Various types of cutters have been provided for this purpose. Scissor type cutters have been popular and are the only ones that can be used in certain applications. The present invention is directed towards a chopping or guillotine type cutter.

Referring more in detail to the drawings illustrating our invention FIGS. 1, 2 and 5, show the chopping type cutter mounted on a sewing machine. Since the machines may vary in the type and manufacture, the

machine 10 illustrated in FIGS. 1 and 2 is merely representative of any type of sewing machine. Mounted at the end of the machine 10 is a holding plate 11 on which is mounted an elongated bracket 12 which extends forwardly of the machine 10 at a slight downward angle. The bracket 12 is provided with an integral supporting slip 13 extending horizontally at right angles to the bracket as shown in FIG. 1. Note that in view of the downward angle of the bracket 12, the surface of the supporting strip 13 is also at an angle from the horizontal. Mounted on the supporting strip 13 is an air cylinder 14 of conventional type from which the piston rod 15 extends downwardly.

The cutter comprises a block 16 illustrated as a square block with eight separate and distinct cutting edges 17. The block is shown for illustrative purposes but other blocks with more or less cutting edges may also be used. The block 16 is mounted in a holder 18 of comparative thickness and weight in the form of a rectangular block tapering downwardly at 19 to a central axial slot 20 into which the cutter 16 fits snugly. A pair of set screws 21 enters transversely into the tapered portions 19 from each side to lock the cutter l6 firmly in place. The holder 18 is provided with a threaded opening 22 in the upper end for mounting on the piston rod 15 as shown in FIGS. 1 and 2.

The sewing machine 10 is provided with the plate 23 on which the presser foot 24 is operable in the conventional manner. Mounted behind the plate23 we now provide a generally rectangular plate 25 having a rectangular cutout portion 26 from the rear edge inwardly and positioned slightly to one side. The large part of the plate, to the right in FIG. 1, is provided with the mounting screws 27 for locking the plate 25 to the machine. The rear edge of the cutout portion 26 is pro vided with a tapered portion 28 providing a flat surface extending downwardly from the top edge of the plate 25 towards the bottom. The cut thread is normally picked off at this point'by any desired device, and conventionally, by a suction device.

As can be seen in FIGS. 1 and 2, downward movement of the piston rod 15 will force the cutter 16 against the plate 25 so that the bottom edge of the cutter hits the top of the plate at an angle 29. For best results this angle should be 19. Applicants have found that at an angle of 19 the cutting action will be virtually without error. However, the device will operate efficiently within a range of plus or minus four degrees. It should be noted that in the operation of the device, compressed air is lead into the cylinder 14, suddenly and the result is that the piston rod 15 will slam the cutter 16 against the plate 25 with great force. Since the cutting distance or movement of the cutter is comparatively small the bulk of the holder 18, with the weight provided thereby, adds considerably to the efficiency of the cutter.

In some installations, it becomes impossible to mount the cutter close enough to the machine, in the manner shown in FIGS. 1 and 2, to keep the cutter at an angle of l9. In such cases the cutter can be mounted as shown in FIGS. 3 and 4. In this form the sewing machine 30 is again provided with the end plate 31 and the bracket 32 is identical to the bracket 12 in FIG. 1. However it should be noted that the bracket 32 is now mounted at a sharp downward angle which extends the cylinder 33 and piston rod 34 at a much greater angle. However at this'angle' the piston rod can move the holder 35 and its accompanying cutter 35 into the same spot under the sewing machine head. This is essential since the cutting action must take place as close to the presser foot as possible. However, in this form the plate 37 is mounted so that the cutting head 36 strikes the tapered surface 38 instead .of the top flat portion of the plate. By tapering the surface 38 at the proper angle, the angle between the cutting edge of the cutter 36 and thetapered portion38 will be l9 at 39. Thus, in this form the cutter strikes the tapered surface such as the surface 28 shown in FIG. 1 instead of the top of the plate to maintain the desired angle of 19 or thereabouts. 1

Operation of this type of cutter is generally provided by the general hookup shown in block diagram in FIG. 6. A source of compressed air 40 is piped through an air filter 41 and pressure regulator 42 to the oiler 43 and the electric air solenoid valve 44. It is the operation of this valve which allows the compressed air to pass into thecylinder l4 and its associated piston. The solenoid on the other hand is operated by a cloth sensor 45 connected to a source of power 46 and through a delay selector 47, which is used to regulate the closeness of the cutter to the cloth, to the entrance and exit'time delay devices 48 and the final pulse 49 to operate the solenoid valve 44.

Since cutters have been used on sewing machines, various circuits have-been provided for sensing and operating a cutting device. The device illustrated in FlG.6 is merely illustrative and any type of circuit may be providedThe device of the present invention therefore provides a guillotine type cutter in which the cutting element is provided with a multiplicity of edges. As one of the cutting edges become dull, it is merely necessary to loosen the set screws 21 and turn the cutter .to a new edge. Furthermore, applicants have found that the weighted holder 18 and the angle of 19 provides avmost efficient cutter with practically no misses. The mounting on a sewing machine with the tapered portion of the plate permits the maintenance of the 19 angle in different types of machines. Furthermore, applicantshave found that the angle of 19 and the type of cutter illustrated herein have one other great advantage. As the cutter is used a small burr is advantages of the present invention will be readily apparent to a person skilled in the art.

We claim:

1. A cutting attachment in combination with a sewing machine comprising a sewing machine having a head and a workplate, a supporting plate mounted at the end of said sewing machine head, a supporting bracket mounted on said plate and extending rear wardly of said head an air cylinder mounted on said bracket, a piston rod extending downwardly from said cylinder, a thread cutter having a cutting surface, means mounting said thread cutter at the end of said piston rod, a base plate mounted on the sewing machine adjacent the back edge of said sewing machine workplate having a rectangular cut out portion, the back edge of said cut out having a tapered surface, said cutter striking said tapered surface at an angle of 19 between said tapered surface and said cutting surface of said thread cutter, and means for activating said cylinder and piston rod to strike said cutter against said base plate on movement of a piece of work through said sewing machine.

2. A cutting attachment as in claim 1, wherein said cutter comprises a block having a plurality of cutting edges.

Claims (2)

1. A cutting attachment in combination with a sewing machine comprising a sewing machine having a head and a workplate, a supporting plate mounted at the end of said sewing machine head, a supporting bracket mounted on said plate and extending rearwardly of said head, an air cylinder mounted on said bracket, a piston rod extending downwardly from said cylinder, a thread cutter having a cutting surface, means mounting said thread cutter at the end of said piston rod, a base plate mounted on the sewing machinE adjacent the back edge of said sewing machine workplate having a rectangular cut out portion, the back edge of said cut out having a tapered surface, said cutter striking said tapered surface at an angle of 19* between said tapered surface and said cutting surface of said thread cutter, and means for activating said cylinder and piston rod to strike said cutter against said base plate on movement of a piece of work through said sewing machine.

2. A cutting attachment as in claim 1, wherein said cutter comprises a block having a plurality of cutting edges.

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