US2707927A - Thread cutting device for sewing machines - Google Patents

Description

May 10, 1955 w. w. ARTZT El AL THREAD CUTTING DEVICE FOR SEWING MACHINES 4 Sheets-$heet 1 Filed May 25, 1954 INVENTORIS. Sill/L fleaek By z mrym w. w. ARTZT El AL THREAD CUTTING DEVICE FOR SEWING MACHINES May 10, 1955 2 a u u 4 m w 2 p w e q u o 4 l T I 2 u 0 l IIII 1 mm w r WM! iHhLPL I .1 u w m 0 FF. J. J K 0 W U W l IIIIIIIII Filed May 25,

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THREAD CUTTING DEVICE FOR SEWING MACHINES 4 Shee ts-Sheet 3 Filed May 25,

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THREAD CUTTING DEVICE FOR SEWING MACHINES Filed May 25, 1854 4 Sheets-Sheet 4 7 9o 7; 32 V86 1 I V I --7a .92 70 Q} I HI I l I I l I T I02 a Q 657 6'4- 'INVENTORS.

WI Luau M RRTZT 4 SM!!- R R United States Patent THREAD CUTTING DEVICE FOR SEWING MACHINES William Walter Artzt, New York, N. Y., and Saul 'Rieger, Allentown, Pa., assignors to Trimless, Inc, New York, N. Y., a corporation of New York Application May 25, 1954, Serial No. 432,136

11 Claims. (Cl. 112-252) The present invention relates generally to sewing machines and is particularly directed to a device associated with a sewing machine for cutting or trimming the thread at the conclusion of a sewing operation.

At the conclusion of a sewing operation performed on a conventional single needle sewing machine, the needle is moved to its uppermost position and the presser foot is raised to free the sewn fabric, whereupon the sewn fabric is drawn from the machine and the upper and lower threads are cut or broken leaving lengths of such threads extending from the sewn fabric which are later removed by a separate trimming operation. Such a separate trimming operation is objectionable in that it results in seconds" by reason of accidental cutting of the fabric during trimming of the thread ends, and is uneconomical, by reason of the labor costs involved in the separate trimming operation and the waste of thread represented by the trimmed-off lengths of thread.

Accordingly, it is an object of the present invention to provide a device for association with a sewing machine which simultaneously cuts or trims the upper and lower threads at the conclusion of a sewing operation, thereby to avoid the necessity for a separate trimming operation and the waste of thread and possibility of damage to the fabric inherent in such a separate operation.

Another object is to provide a device of the described character for association with a sewing machine and including a thread cutter and thread holder embodied in a presser foot to respectively cut and hold the upper thread and simultaneously operated lower thread cutter which cuts and holds the thread drawn from the bobbin.

Another object is to provide a device of the described character, wherein the upper and lower thread cutting and holding members are actuated by electrical solenoids, and the energization of such solenoids is controlled so that operation of the members actuated thereby can occur only when the needle is raised and the presser foot is lowered for preventing damage to either the needle or the thread cutting and holding members.

Another object is to provide a solenoid actuated device of the described character, wherein the electrical circuit for energizing the solenoids includes a control switch which is manually manipulated through a movable member disposed adjacent the hand Wheel of the sewing machine and movable to a control switch closing position only when the hand wheel is in the rotational position thereof corresponding to maximum lift of the needle.

Still another object is to provide a device of the tie scribed character, wherein, during operation of the upper and lower thread cutting members, the tension on the upper thread is automatically released and a suitable length of the lower thread is pulled from the lower bobbin thereby to provide suflicient slack in the upper and lower threads when sewing operation of the machine is again commenced.

A further object of the invention is to provide a presser foot having thread cutting and holding means embodied therein and which is constructed and arranged to accommodate thread of different counts without requiring ad justment and to permit replacement of the bottom plate alone to adapt the presser foot to the conditions requiring a flat foot, compensating foot and the like.

In accordance with an aspect of the present invention, a sewing machine is provided with a presser foot assembly including a rockable body having a bottom plate loosely mounted thereon for floating movement relative to the body and thread holding and cutting blades swingable laterally between the body and bottom plate and resiliently urged in the direction toward the body to first grip the upper thread between the holding blade and confronting surface of the body and then to shear or cut the thread between the cutting blade and upper surface f the bottom plate, the floating movement of the bottom plate and the resilient urging of the blades making it possible to accommodate threads of different counts without requiring adjustment of the presser foot.

In accordance with another feature of the invention, the holding and cutting blades of the aforementioned presser foot assembly are actuated by a related solenoid through a mechanical linkage which includes a lever riding against a cam for controlling separation of the usual thread tension discs whereby actuation of the blades is accompanied by separation of the tension discs to release the tension.

Still another feature of the invention resides in the provision of a lower thread cutting assembly which includes a cutting blade swingable below the usual removable plate which covers the bobbin and has an opening through which the lower thread extends so that the latter is cut or sheared between a cutting edge of the blade and the lower surface of the plate. Further, a resilient thread holding strip is secured to the removable plate and the blade, in cutting the thread, moves between the holding strip and the plate so that the thread is gripped and held between the blade and the resilient holding strip.

A further feature resides in the provision of a lower thread cutting assembly having the above described characteristics, wherein a member extends from the blade and has an eye at the end thereof through which the thread extends so that, during initial swinging of the blade, thread is drawn from the bobbin to provide the necessary slack in the lower thread when sewing operation is resumed, and wherein a solenoid actuating blade of the lower thread cutting assembly is controlled so that initial movement of the blade is at a relatively slow speed to permit drawing of thread from the bobbin, while the remainder of the movement of the blade is at a relatively high speed to provide the desired thread cutting action.

The above, and other, objects, features and advantages of the invention will be apparent in the following description of an illustrative embodiment, presented by "way of example, and to be read in connection with the accom panying drawings, wherein:

Fig. 1 is a front elevational view of a sewing machine having a device thereon embodying the present invention for simultaneously cutting the upper and lower threads at the conclusion of a sewing operation;

Fig. 2 is a side elevational view of the sewing machine of Fig. I; i v

Fig. 3 is a rear elevational view of the sewing machine of Fig. 1

Fig. 4 is a vertical sectional view of a presser foot assembly included in the sewing machine of Figs. 1, 2 and 3, but on an enlarged scale;

Fig. 5 is a transverse sectional view taken alongthe line 55 .of Fig. 4 and showing the thread cutting and holding blades in their normal inoperative positions;

Fig. 6 is a view similar to Fig. 5 but showing the cutting and holding blades in their operative positions;

Fig. 7 is a top plan view of the cutting and holding blades of Figs. 4, 5 and 6;

Fig. 8 is a sectional view taken along line 88 of Fig. 4;

Fig. 9 is a bottom plan view of a lower thread cutting and holding assembly included in the sewing machine of Figs. 1, 2 and 3, with the cutting blade and associated structure being shown in broken lines in the operative position thereof;

Fig. 10 is a side elevational view of the assembly of Fig. 9, with the cutting blade shown in its normal inoperative position;

Fig. 11 is a fragmentary, vertical sectional view through a portion of the assembly of Figs. 9 and 19, but with the blade being shown in its operative position to illustrate the thread cutting and holding actions thereof;

Fig. 12 is an axial sectional view of a dash-pot assembly for controlling the rate of travel of the solenoid actuating the lower thread cutting and holding assembly;

Fig. 13 is a schematic diagram of the electrical circuits included in the illustrated embodiment of the invention, and

Fig. 14 is a fragmentary side elevational view, on a reduced scale, of the actuating mechanism for the lower thread cutting and holding assembly in another embodimerit of the invention.

Referring to the drawings in detail, and initially to Figs. 1, 2 and 3 thereof, a sewing machine having attachments for simultaneously cutting and holding the upper and lower threads at the conclusion of a sewing opchine 10 further includes an automatic top thread tension 24 (Figs. 1 and 2) and a vertically movable thread take-up lever 26, as well as the usual drive means for reciprocating needle bar and raising and lowering the thread take-up lever. Such drive means is driven by an electric motor, preferably through a gear transmission, as

in most commercial machines, or through a belt friction wheel which drives a grooved hand wheel 28.

The sewing machine embodying the present invention includes a presser foot assembly which is generally identified by the reference numeral and is secured to the lower end of a vertically movable presser bar 32 disposed adjacent to needle bar 20. Presser bar 32 is raised by rocking of a lever 34 which is pivotally mounted, intermediate its ends, on arm 16, as at 36 (Fig. 3), and to one end of which the presser bar is suitably connected. The other end of lever 34 is connected to an actuating rod 38 which extends down to a suitable operating treadle (not shown) so that downward movement of rod 38 serves to lift or raise presser bar 32 and the presser foot assembly mounted on the latter.

In accordance with the present invention, means are embodied within the presser foot assembly 30 for cutting and holding the top or over thread at the conclusion of a sewing operation, such means being hereinafter described in detail, while other means, also hereinafter described in detail, are provided below the usual removable cloth plate 40, which is mounted on the bed 12 under the presser foot assembly, for cutting and holding the lower thread drawn from a bobbin (not shown). The top and lower thread cutting and holding means are actuated by electrically energized solenoids which are controlled by a suitable micro-switch 42 carried by a bracket 44 mounted on the front face of stock 1-4- at a location adjacent the top of the latter (Fig. 1). Switch 42 is normally open and includes an operating finger 46 which v,

projects from the switch housing and extends in front of i one end of a switch actuating lever 46 mounted on a suitable bracket St for swinging about a vertical axis. The end of lever 48 remote from switch operating finger 46 carries a plate 52 having a projection 54 which is engageable in a recess 56 provided in the adjacent periphery of hand wheel 28. Thus, in one rotational position of hand wheel 28, corresponding to the uppermost position of needle bar 20, projection 54 fits into recess 56 to permit rocking of lever 48, by pressure applied manually to plate 52, and such rocking of lever 48 displaces operating finger 46 of micro-switch 42 in the direction effecting closing of the switch. From the foregoing, it is apparent that switch 42, which is normally open, can be manipulated to its closed condition only when needle bar 20 and the needle 22 carried thereby are in their uppermost or raised position to withdraw the needle from the cloth plate 46 and the presser foot assembly 30.

As seen in Figs. 4 to 8, inclusive, the presser foot assembly 30 includes a support member 58 having an upwardly open bore in which bar 32 is received and removably secured and a bifurcated lower portion providing a pair of spaced apart legs 69. A lateral pin 62 is carried by the legs and rockably supports a presser foot body 64 intermediate the front and back ends of the latter. Body 64 is formed with a central, forwardly opening slot 66 to receive needle 22 during the reciprocation of the latter. A presser foot plate or sole 68 is loosely mounted below body 64 and is bent upwardly in front of the latter, with the forward portion of plate 68 having a central, forwardly opening slot 70 (Figs. 5, 6 and 8) aligned with the slot 66 and through which the reciprocated needle 22 also passes.

The above mentioned loose or floating mounting of plate 68 under body 64 is achieved by screws 72 which extend loosely or slidably through suitable countersunk bores in body 64, preferably adjacent the four corners of the latter, and are threaded into corresponding tapped bores in the sole or plate 68. From the foregoing, it is apparent that the screws 72 can be threadedly adjusted with respect to the plate or sole 68 so that, when the latter is in contact with the lower surface of body 64, clearance exists between the heads of screws 72 and the bottoms of the countersunk portions of the bores in body 64 receiving such screws, whereby the plate or sole 68 is movable toward and away from the lower surface of body 64.

Body 64 is formed with a vertical bore 74 located in back of the pivot pin 62 and having an enlarged diameter lower portion opening into the rear part of a recess 76 in the bottom surface of body 64, said recess opening laterally at the side edges of body 64. A vertical spindle 78 is rotatable in bore 74 and is formed with an enlarged diameter lower portion 80 which is accommodated in the corresponding enlarged diameter lower portion of bore 74. As seen in Fig. 7, lower portion 80 of the spindle is provided with a diametrically extending, straight sided slot 82 which opens downwardly and receives the straight sided shanks of a top or over thread cutting blade 84 and a top thread holding blade 86, which is superposed on the cutting blade, so that the blades 84 and 86 are swingable by rotation of spindle 78 for lateral displacement within recess 76 at the bottom of body 64. Preferably, a screw 88 extends through the blades 84 and 86 into the center of the spindle to secure the blades to the spindle within slot 82 of the latter.

As seen in Fig. 7, the forward ends of the cutting and holding blades 84- and 86, respectively, are offset laterally with respect to the shanks thereof, with the underlying cutting blade 84 having a forward portion which is offse a greater distance than the forward portion of the superposed thread holding blade 86 so that during swinging of the blades in the counter-clockwise direction, as viewed in Fig. 7, the leading edge 90 of the holding blade will precede the leading or cutting edge 22 of the cutting blade. As seen in Fig. 5, the leading edge 99 of the holding blade is rounded, while the cutting edge 92 of blade 84 is cut square to the surfaces of the blade to cooperate with a cutting edge 94 which is defined by an undercut inclined surface along the right side of slot of the presser foot plate or sole 68, as viewed in Figs. 5 and 6.

Normally, that is, during a sewing operation, spindle 78 is rotationally positioned to dispose the blades 84 and 86 to one side of the slots 66 and 70 (Fig. 5) thereby to avoid interference with the reciprocation of needle 22. However, at the conclusion of a sewing operation, and after the needle has been moved to a raised position withdrawn from the slots 66 and 7t spindle 78 is angularly manipulated to move the blades 84 and 86 laterally across recess 76 and past the slots 66 and 70. During such movement of the cutting and holding blades, edge 90 of the holding blade 86 first comes into contact with the top or over thread T1 extending through the slots 66 and 70 and the thread is pushed to the side, as shown in Fig. 6, and gripped or held between the upper surface of holding blade 86 and the lower surfaces of body 64 to one side of slot 66 which defines the top of recess 76. After the thread has been gripped or held in the above manner, continued lateral movement of the cutting and holding blades brings the cutting edge 92 of cutting blade 84 across the sharp corner or cutting edge 94 of the presser foot plate or sole 68 and thereby shears or cuts the thread T1.

As seen in Fig. 4, a radial actuating arm is secured to the upper end of spindle 78, as by a set screw, and extends in a generally rearward direction from the spindle. A helical compression spring 98 is interposed between the lower surface of arm 96 and the top surface of body 64 thereby to resiliently urge spindle 78 and blades 84 and 86 upwardly relative to the body 64. Thus, holding blade 86 is yieldably held against the upper surface defining recess 76 so that threads of different counts can be held or gripped between the holding blade and the upper surface of the recess without requiring adjustment of the presser foot assembly. For example, if a relatively thick thread is used, the blades 84 and 86 are displaced downwardly with the spindle relative to the body, and the floating mounting described above for the presser foot plate 68 permits such downward displacement of the holding and cutting blades. Since the cutting and holding blades of the presser foot assembly 30 are operated only when the presser foot assembly is in its lowered or cloth holding position, as will hereinafter appear, it is apparent that the pressure of the presser foot assembly on the stitched or sewed cloth will be sufiicient to urge the plate 68 into cutting relationship with respect to the blade 84.

An actuating lever 106 is rockably mounted adjacent its center, as at 102, upon the back of support member 58 of the presser foot assembly to swing in a vertical, laterally extending plane and, at its lower end, lever 100 is formed with a longitudinally extending slot 104 receiving a spherical knob 106 at the free end of actuating arm 96. Thus, rocking of lever 189 about its pivot 102 is converted into angular displacement of arm 96 and spindle 78 about a vertical axis for operation of the blades 84 and 86.

As seen in Figs. 2 and 3, a bent lever 198 is rockably mounted, intermediate its ends, as at 110, on the back of head 18 of the sewing machine for swinging laterally, that is, in a plane parallel to the plane of movement of the lever 1%. At its lower end, lever 108 is formed with a longitudinal slot 112 which slidably receives a pin 114 projecting from the upper end of lever 100 thereby to transmit angular displacement of lever 168 to lever 100 of the presser foot assembly. At its upper end, lever 103 is pivotally connected, as at 116, to an end of a connecting rod assembly which is generally identified by the reference numeral 118. Preferably, connecting rod assembly 118 includes two rod sections 120 and 122 which are adjustably connected by a suitable coupling 124 so that the length of the assembly 118 can be varied to adjust the angular displacement of lever 108, and hence of the cutting and holding blades in the presser foot assembly 30. The end of connecting rod assembly 118 remote from lever 108 is pivotally connected, as at 126, to the head of the movable core of a pull-type solenoid 128 which is carried by a bracket 130 mounted upon the back of stock 14 adjacent the top of the latter. When solenoid 128 is energized, the pull exerted on connecting rod assembly 118 in the direction to the left, as viewed in Fig. 3, is transmitted by levers 108 and 100 to the arm 96 of the presser foot assembly for swinging the cutting and holding blades 84 and 86 from their inoperative positions (Fig. 5) to their operative positions (Fig. 6). The return of the cutting and holding blades of the presser foot assembly 30 to their inoperative positions is effected by a return tension spring 132 which is connected at its opposite ends to a block 134 on the back of head 18 and to a collar 136 mounted on rod section 123 of the connecting rod assembly. Thus, spring 132 yieldably urges the connecting rod assembly 118 to the right, as viewed in Fig. 3, in opposition to the pull exerted by solenoid 123 when the latter is energized. A stop, in the form of a collar 138 on rod section 120 engageable with the block 134, is provided for the purpose of limiting the movement of the connecting rod assembly in the direction of the pull of spring 132 and thereby determines the inoperative positions of the cutting and holding blades within the presser foot assembly.

As seen in Fig. 13, solenoid 12.8 is connected in series with micro-switch 42 which is interposed in the power lines 149 so that the solenoid is energized only when switch 42 is in its closed condition. As previously indicated, switch 42 can be closed, by manually applied pressure on the plate 52 (Fig. i), only when hand Wheel 26 is rotationally positioned for raising or lifting the needle 22 out of the presser foot assembly. Another switch 142 is connected in series with switch 42 and is normally closed when the presser foot assembly is in its lowered or cloth engaging position, switch 142 being opened, to prevent energization of solenoid 128, in response to raising of the presser foot assembly. In order to effect such opening of switch 142, which is mounted on the back of stock 14 (Fig. 3), a collar 144 is mounted on the actuating rod 38 of the presser foot lifting mechanism and is engageable, from above, with a switch opening arm 146 extending from the housing of switch 142. When rod 38 is moved downwardly, to lift or elevate the presser foot assembly 30, collar 144 displaces arm 146 to open switch 142. Accordingly, solenoid 128 is energized only when switches 42 and 142 are simultaneously closed, that is, when the needle 22 is raised and the presser foot assembly 30 is lowered for ensuring that the needle will be out of the path of travel of the blades 84 and 86 within the presser foot assembly.

The rotation of hand wheel 28 to the position wherein projection 54 is engageable in notch 56 of the hand wheel to permit closing of switch 42 may be elfected manually with continuous pressure being applied to plate 52 by the palm of the hand rotating the wheel 28. However,

it is also possible to slowly rotate wheel 23 by the regular drive motor while applying manual pressure against the plate 52 so that, when the projection 54 and notch 56 come into alignment, the projection falls into the notch to prevent further rotation of wheel 28 while lever 48 is rocked to close switch 42. When the hand wheel of a commercial, gear driven sewing machine is to be slowly rotated by the drive motor for the purpose indicated above, a friction clutch 148 (Fig. 13) is preferably inserted between the motor 150 and the gear transmission (not shown) so that, when the rotation of hand wheel 28 is suddenly stopped by engagement of projection 54 in recess 56, the clutch 148 slips to prevent the imposition of excessive impact upon the transmission gears.

in accordance with the present invention, the tension on the top or over thread is released simultaneously with aroma? the cutting and holding of that thread by blades 84 and 36 in the presser foot assembly so that, upon resumption of the sewing operation of the machine, sutlicient slack exists in the top or over thread to permit the formation of the first stitches. In order to provide for automatic release of the tension on the top or over thread when the blades 84 and 85 are operated, a tension release rod 152 extends rearwardly through head 18 from the ten sion device 24 and projects from the rear of the head to there carry a cam plate 154 having an inclined rear surface which is engageable by lever 16-3. Cam plate is shaped so that rocking of lever 1% in the direction operating the cutting and holding blades of the presser foot assembly 36 moves the cam plate 154- and rod 152 forwardly to separate the discs of tension device 24 between which the top or over thread e'itends thereby to release the thread and relax the tension on the latter.

Sewing machine 10 further inclues a lower thread cutting and holding assembly which is generally identified by the reference numeral 156 (Fi s. 9, l0 and ll) and which is mounted below the removable cloth plate 40. As seen in Fig. 9, the assembly 156 includes a blade 158 which is swingable about a pivot screw 160 in a horizontal plane immediately below plate 40. Blade 358 is formed with a tapering or wedge-shaped knife portion 162 which is movable by swinging of the blade between an inoperative normal position, shown in full lines on Fig. 9, and an operative thread cutting and holding position, shown in broken lines on Fig. 9, and during such movement knife portion 162 moves across an opening 164 in plate through which the lower thread T2. extends upwardly from the usual bobbin (not shown). A thread puller 166 extends from the blade 158 and has an eye 168 at its free end and through which the lower thread is extended. The thread puller 166 is dimensioned and positioned so that, when the blade r53 is in its normal or inoperative position, eye 168 is registered with the opening 164 in plate 46*. Thus, as blade 158 swings about its pivot 160, to its operative position, shown in broken lines on Fig. 9 and also in Fig. ll, the lower thread is pulled by its engagement in eye 168 to provide sulilcient slack in the lower thread, upon the return of the blade 158 to its normal position, to permit the formation of the initial stitches when the sewing operation of the machine is resumed.

Also mounted below plate it: is a resilient holding strip 170 having a wedge-shaped free end 172, (Fig. ll) over which the knife portion 162 of blade 158 engages during the movement of the blade to its operative position. In Fig. ll, it will be seen that movement of blade to its operative position is accompanied by drawing of the lower thread T2 under the holding strip l7; through the action of thread puller 166, whereupon ltnife portion 162 moves past opening 164 to cut or shear the lower thread while the portion of the thread below plate 4i is resiliently held or gripped between the confronting inclined surfaces of the wedge-shaped end portion 172. of the holding strip and the knife portion 162 of the blade.

In order to effect operation of blade 158 simultaneously with the operation of blades 84 and 86, which respectively cut and hold the top thread, blade 158 is actuated by a solenoid 174 connected in parallel with solenoid 128 (Fig. 13) to be controlled in the same manner as the latter. Solenoid 174 is also of the pull type and is mounted upon a suitably shaped bracket '76 er;- tending rearwardly and downwardly from bed 12 of the sewing machine, (Figs. 2 and 3). The head of solenoid 174 is connected to a flexible cable 1'73 which extends through a flexible housing 189 and is suitably connected to a pin .lSl disposed on blade 28 at a location spaced from the pivot of the latter so that a pull exerted on cable 178 by the related solenoid causes swinging of the blade 158 from its normal inoperative position to its operative position. Return of blade 358 Lil from its operative position to its normal, inoperative position (shown in full lines on Fig. 9) is effected by tension springs 182 (Figs. 2 and 3) which extend from the opposite ends of a rod 184 passing through the head of the solenoid 174 and are connected to anchoring bolts 186 carried by bracket 176. Thus, when solenoid 174 is energized, it overcomes the resistance of springs 182 to displace cable 178 in the direction for operating blade 158, while deenergization of solenoid 174 permits springs 182 to return blade 15% to its inoperative position through suitable movement of the cable 178.

Preferably, the movement of the core of solenoid 174 is controlled so that initial displacement of blade 153 from its inoperative position is at a relatively slow speed to permit the drawing of thread from the bobbin by the action of the thread puller 166 while avoiding the danger of inadvertently breaking the thread, and then to cause relatively rapid travel of blade 158 during the remainder of its movement to the operative position thereby to provide the proper cutting action as knife portion 162 of the blade moves under opening 164 of plate 40. Such control of the speed of travel of solenoid 174 is provided by a dash-pot assembly which is generally identified by reference numeral 188 and is mounted upon the bracket 176. As seen in Fig. 12, dash-pot assembly 183 includes a cylinder 190 which is held in fixed position with its axis extending parallel to the direction of travel of the core of solenoid 174-. One end of cylinder 190 is closed by a cover 192 having a passage 194 extending therethrough for communicating the interior of cylinder 1.98 with the atmosphere. An adjustable needle valve 126 extends into passage 194 to provide a variable restriction in the latter. A piston 198 is longitudinally reciprocatablc through the open end of cylinder E90 and has a stem 200 extending axially therefrom and formed with a downwardly opening notch or recess 262 receiving the rod 184 which is carried by the head of solenoid 174. Thus, when solenoid 1174 is energized, piston 193 of the dash-pot assembly moves to the left, as viewed in Fig. 12, with the head of the solenoid and the speed of travel of the piston 1925 and hence of the head of solenoid 174 is controlled by the rate at which air is permitted to enter into the interior of cylinder 1%. During initial movement of piston 19S, air enters the interior of cylinder 190 only through the variably restricted passage 194.

In order to provide for the increased rate of travel of piston 19%, and hence of the solenoid core, after the initial movement thereof, an auxiliary radial passage 294 is formed in the side wall of cylinder 1% and is uncovered by the piston i953. following a predetermined initial movement of the latter, so that air can then enter the interior of cylinder 190 through both of the passages 194 and 294 thereby reducing the resistance to travel of the piston and permitting the movement of knife portion 162 of blade 158 past the opening the of plate 49 at a relatively high speed to ensure cutting of the lower thread T2.

in another embodiment of the invention illustrated in Fig. 14, the movement of the core of solenoid 1740, which actuates the lower thread cutting and holding assembly (not shown), is magnetically controlled so that initial movement of the solenoid core and of the cable 1394. extending to the blade is at a relatively slow speed to permit drawing of thread from the bobbin in the manner previously described, while the blade is displaced rapidly during the remainder of its movement to ensure cutting of the lower thread.

Such magnetic control. of the solenoid core movement is effected by a permanent magnet 296 mounted on the core or head or" solenoid 17-h: for movement with the core and cooperating with a plunger 238 which extends slidably through 21 depending portion 216 of the supporting bracket 76a. A spring 212 acts upon the plunge ass to yieldably urge the latter to the position shown in Fig. 14, wherein a shoulder of the plunger 298 abuts against bracket portion 210 to limit the spring urged movement of the plunger in the direction away from magnet 206.

When solenoid 174a is deenergized, return springs 182a act on the head of the solenoid core to draw the latter and magnet 206 to the right, as viewed in Fig. 14, so that the magnet contacts and magnetically adheres to the adjacent end of plunger 208. When the solenoid 174a is energized to actuate the lower thread cutting and holding assembly, initial movement of the solenoid core to the left, as viewed on Fig. 14, is achieved with magnet 206 adhered to slidable plunger 298 so that the initial movement is resisted and slowed by the action of spring 212. However, the resistance to movement of plunger 208 and magnet 296 with the solenoid core is increased by compression of the spring 212 so that, after initial movement of the solenoid core, the resistance of spring 212 becomes greater than the magnetic attraction between magnet 206 and plunger 293, whereupon the magnet separates from the plunger so that the remainder of the movement of the solenoid core can proceed without resistance from spring 212 and hence at a relatively high speed.

From the foregoing, it is apparent that a sewing machine embodying the present invention is capable of trimming or cutting the top or over thread and the lower thread at the completion of a sewing operation, with such threads being cut relatively close to the sewed or stitched cloth so that no further or separate trimming operation is required. The elimination of the separate trimming operation and of the waste involved in the removal of relatively long thread ends from the sewed cloth effects substantial economies in commercial practice. Further, in view of the manner in which the switches 42 and 142 are operated, to prevent the operation of either the top thread cutting and holding means or the lower thread cutting and holding means at a time when the needle 22 is disposed in the paths of travel of the blades 84, 86 and 158, the possibility of damage to the needle or to such blades is positively avoided. It is also to be noted that the plate 52 which is pressed for closing the switch 42, is conveniently located adjacent the hand wheel 28 to facilitate engagement thereof during manipulation of the hand wheel for raising the needle 22.

While the present invention has been described in detail and illustrated in connection with a single needle sewing machine, it is to be understood that the present invention can be similarly employed in connection with other machines, for example, double-needle sewing machines, and that the invention is not otherwise limited to the precise embodiments which have been described in detail and illustrated in the drawings, merely by way of example, since various changes and modifications can be effected therein, by one skilled in the art, without departing from the scope or spirit of the invention as defined in the appended claims.

What is claimed is:

l. in a sewing machine having at least one substantially vertical reciprocated needle, mechanism for re switches are simultaneously closed, means actuated by the mechanism for raising and lowering the presser bar and operative to open said second switch When the presser bar is raised, and means for closing said first switch and cooperating with the hand wheel of the needle reciprocating mechanism to permit closing of said first switch only when the needle is raised, whereby said top and lower thread cutting and holding means can be actuated only when the needle is raised and the presser foot assembly is lowered for avoiding interference between the needle and said top and lower thread cutting and holding means. I

2. In a sewing machine having at least one substantially vertical reciprocated needle, mechanism for reciprocat- 1ng the needle including a rotatable hand wheel, a presser bar and mechanism for raising and lowering said ,bar, a top thread tension device, and a cloth plate under the presser bar having an opening through which a lower thread is passed; the combination of a presser foot assembly carried by the presser bar and including means for cutting and holding the top thread, means for cutting and holding the lower thread and mounted below the cloth plate, means including driving electrical solenoids for actuating said top and lower thread cutting and holding means when the related solenoids are energized, an

electric circuit for energizing said solenoids and including ciprocating the needle including a rotatable hand wheel,

a presser bar and mechanism for raising and lowering said bar, a top thread tension device, and a cloth plate under the presser bar having an opening through which a lower thread is passed; the combination of a presser 7 foot assembly carried by the presser bar and including means for cutting and holding the top thread, means for cutting and holding the lower thread and mounted below the cloth plate, means including driving electrical solenoids for actuating said top and lower thread cutting and holding means when the related solenoids are energized,

an electric circuit for energizing said solenoids and including a first normally open switch and a second normally closed switch'connected in series so that said solenoids are energized only when said first and second a first normally open switch and a second normally closed switch connected in series so that said solenoids are energized only when said first and second switches are simultaneously closed, means actuated by the mechanism for raising and lowering the presser bar and operative to open said second switch when the presser bar is raised, means for closing said first switch and cooperating with the hand wheel of the needle reciprocating mechanism to permit closing of said iirst switch only when the needle is raised, whereby said top and lower thread cutting and holding means can be actuated only when the needle is raised and the presser foot assembly is lowered for avoiding interference between the needle and said top and lower thread cutting and holding means, means operated by said solenoid driven actuating means for the top thread cutting and holding means to release the top thread tension device at the time of operation of said top thread cutting and holding means, lower thread pulling means operated with said lower thread cutting and holding means to provide slack in the lower thread, and dash-pot means cooperating with the solenoid driven actuating means for said lower thread cutting and holding means to provide relatively slow initial operation of the latter, during which the lower thread is pulled to provide slack therein, followed by relatively fast operation, during which the lower thread is cut and held.

3. In a sewing machine having at least one substantially vertical reciprocated needle, mechanism for reciprocating the needle including a rotatable hand wheel,

- a presser bar and mechanism for raising and lowering said bar, a top thread tension device, and a cloth plate under the presser bar having an opening through which a lower thread is passed; the combination of a presser foot assembly carried by the presser bar and including means for cutting and holding the top thread, means for cutting and holding the lower thread and mounted below the cloth plate, means including driving electrical solenoids for actuating said top and lower thread cutting and holding means when the related solenoids are energized, an electric circuit for energizing said solenoids and having a first normally open switch and a second normally closed switch connected in a series so that said solenoids are energized only when said first and second switches are simultaneously closed, means actuated by the mechanism for raising and lowering the presser bar and operative to open said second switch when the presser bar is raised, a rockable control lever for said first switch mounted adjacent the hand wheel and having a projection extending across the periphery of the hand wheel so that the periphery of the hand wheel normally prevents rocking of said control lever in the direction for closing said first switch, the periphery of the hand wheel having a recess therein located to receive said projection of the control lever when the needle is in a raised position then to permit rocking of said control lever in said direction for closing the first switch, whereby said top and lower thread cutting and holding means can be actuated only when the needle is raised and the presser foot assembly is lowered to avoid interference between the needle and said top and lower thread cutting and holding means.

4. In a sewing machine; the combination according to claim 3, further comprising a plate on said rockable control lever adjacent the hand wheel and against which pressure can be manually applied to urge said control lever in said direction for closing the first switch.

5. In a sewing machine having at least one substantially vertical reciprocated needle, mechanism for reciprocating the needle including a rotatable hand wheel, a presser bar and mechanism for raising and lowering said bar, a top thread tension device, and a cloth plate under the presser bar having an opening through which a lower thread is passed; the combination of a presser foot assembly carried by the presser bar and including means for cutting and holding the top thread, means for cutting and holding the lower thread including a cutting blade mounted below the cloth plate for swinging in a horizontal plane across the opening through which the lower thread is passed said cutting blade having a wedge-shaped cutting portion to cooperate with the opening of the cloth plate in cutting the lower thread when said blade swings in one direction across said opening, a resilient holding strip secured at one end to the undersurface of the cloth plate and formed with a downwardly inclined surface at its other end to resiliently engage under said cutting portion of the blade when the latter swings across the opening of the cloth plate thereby to hold the lower thread between said holding strip and cutting portion, an elongated thread pulling member secured to said cutting blade and having an eye at an end thereof spaced from the cutting portion of said blade in said one direction of swinging of the latter so as to register with the opening of the cloth plate when said cutting portion of the blade is spaced from opening so that the lower thread then extends through said eye, swinging of said blade across the opening of the cloth plate causing displacement of said eye away from the opening thereby pulling on the lower thread to provide slack in the latter when said eye is again registered with the opening in the cloth plate, actuating means for said top and lower thread cutting and holding means, and control means cooperating with the hand wheel and with the mechanism for raising and lowering the pressure bar to permit operation of said actuating means only when the needle is raised and the presser foot assembly is lowered on to the cloth plate thereby to avoid interference between the needle and said top and lower thread cutting and holding means.

6. in a sewing machine of the described character; the combination of a cloth plate having an opening through which a lower thread is passed, a cutting blade mounted below the cloth plate for swinging in a horizontal plane across the opening through which the lower thread is passed said cutting lade having a wedge-shaped cutting portion to cooperate with the opening of the cloth plate in cutting the lower thread when said blade swings in one direction across said opening, a resilient holding strip secured at one end to the undersurface of the cloth plate and formed with a downwardly inclined surface at its other end to resiliently engage under said cutting portion of the blade when the latter swings across the opening of the cloth plate thereby to hold the lower thread between said holding strip and cutting portion, an elongated thread pulling member secured to said cutting blade and having an eye at an end thereof spaced from said cutting portion of the blade in said one direction of swinging of the latter so as to register with the opening of the cloth plate when said cutting portion of the blade is spaced from said opening so that the lower thread then extends through said eye, swinging of the said blade across the opening of the cloth plate causing displacement of said eye away from the opening thereby pulling on the lower thread to provide slack in the latter when said eye is again registered with the opening in the cloth plate.

7. in a sewing machine of the described character; the combination according to claim 6, further comprising actuating means for said blade operative to initially move the latter in said one direction toward said opening at a relatively slow speed so that said thread pulling member pulls the lower thread without the danger of breaking the latter, and then to move said blade across said opening at a relatively high speed for ensuring cutting of the lower thread.

8. in a sewing machine of the described character; the combination of a cloth plate having an opening through which a lower thread is passed, a cutting blade mounted below the cloth plate for swinging in a horizontal plane across the opening through which the lower thread is passed, said cutting blade having a wedge-shaped cutting portion to cooperate with the opening of the cloth plate in cutting the lower thread when said blade swings in one direction across said opening, a resilient holding strip secured at one end to the undersurface of the cloth plate and formed with a downwardly inclined surface at its other end to resiliently engage under said cutting portion of the blade when the latter swings across the opening of the cloth plate thereby to hold the lower thread between said holding strip and cutting portion, and an elongated thread pulling member secured to said cutting blade and having an eye at an end thereof spaced from said cutting portion of the blade in said one direction of swinging of the latter so as to register with the opening of the cloth plate when said cutting portion of the blade is spaced from said opening so that the lower thread then extends through said eye, swinging of said blade across the opening of the cloth plate causing displacement of said eye away from the opening thereby pulling on the lower thread to provide slack in the latter when said eye is again registered with the opening in the cloth plate, and actuating means for said blade including a solenoid, connecting means between said solenoid and blade so that the solenoid, when energized, produces movement of said blade across said opening, and a dashpot assembly including a fixed cylinder, a piston reciprocatable in said cylinder and connected to said solenoid to he moved by the latter, said cylinder having a first passage therethrough continuously opening to the atmosphere to admit air to said cylinder in response to movement of said piston by the solenoid, and an au 1- iliary passage through said cylinder and opening to the atmosphere, said auxiliary passage being closed by said piston during initial movement of the latter and then uncovered during the remainder of the movement of the piston for reducing the resistance to said remainder of? the movement of the piston so that said blade is initially moved in the direction toward said opening at a relatively slow speed to permit pulling of the lower thread by said thread pulling member without the danger of breaking the thread, while the remainder of the movement of said blade in said one direction across said opening is accomplished at a relatively high speed for ensuring cutting of the lower thread.

9. In a sewing machine of the described character; the combination according to claim 8, wherein said cylinder further has an adjustable valve interposed in said first passage to provide a variable restriction in the latter for controlling the speeds at which said piston, solenoid and blade travel when said solenoid is energized.

10. In a sewing machine of the described character;

the combination of a cloth plate having an opening through which a lower thread is passed, a cutting blade mounted below the cloth plate for swinging in a horizontal plane across said opening, said cutting blade having a wedge-shaped cutting portion to cooperate with said opening of the cloth plate in cutting the lower thread when said blade swings in one direction across said opening, a resilient holding strip secured at one end to the undersurface of the cloth plate and formed with a downwardly inclined surface at its other end to resiliently engage under said cutting portion of the blade when the latter swings across said opening of the cloth plate thereby to hold the lower thread between said holding strip and cutting portion, an elongated thread pulling member secured to said cutting blade and having an eye at an end thereof spaced from said cutting portion of the blade in said one direction of swinging of the latter, so as to register with the opening of the cloth plate when said cutting portion of the blade is spaced from said opening so that the lower thread then extends through said eye, swinging of said blade across said opening of the cloth plate causing displacement of said eye away from said opening thereby pulling on the lower thread to provide slack in the latter when said eye is again registered with the opening in the cloth plate, actuating means for said blade including a solenoid, connecting means between said solenoid and blade so that the solenoid, when energized, produces movement of said blade in said one direction across said opening, a magnet movable with said solenoid, a slidably mounted plunger disposed for adherence thereto by said magnet, and spring means resisting movement of said plunger with said magnet during energization of the solenoid so that initial movement of the latter is resisted and slowed by said spring means acting on the plunger and said magnet is separated from said plunger when the resistance or" the spring means exceeds the magnetic attraction between said magnet and plunger whereby the remainder of the movement of said solenoid can occur at a relatively high speed so that said blade is initially moved in said one direction at a relatively slow speed to permit pulling of the lower thread by said thread pulling member without the danger of breaking the thread, while the movement of said blade across said opening in said one direction is accomplished at a relatively high speed for ensuring cutting of the lower thread.

11. In a sewing machine having at least one substantially vertical reciprocated needle, mechanism for reciprocating the needle including a rotatable hand wheel,

a presser bar and mechanism for raising and lowering said bar, a top thread tension device, and a cloth plate under the presser having an opening through which a lower thread is passed; the combination of a presser foot assembly carried by the presser bar and including means for cutting and holding the top thread, means for cutting and holding the lower thread and mounted below the cloth plate, means including driving electrical solenoids for actuatin said top and lower thread cutting and holding means when the related solenoids are energized, an electric circuit for energizing said solenoids and including a first normally open switch and a second normally closed switch connected in series so that said solenoids are energized only when said first and second switches are simultaneously closed, means actuated by the mechanism for raising and lowering the presser bar and operative to open said second switch when the presser bar is raised, means for closing said first switch and cooperating with the hand wheel of the needle reciprocating mechanism to permit closing of said first switch only when the needle is raised, whereby said top and lower thread cutting and holding means can be actuated only when the needle is raised and the presser foot assembly is lowered for avoiding interference between the needle and said top and lower thread cutand holding means, means operated by said solenoid driven actuating means for the top thread cutting and holding means to release the top thread tension device at the time of operation of said top thread cutting and holding means, lower thread pulling means operated with said lower thread cutting and holding means to provide SitClx' in the lower thread, and yieldable means magnetically coupled to the solenoid driven actuating means for said lower thread cutting and holding means to provide relatively slow initial operation of the latter, during which the lower thread is pulled to establish slack therein, after which the magnetic coupling to said yieldable means separates to permit relatively fast operation to ettect cutting and holding of the lower thread.

References Qited in the file of this patent UNITED STATES PATENTS 885,310 Allen Apr. 21, 1908 1,592,115 Lindgren July 13, 1926 2,335,827 Gunther Nov. 30, 1943 2,376,417 Chudner May 22, 1945 2,381,817 Gardner et al. Aug. 7, 1945

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