US3354852A - Double lock stitch sewing machines - Google Patents

Description

NOV. 28, 1967 A, KENNEDY ET AL 3,354,852

DOUBLE LOCK STITCH SEWING MACHINES Filed April 16, 1965 7 l5 Sheets-Sheet l A. M. KENNEDY ET L I DOUBLE LOCK STITCH SEWING MACHINES Filed April 16, 1965 Nov. 28, 1967 15 SheetS- Sheet 2 NOV. 28, 1967 N Y ET AL 3,354,852

DOUBLE LOCK STITCH SEWING MACHINES Filed April 16, 1965 15 Sheets-Sheet 3 Nov. 28, v1967 A. M. KENNEDY ETAL 3,354,852

DOUBLE LOCK STITCH SEWING MACHINES l3 Sheets-Sheet 4 Filed April 16, 1965 A. M. KENNEDY ET AL DOUBLE LOCK STITCH SEWING MACHINES Nov. 28, 1967 13 Sheets-Sheet 5 Filed April 16. 1965 1967 A. M. KENNEDY ETAL 3,354,852

DOUBLE LOCK STITCH SEWING MACHINES Filed April 16, 1965 13 Sheets-Sheet 6 Nov. 28, 1967 KENNEDY ETAL 3,354,852-

DOUBLE LOCK STITCH SEWING MACHINES l3 Sheets-Sheet 7 Filed April 16, 1965 FIGIO Nov. 28, 1967 A. M. KENNEDY ET AL 3,354,852

DOUBLE LOCK STITCH SEWING MACHINES Filed April 16, 1965 13 Sheets-Sheet 8 Nov. 28, 1967 A. M. KENNEDY ETAL 3,

DOUBLE LOCK STITCH SEWING MACHINES Filed April 16, 1965 v1s Sheets-Sheet 9 A. M. KENNEDY ET 3,354,352 DOUBLE LOCK STITCH SEWING MACHINES Nov. 28, 1967 l3 Sheets-Sheet l 0 Filed April 16, 1965 Nov. 28, 1967 KENNEDY ETAL DOUBLE LOCK STITCH sra 15 Sheets-Sheet 11 Filed April 16, 1965 Nov. 28, 1967 A. M. KENNEDY ET AL 3,354,852

DOUBLE LOCK STITCH SEWING MACHINES Filed April 16, 1965 13 Sheets-Sheet 12 Filed April 16, 1965 A. M. KENNEDY ET AL DOUBLE LOCK STITCH SEWING MACHINES l5 Sheets-Sheet 13 SE 9 U.

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United States Patent DOUBLE LOCK STITCH SEWING MACHINES Alan Malcoim Kennedy, Collaroy Plateau, New South Wales, and Keith Samuel Wood, Chester Hill, New South Wales, Australia, assignors to Bonds-Wear Pty. Limited, Camperdown, near Sydney, New South Wales, Australia Filed Apr. 16, 1965, Ser. No. 448,592

Claims priority, application Australia, Apr. 24, 1964,

Claims. (Cl. 112--252) ABSTRACT OF THE DISCLOSURE Means incorporated in a 400 type double lock stitch sewing machine which permits an operator to sever, at the completion of a sewing operation, all sewing threads attached to a sewn article, such as a garment, so that the seam or hem does not require further trimming.

This invention relates to double lock stitch sewing machines which make a stitch known as a 400 type stitch. The invention has been devised to provide means to be incorporated in the machine whereby an operator can sever all sewing threads attached to a sewn article, a garment for example, at the completion of a sewing operation so that the seam or hem so made does not require further trimming.

The means of this invention comprise co-acting components, namely:

(i) A presser foot incorporating wiping, holding and cutting blade units mounted on the presser bar of a machine to hold the needle and cover threads and to sever such threads at the completion of a sewing operation adjacent the garment being sewn and to hold the free ends of the threads until they are pulled into the next garment to be sewn.

(ii) A second thread cutting unit mounted On the machine below and juxtaposed the throat plate and including a loop, thread slackener and a pick-up finger;

(iii) Slackeners for the needle and cover threads to minimise the likelihood of breaking such threads at the commencement of a sewing operation; and

(iv) Means to actuate the components (i), (ii), (iii).

One embodiment of the invention is illustrated in the accompanying drawings as applied to a three needle sewing machine. It is to be understood that the invention can be applied to sewing machines of the type referred to, having one or any number of needles.

FIGURE 1 is a front elevation in perspective of a sewing machine incorporating the invention.

FIGURE 2 is a rear elevation in perspective of the same machine showing cam actuating mechanism for the components (i), (ii) and (iii).

FIGURE 3 is a schematic perspective view of the thread tension release mechanism, other mechanism being omitted for clarity.

FIGURE 4 is a fragmentary section on the line 4-4 of FIGURE 3;

FIGURE 5 is a schematic view mainly of the foot lifting mechanism;

FIGURE 6 is a fragmentary section on the line 6-6 in FIGURE 5;

FIGURE 7 is a schematic view of the pick-up finger mechanism associated with the second thread cutting unit;

FIGURE 8 is a schematic view of the actuating mechanism for the cutting and the wiping and holding blades;

FIGURE 9 is an exploded perspective view of the presser foot and of the cutting and the wiping and holding blades incorporated therein;

FIGURE 10 is an enlarged perspective view of the presser foot with the mechanism of FIGURE 9 in the normal at rest position;

FIGURE 11 is a similar view to FIGURE 10 showing the mechanism in position to cut the needle and cover threads;

FIGURE 12 is a fragmentary perspective view of the lower cutter mechanism, positioned below the foot, in its normal at rest position, also showing the looper thread slackener;

FIGURE 13 is a similar view to FIGURE 12 showing the lower cutter mechanism in position to cut the threads, also showing the looper thread slackened;

FIGURE 14 is a schematic view of the looper thread slackener and its actuating mechanism;

FIGURE 15 is an elevation in perspective of the sewing machine wherein the components (i), (ii) and (iii) are actuated by pneumatic units;

FIGURE 16 is an enlarged rear elevation in perspective showing two of the pneumatic units used to actuate the thread cutting mechanisms;

FIGURE 17 is fragmentary perspective view on an enlarged scale, of a modified form of component (iii), in the at rest position; and

FIGURE 18 is a similar view to FIGURE 17 showing the lower cutting mechanism in a position to cut the threads.

The presser foot 1 is a rectangular plate having an upturned end 2 at the front and raised side portions 3 and a bracket 4 at the rear thereof. There is a slot 5 through the plate for the passage of needles 6 and threads 7-151, and a second slot 8 through the upturned end 2 of the presser foot, provides clearance for a wiping blade. The raised side portions 3 form slide guides for a wiping unit 9 which includes a wiping blade 10 adapted to travel across the needle slot 5. The unit 9 also incorporates a lost motion slot 13 in the edge thereof remote from the wiping blade 10 and a post 14. A bellcrank fulcrumed to post 56, has pins 57 on one limb projected on each side of the post 14 and its other limb is connected by rod 59 to actuating means to be described.

The cutter blade is in the form of a lever 17 mounted on a fulcrum pin 12 fixed in the presser foot 1 beneath the unit 9 and it is adapted to travel in shear across the needle slot 5. It is so moved by a pin 18 on the power end thereof which pin projects into the lost motion slot 13. A cover plate 20' fixed to the presser foot 1 above the unit 9, has a guide and travel limit slot 19 therein for the post 14. Movement of lever 17 is effected by contact of pin 18 with the ends of the lost motion slot 13 upon reciprocation of the unit 9.

Adjacent the upturned end 2 of the presser foot 1, a journal pin 21 is mounted in a bracket 22 over the path of the wiping blade 10. A holding blade 23 has a boss 24 thereon whereby it is rotatably mounted on the journal pin 21. A torsion spring 26 on the journal pin 21 acts on the holding blade 23 to hold it in engagement with the presser foot in position to resiliently register with the wiping blade 10 when the latter is moved to thread drawing position.

The sequence of movements of the wiping, holding and cutting components on the presser foot 1 is that the wiping blade 10 and the cutting blade 17 are in the retracted position during a sewing operation. At the completion of such an operation they are moved in sequence by means to be described, across the needle slot 5. The wiping blade 10 carries with it the bight of the needle and cover threads 7-151 under the holding blade 23. On further movement of the wiping blade 10, the pin 18 on the cutting blade 17 is engaged by the adjacent end Wall of the lost motion slot 13 and is moved across the needle slot 5, thus severing the threads 7-151 which are still 3 gripped between the wiping blade and the holding blade 23.

Consequently, at the commencement of the next sewing operation there is no likelihood of the threads 7 being pulled out of the needles. The holding blade 23 ensures that the ends of the threads are held in advance of the next sewing cycle and in a position to be concealed by the stitching of the next sewing cycle and are therefore not loose. The next sewing operation cannot be commenced until the wiping blade 10 and the cutting blade 17, are moved to their respective retracted at rest positions. As the wiping blade 10 is moved towards retracted position by its actuating mechanism, the other end wall of the lost motion slot engages the pin 18 and simultaneously moves the cutting blade to its retracted position. The ends of the threads 74.51 are lightly held by the holding blade 23 and consequently they are drawn into the stitching of the next sewing cycle.

The bracket 4 incorporates a clamping socket 27 whereby the presser foot 1 is mounted on the presser bar 28 of the machine. In effect, the presser foot 1 above described replaces the conventional presser foot and is located in the same position relative to the machine throat plate 29 by the means normally incorporated for raising and lowering the conventional presser foot.

The second thread cutting unit comprises a cutting blade and a pick-up finger to carry the looper thread to a position where it is severed by the cutting blade. The cutting blade 30-, FIGURES 12, 13 is fixed on a shaft 31 in a position where it can be moved in shear with the side of the throat plate 29. The shaft 31 is supported in a bearing bracket 32 on a base plate 33 on the machine. The cutting blade 30 is held in shearing engagement by a spring 33a. It is moved in a cutting operation by a bent crank 34 which is connected by an arm 35 to a reciproeating rod 36. The cutting blade 36 is moved to retracted position by a spring 37 connected to the bent crank 34 and to the base plate 33. The reciprocating rod 36 also has fixed to it, a hook 38 which is located to pull the looper thread 39 through the looper thread part of standard needle and looper thread tension assembly 40, FIG- URE 1 to provide suificient looper thread 39 beyond the cutting position, so that on commencement of the next sewing operation the looper thread 39 is not pulled out of the looper 41, FIGURES 12, 13. The rod 36 is reciprocated by one limb of a bellcrank 42 fulcrumed on the base plate 33. The other limb of the bellcrank 42 is connected by a rod 43 to actuating mechanism to be described.

The pick-up finger 44 of the second thread cutting unit is mounted on a post 45 and this post 45 is fixed to a reciprocating rod 46 mounted in bearings 47-48 on the machine. The rod 46 is connected to a crosshead 49 and a lever 50 fulcrumed as at 51 has its work end slidably located between pins 52 on the crosshead 49. The power end of the lever 50 is connected by links 53 to a push rod 54 which in turn is connected to actuating means to be described.

The next component is the needle thread slackener, the function of which is to provide sufiicient slack for the needle threads 7, between the tensioner assembly 40 and the needles 6, to minimize the likelihood of breaking the threads 7 by excess strain at the commencement of a sewing operation. The needle thread slackener comprises a lever fulcrumed in bracket 61 on the top of the machine. The power end of the lever 60 is actuated by a push rod 62 which is in turn actuated by a foot lift bellcrank 63 through a connecting rod 64 which rod 64 is adapted to be actuated by means to be described. The work end of the lever 60 is in register with a rod 65 which is slidable vertically in guides 66 on the face of the machine and held in upper position by a spring 67. This rod 65 has a crosshead 68 on it and an arm 69 on the crosshead engages the needle threads 7 between the tensioning device 40 and the conventional take-up thread carrier 70. Downward movement of the crosshead 68 and the arm 69 which is in engagement with the needle threads 7 draws such threads through the tensioners 40 in a slackening operation.

One form of means to actuate the components (i), (ii) and (iii) through rods 59, 64 and 43-54, FIGURES 1-13, consist of cams 71, 72, 73 and 74 on shaft 75 mounted in a bracket assembly 76 mounted on the machine. The shaft 75 has a pulley wheel '77 thereon and a chain or cable 78, having at least one turn on the pulley 7'7 and anchored at one end thereto, has its other end connected to the plunger 73a of a pneumatic cylinder 78b actuated by a foot pedal lever 79. The cylinder 78b when energized will rotate the pulley wheel 77 and cam shaft 75 approximately through 270 degrees and a clock type torsion spring 75a will return the shaft 75 to its initial position when the cylinder 78b is deenergized. A collar 80 free on the shaft 75, has a bent arm 81 thereon which is adapted to abut a stop 82 on the bracket 76 and a carrier 83 on the cam 74 and limit the turning movement of the shaft 75 in one direction. A striker 84, also fixed on the cam 74 is adapted to abut the opposite edge of the bent arm 81 on reverse movement of the shaft 75 and in this movement the bent arm 81 actuates the thread slackener in a manner to be described. The distance between the carrier 83 and the striker 84 provides a period of lost motion in the actuation of the thread slackener, which brings this action into the sequence of operation of the other components.

The rod 59, which actuates the wiping and holding blade 16, is connected to one end of a bent cam follower arm 85 which has a bearing 86 on its other end whereby it is supported on a journal pin 87. It has a cam follower 88 projected into a cam groove 89 in the cam wheel 73.

The rod 64, which actuates the needle thread slackener, is connected to a crank 90 on a shaft 91 and the shaft 91 has an arm 92 connected thereto. The arm 92 is connected by links 93, 94 and 95 to an arm 96 rotatably mounted on journal pin 87. The link 94 has an extension in the form of a bearing 97 which is mounted on the camshaft 75. The arm 96 has a cam follower 98 adapted to register with the cam 74. The cam 74 is adapted to move the arm 92 downwardly through the described linkage, against the action of a retracting spring (not shown), and the bent arm 81 is moved by the striker 84 to contact the link 94 and hold the arm 92 in the down position to which it has been moved by the cam 74, for the timed operating sequence.

The rod 43 has an arm 99 fixed on its end and fixed to a rotatable member 100 on the journal pin 87. The rotatable member 100 has a crank 101 thereon and a cam follower 102 on the crank 101 is adapted to be engaged 'by the cam 71. A stop 103 limits throw-out movement. The rod 54 has a crosshead 104 fixed thereon and a cam follower rod 105 pivoted to the crosshead 104 is fixed to shaft 106 rotatable in bearings in the bracket assembly 76. A cam follower 106:: on the rod 105 projects into a cam groove 107 in the cam wheel 73. The cam groove 107 is a continuation of the cam groove 89.

When the threads are to be cut, the lever 60 must be depressed a short distance as indicated in FIGURE 3, without lifting the presser foot 1, so that thread tension can be released at the conventional tensioners 40. The initial 90 degrees of movement of the cam shaft 75 causes the lever 96 to be forced downwardly to the position shown in FIGURE 4 and with it the arm 92. The striker 84 secured to the side of the cam 73 then engages the side of bent arm 81 and after a further degrees of movement the bent arm 81 will be forced into contact with the link 94 forcing it down so that the arm 96 and the cam follower 98 leave the surface of the cam 74 as shown in FIGURE 6. This forces the arm 92 fully down to the position shown in FIGURE 5 thus lifting the presser foot as shown also in FIGURE 5. This movement occurs after the threads have been severed by the mechanism previously described.

Like the needle threads 7, the cover thread 151 passes through a conventional first tensioner 152. This tensioner 152 is opened during the first depression of the lever 60, to release the tension on the cover thread by the wedge end of arm 153. This arm 153 is slotted as at 154 and is slidably mounted on the machine by journal screw 155. The end 156 of this arm is held by a spring (not shown) in abutment with a rocker arm 157 pivotally mounted on the machine. A pin 158 on the rocker arm 157 is entered into an arcuate slot 159 in a bracket 160 on the arm 92 or 92a and the arm 153 is actuated in timed sequence to open the tensioner 152 by the actuating means for the arms 92, 92a previously described.

Like the needle threads 7, which are held by the wiping blade and holding blade 23 for cutting, the cover thread 151 must also be held for the cutting operation. For this purpose a conventional second tensioner 161 is mounted on the machine. It is normally held open to permit free passage of the cove-r thread 151 during a sewing operation, by a wedge 162 on an extension 163- of the rod 65. Again, during the first depression of the lever 60, the wedge 162 is moved clear of the tensioner 161 and the cover thread 151 is held thereby for the cutting operation.

It will be seen that the needles 6 must be in the fully raised position before any thread cutting can take place. A sensing device and quick stop motor is known standard equipment on this type of sewing machine and they normally act so as to halt the machine with the needles 6 fully raised. In case this known mechanism fails an additional safety device is fitted as indicated at 108.

This comprises a pin 109 vertically slidable in a slotted guide 110 'below the main drive shaft 111 of the machine. One end 112 of a lever 113 is entered into a slot in the pin 109 and the other end 114 of the lever is connected to the free end of the lever 92 by a link 115. A blind hole indicated at 116 in a wheel fixed on the main drive shaft 11 is adapted to register with the pin 109 if the machine stops with the needles 6 raised. If the cam mechanism is now actuated by the cylinder 78b the pin 109 will enter the hole 116 in the Wheel and lock the shaft 111 to prevent movement of the needles whilst thread cutting takes place. If, however, the machine does not stop in the correct position with the pin 109 in register with the hole 116, the pin 109 will strike the surface of the wheel and the arm 92 cannot be drawn down from its normal position as shown in FIGURE 2 thus preventing movement of the cam mechanism and the components actuated thereby, before any thread cutting can take place.

The alternative actuating means illustrated .in FIG- URES to 18 consist of pneumatic cylinders. The presser foot 1 and its thread cutting mechanism is the same as that previously described. However, a modified form of the second thread cutting unit is shown in FIGURES 17 and 18. Either form of the second thread cutting unit could be used with the pneumatic actuating means.

As previously described the thread slackeners, thread cutting and presser foot lifting operations must occur in a correctly timed sequence. To achieve this sequence of operations the pedal 79 (FIGURE 15) is adapted to energise a master timing pneumatic cylinder 117 mounted on a horizontal plate 118 secured to the machine bench.

A valve actuator 119 is secured to the plunger of the cylinder 117 by means of a crosshead 120. The valve actuator 119 is slidably mounted on a guide rod 122 rigidly secured between space end plates 123. Four compressed air control valves 124, 125, 126 and 127 are secured between the end plates 123 and adjacent the guide rod 122. When the cylinder 117 is actuated its plunger forces the valve actuator 119 past each valve in turn; the leading edge of the valve actuator 119 opening each valve in sequence.

The initial valve 124 supplies air to a lower vertical pneumatic cylinder 128 which is anchored to one extension of the base plate 118. The base of a second vertical pneumatic cylinder 129 is secured to the plunger 130 of the first cylinder 128 so that the two cylinders are axially in line. The plunger 131 of the second cylinder 129 extends through an aperture in the machine bench top and its upper end is pivotally connected to the end of the presser foot lift arm 92a. Actuation of cylinder 128 via valve 124 causes the lever 92a to be pulled downwardiy the short distance necessary to remove tension from the threads without lifting the presser foot 1. When the final valve 127 is opened, air is supplied to the cylinder 129, the plunger rod 131 is pulled down to its fullest extent so that the arm 92a is pulled right down to lift the presser foot 1.

The intermediate valves 125 and 126 supply air to cylinders 132 and 133, respectively, which are horizontally mounted on an angle bracket 134 on the rear of the sewing machine in the position occupied by the cam mechanism previously described.

The plunger rod 135 of the cylinder 132 is pivotally secured to the bell crank 55 which actuates the cutting and wiping mechanism in the presser foot 1.

The plunger rod 136 of the cylinder 133 is pivotally connected to link bars 137 and 138 which are adapted to actuate the second thread cutting unit.

In the modified form of the second thread cutting unit, the forked end 139 of the bar 138 engages a rod 140 slidably mounted in a guide block 141 secured below the throat plate 29. A horizontal pick-up finger 142 is secured to the free end of the rod 140 adjacent the needle threads 7 and looper thread 39. A horizontal cutter blade 143 is secured to the underside of the throat plate 29 on the opposite side of the needle threads -7 to the pick-up finger 142.

The front face of the pick-up finger 142 is provided with a longitudinal through slot 144 which may have a V notch 145 therein.

When the cylinder 133 is energized the pick-up finger 142 is forced across the thread 39 and picks it up. When the pick-up finger 142 reaches the end of its stroke the slot 144 receives the cutter blade 143 and the thread 39 is severed.

Before the action just described can take place, however, a loop of slack must be taken in the looper thread 39. To effect this a pneumatic cylinder 146 is secured to the sewing machine base. The plunger 147 of the cylinder 146 is normally held in the retracted position shown in FIGURE 17 by an internal spring (not shown). A pipe 148 which supplies air to the cylinder 132 controlling the presser foot mechanism, has a branch pipe 149 which delivers air to the cylinder 146 just described.

When the valve 125 delivers air to the cylinder 132 air will be simultaneously delivered to the cylinder 146 so that its plunger,147 will be projected as shown in FIGURE 18. A finger 150 secured to the end of the plunger 147 engages the looper thread 39 and slackens it as shown in FIGURE 18. This slackening of the looper thread will take place before the thread cutting action as the slackening action is controlled by valve 125 whilst the thread cutting is controlled by valve 126.

When the presser foot 1 is to be lowered to recommence sewing operations, the pedal 79 is moved in the reverse direction so that the master cylinder 117 withdraws the valve actuator 119 from the valves 127, 126, 125 and 124. The plungers in cylinders 132, 133 and 146 are returned to their initial positions and the arm 92a is raised so that the presser foot 1 will be lowered.

The safety device 108 previously described, is actuated by a link 115a secured to the arm 92a. In this form of safety device, the valves 125, 126 can only be opened when the needles 6 are raised, by actuation of a safety valve (not shown), which is opened by downward moveblade units mounted on the presser bar of said machine to hold the needle and cover threads and to sever such threads at the completion of a sewing operation adjacent the garment being sewn and to hold the free ends of the threads until they are pulled into the next garment to be sewn, said presser foot comprising a rectangular plate having an upturned end at the front thereof and raised side portions providing slide guides, a bracket at the rear of said presser foot for mounting it on the presser bar, said presser foot also having a slot for the passage of needles and threads therethrough and a second slot through said upturned end to provide clearance for said wiping blade unit, said wiping blade unit being slidably mounted on the presser foot between the slide guides and including a post and a wiping blade adapted to travel across the needle slot, said wiping blade unit having a lost motion slot in the edge thereof remote from the wiping blade, said cutting blade unit comprising a lever rotatably mounted on the presser foot beneath the wiping unit, a pin on the power end of said lever, said pin projecting into said lost motion slot, a cover plate fixed to the presser foot above the wiping blade unit, said plate having a guide and travel limit slot therein for receiving said post on the wiping unit, said holding blade unit comprising a holding blade rotatably mounted on the presser foot in the path of travel of said wiping blade, a spring engaging said holding blade to hold it resiliently in engagement with the presser foot in position to resiliently register with the wiping blade,

(ii) a second thread cutting unit mounted on the machine below and juxtaposed the throat plate and including a looper thread slackener and a pick-up finger,

(iii) slackeners for the needle and cover threads to minimize the likelihood of breaking such threads at the commencement of a sewing operation; and

(iv) means to actuate said wiping, holding and cutting blade units of said presser foot, said second thread cutting unit, and said slackeners for the needle and cover threads, said means comprising link and lever mechanisms operatively connected to each of said wiping, holding and cutting blade units of said presser foot, said second thread cutting unit, and said slackeners for the needle and cover threads, pneumatic means operatively connected to said link and lever mechanisms, and a foot pedal controlling said pneumatic means.

2. Improvements relating to a 400 type double lock stitch sewing machine according to claim 1, wherein the second thread cutting unit comprises a shaft rotatably supported on said machine, a cutting blade fixed on said shaft in a position Where it can be moved in shear with the side of the machine throat plate by rotation of said shaft, a reciprocating rod mounted on said machine, a pick-up finger fixed on said reciprocating rod in a position where it can be moved to carry a looper thread to the position to be cut, crank means for rotating the shaft on which the cutting blade is fixed, a second reciprocating rod mounted on said machine, said crank means connected to said shaft and to said second reciprocating rod, said second reciprocating rod having .a hook fixed thereon located to pull the looper thread through the looper thread part of said needle and looper thread tension assembly to provide sufficient looper thread beyond the cutting position and to prevent said looper thread from being pulled out of said looper.

3. Improvements relating to a 400 type double lock stitch sewing machine according to claim 1, wherein the needle thread slackener comprises a lever fulcrumed on top of the machine, an arm connected to the work end of said lever, said arm being adapted to engage the needle threads between said needles and looper thread tension assembly and said take-up thread carrier, the power end of said lever being operatively connected to said actuating means; wherein said cover thread slackener comprises first and second thread tensioners mounted on the machine and one on each side of the sewing position and means to open and close the tensioners in timed sequence, the first tensioner being closed to maintain tension on the cover thread during a sewing operation while the second tensioner is held open by said means, said first tensioner being opened by said means to permit slackening of the cover thread at the finish of said sewing operation, said means simultaneously closing the second tensioner to hold to the cover thread for the thread cutting operation; opening means for said first thread tensioner, said opening means comprising an arm connected to the actuating means for the power end of the needle thread slackener lever, and opening means for said second thread tensioner, said last-mentioned opening means comprising a member operatively connected to the arm on the work end of said needle thread slackener lever.

4. Improvements relating to a 400 type double lock stitch sewing machine wherein said sewing machine includes a presser bar, a throat plate, a needle and looper thread tension assembly, a looper, and a take-up thread carrier, said improvements comprising in combination:

(i) a presser foot including Wiping, holding and cutting blade units, mounted on the presser bar of said machine to hoid the needle and cover threads and to sever such threads at the completion of a sewing operation adjacent the garment being sewn and to hold the free ends of the threads until they are pulled into the next garment to be sewn,

(ii) a second thread cutting unit mounted on said machine below and juxtaposed the throat plate and including a looper thread slackener and a pick-up finger,

(iii) slackeners for the needle and cover threads to minimise the likelihood of breaking such threads at the commencement of a sewing operation; and

(iv) means to actuate said wiping, holding and cutting blade units of said presser foot, said second thread cutting unit, and said slackeners for the needle and cover threads, said means comprising link and lever mechanisms operatively connected to each of said wiping, holding and cutting blade units of said presser foot, said second thread cutting unit, and said slackeners for the needle and cover threads, cam followers connected to said link and lever mechanisms, a shaft mounted on the machine, cams mounted on said shaft and engaged by said cam followers, a pedal on said machine, said shaft connected for rotation in one direction to said pedal and spring means acting on said shaft whereby it is rotated in the opposite direction.

5. Improvements relating to a 400 type double lock stitch sewing machine wherein said sewing machine includes a presser bar, a throat plate, a needle and looper thread tension assembly, a looper, and a take-up thread carrier, said improvements comprising in combination:

(i) a presser foot including wiping, holding and cutting blade units, mounted on the presser bar of said machine to hold the needle and cover threads and to sever s u c h threads at the completion of a sewing operation adjacent the garment being sewn and to hold the free ends of the threads until they are pulled into the next garment to be sewn,

(ii) a second thread cutting unit mounted on said machine below and juxtaposed the throat plate and including a looper thread slackener and a pick-up finger,

(iii) slackeners for the needle and cover threads to minimize the likelihood of breaking such threads at the commencement of a sewing operation; and

eners for the needle and cover threads, pneumatic cylinders operatively connected to said link and lever mechanisms and control means comprising control valves for the cylinders, a pneumatic control valve actuator, and a pedal to activate the control valve actuator.

References Cited UNITED STATES PATENTS l0 (iv) means to actuate said Wiping, holding and cutting 1 2 blade units of said presser foot, said second thread 3139849 6/1964 Cohen et a1 1]2 252 cutting unit, and said slackeners for the needle and 3234900 2/1966 Harris 112 252 cover threads, said means comprising link and lever mechanisms operatively connected to each of said Wiping, holding and cutting blade units of said presser foot, said second thread cutting unit, and said slack- 15 JORDAN FRANKLIN, Primary Examiner.

I. R. BOLER, Assistant Examiner.

Claims (1)

1. IMPROVEMENTS RELATING TO A 400 TYPE DOUBLE LOCK STITCH SEWING MACHINE WHEREIN SAID SEWING MACHINE INCLUDES A PRESSER BAR, A THROAT PLATE, A NEEDLE AND LOOPER THREAD TENSION ASSEMBLY, A LOOPER, AND A TAKE-UP THREAD CARRIER, SAID IMPROVEMENTS COMPRISING IN COMBINATION (I) A PRESSER FOOT INCLUDING WIPING, HOLDING AND CUTTING BLADE UNITS MOUNTED ON THE PRESSER BAR OF SAID MACHINE TO HOLD THE NEEDLE AND COVER THREADS AND TO SEVER SUCH THREADS AT THE COMPLETION OF A SEWING OPERATION ADJACENT THE GARMENT BEING SEWN AND TO HOLD THE FREE ENDS OF THE THREADS UNTIL THEY ARE PULLED INTO THE NEXT GARMENT TO BE SEWN, SAID PRESSER FOOT COMPRISING A RECTANGULAR PLATE HAVING AN UPTURNED END AT THE FRONT THEREOF AND RAISED SIDE PORTIONS PROVIDING SLIDE GUIDES, A BRACKET AT THE REAR OF SAID PRESSER FOOT FOR MOUNTING IT ON THE PRESSER BAR, SAID PRESSER FOOT ALSO HAVING A SLOT FOR THE PASSAGE OF NEEDLES AND THREADS THERETHROUGH AND A SECOND SLOT THROUGH SAID UPTURNED END TO PROVIDE CLEARANCE FOR SAID WIPING BLADE UNIT, SAID WIPING BLADE UNIT BEING SLIDABLY MOUNTED ON THE PRESSER FOOT BETWEEN THE SLIDE GUIDES AND INCLUDING A POST AND A WIPING BLADE ADAPTED TO TRAVEL ACROSS THE NEEDLE SLOT, SAID WIPING BLADE UNIT HAVING A LOST MOTION SLOT IN THE EDGE THEREOF REMOTE FROM THE WIPING BLADE, SAID CUTTING BLADE UNIT COMPRISING A LEVER ROTATABLY MOUNTED ON THE PRESSER FOOT BENEATTH THE WIPING UNIT, A PIN ON THE POWER END OF SAID LEVER, SAID PIN PROJECTING INTO SAID LOST MOTION SLOT, A COVER PLATE FIXED TO THE PRESSER FOOT ABOVE THE WIPING BLADE UNIT, SAID PLATE HAVING A GUIDE AND TRAVEL LIMIT SLOT THEREIN FOR RECEIVING SAID POST ON THE WIPING UNIT, SAID HOLDING BLADE UNIT COMPRISING A HOLDING BLADE ROTATABLY MOUNTED ON THE PRESSER FOOT IN THE PATH OF TRAVEL OF SAID WIPING BLADE, A SPRING ENGAGING SAID HOLDING BLADE TO HOLD IT RESILIENTLY IN ENGAGEMENT WITH THE PRESSER FOOT IN POSITION OF RESILIENTLY REGISTER WITH THE WIPING BLADE, (II) A SECOND THREAD CUTTING UNIT MOUNTED ON THE MACHINE BELOW AND JUXTAPOSED THE THROAT PLATE AND INCLUDING A LOOPER THREAD SLACKENER AND A PICK-UP FINGER,

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