US2600424A - Presser foot mechanism for sewing machines - Google Patents

Description

June 17, 1952 T. J. O'LAUGHLIN 2,600,424

PRESSER FOOT MECHANISM FOR SEWING MACHINES Filed Oct. 10, 1950 2 SHEETS-SHEET 1 Inventor Thomas J OLaughlim June 1952 T. J. OLAUGHLIN PRESSER FOOT MECHANISM FOR SEWING MACHINES 2 SHEETS-SHEET 2 Filed Oct. 10, 1950 Inventor Thomas J OLaughlin Patented June 17, 1952 PRESSER FOOT MECHANISM FOR SEWING MACHINES Thomas J. OLaughlin, Boston, Mass., assignor to United Shoe Machinery Corporation, Flemington, N. J a corporation of New Jersey Application October 10, 1950, Serial No. 189,383

2 Claims. 1

The present invention relates to presser foot locking mechanism for shoe outsole sewing machines, more particularly of the type disclosed in United States Letters Patent No. 473,870, granted April 26, 1892, upon application of French'and Meyer, and No. 2,328,011, granted August 31, 1943, upon application of Haas, in which work to be sewed is intermittently clamped and released by the presser foot, the presser foot being locked in clamping position during each stitch forming cycle of the machine by a locking pawl engaging a ratchet connected rigidly to the presser foot.

In the machines of the patents referred to a single pawl is provided engaging a presser foot ratchet with teeth approximately 1% of an inch wide, the nib on the pawl acting reliably to lock the presser foot within a distance from its work clamping position equal to the full width of a ratchet tooth. Accordingly, the presser foot may move nearly of an inch away from clamping position in a direction to release the work before reaching a locked position. To enable the presser foot to be locked in substantially less than the width of a ratchet tooth from its work clamping position it has been proposed to provide two locking pawls, the nibs of which are spaced along the path of the ratchet by a distance equal to half the width of a tooth thereon. Where two pawls are used the presser foot is locked within of an inch from its clamping position. In some instances proper control of the work is partially lost as a result of insecure clamping action even where movement of the presser foot from clamping to locked positions is reduced to 3 2 of an inch. Consequently, it has been proposed that a number of additional spaced locking pawls be employed so that their nibs may engage the ratchet in a reliable manner to insure locking the presser foot within less than 3 2 of an inch from its work clamping position. However, it is necessary to actuate these additional locking pawls simultaneously to engage and disengage theratchet during each sewing cycle so that the work may be released for feeding movement from one stitch toanother and also at the end of a sewing operation the pawls are actuated by the operator to release the work for removal from the machine. These two releasing operations must be capable of being performed independently in a manner not to interfere one with the other.

To disengage the pawls from the ratchet at the v end of a sewing operation when two are used, one of the pawls carries a laterally projecting pin 2 engaged within a slot of a manually actuated link, the pin projecting into the path of the other pawl. The pawls are normally actuated to en gage the ratchet by individual springs and are actuated to disengage the ratchet during sewing by a lever driven from a cam on the main sewing shaft, which lever cooperates with a surface on an arm projecting from each pawl. If the nib on the pawl not carrying the pin is opposite a space between two ratchet teeth while the nib on the pin carrying pawl is in alignment with the point on one of the teeth then the pin carrying pawl will hold the other pawl partially out of the space between the teeth and much of the advantage gained by the additional pawl is' lost through insecure locking action. To avoid this difficulty the pin on the pin carrying pawl may be arranged to engage a surface on the additional pawl only after the nib on the pin carrying pawl has moved the full depth of a space between the teeth. Consequently, to disengage the pawls manually from the presser foot ratchet in a machine having two pawls it is necessary to move the manually actuated link a distance equal at least to twice the depth of a ratchet tooth. If the number of pawls for locking the presser foot in the machine is increased above two'then a still greater movement will be required to disengage them from the ratchet. Such movement of the manually actuated link however is greater than is permissible by the presence of the other operating parts in the machine or by the space available for a sufficiently rigid and effective looking pawl manual releasing mechanism.

The objects of the present invention are to improve the operation oi' a presser foot locking and releasing mechanisms for a shoe outsole sewing machine of the type referred to, which will be effective with more than two locking pawls,,without increasing the required length of movement for the manual pawl releasing mechanism, while at the same time obtaining full advantage of an increase in the number of locking pawls for'such mechanism. A further object is to simplify and improve the operation of the locking pawls and presser foot mechanism for such machine.

The features of the invention as hereinafter described and claimed for the accomplishment of the objects referred to will be apparent from the following detailed specification taken in connection with the accompanying drawings, in which Fig. 1 is a sectional view looking from the right side of so much of a sewing machine embodying the invention as is required for an understanding of it;

Fig. 2 is a detail view on an enlarged scale of a set of locking pawls and a portion of a ratchet engaged thereby in the machine of Fig. l with the pawls disengaged from. the ratchet during sewing operations;

Fig. 3 is a similar view of the same parts with the pawls engaged with the ratchet; and

Fig. 4 is a similar view of the same parts showing the pawls disengaged from the ratchet in positions assumed when the manually actuated releasing mechanism is operated.

The illustrated machine is a Goodyear shoe outsole sewing machine provided with lock stitch forming devices and means for supporting the projecting marginal portions of a shoe in sewing position in the machine. The stitches are formed in the usual way and the work is fed a stitch length after each stitch formation, the work being clamped in operating position during stitch formation. Unless both the feeding and clamping actions are positive and secure the stitches will be inserted improperly requiring frequent stoppages from thread breakage and for adjustments.

Referring more particularly to Fig. 1 of the drawings, the stitch forming devices include a curved hook needle 6 and a. curved work penetrating and feeding awl 8. To clamp the work during stitch formation, it is guided along a fixed work support I and engaged by a presser foot I2 acting in timed relation to the stitch forming devices to secure and release the work. In clamping the work the presser foot is depressed against it with a predetermined pressure and thereafter the presser foot is locked in clamping position. To release the work the presser foot is unlocked, the clamping pressure being relieved so that during feeding movement the work slides easily beneath the presser foot.

To look and unlock the presser foot it is rigidly connected to a presser foot lever 14 pivoted at IS on the frame of the machine and connected to a locking mechanism of particularly advantageous construction and mode of operation. The lever 14 is provided at its rearward end with a ratchet in the form of a block l8 formed with arcuately disposed teeth moving in a fixed path about the pivot I6 concentrically to the curvature of the line of teeth. The teeth on the ratchet block are cut with sufiicient width and depth,

at least of 1% of an inch dimensions, to resist I relatively heavy forces required in clamping and locking the work. Cooperating with the teeth of the ratchet is a pawl 2t and one or more additional pawls rotatable on a single pivot 22,

as will be more fully described. The pawl is arm 24. Above the arm 24 the bolt is surrounded by a sleeve 28 and a compression spring 30 engaged at its upper end by check nuts 32 on the bolt and at its lower end by the sleeve 28. The check nuts are adjusted to exert a relatively heavy force on the presser foot in clamping the work. This force is regulated in accordance with the thickness and quality of the work parts operated upon, which ordinarily are an outsole 34 and a welt 36 of a Goodyear welt shoe.

For actuating the clamping arm 24 for the presser foot it carries at its rearward end a ratchet block 38 engaged by a multitoothed pawl 40. The pawl 40 is pivotally mounted on a lever 42 fulcrumed on a shaft 44 and driven from a cam 46 secured to a main sewing shaft 48 of the machine. The pawl 40 is yieldingly actuated into engagement with the ratchet block by a spring pressed plunger 50 carried by the cam lever 42. During operation of the machine the pawl'40 is raised while engaging the ratchet block 38 to impart a work clamping force to the presser foot, the spring 38 being compressed a predetermined amount. The presser foot is locked in clamping position when the pawl 20 engages the nearest tooth on the ratchet block l8 after which the force of the actuated pawl 40 is relieved by downward movement thereof. The presser foot is displaced and raised slightly from clamping to locked positions as the force of the pawl 46 is relieved until the nearest tooth on the ratchet actually is engaged.

If the single pawl 28 is employed then the presser foot may not be locked until a displacement takes place equal to the width of a single tooth on the ratchet block Hi from the clamped position assumed under the force of the clamping spring 30. If the width of each tooth on the locking ratchet I8 is 3 6 of an inch then the presser foot may be displaced a corresponding distance from its clamped to its locked position when the force of the clamping arm is relieved. In many instances this displacement of the presser foot from clamped to locked positions may so reduce the grip of the presser foot on the work that the work can move easily during formation of a stitch in a manner not conducive to effective stitch formation. Where a seam is being sewn close to the edge of a heavy outsole it may become disengaged entirely from the work support under these conditions.

To avoid difficulties of the nature referred to and to provide a locking pawl arrangement which will prevent undesirable displacement of the presser foot from clamping to locking positions under all conditions through a sufficient distance to have a-detrimental eifect on the secure location of the work in the machine, by a convenient manner in the illustrated construction, four locking pawls including the pawl 20 and additionally those indicated at 52 are rotatably mounted on the same pivot 22 to cooperate with the pawl 20 and provided with individual additional springs 23. The pawls have nibs 54 spaced along the path of movement, indicated at 56, for the teeth on the ratchet block, each by a distance equal to a quarter of the width of a ratchet tooth. In other words the nibs on the pawls are spaced unequal distances radially from the center of their pivot 22, the difference between the spacings being a quarter width of a ratchet tooth, or an of an inch. Thus, any one of the pawls may become engaged to the full depth of a ratchet tooth within a quarter of its width from the position determined by the clamping pressure on the presser foot.

To unlock the presser foot the ratchet block [8 is disengaged simultaneously from the looking pawls 20 and 52. All of the locking pawls are provided with symmetrical rearwardly projecting arms 5'! formed with surfaces disposed in 'alinement when the pawl nibs are alined in parallel relation to the path 56 of the ratchet teeth (see Fig. 2). Cooperating with these surfaces to disengage the pawls is a. lug 58 projecting downwardly from the cam lever 42. The

cam lever moves downwardly in each sewing cycle within a short time after the work is clamped but the lug 58 does not actually engage the surfaces of the arms 56 on the pawls until approximately the extreme lower end of its downward movement. At the same time that the pawls are disengaged from the ratchet block I 8 the clamping pawl 48 is disengaged from the ratchet block 38 so that no substantial pressure is exerted on the presser foot while the work is being fed. To this end the actuating pawl 40 is engaged with a fixed stud 60 in the machine frame, acting to withdraw that pawl from the ratchet block 38 when the cam lever 42 is at the lower end of its downward movement.

To enable the work to be released from the prior patented machine at the end of a seam regardless of the stopping position of the main sewing shaft 48 the presser foot lever 24 has secured to it a hand operated lifting lever 82 and the presser foot pivot It has rotatably mounted on it a manual unlocking lever 64 both of which have their upper ends disposed in readily accessible positions. Due to inherent restrictions in the location of the locking lever from the presence of surrounding parts of the patented machine the movement of the unlocking lever is relatively limited. Its upper end is maintained normally in rearward position by a spring 63 stretched between the lever and the machine frame. The lowerend of the unlocking lever carries a slotted link 88 pivotally connected to the lever with its slot surrounding a pin 10 on the pawl 28, the length of the slot in the link being sufiicient to enable the pawl 28 to enter to the full depth of a tooth on the ratchet block I8 during sewing. The link 68 has also an upward projection arranged to engage a pin 12 on the actuating pawl 60 to disengage that pawl also from the ratchet 38 when the manual unlocking lever is pulled forwardly at' its upper end.

If the pin 18 on the locking pawl 20 is located with respect to the additional locking pawls 52 in such position that all of the nibs 54 are alined in parallel relation to the path 56 of the teeth on the ratchet block I8 as in Fig. 2, when the unlocking lever 64 is actuated forwardly, then the additional pawls 52 may be held at least partially out of the path of the ratchet teeth during sewing if the pawl 28 engages with the point of one of the teeth. The other pawls are then prevented by engagement with the pin 10 from entry to the full depth of a tooth. If a nib on a locking pawl engaging the ratchet does not enter an opening on the ratchet i3 to the full depth of the engaged tooth then the force of the tooth on the nib of the pawl engaged thereby may be sufiicient to cause injury to the point of the tooth or to the nib of the pawl, the surfaces engaged being of inadequate area to resist the force on the presser foot. If the pin 18 is located with respect to the pin engaging surfaces of all the pawls 52 in such relation that each of the pawl nibs is displaced from an adjacent nib by a distance equal to the full depth of a ratchet tooth then it becomes impossible to disengage all of the pawls from the ratchet block on account of the limited movement available in the unlocking lever 64. It is necessary in this latter instance to move the pin 10 at least four times the depth of a ratchet tooth.

To obviate the difficulties of disengaging a plurality of locking pawls in addition to the main locking pawl 28 which carries the pin 18 whenthe manual unlocking lever 64 is operated, in accordance with the present invention, all of the pawls 52 are provided with concave surfaces '14 located to engage the pin 70, all the surfaces being disposed in the same setback relation to said pin when the pawl nibs are alined in parallel relation to the path 5% of the ratchet teeth, as when all of the pawls are disengaged from the ratchet teeth by the projection 58 on the cam lever 42 (Fig. 2). When the manual unlocking lever is actuated with the surfaces 75 thus located, the pin carrying pawl 28 is first Withdrawn completely from the path of the ratchet teeth by the slotted link 68 a distance at least equal to the depth of the ratchet teeth before the nibs on the other three pawls are completely with-drawn from said. path.

The positions of the pawls when manually withdrawn from the ratchet path are shown in Fig. 4. The movement of the link 88 during withdrawal of the pawls does not then exceed the movement of the manual unlocking lever 64 beyond its limiting positions.

If during operation of the machine equipped with the improved pawls the pin carrying pawl 28 engages the point on a ratchet tooth, as illustrated in Fig. 3, a shorter additional pawl 52 is permitted to move into the full depth of the ratchet tooth without having the surfaces 14 thereon engage the pin 78. Complete withdrawal of all the pawls from the path of the ratchet teeth by the cam lever 32 then takes place simultaneously, to the position of Fig. 2. When the machine is stopped and the unlocking lever actuated forwardly manually by the operator the pawl Zilis first disengaged and the pawls 52 disengaged thereafter. When the machine is restarted and the locking pawls are reengaged with the ratchet teeth after being manually disengaged by the operator, at least one moves immediately from its disengaged position of Fig. 4 to that of Fig. 3 without any possibility of engagement to the partial depth of a tooth and with the certainty that the presser foot will be locked securely during the first stitch formation in engagement with the work within a distance from its clamping position of less than a quarter the width of a ratchet tooth. Reducing the displacement from clamping to locking positions of the presser foot during the first stitch formation assists materially in improving the operation of the machine both in retaining the work in the machine during the first stitch and preventing its movement during subsequent stitch formations. Accordingly, the machine equipped with the illustrated locking pawls inserts stitches more accurately and enables the work to be guided with less effort and special precaution on the part of the operator than heretofore considerd possible with this type of sewing machine.

The nature and scope of the invention having been indicated and an embodiment having been described what is claimed is:

1. An outsole sewing machine having a main sewing shaft, a curved hook needle and other stitch forming devices for inserting a lockstitch seam, work clampingdevices including a work support and a presser foot and mechanism for locking and releasing the presser foot from clamping engagement with the Work during operation of the stitch forming devices comprising a toothed ratchet connected to the presser foot and mounted for movement in a fixed path, a pin '7 carrying pawl arranged to engage the ratchet,- a pivot for the pin carrying pawl and a plurality of cooperative pawls on the pin carrying pawl pivot, all of said pawls having nibs spaced unequal distances radially from the said pivot to engage the ratchet at a number of points spaced along the width of a single tooth and having symmetrical arms formed with surfaces disposed in alinement when the pawl nibs are alined in parallel relation to the ratchet path, individual springs for pressing the pawls toward the ratchet, a lever driven from the sewing shaft engaging the surfaces of the arms on the pawls to move them simultaneously out of the path of theratchet, a manually actuated lever for disengaging the pawls from the ratchet at the end of a seam to release the work from the presser foot and a link actuated by the manually actuated lever, said link having a slot connection with the pin on the pin carrying pawl, in combination with pin engaging surfaces on the pawls other than that carrying the pin disposed in setback relation to said pin when the nibs on the pawls are alined in parallel relation to the ratchet path to cause the pin carrying pawl nib to be withdrawn through a distance equal to the depth of the ratchet teeth from the path of the ratchet before the nibs on any of the other pawls are withdrawn from said path, the setback surfaces of all the pawls other than that carrying the pin having the same spacing relatively to the path of the ratchet path when engaged by the pin of the pin carrying pawl to cause all the pawls other than that carrying the pin to be withdrawn from the path of the ratchet path together.

2. A shoe outsole sewing machine having a main sewing shaft, a curved hook needle and other stitch forming devices for inserting a lockstitch seam, work clamping devices including a work support and a presser foot, mechanism for locking and releasing the pr-esser foot from clamping engagement with the work during operation of the stitch forming devices comprising a toothed ratchet connected to the presser .foot and mounted for movement in a fixed path, a pin carrying pawl arranged to engage the ratchet, a fixed pivot for the pin carrying pawl, three other pawls on the pin carryingpawl pivot having nibs arranged to engage the ratchet but spaced unequal distances radially from said pivot to engage the ratchet at points along the width of a single tooth separated from the point engaged by the pin carrying pawl, all of said pawls having symmetrical arms formed with surfaces disposed in alinement when the pawl nibs are alined in parallel relation to the ratchet path, individual springs for pressing the pawls toward the ratchet, a lever driven from the main sewing shaft .for moving the pawls simultaneously out of the path of the ratchet, a manually actuated lever for disengaging the pawls from the ratchet at the end of a seam to release the work from the presser foot and a link actuated by the manually actuated lever having a slot connection with the pin on the pin carrying pawl, in combination with pin engaging surfaces on the three pawls other than that carrying the pin disposed in the same setback relation to said pin while the shaft driven lever engages the alined surfaces on the pawl arms for causing the pin carrying pawl nib to be withdrawn by a distance equal to the depth of the ratchet teeth from the path of the ratchet before the nibs on the other three pawls are withdrawn from said path.

THOMAS J. OLAUGHLIN.

REFERENCES CITED UNITED STATES PATENTS Name Date Sheffield et a1. May 14 1935 Number

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