US3575121A - Sewing machine construction - Google Patents

Abstract

A sewing machine having a mechanism for disengaging the needle bar of the machine from the drive mechanism when the needle carried by the needle bar hits an impenetrable object such as a button, zipper or piece of material. The disengaging mechanism of the preferred embodiment includes an elongated sleeve containing a needle bar tensioned to a fixed axial position within the sleeve by axially aligned spring means and other elements adapted to remain in the axial position under normal operating forces but adapted to permit the needle bar to move axially with respect to the sleeve upon application of abnormal forces when one of the elements is thrown out of normal position. In a modification the disengaging mechanism includes a collar surrounding the needle bar and carrying a spring tension ball bearing adapted to move between a depression in the longitudinal groove in the needle bar. An electrically controlled breaking mechanism disengages the power source of the sewing machine when the needle bar is disengaged in either of the embodiments.

Description

United States Patent 1965 now abandoned. [45] Patented Apr. 13, 1971 [54] SEWING MACHINE CONSTRUCTION 5 Claims, 16 Drawing Figs.

[52] US. Cl 112/221 [51] Int.Cl D05b 69/36 [50] Field of Search 112/221 [56] References Cited UNITED STATES PATENTS 717,848 l/l903 Hatch l 12/221 1,574,184 2/1926 Brigham et al... 112/105 2,218,123 10/1940 Smith 112/221X 2,318,200 5/1943 Cobble et al 112/221X FOREIGN PATENTS 938,946 2/1956 Germany ABSTRACT: A sewing machine having a mechanism for disengaging the needle bar of the machine from the drive mechanism when the needle carried by the needle bar hits an impenetrable object such as a button, zipper or piece of material. The disengaging mechanism of the preferred embodiment includes an elongated sleeve containing a needle bar tensioned to a fixed axial position within the sleeve by axially aligned spring means and other elements adapted to remain in the axial position under normal operating forces but adapted to permit the needle bar to move axially with respect to the sleeve upon application of abnormal forces when one of the elements is thrown out of normal position. in a modification the disengaging mechanism includes a collar surrounding the needle bar and carrying a spring tension ball bearing adapted to move between a depression in the longitudinal groove in the needle bar. An electrically controlled breaking mechanism disengages the power source of the sewing machine when the needle bar is disengaged in either of the embodiments.

Patented April 13, 1971 3,575,121

8 Sheets-Sheet l INVENTOR FELIX LBERUBE ATTORNEYS Patented A iril 13, 1971 3,575,121

'8 Sheets-Sheet '2 mvgNToR FELIX JBERUB'E Patented April 13, 1971 Y 3,575,121

8 Sheets-Shut 4.

INVENTOR FELIX J.BERUBE BY PatentedQApril 13, 1971. 3,575,121

8 Sheets-Sheet 5 WWWM I Pategiied April 13, 1971 3,575,121

8 Sheets-Shoot 6 O Q M/VEA/TOR EW Patented 7 April 13, 1971 8 Sheets-Sheet 8 SEWING MACHINE CONSTRUCTION CROSS-REFERENCE TO RELATED APPLICATIONS This is a division of US. application Ser. No. 722,522, filed Apr. l, 1968, now US. Pat. No. 3,47l,325, dated Oct. 7, 1969, which in turn was a continuation-in-part of Ser. No. 668,283, filed Aug. 30, 1967, now abandoned, which, in turn, was a continuation-in-part of Ser. No. 432,642, tiled Feb. l5, I965, also now abandoned.

BACKGROUND OF THE INVENTION This invention relates to sewing machines and more particularly to sewing machines of the type employing needle bars.

Sewing machines for industrial and home use may be easily damaged by malfunctions or misuse of the machine. For

example, in stitching zippers, buckles, snaps, buttons and other metal or hand attachment to a fabric, it is quite possible inadvertently to bring the metal or hard portion of the article into the path of the needle. In such an event, the needle will usually break or bend. Before the machine can be stopped, the broken or bent needle may damage the fabric being stitched or further damage the sewing machine. A broken or bent needle or even a needle which is slightly misaligned can readily strike the sewing machine plate or some of the mechanism below the plate, necessitating delays and expensive repairs. In addition, such a malfunction may jam the needle which in turn may cause the sewing machine motor which continues to operate during the jam to burn out. In addition, the misuse or malfunctioning of a machine may cause injury to the operator. Such an injury may occur, for example, when the operators fingers are close to the needle at the moment the needle is bent or broken when it strikes a resistant materialsuch as a zipper or a button. Such problems are particularly acute in high speed industrial machines.

SUMMARY OF THE INVENTION It is an object of the present invention to overcome these and other problems by providing a sewing machine construction which is not likely to jam or malfunction when the machine is misused by engaging the pointed end of the needle with a resistant material. It is an object of the present invention to provide an improved sewing machine construction in which needle breakage or damage for reasons such as set forth above are minimized or substantially eliminated. A further object of the present invention is to provide a sewing machine construction in which damage to the sewing machine and its component parts including its motor and injury to operators are minimized. Such advantages are attained by providing a construction in which the needle bar is automatically disengaged from its drive mechanism if the needle is inadvertently engaged by an impenetrable material.

A further object of this invention is to provide a relatively inexpensive sewing machine construction wherein likelihood of damage to the sewing machine head and injury to the operator are minimized.

A further object of this invention is to provide a means in which a sewing machine needle is automatically operatively disengaged from its drive mechanism if the needle hits a foreign impenetrable object, and in which the needle is automatically reengaged with the drive mechanism upon removal of the foreign object.

A further object of this invention is to provide a sewing machine construction in which the motor drive for the needle bar may be automatically turned off or disengaged when the needle engages a foreign impenetrable body.

A further object of this invention is to provide a sewing machine construction in which the needle bar may be rotated.

for threading convenience by a needle bar connecting stud.

A further object of this invention is to provide a sewing machine construction which is not only relatively inexpensive but is also rugged, capable of standing considerable abuse, and is easily and inexpensively repaired.

A further object of this invention is to provide a sewing machine construction having a needle bar which can be automatically disengaged from its drive mechanism in industrial sewing machines operating at extremely high speeds if the needle hits a foreign impenetrable object with the needle automatically reengaging with the drive mechanism upon removal of the foreign object.

In the present invention there is provided a sewing machine construction having a needle bar formed of an elongated shaft with an elongated groove extending longitudinally in the shaft. A depression is formed in the shaft in alignment with the groove and is defined from the groove by an intermediate ridge. A second ridge, if desired, also may be formed in the shaft and extends in a direction circumferential to the depression. A collar or stud supports and surrounds the needle bar. The collar is reciprocated up and down by a suitable drive means connected to a motor drive source. The motor drive source is provided with an on-off switch which may be positioned within the sewing machine head. Means are provided for interengaging the collar and the needle bar, with the collar normally interengaged with the depression and adapted to reciprocate the needle bar and needle carried with it when the collar is so normally engaged. Such interengaging means are spring-tensioned or otherwise suitably arranged so that the collar will move from engagement with the depression to engagement with the elongated groove of the needle bar when a needle carried by the needle bar meets an unusual amount of resistance. When this occurs the collar rides up and down on the needle bar with the needle bar thereby operatively disengaged from the drive mechanism. When the obstruction is removed the collar automatically reengaged the depression and the needle and needle bar are automatically reengaged. Means may be connected to the needle bar for switching the motor off when the collar moves from a normal position in engagement with the depression. Means are also provided for limiting movement of the needle bar in one direction so that the collar will automatically reengage the depression once in each complete cycle of movement of the collar when it is in the nonnormal or nonoperating position of engaging the elongated slot.

In a preferred form of the invention designed for use in industrial sewing machines an elongated tubular sleeve is supported and secured for vertical movement by a collar which is reciprocated by a suitable drive means. The sleeve in turn has its upper end reciprocating in a bushing secured to the machine. A needle bar positioned at the lower end of the sleeve is axially aligned with a heavy spring and elements that are normally designed to be positioned axially with respect to the needle bar. On engaging an impenetrable object one of the elements is axially disengaged from another to permit relative movement of the needle bar and sleeve. A return spring means is provided to return the needle bar to its initial position when it disengages from the impenetrable object.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 4 is an enlarged, fragmentary cross-sectional elevation of the needle bar;

FIG. 5 is a cross-sectional view taken along the line 5-5 of FIG. 4;

FIG. 6 is a fragmentary elevation of the needle bar;

FIG. 7 is a cross section taken along the line 7-7 of FIG. 6;

FIG. 8 is a cross section taken along the line 8-8 of FIG. 6;

FIG. 9 is a cross-sectional fragmentary elevation of the sewing machine head with a needle bar construction of an embodiment designed particularly for high speed industrial machines shown in a retracted position;

FIG. 10 is a cross-sectional fragmentary elevational view of the sewing machine head of FIG. 9 with the needle bar in a down position;

FIG. 11 is a partially cross-sectional elevational enlargement of the needle bar assembly looking from the right of FIG. 10;

FIG. 11A is a cross-sectional view taken on the line llA-11AofFIG.1l;

FIG. 12 is a cross-sectional elevation of a needle bar assembly of FIG. [1 looking from the left side thereof;

FIG 13 is a cross-sectional elevation of a needle bar assembly embodying a further modification of the present invention;

FIG. 14 is a cross-sectional fragmentary elevation of a sewing machine head with a needle bar construction of a preferred embodiment designed particularly for high speed industrial machines; and

FIG. 15 is a fragmentary cross-sectional elevation on an enlarged scale of the bar connection shown in FIG. 14.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention is adapted for use with a wide variety of conventional sewing machines. Consequently, the portions of the sewing machines now shown or otherwise described may be conventional in nature. In the embodiment illustrated, the sewing machine casing 1 has a head 2 to which power is supplied from shaft 3. A lever linkage system 4 interconnects the main drive shaft 3 with the needle bar 5. This linkage system 4 includes a lever 6 connected to shaft 3 and in turn connected to the pitman 7 through a pin 8. The needle bar is supported in upper and lower journals I0 and 11 for vertical movement. Suitable and conventional bushings and locknuts may be positioned at the upper end of the journal as illustrated at 13 to retain the bushing 10 in position and to help support and limit movement of the needle bar 5. Also positioned within the sewing machine head 2 is an on off switch 14 suitably supported by support within the casing. This switch is connected by wires 16 to the motor (not shown) that operates the drive shaft 3. The button 18 of the switch 14 is engaged by and normally controlled by the spring 19 which extends vertically in the casing head 2 with the upper end of the spring 19 engaging the button 18. The upper end of the spring 19 is looped at 20 with one leg of the loop suitably supported on and secured to the switch by a collar and nut arrangement 21. If desired, a light 24 may be supported within the casing head 2 to illuminate the interior of the head when it is open. This light may be supported on a shaft 25 in turn secured at its upper end to an inwardly extending flange 27 by means of a support means 28.

The needle bar construction is best illustrated in FIGS. 4 to 8. The needle bar is formed with a depression 30 in its surface at a point from the ends of the needle bar such that a collar 31 carried by the pitman 7 will move the needle bar in a normal up and down stroke during operation of the machine.

The depression 30 should have sufficient depth to receive a projecting portion of a ball bearing 32 (FIGS. 4 and 5). The lower wall or ridge 34 and a sidewall or ridge 35 that form the depression 30 preferably should be somewhat lower than the curvature of the surface on the bar 5 so as to permit movement of the ball bearing 32 from the depression in directions over the ridges or walls 34 and 35 in a control fwrhion. Longitudinally aligned with depression 30 and extending downwardly from the depression a distance of approximately at least one-fourth the length of the needle bar is an elongated channel or groove 37. This channel or groove 37 is fonned in the surface of the needle bar and has a width sufficient to permit vertical movement of the ball bearing 32 in the channel or groove 37. A laterally extending groove or channel 38 is also formed on the surface of the needle bar in lateral alignment with depression 30. The groove 37 is defined from the depression 30 by the ridge 35.

The collar 31 which supports the needle bar is an annular member having a neck 40 projecting into a collar 41 integral with the lower end of the pitman 7. The collar 31 is formed with a longitudinal opening within which is disposed a spring 44 positioned immediately behind the ball bearing 32. A screw 45 secures the spring within the neck 40 and maintains the spring in adjustable pressure engagement with the ball bearing 32. Ball bearing 32 is secured within the collar by engagement with the walls of the needle bar 5. In a normal operative position the ball bearing 32 is positioned within the depression 30 as illustrated in FIG. 4. If desired, a screw 48 may be threaded through the collar on the side opposite to the collar 41 for selectively securing the collar 41 to the needle bar 5 in fixed substantially permanent relationship for an operation under certain conditions. The screw 48 may be used to secure the elongated leaf spring 51 to the collar. This leaf spring is formed with offset sections 52 and 53 interconnected by member 54. Lower offset section 53 is secured to the collar 31 by the screw 48. The pin 50 projects outwardly from the needle bar 5 and is normally positioned immediately adjacent and in contact with lower offset section 53 of the spring 51. The pin 50, however, may be moved relative to the spring 51 into engagement with the interconnecting member 54 as hereinafter described.

The needle bar 5 is provided with a collar 67 positioned below the bottom wall 68. Removably secured to the needle bar below the bottom wall is the grip 70 and a needle 60.

The operation of this invention may be understood from consideration of FIGS. 1 to 3. FIG. 1 shows the machine in normal operation with the needle bar in an up position. In this arrangement the ball bearing 32 engages the depression 30. On rotation of the drive shaft 3 the needle bar is reciprocated up and down. FIG. 2 shows the normal operation of the machine with the needle 60 in its down position. Here again, the ball hearing 32 normally engages the depression 30 as it did in the up position illustrated in FIG. 1. In these positions the spring 51 is carried by the collar 31 with the pin 50 normally engaging the lower offset section 53 of the spring 51 and in both of these positions the switch 14 is not depressed.

When the needle 60 hits an impervious material, such as a metal plate 63 or a zipper, the needle 60 and consequently the needle bar 5 are restrained from normal movement. When this occurs, ball bearing 32 which serves to key the collar 31 of the driving mechanism to the needle bar rides out of the depression 30 and into the elongated slot or channel 37. When the ball bearing 32 is in the slot 37 the needle bar 5 and the needle 60 remain substantially motionless and in engagement with the impervious material 63. The downward movement of the collar 31 causes a relative movement of the spring 51 to the pin 50. This, in turn, causes the spring 51 to move away from the needle bar 5 as the pin 50 passes over the interconnecting portion 54. This movement of the spring 51 presses the spring 19 which in turn presses the button 18 of the switch M and causes the motor driving the shaft 3 to turn off. The operator may the remove the impervious material 63. After this is done the drive shaft 3 may be turned by hand until the collar 31 recycles to its uppermost position. When it recycles to its uppermost position the collar 31 will move out of the elongated groove 37 and into the depression 30, thereby automatically resetting and retiming various components so that they assume the positions illustrated in FIG. 1. The needle bar 5 which may move with the collar 31 due to the friction between the ball bearing 32 and the sides of the groove 37 is limited in its upward movement by engagement of the collar 67 with the bottom 68 of the casing head.

The machine may operat without a switching mechanism, such as shown at 18, 19, 14. In such an arrangement the drive will continue to operate until the operator stops the machine.

But, while it is operating the ball bearing 32 will move in and out of the depression 30 once each complete cycle of the drive shaft 3. When this occurs, the needle bar 5 will be disengaged on each downward movement of the collar 31 and reengaged upon each upward movement of the collar 31. Thus the needle bar and the needle 60 will have no significant downward force while the impervious material 63 is still obstructing the normal movement of the needle 60.

The lateral groove 30 may be used for ease in rethreading the needle 60. Quite often it is easier for the operator to thread the needle 60 if the needle can be turned at right angles. By utilizing a needle bar such as illustrated, the operator may rotate the needle 60 by turning the grip 7090. This, in turn, will cause the ball bearing 32 to move from the depression 30 into the lateral groove 38 thereby rotating the needle 60 90 so that the eye in the needle faces the operator. Thus as groove 30 is laterally aligned with the depression 30, the operator may readily return the needle bar to its normal position by reengaging the ball bearing 32 with the depression 30.

Referring now to FIGS. 9 to 11 inclusive, there is illustrated an embodiment of the invention designed especially for use with high speed industrial sewing machines in which the very high speeds of operation require use of a mechanism in which the effects of inertia are minimized. In this embodiment the sewing machine casing 1, head 2, shaft 3 and lever linkage system 4 may all be similar to the arrangement previously described. Similarly the on-off switch 14, support 15, wires 16, button 10, spring 19, loop 20, collar nut arrangement 21, light 2 1, shaft 25, inwardly extending flange 27 and support means may be similar in construction to and may be used for purposes similar to the correspondingly numbered elements previously described. in this embodiment the spring 19 may be modified as desired so as to properly be engaged by the actuating mechanism of the needle bar hereafter described.

In this modification the needle bar construction generally illustrated at 100 includes includes an elongated sleeve 101 which is secured to the driving mechanism by collar 31, similar to collar 31 of the previously described embodiment. The tubular sleeve 101 is adapted to be moved axially by the collar 31 with the upper end of the sleeve 101 guided for vertical movement by the bushing 102. Thisbushing 102 is in turn threadingly engaged in the upper end of the casing 1 and may be provided with external threads adapted to permit vertical adjustment of this bushing. Preferably this bushing 102 is provided with a horizontal lower edge 103. A needle bar 104 having a conventional lower end is positioned with is upper end extending into the sleeve 101. This needle bar 104 has a portion 105 that acts as a bearing surface in engagement with the inner surface of the sleeve. The upper end of the needle bar has a section 106 that is flattened or removed to provide a longitudinal space 107. The section 106 in addition to being flattening along one longitudinally extending segment is also of smaller cross-sectional diameter than the lower portion of the needle bar so as to permit the encirclement of this segment 106 by an elongated helical fine spring 100. This spring 100 engages the shoulder 100 formed between the lower portion of the needle bar 104 and the segment 106. The upper end of the fine spring 100 engages a flange 110 that is integrally formed with the segment 106 with the outer periphery of the flange 110 acting in bearing engagement with the inner surface of the sleeve 101. A pin 111 extends across and through the sleeve 101 with the pin 111 positioned in the space 107 and adapted to engage the flattened surface segment of the needle bar to prevent the needle bar from inadvertently rotating. This pin 111 also engages the flange 110 and prevents removal of the needle bar 101 from the sleeve 101. This pin 111 also engages the fine spring 108 at its upper end and is adapted to compress this spring thereby exerting downward tension on the needle bar, in the event the needle bar is moved upwardly relative to the sleeve 101. Extending upwardly from the flange 110 and preferably integrally formed with the needle bar 104, is a vertically extending pin 112. This vertically extending pin 112 is adapted to extend freely through a coaxial hole in the plug 113. Plug 113 is free to move within the sleeve 101. The lower end of plug 113 is supported in spaced relation from the flange by a relatively heavy spring 114 with respect to the light spring 100. The spring 114 has a lower end that engages the upper surface of the flange 110 and an upper end that engages the lower surface of plug 113 with this spring 114 coaxial with pin 112. The upper end of the vertical pin 112 is coplanar with the upper end of the plug 113 under normal conditions with these coplanar ends normally adapted to engage the lower end 115 and the locking arm 116. This locking arm 116 is pivotally secured at is upper end 117 to a plug 110 with the plug 118 normally flxed within the upper end of the sleeve 101. The plug 110 is fixed within the sleeve by means of a horizontally extending setscrew 119 that extends horizontally through the plug 110 and is adapted to be tightened against the inner surface of sleeve 101. This setscrew 119 is thus used for minor vertical adjustments of the plug. The setscrew 119 may be adjusted through an enlarged hole 120 in the upper end of sleeve 101. A setscrew 121 closes the upper end of the sleeve 101 and secures the plug 119 against movement from within the sleeve 101.

The locking arm 116 is adapted to pivot from a position extending longitudinally within the sleeve 101 in which the lower end 115 of the locking arm is in' engagement with the upper surface of the plug 113 with the boss engaging groove 131, to a position in which the locking arm 116 has pivoted through a slot 122 in the sleeve 101 so that the lower end 115 of the locking arm is disengaged from the plug 113. The outward pivoting of this locking arm, as illustrated in FIG. 11, is limited by engagement of the locking arm with the lower edge 103 of the bushing 102.

ln the operation of this device, the needle bar is disengaged from the driving mechanism when the needle carried by the needle bar hits a foreign, impenetrable object. Under these circumstances, the needle bar is restrained against downward movement as the sleeve 101 moves downwardly. This downward movement of sleeve 101 carries the plug 119 downwardly thereby forcing the lower end 115 of the locking arm 116 downwardly with increased force against the plug 113. This causes the plug 113 to move downwardly against the force of the heavy spring 114. ln turn, the upper surface of the plug 113 is moved downwardly below the upper surface of pin 112 thus causing the smaller pin 112 to exert a significant force against the arcuate surface 115 of the locking arm 116. This localized force on the arcuate surface 115 causes the pin 112 to disengage boss 130 and slot 131 and kick the locking arm out of the slot 122 thereby allowing the sleeve 101 to reciprocate freely and independently of movement of needle bar 104 as the drive mechanism is still operating. The upward movement of sleeve 101 on the return cycle after the obstruction has been removed, causes the lower edge of bushing 102 to force the arm 116 back to its original position. At the same time the upper surface of pin 112 is retracted to the level of the upper surface of plug 113 when the pin 110 carried by the sleeve 101 has compressed spring 108 thereby causing the upper end of pin 112 to be retracted within plug 113. Thus, the return of the locking arm 116 is not blocked by 1 the upper end of pin 112. A master on-off control may be actuated by a spring 19A as desired by the operator. In the event the on-off control is made operative, it will function in the same fashion as previously described in connection with switch 14 of FIG. 1.

Referring now to the embodiment illustrated in FlG. 13, there is shown a needle bar 200 of conventional design which in turn may be engaged by a collar 31 of the type previously described. This needle bar 200 is provided with a suitable key to prevent rotation of the needle bar within the sleeve 201. The upper end of this needle bar 200 is engaged by a helical spring 202 that extends longitudinally within the sleeve 201. The upper end of this spring 202 is engaged by a setscrew 203 that is threaded downwardly into the upper end of the sleeve 201. Thus, in this arrangement, the particular adjustment of the setscrew 203 may be used to provide a tension on the upper end of the needle bar 200 forcing it downwardly against restraint of pin 205 which also functions as the abovementioned key extends through an elongated vertical slot 206 in the needle bar 200. Pin 205 is anchored in sleeve 201 and as illustrated at the upper limit of slot 206. When a needle carried by the needle bar 200 is restrained by an impenetrable object, it permits relative movement of sleeve 201 and bar 200 with the degree of movement being determined by the relative adjustment of the setserew 203 and the strength of the spring 202.

There is illustrated in F105. 14 and 15 an embodiment which is particularly useful and intended for extremely high speed industrial machines. This embodiment is designed to operate on industrial sewing machines that have speeds in the order of 4,500 rpm. or more. The modifications previously discussed are not intended for continuous operations in sewing machines that operate at these relatively high speeds. The construction shown in FIGS. 14 and 15 is an integral unit capable of being easily and quickly installed without special equipment or training by a sewing machine operator.

In this arrangement the needle bar 300 is provided with an end 301 adapted to have a conventional sewing needle secured to it in a conventional fashion. The other end 302 of the needle bar extends into a support means generally illustrated at 303. The embodiment illustrated in this support means comprises generally an elongated sleeve with the needle bar 300 having its end 302 extending into it. Support member 303 is secured to drive member 310 of the sewing machine by a collar 311 having suitable keying means for rigidly interengaging the collar 311 to the member 303. Thus on operation of the drive mechanism 310 and the rotation of the arm 312 the member 303 will oscillate in directions longitudinal of its axis, thereby effecting an up and down motion of the needle 314 carried by the needle bar 300.

The needle bar 300 is keyed against rotation by means generally illustrated at 304. This means preferably comprises a slot 305 in the needle bar 300. A pin 306 extends across the slot with the ends of the pin 306 secured in the sleeve 303.

Means are provided for securing the needle bar 300 against longitudinal movement relative to the sleeve 303. This means is generally illustrated at 316 and consists primarily of a pair of elements 317 and 318. Element 317 consists of a frustoconic element having an annular end 315 tapering to a bottom end 319 which preferably is closed except for an axially extending opening. The member 317 is formed with a longitudinal slot 320 that effectively permits the member 317 to function as a spring in a direction normal to its length and as a fixed element in a direction parallel to its length. The element 317 normally interengages the element 318. Element 318 consists of an inner tube which has a beveled end or shoulder 324 adapted to engage the end 315 of the member 317. The outer radius of the member 317 at end is less than the outer radius of the end 324 of tubular element 318 but greater than its inner radius. The normal positions of the ends 32 1 and 315 are in longitudinal butting alignment, as illustrated in H6. 15. The element 317 engages the relatively heavy spring 330 at its end 319. The other end of the helical spring 330 butts and bears against the end 302 of the needle bar 300. Spring 330 has sufficient strength to normally retain the end 302 of the needle bar 300 and the end 319 of the element 317 in fixed relative locations during the dynamic state of the needle bar and also to maintain ends 315 and 324 in longitudinal engagement. However, when an impenetrable object is encountered during the operation of the sewing machine and by the needle 314, the spring 330 will compress.

A pin 331 extends through the opening in bottom 319. One end engages end 302 of the needle bar 300. The other end of the pin 331 engages in fixed or separable relation the stop 333. The stop 333 fits into the element 313 near its end 324 and is adapted to be retained in this position under normal and d namic operating conditions by helical spring 334. Sprin 334 is a helical spring extending lengthwise within elemen 318 and having less power than spring 330. One end of this spring 334 engages stop 336 while the other end of the spring 334 engages and is preferably secured to the boss 338 of the stop 333. Stop 336 closes the end of element or tube 318. This stop is secured in the tube 318 by a pin 341 which extends across or through the stop 336 and has its ends terminating within the tube 318. The stop 336 has an enlarged head 343 which forms a screw with this head having an externally threaded surface engaging threads on the inner surface of sleeve 316.

The stop 333 has an enlarged flange or lip 350 having an outer surface that substantially engages the inner surface 353 of the element 317. Under normal operating conditions surfaces 350 and 353 are in facing engaging relation with one another. Under these conditions the outer periphery of element 317 at end 315 is always in engagement with the end 324 of the element 318. However when the needle 314 hits a relatively impenetrable object the needle bar 300 is forced longitudinally in the direction of arrow 360 against the resistance of spring 330. If there is sufficient force applied, spring 330 is compressed between end 319 and 302. This causes relative movement of the pin 331 with respect to element 317 and in turn causes the stop 333 to move longitudinally within inner tube 318 in the direction of arrow 360 against the resistance of the relatively light spring 334. When the stop 333 moves into the tube 318 the end 315 of the member 317 compresses radially and as it does it will move into the end 324 of the member 318, thus permitting the needle bar 300 to move in the direction of arrow 360 relative to the casing sleeve 316. When the impenetrable object is removed the tension of spring 330 will cause the needle bar 300 to move longitudinally once again relative to the sleeve 316 in a direction opposite to arrow 360. This in turn is coupled with the expansive force of spring 334 which forces the stop 333 and element 317 from within the tube 318, thereby returning the unit to its original relative position before needle 314 hits an impenetrable object.

lclaim: 1. ln a sewing machine construction, a needle bar, a needle carried by said needle bar, a sleeve within which said needle bar may move in an axial direction;

means for vertically reciprocating said sleeve; disengageable means for interlocking said needle bar and sleeve, said disengageable means including a locking arm, means pivotally securing said arm to said sleeve, and means secured to said needle bar engaging said arm under normal dynamic operating conditions and disengaging from said arm when said needle bar is restrained directly and in response to engagement of said needle with an an impenetrable object during axial advancement of said needle bar toward said impenetrable object. 2. A device as set forth in claim 1 wherein said means pivotally securing said arm includes a plug coaxial with and within said sleeve,

means positioning said plug in normal spaced relation to the end of said needle bar and in engagement with said arm;

means secured to said needle bar adapted to move relative to said plug into engagement with said arm to pivot it from engagement with said plug.

3. A device as set forth in claim 2 wherein said means secured to said needle bar includes a pin coaxial with and extending from one end of said bar through into a hole in and coaxial with said plug.

4. A device as set forth in claim 3 including a pair of springs with one spring positioned between said plug and said needle bar and coaxial with said pin, and the other spring coextensive with a portion of said needle bar and engaging said needle bar.

5. A device as set forth in claim 4 including a pin extending across said sleeve and engaging said other spring, said other spring being finer than said first-mentioned spring.

Claims (5)

1. In a sewing machine construction, a needle bar, a needle carried by said needle bar, a sleeve within which said needle bar may move in an axial direction; means for vertically reciprocating said sleeve; disengageable means for interlocking said needle bar and sleeve, said disengageable means including a locking arm, means pivotally securing said arm to said sleeve, and means secured to said needle bar engaging said arm under normal dynamic operating conditions and disengaging from said arm when said needle bar is restrained directly and in response to engagement of said needle with an an impenetrable object during axial advancement of said needle bar toward said impenetrable object.

2. A device as set forth in claim 1 wherein said means pivotally securing said arm includes a plug coaxial with and within said sleeve, means positioning said plug in normal spaced relation to the end of said needle bar and in engagement with said arm; means secured to said needle bar adapted to move relative to said plug into engagement with said arm to pivot it from engagement with said plug.

3. A device as set forth in claim 2 wherein said means secured to said needle bar includes a pin coaxial with and extending from one end of said bar through into a hole in and coaxial with said plug.

4. A device as set forth in claim 3 including a pair of springs with one spring positioned between said plug and said needle bar and coaxial with said pin, and the other spring coextensive with a portion of said needle bar and engaging said needle bar.

5. A device as set forth in claim 4 including a pin extending across said sleeve and engaging said other spring, said other spring being finer than said first-mentioned spring.

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