US3799090A

US3799090A - Needle bar

Info

Publication number: US3799090A
Application number: US00359916A
Authority: US
Inventors: M Sheroff
Original assignee: Individual
Current assignee: Individual
Priority date: 1973-05-14
Filing date: 1973-05-14
Publication date: 1974-03-26
Anticipated expiration: 1991-03-26

Abstract

A sewing machine is provided with an improved mechanism to enable the needle bar, which carries the sewing needle, to be disengaged from the drive mechanism in the event that the needle hits an impenetrable object such as a button, zipper or piece of material. The disengaging mechanism includes an elongated sleeve which receives, axially, the upper end of the needle bar. The needle bar is tensioned in a fixed axial position within the sleeve by a number of elements which are adapted to remain in the fixed axial position under normal forces but are adapted to permit the needle bar to become disengaged from its fixed position with respect to the sleeve upon the development of abnormal forces on the needle bar. Means are provided for adjusting easily the tension at which the needle bar is fixed in its axial position to enable disengagement under relatively light forces, as when employing fragile needles to sew light material, or to preclude completely disengagement when sewing extremely heavy materials with relatively heavy needles. In an improved version the adjusting means includes detent means defining a number of different selectable positions for the adjusting means.

Description

United States Patent Sheroff Mar. 26, 1974 NEEDLE BAR Melvin S. Sheroff, 40 Salisbury Rd., Newton, Mass. 02111 22] Filed: May 14, 1973 21 App1.No.-.359,916

Related US. Application Data [63] Continuation-impart of Ser. No. 183,356, Sept. 24,

[76] Inventor:

Primary ExaminerH. Hampton Hunter [57] ABSTRACT A sewing machine is provided with an improved mechanism to enable the needle bar, which carries the sewing needle, to be disengaged from the drive mechanism in the event that the needle hits an impenetrable object such as a button, zipper or piece of material. The disengaging mechanism includes an elongated sleeve which receives, axially, the upper end of the needle bar. The needle bar is tensioned in a fixed axial position within the sleeve by a number of elements which are adapted to remain in the fixed axial position under normal forces but are adapted to permit the needle bar to become disengaged from its fixed position with respect to the sleeve upon the development of abnormal forces on the needle bar. Means are provided for adjusting easily the tension at which the needle bar is fixed in its axial position to enable disengagement under relatively light forces, as when employing fragile needles to sew light material, or to preclude completely disengagement when sewing extremely heavy materials with relatively heavy needles. In an improved version the adjusting means includes detent means defining a number of different selectable positions for the adjusting means.

21 Claims, 6 Drawing Figures NEEDLE BAR RELATED APPLICATION This application is a continuation-in-part application of previously filed application Ser. No. I83,356 filed Sept. 24, 1971.

BACKGROUND OF THE INVENTION This invention relates to sewing machines and, more particularly, to sewing machine of the type which employ needle bars. The invention is an improvement over the type of needle bar construction shown in US. Pat. No. 3,471,325.

Sewing machines for industrial and home use may be damaged easily by malfunctions or misuse of the machine. For example, in stitching zippers, buckles, snaps, buttons and other metal elements to a fabric, it is quite possible to bring, inadvertently, a relatively impenetrable portion of the article into the path of the needle. This usually results in breaking or bending of the needle. Before the machine can be stopped, the broken or bent needle may damage the fabric being stitched and- /or further damage the sewing machine. A broken or bent needle or even a needle which is misaligned slightly can readily strike the sewing machine plate or some of the mechanisms 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. Furthermore, the misuse or malfunction of a machine may cause injury to the operator, as, for example, when the operators fingers are close to the needle at the moment the needle is bent or broken. Difficulties of this type are particularly acute in high speed industrial machines.

Although the needle bar construction shown in FIG. of the aforementioned US. Patent is effective to perform its intended function, it is not adjusted easily as to the magnitude of force required to initiate disengagement of the needle bar from the drive mechanism. The instant invention is intended to provide a disengageable needle bar including a clutch mechanism which may be adjusted to vary the magnitude of force which will disengage the needle bar over a wide range of forces. This enables the same needle bar mechanism to be employed in the same sewing machine used to sew varied articles. The clutch mechanism may be adjusted easily and simply by the operator to vary the required disengaging force in accordance with the material being sewn in the machine.

For industrial machine applications, wherein the operator of the machine manytimes has knowledge of the workings of the machine, the necessary adjustments can be accomplished quite readily without posing any particular problem. However, especially for household use, the housewife may find it difficult to properly adjust the tension threshold of the machine. Accordingly, in the instant invention the adjusting means has detent means associated therewith for defining different selectable positions that are clearly identified so that different adjustment settings can be made depending primarily upon the needle size employed.

SUMMARY OF THE INVENTION The illustrative embodiment of the invention includes an elongated tubular sleeve which receives, axially, the upper end of the needle bar. The sewing needle is secured to the lower end of the needle bar in the usual manner. During ordinary use, the sleeve and needle bar are reciprocated vertically by an appropriate drive means. The upper end of the needle bar, which is received in the sleeve, bears against the lower end of an axially aligned clutch bushing. The upper end of the clutch bushing bears against the lower end of a compression spring and the upper end of the compression spring bears against a plug which is threaded into the upper end of the sleeve. The engaging ends of the needle bar and clutch bushing may be telescoped from their normally end-to-end abutting relation to enable the bar to slide axially and upwardly within the sleeve thus displacing the needle bar and needle from their normal operating position. Means are provided for precluding the telescoping action of the clutch bushing and needle bar until the axial force acting on the needle bar reaches a predetermined magnitude. The predetermined magnitude may be adjusted by an adjustment screw which is threaded into the stop screw at the upper end of the sleeve. The adjustment screw is exposed from atop the machine and is accessible to the operator for simple adjustment.

An improvement in accordance with the present invention resides in an adjusting assembly which may be substituted for the adjustment screw discussed hereinabove. This adjusting assembly preferably includes a steep pitched lead screw that is rotatable between different detented positions for providing different settings of the tension threshold depending primarily upon the size of the needle used.

It is among the primary objects of the invention to provide an improved telescoping needle bar assembly which is not likely to jam or malfunction when the machine is misused by engaging the pointed end of the needle with impenetrable materials.

Another object of the invention is to provide a telescoping needle bar which is of simple, inexpensive construction.

A further object of the invention is to provide a needle bar construction in which the magnitude of the force required to telescopically engage the needle bar from normal operation may be adjusted easily and simply by the operator.

Still another object of the invention is to provide a needle bar construction of the type described which is adapted for use with a wide variety of materials to be sewn.

A further object of the invention is to provide a needle bar construction of the type described in which after the needle bar has become disengaged it will become reengaged automatically.

Still another object of the invention is to provide a needle bar construction of the type described which is adapted for both home and industrial use.

A further object of the invention is to provide an improved adjusting means in association with the needle bar construction that includes detent means defining different discrete adjustment positions which makes the device particularly useful for the home.

DESCRIPTION OF THE DRAWINGS These and other objects and advantages of the inven tion will be understood more fully from the following detailed description thereof with reference to the accompanying drawings wherein:

FIG. 1 is an elevation of a portion of the sewing machine in which the invention is embodied;

FIG. 2 is an elevation, in section, of the needle bar disengaging mechanism;

FIG. 3 is an illustration of the device in a telescoped configuration;

FIG. 4 is an elevation view partially cut-away showing another embodiment for the needle bar mechanism of this invention;

FIG. 5 is an elevation view in cross-section showing in detail the construction of the mechanism of FIG. 4; and

FIG. 6 is a cross-sectional view taken along line 66 of FIG. 5.

DETAILED DESCRIPTION FIG. 1 shows the usual arrangement of a conventional sewing machine including the sewing machine casing 10 which includes a head 12 to which power is supplied from an appropriate shaft 14. A lever linkage system 16 including a crank arrangement 18 is connected to the needle bar assembly 20 to reciprocate that assembly vertically of the machine. The needle bar assembly 20 is supported in suitable upper and lower journals for such movement. Suitable bushings and fasteners are disposed in the machine to retain the bushings in position and to help support and limit movement of the needle bar assembly.

As shown in FIG. 2 the needle bar assembly, 20 includes an outer sleeve 22 which receives, at its lower end, the needle bar 24. The sewing needle 26 is secured to the lower end of the needle bar 24 in the usual manner. During normal use, the sleeve 22 and needle bar 24 are maintained in fixed axial relation with each other and are reciprocated vertically in unison by the aforementioned drive means. The needle bar assembly includes a clutch assembly 28 which is contained fully within the sleeve 22 and which is operative, in response to engagement of the sewing needle 26 with an impenetrable object, to enable the needle bar 24 to slide and shift axially along and within the sleeve 22 to3ard a disengaged configuration shown in FIG. 3. The axial sliding movement of the needle bar 24 within the sleeve 22 is limited by meansofa transverse slot 30 formed in the needle bar 24 and a transversely extending pin 32 which is secured to the sleeve 22 and is received within the slot 30. In the configuration shown in FIG. 2, the

upper end of the slot 30 bears downwardly against the pin 32, the needle bar being in its operative position.

The clutch assembly includes a clutch collar 34 which is provided with one or more longitudinal-slots 36. The slots 36 extend from the annular upper region of the collar 34 downwardly through the lower surface 38 of the clutch collar 34. The clutch collar 34 thus resembles a castellated or multi-fingered element in which the lower ends of the fingers may be resiliently urged radially and inwardly. The lower ends of the flexible finger portions of the collar 34 normally bear against and rest on the upper end of the needle bar 24. The upper end of the needle bar is formed with an axial bore 42 to define an annular wall 44 at at the upper end of the needle bar. The upper edge of the annular wall 44 is beveled at 46 andis effective, as described below to engage, guide and-urge radially inwardly, the lower ends of the flexible portions 40 of the clutch collar 34, as described below.

The clutch collar 34 and needle bar 24 are mainained in thier normally operative position by means of a relatively heavy compression spring 48. The lower end of the compression spring 48 bears against the upper end of the clutch collar 34 and the upper end of the spring 48 is maintained in place by engagement with a stop screw 50 which is threaded into the upper, open end of the sleeve 22. When the needle engages an impenetrable object this will tend to urge the needle bar 24 and clutch collar simultaneously and in unison upwardly within and in relation to the sleeve 22 to compress the spring 48. The spring 48 has sufficient strength to retain normally the needle bar and sleeve in their substantially fixed relative axial position during operation but will compress when the impenetrable object is encountered. The slight compression of the spring 48 permits a limited amount of unitary axial movement of the needle bar 24 and clutch sleeve 34. The telescoping action of the needle bar and clutch sleeve is controlled by an extent to which the needle bar and collar have moved axially within the sleeve against the axial force of the spring 48.

As described below, the telescoping action of the collar and needle bar is triggered only after the collar and needle bar have been urged axially upwardly within the sleeve to a predetermined extent which corresponds to the axial force at which disengagement is desired.

The arrangement for triggering the telescoping action of the clutch sleeve 34 and needle bar 24 includes a clutch pin or keeper 52 having an upwardly convergent or rounded surface 54 which extends into the lower end of the clutch collar 34 as shown. The surface 54 may be hemispherical as shown or may be of other upwardly convergent configuration which will function effectively as described. Intermediate the ends of the clutch pin 54 is an enlarged flange 56 which is of a diameter of greater than the inner diameter of the relaxed clutch collar 34 and which is slideable axially within the bore 42 in the upper end of the needle bar 24. The clutch pin 52 is biased in the upward position shown in FIG. 2 by means of a helical compression spring 58 which has less power than the compression spring 48. Thus, when the needle engages an impenetrable object, the compression spring 58 and clutch pin 52 will move in unison axially with the needle bar 24 and clutch collar 34.

Means are provided for interrupting the axial foregoing movement of the clutch pin 52. This arrangement includes an abutting rod 60 which is threaded at its upper end through the stop screw 50. The abutting rod 60 extends axially and downwardly through the spring 48 and clutch collar 34 toward the surface 54 of the clutch pin 52. Thus, when the needle engages an impenetrable object, the needle bar 24, clutch collar 34, spring 58 and clutch pin 52 will move in unison within the sleeve 22 until the upper end of the clutch pin 52 abuts the lower inner end of the abutting rod 60. As the needle bar 24 and clutch collar 34 continue to advance in relation to the sleeve 22 and the restrained clutch pin 52, the lower ends of the flexible portion 50 of the clutch collar 34 will be permitted to flex inwardly as they advance along the upper convergent surface 54 of the clutch pin 52. This inward flexing is initiated by engagement of the lower ends of the flexible portions 40 with the beveled surface 46 at the upper end of the needle bar 24. Continued urging of the needle bar 24 through the sleeve causes the flexible finger portions 40 of the collar 34 to flex inwardly and be telescoped into the axial bore 42 of the needle bar 24. As the telescoping action continues, the clutch pin 52 advances downwardly through the bore 42 with the clutch collar. On the return stroke, the

springs

48, 58 tend to extend the various elements axially within the sleeve and restore them to their normal operating configuration.

Among the significant features of the invention is that it enables the operator to adjust simply the degree of impenetrability which will cause the device to telescope. In this regard, the upper end of the needle bar aswembly extends upwardly through and beyond the head 12 of the machine thus exposing the upper end of the threaded abutting rod 60. The operator may simply vary the extent to which the abutting rod 60 projects into the device by adjusting the screw. For example, if the screw is backed off, (upwardly) the inner end of the abutting rod 60 will be initially spaced somewhat from the upper end of the clutch pin 52 thus requiring corresponding more upward travel of the needle bar 24, clutch collar 34 and clutch pin 52 in order to actuate the device. The amount of required increased travel is a direct function of the magnitude of axial force imparted to the needle bar 24 which, in turn, is a direct function of the penetrability of the object which the needle has engaged.

FIGS. 4-6 disclose another embodiment of the present invention similar to that shown in FIGS. 2 and 3, and further including an improved adjusting means. In FIGS. 4-6, reference characters similar to those used with FIGS. 2 and 3 are employed where appropriate.

In FIG. 4, the needle bar assembly includes an outer sleeve 22 which receives, at its lower end, the needle bar 24. The sewing needle 26 is secured to the lower end of the needle bar 24 in the usual manner. It is noted in FIG. 4 that in this alternate embodiment the adjusting tool 64 may be inserted through the top end 66 of sleeve 22 or may be used in an alternative horizontal position engaging with the adjusting means of the invention as depicted in dotted in FIG. 4. These two alternate ways of operating the adjusting means are discussed in more detail hereinafter with reference to FIGS. 5 and 6.

Most of the structure shown in FIG. 5 is substantially identical to the structure previously depicted in FIG. 3. In FIG. 5 the mechanism is shown in its retracted position after the assembly has come into contact with an impenetrable object. FIG. 5 shows the sleeve 22 with its axial bore 42 for accommodating a relatively light spring 58. The keeper or pin 52 is disposed at the top end top of spring 58. The clutch assembly 28 includes a clutch collar 34 which is provided with one or more longitudinal slots 36. In the position shown in FIG. 5, the collar 34 is telescoped inside the upper end of the needle bar and the pin 52 is displaced slightly downwardly from collar 34. The operation of the clutch mechanism and the needle bar has been discussed in sufficient detail herein before.

As previously indicated, the clutch collar 34 and needle bar 24 are maintained in their normally operative position by means of a relatively heavy compression spring 48. The lower end of the compression spring 48 bears against the upper end of the clutch collar 34 and the upper end of the spring 48 is maintained in place by engagement with a stop member 51 which is threaded into the upper, open end of the sleeve 22. The stop member 51 may be maintained in a fixed position in the sleeve 22 in the manner suggested in FIG. 4. For that purpose, the member 51 is provided with a central annular recessed surface 68 having a set screw 70 engaging thereagainst and passing through a threaded hole in the sleeve 22.

In the embodiment shown in FIG. 3, for example, the

stop screw 50 may have to be rotated through a complete turn in order to provide a sufficient adjusting range for abutting rod 60. It is the purpose of the embodiment shown in FIG. 5 to provide a sufficient adjusting range by causing rotation of the lead screw 72 through a relatively small rotational angle of, for example, only 120.

The stop member 51 is internally threaded to receive the lead screw 72. In FIG. 5, it is noted in particular that the lead screw 72 has a fairly steep pitched thread providing sufficient longitudinal movement of the lead screw for each rotation thereof. The lead screw 72 has a downwardly depending post 74 that engages with abutting rod 60 which is in turn engageable with pin 52 upon application of the proper pressure.

In order to adjust the longitudinal movement of lead screw 72 there is provided adjusting member 76 which includes a top cylindrical end 78 and a splined shaft3 0. A relatively weak spring 82 has its top end engaging with the bottom surface of cylindrical end 78 and its bottom end engaging with the top surface of the lead screw 72 thereby biasing the lead screw downwardly and the adjusting member upwardly.

The sleeve 22 is provided with an opening 79 having a number of oval detents 80 into which the set screw 81 may fit as depicted in FIG. 5. The set screw 81 is secured to cylindrical end 78 and the spring 82 maintains the set screw 81 in one of the preselected detents 80. The spline shaft 80 engages with a splined opening in the lead screw 72 and thus the lead screw rotates upon rotation of the adjusting member 76. This in turn provides adjustment for the position of the abutting rod 60.

The cross-sectional view of FIG. 6 shows the sleeve 22 and the top surface 83 of cylindrical member 78. This cylindrical member has a splined opening 84 for receiving the adjusting tool 64 which is shown in FIG. 4. The adjusting tool 64 also has a splined rod 65 for engaging with the splined hole 84 in cylindrical end 78. When the tool 64 is to be used in this manner, the tool is inserted in the cylindrical end and pressure is applied downwardly. The set screw 81 thus disengages from one of its oval detents and the adjusting member can be rotated so that the set screw 81 engages with the desired detent.

The adjusting tool 64, as shown in dotted in FIG. 4 can also be inserted through the opening 79 to engage directly with the set screw 81. In FIG. 5 the set screw 81 is shown having a hexagonal opening rather than a splined opening. In that case, the adjusting tool 64 would have a hexagonal rod for engagement with the set screw. To move the adjusting member to a different position a downward force is applied to the adjusting tool against the bias of spring 82 and once the set screw 81 has been depressed sufficiently, the adjusting member 76 may be rotated to the desired position to either move the lead screw 72 upwardly or downwardly thereby varying the tension and the pressure at which the needle bar assembly disengages upon hitting an impenetrable object.

Thus, I have described an improved arrangement of simplified, inexpensive construction, for a collapsible needle bar assembly. The device is versatile in that it may be employed to sew a wide variety of fabrics such as light fabrics in home use and heavy fabrics in industrial environments. It should be understood, however, that the foregoing description of the invention is intended merely to be illustrative thereof and that other embodiments and modifications may be apparent to those skilled in the art without departing from its spirit.

Having thus described the invention what I desire to claim and secure by Letters Patent is:

l. A device for disengaging operation ofa sewing machine needle from the drive mechanism ofa sewing machine comprising:

support means adapted to be engaged by said drive mechanism to drive said support means reciprocably along an axis;

a plurality of elements mounted to said support means for reciprocating movement in unison therewith, one of said elements comprising a needle bar having means for attaching a sewing needle thereto;

another of said elements comprising a keeper;

means mounting said plurality of elements to said support means for unitary movement in relation to said support means longitudinally of said axis;

abutting means secured to said support means and having a portion disposed along the path of travel of said keeper when said elements move, in unison in relation to said support means;

means responsive to abutment of said keeper with said abutting means for enabling said needle bar to move longitudinally in relation to said support means and the other of said elements; and

means biasing said keeper longitudinally of said axis and away from said abutment means under a force of predetermined magnitude.

2. A device as defined in claim 1 further comprising means enabling the longitudinal position of said abutting means to be adjusted.

3. A device as defined in claim 1 wherein said support means comprises a sleeve and wherein said elements are aligned longitudinally within said sleeve, said needle bar extending outwardly from one end of said sleeve.

4. A device as defined in claim 3 wherein another of said elements comprises:

an intermediate member within said sleeve, said intermediate member being abuttingly engageable with the upper end of said needle bar, said abutting ends of said needle bar and saidintermediate member being so constructed and arranged as to be telescoped, one within the other;

said one element being engageable with the abutting end of at least one of said intermediate member and said needle bar, said one element being so constructed and arranged as to. normally preclude said telescoping action; and

said one element being further constructed and arranged as to permit said telescoping action after it abuts said abutting means.

5. A device as defined in claim 4 wherein said means biasing said one element comprises a spring within said sleeve and in engagement with the upper end of said intermediate member.

6. A device as defined in claim 4 wherein said telescoping action is affected by means comprising;

the upper end of said needle bar being formed with a longitudinal bore;

said intermediate member comprising a collar, the

lower end of which is constructed as to be contractible radially and inwardly to enable the lower contracted end thereof to fit into said bore in said needle bar; I

said one element comprising a pin slideable within said bore, the upper end of said pin being adapted to fit within the lower end of said collar to restrain said radial inward contraction of the lower end of said collar whereby when said unitary movement of said needle bar, pin and collar, longitudinally of said support, is affected, said pin will abut said abutting member, whereby continued longitudinal movement of said needle bar and said collar will cause withdrawal of the upper end of said pin from the lower end of said collar thereby enabling the lower end of said collar to contract radially and inwardly.

7. A device as defined in claim 6 further comprising:

a helical spring disposed within said bore, the upper end of said helical spring being in engagement with the under side of said pin to bias said pin upwardly toward the lower end of said collar, said pin having a flange formed circumferentially thereabout for engagement with the lower end of said collar.

8. A device as defined in claim 6 further comprising:

the upper edge of said needle bar being beveled inwardly to guide and facilitate said radially inward contraction of the lower end of said collar.

9. A device as defined in claim 6 further comprising:

the upper end of said pin being upwardly convergent.

10. A device as defined in claim 6 wherein said abutting means comprises:

a stop member secured to said sleeve adjacent the upper end thereof, said stop member extending downwardly therefrom through said collar and toward said pin in axial alignment with said pin.

11. A device as defined in claim 10 further comprismg:

said stop member being secured to said sleeve for adjustment longitudinally of said sleeve; and

said sleeve being open at the upper end thereof to expose a portion of said stop member thereby to enable the position of said stop member to be adjusted exteriorly.

12. In a device for disengaging operation of a sewing machine needle from the drive mechanism of a sewing machine including;

support means adapted to be engaged by said drive mechanism for reciprocable movement thereof along an axis,

a needle bar having means for attaching a sewing needle thereto and arranged for reciprocating movement in unison with the support means,

abutting means secured to said support means for permitting relative movement between said needle bar and support means upon application of sufficient force to said needle bar,

and means biasing said needle bar longitudinally of said axis and away from said abutting means,

the improvement comprising means for adjusting the position of said abutting means, relative to said needle bar including a stop member fixed in position relative to said support means and an adjusting member moveable relative to stop member and having means engaging with an end of said abutting means,

13. The device of claim 12 wherein said adjusting member includes means for receiving an adjusting tool and a lead screw having a steep-pitched thread.

14. The device of claim 13 wherein said support means has an internal thread for receiving an externally threaded stop member which is in turn internally threaded to receive the lead screw.

15. The device of claim 14 wherein said means for receiving includes a cylindrical member having a shaft connecting to said lead screw.

16. The device of claim 15 including biasing means disposed intermediate said lead screw and cylindrical member.

17. The device of claim 12 wherein said adjusting member includes means for receiving an adjusting tool from opposite orthogonal directions.

18. The device of claim 12 wherein said adjusting member includes means for receiving an adjusting tool and detent means for limiting the position of said adjusting member to a number of discrete positions.

19. The device of claim 18 wherein said detent means is at least partly formed by a channel in said support means having a number of detented cutouts for receiving a protruding member from said adjusting means.

20. The device of claim 10 including a lead screw received by said stop member and having a steep-pitched thread, and means for receiving an adjusting tool to cause rotation of said lead screw and attendant longitudinal movement of said abutting means.

21. The device of claim 20 including means for receiving an adjusting tool in orthogonal directions.

Claims

1. A device for disengaging operation of a sewing machine needle from the drive mechanism of a sewing machine comprising: support means adapted to be engaged by said drive mechanism to drive said support means reciprocably along an axis; a plurality of elements mounted to said support means for reciprocating movement in unison therewith, one of said elements comprising a needle bar having means for attaching a sewing needle thereto; another of said elements comprising a keeper; means mounting said plurality of elements to said support means for unitary movement in relation to said support means longitudinally of said axis; abutting means secured to said support means and having a portion disposed along the path of travel of said keeper when said elements move, in unison in relation to said support means; means responsive to abutment of said keeper with said abutting means for enabling said needle bar to move longitudinally in relation to said support means and the other of said elements; and means biasing said keeper longitudinally of said axis and away from said abutment means under a force of predetermined magnitude.

4. A device as defined in claim 3 wherein another of said elements comprises: an intermediate member within said sleeve, said inteRmediate member being abuttingly engageable with the upper end of said needle bar, said abutting ends of said needle bar and said intermediate member being so constructed and arranged as to be telescoped, one within the other; said one element being engageable with the abutting end of at least one of said intermediate member and said needle bar, said one element being so constructed and arranged as to normally preclude said telescoping action; and said one element being further constructed and arranged as to permit said telescoping action after it abuts said abutting means.

6. A device as defined in claim 4 wherein said telescoping action is affected by means comprising; the upper end of said needle bar being formed with a longitudinal bore; said intermediate member comprising a collar, the lower end of which is constructed as to be contractible radially and inwardly to enable the lower contracted end thereof to fit into said bore in said needle bar; said one element comprising a pin slideable within said bore, the upper end of said pin being adapted to fit within the lower end of said collar to restrain said radial inward contraction of the lower end of said collar whereby when said unitary movement of said needle bar, pin and collar, longitudinally of said support, is affected, said pin will abut said abutting member, whereby continued longitudinal movement of said needle bar and said collar will cause withdrawal of the upper end of said pin from the lower end of said collar thereby enabling the lower end of said collar to contract radially and inwardly.

7. A device as defined in claim 6 further comprising: a helical spring disposed within said bore, the upper end of said helical spring being in engagement with the under side of said pin to bias said pin upwardly toward the lower end of said collar, said pin having a flange formed circumferentially thereabout for engagement with the lower end of said collar.

8. A device as defined in claim 6 further comprising: the upper edge of said needle bar being beveled inwardly to guide and facilitate said radially inward contraction of the lower end of said collar.

9. A device as defined in claim 6 further comprising: the upper end of said pin being upwardly convergent.

10. A device as defined in claim 6 wherein said abutting means comprises: a stop member secured to said sleeve adjacent the upper end thereof, said stop member extending downwardly therefrom through said collar and toward said pin in axial alignment with said pin.

11. A device as defined in claim 10 further comprising: said stop member being secured to said sleeve for adjustment longitudinally of said sleeve; and said sleeve being open at the upper end thereof to expose a portion of said stop member thereby to enable the position of said stop member to be adjusted exteriorly.

12. In a device for disengaging operation of a sewing machine needle from the drive mechanism of a sewing machine including; support means adapted to be engaged by said drive mechanism for reciprocable movement thereof along an axis, a needle bar having means for attaching a sewing needle thereto and arranged for reciprocating movement in unison with the support means, abutting means secured to said support means for permitting relative movement between said needle bar and support means upon application of sufficient force to said needle bar, and means biasing said needle bar longitudinally of said axis and away from said abutting means, the improvement comprising means for adjusting the position of said abutting means, relative to said needle bar including a stop member fixed in position relative to said support means and an adjusting member moveable relative to stop member and having means engaging with an end of said abutting means.