US2965057A

US2965057A - Sewing machine apparatus to prevent backlash of bobbin thread

Info

Publication number: US2965057A
Application number: US776033A
Authority: US
Inventors: James W Lakin
Original assignee: American & Efiral Mills Inc
Current assignee: American & Efiral Mills Inc
Priority date: 1958-11-24
Filing date: 1958-11-24
Publication date: 1960-12-20
Anticipated expiration: 1977-12-20

Description

Dec. 20, 1960 J. w. LAKIN 2,965,057

SEWING MACHINE APPARATUS TO PREVENT BACKLASH OF BOBBIN THREAD Filed Nov. 24, 1958 7 I I I l p. I 5 I I I I 5 o llrlll'lnlllll (A 1; I I j -2| 3 fig- 4 5 4 @WW JAMES Wigwa BY 5131 64 ws ifigw ATTORNEYS Unite States Patent F SEWING MACHINE APPARATUS TO PREVENT BACKLASH OF BOBBIN THREAD James W. Lakin, Mount Holly, N.C., assignor to American & Efiral Mills, Inc., Mount Holly, N.C., a corporation of North Carolina Filed Nov. 24, 1958, Ser. No. 776,033

1 Claim. (Cl. 112-231) This invention relates to the prevention of backlash in sewing machines wherein lightweight plastic bobbins are used.

Metallic bobbins have long been used in sewing machines. The weight of a metallic bobbin is sufiiciently great to prevent any residual backlash of the metallic bobbin within its bobbin case whenever the operation of the sewing machine is stopped for any purpose. The use of a relatively light plastic bobbin in a sewing machine as a substitute for the metallic bobbin has been contemplated because the plastic bobbin is cheaper to produce and may be made transparent for permitting the amount of thread remaining thereon to be readily visible at all times. Plastic bobbins having smooth exterior surfaces have been manufactured for use in sewing machines, but the use of such bobbins is not without its attendant difliculties. The weight of a plastic bobbin is but a fraction of its metallic counterpart. Thus, upon ceasing the operation of a sewing machine in which a plastic bobbin having smooth exterior surfaces is installed, there is a general tendency on the part of the relatively light plastic bobbin to slip along the surface of the bobbin case in engagement with the plastic bobbin because of residual backlash from the sewing machine, resulting in entanglement of the bobbin thread and subsequent jamming of the sewing machine.

To overcome this problem of residual backlash, the smooth surfaced plastic bobbin has required the assistance of a separate shim element interposed between it and the bobbin case for preventing slippage of the bobbin relative to the bobbin case upon stopping the sewing machine. While this arrangement has been satisfactory for its intended purpose, the use of the shim element has proved to be a nuisance because such an element is not always readily available when needed for installation of the smooth surfaced plastic bobbin in the bobbin case of a sewing machine and is frequently lost as well.

It is a primary object of this invention to provide in combination with the bobbin case of a sewing machine, a relatively light plastic bobbin having a head thereon in engagement with a wall of the bobbin case, and means on the head of the bobbin to prevent slippage between the bobbin and the bobbin case when the sewing machine is stopped.

It is another object of this invention to provide in combination with the bobbin case of a sewing machine, a relatively light plastic bobbin having a head thereon in engagement with a wall of the bobbin case, the head of the bobbin being provided with a circular band of splines or projections which serve to insure the frictional gripping of the bobbin with the bobbin case, thereby preventing relative slippage therebetween which could otherwise occur because of residual backlash from the sewing machine when its operation is abruptly stopped.

It is another object of this invention to provide in combination with the bobbin case of a sewing machine, a lightweight plastic bobbin having a head thereon in engagement with a wall of the bobbin case. A circular 2,965,057 Patented Dec. 20, 1930 band of spaced radially extending ribs or splines are integrally formed on the bobbin head for frictional gripping of the bobbin case to prevent relative slippage therebetween when the sewing machine is stopped. During the operation of the sewing machine when relative rotation may occur between the plastic bobbin and the bobbin case, the ribs act in the nature of fans or impellers to circulate air through the spaces between adjacent ribs for cooling purposes to counterbalance the additional heat which is created by the increased frictional resistance, thus permitting frictional gripping between the bobbin and the bobbin case without developing a resultant heat of friction of increased magnitude.

Some of the objects of the invention having been stated, other objects will appear as the description proceeds, when taken in connection with the accompanying drawings, in which-- Figure 1 is a fragmentary isometric view of a sewing machine, showing the bed slide plate moved to open position to expose the bobbin case and the plastic bobbin disposed therein;

Figure 2 is an enlarged vertical sectional view of the bobbin case with the improved splined plastic bobbin disposed therein, taken along line 2-2 in Figure 1;

Figure 3 is an enlarged vertical sectional view similar to that shown in Figure 2, but illustrating a smooth faced plastic bobbin disposed within the bobbin case and showing entanglement of the bobbin threads caused by the slippage of the smooth faced plastic bobbin relative to the bobbin case because of residual backlash developed by the stopping of the sewing machine; and

Figure 4 is a greatly enlarged isometric view of the improved splined plastic bobbin within the bobbin case, the bobbin case and the splined bobbin being partially broken away for purposes of clarity.

Referring more specifically to the drawings, Figure 1 illustrates a sewing machine designated generally by the reference numeral 10 with its bed slide plate 11 moved to open position to expose a bobbin case or housing 2% which receives a plastic bobbin 40.

The bobbin case 20 comprises a cylindrical shell 21 having a planar circular bottom wall 22. The cylindrical shell 21 of the bobbin case 20 includes a curved slot 23 extending from its upper edge to a medial point thereon and terminating in a delivery eye 24, as shown in Figure 2.

An elongate leaf spring 30 is suitably attached at one end to the exterior surface of the cylindrical shell 21, the upper edge of the leaf spring 30 being substantially flush with the upper edge of the cylindrical shell 21. The leaf spring 30 substantially overlies the curved slot 23 formed in the cylindrical shell 21 of the bobbin case 20.

The relatively light plastic bobbin 40 relating to the present invention is disposed within the bobbin case 20, as illustrated in Figures 2 and 4. The bobbin 40 includes a cylindrical barrel or body portion 41 having a longitudinal bore 42 therethrough and a circular disc-like head 43 at each end thereof, the circular heads 43 being of enlarged diameter relative to that of the barrel portion 41. Thread or yarn T is wound about the barrel portion 41 of the bobbin 40 for feeding to the sewing machine 10. The bobbin 40 is of unitary construction, being molded from a suitable transparent plastic material such as crystal polystyrene, modified polystyrenes, nylon, phenolic, cellulose acetate, modified cellulose acetate, methacrylate, polyethylene, ethyl cellulose, ureas or melamines. Crystal polystyrene is a preferred plastic, however, because of its low cost and its low static characteristics. The latter characteristic is of great importance, since the formation of static electricity on the surfaces of a bobbin may result in serious problems, such as the tangling and breaking of the thread wound about the bobbin.

The outer surface on each circular head 43 of the bobbin 40 is provided with means for insuring that the bobbin 40 will frictionally grip the bobbin case 20 and will not be subject to slippage with respect thereto upon the operation of the sewing machine being suddently stopped. As shown most clearly in Figure 4, this means takes the form of a circular band of spaced radially eX- tending ribs, splines or projections 44, the circular band of ribs 34, in each instance, being arranged concentrically with the bore 42 through the barrel portion 41. The inner edges of the ribs 44 are spaced radially outwardly of the bore 42 through the barrel portion 41 to define therebetween a flat annular surface and the outer edges of the ribs 44 are spaced radially inwardly from the periphery of each circular head 43. Thus, a band of ribs 44 projects outwardly from the outer surface of each circular head 43 to provide frictional engagement between the plastic bobbin 40 and the bottom wall 22 of the bobbin case 20.

Since a circular band of ribs 44 is provided on the outer surface of each circular disc-like head 43% of the plastic bobbin 40, the bobbin 40 may be disposed within the bobbin case with either of its circular heads 43 in engagement with the bottom wall 22 of the bobbin case 20. A frictional gripping engagement is thereby assured between the plastic bobbin 40 and the bobbin case 20 to prevent the relatively light plastic bobbin 40 from slipping with respect to the bobbin case 20 because of residual backlash from the sewing machine 10 whenever its operation is stopped. Consequently, no problem of the bobbin thread T becoming entangled because of this residual backlash is encountered.

It will be observed in Figure 4 that the spaces between adjacent ribs 44 comprising the circular band on the lower head 43 define a plurality of radially extending passageways linking the central flat annular surface of the head 43 with its periphery. When the sewing machine 10 is in operation, relative rotation may occur between the plastic bobbin 40 and the bobbin case 20. In such an instance, the ribs 44 on the lower head 43 act in the nature of fans or impellers for circulating air to aid in cooling the engaging surfaces of the plastic bobbin 40 and the bobbin case 20, the air being circulated through the passageways defined by the spaces between adjacent ribs 44 to cool the entire outer surface on the lower head 43 of the plastic bobbin 40. Thus, any additional heat which may be created by the frictional gripping of the ribs 44 with the bottom Wall 22 of the bobbin case 20 is counterbalanced by the cooling effect described hereinabove.

Figure 3 illustrates a tangled condition of bobbin thread T wound on a relatively light plastic bobbin 40' having smooth planar outer surfaces on its circular disc-like heads 43' and disposed within a bobbin case 20'. In this instance, the smooth outer surface of the circular head 43' in engagement with the bottom wall 22 of the bobbin case 20', affords no frictional gripping engagement therewith. As a generalization, a smooth plastic surface has an inherent slippery characteristic. Thus, when the sewing machine 10 is stopped for any reason, the residual backlash therefrom is frequently effective to rotate the plastic bobbin 40' within the bobbin case 20' because its relatively light weight is easily overcome by such backlash action. As can be seen in Figure 3, the slippage of the plastic bobbin 40' relative to the bobbin case 20' en- '4 courages entanglement of the thread T wound about the bobbin 40' which jams the sewing machine 10 upon its subsequent operation, requiring the operator to stop the sewing machine 10 and clear the entangled thread condition before resuming work.

The cooperation between the circular band of ribs 44 provided on the outer surface of the downwardly disposed circular disc-like head 43 of the plastic bobbin 40 with the planar bottom wall 22 of the bobbin case 20 obviates any such difficulties as described in the preceding paragraph. Thus, the use of relatively light plastic bobbins in sewing machines may be accomplished in the absence of shim elements without creating any backlash problem, which otherwise would result in entanglement of the bobbin thread. Since such a bobbin may be made from a transparent plastic material, the amount of thread remaining thereon is at all times readily visible through the upturned circular disc-like head thereof enabling the operator to determine when the bobbin requires refilling. 7

There has been disclosed an improved relatively light plastic bobbin having ribs or splines provided on the outer surfaces of its circular disc-like heads for frictional gripping engagement with the bottom wall of a bobbin case. Such an arrangement makes it practical to use a transparent plastic bobbin as a replacement for the heavier metallic bobbin without encountering a backlash problem.

In the drawings and specification, there has been set forth a preferred embodiment of the invention and, although specific terms are employed, they are used in a. generic and descriptive sense only and not for purposes of limitation, the scope of the invention being defined in the claim.

I claim:

In a sewing machine having a bobbin case, the combination therewith of a relatively lightweight plastic bobbin received within said bobbin case, said bobbin comprising a cylindrical barrel portion and a pair of disc-like heads of enlarged diameter relative to said barrel portion on opposite ends of said barrel portion, each of said heads having an outer surface provided with a flat circular central portion and a circular band of radially extending ribs projecting outwardly from said outer surface in raised relationship with respect to said flat circular central portion, said circular band of ribs bounding the flat circular central portion of said head so as to be spaced radially outwardly with respect to said cylindrical barrel portion, the circular band of ribs on one of said heads being in friction-gripping engagement with a Wall of said bobbin case, the outer surface of said one head and said circular band of ribs thereon defining radially extending passageways between adjacent ribs in said circular band, the passageways communicating with the flat circular central portion of said one head at their inner ends, and said ribs serving as impellers upon relative rotation occurring between said bobbin and said bobbin case to circulate air through the passageways and over the outer surface of said one head for cooling said outer surface, thereby offsetting the heat developed by the frictional engagement between the circular band of ribs and the wall of the bobbin case.

References Cited in the file of this patent UNITED STATES PATENTS 2,019,952 Chaflin Nov. 5, 1935 2,116,982 Rubel May 10, 1938 2,200,721 Marinsky et al May 14, 1940 2,254,606 Gomez Sept. 2, 1941 UNITED STATES PATENT OFFICE CERTIFICATION OF CORRECTION Patent No 2,965,057 December 20, 1960 James W, Lakin It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

In the grant, lines 2 and 12, and in the heading to the printed specification, lines 4 and 5, name of assignee, for "American 81 Efiral Mills, Inca. read American 81 Efird Mills, Inc,

Signed and sealed this 30th day of May 1961,

(SEAL) Attest:

ERNEST W. SWIDER DAVID L. LADD Attesting Officer Commissioner of Patents