US2768796A

US2768796A - Magnetic thread-tensioners

Info

Publication number: US2768796A
Application number: US449426A
Authority: US
Inventors: Levine Paul
Original assignee: Individual
Current assignee: Individual
Priority date: 1954-08-12
Filing date: 1954-08-12
Publication date: 1956-10-30
Anticipated expiration: 1973-10-30

Description

Oct. 30, 1956 P. LEVINE 2,768,796

MAGNETIC THREAD-:TENSIONERS Filed Aug. 12, 1954 INVENTORZ PAUL LEVINE,

WNW

ATTORNEY United States Patent MAGNETIC THREAD-TENSIONERS Paul Levine, Jamaica, N. Y.

Application August 12, 1954, Serial No. 449,426

2 Claims. (Cl. 242-155 This invention relates to thread-tensioning devices for sewing machines and, more particularly, to a thread-tensioning device to maintain a uniform tension of the thread regardless of irregularities in the thread which is wound on a pulley by means of a permanent magnet.

A primary object of the invention is therefore to maintain a uniform tension of the thread as it is fed from a pulley to the needle of a sewing machine by means of a permanent magnet.

Another object of the invention is to adjust to and maintain a desired tension of the thread by a permanent magnet which is adjustably mounted on a stud, with the magnetic attraction of the magnet causing a V-shaped grooved steel pulley on which the thread is wound and which is also mounted on the stud, to be drawn axially toward the magnet and into a tight or loose engagement with a friction plate mounted on the stud between the magnet and the pulley creating a drag on the pulley and maintaining a desired tension of the thread as it leaves the pulley.

A further object is to provide a pulley with the sides of the V-shaped groove at a very small angle so the thread will be wedged into the groove adjacent its apex and thereby causing the pulley to rotate.

Another object is to provide a pulley with a very small angular groove so that any lint which may be on the thread will be carried along by the pulley.

A'further object of the invention is to provide a magnetic thread tension unit so that if the thread breaks due to a knot which will not pass through the eye of the needle, the thread is not pulled back through the thread guides of the sewing machine.

Another object of the invention is to provide a magnetic thread-tension unit which is simple in construction and relatively few parts.

These objects and other objects which may appear hereinafter all form part of this invention.

There is thus provided a magnetic thread-tension unit which may be secured to the head of a sewing machine to provide the proper tension to the thread as it is fed from a pulley to the need-1e. The unit comprising a permanent magnet adjustably mounted on a stud along with a small angular V-shaped grooved steel pulley and a friction plate interposed between the magnet and the pulley, with the magnetic attraction ofthe magnet causing the pulley to be drawn axially toward the magnet and against the friction plate creating a drag on the pulley and tensioning the thread which is wound on the pulley. It may thus be seen that the closer the magnet is positioned to the pulley the greater will be the magnetic attraction on the pulley and the greater the pressure between the pulley and the friction plate thereby placing a greater tension on the thread as it leaves the pulley.

Referring to the drawings in detail:

Fig. llis a side elevation showing the magnetic thread tension unit attached to a sewing machine head, a frag ment of which is shown;

Fig. 2 is an end view showing the plate of magnetic material which is secured to the north and south poles of the magnet to form a horseshoe magnet;

Fig. 3 is a longitudinal sectional elevational view taken along line 22 of Fig. 2 showing the parts of the magnetic tension unit in assembled relationship;

Fig. 4 is a transverse section taken along line 33 of Fig. 1 showing the north and south poles of the magnet mounted in the non-magnetic block;

Fig. 5 is a detail section of the pulley in elevation taken along line 4-4 of Fig. 3 showing the manner of winding the thread on the pulley;

Fig. 6 is an exploded view showing the magnetic threadtension unit disassembled.

Having reference to Fig. 6 a stud of non-magnetic material generally designated 10 which is circular in cross section. The stud 10 has approximately one-half its length threaded at one end at 11 terminating in an unthreaded bearing portion 12 and an enlarged diameter unthreaded shoulder portion 13 which terminates in a reduced diameter threaded end portion 14. Rotatably positioned on the unthreaded bearing portion 12 is a steel pulley 15 composed of two

halves

16 and 17 respec' tively which are pressed together to form the assembled pulley. The pulley has an unthreaded bore 13 to permit it to be rotatably positioned over the bearing portion 12. The two

halves

16 and 17 thus assembled form a small angular V-shaped groove G of approximately 8 in which the thread T is wound to be wedged between the side faces 19 and 20 of the groove closely adjacent its apex causing the pulley to turn. The two

halves

16 and 17 also have external side faces 21 and 22 respectively.

Threadably secured on the threaded end 11 of the stud 10 is a non-magnetic face plate or disk 23, preferably of brass, formed with a boss or collar 24. To the outside face 25 of the disk 23 is glued or otherwise secured a cork facing 26 or other friction material which is adapted to frictionally engage the external face 21 of pulley 15.

The face plate or disk 23 has an internally threaded bore 27 with the threads of the bore engaging the threads 28 of the threaded end 11 when the disk is positioned on the stud 10. The disk 23 is rotated until the threaded bore 27 engages the last thread 28 of the threaded end 11 so the cork facing 26 may frictionally engage the external face 21 of the pulley 15.

A permanent magnet designated M comprises magnetic poles north and south which are held within a solid centrally bored block B of any suitable non-magnetic material, preferably brass, with the poles connected at their outside ends by a plate P of magnetic material having a central bore 29, and the plate being secured to the poles by means of screws 30 thus forming a horseshoe magnet.

The block B has a central threaded bore 31 at one end and which is enlarged and unthreaded at the other end forming a recess 32 for the boss or collar 24 of the disk 23.

tioned on the stud to prevent axial movement outwardly of the magnet.

In Fig. 5 there is shown the thread T wound around the pulley G as it comes from the feeding spool, not

shown, on the sewing machine, and T shows the thread was it leaves the pulley to pass through a hook or guide, 3

3 not shown, mounted upon the sewing. machine head H and thence to the needle. It may thus be seen that the thread T leaves the pulley 15- at a tangent permitting the thread to slip out of the groove G easily and therefore not bind.

In operation and with the parts assembled as best shown in Fig. 3 the thread T'is. pulled through:v the machine by the action of the stitches being formed and fed away from the needle. Since a sewingmachine must operate with a very light thread tension in order to prevent puckering of the stitches, the conventional 60 or U-shaped grooved pulleys are not suitablebecause the untensioned thread will slip over the pulley rather than revolve it. To place the maximum but comparatively light tension on. the thread. T it.may' bev seen from the figure that the magnet M will exert-its" greatest magnetic attraction to pull the pulley 15 axially toward the magnet and against the cork facing 26 of the face plate or disk 23- when the magnet is positioned in abutting: relationship with the plate 23 thus creating amaximum drag on the pulley 15 and placing the thread T under a steady but light tension.

If it is desired to obtain a lighter tension on the thread T the nut 33. is loosened releasing the lock washer 34- permitting the magnet M to be moved axially along the threaded end 11' of the stud 10 and away from the disk- 23 any desired distance thus decreasing the magnetic attraction. between the pulley 15 and the magnet M and thereby decreasing the frictional contact between the cork facing 26 and the external face 21 of the pulley. The

tension of the thread T may thus be varied anyamount larities in the thread or different diameterthreads willhave no eifect on the formation of the stitch. Anylint which may be on the thread T will be carried along in-- stead of getting caught between the pulley as new happens between the pressure washers of the conventional tension devices where. accumulated lint forces the washers open and causes the tension to be released.

Since the thread tension unit is not of the hysteresis type, if the thread T breaks due to a knot which will not pass through the eye of the needle, the thread is not pulled back through the guides of the sewing machine as occurs when the thread breaks in the hysteresis type of tension device. It is only necessary to-rethread the needle and not the guides, thereby saving the operator considerable time.

As this invention may be embodied in several forms without departing from the spirit or essential characteristics thereof, the present embodiment is therefore illustrative and not restrictive, since the scope of the invention is defined by the appended claims rather than by the description preceding them, and all changes that fall within the metes and bounds of the claims or that formtheir functional as well as conjointly cooperative equivalents, are therefore intended to be embraced by those claims.

What is claimed is:

1. A thread-tensioning device for sewing machines comprising a stud of non-magneticmaterial' having at one end an end portion of a shape for securing to a sewing machine, said stud having a threaded part extending inwardly from its other end and having an unthreaded bearing portion adjacent the inner end of said' threaded part with an enlarged diameter portion inwardly of said unthreaded portion forming a shoulder at the inner end thereof, a solid cylindrical block of non-magnetic material having a central longitudinally extending threaded bore in adjustable threaded engagementwith said threaded part of the stud providing for longitudinal adjustment of said block on the stud, a permanent magnet mounted on said block, a circular plate of non-magnetic material having a central hub part fixed on the stud at the outer end of said unthreaded bearing portion of the stud at the inner side of said block, and said plate having a friction facing on the inner side face thereof, a small V- shaped grooved pulley of magnetic material mounted for rotation and free axial movement onsaid unthreaded bearing portion of the stud, the pulley having side wall portions fixed with relation to each other and the central part of the pulley, and a lock nut on the threaded part of the stud for holding said block with the magnet thereon in different positions of adjustment on the stud, said magnet through its magnetic attraction on the pulley causing the pulley to be moved axially to bring one of its side faces against the friction facing of said plate and thereby effect adrag on the pulley and tensioning of the thread.

2; A thread-tensioning device for sewing machines comprising a stud of non-magnetic material having at one end an end portion of a shape for securing to a sewing machine, said stud having a threaded part extending inwardly from its opposite end and having an unthreaded portion adjacent the inner end of said threaded part with an enlarged diameter portion inwardly of'said unthreaded portion forming a stop shoulder at the inner end thereof,. a solid cylindrical block of non-magnetic material having a central longitudinally extending threaded bore in threaded engagementwith' said threaded part. of the stud providing for longitudinal adjustment of said block on the stud; and said block having apair of longitudinal bores extending from end to end thereof at diametrically opposite locations outwardly of the central bore, a horse shoe magnet comprising elongated north and south pole elementsheld in said pair of bores in the block and each extending from end to end' of the block and having a threaded aperture in its outer end, a

connector plate of magnetic material fitting against the outer ends of said pole elements and the block, said connector plate having a central aperture to accommodate the outer end of said unthreaded bearing portion of the stud at the inner side of said block, and said'plate' having a friction facing on the inner side face thereof, a small V-shaped grooved pulley of magnetic material mounted for rotation and free axial movement on said'unthreaded bearing portion of the stud, the pulley having side wall portions fixed with relation to each other and the central part of the pulley, and a lock nut on the threaded part of the stud for holding said block with the magnet thereon in different positions of adjustment on the stud, said magnet through its magnetic attraction on the pulley causing the pulley to be moved axially to bring one of its side faces against the fraction facing of said plate and thereby effect a drag on the pulley and tensioning of the thread.

References Cited in the file of this patent UNITED STATES PATENTS 22,045 Wheeler Nov. 9, 1858 751,930 Lundgren Feb. 9, 1904 2,073,818 Viens Mar. 16, 1937 2,361,239 Ransom Oct. 24, 1944 2,605,301 Barnes July 29, 1952 2,614,773 Ammerall Oct. 21, 1952 2,650,043 Grein Aug. 25, 1953 2,724,065 Saxl Nov. 15, 1955 FOREIGN PATENTS 864,717 France Jan. 27-, 1941