US3924552A - Motor drive for sewing machines - Google Patents

Abstract

There is disclosed a sewing machine adapted to be driven by an electric motor supported from the sewing machine bed on cantilever brackets which extend beneath the machine supporting work tables rearwardly of the hinges by which the machine is pivotally mounted on the work table. In combination with the length and small diameter of this motor, this physical arrangement of the motor provides advantageous leg room for a machine operator, and permits pivoting the machine back for inspection and the like without disturbing the driving relationship of the motor to the sewing machine.

Description

United States Patent [191 Wendel 1 MOTOR DRIVE FOR SEWING MACHINES [75] Inventor: Lorenz A. Wendel, Somerville, NJ.

[73] Assignee: The Singer Company, New York,

[22] Filed: Feb. 24, 1975 [21] Appl. No.: 552,466

[52] US. Cl. 112/217.1 [51] Int. Cl. D05B 75/00 [58] Field of Search 112/217.l, 258, 260

[56] References Cited UNITED STATES PATENTS 1,783,836 12/1930 Finlayson 112/217.1 X 1,792,361 2/1931 Christensen 112/217.1

2,477,433 7/1949 Webb 112/258 2,899,249 8/1959 Kishibay 112/217.1

FOREIGN PATENTS OR APPLICATIONS 957,419 8/1949 France 112/260 Dec.9, 1975 355,342 8/1961 Switzerland 112/260 Primary Examiner-George H. Krizmanich Attorney, Agent, or Firm-Edward L. Bell; Robert E. Smith; Marshall .I. Breen [57] ABSTRACT There is disclosed a sewing machine adapted to be driven by an electric motor supported from the sewing machine bed on cantilever brackets which extend beneath the machine supporting work tables rearwardly of the hinges by which the machine is pivotally mounted on the work table. In combination with the length and small diameter of this motor, this physical arrangement of the motor provides advantageous leg room for a machine operator, and permits pivoting the machine back for inspection and the like without disturbing the driving relationship of the motor to the sewing machine.

5 Claims, 2 Drawing Figures U.S. Patent Dec. 9 1975 Sheet 1 of2 3,924,552

US. Patent Dec. 9 1975 Sheet 2 of2 MOTOR DRIVE FOR SEWING MACHINES BACKGROUND OF THE INVENTION This invention relates to sewing machines, particularly of the industrial type, and to the electric motor drive means therefor. In sewing machines for household use the speed of operation of the sewing machine does not play an important role. However, in the use of industrial type sewing machines it is necessary to run the machine at a high speed and this high speed must be obtained instantaneously with the start of the machine. Traditionally, in such sewing machines an electric motor driven power transmitter is used to drive the sewing machine. Such a power transmitter forms the subject matter of the US. Pat. No. 3,738,462 issued June 12, 1973. In use the rotor shaft of the power transmitter runs continuously and a clutch mechanism is used for coupling the sewing machine to the continuously rotating rotor shaft. Thus, the sewing maching will run at full speed almost immediately after shifting of the clutch to the driving position. In order to stop the sewing machine as instantaneously as it is started, the clutch is arranged to be shifted to engage a brake member. The machine will therefore also stop substantially instantaneously.

As is customary the sewing maching is supported in a cut-out provided in the table top of a power table assembly, and the power transmitter is supported beneath the table top close to the rear edge thereof. The power transmitter is connected by an endless belt to the main shaft of the sewing machine. One of the disadvantages of this type of drive is that each time the sewing maching is tilted back on its hinges it is necessary to remove the endless belt from the pulley on the sewing maching main shaft. Several other disadvantages that exist are nonuniform torque output resulting from imput mechanical shock caused by clutch, brake and belt action. Also the operating performance of the sewing machine varies as a function of clutch, brake, belt and pulley wear. Further, the motor continually consumes energy during periods when the sewing machine is idle.-

With the introduction of low-inertia, moving-coil and surface-wound annature DC. motors during the past few years, it is possible to overcome all the deficiencies of the present clutch-brake power transmitter drives. These DC. motors are equipped with rotary arrnatures consisting of a very low-inertia copper coil or surfacewound rotor containing no iron and immersed in a constant flux field preferably supplied by permanent magnets. In actual use it is the practice to connect a DC. motor of the above type directly to the main shaft of a sewing machine and by providing controlled rectifier circuitry for supplying a controlled direct current to the motor for deriving a driving torque, or selectively, by supplying an electrical load to the armature for deriving a dynamic braking torque from the motor, all the functions presently performed by flywheel induction motors with clutch and brake can be performed in equal or better manner and without the disadvantages inherent in the above described power transmitters. A DC. motor used on a sewing machine as above described forms the subject matter of the US. Pat. No. 3,597,672 issued Aug. 3, 1971 and US. Pat. No. 3,667,413 issued June 6, 1972.

With respect to the use of direct drive D.C. lowinertia motors, it has been discovered that the armatures of these motors, having a very thin disc-like construction and having just a minimum of copper, are very fragile and are prone to self-destruction. The high pulse current required in starting and stopping the sewing machine develops in the armature considerable heat which must be dissipated as quickly as possible. It has been determined that without air cooling the maximum number of sewing machine starts and stops is approximately 16 per minute, and if cooling is provided a maximum number of 40 starts and stops is the limit.

SUMMARY OF THE INVENTION It is the primary object of the present invention to provide a sewing apparatus including a power table having a table top provided with a sewing machine receiving cut-out, a sewing machine mounted in said cutout and having a rotary main shaft, hinge means supporting said machine on said table top providing for tilting said sewing machine backwardly to expose mechanism within the bed of the sewing machine, at least one motor supporting bracket secured to said sewing machine beneath the table top and disposed to extend downwardly and rearwardly of the cut-out, a motor secured to said bracket, and belt means connecting said motor to said sewing machine main shaft, said motor dimensioned and connected to said bracket so that the sewing machine may be tilted back on its hinges without removing the belt means from the sewing machine and the motor and without having interference between the motor and the table top in the movement of the machine from its operative position to its tilted back inoperative position.

This object is attained by the inclusion of an electric motor in which the diameter of the motor armature is considerably smaller than the length of the armature. The result of this motor configuration is a low inertia motor having a small vertical height, permitting the motor to be supported directly by the bed of the sewing machine without encroaching on the space occupied by the legs of the sewing machine operator.

BRIEF DESCRIPTION OF THE DRAWINGS The above object and advantages of the invention will become apparent from the following description taken in conjunction with the accompanying drawings, in which:

FIG. 1 is a front elevational view, partly in section, showing a portion of the power table with the sewing machine resting in the cut-out in the table top, the motor fastened on the machine bed, and the belt drive from the motor to the main shaft of the sewing machine; and

FIG. 2 is a left end elevational view, partly broken away, showing in full lines the sewing machine and its driving motor disposed in the normal operative position, and in dotted lines the sewing machine and its driving motor in the hinged back position of the sewing machine.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to the accompanying drawings wherein like reference numberals denote similar parts, there is disclosed a conventional power table, indicated as 10, having a table top 11 provided with the usual machine cut-out l2. Disposed within the cut-out 12 is the bed portion 13 of a sewing machine, preferably of the industrial type. The bed portion 13 is formed with a depending rear wall 13' which extends substantially the 3 full length of the bed 13. The sewing machine. as is usual, has an upstanding standard 14 that merges into an overhanging bracket arm 15 terminating in a head 16in which is journaled for endwise reciprocation: a needle bar 17 carrying a needle 18. Journaled in the bed 13 is a rotary main shaft 19 connected by a belt 20 tlo5 a rotary arm shaft 21 journaled in the bracket arm Secured to the rear wall 13' of the bed 13 of the sewing machine, by means of cantilever brackets 2222, is an electric driving motor 23 having mounted on its rotor shaft 24 a toothed belt pulley 25. Through the use of the brackets the motor is fixed in unitary relationship with the sewing machine, the brackets being formed so that the motor 23 is located behind the rear wall 13'of the bed and also behind the pivotal axis of the hinge means 28. The belt pulley 25 is connected by a belt 26 to a toothed pulley 27 faston the bed shaft 19. In its preferred form the electric motor 23 is a permanent magnet D.C. low inertia motor having an armature of small diameter and appreciable length. This ratio of armature length to armature diameter is substantially 3 to l or greater and this contributes materially to the advantages gained from the present invention. Firstly, the small diameter results in a low inertia drive, whereby extremely fast starts and stops can be obtained and the clutch-brakearrangement of the conventional electric transmitter can be eliminated. Further, the vertical compactness of the motor allows it to be supported in depending fashion on the bed of the sewing machine as clearly shown in FIG. 2. It will be noted that when the sewing machine is in its normal operative position, shown in full lines in FIG. 2, the motor is located behind the sewing machine and relatively close to the underside of the table top 11. This desirable location of the motor provides considerable leg-room for the operator, and any heat that may be generated in the motor is dissipated without discomfort to the operator.

Another advantage flowing from the present invention is that the sewing machine can be tipped back about hinges 28 (see FIG. 2) from its normal operative position to an inoperative position, whereby the mechanism in the sewing machine bed can be inspected or lubricated, without requiring that the belt 26 be removed from the sewing machine or the motor. Moreover, the dimensions of the motor are such that the cutout 12 in the table top 11 is minimum and only sized to fit the sewing machine bed 13.

Numerous alterations of the structure herein disclosed will suggest themselves for those skilled in the art. However, it is to be understood that the present disclosure relates to a preferred embodiment of the invention which is for the purpose of illustration only and not to be construed as a limitation of the invention. All such modifications which do not depart from the spirit of the invention are intended to be included within the scope of the appended claims.

Having thus set forth the nature of the invention what is claimed herein is: p

1. A sewing apparatus including a power table having a table top provided with a sewing machine receiving cut-out, a sewing machine mounted in said cut-out and having a bed and a rotary main shaft, hinge means supporting said machine on said table top providing for tilting said sewing machine backwardly to expose mechanism within the bed of the sewing machine, at least one motor supporting bracket secured to said sewing machine beneath the table top and disposed to extend downwardly and rearwardly of the cutout, a motor fixed downwardly of the cut-out, a motor fixed in unitary relation relatively to said sewing machine by said bracket, and belt means connecting said motor to said sewing machine main shaft, the dimensions and unitary relation of said motor to said sewing machine being such that the sewing machine may be tilted back on said hinges without removing the belt means from the sewing machine or the motor and without causing interference between the motor and the table top in the movement of the machine from its operative position to its tilted back inoperative position.

2. A sewing apparatus as called for in claim 1 wherein the sewing machine bed has a depending rear wall and said at least one hinge means is connected to said rear wall.

3. A sewing apparatus as called for in claim 2 wherein said at least one hinge means is connected to and located behind said rear wall and said at least one motor supporting bracket is secured to said rear wall and is so formed as to support the motor beneath and rearwardly of the cut-out in said table top.

4. A sewing apparatus as called for in claim 3 wherein the motor is constructed so that the ratio of motor length to motor diameter is substantially 3 to l or larger.

5. A sewing apparatus as called for in claim 1 wherein the rotary main shaft is journaled in the bed of the sewing machine and the motor is belt-connected to said rotary main shaft.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION PATENT NO. 2 3,924,552

DATED December 9, 1975 INVENTOR(S) Lorenz A. Wendel It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Claim 1, lines 19 and 20 Cancel "a motor fixed downwardly of the cut-out,"

Signed and Sealed this thirteenth Day of April1976 [SEAL] AIIeSI.

RUTH C. MASON C. MARSHALL DANN Atftstl'ng Offiter ('mnmissr'mzvr uflarer'rts and Trademarks

Claims (5)

1. A sewing apparatus including a power table having a table top provided with a sewing machine receiving cut-out, a sewing machine mounted in said cut-out and having a bed and a rotary main shaft, hinge means supporting said machine on said table top providing for tilting said sewing machine backwardly to expose mechanism within the bed of the sewing machine, at least one motor supporting bracket secured to said sewing machine beneath the table top and disposed to extend downwardly and rearwardly of the cut-out, a motor fixed downwardly of the cut-out, a motor fixed in unitary relation relatively to said sewing machine by said bracket, and belt means connecting said motor to said sewing machine main shaft, the dimensions and unitary relation of said motor to said sewing machine being such that the sewing machine may be tilted back on said hinges without removing the belt means from the sewing machine or the motor and without causing interference between the motor and the table top in the movement of the machine from its operative position to its tiLted back inoperative position.

2. A sewing apparatus as called for in claim 1 wherein the sewing machine bed has a depending rear wall and said at least one hinge means is connected to said rear wall.

3. A sewing apparatus as called for in claim 2 wherein said at least one hinge means is connected to and located behind said rear wall and said at least one motor supporting bracket is secured to said rear wall and is so formed as to support the motor beneath and rearwardly of the cut-out in said table top.

4. A sewing apparatus as called for in claim 3 wherein the motor is constructed so that the ratio of motor length to motor diameter is substantially 3 to 1 or larger.

5. A sewing apparatus as called for in claim 1 wherein the rotary main shaft is journaled in the bed of the sewing machine and the motor is belt-connected to said rotary main shaft.

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