US3804038A

US3804038A - Sewing machine braking mechanism

Info

Publication number: US3804038A
Application number: US00370720A
Authority: US
Inventors: A Martin; E Albrecht
Original assignee: Pfaff Industriemaschinen GmbH
Current assignee: Pfaff Industriemaschinen GmbH
Priority date: 1972-06-27
Filing date: 1973-06-18
Publication date: 1974-04-16
Anticipated expiration: 1991-04-16
Also published as: IT986590B; DE2231482C2; JPS4967751A; JPS575555B2; DE2231482B1

Abstract

A sewing machine comprises a main drive shaft which is driven through a clutch mechanism which includes a clutch disc having a stopping groove. The groove is engageable by a locking member of an operating lever. A centrifugal braking mechanism includes a weighted brake member which is supported around the shaft on a spring which biases the brake member to engage a fixed abutment of the housing surrounding the shaft. The brake member is held during rotation of the shaft by a holding collar which engages an outward extension of the brake member under the force of a biasing coil spring. The operating lever is held by a locking lever which may be released under the action of a control cam to permit displacement of the locking member out of the locking groove after the speed of the main shaft drops below a certain value. When the shaft does return below a predetermined speed, the weights move inwardly toward the shaft and they engage with the holding collar which is returned to an engagement position by its associated spring after the locking lever is moved to a position permitting the operating lever to move out of engagement with the clutch disc stop groove.

Description

United States Patent [191 Martin et a1.

[73] Assignee: Firma Piaii Industrie-maschinen GmbH 22 Filed: June 18, 1973 21 Appl.No.:370,720

[30] Foreign Application Priority Data June 27, 1972 Germany 2231482 [52] US. Cl. 112/67, 112/219 R [51] 3 *Int. Cl. D05b 69/20, D05b 69/22 [58] Field of Search 112/67, 219 R, 219 A, 220,

[56] References Cited UNITED STATES PATENTS 5/1945 Reece 112/219 R X 7/1922 Valois.... 112/219 R 2/1963 Bono 112/219 R FOREIGN PATENTS OR APPLlCATlONS Germany 112/219 R 1 1 3,804,038 51 Apr. 16, 1974 Primary Examiner-11. Hampton Hunter Attorney, Agent, or FirmMcGlew & Tuttle [5 7] ABSTRACT the shaft. The brake member is held during rotation of the shaft by a holding collar which engages an outward extension of the brake member under the force of a biasing coil spring. The operating lever is held by a locking lever which may be released under the action of a control cam to permit displacement of the locking member out of the locking groove after the speed of the main shaft drops below a certain value. When the shaft does return below a predetermined speed, the weights move inwardly toward the shaft and they engage with the holding collar which is returned to an engagement position by its associated spring after the locking lever'is moved'to a position permitting the operating lever to move out of engagement with the clutch disc stop groove.

5 Claims, 4 Drawing Figures PATENTEUAPR 16 1914 3,804 038 SHEET 1 OF 2 SEWING MACHINE BRAKING MECHANISM BACKGROUND OF THE INVENTION ful sewing machine which includes an engaging and disengaging drive mechanism and a stopping device which comprises a braking means mounted on the main shaft of the sewing machine and a stationary brake abutment cooperating therewith and which also includes a stopping member adapted to engage into a stopping groove as soon as the speed of the main shaft of the sewing machine drops below a certain value.

2. Description of the Prior Art In order to stop a sewing machine in a predetermined position of the needle bar, it is known to brake the main shaft of the machine which is initially rotating at a certain speed down to a lower speed. After the lower speed is attained, the machine is brought instantaneously to a stop in a predetermined position, for example in the uppermost position of the needle, by

bringing a mechanical locking member into a locking position. It is desirous to provide a stopping device for sewing machines, particularly for group stitch sewing machines, in which the braking force becomes effective at the beginning of the braking operation and it is directly proportional to the output. speed of the main shaft of the machine, but once the main shaft is braked down to a certain speed, it becomes ineffective below this speed.

SUMMARY OF THE lNVENTlON In accordance with the invention, sewing machines having an engaging and disengaging driving mechanism and a stopping device which comprises a braking means mounted on the main shaft of the machine and a stationary brake abutment which cooperates therewith is provided with a locking member engaging into a stopping groove as soon as the speed of the main shaft of the machine drops below a certain value. With the invention, at a speed exceeding this value, the braking means, which counteracts the force of a return spring, can be moved by centrifugal force against the brake abutment and for thispurpose, it is advantageously supported on a resilient element such as a spring which permits it to move outwardly under the influence of centrifugal force. Thus, the braking force which depends on the square of the angular velocity of the main shaft becomes effective at the beginning of the braking operation and as soon as the main shaft is braked down to a speed which is harmless for applying a stopping device, which automatically drops the speed down to a zero value. Thus, it is also assured that at that time, the main shaft still has a rotational energy necessary for one revolution.

A space saving solution from the constructional point of view is obtained when the braking means is provided in the form of leaf springs which are mounted on collars so that they extend parallel to the main shaft and carry weights at their free ends which have lateral extensions cooperating with a recess provided in a control socket which may be axially shifted along the main shaft. In

sewing machines in which the stopping and starting operations are effected by means of a single control lever, care is to be taken when using a centrifugal brake initially arrested in its ineffective position and only thereafter is the locking member engaged in the clutch disc and fully released. In the stopping operation, first the braking means is made ineffective, and thereafter, the locking member is brought into the action range of the clutch disc.

Accordingly, it is an object of the invention to provide an improved sewing machine which has a main drive shaft with an engaging and disengaging drive mechanism for driving the shaft and which has a clutch disc with a stopping groove which is engageable with a locking member after the machine is brought down to a predetermined speed and which also includes a braking mechanismin the form of a brake weight which is carried on a spring and biased outwardly toward en-- gagement with a stationary brake abutment, but which is held by a locking collar which is released when the locking member engages into the stopping groove.

A further object of the invention is to provide a sewing machine which is simple in design, rugged in construction and economical to manufacture.

For an understanding of the principles of the invention, reference is made to the following description of typical embodiments thereof as illustrated in'the accompanying drawings. i

BRIEF DESCRIPTION OF THE DRAWINGS GENERAL DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to the drawings in particular, the invention embodied therein comprises a sewing machine having a housing 1 with a main shaft 2 rotatably supported in the housing and in a position to drive a needle bar (not shown). The shaft 2 carries a pulley 52 which drives a belt 3 and a pulley 53 carried on a lower shaft or control shaft 4. The shaft 4 carries a worm 5- which drives a worm gear 5a of a shaft 6a having a gear 6 which drives a gear 617 to rotate a control disc 7.

The main drive shaft 2 is rotated by an engaging and disengaging driving mechanism which includes a clutch disc 8 which is secured to the shaft 2 for rotation therewith and which is rotated by a driving disc 9 which is freely mounted on the shaft 2 and which maybe shifted axially. The drive disc 9 is formed integral with a V'beIt pulley which is driven by a V-belt 11 which is operated by a rotating motor (not shown).

In order to permit the shifting of the driving disc 9, a clutch ring 12 is rotatably mounted on a neck portion of the V-belt pulley 10 and it carries diametrically opposite

parallel slots

13, 13 therein. Rollers 14 of an actuating fork 15 engage into the respective slots 13 and the actuating fork 15 is rotatable about a pivot 16 provided on the arm 17 of an operating lever 18. The operating lever 18 is rotatable about a fixed pivot 19 and is connected to an intermediate lever 21 by means of a link 20. One end of the intermediate lever 21 is rotatable about a fixed pivot 22 and the other end is hinged to a pull rod 23 whose lower end is connected to a pedal (not shown).

The operating lever 18 is held in its rest position by a spring 24 having one end which is attached to the link and an opposite end which is connected to the housing 1. In the rest position, the driving disc 9 and the clutch 8 are separated from each other and no rotation of the shaft 2 takes place. A locking member 25 is carried at the upper end of the operating lever 18 and is adapted to engage into a stopping groove 26 of the clutch disc 8.

A retaining pawl 27 is provided on the operating lever 18 and it is adapted to engage into a stepped recess 28 of a spring-loaded locking lever 29 which is rotatably mounted on a fixed pivot 30 and connected to a cam lever 32 by means of tie rod 31. The free end of the cam lever 32 cooperates with th series of stepped cams 33 provided on the main control disc 7.

A leaf spring support or mounting collar 34 is mounted on the shaft 2 and it is provided with slots 35 which extend axially in respect to the shaft 2 and are spaced circumferentially around the periphery of the support. Each leaf spring 36 is mounted within a slot 35 and it has a free end which projects axially from the support and is loaded with a brake weight 37. Externally' the brake weights 37 are provided with a brake lining 38 which forms braking means 39 cooperable with a fixed annular brake abutment 40.

The leaf springs 36 are biased by a certain amount so that their biasing force which is directed against the shaft 2 overbalances the centrifugal force acting on the weights 37, but only up to a certain speed of the main shaft which is referred to as the stopping speed.

As shown in FIG. 2, on the front side of the support 34, each weight 37 is provided with an arc-shaped extension 41 which is adapted to engage into an annular recess 42 of a flanged control socket or collar 44 which comprises operating means generally designated 43. The collar 44 is mounted so as to be axially shiftable on the main shaft 2 and it is held in an engaging relationship with the extension 41 of the weights 37 by means of a spring 45 which is anchored at one end against the abutment'l of the housing and has an opposite end which engages against the collar 44. An actuating lever 46 is pivoted to the housing 41 and it provides means for shifting the control socket or collar 44. The actuating lever 46 carries a roller 47 which cooperates with a lateral face of the control socket 44. The lower end of the actuating lever 46 is provided with a pin 48 which extends through a slotted hole 49 of an intermediate lever 50. A spring 51 is located between the actuating lever 46 and the intermediate lever 50 and establishes a frictional contact therebetween. The other end sition off the reach of the rotating clutch disc 8. In addi- I tion, the control socket 44 looks the centrifugal weights 37 in their ineffective non-braking position.

In order to bring the main shaft 2 of the machine to a stop, first the locking lever 29 is turned clockwise as shown in FIG. 1, through a predetermined angle through the action of the

linkage

31, 32 in cooperation with the lower step of a cam 33 which is provided on the main control disc 7. Thereby, the retaining pawl 27 is disengaged from the lower step of the recess 28 and engages with the upper step of the recess 28.

Simultaneously, the operating lever 18 is turned clockwise about the pivot 19. In consequence, by the action of the arm 17, the driving disc disengages from the clutch disc 8 and, through the intermediate lever 50 and the actuating lever 46, the control socket 44 is shifted along the main shaft 2 by a predetermined distance to the right, as shown in FIG. 2, against the force of the spring 45. The extensions 41 of the centrifugal weights 37 thereby become released so that the weights can move outwardly against the biasing force of the leaf springs 36. The brake lining 38 then applies against the fixed brake abutment 40 and brakes the main shaft of the machine down to a speed depending on the square of the angular output velocity of the main shaft 2. As soon as the main shaft 2 slows down to a speed at which the stopping device may become effective without risking a damage, i.e., when it slows down to a stopping speed, the biasing forces of the leaf springs 36 exceed the centrifugal forces acting on the weights 37 so that the weights 37 are returned to their ineffective position. The main shaft of the machine continues to rotate at the stopping speed.

Through the action of the cam lever 32 and the tie rod 31 the higher step of the cam 33 causes the full release of the locking lever 29. The operating lever 18, urged by the retraction of the spring 24, effects a clockwise pivotal movement and the locking member 25 engages into the stopping groove 26 of the clutch disc 8 whereby the main shaft 2 of the machine is brought to a stop in the predetermined position. This movement of the operating lever 18 remains without effect on the actuating lever 46, because spring 51 is able to transmit only a certain torque due to the frictional interengagement so that during this motion, of the operating lever 18, the intermediate lever 50 moves only relatively to the actuating lever 46.

When restarting the machine, the pull rod 23 moves downwardly and the intermediate lever 21 turns about its pivot 22. Consequently the operating lever 18 connected through the link 20 turns about its pivot 19 against the force of the stretching spring 24. During this pivotal movement, first the intermediate lever 50 is moved to the left, as shown in both FIGS. 1 and 2. Thereafter, the actuating lever 46 releases the control socket 44 and the expanding spring 45 urges the control socket 44 along the main shaft 2 to the left. The

' ing lever 18, the locking member 25 is removed from the stopping groove 26 of the clutch disc 8. At the same time, the clutch disc 8 is brought into driving connection with the driving disc 9. The portion of the move- .ment of the operating lever in which the retaining pawl 27 finally engages in the lower step of the recess 28 has no effect on the actuating lever 46 nor on the control socket 44 so that the intermediate lever 50 only moves relatively to the lever 46 by an amount which is determined by the size of the slotted hole 49.

While a specific embodiment of the invention has been shown and described in detail to illustrate the application of the principles of the invention, it will be understood that the invention may be embodied without departing from such principles.

What is claimed is:

l. A sewing machine comprising a main drive shaft, an engaging and disengaging driving mechanism for driving said main drive shaft having a disc with a stopping groove, a stopping device comprising a braking means arranged on said main drive shaft, spring means biasing said braking means inwardly, a stationary brake abutment surrounding said brake means and cooperating therewith, a locking member adapted to engage into the stopping groove as soon as the speed of the main shaft of the machine drops below a certain value and owing to the centrifugal effect, said braking means counteracting the force of said spring means and being movable against said brake abutment, and operating means associated with said braking means for holding it out of engagement with said abutment and for releasing said braking means for movement under the centrifugal force acting to engage said abutment.

2. A sewing machine, according to claim 1, wherein said braking means comprises at least one weight and a leaf spring mounted on said shaft and holding said weight outwardly therefrom, said weight having an extension, said operating means including a control collar shiftable alongsaid shaft.

3. A sewing machine, according to claim 1, including a single control lever for effecting the starting and stopping of said shaft, an operating lever pivoted on said housing and carrying said locking member, said operating means being connected to said operating lever by a friction coupling having a displaceable idle stroke.

4. A sewing machine comprising a housing, a rotatable main needle drive shaft rotatably mounted in said housing, a stationary brake abutment supported in said housing adjacent said shaft, a centrifugal weight brake, a spring carried on said shaft and supporting said weight brake at its free end for movement outwardly of said shaft to contact said brake abutment by centrifugal force during rotation of said shaft beyond a predetermined speed, a control collar surrounding said shaft engageable with said weight brake and holding said brake towards said shaft and out of engagement with said brake abutment, a drive member secured to said shaft for rotation therewith and having a stop groove, an operating lever having a locking member engageable with said stop groove and being pivotally mounted on said housing, a locking lever having an engagement step engageable with said operating lever, a rotatable disc cam having cams thereon connected to said main shaft for rotation thereby, follower means engageable with said cams for displacing said locking lever to release said operating lever, said locking member of said operating lever being movable out of engagement with said stop groove upon rotation of said operating lever and an intermediate lever connected between said operating lever and said control collar for shifting said control collar to release said weight brake to permit it to engage said brake abutment.

5. A sewing machine, according to claim 4, including a pull rod connected to said operating lever to operate said operatinglever and an intermediate lever connected between said operating lever and said control collar and having a lost motion engagement therewith so that said intermediate member is moved only after a predetermined movement of said operating lever.

Claims

1. A sewing machine comprising a main drive shaft, an engaging and disengaging driving mechanism for driving said main drive shaft having a disc with a stopping groove, a stopping device comprising a braking means arranged on said main drive shaft, spring means biasing said braking means inwardly, a stationary brake abutment surrounding said brake means and cooperating therewith, a locking member adapted to engage into the stopping groove as soon as the speed of the main shaft of the machine drops below a certain value and owing to the centrifugal effect, said braking means counteracting the force of said spring means and being movable against said brake abutment, and operating means associated with said braking means for holding it out of engagement with said abutment and for releasing said braking means for movement under the centrifugal force acting to engage said abutment.

2. A sewing machine, according to claim 1, wherein said braking means comprises at least one weight and a leaf spring mounted on said shaft and holding said weight outwardly therefrom, said weight having an extension, said operating means including a control collar shiftable along said shaft.

5. A sewing machine, according to claim 4, including a pull rod connected to said operating lever to operate said operating lever and an intermediate lever connected between said operating lever and said control collar and having a lost motion engagement therewith so that said intermediate member is moved only after a predetermined movement of said operating lever.