GB2043719A - Improvements in or relating to sewing machines - Google Patents

Abstract

An improved device for operating a needle in a sewing machine having a needle-supporting clamp (2) that is guided for sliding movement in a vertical plane by a needle bar (4). The needle bar (4) is pivotably mounted on and depends from an adjustable support (16), which causes the needle bar to automatically align itself and follow the effective path of travel of the needle-supporting clamp (2). The support (16) is mounted on the machine frame (1) and is eccentrically positionable, which provides a means whereby it can be selectively located in a position at which the needle bar (4) depending therefrom will never be subjected to more than a minimum amount of resistance by the needle-supporting clamp (2) during the sliding movement of the clamp on the needle bar. <IMAGE>

Description

SPECIFICATION Improvements in or relating to sewing machine The present invention relates to sewing machines, and has particular reference to a device for operating and controlling the needle in a sewing machine of the type having a needle supporting clamp which is mounted and guided for sliding movement on a stationary needle bar.

In such machines, the needle bar is mounted on the frame of the machine and pivotably connected to one end of a control lever that is pivotably supported intermediate its ends on a crank which forms the end of an oscillatably driven shaft of the machine. The opposite end of the control lever is pivotably connected to one end of a movable lever element, the opposite end of which is also pivotably supported by the frame of the machine.

Devices of this type are well known in the art and are utilized because their particular design ensures low loading on the support bearing and on the pivot elements. This is attributed to the fact that the needle-supporting clamp has its fulcrum on that end of the control lever which is caused to move along a path which is substantially rectilinear and the needle bar is carried by the frame of the machine in a manner to effect a secondary function of serving as a means for movement of the needle about the fulcrum which interconnects said control lever with the needle-supporting clamp.

However, a number of disadvantages have been experienced with these known devices, the disadvantages deriving from the fact that the needle bar is mounted on the frame in an operative position which is statically determined (i.e.;when the machine is not operating) and from the fact that the path through which the control lever passes is not a true rectilinear path. The path is, rather, similar two a double, very elongated, "S", the width of which is about one hundredth of a millimetre. These disadvantages or drawbacks are accentuated by the additional fact that each device has its own unique dimensions which differ from one another due to the tolerances which differentiate the individual components from each other.As a result, with each operating device mounted on a machine frame, it is necessary to separately determine the most desirable operating position of the needle bar relative to the path through which the needle-supporting clamp travels so as to reduce friction between the surfaces in sliding contact and consequently to reduce wear thereof.

The positioning of the needle bar with respect to the operating device is determined empirically by displacing and inclining said needle bar in its assembled seat until a position is found at which sliding of the needle-supporting clamp can be accomplished with a minimum of resistance.

Consequently, this manner of positioning depends very much on the skill of the person employed for the assembly of the machine, as a result of which even the wear of the two elements coupled together is influenced by a human factor.

It was further found that the needle-supporting clamp bears the major part of the negative effects of rubbing against the needle bar and that the most clear evidence of wear is found in particular at the extreme and opposing faces of the hole in said supporting clamp within which said needle bar is disposed.

This condition is due to the fact that a poorly positioned needle bar reacts to the stresses caused by the needle-supporting clamp, particularly at points corresponding to the extreme points of its path, since the double "S" has its greatest deviations at these extreme points.

A further negative factor encountered in known operating devices, and which favored wear of the needle clamp, is caused by the centrifugal force generated by the crank that is fixed to the oscillating shaft of the machine and pivotably connected at a central location on the control lever.

This crank, which as is known, is disposed in spaced relation to the needle bar and commences to generate a centrifugal force as soon as it starts to oscillate. A large amount of force is transmitted to the movable lever element of the pivoting arrangemenu thus causing the needle-supporting clamp to place a greater load on the needle bar. Wear of the needle carrying clamp creates an increase in the amount of clearance or play between the hole provided in its for sliding movement on the needle bar and consequently leads to a gradual reduction of the loading forces thereon. However, this increase in clearance reduces the effectiveness of the specific function of the needle bar, which is that of maintaining the operative phasing between the needle and the lower stitching instrumentalities of the sewing machine.

According to the present invention there is provided a sewing machine comprising a needlesupporting clamp mounted for sliding and guided movement in a vertical plane on a needle bar and pivotally attached to a control lever, which is pivotally connected at one end to a movable lever element and intermediate its ends to a crank fixed on an oscillatingly drivable shaft of the machine, the needle bar being mounted on a frame of the machine by an adjustable support comprising a mounting member mounted in and extending from a fixed seat in the frame, the mounting member having an axis extending perpendicularly to said vertical plane, support means operatively connected to the mounting member and having an axis spaced from and extending parallel to said axis of the mounting member, coupling means attached to the upper end of the needle bar and pivotally coupling the needle bar to the support means, and position control means operatively associated with the mounting member for adjusting the position of the support means to thereby selectively vary the distance between the needle bar and the point of pivotal connection of the control lever to the crank.

In a sewing machine embodying the invention it is no longer necessary for the needle bar to be mounted on the frame under conditions which cannot be statically determined, and which is a condition that exacerbates the above described negative factors.

The main advantage provided by such means of supporting the needle bar is that it may eliminate the need to manually or empirically find the most desir able operating position for the needle bar with respect to the other elements with which it must co-operate during the performance of its intended function. The adjustable support serves as an intermediary between the needle bar and the frame of the machine for quickly and easily obtaining the most desirable position for the needle bar, and the amount of displacement required can be determined by conventional measuring instruments.

A further characteristic which distinguishes a sewing machine embodying the present invention is that the needle bar is mounted for pivotal movement on the adjustable support which permits the needle bar to swing with respect to the support means and to thus follow the needle-supporting clamp through its displacements while travelling, which, as is known, is not a true rectilinear path.

The main advantage derived from this characteristic is that it eliminates the time-consuming problem of locating the needle bar in its most desirable operating position and allows said needle bar to automatically align itself with the pathway followed by the needle-supporting clamp and to be subjected to a minimum of resistance by the latter. With the features described above, it is now possible to position the needle bar on the frame at a location that corresponds to the dimensions of the control lever and other operating components and in particular at a distance which corresponds to the precise length of their control lever. Additionally, the needle bar can be inclined in accordance with the intermediate axis that contains the deviations of the double "S" shape of the pathway through which the needlesupporting clamp is caused to travel.These features also provide a consistent relationship between the needle-supporting clamp and needle bar from one operating phase to the next, whereby said needle bar is never subjected to more than a minimum amount of sliding resistance.

A still further advantage is that the distance the needle-supporting clamp travels in an upward direction can now be increased, which makes it possible to perform seaming operations on workpieces of greater thicknesses. This is made possible due to the fact that the needle bar is now capable of pivoting movement which permits it to align itself automaticalls with the needle-supporting clamp and is no longer subjected to bending forces which it had to resist with known devices utilizing the double "S" shape of pathway.

An embodiment of the present invention will now be more particularly described by way of example with reference to the accompanying drawings, in which: Fig. 1 is a perspective view of a portion of a sewing machine showing a needle-operating device in a sewing machine according to the said embodiment; and Fig. 2 is a perspective view showing a modification of the adjustable support for the needle bar.

With reference to Fig. 1 of the drawings, the device for operating the needle is mounted on the frame 1 of the sewing machine, which for purpose of simplicity has been shown only in outline form. The operating device includes among its various parts, a needle-supporting clamp 2 with a needle 3 mounted therein and with said clamp 2 being disposed for sliding movement on a needle bar 4. This needle bar 4 is of the stationary type and is mounted on the frame of the machine in a manner that will be more fully described hereinafter.

The needle-carrying clamp 2 is pivotably mounted on one end 5 of a control lever 6 which is also pivotably mounted at a point intermediate its ends on a pivot pin 7. This pivot pin 7 is operatively connected to a crank 8 which is fixedly assembled on one end of an oscillatably driven shaft 9 of the sewing machine.

The end of the control lever 6 opposite end 5 is identified by numeral 10 and is pivotably connected to a movable lever element generally indicated by numeral 11 that is mounted for swinging movement on a pivot pin 12 which is supported by the frame of the machine.

This movable element 11 defines a forked lever 13 and operatively connects the end 10 of the control lever 6 in the forked portion thereof the means of a pin 14. This forked lever 13 provides a means whereby the end 10 of the control lever 6 can be displaced substantially rectilinearly in a direction that is perpendicular to the needle bar4 and simultaneously allows said control lever 6 to swing with the crank 8.

As is well known to these conversant in the art this manner of effecting movement of the end 10 of the control lever 6 is required in order that the opposite end 5 of the latter will travel in a pathway which is substantially rectilinear and parallel to needle bar 4.

The oscillatably driven shaft 9 moves the crank 8 so that it defines an arc of a circle about the shaft and the control lever 6 being connected to said crank by means of pivot pin 7 is caused to pivot on pin 14 and effect alternate upward and downward travel of the end 5 thereof.

Simultaneously with its pivoting movement on pin 14, the control lever is caused to be displaced short distances both in a forward and rearward direction with respect to the needle bar 4 which permits it to follow the curve of the arc of the circle defined by the crank 8.

The combination of the two movements of the control lever 6 described above effects movement of the needle-supporting clamp 2 in a like manner which is mounted on the end 5 of said control lever.

To prevent any possible interference or other negative factor with the desired movement of a needle supporting clamp 2, it is necessary that the needle bar 4 be separately and independently positioned in order to obtain their most desirable operating position in each device applied to a sewing machine. A needle bar cannot be mounted on the frame of a sewing machine in a predetermined position because the various elements with which it co-operates to perform its intended function have dimensions which vary and which is attributed to differences in manufacturing tolerances.Additionally differences in manufacturing tolerances are also present between the locations of the seats in the frame that are adapted to support the pivot pin 12, the oscillatably driven shaft9 and the needle bar4 the invention provides a means whereby it is mounted on an adjustable support 16 that is assembled in and extends from a fixed seat 17 formed in frame 1. The adjustable support 16 includes a body portion 18 having a regulating means that defines a support pin 19 that provides a fulcrum for said adjustable support and is adapted to assemble in the fixed seat 17 wherein it can be selectively positioned and maintained in a desired position by a locking member defining a set screw 20.

A pin member 21 is attached to the body portion 18 so as to extend outwardly from the frame and provide a means for pivotably supporting the needle bar 4. The axis of this pin member 21 is disposed in spaced relation to a common axis 22 of the fixed seat 17 and support pin 19 but extends in a direction that is parallel therewith. This common axis 22 is oriented perpendicularly to a vertical plane which extends to the machine's worksurface 23. This vertical plane contains the control lever 6 at a location intermediate the worksurface 23 and the common axis 22 which is disposed in spaced relation to said worksurface but extends parallel therwith. The needle bar 4 depends from a head 24 of "T" shaped configuration which is adapted to be pivotably supported on the pin member 21 and is eccentrically positionable by means of the adjustable support 16.

The head 24 is attached to the needle bar in a manner whereby the longitudinal extent of the latter extends parallel to the aforementioned vertical plane which contains the control lever 6.

With the needle bar supported in this manner it is capable of independent pivoting relative to the adjustable support 16 so that when the latter is selectively rotated about the common axis 22, the preferred location of the needle bar is arrived at by locating the pin member 21 at its most favorable operating distance from the pivot pin 7. In other words, the adjustable support 16 provides a means for obtaining the most effective position of the needle bar relative to the distance which separates it from the pivot pin 7 of the control lever 6. The head 24 being pivot ably supported on pin member 21 permits the needle bar 4 to follow the deviations which the needle supporting clamp 2 is caused to make during its sliding movement thereon so that said needle bar is never subjected to more than a minimum amount of resistance from said needle supporting clamp.

Axial displacements of the adjustable support 16 with respect to the fixed seat 17 in the frame 1 provide a means which make it possible to eliminate any negative condition that could possible exist between the needle bar and the needle-carrying clamp which, for example, could be caused by inadequate reciprocal positioning between the control lever 6 and the crank 8 which is fixed to the oscillating driven shaft 9 of the machine. The adjust able support 16 has been shown as formed by two separate elements comprising a body portion 18 and a support pin and pin member 19 and 21, respectively. The combination of these elements, as has been heretofore described, serves to position the support 16 in an adjustable manner on the frame and to provide a fulcrum for the needle bar.

Referring now to Fig. 2, the modification of the adjustable support is identified generally by numeral 25 and includes a support bushing 26 whimh defines a fulcrum for said adjustable support; This support bushing is adapted to be assembled in the fixed seat 17 provided in the frame 1 and is provided with an off-centre hole 27 extending therethrough, the axis of which is spaced from but extends parallel with the axis of said support bushing. A pin 28 assembles within the hole 27 and extending therefrom its outer portion can be selectively positioned eccentrically in the same manner as pin member 21 of the adjustable support 16. In Fig. the needle bar is identified by numeral 4' which depends from a head 24' having an outer configuration that is generally spherical.

The outer end of the pin 28 has a spherical member 29 fixed thereon and is adapted to assemble within the head 24' which has a configuration, identified by numeral 30, that conforms to the outer surface of said spherical member 29 and the combination define a ball and socket arrangement for pivotably supporting the needle bar 4'. It should be understood that the combination of the bushing 26 and pin 28 could also be utilized to pivotably support and selectively position the head 24 of "T" shaped configuration of the adjustable support 16 and would function in the same manner as provided for by the supporting elements for said head 24. As with the elements of the adjustable support 16, the ball and socket arrangement of the adjustable support 25 permits the needle bar 4' to follow the deviations which the needle supporting clamp 2 is caused to make during its sliding movement thereon. In other words, the needle bar 4' is capable of automatic alignment with the pathway of the supporting clamp 2 should the latter be caused to function in a plane that is not truly orthogonal to the plane containing the common axis 22.

Although the present invention has been described in connection with a preferred embodiment, it is to be understood that modifications and variations may be resorted to without departing from the scope of the invention as defined in the appended claims.

Claims (10)

1. A sewing machine comprising a needlesupporting clamp mounted for sliding and guided movement in a vertical~plane on a needle bar and pivotally attached to a control lever, which is pivotally connected at one end to a movable lever element and intermediate its end to a crank fixed on an oscillatingly drivable shaft of the machine, the needle bar being mounted on a frame of the machine by an adjustable support comprising a mounting member mounted in and extending from a fixed seat in the frame, the mounting member having an axis extending perpendicularly to said vertical plane, support means operatively connected to the mounting member and having an axis spaced from and extending parallel to said axis of the mounting member, coupling means attached to the upper end of the needle bar and pivotally coupling the needle bar to the support means, and position control means operatively associated with the mounting member for adjusting the position of the support means to thereby selectively vary the distance between the needle bar and the point of pivotal connection of the control lever to the crank.

2. A sewing machine as claimed in claim 1, wherein the mounting member comprises a support pin having a connecting element at one end thereof.

3. A sewing machine as claimed in claim 2, wherein the support means comprises a pin member fixed on and extending from the side of the connecting element remote from the support pin.

4. A sewing machine as claimed in claim 3, wherein the coupling means comprises a substantially T-shaped head pivotably mounted on the pin member.

5. A sewing machine as claimed in claim 1, wherein the mounting member comprises a support bushing.

6. A sewing machine as claimed in claim 5, wherein the support means comprises a spherical member fixed to the free end of a pin mounted in and extending from the support bushing, the axis of the pin being spaced from and extending parallel to the axis of the support bushing.

7. A sewing machine as claimed in claim 6, wherein the coupling means comprises a head having an internal surface conforming to and engaged around the spherical member.

8. A sewing machine as claimed in any one of the preceding claims, wherein the position control means comprises a locking member mounted in the frame in operative association with the fixed seat.

9. A sewing machine substantially as hereinbefore described with reference to Fig. 1 of the accompanying drawings.

10. A sewing machine as claimed in claim 9 and as modified with reference to Fig. 2.