US2344414A - Presser mechanism for sewing machines - Google Patents

Description

March 14, 1944. H RFI-TER PRESSER MECHANISM FOR SEWING MACHINES Filed Nov. 14, 1942 W M M u a m @45 dni? Patented Mar. 14, 1944 UNITED STATES 'if- PRESSER MECHANISM FR SEWING MACHINES Application November 14, 1942, serial No. 465,533

(ci. i12-235) 8 Claims.

This invention relates to sewing machines and more particularly to presser mechanisms for sewing machines.

vThe usual sewing machine is provided with a lower four-motion feed-dog movable in parallel vertical planes and traversing an elliptical path which has its major aXis substantially parallel to the sewing 'machine throat-plate. The feeddog is positioned relative to the throat-plate so that when the feed-dog is traversing the upper portion of its path the feed-dog teeth will project above the top surface of the throat-plate. Therefore, during the first half ofthe feeding movements of the feed-dog, when the dog is above the top surface of thethroat-plate, the feed-dog will move both upwardly and in the direction of feed, thereby to grip fthe work against the presser-foot and-actually lift the presser-foot and presser-bar a short-distance. During the latter half of the feeding movement the feed-dog moves both a downwardly and in the direction'of feed before dropping below the top surface of the throatplate. The downwardly spring biased presserfoot and the presser-bar drop with thefeed-dog until thedown-movement of the work is arrested by the throat-plate. The work then remains stationary while the feed-dog returns below the level of the'throat-platel to its initial position ready to begin another feeding stroke. These engagementsY of the feed-dogwith the work occur'once 2" for each stitch made by the machinaand the presser-bar and foot'must rise andfall with the feed-dog once for each stitch.

Due to the movement of the feed-dog in the direction of feed the work is drawn under the sole portion ofthe presser-foot thereby introducing a sidewise thrust into the presser-bar. This sidewisethrust sets up frictional forces between the presser-bar and its bearings and thus this frictional forcecoupled with'the natural inertia of the -usual presser-bar tends to prevent the presser-bar from returning quickly to its-lower position when the feed-dog movesgdownwardly.

As the speed of a sewing machineis advanced it becomes increasingly ydilcultto return the presser-foot. quickly andforceably down upon the work at the end of the feed-advance stroke of the feed-dog. Atthese higher speeds of operation of the machine, the'friction between the usual presser-barand its bearings is so materially increased-*clue to the increased speed of the work under the presser-foot sole portion, that the spring Iwhich is used to yreturn or lower the presser-barcannot function to completely lower the presser-foot between consecutive work-disengaging and work-engaging movements of the feed-dog. In this 'connection it is to be understood thatthere are limits to the pressure which may be exerted, without detriment, by presserbar springs and particularly with ycertain classes of work.

This sidewise thrust which is developed in the presser-bar when the machine is operating at high speed is increased greatly whenever the presser-foot encounters a cross-seam or a slight increase in thickness of the work. Such an increase in work thickness forms an obstruction whichraises the toe portion of the presser-foot thereby to introduce a relatively large backward force into the presser-foot, which force increases the sidewise thrust of the presser-bar. Consequently it is diiiicult to stitch work of irregular thickness at high speeds on sewing machines of the type heretofore used.

It is an object of the present invention to providea presser mechanism which is adapted for high speed operation and constructed so as to minimize the bearing friction therein.

It is a further object of the present invention to provide a presser mechanism having a very small amount of inertia so that the presser-foot will readily follow the vertical movement of the' feed-dog.

The invention both in structure and in operation, as well as additional objects thereof, will be best understood from the following description taken in conjunction with the accompanying drawing in which:

Fig. 1 is a front elevation of the head of a sewing machine embodying my invention, the faceplate being removed.

Fig. 2 is a side elevation partly in section of a portion of the present presser mechanism.

Fig. 3 is a front elevation, partly in section, of a portion of the present presser mechanism.

Fig. 4 is a sectional view taken substantially along line 4- of Fig. 1.

In the embodiment selected for illustration IG represents the hollow' head of a sewing machine frame into which projects the forward end of the usual rotary needle-bar shaft Il. This end of the shaf t l l carries the usual take-up and needlebar operating cranks 2 and I3, respectively. The needle-bar crank i3 is directly connected by means of the link lil to a needle-bar l5, carrying the eye-pointed needle I6 and journaled in the bearings Vl and lt fixed in the hollow head l.

The take-up is of the so-called link or crank operated type and comprises the usual anglelever having rigidly related arms i9 and 20, the

former of which embraces the take-up operation crank I2, and the latter of which is formed with the thread-eye 2|. The lever I9, 20 is pivotally connected at the junction of its arms to one end of the anchor-link 22, the opposite end of which is pivoted at 23 to the head Hl of the machine. It will be understood that the arm 2n of the takeup lever extends through a slot 24 in the head of the machine.

The above partially described machine is fully disclosed in the patent to Richard Kaier, No. 2,206,285, dated July 2, 1940, to which reference may be had for a more complete description of the sewing machine.

Also located within the hollow head l is a presser-bar 25 journaled in the bearing 26 which is fixed within the head lll by means of a set screw 21. The presser-bar 25 is yieldingly urged downwardly by means of a compression spring 28 the top portion of which bears against the adjusting screw 29 and the bottom of which engages a block 36 fixed to the presser-bar 25. This block 30 may be adjusted along the presser-bar throughv the medium of the set screw 3| which secures the block in place. Loosely surrounding the presser-bar 25 is a collar 32 having a shoulder 33 to which the bottom portion of a link 34 is pivotally secured. The top portion of the link 34 is apertured at 35 and receives one end 36 of the usual treadle-operated presser-bar lifter. When this lifter 36 is raised it carries the collar 32 with it and the collar by engaging the block 36 raises the presser-bar against the action of the compression spring 28.

The presser-bar 25 may also be raised by swinging the usual hand lever 31 upwardly about its pivot 38 thereby to engage the shoulder 33 which in tum bears against and lifts the block 30.

Secured upon the lower end portion of the presser-bar 25 by means of a set screw 39 is a bracket 40 from which extends the inclined bearing tube 4l. Slidably mounted within the tube 4| is a presser-foot plunger 42 to the lower end portion of which is rigidly secured the usual presser-foot 43 by means of the screw 44. The tube 4l and plunger 42 are located in a vertical plane containing the line of feed and they are inclined upwardly in the direction of feed at an angle of about 60 with the usual machine clothplate or work-support 45. The presser-foot is normally situated directly beneath the presserbar 25.

The presser-bar 25 is in the form of a hollow tube which slidingly receives within its lower end the spherical head 46 of a relatively short thrustpin 41 of which the lower sharpened end pivotally engages a notched portion 48 of the plunger 42. Contained within the hollow presser-bar 25 is a vertically disposed compression spring 49 the upper end of which engages the depending rod 56 and the lower end of which engages the spherical head 46 of the thrust-pin 41, thereby to apply the required spring pressure to the presser-foot 43. This pressure may be varied by turning the adjusting screw 29 in the normal manner. The upper end of the rod 50 is fixed to the adjusting screw 29 and the lower end thereof is slidingly received within the upper end of the presser-bar 25. The downward movement of the presserbar 25 is limited by the position of the hand lever 31 against which the collar 32 bears and the spring 28 is strong enough to hold the presserbar 25 in its lowest position during the feeding operations of the mechanism. Fig 1 shows the presser-bar 25 in its lowest position and by adjusting the block 30 the lower or normal sewing position of the presser-bar may be varied.

The upper portion of the tube 4l is cut away as at 5I to afford a slideway for a block 52 which is secured to the plunger 42 by means of a screw 53. Whenever the presser-bar is raised by either the member 36 or the lever 31 the tube 4| will be raised and in so doing a shoulder 54 thereof will engage the block 52 thereby to elevate the plunger 42 and presser-foot 43 assembly against the action of the spring 49 the top portion of which is prevented from any upward movement by means of the normally stationary rod 50.

Thel work to be stitched is intermittently advanced across the cloth-plate 45 by a feeding mechanism of the lower four-motion type and including a feed-dog 55, carried by a feed-bar 56 and projected through suitable feed-slots in the throat-plate 51. Any suitable mechanism may be employed for imparting the usual rising and falling, and the work-advancing and return movements to the feed-dog 55.

As hereinabove described, the feed-dog 55 in its work-advancing stroke raises the presser-foot 43 and exerts a. backward and an upward thrust thereupon. Thus the present presser-foot, when raised by the feed-dog, must move both upwardly and baokwardly against the action of the spring 49, as guided by the tube'4l, and the thrust-pin 41 will pivot about its spherical head 46 within the presser-bar to permit its sharpened end to follow the presser-foot plunger 42. The tube 4| has been tilted substantially with the clothplate 45 as it has been found that by so doing the plunger 42 will lie substantially in the direction of the resultant feed-dog thrust. The presser-foot, therefore, in moving upwardly and backwardly moves in the direction of feed-dog thrust thereby to obviate the usual presser-bar bearing friction resulting from the excessive side pressure of the presser-bar upon its lower bearing.

Fig. 2 illustrates the presser-foot 43 as it first engages a cross-seam 58 of a work-piece 59. It may be readily seen that such a cross-seam would cause the presser-foot not only to rise vertically but it would also tend to move the foot in a backward direction. Thus in the present case the presser-foot may move both in a backward as well as in an upward direction without causing any binding in the presser-bar bearing 26. These movements of the presser-foot, due to the variations in work thickness and the rising and falling of the feed-dog, are not transmitted to the presser-bar 25 which, because of its relatively greater inertia and the frictional forces that are exerted upon it by the rod 56 and the bearing 26, tends to remain in a xed position. The relatively light compression spring 49 is therefore able to return the presser-foot quickly to its downward position when the feed-dog 55 completes its work-advancing stroke.

Having thus set forth the nature of the invention what I claim herein is:

1. The combination in a sewing machine having a work-support, a, head spaced from said work-support, and a needle-bar recprocably journaled within said head and operable in a path substantially perpendicular to said worksupport, of bearing means sustained by said head, a plunger journaled for endwise movement within said bearing means, said plunger being inclined relative to said work-support, a presser-foot secured upon the lower end of said plunger, and spring means in engagement with said plunger,

said spring means exerting a, thrust upon said plunger in a direction penpendicular to said worksupport.

2. In a presser-mechanism for sewing machines, a hollow presser-bar, means to hold said presserbar stationary at a predetermined operative position, bearing means carried at the lower end of said presser-bar, a plunger slidably mounted within said bearing means and being disposed at an angle with the axis of and in a plane containing said presser-bar, a, compression spring carried within said hollow presser-bar, the lower end of said spring being operatively connected with said plunger to force the latter in a downward direction, and a presser-foot carried by the lower end of said plunger.

3. In a sewing machine, a frame including a hollow head, a presser-bar endwise slidably mounted in said head and formed with a cavity extending longitudinally thereof, a bracket xed to the lower end of said presser-bar beneath said head, a plunger slidingly mounted within said bracket and inclined relative to said presser-bar, a spring disposed in the cavity in said presser-bar, means at one end of said spring to transmit the force thereof to said plunger, and a presser-foot carried by the lower end of said plunger.

4. In a sewing machine, a frame including a hollow head, a needle-bar endwise slidably mounted in said head, a bracket sustained by and disposed beneath said head, a plunger slidably carried within said bracket, said plunger being inclined relative to said needle-bar, a spring disposed within said head, means at one end of said spring to transmit the force thereof to said plunger, and a presser-foot carried by the lower end of the plunger.

5. The combination in a sewing machine having a frame including a hollow head, a work-support, and a lower four-motion feed dog, of a presserbar endwise slidably mounted in said head and formed with a cavity extending longitudinally thereof, a bracket iixed to the lower end of said presser-bar beneath said head, a plunger slidably mounted within said bracket, said plunger being inclined relative to said Work-support and being contained within a plane disposed in the direction of feed, a. presser-foot carried by the lower end of said plunger, a spring carried Within the cavity of said presser-bar, means at one end of said spring to transmit the force thereof to said plunger, and means extending into said hollow head for varying the force of said spring.

6. In a sewing machine, a frame including a hollow head, a hollow presser-bar endwise slidably mounted in said head, means to hold said presserbar stationary at a predetermined operable position, a bracket fixed to the lower end of said presser-bar, a tubular bearing member extending upwardly from said bracket and being inclined relative to said presser-bar, a plunger slidably journaled within said tubular bearing member, a presser-foot mounted upon the lower end of said plunger, a spring disposed within said hollow presser-bar, and pivotal means at one end of said spring for engaging said plunger and transmitting the force of the spring thereto.

7. In a sewing machine, a frame including a hollow head, a needle-bar endwise slidably mounted in said head, a bracket sustained by and disposed beneath said head, a tubular bearing member extending from said bracket, said tubular bearing member having its longitudinal axis forming an angle of about 30 with the axis of and lying in a plane containing said needle-bar, a plunger slidably journaled within said tubular bearing member, means associated with said plunger to limit its downward movements, a presser-foot carried upon one end of said plunger, a spring sustained by said head, and means at one end of said spring to transmit the force thereof to said plunger.

8. In a presser-mechanism for sewing machines, a, hollow presser-bar, means to hold said presser-bar stationary at a predetermined operative position, a bracket sustained by and disposed upon the lower portion of said presser-bar, a tubular bearing member extending upwardly from said bracket and being inclined relative to the axis of and lying in a plane containing said presser-bar, a plunger slidably journaled within said tubular bearing member, a presser-foot carried upon the lower end of said plunger, a compression spring carried within said hollow presser-bar, and a thrust-pin having one end thereof in engagement with said spring and its other end pivotally engaging said plunger.

HERMAN RITTER.

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