US3927629A

US3927629A - Sewing machine presser foot and feed dog lifting mechanism

Info

Publication number: US3927629A
Application number: US507214A
Authority: US
Inventors: Kurt Vollmar
Original assignee: Pfaff Industriemaschinen GmbH
Current assignee: Pfaff Industriemaschinen GmbH
Priority date: 1973-10-20
Filing date: 1974-09-18
Publication date: 1975-12-23
Anticipated expiration: 1992-12-23
Also published as: DE2352731C2; JPS5714872B2; DE2352731B1; JPS5066354A; IT1020702B

Abstract

A sewing machine includes a presser foot carried at the end of a vertically movable bar which is biased outwardly to urge the presser foot against the workpiece which is being fed. A feeding dog mechanism includes a lower feed dog below the presser foot and an upper feed dog which overlies a portion of the lower feed dog which is on a pivotal carrier arm linked to the support for the presser foot. The feed dog may be lifted independently of the presser foot by pivotal movement of a lever under the control of the pivotal movement of a bell crank or movable arm of the lifting mechanism. The movable arm and the lever both contain roller means and an endless belt is guided over the roller means on the movable arm and the pivotal lever so that when the lifting mechanism causes movement of the arm in one direction, the belt tightens between the roller means and causes pivotal movement of the lever to lift the lifting dog. Movement in an opposite direction causes a loosening of the endless belt and a relaxation thereof between the roller means of the movable arm and the lever. The endless belt comprises a flat belt having glass fiber reinforcement therethrough and an elastic covering. The presser foot may be lifted in addition to the feed dog by pivotal movement of a hand lever to move it upwardly against its biasing spring force.

Description

United States Patent Vollmar 1 SEWING MACHINE PRESSER FOOT AND FEED DOG LIFIING MECHANISM Primary ExaminerGe0. V. Larkin Attorney, Agent, or Firm-McGlew and Tuttle [5 7] ABSTRACT A sewing machine includes a presser foot carried at the end of a vertically movable bar which is biased outwardly to urge the presser foot against the workpiece which is being fed. A feeding dog mechanism includes a lower feed dog below the presser foot and an upper feed dog which overlies a portion of the lower feed dog which is on a pivotal carrier arm linked to the support for the presser foot. The feed dog may be lifted independently of the presser foot by pivotal movement of a lever under the control of the pivotal movement of a bell crank or movable arm of the lifting mechanism. The movable arm and the lever both contain roller means and an endless belt is guided over the roller means on the movable arm and the pivotal lever so that when the lifting mechanism causes movement of the arm in one direction, the belt tightens between the roller means and causes pivotal movement of the lever to lift the lifting dog. Movement in an opposite direction causes a loosening of the endless belt and a relaxation thereof between the roller means of the movable arm and the lever. The endless belt comprises a flat belt having glass fiber reinforcement therethrough and an elastic covering. The presser foot may be lifted in addition to the feed dog by pivotal movement of a hand lever to move it upwardly against its biasing spring force.

10 Claims, 2 Drawing Figures US. Patent Dec. 23, 1975 3,927,629

SEWING MACHINE PRESSER FOOT AND FEED DOG LIFTING MECHANISM FIELD AND BACKGROUND OF THE INVENTION This invention relates in general to the construction of sewing machines and, in particular, to a new and useful lifting apparatus for effecting the lifting of an upper dog of a feed dog mechanism and a presser foot.

DESCRIPTION OF THE PRIOR ART The present invention deals particularly with the construction of a lifting mechanism for lifting a presser foot and an upper dog of a feed dog mechanism. In the known devices of this kind, a lifting motion between the drive member and the associated feed element acting on the presser foot is provided in order to ensure that in its lowered position the foot applies against the work material only under the pressure of the spring associated therewith. As the drive member impinges upon the feed element, loud noises are produced, and undesirable oscillations are generated, due to the inertia forces of the moved masses, particularly at high sewing speeds. These oscillations considerably affect the accuracy of advance of the work material.

SUMMARY OF THE INVENTION The invention provides a lifting mechanism which makes it possible to avoid the disadvantages of the prior art constructions and permit the abrupt transition between the rest and the lifting phases of the feed dog. For this purpose, the invention provides a connection between a lifting member or lever for effecting the upward motion of the feeding dog associated with the presser foot is connected to a mechanism for operating the lifting lever by means of an endless belt which is engaged around rollers on the respective members which are to be moved. The endless belt establishes a connection between the feed dog and the associated lifting mechanism through a damping element in the form of the endless belt. The belt has a constant length and is looped around rollers which are carried on a pivotal lever connected to the lifting dog and the pressor foot and a similar roller, carried on a crank arm, which is part of the operating mechanism. The belt is advantageously made of elastic material with fiber reinforcements therethrough and it acts, not only as a damping element, but it provides an advantage inasmuch as it has a very small mass. The fiber glass reinforcement ensures that the belt remains at a constant length and the elastic covering ensures a sufficient damping.

Accordingly, it is an object of the invention to provide an improved mechanism for lifting an upper feed dog and a pressor foot by the operation of a lifting mechanism which is connected to a pivotal lift member or lifting lever connected to the dog and to the pressor foot by a transmitting damping member in the form of an endless belt which is connected between rollers on the lifting lever and the movable arm of the lifting mechanism.

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

The various features of novelty which characterizes the invention are pointed out with particularity in the claims annexed to and forming a part of this disclosure.

For a better understanding of the invention, its operating advantages and specific objects attained by its uses, reference should be had to the accompanying drawing and descriptive matter in which there is illustrated a preferred embodiment of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to the drawings in particular, the invention embodied therein comprises a sewing machine which has a presser bar 3 which is mounted in a bushing 2 secured on a housing 1 of the sewing machine and which may be displaced vertically in the bushing. A support 4 is secured to the lower end of the presser bar 3 and it includes a rearwardly extending arm portion 4a, an extension for a double arm link 22 and a link 26 and a forward portion 4b which carries a presser foot 6.

In accordance with the invention, the lifting mechanism includes a rotatable arm shaft 7 which is driven by drive means (not shown) and which contains separate eccentrics 10 and 11 at spaced locations therealong. The machine also includes a driving mechanism (not shown) for driving a needle bar 8 with a needle 9. Eccentric 10 is embraced by an eccentric lever, 12 and it carries a sliding block at its outer end 14 which is guided in an adjusting link 13. Link 13 is carried on an adjusting shaft 15 which may be rotated in order to position the block at a desired location in respect to the eccentric lever 12. The sewing machine also includes a feed mechanism which includes a lower feed dog 17 which projects through a needle plate 16 over which the workpiece (not shown) is fed and an upper dog 43 which is cooperable with the workpiece to advance it in respect to the presser foot 6. A hand lever (not shown) is adjustable to determine the extent and direction of the feed motion of the lower feed dog 17.

In accordance with the positioning of the sliding block 14 by the setting of adjusting shaft 15, a lateral movement is imparted through a link 18 which is connected to the upper end of a lever 19 mounted in the housing. The lower end of lever 19 is connected to a second link 20 which in turn is pivotally connected to a stud 21 which is carried by a two-bar link 22 hinged to the arm portion 4a of support 4.

The lifting mechanism also includes the eccentric 11 which carries an eccentric lever 23 which is connected to one arm of abell crank 24. The bell crank is pivotally mounted at 24a on the housing and it has an opposite arm with an eyelet 31 carrying a roller pin 32 having a roller 30 and an outer guide 36. Movement of the bell crank arm 24b in one direction causes tightening of an endless belt 25 which is engaged around the roller 30 and around a counter-roller 33 which is carried on 3 covering 29.

Lever 27 is pivotally mounted on link 26 and its lower end is provided with a fork 28 which engages around a roller 40 carried on a pin 39 affixed to the upper end of a bifurcated portion 41 of a carrier arm 42 for the upper feed dog 43. The carrier arm 42 is supported on a stud 21 which is also connected to the link The presser foot 6 is urged in a direction toward engagement with the workpiece by a flat spring 44 which is secured at one end to the housing 1 and applies at its free end against a ball 46 which is received in the recess 45 of the upper end of the presser bar 3. The ball transmits the pressure through the presser bar 3 to the presser foot 6 to the work material which is pressed on the lower feed dog 17 and on the needle plate 16.

A flat spring 47 is secured at its one end on the outside of housing 1 and its opposite free end extends downwardly and is biased against the pin 35. Set screw 48 is threaded into a portion of the housing 1 and it is located so that it may be threaded to adjust its outer end which bears against the spring 47 in order to adjust the force of the spring. The spring 47 acting through the pin 35 adjusts the pressure of the upper feed dog 43 upon the work material and this may be changed by the threaded adjustment of the set screw 48.

A separate lifter for lifting the presser bar 3 comprises a lever member 52 having a surface 51 which engages against a surface 50 of a collar member 49 which is secured to the presser bar and movement of the hand operated lever 52 will effect a separate movement of the presser bar along with the presser foot 6 against the biasing force of a spring 44.

The device operates as follows:

Upon rotation of the arm shaft 7, the two eccentrics 10 and 11, as well as the other sewing mechanisms of the machine, are driven. Eccentric 10 causes the pivoting of eccentric lever 12 so that the sliding block 14 is displaced on an adjusting link 13. According to the orientation of link 13 which may be changed by the adjusting shaft 15, double-lever 19 is moved by the link 18 through a predetermined angle as set by the adjustment. In response to this movement, the carrier arm 42, which is linked to the double lever 19 and to the upper feed dog 43, executes stroke motions of a corresponding extend in the direction of advance of the feed.

Eccentric 11 causes a pivotal movement of lever 27 through eccentric lever 23, bell crank 24 and belt 25. During this movement, belt 25 tightens around its

respective rollers

30 and 33 and the fork 38 of lever 27 is lifted and lowered. Some motion is also transmitted through the link 26 to the arm portion 4a of the support 4 for the presser foot 6.

When bell crank 24 is pivoted counter-clockwise, belt 25 slackens on its associated

rollers

30 and 33 as soon as the upper feed dog 43 applies against the work material or against the lower feed dog 17 under the action of the biasing spring 47. At that time, presser foot 6 which is loaded by flat spring 44 and the upper feed dog 43 under the action of flat spring 47, apply conjointly against the work material.

As the bell crank subsequently pivots clockwise, belt 25 is stretched and firmly applied against the two

rollers

30 and 33 and takes lever 27 along in the counterclockwise direction. Due to its elastic sheathing 29, the belt 25 applies against

rollers

30 and 33 without any substantial impingement effect and without any noise.

Upon lifting of fork 38, slide roller 40, and thereby, bifurcated portion 41 carrying upper feed dog 43, are also displaced upwardly. This lifting motion takes place against the action of flat spring 47 which biases lever 27. After the upper feed dog 43 has been lifted from the work material, the work material is held down only by the presser foot 6 which is loaded by the flat spring 44.

If presser foot 6 is to be lifted, hand lever 52 must be swung upwardly. When hand lever 52 is swung inwardly, stop portion 51 applies against the lifter collar 49 and lifts the pressure bar 3 along with the presser foot 6. Since the upper feed dog is pivotally connected to the support arm 4a through the two-bar link 22 and the lever 27 and the extension 26, the upper feed dog 43 is also lifted at the same time.

The use of the belt 25 in transmitting the force for effecting lifting of the upper feed dog is only one example of such an operating device. Such a belt transmission is also usable with similar advantages in other periodically controlled presser foot lifting operations.

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 otherwise without departing from such principles.

What is claimed is:

1. A sewing machine, comprising a presser foot engageable with a workpiece during the feeding thereof, spring means biasing said presser foot toward engagement with the workpiece, feed dog means including an upper feed dog, a lift member connected to said upper feed dog and said presser foot and being movable to lift at least said upper feed dog therewith, a lifting mechanism including a movable arm, said arm and said -lift member having roller means thereon, and and endless belt of constant length engageable over said roller means of said arm and said lift member and being movable in one direction of motion of said lift member to move said arm therewith to raise said upper feed dog, and being movable upon the movement of said lift member in another direction to loosen between said roller means of said lift member and said roller means of said arm.

2. A sewing machine, according to claim 1, wherein said endless belt comprises an elastic member having reinforcing strands therein.

3. A sewing machine, according to claim 1, including a presser bar carrying said presser foot, means for guiding said presser bar for vertical movement, a lift collar on said presser bar, and a lift lever pivotally mounted adjacent said presser bar and being movable to engage said lift collar to lift said presser bar with said presser foot.

4. A sewing machine, according to claim 3, including a support at the lower end of said presser bar having one portion carrying said presser foot and having an opposite end portion, a link connected between said opposite portion and said upper feed dog, a lever support link connected to said support at one end and having an opposite end, said lift member comprising a lever pivoted on said opposite end of said lever support link.

5. A sewing machine, according to claim 4, wherein said movable arm comprises a crank arm, a rotatable shaft having an eccentric with a lever connected to said crank arm and being movable to displace said crank arm, .said crank arm having an opposite arm portion from the connection to said eccentric having said arm roller means thereon, said lever member carrying said lift member roller means.

6. A sewing machine, according to claim 5, wherein said roller means includes rotatable rollers having; outer disc guides thereon for preventing lateral withdrawal of the endless belt.

7. A sewing machine, according to claim 6, including a spring biased against said lever and urging it in a direction to move said upper feed dog downwardly against said workpiece.

8. A sewing machine, according to claim 7, including means for adjusting the force of said spring.

9. A sewing machine, comprising a presser foot engageable with a workpiece during the feeding thereof, a presser bar carrying said presser foot, first spring means biasing said presser foot toward engagement with the workpiece, feed dog means including an upper feed dog, a lift member connected to said upper feed dog, and being movable to lift said upper feed dog therewith, said lift member being pivotally mounted on said presser bar, second spring means biased against said lift member and urging it in a direction to move said upper feed dog downwardly against said workpiece, said lifting mechanism also including a movable arm, said arm and said lift member having roller means thereon, and an endless belt of constant length engageable over said roller means of said arm and said lift member and being movable in one direction of motion of said lift arm to move said lift member therewith to raise said upper feed dog, and being movable upon the movement of said arm in another direction to loosen between said roller means of said lift member and said roller means of said arm.

10. A sewing machine, comprising a housing, a feed dog in said housing, spring means acting on said feed dog to press the dog against a workpiece dyring the feeding thereof, first drive means connected to said feed dog to impart a motion in the feed direction to the feed dog, second drive means connected to impart a motion to the feed dog lifting the feed dog temporarily from the workpiece against the action ofsaid spring means, coupling means between the second drive means and the feed dog effective only in one direction of motion, a movable member having first roller means, said second drive means being connected to said movable member, a support secured to said housing, a swing arm pivotally mounted on said support and connected to said feed dog, second roller means, said coupling means comprising an endless flat belt having a constant length and provided with an elastic coating,

which is passed around said first and second roller means.

Claims

1. A sewing machine, comprising a presser foot engageable with a workpiece during the feeding thereof, spring means bising said presser foot toward engagement with the workpiece, feed dog means including an upper feed dog, a lift member connected to said upper feed dog and said presser foot and being movable to lift at least said upper feed dog therewith, a lifting mechanism including a movable arm, said arm and said lift member having roller means thereon, and and endless belt of constant length engageable over said roller means of said arm and said lift member and being movable in one direction of motion of said lift member to move said arm therewith to raise said upper feed dog, and being movable upon the movement of said lift member in another direction to loosen between said roller means of said lift member and said roller means of said arm.

5. A sewing machine, according to claim 4, wherein said movable arm comprises a crank arm, a rotatable shaft having an eccentric with a lever connected to said crank arm and being movable to displace said crank arm, said crank arm having an opposite arm portion from the connection to said eccentric having said arm roller means thereon, said lever member carrying said lift member roller means.

6. A sewing machine, according to claim 5, wherein said rollelr means includes rotatable rollers having outer disc guides thereon for preventing lateral withdrawal of the endless belt.

10. A sewing machine, comprising a housing, a feed dog in said housing, spring means acting on said feed dog to press the dog against a workpiece dyring the feeding thereof, first drive means connected to said feed dog to impart a motion in the feed direction to the feed dog, second drive means connected to impart a motion to the feed dog lifting the feed dog temporarily from the workpiece against the action of said spring means, coupling means between the second drive means and the feed dog effective only in one direction of motion, a movable member having first roller means, said second drive means being connected to said movable member, a support secured to said housing, a swing arm pivotally mounted on said support and connected to said feed dog, second roller means, said coupling means comprising an endless flat belt having a constant length and provided with an elastic coating, which is passed around said first and second roller means.