US2957645A

US2957645A - Device for adjusting the tension of the upper thread of sewing machines

Info

Publication number: US2957645A
Application number: US715113A
Authority: US
Inventors: Wenz Herbert; Berg Heinrich
Original assignee: GM Pfaff AG
Current assignee: GM Pfaff AG
Priority date: 1957-02-21
Filing date: 1958-02-13
Publication date: 1960-10-25
Anticipated expiration: 1977-10-25
Also published as: CH359965A; DE1033493B; FR1198857A; GB826538A

Description

Oct. 25, 1960 Filed Feb. 13, 1958 2 ET AL 2,957,645

H. WEN DEVICE FOR ADJUSTING THE TENSION OF THE UPPER THREAD OF SEWING MACHINES 3 Sheets-Sheet 1 INVENTOR Oct. 25, 1960 H WENZ EIAL 2,957,645

DEVICE FOR AD JUSTING THE TENSION OF THE UPPER THREAD F SEWING MACHINES Filed Feb. 13, 1958 3 Sheets-Sheet 2 FIG-Z2 E h M 2 2 I? 45 7.27

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Oct. 25, 1960 H. WENZ ET AL 2,957,645

DEVICE FOR ADJUSTING THE TENSION OF THE UPPER THREAD 0F sswmc MACHINES ZWW United States Patent @fiiice 2,957,645 Patented Oct. 25, 1960 DEVICE FOR ADJUSTING THE TENSION OF THE UPPER THREAD OF SEWING MACHINES Herbert Wenz and Heinrich Berg, Kaiserslautern, Pfalz,

Germany, assignors to G. M. Pfalf A.-G., Kaiserslautern, Pfalz, Germany Filed Feb. 13, 1958, Ser. No. 715,113 Claims priority, application Germany Feb. 21, 1957 4 Claims. (Cl. 242-150) The invention relates to a device provided on the housing of a sewing machine for adjusting the tension of the upper thread.

Devices of this type known heretofore comprise tension disks which rest against each other under the pressure of a spring. The force applied against the disks by a pressure spring can be changed by varying the setting of a turning knob. The rotatable or turning knob has already been constructed in the form of a cap and brought closer to the housing of the machine; however, the part of the tensioning spring which rests against the thread extends beyond the device, and as a result the thread tensioning spring can be easily damaged as a result of inadvertence. Furthermore, the structural length of the devices in accordance with the prior art is relatively great.

It is therefore an object of the invention to arrange the thread tensioning spring in a shielded manner so that it is not accessible from the outside except for the thread.

It is a further object of the invention to provide a device of this type of shortest possible structural length and imparting thereto an enclosed overall appearance.

in accordance with the invention these objects are achieved by locating the thread tensioningspring completely within the space formed by the rotating knob, the thread insertion slot and the adjacent portion of the housing, while a guiding member for the thread, which is known per se and has a guiding edge for automatically leading the thread into a reversing hook and which covers a circumferential portion of the thread insertion slot from the inside, is arranged between said slot and the portion of the thread tensioning spring which rests against the thread.

Suitably the said guiding member is cylindrically curved and consists of a unitary device having a supporting cylinder to which the helically shaped rear end of the thread tensioning spring is anchored. This cylinder has an outer diameter which is smaller than the inner diameter of the thread guiding member by at least the thickness of the thread tensioning spring, while in the stepped intermediate portion which is located between the two, a slot is provided which limits the amount of projection and the movements of the portion of the thread tensioning spring which rests against the thread.

It is possible to obtain a particularly short structural length in the design of the device while avoiding the danger of any wedging thereof even for a short time in that in accordance with a further concept of the invention the tensioning disks and a nest of plate springs serving as a pressure spring are disposed upon a carrier sleeve which slides axially upon a stationary shaft and which must be brought into operative engagement with a release pin disposed in the axial bore of the shaft. Between the part carrying the tensioning disks and the plate springs, a separating disk is rigidly connected to the carrier sleeve. The part carrying the plate springs has an inner diameter which is greater than the outer diameter of an internally threaded member which extends inwardly from the turning knob. Furthermore, an abutment is provided in the interior of the rotating knob for the limiting of the turning knob setting in a known manner to one turn, which abutment cooperates with a lug on the thread guiding member.

Further objects and details of the invention will become apparent from the drawing which illustrates embodiments of the invention and in which Fig. 1 is an overall view of the new device secured to the head of a sewing machine,

Fig. 2 is a cross section through the device drawn to a considerably enlarged scale,

Fig. 3 illustrates separate components of the device in an exploded view, and

Fig. 4 is a section through a different embodiment.

The head 1 of the sewing machine is provided with a cavity 2 which is surrounded by a tubular projection 3 which extends inwardly of the head 1. A supporting member 4 is secured in said projection by means of a set screw 6 which engages a tapered annular groove 5 in member 4.

The supporting member 4 is provided with an axial cylindrical bore 7 to receive a hollow shaft 8 which is illustrated in Fig. 3. The hollow shaft 8 has a section provided with a slot 9 and with a threaded portion 10, an intermediate portion 12 connected therewith and having a longitudinal slot 11, and behind that a section 13 of somewhat larger diameter which corresponds to the inner diameter of the bore 7. At the end of section 13 an annular groove 14 is provided which receives a spring ring 15 (Fig. 2). The shaft 8 furthermore is, provided with a bore 16 which extends from the rear end up to the longitudinal slot 11 and is there provided with a suitably smaller inner diameter corresponding to the smaller outer diameter of shaft '8 in that location. The axial bore 16 the arrow (Fig. 2) when the presser foot is lifted. These two pins may also be made in a single unit.

Shaft 8 is secured in the supporting member 4 by means of a set screw 20 which is in threaded engagement with a radial bore 19 in the supporting member 4. A supporting sleeve 21 is slidingly received upon the center section 12 of the shaft 8, which sleeve is provided at its rearward end with two slots 22 which receive the ends of an actuating bridge 23 which extends through the longitudinal slot 11 and which cooperates with the transfer pin 18. The supporting sleeve 21 has a portion 24 which slides on the center section 12 of shaft 8 and upon which three annular tensioning disks 2'5, 26, 27 are aligned. A

nest of annular disk springs 29 is arranged upon a further portion 28 of the supporting sleeve 21 which is of somewhat greater diameter. A separating disk 30 which constitutes a unitary structure with the carrier sleeve 21 is located between the portions 24 and 28.

The inner diameter of the portion 28 which carries the disk springs 29 is greater than the outer diameter of a threaded member 32 which extends axially inwardly from the turning or setting knob 31 and by means of which the turning or setting knob 31 is mounted upon the thread 10 on shaft 8. The disk springs 29 rest against the inside of turning knob 31.

In setting the turning knob 31 the threaded member 32 and the portion 38 carrying the disk springs 29 can telescope one into the other, so that without lengthening of the knob 31 and without weakening the supporting thread, the end of shaft 8 can be set behind the front surface of turning knob 31 in any position of adjustment. As a result of the use of plate springs only a short axial movement of the turning knob 31 is necessary to cover the entire range of resiliency of disk springs 29. It is possible to achieve this even with threads having a small pitch with a single rotation of the rotating knob 31.

A carrier cylinder 33 is secured to the supporting member 4 by means of pins 34 to which is fastened a cylindrioally curved thread guiding member 36 by way of a stepped intermediate portion 35. As viewed in Fig. 1 at the right half of the device the thread guiding edge 37 of this member extends proximate the head 1 and rises in the left half from the bottom upwardly as an enlarged portion of the guiding member 36 defining a curve which leads to a deflecting hook portion 38 as seen in the upper half of Fig. 2. A lug 39 projecting from the guiding member 36 cooperates with an abutment 40 provided in the interior of the turning or setting knob 31 and limits the movement of the turning knob 31 to one turn. A-tongue 41 stamped out of the lug 39 serves as indicator for a scale provided on the outer surface 42 of the turning knob 31.

The supporting cylinder 33 is provided with apertures 44 above the annular groove 43 of the supporting member 4 for inserting and anchoring the bent end of the thread tensioning spring 45. The helically formed part of this spring is slidingly received on the supporting cylinder 33, while its part 46 which rests against the thread extends through a slot 47 in the stepped intermediate portion 35. The portion 46 of the thread tensioning spring 45 which engages the thread is thus located below and shielded by the thread guiding member 36 and this in turn is located below the gap 48 remaining open between head 1 and turning knob 31 for introducing the thread.

In assembling the device the supporting cylinder 33 is first connected with the supporting member 4 by means of pins 34, and the set screw 20 is threaded into the thread bore 19. Thereupon the tensioning disks 25, 26, 27 are aligned upon the part 24 of the supporting sleeve 21, the part 24 is placed upon the center section 12 of shaft 8 (Fig. 3) and the ends of the actuating bridge 23 which is received in the longitudinal slot 11 are located in the slots 22. The section 13 of the shaft provided with the carrying sleeve 21 and the tensioning disks 25, 26, 27 is introduced from the front into the bore 7 of the supporting member 4 to an extent that the annular groove 14 projects from the opposite end of the bore 7 and can thus be provided with the split ring 15. The shaft 8 is then secured in place by means of set screw 20 in a manner that the spring ring 15 rests against the supporting member 4. Thereupon the disk springs 29 are aligned upon member 28 of the supporting sleeve 21, and the turning knob 31 is mounted upon the thread of the shaft 8 until the abutment 40 contacts the lug 39. Now the set screw 20 is again somewhat loosened, whereupon shaft 8 is rotated to the left by means of a screw driver inserted in slot 9 while the turning knob 31 is held in place. In this manner the turning knob 31 can be threaded upon the shaft 8 to a point where the force exerted upon the tensioning disks 25, 26, 27 corresponds to that indicated by the pointer 41 along the scale 42. In this connection the disk springs 29 apply a force to shaft 8 by way of turning knob 31 so that the split ring is in contact with the supporting member 4, as a result of which shaft 8 is fixed in position axially in spite of set screw being loosened. For securing the tensioning adjustment of the disk springs 29 in the position corresponding to that indicated, the set screw 20 is again tightened. Finally, the thread tightening spring 45 is placed upon the supporting cylinder 33 and its part 46 is inserted through the slot 47. The other turned up end of the thread tightening spring 45 is hooked into one of the openings 44 so that the spring will have the desired tension.

It is now possible to mount the structure thus assembled as a unit in the cavity 2 of the head 1 of the sewing machine where it is secured by means of the set screw 6.

The thread is inserted by passing it through the guide member 49, whereupon the loose end between the operators hand and member 49 is moved into the slot 48 from the right. The end of the thread held in the hand is then wound about the device in a clockwise direction. Thus the thread engages the lead edge 37, and sliding along the edge it comes into engagement with the end of member 46, carrying the same along until it slides behind the reversing hook 38. After the free end of the thread is pulled through eyelet 50 of the thread feeding lever and eyelet 51 on the lid of the machine head the position of the thread is established as shown in Fig. 1.

In the embodiment of the device in accordance with the invention illustrated in Fig. 4 a supporting member 104 is located in the tubular projection which surrounds the cavity 2 in the head 1, where it is secured by means of set screw 6. In a manner similar to that shown in Fig. 2 the supporting cylinder 33 having a guiding edge 36 and supporting the thread pulling spring 45 is secured to the supporting member 104. Similar parts are identified by the same reference numeral. A hollow shaft 108 which is provided with a longitudinal slot 111 at its forward end is secured in a bore 107 of the supporting member by means of a set screw 120. A bolt 132 which is securedly connected to turning knob 131 is journalled in the bore 116 of the hollow shaft 108 and carries the tension disks 25, 26, 27, and the end of said bolt is provided with a male thread 110. An internally threaded member 121 which presents two arms 123 which project through the longitudinal slot 111 is mounted on the bolt. A disk 130, slidingly received upon hollow shaft 108 engaging these arms is contacted by the disk springs 29 which are supported against an abutment 52 which is securely connected with the sleeve 108. The turning or setting knob 131 is provided with an abutment 140 which cooperates with the lug 39 of the thread guiding member 36, and it also carries a scale around its outer surface 142.

Rotating the turning knob 131 changes the axial position of the threaded member 121 which is guided in the slot 111 by the arms 123 and thus the pressure exerted by the disk upon the disk springs 29. The counter pressure of the springs 29 which is the same is applied to the tensioning disks 25, 26, 27 by way of the disk 130, threaded member 121, bolt 132 and turning knob 131. In this manner the tensioning disks are pressed with variable pressure against the front end of the sleeve 108.

The threading is effected in the same manner as in connection with the embodiment according to Fig. 2. During releasing of the device by means of the pressure pin 17 the turning knob 131 is raised from the tensioning disks 25, 26, 27 while the disk springs 29 are pressed together.

Having now described our invention with reference to the embodiments illustrated in the drawings, we do not Wish to be limited thereto, but what we desired to protect by Letters Patent of the United States is set forth in the appended claims.

We claim:

1. Device for adjusting the tension of the upper sewing thread in a sewing machine by means of pressure disks which engage one another under spring pressure, said device comprising a support member adapted to be received in an aperture provided in the housing proximate the head of the machine and means for securing said support member in said housing, a setting knob disposed externally of and spaced from said housing having a rearwardly extending circumferential wall portion, a threaded shaft operatively associated with said knob exextending into said support member, a plurality of pressure disks and pressure spring means disposed coaxially of said threaded shaft and operatively related to said shaft for applying variable pressure from said spring means to said disks, a guiding member extending around.

mun? a circumferential portion of said pressure disks in the space between said support member and said knob and presenting a thread deflecting portion and a guiding edge in communication with said thread deflecting portion projecting under said circumferential wall portion and enclosing a portion of the space intermediate said knob and said support member, said thread deflecting portion extending substantially transversely of said guiding edge, and a thread tensioning spring mounted around said support member having one end extending transversely of and below said guiding member and said guiding edge, said spring being disposed in its entirety in the space between said knob, said guiding member and the proximate wall of said housing defining said aperture and said end being shielded by said guiding member in the space intermediate said knob and said housing.

2. Device for adjusting the tension of the upper sewing thread in a sewing machine by means of pressure disks which engage one another under spring pressure, said device comprising a support member adapted to be received in an aperture provided in the housing proximate the head of the machine and means for securing said support member in said housing, a setting knob disposed externally of and spaced from said housing having a rearwardly extending circumferential wall portion, a threaded shaft operatively associated with said knob extending into said support member, a plurality of pressure disks and pressure spring means disposed coaxially of said threaded shaft and operatively related to said shaft for applying variable pressure from said spring means to said disks, a guiding member extending around a circumferential portion of said pressure disks in the space between said support member and said knob and presenting a thread deflecting portion and a guiding edge in communication with said thread deflecting portion projecting under said circumferential wall portion and enclosing a portion of the space intermediate said knob and said support member, and a thread tensioning spring mounted around said support member having one end extending transversely of and below said guiding member and said guiding edge, said spring being disposed in its entirety in the space between said knob, said guiding member and the proximate Wall of said housing defining said aperture and said end being shielded by said guiding member in the space intermediate said knob and said housing, said guiding member being cylindrically curved and including a supporting cylinder presenting anchoring means retaining the other end of said thread tensioning spring, said supporting cylinder having an outer diameter smaller than the inner diameter of said guiding member by at least the material thickness of said thread tensioning spring and a stepped intermediate portion connecting said supporting cylinder and said guiding member and defining a slot receiving said one end of said spring.

3. Device for adjusting the tension of the upper sewing thread in a sewing machine by means of pressure disks which engage one another under spring pressure, said device comprising a support member adapted to be received in an aperture provided in the housing proximate the head of the machine and means for securing said support member in said housing, a setting knob disposed externally of and spaced from said housing having a rearwardly extending circumferential wall portion, a threaded shaft operatively associated with said knob extending into said support member, a plurality of pressure disks and pressure spring means disposed coaxially of said threaded shaft and operatively related to said shaft for applying variable pressure from said spring means to said disks, a guiding member extending around a circumferential portion of said pressure disks in the space between said support member and said knob and presenting a thread deflecting portion and a guiding edge in communication with said thread deflecting portion projecting under said circumferential wall portion and enclosing a portion of the space intermediate said knob and said support member, and a thread tensioning spring mounted around said support member having one end extending transversely of and below said guiding member and said guiding edge, said spring being disposed in its entirety in the space between said knob, said guiding member and the proximate Wall of said housing defining said aperture and said end being shielded by said guiding member in the space intermediate said knob and said housing, said setting knob having a threaded portion and said threaded shaft comprising a solid portion engaging said threaded portion and a hollow portion, and a carrier sleeve slidingly received on said solid portion, said sleeve supporting a plurality of annular disks defining said pressure spring means and said pressure disks and having a rigid spacing disk between said spring means and said pressure disks, the portion of said carrier sleeve supporting said spring means being of greater outer diameter than the portion supporting said pressure disks and of greater inner diameter than the outer diameter of said threaded portion of said knob.

4. Device for adjusting the tension of the upper sewing thread in a sewing machine by means of pressure disks which engage one another under spring pressure, said device comprising a support member adapted to be received in an aperture provided in the housing proximate the head of the machine and means for securing said support member in said housing, a setting knob disposed externally of and spaced from said housing having a rearwardly extending circumferential wall portion, a threaded shaft operatively associated with said knob extending into said support member, a plurality of pressure disks and pressure spring means disposed coaxially of said threaded shaft and operatively related to said shaft for applying variable pressure from said spring means to said disks, a guiding member extending around a circumferential portion of said pressure disks in the spacebetween said support member and said knob and presenting a thread deflecting portion and a guiding edge in communication with said thread deflecting portion projecting under said circumferential wall portion and enclosing a portion of the space intermediate said knob and said support member, and a thread tensioning spring mounted around said support member having one end extending transversely of and below said guiding member and said guiding edge, said spring being disposed in its entirety in the space between said knob, said guiding member and the proximate wall of said housing defining said aperture and said end being shielded by said guiding member in the space intermediate said knob and said housing, said setting knob having a threaded portion and said threaded shaft comprising a solid portion engaging said threaded portion and a hollow portion, and a carrier sleeve slidingly received on said solid portion, said sleeve supporting a plurality of annular disks defining said pressure spring means and said pressure disks and having a rigid spacing disk between said spring means and said pressure disks, the portion of said carrier sleeve supporting said spring means being of greater outer diameter than the portion supporting said pressure disks, said knob having an inwardly extending abutment and said guiding member presenting a lug adapted to be engaged by said abutment for limiting the rotation of said knob.

References Cited in the file of this patent UNITED STATES PATENTS 1,167,823 Huffman et al. Jan. 11, 1916 1,534,264 Hanson Apr. 21, 1925 2,166,770 Roberts July 18, 1939 2,462,812 Parry et al Feb. 22, 1949 2,518,703 Marsac Aug. 15, 1950 2,609,772 Roberts Sept. 9, 1952