US2729179A

US2729179A - Sewing machine bearing and pitman construction

Info

Publication number: US2729179A
Application number: US310295A
Authority: US
Inventors: John G Attwood
Original assignee: Union Special Machine Co
Current assignee: Union Special Machine Co
Priority date: 1952-09-18
Filing date: 1952-09-18
Publication date: 1956-01-03
Anticipated expiration: 1973-01-03
Also published as: GB726638A; DE953482C; FR1080957A

Description

Jan. 3, 1956 J. G. ATTWOOD 2,729,179

SEWING MACHINE BEARING AND PITMAN CONSTRUCTION Filed Sept. 18, 1952 6 Sheets-Sheet 2 INVEN TOR. JOHN G. ATTWOOD ATTORNEY Jan. 3. 1956 J. G. ATTWOOD SEWING MACHINE BEARING AND PITMAN CONSTRUCTION 6 Sheets-Sheet 3 Filed Sept. 18, 1952 INVENTOR JOHN G. ATTWOOD v QI ATTORNEY Jan. 3, 1956 J. G. ATTWOOD SEWING MACHINE BEARING AND PITMAN CONSTRUCTION Filed Sept. 18, 1952 6 Sheets-Sheet 4 INVENTOR JOHN G. ATTWOOD ATTORNEY Jan. 3, 1956 J. 5. ATTWOOD SEWING MACHINE BEARING AND PITMAN CONSTRUCTION Filed Sept. 18, 1952 6 Sheets-Sheet 5 INVENTOR. JOHN G. ATTWOOD ATTORNEY Jan. 3, 1956 .1. s. ATTWOOD SEWING MACHINE BEARING AND PITMAN CONSTRUCTION FIG.22

Filed Sept. 18, 1952 FIG.2I

INVENTOR JOHN G. ATTWOOD A C (1 y ATTORNEY United States Patent SEWING MACHINE BEARING AND PITMAN CONSTRUCTION John G. Attwood, Oak Machine Company, Illinois Park, Ill., assignor to Union Special Chicago, 11]., a corporation of The present invention relates to sewing machines and more particularly to bearing and pitman elements for use therein.

In many sewing machines, the top operating speed is limited by failure of cooperating relatively moving parts due to misalignment. For example, in flat bed sewing machines of the type disclosed in U. S. Patent 2,446,342, issued August 3, 1948, to A. C. Peterson et al., failure of the ball crank in the needle lever mechanism is one of the chief factors in limiting the top operating speed. In a sewing machine of this type, the needle bar lever is oscillated about a pin in the center of the overhanging arm by means of a pitman interconnecting one end of the needle bar lever and the lower driving shaft. Since the length of the needle bar lever between the pivot pin and the pitman is constant, the end of the pitman fastened to and driving the needle bar lever travels in an are as the needle bar lever rocks about its pivot. Forced angular movement resulting from the arcuate path imparted to the upper end of the pitman causes burning and binding of the ball crank on the drive shaft which, at high operating speeds, generally causes failure of the parts.

Similar burning and binding due to forced angular misalignment or due to misalignment resulting from poor or out-of-line construction would tend to cause failure of a straight bearing on a crank.

Burning and binding due to misalignment in a crank or eccentric and pitman assembly employing needle bearings may be reduced by removing one of the needles from the hearing. In such a construction, those forces which produce binding will urge all of the remaining needles of the bearing away from the point at which binding would normally occur, leaving the space of the omitted needle at that point. While this arrangement affords some improvement, it is by no means completely satisfactory in that the construction is noisy and the operating speeds attainable without undue burning and binding are not sufiiciently great.

The principal object of the present invention has been to provide a novel and improved pitman and bearing construction for sewing machines which will permit the attainment of higher operating speeds.

More particularly, tion to provide an improved pitman and bearing construction for sewing machines in which burning and binding of relatively moving parts resulting from forced angular it has been an object of the invenhighly loaded misalignment or from poor or out-of-line construction is materially reduced. a

Another object of the invention has been to provide an improved crank and pitman construction for fiat bed sewing machines operating at relatively high speeds.

A further object of the invention has been to provide an improved eccentric and pitman construction for high speed sewing machines.

A feature of the invention has been to provide a bearing construction in which substantial shake, i. e., flexibility 2,729,179 Patented Jan. 3, 1956 or freedom of movement allowing misalignment without burning and binding, is achieved.

Other and further objects, features and advantages of the invention will appear from the detailed description of certain illustrative forms of the invention to be given hereinafter.

In accordance with the invention, its objects are achieved by providing the driving connections for one or more of the stitch forming and work feeding elements of a sewing machine with a shaft member, means to impart rotary motion to the shaft member, an oscillatable ele ment, a pitman, a drive connection with the shaft member, involving a crank or eccentric on the shaft member and a strap for connecting the end of the pitman to the crank or eccentric, and a coupling means, such as a ball and strap connection, for connecting the other end of the pitman to the oscillatable element whereby rotary moing assembly interconnecting the same;

Fig. 4 is an enlarged plan view of the main driving shaft and crank of the machine of Fig. 1;

Fig. 3 is an enlarged side elevational view of the main driving shaft and crank;

Fig. 6 is an enlarged cross sectional view taken along the line 66 of Fig. 4;

Fig. 7 is an enlarged cross sectional view taken along the line 7-7 of Fig. 5;

Fig. 8 is a view similar to Fig. 4 and illustrating a modification of the crank element construction according to the invention;

Fig. 9 is a view similar to Fig. 5 and illustrating the modification shown in Fig. 8;

Fig. 10 is an enlarged cross sectional view taken along the line 10-10 of Fig. 9;

Fig. 11 is an enlarged cross sectional vie the line 1111 of Fig. 8;

Fig. 12 is an elevational view of an adjustable eccentric and bearing construction, according to the invention, for connecting a shaft and pitman, the shaft being shown in section;

Fig. 13 is a view similar to Fig. 12 but with the shaft and eccentric assembly shifted relative tothe pitman and with the eccentric also shown in section;

Fig. 14 is a cross sectional view taken along the line 14-14 of Fig. 13;

Fig. 15 is a cross sectional view taken along the line 15- 15 of Fig. 12;

Fig. 16 is a cross 16-16 of Fig. 13;

Fig. 17 is a view partly in elevation and partly in cross section, of a modified form of adjustable eccentric w taken along sectional view taken along the line and bearing construction on a shaft, according to invention, for driving a pitman;

Fig. 18 is a cross sectional view taken along the line 18-18 of Fig. 17;

Fig. 19 is a cross sectional view taken along the line 19-19 of Fig. 17;

Fig. 20 is an enlarged detail view, partly in cross section, illustrating a modification, according to the invention, of the crank portion of a shaft and its associated bearing and strap elements for driving a pitman",

Fig. 21 is a cross sectional view taken along the line 21-21 of Fig. 20; and

Fig. 22 is a cross sectional view taken along the line 22.22 of Fig. 20.

Referring now to the drawings and more particularly to Fig. 1, there is illustrated a flat bed sewing machine embodying one form of the invention. The sewing ma chine comprises a frame having a hollow base 20 and a hollow vertical standard 21 rising therefrom adjacent one end of the base and communicating therewith. Extending laterally from and supported by said standard is a hollow arm 22 which overhangs the base and terminates at its free end in a hollow head, 23. Mounted the in the upper and lower walls of the head 23 are a pair of bushings 24 and 25, respectively, and journaled in these bushings for generally vertical reciprocation is a needle bar 26. The needle bar 26 is provided at its lower end with suitable needle holding means 27 adapted to retain one. or more needles. Mounted on the needle bar is a collar 28' held in place by a pair of screws 29 and provided with a lug 30 to which one end of a link 31 is pivotally attached.

A pair of bushings 32 are mounted in the front and back walls of the arm 22 and a shaft 33 is journaled for rocking motion in the bushings 32. Mounted on the shaft 33 and adapted for rocking movement is a needle lever 34. The left hand end of the lever 34 is pivotally connected to the link 31 bymeans of' a pin 35.

The right hand end of the lever 34 is provided with a ball stud 36 which is secured to the lever in any suitable way, as by means of the set screws shown. The lever 34 is driven by a pitman or connecting rod 37 having attached to its upper end a split, socket-like strap 38 having a spherical seat which cooperates with the ball stud 36. The pitman 37, as best shown in Fig. 2, preferably comprises two generally vertical, hollow tubular members'39 and 40 disposed on opposite sides of the ball stud 36.

Members

39 and 40 are provided at their upper ends with internally threaded

cap elements

39a and 40a, respectively. These are secured to the rods by welding, or the like, and are adapted to receive screws 41' and 42 which pass freely through aligned openings in the upper and lower sections of the strap 33. Tightening of the

screws

41 and 42 will thus serve to clamp the two sections of the strap. together and hold them. against the upper surfaces of the

caps

39a and 40a.

Journaled in the base 20 is a drive shaft provided with a crank 51. Mounted on the shaft 50 toward its right hand end outside the base 20 is a combined hand wheel and belt pulley51a for driving the shaft 50. The pulley 51a may be driven by a belt from a conventional transmitter unit, not shown. The, crank shaft 50, in addition to operating the needle bar driving connections in a manner to be described, also'operates various stitch forming and work feeding elements located within the base 20.

As shown most clearly in Fig. 2, the

members

39 and 40 of pitman 37 are provided with cap elements 3% and 40b at their lower ends, these beingwelded or otherwise secured to the members and being provided with threaded extensions 39c and 400 for cooperation with a split strap 52. The threaded extensions pass freely through the section of the strap and are'screwed' into the lower section. The extensions 39c and- 400 terminate in oilsplashers 3% and 40e, respectively.

In assembling the pitman 37 with the straps at the two ends, the lower ends of

members

39 and 40 are first screwed down tightly at their lower ends to retain the sections of the strap 52 together in the manner described.

Pins

39d and 40d carried by the caps 39b and 40b facilitate this assembly. Then the

screws

41 and 42 are inserted and tightened to complete the assembly at the upper end of the pitman in the manner described. Strap 52 provides an annular bearing surface for the pitman 37 and is operatively connected to a crank element 53 by a plurality of closely spaced roller or needle bearing elements 54. As best shown in Fig. 3, the crank element 53 extends between cheeks or

flanges

55 and 56, respectively, of crank

arms

57 and 58, respectively. The bearings 54 are restrained from axial movement along the surface of the crank element 53 by means of cages formed by narrow, inwardly extending, annular extensions 54' of the strap 52. The extensions 54 are located adjacent the ends of the bearing elements 54. Strap 52 may be provided with axially extending lugs 52' which permit the strap 52 totilt without binding. The lugs- 52' are arranged to cooperate with the adjacent side surfaces of the

flanges

55 and 56. of the crank 51 to prevent binding of the strap due to excessive axial movement thereof. The clearance between the side faces of the lugs and the respective faces of the cooperating flanges might be, for example, about .003 inch to .010 inch.

When the shaft 50 and the crank 51 rotate, the pitman 37 translates the rotary motion into reciprocating motion, and, through the ball stud 36 and strap 38, causes the needle lever 34 to rock about the axis of the shaft 33. The rocking motion of lever 34 causes the needle bar 26 to reciprocate vertically.

Since the length of the needle lever between the shaft 33 and the pitman 37 is fixed, it is evident that the strap 38, which is affixed to the upper end of the pitman 37, will travel in an arcuate path as the needle lever 34 rocks about the axis of shaft 33. Due to this arcuate path of the upper end of the pitman, forced angular misalignment of the strap 52, the needle bearings 54 and the crank element 53 will occur at different points in the cycle of rotation of the shaft 50. It will be understood that misalignment of the pitman strap and crank element 53 will occur at such times at which the upper end of the pitman 37 is not vertically disposed. Such misalignment may also occur, or be made more serious, due

to poor or out-of-line construction or assembly of the connected parts and burning out of the cooperating, relatively moving surfaces at high operating speeds.

As shown in Figs. 3-7, one form of the invention involves the provision of reliefs or cut-out portions in the crank element 53' to prevent or minimize the binding and/or'burning which occurs due to the misalignment. The reliefs are provided to permit relative angular displacement or relative twisting movement of the pitman, crank element and needle bearing whereby the upper end of the pitman may follow the arcuate' path imparted thereto without causing a corresponding burning or binding of the strap 52, needles 54 and crank element 53. The reliefs effectively provide flexibility in the driving connections by permitting the pitman to tilt the needle or roller bearings relative to the crank element. It should be observed that similar burning and binding occurs at high operating speeds when the lower end of the pitman is coupled to the crank shaft through a ball crank arrangement as shown in the aforementioned Peterson et al. patent.

Thev location of. the reliefs on. the crank element is dependent upon'tlie loading of this element. Preferably, the reliefs are located. to be effective in providingfiexibility-when. bearing loading is at aminimum. With this preferred location of the reliefs, little. or none of the bearingaarea; used. at high load positions is removed. In alflat bed sewing machine of.the type illustrated in Fig. 1, the force of needle penetration is usually neglitends to cause excessive wear and mam gible so that the bearings are almost entirely inertia loaded. Accordingly, in the sewing machine of Fig. 1, the high load conditions correspond to the top and bottom of the needle stroke or, in other words, the uppermost and lowermost positions of the right hand end of the needle lever 34. The loading will be at a minimum midway between these positions. Therefore, by so correlating the parts that the pitman 37 is substantially vertical at the top and bottom of its stroke, there will be no alignment under maximum load conditions and misalignment is at a maximum at the middle of the stroke where the loading is light. Thus in the sewing machine of Fig. 1, the reliefs are preferably located on the crank element 53 so as to be effective in the middle portion of each stroke of the pitman 37. It will be appreciated that very little movement of the pitman, and hence very little misalignment, takes place during a substantial arc of movement of the crank element at the top and bottom portions of its path. Therefore, the crank element may have portionsof substantial arcuate extent which provide full bearing contact in the regions where maximum load conditions are encountered.

To compensate for misalignment of the pitman 37, four reliefs may be provided on the crank element 53.

As shown in Fig. 3, which illustrates the crank 51 with pitman 37 substantially in its uppermost position, two

reliefs

60 and 61 are provided on the front side of the crank element 53.

Reliefs

60 and 61 are located on opposite sides of a plane passing through the center of crank element 53 and perpendicular to the axis of shaft 50. Two similar reliefs 62 and 63 (Fig. 4) are provided on the back side of crank element 53. The diagonally disposed

reliefs

60 and 63 cooperate to overcome burning and binding during a major portion of either the up or the downstroke of pitman.37, depending on the direction of rotation of shaft 50.

Reliefs

61 and 62 cooperate similarly on the other pitman stroke. The maximum radial depth, the axial length, the taper and the circumferential extent of each relief is dependent on the amount and character of the misalignment to be compensated. As shown in Fig. 3, the reliefs are semicircular in shape with their diameters adjacent the

respective flanges

55 and 56 and with their maximum depths adjacent the extremities of the crank pin. The diameters of the semicircular reliefs in Fig. 3 are somewhat less than the diameter of crank element 53, thus providing a full bearing surface for the maximum load conditions occurring when the pitman 37 is at the top of its stroke and at the bottom thereof.

Reliefs

62 and 63 have the same shape and extent as

reliefs

60 and 61.

The crank element 53 with its reliefs is shown in a position corresponding to the uppermost pitman travel in plan view in Fig. 4 and in side elevational view in Fig. 5. The varying radial depths of the reliefs can be clearly seen in Figs. 6 and 7. As best shown in Fig. 6, each relief increases in depth, at any transverse plane, from the circumference of the semicircular outline toward the line which divides the semicircle into quadrants. This provides for maximum tilting of the bearing elements when the misalignment is greatest and the load the smallest. Y

The maximum amount of misalignment which can be compensated is dependent on the maximum depth and extent of the reliefs. The latter are, in turn, limited by the requirement that there be sufficient bearing area in the maximum load position. The relative location of the parts determines where the reliefs should be located. Pitman 37 and the related parts may be arranged to place the pitman in vertical position at any portion of its stroke, preferably coinciding with maximum load conditions for the parts being operated, and the reliefs would then need to be located correspondingly.

Since a crank element or eccentric on a rotary shaft is always turning in relation to the cooperating bearing, the same portion of the face of the crank element or eccentric normally takes the load at the top and at the bottont of the stroke of the associated pitman or connecting rod. Thus where the primary load is due to the inertia and momentum of the driven parts at the portions of the cycle in which they reverse their direction of movement, the load is applied to the radially innermost portion of the crank element. This permits a modification of the form of the invention shown in Figs. 1 through 7. This modification, which is illustrated in Figs. 8 through 11, provides about 20% more shake than the four relief construction and is also easier and less expensive to manufacture.

Referring now particularly to Figs. 8 through 11, the modified arrangement comprises a crankshaft 70 and a crank 71. The crank 71 comprises a pair of crank

arms

72 and 73 having

flanges

74 and 75, respectively, between which extends a crank element 76. The crank element 76 is provided with two

reliefs

77 and 78 which extend circumferentially about 300 degrees at each end of the crank element. The circumferential extent of the reliefs at the ends or" the crank element preferably lies within the range of about 270 to 360. Of course, the maximum relief is provided at the ends of the crank element, the circumferential extent thereof decreasing on a curve to-provide a 360 bearing area of suitable width at the center of the crank element. The

reliefs

77 and 78 extend from points near the central transverse plane through the crank element to the respective ends of the crank element and increase in radial depth from such central plane outward, as shown best in Figs. 10 and 11. It will be observed that a small circumferential portion 79 of the crank element adjacent the center thereof remains at full diameter to take the load at points other than that corresponding to maximum load. Furthermore, a small axially extending portion 80 of the crank element is maintained at full diameter for the entire length of the crank element toprovide full line contact with the needle or other bearing means at the times of maximum load conditions.

An eccentric and pitman operating at high speeds are often subjected to burning and binding due to forced angular misalignment and/or poor or out-of-line construction. This burning and binding may be relieved, in accordance with the invention, in the same way as described above in connection with a crank element and pitman. An illustrative. embodiment of the invention, as applied to an adjustable eccentric of the type shown in the copending patent application of George M. Reimer, Serial No. 150,843, filed March 21, 1950, will now be described in connection with Figs. 12 through 16.

A pitman 90, which may form part of the feed dog driving connections as disclosed in the aforementioned Reimer application, is provided at one end thereof with an annular strap which surrounds an eccentric 91. The eccentric 91 surrounds and snugly fits an inner eccentric 92 carried by a shaft 93. The eccentric 92 is adapted to be turned relative to the shaft 93, while the eccentric 91 turns with the shaft, as explained in the said Reimer application, to vary the eccentricity of the eccentric 91 relative to the axis of shaft. Eccentric 91 is recessed or counterbored as indicated at 94 (Fig. 14) to receive a coiled spring 95 which is compressed between the shoulder formed atthe base of the counterbore and a radially extending flange 96 on the adjacent end of the eccentric 92. The spring95 urges the two eccentrics axially in opposite directions. A cylindrical collar or housing 97 surrounds portions of the two eccentrics in the region of the spring 95, this collar being secured to a disc 98 by means of a screw or screws 99. Disc 98 is in turn secured to the shaft 93 by screws or other suitable means not shown. A friction element 100 is interposed between the flanged end of the eccentric 92 and the inner face of the disc 98. This insures rotation of the inner eccentric 92 with the shaft in the normal operation of the machine but permits relative turning between these parts for adjustment of the throw of the outer eccentric as explained. A radially extending shoulder 101 adjacent the inner end of the eccentric 91 is arranged to cooperate with a; portion of an inwardly extending flange 102- at the inner end of the collar 97. The relationship between the flange 102, the shoulder 101 and the main body of the collar 97 is such that relative movement in a radial direction may take place between the eccentric 91 and the collar 97 as the eccentric is adjusted. At all times there will be some portion of the flange 102 in engagement with shoulder 101 to resist outward axial movement of the eccentric 91 in relation to the collar 97 under the force of spring 95. By virtue of the coaction between flange 102 and surface 101, as mentioned, and the engagement of friction disc with the disc 98, relative axial movement of the two eccentrics in response to the force of the spring is prevented. A driving connection is provided between the disc 98 and the eccentric 91 so that the latter will rotate at all times with the shaft 93. This connection comprises a pin 103 inserted in an opening in a disc 98 and having an enlarged head operate with a notch formed in the enlarged end or flanged portion of the eccentric 91. o o

The inner surface of the strap 90 is separated from the outer surface of the eccentric 91 by a plurality of closely spaced roller or needle bearing elements 105. The surface of eccentric 91 which cooperates with bearing elements 105 is provided with four reliefs or cut out

portions

106, 107, 108 and 109 which have the same general shape and extent as the reliefs shown in Figs. l7. As in the case of a crank element, the reliefs are preferably effective at points of minimum load, while full line contact is preferably provided at points of maximum load. The relative positioning of the eccentric 91 and pitman 90 in Fig. 12 corresponds to a minimum load condition, while that in Fig. 13 corresponds to a maximum load condition. If the load conditions were different, the location of the reliefs around the periphery of the eccentric 91 should be changed accordingly.

The eccentric 91 may, if desired, be provided with only two reliefs, as described for a crank element in connection with Figs. 8-11. Such a construction is illustrated in Figs. l7, l8 and 19. The eccentric 91 is provided with two

reliefs

110 and 111 which have a circumferential extent of about 300 degrees at the ends of the eccentric 91. A portion 112 of eccentric 91 extending axially along the surface thereof for the full width of the eccentric, over an arc of about 60, is maintained at full diameter to provide full line contact with the needle or roller bearings in this area in which maximum load is involved, while a narrow portion 113 of the eccentric 91, extending circumferentially completely around the same is maintained at full diameter to take the loading at other points. It will be understood that the specific linear and. angular dimensions of the various surfaces may be varied considerably, as previously set forth, to suit particular requirements.

As pointed out hereinbefore, the depth, taper and extent of the relief provided are dependent on the amount of misalignment to be compensated. Moreover, the reliefs may be provided on either the crank element (or eccentric) or on the confining strap. In certain applications, it may be desirable to provide reliefs on both the crank element (or eccentric) and on the confining strap. An example of reliefs provided on the strap is illustrated in Figs. 2022.

Referring now to Figs. 20-22, the construction shown is applicable to a flat bed sewing machine of the type shown inFig. 1 and the shaft 50' of Fig. 20 corresponds to the shaft 50 of Fig. l. The shaft 50 is provided with a

crank comprising arms

121 and 122 having flanges or

cheeks

123 and 124, respectively, between which extends a crank element 125. The crank element 125 differs from the crank element 53' in that it is not provided with reliefs. It is of simple cylindrical form. A pitm'an 37, corresponding to the'pitrnan' 3710f Fig. 1', is provided with a split strap member 126 which provides" an annular 104 provided. with flat sides which coof the type shown in Fig. 1.

bearing surface for the pitman 37' and is operatively connected to the crank element 125 by a plurality of closely' space'd roller or needle bearing elements 127. Strap 126 has its two sections held together by the screw threaded extcnsions of pitman rods 37' in the manner explained in relation to Fig. 2. The bearing elements 127 may be restrained from axial movement along the surface of the crank element 125 by means of a suitable cage.

The strap 126 is provided with two reliefs or

clearance cuts

129 and 130. These reliefs, which are located on opposite ends of the strap 126, extend throughout respective halves of the circumference of the strap. The relief 129 is shown by the shading on strap 126 in Fig. 22, while the relief 130 is shown by the shading on strap 126 in Fig. 21. For simplicity of manufacture, each of the reliefs is preferably of the same radial extent in transverse plane throughout its semicircular form and each provides a frusto=conical surface from a central tranverse plane through the strap to its outer edge. The slope of the surface depends upon the degree of angling desired. The arrangement is such that misalignment in one direction only can be compensated, since relative angular displace ment of the strap 126 and the bearings 127 can only occur with respect to rocking movements of pitman 37' to the right of the vertical position thereof in Fig. 20. However, it will be observed that misalignment in the sewing machine ofFig. 1 occurs only by displacement of the top pi'tman 37 to the right of its vertical position, so that the construction of Figs. 20 22 is suitable for use in a machine v This construction is also applicable to eccentrics.

If it were desired to employ the construction of Figs. 20-22 to compensate for misalignment in two directions, thenitwould generally be necessary to have the strap relieved throughout its entire circumference on both sides. Such an arrangement would not be desirable in most instances since it would result in a very short line contact or even a point contact at the points of maximum bearing load as well as at points of minimum bearing load.

The invention has been described in connection with rotating cranks and eccentrics, but it is evident that it is equally applicable to oscillating cranks and eccentrics.

While the invention has been described in connection with particular embodiments thereof and in particular uses, it should be un'derstoodthat it is not limited thereto for obvious modifications thereof will occur to those skilled in the art without departing from the spirit and scope of the invention as set forth in the appended claims.

What is claimed is:

1. In a sewing machine having a driven oscillatory member, a t'urnable shaft and means for turning the same, the combination of connections from said shaft to said member for oscillating the latter which comprises an eccentrically disposed driving element carried by said shaft, a= pit'man having a strap surrounding said driving element and having its opposite end connected with said oscillatory member, said opposite end of the pitman being moved through an arcuate path having a component parallel with the axis of said shaft, whereby said pit'rnarr is rocked in said direction about said driving element about an axis transverse to the axis of said element, said driving element and said strap carrying coacting bearing surfaces, certain portions of said coacting surfaces being of true cylindrical contour and having bearing engagement along a line extending axially of said driving element for substantially the full axial length of said coacting surfaces, and other portions of said surfaces being relieved adjacent the ends thereof toprovide a narrower bearing engagement between the other portions of said surfaces than is provided between said certain portions thereof, the narrower bearing engagement between said other portions of said surfaces enabling said rocking movements of the pitman.

2. In a sewing machine having a driven oscillatory member, athrnablesliaff and meansfor turning the same,

the combination of connections from said shaft to said member for oscillating the latter, which comprises an eccentrically disposed driving element carried, by said shaft, a pitman having a strap surrounding said driving element and having its opposite end connected with said oscillatory member, said opposite end of the pitman being moved through an arcuate path having a component parallel with the axis of said shaft, whereby said pitman is rocked in said direction about said driving element about an axis transverse to the axis of said element, said driving element and said strap carrying coacting bearing surfaces, certain portions of the bearing surface of said driving element being truly cylindrical in contour to provide bearing engagement along a line extending axially of said driving element'for substantially the full axial length of said coacting surfaces and other portions of the bearing surface of said driving element being relieved adjacent its ends thereby to provide a narrower bearing engagement between the other portions of the bearing surface of said driving element and the coacting portions of the bearing surface of said strap than is provided between said certain portions of the bearing surface of said driving element and the bearing surface of said strap so as to enable said rocking movements of the pitman.

3. A sewing machine, comprising stitch forming and Work feeding elements and driving connections therefor, said driving connections comprising a shaft member, means to impart rotary motion to said shaft member, an oscillatable element, a pitman, a first coupling means for connecting one end of said pitman to said shaft member and a second coupling means for connecting the other end of said pitman to said oscillatable element whereby rotary motion of said shaft member is translated into oscillatory motion of said oscillatable element, said first coupling means comprising an eccentrically disposed driving surface on the shaft member and a bearing surface on said pitman arranged to coact with said driving surface, said portions of the coacting surfaces of said shaft member and said pitman being of truly cylindrical contour and other portions of at least one of said surfaces being relieved toward its ends to provide a rockable connection between said pitman and said shaft member to compensate for misalignment therebetween during certain portions of the travel of said pitman and otherportions of said coacting surfaces having bearing engagement along a line extending axially of said shaft member for substantially the full axial length of said coacting surfaces to provide a relatively rigid connection between said pitman and said shaft member during other portions of the travel of said pitman.

4. A sewing machine, comprising stitch forming and work feeding elements and driving connections therefor, said driving connections comprising a shaft member, means to impart rotary motion to. said shaft member, an oscillatable element, a pitman, a first coupling means for connecting one end of said pitman to said shaft member and a second coupling means for connecting the other end of said pitman to said oscillatable element whereby rotary motion of said shaft member is translated into oscillatory motion of said oscillatable element, oscillation of said oscillatable element providing a varying load on said first coupling means, said first coupling means having a bearing surface which is relieved toward its ends in certain diametrically opposed portions of its circumference to provide a rockable connection between said pitman and said shaft member to compensate for misalignment therebetween during certain portions of the travel of said pitman, other portions of said bearing surface being of cylindrical form over a sufficiently wide area substantially to prevent rocking of said pitman on said shaft member to thereby maintain said pitman substantially perpendicular to the axis of said shaft member during other portions of the travel of said ment whereby rotary "10 pitman, said certain portions ofsaid travel corresponding to a relatively low load on said first coupling means and said other portions of said travel corresponding to relatively high load on said first coupling means.

5. A sewing machine, comprising stitch forming and work feeding elements and driving connections therefor, said driving connections comprising a shaft member, means to impart rotary motion to said shaft member, an oscillatable element,-a pitman, a first coupling means for connecting one end of said pitman to said shaft member and a second coupling means for connecting the other end of said pitman to said oscillatable element whereby rotary motion of said shaft member is translated into oscillatory motion of said oscillatable element, oscillation of said oscillatable element providing a load on said first coupling means, said load varying between a maximum value and a minimum value in the course of a cycle of oscillation of said element, said first cou pling means comprising an eccentrically disposed driving surface on the shaft member and a bearing surface on said pitman arranged to coact with said driving surface, certain portions of at least one of said surfaces being relieved to provide a rockable connection between said pitman and said shaft member to compensate for misalignment therebetween during certain portions of the travel of said pitman and other portions of said coacting surfaces having bearing engagement along a straight line extending parallel with the axis of said shaft memher for substantially the full axial length of said coacting surfaces to provide a substantially non-rockable connection between said pitman and said shaft member during other portions of the travel of said pitman, said certain portions of the travel of said pitman including the times of application of said minimum load and said other portions of the travel of said pitman including the times of application of said maximum load in the course of said cycle.

6. A sewing machine, comprising stitch forming and work feeding elements and driving connections therefor, said driving connections comprising a shaft member, means to impart rotary motion to said shaft member, an oscillatable element, a pitman, a first coupling means for connecting one end of said pitman to said shaft member and a second coupling means for connecting the other end of said pitman to said oscillatable elemotion of said shaft member is translated into oscillatory motion of said oscillatable element, said first coupling means comprising a bearing surface which is relieved toward opposite ends thereof at diametrically opposite points in certain regions to provide a rockable connection between said pitman and said shaft member to compensate for misalignment therebetween during certain portions of the travel of said pitman, said bearing surface having certain diametrically opposed regions not more than one of which is relieved, thereby providing straight line engagement of the cooperating portions of said pitman and bearing surface and thus affording a substantially non-rockable connection between said pitman and said shaft member during other portions of the travel of said pitman.

7. A sewing machine, comprising stitch forming and work feeding elements and driving connections therefor, said driving connections comprising a shaft member, means to impart rotary motion to said shaft member, an oscillatable element, a pitman, a first coupling means for connecting one end of said pitman to said shaft member and a second coupling means for connecting the other end of said pitman to said oscillatable element whereby rotary motion of said shaft member is translated into oscillatory motion of said oscillatable element, oscillation of said oscillatable element providing a varying load on said first coupling means in the course of a cycle of oscillation of said element, said first coupling means comprising an eccentrically disposed driving surface on the shaft member and a bearing surface on said pitman arranged to coact with said driving surface, at least one portion of at least one of said surfaces being relieved so as to provide a rockable connection between said pitman and said shaft member to compensate for misalignment therebetween during certain portions of the travel of said pitman corresponding to a relatively low load on said first coupling means, at least one other portion of said coacting surfaces having bearing engagement along a straight line extending parallel with the axis of said shaft member for substantially the full axial length of said coasting surfaces to provide a relatively rigid connection between said pitman and said shaft member during other portions of the travel of said pitman corresponding to a relatively high load on said first coupling means.

8. A sewing machine, comprising stitch forming and work feeding elements and driving connections therefor, said driving connections comprising a shaft member, means to impart rotary motion to said shaft member, an oscillatable element, a pitman, a first coupling means for connecting one end of said pitman to said shaft member and a second coupling means for connecting the other end of said pitman to said oscillatable element whereby rotary motion of said shaft member is translated into oscillatory motion of said oscillatable element, said first coupling means comprising a crank arranged to rotate with said shaft member and having a crank element, a strap connected to said pitman and arranged to surround said crank element and a plurality of roller-type bearing elements interposed between said crank element and said strap, said crank element and said strap having bearing surfaces arranged to engage said roller-type bearing elements, portions of at least one of said bearing surfaces being cut away thereby to provide a rockable connection between said pitman and said shaft member to compensate for misalignment therebetween during certain portions of the travel of said pitman, other portions of said one of said bearing surfaces being of true cylindrical contour and having bearing engagement with said bearing elements along lines extending axially of said shaft member for substantially the full axial length of said bearing elements to provide a substantially non-rockable connection between said pitman and said shaft member during other portions of the travel of said pitman.

9. A sewing machine, comprising stitch forming and work feeding elements and driving connections therefor, said driving connections comprising a shaft member, means to impart rotary motion to said shaft member, an oscillatable element, a pitman, a first coupling means for connecting one end of said pitman to said shaft member and a second coupling means for connecting the other end of said pitman to said oscillatable clement whereby rotary motion of said shaft member is trans lated into oscillatory motion of said oscillatable element, said first coupling means comprising a crank arranged to rotate with said shaft member and having a crank element, a strap connected to' said pitman and arranged to surround said crank element and a plurality of rollertype bearing elements interposed between said crank element and said strap, said crank element and said strap having bearing surfaces arranged to engage said rollertype bearing elements, portions of the bearing surface of said crank element being cut away thereby to provide a rockable connection between said pitman and said shaft member to compensate for misalignment therebetween during certain portions of the travel of said pitman, other portions of 'said' crank element having a true cylindrical contour and having bearing engagement with said bearing elements along a line extending axially of said shaft member for substantially the full axial length of the bearing surface of said crank element to provide a substantially non-rockable connection between said pitman and said shaft member during other portions of the travel of said pitman.

10. A sewing machine, comprising stitch forming and work feeding elements and driving connections therefor, said driving connections comprising a shaft member, means to impart rotary motion to said shaft member, an oscillatable element, a pitman, a first coupling means for connecting one end of said pitman to said shaft member and a second coupling means for connecting the other end of said pitman to said oscillatable element whereby rotary motion of said shaft member is translated into oscillatory motion of said oscillatable element, said first coupling means comprising a crank arranged to rotate with said shaft member and having a crank element, a strap connected to said pitman and arranged to surround said crank element and a plurality of roller-type bearing elements interposed between said crank element and said strap, said crank element and said strap having bearing surfaces arranged to engage said roller-type bearing elements, portions of the bearing surface of said strap being cut away thereby to provide a rockable connection between said pitman and said shaft member to compensate for misalignment therebetwcen during certain portions of the travel of said pitman, other portions of said strap having a true cylindrical contour and having bearing engagement with said bearing elements along a line extending axially of said shaft member for substantially the full axial length of the bearing elements to provide a substantially nonrockable connection between said pitman and said shaft member during other portions of the travel of said pitman.

11. A sewing machine, comprising stitch forming and work feeding elements and driving connections therefor, said driving connections comprising a shaft member, means to impart rotary motion to said shaft member, an oscillatable element, a pitman, a first coupling means for connecting one end of said pitman to said shaft member and a second coupling means for connecting the other end of said pitman to said oscillatable element whereby rotary motion of said shaft member is translated into oscillatory motion of said oscillatable element, said first coupling means comprising a crank arranged to rotate with said shaft member and having a crank element, a strap connected to said pitman and arranged to surround said crank element and a plurality ofclosely spaced needle bearing elements interposed between said crank element and said strap, said crank element and said strap having bearing surfaces arranged to engage said needle bearing elements, two portions of the bearing surface of said strap being cut away thereby to provide a rockable connection between said pitman and said shaft member to compensate for misalignment therebetween during certain portions of the travel of said pitman, other portions of said strap having a true cylindrical contour and providing a substantially non-rockable connection between said pitman and said shaft member during other portions of the travel of said pitman, each of saidcut away portions having a circumferential extent-of-about one half the circumference of said strap and being located adjacent opposite ends of said strap and on diametrically opposite sides thereof, said cut away portions having tapering cross sections increasing in depth from the center of said'strap toward the respective ends thereof.

12. A sewing machine, comprising stitch forming and work feeding elements and driving connections therefor, said driving connections comprising a shaft member, means to impart rotary motion to said shaft member, an oscillatable element, a pitman, a first coupling means for connecting one-end of saidpitinan to said shaft member and a second coupling means for connecting the other end of said pitman to said'oscillatable element whereby rotary motion of said'shaft member is translated into oscillatory motion of said oscillatable element, said first coupling means comprising a crank arranged to rotate with said shaft member andhaving a crank element, a strap connected to said pitmanand arranged to surround said crank element and a pluralityof' closely spaced needle bearing elements interposed between said crank element and said strap, said crank element an'd said strap having bearing surfaces arranged to engage said needle bearing elements, four spaced portions of the bearing surface of said crank element being cut away thereby to provide a rockable connection between said pitman and said shaft member to compensate for misalignment therebetween during certain portions of the travel of said pitman, other portions of said crank element having a true circuluar contour and providing a substantially non-rockable connection between said pitman and said shaft member during other portions of the travel of said pitman, first and second ones of said cut away portions of said crank element being located on the diametrically opposed side of said crank element from the third and fourth ones thereof, and said first and third cut away portions being located adjacent the end of said crank element opposite from said second and fourth cut away portions, said cut away portions having tapering cross sections decreasing in depth from the respective ends of said crank element toward the center thereof.

13. A sewing machine, comprising stitch forming and work feeding elements and driving connections therefor, said driving connections comprising a shaft member, means to impart rotary motion to said shaft member, an oscillatable element, a pitman, a first coupling means for connecting one end of said pitman to said shaft member and a second coupling means for connecting the other end of said pitman to said oscillatable element whereby rotary motion of said shaft member is translated into oscillatory motion of said oscillatable element, said first coupling means comprising a crank arranged to rotate with said shaft member and having a crank element, a strap connected to said pitman and arranged to surround said crank element and a plurality of closely spaced needle bearing elements interposed between said crank element and said strap, said crank element and said strap having bearing surfaces arranged to engage said needle bearing elements, two portions of the bearing surface of said crank element being cut away thereby to provide a rockable connection between said pitman and said shaft member to compensate for misalignment therebetween during certain portions of the travel of said pitman, other portions of said crank element having a true circular contour and providing a substantially nonrockable connection between said pitman and said shaft member during other portions of the travel of said pitman, said cut away portions being located adjacent opposite ends of said crank element and having minimum depths adjacent the center of said crank element and maximum depths adjacent said ends thereof, each of said cut away portions having a circumferential extent adjacent the respective ends of said crank element lying within the range of about 270 to 360.

14. A sewing machine, comprising stitch forming and work feeding elements and driving connections therefor, said driving connections comprising a shaft member, means to impart rotary motion to said shaft member, an oscillatable element, a pitman, a first coupling means for connecting one end of said pitman to said shaft member and a second coupling means for connecting the other end of said pitman to said oscillatable element whereby rotary motion of said shaft member is translated into oscillatory motion of said oscillatable element, said first coupling means comprising an eccentric element arranged to rotate with said shaft member, a strap connected to a said pitman and adapted to surround said eccentric and a plurality of roller-type bearing elements interposed between said eccentric and said strap, said eccentric and said strap each having a bearing surface arranged to en-- gage said roller-type bearing elements, portions of at least i one of said bearing surfaces being cut away thereby to provide a rockable connection between said pitmanand said shaft member to compensate for misalignment therebetween during certain portions of the travel of said pitman, other portions of said bearing surfaces being truly cylindrical and having bearing engagement with said bearing elements along lines extending axially of said shaft member for substantially the full axial length of said 14 bearing elements to provide a substantially non-rockable connection between said pitman and said shaft member during other portions of the travel of said pitman.

15. A sewing machine, comprising stitch forming and work feeding elements and driving connections therefor, said driving connections comprising a shaft member, means to impart rotary motion to said shaft member, an oscillatable element, a pitman, a first coupling means for connecting one end of said pitman to said shaft member and a second coupling means for connecting the other end of said pitman to said oscillatable element whereby rotary motion of said shaft member is translated into oscillatory motion of said oscillatable element, said first coupling means comprising an eccentric element arranged to ro tate with said shaft member, a strap connected to said pitman and adapted to surround said eccentric and a plurality of closely spaced needle bearing elements interposed between said eccentric and said strap, said eccentric and said strap each having a bearing surface arranged to engage said needle bearing elements, four portions of the bearing surface of said 7 eccentric being cut away thereby to provide a rockable connection between said pitman and said shaft member to compensate for misalignment therebetween during certain portions of the travel of said pitman, other portions of said bearing surface being truly circular in contour and providing a substantially non-rockable connection between said pitman and'said shaft member during other portions of the travel ofsaid pitman, first and second ones of said cut away portions of said eccentric being located on the diametrically opposite side of said eccentric from the third and fourth ones thereof and said first and third cut away portions being located adjacent the opposite end of said eccentric from said second and fourth cut away portions, said cut away portions having tapering cross sections de creasing in depth from the respective ends of said eccentric toward the center thereof. 7

16. A sewing machine, comprising stitch forming and work feeding elements and driving connections therefor, said driving connections comprising a shaft member, means to impart rotary motion to said shaft member, an oscillatable element, a pitman, a first coupling means for connecting one end of said pitman to said shaft member and a second coupling means for connecting the other end of said pitman to said oscillatable element whereby rotary motion of said shaft member is translated into oscillatory motion of said oscillatable element, said first coupling means comprising an eccentric element arranged to rotate with said shaft member, a strap connected to said pitman and adapted to surround said eccentric and a plurality of closely spaced needle bearing elements interposed between said eccentric and said strap, said eccentric and said strap each having a bearing surface arranged to engage said needle bearing elements, two portions of the bearing surface of said eccentric being cut away thereby to provide a rockable connection between said pitman and said shaft member to compensate for misalignment therebetween during certain portions of the travel of said pitman, other portions of the bearing surface of said eccentric being of truly circular contour and providing a substantially non-rockable connection between said pitman and said shaft member during other portions of the travel of said pitman, each of said cut away portions being located adjacent opposite faces of said'eccentrio and having minimum depths adjacent the center of said eccentric and maximum depths adjacent the faces thereof, each of said cut away portions having a circumferential extent adjacent the respective faces of said eccentric lying within the range of about 270 to 360.

17. In a flat bed sewing machine having a needle bar, a needle lever for reciprocating said needle bar, said needle lever being arranged to rock about a fixed axis, and a main driving shaft, connecting means inter-coupling said main driving shaft and said needle lever whereby turning of the former produces rocking movement of the latter, said connecting means comprising a pitman element,- means for connecting one end of said pitman element to said needle lever, and means for connecting the other end of said pitman element to said shaft, said latter means comprising an eccentrically disposed driving surface on the main driving shaft and a bearing surface on the pitman element arranged to coaet with said driving surface, certain portions of at least one of said coacting surfaces being relieved toward the ends thereof to provide a rockable connection between said pitman and said shaft to compensate for misalignment therebetween during certain portions of the travel of said pitman, other portions of said coacting surfaces having bearing engagement along a straight line extending parallel with the axis of said driving shaft for substantially the full axial length of said eoacting surfaces to provide a substantially nonr'oek able connection between said pitman and said shaft during other portions of the travel of said pitman.

18. Ina flat bed sewing machine having a needle bar, a needle lever for reciprocating said needle bar, said needle lever being arranged to rock about a fixed axis, and a main driving shaft, connecting means intercoupling said main driving shaft and said needle lever whereby turning of the former produces rocking movement of the latter, said connecting means comprising a pitman element, means for connecting one end of said pitman element to said needle lever, and means for connecting the other end of said pitman element to said shaft, said latter means comprising a crank arranged to rotate With said shaft and having a crank element, a strap connected to said pitman and adapted to surround said crank element and a plurality of closely spaced roller-type bearing elements interposed between said strap and said crank element, said crank element and said strap each having a bearing surface arranged to engage said roller-type bearing elements; portions of at least one of said bearing surfaces being cut away to provide a rockable connection between said pitman and said crank element to compensate for misalignment therebetween during certain portions of the travel of said pitman, other portions of said bearing surfaces being of truly cylindrical contour and having bearing engagement with said bearing elements along lines extending axially of said shaft for substantially the full axial length of said bearing elements to provide a substantially non-rockable connection between said pitman and said crank element during other portions of the travel of said pitman.

19. In a fiat bed sewing machine having a needle bar, a needle lever for reciprocating said needle bar, said needle'lever being arranged to rock about a fixed axis, and a main driving shaft, connecting means intercoupling said main driving shaft and said needle lever whereby rotation of the former produces rocking movement of the latter, said connecting means comprising a pitman, means for connecting one end of said pitman to said needle lever, and means for connecting the other end of said pitman-to said shaft, said latter means comprising a crank arranged to'rotate with said shaft and having a crank element, a strap connected to said pitman and adapted to accommodate said crank element and a plurality of closely spaced roller-type bearing elements intcrposed between said strap and said crank element, said crankrelement and said strap each having a bearing surface arranged to engage said roller-type bearing elements, portions of the bearing surface of said crank element being cutaway to provide a rockable connection between said pitman and said crank element to compensate for misalignment therebetween during certain portions of the travel of said pitman corresponding to a relatively low loading on said pitman, other portions of the bearing surface of said crank element having bearing engagement with said-bearing elements along a straight line extending parallel with the axis of said driving shaft for substantially the full axial length of the bearing surface of said crank element to provide asubstantially non-rockable connection between said pitman and said shaft dur- 16 ing other portions of the travel of said pitman corresponding to a relatively high loading on said pitman.

20. In a fiat bed sewing machine having a needle bar, a needle lever for reciprocating said needle bar, said needle lever being arranged to rock about a fixed axis, and a main driving shaft, connecting means inter-coupling said rnain driving shaft and said needle lever whereby rotation of the former produces rocking movement of the latter, said connecting means comprising a pitman, means for connecting one end of said pitman to said needle lever, and means for connecting the other end of said pitman to said shaft, said latter means comprising a crank arranged to rotate with said shaft and having a crank element, a strap connected to said pitman and adapted to surround said crank element and a plurality of closely spaced roller-type bearing elements arranged operativcly to connect said strap and said crank element, said crank element and said strap each having a bearing surface arranged to engage said roller-type bearing elements, portions of the bearing surface of said strap being cut away to provide a rockable connection between said pitman and said shaft to compensate for misalignment therebetween during first selected portions of the travel of said pitman corresponding to a relatively low loading on said pitman, other portions of the bearing surface of said strap being of truly cylindrical contour and providing bearing contact between said strap and said roller-type bearing elements along a line extending axially of said shaft for substantially the full axial length of the bearing elements to provide a substantially nonrockable connection between said pitman and said shaft during other portions of the travel of said pitman corresponding to a relatively high loading on said pitman.

21. In a' flat bed sewing machine having a needle bar, a needle lever for reciprocating said needle bar, said needle lever being arranged to rock about a fixed axis, and a main driving shaft, connecting means inter-coupling said main driving shaft and said needle lever whereby rotation of the former produces rocking movement of the latter, said connecting means including a pitman comprising a pair of substantially parallel generally vertical rods disposed on respective sides of said shaft and of said needle lever, means for connecting one end of each of said rods to said needle lever, and means for connecting the other end of each of said rods to said shaft, said latter means comprising a crank arranged to rotate with said shaft and having a crank element, a strap connected to said other ends of said rods and adapted to surround said crank element and a plurality of closely spaced rollertype bearing elements arranged operatively to connect said strap and said crank element, said crank element and said strap each having a bearing surface arranged to engage said roller-type bearing elements, portions of at least one of said bearing surfaces being cut away to provide a rockable connection between said pitman and said shaft to compensate for misalignment therebetween during certain portions of the travel of said pitman, other portions of said bearing surfaces being of true cylindrical contour to provide a line bearing engagement between said bearing surfaces and said roller-type bearing elements along lines extending axially of said driving shaft for substantially the full axial length of said bearing elements during other portions of the travel of said pitman.

References Cited in the file of this patent UNITEDSTATE-S PATENTS