US3566815A

US3566815A - Skip stitch mechanism for blind stitch sewing machine

Info

Publication number: US3566815A
Application number: US860217A
Authority: US
Inventors: William T Richards
Original assignee: Union Special Machine Co
Current assignee: Union Special Machine Co
Priority date: 1969-09-23
Filing date: 1969-09-23
Publication date: 1971-03-02
Anticipated expiration: 1988-03-02
Also published as: GB1304087A

Abstract

Blind stitch sewing machine having an improved mechanism adapted to form blind stitches of either the skip or nonskip type. Includes a pivoted work support table lockable to stationary position and unlockable to permit swinging movement of the table. A first pitman and a second pitman operate in response to rotation of the main shaft of the machine. The forward end of the first pitman is connected to a rockable node former shaft which rocks in a rockable cradle under the work support table. The forward end of the second pitman is connected to the cradle. Means are provided for adjusting the machine to nonskip position in which the second pitman idles and to skip position in which the second pitman is fulcrumed so that it causes the cradle to be rocked.

Description

United States Patent [72] Inventor William T. Richards Chicage, Ill.

[21] Appl. No. 860,217

[22] Filed Sept. 23, 1969 [45] Patented Mar. 2, 1971 73] Assignee Union Special Machine Company Chicago, Ill.

[54] SKIP STITCHMECHANISM FOR BLIND STITCH 2,725,839 12/1955 7 Parry Primary Examiner-H. Hampton Hunter Attorney F urman Rinehart ABSTRACT: Blind stitch sewing machine having an improved mechanism adapted to form blind stitches of either the skip or nonskip type. Includes a pivoted work support table lockable to stationary position and unlockable to permit swinging movement of the table. A first pitman and a second pitman operate in response to rotation of the main shaft of the machine. The forward end of the first pitman is connected to a rockable node former shaft which rocks in a rockable cradle under the work support table. The forward end of the second pitman is connected to the cradle. Means are provided for adjusting the machine to nonskip position in which the second pitman idles and to skip position in which the second pitman is fulcrumed so that it causes the cradle to be rocked.

PATENTEU MAR 215m SHEET 1 [IF 5 PATENTEDHAR 215m 3.566815 SHEEI 2 0F 5 my: 1 Q

HO\ HI PATENIEU MR 2 Ian SHEET 3 [IF 5 SKIP STITCH MECHANISM FOR BLIND STITCH SEWING MACHINE This invention relates to improvements in construction of a blind stitch sewing machine capable of operation at high speeds, which has mechanisms which may be adjusted so that selectively the machine will form successive stitches or skipstitches.

More particularly the invention relates to the ridge former driving mechanism and the mechanisms which are operative and adjustable for skip-stitch and nonskip stitch operation of the machine.

A feature of the invention is the provision of a ridge former mechanism wherein two pitmans are employed, each having a ,separate eccentric driven by the main shaft of the sewing machine and a further feature is mechanismfor causing the cradle which cooperates with the ridge former mechanism to swing to a selected first position in which the machine forms skip-stitches in the work being stitched and to swing to a selected second position in which the machine forms successive stitches without requiring rocking movement of the worksupporting member.

The machine is provided with locking mechanisms to render the work-supporting member completely stationary during the sewing operation and to release the locking mechanism to permit movement of the support table for inserting work in the machine or for removing it. Also; meansare provided for adjusting the amount of penetration of the needle in the work.

For a better understanding of the field of this invention and of certain prior art, reference is made to Roth et al. U.S. Pat. No. 3,288,094 (1966), for Blindstitch Sewing Machine; Mueller et a]. US. Pat. No. 2,632,416 (1953) for Node Former Adjusting Means for Blind Stitch Sewing Machines and my copending application Ser. No. 838,517 filed July 2, l969 for Blindstitch Sewing Machine. Inasmuch as the machine disclosed herein is similar in construction to the machine disclosed in my said copending application, except for the ridge former driving mechanism and the skip stitch mechanism, which are described in detail hereinafter, it is deemed unnecessary to describe in detail the other parts of the machine which are disclosed in said application. Reference is hereby made to said copending application for details of those parts which are already disclosed in said application.

This invention is shown as applied to a blindstitch sewing machine of the general kind as disclosed in said Roth et al.

FIG. 7 is a front elevational view of the skip-stitch knob shown in FIG. 6.

Referring now to the drawings in which like reference characters throughout the several views indicate like parts, the machine is provided with a base portion 10, from. the rearward portion of which rises a vertical hollow standard 11, also serving as a housing. A rotatable main drive shaft 12, journaled in suitable bearings, extends horizontally through the upper portion of the vertical standard 11. At the upper end of the vertical standard 11 there is provided a forwardly extending overhanging arm 11b at the forward end of which is stitch forming mechanism (not shown), comprising a curved needle, carried by an arm mounted on a shaft which is oscillated back and forth during each cycle of operation of the machine through connections of the character disclosed in the Roth et al. patent, and also other elements as disclosed in said patent. The stitch forming mechanism operates in conventional manner by suitable connections from the main drive shaft 12, all as shown for example, in the Roth et al. patent.

Fixedly secured to'the main shaft 12, and positioned within the housing provided by standard 11, are sprockets l3 and 14. An endless tooth-timing belt 15 is trained over sprocket l3 and over a sprocket 16 (see FIGS. 2 and 5) mounted for rotation on a fixed shaft 17 horizontally mounted in the lower end portion of the housing standard 11 in the base 10; the shaft 17 being maintained in fixed position by screw 18 threaded in a bore through the housing. An endless toothed timing belt 19 is trained over sprocket l4 and over a sprocket 20 mounted for rotation on fixed shaft 17. Sprocket 16 is fixedly mounted on the circular hub portion 21 of an eccentric 22 by press fit and a suitable cement so that the eccentric and sprocket rotate on shaft 17 as a unit. Sprocket 20 is fixedly mounted on the circular hub portion 23 of eccentric 24 by press fit and a suitable patent and more particularly to the type of machine disclosed in my said copending application Ser. No. 838,517. However, various changes have been made in the construction disclosed in my said copending application to bring about the different manner of the operation of the ridge former mechanism and the obtaining of skip-stitch operation by lowering the cradle within the work-supporting table.

Although the novel features which are believed to be characteristic of this invention are pointed out in theannexed claims, the invention itself as to its objects and advantages and the manner in which it may be carried out may be better understood by reference to the following more detailed description, taken in connection with the accompanying drawings forming a part hereof, in which:

FIG. 1 is a view partly in elevation and partly in vertical section through the right-hand portion of the machine;

FIG. 2 is a view partly in elevation and partly in vertical section taken substantially along a plane containingthe axis of the ridge former shaft in the work supporting table;

FIG. 3 is a plan view partly in horizontal section through various portions of the machine frame;

FIG. 4 is a vertical section taken along line 4 4 of FIG. 3,

showing the skip-stitch driving arrangement;

FIG. 5 is a partial vertical section taken alongline 5-5 of FIG. 1, showing the driving mechanism;

FIG. 6 is a partialplan view showing the skip-stitchadjusting knob; and

cement so that this eccentric and sprocket rotate onshaft 17 as a unit. Hence these eccentrics rotate with sprockets l6 and 20 about the fixed shaft 17. Sprocket 20 istwice the diameter of sprocket 16. Hence when main shaft 12 is rotated, sprocket 16 will rotate at twicethe angular speed of sprocket 20; this being explained further later on. A block 25, provided with a suitable bore 25a, is mounted on eccentric 24 so that the eccentric may rotate in the bore and the block 25 will move back and forth in linear direction upon rotation of the eccentric; the block being mounted between the prongs of the bifurcated end of a pitman 29, later described.

A pitman 26 is mounted in the portion of the housing in the base 10. The rearward end 27 of this pitman is provided with a bore 28 and it'slidably fits over the eccentric 22. Another pitman 29 is mounted in parallel spaced relation with pitman 26. This pitman has a forked or bifurcated end, having

arms

30, 30a in which are slidingly received the block 25.

A freely rotatable flat spacer ring 33 is mounted on shaft 17 between the

eccentrics

22 and 24 and serves as guiding and aligning surfaces for the pitmans '26 and 2-9. Retaining

collars

35 and 36 mounted on shaft 17 and secured by screws 37 restrain the mechanism between them from. lateral movement on the shaft.

Pitman 26 extends forwardly within the machine frame and is curved upwardly at its forward end portion 260 and extends into the interior space of the work support table 40 (see FIG. 1); the support table being mounted on a pivot shaft .39, carried by the base of the machine. A headed pin 41 (see FIG. 2) extends through a bore 42 in the forward end of the pitman 26, the pin extending through a bore in the lower end of a link 43. Pin 41 is held in the bore of the link 43 by a set screw 44. The upper end of link 43 is fixedly secured to the right end portion of ridgeformer shaft45, it being observedthat a split clamping member 47 at the end of link 43 extends around and is fixedly clamped on the shaft 45 by'means of screw 46. The inner face 50 0f the clamping member 47 of link 43 bearsor thrusts against the right end face of the bearing portion 58 of the cradle 51. Thecradle 51 is of the general type disclosed in the above-mentioned Mueller patent and is like the cradledisclosed in my aforesaid application Ser. No. 838,517. It .is

deemed unnecessary to describe it in detail here other than to say that it is contrived and mounted for rocking movement in relation to the work support table 40. The cradle is rockable about the axis of pins 52 and 53 (see FIG. 3), having conical ends extending into and cooperating with openings or cavities in the

end portions

54 and 55 of the main body of the cradle 51. The

pins

52 and 53 are mounted in bores in the walls of the work support table 40 and are held in place by

set screws

56 and 57. The cradle has offset

portions

58 and 59 which serve to provide bearings for the ridge former shaft 45; the shaft being rockably mounted in said bearings, all as disclosed in further detail in my aforementioned application. Referring again to link 43, which is clamped on ridge former shaft 45, this link serves to prevent lateral movement to the left of the ridge former shaft (see FIGS. 2 and 3). Lateral movement of this shaft to the right is prevented by a collar 60 secured on the shaft 45 at the opposite end of the bearing portion 58 of the cradle; a set screw 61 serving to fixedly secure the collar on the shaft.

Pitman 29 extends forwardly within the machine base and has a curved forward end portion 29a which extends upwardly into the space within the work support table 40. The forward end of this pitman has a bore 65 (see FIG. 4) and the forward end is received in a downwardly extending fork or clevis portion, having

arms

68 and 69, ofa link 67 (see FIG. 2). A pin 70 extends through registering bores in the

arms

68 and 69 of the clevis portion of the link 67 and through the bore 65 of the pitman. Pin 70 is held in the clevis by

set screws

73 and 74 in threaded bores in these arms. The upper end of link 67 is secured to the right end portion of the offset bearing portion 58 of the cradle 51 by means ofa split strap member 76 which is clamped by means of screw 77 to the bearing member of the cradle.

Intermediate the ends of the pitman 29, there is a widened portion 80 (see FIG. 3) which, as shown, is approximately equidistant from each end of the pitman. A longitudinal recess 81 of rectangular shape is provided in the top surface of the widened portion 80. Fitted in the recess 81 is a block 82 of rectangular shape having upper surface 83 which is inclined upwardly and forwardly toward the forward end of the block, as shown perhaps most clearly in FIGS. 1 and 4. The block 82 is maintained in fixed position on the pitman in the recess 81 by screws 84. The inclined surface 83 serves as a fulcrum contact surface for the pitman 29, as described later on.

Mounted in horizontally disposed wall portion 11a of the machine frame and above the block 82 is a mechanism 85 (herein referred to as the skip-stitch actuating mechanism) for causing the machine to produce successive stitches when the skip-stitch mechanism is adjusted to nonskip position and to produce skip-stitch when it is adjusted to skip-stitch position. This adjustable skip-stitch actuating and adjusting means 85 (see FIG. 4) comprises a fulcrum stud member 86 having an upwardly extending threaded stud shank 87, this threaded shank at its lower end terminating in a convex end surface 88 and a U-shaped bifurcated end member 89 (see FIG. 7) having downwardly extending

legs

90 and 91 which extend downwardly over the sides of the pitman with the convex surface 88 positioned between the legs and directly over the inclined surface 83 of the block 82. The threaded portion 87 of the member 86 is threaded into a corresponding threaded bore 92 in an internally threaded, rotatable hollow cylindrical body member 93 which has a reduced diameter, upwardly extending stud shank 95; thus providing an annular shoulder 94. The upwardly extending shank portion 95 extends rotatably through a bore 96 in the frame wall. The internally threaded hollow body portion of the member 93 is rotatably mounted in the cylindrical bore of the frame wall with the annular shoulder 94 engaging the inwardly extending annular lip 97. Now it will be seen that rotation of hollow stud member 93 will cause the member 86 to move vertically when the member is rotated on its vertical axis and to move vertically in the opposite direction when the member is rotated in the opposite angular direction. The

legs

90 and 91 which engage the sidewalls of the pitman 29 prevent the stud member 86 from turning and when the hollow stud member 93 is rotated, the thread on the shank 87 of stud member 86 causes this shank to move in only vertical direction without rotation. The direction of rotation of member 93 will determine whether the member 86 will move in upward or in downward direction.

An adjusting knob 100 has an annular flange 101 extending outwardly from the body portion of the knob and has a central blind bore 102 into which the upstanding shank of hollow member 93 snugly fits. A screw 103 fixes the rotatable knob to the shank 95. Hence when the knob is rotated, the member 93 is rotated and stud member 86 is correspondingly raised or lowered, depending on the direction of angular rotation of the knob. The arrangement is such that the convex fulcrum surface 88 may be lowered into contact with the inclined face 83 and raised out of contact with face 83.

Although the knob is rotatable with reference to the frame wall 11a, the amount of rotation is limited. In the bottom face of flange 101 there is an arcuate recess slot 104 extending 180 around the bottom face of the knob. Cooperating with the slot 104 is a stop pin 105, secured in the machine frame and extending upward into the slot. When the knob is turned in clockwise direction until the end of the slot engages the stop pin 105, the convex surface 88 of stud member 86 is lowered and engages the inclined fulcrum surface 83 of the pitman block 82; this position being herein referred to as skip-stitch position. When the knob is rotated in the opposite direction the stud member is moved upwardly and when the pin 105 engages the other end of slot 104 (as shown in FIG. 6) the convex surface 88 of stud member 86 is disengaged from inclined surface 83 of pitman block 82; this position being herein referred to as nonskip-stitch position. As explained later on, the mechanism is such that when the knob 100 is adjusted to nonskip position, the pitman 29 oscillates back and forth in idling manner and when adjusted to skip-stitch position, the pitman in its back and forth movement also is fulcrumed at the place the convex surface 88 engages the inclined surface 83 of pitman block so that the cradle 51, as explained later on, is rocked every other cycle by pitman 29 so that alternate stitches are skipped.

The work support table 40 is mounted for rocking movement within limits about a fixed shaft 39 which is secured in the base frame walls and the table support may be locked in stationary position during a stitching operation and may be unlocked so that the work support table may be rocked about pivot shaft 39 for conveniently introducing or removing work from the machine. Also means are provided for adjusting the penetration of the needle of the sewing machine in the work, all as disclosed and described in my said copending application Ser. No. 838,517. As disclosed in said application, the cradle 51 is provided with a downwardly extending pin 108 secured to the cradle. A yieldable spring 109, secured at its lower end to the pin and at its other end to a sidewall 40a of the work support 40, yieldably maintains the cradle normally in a desired position, the spring 109 yieldably urging said cradle to swing upwardly about its mounting pivots 53 and 54, against an adjustable stop means 110 mounted in the upper horizontally disposed wall 40b of work support table 40. The position in which the cradle is normally held by spring 109 may be varied by adjusting the screw 111 of the stop means 110. For further details as to this needle penetration adjustment means, reference may be made to the above mentioned Mueller US. Pat. No. 2,632,416.

A spring 115 is connected at one end with a pin 116 mounted in the downwardly extending skirt portion 40c of the work support table 40 and at its other end is connected with a pin 117 secured to a portion of the base frame of the machine. Also mounted in the downwardly extending skirt 40c of the work support table is an adjustable screw 118, the inner end of which engages a wall portion 100 of the base 10 of the machine frame. By adjustment of this screw 118, the work support table is retained in the desired position, in which it may be releasably locked by locking mechanism.

As has been mentioned in the foregoing, the machine is contrived so that the work support table 40 .may be locked and held in a fixed or stationary position during the stitch forming operation and so that the work support table may be unlocked so that it may be swung on the axis of pivot mounting shaft 39 for conveniently inserting or releasing the work to be stitched. The locking mechanism 120 comprises a slidable lock bar 121 adapted to be moved into engagement with a rigid member 122 extending downwardly from skirt 40d of the work support table and secured thereto by screws 123. The lock bar 121 is slidable forwardly to engage member 122 to hold the work support table in desired stationary position and rearwardly to disengage so that the work support table is freed to swing about ,its pivot 39; the shaft 39 being secured to machine frame by screws 128. A downward extending pin 124 carried by the lock bar 121 has one end of a spring 125 connected to it; the other end of the spring being connected to a pin 126 secured to a U-shaped retaining member 127 secured to the underside of wall d of the base 10; the lock bar being slidable along channel 128 of the member 127. The lock bar has a downward extending block 129 extending through a slot in member 127; the block having a cam face 130. The spring 125 normally urges the lock bar 121 forwardly to hold the lock bar in engagement with rigid element 122 to hold the work support table stationary but the lock bar is shifted rearwardly upon actuation of a knee press member adapted to rotate a rockable shaft 131.

For shifting the lock bar 121 rearwardly there is provided, as disclosed in my said copending application, a conventional rock shaft 131 having secured to its outer end (toward the left in FIG. 1) a downwardly extending arm 132 to which is connected a conventional knee pad through which the operator may rotate the shaft through a suitable angle. Secured to the rock shaft 131 is a block having an upwardly extending pin 134 to cooperate with the cam face 130 of the block 129 extending downwardly from the lock bar 121.- When rocker shaft 131 is turned counterclockwise (as viewed in FIG. 2) by action of the knee press, this will cam the locking face rearwardly and disengage the lock bar from element 122 on the work support table and thus release the work support table so that the table may be swung downwardly about the axis of pivot shaft 39 to facilitate removal of stitched work and to facilitate introduction of a new workpiece to be stitched. Release of the knee press will return the lock bar forwardly to lock the work support to normal stationary position.

Upon rocking shaft 131 by the action of the knee press, an arm 135, secured to the shaft by collar 136 and screws 136a, is moved downwardly. After the shaft has been rotated sufficiently, a pin 137 through arm 135, engages the lower end of a slot 143 in another arm 138 and moves arm 138 downwardly; arm 138 has a collar 133 mounted on the shaft 131 for free rotation; collar 133 being held from lateral movement by retaining collar 142 fixed on shaft 131. One end of a link 139 is attached to arm 138 and the other end to a pin 140 extending from a wall 141 which is an integral part of work support 40 (see FIG. 2). Thus the actuation of the knee pad arm 132 will not only move the lock bar 121 to unlocked position and release the work support table 40 for swinging movement on its pivot mounting shaft 39, but will also impart swinging movement of the work table, for insertion or removal of a workpiece.

Mounted on the end of the rockable shaft 45 is a node former 145 (see FIG. 3) of the character disclosed in the above mentioned Roth et al. patent. Preferably the node former 145 is disclike in form and is provided with two segments 180 apart which may be selectively placed and maintained in operative angular position by suitable means, such as an end nut threaded on the end of the shaft 45. One of the segments is for operation when relatively soft fabrics are stitched and the other for relatively hard fabrics. As heretofore known ,(for example see said Mueller US. Pat. No. 2,632,416), the

depth of penetration of the curved needle of the stitching mechanism of the machine may be selectively adjusted by means of the threaded stud pin 111 of the cradle positioning and adjusting mechanism 110. The pin 111 when adjusted downwardly will cause the cradle 51 to assume a normal position in which the nodeformer is adjusted downwardly away from the presser foot of the machine (not shown). When the threaded stud is moved upwardly, this will adjust the cradle so that the node former 145 is adjusted upwardly toward the presser foot of the machine.

As mentioned above, the sprocket 16 is the same size as its driving sprocket 13 and therefore will be rotated at the same angular speed as main shaft 12. Sprocket 20 is twice the size of sprocket14, and therefore, it will be driven at one half the angular speed of main shaft 12. The ridge former shaft 45 will be oscillated, by the eccentric 22, the pitman 26, and link 43. with each revolution of main shaft 12. With the knob adjusted in the nonskip position, as described in the foregoing, theconvex surface 88 of the stitch adjusting mechanism will be raised out of contact with the inclined surface 83 of the block 82 mounted on pitman 29. When the mechanism is adjusted in this nonskip position, the pitman 29, upon rotation of eccentric 24, will pivot about pin 70 in link 67 and upon back and forth movement of the pitman 29, this pitman with its

bifurcated end

30, 30a will slide back and forth on block 25 (see FIG. 4). In effect, the pitman 29 is idling and only the pitman 26 is effective to oscillate the ridge former shaft 45, which is oscillated at each stroke of pitman 26; the pitman 29 which is connected through link 67 to the bearing portion 58 of the cradle being ineffective to oscillate the cradle 51, when the machine is adjusted for nonskip stitching. Hence, the stitching mechanism will form successive stitches when it is adjusted in the nonskip position. On the other hand, when the knob 85 is rotated andadjusted to skip position with the end of the slot 104 in engagement with stop pin 105, (as shown in FIG. 6), the convex surface 88 of member 86 will have been moved downwardly into engagement with inclined surface 83 of block 82 on the pitman 29. When changing the adjusting knob from nonskip to skip position themachine driving pulley and handwheel 150 is rotated until the knob can be turned through 180 of rotation. At this point the knob will be stopped by pin and the convex surface 88 will be in contact with the inclined surface 83 of block 82. Also, at this stage the skip-stitch eccentric 24 will be at its low point and the ridge former driving eccentric 22 will be at its forwardmost point. The point or locus at which the convex surface 88 contacts the angled surface 83 of block 82 now becomes a fulcrum point for the skip-stitch pitman 29. Now when the eccentric 24 reaches its high point, the pitman 29 will pivot at the fulcrum point which is provided at the locus of contact of convex surface 88 and inclined surface 82 of the pitman. As a result, the cradle 51 iscaused to swing downwardly on its

pivot

54, 55, by means of link 67. This causes the ridge former shaft 45 to move downwardly, carrying the node former 144 downwardly so that the needle of the machine does not penetrate the workpiece, thus resulting in a skip-stitch. Upon the next full oscillatory stroke of the ridge former shaft 45 by means of eccentric 22, pitman 26 and link 43, the skip-stitch eccentric 24 will move only from its high point to its low point of rotation, bearing in mind the sprocket 20 is twice the diameter of sprocket 16, which oscillates the ridge former shaft 45. Hence, the cradle 51 will be returned to its normal position by means of link 67, thus resulting in a normal stitch. The two

eccentrics

22 and 24 are timed so that each time the ridge former shaft 45 reaches the inwardmost position of its stroke, the skip-stitch eccentric 22 will be either at its high point or at its low point, thus resulting in a skip-stitch on one stroke of the ridge former and a normal stitch on its next stroke.

When the ridge former shaft with its node former with its connected ridge former shaft 45 is adjusted to provide the desired penetration by the needle of the machine and the cradle is moved downwardly by swinging about its pivot shaft 39, the pitman 29 will move rearwardly and downwardly on an angle, pivoting about eccentric 24 and sliding on the block 25.

The block 82 will therefore change its position in relation to the element 86 which has the convex surface 88. But due to the inclined surface 83, which is at the same angle as the angled movement of the pitman 29, the space between the convex surface 88 and the inclined surface 83 will remain constant during raising or lowering of the cradle 51 (as by raising or lowering the threaded stud 111) for penetration adjustment. Also, with the machine adjusted to the skip-stitch position, the inclined surface 83 of block 82 and the convex surface 83 of element 86 will be caused to remain in contact with each other during any raising or lowering of the cradle for penetration adjustment.

The terms and expressions which have been employed herein are used as terms of description and not of limitation, and there is no intention, in the use of such terms and expressions, of excluding any equivalents of the features shown and described or portion thereof, but it is recognized that various modifications are possible within the scope of the invention claimed.

I claim:

1. A blind stitch sewing machine having a frame, a main drive shaft mounted for rotation on said frame, a work support table rockably mounted on said frame, a cradle rockably mounted on said table, locking means operative to maintain said table in fixed position in relation to said frame during a stitching operation, a ridge former shaft rockably mounted on said cradle and a driving mechanism for rocking said ridge former shaft and said cradle in timed relation; said driving mechanism comprising a second shaft mounted on said frame, a first eccentric mounted for rotation about the axis of said second shaft, a first pitman connected at its rearward end with said first eccentric and at its forward end pivotally connected through linkage to said ridge former shaft, a second eccentric mounted for rotation about the axis of said second shaft, a second pitman connected at its rearward end with said second eccentric and at its forward end pivotally connected through linkage to said cradle, said eccentrics being rotated about the axis of said second shaft in response to rotation of said main shaft, and means for adjusting said machine for producing skip-stitch and for producing nonskip-stitches mounted on said frame including an adjustable member cooperating with said second pitman adjustable to nonskip'stitch position in which said machine is operative to form successive stitches and to skip-stitch position in which said machine is operative to form skip-stitches.

2. A blind stitch sewing machine in accordance with claim I in which said means for adjusting said machine for producing skip-stitches and nonskip-stitches includes a first member mounted on said frame movable to a first position and to a second position, a vertically movable second member cooperating with said first member and being moved downwardly into engagement with said second pitman when said first member is moved to said first position, and said second member being moved upwardly out of engagement with said second pitman when said first member is moved to said second position, said second member forming a fulcrum about which said second pitman rocks thereby rocking said cradle upon actuation of said second eccentric when said first member is in said first position, said second pitman, when said first member is moved to said second position and said second member is out of engagement with said second pitman, merely idling without rocking said cradle.

3. A blind stitch sewing machine according to claim 1 in which first and second sprockets are fixedly mounted on and are rotated by said main shaft, said first eccentric is fixedly mounted on a third sprocket rotatable about the axis of said second shaft and said second eccentric is fixedly mounted on a fourth sprocket rotatable about the axis of said second shaft, a timing belt trained over said first and third sprockets, a timing belt trained over said second and fourth sprockets, and said sprockets are dimensioned so that upon rotation of said main shaft said fourth sprocket rotates at half the angular speed of said third sprocket.

4. A blind stitch sewing machine according to claim 1 in which said means foi' adjusting said machine for skip and nonskip-stitching comprises an adjustable vertically movable member, means secured to said frame and mounting said vertically movable member and including means to move said vertically movable member into engagement with said second pitman at a place intermediate the ends of said second pitman and out of engagement with said second pitman, said vertically movable member when in engagement with said second pitman providing a fulcrum about which said second pitman is rocked.

5. A blind stitch sewing machine in accordance with claim 1 in which said means for adjusting said machine for producing skip-stitches and nonskip-stitches includes means mounted on said second pitman intermediate its ends providing an inclined fulcrum surface, and includes a skip-stitch actuating means mounted on said frame, said actuating means comprising an externally threaded shank member terminating at one end in a bifurcated end having legs straddling the sides of said second pitman and having a convex fulcrum surface positioned between said legs, a shank member mounted in a wall of said frame for rotation and having a hollow internally threaded sleeve into which said externally threaded shank member extends, said externally threaded shank member moves in upward direction in response to rotation of said sleeve in one angular direction and in downward direction in response to rotation of said sleeve in the opposite angular direction, and means for rotating said sleeve to a first position in which said convex surface engages said inclined surface and said machine is adjusted for skip-stitch stitching and to a second position in which said convex surface and said inclined surface are not engaged and said machine is adjusted for nonskip-stitching.

6. A blind stitch sewing machine according to claim 2 in which said second pitman at its rearward end is bifurcated to provide arms providing a longitudinal slot therebetween, and in which a block is slidably mounted in said slot, said block having a bore slidably fitted over said second eccentric.

7. A blind stitch sewing machine according to claim 3 in which said first, second and third sprockets are equal in diameter and said fourth sprocket is twice the diameter of said third sprocket.

8. A blind stitch sewing machine according to claim 7 in which said means for adjusting said machine for skip and nonskip-stitching comprises, a fulcrum stud member having an upwardly extending externally threaded stud shank terminating at its lower end in a convex fulcrum surface and a bifurcated end having downwardly extending legs which straddle the sides of said second pitman with said convex surface overlying said pitman at a fulcrum area intermediate the ends of said second pitman, a vertically extending stud shank having a hollow internally threaded sleeve portion at its lower end portion into which said upwardly extending threaded stud shank is in threaded engagement, said externally threaded stud shank being movable downwardly in response to rotation of said sleeve in one angular direction to a first position in which said convex surface engages said second pitman at said fulcrum area and said externally threaded shank being movable upwardly in response to rotation of said sleeve in the opposite angular direction to a second position in which said convex surface is not in engagement with said second pitman and means connected to said sleeve member for rotating said sleeve to and from said first and second positions.

9. A blind stitch sewing machine adjustable for operation to form successive stitches or for operation to form skip-stitches, having a rotatable main drive shaft mounted on said frame, a first and a second sprocket fixedly mounted on said drive shaft for rotation therewith, a work support table rockably mounted on said frame, a cradle rockably mounted on said table, locking means operative to move to locked position to maintain said table in fixed position in relation to said frame and to unlocked position to permit rocking movement of said table, a ridge former shaft rockably mounted on said cradle, a driving mechanism for rocking said ridge former shaft in relation to said cradle and for rocking said cradle in relation to said table and a skip-stitch actuating means; said driving mechanism including a fixed shaft fixedly mounted in the base portion of said frame, a third sprocket and a fourth sprocket mounted for rotation on said fixed shaft, a first eccentric secured to and rotatable in response to rotation of said third sprocket, a second eccentric secured to and rotatable in response to rotation of said fourth sprocket, driving means connecting said sprockets so that said third and fourth sprockets rotate in response to rotation of said first and second sprockets, a first pitman having a bore at its rearward end slidably mounted over said first eccentric, a link fixedly mounted at one end on said ridge former shaft and at its other end pivotally connected to the forward end of said first pitman, a block having a bore slidably mounted over said second eccentric, a second pitman, having a bifurcated end, mounted for slidable movement back and forth on said block, a link fixedly mounted at one end on said cradle and at its other end pivotally connected to the forward end of said second pitman, a fulcrum block, having an inclined fulcrum surface, mounted on theupper side of said second pitman about midway of its length, said skip-stitch actuating mechanism including a vertically mounted externally threaded member terminating at its lower end in a convex fulcrum surface and downwardly extending legs straddling the sides of said second pitman, a rotatable shank member having a hollow internally threaded sleeve member into which extends said externally threaded member, said hollow sleeve member being mounted in a wall of said frame for rotation, means to rotate said sleeve member to a first position, causing said convex surface to move into engagement with said inclined fulcrum surface in which position said second pitman will be fulcrumed at the'place of engagement so that upon actuation of said second pitman in response to rotation of said second eccentric, said cradle will be rocked.

Claims

1. A blind stitch sewing machine having a frame, a main drive shaft mounted for rotation on said frame, a work support table rockably mounted on said frame, a cradle rockably mounted on said table, locking means operative to maintain said table in fixed position in relation to said frame during a stitching operation, a ridge former shaft rockably mounted on said cradle and a driving mechanism for rocking said ridge former shaft and said cradle in timed relation; said driving mechanism comprising a second shaft mounted on said frame, a first eccentric mounted for rotation about the axis of said second shaft, a first pitman connected at its rearward end with said first eccentric and at its forward end pivotally connected through linkage to said ridge former shaft, a second eccentric mounted for rotation about the axis of said second shaft, a second pitman connected at its rearward end with said second eccentric and at its forward end pivotally connected through linkage to said cradle, said eccentrics being rotated about the axis of said second shaft in response to rotation of said main shaft, and means for adjusting said machine for producing skip-stitch and for producing nonskipstitches mounted on said frame including an adjustable member cooperating with said second pitman adjustable to nonskip-stitch position in which said machine is operative to form successive stitches and to skip-stitch position in which said machine is operative to form skip-stitches.

2. A blind stitch sewing machine in accordance with claim 1 in which said means for adjusting said machine for producing skip-stitches and nonskip-stitches includes a first member mounted on said frame movable to a first position and to a second position, a vertically movable second member cooperating with said first member and being moved downwardly into engagement with said second pitman when said first member is moved to said first position, and said second member being moved upwardly out of engagement with said second pitman when said first member is moved to said second position, said second member forming a fulcrum about which said second pitman rocks thereby rocking said cradle upon actuation of said second eccentric when said first member is in said first position, said second pitman, when said first member is moved to said second position and said second member is out of engagement with said second pitman, merely idling without rocking said cradle.

4. A blind stitch sewing machine according to claim 1 in which said means for adjusting said machine for skip and nonskip-stitching comprises an adjustable vertically movable member, means secured to said frame and mounting said vertically movable member and including means to move said vertically movable member into engagement with said second pitman at a place intermediate the ends of said second pitman and out of engagement with said second pitman, said vertically movable member when in engagement with said second pitman providing a fulcrum about which said second pitman is rocked.

9. A blind stitch sewing machine adjustable for operation to form successive stitches or for operation to form skip-stitches, having a rotatable main drive shaft mounted on said frame, a first and a second sprocket fixedly mounted on said drive shaft for rotation therewith, a work support table rockably mounted on said frame, a cradle rockably mounted on said table, locking means operative to move to locked position to maintain said table in fixed position in relation to said frame and to unlocked position to permit rocking movement of said table, a ridge former shaft rockably mounted on said cradle, a driving mechanism for rocking said ridge former shaft in relation to said cradle and for rocking said cradle in relation to said table and a skip-stitch actuating means; said driving mechanism including a fixed shaft fixedly mounted in the base portion of said frame, a third sprocket and a fourth sprocket mounted for rotation on said fixed shaft, a first eccentric secured to and rotatable in response to rotation of said third sprocket, a second eccentric secured to and rotatable in response to rotation of said fourth sprocket, driving means connecting said sprockets so that said third and fourth sprockets rotate in response to rotation of said first And second sprockets, a first pitman having a bore at its rearward end slidably mounted over said first eccentric, a link fixedly mounted at one end on said ridge former shaft and at its other end pivotally connected to the forward end of said first pitman, a block having a bore slidably mounted over said second eccentric, a second pitman, having a bifurcated end, mounted for slidable movement back and forth on said block, a link fixedly mounted at one end on said cradle and at its other end pivotally connected to the forward end of said second pitman, a fulcrum block, having an inclined fulcrum surface, mounted on the upper side of said second pitman about midway of its length, said skip-stitch actuating mechanism including a vertically mounted externally threaded member terminating at its lower end in a convex fulcrum surface and downwardly extending legs straddling the sides of said second pitman, a rotatable shank member having a hollow internally threaded sleeve member into which extends said externally threaded member, said hollow sleeve member being mounted in a wall of said frame for rotation, means to rotate said sleeve member to a first position, causing said convex surface to move into engagement with said inclined fulcrum surface in which position said second pitman will be fulcrumed at the place of engagement so that upon actuation of said second pitman in response to rotation of said second eccentric, said cradle will be rocked.