A MECHANISM FOR ACTUATING THE HOOK AND CLAW AND FOR STITCH SETTING IN PORTABLE SEWING MACHINE

Abstract: In an actuating mechanism for the hook of portable sewing machines, a hook actuating profiled cam is provided which is additionally provided with a pin for simultaneously actuating the material transport claw through an interposed linkage having an adjustable element. By providing a hook formed with a respective eye, a double chain stitch seam can be effected. By further providing a profile cam with a depression for containing the hook swinging foot therein during an oscillation of the foot, a greatly reduced overall becomes achievable. Thanks to the adjustable element it becomes possible to change the stitch length.

Description: This invention relates to a mechanism for actuating the hook and claw and for stitch setting in portable sewing machines. Portable sewing machines are employed to sew closed with chain stitch seams packages, sheets, and paper or canvas bags e.g. for packaging potatoes, granulated fodder, and so forth. Such machines are subjected, accordingly, to severe operating environments brought about, among other factors, by the nature of the materials handled, a dusty environment, the high sewing speeds sought, and so forth. These machines, moreover, are required to be reliable in operation and as light in weight as feasible. With prior machines, chain stitching is of the plain type, that is, the chain is formed by a sequence of individual loops which are intertwined progressively the one after another, the same being formed by means of a needle having an associated hook set to swing reciprovatingly around it over an angle of about 150-160°. A wider angle of rotary reciprocation of the hook is not presently achievable owing to constructional limitation inherent to prior designs. The hook is driven by the driveshaft through a cam, the latter having two spaced-apart detents cooperating with two detents, also spaced apart, which are provided rigidly with the hook carrier shaft. Such a conformation is disclosed in Italian Patent No. 829,852. Prior machines further include a mechanism for actuating the feeder claw for the material being sewn. Such mechanisms require a large number of components, and accordingly, are bulky and heavy. This results in increased overall dimensions of the sewing machine, and attendant heavier weight thereof. Prior sewing machines are also provided with a mechanism made up of several parts for setting the sewing stitches to different lengths. This brings about, in turn, similar problems to the above. With prior machines, the large number of moving parts also pose wear problems and of attendant play formation. The net result is noisy operation and the need for frequent lubrication. In practice, moreover, it has been found that incidental breakage of some plain chain stitches can often result in running of the adjacent stitches and consequently in the bag or the like being opened and its contents, e.g. granulated fodder, lost. This is specially likely to also occur while handling, shifting, or shipping such bags and the like, as well as on account of faulty seams. The document US-A-1 657 989 discloses several embodiments of sewing mechanisms, whereby the loop formed by the needle is formed into two loops, a small loop and a large one. The shown mechanisms comprise a hooked finger provided with oscillating means, a strand deflecting member also provided with own rocking means and a usual rotary looper. The disclosed sewing mechanisms are made up of a large number of moving parts and are not fit either for actuating simultaneously the hooked finger and the claw or for setting the stitch length. The document DE-C-144 782 shows a sewing machine with a ring needle provided with a central hook-like projection. The rocking movement of the ring needle is derived from the main shaft of the sewing machine by means of a crank driving a rack which engages a sprocket mounted on the shaft of the ring needle. Means for setting the stitch length as well as means for operating the claw are neither suggested nor shown. This invention is based on the aim to provide mechanisms for actuating the hook and claw, and for setting the stitch length, which are simplified and afford an increased angle of rotary hook reciprocation, the proposed mechanism also affording double chain stitching ability and variability of the stitch length to suit the material being sewn or its contents, from the machine outside. Within the above aim, the proposed mechanism is to have a reduced number of parts, and therefore, overall size and weight. The proposed mechanism should also afford high sewing speed ability, be highly reliable in operation even in heavy-duty applications, and make the usual lubrication practically unnecessary. Starting with, a sewing machine comprising, for hook actuation, a cam profile cut with two oscillation detents, being associated with the machine driveshaft and carried in a box-type casing attached to the machine casing and cooperating with two counter-detents rigid with the hook shaft, supported obliquely on said box-type casing, the aim of this invention is achieved by that: i. the profile cam for the hook oscillatory movement also has a claw driving pin operating through a linkage, an element of said linkage being arranged to have a variable length to thereby vary the stitch length; ii. the two counter-detents for the hook oscillation are formed by the ends of a list foot of the hook carrier shaft, and the two cam oscillation detents consist of two sectional cross sides thereof, between which cross sides, and adjacently thereto, said cam is recessed to enable formation of said detents and free oscillation, within the cam, of said list foot of the hook during the hook oscillatory movement; iii. the hook has on its base portion the configuration of a curled up strip chip-like or coil-like by about a full turn, in the free end of the hook there being formed a yarn eye to form a double chain stitch; iv. a yarn feeding means for the double chain loop on the hook and a means of guiding the yarn into the double chain loop are also provided; v. the box-type casing accommodating the cam has juts for its mounting matingly in the sewing machine casing. According to the invention, the profile cut cam is a disk-like type of cam and the box-type casing has a cylindrical chamber accommodating said cam. Further according to the invention, the yarn guiding means consists of a peripheral shoulder one end of which starts from the junction to the hook base, which junction also forms a groove opening to a location close to the eye in the hook. The yarn feeding means for the double chain loop consists, according to the invention, of a guide tube on the exterior of the sewing machine casing which opens to a location close to the hook, some segments of said tube skirt, facing outwards from the sewing machine, being removed for better convenience in setting the yarn. According to the invention, moreover, the juts for a matching fit of the box-type casing into the sewing machine casing consist of an annulus. The bracket drive pin consists advantageously, according to the invention, of a pin received in a seating hole in the cam. The latter also has, on a front side thereof, a closure ring fitting with a slight clearance in the bottom wall of said box-type casing. According to the invention teachings, the advantage is thus afforded of a single mechanism driving in common the hook and claw, which mechanism is advantageously formed of a small number of easily and quickly assembled parts, and enables the stitch length to be varied from its maximum value of about 11mm to its minimum value of about 3mm. The stitch length can be advantageously set from the machine exterior. That assembly, moreover, requires no complicated initial adjustment operations. Weight can be quite low and the overall size small. Operation is made advantageously highly reliable even at high sewing speeds. The latter may also be attained on account of the wider angle of rotary reciprocation now attainable with the proposed structure. Another advantage of the proposed mechanism is that a double chain stitch seam can be formed with a single hook. Given the small number of the parts and their association, wear rate is also low and the traditional lubrication at frequent intervals made unnecessary. The net result is, therefore, a sewing machine which is lightweight, reliable and safe to operate even at high speeds and in severe operating conditions. Reliable operation is ensured by that a positive form of yarn pick up by the hook is provided regardless of the yarn position, since the hook tip, which can be rotated to a very small distance from the needle axis, e.g. on the order of about 0.2mm, affords a very short path of movement around the needle. Sewing machines according to the invention may thus be as light as about 1.9kg versus about 5kg for comparable prior sewing machines. Further features, advantages, and details of the mechanism for actuating the hook and claw in portable sewing machines for double chain stitch sewing according to the invention will become apparent from the following description, given herein by way of example and not of limitation with reference to the accompanying drawings, which show diagramatically and to different scales, in Figure 1 a side elevation view of a sewing machine with the device of this invention depicted in phantom lines; in Figure 2 a front view of the sewing needle side of the same; in Figures 3 and 4, respectively a front view of the needle side of the part of the inventive mechanism, with the closure cover removed and at different rotational positions of the actuating cam; in Figures 5,6,7 and 8, various views of the hook of this invention, namely a view from below, a view from above, and two side elevation views from opposite sides thereof; in Figure 9 a vertical mid-sectional view taken through the actuating cam according to the invention in its cup-like casing supporting the hook. in Figures 10,11 and 12, views of the inventive actuating cam, namely a front view of the front side opposing the bottom of the cup-like casing, a front view of the opposite side, and a view from above; in Figures 13 and 14, respectively a view of the actuating cam in its casing, and specifically in the two striking positions of the cam and hook foot marking the starts of two respective rotary reciprocations of the hook; in Figure 15 a view of the outer side of the cam casing with the claw drive parts removed for clarity; in Figure 16 a side elevation view of the actuating linkage for the claw and for changing the stitch length; in Figure 17, a view of the linkage taken in the direction of the arrow F in Figure 16; in Figures 18,19,20 and 21, perspective views of the block, connecting rod, linkage bracket, and stationary holder for the sane, respectively; in Figure 22 a detail view of the phase of penetration of the hook by the needle; and in Figures 23 and 24 an illustration of a plain chain stitch and double chain stitch seam section, respectively. Indicated at 1 is a sewing machine incorporating the mechanism of this invention. The same has a casing 2 accommodating the drive motor and power transmission of conventional design, no further illustrated herein. The output shaft of the drive system is indicated at 3. The same enters the chamber 4 housing the proposed mechanism. The latter comprises substantially a profile cut disk-like cam 5 keyed to the drive shaft 3 and being accommodated in a cup-like receiving seat 6 provided in the sacing 7 supporting said profile-cut cam 5. The casing 7 has a casing bottom 8 apertured in the middle at 9, and a flange 10 apertured as at 11 to let through screws 12 for fastening to the partition wall 13 of the chamber 4. Indicated at 14 is a ring collar of the casing 7 for geometrical engagement in a corresponding seat 15 in said wall 13. The casing 7 also has removed segments, as may be seen from the figures, for minimizing its overall size. Also provided on the casing 7 is a bored projection 16 (Figures 9,15) for supporting a pin 17 carrying on one end, by means of a dowel 18, the base 19 of the chip-like hook 20, and on the opposite end, a list foot 21 (Figures 9,13,14). The conformations of the hook list 19a and the foot 21 may be seen from the various figures. Indicated at 22 and 23 are the counter-detents for the foot 21, which cooperate, to start a reciprocating oscillation, with a detent 24,25, respectively, in the form of corners cut to profile on the profile cut cam 5. As may be seen from Figure 10, the cam 5 is composed substantially of a first segment 26 and a second segment 27, the same having curvature radii R and r which differ from each other as explained hereinafter. The cam 5 has in the segment 26, on the side facing the bottom 8 of the casing 7, a profile cut depression 28, as may be seen from Figures 9,11, to allow the foot 21 to oscillate freely therein. Thus, a greatly reduced overall size is attained. According to the invention, in the cam 5 there is also provided a seat 29 for accommodating a drive pin 30 for the claw 31 arranged to drive the claw through a linkage comprising a connecting rod 32 accommodating the drive pin 30, a bracket 33 hingedly connected on one side at 33a to the connecting rod 32, and on the other side at 33b to a stationary support 34 attached at 34a to the casing 2, and a block 32 for setting the stitch length. The block 35 is hinged at the bottom at 35b to the connecting rod 32 and has at the top a head 35a to which there are hinged at 35c the arms 31b of the claw 31 being radiused together by a cross side 31c. The claw 31 has a middle head 31a the bottom side 31d whereof has a maximum oscillation distance a from the top side 35d of the head 35a, wherein an oscillation setting screw 47 having a head 47a is accommodated inside the threaded hole 35d. The wider the oscillation of the claw 31 on the block 35, the shorter will be the claw 31 drive component for the bracket and the length of the stitches. The maximum distance a is attained by loosening the screw 47 until its striking end reaches below the top side 35e of the block head 35a. With the screw 47 bottoming out, the cross side 31c will strike the head 35a and the block 35 and claw 31 form accordingly a rigid piece. In practice, the range of length variation of the stitches is from about 10-11mm to about 3mm. To reach the screw 47 with a screwdriver, a hole 48 is provided in the bottom 4a of the chamber 4 and a hole 49 is provided through the connecting rod 32. Indicated at 50 is a closure cover hinged at 51. Reverting in particular to Figures 6,9,14 and 15, it can be further seen that the hook list 19a has an open coil or chip-like configuration with an eye 36 close to its end for conducting a double chain stitch yarn 37 shown in dotted lines for claruty in Figure 24, whereas at 38 there is indicated the traditional plain chain stitch yarn led by the needle 39, with which the hook 20 is arranged to cooperate in a manner known per se. Indicated at 40 is a yarn guide means 37 which comprises a small tube 40 on the casing 2 outside and has a yarn inlet end 41 and a bent end 42 extending inside the chamber 4 and being terminated close to the hook 20. For convenience of introduction of the yarn 37, the tube 40 has removed skirt portions along its length, no further shown in the drawing. Indicated at 43 is a washer keyed to the annular seat 44 of the cam 5 to cover the cited aperture 9. Provided on the hook 20 is a means of guiding the double chain stitch yarn 37 consisting of a peripheral shoulder 45 starting at one end from the junction of the hook coil to the base thereof, said shoulder extending then to form a groove 46 over the lower portion of the hook which opens close to the eye 36 thereof. The operation of the proposed mechanism, whereby the hook and claw can be advantageously actuated, the double chain stitch length varied, and the hook made to complete an angle of rotary reciprocation as large as 180°, will be now described briefly. Starting from the position shown in Figure 13, whereat the detent 24 of the cam 5 strikes the counter-detent 22 of the foot 21, on rotating the cam 5 this will bring about a first rotary oscillation of the foot 21 about itself through 180° inwards, the offcentered positioning of the foot 21 from the axis of its carrier pin 17 favoring said rotational movement by gravity force. In this rotation, the foot 21 moves in the cited depression 28 (Figure 9). On completion of this first 180° turn in one direction, the foot 21 will occupy the position shown in Figure 14, whereat the detent 25 of the cam 5 is striking the counter-detent 23 of said foot 21. As the rotation of the cam 5 is continued, there will first occur a 180° turn of the foot 21 in the opposite direction to the former, that rotation being brought about by the profile 25a. This is followed by a sliding engagement of an arcuate surface 21a of the foot 21 on the outside on the segment 27 of radius r, which for this reason is made smaller than the radius R of the segment 26, said segment 27 extending advantageously over about 225°. This engagement is then ensured mechanically, that is by positive mechanical sliding engagement, and during it there occurs a phase of hook stopping. Thus, we are back to the position of Figure 13. During this rotation, there has also occurred a command to move the claw 31 forward by means of the drive pin 30 and of the cited linkage, as previously adjusted in the setting screw as specified above. Shown in phantom lines in Figure 4 is the the lifted position of the claw 31. The intermediate phases are obvious ones, and hence, no further illustrated. It may be appreciated from the foregoing that the mechanism of this invention fully achieves the aim set forth for it and that the advantages mentioned in the preamble are afforded. With a single mechanism, comprising a limited number of components, it is now possible, therefore, to simultaneously actuate the hook and claw of portable sewing machines allowing, through the application of an eye 36 to the hook 20, insertion into the plain chain stitch of a yarn 37 to produce a double chain stitch. This may be accomplished by a clever cluster of kinematic and structural expedients according to the invention, which also enable adjustment of the stitch length within a broad range and the achievement of a 180° angle of rotary reciprocation for the hook. The net result is a mechanism which has greatly reduced space requirements and a very low weight. A sewing machine of the type indicated and incorporating the mechanism of this invention can have a lighter weight than 1.9kg. For further advantages to be obtained hereby, reference can be had to what has been put forth in the preamble. In practice, the proposed mechanism can have its parts modified in any way by a skilled person. All the features to be inferred from the description, claims, and drawings are regarded as being substantial to this invention, either singly or in any desired combination thereof.

Claims: A mechanism for actuating the hook and claw in portable sewing machines for chain stitch sewing, comprising a profile cut cam having two oscillation detents and being associated with the machine drive shaft, and carried on a box-type casing secured to the sewing machine casing and cooperating with two counter-detents formed on a foot rigid with the hook shaft, obliquely supported on said box-type casing, characterized in that: i. the profile cut cam (5) for oscillating the hook (20) also has a drive pin (30) for actuating the claw (31) through an intervening linkage (32, 33, 34, 35), an element (35) of said linkage (32, 33, 34, 35) being arranged to have a variable length to vary the stitch length; ii. the two hook counter-detents (22, 23) are the ends of a list foot (21) of the hook carrying pin (17) and the two cam detents (18, 19) are two profile cut cross sides of said cam (5) between which cross sides and adjacently whereto, said cam (5) is recessed (28) to allow for the formation of said detents (24, 25) on the cam and unrestricted oscillation within the cam (5) of said list foot (21) of the hook (20) as said hook is oscillating; iii. the hook (20) has, on its base portion (19), a curled list-like conformation (19a) resembling a chip or a coil over about one complete turn, in the free end of said hook list (19a) there being formed an eye (36) for a double chain stitch-forming yarn (37); iv. a guide means (45, 46) is provided for the double chain stitch yarn (37) on the hook (20) along with a means (40) of taking in said double chain stitch-forming yarn (37); v. the box-type casing (7) accomodating the cam has (5) a projection (14) for fitting said casing (7) in matching shape relationship into the sewing machine casing (13). A mechanism according to Claim 1, wherein said linkage (32, 33, 34, 35) comprises a connecting rod (32) journalled at one end to the claw drive pin (30), and at the other end to a bracket (33) which is in turn pivoted with its free end on a support (34) affixed to the sewing machine casing (2), to an intermediate point on the connecting rod (32) there being journalled a stitch length setting block (35), said block having at its opposite end a head (35a) with an oscillation setting screw (47) engaging against a juxtaposed head (31a) of the claw (31), and enabling the angle between said mutually oscillable heads (35a, 31a)to be varied. A mechanism according to Claim 1, wherein the profile cut cam (5) is of the disk-like cam type, the same having two opposed cam segments (26, 27) with different radii (R, r) of curvature. A mechanism according to Claim 1, wherein the box-type casing (7) supporting the cam (5) has a cup-like seat (6) formed therein for said cam (5). A mechanism according to Claim 1, wherein the means of guiding the double chain stitch yarn (37) on the hook (20) comprises a peripheral shoulder (45) which extends to form a groove (46) on the bottom side of the hook list (19a), said groove (46) opening to an area close to the hook eye (36). A mechanism according to Claim 1, wherein the means of taking in the double chain stitch yarn (37) comprises a guide tube (40) the hook side end (42) whereof is terminated a short distance away from said hook (20), and some outer skirt segments of said tube (40) are removed to allow for easier manual insertion of the yarn (37). A mechanism according to Claim 1, wherein the juts (14) for fitting the box-type casing (7) in matching shape relationship into the sewing machine casing (2, 13) comprises an annulus (14). A mechanism according to Claim 1, wherein the profile cut cam (5) has, on its side facing the claw drive pin (30), an annulus-like projection (44) for supporting a closure ring (43) adapted to close, with a slight clearance, an aperture (9) formed in the bottom wall (8) of the box-type casing (7) supporting the cam (5). A mechanism according to Claim 1, characterized in that in the bottom of the chamber (4) accommodating the hook and claw drive, as well as in the connecting rod (32), there are provided respectively a through hole (48, 49) aligned to the axis of the stitch lenght setting screw (47).

Inventors: BUZZI, RICCARDO
Applicants: METALPLAST S.R.L.
Application year: 1986
Main classification: D05B1
IPC codes: D05B13, D05B57, D05B1