Abstract:
A transfer needle for loop forming machines includes an elongated needle shank having a needle back, an outer side face and a top face opposite the needle back; a transfer spring attached to the needle shank and defining an intermediate space therewith; and a lateral recess provided in the needle shank and forming part of the intermediate space. The recess is defined by a guide face extending from the needle back to the outer side face of the needle shank. The guide face includes a first length portion bordering the outer side face of the needle shank and extending toward the needle back; and a second length portion bordering the needle back and extending toward the outer side face of the needle shank. The first and second length portions meet in an obtuse angle open toward the transfer spring.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application claims the priority of German Application No. 199 05 668.4 filed Feb. 11, 1999, which is incorporated herein by reference. 
     BACKGROUND OF THE INVENTION 
     This invention relates to a transfer needle for loop-forming machines making flat textile knitwear. 
     For making, for example, patterned knitwear, circular knitting machines with cylinder needles and dial needles may be used. Dependent on the pattern, individual loops are transferred from the cylinder needles to the dial needles and conversely. For this purpose special needles are used which have loop transfer elements and are designated as transfer needles. 
     German Patent No. 42 31 015 discloses transfer needles configured as compound needles which have a slide extending longitudinally along the needle shank and serve for opening and closing a hook (head) carried by the needle shank. A transfer spring secured to the side of the compound needle defines with the needle shank an intermediate space through which the hook and the shank of another needle may pass. The transfer spring is held only at one of its ends on the needle shank. For a suitable configuration of the intermediate space between the transfer spring and the needle shank the latter is provided with a recess which intersects the slide as well as the shank. 
     The intersecting faces of the slide and the shank each form guide faces which are to facilitate the penetration of another needle into the intermediate space. 
     German Patent No. 1,560,996 discloses a transfer needle which is configured as a latch needle rather than a compound needle. Accordingly, it has a solid needle shank without a slide element. To effect loop transfer, the latch needle has a laterally bent shank. That part of the shank which extends from the hook and which is designated as the main shank is of stepped structure having a high and a low portion. Starting from the low portion, a groove extends over the needle back to the high shank portion in which the groove is entirely open towards the side face of the needle. 
     A lateral bent portion of the shank is, however, in many instances undesirable. 
     German Patent No. 31 45 708 discloses a transfer needle for flat knitting machines. The needle has a transfer spring on its side for transferring the loops. The spring is a leaf spring and is affixed at one of its ends to the needle shank. The other, free end of the leaf spring forms, together with the needle shank, an intermediate space into which another needle may penetrate with its hook and shank. The leaf spring as well as the needle shank are, at their respective underside, provided with an oblique guide face which is intended to facilitate the penetration of another needle into the intermediate space between the transfer spring and the needle shank. The guide face provided on the shank is substantially planar and extends from the needle back to the outer side face of the needle. 
     Particularly the transfer spring of the transfer needle is exposed to substantial dynamic loads during operation. For the loop transfer first the hook and one part of the shank of another transfer needle enters the intermediate space in the vicinity of the free end of the transfer spring. This event may already cause the free end of the transfer spring to be pushed away laterally from the needle shank at which the transfer spring is secured. If such an occurrence takes place in a narrow needle guide channel where the transfer spring lies against the channel flanks, the transfer spring may undergo substantial local bending deformations which lead to high stresses. If such an occurrence causes breakage of the spring, the transfer needle becomes useless, and the knitting machine has to be stopped for servicing. 
     SUMMARY OF THE INVENTION 
     It is an object of the invention to provide an improved transfer needle of the above-outlined type whose service life is lengthened. 
     This object and others to become apparent as the specification progresses, are accomplished by the invention, according to which, briefly stated, the transfer needle for loop forming machines includes an elongated needle shank having a needle back, an outer side face and a top face opposite the needle back; a transfer spring attached to the needle shank and defining an intermediate space therewith; and a lateral recess provided in the needle shank and forming part of the intermediate space. The recess is defined by a guide face extending from the needle back to the outer side face of the needle shank. The guide face includes a first length portion bordering the outer side face of the needle shank and extending toward the needle back; and a second length portion bordering the needle back and extending toward the outer side face of the needle shank. The first and second length portions of the guide face meet in an obtuse angle which is open toward the transfer spring. 
     Thus, the transfer needle according to the invention has at its side face a recess which is covered by a transfer spring. The transfer spring is, at one of its ends, connected with the needle shank and has a preferably pointed tongue which lies in a depression of the needle shank. The recess positively defines a guide face at the needle shank along which a penetrating hook of another needle may slide. The guide face extends along the recess from the needle back to the lateral needle face, while its angle formed with the needle back changes. Stated differently, the guide face has a first portion adjoining the needle back and a second portion adjoining the lateral needle face, and the two portions form an obtuse angle with one another, whereby the guide face is concave. This measure prevents an excessive weakening of the needle shank in the region of the recess. This measure also permits an enlargement of the depth of the recess compared to conventional configurations without causing an excessive weakening of the needle shank. Also, the displacement/time relationship concerning the excursion of the transfer spring may be positively affected, and a spring breakage is prevented which could otherwise occur as a result of dynamic loads on the transfer spring, particularly in the region of its free end. The service life or service expectancy of such a transfer needle is thus lengthened. 
     The transfer needle according to the invention may be configured such that the guide face forms, in vicinity of the needle back, a small angle with the principal direction of motion of a penetrating transfer needle. In this manner a penetrating transfer needle is relatively slowly deflected laterally and is relatively gradually accelerated. Thus, not only the transfer spring but also the penetrating transfer needle is gently handled. 
     Due to the particular configuration of the guide face, in the transfer needle according to the invention a smooth transition from the upper side (top face) of the needle to the outer side face thereof for forming the loop support edge is not affected. The depth of the penetration space, however, may be enlarged. The recess may be configured such that it terminates at the side face of the transfer needle. By virtue of this arrangement, in this region the loop supporting edge may configured without a profile change caused by the recess. This ensures that the loops glide gently and without damage over the loop supporting edge. 
     The concave shape of the guide face may be obtained in various ways. For example, the guide face may be at least partially arcuate in the longitudinal direction of the transfer needle. Additionally, the guide face may be at least partially arcuate or kinked at least once in a direction defined by the penetrating motion of another transfer needle. The curvature may be circular, parabolic or of any other shape. In any event, the recess may be deeper than it has been possible heretofore without adversely affecting the loop supporting edge or the stability of the loop forming region of the transfer needle. It has been found that the depression, compared to transfer needles having a linear guide face could be deepened by 0.1 mm at the height of the bottom edge of the transfer spring, corresponding at least to one-half of the thickness of the transfer spring. By making the depression deeper, the displacement/time relationship of the motion of the transfer needles and their parts during the loop transfer step is positively influenced in that the transfer spring bends to a lesser extent which means a relief of the transfer spring. Further, the introducing step is facilitated by the enlargement of the space between the transfer spring and the guide face; as a result, more space is provided for the penetrating transfer needle. 
     In the alternative, and in principle with the same effect, the guide face may have a kink line defined by two essentially planar surface regions. 
     The angle which the lower part of the guide face (in the vicinity of the needle back) forms with a line which is perpendicular to the needle back is preferably less than 20° (preferably 18°), and such an angle for the upper part of the guide face (which borders the lateral needle face) is preferably more than 20°. On the outer side face of the needle the angle is preferably substantially greater and amounts to, for example 25° or even more than 30°. The depth of the depression may so dimensioned that at the needle back it occupies more than one-half of the width of the transfer needle. At the height of the bottom edge of the transfer spring the depth of the depression is, however, preferably less than one-half of the shank thickness. At this height a kink line may be arranged at which the inclination of the guide face changes. In the alternative, a curved part of the guide face may start or may terminate at that location. 
     Advantageous geometrical conditions and advantageous conditions for the motion of the penetrating transfer needle are obtained when the depression on the needle back occupies more than one-half the width of the transfer needle. The transition of the guide face from a first angular orientation to a further angular orientation preferably occurs essentially at the height of the lower edge of the transfer spring. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a simplified perspective view of one part of the transfer needle incorporating the invention. 
     FIG. 2 is a side elevational view of one part of the transfer needle shown in FIG.  1 . 
     FIG. 3 is a top plan view of one part of the needle shown in FIG. 2, also showing a channel side wall contacted by the transfer needle. 
     FIG. 4 is a sectional view taken along line IV—IV of FIG.  2 . 
     FIGS. 5 a ,  6   a  and  7   a  are top plan views of a conventional transfer needle shown in different operational positions. 
     FIGS. 5 b ,  6   b  and  7   b  are top plan views of a transfer needle according to the invention shown in the same operational positions as those illustrated in the respective FIGS. 5 a ,  6   a  and  7   a.   
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     FIG. 1 shows a transfer needle  1  including a shank  2 , a head  3  and the associated elements. The needle butt is not shown. The shank  2  is divided into a high length portion  4  and a low length portion  5 . Both length portions  4  and  5  extend upwardly from a common needle back  6 . The transition from the high length portion  4  of the shank  2  to its low length portion  5  is formed by a step  8 . On either side of the step  8  the shank  2  extends without a bend and linearly in the longitudinal direction L which coincides with the principal direction of motion of the transfer needle  1 . 
     In the needle shank  2 , in the zone of the transition between the length portions  4  and  5 , that is, approximately underneath the step  8 , a recess  11  is provided which serves for receiving the head  3  of another transfer needle  1 ′, as particularly well seen in FIG.  2 . The recess  11  constitutes a lateral opening in the shank  2  and thus extends from the needle back  6  to an outer needle side face  12  extending between the needle back  6  and the upper needle surface (top face)  7 . Between the outer side face  12  and the top face  7  of the needle a loop supporting edge  14  is formed which is spaced from the recess  11 . 
     The recess  11  is substantially covered by a transfer spring  15  which is a leaf spring having a linear, essentially rectangular mounting portion  16  held in a lateral depression  17  of the needle shank  2 , for example, by means of a plurality of embossments  18 . Starting from an end of the mounting portion  16  the transfer spring  15  is offset from the needle shank  2 , whereby a further length portion  19  of the transfer spring  15  extends parallel to and at a distance from the remaining needle shank  2 . In the corresponding zone adjacent the spring length portion  19  the shank  2  may have a slightly reduced thickness. Thus the shank  2 , starting from a location  21  situated at the start of the offset of the spring  15 , is slightly narrower than in the remaining shank regions. 
     The height of the length portion  19  of the transfer spring  15  is reduced in the length direction L of the shank  2  with a step  22  approximately at the same location where the height of the shank  2  is reduced. Such an arrangement is particularly well seen in FIG. 2 which illustrates the transfer needle  1  in side elevation. Starting from the step  22  the transfer spring  15  is further reduced so that eventually it ends approximately in a point at its terminus  23 . The bent configuration of the transfer spring  15  may be best observed in FIG.  3 : The transfer spring  15  extends, starting from the bend  24 , approximately parallel to the shank  2 ; the tapering portion with its end  23  is bent towards the shank  2  and lies under bias in a groove  25  provided in the shank  2 . Between the length portion  19  and an adjoining, tapering length portion  9  of the transfer spring  15  and the shank  2  thus an intermediate penetration chamber  27  is formed. Between the bend  24  of the transfer spring  15  and the step  22  of the needle shank  2  the transfer spring  15  has the planar, plate-like length portion  19 . The latter and/or the length portion  9  engages a flank F of a needle channel or may contact the flank F at least at one location of the spring  15 . 
     Opposite the recess  11  on the top face  7  of the shank  2  a cutout  28  is formed which extends into the adjoining lateral shank surface and which serves for guiding the loops lying on the shank  2 . Since the cutout  28  is situated opposite the recess  11 , a reduction of the cross section of the shank  2  is obtained. In order to maintain such a reduction to a possibly small value, the relatively larger recess  11  has a specific shape as shown in FIG.  4 . 
     The recess  11  is bordered towards the shank  2  by a guide face  29  which extends at the needle back  6  in an acute angle to the direction V (FIGS. 1 and 4) which, in turn, is oriented at 90° to the needle back  6  and is indicating approximately the direction in which a penetrating transfer needle  1 ′ (FIG. 3) is moved. The guide face  29  is concave relative to the lateral needle face  12 . The guide face  29  has a first surface region  31  which adjoins immediately the needle back  6  and a central surface region which is at least approximately planar. In the longitudinal direction L the recess  11  terminates in a preferably planar shape at both ends; the surface region  31  may be slightly arcuate. 
     Referring once again to FIG. 4, approximately at the same height as a linearly extending bottom edge  32  of the transfer spring  15 , the guide face  29  changes its angle of inclination. It changes at a kink line  33 , for example, into a planar second surface region  34  which is inclined at an angle larger than 25°, for example, 30° to the direction V. For illustrating the effect of this measure, a broken line  35  shows the course of a guide face which would result in case of an angle of 25°. It is seen that the recess is significantly smaller. The additionally obtained free space of the recess is designated at  30 . In contrast, a throughgoing arrangement of the guide face  29  at an angle of 18° would result in the guide face  29  reaching the loop supporting edge  14 . By subdividing the guide face  29  into two planar or curved surface regions  31  and  34  arranged at an obtuse angle to one another, the cross-sectional region of the shank  2  shown closely shaded in FIG. 4 ensures a stability of the shank  2 . The depth  30  of the recess  11 , measured at the bottom edge  32  of the transfer spring  15 , is significantly enlarged compared to a throughgoing guide surface having an angle of 25°. The increase of the depth of the recess  11  may be more than one-half of the thickness of the transfer spring  15 . The guide face  29  has an overall concave shape, which reduces the dynamic loads of the transfer spring  15 . The arrangement of such an overall concave shape may be explained with reference to FIG. 4 as follows: the earlier-noted broken straight line  35  may also be regarded as connecting an upper edge  29   a  of the guide face  29  lying in the lateral needle face  12  and a lower edge  29   b  lying in the needle back  6 . It is seen that the entire guide face  29  as viewed cross-sectionally in FIG. 4 is situated solely on one side of the broken line  35  and furthermore, as viewed between the edges  29   a  and  29   b , the cross-sectionally viewed guide face  29  is throughout of concave configuration. 
     The second surface region  34 , as indicated with a line  36  in FIG. 4, may be planar, that is, it may be straight within the sectional plane. It may, however, also have a radius R, that is, it may be of arcuate shape. The radius of curvature may be constant. In the alternative, the radius of curvature may change as a function of the angle so that curvatures different from a circular arc may be obtained. 
     In the description which follows, the operation of the above-described transfer needle  1  will be set forth, particularly in conjunction with FIG.  2 . 
     For transferring loops which lie on the length portion  5  of the shank  2 , another transfer needle  1 ′ penetrates into the chamber  27  at which time the end  23  of the transfer spring  15  lies in the groove  25  of the shank  2 . FIGS. 5 a  and  5   b  compare a transfer needle  1  according to the invention (FIG. 5 b ) with a conventional transfer needle  1   a  (FIG. 5 a ) at the beginning of the penetration by another transfer needle shown in section and designated at  1 ′ and  1 ′ a,  respectively. Based on the deepening of the recess  11  because of the subdivision of the guide faces compared to the conventional transfer needle  1   a,  the end  23  of the transfer spring  15  does not lift off the shank  2  of the transfer needle  1 , in contrast to the transfer needle  1   a.    
     Thus, the conditions are different in the transfer needle la according to the prior art as illustrated in FIGS. 5 a ,  6   a  and  7   a.    
     As seen in FIG. 5 a , at the beginning of the penetrating step the transfer spring  15   a  of the conventional transfer needle la is lifted from the needle shank  2   a  by the penetrating transfer needle  1   a ′. The transfer spring  15   a  is pushed against the flank F of the needle channel in which the transfer needle  1   a  runs. The support point onto which the transfer spring  15   a  runs onto the flank F is designated at  40 . There is obtained a short leverage length of the outwardly moved portion of the transfer spring  15   a  at the tapering portion  9   a  of the transfer spring  1   a.  This results in a high material stress which, as shown in FIG. 5 b , is avoided in the transfer needle  1  according to the invention. 
     The penetration step shown in FIG. 2 in side elevation first starts in the vicinity of the free end of the transfer spring  15 . Upon penetration, the penetrating transfer needle  1 ′ is moved in the direction of the obliquely upward directed arrow  41 . Accordingly, in the course of the penetrating step, the penetrating transfer needle  1 ′ or  1   a ′ moves away from the free end  23  of the respective transfer spring  15  or  15   a . As the penetrating step progresses, the transfer spring  15  of the transfer needle  1  according to the invention (FIG. 6 b ) is in engagement with the shank  2  as before, while the conventional transfer needle  1   a,  as shown in FIG. 6 a , is lifted off the shank  2  as before. 
     Only as the penetrating step further progresses, as shown in FIGS. 7 a  and  7   b , does the penetrating transfer needle  1 ′ advance into the penetrating chamber  27  to such an extent that it leaves the guide face  29  with its head and reaches the side face  12  of the transfer needle  1 . At the same time, the penetrating transfer needle  1 ′ has advanced to such an extent in the direction of the arrow  42  (FIG. 2) that it reaches a region of sufficient distance between the transfer spring  15  and the side face  12  to be able to move forward without causing an appreciable excursion of the transfer spring  15 . The penetrating step performed by the transfer needle  1 ′ is optimized to such an extent by virtue of the shape of the guide face  29  altered by the invention that the bending stress of the transfer spring  15  is reduced compared to the prior art and thus the service life of the needle is lengthened. 
     It will be understood that the above description of the present invention is susceptible to various modifications, changes and adaptations, and the same are intended to be comprehended within the meaning and range of equivalents of the appended claims.