Patent Publication Number: US-6209360-B1

Title: Latch needle having a latch supported on a pin

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application claims the priority of German Application No. 199 14 928.3 filed Apr. 1, 1999, which is incorporated herein by reference. 
     BACKGROUND OF THE INVENTION 
     This invention relates to a latch needle having a head (hook) cooperating with a pivotally supported latch. The latch needle further has a needle cheek which is provided with a sawslot defined between two side walls of the needle cheek. The latch has a latch shank accommodated in the sawslot and provided with a latch hole. The latch needle further has at least one latch bearing which is formed by at least one projection constituted by a plastic deformation of at least one of the cheek side walls. The material from which the projection is formed leaves a depression in the respective side wall. The projection extends into the hole of the needle latch. Latch needles of this type are used, for example, in knitting machines. 
     The latch may be pivoted into a first position in which the latch lies on the free end of the needle head and a second position in which the latch is swung away from the head and thus opens the same. In this arrangement an accurate support of the latch is very important. The latch has to move freely to ensure that it may be pivoted back and forth by small operating forces. On the other hand, the latch has to be guided with such an accuracy that, in the course of the closing motion, the latch spoon arrives into a precise engagement with the hook. Such a result has to be ensured for the entire service life of the latch needle. 
     As noted earlier, the latch is usually supported on the latch needle by a pin extending through a latch hole which is provided in the needle latch for this purpose. In the vicinity of the needle head a cheek region is formed which has a sawslot. On both sides of the sawslot side walls are arranged from which a pin is formed or between which a separate pivot pin is held. The latch shank extends between the side walls into the sawslot and journals on the pin. 
     Various embodiments have become known for forming a pin to support the latch or for inserting a pin into holes provided in the side walls of the needle cheek. Thus, U.S. Pat. No. 3,526,104, to which corresponds German Offenlegungsschrift (application published without examination) 15 85 091 discloses a latch needle having an inserted pivot pin. The holes which are provided for receiving the pivot pin in the side walls of the needle cheek are in alignment with one another and conically flare towards the outer side faces of the needle. The pivot pin is a separately made wire component which is inserted into the aligned holes and is riveted at both ends whereby convex rivet heads are formed. 
     U.S. Pat. No. 5,509,280 discloses a latch needle in which, for supporting the latch, two obliquely adjoining half pins are provided which are pressed out from the side walls defining the sawslot. The half pins are of asymmetrical configuration related to the pivot axis of the latch. The half pins are formed by plastically deforming the side walls with a suitable puncturing tool. The penetration depth of the tool is not constant along the circumference of each pin, whereby the flow conditions of the material are not uniform along the circumference. 
     Further, for supporting a latch on a latch needle, it is known from German Patent No. 608,619 to make half pins by plastic deformation of the side walls on both sides of the sawslot. For this purpose, puncturing tools with planar end faces are used. The puncturing tools have at their frontal end a cylindrical bit with a planar end face whose diameter is smaller than the diameter of the half pin to be made. 
     The half pins form projections which extend into the sawslot and penetrate into the latch hole. The purpose of this arrangement is to ensure a lasting, accurate positioning of the latch. 
     SUMMARY OF THE INVENTION 
     It is an object of the invention to provide an improved latch needle which ensures a durable and accurate functioning of the needle latch. 
     This object and others to become apparent as the specification progresses, are accomplished by the invention, according to which, briefly stated, the latch needle includes a head; a cheek having two facing side walls each having an inner wall face and an outer wall face; a sawslot defined by the inner wall faces of the side walls; and a pivot pin being formed at least on one of the side walls by plastically deforming the side wall. The pivot pin extends from the inner wall face of the side wall into the sawslot. The latch needle further has a first depression provided in the outer wall face of the side wall in alignment with the pivot pin. The first depression includes a bottom having a peripheral region in which a second depression is provided. A needle latch cooperates with the head and has a latch shank accommodated in the sawslot. The latch shank has a hole into which the pivot pin extends for forming a bearing support for the needle latch. 
     Thus, stated generally, the object of the invention is achieved by increasing the pin&#39;s carrier part which is ideally 100% of the latch thickness. 
     The latch needle according to the invention has, for providing a latch support, at least one projection formed by plastic deformation. The projection extends into the sawslot and penetrates into the latch hole of a needle latch accommodated in the sawslot. The projection thus forms a pin or a half pin for supporting the latch. On the outer side faces of the needle shank, in an axial prolongation of the depression, a further, second depression is provided which preferably extends parallel to the circumference of the pin and may be interrupted or subdivided. The additional depression positively affects the flow of material when the projection (pivot pin) is formed. By virtue of this arrangement it is feasible to obtain a pin or half pins with only a slight bulging of the free end face thereof. Thus, the end face of the pivot pin may be maintained relatively planar so that the size of the lateral pin surface serving for supporting the latch may be maximized. The axially measured height of such a lateral surface is ideally identical to the latch thickness. 
     In case of a symmetrical construction, both side walls are provided with depressions and each has an additional depression. The pins produced in this manner abut each other approximately in the middle of the sawslot. By virtue of their planar end faces the width of the gap between the lateral surfaces of the two pins, that is, the approximately annular interruption of the latch supporting surface is minimized, regardless of whether the half pins (projections) are welded to one another at their end faces. The obtained maximization of the supporting surface and the only slight deformation of the inner flanks of the sawslot provide for a durable and accurate (that is, a small-clearance) latch support so that latch needles operate with high precision even after a long service. Such a result is made possible by the depression which is provided in the outer side face of the needle and which has at least one further depression adjoining its bottom. The configurations of the depressions may have different embodiments. Thus, for example, the bottom may be surrounded by a circumferentially extending uninterrupted groove and may otherwise be of arcuate or planar shape. It is also feasible to interrupt the groove (that is, the second depression) once or several times. The groove may adjoin directly the wall of the first depression in which case it is then arranged radially externally of the first depression. It is furthermore possible that it is arranged further inwardly and to form an annular step between the wall of the first depression and the groove. 
     A stepped transitional region may be provided between a groove situated at the outer periphery of the bottom of the second depression and the planar or arcuate middle zone. Such a region may be a conical annular surface or a real step formed as an almost cylindrical annular surface. The annular groove provided in the bottom of the first depression may have a groove bottom and groove flanks which have a curvilinear transition into one another. The radius of the transition is preferably significantly smaller than one-half of the groove width, preferably smaller than one-third or one-fourth of the groove width. The radius depends from the latch needle. 
     The middle region of the first depression is preferably planar. It may be, however, of concave configuration in sections or may be provided with further depressions. It is essential for the configuration of the depressions according to the invention that an external region is provided which is deeper than a middle region. The external region does not have to be annularly continuous. 
     Advantageously, the depressions have an essentially cylindrical wall face. The diameter of the depressions is expediently as large as the diameter of the projection (that is, the pin or half pin). It may, however, also be advantageous to provide slightly different diameters. 
     The projection is formed from the side wall defining the sawslot and is preferably connected therewith. Such a connection prevents a separation of the projection from the latch needle even after prolonged service. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a schematic perspective view of a frontal part of a latch needle incorporating the invention. 
     FIG. 2 is an enlarged side elevational view of one part of FIG.  1 . 
     FIGS. 3,  4 ,  5 ,  5   a,    6  and  6   a  are sectional end elevational views of six preferred embodiments of the invention, each taken along section line II—II of FIG.  2 . 
     FIG. 7 is an enlarged sectional view of one part of the structure shown in FIG.  3 . 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Turning to FIG. 1, the latch needle generally designated at  1  has a shank  2  having a frontal end which carries a hook-shaped head  3 . Between the head  3  and the shank  2  a slightly bulging needle portion is provided which constitutes a cheek  4 . The cheek  4  serves for holding a latch  5  which is supported for pivotal motion about a rotary axis  6  as shown in FIG.  2 . The latch  5  extends with the latch shank  10  into a sawslot  7  which traverses the needle cheek  4  and divides the latter into two lateral walls  8  and  9 . 
     Also referring to FIGS. 2 and 3, for supporting the latch  5  about the rotary axis  6  oriented transversely to the needle shank  2 , half pins  11  and  12  are provided which are connected with the respective side walls  8 ,  9 . The half pins  11 ,  12  thus form a common bearing  13  for the latch  5  and its latch shank  10 . The latch shank  10  is provided with a latch hole  14  into which extend, from opposite sides of the latch shank  10 , the two half pins  11  and  12  which thus together define an essentially cylindrical bearing surface  15  whose diameter is slightly less than the diameter of the latch hole  14 . Approximately centrally along its length, the bearing surface  15  is interrupted by a gap  16  where the end faces of the half pins  11  and  12  are in close proximity or are in abutment with one another. The bearing face  15  is thus subdivided into individual partial bearing faces  15   a  and  15   b.  The partial bearing face  15   a  constitutes the circumferential surface of the half pin  11  whereas the partial bearing face  15   b  constitutes the lateral face of the half pin  12 . 
     The geometrical relationships are also shown in detail in FIG.  7 . The end face  17  of the half pin  11  is essentially planar and the partial bearing face  15   a  is essentially cylindrical. A transitional region  21  between the end face  17  and the partial bearing face  15   a  is rounded; in case of an ideal cylindrical shape the region  22  shown in phantom line in FIG. 7 is very small or is missing altogether. 
     As may be seen in FIGS. 3 and 7, in an axial prolongation of the half pin  11  a depression  24  is formed which has essentially a cylindrical lateral surface  25  having approximately the same diameter as the half pin  11 . The depression  24  has a bottom  26  adjoined by at least one further depression  20 . Stated differently, a mid region  27  projects axially beyond an outer region  28  which extends along the periphery of the bottom  26 . The second depression  20  is situated along the edge zone of the latch hole  14 . The second depression  20  is an annular groove and has, as particularly well seen in FIG. 7, an essentially planar groove bottom  29  which is adjoined outwardly by a groove flank which may be formed by the cylindrical wall face  25 . The transition between the groove bottom  29  and the wall face  25  is formed by an arcuate surface region  31  which has a relatively small radius. 
     Between the groove bottom  29  of the second depression  20  and the mid region  27  a conical groove flank (annular surface)  32  is provided which joins the groove bottom  29  with an arcuate surface region  33 . The surface region  33  is preferably also rounded and has a small radius of curvature. 
     The side wall  8  has at its side oriented towards the sawslot  7  a substantially planar flank  36  which extends to the partial bearing surface  15   a  of the half pin  11 . The latch  5  is guided by the respective flanks of the sawslot  7  such that the latch  5  is essentially prevented from tilting laterally notwithstanding its low-friction pivotal support about the rotary axis  6 . The relatively large-surface guidance of the latch  5  makes possible an accurate prolonged service. The same applies to the bearing surfaces  15   a,    15   b  of the respective half pins  11 ,  12 . The bearing surface  15  is almost closed, that is, the gap  16  has ideally a zero width. 
     The half pins  11  and  12  are components of the respective side walls  8  and  9 . They are obtained by plastically deforming the side walls  8  and  9 . If required, the end faces  17 ,  18  of the respective half pins  11 ,  12  may be welded to one another, for example, by a laser beam which is directed into the depression  24 . 
     The half pins  11 ,  12  are preferably arranged in mirror symmetry; thus the earlier description relating to the half pin  11  applies equally to the half pin  12 . In other embodiments, no such mirror symmetry of the half pins exists. 
     While in the embodiment of the latch needle  1  described in connection with FIGS. 3 and 7 the width of the second depression  20  is in the outer region  28  greater than its depth and the groove flank  32  is frustoconical, the relationships in the embodiment shown in FIG. 4 are slightly different: The second depression  20  has an approximately quadratic cross section in the outer region  28  and the groove flank  32  has thus a cylindrical surface. It is also possible to dimension the groove width to be greater or smaller than the groove depth. In other aspects, the structural features of the FIG. 4 embodiment are the same as those described in connection with FIGS. 3 and 7. The second depression  20  in the outer region  28  makes possible to produce the half pins  11  and  12  with an approximately cylindrical shape whereby the size of the bearing surface  15  is maximized. 
     A further embodiment of the latch needle according to the invention is illustrated in FIG.  5 . This embodiment too, differs from the embodiments of FIGS. 3 and 4 in the configuration of the depression  24 . As in the previous embodiments, the wall  25  of the depression  24  is approximately cylindrical and has essentially the same diameter as the partial bearing surface  15   a  of the half pin  11 . The same applies to the half pin  12 . As a departure from the previously described embodiments, the bottom  26  of the depression  24  is arcuate in its entirety. Its mid region  27  immediately changes to the second depression  20  in the outer region  28  which, instead of a groove, forms the edge of a spherically convex surface. The transition between the second depression  20  and the wall  25  is formed by the surface region  31  which has a very small radius of curvature. In this embodiment too, it is feasible to obtain at least approximately planar flanks  36  in the sawslot  7  and at least approximately cylindrical partial bearing surfaces  15   a,    15   b  for the half pins  11  and  12 . In all other aspects, this embodiment corresponds to those previously described. 
     A further embodiment of the latch needle  1  according to the invention is illustrated in FIG.  6 . The latch needle  1  shown therein differs from the latch needle according to FIG. 3 essentially in that the depth of the second depression  20  is greater than its width. This embodiment too, makes possible to obtain an essentially cylindrical half pin  11 ,  12  on which the carrier portion (that is, the partial bearing surfaces  15   a,    15   b  of the bearing surface  15 ) is relatively large. Ideally, it is identical to the latch thickness and the gap  16  situated between the two partial bearing surfaces  15   a  and  15   b  is relatively narrow and ideally equals zero. Stated differently, the half pins  11 ,  12  may have a relatively sharp-edged transition between the end faces  17 ,  18  and the respective partial bearing surfaces  15   a,    15   b.    
     In the embodiment illustrated in FIGS. 3-6 the end faces  17 ,  18  of the respective half pins  11 ,  12  extend parallel to one another and to the respective flanks  36  of the side walls  8 ,  9 . 
     In the embodiments shown in FIGS. 5 a,    6   a,  on the other hand, while the end faces  17   a  and  17   b  of the respective half pins  11 ,  12  extend parallel to one another, they are oriented obliquely (that is, at an angle other than zero) to the respective flanks  36  of the side walls  8 ,  9 . 
     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.