Abstract:
A vertical axis hook ( 10 ) for a lockstitch sewing machine comprises a hook body ( 11 ) with a hook point and a peripheral needle guard plate ( 12 ) mounted on the hook body, the plate comprising a fastening and positioning portion and an adjustable portion integral with each other. It further comprises a plate adjustment means to adjust the radial position of the adjustable portion with respect to the hook point. The plate adjustment and positioning means ( 16 ) acts in a position of the adjustable portion of the plate which is near the fastening portion thereof.

Description:
FIELD OF THE INVENTION 
     The present invention refers to adjustment of the needle guard plate on a vertical axis hook or crochet of a lockstitch sewing machine. 
     BACKGROUND OF THE INVENTION 
     In lockstitch sewing machines the crochet or hook has a peripheral “hook point” extending for a distance along the circumference of the hook. The hook, by rotating around its own axis, grips with said point the loop formed by the upper thread or needle thread, a loop which forms at the start of the movement of withdrawal or raising of the needle. The point of the hook must brush the needle to grip the loop of thread. Any bending of the needle, due for example to the force exerted thereon by a sideways translation of the fabric, could bring it to be situated on the trajectory of the hook point and could cause a collision with probable breakage of the needle or splintering of the hook point. In order to avoid this, a needle guard plate is provided which serves to prevent the needle from bending in the direction of the hook tip. The plate has an arched shape, in its working portion seen in a plan view, and rotates integrally with the hook body. 
     FIG. 28 is a top perspective view illustrating a vertical axis hook  1 , according to the prior art, provided with a hook point  2 , and a needle-protecting plate, or needle-guard plate, denoted by reference numeral  3 . 
     Adjustment of the position of the plate in a radial direction with respect to the axis of the hook is generally required or desirable to adapt the hook to the type and size of needle used. The state of the art comprises various solutions for mounting plates on the hook body, so as to be able to perform said adjustment. Needle guard plates are generally considered to be grouped into three families according to the type of construction: a first family comprises so-called “flange plates”, formed by a sheet of metal bent into an L-shape which is placed with the flat part between the hook and its axial resting point on the sewing machine; a second family comprises “flange-mounted plates” wherein a flange is fastened to the rear part of the hook; a third family comprises the “peripheral plates”, obtained from sheet metal bent in an arch and fastened to the side of the hook body. 
     The subject matter of the present invention concerns the field of peripheral plates. 
     Peripheral plates are positioned on and fastened to the body of the hook. Some currently known and used methods of fastening will be described briefly. 
     According to a first method, the plate is mounted on the side of the hook by means of two head countersunk screws which centre the respective seats on the plate and therefore perform both the positioning function and that of fastening of the plate. The two screws are in proximity to the opposite end of the plate with respect to the hook point and leave the part of the plate near the hook point projecting. A variant of said system consists in fastening with four screws, two for each end of the plate. 
     In a second manner, the plate is positioned in a circumferential groove on the side of the hook and is fastened by means of two flat-headed screws, which therefore serve no positioning function, but only that of fastening. 
     As far as adjustment of peripheral plates is concerned, the following three systems are known and used. 
     a) The mounted plate is adjusted only by manual deformation of the bending curve of the projecting part with respect to the positioning and fastening system. Adjustment can therefore be only rough. 
     b) A third screw is placed on the side of the body of the hook at the opposite end of the needle guard plate with respect to the positioning and fastening portion. The screw, when it is loosened, presses on the tip of the plate and obliges outward deformation thereof. The screw normally requires a braking system (typically a locking thread) and holds the disadvantage of not being able to be applied to all hooks, in that it requires an adequate space, on the side of the hook and near the hook tip, a space which often is not available. Such an adjustment system is described in patents DE G 8116870 and IT 1151267. 
     c) In the case of the hook with a plate positioned in the groove, whilst positioning of the plate is performed by the groove and fastening of the plate by the flat-headed screw nearest the end of the plate, for fine adjustment use is made of the second screw, positioned between the fastening screw and the tip of the plate at the hook point. In this case the plate has a double bend which, without the second screw, would position it far to the outside of the hook tip. By screwing the second screw, on the other hand, the plate is forced inwards. 
     SUMMARY OF THE INVENTION 
     An object of the present invention is to reduce production costs of hook with an adjustable plate. 
     A further object is to be able to apply a finely adjustable plate on a hook where this was not hitherto possible because of problems of space. 
     The object has been achieved with a hook as stated in claim  1 . Further new and useful characteristics are disclosed in the dependent claims. 
     In other words, in the hook of the invention fine adjustment of the peripheral needle guard plate is achieved without the need for a third screw in proximity to the point of the hook and with the sole function of adjustment, and without the need for a slot for positioning of the plate. 
     In one embodiment, three screws (two countersunk head for fastening and positioning and one for adjustment), all positioned on the portion of plate opposite that facing towards the hook point. The plate has a double bend and the third screw forces the plate inward. 
     In another embodiment, two countersunk head screws are used, one of which serves for positioning and fastening, whereas the second serves for positioning and adjustment. The plate has a double bend and the second screw forces the plate inwards. 
     In a third embodiment, two screws are used, one countersunk head for fastening and the second flat-headed for positioning and adjustment, having a cylindrical shape between the head and the thread which couples with a horizontal slot on the plate. 
     In a fourth embodiment two screws are used, the first being countersunk head and having a positioning and fastening function, whereas the second, serving for positioning and adjustment, works in thrust and is shaped with a cylindrical pin protruding from the head of the screw. Said pin enters a hole or slot in the plate and it is also possible from the pin to act to tighten or loosen said screw. The plate is naturally bent inwards and is forced outwards by loosening the screw. 
     In a fifth embodiment two screws are used, the first of which is countersunk head and serves for positioning and adjustment, whereas the second serves for positioning and adjustment. The second screw serves for “dual effect” adjustment: that is, it works both in traction and in thrust, depending on whether it is more or less tightened. The plate is bent to be level with the hook point with the adjustment screw half tightened. The adjustment screw has two flanges that remain one on the inside and one on the outside of the needle guard plate. The outer flange is flat in shape. 
     A sixth embodiment is similar to the fifth but the outer flange of the adjustment screw is conical. 
     The invention achieves the aforementioned objects, in particular it achieves lower production costs for the hook and allows simplified adjustment where it was not otherwise possible. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Exemplary embodiments of the invention, will be described hereunder by way of non-limiting illustration with reference to the appended figures, wherein: 
     FIG. 1 is a partially sectional plan view of a vertical axis hook according to a first embodiment of the invention; the plate is drawn with a slid line in an extreme position of adjustment near the axis a 10  of the hook, with a dashed line in the other extreme position of adjustment farther from the axis a 10 ; 
     FIG. 2 is a side view from the right of FIG. 1; 
     FIG. 3 is a view of the hook plate of FIGS. 1 and 2, on an enlarged scale and in the extended position; 
     FIG. 4 is a side view on an enlarged scale of a fastening and adjustment screw for the plate of the first embodiment; 
     FIG. 5 is a partially sectional plan view of a hook according to a second embodiment of the invention, with the adjustable plate in the extreme position nearest the axis a 20  and the adjustment screw completely tightened; the plate in the adjusted position furthest from the axis a 20  of the hook is shown with a dashed line, 
     FIG. 6 is a view from the right with respect to FIG. 5, 
     FIG. 7 is a view of the plate of the hook of FIGS. 5 and 6, on an enlarged scale and in the extended condition, 
     FIG. 8 is a partially sectional plan view of a third embodiment of the hook according to the invention, with plate indicated with a solid line in one extreme position and with a dashed line in the other extreme position, 
     FIG. 9 is a side view from the right of FIG. 8, 
     FIG. 10 is a view of the plate of the hook of FIGS. 8 and 9, on an enlarged scale and in the extended condition, 
     FIG. 11 is an enlarged side view of an adjustment screw for the plate of the hook of FIGS. 8 and 9, 
     FIG. 12 is a plan view of a hook according to a fourth embodiment, with the plate drawn with a solid line in one extreme position and with a dashed line in the other extreme position, 
     FIG. 13 is a side view from the right of the hook of the preceding figure, 
     FIG. 14 is an enlarged side view of the plate of the hook of FIGS. 12 and 13 in the extended condition, 
     FIG. 15 is an enlarged side view of an adjustment screw for the hook of FIGS. 13 and 14, 
     FIG. 16 is a partially sectional plan view of a hook according to a fifth embodiment, with the plate drawn with a solid line in one extreme position and with a dashed line in the other extreme position, 
     FIG. 17 is a side view from the right of the hook of FIG. 16, 
     FIG. 18 is an enlarged side view of the plate of the hook of FIGS. 16 and 17, in the extended condition, 
     FIG. 19 is an enlarged side view of the plate of the hook of FIGS. 16 and 17, in the extended condition, 
     FIG. 20 is an enlarged side view of another variant of the plate of the hook of FIGS. 16 and 17, in the extended condition, 
     FIG. 21 is an enlarged side view of an adjustment screw for the plate of the hook in FIG. 18, 
     FIG. 22 is a partially sectional plan view of a hook according to a sixth embodiment, with the plate drawn with a solid line in one extreme position and with a dashed line in the other extreme position, 
     FIG. 23 is a side view from the right of the hook of FIG. 22, 
     FIG. 24 is an enlarged side view of the plate of the hook of FIGS. 22 and 23, in the extended position, 
     FIG. 25 is an enlarged side view of a variant of the plate of the hook of FIGS. 22 and 23, in an extended position, 
     FIG. 26 is an enlarged side view of another variant of the plate of the hook of FIGS. 22 and 23, in an extended condition, 
     FIG. 27 is an enlarged side view of an adjustment screw for the plate of the hook of FIGS. 22-26; 
     FIG. 28 is a perspective view of a hook according to the state of the art. 
     A hook according to the prior art has been described above with reference to FIG.  28 . 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     With reference first to FIGS. 1 to  4 , a hook according to the invention is designated as a whole with reference numeral  10 , is rotatable around its own axis denoted by a  10  and comprises a hook body  11 , with a hook point,  11   a , and a needle-guard plate of the hook,  12 . 
     The plate  12  can be seen better in FIG. 3, wherein it is illustrated enlarged and extended. The plate comprises a working portion  12   a  facing towards the tip of the hook and designed to cooperate therewith, and a fastening and positioning portion  12   b . The working portion, in the view of FIG. 3, has a tapered and rounded shape at the distal end, having a narrow neck  12   c  and an adjustment hole or slot  13  at the proximal end. The fastening portion of the plate is substantially rectangular in shape and has two aligned fastening and positioning holes, denoted by  14 ,  15 . All three holes  13 ,  14 ,  15  have an outwardly countersunk aperture. The plate  12  is applied to the hook. The fastening portion  12   b  thereof is curved in an arc of a circle, in a manner corresponding to the curvature of the hook body. The working portion  12   a  has a double curvature, that is to say, it is curved outwardly (with respect to the axis of the hook crochet) in the area corresponding to the line b 12  drawn dashed, between the holes  13  and  14 , and it is curved in an arch around the axis of the hook in its distal portion. 
     The plate  12  is applied to the hook by means of three screws indicated by  16 ,  17  and  18  (FIG.  1 ). The screw  16  is an adjustment screw and occupies the hole  13  of the plate, the screws  17  and  18  are fastening and positioning screws, and occupy the holes  14  and  15  of the plate. The three screws screw into the threaded holes  13 ′,  14 ′ and  15 ′ in the hook body. In this embodiment, the three screws  16 ,  17  and  18  are identical. In FIG. 4 the screw  16 , which is of a per se known type, comprising a threaded shank  16   a  and a countersunk head  16   b , is illustrated. The head of the screw  16  could also be cylindrical and consequently not require countersinking of the hole  13 . 
     The plate  12  is mounted on the body of the hook around the periphery thereof, and fastened and positioned level with its fastening portion with the screws  17  and  18 , in a per se known manner. Owing to the deformation that has been imparted to it, the plate is disposed with its working portion slightly distanced from the periphery of the hook body (position indicated by dashed line). The screw  16  engages the working portion of the blade and the body. By tightening the screw  16  the blade is forced toward the hook crochet body (axis), by loosening the screw the very elasticity of the plate moves it away from the hook body; it is thus possible to adjust the position of the plate with respect to the point  11  (to the axis a  10 ) of the hook. 
     A second embodiment of the hook (rotatable around the axis a 20 ) with adjustable plate is indicated by reference numeral  20  and illustrated in appended FIGS. 5,  6  and  7 ; it comprises a hook body  21  with a hook point  21   a , and a hook plate  22 . 
     The plate  22  can be seen better in FIG. 7, wherein it is illustrated enlarged, and extended. The plate comprises a working portion  22   a  facing towards the hook point and designed to cooperate therewith and a fastening and positioning portion  22   b . The working portion, in the view of FIG. 7, is tapered and rounded in shape at the distal end, has a narrow neck  22   c  and an adjustment hole  23  at the proximal end. The fastening portion  22   b  of the plate is substantially rectangular in shape and has a fastening and positioning hole, indicated by  24 . The holes  23 ,  24  have an outwardly countersunk opening. The plate  22  is applied to the hook. The fastening portion  22   b  thereof is curved in an arc of a circle, in a manner corresponding to the curvature of the hook body. The working portion  22   a  has a double curvature, that is to say it is curved outward (with respect to the hook axis) in the area corresponding to the dashed line b 22 , between the holes  23  and  24 , and it is curved in an arch around the axis of the hook in its distal portion. 
     The plate  22  is applied to the hook by means of two screws indicated by  26  and  27 . The screw  26  is a positioning and adjustment screw, the screw  27  is a fastening and positioning screw. In this embodiment, the two screws  26 ,  27  are identical and identical to the screw  16  illustrated in FIG.  4 . 
     The plate  22  is mounted on the hook body around the periphery thereof, and fastened and positioned at its fastening portion with the screw  27 , in a per se known manner. Owing to the deformation that has been imparted to it, the plate is disposed with its working portion slightly distanced from the periphery of the hook body. The screw  26  engages the working portion of the plate and the body. By tightening and loosening the screw  26  it is possible to adjust the position of the plate  22  with respect to the point  21   a  of the hook  21 . The screw  26  serves for adjustment and positioning of the plate, that is to say it adjusts the position of the plate towards or away from the hook point (from the axis of the hook) and positions the plate in the direction of the axis a  20 . 
     A third embodiment of the hook with an adjustable plate is indicated by reference numeral  30  and illustrated in appended FIGS. 8,  9 ,  10  and  11 ; it comprises a hook body  31  with a hook point  31   a  and a hook plate  32 . 
     The plate  32  can be seen better in FIG. 10, wherein it is illustrated enlarged and extended. The plate comprises a working portion  32   a  facing towards the hook point, and designed to cooperate therewith, and a fastening and positioning portion  32   b . The working portion, in the view of FIG. 10, is tapered and rounded in shape at the distal end, has a narrow neck  32   c  and an adjustment slot  33  at the proximal end. The shape of the slot  33  is elongated longitudinally with respect to the plate. The fastening portion of the plate is substantially rectangular in shape and has a fastening and positioning hole, indicated by  34 , with an outwardly countersunk opening. The plate  32  is applied to the hook. The fastening portion  32   b  thereof is curved in an arc of a circle, in a manner corresponding to the curvature of the hook body. The working portion  32   a  has a double curvature, that is to say it is curved outward (with respect to the hook axis) in the area corresponding to the line b 32  drawn with a dashed line, between the holes  33  and  34 , and is curved in an arch around the axis of the hook in the distal portion thereof. The plate  32  is applied to the hook by means of two screws denoted by  36  and  37 . The screw  36  is an adjusting and positioning screw, the screw  37  is a fastening and positioning screw. The screw  37  is identical to the screw  16  illustrated in FIG.  4 . The screw  36  is illustrated in FIG.  11  and has a threaded shank  36   a , a cylindrical neck  36   b , and a widened cylindrical head  36   c . The diameter of the neck is smaller that the transverse measurement of the slot  33 , the diameter of the head is greater that the transverse measurement of the slot. The plate  32  is mounted on the hook body around the periphery thereof, and fixed and positioned at its fastening portion with the screw  37 , in a per se known manner. Owing to the deformation that has been imparted thereto, the plate is disposed with its working portion slightly distanced from the periphery of the hook body. The screw  36  engages the working portion of the plate with its portion  36   b  and the shoulder  36 &#39; c  of the head  36   c  and the hook body with its threaded part  36   a.    
     By tightening and loosening the screw  36  it is possible to adjust the position of the plate with respect to the hook point  31 . 
     A fourth embodiment of the hook with an adjustable plate is indicated by reference numeral  40  and illustrated in appended FIGS. 12,  13 ,  14  and  15 ; it comprises a hook body  41  with a hook point  41   a , and a hook plate  42 . 
     The plate  42  can be seen better in FIG. 14, wherein it is illustrated enlarged and extended. In this view, it is identical to the plate  32  of the previous embodiment. It therefore comprises a working portion  42   a  facing towards the hook point and designed to cooperate therewith, and a fastening and positioning portion  42   b . The working portion, in the view in FIG. 14, is tapered and rounded in shape at the distal end, has a narrow neck  42   c  and an adjustment slot  43  at the proximal end. The shape of the slot  43  is elongated longitudinally with respect to the plate. The fastening portion of the plate is substantially rectangular in shape and has a fastening and positioning hole, denoted by  44 , with an outwardly countersunk opening. The plate  42  is applied to the hook and is curved in an arc of a circle, in a manner corresponding to the curvature of the hook body. The working portion  42   a  is preliminarily curved inward, towards the axis of the hook, with respect to the hook point  41   a.    
     The plate  42  is applied to the hook crochet by means of two screws denoted by  46 ,  47 . The screw  46  is a plate adjusting and positioning screw, the screw  47  is a fastening and positioning screw identical to the screw  16  illustrated in FIG.  4 . The screw  46  (FIG. 15) has a threaded shank  46   a , a countersunk flange  46   b , and a cylindrical head  46   c . The maximum diameter of the countersunk flange is greater than the transverse measurement of the slot  43 ; the diameter of the head  46   c  is smaller than the transverse measurement of the slot. 
     The plate  42  is mounted on the hook body around the periphery thereof, and fastened and positioned at its fastening portion with the screw  47 , in a per se known manner, after having engaged the adjustment screw  46  in a suitable countersunk hole in the hook body. The screw  46  engages the slot  43  of the plate with its cylindrical head and the surface of the plate facing toward the hook body with the abutment surface  46 &#39; b  of the countersunk flange. By loosening the screw  46  it is possible to adjust the position of the plate bringing it away from the hook axis, by tightening the screw  46 , the plate is returned towards the hook axis by its own elasticity. 
     A fifth embodiment of the hook with an adjustable plate is indicated by reference numeral  50  and illustrated in appended FIGS. 16-21; it comprises a hook body  51  with a hook point  51   a  and a hook crochet plate  52 . The plate  52  can be seen better in FIG. 18, wherein it is illustrated enlarged and extended. It comprises a working portion  52   a  facing towards the hook point, and designed to cooperate therewith, and a fastening and positioning portion  52   b.    
     The working portion, in the view of FIG. 18, is tapered and rounded in shape at the distal end, has a narrow neck  52   c  and an adjustment slot  53  open on one side. The fastening portion of the plate is substantially rectangular in shape and has a fastening and positioning hole, designated by  54 , with an outwardly countersunk opening. The plate  52  is applied to the hook crochet with the fastening portion  52   b  thereof, curved in an arc of a circle, in a manner corresponding to the curvature of the hook body. The working portion  52   a  is also curved according to the periphery of the hook body. 
     The plate  52  is applied to the hook by means of two screws denoted by  56 ,  57 . The screw  56  is a plate adjusting and positioning screw; the screw  57  is a fastening and positioning screw identical to the screw  16  illustrated in FIG.  4 . The screw  56  has a threaded shank  56   a , a countersunk flange  56   b , a cylindrical flange  56   c , and a neck  56   d  therebetween. The maximum diameter of the flanges is greater than the width of the slot  53 ; the diameter of the neck  56   d  is smaller than the transverse measurement of the slot. 
     The plate  52  is mounted on the hook body around the periphery thereof after the screw  56  has been inserted with the neck  56   d  in the slot  53 , and is fastened and positioned at its fastening portion with the screw  57 , in a per se known manner. The screw  56  engages the slot of the plate with the neck  56 d, and engages the surface of the plate facing towards the body of the hook with the abutment surface of its countersunk flange  56   b , or the outer surface of the plate with the abutment surface of the cylindrical outer flange  56   c , depending on whether the screw is acted upon to bring plate away from or toward the hook axis. 
     FIGS. 19 and 20 present variants of the plate that it is possible to use with the hook  50  and the screw  56 . The plate  52 ′ has, instead of the slot  53 , a slot  53 ′ made up of two portions with different diameters, with their axes aligned transversally to the longitudinal dimension of the plate. The portion with the largest diameter allows the passage of the flanges of the adjustment screw; the portion with the smallest diameter has a smaller diameter than the flanges and a larger diameter than the neck  56   d  of the adjustment screw. The plate  52 ″ is similar to  52 ′ except that the slot with two diameters  53 ″ has the axis of the two portions aligned longitudinally with respect to the plate. 
     A sixth embodiment of the hook with an adjustable plate is indicated by reference numeral  60  and illustrated in appended FIGS. 22-27; it comprises a hook body  61  with a hook point  61  a and a hook plate  62 . 
     The plate  62  and its variants  62 ′,  62 ″ can be seen better in FIGS. 24,  25  and  26 , wherein they are illustrated enlarged and extended. The plates correspond substantially to the plates  52 ,  52 ′ and  52 ″, except that the adjustment slot  63 ,  63 ′,  63 ″, or the part of the adjustment slot with the smallest diameter, has countersunk walls. No detailed description of the plates  62 ,  62 ′,  62 ″ will therefore be given. 
     The plate  62  is applied to the hook by means of two screws designated  66 ,  67 . The screw  66  is an adjusting and positioning screw; the screw  67  is a fastening and positioning screw identical to the screw  16  illustrated in FIG.  4 . The screw  66  has a threaded shank  66   a , a proximal countersunk flange  66   b , a distal countersunk flange  66   c , and a neck  66   d  therebetween. The maximum diameter of the flanges is greater than the width of the slot or of the part of the plate slots with the smallest diameter; the diameter of the neck  66   d  is smaller than the transverse measurement of the slot or of the part of the slot with the smallest diameter. 
     The screw  66  engages the slot of the plate with the neck  66   d , and engages the surface of the plate towards the hook body with its proximal flange  66   b , or the outer surface of the plate with respect to the hook with its distal flange  66   c , depending on whether the screw is acted upon to move the plate away from or toward the hook axis. 
     Further variants are possible and it is understood that all variants accessible to a person skilled in the art of normal experience in any case come within the scope of the invention as set forth in the appended claims.