Abstract:
A lock pin with pushbutton-operated axial locking has two locking elements which point in opposite directions and are mounted in radially outwards directed recesses in the body. To ensure a good, wear-resistant pivotal mounting of the two locking elements, combined with good locking action and resistance to shearing, the invention provides that the locking elements create a virtual, freely guided pivoting axis in their connection zone. The result is a pinless mounting of the locking elements.

Description:
BACKGROUND OF THE INVENTION  
   The subject-matter of the invention is a lock pin with pushbutton-operated axial locking according to the introductory part of Claim  1 . Lock pins of this type are used as machine elements. The pin part is inserted through a seat in a machine part so that it transfixes two machine parts possessing a common aligned bore. Pushbutton-operated spring-loaded locking elements are arranged at the forward free end of the pin part. 
   DE 10154692.0-24 originating from the same applicant, and constituting a prior right, describes a lock pin with pushbutton-operated axial locking according to the introductory part of claim  1  wherein the locking elements are configured as catches. The same document also showed that the locking element can have a film hinge, provided that it is made from plastic material. Here, however, there are conflicting objectives, since on the one hand the material needs to be sufficiently flexible to form a serviceable film hinge, and on the other hand the locking elements need to have sufficient mechanical strength not to shear off while in locking engagement. 
   Known from the unrelated field of hinged dowels are shaft-mounted pivotable locking elements which are initially passed through a hole in a wall-opening in the folded-down position and are then deployed and pivoted into the locking position by means of a screw thread. 
   Such hinged dowels, however, are not suitable for the repeated operation required in the context of machine parts. In particular, they are not designed for fatigue loading, as the locking position usually has to be provided only once. 
   Incidentally, these unrelated catches lock in only one direction, whilst in the other direction, they are retractable. 
   Therefore the problem which lies at the basis of the invention is to develop a lock pin with pushbutton-operated axial locking of the kind stated at the outset so that it can be used repeatedly for machine elements, and is able to sustain high breaking loads and shear forces. 
   SUMMARY OF THE INVENTION  
   For the solution to this problem, the invention is characterized by the technical teaching of Claim  1 . The essential feature of the invention is that the locking elements according to the invention have a rigid, rather than a flexible, design, and the hinge axis is designed as a virtual bearing-axis. Therefore a hinge pin that could become worn or even break under repeated flexing is no longer needed. 
   In a first preferred embodiment, the end of the pushrod forms a bearing shaft, while the catches themselves form bearing shells with a semi-circular configuration. This engineering design has proved effective. Nevertheless assembly is difficult where such a locking element is intended for use in through bores of less than 6 mm diameter. In another configuration of the present invention, the bearing of the catch is shifted outwards to a plunger that has a semi-circular slot in which lobes, shaped as quadrants, of the two catches are carried. 
   Instead of the configuration shown, i.e. a lobe, the bearing of the catches may also be provided as a rib configured as a quadrant and extending over the full width. 
   In a third variant of the invention, the pushrod has an approximately rectangular recess in which the two catches are mounted. In this case the catches have separate, slightly outwards-displaced bearing-axes. 
   The recess can of course be located on the opposite side, e.g. by configuring accordingly a spring plunger like the one used in the second embodiment. 
   A further feature is that the pushrod is steadied on the other side by being “guided” in the above-mentioned spring-loaded plunger. At the same time, by resting on this plunger, the bearing-axes of the catches have a better mounting, that is to say, they are supported on both sides. 
   The pushrod may be guided in the plunger by a slot or an annular groove, or simply by guiding the pushrod externally or internally on the above-described recess. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS  
     The invention will now be described in detail with the aid of a drawing showing just one way of carrying out the invention. Further essential features and advantages of the invention will follow from the drawing and from its description. 
     In the drawings: 
       FIG. 1  shows a section through a first embodiment of a lock pin according to the invention in the locked condition, 
       FIG. 2  shows the view of  FIG. 1  in the unlocked condition, 
       FIG. 3  is a perspective view of a locking element, 
       FIG. 4  shows a section through a second embodiment of a lock pin in the locked condition, 
       FIG. 5  shows the view of  FIG. 4  in the unlocked condition, 
       FIG. 6  shows an enlarged view as  FIG. 4  but with spring omitted, 
       FIG. 7  shows an enlarged view as  FIG. 5 , 
       FIG. 8  is a perspective view of the locking element, 
       FIG. 9  shows a third embodiment of the invention, in section, in the locked condition, 
       FIG. 10  shows the view of  FIG. 9  in the unlocked condition, 
       FIG. 11  shows a modified form of the embodiment shown in  FIG. 9 , 
       FIG. 12  is a view from above of the embodiment of  FIG. 11 , with the locking elements omitted, 
       FIG. 13  is a perspective side view of a locking element, 
       FIG. 14  shows a section through a fourth embodiment of a lock pin in the locked condition, 
       FIG. 15  shows the view of  FIG. 14  in the unlocked condition, 
       FIG. 16  shows, in section and on an enlarged scale, a modified form of the embodiment shown in  FIG. 14 , 
       FIG. 17  is an end view of the pushrod, 
       FIG. 18  is a side view of the pushrod, 
       FIG. 19  is a perspective view of a locking element for use in  FIGS. 14 to 18 . 
   

   DETAILED DESCRIPTION OF THE INVENTION  
   The lock pin  1  shown in  FIGS. 1 and 2  consists of an approximately cylindrical or square body  4  in whose central recess a pushrod  8  is longitudinally displaceably guided. As  FIGS. 4 and 5  show, the pushrod  8  has at its upper end an operating button  23  which is displaceable relative to a bearing block  44  fixed with respect to the body of the pin. A circumferential recess  18  into which cap  17  is latched by inwards directed projections  16  is arranged at the free, lower end of the body  4 . 
   It is also feasible to provide the cap  17  with a screwed connection to the body  4 , instead of the latched connection  16 ,  18 . 
   The body  4  is extended downwards in the form of a bearing thimble  15 . The circumferential recess  18  is located in this area. 
   A spring element  19  is contained interior  14  the bearing thimble  15 . This spring element  19  bears at one end on the bottom of the cap  17  and at the other end on the underside of two locking elements  2 ,  3  which point in opposite directions. 
   In the locked condition, each locking element  2 ,  3  sticks out of a recess  5 . These recesses  5  are opposite each other and are approximately radially aligned. 
   According to the invention the bearing-axis of the two locking elements  2 ,  3  is pinless. That is to say, as shown in  FIG. 3 , each locking element  2 ,  3  is configured as a one-sided bevel  7  which springs from an approximately rectangular locking body  6  and on the forward, free end of which, two claws  9 ,  10 , approximately semi-circular in shape and spaced apart from each other, are formed. 
   A gap  11  is formed between the two claws; and the space between the claws  9 ,  10  of one locking element  2  forms a bearing shell  22  for the opposite locking element  3  (not shown in the drawing), which engages by a single, likewise semi-circular, claw into the gap  11  between the claws  9 ,  10  of the locking element  2 . 
   Thus, the two locking elements  2 ,  3  fit together in the region of a common bearing shell  22 , so forming the said virtual hinge axis  12 . 
   As  FIG. 1  shows, the pushrod  8  reaches into the two locking elements by its lower end, which is configured as a blade  13 . 
   It can be seen from  FIG. 1  how the claw  20  on the locking element  3  engages in the gap  11  between the claws  9 ,  10  of the locking element  2 . 
   Upon operation of the pushbutton  23 , the pushrod  8  is pushed down against the spring element  19 , and the two locking elements  2 ,  3  are tilted downwards in the recess  5 , producing the unlocked position shown in  FIG. 2 . 
     FIG. 1  also shows the central recess  31  in the bearing thimble  15  in which the spring element  19  is mounted. 
   Instead of a helical compression spring, any other known stored-energy device such as elastomer springs, leg springs or spiral springs can, of course, be used. 
   Upon operation of the pushrod  8 , the virtual bearing-axis between the two locking elements  2 ,  3  therefore undergoes an axial displacement in the direction of the arrow  21  of  FIG. 3 . 
   Instead of forming the hinge axis  12  by the interlocking claws  9 ,  10 ,  20 ,  FIGS. 4 to 7  show a different embodiment. 
   Here, as shown in  FIGS. 4 to 8 , the bearing-axis is defined by forming a guide web  27 , approximately in the shape of a quadrant, on each locking element  32 ,  33 . 
   Each locking element  32 ,  33  again consists of an approximately rectangular solid body, with a bevel  26  at its inner end. The bevel  26  tapers to a stop fin  28  on the end face. 
   Both guide webs  27  of the locking elements  32 ,  33  engage in a guide slot  29  in a bearing plunger  24 , as shown in  FIG. 6 . 
   In  FIGS. 6 and 7  the spring element  19  has been omitted in order to simplify the drawing. 
   Nevertheless  FIG. 6  shows that when the bearing plunger  24  is in the raised position it bears, by a radially outwards directed shoulder  25  with increased diameter, on the underside of the locking elements  32 ,  33  pointing radially in opposite directions. 
   Upon operation of the pushrod  8 , the blade  13  of the pushrod  8  moves into the gap between the two locking elements  32 ,  33  and strikes both stop fins  28 . 
   This causes the two locking elements  32 ,  33  to tilt in the recess  5  concurrently with the axial downward displacement of the bearing plunger  24 , as shown in  FIG. 7 . 
   Thus in the lock pin  30  shown in  FIGS. 4 to 8  the virtual pivot-bearing between the two locking elements  32 ,  33  is formed by a pivoting bearing of each guide web  27  in a guide slot  29  in a bearing plunger  24  that is axially guided under spring loading. 
   It will be obvious that additional axial guidance of the bearing plunger  24  can also be provided in the region of the recess  31 . 
   Such axial guidance of the bearing plunger  24  can thus be provided in the region of both the surrounding bearing thimble  15  and of the bearing shell  14 . 
   The advantage of this arrangement is that it, too, provides a pinless pivot-bearing between the locking elements  32 ,  33 . This pivot-bearing therefore works with little or no wear and can be rated for a high number of load cycles. 
   Although the guide web  27  of  FIG. 8  on the underside of each locking element  32 ,  33  is relatively narrow, it can, in another embodiment, be made wider. The width of the guide web can also be matched to that of the locking element  32 ,  33 . 
   In the further embodiment shown in  FIGS. 9 to 13 , an approximately rectangular recess is formed at the lower end of the pushrod  8  between two parallel, endwisely-arranged fork-extensions  38 . 
   Somewhat pin-like, round-profiled bearing-axles  37 , which are straddled by the fork-extensions  38 , are arranged at the inward ends of the two locking elements  34 ,  35 . 
   The bearing-axles  37  press on the shoulder  25  of increased diameter which is joined to the spring-loaded axially displaceable bearing plunger  36 . 
   Thus, when pressure is applied to the pushrod  8 , the bearing plunger  36  is displaced downwards into the region of the cap  17 , against the force of the spring element  19 , and the two locking elements  34 ,  35  pivot inwards into the unlocked position. 
   Incidentally,  FIG. 13  shows that the locking elements  34 ,  35  can have slots  41  instead of being joined to bearing-axles  37 . 
   The fork-extensions  38  of the pushrod  8  engage in these slots  41  so that here, too, a virtual pivot-bearing of the locking elements  34 ,  35  manifests itself. 
   The locking elements  34 ,  35  are thereby juxtaposed in the region of their bevels  26 , as shown in  FIG. 10 . 
   As  FIGS. 9 and 10  show, the bearing plunger  36  is guided axially, and prevented from skewing, in the bearing thimble  15  on the opposite side to the pushrod  8 . For this purpose the shoulder  25  of the bearing plunger  36  has radially outwards directed extensions  39  affording linear guidance on the bearing thimble  15 . 
   The bearing-axes thereby created on the locking elements  34 ,  35  are thus supported in all directions. 
   In a modified embodiment shown in  FIGS. 14 to 19 , the fork-extensions  38  described above with reference to  FIG. 11  can also be axially extended, and can engage in seats  42  in the region of the spring-loaded axially-guided bearing plunger  43 . This provides trouble-free axial longitudinal guidance of the bearing plunger  43  in the lock pin  40  shown in  FIGS. 14 and 15 . 
   In a similar embodiment to  FIGS. 9 to 13 , the fork-extensions  38  can in this case too engage in slots  41  in the opposite-way locking elements  34 ,  35 , so replacing the bearing-axles  37  formed on the locking elements  34 ,  35  as shown in  FIG. 16 .  FIG. 19  illustrates this. 
   A feature common to all embodiments is that a pinless pivot-bearing of the locking elements  2 ,  3 ;  32 ,  33 ;  34 ,  35  is shown, and that the locking elements, as rigid, rather than flexible, bodies, have an excellent locking action combined with good resistance to shear forces. 
   DRAWING LEGEND 
   
       
         1  lock pin 
         2  locking element 
         3  locking element 
         4  body 
         5  recess 
         6  locking body 
         7  bevel 
         8  pushrod 
         9  claw 
         10  claw 
         11  gap 
         12  pivot axis 
         13  blade 
         14  interior of bearing thimble 
         15  bearing thimble 
         16  projection 
         17  cap 
         18  recess 
         19  spring element 
         20  claw 
         21  direction arrow 
         22  bearing shell (of  2 ,  3 ) 
         23  operating button 
         24  bearing plunger 
         25  shoulder 
         26  bevel 
         27  guide web 
         28  stop web 
         29  guide slot 
         30  lock pin 
         31  recess 
         32  locking element 
         33  locking element 
         34  locking element 
         35  locking element 
         36  bearing plunger 
         37  bearing-axle 
         38  fork-extension 
         39  extension 
         40  lock pin 
         41  slot 
         42  seat 
         43  bearing plunger 
         44  bearing block