Abstract:
The invention relates to a pneumatic gripper assembly structure which comprised a supporting body ( 11, 111 ) composed of at least two wall elements or symmetrical half-shells ( 15, 115 ), realized and finished individually using a forming process and then put together to form a single body capable of receiving, supporting and guiding other structural and functional components of the gripper assembly. The complementary wall elements or half-bodies are produced using die-casting, sintering or forging techniques with material compatible for such processes and provides a housing for jaws and a drive piston of the gripper.

Description:
FIELD OF INVENTION 
   This invention concerns pneumatic gripper assemblies in general used for securing items being machined and/or for automatic manipulation, and refers in particular to improved components for setting up such assemblies. 
   STATE OF THE ART 
   Both linear and angular pneumatic grippers, of the type taken into consideration here, are well known as regards to structure and functioning. They can be of different shapes, sizes and capacity, but each one is made up essentially of a supporting body, a simple or double-acting piston, moving either in a chamber or jacket in said body, and two jaws supported and guided in the body, working in conjunction with the piston, moving straight or at an angle in opposite directions in response to the alternating movements of the piston and supporting two item gripper jaw. 
   According to the known techniques, the components of said pneumatic gripper assemblies are machined on tool machines. In particular the body of a pneumatic gripper assembly is enbloc and is made starting from an unfinished piece, machined and bored as required to receive the operating components and the accessories which make up the gripper assembly. 
   As the technicians in this sector are well aware, the construction process of similar gripping assemblies is extremely laborious and painstaking due to the machining and operating times needed and often because of the fine tolerances required. The need to find innovative methods to produce pneumatic gripper assemblies of the type subject of this invention which are simpler and less costly, without having to machine or at least which reduce the machining operations greatly stems from this requirement. 
   On the other hand, forming techniques of elements such as die-casting, sintering, and forging which enable the production of items, even finished, with relatively complex shapes, with fine tolerances or however with a high level of precision, both as regards to size and surface finishing, and with the possibility of surface treatments, depending on necessity, at least in the case of sintered items, are well known. 
   These forming techniques, although well established in practice, have never been adopted in the gripper assembly manufacture field or if used only limited to basic components also because the configuration of the elements of these grippers, used in the traditional way, do not enable it. 
   OBJECTIVES AND SUMMARY OF THE INVENTION 
   This invention has been conceived to meet the above-mentioned requirement and to be able to take good advantage of the forming techniques of the items referred to above also in the manufacture of pneumatic gripper assemblies and to create the conditions to eliminate or at least minimise machining and assembling times and costs. 
   It in fact an objective of this invention to present and supply components for setting up pneumatic gripper assemblies, designed so as to be able to be produced using one or the other of the forming techniques for die-casting, sintering and forging and then assembled using simple fixing systems. 
   Another objective of the invention is the realisation of pneumatic gripper assemblies, each one made up of a limited number of pre-formed elements capable of fitting complementarily one with the other and with inserted auxiliary elements, ensuring the functionality of the resulting group improving in fact performance and life. 
   A further objective of the invention is to supply a linear or angular pneumatic gripper assembly which is easy to set up using a “sandwich” type assembly of the supporting and functional components. 
   To achieve the invention, the supporting body of a gripper assembly was disassembled into complementary parts to be produced separately using one of the above said techniques and then to be assembled to form one solid group capable of receiving, supporting and guiding other structural and functional components of the gripper. 
   The structure of a pneumatic gripper assembly according to the invention is substantially the one conforming with claim  1 . 

   
     BRIEF DESCRIPTION OF DRAWINGS 
     Greater details of the invention will become more evident in the following description made with reference to the indicative and non-limiting drawings enclosed, in which: 
       FIG. 1  is an exploded view in prospective of the components for the construction of a linear pneumatic gripper assembly; 
       FIG. 2  is an enlarged view of a half-body for the formation of the gripper assembly body; 
       FIG. 3  is a linear pneumatic gripper assembly with the components in  FIG. 1  partially assembled; 
       FIG. 4  is a view in prospective of the linear pneumatic gripper assembly, completed assembled; 
       FIG. 5  is a longitudinal cross-section of the assembled gripper unit in direction of arrows V-V in  FIG. 6 ; 
       FIG. 6  is a cross-section of the assembled gripper in the direction of arrows VI-VI in  FIG. 5 ; 
       FIG. 7  is a further cross section of the gripper assembly on a level with the two anchoring bolts; 
       FIG. 8  is an exploded view in prospective of the components of a linear pneumatic gripper assembly in compliance with a variation in construction; 
       FIG. 9  is a partially assembled linear pneumatic gripper assembly as shown in  FIG. 8 ; 
       FIG. 10  is a view in prospective of the completely assembled linear pneumatic gripper assembly; 
       FIG. 11  is an exploded view of the components of an angular pneumatic gripper assembly; 
       FIG. 12  is a view in prospective of the fully assembled angular pneumatic gripper assembly. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   Both the linear and angular pneumatic gripper assembly represented comprises a supporting body  11 , an alternating piston  12  moving in said body, a drive system  13  associated with the piston and two jaws  14  driven by the piston, moving in opposite directions by means of the drive system  13  and each one can be equipped with jaw shoes not shown. The only difference between the two types of pneumatic grippers is that the jaws in the linear grippers are subjected to rectilinear movements in opposite directions, whereas in the angular grippers the jaws turn each one on a pin, performing angular movements in opposite directions in response to the movements of the piston. 
   According to a construction method as illustrated in  FIGS. 1-7 , the supporting body  11  is made up of two exactly equal elements or symmetric half-bodies or shells  15 . They therefore can be made advantageously from the same mould, using die-casting, sintering or a forging systems in any appropriate material. 
   The two half-bodies  15  are placed one facing the other, they fit one into the other and are fixed together. Each one has a support plane  16  from which an intermediate part rises  17 , with two sides  17 ′, which is topped by a straight flat section  18 . 
   The supporting plane  16  forms a support base  16 ′ and, on the two opposite sides it has two ears  19  protruding from the intermediate section  17  each one having a half hole  20  perpendicular to the support base  16 ′ and open towards the opposite semi-body. At the height of each half hole  20  a semi-hexagonal recess  20 ′ can be formed. 
   A cylindrical cavity  21  has been machined at the height of the intermediate section  17 , the axis of which is parallel to the support base  16 ′. The cavity  21  is closed by a bottom wall  22  in which a hole  22 ′ is provided and opens towards the half-body opposite. In the top part of cavity  21 , there is a slide surface  23  at one end of which, on the open side of the cavity itself, has been formed a semi-slot  23 ′. On the parts opposite to cavity  21 , on a parallel with its axis, holes  24  have been provided, for example two on each side placed symmetrically to each other. Preferably, centring protrusions  24 ′ are provided at the height of the two said diagonally opposite holes  24 , on the open side of cavity  21 , whereas at the height of the other holes there are complementary housings  24 ″. On each side  17 ′ of the intermediate section  17  a duct  25  is provided which runs parallel to the axis of cavity  21 . 
   The top part  18  of the half-body  15  is at a right angle to the cylindrical cavity  21  axis. A flexing groove  26  is provided externally, between the top part  18  and the intermediate part  17 . Two or more transversal holes  27  are provided in the top part  18  on at one level and, above these, in the internal face of the part itself a longitudinal groove divided by an intermediate baffle has been formed. A tongue  29  has been provided in a central position on the top side of part  18  facing inwards, that is to say towards, a similar tongue on the opposite half-body. 
   The drive system  13  as well as the jaws can also be produced using the same forming techniques used in making the half-bodies  15 . 
   In particular, the drive system  13  has a central hole  30  and, on the opposite sides to the latter, two slots  31  in a V formation. 
   The jaws  14  are the identical and can be made from the same mould. Each jaw  14  has a connecting pin  32  for coupling with the drive system  13 , transversal holes  33  at the top, and on each side a groove  34  which will be at the same height and opposite the groove  28  on the internal face of the top part  18  of the adjacent half-body. 
   When setting up a gripper assembly, the two elements or half-bodies  15  are placed one in front of the other and bolted tightly together using bolts  35  inserted in the transversal holes  24  in the sides of the cylindrical cavity  21  and other bolts  36  inserted in the transversal holes  27  at the height of the top part  18 . When the two half-bodies are united, their cavities  21  are in line and form a chamber  37 — FIG. 5 ,  6 —in which the piston  12  driving the jaws  14  is housed. If the piston is double-acting, the piston  12  is driven by a fluid under pressure, delivered/discharged alternately in the chamber  37  by means of ducts connected to the bottom walls of the cavity at the same level as holes  22 ′. If the piston is single-acting, the piston is driven in one direction by the fluid fed to chamber  37  and return is spring driven. 
   When the half-bodies are assembled together, the side ears form with there half-holes, holes for the anchoring screws  38  of the gripper unit on the support. Advantage only each of said holes, thanks to the semi-hexagonal hollows  20 ′, can house and hold a nut  39  which means that the respective anchoring screws can be applied both from the top or bottom according to needs— FIG. 5 . 
   The driver  13  is positioned on the slide surface  23  above the piston chamber  12  and is connected to the latter by means of a pin  40  inserted into its central hole  30  and passing through to insert into the slot formed by the half-slots  23 ′ of the two united half-bodies. 
   The top facing parts  18  of the two half-bodies  15  form a guide housing  41 , and the jaws  14  are placed in said housing together with interposed ball bearings  42 . Each jaw is associated, through its respective connecting pin  32 , with a slot  31  of the driver  13  so that the jaws move in opposite directions in response to the alternating movements of the piston  12 . 
   The bearings  42  are positioned between the internal grooves  28  of the top part  18  of the half-bodies and the lateral grooves  34  of the jaws themselves. Furthermore, by tightening or loosening the anchoring screws  36  passing through the transversal holes  27  in the top parts of the half-bodies and thanks to the flexing groove  26  along the base of each of said parts it is possible to calibrate their nearness in order to establish a correct preload of the assembled functional elements and to be able to recover play and coupling wear. 
   Jaws shoes can be fixed to the holes  33  of the jaws  14  as required. The top tongues  29  of the top part of the half-bodies, when brought together form a protective portion—FIG.  4 —suitable for stopping dust or dirt entering the space between the grippers  14 . The lateral ducts  25  of the half-bodies  15  can be used to apply accessories to the gripper assemblies, such as for example end of stroke sensors and so on. 
   In compliance with the invention and according to a another method of construction illustrated in  FIGS. 8-12 , the gripper assembly has a supporting body  111  made up of several complementary parts which include two opposite wall elements  115  and two side elements  116 , all those elements being formed by die-casting, sintering or forging of any appropriate material. 
   The two wall elements or cheek  115  are the identical, therefore can be made from the same mould. They are positioned one facing the other, and each one has a base plane  117 , at least one lower couple of transversal holes  118  just above the base plane and at least one higher couple of transversal holes  119  at a different level. 
   The base plane  117  has two semi-holes  120  perpendicular to each of its ends, one facing inwards and the other facing outwards in relation to the body. 
   Longitudinally, the internal face of each cheek  115 , the one facing the other cheek, has a recess  121  which may be cylindrical, but preferably with faceted surfaces, that is polygonal, viewed in cross-section. Each cheek  115  has a groove  122  on the internal surface which runs parallel to the longitudinal recess  121  above it and closed at both ends. 
   Longitudinally, the external face of each cheek  115  has a semi-duct  123  at one level and a flexing groove  124  at a higher level, between the bottom and top couple of holes  118 ,  119 . On the top of each cheek  115  there is a central positioned recess  125  with a coupling lug  126 . 
   The two side elements  116  are the identical, therefore can be made from the same mould. Each one is positioned externally and positioned against a relative wall element or cheek  115  and is lower in height to the level of the top couple of holes  119  of the cheeks. 
   Each side element has a base plane  127  with two semi-holes  128  at its ends on the side facing towards the adjacent cheek, and above the base plane, a couple of transversal holes  129  in line with the bottom couple of holes  118  of the cheeks  115 . In addition, on the internal face, the one facing the adjacent cheek, each side element has a complementary semi-duct  130  running longitudinally and at the same level as the external semi-duct  123  of said cheek. 
   The external walls of the opposite wall elements or cheek  115  and the side elements  116  are screwed tightly together to form the supporting body using bolts  118 ′,  119 ′ passing through the couple of transversal holes  118 ,  119  in line. Consequently, the semi-holes  120 ,  128  at the ends of the base plane of the wall elements and the side elements form in combinations of two by two the holes of the gripper assembly anchoring screws. The wall elements with the recesses  121  on the adjacent faces form a housing for two casings or cylinders  131  Which determine two separate sleeves or chambers in which to house a piston  112  with its opposite ends. 
   The casings or cylinders  131  can also be made using a forming and finishing technique as used to make the wall and side elements. To be noted that the casings or cylinders  131  have a polygonal external surface which fit together with the one with the recesses  121  forming the housing they fit into. In this way the casings or cylinders are prevented from turning without having to provide other additional systems. Furthermore, each casing or cylinder  131  has a tapered neck  131 ′ in which an anchoring bolt  118 ′ passes which besides helping in assembling the body  11  helps to achieve axial blocking of the respective casing or cylinder without having to insert flanges or covers as are required in the known technique. 
   Ball bearing raceway retainers  132  are fitted into the grooves  122  in the internal faces of the wall elements or cheek  115 , which in linear gripper assemblies—FIGS.  8  and  9 —act as linear guide bearings for the movements of the jaws  113 . 
   These jaws  113 , as is also the case for the jaws  113 ′ for an angular pneumatic gripper assembly, may also be achieved with one of the abovementioned forming techniques. 
   Both the jaws  113  for a linear gripper assembly and the oscillating jaws  113 ′ for angular gripper assemblies are coupled to the alternating piston  112  in the known way. In the case of oscillating jaws  113 , antifriction and protective lining elements  133  can be inserted between the latter and the cheeks against penetration of dirt from outside. 
   The piston can be double-acting, in which case each casing or cylinder is connected to a source of fluid under pressure by means of a coupling  131 ″, with alternating delivery/discharge of the fluid in the two sleeves. 
   The piston  112  can also be single-acting, in which case one of the chambers formed by the casings or cylinders  131  is fed/discharged alternately by a fluid under pressure, while in the other chamber, between the latter and the piston, there will be a return spring, not shown. 
   Furthermore, in the top part of the wall elements, in line with the central recesses  125  a protection plate  134  suitable for preventing dust and dirt penetrating between jaws  113 ,  113 ′ is assembled and snap locked thanks to the coupling lugs  126 . 
   The adjacent semi-ducts  123  and  130  of each wall element or cheek  115  and respective side element  116  forming together a duct along which accessories such as magnetic end of stroke sensors can be made available and positioned. 
   In addition and worthy of note is that the casings or cylinders  131  forming the chamber for the piston  112  are separated at an axis one from the other leaving a space between them which means a permanent ring magnet  135  can be applied around the piston  112  moving with it which has a greater bore than the external diameter of the piston itself. With this expedient, the magnet  135  is closer to the end of stroke magnetic sensors which may be inserted and positioned along the external ducts of the body. 
   By tightening or loosening the anchoring screws  119 ′ passing through the top couple of transversal holes  119  and thanks to the flexing groove  124  along each wall element  115  it is possible to calibrate their nearness of the wall elements order to establish a correct preload of the assembled functional elements and to be able to recover play and coupling wear. 
   It consequently seems evident that a type of gripper assembly as described here can be realised starting from a minimum number of pre-formed components, which in substance do not require machining and which are undemanding to assemble using only anchoring screws.