Abstract:
In a gripper device for manually operated or automatic handling devices, having a gripper housing, at least one base jaw displaceably seated in the gripper housing, and a drive for the base jaw, wherein the drive comprises a hydraulically or pneumatically chargeable piston displaceably seated in a cylinder and a spline hook gear, an optimal sealing of the base jaw in the gripper housing is achieved in that the base jaw has a sealed, for example circular or polygonal, cross section at least in the section extending from the gripper housing when the gripper device is opened.

Description:
BACKGROUND OF THE INVENTION 
     1. Technical Field 
     The present invention relates to a gripper or clamping device for manually operated or automatic handling devices, having a gripper housing, at least one base jaw displaceably seated in the gripper housing, and a drive for the base jaw, wherein the drive comprises a hydraulically or pneumatically chargeable piston displaceably seated in a cylinder and a spline hook gear. 
     2. Background Art 
     A gripper device of this type is known from DE 89 02 325 U1, for example. In order to be able to grip tools simply and yet precisely with a handling device or a robot arm, parallel grippers which are pneumatically or hydraulically actuated are employed as a rule. In the process a piston, which is displaceably seated in a cylinder provided in the gripper housing, is acted upon by a pressure medium. A spline hook gear is actuated by the displacement of the piston, so that the gripper jaws are extended out of the gripper housing or are retracted into the gripper housing. The base jaws have a T-shaped cross section and are seated in appropriate guides. The essential advantage of these base jaws, besides the relatively large gripping force, is the great lateral stability and small tendency for tilting. However, it has been found that the base jaws, and in particular their running surface, are subject to great wear, since the rinsing fluid which is sometimes used in the work area washes the lubricants off the guide surfaces because of the open guides, and furthermore, dirt particles penetrate between the housing and the base jaws. The dirt particles in particular cause a great amount of abrasion on the sliding surfaces, so that exact guidance and freedom from play is lost after a short time. 
     SUMMARY OF THE INVENTION 
     The present invention is therefore based on the object of further developing a gripper device of the type mentioned at the outset in such a way that wear is reduced, even when it is used in very dirty areas and also in case of contamination with rinsing liquids and similar fluids, and that the gripper device still moves easily even after longer use. 
     This object is attained in accordance with the present invention in that the base jaw has a sealed, for example circular or polygonal, cross section at least in the section extending from the gripper housing when the gripper device is opened. 
     The circularly shaped base jaws can be guided in a considerably more sealed manner in the housing, since the passages or receiving openings for the base jaws in the gripper housing can be manufactured considerably more precisely than a T-shaped opening for T-shaped base jaws. Neither foreign particles nor liquids can enter into the space between the housing and the base jaws because of the more precise fabrication of these receiving openings. The service life of such a gripper device is increased considerably over that of the known gripper devices in accordance with the prior art. 
     In connection with a preferred further embodiment it is provided that the housing is equipped with sealing elements enclosing the circular section of the base jaws. These sealing elements have the purpose of closely surrounding the base jaws and by means of this to prevent the possible further penetration of solid bodies or liquids or even gases. In addition, the sealing elements have the advantage that no lubricant emerges from the housing. 
     In order to protect the seals of the sealing elements, they can be advantageously provided with strippers, so that dirt and liquid adhering to the base jaws is stripped off. In this case the seals and strippers are advantageously combined into a single sealing element or are made of one piece. The latter is inserted into the housing in the area of the housing opening. The gripper in accordance with the present invention can now also be employed without problems in very dirty rooms where, for example, cast parts are dressed and abrasive cast dust accumulates. 
     In a further embodiment of the gripper device it is provided in accordance with the present invention that at least one of the base jaws is equipped with a protection against torsion. The lateral stability of the base jaws and therefore that of the gripper jaws is considerably increased by means of this protection against torsion, and the tendency to tilt is reduced. The workpieces can now be gripped and held by the gripper jaws which are secure against torsion. 
     It is provided in connection with a preferred embodiment that the protection against torsion has a groove provided in the base jaw, which is engaged by a feather key supported on the housing. In this case the groove for the feather key extends parallel with the longitudinal axis of the base jaw, wherein the groove is only provided in the section of the base jaw which remains in the housing. The section of the base jaw being extended out of the housing therefore has no groove, so that sealing is assured. 
     In order to be able, in a simple, but effective manner to compensate for tolerances, the feather key is floatingly seated in the housing, i.e. the feather key is fastened on a housing cover and is in particular made of one piece with it. In this way the insertion of the feather key into the grooves of the base jaws is possible without problems, even if the grooves in the base jaw are not exactly aligned with the housing opening receiving the feather key. The housing is open in the area of the groove, wherein this opening, however, is wider as well as longer than the feather key, and this housing opening can be closed by means of a cover which has the feather key. The feather key is inserted into the corresponding grooves when the cover is placed on the housing and the housing is closed, and as a result the base jaws are secured against torsion. Therefore the entirety of the forces acting on the feather key are supported by means of the cover of the housing. Large forces can be transmitted because of the relatively wide cover. 
     In one exemplary embodiment it is provided that the protection against torsion for the base jaws is provided on the sides opposite the drive for the base jaws. In this way both assembly and maintenance are made easier. The cover having the feather key is advantageously screwed to the housing and sealed in respect to the housing. By means of the screwed attachment it is possible to compensate for tolerances regarding the position of the grooves in the base jaws and the housing. 
     Because, in accordance with the present invention, the chamber of the housing with the spline hook gear is fluidically connected with the side of the cylinder chamber facing away from the spline hook gear, no underpressure is generated when the base jaws are extended or the base jaws are retracted into the housing. Underpressure would have the serious disadvantage that gases or liquids, for example rinsing liquid, could be aspirated through the gap between the base jaws and the housing, because of which the lubricant film on the base jaws could be destroyed. Furthermore, dirt would be carried in by these liquids. The connection of this spline hook gear chamber with the chamber which is under pressure when the base jaws are extended has the considerable advantage that the spline hook gear chamber is always under pressure and therefore no medium can enter, at most fluids could run out in case of leaks. 
     The base jaws can preferably be equipped with gripper jaws on the front. These are flanged to them, for example by means of screws, wherein they can be centered in addition. 
     The base jaws can preferably be retracted completely over their entire length into the housing. In the process they are completely surrounded over their entire length by the housing, so that only their front ends, on which the gripper jaws are fastened, are accessible. This has the considerable advantage that in the course of retraction into the housing the base jaws are both cleaned and also freshly lubricated. 
     In one exemplary embodiment the base jaws advantageously have receptacle openings for elements for position determination. The open position and the closed position of the gripper device can be determined by means of position detection elements, and the controls can be correspondingly triggered. 
     The present invention is not limited to two-finger parallel grippers, for example, but also includes grippers with several base and gripper jaws, for example three-finger centric grippers. 
     Further advantages, features and details of the present invention ensue from the following description, wherein two particularly preferred exemplary embodiments are described in detail, making reference to the drawings. The features represented in the drawings and mentioned in the claims and specification can be important for the present invention here either individually by themselves or in any arbitrary combination. The drawings show in: 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a longitudinal section through a first embodiment of the gripper device in accordance with the present invention; 
     FIG. 2 is a perspective plan view of the housing of the gripper device in FIG. 1, 
     FIG. 3 is a perspective plan view of a housing cover in an enlarged representation, 
     FIG. 4 is a perspective representation of a base jaw, 
     FIG. 5 is a perspective representation of a housing of a second embodiment of the gripper device of the present invention for three base jaws, and 
     FIG. 6 is a perspective representation of a housing cover for the housing in accordance with FIG.  5 . 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The representation shown in FIG. 1 is a longitudinal section through a two-finger parallel gripper with a housing  1 , two base jaws  2  and  3 , a drive  4  for the base jaws  2  and  3 , and a piston  5  displaceably seated in a cylinder  6 . The housing  1  has an essentially T-shaped cross section, wherein the two base jaws  2  and  3  are displaceably seated in the two oppositely located legs of the housing  1 . The leg of the housing  1  which is vertical with respect to these legs has the cylinder  6 , which is divided into two cylinder chambers  7  and  8  by the piston  5 . In FIG. 1, the piston  5  is in its one end position, in which the two base jaws  2  and  3  are retracted into the housing  1  by means of the drive  4 . In this position of the piston  5  the cylinder chamber  8  takes up its minimal and the cylinder chamber  7  its maximum volume. 
     The piston  5  is screwed onto piston rod  9 , wherein the piston rod  9  makes a transition into the head  10  of a spline hook gear  11 , which constitutes the drive  4 . The head  10  is coupled by means of the spline surfaces, known per se, with corresponding spline surfaces  12 ,  13  of the base jaws  2  and  3 . A movement of the piston  5  in the vertical direction is deflected by means of the spline hook drive  11  into a movement of the base jaws  2  and  3  with the horizontal direction, i.e. orthogonally in respect to the movement direction of the piston  5 . In the process both tension and pressure forces are transmitted. 
     A seal  14 , which encloses the piston rod  9  and is seated in a housing shoulder  15  which guides the piston rod  9 , a seal  16 , which is cut into the circumferential surface of the piston  5  and seals the piston  5  with respect to the wall of the cylinder  6 , and a flat seal  17 , which seals the cylinder chamber  8  against the atmosphere, are used for sealing the cylinder chambers  7  and  8 . The flat seal  17  is situated between a housing cover  18  and the bottom of a recess  19  in the housing  1  for receiving the housing cover  18 . 
     It can furthermore be seen in FIG. 1 that in the area of their free front faces the two base jaws  2  and  3  are enclosed by respectively one sealing element  22  or  23  (first sealing means), so that the interior chamber  24  receiving the base jaws  2  and  3  is sealed against the atmosphere. The sealing elements  22  and  23  consist of a seal and a stripper, these two elements being combined in the sealing elements  22  or  23 . It is also to be pointed out that the interior chamber  24  is directly or indirectly connected with the cylinder chamber  8  by means of a conduit, not shown. It is prevented in this way that an underpressure is created in the interior chamber  24  when the base jaws  2  and  3  are extended out of the housing  1 . 
     A base jaw  2  or  3  is represented in FIG. 4, wherein the circular cross section of the section  25  (first section) extending out of the housing  1  is clearly discernible. The section  26  (second section) is provided with a longitudinal groove  27  (rotation-protection means), which is situated opposite to the spline surfaces  12  and  13  and therefore of the drive  4  in relation to the longitudinal axis. The longitudinal groove  27  is open toward the exterior and suited for receiving a feather key  28  (FIGS.  1  and  3 ). This feather key  28  is formed as one piece with a housing cover  29 , as can also be seen in FIGS. 1 and 3. In the course of extending the two base jaws  2  and  3 , the longitudinal grooves  27  of these two base jaws  2  and  3  slide along the feather key  28 , while the feather key  28 , however, remains in continued engagement with the longitudinal groove  27 . A protection against torsion for the two base jaws  2  and  3  is created by means of the groove and key connection, by means of which not only a great lateral stability is assured, but tilting of the base jaws  2  and  3  is also prevented. 
     Following the insertion of the feather key  28  into the corresponding longitudinal grooves  27  of the base jaws  2  and  3 , the housing cover  29  is screwed to the top (FIG. 2) of the housing  1  and the connection of the feather key  28  with the housing is provided in this way. A seal  31  is inserted into a recess  32  provided for the seal between the housing cover  29  and the housing  1 . The interior housing chamber  24  is sealed in this way on the cover side. Because of negligible tolerances in the threaded bores  33  of the housing  1  and the screw holes  34  of the housing cover  29 , the housing cover  29  can lightly float on the top  30  of the housing  1  before the screws are tightened, which has the advantage that tolerances when cutting the longitudinal groove  27  can be compensated. The housing opening  35  is selected to be correspondingly large, so that the feather key  28  can be slightly displaced in this housing opening  35 . 
     It can be stated in summation that with this first embodiment an optimal seal of the housing interior  24  with respect to the atmosphere is achieved by the circular shape of the section  25  of the base jaws  2  and  3 , so that neither fluids nor solid particles can enter and damage the running surfaces. A protection against torsion is achieved in that the flanks  36  of the longitudinal groove  27  can be supported on the lateral faces  37  of the feather key  28 , wherein the feather key  28  is rigidly connected with the housing  1  by means of the screwed connection of the housing cover  29 . 
     In addition, a lateral opening  38  in the basic jaw  2  or  3  can be seen in FIG. 4, into which elements for position detection, for example a magnet or the like, can be inserted. Such an opening is also located on the opposite side of the base jaw  2  or  3  (facing away from the viewer in FIG. 4) which, however, has been disposed offset with respect to the opening  38 , i.e. it is further displaced in the direction toward the front face  20  or  21  or in the direction of the oppositely located side having the spline surfaces  12  and  13 . The two base jaws  2  and  3  are embodied to be identical, so that by means of the magnet in the one opening  38  the extended position, for example, can be determined, and by means of the magnet in the other opening the retracted position of the base jaw  2  or  3 . 
     Sensors, for example Hall sensors fastened on the exterior of the housing, cooperate with the elements located in the base jaws  2  and  3 . To this end a lateral face  39  of the housing  1  has a longitudinal groove  40 , which is provided parallel with the axis of displacement of the base jaws  2  and  3  and on their level. Sensors, for example Hall sensors, can be inserted into this longitudinal groove  40  and fixed in place in any arbitrary position. 
     A second exemplary embodiment of the present invention is represented in FIGS. 5 and 6, wherein this gripper device can be equipped with a total of three base jaws (FIG.  4 ). To this end the gripper housing  41  has three receiving bores  42 , into which the base jaws can be inserted. Here, too, sealing elements can be inserted into corresponding circumferential grooves (corresponding to FIG.  2 ), which cause sealing as well as the stripping off of dirt from the surfaces of the base jaws. In this exemplary embodiment the protection against torsion is also obtained by means of a groove-spline connection, wherein a leg  44 ,  45 , or  46  of a feather key  47  respectively engages the longitudinal grooves  27  of the base jaws. This feather key  47  is also formed on a housing cover  48 , essentially embodied in a star-shape, and engages a housing opening  49  of the gripper housing  1 . Sealing of the housing cover  48  against the interior housing chamber  24  takes place by means of a seal inserted between the housing cover  48  and a recess  50 . Following the insertion of the feather key  47  into the corresponding longitudinal grooves  27  of the base jaws, the housing cover  48  is screwed on the top  30  of the gripper housing  41 . The feather key  47  is floatingly seated prior to tightening the screws, which is used for compensating the tolerances. 
     The gripper housing  41  is also provided with longitudinal grooves  40  on the lateral surface  39 , into which sensors, by means of which the position of the gripper jaws can be scanned, can be inserted and fixed in place.