Abstract:
A vacuum gripping device comprising a plurality of suction bodies, each comprising a suction chamber for applying to a workpiece to be gripped, a suction valve is associated with each suction point, wherein each suction valve comprises a vacuum supply side for connection to a vacuum supply device and a suction side connected to the suction chamber of the assigned suction body, wherein the suction valve comprises a valve body, moveable between an open position and a closed position, wherein the valve body is arranged on a flexible control membrane which delimits a control chamber; in such a way that the valve body is moveable from the open position into the closed position using deformation of the control membrane, and wherein a membrane cloth extending across multiple or all suction points is arranged in the gripper housing.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The present application is a National Phase of International Patent Application No. PCT/EP2014/069706, filed on Sep. 16, 2014, which claims priority to and all the benefits of German Patent Application No. 10 2013 222 377.3, filed on Nov. 4, 2013, both of which are hereby expressly incorporated herein by reference in their entirety. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention relates to a vacuum gripping device, in particular a surface vacuum gripper. 
     2. Description of the Related Art 
     Vacuum gripping devices are usually equipped with a plurality of suction bodies disposed adjacent to one another at suction points of a working surface of a gripper housing. The suction bodies are each designed to apply a suction to a workpiece that is to be gripped. With vacuum gripping devices of this type, a suction valve is allocated to each suction element. A vacuum gripping device having features of this type is described in DE 690 08 874 T2. 
     Those suction valves, in particular, which close automatically when the suction point is unoccupied, and thus prevent an undesired leakage from the suction side of the valve to the vacuum supply side, are suited for this. A valve of this type is disclosed, for example, in DE 198 14 262 C2. This valve has a valve body, which is disposed on a flexible, wall-like section that delimits a control chamber of the valve. The control chamber is connected to the vacuum supply side. The pressure of the suction side of the valve bears on the other side of the wall-like section. The control chamber, however, is closed off from the suction side, in terms of flow, by the wall-like section. When the control chamber is compressed, the flexible section is deformed, such that the valve body is moved to its closed position. If a suction occurs in the unoccupied state of the suction side, then no appreciable vacuum is obtained at the suction side. As a result, the control chamber is compromised, due to the static pressure difference between the control chamber and the suction side, and thus the valve body is brought into its closed position. The valve thus closes automatically when the suction side is unoccupied. Such valves have a complex structure and must be adjusted to the properties of the suction device that is to be controlled pertaining to flow technology, in particular in order to adjust the response sensitivity of the automatic closing. The integration of such valves in a vacuum gripping device is thus associated with structural challenges. 
     Other types of vacuum gripping devices are described in U.S. Pat. Nos 8,070,156 B2, 5,374,021 A, FR 2 561 221 A1 and WO 83/04384 A1. These, however, do not have any suction bodies allocated to the suction points. Instead, these vacuum gripping devices have a flat terminal suction plate that is to be placed on the workpiece that is to be gripped. 
     SUMMARY OF THE INVENTION 
     The invention addresses the object of providing a vacuum gripping device having integrated suction valves for the suction elements, wherein the suction valves can be adjusted to the individual suction elements during the manufacture thereof, and wherein a reliable and economical production and assembly thereof is enabled. 
     This object is achieved by a vacuum gripping device, having a plurality of suction bodies, which are disposed at suction points of a working surface of a gripper housing. Each suction point is allocated one suction valve integrated in the gripper housing thereby. Each suction valve has a vacuum supply side having a suction connection for connecting to a vacuum supply device, and a suction side connected to the suction chamber of the suction body allocated thereto. The suction side of the actual valve can have a suction opening that communicates with the suction chamber. Each suction valve has a valve body that can move between an open position and a closed position, wherein the flow connection between the suction side and the vacuum supply side is interrupted when in the closed position, and a suctioning from the suction side through the suction valve to the vacuum supply side is enabled when in the open position. The valve body is disposed on a flexible control membrane, which delimits a control chamber in the gripper housing. As a result, the valve body can move from the open position to the closed position, depending on a vacuum that can be obtained in the control chamber by deforming the flexible control membrane. The control membranes of most or all of the suction valves are formed by control sections of a membrane sheet, which extends in the gripper housing over most or all of the suction points. 
     The valve bodies for the various suction valves are disposed at the control sections of the membrane sheet. Because the membrane sheet extends over numerous suction points, and provides the control membranes for the respective suction valves, it can be installed in a convenient manner and integrated in the gripper housing for the function of a substantial portion of the assembly. The response behavior of the suction valve is affected by, among other things, the properties of the control membrane, in particular by its tensioning and flexibility. The use of a shared membrane sheet thus makes it possible to provide, as needed, numerous suction valves having the desired properties; in particular, it is possible to provide a large number of identical suction valves in the vacuum gripping device. 
     In order to simplify the assembly, the gripper housing can have a multi-part construction, and in particular, can comprise a housing upper part, and a housing lower part having the working surface. The membrane sheet can then be disposed between the housing upper part and the housing lower part, and in particular, it can be clamped between the housing upper part and the housing lower part during the assembly. 
     A valve accommodating chamber is formed in the gripper housing, in particular for each suction point, which chamber extends away from the working surface along a valve longitudinal direction. The membrane sheet stretches across the valve accommodating chamber thereby. The section of the membrane sheet passing through the valve accommodating chamber forms the control section and thus the control membrane for the respective valve. Preferably, the membrane sheet extends parallel to the working surface. The membrane sheet is preferably secured in the valve accommodating chamber along an edge encompassing the control section. The valve accommodating chamber is preferably a cylindrical opening in a housing section spaced apart from the working surface, e.g. the aforementioned housing upper part. The valve bodies are preferably designed such that they each extend into the valve accommodating chamber. When the membrane sheet is clamped between the housing upper part and the housing lower part, then the control chambers of the suction valves delimited by the control membranes each extend into the housing upper part. 
     In order to adjust the switching properties of the valve, the membrane sheet is attached, in particular in a tensioned manner, in the valve accommodating chamber, such that the valve body is tensioned in the open position against a movement toward the closed position. For this, the valve body is disposed at the respective control section, in particular at a spacing to the encompassing edge, preferably in the center thereof. 
     The valve bodies of the various suction valves can be designed as an integral part of the respective control sections of the membrane sheet, thus enabling a simple production of this essential component of the suction valve. 
     The membrane sheet can have a different thickness and/or different flexibility in at least two different suction points, in order to design the response sensitivity and closing time of various suction valves differently. As such, the suction valve of a suction element at the edge of the vacuum gripping device can be set differently than the suction valve for the central suction element. 
     The suction bodies at the various suction points are preferably each disposed flush with the allocated valve bodies on the working surface. The suction bodies can be movably coupled thereby to the allocated control sections and/or the allocated valve bodies of the respective activating suction valve (e.g. mechanically connected), such that when the valve body moves from the open position to the closed position, the respective suction body is moved from an advanced suction position to a retracted passive position. If the allocated suction valve switches to the closed position, then the respective suction body is retracted to its passive position. As a result, it is possible to prevent such suction elements that bear on a workpiece that is to be gripped at the edges thereof, such that they are not entirely resting thereon in a sealed manner, from pushing the gripped workpiece away from the working surface of the vacuum gripping device, against the suction of the other suction elements, due to their elasticity. 
     The suction valves are preferably valves of the type that close automatically, when drawing freely with an unoccupied suction side, in order to avoid undesired leakage. This can be implemented in a variety of ways with suction valves of the type described. 
     By way of example, the valve body can have a sealing section, which closes a suction passage when in the closed position, which passage connects the control chamber to the vacuum supply side of the respective suction valve, and in the open position, leaves the suction passage open. This valve body has a suction side passage having a choke point, which establishes a flow connection of the suction side to the control chamber when the valve is in the open position. In the open position, the vacuum provided by the vacuum supply is thus present in the respective control chamber, and this vacuum acts on a compression of the control chamber. Air suctioned from the suction side flows through the suction side passage into the control chamber, wherein this flow is limited by the choke point. If the suction side is unoccupied, then the comparatively large flow over the choke point leads to a pressure difference and thus to a pressure deficit in the control chamber in relation to the suction side. If this pressure difference reaches a predetermined, or pre-determinable value, then this difference leads to a compression of the control chamber by a deformation of the respective control membrane, and thus to a movement of the valve piston into its closed position. The sealing section bearing on an allocated seal seat then closes the suction passage. Due to the vacuum present at the vacuum supply side, the sealing section is retained in the closed position and the valve remains closed. 
     A suction valve that closes automatically can also be realized in that the valve body has a suction side passage having a choke point for establishing a flow connection of the control chamber to the suction side, and furthermore has a sealing section, which bears against a seal seat allocated thereto, when in the closed position, wherein the sealing section and the seal seat are disposed such that, when in the closed position, the flow connection is already closed in a sealed manner, starting from the suction side, through the suction side passage. The control chamber is connected here, in particular constantly (both in the open position as well as in the closed position), to the vacuum supply side. The seal seat and the sealing section are preferably disposed outside the control chamber. As a result, the volume of the control chamber can be kept small, which leads to short response times of the valve. In the open position, the air suctioned in at the suction side flows through the suction side passage into the control chamber. If the suction side is unoccupied, the large flow results in a pressure difference, via the flow resistance of the choke point, and thus to a pressure deficit in the control chamber in relation to the suction side, wherein the valve piston is guided into its closed position, by deforming the control membrane to reduce the volume of the control chamber occurs. In this closed position, the sealing section bears on the allocated seal seat, and is suctioned securely thereto. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Other advantages of the invention will be readily appreciated as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings, wherein: 
         FIG. 1  is a sectional view of a surface vacuum gripper according to the invention; 
         FIG. 2  is an enlarged sectional view of one of the valves of the surface vacuum gripper illustrated in  FIG. 1  shown in the open position. 
         FIG. 3  is an enlarged sectional view of one of the valves of the surface vacuum gripper illustrated in  FIG. 1  shown in the closed position. 
         FIG. 4  is a sectional view of another embodiment of a surface vacuum gripper according to the invention. 
         FIG. 5  is an enlarged sectional view of one of the valves of the surface vacuum gripper illustrated in  FIG. 4  shown in the open position. 
         FIG. 6  is an enlarged sectional view of one of the valves of the surface vacuum gripper illustrated in  FIG. 4  shown in the closed position. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The same reference symbols are used for identical features, or features corresponding to one another in the following description as well as in the Figures. 
       FIG. 1  shows a section of a surface vacuum gripper  10 , in a sectional view. The surface vacuum gripper has a gripper housing  12 , having a multi-part construction, and having a housing upper part  14  and a housing lower part  16 . The housing lower part  16  has a (planar, for example) working surface  18 , which faces a workpiece that extends in a planar manner, for example, for the handling thereof. Numerous suction bodies  20  are disposed on the working surface  18 , which extend over the working surface  18  such that they can be brought to bear on a workpiece that is to be gripped. Each suction body  20  delimits a suction chamber  22 , which is open in a suctioning direction, and bears against a workpiece in a sealed manner in order to adhere thereto by suction. 
     Vacuum supply channels  24  are formed in the gripper housing  12 , in this case, concretely, in the housing upper part  14 , which are connected to a vacuum supply device, through which air or some other fluid can be evacuated from the vacuum supply channels  24 . 
     The suction bodies  20  each define suction points  26   a  to  26   e  of the surface vacuum gripper  10 . One suction valve  30 , integrated in the gripper housing  12 , is allocated to each suction point  26   a  to  26   e , wherein, in the exemplary depiction in  FIG. 1 , the construction of the numerous suction valves  30  is identical. Each suction valve  30  has one vacuum supply side  32  having one suction connection, which is connected to the vacuum supply channels  24 . On the other hand, each suction valve  30  has a suction side  34  connected to the suction chamber  22  of the respective suction point  26   a  to  26   e , having a suction opening that is open toward the suction chamber  22 . 
     Each suction valve comprises a valve accommodating chamber  35 , extending along a valve longitudinal direction, away from the working surface  18 , in which, in each case, a valve body  36  can be displaced along the valve longitudinal direction. The valve body  36  can be displaced between a closed position and an open position (which is depicted in  FIG. 1 ). When in the closed position, the valve body closes the flow connection between the suction side  34  and the vacuum supply side  32  of the respective suction valve  30 . In the open position, the flow connection is opened, such that air can be suctioned from the suction side  34  through the respective suction valve  30  to the vacuum supply side  32 . 
     The movement of the valve body  36  between the open position and the closed position is controlled thereby by the pressure in a control chamber  38 . The control chamber  38  is delimited in the gripper housing  12  for each suction valve  30  by a control membrane  40 , which stretches across the respective valve accommodating chamber  35 . 
     The valve body  36  is disposed thereby on the control membrane  40 , such that, with the movement of the valve body  36  from the open position shown in  FIG. 1  into the closed position, the control membrane  40  is deformed (more precisely: it is caused to bulge toward the vacuum supply side  32 ), and as a result, the volume of the control chamber  38  is reduced. The valve piston  36  is thus moved into its closed position when there is a pressure deficit in the control chamber  38  in relation to the pressure prevailing on the other side of the control membrane  40 . 
     The control membranes  40  of the suction valves  30  at the suction points  26   a  to  26   e  are formed by the membrane sheet  42  extending over the suction points  26   a  to  26   e  disposed in the gripper housing  12 . The control membranes  40  are each formed by control sections of the membrane sheet  42 . The membrane sheet  42  is clamped, in particular, between the housing upper part  14  and the housing lower part  16 , such that it extends substantially parallel to the working surface  18 , in each case through the valve accommodating chambers  35  of the suction valves  30 . The membrane sheet  42  delimits, in each case, the control chamber  38  of the respective suction valve  30  thereby, with its respective control section  44  in the housing upper part  14 . Preferably, the membrane sheet  42  is secured thereby, in each case, in the valve accommodating chamber  35  along an encompassing edge  46 . 
     A tensioning force for a movement of the valve body  36  from its open position to the closed position can thus be defined by the tension of the membrane sheet  42 , and in particular the tension of the respective control section  44  within the encompassing edge  46 . 
     The suction valves  30  depicted in  FIG. 1  are designed such that they switch to the closed position when suctioning freely with unoccupied suction points  26   a  to  26   e . In  FIG. 1 , the control chamber  38  of each suction valve  30  is connected to the vacuum supply side  32  and thus to the vacuum supply channels  24  via a suction passage  48 . The valve bodies  36  each have a sealing section  50 . This sealing section is disposed in the control chamber  38 , and is designed such that the sealing section  50  covers the suction passage  48  when in the closed position, such that there is no flow connection from the vacuum supply side  32  to the respective control chamber  38 . 
     The valve body  36  has, furthermore, a suction side passage  52  having a choke point  54 . The suction side passage  52  opens into the control chamber  38  on one hand, and, at the suction side  54 , via the choke point, on the other hand. In this respect, the suction side passage  52  establishes a connection from the control chamber  38  through the control membrane  40  to the suction side  34 . Due to the choke point  54 , the flow from the suction side  34  into the control chamber  38  is limited. A flow resistance is provided by the choke point  54  for the flow through the suction side passage  52 . If the suction point  26   a  to  26   e  for one of the suction valves  30  is unoccupied (free suctioning), due to the relatively large flow via the choke point  54 , then there is a pressure deficit in the control chamber  38 , suctioned off by the suction passage  48 , in relation to the suction side  34 . As a result, the valve body  36  is moved into its closed position against a tension force applied by the control membrane  40 . The sealing section  50  ends up in a sealing bearing against the suction passage  48 , and is securely suctioned thereto. 
     If the respective suction point  26   a  to  26   e  is occupied, however, by a workpiece, not shown in  FIG. 1 , then the suction chamber  22  of the respective suction element  20  is evacuated, and no appreciable flow can occur via the choke point  54 , and thus, no sufficient vacuum can be built up in the control chamber  38 . The valve body  36  then remains in its open position, as depicted in  FIG. 1 . 
     In order to assemble the surface vacuum gripper  10 , the valve bodies  36  can be attached to the respective control sections  44  of the membrane sheet  42 . By way of example, the valve bodies can extend through the membrane sheet  42  and be bonded thereto with an adhesive. An integral design of the valve bodies and membrane sheet is also possible. The unit comprising a membrane sheet  42  and valve bodies  36  can then be placed in the housing upper part  14 , for example, such that the valve bodies  36  engage in the valve accommodating chambers  35  at their sealing sections  50 . The housing lower part  16  can be placed thereon, such that the membrane sheet  42  is clamped between the housing upper part  14  and the housing lower part  16 . 
     The surface vacuum gripper  60  depicted in  FIG. 2  differs from the surface vacuum gripper  10  substantially with regard to the design for the suction valve  30 . Concerning the rest, reference is made to the description above. 
     The membrane sheet  42  is clamped in the surface vacuum gripper  60  between the housing upper part  14  and the housing lower part  16  of the gripper housing  12 . A valve body  36  is disposed, in each case, on the control sections  44  of the membrane sheet  42 , which sections form, in each case, the control membrane  40  of a suction valve  30 , such that it can be displaced between an open position (depicted in  FIG. 2 ) and a closed position. With this surface vacuum gripper  60  as well, the membrane sheet  42  delimits a respective control chamber  38  in the housing upper part  14  having the respective control section  44 . With this surface vacuum gripper  60 , the control chamber  38  has a flow connection to the vacuum supply side  32 , which connection is independent of the position of the valve body  36 . 
     With this surface vacuum gripper  60 , the sealing section  50  is disposed outside the respective control chamber  38  at a guide section of the valve body  36  extending along a valve longitudinal direction, away from the control membrane  40 . In the depicted example, the sealing section  50  is formed by a flexible sealing material, in the manner of a coil-like section encompassing the valve body. The internal space of the housing lower part accommodating the valve body  36  has a radial projection that forms a seal seat  62  for the sealing section  50 . The sealing section  50  and the seal seat  62  are disposed such that, when in the closed position of the valve piston  36 , the sealing section  50  bears on the seal seat  62  and as a result, a flow connection from the suction side  34  to the suction side passage  52  is interrupted. In this regard, the interruption of the flow connection already occurs here outside the control chamber  38 , on the side of the control membrane  40  facing away from the control chamber  38 . The control chamber  38  can be created with comparatively smaller volumes than with the surface vacuum gripper  10  as a result, wherein, depending on the design, a short response time of the suction valve  30  can be obtained. 
     The design with the membrane sheet  42 , on which the valve bodies  36  are each disposed at the control sections  44 , also enables a reliable and simple assembly with the surface vacuum gripper  60 . By way of example, the membrane sheet  42  can be clamped between the housing upper part  14  and the housing lower part  16 , as explained in reference to  FIG. 1 . 
     The invention has been described in an illustrative manner. It is to be understood that the terminology which has been used is intended to be in the nature of words of description rather than of limitation. Many modifications and variations of the invention are possible in light of the above teachings. Therefore, within the scope of the appended claims, the invention may be practiced other than as specifically described.