Abstract:
The invention concerns an underpressure valve with a multi-part housing and a disc-like closing body which has at least one opening, and with an opening-free section disposed in alignment with the flow channel of the housing.

Description:
This application claims Paris Convention priority of DE 102 16 220.4 filed Apr. 08, 2002 the complete disclosure of which is hereby incorporated by reference. 
   BACKGROUND OF THE INVENTION 
   The invention concerns an underpressure valve comprising a multi-part housing and a disc-like closing body. 
   DE 198 14 262 A1 discloses a valve for underpressure handling or clamping means which comprises a multi-part housing and a plunger disposed inside the housing for displacement in a longitudinal direction. One end of the plunger comprises a valve body which closes the valve to prevent any leaking flow when no object is being suctioned. Although this valve minimizes any leaking flow, the design of the valve is relatively demanding and therefore expensive. 
   It is the underlying object of the invention to provide an underpressure valve of simple construction which nevertheless has small leaking air flow. 
   SUMMARY OF THE INVENTION 
   This object is achieved in accordance with the invention with a valve of the above-mentioned type in that the, preferably, disc-like closing body has at least one opening and one opening-free section of the closing body is disposed in alignment with the housing flow channel. 
   In the inventive underpressure valve, the closing body is formed, in particular, by a disc-like element which has at least one opening for the passage of air. An opening-free section of the closing body is located in alignment with the flow channel so that this opening-free section will be suctioned towards the flow channel above a certain flow velocity, thereby sealing the channel. The principle is known e.g. from return valves wherein a ball is suctioned into a conical end of a flow channel and seals off the flow channel at that location. The opening-free section may be disc-shaped, ball-shaped, or spherical. 
   The use of a disc-like closing body has the substantial advantage that the production of the disc-like closing body is simpler and therefore less expensive than of a ball, since the closing body can be produced e.g. using a punching method. 
   In a further development, the housing consists of two parts and the closing body is disposed between the two housing parts. This substantially facilitates mounting of the underpressure valve since the closing body must merely be disposed between the two housing parts. 
   Mounting is thereby advantageously effected by clamping the edge of the closing body between the two housing parts thereby fixing the position of the closing body. Large forces may act on the closing body without displacing same inside the housing. This ensures that the opening-free section of the closing body is always aligned with the flow channel so that the channel may be closed. 
   The first housing part is preferably screwed at least partially into the second housing part. The screw connection provides a secure joining of the two housing parts, wherein the first housing part can be easily released from the second housing part e.g. for maintenance or repair. 
   In a further development, the first housing part is substantially pot-shaped and engages with its free edge in a pot-shaped receiving opening of the second housing part thereby forming a receiving space inside the housing for accepting the closing body. 
   The free edge of the first housing part is thereby supported on the closing body and fixes same within the housing. For mounting, the closing body is merely loosely disposed into the receiving opening of the second housing part, wherein the first housing part effects fixing. 
   The pot-shaped receiving opening preferably has a central depression which is disposed directly in alignment with the opening-free section of the closing body. The at least one opening of the closing body communicates with an axial extension of the depression so that the air can flow via the opening into the depression. 
   The depth of the depression can be advantageously varied. This is effected e.g. through insertion of suitable spacers or similar elements. The depth of the depression adjusts the response behavior of the underpressure valve, in particular the point in time at which closing and opening occurs. 
   The closing body is preferably formed by an edge and an opening-free section which is located within the edge, wherein the opening-free section is connected to the edge via at least two, in particular, three bridges. The air flows through the openings from one housing part to the other and bypasses the opening-free section required for closing the valve. The bridges separating the openings thereby form elastic holding means for the opening-free section so that its position within the valve can be changed. The bridges are thereby uniformly distributed about the periphery and extend in a radial direction. 
   The closing body is preferably formed by an elastomeric disc which is sufficiently flexible to move from a resting position into a deflected position in which it closes the valve. It also has optimum sealing properties when it abuts the flow channel. 
   Each housing part has an element for connection to an underpressure supply, a vacuum connection, an underpressure guide element or suctioning elements. 
   In one embodiment, several first and several second housing parts are combined into a first and a second surface gripping part thereby forming grippers for gripping large-surface objects, in particular having irregular contours. The production of such surface grippers is relatively simple since the individual surface gripping parts must merely be interconnected, with the closing body mat being fixed between them. The surface gripper parts or at least their active elements may be made from plastic material. 
   Further advantages, features and details of the invention can be extracted from the following detailed description of a particularly advantageous embodiment with reference to the drawings. The features shown in the drawing and mentioned in the description and in the claims may be essential for the invention either individually or collectively in arbitrary combination. 

   
     BRIEF DESCRIPTION OF THE DRAWING 
       FIG. 1  shows a longitudinal section through an underpressure valve comprising a closing body in the rest position; 
       FIG. 2  shows a longitudinal section through the valve in accordance with  FIG. 1  with a valve body disposed in the working position; and 
       FIG. 3  shows a perspective explosive view of the valve. 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENT 
     FIG. 1  shows an underpressure valve designated in its totality with  10  with a first housing part  12  and a second housing part  14  and an intermediate closing body  16 . Both housing parts  12  and  14  have elements  18  and  20  for connection to an underpressure supply or vacuum connection. The first housing part  12  is pot-shaped and has an external thread  22  around its outer periphery, wherein the free edge  24  has a bead  26  projecting at the end face. A flow channel  30 , which widens in the region of the free pot-shaped end, is located in the axis  28  of the first housing part  12 . 
   The second housing part  14  is also pot-shaped and has an inner thread  24  at its inner pot wall  32  into which the outer thread  22  of the first housing part  12  is screwed. The free edge  36  of the second housing part  14  abuts a shoulder  38  of the first housing part  12  which limits the screwing depth. The second housing part  14  is also penetrated by an axial flow channel  40  which merges into a central depression  42  in the region of the pot. 
   The central depression  42  is opposite to the closing body  16  which is inserted in the pot of the second housing part  14 . The closing body  16  (shown in more detail in  FIG. 3 ) is thereby non-displaceably held at its edge  44  by the free edge  24  of the first housing part  12 . The bead  26  thereby penetrates into the edge  44  of the closing body  16 . An opening-free section  46  is opposite the two flow channels  30  and  40  and has the shape of a circular disc (FIG.  3 ). A total of three openings  48  are disposed between the edge  44  and the opening-free section  46  which provide passage for air flow from the flow channel  30  to the flow channel  40 . The openings  48  are thereby located in alignment with the central depression  42 . 
   If the flow channel  40  is connected to an underpressure source and the flow channel  30  is connected to the surroundings, a relatively large amount of air is suctioned. A high flow velocity is produced within the depression  42  due to the small flow cross-section (small depth T). Due to the underpressure in the depression  42  produced by the high flow velocity, the opening-free section  46  of the closing body  16  is drawn against the free end of the flow channel  40  (FIG.  2 ). The edge  50  of the flow channel  40  is thereby tightly sealed by the closing body  16  so that air is no longer suctioned from the flow channel  30 . The closing body  16  is thereby held at the edge  44  and the opening-free section  46  abuts the edge  50  of the flow channel  40  due to the deformation of the bridges  52 . The constant suctioning of air produces an underpressure in the flow channel  40  which keeps the section  46  continuously pressed against the edge  44 . 
   The depth T of the central depression sets the response behavior of the underpressure valve  10 , in particular the flow volume at which the valve closes. The larger the depth T, the larger the flow volume needed to close the valve. Adjustment of the response behavior can also be produced through changing the diameter of the depression  42 . 
   In a preferred fashion, a bypass can be provided which connects the depression  42  with the flow channel  40  and through which air also flows when the valve is closed, i.e. when the opening-free section  46  abuts the edge  50 . Advantageously, the cross-section of this bypass can be set so that the leaking air flow there can be set to a desired value.