Abstract:
A three piece vacuum cup is made from rubber to resist damage and facilitates reconfiguring when badly damaged or for specific applications. The vacuum cup includes top, center, and bottom parts. The top is easily and inexpensively replaceable. A flexible lip seal surrounds the top edge of the top to seal against irregular surfaces and damage to the lip seal may be addressed by inserting a cord seal into slots in the top to form a second seal. Part of the top may be cut away to use with small parts and sealed using the cord seal. The center includes a family of passages which may be selectively blocked to permit use of partial tops. A bar pattern on the top has bars aligned in perpendicular directions to better hold material in all cutting directions.

Description:
The present application is a Continuation in Part of U.S. patent application Ser. No. 11/484,041 filed Jul. 10, 2006, which application is incorporated in its entirety herein by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     The present invention relates to vacuum hold downs and in particular to vacuum cups for CNC machines. 
     Various machines exist for performing operations on various types of materials. Vacuum is often used to hold the material in place while the operations are performed. Examples of such machines are Biesse machines made for boring and routing of engineered (for example, particle board) and solid wood, composited, plastics, and soft metals (for example, aluminum). These, and other machines, often utilize vacuum pods or cups which may be positioned for a particular work piece or operation. The cups may interface with the machine in various manners, and are generally approximately square and approximately six inches across, although the size and shape may vary. 
     Known cups are made from a phenolic material. Phenolic material is generally a plastic-like resin which is both hard and strong. Phenolic material is commonly used as a wood worked surface, for example, as an insert for router tables, because cutters can cut into the phenolic material without damaging the cutter. Vacuum cups generally have narrow edges outlining the perimeter of a top surface of the cups for providing a vacuum seal, and cups made from the phenolic material are easily damaged when a cutter meets the narrow edges or when material is loaded onto the machine. The edges may be cracked, or a portion of the edge may break away. Unfortunately, even a small crack or chip is likely to spoil the cup&#39;s ability to maintain vacuum and prevent further use. The Phenolic (or similar hard material) also requires a gasket to form a vacuum seal and material may slip on the hard surface. Such gaskets are often expensive and may easily be damaged. 
     U.S. patent application Ser. No. 11/484,041 for “VACUUM HOLD DOWN” discloses a rubber vacuum cup with many advantages over known cups made from phenolic material. However, the vacuum cups disclosed in the &#39;041 application are not suitable for all CNC machines, and a need remains for new vacuum cups for additional CNC machines. 
     BRIEF SUMMARY OF THE INVENTION 
     The present invention addresses the above and other needs by providing a three piece vacuum cup which is made from rubber to resist damage and facilitates reconfiguring when badly damaged or for specific applications. The vacuum cup includes top, center, and bottom parts. The top is easily and inexpensively replaceable. A flexible lip seal surrounds the top edge of the top to seal against irregular surfaces and damage to the lip seal may be addressed by inserting a cord seal into slots in the top to form a second seal. Part of the top may be cut away to use with small parts and sealed using the cord seal. The center includes a family of passages which may be selectively blocked to permit use of partial tops. A bar pattern on the top has bars aligned in perpendicular directions to better hold material in all cutting directions. 
     In accordance with one aspect of the invention, there is provided a vacuum cup comprising a substantially solid rubber body having a bottom surface, a top surface, and sides. A vacuum area is formed on the top surface and a vacuum passage passes between the bottom surface and the vacuum area. A raised edge resides around the top surface of the body for forming a seal with a work piece. Mounting features reside on the bottom surface for mounting the vacuum cup on a machine. 
     In accordance with another aspect of the invention, there is provided a three piece vacuum cup having a top rubber body, and center portion, and a bottom rubber body. The top rubber body includes a sealing lip around the top edge forming a first seal and recessed channels in a top surface of the top rubber body which receive a sealing cord to form a second redundant seal. If the sealing lip is damages, or if a portion of the top rubber body is cut away, the vacuum cup is still functional using the second seal. 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING 
       The above and other aspects, features and advantages of the present invention will be more apparent from the following more particular description thereof, presented in conjunction with the following drawings wherein: 
         FIG. 1A  is a top perspective view of a first embodiment of a vacuum cup according to the present invention. 
         FIG. 1B  is a bottom perspective view of the first embodiment of the vacuum cup according to the present invention. 
         FIG. 2  is a bottom perspective view of a second embodiment of the vacuum cup according to the present invention. 
         FIG. 3  is a bottom perspective view of a third embodiment of the vacuum cup according to the present invention. 
         FIG. 4A  is a top perspective view of a fourth embodiment of the vacuum cup according to the present invention. 
         FIG. 4B  is a bottom perspective view of the fourth embodiment of the vacuum cup according to the present invention. 
         FIG. 5A  is a top view of the second embodiment of the vacuum cup. 
         FIG. 5B  is a bottom view of the second embodiment of the vacuum cup. 
         FIG. 5C  is an end view of the second embodiment of the vacuum cup. 
         FIG. 6A  is a cross-sectional view of the second embodiment of the vacuum cup taken along line  6 A- 6 A of  FIG. 5A . 
         FIG. 6B  is a cross-sectional view of the second embodiment of the vacuum cup taken along line  6 B- 6 B of  FIG. 5A . 
         FIG. 7A  is a top perspective view of a fifth embodiment of the vacuum cup according to the present invention. 
         FIG. 7B  is a bottom perspective view of the fifth embodiment of the vacuum cup according to the present invention. 
         FIG. 8  is a cross-sectional view of the fifth embodiment of the vacuum cup taken along line  8 - 8  of  FIG. 7A . 
         FIG. 9  is an insert molded into a vacuum cup to reduce or prevent bending which may cause vacuum leaks. 
         FIG. 10  is a top perspective view of a three piece vacuum cup assembly according to the present invention. 
         FIG. 11A  is a side view of the three piece vacuum cup assembly according to the present invention. 
         FIG. 11B  is an end view of the three piece vacuum cup assembly according to the present invention. 
         FIG. 11C  is a top view of the three piece vacuum cup assembly according to the present invention. 
         FIG. 12  is a top perspective view of a top rubber body assembly according to the present invention. 
         FIG. 13A  is a side view of the top rubber body according to the present invention. 
         FIG. 13B  is a top view of the top rubber body according to the present invention. 
         FIG. 13C  is a bottom view of the top rubber body according to the present invention. 
         FIG. 14  is a cross-sectional view of the top rubber body according to the present invention taken along line  14 - 14  of  FIG. 13B . 
         FIG. 15A  is a cross-sectional view of detail  15 A of the  FIG. 14  of a top sealing lip of the top rubber body according to the present invention. 
         FIG. 15B  is a cross-sectional view of detail  15 B of the  FIG. 14  of a groove pattern on a bottom surface of the top rubber body according to the present invention. 
         FIG. 16A  is a top perspective view of a half size top rubber body assembly according to the present invention. 
         FIG. 16B  is a bottom view of the half size top rubber body according to the present invention. 
         FIG. 17A  is a side view of a center portion of the three piece vacuum cup assembly according to the present invention. 
         FIG. 17B  is an end view of the center portion of the three piece vacuum cup assembly according to the present invention. 
         FIG. 18  is a cross-sectional view of the center portion of the three piece vacuum cup assembly according to the present invention taken along line  18 - 18  of  FIG. 17A . 
         FIG. 19  is a cross-sectional view of the center portion of the three piece vacuum cup assembly according to the present invention taken along line  19 - 19  of  FIG. 17B . 
         FIG. 20  shows a plug according to the present invention for blocking individual vertical passages in the center portion. 
         FIG. 21A  shows a side view of the bottom rubber body according to the present invention. 
         FIG. 21B  shows a top view of the bottom rubber body according to the present invention. 
         FIG. 21C  shows a bottom view of the bottom rubber body according to the present invention. 
     
    
    
     Corresponding reference characters indicate corresponding components throughout the several views of the drawings. 
     DETAILED DESCRIPTION OF THE INVENTION 
     The following description is of the best mode presently contemplated for carrying out the invention. This description is not to be taken in a limiting sense, but is made merely for the purpose of describing one or more preferred embodiments of the invention. The scope of the invention should be determined with reference to the claims. 
     A top perspective view of a first embodiment of a vacuum cup  10   a  according to the present invention is shown in  FIG. 1A , and a bottom perspective view of the first embodiment of the vacuum cup  10   a  is shown in  FIG. 1B . The top of the vacuum cup  10   a  includes a raised edge  12  for sealing with a work piece supported and held by the vacuum cup  10   a , and work piece supports  14  for supporting the work piece. The work piece supports  14  preferably comprise a group of parallel bars and reside on support bases  16 . A vacuum passage  18  passes through the vacuum cup  10   a  and connects to a vacuum source. The interior of the raised edge  12  defines a vacuum area for creating a hold down force for holding the work piece. 
     The bottom of the vacuum cup  10   a  includes a machine interface  20  for cooperating with known CNC machines, for example a Biesse Rover  22  CNC Machining Center or a Biesse Rover  24  CNC Machining Center. The machine interface  20  is a cylindrical protrusion and includes indexing features (or fingers)  22  for cooperation with indexing grooves in CNC machines, and centering pads  24  for cooperation with a corresponding opening in the CNC machines. The vacuum passage  18  is shown extending through the bottom of the vacuum cup  10   a , and is partially blocked to provide a stop of a known check valve commonly used with vacuum cups. 
     Known vacuum cups are manufactured from a phenolic material. Phenolic material is generally a plastic-like resin which is both hard and strong. Unfortunately, such known cups break easily and must be replaced frequently. If a replacement is not available when needed, an expensive machine may be sit idle until a new part is obtained. The vacuum cup  10   a  according to the present invention is molded from substantially solid rubber and is much less susceptible to breaking. The vacuum cup according to the present invention is approximately one inch thick and preferably has a Shore hardness of approximately 80 Shore A. An example of a suitable material is compound number EXP7654-80B provided by R&amp;S Processing in Paramount, Calif. Compound Number EXP7654-80B is a natural rubber and is non-blooming. Blooming refers to a tendency of some compounds to give off a powder like material. Such powder reduced friction and would reduce the holding power of the vacuum cups. The compound is crosshatched during molding to equalize shrinkage across the part. Such crosshatching is important to maintain close dimensional tolerances. 
     Because the material used by the present invention is not stiff like the phenolic material used in known vacuum cups, the vacuum cups  10   a  may flex when vacuum is applied. Such flexing often affects the seal between the material and the vacuum cup. As a result, a vacuum cup according to the present invention often requires additional support structure to prevent flexing. In the instance of the cup  10   a , the additional support structure is a support ring  21  added to the bottom of the cup. Such support ring  21  rests against a solid surface and thereby provides a support structure. 
     A bottom perspective view of a second embodiment of the vacuum cup  10   b  according to the present invention is shown in  FIG. 2 , and a bottom perspective view of a third embodiment of the vacuum cup  10   c  according to the present invention is shown in  FIG. 3 . The vacuum cups  10   b  and  10   c  include alignment features  26   a  and  26   b  respectively. The alignment features  26   a  and  26   b  are preferably rounded or a bullnose shape. The alignment features  26   a  and  26   b  are suitable for use with known CNC machines, and are configured to cooperate with grooves in a flat table machine to position the vacuum cup on the flat table machine. 
     A top perspective view of a fourth embodiment of the vacuum cup  10   d  according to the present invention is shown in  FIG. 4A , and a bottom perspective view of the fourth embodiment of the vacuum cup  10   d  is shown in  FIG. 4B . The vacuum cup  10   d  is similar to the vacuum cups  10   a ,  10   b , and  10   c , but includes side pads  28  along one edge of the vacuum cup bottom to cooperate with support rails of a machine. Such cup is used on machines such as a Biesse Rover  20  machine. The vacuum cup  10   d  further includes four fastener passages  30  for securing the cup to the machine. 
     A top view of the second embodiment of the vacuum cup  10   b  is shown in  FIG. 5A , a bottom view of the second embodiment of the vacuum cup  10   b  is shown in  FIG. 5B , and an end view of the second embodiment of the vacuum cup  10   b  is shown in  FIG. 5C . A cross-sectional view of the second embodiment of the vacuum cup  10   b  taken along line  6 A- 6 A of  FIG. 5A  is shown in  FIG. 6A , and a cross-sectional view of the second embodiment of the vacuum cup  10   b  taken along line  6 B- 6 B of  FIG. 5A  is shown in  FIG. 6B . The raised edge  12  rises approximately 0.2 mm above the work piece supports  14 . 
     A top perspective view of a fifth embodiment of the vacuum cup  10   e  according to the present invention is shown in  FIG. 7A , a bottom perspective view of the fifth embodiment of the vacuum cup  10   e  is shown in  FIG. 7B , and a cross-sectional view of the fifth embodiment of the vacuum cup  10   e  taken along like  8 - 8  of  FIG. 7A  is shown in  FIG. 8 . The vacuum cup  10   e  is similar to the vacuum cups  10   a ,  10   b ,  10   c  and  10   d , but includes recesses  34 , a “V” shaped vacuum slot  19 , and a support structure comprises an insert  32 . The insert  32  is a plate embedding in the vacuum cup  10   e  and is preferably a nylon insert, and more preferably a Delrin® insert, and is preferably approximately ⅜ inches thick. The insert  32  is preferably etched to provide better adhesion of the rubber vacuum cup body to the insert  32 , and more preferably the insert  32  is etched using plasma surface modification. 
     An example of a suitable plasma surface modification of the insert  32  is performed using a 2051 Series Plasma System made by TriStar Plastics, Corp. In Brea, Calif. Plasma is a state-of-matter which is different from the other three states (solid, liquid, or gas). In a steady state condition, plasma is a quasineutral cloud which contains free electrons and ions. In a disassociated state, plasma consists of electrons, ions, unexcited molecules and free radicals. Plasma may be generated by turning non-reactive molecules into reactive molecules by introducing energy, such as an electrical charge. Extremely reactive plasmas may be created by using an electrical charge to break up safe inert gases, for example, freons. When freons are electrified, they produce large quantities of chlorine and fluorine, both highly reactive compounds. These are the compounds which contain the ions and free radicals which actually do the “etching”. In addition, the directionality and degree of reactivity can be controlled by the amount of applied power. The ability to control the directionality and degree of reactivity of the plasma etching process enables the engineer to “control the etch”, which makes dry etching (e.g., plasma etching) more controllable than wet etching. 
     Methods for selecting parameters for plasma etching are well known to those skilled in the art. For plasma etching of the insert  32 , the plasma pressure is preferably maintained between 0.05 Torr to 2.0 Torr, and more preferably between 0.250 Torr and 0.350 Torr. The RF power setting is preferably between 20 Watts to 2500 Watts, and more preferably between 800 Watts and 1,000 Watts. The RF generator frequency is variable, but is preferably approximately 13.56 MHZ. The gas species used in this invention may be any pure gas or gas mixture which would provide an oxidized surface. Commonly preferred gasses include oxygen (O2), nitrous (N2O), argon (Ar), helium (He), carbon dioxide (C2O), or any mixture there of. The duration of the treatment is variable based on polymer load (i.e., the quantity of polymer parts in the chamber to be treated) and surface area of the polymer load. Based on standard polymer load, and size of substrate the time is preferably between 2 to 45 min, and more preferably, the time is between 15 minutes to 25 minutes. Those skilled in the art would generally modify the time for their specific machine setup. 
     After a substrate has been treated using the above method, the surface is molecularly etched and chemically modified. This type of surface activation can be measured via goniometry (contact angle measurement) or dynes inks. The governing equation is Young&#39;s equation where:
 
 Ysv−Ysl=Ylv*Cos Θ 
 
where Ysv is the surface free energy of the solid in contact with vapor, Ysl is the surface free energy of the solid covered with liquid, Ylv is the surface free energy of the liquid-vapor, and interface Θ is the contact angle.
 
     Contact angles are measured in degrees. “Low” is below about 20° and “high” as 90° or above. Water on poly-tetrafluoroethylene PTFE is about 112°, very high. Low angles mean wettable. Surface energy (the terminology generally used for solids) and surface tension (the terminology generally used for fluids) are measured in dynes/cm. Water has a surface tension of 72.8 dynes/cm at room temperature. The surface energy of most solids falls between 15 and 100 dynes/cm. If the surface tension of the fluid is below the surface energy of the solid, the fluid will spread rather than staying in a little droplet. Polymer surfaces are often treated to improve this wettability by raising their surface energy. 
     A detailed top perspective view of the insert  32  is shown in  FIG. 9 . The insert  32  is preferably made or pre-drilled with passages  30   a  aligned with the fastener passages  30  and passages  18   a  aligned with the vacuum passages  18  in the vacuum cup to simplify molding the vacuum cup  10   e . The fastener passages  30   a  and the vacuum passages  18   a  are preferably over-sized to allow inside edges of the fastener passages  30   a  and the vacuum passages  18   a  to be embedded within the vacuum cup. The outside dimensions of the insert  32  are undersized compared to the vacuum cup to allow embedding of the insert  32  within the vacuum cup. Additional holes  18   b  (one of a multiplicity of holes  18   b  is labeled in  FIG. 9 ) are spaced apart on the insert  32  to allow molding material to flow through the insert  32  to prevent the vacuum cup from ballooning when vacuum is applied thereto. A second “V” shaped vacuum slot  19   a  may be provided in the insert  32 , for example, to distribute vacuum and several of the holes  18   b  may be aligned with the slot  19   a  to help distribute vacuum. 
     A top perspective view of a three piece vacuum cup assembly  40  according to the present invention is shown in  FIG. 10 , a side view of the three piece vacuum cup assembly  40  is shown in  FIG. 11A , an end view of the three piece vacuum cup assembly  40  is shown in  FIG. 11B , and a top view of the three piece vacuum cup assembly  40  is shown in  FIG. 11C . The three piece vacuum cup assembly  40  is assembled from a top rubber body  42 , and center portion  44  and a bottom rubber body  46 . The top rubber body  42  has a top surface  42   a  having a sealing lip  48  forming a closed perimeter around the top edge of the top rubber body  42  and providing a first seal, and a perimeter recessed channel  50  on the top surface  42   a  forming a closed path just inside the sealing lip  48  for receiving a sealing cord  51  (see  FIG. 15 ) to provide a redundant second seal. If the sealing lip  48  is cut or otherwise damaged to prevent forming the first seal, the sealing cord  51  may be inserted into the channels  50  to form the second seal. Additionally, at least one interior recessed channel  52  is formed on the top surface  42   a  and if part of the top rubber body  42  is cut away the sealing cord  51  may be inserted into a close path formed from part of the perimeter recessed channel  50  and at least one of the interior recessed channels  52  to form the second seal. A check valve  54  resides in the top rubber body controlling the communication of a vacuum signal to the top surface  42   a  and the top rubber body  42  may further include any of the features described for the single piece vacuum cups above. 
     The center portion  44  forms a spacer to separate the top rubber body  42  from the bottom rubber body  46 . The center portion  44  further provides structure (for example, vertical channels  60 , see  FIGS. 18 and 19 ) for control the communication of vacuum between the bottom and top rubber bodies  46  and  42 . A more detailed description of the center portion  44  follows. The bottom rubber body  46  mates to the center portion  44  and cooperates with a machine surface  47  for support and for communication to a source of vacuum. 
     A top perspective view of the top rubber body  42  according to the present invention is shown in  FIG. 12 , a side view of the top rubber body  42  is shown in  FIG. 13A , a top view of the top rubber body  42  is shown in  FIG. 13B , and a bottom view of the top rubber body  42  is shown in  FIG. 13C . If the sealing lip  48  is damaged, or if a large portion of the top rubber body  42  is accidentally cut away, a length of the sealing cord  51  (see  FIG. 15A ) may be inserted into a combination of the perimeter recessed channel  50  and/or the interior recessed channel  52  to form a new second seal to replace a seal formed by the sealing lip  48 . The sealing cord  51  may be round or oval or have a “D” cross-section and a length of the sealing cord  51  is inserted into the perimeter recessed channels  50  and/or the interior recessed channel  52  with ends of the sealing cord  51  butted together to form a closed path. A groove pattern  53  is formed in the bottom surface of the top rubber body  42 . The groove pattern  53  matches the top edge of the center portion  44  and cooperated with the top edge of the center portion  44  to fit the top rubber body  42  to the center portion  44 . A fixed vacuum passage  55  passes through the top rubber body  42  to communicate a vacuum signal to the top surface of the top rubber body  42 . 
     A cross-sectional view of the half size top rubber body  42 ′ taken along line  14 - 14  of  FIG. 13B  is shown in  FIG. 14 , a cross-sectional view of detail  15 A of the  FIG. 14  of the top sealing lip  48  of the half size top rubber body  42 ′ is shown in  FIG. 15A , and a cross-sectional view of detail  15 B of the  FIG. 14  showing the groove pattern  53  on the bottom surface of the top rubber body  42  is shown in  FIG. 15B . The sealing lip  48  reaches upward and outward from the rubber body  42  at an angle A 1 , and preferably at an angle A 1  of approximately 40 degrees. A top lip surface  48   a  forms a bowl around the first top surface  42   a  of to top rubber body  42 . A “V” shaped cut  48   b  in the sides of the top rubber body  42  completes a closed path around the top rubber body  42  and allows the sealing lip  48  to conform to irregular shaped work pieces. The groove pattern  53  in the bottom surface  42   b  of the top rubber body  42  matches a pattern of vertical walls  62  (see  FIGS. 18 and 19 ) of the center portion  44  allowing the vertical walls  62  to reach into the first bottom surface of the top rubber body  42 . A tapered wall  53   a  outlines the groove pattern  53  and tapers in narrowing the groove pattern to pinch the vertical walls  62  to provide a tight fit between the groove pattern  53  of the top rubber body  42  and the vertical walls  62  of the center portion  44 . A cross-section of the sealing cord  51  is shown with the sealing cord  51  inserted into the perimeter recessed channels  50 . The sealing cord  51  may have a round, elliptical, oval, or “D” shaped cross-section and the closed path of the seal is formed by butting ends of a length of the sealing cord  51  together. The sealing cord  51  may thus be used with any length closed path including a combination of the perimeter recessed channels  50  and/or one or more of the interior recessed channels  52 . 
     A top perspective view of a half size top rubber body  42 ′ according to the present invention is shown in  FIG. 16A  and a bottom view of the half size top rubber body  42 ′ is shown in  FIG. 16B . A novel advantage of the present invention is the ability to form a second seal if the sealing lip  48  is damaged. Additionally, a smaller top rubber body, such as the half size top rubber body  42 ′ may be used for small parts. The half size top rubber body  42 ′ includes the same features as the top rubber body  42 , but has half the length of the top rubber body  42 . 
     A side view of a center portion  44  of the three piece vacuum cup assembly  40  is shown in  FIG. 17A , an end view of the center portion  44  is shown in  FIG. 17B , a cross-sectional view of the center portion  44  taken along line  18 - 18  of  FIG. 17A  is shown in  FIG. 18 , and a cross-sectional view of the center portion  44  taken along line  19 - 19  of  FIG. 17B  is shown in  FIG. 19 . The center portion  44  includes interior walls  62  forming a rectangular array of vertical passages  60  reaching from the bottom to the top of the center portion  44 . The vertical passages  60  are connected by ports  64  at a base of the center portion  44 , the vertical passages  60  connecting the vertical passages  60  placing all the vertical passages  60  in communication with the vacuum source through the ports  64  to provide vacuum to all of the vertical passages  60  when the vacuum is applied to one of the vertical passages  60 . 
     A plug  66  is shown in  FIG. 20 . The plugs  66  are used for blocking individual vertical passages  60  in the center portion  44  when less than the entire top rubber body  42  is used to prevent a vacuum leak, and the plug  66  thus has a horizontal cross-section approximately matching the horizontal cross-section of the vertical passage  60  to allow using the plug  66  to block the vertical passage  60 . For example, when the half size top rubber body  42 ′ is used, half of the vertical passages are blocked. Further, the vacuum cup  40  may be cut into during use damaging the top rubber body  42  and sometimes the center portion  44 . The plugs  66  are used to seal any of the vertical passages  60  which otherwise would create a vacuum leak. The plug  66  preferably had rounded or radiused edges and is preferably tapered having a smaller top insertable into a vertical passage  60  and a larger bottom to resist complete insertion into the vertical passage  60 . 
     A side view of a bottom surface of a bottom rubber body  46  according to the present invention is shown in  FIG. 21A , a top view of the bottom rubber body  46  is shown in  FIG. 21B , and a bottom view of the bottom rubber body  46  is shown in  FIG. 21C . The top surface of the bottom rubber body  46  includes the groove pattern  53  for attaching and sealing to the center portion  44 . The bottom surface of the bottom rubber body  46  is similar to the top surface of the top rubber body with two additional features. The bottom surface of the bottom rubber body  46  includes three long grooves  72  for receiving metal bars, the metal bars for attracting the vacuum cup  40  to magnets in a machine. The metal bars may be held by adhesive or molded into the bottom rubber body or any suitable means. The bottom surface of the bottom rubber body  46  further includes two pairs of partitioning walls  70  blocking the communication of vacuum between a right side, and center, and a left side of a vacuum area on the bottom surface of the bottom rubber body  46  for controllably allowing a first vacuum source to hold the vacuum cup  40  to the machine and a second vacuum source to hold the work piece to the vacuum cup  40 . 
     While features of the top rubber body  42  were only shown with the three piece vacuum cup assembly  40 , such features are also compatible with single piece vacuum cups shown in  FIGS. 1-9 , and vacuum cups with any combination of the features disclosed herein are intended to come within the scope of the present invention. For example, the sealing lip  48 , the channels  50  and  52 , and the sealing cord  51  may be applied to any of the vacuum cups shown in  FIGS. 1-9 . 
     While the invention herein disclosed has been described by means of specific embodiments and applications thereof, numerous modifications and variations could be made thereto by those skilled in the art without departing from the scope of the invention set forth in the claims.