Abstract:
A vacuum table and mat system having a removable and replaceable mat which retains workpieces via vacuum created suction. The mat has a base sheet with a plurality of perforations and channels therein, and a flexible rubber sheet atop the base sheet. Vacuum is applied to retain a workpiece via suction-cup like indentations formed when the rubber sheet is pulled into the perforations of the base sheet.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims the benefit of U.S. Provisional Patent Application Serial No. 60/094,662, filed Jul. 30, 1998. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates generally to vacuum tables. More specifically, the invention is a vacuum table for securing a removably attached matting. 
     2. Description of Related Art 
     Vacuum tables have been used in the engraving and manufacturing industries for many years. Often, the table is damaged during engraving, milling, drilling, or other applications. This necessitates either costly repair or repurchase of a vacuum table, and adds to machine down time. A vacuum table with a removable and replaceable mat would therefore be beneficial. 
     Understandably, vacuum tables and related devices have been the subject of previous patents. U.S. Pat. No. 5,374,021, issued to Kleinman on Dec. 20, 1994, discloses a vacuum holder particularly useful as a vacuum table. The device includes a vacuum chamber divided into a plurality of sub-chambers which ultimately lead to a plurality of suction opening which extend through an outer holding surface for applying suction to a workpiece. U.S. Pat. No. 4,301,999, issued to Higgins et al. on Nov. 24, 1981, discloses a vacuum hold-down table for working with sheet metal. The table includes a plurality of foam layers united to form a laminated core having a plurality of apertures such that a vacuum may be applied through these apertures for holding sheet metal in place. U.S. Pat. No. 4,205,835, issued to Gerber on Jun. 3, 1980, discloses a bristle bed for a vacuum table. The bristle board includes aperture in the base that provide passageways for airflow through a mat in communication with a vacuum source. 
     Document scanners and copiers have benefitted from the use of vacuum tables for holding papers in place. U.S. Pat. No. 5,486,932, issued to Leonard on Jan. 23, 1996, and its European counterpart, EPO patent document 0,603,430 published Jun. 29, 1994, disclose a document scanner and vacuum table therefor. The table uses an array of openings to exert suction pressure generated by a vacuum on an object above to hold the object in place. 
     Vacuum tables have also been developed for other tasks, such as decal welding and laser engraving. U.S. Pat. No. 5,695,600, issued to Goin on Dec. 9, 1997, and U.S. Pat. No. 5,504,301, issued to Eveland on Apr. 2, 1996, are respective examples thereof. 
     Other devices using the power of vacuum have also been the subject of previous patents. Among them are: U.S. Pat. No. 5,685,513 (vacuum-suction attachment pad) issued to Tsukushi on Nov. 11, 1997; EPO document 0,265,648, published on May 4, 1988; and EPO document 0,505,668, published on Sep. 30, 1992. 
     Although many vacuum table designs exist, a system using a replaceable mat in a vacuum table which retains workpieces with a suction-cup like grip would be both useful and beneficial for various applications. 
     None of the above inventions and patents, taken either singly or in combination, is seen to describe the instant invention as claimed. 
     SUMMARY OF THE INVENTION 
     A vacuum table according to the present invention includes a vacuum plate, a mat, and a vacuum system. The vacuum plate forms a base for the unit and is provided with an aperture through which air is pulled by a vacuum pump. The mat rests on the vacuum plate and is sealed therewith by a gasket. A base sheet of the mat is provided with a plurality of perforations which are connected on the underside of the base sheet by a network of channels. The channels allow for even pull of air from under the mat through to the vacuum pump. A rubber sheet is affixed to the upper surface of the base sheet. A plurality of small holes are defined by the rubber sheet corresponding to the perforation of the base sheet. A vacuum pull beneath the mat forces the rubber sheet to cave in at each perforation of the base sheet, thereby creating a plurality of suction-cup like indentations on the upper surface which ultimately hold a workpiece in place. 
     Accordingly, it is a principal object of the invention to secure a workpiece to a work surface via vacuum pressure. 
     It is another object of the invention to secure a work piece to a work surface via vacuum pressure exerted below a mat causing the mat perform in a suction-cup like manner. 
     It is a further object of the invention to facilitate ease of repair of a vacuum table. 
     It is an object of the invention to provide improved elements and arrangements thereof in an apparatus for the purposes described which is inexpensive, dependable and fully effective in accomplishing its intended purposes. 
    
    
     These and other objects of the present invention will become readily apparent upon further review of the following specification and drawings. 
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective view of a first embodiment of a vacuum table and mat according to the present invention. 
     FIG. 2 is side, partially sectional view of the first embodiment of a vacuum table, illustrating air flow via the vacuum pump. 
     FIG. 3 is a side, partially sectional view of a second embodiment of the vacuum system according to the invention, illustrating airflow in the on position. 
     FIG. 4 is a top perspective view of a slide valve regulator used with all three embodiments of the vacuum system according to the invention, illustrating air flow in the off position. 
     FIG. 5 is a greatly enlarged detail sectional view of the area forming the suction-cup like depression of the mat below the work piece. 
     FIG. 6 is a side view of a vacuum system used with the first and second embodiments of the vacuum system according to the invention. 
     FIG. 7 is a perspective view of a third embodiment of a vacuum table and mat according to the present invention. 
     FIG. 8 a side, partially sectional view of a third embodiment of the vacuum system according to the present invention, illustrating airflow in the on position. 
     FIG. 9 is a top view of a vacuum manifold used in the third embodiment of the vacuum system according to the present invention, illustrating airflow in the on position. 
     FIG. 10 is a top view of a vacuum manifold used in the third embodiment of the vacuum system according to the present invention, illustrating airflow in the off position. 
     FIG. 11 is a top perspective view of a second embodiment of the vacuum table according to the present invention. 
     Similar reference characters denote corresponding features consistently throughout the attached drawings. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The present invention is a vacuum table especially useful in holding a workpiece to a surface for engraving or other purposes. Referring to the Figures, the table  50  is made up of a vacuum plate  10 , a replaceable mat  52  on which work items may be held, and a vacuum assembly  54 . 
     Referring to FIGS. 1,  7 , and  11 , the vacuum plate  10  forms a base for the table  50 . The mat  52  has been omitted from FIG. 11 for simplicity, as this mat is identical to those appearing in FIGS. 1 and 7. In a preferred embodiment, the plate  10  is made from aluminum. The plate  10  is preferably rectangular and defines a groove  56  (FIGS. 2-3) about its perimeter. An aperture  14  (FIGS. 4,  10 ), ultimately used to pull air to the vacuum pump, is defined by the plate  10 . A pair of graduate rules  16  preferably bound the plate  10  at its uppermost and leftmost sides permit measurement of a workpiece on the table. 
     A gasket  18  mounts within the perimetric groove  56  of the vacuum plate  10 . The gasket  18  may be secured with adhesive on its underside to the vacuum plate  10 . Protruding slightly above the level of the plate, the gasket  18  may later be compressed to form an air tight seal with the mat. The protrusion of the gasket  18  above the plate will preferably be 0.020 inch. 
     Referring to FIGS. 1,  2 , and  7 , the plate  10  may include a plurality of holes  58  along its edges for mating with the guide pins on the workholding vise assemblies of engraving machines having such workholders. Portions of the vacuum assembly  54 , described in detail below, may attach to the bottom surface of these plates  10 . Alternatively, referring to FIGS. 3 and 11, the plate  10  may be completely planar for mounting on the T-slot tables of engraving machines having these alternative workholders. The vacuum assembly  54  must attach to the end of such plates  10 , with the appropriate airflow passages contained within the plates  10 , as is also explained in detail below. 
     A replaceable mat  52  is mounted on the vacuum plate  10 , engaging the gasket  18 . An airtight seal is formed by the gasket  18  when vacuum is applied to the system. The mat  52  forms the work surface to which a work piece W is ultimately held by the vacuum forces. The mat  52  has two layers, a base sheet  40  and a rubber sheet  50 , preferably adhered to one another by an adhesive layer  60 . 
     The base sheet  40  is preferably formed of polyvinyl chloride (PVC) plastic. The base sheet  40  defines an upper surface  42  to which the rubber sheet  50  is affixed, and a lower surface which engages the gasket  18 . A plurality of perforations  46  are defined by the base sheet  40 . Each perforation is preferably one quarter of an inch in diameter, although other sizes may be used. The perforations  46  are arranged in an orderly fashion, each preferably separated by a distance of one half inch. Each perforation passes completely through the base sheet  40 , from the upper surface  42  through the lower surface. A network of channels  48  interconnect each perforation. The channels  48  are defined only on the lower surface, and do not pass completely through the base sheet  40 . 
     The resilient upper sheet  50  is affixed, with adhesive, to the upper surface of the base sheet  40 . Resilient sheet  50  is preferably made from rubber. A plurality of pin holes  52 , preferably 0.004 inch in diameter, are aligned with and centrally disposed above each perforation of the base sheet  40 . When a vacuum is applied under the base sheet  40 , portions of the rubber sheet  50  are pulled into the perforations  46 , resulting in a plurality of suction-cup like indentations  54  of the rubber sheet  50 . It is these suction-cup like indentations  54  which ultimately engage and hold a workpiece in place on the vacuum table, as best seen in FIG.  5 . 
     The vacuum assembly  54  preferably is one of the three embodiments described below. The first vacuum assembly  54 , for a workholding vise assembly, is illustrated in FIGS. 1,  2 ,  4 , and  6 . The aperture  14 , passing completely through plate  10 , connects to hose  28 , preferably by pipe-tapping aperture  14 . Hose  28  includes a slide valve regulator  24 , which is preferably configured as a tube encircling the hose  28 . The slide valve regulator  24  reciprocates between a closed position wherein it covers an aperture  25  in hose  28 , and an open position wherein it exposes the aperture  25 . When the aperture  25  is covered, all air flow into hose  28  must be from aperture  14 , maximizing suction at plate  10 , whereas opening aperture  25  allows air to enter hose  28  through aperture  25 , reducing suction at plate  10 . 
     Hose  28  connects at its opposite end to a pressure gauge  22 , air filter  60 , and finally to vacuum pump  62 . The vacuum pump  62  supplies vacuum pressure to the system, which can be measured by the pressure gauge  22 . 
     The second embodiment of the vacuum apparatus  54 , for use with T-slot workholders, is illustrated in FIGS. 3,  4 ,  6 , and  11 . The aperture  14  passes only partially through plate  10 , and connects with pipe-tapped air passage  64 . The pipe-tapped air passage  64  connects to hose  28 . Hose  28  includes a slide valve regulator  24 , reciprocating between a closed position wherein it covers an aperture  25  in hose  28 , and an open position wherein it exposes the aperture  25 . When the aperture  25  is covered, all air flow into hose  28  must be from aperture  14 , maximizing suction at plate  10 , whereas opening aperture  25  allows air to enter hose  28  through aperture  25 , reducing suction at plate  10 . 
     Hose  28  connects at its opposite end to a pressure gauge  22 , air filter  60 , and finally to vacuum pump  62 . The vacuum pump  62  supplies vacuum pressure to the system, which can be measured by the pressure gauge  22 . 
     The third embodiment of the vacuum apparatus  54  includes a manifold block  20  mounted under the vacuum plate  10 . The manifold block  20  includes a vacuum gauge  22  for measuring the amount of vacuum pressure being applied by the system and a slide valve regulator  24  which are in fluid communication via conduits and hoses with the vacuum plate  10  and the vacuum pump. The manifold is connected at one end via a conduit  26  to the aperture  14  in the vacuum plate  10  and at another end via hoses  28  to the vacuum pump (not shown). The slide valve regulator  24  works to control the vacuum applied to the vacuum plate  10 . The slide valve selects between closing the system (creating a vacuum) and opening the system (releasing the vacuum). To close the system, the slide valve covers an opening  25  in the manifold block  20  forcing air to be evacuated from the vacuum plate  10 . In contrast, the opening  25  is exposed, causing the pump to pull from the path of least resistance, which leads to the open atmosphere, and the vacuum within the table is broken. 
     In operation, a workpiece is place on the rubber sheet  50  of the mat, which is in place over the vacuum plate  10 . The vacuum pump is started, pulling air from the system. If the slide valve is open as seen in FIG. 4, air is pulled from the atmosphere, and no vacuum is created within the table. Once the slide valve is closed, as seen in FIG. 3, the pump pulls air from within the table. 
     Ultimately, the internal vacuum pulls on the rubber sheet  50  through the perforations  46  in the base sheet  40  of the mat. The rubber sheet  50  is pulled partially into each perforation. The pulling of the rubber sheet  50  creates a small space between the rubber sheet  50  and the workpiece. The space also creates a vacuum which holds the workpiece in place, much like a suction-cup. The pin holes  52  in the rubber sheet  50  correspond to the center of each suction-cup like indentation thus formed. The work piece actually seals the cups allowing air to be drawn downward into the system, creating a plurality of miniature vacuum chambers. Because the pin holes  52  are relatively tiny, the rubber sheet  50  is still pulled into the perforation of the base sheet  40 , but an additional amount of air is evacuated from the cavity formed between the rubber and the workpiece causing the workpiece to be held firmly in place until the system is opened via the slide valve. 
     Because the mat is replaceable and constructed of relatively inexpensive materials, it may be discarded if it becomes damaged. Only the mat need be replaced, not the entire vacuum table. This design also obviates the need to send the table out for repairs in the event the surface becomes marred. A simple replacement of the mat readies the system for extended use. 
     Although the mat and vacuum table may be made in many different shapes and sizes, the preferred form is a rectangular table having a mat of any of the following dimensions: 3.5 by 9 inches, 8.25 by 12.25 inches, and 19.75 by 25.25 inches. The vacuum table is especially well suited for holding items for engraving applications, but may be used for other purposes. 
     It is to be understood that the present invention is not limited to the sole embodiments described above, but encompasses any and all embodiments within the scope of the following claims.