Abstract:
A vacuum support includes a vacuum plate having a top surface and a bottom surface, the vacuum plate having a mechanical stop extending from the bottom surface; an elastomeric seal extending along a periphery of the bottom surface, the vacuum plate and the elastomeric seal defining a vacuum space; and a vacuum source in communication with the vacuum space. Upon attaching the vacuum plate to a mounting surface by reducing pressure in the vacuum space, the stop is in engagement with the mounting surface.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
   This application claims the benefit of U.S. provisional patent application Ser. No. 60/359,743 filed Feb. 26, 2002, the entire contents of which are incorporated herein by reference and claims the benefit of U.S. provisional patent application Ser. No. 60/409,160 filed Sep. 9, 2002, the entire contents of which are incorporated herein by reference. 

   TECHNICAL FIELD 
   This invention relates to stable supports. In particular, this invention relates to stable supports employing a vacuum. 
   BACKGROUND 
   There are many instances where a stable support is required to ensure that the object or device being supported remains fixed with respect to a table or other sturdy structure. For example, laboratory equipment and measurement equipment, such as a three-dimensional digitizer, are usually required to remain fixed with respect to a sturdy object or the floor. 
   One common method of ensuring stability of an apparatus has been physically bolting the apparatus to a table or floor. However, this method requires permanently altering the table or floor and makes repositioning difficult. 
   Another method of ensuring stability of an apparatus employs a high-strength magnet to fix the apparatus to a ferromagnetic surface, such as a steel table. This provides a strong sturdy support and is easily repositionable, but requires that a ferromagnetic surface be available. 
   SUMMARY 
   The above-discussed and other drawbacks and deficiencies of the prior art are overcome or alleviated by a vacuum support comprising a vacuum plate having a top surface and a bottom surface, the vacuum plate having a mechanical stop extending from the bottom surface; a seal extending along a periphery of the bottom surface, the vacuum plate and the seal defining a vacuum space; and a vacuum source in communication with the vacuum space. Upon attaching the vacuum plate to a mounting surface by reducing pressure in the vacuum space, the stop is in engagement with the mounting surface. 
   The above discussed and other features and advantages of the present invention will be appreciated and understood by those skilled in the art from the following detailed description and drawings representing the preferred embodiment. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The present invention will now be described by way of example with reference to the accompanying drawings in which: 
       FIG. 1  shows a perspective view of a vacuum adapter; 
       FIG. 2  shows a perspective view of a vacuum adapter with a vacuum source illustrated schematically; 
       FIG. 3  shows an exemplary three-dimensional digitizer for use with the vacuum adapter; 
       FIG. 4  shows an isometric view of another embodiment of a vacuum adapter; and 
       FIG. 5  shows a cross section view of the vacuum adapter of  FIG. 4 . 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
   An exemplary vacuum adapter  10  is shown at  FIG. 1 . This vacuum adapter comprises a high strength vacuum plate  16  having a plurality (e.g., at least three) mechanical solid stops or feet  22 , and a seal  18  formed of rubber or synthetic elastomeric material. The seal  18  extends beyond the bottom of vacuum plate  16  to define a vacuum space beneath the bottom surface of the vacuum plate  16 . 
   While relative dimensions and strengths of materials may vary depending upon the application, it is preferred that vacuum plate  16  comprise a high strength material. Aluminum is a preferred material for combining low weight, corrosion resistance, and strength. For example, vacuum plate  16  may include a 6061-T6 jig aluminum plate, which is a high tensile strength aluminum alloy used in the aerospace industry. While a cloverleaf configuration is shown, the shape is not critical. The vacuum plate  16  may be a round plate approximately eight inches (20.3 cm) in outside diameter with a vertical profile of one and a quarter inches (3.2 cm). Seal  18  is disposed in a groove formed in the bottom surface of vacuum plate  16 . Vacuum plate  16  includes a recess underneath to increase the volume of space between vacuum plate  16  and the mounting surface. Furthermore, a hole is drilled through vacuum plate  16  and tapped for mounting vacuum gauge  35  (discussed in more detail below). The surface of vacuum plate  16  may be left as raw aluminum, or it may be covered by a plastic housing  14  formed of impact-resistant plastic attached via about four holes (not shown) drilled and tapped into vacuum plate  16  to accept mounting screws (not shown) securing the plastic housing. The plastic housing covers all vacuum components discussed in more detail below. 
   As a suction is applied between vacuum plate  16  and a solid non-permeable mounting surface (not shown), feet  22  provide stability to the vacuum plate  16  by preventing the plate from moving with respect to the surface as would be the case if seal  18  was relied upon to support vacuum plate  16 . Steel plate  24 , preferably a one-half inch thick (1.3 cm) SS416 steel alloy plate having a 3 inch (7.6 cm) diameter, is bolted or otherwise securely attached to vacuum plate  16 . More preferably, the surface of steel plate  24  is ground and passivated to reduce oxidation. For example, steel plate  24  may be attached with bolts (not shown) extending into four holes drilled into vacuum plate  16  radially about the center thereof. Corresponding holes formed into steel plate  24  are tapped to accept the bolts. A recess  26 , e.g., having a 3 inch (7.6 cm) diameter to accept steel plate  24  is formed in vacuum plate  16  to assist in centrally positioning the apparatus over steel plate  24 . Recess  26  may be machined into the top surface of vacuum plate  16  or other means may be employed. A vacuum gauge  35  provides visual indication of the status of the vacuum between vacuum plate  16  and the surface to which adapter  10  is mounted. 
   A number of methods may be used for generating the vacuum. First, a pump  30 , such as hand pump or electrically motorized pump may be provided. Such hand pumps and motorized pumps are generally known in the art and are generally available. The vacuum plate  16  includes an internal path so that the pump  30  is in fluid communication with the vacuum space beneath the vacuum plate  16 . 
   In a second embodiment, a source of compressed air is applied through a venturi, which is then used to draw a vacuum from the vacuum space below the vacuum plate  16 . For example,  FIG. 2  shows a source  40  of compressed air that is directed via line  42  to a pressure regulator  44  and venturi  46  which may be positioned within housing  14 . Pressure regulator  44 , and venturi  46  are enclosed within housing  14 , which includes a slip fitting for connecting an air supply hose to the internal vacuum components. As compressed air is applied to venturi  46 , a low-pressure region is developed at the neck of the venturi which includes a port that extends to a one-way valve  48  and then to the vacuum space between vacuum plate  16  and the surface. Air is then exhausted at exhaust port  56 . This mechanism provides a very reliable and inexpensive source of vacuum. As an example, a “P-5 Mini Chip” venturi manufactured by PIAB (Täby, Sweden) generates about 25-26 inches (63.5-66 cm) of mercury with 0.68 cubic feet (19 liters) per minute at 55 pounds per square inch (380 KPa). Pressure regulator  44  is, for example, a miniature regulator such as those available from Wilkerson Corporation (Englewood, Colo.). Pressure regulator  44  controls the air inflow to optimize the performance of venturi  46 . 
   In a third embodiment, an external vacuum pump is placed in communication with the vacuum space below the vacuum plate  16  via a vacuum hose and external connection. A one-way valve as described above may be integrated with adapter  10  to prevent air from leaking into the device after the vacuum is drawn. 
   In operation, a user places the vacuum adaptor on a non-porous sturdy surface such as a granite table, operates the pump or apply compressed air as discussed above to evacuate the vacuum space until the required vacuum is reached. Vacuum gauge  35 , preferably a center back mounted gauge having a 2″ diameter gauge face, may be used to determine when the proper vacuum level is achieved at which point the pump or compressed air is disengaged. The user may then attach a device  8 , shown in  FIG. 3 , having magnet mount  5  to adapter  10  by inserting the magnetic chuck into recess  26 . 
   While any device may be used with vacuum adapter  10 , in the embodiment of  FIG. 3 , device  8  is a portable coordinate measurement machine that includes a base  60  having magnet mount  5  at the bottom thereof. A jointed, articulated arm  62  extends upwardly from base  60  and terminates at a measurement probe  64 . 
   To release adapter  10 , a miniature on/off ball valve (not shown) may be used. A three-way valve with the third port open to the atmosphere will release the plate when the valve is turned off, thereby placing the vacuum in communication with the atmosphere. 
   Another embodiment of a stable support will now be described with reference to  FIGS. 4 and 5 . In this embodiment, vacuum plate  16  is formed of a ferromagnetic material, preferably ferromagnetic steel, e.g., 416 stainless steel, which is one of the most magnetic steels. Thus, a separate steel plate for attaching a magnetic base is not required. A recess  26  has a flat surface therein for receiving a magnet from the object or device being supported. Vacuum plate  16  also includes a circumferential rim  72  extending around rubber seal  18  in place of the feet  22  within the seal as shown in the previous embodiment. Note that, a solid rim and/or discrete feet may be used, either within the seal or external thereof, to support the vacuum plate  16  when a vacuum is established in the vacuum space between vacuum plate  16  and the mounting surface. 
   Seal  18  is retained on the lower side  78  of vacuum plate  16  by a retaining means such as interlocking retention collars  74 ,  76  formed on the seal and vacuum plate  16 , respectively. Alternatively, other interlocking structures may be used. In addition or alternatively to such interlocking structures, the upper surface of inner collar  77  is attached to lower surface  78  using a suitable adhesive (not shown). 
   Seal  18  includes a flexible portion  84  that extends radially from the retaining means to sealing surface  82 . Flexible portion  84  allows the sealing surface  82  to become sealingly engaged with the mounting surface. Specifically, the pressure differential above and below the flexible portion  84  causes a downward pressure to be applied to sealing surface  82  sufficient to maintain a vacuum within seal  18 . While flexible portion extends radially outward from retaining means to sealing surface  82 , the retaining means could also be circumferentially disposed around sealing surface  82 , such that the flexible portion extends radially inward from the retaining means to sealing surface  82 . 
   A seal rim  86  projects toward and approaches the inside surface of rim  72  to improve the appearance of the underside of vacuum adapter  16  and to prevent foreign objects from entering the space above flexible portion  84 . 
   As shown in  FIGS. 4 and 5 , the vacuum is produced using a hand pump  60  that is external to vacuum plate  16  and connected thereto by a vacuum hose  62 . An internal conduit provides fluid connection between the hose  62  and the vacuum space beneath vacuum plate  16 . A quick disconnect  64  is provided between vacuum hose  62  and vacuum plate  16 . Hand pump  60  includes a vacuum meter  35  and is available, for example, from TRI-ESS Sciences, part V183. In operation, vacuum hose  62  is connected to vacuum plate  16  and lever handle  66  is repeatedly operated until vacuum gauge  35  indicates the required amount of gauge pressure. Once the required amount of vacuum is achieved, and is found to be stable, i.e., not leaking, vacuum adapter  10  is ready to be utilized as a stable support. When it is required that vacuum adapter  10  be moved to a new location or removed from the support surface, a pressure release valve (not shown) on hand pump  60  is operated to relieve the vacuum thereby enabling easy removal of vacuum adapter  10 . 
   While preferred embodiments have been shown and described, various modifications and substitutions may be made thereto without departing from the spirit and scope of the invention. For example, the one-way valve may be eliminated which would require continuously operating the vacuum source, e.g., continuously applying compressed air  40  to said venturi during use of adapter  10  thereby ensuring that the vacuum is maintained within vacuum plate  16 . Many other such modifications are possible without departing from the spirit and scope of this invention. Accordingly, it is to be understood that the present invention has been described by way of illustration and not limitation.