Abstract:
A vacuum holddown device for retaining a workpiece at a desired machining location on a horizontal work support surface, including a plurality of cylindrical actuators arranged in cavities contained in the upper surface of the work support. E ach of the actuators includes a vertically displaceable sensor member having a rounded surface that protrudes upwardly above the upper work support surface for engagement by the workpiece. When the sensor is depressed by the workpiece, a vacuum chamber in the actuator applies suction to the workpiece to maintain the same in the machining location. The actuators are selectively operable between flush and elevated positions relative to the work support. Attachment members may be selectively connected with the cylindrical actuators.

Description:
SPECIFICATION  
       FIELD OF THE INVENTION  
         [0001]    The present invention relates to a holddown device for machining workpieces, and more particularly to a holddown device which utilizes a vacuum source to maintain a workpiece against a work surface upon the activation of at least one actuator arranged adjacent on the work surface.  
         BACKGROUND OF THE INVENTION  
       BRIEF DESCRIPTION OF THE RELATED ART  
         [0002]    Various types of vacuum holddown devices for workpieces have been proposed in the patented prior art, as evidenced by the patents to Greene No. 4,946,149, Schmalz No. 6,095,506, and Moran No. 5,987,729.  
           [0003]    In Greene a holddown device is disclosed that retains materials horizontally by stops and vertically by suction chucks. A configuration to support a given workpiece to be machined is manually determined and then manually programmed into the machine, thereby allowing the holddown device to machine workpieces of identical dimensions in a rapid succession. However, this design does not allow for automatically configuring the various stops to adjust to different sized workpieces. The present invention is not manually programmed, but rather reacts to the dimensions of the material, thereby allowing the manufacturing of workpieces of different size and shape without having to manually adjust stops on the work surface.  
           [0004]    In the Schmalz patent, a vacuum holddown device is disclosed in which vacuum suction devices must be configured to match the dimensions of the workpiece. The present invention eliminates the configuration requirement by providing actuators throughout the work support. The actuators control when the vacuum pressure engages the workpiece through the work support.  
           [0005]    Moran discloses a work support with a plurality of vacuum apertures which are continuously engaged with the vacuum pressure. Additionally, the Moran patent utilizes stops that are manually placed on the work surface, thereby requiring set up time. The present invention was developed to provide an improved device in which a vacuum force to the specific area of the work surface where an actuator is activated, thereby utilizing the vacuum force more efficiently. Further, the actuators of the present invention can be adjusted to various heights and act as stops for the workpiece, thereby eliminating the need for additional pieces which need to be applied to the work surface to act as stops as disclosed in the Moran reference. The actuators also continue to provide an active vacuum source when the actuator is in an adjusted, heightened position.  
         SUMMARY OF THE INVENTION  
         [0006]    The improved holddown device according to the present invention is characterized by the provision of a work support that contains at least one cavity within which an actuator means is arranged for engagement by a workpiece, thereby to hold the workpiece by suction on the work support. The actuator means includes an actuator housing which is adjustably arranged at different heights relative to the work support. When the actuator housing is arranged at a first height above the work surface, the actuator housing acts as a stop for the overall work support and can thereby position a workpiece in a desired location. Additionally, the actuator means continuously connects a vacuum chamber in the actuator housing with a vacuum source when the actuator housing is in one of a plurality of raised positions, thereby permitting the machining of workpieces of various shapes. An actuator sensor member is arranged within, and protrudes outwardly from, the actuator housing. When a workpiece is placed on one side of the work support, the workpiece activates the actuator tip, thereby to produce a vacuum force to hold the workpiece on the work support. The actuator sensor member is biased outwardly from the actuator housing by a compression spring. The tension of the spring and the resulting biasing force on the actuator tip sensor member is adjustable, thereby to control the activation force required to activate and engage the actuator sensor member to allow a vacuum force to be applied to a workpiece. Additionally, the actuator sensor member includes a sphere which provides a surface for easily sliding a workpiece across the work support. Further, a plurality of attachment accessories may be selectively attached to the upper side of the actuator to provide the capability to machine workpieces of various shapes.  
           [0007]    According to a more specific object of the invention, an actuator housing is selectively displaceable relative to the work support between flush and elevated positions, rise being made of a C-shaped slot having a pair of horizontal leg portions joined by a vertical portion. The housing is spring-biased upwardly toward the elevated position, and is mounted for displacement relative to an annular mounting ring that is mounted in a cavity contained within the upper surface of the work support. To adjust the position of the cylindrical housing, it is rotated through 90° to position a radially inwardly directed pin on the mounting ring opposite the vertical connecting portion of the slot, whereby the housing may be axially displaced relative to the mounting ring.  
           [0008]    According to another feature of the invention, various attachments may be connected with a quick-release quarter-turn bayonet type connection regardless of whether the housing is in it flush or elevated positions.  
           [0009]    The opening in the upper end of the suction chamber is normally closed by a spherical sensor having a rounded surface that protrudes through the opening when the sensor is in the closed position, whereby the sphere is displaced downwardly toward the open position when a workpiece is mounted on the work support. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0010]    Other objects and advantages of the invention will become apparent from a study of the following specification when viewed in the light of the accompanying drawings, in which:  
         [0011]    [0011]FIG. 1 is a partly sectioned detailed view of the actuator means of the present invention mounted in a cavity contained in a work support;  
         [0012]    [0012]FIG. 2 is an exploded view of the actuator means of FIG. 1, and FIG. 2A is a detailed elevational view of the cylindrical housing of the actuator means of FIG. 2;  
         [0013]    [0013]FIGS. 3 and 4 are sectional views of the actuator means with the sensor member in the closed and open positions, respectively;  
         [0014]    [0014]FIG. 5 is a detailed sectional view illustrating the cylindrical housing of the actuator means in the elevated position relative to the work support;  
         [0015]    [0015]FIG. 6 is a sectional view illustrating the holddown system with one of the actuator housings in the elevated position, thereby serving as a positioning stop;  
         [0016]    [0016]FIG. 7 is a sectional view illustrating the manner of adjusting the tension of the tensioning spring associated with the sensor member;  
         [0017]    [0017]FIG. 8 is a perspective view illustrating the operation of certain of the actuator members as stops in positioning a pair of workpieces on the work support;  
         [0018]    [0018]FIG. 9 is a sectional view illustrating the manner for transporting a workpiece from a transfer system to the work support;  
         [0019]    [0019]FIG. 10 is a detailed sectional view illustrating the manner in which an attachment member is connected with the cylindrical housing of the adapter means;  
         [0020]    [0020]FIG. 11 is a top plan view of the upper end of the cylindrical housing of FIG. 10;  
         [0021]    [0021]FIGS. 12 and 13 are side elevation and bottom plan views, respectively, of the connector means of FIG. 11 for connecting an attachment member with the cylindrical housing; and  
         [0022]    FIGS.  14 - 16  are partly sectioned views of three types of attachment members suitable for use with the embodiment of FIG. 10. 
     
    
     DETAILED DESCRIPTION  
       [0023]    Referring first more particularly to FIGS. 1 and 2, the horizontal planar work station  2  has an upper surface  2   a  that contains a plurality of cavities or vertical bores  3  in which are mounted a plurality of suction actuator means  6  that define a plurality of suction stations, respectively. More particularly, in the upper end of each of the cavities  3  is mounted an annular support ring  5  having an upper surface  5   a  that is co-planar with the upper surface  2   a  of the work support  2 . Slideably mounted for vertical displacement within the mounting ring  5  is a cylindrical housing  6  having upper and lower end surfaces  6   a  and  6   b , respectively. The lower surface  6   b  contains a vacuum chamber  7 , and the upper surface  6   a  of the housing contains an opening  26  that provides communication with the vacuum chamber  7 . A vacuum source  16 , having for example a negative pressure of about 29 inches mercury, is connected with the vacuum chambers of the cavities  3  by a conduit  18  containing shutoff valve  19 , fitting  20 , manifold  21 , and openings  24  contained in the bottom surface  2   b  of the work support  2 , respectively.  
         [0024]    Mounted for movement within the vacuum chamber  7  is a sphere or ball  32  that is rotatably supported by a carrier  12 . The sphere  32  is biased toward its illustrated closed position relative to the radially inwardly directed lip portion  26   a  of opening  26  by a first compression spring  14  that reacts between the carrier  12  and a tension adjusting disk  10  that is threadably connected with the interior peripheral wall of the cylindrical housing  6 . The tension adjusting disk  10  is perforated to define passages  11  that maintain the vacuum chamber  7  in constant communication with the vacuum source  16  via the first opening  24 . When the sphere  32  is in the illustrated closed position of FIG. 1, the vacuum chamber  7  is sealed by first annular seal means  30  arranged concentrically about the sphere carrier  12  for reaction between the carrier and the adjacent surface of the vacuum chamber. Second annular seal means  38  are arranged concentrically about the opening  24  between the bottom surface  6   b  of the cylindrical housing and the bottom wall  3   a  of the cavity  3 . These annular seals are formed of a conventional seal material, such as neoprene or cell sponge seals.  
         [0025]    In accordance with an important feature of the invention, the cylindrical housing  6  is vertically displaceable from its illustrated flush position of FIG. 1 toward an elevated position shown in FIG. 5. More particularly, the housing  6  is normally biased upwardly relative to the work support  2  by a second compression spring  34  arranged between the tension adjusting disk  10  and the cavity bottom wall  3   a . The housing  6  is retained in its FIG. 1 position against the force of the second compression spring  34  by a pair of pins  8   a  carried set screws  8  which extend inwardly into a corresponding pair of oppositely arranged grooves  50  provided in the outer peripheral wall of the housing  6 , as best shown in FIG. 2A. More particularly, each groove  50  has a generally C-shaped configuration defining horizontal upper and lower leg portions  50   a  and  50   c  that are connected by a vertical portion  50   b.  Thus, in the FIG. 1 position, the housing  6  is maintained in the flush position by the cooperation between the pins  8   a  and the upper groove legs  50   a , while in the FIG. 5 elevated position, the housing  6  is retained in position by the cooperation between the pins  8   a  and the lower horizontal groove portions  50   c . The housing  6  is provided at its lower end with an annular peripheral flange  6   c  that cooperates with an annular third seal  15  that is arranged between the lower surface  5   b  of the mounting ring and the upper surface  6   d  of the flange  6   c  when the housing  6  is in the elevated position shown in FIG. 5, thereby to further seal the suction chamber  7 . A fourth annular seal  13  is arranged on the upper surface  6   a  of the housing in concentrically spaced relation about the opening  26 , thereby to provide a seal of the chamber defined around the opening when the sensor member  32  is depressed by a workpiece, as will be described in greater detail below.  
         [0026]    Referring now to FIGS. 3 and 4, it will be seen that when the curved portion of the sphere  32  that protrudes upwardly through the opening  26  is engaged by the workpiece  40  and is depressed against the restoring force of spring  14 . the chamber defined between the workpiece  40  and the upper surface  6   a  of the housing  6  within the annular seal  13  is connected with the vacuum source via the channels  11  and opening  24 , thereby to maintain the workpiece  40  by suction on the upper surface of the work support  2   a  at the desired machining location. The suction chamber  7  is further sealed by the cooperation of the annular seal  38  between the bottom surface  6   b  of the housing  6  and the bottom surface  3   a  of the cavity  3 .  
         [0027]    To elevate the housing from the flush position of FIGS. 1 and 3 to the elevated position of FIG. 5, the housing  6  is rotated through about 90° relative to the mounting ring  5  until the pins  8   a  are within the vertical portion  50   b  of the groove  50 , whereupon the spring  34  biases the housing  6  upwardly toward the elevated position of FIG. 5. The housing  6  is then rotated about its axis in the opposite direction to cause the pin portions  8   a  of the set screws  8  to extend within the lower horizontal leg portions  50   c  of the slots  50 , thereby maintaining the housing  6  in the elevated position of FIG. 5. As shown in FIG. 6, the left hand housing  6 ′ has been raised to its elevated position, thereby to serve as a stop for maintaining the workpiece  40  at a desired machining position on the upper surface  2   a  of the work support  2 . As shown in FIG. 8, a plurality of the housing  6 ′ may be raised to their elevated positions, thereby to position a pair of workpieces  40  and  41  on the work support  2 , as desired.  
         [0028]    As shown in FIG. 7, the tension of the first spring  14  may be adjusted by means of screwdriver  42  engaging slot  43  in the bottom of the tension adjusting disk  10 , thereby to rotate the same relative to the housing  6  and then adjust the tension of the first compression spring  14 .  
         [0029]    Referring now to FIG. 9, the workpiece  40  may be transported by transport conveyor means  50  having spherical members  44  supported by supports  46 . The workpiece  40  is transported to a desired location on the work support  24  as determined by selectively operated stops  6 ′, whereupon the weight of the workpiece causes the spherical elements  32  of the other actuator means  6  to be lowered to their open positions. The shutoff valve  19  is then opened to establish vacuum in the associated vacuum chambers  7 , thereby to maintain by suction the workpiece  40  on the work support  2 .  
         [0030]    Referring now to FIGS.  10 - 13 , in accordance with another important feature of the invention, attachment means are provided for connecting an attachment  60  to the opening  26  contained in the upper end of the cylindrical housing  106 . The connector  62  of FIG. 12 has a pair of lateral projections  64  that cooperate with diametrically opposed slots  126   b  contained in the inwardly directed lip portion  126   a  of opening  126 , thereby to define a quick-release bayonet-type connection between the attachment member  60  and the opening  126 . The attachment member  60  is threadably connected with the upper threaded portion  62   a  of the connector  62 , whereupon the sphere  132  is opened from its seat, and the chamber  61  within the attachment  60  is connected with the vacuum chamber  107  by the axially directed flutes  62   c  on the inner periphery of the connector  62 . Thus, the chamber  61  is connected with suction via the flute  62   c  and the space in the opening resulting from the downward displacement of the sphere  132  relative the cylindrical housing  106 .  
         [0031]    As shown in FIGS.  14 - 16 , various types of attachments may be connected with the openings  26  and  126  of the cylindrical housings  6  and  106 . For example, in the embodiment of FIG. 14, the attachment  70  contains a chamber  78  that is in communication with the vacuum chamber  107  of the housing  106 , the attachment being provided with an annular seal  76  that extends concentrically around the attachment central chamber  78 . In the embodiment of FIG. 15, the attachment  80  comprises a stop member that is selectively connected to the upper openings of either of the housings  6 ,  106  by a quick-release quarter-turn bayonet fitting. In the embodiment of FIG. 16. the attachment  90  comprises a suction cup having a resilient outwardly flared upper portion  90   b  that extends concentrically about the chamber  90   a  that communications with the suction chamber  7  in the associated housing  6  or  106 .  
         [0032]    As shown in FIG. 5, the effective height d of the upper surface  6   a  can be extended to the greater height d′ by the addition of the attachment  70 , as shown in phantom. This is important when the various workpieces to be machined are of nonuniform thickness throughout their lengths or require special milling or drilling techniques. In any event, the workpiece may be supported by suction at the various suction stations and at various elevations as selectively chosen by the operator.  
         [0033]    While in accordance with the provisions of the Patent Statutes the preferred forms and embodiments of the invention have been illustrated and described, it will be apparent to those skilled in the art that various changes may be made without deviating from the inventive concepts set forth above.