Patent Publication Number: US-3967849-A

Title: Vacuum control system

Description:
This is a continuation of application Ser. No. 369,861, filed June 14, 1973, now abandoned, which a continuation of application Ser. No. 147,322, filed May 27, 1971, now abandoned. 
    
    
     BACKGROUND AND SUMMARY OF THE INVENTION 
     Vacuum cup type holding devices are widely used in industry to grip and hold parts during transfer, manufacturing, assembly, and other operations. It is common practice to obtain the necessary vacuum by flow of high pressure air through a vacuum creating device. In some uses of such devices, it is necessary or desirable to be able to quickly and reliably release the parts and one of the problems of prior art devices has been a failure to provide quick and reliable release of the parts. 
     It is a primary objective of the present invention to provide a new and improved vacuum control system in which a vacuum condition and a non-vacuum condition are positively, reliably, and quickly established by merely stopping and starting air flow through a vacuum creating device. To this end, new and improved vacuum control means have been associated with a vacuum creating device in a new and improved manner. In the presently preferred embodiment of the inventive concepts, the vacuum control means comprises a vacuum forming member movable by the presence or absence of high pressure air between a vacuum forming position and a non-vacuum position. The vacuum forming member is moved to a vacuum forming position when connected to a high pressure air source and is held in that position as long as it is connected to that source. A return means is independently rendered operable by the high pressure air and is operationally independent of the vacuum forming member until disconnected from the high pressure air source whereupon the return means is immediately effective to move the vacuum forming member from the vacuum forming position to the non-vacuum position. In addition, positive vacuum dissipating means are associated with the movable vaccuum forming member and rendered operable immediately upon initiation of movement of the member toward the non-vacuum position to obtain quick and reliable release of parts held by vacuum. 
    
    
     BRIEF DESCRIPTION OF THE DRAWING 
     An illustrative and presently preferred embodiment of the inventive concepts is shown in the accompanying drawing wherein: 
     FIG. 1 is a cross-sectional side elevational view of a vacuum forming device and an attached vacuum cup; 
     FIG. 2 is a cross-sectional side elevational view of the vacuum forming device of FIG. 1 in another operational position; and 
     FIG. 3 is another cross-sectional view of the vacuum forming device of FIG. 1 in still another operational position. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring now to FIG. 1, a relatively large diameter, e.g. 5 inch, relatively deep, e.g. 1-1/2 inch, vacuum cup 10 is connected to a vacuum creating device 12 by a threaded coupling 14 comprising a connector member 16 and a locking bolt 18 defining a central air passage 20. 
     The vacuum creating device 12 comprises an annular housing 22 closed at one end by an annular vacuum forming venturi plug 24 and at the other end by an annular air connection plug 26. An annular axially movable outer sleeve member 28 is slidably mounted on the inner peripheral surface 30 of the housing and sealed relative thereto by sealing means 32. A compression spring 34 is mounted between the sleeve member 28 and the venturi plug 24 to normally bias the sleeve member to an extended position in abutting engagement with the air connection plug 26. The spring 34 is mounted circumjacent hub portions 36, 38 of the outer sleeve member 28 and the venturi plug 24, respectively. An annular movable inner sleeve member 40 provides an axially movable vacuum forming member slidably mounted at one end in an annular chamber 42 in the outer sleeve member 28 and at the other end in annular chamber 44 in the venturi end plug 24. In the presently preferred embodiment, the inner sleeve member 40 is at least partially sealed relative to the outer sleeve member 28 by sealing means 46 carried in an annular piston flange 48 in chamber 42 and sealing means 50 surrounding the annular periphery of central elongated portion 52 of the inner sleeve member. The arrangement is such that the inner sleeve member and the outer sleeve member will move axially as a unit under certain conditions and will be relatively movable under other conditions. While the exact mode of operation under all conditions is not exactly understood at this time, it is believed that the inner and outer sleeves move together as a result of frictional resistance therebetween and due to incompressibility of air trapped therebetween in chamber 42. 
     A central air passage extending through the vacuum creating device comprises an annular air inlet portion 54 in the end plug; an annular air inlet chamber 56, an annular centrally located air nozzle portion 58, and a plurality of radially outwardly located and circumferentially spaced annular bypass passages 60, 62, there being six in the presently preferred embodiment, in the inner sleeve member 40; a relatively large diameter annular bypass chamber 64 defined by sleeve member 40 and venturi plug 24 in a release position of FIG. 1, an annular outlet chamber 66 of smaller diameter than the bypass chamber and connected thereto by a transverse shoulder 68, and an annular outlet passage 70 of smaller diameter than the outlet chamber 66 and connected thereto by a tapered shoulder 72 in the venturi end plug 24. A transverse vacuum passage 74 is connected to chamber 66 adjacent the tapered shoulder 72 and a transverse vent passage 76 connects the interior of housing 22 to the atmosphere to prevent accumulation of high pressure air therewithin which might block movement of the sleeves 28, 40. A frusto-conical nozzle portion 78 protrudes from the outlet end of the inner sleeve 40 and has a size such as to be radially spaced from and provide a flow passage 80 between the inner wall of chamber 66 in a release position, as shown in FIG. 1, while sealingly abuttingly engaging the intersection edge of surface 68 and chamber 66 to maintain inner sleeve end surface 82 in axially spaced relationship with shoulder 68 in an extended vacuum position as shown in FIGS. 2 and 3. 
     OPERATION 
     In operation, with the air inlet passage 54 suitably connected through an on-off type valve 84 to a source of high pressure air 86 of, for example, 80 psi as found in most industrial plants, and the apparatus in a normal non-vacuum, release position as shown in FIG. 1 the high pressure air flows into inlet passage 54 and inner sleeve chamber 56. The high pressure air acts against piston means provided by transverse surfaces 88, 90 and immediately forces the inner sleeve to slide axially from the non-vacuum, release, position of FIG. 1 to a vacuum position as shown in FIGS. 2 and 3 with the tapered outer surface of nozzle 78 seated against the intersection edge of surface 68 to close bypass ports 60, 62 and position the nozzle outlet 90 closely adjacent the outlet passage 70. The outer sleeve 28 is also moved axially against the bias of compression spring 34, during or slightly after the movement of the inner sleeve as indicated, in FIG. 2, by action of the high pressure air against piston means provided by transverse surfaces 92, 94 and by frictional engagement between the inner sleeve and the outer sleeve. There is sufficient leakage of high pressure air around seal 46 to fill chamber 42 in a relatively short time and, if necessary, a port may be provided through the central sleeve portion 52. Chamber 42 provides lost motion means enabling relative movement between the outer sleeve and the inner sleeve so that the inner sleeve will immediately move to the vacuum forming position and remain seated against the intersection edge of surface 68 regardless of variations in the force relationship between the compression spring and the air pressure acting on the piston surfaces. The high pressure air flows through nozzle passage 58 into outlet passage 70 thereby creating a low pressure zone in chamber 66 and causing a flow of air from the vacuum cup through vacuum passages 20, 74. Thus, a workpiece beneath the vacuum cup will be held fast thereagainst until the vacuum condition is dissipated by terminating the flow of high pressure air through the vacuum forming device 12 as hereinafter described. 
     In the present invention, automatic release means are provided to immediately dissipate the vacuum condition in chamber 66, passages 20, 74, and the vacuum cup when the high pressure air flow is terminated. The outer sleeve 28 and compression spring 34 provide return means for the vacuum forming member 40 which is rendered operative as previously described during the vacuum forming operation by the effects of the high pressure air and held more or less in the position shown in FIG. 3 as long as the high pressure air is on regardless of normal fluctuations in air pressure at the source. During vacuum forming operation, the chamber 42 between the inner and outer sleeves remains filled with high pressure air leaking around the partial seal 46 or through other air passages. When the high pressure air is shut off, the compression spring 34 is immediately effective upon reduction in air pressure to move the outer sleeve to the release position of FIG. 1 with surface 92 abutting the end plug 26. The inner sleeve 52 is also moved simultaneously with the outer sleeve 28 by connecting means provided by friction therebetween and the high pressure air trapped in the chamber 42 which is instantaneously incompressible therein. As soon as bypass ports 60, 62 are opened, a portion of the remaining high pressure air flows through the bypass ports against shoulder 68 to give additional impetus to the movement of the inner sleeve. Thus, the inner sleeve and the outer sleeve are returned more or less as a unit with abutment surface 78 being moved away from shoulder 68 to open passages 60, 62 whereby the remaining high pressure air in the system is discharged through vacuum dissipating air passage means as provided by passages 60, 62, as well as nozzle passage 58 which flow not only destroys further vacuum creating capability by changing the vacuum forming relationship of the parts, but also positively dissipates the existing vacuum in chamber 66 by discharging the remaining high pressure air in the system through both the outlet passage 70 and the vacuum passages 20, 74. Thus, one of the primary difficulties of prior art vacuum cup apparatus has been solved by provision of automatic release control means instantaneously operable when the high pressure air is shut off. A primary advantage of the present invention is the relative insensitivity of the release control means to normal fluctuations in air pressure while at the same time being immediately responsive to the on-off condition of the air supply.