Abstract:
A valve arrangement for a vacuum pump assembly selectively opens and closes communication between a vacuum pump, evacuation vessel, and a volume to be evacuated. The valve arrangement allows the evacuation vessel and any conduit connecting the vacuum pump and evacuation vessel to the volume to first be evacuated without providing a vacuum to the volume. The valve arrangement also allows the volume to be connected to the evacuation vessel but cut-off from the vacuum pump so that at initial stages of the evacuation process for the volume dead air contained within the volume may be communicated to the evacuation vessel rather than drawn out by the vacuum pump. Once the dead air, or portions thereof, has been removed from the volume, the valve arrangement may cut-off communication with the evacuation vessel, establish communication between the vacuum pump and the volume, and allow the vacuum pump to provide negative air pressure to the volume so that the volume may be evacuated.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims the benefit of U.S. Ser. No. 60/747,020, filed May 11, 2006, the disclosure of which is incorporated herein by reference. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    This invention pertains to a system and method for evacuating a volume or chamber, such as for use in vacuum packaging or in any other application in which a chamber or volume is subjected to negative air pressure. 
         [0003]    In a conventional evacuation system, a volume to be evacuated, such as a vacuum chamber, is initially at ambient atmospheric air pressure. When it is desired to evacuate the volume, a vacuum pump is operated so as to subject the volume to negative air pressure. In order to evacuate the volume, the vacuum pump must remove air from the volume as well as from the pipes, hoses, fittings, etc., that extend between the vacuum pump and the volume. This requires movement of a significant amount of dead air before the required negative air pressure is reached within the interior of the volume. In many applications, the volume of dead air that must be moved makes it necessary to utilize a relatively high capacity vacuum pump in order to evacuate the interior of the volume within a desired period of time. For example, in equipment that operates in a cyclic manner, such as vacuum packaging equipment, the time required to evacuate the interior of the vacuum chambers often can be the limiting factor in reducing cycle times. In applications that are not cyclic in nature, such as single chamber vacuum packaging equipment, metalizing chambers, vacuum chambers for semiconductor manufacture, etc., the evacuation time simply translates into operator downtime while waiting for the volume or chamber to be evacuated. 
       BRIEF DESCRIPTION OF THE INVENTION 
       [0004]    The present inventors have discovered that an evacuation system incorporating an evacuation vessel in fluid communication with the vacuum pump and volume to be evacuated and a valve arrangement that selectively opens and closes communication between the vacuum pump, evacuation vessel, and volume to be evacuated, functions to overcome some of the drawbacks generally associated with conventional evacuation systems, such as those enumerated above. In one embodiment of the present invention, the valve arrangement allows the evacuation vessel and any conduit connecting the vacuum pump and evacuation vessel to the volume to first be evacuated without providing a vacuum to the volume. The valve arrangement also allows the volume to be fluidly connected to the evacuation vessel but cut-off from the vacuum pump so that at initial stages of the evacuation process, dead air contained within the volume may be communicated to the evacuation vessel rather than drawn out by the vacuum pump. Once the dead air, or portions thereof, has been removed from the volume, the valve arrangement may cut-off communication with the evacuation vessel, establish communication between the vacuum pump and the volume, and allow the vacuum pump to provide negative air pressure to the volume so that the volume may be evacuated in preparation for a subsequent evacuation of the volume. 
         [0005]    It is therefore an object of the present invention to provide a system and method for evacuating a volume or chamber, which is capable of evacuating the volume or chamber in much less time than is required with conventional evacuation systems. It is a further object of the invention to provide such a system and method that enables use of a smaller vacuum pump than has been heretofore required for vacuum systems. Yet another object of the invention is to provide such a system and method which is relatively simple in implementation, and which can easily be adapted for use in any type of vacuum system either during original manufacture or in a retrofit application. 
         [0006]    Various other features, objects and advantages of the present invention will be made apparent from the following detailed description and the drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0007]    The drawings illustrate one preferred embodiment presently contemplated for carrying out the invention. 
           [0008]    In the drawings: 
           [0009]      FIG. 1  is an isometric view of a linear motion vacuum packaging system, which is a representative application for the system and method for evacuating a volume or chamber in accordance with the present invention; 
           [0010]      FIG. 2  is an isometric view of a control valve system incorporated into the vacuum packaging system of  FIG. 1  for carrying out the evacuation system and method of the present invention; 
           [0011]      FIG. 3  is a section view of the control valve system taken along line  3 - 3  of  FIG. 2 ; 
           [0012]      FIG. 4  is a schematic view of the evacuation system and method of the present invention, in which a control valve system as in  FIG. 3  is operative to provide negative pressure to a conduit connecting a vacuum pump to a vessel and a volume to be evacuated; 
           [0013]      FIG. 5  is a view similar to  FIG. 4  showing the control valve system operative to cut-off communication between the vacuum pump and the volume to be evacuated but allowing communication between the vessel and the volume to be evacuated; 
           [0014]      FIG. 6  is a view similar to  FIGS. 4-5  showing the control valve system operative to cut-off communication between the volume to be evacuated and both the vacuum pump and the vessel; and 
           [0015]      FIG. 7  is a view similar to  FIGS. 4-6  showing the control valve system operative to cut-off communication between the volume to be evacuated and the vessel but allow communication between the vacuum pump and the volume to be evacuated. 
       
    
    
     DETAILED DESCRIPTION 
       [0016]      FIG. 1  illustrates a representative embodiment of a vacuum packaging system  10  incorporating a pair of control valve systems  12  to selectively connect a pair of vacuum pumps  14 , a pair of evacuation vessels  16 , and a volume to be evacuated to one another. In the illustrated example, the vacuum packaging system  10  is a linear motion vacuum packaging system and thus includes a conveyor  18  that advances items (not shown) to be vacuum packaged along the length of the vacuum packaging system  10  in a linear primary path of travel. The vacuum packing system  10  further includes an evacuation arrangement  20 , which is mounted to a vertical support  22  that also holds the pair of evacuation vessels  16 , with the control valve systems  12  mounted thereto, suspended above the evacuation arrangement  20 . The control valve system  12  cooperates with conveyor  18  to evacuate and seal the items to be vacuum packaged as those items are conveyed by conveyer  18 . 
         [0017]    Conveyor  18  includes a series of platens  24 , each of which is adapted to receive and support an article and receptacle (not shown). Generally, any article suitable for vacuum packaging, such as a perishable food products, may be vacuum packaged by the vacuum packaging system  10  and the receptacle may be any satisfactory open-ended receptacle sized to receive the article and suitable for vacuum packaging, as is known in the art. Conveyor  18  may be configured to advance incrementally at spaced intervals in an indexing fashion, or may be configured to provide continuous advancement of items supported by conveyor  18 , either at a continuous rate of speed or at variable rates of speed. The platens  24  are advanced by conveyor  18  and cooperate with evacuation arrangement  20  to evacuate and seal an article within a receptacle. 
         [0018]    The evacuation arrangement  20  includes a series of identical vacuum chambers or heads  26   a - c,  each of which is associated with a vacuum valve  28   a - c  that controls the supply of vacuum to the interior of the associated vacuum chambers  26   a - c.  More particularly, each vacuum chamber  26   a - c  is provided with negative pressure by a header  30  that is fluidly connected to pumps  14  by conduits  32 , which may be hose, tubing, pipe, or the like. The header  30  includes fittings  34  that mate with conduits  32  to deliver negative pressure provided to the conduit  32  by pumps  14 . When valves  28   a - c  are open, negative pressure is delivered from the header  30  to the vacuum chambers  26   a - c.  Header  30  acts as a combination vacuum manifold and support for vacuum heads  26   a - c,  and replaces the need for each vacuum chamber  26   a - c  to be directly connected to pumps  14 . 
         [0019]    The vacuum packaging system  10  and evacuation arrangement  20  include components not specifically described herein, but which are known in the art, such as a user interface module, various drive motors, drive belts, belt tensioners, guide rollers, and pulleys, as described in PCT Application PCT/US2005/015833, the disclosure of which is incorporated herein by reference. 
         [0020]    Referring now to  FIGS. 2-3 , a representative embodiment of a control valve system  12  for selectively connecting a vacuum chamber, e.g.,  26   a,    26   b,  or  26   c,  to either vacuum pump  14  or evacuation vessel  16  includes a central body  36  providing an internal chamber  38  that communicates with one of vacuum pumps  14  through a pipe, hose, or tube attached to a fitting  40 . Similarly, the internal chamber  38  communicates with header  30  through a pipe, hose, or tube attached to fitting  42 , which is shown as conduit  32  in  FIG. 1 . The internal chamber  38  further includes an outlet  44  that fluidly communicates with an inlet of an evacuation vessel  16 . A valve body  48  is mounted in a sealed manner to one end  46  of the central body  36 , and contains a valve  50  that is controlled to selectively establish fluid communication between the vacuum pump  14  and either evacuation vessel  16  or header  30 . Valve  50 , in one embodiment, is pneumatically controlled, and includes a valve plate  52  connected to a piston or armature  54  by a pair of transverse members  56 . The valve body  48  provides a sealed volume  58  in which the armature  54  reciprocates. 
         [0021]    The internal chamber  38  is partially defined by a sidewall  60  having an opening  62  that forms an internal fluid passage between the internal chamber  38  and the vacuum pump  14  when valve  50  is in an open or retracted position. When the valve  50  is in a closed position, as shown in  FIG. 3 , pressure maintained in the sealed volume  58  forces armature  54  inwardly thereby causing plate  52  to cover, in a sealed manner, opening  62 . As a result, fluid communication between the internal chamber  38  and the vacuum pump  14  is prevented. When the armature  54  is forced outwardly, the plate  52  is drawn away from the opening  62  thereby establishing communication between the internal chamber  38  and the vacuum pump  14 . 
         [0022]    A valve body  66  is mounted in a sealed manner to an opposite end  64  of the central body  36 , and contains a valve  68  that is controlled to selectively establish fluid communication between the evacuation vessel  16  and either pump  14  or header  30 . Valve  68  is similar in construction to valve  50  described above. Specifically, valve  68 , in one embodiment, is pneumatically controlled, and includes a valve plate  70  connected to a piston or armature  72  by a pair of transverse members  74 . The valve body  66  provides a sealed volume  76  in which the armature  72  reciprocates. 
         [0023]    The internal chamber  38  is also partially defined by sidewall  78 , opposite sidewall  60 , and similarly has an opening  80  that forms an internal fluid passage between the internal chamber  38  and the evacuation vessel  16  through outlet  44  when valve  68  is in an open or retracted position. In one embodiment, openings  62 ,  80  are generally aligned with one another. 
         [0024]    In operation, when the valve  68  is at a closed position, as shown in  FIG. 3 , pressure maintained in the sealed volume  76  forces armature  72  inwardly thereby causing plate  70  to cover, in a sealed manner, opening  80 . As a result, fluid communication between the internal chamber  38  and the evacuation vessel  16  is prevented. When the armature  72  is forced outwardly or retracted, the plate  70  is drawn away from the opening  80  thereby establishing communication between the internal chamber  38  and the evacuation vessel  16 . 
         [0025]    As described above, valve bodies  50 ,  68  each provide a sealed volume  58 ,  76 , respectively, in which armatures  54 ,  72 , respectively, are reciprocated to selectively control opening and closing of the valves. In one embodiment, the armatures  54 ,  72  are linearly reciprocated in their respective valve bodies pneumatically. In this regard, each valve body  48 ,  66  is fluidly connected to a pair of conduits  82 ,  84  and  86 ,  86 , respectively, that deliver air to the respective volumes  58 ,  76  to cause liner motion of armatures  54 ,  72 , respectively. 
         [0026]    For example, referring to  FIG. 3 , valve body  48  includes a pair of openings  90 ,  92  coupled to conduits  82 ,  84 , respectively. Conduit  82  provides air to the volume  58  through opening  90  that bear against rear surface  94  of armature  54 . As air is delivered through opening  90 , air is extracted, either forcibly using a pump or passively, from biasing a front surface  96  of the armature  54 . Thus, the armature  54  travels inwardly until plate  52  engages sidewall  60  thereby closing opening  62 . To retract the armature  54 , air is removed from volume  58  through opening  90  and air is provided forward of the front surface  96  of the armature  54  through opening  92 . Valve  68  is similarly controlled by air supplied and removed through conduits  86 ,  88 . 
         [0027]    Operation of the control valve system to selectively establish communication between a vacuum pump, evacuation vessel, and vacuum chamber will be described with respect to  FIGS. 4-7 . With reference to  FIG. 4 , a vacuum pump P, such as pump  14 , is interconnected with a conduit  98 , which may be a pipe, tube, hose or any other satisfactory closed conveying member. A vacuum volume or chamber C, such as one of vacuum chambers  26   a - c,  is interconnected with a conduit  100 , which likewise may be a pipe, tube, hose or any other satisfactory closed conveying member. Volume or chamber C may be a vacuum head which, in a manner as is known, is adapted to be brought into contact with an underlying platen  24  for evacuating a volume defined by the chamber C and platen  24 , such as in a vacuum packaging application. It is understood, however, that volume or chamber C may be any closed volume to which negative air pressure is to be supplied, for evacuating the closed volume. A valve V 1 , such as valve  28   a,  is positioned between the interior of chamber C and the passage of conduit  100 , for selectively establishing and cutting off communication between the interior of chamber C and the passage of conduit  100 . 
         [0028]    A closed, fixed-volume evacuation tank  102 , which may be in the form of evacuation vessel  16 , defines an internal volume that is adapted to be selectively exposed either to the internal passage of conduit  98 , the internal passage of conduit  100 , or both. Preferably, the volume of vessel  102  is at least equal to the volume to be evacuated, i.e. the volume of chamber C in combination with the volume defined by the conduit  100  between the outlet of vessel  102  and chamber C. A valve V 2 , such as valve  68 , is configured to selectively open or close the outlet of vessel  102 . A valve V 3 , such as valve  50 , is configured to selectively open or close the internal passage of conduit  98 . 
         [0029]    Vessel  102 , in combination with valves V 1 , V 2  and V 3 , functions to deliver negative air pressure to the interior of chamber C much more efficiently, and in a shorter time period, than is possible in the prior art. Essentially, vessel  102  acts as a vacuum or negative air pressure volume or reservoir that is selectively exposed to the interior of chamber C, and then isolated from chamber C and exposed to pump P, to enable pump P to quickly and efficiently attain a desired level of negative air pressure within the interior of chamber C. 
         [0030]    In an initial position, as shown in  FIG. 4 , valve V 1  is closed and valves V 2  and V 3  are open. Vacuum pump P is operated so as to evacuate conduits  98 ,  100 , as well as the interior of vessel  102 . In the closed position, valve V 1  prevents the interior of chamber C from being exposed to the negative air pressure in the passage of conduit  98 , so that the interior of chamber C is at ambient air pressure. 
         [0031]      FIG. 5  illustrates the positions of valves V 1 , V 2  and V 3  when negative air pressure is to be delivered to the interior of chamber C such as, for example, when chamber C is lowered onto platen  24  for evacuating a package supported on the platen  24 . As shown in  FIG. 5 , valve V 3  is closed and valves V 1  and V 2  are open. Immediately upon opening both valves V 1  and V 2 , the negative pressure within the interior of vessel  102  is communicated through the vessel outlet to the passage of conduit  100 , and through valve V 1  to the interior of chamber C. While this action functions to raise the air pressure within the interior of vessel  102 , it immediately and significantly lowers the air pressure within the interior of chamber C. 
         [0032]    As shown in  FIG. 6 , valve V 2  is then closed so as to isolate the interior volume of vessel  102  from the interior of conduit  100  and the interior of chamber C. Valve V 1  remains open. The system then immediately progresses to open valve V 3 , as shown in  FIG. 7 , so that negative air pressure from conduit  98  and pump P is communicated through valve V 3 , the passage of conduit  100 , and valve V 1  to the interior of chamber C. Vacuum pump V thus begins its evacuation cycle with the interior of chamber C already at a significant negative air pressure due to exposure of the interior of chamber C to the negative air pressure within vessel  102  as shown in  FIG. 5 . 
         [0033]    With this system and method, it is possible to use a similarly sized vacuum pump as is in the prior art while significantly reducing the amount of time that it takes to fully evacuate the interior of chamber C, since the interior of chamber C is already at a relatively low negative air pressure before pump P begins the evacuation cycle. It has been found that, in vacuum delivery systems, vacuum pumps do not operate efficiently in initially removing the dead air required to evacuate a volume, which often is contained within hoses, pipes, fittings and the like. Efficiency of a vacuum pump increases significantly as vacuum. pressure is lowered. With the efficiencies offered by the initial delivery of negative air pressure to the volume to be evacuated, by operation of selective exposure of the interior of chamber C to the negative air pressure in the interior of tank  102 , the vacuum pump P is able to begin operation in the range of increased efficiency without having to move the dead air volume as in the prior art. 
         [0034]    In addition, in the event the evacuation time is not critical, it is possible to use a smaller vacuum pump than in the prior art in order to achieve the required vacuum pressure level within the interior of the chamber C. Since chamber C is already exposed to a significant vacuum pressure even before operation of pump P commences, pump P is able to operate in its more efficient range so as to deliver the required level of vacuum pressure to the interior of chamber C. The ability to use a smaller vacuum pump than in the prior art is significant, since vacuum pumps are very expensive items and the cost of a vacuum pump increases with size and capacity. In addition, the present invention enables the vacuum pump to be at a remote location, or at least farther away, from the chamber C than is possible in the prior art. In the past, it has been desirable to position the vacuum pump as close as possible to the chamber, so as to reduce the length of the pipes or hoses and therefore the volume of air that must be moved in order to achieve the desired vacuum level. 
         [0035]    The vacuum packaging system has been shown as having two pumps connected to a header at two ports and also having two evacuation vessels. It is understood that more than two pumps or a single pump may be used, or more than two evacuation vessels or a single evacuation vessel may be used. 
         [0036]    The present invention has been described in terms of the preferred embodiment, and it is recognized that equivalents, alternatives, and modifications, aside from those expressly stated, are possible and within the scope of the impending claims.