Abstract:
A fluid cylinder assembly including a cylinder, a rod assembly, and a valve assembly. The rod assembly includes a rod having a first end and a second end and a piston connected to the first end of the rod. The piston is slidingly positioned in the cylinder. The second end of the rod extending from the cylinder. The valve assembly is in fluid communication with the cylinder. The valve assembly is configured to moderate pressure within the cylinder when an external force is applied against the second end of the rod.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This is a non-provisional application based upon U.S. provisional patent application Ser. No. 61/648,314, entitled “PNEUMATIC CYLINDER WITH PRESSURE MODERATOR”, filed May 17, 2012, which is incorporated herein by reference. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The invention relates to a pneumatic actuator, and more particularly to a pressure moderated pneumatic cylinder. 
         [0004]    2. Description of the Related Art 
         [0005]    Pneumatic cylinders are mechanical devices used to provide motive force in a variety of uses including, but not limited to, closing a sliding door. In many of these uses, such as the sliding door, the motive force may present danger of bodily injury if it moves too quickly. In prior art, a simple cylinder comprised of a piston, rod and housing provides the motive force by supplying compressed air to either one or the other side of the piston. When compressed air is directed to the side of the piston opposite the piston rod, the piston rod will extend out of the housing. Also in prior art, if an external force acts to overcome the air pressure on the piston and force the piston rod back into the housing, the developed air pressure inside the cylinder may actually exceed the supplied air pressure if it is not allowed to quickly bleed back into the pressure supply system, to a larger storage vessel or to atmosphere. This excess air pressure inside the cylinder may cause the piston rod to extend too quickly when the external force is removed and present danger of bodily injury. Methods used in prior art to control the speed of the cylinder typically increase the size and complexity of the cylinder thru the addition of external speed dampeners or addition of air flow controls that often do not prevent the excess air pressure caused by external forces. 
         [0006]    What is needed in the art is a cost effect apparatus and method of moderating the movement of a pneumatic articulator. 
       SUMMARY OF THE INVENTION 
       [0007]    The present invention is directed to a pneumatic articulator, and more particularly to a method of moderating the outward movement of the pneumatic articulator after it encounters an opposing force. 
         [0008]    The invention in one form is directed to a movable assembly including a movable structure with a fluid cylinder assembly coupled to the movable structure. The fluid cylinder assembly includes a cylinder, a rod assembly, and a valve assembly. The rod assembly includes a rod having a first end and a second end and a piston connected to the first end of the rod. The piston is slidingly positioned in the cylinder. The second end of the rod extending from the cylinder. The valve assembly is in fluid communication with the cylinder. The valve assembly is configured to moderate pressure within the cylinder when an external force is applied against the second end of the rod. 
         [0009]    The invention in another form is directed to a fluid cylinder assembly including a cylinder, a rod assembly, and a valve assembly. The rod assembly includes a rod having a first end and a second end and a piston connected to the first end of the rod. The piston is slidingly positioned in the cylinder. The second end of the rod extending from the cylinder. The valve assembly is in fluid communication with the cylinder. The valve assembly is configured to moderate pressure within the cylinder when an external force is applied against the second end of the rod. 
         [0010]    The invention in yet another form is directed to a method of moderating a movement of a pneumatic cylinder assembly. The method including the steps of fluidically coupling a valve assembly to the pneumatic cylinder assembly, and of moderating pressure within the pneumatic cylinder by way of a valve position selection such that when an external force is applied against movement of an end of a rod extending from the pneumatic cylinder assembly a substantially equal fluidic pressure is applied to both sides of a piston coupled to the rod. 
         [0011]    The present invention is directed to an improved cylinder incorporating features with minimal increase in size or complexity that moderate the development of excess air pressure when an outside force acts on the piston rod—in particular when the outside force acts to force the piston rod back into the cylinder housing. 
         [0012]    The present invention provides a pneumatic cylinder with integral cartridge style relay valves used to connect pressurized air to either side of a piston inside the cylinder. The present invention also provides an internal passage to communicate pressurized air from the relay valves in the cap block to the piston rod side of the piston. 
         [0013]    To extend the piston rod out of the cylinder the valve circuit communicates pressurized air to both sides of the piston. A net difference in the piston surface areas due to the presence of the piston rod on the rod side of the piston causes an imbalance of applied force on the piston from the pressurized air causing the piston rod to extend. To retract the piston rod back into the cylinder, the valve circuit communicates pressurized air to only the piston rod side of the piston while the air on the opposite side of the piston is exhausted. In prior art the piston rod is relatively small in comparison to the piston size and the net difference in piston areas then yields relatively low force to extend the piston rod. In this embodiment, the piston rod and piston diameters are selected to provide nearly equal net surface areas when pressurized air acts on both sides of the piston to extend the rod and acts only on the piston rod side of the piston to retract the rod. This reduces the physical size of the cylinder that is required in order to produce the desired extending force in the piston rod. By communicating pressurized air to both sides of the piston in order to extend the piston rod, a pathway is provided to maintain balanced air pressure on both sides of the piston when an outside force acts to overcome air pressure and cause the piston rod to retract. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0014]    The above-mentioned and other features and advantages of this invention, and the manner of attaining them, will become more apparent and the invention will be better understood by reference to the following description of an embodiment of the invention taken in conjunction with the accompanying drawings, wherein: 
           [0015]      FIG. 1  shows an exploded perspective view of the cylinder assembly according to one embodiment of the present invention; and 
           [0016]      FIG. 2  is a schematic view of the cylinder assembly of  FIG. 1 . 
       
    
    
       [0017]    Corresponding reference characters indicate corresponding parts throughout the several views. The exemplification set out herein illustrates an embodiment of the invention, in one form, and such exemplification is not to be construed as limiting the scope of the invention in any manner. 
       DETAILED DESCRIPTION OF THE INVENTION 
       [0018]    Referring now to the drawings and more particularly to  FIGS. 1 and 2 , there is shown a fluid articulator assembly  10 , which may be a pneumatic articulator assembly  10 , also referred to as a pneumatic cylinder assembly  10 , including a cylinder assembly  12 , a rod  14 , a piston assembly  16  and a valve assembly  18 . Cylinder assembly  12  includes a tube  20  affixed with end block assemblies  22  and  24  to form a cylinder housing. Tube  20  includes a main piston bore  26  and an internal air passageway  28  that extends through the entire length of tube  20 . Seals  30 ,  31 ,  32  and  34  seal piston bore  26  and air passageway  28  in an airtight manner to end block assemblies  22  and  24 . Tube  20  is illustrated as being an extrusion with interior air passageway  28  being integral therewith. 
         [0019]    Piston assembly  16  and rod assembly  14  are slidable within cylinder assembly  12 . In the embodiment illustrated of this invention, piston assembly  16  includes and is affixed with bi- directional piston seals  36  and a piston bearing  38 . Rod end block assembly  22  includes a rod bearing  40  and a rod seal  42  affixed in block  44 . Cap end block assembly  24  includes valve cavities  46  and  48  to accommodate an extend valve  50  and a retract valve  52  as well as internal passageways (shown schematically in  FIG. 2 ) to communicate between valves  50  and  52 , and piston bore  26 , tube  20  internal passageway  28 , breather vents  54  and  56 , and a pressurized air supply port  58 . 
         [0020]    Referring now to  FIG. 2 , there is shown a schematic illustration of pneumatic articulator assembly  10 . When retract valve  52  is in the position shown it interconnects rod end chamber  60  and head end chamber  62 . Valve  50  has ports  64 ,  66  and  68  and valve  52  has ports  70 ,  72  and  74 . As illustrated, retract valve  52  interconnects ports  72  and  74 , and if extend valve  50  interconnects ports  64  and  66 , then fluid pressure is applied to both sides of piston assembly  16 , and the difference in surface area between the head end and the rod end of piston assembly  16  causes piston assembly  16  to move to the extended position adjacent end block assembly  22 . 
         [0021]    On the other hand, when extend valve  50  is in the position shown it interconnects ports  66  and  68 , and when retract valve  52  is positioned to interconnect ports  70  and  72 , then fluid pressure is applied to the rod end of piston assembly  16 , and piston assembly  16  moves to the retract position adjacent to end block assembly  24  (shown). 
         [0022]    In another embodiment, the rod bearing  40  and the rod end block  22  may be made as an integral assembly with the rod end block  22  bore surfaces used in place of a separate bearing  40 . 
         [0023]    In another embodiment, the piston bearing  38  may be omitted from the cylinder assembly. 
         [0024]    In another embodiment a single uni-directional seal may replace the bi-directional seals  36 . 
         [0025]    In another embodiment, internal passageway  28  may be replaced by external tubing and fittings as a means of communicating pressurized air from the valves  50  and  52  to end block assembly  22 . 
         [0026]    In another embodiment, external valves connected to the cylinder by tubing may replace the cartridge style relay valves  50  and  52  and fittings or o-ring face seal type connections. 
         [0027]    The diameter of rod  14  and piston assembly  16  are selected to provide approximately equal, nearly equal, or substantially equal, net surface areas when pressurized air acts on both sides of piston assembly  16  to extend rod  14  and acts only on the piston rod side of piston assembly  16  to retract rod  14 . This is accomplished by making the surface area on piston assembly  16 , proximate to head end chamber  62 , twice the surface area on piston assembly  16  proximate to rod end chamber  60 . The selection of the cross-sectional area of rod  14  to be approximately the same as the piston assembly  16  surface area associated with rod side chamber  60  allows for approximately the same force being applied to rod  14 , in opposite directions, when valves  50  and  52  are sequenced as discussed herein. Advantageously, this reduces the physical size of the cylinder that is required in order to produce the desired extending force in rod  14 . Rod  14  is connected to a mass  76 , which can be a movable member  76  such as a door. The overall assembly of mass  76  with articulator assembly  10  can be referred to as a movable assembly. As mass  76  is extended away from articulator assembly  10 , it may encounter an obstacle  78 . In the prior art, pressure may build in head end chamber  62  and when obstacle  78  is removed, or yields, the built up pressure in head end chamber  62  (unchecked by pressure in rod end chamber  60 ) would cause mass  76  to be rapidly moved causing possible damage to the prior art cylinder assembly or to something that mass  76  may contact. In the present invention, this is prevented or moderated by communicating pressurized air to both sides of the piston as rod  14  is extended, a pathway is provided to maintain balanced air pressure on both sides of the piston when an outside force acts to overcome air pressure and cause the piston rod to retract. 
         [0028]    The term “moderate pressure” is what occurs within the cylinder such that compressible fluid pressure is applied to both sides of a piston so that movement of rod  14  is moderated when mass  76  encounters an obstacle  78 . This is also described as a damping method. The moderation takes the form of reduced outward movement of rod  14  when obstacle  78  is taken away so that rod  14  continues an outward movement in the form of a “moderated” movement as compared to what would happen without the application of compressible fluid pressure to both sides of the piston. 
         [0029]    While this invention has been described with respect to at least one embodiment, the present invention can be further modified within the spirit and scope of this disclosure. This application is therefore intended to cover any variations, uses, or adaptations of the invention using its general principles. Further, this application is intended to cover such departures from the present disclosure as come within known or customary practice in the art to which this invention pertains and which fall within the limits of the appended claims.