Abstract:
A pneumatic motor having a motor body having a main piston chamber with opposed first and second chamber ends, at least two spool chambers in fluid communication with the main piston chamber, an inlet for flowing a pressurized fluid into each of the at least two spool chambers, and an outlet provided in the housing for exhausting the pressurized fluid from the main piston chamber and each of the spool chambers. At least two spool members are in the two spool chambers, with each spool member adapted to be movable in a first direction to permit pressurized fluid to be supplied to the main piston chamber and also in a second direction to permit the pressurized fluid to be exhausted from the main piston chamber. A piston member is movable in a reciprocating manner in the main piston chamber in response to movement by the spool members. The piston has first and second piston ends and an annular piston chamber located between and in fluid communication with the first and second chamber ends, the first and second piston ends defining, with the first and second chamber ends, a first chamber and a second chamber, respectively, in the main piston chamber during reciprocation of the piston. First and second seals between the piston ends and the annular piston chamber are provided such that while the piston reciprocates within the main piston chamber, the first and second seals alternately exhaust the first and second chambers into the annular piston chamber.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    This invention generally relates to pneumatic motors, and more particularly to pneumatic shift reciprocating motors for pneumatic piston pumps.  
           [0002]    Pneumatic shift reciprocating motors are known with an example being shown in commonly assigned U.S. Pat. No. 5,586,480, issued Dec. 24, 1996 to the inventor of the present invention, the disclosure of which is incorporated by reference herein. U.S. Pat. No. 5,586,480 discloses a pneumatic motor having a piston chamber with a major piston and two valve chambers having three-way spool valves located therein. Operation of the piston is accomplished by alternately connecting opposite ends of the piston chamber to a pressurized air inlet or to exhaust. Shifting of the three-way spool valves is accomplished pneumatically by air that is supplied to an annular piston chamber continuously throughout the motion of the piston. Because the annular piston chamber was always connected to an air supply, the length of the major piston was the length of the stroke length, thereby causing such pneumatic motors to have longer overall lengths. This in turn created a motor having a less compact design and having longer internal air passages located therein. Additionally, the three-way spool valves as constructed therein contained multiple component parts including seals and also internal air passages to supply air to the end of the spools. The foregoing illustrates limitations known to exist in present pneumatic devices. Thus it is apparent that it would be advantageous to provide an alternative directed to overcoming one or more of the limitations set forth above. Accordingly an alternative pneumatic motor is provided including the features more fully disclosed hereinafter.  
         SUMMARY OF THE INVENTION  
         [0003]    A pneumatic motor having a motor body having a main piston chamber with opposed first and second chamber ends, at least two spool chambers in fluid communication with the main piston chamber, an inlet for flowing a pressurized fluid into each of the at least two spool chambers, and an outlet provided in the housing for exhausting the pressurized fluid from the main piston chamber and each of the spool chambers. At least two spool members are in the two spool chambers, with each spool member adapted to be movable in a first direction to permit pressurized fluid to be supplied to the main piston chamber and also in a second direction to permit the pressurized fluid to be exhausted from the main piston chamber. A piston member is movable in a reciprocating manner in the main piston chamber in response to movement by the spool members. The piston has first and second piston ends and an annular piston chamber located between and in fluid communication with the first and second chamber ends, the first and second piston ends defining, with the first and second chamber ends, a first chamber and a second chamber, respectively, in the main piston chamber during reciprocation of the piston. First and second seals between the piston ends and the annular piston chamber are provided such that while the piston reciprocates within the main piston chamber, the first and second seals alternately exhaust the first and second chambers into the annular piston chamber.  
           [0004]    The foregoing and other aspects will become apparent from the following detailed description of the invention when considered in conjunction with accompanying drawing figures. 
       
    
    
     DETAILED DESCRIPTION OF THE DRAWINGS  
       [0005]    FIGS.  1 - 5  are partial schematic, cross-sectional views of a pneumatic motor according to an embodiment of the present invention moving through successive stages of a pumping stroke;  
         [0006]    [0006]FIG. 6 is a top view of a motor body according to an embodiment of the present invention showing the main piston and spool chambers;  
         [0007]    [0007]FIG. 7 is an enlarged perspective view illustrating directional check valves incorporating seals according to an embodiment of the present invention;  
         [0008]    FIGS.  8 - 11  are partial schematic, cross-sectional views of a pneumatic motor according to another embodiment of the present invention moving through successive stages of a pumping stroke;  
         [0009]    [0009]FIG. 12 is a top view of a motor body according to another embodiment of the present invention showing the main piston and spool chambers; and  
         [0010]    [0010]FIG. 13 is an enlarged perspective view illustrating a piston having directional check valves incorporating seals according to another embodiment of the present invention. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0011]    The invention is best understood by reference to the accompanying drawings in which like reference numbers refer to like parts. It is emphasized that, according to common practice, the various dimensions of the diaphragms and the associated pump parts as shown in the drawings are not to scale and have been enlarged for clarity. Moreover, as used herein, the term “up”, “upward,” “down,” and “downward” are all taken with respect to the drawing figures as shown. Referring now to the drawings, FIG. 6 shows a top view of a motor housing of a first embodiment of a pneumatic motor according to the present invention. This motor includes a major cylinder having a bore that defines a piston chamber  1  and two minor cylinders that define spool chambers  2  and  3 . The embodiments of the air motor of the present invention are generally similar in construction to that shown in U.S. Pat. No. 5,586,480, which patent is incorporated by reference herein with the differences with the embodiments of the present invention being described in greater detail below.  
         [0012]    Turning to FIGS.  1 - 5 , shown are partial schematic views of a longitudinal cross-sectional of the motor with its component parts according to a first preferred embodiment. For clarity, the spool chambers  2  and  3 , which usually would be located side-by-side and share a single air inlet, are shown on opposite sides of the piston chamber  1  to show the operating relationship between the chambers and their component parts. The single air supply is provided by the same passage to chambers  2  and  3  with this supply being shown schematically to both chambers but described collectively as supply  101 . Spool chambers  2  and  3  have passages  17  and  8 , respectively, that are in fluid communication with piston chamber  1 . Spool chambers  2  and  3  also have ports  12 ,  112 , and  27 ,  25 , respectively, that are in fluid communication with piston chamber  1 . These ports, passages, and their operation will be described in greater detail below.  
         [0013]    Shown in spool chambers  2  and  3  are spools  11  and  4 , respectively. Spools  11  and  4  have large diameter ends with seals  13 ,  126 ,  102  and  28 ,  26 ,  7 , respectively, that move into and out of engagement with their respective spool chambers as described in detail below. On the ends opposite the larger diameters, spools  11  and  4  have relatively smaller diameter ends with seals  14 ,  15  and  6 ,  5 , respectively, around grooved portions  50  that form spool valves at the end of the small diameter ends of the spools. These spool valves move into and out of engagement with stepped portions located in their respective spool chambers to exhaust on their ends as described in detail below. By providing spools  11  and  4  each with large and small diameter ends, shifting is accomplished by the differential in the cross-sectional areas provided at these ends as described in detail below. Additionally, because air is supplied to the ends of the spools by porting described below, the need for internal air passages to supply air to the spool end as shown in the &#39;480 patent is eliminated. It will be understood, that either type of spool may be incorporated, however, the spool taught by the &#39;480 patent requires two additional internal passages. Also provided on spools  11  and  4  are passages  30  and  29 , respectively, that channel air through the spools as described in greater detail below.  
         [0014]    Head caps  35  and  40  are provided that close off the ends of the spool chambers containing the larger diameter ends of the spools  4  and  11  while leaving the exhaust ends of the spool chambers (i.e., the ends that contain the smaller diameter ends of the spools) at least partially open to atmosphere. Preferably, protuberances  45  are also provided to prevent the spool members from sticking during operation of the motor.  
         [0015]    As shown in FIGS.  1 - 5 , located within the piston chamber  1  is a piston  10  on which are provided seals  18  and  19  that are always sealed against the piston chamber  1  of the major cylinder and define chambers  9  and  16  and an annular piston chamber  20 . Also provided on main piston  10  are seals  21  and  22  that are located in “V”-grooves located circumferentially around main piston  10  as shown in greater detail in FIG. 7. The “V”-grooves each provide two seal points shown as “A” and “B” in and define annular chambers  250  in which seals  21  and  22  respectively sit and act as check valves. The check valves provided by seals  21  and  22  are one-way valves that permit air passing from passages  23  and  24  into annular chambers  25  and  26  to pass into annular piston chamber  20  while they prevent reverse flow from annular piston chamber  20  due to the elasticity of the seal and pressure caused by the air pressure in annular piston chamber  20 . This construction allows these seals to become unsealed and pass air at a low pressure since the effective area is the diameter of the seal, not the port. This is an improvement over prior art seals such as those used in paint sprayers that incorporate the use of a flat seal over a port and require more pressure to unseat the seal.  
         [0016]    Operation of the motor shown in FIGS.  1 - 5  will now be described. Referring now to FIG. 1, air supply  101  (shown on both sides of the motor) provides air that fills spool chamber  2  and spool chamber  3 . With respect to air passing into chamber  3 , a seal  7  is provided having a larger diameter and, therefor, a larger effective surface area than seal  5  for the air to act on. As a result the pressure acting on the larger surface area of seal  7  generates a larger force that moves spool  4  up in chamber  3  to the position shown in FIG. 1. With spool  4  in this position, seal  5  and seal  7  on spool  4  seal against the sides and define chamber  3  as shown. Seal  6  does not seal in this position, however, and causes main piston  10  to move upward by permitting air from chamber  3  to enter chamber  9  through passage  8 . Air passing into chamber  9  also passes through port  12  to force spool  11  upward to the position shown in FIG. 1. This upward force on spool  11  is generated because seal  13  is provided with a larger diameter and thus a larger effective surface area than seal  14  or seal  15 .  
         [0017]    As main piston  10  approaches the fully upward position in FIG. 1, when seal  18  crosses port  25  the air in annular piston chamber  20  can go nowhere because port  25  is blocked by seals  26  and  7 . When seal  18  crosses port  27  at the end of the stroke of main piston  10 , however, air in chamber  9  enters via passage  23  across a one-way check valve formed by seal  21  into annular piston chamber  20 . The air in annular piston chamber  20  then goes through port  27  and forces spool  4  down because seal  28  is larger than and provides a larger effective surface area than seal  5  or seal  6 . As spool  4  moves down to the position shown in FIG. 2, seal  26  crosses over port  25  connecting air in chamber  3  to the top of spool  4  through passage  29 , port  25 , annular piston chamber  20  and port  27 . Thus, in the fully downward position shown in FIG. 2, spool  4  is held down even when no air signal is supplied from chamber  9  through passage  23 . Additionally, as shown in FIG. 2, when seal  6  contacts the walls of chamber  3 , supply air to chamber  9  is disconnected from passage  8  and seal  5  no longer seals against chamber  3  thereby connecting chamber  9  to exhaust through passage  8  past seal  5 . Because chamber  9  is connected to exhaust via passage  8 , port  12  is also open to exhaust, so spool  11  is forced down (as shown in FIG. 3) by supply air entering chamber  2 . With spool  11  moved to the downward position shown in FIG. 3, seal  14  no longer contacts chamber  2  and thereby permits supply air entering chamber  2  to pass through port  17  into chamber  16 . Because port  8  is already connected to exhaust, major piston  10  is forced downward as shown in FIG. 3.  
         [0018]    As main piston  10  approaches the fully downward position in FIG. 4, when seal  19  crosses port  112  the air in annular piston chamber  20  can go nowhere because port  112  is blocked by seals  126  and  102 . When seal  19  crosses port  12  at the end of the stroke of main piston  10 , however, air in chamber  16  enters via passage  24  across a one-way check valve formed by seal  22  into annular piston chamber  20 . The air in annular piston chamber  20  then goes through port  12  and forces spool  11  up because seal  13  is larger than and provides a larger effective surface area than seal  14  or seal  15 . As spool  11  moves up to the position shown in FIG. 5, seal  126  crosses over port  112  connecting air in chamber  2  to the bottom of spool  11  through passage  30 , port  112 , annular piston chamber  20  and port  12 . Thus, in the fully upward position shown in FIG. 5, spool  11  is held up even when no air signal is supplied from chamber  16  through passage  24 . Additionally, as shown in FIG. 5, when seal  14  contacts the walls of chamber  2 , supply air to chamber  16  is disconnected from passage  17  and seal  15  no longer seals against chamber  2  thereby connecting chamber  16  to exhaust through passage  17  past seal  15 . Because chamber  16  is connected to exhaust via passage  17 , port  27  is also open to exhaust, so spool  4  is forced upward to the position shown in FIG. 1 by supply air entering chamber  3 . With spool  4  moved to the upward position shown in FIG. 1, seal  6  no longer contacts chamber  3  and thereby permits supply air entering chamber  3  to pass through port  8  into chamber  9 . Because port  17  is already connected to exhaust, major piston  10  is forced upward to the position shown in FIG. 1 and the cycle is repeated as described above. Piston  10  will continue to reciprocate up and down as long as there is an air supply provided.  
         [0019]    In yet another embodiment shown in FIGS.  8 - 11  are sequential schematic diagrams that show the operation of the motor housing shown in the top view in FIG. 12. The pneumatic motor is shown having a major cylinder having a bore that defines a piston chamber  100  and two minor cylinders that define spool chambers  102  and  103 . The air motor is similar in construction to that shown and described above with respect to FIGS.  1 - 7  except that in addition to other features described further in detail below, generally, the spools do not contain any through passages, the main piston does not contain internal porting and the spool chambers are in fluid communication via two interconnecting passages. For clarity, the two interconnecting passages between chambers  102  and  103  are shown schematically and described with respect to these chambers as ports  104  and  104 A (for the first passage) and ports  105  and  105 A (for the second passage). Similarly, one air supply is provided by the same passage to chambers  102  and  103  with this supply being shown schematically and described as air supply  106  and  106 A, respectively.  
         [0020]    Turning to FIGS.  8 - 11 , shown are partial schematic views of a longitudinal cross-sectional of the motor with its component parts shown sequentially in operation. For clarity, the spool chambers  102  and  103 , which usually would be located side-by-side and share a single air inlet, are shown on opposite sides of the piston chamber  100  to show the operating relationship between the chambers and their component parts. Spool chambers  102  and  103  have passages  112  and  120 , respectively, and ports  124  and  115 , respectively, that are in fluid communication with piston chamber  100 . These ports, passages, and their operation will be described in greater detail below.  
         [0021]    Shown in spool chambers  102  and  103  are spools  107  and  108 , respectively. Spools  107  and  108  have large diameter ends with seals  116  and  109 , respectively, that move into and out of engagement with their respective spool chambers as described in detail below. On the ends opposite the larger diameters, spools  11  and  4  have relatively smaller diameter ends with grooved portions  50  that form spool valves at the end of the small diameter ends of the spools. These spool valves move into and out of engagement with seals located on the interior of their respective spool chambers to exhaust on their ends as described in detail below. By providing spools  107  and  108  each with large and small diameter ends, shifting is accomplished by the differential in the cross-sectional areas provided at these ends as described in detail below. Additionally, because air is supplied to the ends of the spools by porting described below, the need for internal air passages to supply air to the spool end as shown in the &#39;480 patent is eliminated, although it will be understood, that the spool taught by the &#39;480 patent may be incorporated with the two additional internal passages as taught in the &#39;480 patent.  
         [0022]    Head caps  135  and  140  are provided that close off the ends of the spool chambers containing the larger diameter ends of the spools  107  and  108  while leaving the exhaust ends of the spool chambers (i.e., the ends that contain the smaller diameter ends of the spools) at least partially open to atmosphere. Preferably, protuberances  145  are also provided to prevent the spool members from sticking during operation of the motor.  
         [0023]    As shown in FIGS.  8 - 12 , located within the piston chamber  100  is a piston  114  that divides the piston chamber into a chamber  113  located above the piston and a chamber  119  located below the piston. Piston  114  is provided with a large annular depression that forms an annular piston chamber  210  and has two additional depressions in which are provided unidirectional seals  122  and  123  that provide sealing in one direction. Preferably, these seals are “U”-Rings as shown in FIG. 13 having a lip  124  that does not seal in one direction. Most preferably seals  122  and  123  are non-symmetrical PARKER UR Series “U”-Rings having a back-beveled lip, which seals are available from the Packing Division of Parker Hannifin Corporation, Salt Lake City, Utah.  
         [0024]    The dimensions of piston  114  are configured with its largest cross-sectional outer diameter being slightly smaller than the inner diameter of piston chamber  100  and so that when placed inside piston chamber  100 , the back-leveled lip portions  124  contact the inner surface of piston chamber  100 . This configuration permits air to pass through the one-way seals to annular piston chamber  210  as described below. As shown in FIG. 13, seals  122  and  123  are mounted to face each other so that during operation of the motor, when air enters into chamber  113  the back-beveled lip of seal  122  deflects inward to permit air to fill annular piston chamber  210  while the back-beveled lip of seal  123  deflects outward to engage the inner surface of piston chamber  100  thereby preventing air from passing into chamber  119 . Similarly, when air enters into chamber  119  the back-beveled lip of seal  123  deflects inward to permit air to fill annular piston chamber  210  while the back-beveled lip of seal  122  deflects outward to engage the inner surface of piston chamber  100  thereby preventing air from passing into chamber  113 . When moving in either direction, however, seals  122  and  123  prevent air from moving from annular piston chamber  210  into chambers  113  and  119 , respectively.  
         [0025]    Operation of this alternative embodiment will now be described beginning with FIG. 8 in which air is provided via supply  106 A enters into spool chamber  103  to act against seal  109  on spool  108 , thereby holding it in a downward position as shown. Supply air from supply  106 A travels past seal  110  through passage  112  to chamber  113  forcing piston  114  downward. Supply air in chamber  113  passes through port  115  and acts on seal  116  which is larger than seal  117  and  118 , thereby forcing spool  107  down to the position shown. While in the downward position, spool  107  permits chamber  119  located under piston  114  to be vented to exhaust through passage  120  and past seal  118 . When piston  114  is going down, air from chamber  113  causes seal  122  to open and seal  123  to close thereby permitting air to pass by seal  122  into annular piston chamber  210  while seal  123  prevents air from passing into chamber  119 . Annular piston chamber  210  is thus filled by air passing between seals  122  and  123 .  
         [0026]    When piston  114  nears the bottom of its stroke, seal  123  crosses port  124  thereby connecting the bottom portion of spool chamber  103  beneath seal  109  to supply air passing sequentially from chamber  113 , annular piston chamber  210 , and through port  124 . Because seal  109  is larger than seal  111 , the supply air forces spool  108  upward to the position shown in FIG. 9, thereby disconnecting passage  112  from supply air and connecting port  112  to exhaust past seal  111 . Prior to spool  108  reaching the fully upward position and before seal  110  seals against spool  108 , however, as seal  109  passes port  105 A the air supply from spool chamber  102  is connected to the bottom of spool  108  via port  105  thereby holding spool  108  upward even after the air supply from annular piston chamber  210  is stopped by seal  110  sealing against spool  108 .  
         [0027]    With spool  108  moved into the fully upward position shown in FIG. 9, chamber  113  is connected to exhaust through passage  112  and past seal  111 . The top (larger diameter) portion of spool  107  is also connected to exhaust sequentially through port  115 , chamber  113 , and passage  112 . Because the bottom side of seal  116  is always connected to air supply  106 , spool  107  is forced up to the position shown in FIG. 10. In this position, the exhaust of chamber  119  through passage  120  is closed by seal  118  engaging spool  107  and opens chamber  119  to supply air by unsealing seal  117 , thereby forcing piston  114  upward as shown in FIG. 11. As piston  114  changes direction and begins to moves upward, air from chamber  119  causes seal  123  to open and seal  122  to close thereby permitting air to pass by seal  123  into annular piston chamber  210  while seal  122  prevents air from passing into chamber  113 . Annular piston chamber  210  is thus filled by air passing between seals  122  and  123 .  
         [0028]    As piston  114  nears the top of its stroke, seal  122  crosses port  115  thereby connecting the top portion of spool chamber  102  above seal  116  to supply air passing sequentially from chamber  119 , annular piston chamber  210 , and through port  115  to repeat the process. Thus, piston  114  will continue to reciprocate up and down as long as air is supplied to the air inlet.  
         [0029]    Thus, by supplying an annular piston chamber with initial signal air supplied from either end of the piston through directional check valves, the present invention provides, inter alia, a pneumatic motor having a more compact design with a major piston that can be shorter in length than prior art motors. When the initial signal is stopped due to the valve shifting, the signal is maintained through the spool to the annular piston chamber between seals located on the major piston. Moreover, because the major piston does not have to be connected to air supply, the need for a center hole in the major cylinder can be eliminated. As a result, this valve lends itself to be a separate part and easily be attached to any cylinder. This becomes more apparent in larger diameter cylinders where multi-chamber extrusions become impractical.  
         [0030]    While embodiments and applications of this invention have been shown and described, it will be apparent to those skilled in the art that many more modifications are possible without departing from the inventive concepts herein described. For example, although the present invention is shown and described with different piston arrangements, these pistons may be interchanged and used with the spool chamber configuration of the other. It is understood, therefore, that the invention is capable of modification and therefore is not to be limited to the precise details set forth. Rather, various modifications may be made in the details within the scope and range of equivalents of the claims without departing from the spirit of the invention.