Abstract:
An oilless air motor assembly and method useable for driving hydraulic pumps and the like. The air motor assembly comprises a slide valve that moved back and forth relative to a valve sleeve situated about the slide valve. A low friction or lubricious dry seal member is disposed between the slide valve and the valve sleeve, thereby eliminating the need for added oil or lubricant and additionally avoiding the need for precise machining and matching (e.g., honing and lapping) of the slide valve and valve sleeve. Also provided is a kit for converting a previously manufactured air motor assembly that requires oil or added lubricant to an oilless air motor assembly. Such kit comprises the slide valve, valve sleeve and dry seal member as well as other optional parts associated with those elements.

Description:
This is a continuation of application Ser. No. 09/954,828 filed on Sep. 18, 2001 now U.S. Pat. No. 6,676,386. 

   FIELD OF THE INVENTION  
   The present invention relates generally to hydraulic pumps and more particularly to a hydraulic pump that may be operated without the need for added lubrication or atomized oil in the air source. 
   BACKGROUND OF THE INVENTION  
   The prior art has included a number of rotating and reciprocating air motors useable to drive hydraulic pumps and the like. One such air motor is described in U.S. Pat. No. 3,272,081(Vedder, et al.) entitled Air Motor, the entirety of which is expressly incorporated herein by reference. 
   One drawback associated with at least some of the reciprocating air motors of the prior art, including that described in U.S. Pat. No. 3,272,081, is that slide valve(s) within the air motor ride in metal to metal contact with valve sleeve(s) or other parts of the apparatus and continual lubrication must be dispensed into, such metal to metal interface to avoid excessive wear of the piston(s) and to maintain a reasonable service life for the air motor. Additionally, the slide valve(s) and sleeve(s) or other parts between which the metal to metal fit is required must be precisely machined for a high tolerance fit and are typically required to be made of hard. machinable metal such as stainless steel. The application of lubricant upon the engaged metal surfaces was typically accomplished by atomizing oil in the air that is used within the air motor such that the atomized oil will deposit on the piston(s) and other parts of the air motor apparatus that frictionally interface with the piston(s). However, when the air exhausts from the air motor, some amount of atomized oil typically remains in the exhausted air and presents a health risk to workers who incur long term respiratory exposure to the said atomized oil that is exhausted by the air motor. Additionally, the use of atomized oil in the air can be laborious, cumbersome and adds expense to the operation in which it is used. 
   In view of the foregoing, there exists a need in the art for the development of an oilless reciprocating air motor of the type described in U.S. Pat. No. 3,272,081 wherein self lubricating or lubricious materials are positioned between the slide valve(s) and valve sleeve(s) or other portions of the air motor that frictionally interface with the slide valve(s), thereby eliminating the need for precisely machined, high tolerance fits between such parts and also eliminating the need for the use of atomized oil, other added oil or grease or added lubricant during routine operation of the air motor. 
   SUMMARY OF THE INVENTION  
   The present invention comprises an oilless air motor that is useable in a variety of applications, including the driving of a reciprocating pump component such as the ram or piston of a hydraulic pump. 
   In accordance with this invention, there is provided an air motor comprising a body having a bore, an air cylinder that extends from said body and opens to said bore, a first manifold, a second manifold, a third manifold, an air inlet port that leads to the first manifold, an air exhaust port that leads to the second manifold, and at least one passageway that leads from the third manifold and opens into the upper end of the air cylinder, an air piston in said cylinder provided with a hollow stem operative in the body bore and having ports opening through the bottom thereof, a slide valve sleeve disposed in the bore about the air piston, slide valve sleeve being moveable between an upper position and a lower position, slide valve sleeve providing communication (i) between the air inlet and the body bore and between the air exhaust and the upper portion of the air cylinder via the passageway, when the valve sleeve is in one of said positions; and, (ii) between the air inlet and the upper end of the air cylinder via the passageway and between the body bore and the air exhaust, when the sleeve valve is in the other of said positions; a pilot valve disposed within the valve sleeve, the pilot valve having an axial bore with a piston at one end, said pilot valve being shiftable by air pressure from the inlet entering the body bore, as controlled by the valve sleeve; a first check valve carried by the pilot valve to allow air to be received through the ports of the air piston; a second check valve carried by the pilot valve to allow air to pass from beneath the air piston into the body bore; and, a dry seal member disposed between the valve sleeve and a part of the air motor adjacent the valve sleeve to allow the valve sleeve to move back and forth without the need for oil or other lubricant between the valve sleeve and the part of the air motor adjacent the valve sleeve. In some embodiments, a slide valve will be positioned about the air piston and the dry seal will be disposed between the slide valve and the valve sleeve. 
   Further in accordance with the invention, the dry seal member may be formed at least partially of a lubricious material, such as a lubricious polymer or a graphite-containing or graphite-impregnated polymer. 
   Still further in accordance with the invention, a retaining apparatus such as a retaining ring that snap fits into an annular groove on the slide valve or other portion of the air motor adjacent to the valve sleeve to limit or prevent unwanted slippage or movement of the dry seal as the air motor operates. 
   Still further in accordance with the invention, there is provided a kit for replacing parts of an existing air motor that requires atomized oil or other added lubrication to eliminate the need for the continued use of atomized oil in the air or other added lubrication. Such kit may comprise a replacement air piston assembly comprising a slide valve, a valve sleeve that substantially surrounds the slide valve and a dry seal formed of lubricious material and disposed between the slide valve and the valve sleeve to prevent direct friction between the slide valve and the valve sleeve. 
   Further aspects and elements of this invention will become apparent to those of skill in the art upon reading the detailed description that appears herebelow in reference to the accompanying drawings. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS  
       FIG. 1   a  is a longitudinal sectional view of an oilless air motor apparatus according to the present invention, taken through a vertical plane with the air piston in the down position. 
       FIG. 1   b  is another longitudinal sectional view of the oilless air motor apparatus of  FIG. 1   a  taken through a plane that is rotated 90 degrees from the plane through which the section of  FIG. 1   a  was taken. 
       FIG. 1   c  is a longitudinal sectional view of an oilless air motor apparatus according to the present invention, taken through a vertical plane with the air piston in the up position. 
       FIG. 1   d  is another longitudinal sectional view of the oilless air motor apparatus of  FIG. 1   c  taken through a plane that is rotated 90 degrees from the plane through which the section of  FIG. 1   c  was taken. 
       FIG. 2  is an enlarged sectional view of the air piston actuating valve assembly of an oilless air motor apparatus of the present invention. 
       FIG. 3  is an exploded perspective view of the air piston actuating valve assembly of  FIG. 2 . 
       FIG. 4  is a longitudinal sectional view of the pilot valve assembly of an oilless air motor apparatus of the present invention. 
       FIG. 5  is an exploded perspective view of the pilot valve assembly of  FIG. 4 . 
       FIG. 6  is a longitudinal sectional view of the air check assembly of an oilless air motor apparatus of the present invention. 
       FIG. 7  is a perspective view of the air check assembly of  FIG. 6 . 
       FIG. 8  is an exploded perspective view of the air check assembly of  FIG. 7 . 
   

   DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS  
   The following detailed description, and the drawings to which it refers, are provided for the purpose of describing and illustrating certain examples or embodiments of the invention only and are not intended to exhaustively describe or show all possible embodiments or examples of the invention. 
   An example of an oilless hydraulic pump apparatus of the present invention is shown in  FIGS. 1–8 , as follows: 
   A. An Oilless Air Motor Apparatus 
   The embodiment of the air motor shown in  FIGS. 1–8  comprises an air motor useable to cause a member, such as a piston or cam of a hydraulic pump, to reciprocate. This embodiment of the air motor comprises a body  5  that has an air inlet port  6  that leads to a first manifold  7 , an air exhaust port  8  that leads to a second manifold  9 , and one or more air passages  10  that lead from a third manifold  11  and open into the upper end of an air cylinder  12  extending from the lower end of the body  5 . Said body  5  has a small bore  13  in its upper end with a compressible bumper  14  at the upper end of the bore, an O-ring seal  15  being provided adjacent the lower end of said bore. A counterbore  16 , provided with a bumper  17 , extends from the lower end of the small bore  13 . 
   A larger counterbore extension  18  of the counterbore  16  has the bumper  17  at its upper end, a still larger counterbore  19  extending from the counterbore  18 , the three manifolds  7 ,  9  and  11  opening on the bore  19 . A bearing  20  is fitted into a counterbore extension  21  at the lower end of the body  5 , a sealing O-ring  22  in the body sealing the fit. A bumper  23  is provided in the upper face of said bearing  20  which has an inner bore  24  in which an O-ring  25  is fitted. 
   A liner  26  is fitted into the counterbore  19  between the bearing  20  and the shoulder that is formed between the latter counterbore and the bore  18  from which it extends. Said liner is provided with lower longitudinally spaced ports  27  that connect the manifold  7  with the inner bore of said liner, with upper longitudinally spaced ports  28  that connect the manifold  11  with said liner bore, and with intermediate ports  29  that connect the manifold  11  with said liner bore. 
   A four-way slide valve  30 , in the form of a tubular portion  31 , has a sliding fit in the bore of the liner or valve sleeve  26 , with its upper end  32  engaged with the bumper  17  when the valve  30  is in raised position, as in  FIG. 1A , and with its lower end  33  engaged with the bumper  23  in the upper face of the bearing  20 , when said head is in lowered position, as in  FIG. 1C . An inner flange wall  34 , provided with an O-ring  35  in the bore of said wall extends from the tubular portion  31  of the head  30 . Ports  36  are provided in the part of the portion  31  that extends above the flange wall  34 . An annular external groove  37  has operative association with the ports  27  and  28  to communicate the same, according to the raised and lowered positions of the head, with the ports  29 . It will be noted that the bore  30  and the bore of the flange wall  34  are the same diameter. A spring  38  between said flange wall  34  and an abutment wall formed by bores  13  and  16 , biases the valve  30  to its lower position. 
   In this embodiment a ring shaped dry seal  100  extends around the outer surface of the slide valve  30  and formed a seal between the slide valve  30  and the valve sleeve  26 . A retaining ring  102  snap fits within a groove formed about the slide valve  30  and the upper end of the dry seal  100  abuts against the retaining ring  102 . In this manner the retaining ring  102  prevents the dry seal  100  from sliding or migrating upwardly on the body of the slide valve  30  as the air motor operates. The dry seal is preferably formed of wear-resistant, smooth and/or lubricious material, such as a polymer or graphite-containing, graphite-filled or graphite-impregnated polymer. In the embodiment shown, the dry seal  100  is formed of 25% carbon/graphite filled polytetrafluoroethylene (PTFE). An O-ring seating notch may be formed about the lower end of the inner surface of the dry seal  100  to receive an O-ring  104 , as shown. This O-ring  104  may be any suitable type of O-ring, such as a Buna O-ring formed of material having a Shore hardness of  70 . The function of this O-ring  104  is to exert outwardly directed radial pressure against the inner surface the dry seal  100 , thereby causing the outer surface of the dry seal  100  to seal against the valve sleeve  26 . This dry seal assembly which comprises the dry seal  100 , retaining ring  102  and O-ring  104 , serves to provide a low friction or lubricious interface between the slide valve  30  and valve sleeve  26 , thereby eliminating the need for the use of atomized oil in the air received within the air motor or the application of oil, grease or other added lubricant. Also, the interposition of this dry seal  100  between the slide valve  30  and sleeve  26  eliminates the need for a high tolerance, precisely machined and matched (e.g. honed and lapped) fit between the outer surface of the slide valve  30  and inner surface of the sleeve  26 , as had been required in prior art air motors of this type. In view of this, the slide valve  30  need not necessarily be formed of stainless steel, but rather may be formed of aluminum or other material. In the particular embodiment shown, the valve sleeve  26  is formed of stainless steel and has an inner diameter that allows a gap or space between the inner surface of the sleeve  26  and the outer surface of the slide valve  30 , the width of such gap or space being the same as the width of the dry seal  100  such that firm sealing contact will be established between the slide valve  30 , seal  100  and valve sleeve  26 . 
   O-rings  105  and  106  facilitate the desired function of the piston activating valve. When the slide valve  30  is in its down position as shown in  FIGS. 1   c  and  1   d , upper O-ring  105  is positioned to allow air to flow from manifold  7 , through upper ports  27  and lower O-ring  106  is positioned to seal the lower ports  27 . This causes air to pass through manifold  11  into the air cylinder above air piston  52 . When the slide valve  30  is in its up position as shown in  FIGS. 1   a  and  1   b , the upper O-ring  105  is positioned to seal and prevent flow through upper ports  27  and the lower O-ring  106  is positioned to allow air to flow from manifold  7  through lower ports  27 . This causes the air to enter the tubular portion or bore  31 , overcoming the force created by the spring  38  and thereby causing the slide valve  30  to move to its up position with the air passing through ports  41  and  42 , opening the air check and accumulating below the air piston  52  as described herebelow. 
   A pilot valve  39  has a sliding fit in the mentioned bore  31  and the bore of the flange wall  34 , the same having an axial bore  40  that is closed at the top and is provided with two sets of radial ports  41  and  42  that pass air from within the four-way valve  30  to the bore  40 . The lower end of pilot valve  39  comprises a piston  43 , a skirt  44  below said piston being provided with radial ports  45 . 
   The valve  39 , in its bore  40 , fixedly mounts a valve seat  46  against which a spring  47  biases a valve body  48  which has angular ports  49  in its wall as well as a set of longitudinal passages  50 . Said latter ports and passages are open to the bore  40  of the valve  39 , the former being closed when the body  48  is seated on seat  46 , and the latter being closed by a check valve  51  which opens only in a downward direction under pressure of air in the valve passage  40 . 
   An air piston  52  has sliding operative engagement in the cylinder  12  which is of larger size than the largest bore in the body  5 , the same being fitted with an O-ring  53  to seat against the cylinder. Said piston carries an axially disposed ram  54  of considerably smaller size than the piston, said ram, due to its smaller size, having a power or pressure factor on its operative end that is the same as the total air pressure on either side of the piston. 
   The air piston  52  is provided with an upwardly directed stem  55  that comprises a tubular extension that has sliding fit in the bore  24  of bearing  20  and an inner surface that constitutes a cylinder for the piston  43 . A ported inwardly directed flange  56  at the upper end of said stem  55  over stands the piston  43 , an O-ring  57  forming a bumper between said flange and said piston. An O-ring  58  on the upper end of said stem  55  is arranged to seal against the bore  24  of the bearing  20  when the piston  52  is at the end of its down stroke. Ports  59  open on a relieved portion of the outer surface of the stem  55 . 
   The ram  54  is provided at its upper end with an enlargement  60  that is connected to a lower extension of the air piston  52 . The upper portion of said enlargement is provided with a bumper pad  61  which is adapted to be abutted by the lower skirt end  44  of the valve  39 . Above said enlargement, the air piston is provided with passages  62  that open from the inner cylinder bore  63  in which the piston  43  of said valve  39  operates and into which the radial ports  45  open. 
   B. Operation of the Air Motor Apparatus 
   At the end of the down stroke of the ram  54 , the four-way valve  30  is in the raised position of  FIG. 1A . Compressed air at inlet  6  will pass through the lower of the ports  27  of liner  26  and enter the bore of the valve  30 . This air, through ports  41  and  42 , enters the bore  40  of the pilot valve  39 , creating an upward force against the blind end of the bore  40  that raises through ports  50  in the valve body  48  and opens the check valve  51 , said air then entering the bore  63  and passing through passages  62  to create a force in the direction of arrow  64  between the bottom of the cylinder  12  and the under surface of the air piston  52 . 
   As a result of such air flow, the valve  39  will move upwardly while the air piston  52  is moving through its up stroke. During this up stroke of the air piston, the same displaces air in the upper end of the cylinder; this air, by way passages  10 , port  29 , groove  37 , and the lower ports  28 , exhausts through the port  8 . 
   It will be noted that the valve  39  cannot move up faster than the piston  52  due to the interengagement of the piston  43  of said valve and the flange  56 . This insures that the valve  39  cannot prematurely reach its four-way valve-reversing position. This interengagement, however, allows the piston  52  to make its full upward recovery movement to the position of  FIG. 1C  before the valve reaches its maximum raised position against the bumper  14 , as shown. In practice, said valve  39  need not raise to such maximum position, but only enough so that the ports  42  thereof pass the O-ring  35  of the distributor head  30  so that the air pressure in the bore  40  can enter the counterbore  16  of the body  5 . Since, by the time the ports  42  pass O-ring  35 , the upper end of the valve  39  has entered the bore  13  and is sealed by O-ring  15 , the pressures in said counterbore  16  and in the inside of the air distributor  30  below the flange  34 , are equalized. As a consequence, the spring  38  becomes effective to move the four-way valve downward to the position of  FIG. 1C . 
   In this position, compressed air at inlet  6  will pass through the upper of the ports  27 , groove  37 , and passages  10 , and enters the upper end of the cylinder  12  to produce a force on the piston  52 , according to arrow  65 , to move the latter downward in its power stroke. This down stroke of the piston  52  causes displacement of air in the cylinder  12  below said piston, this air passing through ports  62  into bore  63 , unseating the valve body  48  and passing through angular ports  49  into the bore  40  of the valve  39 . This air passes through ports  41  when the same become uncovered due to the downward movement of the tubular extension  55  and its flange  56  of the piston  52 , into the interior bore of the four-way valve  30 . At the same time, air from bore  40  will pass through ports  42  into counterbores  16  and  18  and will exhaust through the upper of ports  28  through the exhaust port  8 . Upon such exhaust taking place, the pressure within the four-way valve  30  will become effective to shift the latter upwardly to the position of  FIG. 1A , terminating the down or power stroke and completing the cycle of operation. 
   Due to the sliding fit among the valves  30  and  31 , the liner or sleeve  26 , the stem  55  and the piston  52  in the cylinder  12 , the fit between the bearing  20  and the stem  55  is quite loose. When the annular clearance at the point is added to the small ports  59  and the ports in the flange  56 , the air-passing area between the interior of the four-way valve and the upper port of the air cylinder is large. 
   Under low air pressure of between five and twenty pounds, the pressure in the interior of valve  30  leaks to the air cylinder  12  too rapidly for the air inlet through the lower of the ports  27 , as the same is being uncovered, to complete the full up movement of the valve  30 . The latter may “hang” in an intermediate position resulting in a constant bypass of air around the bearing  20 . The O-ring  58  is provided to prevent such bypass of air, since the same closes the annular clearance between said bearing and the piston stem  55 , leaving only the small ports  59  and those in the flange  56  to exhaust the interior of the four-way valve. Hence, the four-way valve will shift fully to its maximum opening of the lower of the ports  27 . 
   It is this feature that enables the present air motor to operate with compressed air as low as five psi and as high as one hundred psi, or more. 
   While the foregoing has illustrated and described what is now contemplated to be the best mode of carrying out the invention, the construction is, of course, subject to modification without departing from the spirit and scope of the invention. Therefore, it is not desired to restrict the invention to the particular form of construction illustrated and described, but to cover all modifications that may fall within the scope of the appended claims. 
   Although exemplary embodiments of the invention have been shown and described, many changes, modifications and substitutions may be made by those having ordinary skill in the art without necessarily departing from the spirit and scope of this invention. Specifically, elements or attributes described in connection with one embodiment may also be used in connection with another embodiment provided that the inclusion or use of such element or attribute would not render the embodiment in which it is incorporated unuseable or otherwise undesirable for an intended application. Accordingly, all such additions, deletions, modifications and variations to the above-described embodiments are to be included within the scope of the following claims.