Abstract:
There is provided an airless paint spray pump wherein the pump is a double acting piston pump having an inlet communicating with a source of paint, a motor for driving the pump, a pressure controller for controlling the pressure of the pressurized paint delivered by the pump, and a filter for filtering the paint delivered by the pump. The pump includes features which increase the accessibility of the components thereof, prevent the incorrect installation of the seal packings in the pump cylinder, and allow the assembly of the piston in the pump cylinder properly aligned with the cylinder so as not to damage the seal packings therein.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates generally to paint pumps adapted to pump liquid paint to such a high pressure that, upon release of the pressurized paint from a spray opening or nozzle in a spray gun, the paint is atomized and thereby rendered suitable for spray painting. More particularly, the present invention relates to an improved high pressure paint pump wherein the parts and components are so constructed and arranged as to provide maximum accessibility, ease of disassembly and mistake-proof reassembly of the parts of the pump. 
       BACKGROUND OF THE INVENTION 
       [0002]    In hydraulic or airless paint spraying, a pump is utilized to pressurize the paint to pressures of 2,000 pounds per square inch and greater so that the paint can be atomized upon release from a nozzle in a spray gun. The type of pump preferably used for this purpose is the double acting piston pump because of the piston pump&#39;s ability to handle high viscosity paints or coatings easily and the capability of the double acting pump to pump fluid on both the upstroke and downstroke of the piston thereby providing a relatively even flow of paint to the nozzle of the spray gun. In the double acting piston pump a stepped piston reciprocates in a cylinder having an inlet at one end and an outlet at the second end whereby two chambers are formed in the cylinder by the stepped piston. The first or inlet chamber is defined by the piston head and the cylinder and the outlet or exhaust chamber is formed at the opposite end of the piston and is defined by the stepped down portion of the piston and the cylinder wall. A transfer or bypass valve is disposed in the piston to transfer paint from the inlet chamber to the outlet chamber. On the intake stroke of the piston the transfer valve is closed while simultaneously the inlet valve is opened by vacuum so as to draw paint into the inlet chamber. On the down or exhaust stroke of the piston, the inlet valve is closed by the fluid pressure exerted on it while the bypass valve is opened by the fluid pressure exerted on it so as to permit the paint in the inlet chamber to pass through the transfer valve and into the exhaust chamber, Because of the volume difference between the inlet and exhaust chambers, approximately half the paint transferred to the exhaust chamber is forced through the pump outlet during this stroke while the other half remains in the exhaust chamber. On the next intake stroke, as the piston withdraws in the cylinder it forces the remaining paint in the exhaust chamber through the pump outlet while at the same time paint is brought in through the inlet valve into the inlet chamber. An upper seal packing located at the upper extremity of the cylinder sealingly engages around the stepped down portion of the piston and seals the outlet chamber of the cylinder from the exterior. A lower seal packing located within the cylinder sealing engages around the piston head and separates the outlet and inlet chambers. 
         [0003]    Such hydraulic or airless high pressure paint pumps are used extensively in the painting industry for the painting of new constructions, industrial installations, etc. For the most part the only maintenance required for such pumps is the replacement of parts or components which are subject to wear, Such replacement of worn parts requires a rebuilding or refurbishing of the pump and generally involves the replacement of the packings or seals in the pumps which eventually leak as a result of wear and the replacement of the inlet and bypass valves which are also subject to wear and leakage. In order to accomplish this pump rebuilding or refurbishing, it is necessary to dismantle the pump section which includes removal of the pump piston so as to gain access to the seal packings and the inlet and bypass valves. The high pressure or airless paint sprayers or pumps currently available in the market are adapted to have their pump or fluid sections disengaged and removed from the driving components of the pump system so as to permit the dismantling thereof. However, because of the relatively complex nature of pump construction and arrangement of the parts therein, rebuilding of the pump and reassembly of the parts thereof requires special care and close attention and sometimes the use of special tools in order to insure a correct and proper rebuilding and reassembly, otherwise, damage or leakage in operation may result. Specifically, the packing seals used in such pumps generally consist of a plurality of sealing elements which may be formed into a unit wherein the sealing elements or sealing lips of the seal are oriented in one direction for effective sealing. The pump&#39;s upper packing has its sealing lips oriented downwardly while the lower packing has its sealing lips oriented or directed upwardly. If these seals are incorrectly oriented during assembly of the pump, improper sealing will result and leakage will occur. It is also critical during reassembly of the pump that the piston rod be properly centered and aligned for insertion into the pump cylinder otherwise again the seals may be damaged causing the pump to leak during operation. This piston insertion step is further exacerbated because a significant amount of force is required in order to overcome the resistance exerted by the seals during insertion of the piston rod into the cylinder so that the use of a hammer or mallet is frequently necessary to drive the piston rod into place. Thus, included with pump rebuilding kits provided by manufacturers are detailed instructions on the proper installation of the packing seals and assembly of the piston and cylinder and some manufacturers also include a guide tool to insure the proper alignment of the piston and cylinder during assembly. However, pumps rebuilt by painting contractors or their employees frequently leak in operation or are otherwise damaged because of the difficulty of such rebuilding or the inability or failure to follow rebuilding instructions carefully. An alternative available to painting contractors is to have the pumps rebuilt by the manufacturers thereof. The obvious drawbacks to this are the extended period of time that the pump is unavailable to the contractor and the expense therefor. 
         [0004]    Another problem relating to the rebuilding of such pumps concerns the replacement of worn valves particularly the lower inlet valve. This valve is located in the well of the inlet valve housing at the pump inlet and the elements consist of a valve seat, a ball or flat valve, and a valve cage for limiting and guiding the movement of the ball or flat valve. A retainer is employed for retaining the valve elements in the valve housing. In rebuilding this portion of the pump the retainer must first be removed from the valve housing in order to gain access to the valve elements; next the valve cage is removed, then the ball or flat valve is removed and finally the valve seat is removed. However, after a period of use in pumping paint, a residual of paint accumulates in and around the valve elements and particularly the valve cage and after drying makes it difficult to remove the valve cage from the well of the housing. In such a case it is often necessary to utilize a tool, such as a screwdriver or pick, to pry the valve cage loose from the valve housing well so as to free the remaining valve elements for removal. 
       SUMMARY OF THE INVENTION 
       [0005]    It is, therefore, a primary object of the present invention to provide a paint pump adapted to pressurize paint so that the paint can be atomized and sprayed onto a surface by means of a spray gun wherein the parts and components of the pump are so constructed and arranged as to provide maximum accessibility, ease of disassembly and mistake-proof reassembly of the pump. 
         [0006]    The above object, as well as others which will hereinafter become apparent, is accomplished in accordance with the present invention by a high pressure, double acting piston paint pump which is an improvement over prior art pumps wherein the accessibility of the inlet valve elements is increased, the upper and lower packing seals located in the pump body can be installed in the proper orientation thereof without error, and the piston can be easily assembled with the pump cylinder and properly aligned therewith without the need for special tools or undue effort. The pump according to the present invention includes a piston guide/retainer wherein the inlet valve cage is formed integral therewith and the guide is inserted into the well of the inlet valve housing so as to retain the inlet valve seat and inlet ball valve at the bottom of the well at the inlet. Thus, upon removal of the piston guide/retainer from the inlet valve housing well, the valve cage is likewise removed whereby the ball valve and inlet valve seat are accessible and easily removed. In assembling the piston with the pump cylinder, the piston head is inserted into the piston guide/retainer disposed in the inlet valve housing thereby stabilizing the piston and serving to center and guide the piston during assembly with the pump cylinder. According to another aspect of the invention, both the upper and lower packing seals are designed to be positionable in the cylinder of the pump body so that the correct orientation of the sealing lips is easily sustainable. According to yet another aspect of the invention, means are provided permitting co-operation between the inlet valve housing and the pump body or fluid housing during assembly of the piston rod with the pump cylinder whereby the piston is driven into the cylinder by a uniform and steady pressure which overcomes the resistance of the upper and lower seal packings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0007]    Other objects and features of the present invention will become apparent from the following detailed description considered in connection with the accompanying drawings. It is to be understood that the drawings are designed as an illustration only and not as a definition of the limits of the present invention. 
           [0008]    In the drawings wherein similar reference characters denote similar elements throughout the several views: 
           [0009]      FIG. 1  is a perspective front elevational view of an airless paint sprayer or paint spray pump system incorporating the high pressure paint pump of the present invention; 
           [0010]      FIG. 2  is a rear elevational view of the high pressure pump as utilized in the pump system of  FIG. 1 ; 
           [0011]      FIG. 3  is a cross-sectional exploded view of the high pressure pump of  FIG. 2 ; 
           [0012]      FIG. 4  is a cross-sectional view of the high pressure pump of the present invention showing the pumping action of the pump on the upstroke of the piston; 
           [0013]      FIG. 5  is a cross-sectional view of the pump similar to that of  FIG. 4  showing the pumping action of the pump on the downstroke of the piston; 
           [0014]      FIG. 6  is a cross-sectional view of the high pressure pump of the present invention showing the first step in the assembly thereof; 
           [0015]      FIG. 7  is a cross-sectional view of the high pressure pump similar to that of  FIG. 6  showing the second step in the assembly thereof; and 
           [0016]      FIG. 8  is a cross sectional view of the high pressure pump similar to that of  FIGS. 6 and 7  showing the final assembly thereof. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0017]    Turning to the drawings, there is shown in  FIG. 1  a high pressure paint spray pump system, generally designated  10 , including a motor section  12 , a gear box  14  and a pump section  16 . Motor section  12  includes an electric motor whose drive shaft drives the pump of pump section  16  through a reduction gear and crank shaft housed in gear box  14 . A motor controller, designated  18 , controls the operation of the motor through an on/off switch (not shown) and a pressure control knob  20 . A handle, designated  22 , is provided at the top of gear box  14  to permit lifting and carrying of pump system  10 . The inlet  24  of pump section  16  is connected by means of down tube  26  to a source (not shown) of paint such as a bucket or container of paint. The outlet  28  of pump section  16  communicates via a high pressure hose  30  with a spray gun (not shown) which atomizes the high pressure paint suitable for painting. A pressure relief valve located in pump section  16  is controlled by knob  32  and permits the dumping or releasing of pressurized paint contained in the pump section upon shut down which is returned to the paint source via tube  34  connected to relief valve outlet  36 , Pump system  10  may be mounted on a wheeled cart (not shown) for ease of movement or on support legs (not shown). 
         [0018]      FIG. 2  shows pump section  16  disconnected from pump system  10  which is accomplished by removing the connecting bolts (not shown) which secure pump section  16  to gear box  14  and disconnecting the slotted piston rod  38  from the crank shaft connecting rod located in the gear box. A pressure sensor (not shown) is connected to pump section  16  at fitting  40  located near outlet  28  of the pump section in order to measure the pressure of the paint leaving the pump section. This pressure sensor is in operative communication with the pressure control elements of controller  18 . A filter (not shown) is housed in removable filter housing  42  adjacent to pump outlet  28  so as to filter the pressurized paint as it leaves pump section  16 . 
         [0019]      FIG. 3  is an exploded view of pump section  16  which basically comprises inlet valve housing  44 , piston guide/retainer  46 , transfer valve assembly  48 , piston rod  38 , lower seal packing  50 , pump or fluid body  52 , upper seal packing  54 , and upper retainer/guide  56 . Inlet valve housing  44  is provided with a deep-set well  58  at its end opposite pump inlet  24  adapted to accept therein inlet valve seat  60 , “O” ring seal  62 , ball valve  64 , and piston guide/retainer  46 . Piston guide/retainer  46 , fits snugly in well  58  and includes an inlet valve cage  66  integrally formed at the bottom of the guide for containing and limiting the movement of ball valve  64  to permit fluid to pass thereby and retain valve seat  60  and “O” ring seal  62  at the bottom of well  58  at the pump inlet  24 . A central bore  68  in piston guide/retainer  46  is sized to accept therein with sliding clearance the lower end or head of piston  38  and serves as the lower part of the pump cylinder. A laterally extending rim or lip  70  is provided at the upper end of piston guide/retainer  46  and permits the easy removal of the guide/retainer from the well  58  of housing  44  with the aid of a screwdriver blade inserted in the small groove or channel  71  (see  FIGS. 4 and 5 ) provided between rim  70  and the upper end  72  of housing  44 . Piston rod  38  is stepped to provide a large diameter lower piston section or piston head  74  and a relatively smaller diameter upper piston section or piston base  76 . Piston transition section  78  connecting lower piston section  74  to the upper piston section  76  is gradually tapered. The upper extremity of piston rod  38  is provided with slots  80  in order to facilitate connection with the connecting rod in gear box  14 . Between piston section  76  and slots  80 , piston rod  38  is provided with a gradually tapered piston section  81 . The reasons for the tapering of piston sections  78  and  81  are explained below. Extending centrally through lower piston section or piston head  74  is a bore  82  which terminates at a cross-bore or piston outlet  84  located at transition section  78 . Transfer valve assembly  48  includes ball valve  86  and valve seat/retainer  88  wherein a through bore  90  in retainer  88  terminates at an integral valve seat  92 . Valve seat/retainer  88  has external threads  94  engageable with internal threads  96  in bore  82  of piston  38  so that upon combining transfer valve assembly  48  with piston  38  the transfer or by-pass valve is established in valve chamber  98  communicating with piston outlet  84 . 
         [0020]    Pump body  52  is provided with a through bore  100  segmented along its length to accept the various component parts of the pump. Specifically, central bore segment  102  serves as the upper part of the pump cylinder and is sized to slidingly receive piston head  74  of piston  38 . Bore segment  104  is adapted to receive therein lower seal packing  50  which is provided at its lower end with an outwardly extending rim  106  adapted to seat on shelf  108  in bore  100  while the upper end  107  of seal packing  50  is adapted to seat on shelf  109  in bore  100 . Bore segment  110  is adapted to receive therein upper seal packing  54  which is provided at its upper end with an outwardly extending rim  112  adapted to seat on shelf  114  in bore  100  while the lower end  113  of seal packing  54  is adapted to seat on shelf  115  in bore  100 . Bore segment  116  at the upper extremity of bore  100 , is internally threaded and sized to accept threaded retainer/guide  56  which abuts against rim  112  of seal packing  54  to secure the packing in position between shelves  114  and  115 . Stepped piston  38  is inserted in bore  100  to extend through seal packings  50  and  54  and extend beyond retainer/guide  56  so that its upper end with slot  80  protrudes from pump body  52  as shown in  FIG. 2 . Lower seal packing  50  seals against lower piston section  74  and upper seal packing  54  seals against upper piston section  76  and delineates between them central bore segment  102  of bore  100 . Each of the seal packings is comprised of a plurality of chevron seals whose flexible sealing lips  118  have sealing ends directed inwardly toward central bore segment  102  except for the bottom most sealing lip  120  of lower seal packing  50  whose sealing end is oppositely directed, the reason for which is explained below. Bore segment  122 , at the lower extremity of bore  100 , is adapted to receive inlet valve housing  44  assembled with piston guide  46  and the inlet valve. Inlet valve housing  44  is provided with external threads  124  which engage with internal threads  126  in bore segment  122  so that when valve housing  44  is screwed into bore segment  122 , rim  70  of piston guide/retainer  46  abuts against rim  106  of lower seal packing  50  to secure the packing in position between shelves  108  and  109 . An outlet bore  128  is provided in pump section  16  intersecting with central bore segment  102  and extending to the outlet section  130  of pump body  52 . Outlet section  130  includes a well  132  for receiving the pump filter and threaded filter housing  42 . Well  132  also communicates with pump outlet  28  and pressure relief valve chamber  134  via bore  136 . 
         [0021]      FIGS. 4 and 5  show the pumping operation of the pump according to the present invention. The upstroke of piston rod  38  in the direction “A” is shown in  FIG. 4  where ball  64  of the inlet valve is lifted off its seat  60  by the suction created by the rising piston which suction causes liquid paint to be drawn into inlet chamber  138  through pump inlet  24 . Simultaneously, the liquid paint contained in outlet chamber  140  is discharged under pressure by the piston through outlet bore  128  to outlet section  130  where it passes through the filter and exits pump section  16  via pump outlet  28 . As piston  38  is withdrawn in inlet chamber  138 , ball  86  of the transfer valve in piston  38  is forced onto its seat  92  thereby preventing any liquid paint from being transferred to outlet chamber  140  through cross-bore or outlet  84  in piston  38 . The downstroke of piston rod  38  in the direction “B” is shown in  FIG. 5  where the ball  64  of the inlet valve is forced onto its seat  60  by the downward pressure exerted on it by the pressurized liquid paint in inlet chamber  138  thereby preventing paint from exiting inlet chamber  138  through pump inlet  24 . Simultaneously, ball  86  of the transfer valve in piston  38  is lifted off its seat  92  by the pressure of the fluid paint being discharged from inlet chamber  138  and through bore  90  in valve seat/retainer  88 . After passing ball  86  of the transfer valve, the fluid paint passes through piston outlet  84  and into outlet chamber  140 . Because of the greater volume of fluid paint being pumped from inlet chamber  138  to outlet chamber  140 , the excess in outlet chamber  140  is discharged through outlet bore  128  to outlet section  130 , through the pump filter and finally to the pump outlet  28 . 
         [0022]    As clearly seen in  FIGS. 4 and 5 , lower seal packing  50  tightly seals against piston head section  74  while upper seal packing  54  tightly seals against piston base  76  thereby effectively sealing outlet chamber  140  from the exterior and from inlet chamber  138  during the upstroke and downstroke of piston  38 . The bottom sealing lip  120  of lower seal packing  50 , has its sealing end directed toward inlet chamber  138 , which prevents any particles or debris in inlet chamber  138  from passing lip  120  and being entrapped by sealing lips  118  of seal packing  50  and scoring piston head  74  during the up and down movement of piston rod  38 . 
         [0023]      FIGS. 6 ,  7  and  8  depict the assembly of pump section  16  after replacement of the worn parts thereof. Initially, lower seal packing  50  and upper seal packing  54  are inserted into bore  100  so that the sealing lips  118  thereof have their sealing ends directed inwardly towards bore segment  102  of bore  100 . The respective rims  106  and  112  of the lower and upper seal packings come to rest on the respective shelves  108  and  114  in bore  100  so as to properly position and orient the seal packings within bore  100  of pump body  52 . It should be pointed out that in the event the seal packings are mistakenly inserted so as to be inverted with respect to their proper orientation, the respective rims  106  and  112  of the lower and upper seal packings will still come to rest on the respective shelves  108  and  114  in bore  100  so that the bodies of the seal packings, having axial dimensions “C” and “D” respectively, project in directions opposite to the intended directions. Because of the axial dimensions “C” and “D” of seal packings  50  and  54 , the bodies of the incorrectly installed lower and upper seal packings form obstructions which effectively prevent the complete assembly of retainer/guide  56  and inlet valve housing  44  with pump body  52 . As a result, the improper installation of the upper and lower seal packings  54  and  50  is clearly and easily ascertainable and can thus be rectified. As clearly seen in  FIG. 6 , the lower piston section or piston head  74  is inserted into bore  68  of piston guide/retainer  46  which has previously been assembled with inlet valve housing  44 . Piston  38  is then aligned with bore  100  of pump body  52  in anticipation of being inserted therein. 
         [0024]    The next step in assembling pump section  16  is shown in  FIG. 7  where it can be seen that piston  38  has been inserted into bore  100  of pump body  52  to the extent that tapered sections  78  and  81  are on the verge of engaging with the chevron seals of lower seal packing  50  and upper seal packing  54 , respectively. At this point in the assembly of the pump section, the threads  124  of valve housing  44  commence their engagement with threads  126  in bore segment  122  of bore  100  of pump body  52 . The continued screwing or rotation of inlet valve housing  44  relative to pump body  52  drives housing  44  together with piston guide/retainer  46  and piston  38  further into bore  100  without excessive effort or force because of the mechanical advantage of the screw. The purpose for the tapered sections  78  and  81  of piston  38  is to allow the gradual deformation of flexible sealing lips  118  of seal packings  50  and  54  and the oppositely directed sealing lip  120  of packing  50 . Because of this gradual deformation or widening of the sealing lips  118  and  120  by the gradual upward movement of the tapered sections of the piston  38 , the flexible sealing lips are prevented from being upset or directionally inverted. During this insertion step, as inlet valve housing  44  is threaded into pump body  52 , piston guide/retainer  46  maintains piston rod  38  in alignment with the axis of bore  100  whereby any possible damage to packing seals  50  and  54  is avoided. 
         [0025]      FIG. 8  shows the assembled pump section  16  following completion of the piston insertion step. As clearly seen, intake valve housing  44  is fully threaded into bore segment  122  of bore  100  of pump body  52  so that lower seal packing  50  sealingly engages with lower piston section  74  and upper seal packing  54  sealingly engages with upper piston section  76 . With intake valve housing  44  fully threaded into pump body  52 , the upper extremity of piston rod  38  extends from bore  100  and above retainer/guide  56  so that it may be grasped to allow attachment of piston  38  to the connecting rod in gear box  14 . 
         [0026]    While only a single embodiment of the present invention has been shown and described, it will be obvious that many changes and modifications may be made thereto without departing from the spirit and scope of the invention.