Patent Publication Number: US-6981854-B1

Title: Small piston pump

Description:
BACKGROUND OF THE INVENTION 
   1) Field of the Invention 
   This invention relates to small piston pumps generally and more specifically to such a pump having two check valves in a small space along with the piston. 
   2) Description of the Prior Art 
   Many devices incorporating elastic bands, such as O rings, as check valves are known in the art, for example U.S. Pat. No. 4,549,565 includes an O ring 38 which serves as a closure member over a discharge port. However, this O ring does not act in conjunction with a slit valve, with both being disposed adjacent to and functioning in conjunction with a small diameter pump stem to dictate the operation of pump. 
   SUMMARY OF THE INVENTION 
   The piston pump of this invention has a small diameter reciprocating pump stem which can be connected to and driven by a diaphragm water motor thereby to pump chemical additive to the primary water operating the water motor. Since this is a small additive pump, in prior designs, there was no space to provide a pair of check valves in close conjunction with the small piston. To provide two such check valves in a small space, a flat check valve with a 45 degree cut was selected as the open-close gate valve and an elastic material annular band disposed on the outside of the pump cylinder overlying the pump&#39;s exhaust port as an output check valve. The confined space between the flat check valve and the elastic material annular band and between these valves and the piston provide a pressure build up area between the annular band and the flat check valves so that the pressure additive fluid can easily open the output check valve and outflow to be directed to a second piston carried by said first piston which forces the fluid out of the pump to the primary water. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a longitudinal cross sectional view showing the piston pump of this invention with the piston moving in the intake direction with the slit valve open and the elastic material annular band in the form of a flat annular band in the closed position; 
       FIG. 2  is an enlarged fragmentary view of the view of  FIG. 1  with the piston moving in the output direction and with the slit valve closed and the annular band in the open position; 
       FIG. 3  is an enlarged end view of the slit valve when view from the left in  FIG. 1 ; 
       FIG. 4  is a sectional view taken along the line  4 — 4  in  FIG. 3 ; 
       FIG. 5  is view of the pump cylinder of  FIG. 1  with the annular elastic band shown as an O ring; 
       FIG. 6  is a view of the pump cylinder of  FIG. 1  taken along the line  6 — 6  in  FIG. 7  with the annular elastic band shown as a flat annular band; and 
       FIG. 7  is a view in full lines of the pump cylinder when seen in the direction of the arrows  7 — 7  in  FIG. 6 . 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
   Referring now to the drawings, and more particularly to  FIGS. 1 and 2 , a small additive piston pump is shown generally at  10  and includes a housing  12  having a central bore shown generally at  14 , which bore has a piston receiving portion  15  on the left portion thereof, a short counterbore portion  16  to the right of bore portion  15 , and a larger right end bore portion  18  at the right end of the housing  12 . The peripheral surface of the housing  12  at the right end thereof is threaded at  20 , and an end cap  22 , having an end wall  26  and internal threads  27 , is threadedly received on the threads  20  of the housing  12 . The end cap  22  has a pintle  24  with a central bore  25  therein; the pintle extending to the right from the end wall  26  of the cap  22  and the bore  25  being confluent with the interior of the end cap  22 . 
   Disposed in the bores  16  and  18  of the housing  12  is an annular sleeve  30  having an annular peripheral wall  32  and an internal cylindrical bore  34 , which bore has a shoulder  36  adjacent the left end thereof. The shoulder  36  has an annular groove  38  therein intermediate the ends thereof, in which groove is sealingly received an annular sealing ring  40 , which ring, on the internal surface thereof, sealingly and slidingly engages the periphery  41  of an elongated piston  42  whose right end  43  reciprocates in the bore  34 , such engagement being adjacent the said right end  43 . The right end of the sleeve  30  is supportingly received in an annular undercut  46  in the left face  48  of an annular slit valve  50 , more clearly seen in  FIGS. 3 and 4 . The valve  50  has a 45 degree angled slit  52  positioned centrally therein and extending axially therethrough while extending radially a relatively short distance as clearly seen in  FIG. 3 . The periphery of the valve  50  is received in the right end of a bore  29  formed in the cap  22 , and the right face  51  of the valve abutting the inner end wall  29 A of the end cap  22  with the slit  52  overlying the bore  25  in the pintle  24 . The left end  31  of the sleeve is fittingly received and supported in the counterbore  16 , and the sleeve  30  has a plurality of detents  54  formed therein, which detents are open to the periphery of the sleeve  30 , while being closed to the bore  34  of the sleeve. The detents  54  are deep enough (extend to the right sufficiently) so that where the detents are open to the periphery of the sleeve, the sleeve periphery is spaced from the tapered surface of the counterbore  16 , and the left end  31  of the sleeve  30  abuts the shoulder  17  formed at the left end of the bore  16 . While the periphery of the sleeve  30  intermediate the detents  54  engages the bore  16 , since the bore  16  is tapered, the peripheral detent openings are spaced from the bore  16  and form an open passageway leading from the area  56  which lies between the periphery  32  of the sleeve  30  and the bore  18  of the housing  12 , to the area  58  which lies between the piston  42  and the bore  14 . The cylindrical sleeve  30  has an annular flat bottomed and flat sided peripheral groove  30 A therein adjacent the right end thereof, which groove has a plurality of circumferentially spaced openings  30  B extending from the bottom of the groove and opening to the bore  34  of the sleeve  34 . In the embodiment of FIGS.  1 , 2 , and  6 , an annular elastomeric band  30 C, having a flat external and internal periphery, is sealingly disposed in the groove  30  A; which band resiliently seals the openings  30  B unless the band is acted upon. In  FIG. 5 , the groove  30 AA is semicircular and the elastomer member is a O ring  30 CC, whose function is the same as the flat ring  30 C described above re  FIG. 6 . 
   The piston  42  has a stem portion  42 A on the right side thereof, which portion is sealingly and slidingly received in the sealing ring  40 , while the left side portion of the piston  42  includes an enlarged cylindrical shoulder  60  which has an annular grove  62  formed therein. Received in the grove  62  is a elastomeric sealing ring  64 , which slidingly and sealingly seals the juncture of the piston&#39;s shoulder  60  with the piston receiving portion  15  of the bore  14 . To the left of the shoulder  60  an attaching projection  66  extends out of and projects from an opening  68  in the left end wall  70 ; which opening and the projection are formed with a matching irregular shape that allows relative axial movement while preventing relative rotation. The projection  66  can be attached to a suitable source of axial reciprocating driving force to operate the pump  10  in a manner hereinafter described, such as a water motor being driven by primary water, with the piston pump  10  supplying an additive to the primary water. The housing  12  of the pump  10  includes a radially extending externally threaded projection  72 , which projection has a central bore  74  therein which is confluent with area  58  in the bore portion  15  of the bore  14 . A suitable conduit (not shown) connects the projection, and thereby the pump&#39;s effluent, to the desired receiving location, such as the primary water (not shown). 
   The operation of the pump  10  will now be described: upon movement of the projection  66  to the left as seen in  FIG. 1 , the right end  43  of piston  42  increases the volume in the cylinder  30  in the area  76  to the right of the sealing ring  40 . The accompanying reduction of pressure in area  76  moves the flat elastomeric member  30 C to tightly close the openings  30 B and causes the slit  52  in the adjacent valve  50  to open to thereby admit additive fluid to area  76  from the bore  25 . Upon reciprocal movement of the projection  66  to the right from its leftward position, as shown in  FIG. 2 , the piston  42  decreases the area  76  thereby increasing the pressure therein, with the result that the slit valve  50  closes and the band  30 C opens the openings  30 B so that additive fluid in the area  76  can move radially outwardly to the space  78  surrounding the sleeve  30 , thence through the detents  54  to the area  58  and from the latter out through the opening  74  where it can be conducted to join the primary water. 
   While only a single embodiment along with a valve modification has been shown and described, it is understood that changes can be made therein without departing from the scope of this invention as hereinafter claimed.