Patent Publication Number: US-3874821-A

Title: Hydraulic pump

Description:
United States Patent Nagorski et al.  
 HYDRAULIC PUMP inventors: Witold Nagorski, 13, Creighton Ave., London; Zdzislaw Bieganski, Brushwood, Kingsbourne Green, Harpenden, both of England Filed: Apr. 17, 1974 Appl. N0; 461,517  
 Foreign Application Priority Data Apr. 27, 1973 United Kingdom 20028/73 U.S. C] 417/235, 417/554, 60/477, 60/479, 60/481 Int. Cl. F04!) 21/00 Field of Search 60/477, 479, 481; 417/235, 417/554, 903  
 References Cited UNITED STATES PATENTS 6/1951 Lynn 60/477 X 10/1971 Trotta 60/477 X Apr. 1, 1975 FOREIGN PATENTS OR APPLICATIONS Primary Examiner-Edgar W. Geoghegan Attorney, Agent, or Firm-Marshall &amp; Yeasting [57] ABSTRACT A hydraulic pump comprises a pair of chambers and a plunger which extends axially through both chambers and provides a valvecontrolled fluid flow path between the two chambers such that fluid is transferred from one chamber, acting as a reservoir, to the other chamber in response to reciprocation of the plunger. The plunger is displaceable by means of a lever system which is effective to vary the rate of displacement of the plunger so that plunger travel for a given lever movement is greater initially than towards the end of the plunger stroke. The lever system is arranged so that it imparts only substantially axial forces to the plunger during reciprocation thereof.  
 11 Claims, 1 Drawing Figure HYDRAULIC PUMP BACKGROUND OF THE INVENTION This invention relates to a hydraulic pump and is particularly but not exclusively concerned with a manually-operable hydraulic pump for operating a ram assembly incorporating a pair of relatively movable jaws for effecting crimping or cutting operations for example.  
 SUMMARY OF THE INVENTION In accordance with the present invention we provide a hydraulic pump comprising a first fluid-containing chamber. a plunger reciproeable axially within said first chamber and providing a fluid flow path between said first chamber and a second chamber. a valve operably associated with the plunger and arranged to permit fluid flow along said path in response to movement of the plunger in one direction and to prevent fluid flow during movement of the plunger in the opposite direction and lever means operable to reciprocate the plunger. said lever means being connected to the plunger in such a way as to impart only substantially axial forces to the plunger during reciprocation.  
  Preferably the lever means is arranged so that movement of the plunger is non-linearly related to move ment of the lever means whereby a high pressure may be developed during the latter part of the plunger stroke in said opposite direction.  
  According to a preferred feature of the invention all potential leakage paths around the plunger from said second chamber terminate in said first chamber thereby avoiding the need for complicated and expensive sealing arrangements as any leakage that may occur takes place between said second chamber and said first chamber and not between said second chamber and atmosphere.  
  The pump preferably includes a pressure-relief valve which acts between the first and second chambers. The pump preferably further includes a one-way valve permitting admission of fluid to the second chamber but preventing discharge from the second chamber via said fluid flow path provided by the plunger. and a controllable discharge valve for permitting discharge of fluid from the second chamber to the first chamber.  
  Conveniently. the second chamber accommodates a ram having a stem projecting front said chamber for cooperation with one ofa pair of relatively movable members constituting. for example. a crimping or cutting tool. and mounted on a casing defining said second chamber. Preferably said pair of members are dismountable as a unit from the casing so that the pump may be used in conjunction with different tools. For this purpose. the tools and said casing are releasably interengageable. by way of. for example. a bayonet connection.  
  Preferably. the lever means comprises a pair of toggle levers disposed on diametrically opposite sides of the pump and each connected to a sleeve which is slidablc axially in response to pivoting of the levers. the sleeve being connected to a projecting part of the plunger to impart reciprocating movement thereto.  
 BRIEF DESCRIPTION OF THE DRAWING The drawing is a longitudinal section of a hydraulic pump embodying the invention.  
 DESCRIPTION OF THE PREFERRED EMBODIMENT As shown. a hydraulic pump in accordance with the invention comprises a pair of generally tubular castings II and 12 each formed with tubular extensions 13 and I4 which interfit to define an axial passage which reccives a plunger [5. A cylindrical rubber sleeve I6 extends between the castings l1 and I2 and defines together with the extensions 13 and I4 a first tluid&#39; containing chamber 17. The plunger 15 is formed with an axial passage 18 which communicates with the chamber I7 via ports 19 and 20 and a filter element 2]. The passage 18 is eounterbored and accommodates a ball valve 22 which is spring-urged to seat against the mouth of passage IS.  
  The axial passage 18 leads into a second chamber 23 defined by casting I2 and an end cap 24 secured thereto. Fluid flow from the plunger 15 into the chamber 23 is controlled by a one-way valve 25. The casting 12 is formed with a pair of lateral. axial passages 26 and 27 which extend between the chambers 17 and 23. Passage 26 is controlled by a pressure-relief valve 28 which is adjustable by means of a slotted head portion projecting through the casting II. The passage 27 is controlled by a ball valve 29 which normally closes the passage 27 but may be permitted to move by operation of a control rod 30 which is operable externally of the pump.  
  Reciprocation of the plunger 15 is effected by means of a pair of toggle levers SM and 3Ib through the agency of a sleeve 32 which encloses the rubber sleeve I6 and is slidable axially in response to pivoting of the levers 31c! and 31h.  
  In the drawing. lever 31a is shown in the position it occupies when the plunger I5 is retracted and lever 31b in the position it occupies when the plunger is advanced fully towards the second chamber. As shown. each lever 31a and 3lh comprises a main lever arm 33 pivotally connected to the end cap 24 and a toggle link 34 pivotally connected between the lever arm 33 and the sleeve 32. A bracket 35 limits outward pivoting of each lever arm 33.  
  It will be noted that movement of the sleeve 32 and hence the plunger 15 is non-linearly related to angular movement of levers 31a and 31h. Thus. initial advance of the plunger I5 towards the chamber 23 takes place rapidly but progressively slows down and final movement thereof is small in relation to the corresponding movement of the levers 31a and 3). This arrangement permits initial movement of the plunger I5 accompanied by the production of low pressure in chamber 23 and slow final movement accompanied by the production of an increasingly larger pressure in the chamber 23. The non-linear relationship between the levers 31a and 3th and the plunger I5 may be varied by suitable positioning of the pivotal connection between the link 34 and the sleeve 32.  
  In the illustrated embodiment, the pressure created in chamber 23 is used to displace a ram 36 which projects through the cap 24. The cap 24 is provided with a bayonet connection so that a pair of relatively movable crimping or cutting tools may be mounted thereon with one of the tools being actuated by the ram 36.  
  In operation, the pump is actuated by pivoting the levers 31a and 31!) thereby reciprocating the plunger 15.  
 As the latter moves to the right, the valve 22 opens due to the inertia of the ball thereby admitting fluid from chamber 17 and passage 18. The fluid so admitted is pumped into the chamber 23 during the return stroke ofthe plunger 15. It will be noted that all possible leakage paths from the chamber 23 around the various movable components of the pump lead into the chamber l7 thereby greatly simplifying sealing. Also all fluid passageways of the pump extend axially thereof.  
  What we claim is: l. A hydraulic pump comprising: an elongate body defining first and second axially successive chambers. an axial fluid-passageway extending between said first and second chambers; a plunger, having one end projeeting from the elongate body, which is rcciprocable axially within said first chamber and extends into said fluid-passageway: and valve means controlling admission of fluid from said first chamber into said fluid passageway. operation of the valve means being coordinated with movement of the plunger in such a way that admission of fluid into said passageway from said first chamber occurs in response to axial movement of the plunger away from the second chamber and is prevented in response to axial movement of the plunger towards said second chamber. whereby in the latter movement thc plunger forces fluid from said passageway into the second chamber; wherein the improvement comprises a coupling member mounted on the elongate body of the pump and guided thereby for reciprocation axially of the pump body and parallel to the plunger.  
 said member being drivingly coupled to the end of the plunger which projects from the elongate body; and  
 lever means which acts between the pump body and said coupling member and is operable to reciprocate said coupling member and hence the plunger.  
  2. A hydraulic pump according to claim I wherein the plunger is formed with an axially-extending bore which is open at the end of the plunger presented towards said second chamber and which, adjacent its opposite end, communicates with a radial port formed in the plunger, said radial port allowing admission of fluid into said opposite end of the bore from the first chamher; said valve means comprises a valve seat formed within said bore and a valve member which is movably accommodated within the bore between the open end thereof and the valve seat and is yieldably biased into engagement with said valve seat; and said fluidpassageway comprises a check valve which prevents return flow of fluid from said second chamber into said fluid passageway during movement of the plunger away from the second chamber.  
  3. A hydraulic pump as claimed in claim 1 including a further fluid-passageway extending axially between said first and second chambers. and a valve member in said further fluid-passageway. coupled to an actuating member which extends externally of the pump and is operable to selectively close and open said further fluid-passageway. I I  
  4. A hydraulic pump as claimed in claim 1 including pressure relief means comprising a return passageway extending axially between said first and second chambers and having a mouth opening into said first chamber. and a valve member mounted for axial movement in said first chamber and spring urged into sealin gagement with the mouth of said return passageway.  
  5. A hydraulic pump according to claim 1 wherein lever means in constituted by a toggle lever system comprising a first arm which is pivotally coupled to the pump body adjacent the end enclosing said second chamber and which extends towards and beyond the opposite end of the body, and a second arm which is pivotally coupled to said coupling member intermediate the ends of the coupling member and is pivotally coupled to said first arm at a position beyond said op&#39; positc end of the pump body.  
  6. A hydraulic pump according to claim 5 wherein the coupling member is constituted by an elongate sleeve which encircles the pump body and is constrained thcrcby to slide axially.  
  7. A hydraulic pump according to claim 6 wherein said toggle lever system is duplicated on diametrically opposite sides of said sleeve.  
  8. A hydraulic pump according to claim 1 wherein the coupling member is constituted by an elongate sleeve encircling the pump body and constrained to slide axially thereby.  
  9. A hydraulic pump according to claim 8 wherein said lever means is duplicated on diametrically opposite sides of the sleeve.  
  [0. A hydraulic pump according to claim 8 wherein the first chamber is completely filled with fluid and is defined by a pair of axially-spaced apart, rigid end walls connected together by a hollow central stem through which said plunger passes, and a sleeve of flexible, nonpermcablc material extending between said end walls so as to sealingly enclose the space thercbctwcen and encircle said central stem. and wherein said elongate coupling sleeve encloses said flexible sleeve and is constrained to slide axially upon said rigid end walls defm ing the first chamber.  
  ll. A hydraulic pump comprising: an elongate body defining first and second axially successive chamber; an axial fluid-passageway extending between said first and second chambers; a plunger which is reciprocable axially within said first chamber and extends into said fluid-passageway. valve means controlling admission of fluid from said first chamber into said fluidpassageway, operation of the valve means being coordinated with movement of the plunger in such a way that admission of fluid into said passageway from said first chamber occurs in response to axial movement of the plunger away from the second chamber and is prevented in response to axial movement of the plunger towards said second chamber, whereby in the latter movement the plunger forces fluid from said passageway into the second chamber; and lever means acting between the pump body and the plunger and operable to effect reciprocation of the plunger; wherein the improvement comprises a pair of axially spaced apart, rigid end walls connected together by a hollow central stem through which said plunger passes, and a sleeve of flexible, non-permeable material which extends between said end walls so as to sealingly enclose the space therebetween and encircle said central stem, said first chamber being defined by said flexible sleeve and end walls and being completely filled with fluid.