US 3209701 A
Description (OCR text may contain errors)
D. D. PHINNEY Oct. 5, 1965 PUMP Filed Oct. 5, 1962 ATTY'S.`
United States Patent O 3,209,701 PUMP Damon D. Phinney, Boulder, Colo., assignor to Sundstrand Corporation, a corporation of Illinois Filed Oct. 5, 1962, Ser. No. 228,649 12 Claims. (Cl. 103-173) This invention relates generally to pumps of the reciprocating type and more particularly to a cylinder block construction for such pumps providing for lubricating of such pumps for use in pumping of lluids having poor lubricating properties.
Although in the pumping of fluids having good lubricating properties, the working parts of piston pumps, and especially the side walls of the pistons and cylinders thereof, may receive adequate lubrication from the lubricating fluid being pumped, where it is desired to pump lluids having poor lubricating properties, such as water, hydrazine, hydrogen peroxide, liquid gases, etc., lubrication must be applied from another source. ln using piston pumps such as check valved piston pumps for pumping liuids with poor lubricating properties it is sometimes desirable to use a pump designed to reduce weight and complexity. The provision of a large swashplate angle in a piston pump is one design feature which may be used to reduce the weight and complexity of the pump. However, the use of the large swashplate angle produces greater side forces on the piston in the cylinders. Such side forces can lead to galling and wear of the piston or cylinder. It is desirable to minimize or eliminate the effect of such side forces. It may also be desirable in other piston pumps for use in other applications to lessen such side forces as may occur in the pumps.
It is an object of this invention to provide new and useful means for reducing side forces between piston and cylinder in a piston pump.
It is another object of this invention to provide a piston pump wherein the pumping ends of the pistons reciprocate in a transversely movable cylinder means for reduction of side forces between piston and cylinder.
It is still another object of this invention to provide a pump for pumping non-lubricating fluids including means for adequately mounting and lubricating the non-pumping ends of the pistons and including means for reducing side forces between the piston and cylinder including the provision of transverse motion of the cylinder means portion in which the pumping end of the piston reciprocally travels, the transverse motion being with respect to axis of the piston.
An additional object of this invention is to provide a check Valved piston pump for pumping non-lubricating fluids which includes a stationary crosshead mounted within the housing and dividing the interior of the housing into two separate enclosures, one containing the swashplate and the other containing the cylinder block, the pistons passing through these crossheads from cylinder block to swashplate which is rotatably mounted at a large swashplate angle, and to provide in such a pump means for mounting and lubricating the pistons within the crosshead, the lubricating means extending from the swashplate enclosure through the crosshead to the pistons, and to further provide in the pump means for reducing side forces between the piston and cylinder and in association with the pumping ends of the pistons.
An additional object is to provide a pump in accordance with the foregoing objects wherein a crosshead and cylinder block are separated from each other and wherein there is provided ring seal means between each piston and its corresponding crosshead chamber, means for opening the pump housing adjacent the swashplate and crosshead, means for removing the crosshead and means for replacing ring seals which may become worn or otherwise bgfbl Patented @cia 5, 1965 ice rendered undesirable for use in the operation of the pump.
Other objects and advantages will become readily apparent from the following detailed description taken in connection with the accompanying drawings, in which:
FIG. 1 is a vertical section of an embodiment of the pump of this invention; and
FIG. 2 illustrates an enlarged vertical section of an embodiment of a pumping cylinder usable in the pump illustrated in FIG. 1.
While an illustrative embodiment of the invention is shown in the drawings and will be described in detail herein, the invention is susceptible of embodiment in many diiierent forms, and it should be understood that the present disclosure is to be considered as an exemplication of the principles of the invention and is not intended to limit the invention to the embodiment illustrated. The scope of the invention will be pointed out in the appended claims.
Referring now to the drawings, numeral 30 designates a pump housing comprising casings 31 and 32 which are separably joined by suitable means such as bolts, for example as shown at 33, threaded in the casings. A drive shaft 34 having splines 35 for attachment to a prime mover is rotatable in the housing and is splined at 39 to swashplate 21 which is mounted in swashplate bearings 37 and i0 and is rotatable with shaft 34. Thrust bearing member 41 is rotatably mounted on swashplate 21 by snap ring 38 and bearings 42.
A plurality of axial pistons in annular array is provided within the pump and although only piston 12 is shown in the drawings it is to be understood that each piston of the plurality abuts against thrust bearing member 41 at its non-pumping end and each is attended by other elements in an environment similar to that of piston 12 as will be described. Piston 12 is reciprocally mounted in a bronze sleeve or bushing 13 seated in a mounting block or crosshead l0 for the purpose of maintaining longitudinal alignment of the piston. A suitable lubricating oil is contained within the housing in the chamber formed by crosshead 10 and casing member 31, on the swashplate side of crosshead 1t). The chamber may be, for example, about half full of the lubricating oil and the lubricating oil is in communication with the swashplate. A ported annular conduit 23 surrounds piston 12 internally in sleeve 13 providing lubrication of the piston within crosshead 10 and particularly within bushing 13. The lubricating oil is pumped into conduit 23 by rotation of swashplate 21 which swirls the oil and causes a static pressure to develop in the outside of the chamber containing the rotating parts. This pressure forces oil to flow radially inward wherever static passageways are provided. The general ilow of lubricating oil to conduit 23 is indicated by the dotted lines and arrows shown at 14. Piston seal 15, which is an O-ring 15a and Tellon (polytetralluoroethylene) boot 15b, constitutes a seal between piston 12 and crosshead 10 preventing ow of pumped lluid to the opposite or non-pumping side of crosshead 10. Piston seal 15 is carried in a seal cavity and is removable therefrom for replacement of the seal upon removal of a retainer plate 15e normally abutting the crosshead.
Crosshead 19, which is composed of stainless steel, abuts snap ring 43, retainer plate 15e abuts crosshead 10 and cylinder block 11 abuts retainer plate 15C. Springs, e.g., as shown at 11a urge cylinder block 11, retainer plate 15C and crosshead 10 against snap ring 43 in casing 32. Cylinder block 11 is also stainless steel but any other suitable material may be used in construction of the crosshead and the cylinder block, since the design irnposes neither high strength nor wear resistance requirements on these parts. Piston 12, one of a plurality of pistons is slidably mounted in a bore defined by crosshead 10, bushing 13 and sealing means 15. Due to the angle of swashplate 21, piston 12 is side loaded with a force equal to 17.6% of the hydraulic load on the pumping end 12a of piston 12 for the design shown.
Pumping end 12a of piston 12 extends loosely into cylinder block 11 and closely tits into pumping cylinder 16 which is carried by piston 12. Pumping cylinder 16 is positioned loosely within a recess in cylinder block 11 and is free to move transversely to the reciprocal axis of piston 12. Reference numeral 17 indicates the metalto-metal seat of pumping cylinder 16 on cylinder block 11. An alternative seat is shown in FIG. 2 wherein Telflon ring 17a, which is machined to tit and bonded to pumping cylinder 16, forms a seating surface on the pumping cylinder for seating in block 11. Spring loaded discharge valve 25 assists in seating cylinder 16 in block 11, especially by exerting a slight clamping force against cylinder 16 during start-up of the pump.
In operation, a prime mover attached by spline 35 to shaft 34 causes rotation of swashplate 21. Rotation of the swashplate with counterbalance 21a on the circumference or periphery thereof, causes the lubricating oil in housing 30 to be hurled against the inside wall of the housing and circulated for lubrication of moving parts as desired. Dotted and arrowed lines indicated at 14a in FIG. 1 show circulation of lubricating oil to such parts as the swashplate bearings. The dotted and arrowed lines indicated at 14 show circulation of lubricating oil to passage or conduit 23 for lubrication of piston 12 Within bushing 13. The force of the side load of piston 12 is taken against bushing 13 in the crosshead and lubrication between the piston and bushing is highly desirable.
The fluid being pumped, such as hydrazine, enters through inlet 19 to inlet chamber 24 in cylinder block 11, and is admitted through suitable intake valve 20 in piston 12 to pumping cylinder 16. Intake valving 20 is a floating check valve retained in piston 12 by a snap ring. During the pumping stroke of piston 12, intake valve 20 is closed by the pressure of the Huid being pumped. During the intake stroke valve 20 is opened by the pressure of intake iiuid in intake chamber 24, and piston 12 is returned by the pressure of the intake fluid in the pumping chamber, a greater pressure than that on the swashplate side of crosshead 10.
Pumping cylinder 16 floats in cylinder block 11 in the recess provided and is free to move transversely to the reciprocal axis of piston 12, thereby substantially reducing side forces between pumping end 12a of the piston and pumping cylinder 16. Piston seal serves to prevent the hydrazine at inlet pressure, e.g., 80 p.s.i., from leaking into the lubricating oil. If desired, Teon ring 17a acts as a suitable friction reducing seat between pumping cylinder 16 and its seat in cylinder block 11. Pumping cylinder 16 is clamped on its seat in the cylinder block by the valve spring acting across discharge check valve 25 and acting against the end of pumping cylinder 16. More important, the pumping cylinder 16 is urged against its seat by hydraulic force during pumping. Thus, the maximum side load on the piston pumping end 12a, where there is little if any lubrication, is that required to slide pumping cylinder 16 on its seat.
Although the operation of the device and the device itself has been illustrated with respect to only one piston, i.e., piston 12, the pump includes a plurality of pistons of the same structure and attended by the same structures, reciprocating axially in succession in their annular array about the protracted axis of the drive shaft giving a pumping action of the fluid entering inlet 19. In the pumping of the fluid, the fluid ows from inlet 19, through inlet chamber 24, through piston 12 and follows the route of the arrowed lines shown at 26 in the drawing to outlet 22 where the uid is discharged from the pump. Spring loaded relief valve 27 is provided to permit How of pumped fluid from outlet 22 to inlet chamber 24 to relieve excessive pressure.
The disclosed construction is advantageous in that the normal one piece cylinder block construction is avoided without very expensive alignment of the holes in the two blocks. The split in the block exposes the piston seals facilitating initial assembly and replacement. Such construction is further advantageous in that it permits the use of bronze or other suitable crosshead materials for improved bearing conditions and further permits the use of hardened steel or other suitable materials in the pumping cylinders without giving rise to the ditiicult machining problem inherent in maintaining perfect alignment between ditlerent materials normally finished by different machining methods, e.g., boring for bronze in the crosshead and grinding followed by honing for steel in the pumping cylinders. In order to further reduce the side forces of the pistons against the cylinder walls, with reference to the drawings a looser fit may be provided between pumping cylinder 16 and piston 12 than between crosshead bushing 13 and piston 12 where efficiency is not critical.
The construction of the illustrated embodiment provides for separation of the casing 31 and 32, e.g., by removal of securing bolts 33 and ease of removal of crosshead 10 by removing snap ring 43 and withdrawing crosshead 10 from the housing. The ready removability of crosshead 1t) provides for easier replacement of worn parts and especially piston seals, such as indicated at 15.
1. In a swashplate-piston pump wherein pumping action is achieved by action of an inclined swashplate driving a plurality of pistons slidably mounted in annular array in axial cylinders of the cylinder block and wherein the driving is a result of inclination of the swashplate relative to the axis of the array of cylinders, the improvement comprising crosshead means between said block and said swashplate, said pistons slidably extending through said crosshead means, said crosshead means and pistons being adapted to contain uid lubricant on the swashplate or non-pumping side of said crosshead means and sealing means on said crosshead to prevent lubricant from contacting the cylinders and to prevent the tluid being pumped from entering the crosshead and each of said cylinder means being movable in said block transversely to the reciprocal piston axis responsive to side loads between piston and cylinder means and each cylinder containing the reciprocal travel of the pumping end of a piston.
2. The pump of claim 1 which includes conduit means within the crosshead means and extending from the nonpumping side of said crosshead means to the outer surfaces of the pistons therein.
3. A pump for pumping non-lubricating fluids having a housing, a drive shaft, rotatably mounted through said housing, a swashplate attached to and rotatable with said drive shaft, a stationary cylinder block within said housing and opposing said swashplate, a stationary crosshead across said housing between said block and said swashplate defining a block enclosure and a separate swashplate enclosure within said housing, a plurality of cylinder means within said block, each of said cylinder means having a pumping piston with a pumping end slidably extending therein, said cylinder means being movable in said block transversely to the piston axis responsive to side loads between the piston and cylinder means, a plurality of chambers through the crosshead, each of said chambers aligned with one of said cylinder means, said piston extending through said chambers to said swashplate, said crosshead preventing Huid ow between said enclosures, means for charging a lubricant to said swashplate enclosure, conduit means to each chamber in said crosshead for conducting lubricant to each piston, said swashplate impelling lubricant into said conduit means, and ring seal means between each piston and cylinder adjacent the block enclosure and adapted to prevent tlow of pumped fluid from said block enclosure to said swashplate enclosure during operation of the pump.
4. In a reciprocable piston pump, a piston mounting blocks, at least one piston reciprocably mounted in said block, a cylinder support spaced axially from said mounting block, a cylinder slidably receiving the pumping end of said piston and providing a pump chamber therefor, said cylinder being mounted on said support for movement transverse to the axis of the piston in response to side loading of the piston, thereby to reduce wear of the interengaged piston and cylinder surfaces, sealing means in said block for preventing entry of the pumped fluid into said mounting block, means for reciprocating the piston through intake and exhaust strokes, intake valve means for admitting fluid to the pump chamber during piston intake strokes, and exhaust valve means for exhausting fluid from the pump chamber during piston exhaust strokes.
5. An axial piston pump for handling uids which lack lubricating qualities, comprising, a housing, a cylinder block mounted in the housing, a separable crosshead mounted in the housing adjacent the cylinder block, a swashplate rotatably mounted in the housing adjacent the crosshead, an annular series of axially disposed pistons extending through the crosshead and having ends disposed to engage the swashplate and opposite ends extending loosely into the cylinder block, means mounting the pistons in the crosshead to take substantially the entire side loading on the pistons during pump operation, a plurality of cylinders respectively slida'ble on said opposite piston ends and providing pump chambers therefor, said cylinders being mounted in said cylinder block respectively for movement transverse to the associated piston axis thereby to reduce wear of the interengaged piston and cylinder surfaces, means for rotating the swashplate to move the pistons through pump strokes, means for moving the pistons through intake strokes, intake and exhaust valve means for successively admitting iluid to and exhausting fluid from said pump chambers as the swashplate is rotated, means for lubricating said piston mounting means in said crosshead, and sealing means on said crosshead for preventing the flow of lubricant to said cylinders.
6. A pump as defined in claim 5, including abutment means in said housing adjacent said swashplate engageable by said crosshead, and spring means bearing against the cylinder block and housing, urging the crosshead, sealing means and cylinder block toward said abutment means.
'7. A pump as dened in claim 5, wherein said cylinders are mounted in recesses in said cylinder block opening toward the end of said cylinder block remote from said crosshead and axially movable therein, wherein each of said exhaust valve means comprises a check valve normally closing the remote end of said cylinder, and spring means acting against said housing and said check valve member.
`8. In a pump of the type having a housing, a drive shaft, and a swashplate driven by the drive shaft, the improvement comprising: a cylinder block mounted in said housing and spaced from one end of said housing thereby defining a space constituting a portion of a pump outlet passage, cylinders in said cylinder block freely movable transversely with respect thereto and spaced from said end of said housing so that at least a portion of one end of each of said cylinders continuously communicates with said space, pistons slidable in said cylinders and engaging the swashplate to be recprocated thereby as the swashplate rotates, outlet passage means in said housing communicating with said space and adapted to convey Huid under discharge pressure from said housing, inlet means in said housing for delivering fluid to said cylinders on piston intake strokes, outlet valve means associated with each cylinder including a resiliently biased check valve engaging said one end of each of said cylinders for urging the other ends of the cylinders into sealing engagement with the cylinder block so that the check valves maintain the cylinders in position during the initial rotation of the pump, and thereafter discharge uid in the space maintains the cylinders in position thereby permitting transverse movement of the cylinders and eliminating side loads thereon.
9. In a pump as defined in claim 8 and further including, a ring mounted on said other end of each of said cylinders having a low co-eicient of friction compared to the cylinders and engaging said cylinder block to facilitate the transverse movement of said cylinders.
10. In a pump as defined in claim 8 and further including a crosshead having a plurality of axial cylindrical chambers for receiving said pistons, said crosshead being ixedly mounted in said housing to absorb the radical loads from the pistons.
11. In a pump as defined in claim 10 wherein said `crosshead and said cylinder block are separable, and further including ring seal means around each piston mounted in the respective crosshead chambers, removable closure means for opening said housing adjacent the swashplate and crosshead, means removably mounting the crosshead in said housing to facilitate the replacing of said seal means.
12. In a pump as dened in claim 10, and further including means in said crosshead for supplying lubricating fluid to each of the pistons.
References Cited by the Examiner UNITED STATES PATENTS 1,274,391 8/18 Davis 103-162 2,238,252 4/41 Davis 103-173 2,374,595 4/ 45 Franz 103-173 2,433,222 12/47 Huber 103-173 2,669,185 2/54 Tallis 103-173 2,797,647 7/57 Floraday 103-173 3,018,737 1/62 Cook et al 103-173 3,067,694 12/ 62 Fancher 103-173 3,090,313 5/63 Budzich 103-173 3,160,102 12/64 Budzich 103-173 FOREIGN PATENTS 830,959 3/60 Great Britain.
LAURENCE V. EFNER, Primary Examiner. JOSEPH H, BRANSON, JR., Examiner,