US 3312171 A
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United States Patent Ofiice 3,312,171 Patented Apr. 4, 1967 3,312,171 PUMPS Francis H. Cary, Hope, R.l., assignor to The New York Air Brake Company, a corporation of New Jersey Filed Oct. 12, 1965, er. No. 495,105 Claims. (Cl. 103-44) This invention relates to hydraulic pumps of the pulsator type wherein a secondary liquid is pumped by an elastic tubular diaphragm which is pulsed by a primary or operating liquid which is cyclically forced into and withdrawn from its interior.
The primary object of the invention is to simplify the construction of these pumps, and thereby reduce manu facturing costs, and to reduce the adverse effects resulting from the compressibility of the primary and secondary liquids. According to the invention, the improved pump i characterize-d by an upright casing having three separa- :ble sections, the central one of which contains a through bore which defines the outer wall of the pumping chamber and which is closed by the other two sections, and by a molded, one-piece, elastic pumping element which provides not only the expansible pumping diaphragm but also a pair of seals for the joints between casing sections, a pair of cylindrical lands which fit the wall of the bore in the central section and perform a self-centering function for the diaphragm, and a transverse wall for the pumping chamber which is directed toward the outlet port and encourages the escape of gas from that chamber.
The preferred embodiment of the invention is described herein with reference to the accompanying drawing in which:
FIG. 1 is an axial sectional view of the improved pulsator rpump.
FIG. 2 is a sectional view taken on line 2-2 of FIG. 1.
FIG. 3 is an enlarged sectional view of a portion of the foraminous support for the diaphragm.
As shown in the drawing, the pum comprises a vertical casing 11 including three separable sections 12-14 which are held together, and to the bottom wall of a support 15, by a plurality of bolts 16 which extend through openings formed in the end sections 12 and 14. Central section 13 is formed with a through circular bore 17 which defines the outer wall of the pumping chamber 18 and which, at its upper end, is intersected by a combination inlet and discharge passage 19. This passage 19 leads to a passage 21 extending through flange fitting 22, and thence, thnough the reverscly set check valves 23 and 24, to the inlet and discharge ports 25 and 26 formed in housings 27 and 28, respectively. The check valves, which are of the type described in my copending application Ser. No. 474,626, filed July 26, 1965, are clamped in place between the flange fitting and the housings 27 and 28 by bolts 29.
The inner wall of pumping chamber 18 is defined by a tubular diaphragm 31 which has a circular shape in cross section and is molded as an integral part of a pumping element 32. This element 32, which is made of an elastomeric material such as Hypalon chlorosulforated polyethylene or Viton fluorocarbon rubber, both marketed by E. I. du Pont de Nemou-rs & Company, is formed with steps on its outer periphery which separate the diaphragm portion 31 from a pair of enlarged end lands 33 and 34. The diameter of these lands is just slightly less than the diameter of bore 17, and, therefore, the lands form a snug fit with the bore and serve to center the diaphragm portion 31 within the pumping chamber 18. The transverse end face 35 of land 33 lies in a plane which is inclined toward the passage 19 so that gases released from the pumped liquid are prevented from accumulating in the pumping chamber 18. The pumping element 32 also is formed with a pair of O-rings 36 and 37, which are of circular cross section and which are joined to the ends of lands 33 and 34, respectively, by short, centrally located, annular webs 38 and 39. These O-rings and webs are received in recesses defined by the mating surfaces of the casing sections 12, 13 and 14, and are compressed during assembly to eflectively seal the casing joints.
The pumping element 32, and in particular, the diaphragm portion 31 thereof, is supported internally by a rigid, forarninous cylinder 41 whose upper end is seated in a counterbore in casing section 14 and whose lower end surrounds and is supported by the pintle 42 of section 12. Although the cylinder 41 can take many different forms, the one illustrated is a Metal Edge filter element, marketed by Purolator Products, Inc., and comprises a helically coiled flat metal wire 43 which, on one side, carries spaced, tapered projections 44 that separate adjacent turns in the finished coil. The outside diameter of cylinder 41 is greater than the inside, diameter of pumping element 32 when the latter is in a state of repose, and therefore, it will be understood that the diaphragm 31 is, in effect, prestressed.
The diaphragm 31 is pulsed by a drive piston 45 which is guided in a central bore extending through casing sec tion 14 and projects into the interior of cylinder 41, The piston 45 is formed with intersecting axial and radial passages 46 and 47, respectively, which lead to a liquidfilled reservoir 48 contained within support 15. Piston 45 is reciprocated by a crank mechanism (not shown) located in the upper portion of the reservoir 48, and is encircled by a sleeve 49 whose upper end face 51 cooperates with radial passages 47 to define a spill-back valve for the pulsing pump. The position of the sleeve 49 along the path of travel of piston 45 is adjusted by a rotary threaded actuator 52, and determines the point in the stroke of piston 45 at which communication between the interior of diaphragm 31 and reservoir 48 is internrped. Therefore, as those skilled in the art will readily understand, the spill-back valve constitutes a device for varying the quantity of operating liquid which is forced into the diaphragm on each stroke of piston 45, and consequently serves to vary the quantity of secondary liquid which is displaced from pumping chamber 18 during each of such strokes.
During operation, the reservoir 48 is filled with operating liquid, inlet port 25 is connected with a source of the secondary liquid which is to be pumped, and discharge port 26 is connected to the system to which the secondary liquid is to be delivered. Assuming that spill-back sleeve 49 is an intermediate displacement position, and that piston 45 is in its top dead center position, the primary fluid displaced from within diaphragm 31 during the initial portion of the downward or discharge stroke of piston 45 escapes freely to the reservoir 48 through axial and radial passages 46 and 47. Therefore, during this portion of the discharge stroke, diaphragm 31 remains contracted. However, once piston 45 reaches a position in which the passages 47 are Wholly Within, and thus closed by, sleeve 49, further downward movement will produce expansion of the diaphragm. If pumping chamber 18 is liquidfilled, this expansion of the diaphragm will displace a portion of the secondary liquid from that chamber and cause it to fiow through check valve 24 and port 26 to the system. As the piston 45 commences to move on itssuction stroke (i.e., in the upward direction), the diaphragm will contract, as a result of its inherent elasticity, and draw secondary liquid into the pumping chamber 18 through port 25, check valve 23, and passages 21 and 19. When the piston 45 moves beyond the cut-off position established by sleeve 49, and passages 47 again communicate with reservoir 48, any liquid lost from the operating circuit through leakage will automatically be replaced.
Thus, unless the position of spill-back sleeve 49 is changed, the pump will discharge substantially equal quantities of secondary liquid during the succeeding pumping cycles.
When the spill-back sleeve 49 is in the illustrated lowermost position, it does not close passages 47 until piston 45 reaches the bottom dead center position. Thus, in this case, all of the primary liquid displaced by piston 45 during its discharge stroke spills back to reservoir 48, and, diaphragm 31 is never expanded. Consequently, the output of secondary liquid is zero. On the other hand, when sleeve 49 is in its uppermost position, the spill-back passages 47 are closed just shortly after the piston 45 commences its downward stroke, and consequently almost all of the primary liquid displaced by the piston 45 is effective to produce expansion of diaphragm 31. In this case, therefore, the output of secondary liquid per stroke of piston 45 is a maximum.
In pumps of the type under discussion here, the compressibility of the fluids trapped between the drive piston 45 and the inlet and discharge check valves 23 and 24 is of great importance. This is so because, as discharge pressure rises, a progressively larger portion of the piston stroke is wasted in compressing the fluids. As a result, the rate of discharge from port 26 decreases. The illustrated pump incorporates certain features which reduce this effect. First, the use of the inclined face 35 on land 33 encourages the escape of gases from the circuit of the secondary liquid, and thereby tends to eliminate one highly compressible component of this fluid. Second the clearance volume of the secondary liquid circuit, i.e., he total volume of passages 19 and 21, and pumping chamber 18 when diaphragm 31 is fully expanded, can be made quite small because of the self-centering action of the lands 33 and 34. In the absence of this feature, the radial clearance between the expanded diaphragm and the wall of bore 17 would have to be increased in order to insure that the diaphragm would not contact, and thus rub, the wall during operation as a result of misalignment during assembly. Finally, the clearance volume of the primary liquid circuit is kept to a minimum by using the pintle 42, and by using a close clearance between piston 45 and the central bore in casing section 14.
As stated earlier, the drawing and description relate only to the preferred embodiment of the invention. Since changes can be made in the structure of this embodiment without departing from the inventive concept, the following claims should provide the sole measure of the scope of the invention.
What is claimed is:
1. A one-piece pumping element made of an elastomer and comprising (a) an elongated tubular body of circular cylindrical shape having a pair of steps on its outer periphery that define a central diaphragm portion of one diameter and a pair of end lands of larger diameter, the
transverse face of one land being inclined with respect to the longitudinal axis of the body;
(b) a pair of sealing rings coaxial with and encircling the body, one ring being located adjacent each end of the body; and
(c) radially extending web members connecting the rings with the lands.
2. A pumping element as defined in claim 1 in which the transverse face of .said one land lies in a plane.
3. A pumping element as defined in claim 1 in which the sealing rings have a circular cross section; the webs lie in planes which bisect the rings; and said end lands have equal diameters.
4. In a pulsator pump of the type embodying a tubular diaphragm, the combination of (a) a three-part casing comprising an upright central section containing a through axial bore, and a pair of end sections having annular surfaces which are adjacent the end faces of said central section, the central section containing a port which intersects the axial bore near its upper end; and
(b) a one-piece pumping element as defined in claim 1 located within the casing,
(c) the diameters of the end lands of said element being so dimensioned that these portions fit snugly within the axial bore,
(d) the sealing rings and the webs of said element being compressed between the end faces of the central body and the annular surfaces on the end sections, and
3') (e) the transverse face of said one land of the pumping element being inclined upward toward said port in the central body.
5. A pulsator pump as defined in claim 4 wherein one 40 end section carries a central pintle which projects into the space within the pumping element.
References Cited by the Examiner UNITED STATES PATENTS ROBERT M. WALKER, Primal Examiner.