WO1994018488A1

WO1994018488A1 - Pulsation damper device

Info

Publication number: WO1994018488A1
Application number: PCT/US1993/002120
Authority: WO
Inventors: Edward D. Paley; Gregory E. Leemhuis; Kerry A. Machesney
Original assignee: Hydraulic Power Systems, Inc.
Priority date: 1993-02-09
Filing date: 1993-03-08
Publication date: 1994-08-18

Abstract

A pulsation damper and noise attenuator assembly comprising a housing having an inlet port (214) and an outlet port (216) fluidly connecting the interior of the housing to the flow path of the fluid flow system. A base (220) is mounted to the housing and comprises a vent (248) fluidly connecting the interior of the housing to the atmosphere. A piston (228) seated within the housing creates a fluid tight seal between the fluid flow path and the vented atmospheric pressure. Belleville springs (236) bias the piston in a forward direction. The piston absorbs the full force of the hydraulic shock waves or pulsation within a high pressure fluid flow system as the assembly is mounted directly within the flow path of the fluid. The shock wave is exposed across the full face of the piston and dampened prior to the fluid continuing along the flow path. In a second embodiment, a sealing member such as an expandable bellows (30) or piston (130) is seated within the housing and creates a fluid tight seal between the fluid flow path and the external fluid source sealing member. The sealing member acting against the N2 fluid under pressure absorbs the full force of the hydraulic shock waves or pulsation within a high pressure fluid flow system as the assembly is mounted directly within the flow path of the fluid. The shock wave is exposed across the full face of the sealing member and dampened prior to the fluid continuing along the flow path.

Description

PULSATION DAMPER DEVICE

BACKGROUND OF THE INVENTION

I. Field of the Invention The present invention relates to a pulsation damper and noise attenuator assembly for use in a fluid flow system. More particularly, the present invention relates to a pulsation damper and noise attenuator assembly that is mounted directly in the fluid flow path of the fluid flow system.

II. Description of the Prior Art

A pulsation damper and noise attenuator assembly is generally used in a fluid flow system to dampen or prevent development of pressure pulsation in a system where it is desired to continuously deliver fluids under pressure. Fluid pressure pumps, and, in particular positive displacement pumps create pressure pulsations during normal operation which can cause excessive strain and/or damage to the conduits and within the fluid system. Further, the airborne sound generated by the pulsation traveling through the conduit may be very loud and poses an annoyance or possible hazard to the user of the equipment.

To overcome these phenomenons, several prior art fluid devices have been developed. A disadvantage of these previously known control devices is that the apparatus is not placed directly in the flow path of fluid but is instead usually coupled to the end of a T- shaped connection. Removing the prior art device from the fluid flow path prevents the device from absorbing the full force of the pulsation as the wave is not forced to flow directly through the device. Therefore, any pulsation that interrupts the fluid flow may not be suppressed by the device due to its indirect application in the flow path.

A still further advantage of the prior art devices is that the fluid flow is not exposed to the complete surface area of the dampening device. That is, the path of the pulsation is not directed across the full face of the piston used to absorb the pulsation. Therefore, complete absorption or dampening of the pulsation is not provided by the prior art devices and, as such, the pulsation is allowed to dissipate throughout the entire fluid flow path.

SUMMARY OF THE PRESENT INVENTION The present invention provides a pulsation damper and noise attenuator assembly which overcomes the disadvantages of the previously known fluid control apparatuses.

The pulsation damper and noise attenuator assembly of the present invention comprises a housing having an inlet port fluidly connecting a first interior chamber of the housing to an external fluid pressure source such as pressurized nitrogen. The housing, further comprises an inlet port and an outlet port which fluidly connect a second interior chamber of the housing to the flow path of a fluid flow system such as, respectively, a fluid pump and a motor connect in an open and/or closed loop system.

A sealing member, such as a free floating piston in a first embodiment or an expandable bellows in a second embodiment, or other sealing members such as a diaphragm, is seated within the interior of the housing (of suitable shape, e.g., cylindrical, round, spherical, etc.) and separates the housing interior into the first and second chambers. In use the assembly inlet is in communication with a source of fluid under pressure and all flow in the system passes through the second aforementioned chamber. Therefore, any hydraulic shock wave or pulsation is directed into the assembly to allow the sealing member to absorb the pulsation. The sealing member counterbalances the high pressure fluid by the external fluid, preferably an inert gas such as nitrogen, which is communicated under pressυre to the first pressurized housing chamber.

Unlike the previously known fluid control apparatuses, the present invention provides that the force of a hydraulic shock waves or pulsations within the fluid flow system is directed across the entire forward face of the sealing member. By exposing the pulsations to a larger area, this insures that the pulsations will be absorbed by the assembly and dissipates the same with minimal affect on the high pressure fluid flow within the system. Further, by placing the assembly directly in the flow path of the fluid flow system the shock waves or pulsations is forced to be directed within the assembly and absorbed thereby. Another example of_. the present invention comprises a housing having inlet port and an outlet port. The ports are fluidly connected by a fluid chamber within the interior of the housing such that the housing interior becomes part of the fluid flow system. A cover, threadably mounted on the housing comprises a cylindrical projection defining a chamber which in turn is vented to the atmosphere. A piston is slidably received within the cylindrical projection such that the forward portion of the section defines a pressure responsive area directly exposed to the fluid flow path.

A plurality of washer springs such as Belleville springs are mounted about the exterior of the covers cylindrical projection and bias the piston towards the housing fluid chamber. An advantage of this assembly is that the fluid flow path is directed across the entire face of the piston, thereby receiving the full effect of the pressure increases caused by the pulsations. An advantage of the non-gas embodiments is that there is no need for concern for leakage of the gas and a drop in spring rate.

Further, since the stacked Belleville springs can sustain relatively large loads with small deflections, a smaller envelope of stacked springs (as compared to a coil spring) is required to resist the force which may be created by the pulsation acting against the pressure response area of the piston. Therefore, the use of Belleville springs eliminates the need for a larger coil compression spring of equivalent load bearing capacity. The area required by the Belleville springs is much smaller and reduces the size of the device itself. Other advantages and features of the present invention will become more apparent from the following detailed description when read in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS The present invention will be more fully understood by reference to the following detailed description of the preferred embodiments of the present invention when read in conjunction with the accompanying drawings, in which like reference characters refer to like parts throughout the views, and in which:

Fig. 1 is a cross-sectional side view illustrating a first preferred embodiment of the present invention with the sealing member in its fully contracted position; Fig. 2 is a side cross-sectional view of the preferred embodiment of Fig. 1 illustrating the sealing member in its fully expanded position;

Fig. 3 is a side cross-sectional view illustrating a second preferred embodiment of the present invention; and

Fig. 4 is a longitudinal cross-sectional view of a third embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to Fig. 1 wherein there is illustrated a first preferred embodiment of the present invention in the form of a pulsation damper and noise attenuator assembly 10 which comprises a housing 12 formed of an elongate hollow cylinder and sealed at one end by a valve assembly 14. A base assembly 16 is mounted to the opposite end of the housing 12 by suitable mounting means such as screws (or welded) 18. A seal such as an elastimer seal or metallic ring 20 about the perimeter of the base assembly 16 creates a fluid tight seal between the housing 12 and the base assembly 16. Valve assembly 14 is preferably mounted to the housing 12 by welding (or screw-in) as shown at 22 and completely seals the interior of the housing 12.

The valve assembly 14 includes a passageway 24 for fluidly connecting an inner chamber 42 of a sealing member to an external pressure fluid source such as an inert gas, preferably nitrogen. In this preferred embodiment, the sealing member is preferably a bellows 30 that is expandable and retractable in reaction to fluid pressure acting thereon. The bellows 30 is sealed at one end 32 to a member 36 having pressure response surface 34 and is movable therewith to expand and contract. The opposite end 40 of the bellows 30 is mounted to support 28 of the valve assembly 14 to create a fluid tight assembly between the valve assembly 14 and the bellows 30 to define the fluid tight inner chamber 42. The fluid tight seal of the bellows 30 about the support 28 ^■ prevents the nitrogen from seeping into the interior chamber 26 of the housing 12.

Stops such as cylinders 44, 46 are mounted by bolts 48 to the support 28 within the interior chamber 42 of the bellows 30. Cylinders 44, 46 prevent the bellows 30 from retracting within the interior 26 of the housing 12 beyond the faces 50 of the cylinders 44, 46. A check valve 54 is provided within the passageway 24 to permit the entry of N into the chamber 42 and prevent back flow of nitrogen from the chamber 42. Base assembly 16 comprises an inlet port 56 and an outlet port 58 fluidly connecting the interior chamber 26 of the housing 12 with the flow path of the fluid flow system. Preferably the inlet port is connected in close proximity to the outlet of the source of the pressure pulsation, such as a piston pump. Mounting members such as ring 60 is fixedly mounted to the base assembly 16 by bolts 64 (or other permanent mounts such as welds or stops) within the interior 26 of the housing 12 to limit the bellows 30 movement toward the inlet and outlet ports (see Fig. 2) .

Flow path A exemplifies the flow path of the fluid flowing within the system.

In use, the pulsation damper and noise attenuator assembly 10 is advantageously placed directly within the flow path of the fluid flow assembly such as between a fluid pump and fluid motor. In this way, any hydraulic shock waves or pulsations that develop in the high pressure system are directed into the assembly 10 to be dissipated by the retracting bellow 30. Further, the pulsation is exposed to the full pressure responsive surface 34 of member 36 to be absorbed by the bellows 30 acting against N₂ filled chamber under pressure to provide a gas spring pulsation absorber. A larger area of deflection is afforded by this system.

Nitrogen from an external fluid source fills the inner chamber 42 of the bellows 30 to a predetermined pressure (e.g., 2000 psi) . In its steady state, bellows 30 is expanded to an intermediate position between the ring 60 and the cylinders 44 and 46.

Pulsation within the fluid flow path flow along flow path A through inlet port 56 of the assembly 10. The pulsation is absorbed by the bellows 30 acting against the N₂ chamber 42 and forces it to contract. The balancing force of the nitrogen within the bellows counters and reduces and/or eliminates pulsation. The pulsations are absorbed by the nitrogen spring within the bellows 36. The charge of N₂ is prepressured to be between 50% and 70% of the pressure of the fluid system. With reference now to Fig. 3, a second preferred pulsation damper and noise attenuator assembDy 110 is illustrated. In this embodiment, a housing 112 comprises an inlet port 124 fluidly connecting an interior chamber 142 of the housing 112 to an external fluid source, preferably an inert gas such as nitrogen so as to pressurize the chamber 142 to a predetermined amount, say 1500 psi.

A base assembly 116 is mounted to the housing 112 preferably by welding means as shown at 122 (threaded or bolts or snap rings or other suitable retention means may be used) to create a fluid type seal between the housing 112 and the base assembly 116.

Base assembly 116 comprises an inlet port 156 and an outlet port 158 fluidly connecting the interior of the housing 112 to the flow path of a fluid flow system.

A sealing member in the form of a free floating piston 130 is freely slidable within the interior of the housing 112 and defines a movable wall of the inner chamber 142 that is exposed to the pressurized nitrogen and an outer chamber 144 exposed to the fluid within the flow path of the assembly 110. Piston 130 comprises a seal such as an elastimer seal or a metallic ring 146 creating a fluid tight seal that prevents the nitrogen from mixing with the fluid in the chamber 144. Piston 130 also comprises restraining means in the form of a ring shaped shoulder 148 extending around the perimeter of the piston 130. Restraining means 148 prevents the front face 136 of the piston 130 from seating directly on the inlet and outlet ports 156 and 158.

In use, the assembly 110 is advantageously placed directly within the flow path of the fluid thereby directing the full force of the pulsation into the assembly 110. Flow path A' is the direction of the fluid within the flow path of the system such as from a piston pump to a fluid motor. Flow path B' shows the flow path of the nitrogen as it is initially directed into the interior of the housing 112 to pressurize the chamber 142. In use, inner chamber 142 is filled with nitrogen via the external fluid source through the inlet port 124. The free floating piston 130 is stabilized within the system and seated as shown in Fig. 3. Fluid flows through the inlet port 156 and is exposed to the entire outer face 136 of the piston 130. The nitrogen counterbalances the force of the high pressure fluid against the entire face of the piston 136, forcing the piston 136 to stabilize at some intermediate position while fluid flows through to the outlet port 158 into the fluid flow path. When a pulsation is developed within the system, the pulsation is directed across the full outer face 136 of the piston 130. The excessive pressure forces the piston 130 rearward toward the inlet port 124 and, in turn, is forced into a forward position by the nitrogen counteracting the pulsation along the inner face 134 of the piston 130. Because the piston 130 free floats within the interior of the housing 112 the excessive force created by the pulsation is dampened by the action of the piston acting against the N₂ chamber 142 within the housing 112.

The spring rate may be further controlled by the use of a spring used inside the chamber 42 and/or 142 as shown by the numeral 200 in Figs. 2 and 3.

With reference to Fig. 4, a preferred embodiment of the present invention is illustrated as a pulsation damper and noise attenuator assembly 200 which is positioned in a fluid circuit as close as possible to the source of pressure pulsations, such as at the outlet side of a positive displacement pump.

The assembly 200 comprises a cylindrical housing 212 the side wall and base 213 thereof defining an interior chamber 218 which connects an inlet port 214 to an outlet port 216 to define the flow path A of a fluid flow system. For example, the fluid flow system could include a pump and a motor connected in a conventional open and/or closed loop system.

The as embly 210 further comprises a cover 220 threadably secured to the housing 212 by well known means such as external threads 222 and in which an elastomeric seal 224 is used to provide a fluid seal. Cover 220 may be attached by other means such as by welding.

The cover 220 further comprises a hollow cylinder 220 projecting inwardly into the interior chamber 218 of the housing 212. A piston 228 comprising a head 230 and a hollow projection 232 is slidably received within the cylinder 226.

The outside diameter of the piston head 230 is slightly smaller than the inside diameter of the housing 212 and extends radially beyond the cylinder 226. The outside diameter of the boss 232 is slidably received within the inside diameter of the cylinder 226. An elastomeric seal 234 seated about the projection 232 creates a fluid tight seal between the projection 232 and the interior 250 of the cylinder 226 all of which will be described in detail hereinafter.

A series of Belleville springs 236 are mounted in the housing interior chamber 218 of the annular space 251 defined by the inner wall of the housing 212 and the cylinder 226 and are seated between the cover facing side 238 of the piston 228 and an annular shoulder 240 of the cover 220. Spacer rings 242 support the Belleville springs 236 in position as shown biasing the piston 228 toward the housing base 213. Belleville springs 236 can sustain relatively large loads with small deflections and the load magnitude and stiffness can be altered by the stacking arrangement of the springs 236. In the preferred embodiment, one set of springs 244 comprises tow individual springs stacked one upon another in a parallel relationship. A second set of parallel springs 246 are also stacked one upon another and placed in an opposing orientation. This alternate stacking over the full length of the conduit reduces the spring rate of the total combination to the desired level. Other variations in spring stacking arrangements are possible depending on the application and desired spring characteristics.

The cover 220 has a vent 248 that fluidly connects the interior 250 of the cylinder 226 to the outside atmosphere. Mounting means 252, such as a socket, is provided within the cover 220 to facilitate securing the cover 220 to the housing 212. An alternate outlet port 254 is also provided within the cover 220 to allow for an alternate flow path B through the assembly 210. If the port 254 is in use then port 216 is plugged and vice versa. Piston 228 also comprises a plurality of apertures 256, 258 fluidly connecting the forward portion of the housing interior chamber 218 with the annular space 251 on the opposite side of the piston 228.

Piston 228 is spring biased towards the forward interior chamber 218 of the housing 212 by the Belleville springs 236. Piston ring seal 234 seals the cylinder 226 preventing the flow of fluid into the interior 250 of the cylinder 226 which, as aforementioned, is connected to the atmosphere via connection 228. In the first preferred flow path A of the fluid flow system, fluid flows through inlet port 214 and is exposed to the full forward face 264 of the piston head 230 and is exhausted through the outlet 216. Pressure pulsation within the fluid acts against the pressure response area surface of the piston 228 creating a force urging the piston toward the cover 220 against the Belleville washers 236 which functions to minimize the effects of the pressure pulsation. The effective pressure responsive area of piston 228 is the cross- sectional area of the interior 250 of cylinder 226. The fluid flows through apertures 256, 258 and thus equalizes the force acting on the radial extension of the piston head 230.

The counter balancing of the piston 228 by the Belleville springs 244, 246 provides means to absorb the full force of the pulsation. Shock is reduced by the piston 228 movement within the cylinders 226.

An alternate flow path of the fluid flow within the fluid flow system is shown at B. In this second flow path, the action is the same as described hereinbefore except that the fluid flows through apertures 256, 258 and outward through an alternate outlet port 254. In this configuration the outlet port 216 is closed. Other locations of the outlet port may be provided to accommodate individual designs of the fluid flow path.

In related apparatuses the chamber 262 can be closed by a suitable check valve located in passage 248 and an inert gas such as N can be used to provide a different spring rate. Having described our invention, however, many modifications thereto will become apparent to those skilled in the art to which it pertains without deviation from the spirit of the invention as defined by the scope of the appended claims.

Claims

What is claimed is:

1. A pulsation damper and noise attenuator assembly for use in a fluid flow system comprising: a housing having an inlet port and an outlet port, said ports fluidly connecting an interior of said housing to a flow path of said fluid flow system; a base mounted to said housing and having a vent fluidly connecting said housing interior to the atmosphere, said base having a hollow cylinder extending inwardly from said base to said housing interior; and a piston slidably received within said housing interior and separating said housing interior into a forward housing area exposed to said fluid flow path and a rearward housing area exposed to said atmosphere, said piston having a boss fixedly mounted to one end, said boss slidably received within said cylinder and means for sealing said boss within said cylinder; wherein said fluid flow path is directed across an entire forward face of said piston.

2. The invention as defined in claim 1, said piston further comprising at least one aperture fluidly connecting said forward housing area with said rearward housing area.

3. A pulsation damper and noise attenuator assembly for use in a fluid flow system comprising: a housing having an inlet port and an outlet port, said ports fluidly connecting an interior of said housing to a flow path of said fluid flow system; a base mounted to said housing and having a vent fluidly connecting said housing interior to the atmosphere, said base having a hollow cylinder extending inwardly from said base to said housing interior; a piston slidably received within said housing interior and separating said housing interior into a forward housing area exposed to said fluid flow path and a rearward housing area exposed to said atmosphere; and spring means for biasing said piston toward said forward housing area; wherein said fluid flow path is directed across an entire forward face of said piston.

4. The invention as defined in claim 3, said pulsation damper and noise attenuator assembly wherein said spring means comprises a plurality of spring washers.

5. The invention as defined in claim 4, wherein said spring washers are Belleville springs.

6. A pulsation damper and noise attenuator assembly for use in a fluid flow system comprising: a housing having an inlet port and an outlet port, said ports fluidly connecting an interior of said housing to a flow path of said fluid flow system; a base mounted to said housing and having a vent fluidly connecting said housing interior to the atmosphere, said base having a hollow cylinder extending inwardly from said base to said housing interior, and an alternate outlet port fluidly connecting said housing interior with said fluid flow path; and a piston slidably received within said housing interior and separating said housing interior into a forward housing area exposed to said fluid flow path and a rearward housing area exposed to said atmosphere; wherein said fluid flow path is directed across an entire forward face of said piston.

7. A pulsation damper and noise attenuator assembly for use in a fluid flow system comprising: a housing having an inlet port and an outlet port, said ports fluidly connecting an interior of said housing to a flow path of said fluid flow system; a base mounted to said housing and having a vent fluidly connecting said housing interior to the atmosphere, said base having a hollow cylinder extending inwardly from said base to said housing interior; and a piston slidably received within said housing interior and separating said housing interior into a forward housing area exposed to said fluid flow path and a" rearward housing area exposed to said atmosphere, said piston having a boss fixedly mounted to one end, said boss slidably received within said cylinder and means for sealing said boss within said cylinder; wherein said assembly is mounted directly in the fluid flow path of said fluid flow system.

8. A pulsation damper and noise attenuator assembly for use in a fluid flow system comprising: a housing having an inlet port and an outlet port, said ports fluidly connecting an interior of said housing to a flow path of said fluid flow system; a base mounted to said housing and having a vent fluidly connecting said housing interior to the atmosphere, said base having a hollow cylinder extending inwardly from said base to said housing interior; a piston slidably received within said housing interior and separating said housing interior into a forward housing area exposed to said fluid flow path and a rearward housing area exposed to said atmosphere; and a plurality of spring washers mounted about said cylinder and biasing said piston toward said forward housing area; wherein said assembly is mounted directly in the fluid flow path of said fluid flow system.

9. The invention as defined in claim 8, said pulsation damper and noise attenuator assembly further comprising means for retaining said spring washers about said cylinder.

10. The invention as defined in claim 8, wherein said spring washers are Belleville springs.

11. A pulsation damper and noise attenuator assembly for use in a fluid flow system comprising: a housing having an inlet port and an outlet port, said ports fluidly connecting an interior of said housing to a flow path of said fluid flow system; a base mounted to said housing and having a vent fluidly connecting said housing interior to the atmosphere, said base having a hollow cylinder extending inwardly from said base to said housing interior, and an alternate outlet port fluidly connecting said housing interior with said fluid flow path; and a piston slidably received within said housing interior and separating said housing interior into a forward housing area exposed to said fluid flow path and a rearward housing area exposed to said atmosphere; wherein said assembly is mounted directly in the fluid flow path of said fluid flow system.

12. A pulsation damper and noise attenuator assembly for use in a fluid flow system comprising: a housing having an inlet port and an outlet port, said ports fluidly connecting an interior of said housing to a flow path of said fluid flow system; a base mounted to said housing and having a vent fluidly connecting said housing interior to the atmosphere and a hollow cylinder extending inwardly from said base to said housing interior; a piston slidably received within said housing interior and separating said housing interior into a forward housing area exposed to said fluid flow path and a rearward housing area exposed to said atmosphere; a plurality of spring washers mounted about said cylinder and biasing said piston toward said forward housing area; a plurality of retaining washers mounted on either side of said spring washers to retain said spring washers about said cylinder; said piston further comprising a boss fixedly mounted to one end, said boss slidably received within said cylinder and comprising means for sealing said boss within said cylinder; and at least one aperture fluidly connecting said forward housing area with said rearward housing area; wherein said assembly is mounted directly in the fluid flow path of said fluid flow system and said fluid flow path is directed across an entire forward face of said piston.

13. The invention as defined in claim 12, wherein said spring washers are Belleville springs.

14. The invention as defined in claim 12, said base further comprising an alternate outlet port fluidly connecting said housing interior with said fluid flow path.

15. The invention as defined in claim 12 wherein the fluid flow path surrounds the cylinder.

16. A pulsation damper and noise attenuator assembly for use in a liquid flow path of a fluid flow system comprising: an elongated housing having a longitudinal axis with first and second ends; a base mounted to said housing at one end defining an internal chamber in cooperation with said housing; a rigid movable member having a forward face extending substantially across an entire cross-sectional area of said housing, said movable member disposed within said internal chamber of said housing for longitudinal reciprocation, said movable member separating said internal chamber of said housing into an expandable first chamber and an expandable second chamber; a fluid tight seal member for connecting said movable member to said housing; a first inlet port formed in said housing fluidly connecting said first chamber of said housing to an external pressurized gas source, such that said moveable member is normally disposed, during a stable steady liquid flow, in an intermediate position between said first and second ends of said housing; a second inlet port and an outlet port formed in said base, said second inlet port having a central axis parallel with said longitudinal axis of said housing, said second inlet port and said outlet port fluidly connecting the second chamber of said housing to the liquid flow path of said fluid flow system, such that said liquid flow path directly impacts said entire forward face of said movable member; at least one stop connected to the housing for restraining movement of said movable member, such that said first chamber is prevented from fully contracting within said housing; at least one ring-shaped shoulder connected to one of the movable member and the base for restraining movement of said movable member, such that said first chamber is prevented from fully expanding within said housing; and a check valve connected to the first inlet port for allowing gas flow from said external pressurized gas source into said first chamber and preventing back-flow of gas out of said first chamber; wherein said assembly.is mounted directly in the liquid flow path of said fluid flow system and said liquid flow path is directed across the entire forward face of said movable member.

17. The pulsation damper and noise attenuator assembly of claim 17, wherein said sealing member is a bellows.

18. The pulsation damper and noise attenuator assembly of claim 17, wherein said movable member is a piston.

19. The pulsation damper and noise attenuator assembly of claim 18, wherein said sealing member is an annular seal ring disposed on said piston.

20. The pulsation damper and noise attenuator assembly of claim 17 further comprising a spring for biasing said movable member toward said base.

21. The pulsation damper and noise attenuator assembly of claim 20 wherein said spring is disposed in the first chamber.

22. A pulsation damper and noise attenuator assembly for use in a liquid flow path of a fluid flow system comprising: an elongated housing having a longitudinal axis with first and second ends; a base mounted to said housing at one end defining an internal chamber in cooperation with said housing; a rigid movable member having a forward face extending substantially across the^~cross-sectional area of said housing, said movable member disposed within said internal chamber of said housing for longitudinal reciprocation, said movable member separating said internal chamber of said housing into an expandable first chamber and an expandable second chamber; a fluid tight seal between said movable member and said housing for preventing fluid communication between said first and second chambers; said first chamber of said housing having a gas pressurized to a predetermined pressure, such that said movable member is normally disposed, during a stable steady liquid flow, in an intermediate position between said first and second ends of said housing; an inlet port and an outlet port formed in said base, said inlet port and said outlet port fluidly communicating with said second chamber of said housing and adapted to connect said second chamber to the liquid flow path of said fluid flow system, such that said liquid flow directly impacts the entire forward face of said movable member; stop means connected to one of the movable member and the base for restraining forward movement of said movable member toward said ports, such that said second chamber is prevented from fully contracting within said housing and said ports are always in fluid communication with said second chamber; and said assembly is mounted directly in the liquid flow path of said fluid flow system and said liquid flow path is directed across the entire forward face of said movable member.

23. The pulsation damper and noise attenuator assembly defined in claim 22 further comprising stop means connected to one of the movable member arid the base for restraining rearward movement of said movable member such that said first chamber is prevented from fully contracting with said housing.