GB2573274A

GB2573274A - Filter for an accumulator

Info

Publication number: GB2573274A
Application number: GB1806221.6A
Authority: GB
Inventors: Scott Krejci Adam
Original assignee: Caterpillar Inc
Current assignee: Caterpillar Inc
Priority date: 2018-04-17
Filing date: 2018-04-17
Publication date: 2019-11-06
Also published as: GB201806221D0

Abstract

An accumulator 104 for a hydraulic system 100 is provided. The accumulator 104 includes a housing 106 defining an internal cavity 118 and a port 122 configured to facilitate flow of a hydraulic fluid into the housing 106. The accumulator 104 includes a piston 124 disposed in the internal cavity 118 such that the piston 124 divides the internal cavity 118 into a first chamber 126 and a second chamber 128. The second chamber 128 is configured to receive the hydraulic fluid from the port 122. The accumulator includes a biasing member 130 disposed in the first chamber 126 and configured to bias the piston 124 towards the hydraulic port 122 and one or more seals 134 disposed between the piston 124 and an internal wall 109 of the housing 106. The accumulator 104 also includes a filter 136 disposed in the port 122. The filter 136 includes an insert 138 coupled to the housing 106 and a filtering element 150 disposed in the insert 138 and configured to restrict flow of one or more contaminants present in the hydraulic fluid into the second chamber 128.

Description

FILTER FOR AN ACCUMULATOR

Technical Field [0001] The present disclosure generally relates to an accumulator. More particularly, the present disclosure relates to a filter for preventing entry of contaminants into the accumulator.

Background [0002] Hydraulic systems, typically, include hydraulic accumulators for a variety of applications, for example for storing energy, emergency actuation, leaking oil compensation, volume compensation, shock absorption, pulsation damping, and the like. The hydraulic accumulator may be defined as a pressure storage reservoir in which a non-compressible hydraulic fluid is received and subsequently held under pressure generated by a biasing member.

[0003] It is desired that such accumulators be able to last for a large number of charging and discharging cycles without need for repair. However, during servicing, debris, contaminants, etc. (dirt, metal contaminants, pressurized air) may contaminate the hydraulic fluid present in the hydraulic system. During operation, the contaminated hydraulic fluid may enter the accumulator and may damage internal elements of the accumulator, thereby, rendering the accumulator unable to perform its intended purpose.

[0004] Japanese Patent application number 09242705A (hereinafter referred to as JPH09242705A) is directed to an accumulator that includes a bellow. More particularly, JPH09242705A discloses a filter for preventing the flowing-out of broken/damaged bellow pieces from within the accumulator into a fluid line.

-2Summary of the Invention [0005] In an aspect of the present disclosure, an accumulator for a hydraulic system is disclosed. The accumulator includes a housing defining an internal cavity. The housing includes a port configured to facilitate flow of a hydraulic fluid into the housing. The accumulator further includes a piston slidably disposed in the internal cavity such that the piston divides the internal cavity into a first chamber and a second chamber wherein the second chamber is configured to receive the hydraulic fluid from the port. The accumulator also includes a biasing member disposed in the first chamber configured to bias the piston towards the hydraulic port and one or more seals disposed between the piston and the internal wall of the housing. The one or more seals configured to prevent fluid communication between the first chamber and the second chamber. The accumulator also includes a filter disposed in the port and coupled to the housing. The filter includes an insert coupled to the housing and a filtering element disposed in the insert. The filtering element is configured to restrict flow of one or more contaminants present in the hydraulic fluid into the second chamber.

Brief Description of the Drawings [0006] FIG. 1 shows an exemplary hydraulic system having an accumulator, in accordance with an embodiment of the present disclosure;

[0007] FIG. 2 illustrates a filter for the accumulator, in accordance with an embodiment of the present disclosure;

[0008] FIG. 3 illustrates a disassembled state of the filter relative to a fluid end member of the accumulator, in accordance with an embodiment of the present disclosure;

[0009] FIG. 4 illustrates an exploded view of the filter, in accordance with an embodiment of the present disclosure;

[0010] FIG. 5 illustrates an alternate filter used in the accumulator, in accordance with an alternate embodiment of the present disclosure;

-3[0011] FIG. 6 illustrates an exemplary situation of the accumulator where the piston is biased to a maximum extent possible in a direction towards the fluid end member;

[0012] FIG. 7 illustrates the accumulator when a surge in pressure is encountered in a fluid line coupled to the accumulator; and [0013] FIG. 8 illustrates the accumulator when an additional surge in pressure is encountered in the hydraulic fluid flowing in a fluid line of the hydraulic system.

Detailed Description [0014] Reference will now be made in detail to embodiments of the disclosure, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or like parts.

[0015] With reference to FIG. 1, a portion of the hydraulic system 100 is illustrated. The hydraulic system 100 may be applied to hydraulic systems in excavators such as hydraulic excavators and loader excavators and various other construction machines using hydraulic pumps such as cranes, pile drivers, etc. In addition to hydraulic applications in construction machines, the hydraulic system 100 as disclosed in the current disclosure may also be implemented in machines using pneumatic pressure. The hydraulic system 100 may include a fluid line 102. The fluid line 102 may be configured to allow a flow of a hydraulic fluid to and/or from other components of the hydraulic system such as, but not limited to, check valves, spool valves, two way valves, fluid reservoir, motors, and pumps.

[0016] The hydraulic system 100 may also include an accumulator 104, in accordance with an embodiment of the present disclosure. The accumulator 104 may be disposed on the fluid line 102 and may be configured for storing energy, instant actuation, leaking oil compensation, volume compensation, shock absorption, pulsation damping, and the like.

-4[0017] The accumulator 104 includes a housing 106. The housing 106 may be a vessel configured to selectively store high pressure hydraulic fluid therein. The housing 106 may include a hollow cylinder 108, a gas end member 110 and a fluid end member 112. The hollow cylinder 108 may include a first end 114 and a second end 116. The hollow cylinder 108 may extend between the first end 114 and the second end 116 to define a height of the hollow cylinder 108. The hollow cylinder 108 may also include an internal surface 109 defining a bore in the hollow cylinder 108. The gas end member 110 may be coupled to the first end 114 of the hollow cylinder 108 and the fluid end member 112 may be coupled to the second end 116 of the hollow cylinder 108. The internal surface 109 of the hollow cylinder 108, the gas end member 110 and the fluid end member 112 define an internal cavity 118.

[0018] The gas end member 110 may define a gas port 120. The gas port 120 may be defined as an aperture in the gas end member 110 configured to allow flow of gas into the housing 106. Similarly, the fluid end member 112 may define a hydraulic port 122. The hydraulic port 122 may be defined as an aperture in the fluid end member 112. The hydraulic port 122 may be configured to allow flow of fluid into the housing 106.

[0019] The hollow cylinder 108, the gas end member 110 and the fluid end member 112 may be made up of materials such as, but not limited to, steel, carbon fiber wrap, E-glass, or one of many other strong materials capable of withstanding high pressure. In the embodiment illustrated, the housing 106 is illustrated as a cylindrical structure. However, in various other embodiments, the housing 106 may take different shapes and configurations. In the embodiment illustrated, the housing 106 includes the hollow cylinder 108, the gas end member 110 and the fluid end member 112, however, in various other embodiments the housing 106 may be an integral unit, defining the gas port 120 and the hydraulic port 122 at either ends of the housing 106.

-5[0020] The accumulator 104 may further include a piston 124 slidably disposed within the internal cavity 118. The piston 124 divides the internal cavity 118 into a first chamber 126 and a second chamber 128. The first chamber 126 may be configured to include a biasing member 130. The biasing member 130 may be configured to move and bias the piston 124 towards the hydraulic port 122/ second end 116 of the hollow cylinder 108. In the embodiment illustrated, the biasing member 130 may be any gas adapted to be compressed under pressure such as, but not limited to, Nitrogen, Argon or other inert gases. More particularly, the gas port 120 may be coupled to a gas bottle 132 (a gas reservoir) and may be configured to allow flow of a gas capable of being compressed into the first chamber 126. While the embodiments illustrated in FIG. 1 - FIG. 7 depict the biasing member 130 as a gas adapted to be compressed under pressure, in various other embodiment the biasing member 130 may be a spring or a bellow.

[0021] The second chamber 128 is configured to receive the hydraulic fluid from the fluid line 102. More particularly, the hydraulic port 122 is coupled to the fluid line 102 and facilitates entry of the hydraulic fluid from the fluid line 102 into the second chamber 128.

[0022] The accumulator 104 also includes one or more seals 134 disposed between the piston 124 and the internal surface 109 of the hollow cylinder 108. The one or more seals 134 are configured to prevent fluid communication between the first chamber 126 and the second chamber 128. The one or more seals 134 may be ring seals, piston seals and the like. In the embodiment illustrated, the one or more seals 134 may correspond to O-ring seals configured to prevent leakage of fluids from the first chamber 126 into the second chamber 128 and vice versa.

[0023] The accumulator 104 also includes a filter 136 disposed in the hydraulic port 122 and coupled to the housing 106, as shown in FIG. 1 and FIG.

2. The filter 136 includes an insert 138, filtering element 150 and a locking member 160.

[0024] The insert 138 may be a hollow elongated structure. The insert 138 includes a first end 140 and a second end 142. More specifically, the insert 138 is a hollow cylindrical structure extending between the first end 140 and the second end 142, as shown in FIG. 2. The insert 138 may be composed of stainless steel, Inconel®, Incoloy®, and/or other metal and alloys exhibiting suitable corrosion and erosion resistance from the hydraulic fluid present in the hydraulic system 100. If desired, coatings and surface treatments may be applied to the surfaces of the insert 138 to improve the corrosion and erosion characteristics thereof.

[0025] The insert 138 is received within the hydraulic port 122 and is coupled fluid end member 112 of the housing 106, as shown in FIG. 1 and FIG. 3. In an embodiment illustrated, the insert 138 may be coupled to the housing 106 of the accumulator 104 by press fitting the insert 138 into the hydraulic port 122 of the housing 106. In such a configuration, the insert 138 may be sized such that a cross-sectional area of the insert 138 is larger than a cross-sectional area of the hydraulic port 122 present in the housing 106. For example, the hydraulic port 122 defined in the fluid end member 112 may have a constant radius ‘RT throughout a width of the fluid end member 112. On the other hand, an outer periphery of the insert 138 may have a radius ‘R2’ (‘R2’ being greater than ‘Rl’). R2 may be constant throughout a length (i.e. a length of the insert 138 extending between the first end 140 and the second end 142) of the insert 138.

[0026] In the embodiment illustrated, the second end 142 of the insert 138 may include a flanged region 146, as illustrated in FIG. 2. The flanged region 146 may be defined as a portion of the insert 138 at the second end 142 having a cross-section significantly larger than the cross section of the hydraulic port 122. The flanged region 146 may be configured to abut the fluid end member 112 of

-7the housing 106 and prevent an axial movement of the insert 138 in a direction towards/into the second chamber 128.

[0027] The insert 138 further includes an internal surface 143 and an outer surface 144. In the embodiment illustrated in FIG. 2, the insert 138 is a hollow structure that has a shape similar to that of the hydraulic port 122. For example, the hydraulic port 122 is illustrated as a hollow cylindrical cavity and the insert 138 is illustrated as a hollow elongated member having a cylindrical shape.

[0028] Referring to FIG. 3, the internal surface 143 of the insert 138 may define a stepped profile 148. For example, the insert 138 may include a first portion having a thickness ‘a’ and a second portion having a thickness ‘b’ (where ‘b’ < ‘a’). The stepped profile 148 may be defined as a profile defined on the internal surface 143 at an interface of the first portion and the second portion. In the embodiment illustrated, the stepped profile 148 may be defined as an Lshaped profile defined on the internal surface 143 at the interface of the first section and the second section.

[0029] The filtering element 150 is disposed on the stepped profile 148 of the insert 138. The locking member 160 is disposed over the filtering clement 150 and may be coupled to the insert 138 via press fitting, welding or via threads present on the insert 138 and the locking member 160. In such a configuration, the filtering element 150 gets sandwiched between the stepped profile 148 of the insert 138 and the locking member 160.

[0030] The filtering element 150 may be a mesh or sieve structure made up of a wire. The filtering element 150 may be designed for straining contaminants from the hydraulic liquids i.e. for separating any coarse/irregular object from the hydraulic fluid when the hydraulic fluid enters the accumulator 104.

[0031] In an embodiment, the filtering element 150 may be a planar mesh structure as shown in FIG. 1 and FIG. 2. In an alternate embodiment, the filtering element 150 may be conical mesh as illustrated in FIG. 5. More particularly, the filtering element 150 may be cone shaped mesh structure

-8disposed between the stepped profile 148 of the insert 138 and the locking member 160. The conical filtering element 150 may include a base portion 152 and an apex portion 154. The base portion 152 may be configured to be sandwiched between the stepped profile 148 of the insert 138 and the locking member 160. In such a configuration, the apex portion 154 of the conical filtering element 150 extends towards the fluid line 102.

[0032] The locking member 160 may be a hollow elongated structure. More specifically, locking member 160 is a hollow cylindrical structure, as shown in FIG. 2 and FIG. 4. The locking member 160 may be composed of stainless steel, Inconel®, Incoloy®, and/or other metal and alloys exhibiting suitable corrosion and erosion resistance from the hydraulic fluid present in the hydraulic system 100. If desired, coatings and surface treatments may be applied to the surfaces of the locking member 160 to improve the corrosion and erosion characteristics thereof.

[0033] The locking member 160 is received within the insert 138 of the filter 136. The locking member 160 includes a first end 162 and a second end 164. In an embodiment illustrated, the locking member 160 may be coupled to the insert 138 of the filter 136 by press fitting the locking member 160 into the insert 138 of the filter 136. In such a configuration, the locking member 160 may be sized such that an outer diameter of the of the locking member 160 is larger than an internal diameter of the stepped profile 148 of the insert 138. In an alternate embodiment, the locking member 160 may be coupled to the insert 138 by use of a welding process. In an alternate embodiment, the locking member 160 may be threadedly coupled to the insert 138.

[0034] The operation of the accumulator 104 having the filter 136 assembled within the hydraulic port 122 will now be explained with reference to FIG. 6 to FIG. 8. Let us assume that at an instant the fluid line 102 of the hydraulic system 100 is carrying the hydraulic fluid at a pressure of magnitude ‘X’ psi (pressure per square inch). Further, let us assume that the biasing member 130 also exerts a

-9pressure of magnitude ‘X’ psi on the piston. In such a scenario, the hydraulic fluid in the fluid line 102 will not enter the second chamber 128 of the accumulator 104, as shown in FIG. 5. However, a surge in the pressure value of the hydraulic fluid present in the fluid line 102 during operation of the hydraulic system 100, will cause the pressure value to increase beyond the value ‘X’ psi. In such an event, the pressure exerted by the hydraulic fluid on the piston 124 is more than the pressure exerted by the biasing member 130 on the piston 124. Thus, the pressure of the hydraulic fluid will force the piston 124 upwards towards the gas end member 110 and the hydraulic fluid will accumulate in the second chamber 128, as shown in FIG. 6. When the pressure value of the hydraulic fluid in the fluid line 102 drops below the value ‘X’ psi, the pressure exerted by the hydraulic fluid on the piston 124 is less than the pressure exerted by the biasing member 130 on the piston 124. Accordingly, the biasing member 130 forces the accumulated fluid to exit the second chamber 128 and flow back to the fluid line 102, as illustrated in FIG. 5.

Industrial Applicability [0035] Typically, hydraulic systems include accumulators for a variety of applications, for example for storing energy, emergency actuation, etc. The accumulators may be adapted for storing pressurized hydraulic fluid therein to perform the aforementioned functions (storing energy, emergency actuation, and the like). However, during servicing or during operation debris, contaminants, etc. (dirt, metal contaminants, pressurized air) may contaminate the hydraulic fluid flowing in the hydraulic system. The contaminated hydraulic fluid enters the accumulator and causes damage to critical elements/areas of the accumulator, thereby, rendering the accumulator unable to perform its intended purpose.

[0036] In an aspect of the present disclosure, an accumulator 104 is disclosed. The accumulator 104 includes the filter 136. The filter 136 is disposed at the hydraulic port 122 of the housing 106 i.e. the entry point of the hydraulic fluid into the accumulator 104. Such filter(s) 136 strains the hydraulic fluid entering

-10the accumulator 104, thereby preventing entry of contaminated fluid into the accumulator 104. Thereby, reducing the wear and tear of the components of the accumulator 104 via the hard and/or abrasive contaminants circulating in the hydraulic fluid. The filter 136 as disclosed herein prolongs the life of the accumulator 104 by preventing the interaction of contaminants with the piston 124 and the one or more seals 134.

[0037] In another aspect of the present disclosure, the filter 136 includes a conical filtering element 150, as shown in FIG. 4. The conical filtering element 150 filters the hydraulic fluid entering the accumulator in such a way that the contaminants get trapped near the base portion 152. Since the contaminants are steered to the base portion 152, the apex portion 154 always remains clean without any contaminants accumulated there. Such a filtering element 150 ensures that there is no blockage to the fluid flow into and out of the accumulator 104 even if the contaminants are present in large amounts (because the contaminants will get accumulated near the base portion 152 ensuring a relatively unobstructed apex portion 154).

[0038] While aspects of the present disclosure have seen particularly shown and described with reference to the embodiments above, it will be understood by those skilled in the art that various additional embodiments may be contemplated by the modification of the disclosed machines, systems and methods without departing from the spirit and scope of what is disclosed. Such embodiments should be understood to fall within the scope of the present disclosure as determined based upon the claims and any equivalents thereof.

Claims

What is claimed is:

1. An accumulator for a hydraulic system, the accumulator comprising:

a housing defining an internal cavity, the housing including a port configured to facilitate flow of a hydraulic fluid into the housing;

a piston slidably disposed in the internal cavity such that the piston divides the internal cavity into a first chamber and a second chamber wherein the second chamber is configured to receive the hydraulic fluid from the port;

a biasing member disposed in the first chamber, the biasing member configured to bias and move the piston to release the hydraulic fluid received in the second chamber through the port;

one or more seals disposed between the piston and an internal wall of the housing, the one or more seals configured to prevent fluid communication between the first chamber and the second chamber; and a filter including:

an insert disposed in the port and coupled to the housing: and a filtering element disposed in the insert, the filtering element configured to restrict flow of one or more contaminants present in the hydraulic fluid into the second chamber.