WO2005026551A1 - Pump piston force modulator - Google Patents

Pump piston force modulator Download PDF

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Publication number
WO2005026551A1
WO2005026551A1 PCT/ZA2004/000107 ZA2004000107W WO2005026551A1 WO 2005026551 A1 WO2005026551 A1 WO 2005026551A1 ZA 2004000107 W ZA2004000107 W ZA 2004000107W WO 2005026551 A1 WO2005026551 A1 WO 2005026551A1
Authority
WO
WIPO (PCT)
Prior art keywords
piston
pump
force
spring
spring assembly
Prior art date
Application number
PCT/ZA2004/000107
Other languages
French (fr)
Inventor
Terence Dumont
Original Assignee
Terence Dumont
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Terence Dumont filed Critical Terence Dumont
Publication of WO2005026551A1 publication Critical patent/WO2005026551A1/en

Links

Classifications

    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
    • F04B—POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS
    • F04B9/00—Piston machines or pumps characterised by the driving or driven means to or from their working members
    • F04B9/02—Piston machines or pumps characterised by the driving or driven means to or from their working members the means being mechanical
    • F04B9/025—Driving of pistons coacting within one cylinder
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
    • F04B—POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS
    • F04B11/00—Equalisation of pulses, e.g. by use of air vessels; Counteracting cavitation
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
    • F04B—POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS
    • F04B39/00—Component parts, details, or accessories, of pumps or pumping systems specially adapted for elastic fluids, not otherwise provided for in, or of interest apart from, groups F04B25/00 - F04B37/00
    • F04B39/0005—Component parts, details, or accessories, of pumps or pumping systems specially adapted for elastic fluids, not otherwise provided for in, or of interest apart from, groups F04B25/00 - F04B37/00 adaptations of pistons
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
    • F04B—POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS
    • F04B39/00—Component parts, details, or accessories, of pumps or pumping systems specially adapted for elastic fluids, not otherwise provided for in, or of interest apart from, groups F04B25/00 - F04B37/00
    • F04B39/0027—Pulsation and noise damping means
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
    • F04B—POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS
    • F04B53/00—Component parts, details or accessories not provided for in, or of interest apart from, groups F04B1/00 - F04B23/00 or F04B39/00 - F04B47/00
    • F04B53/001—Noise damping
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
    • F04B—POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS
    • F04B53/00—Component parts, details or accessories not provided for in, or of interest apart from, groups F04B1/00 - F04B23/00 or F04B39/00 - F04B47/00
    • F04B53/14—Pistons, piston-rods or piston-rod connections

Definitions

  • This invention relates to positive displacement piston pumps and in particular to a force modulating device, which limits the forces exerted on the mechanical and electrical components within a pump.
  • a pump piston force modulator comprises a predetermined preloaded spring assembly adapted for use in conjunction with a positive displacement reciprocating pump mechanism having a piston and a cylinder, the arrangement being such that the spring assembly acts to modulate the force applied to the piston during pumping by allowing reverse piston displacement relative to the pump cylinder when the force on the piston exceeds the predetermined preload force in the spring assembly.
  • the spring assembly is mounted on the non fluid displacing end of the piston.
  • the spring assembly is mounted on the cylinder. In yet another embodiment of a pump piston force modulator the spring assembly is mounted on the reciprocating mechanism.
  • the spring assembly comprises a housing which acts as a primary guide for the piston, a piston holder secured to the non fluid displacing end of the piston, said holder acting as an interface with a spring also contained in the housing, and retaining means for retaining the spring in a predetermined preloaded condition.
  • the spring in one form of the invention is a stack of Belleville washers.
  • the retaining means to secure the spring under a preload force within the housing is a circlip.
  • the invention is also directed to a method of pumping fluid which includes using a positive displacement reciprocating pump equipped with a pump piston force modulator as described in the preceding paragraphs.
  • the invention is also directed to a positive displacement reciprocating pump mechanism which has associated with it a force modulator as described in the preceding paragraphs.
  • Figure 1 is a cross-sectional view of one example of a force modulator assembly indicating all the internal components as well as the external fluid displacing piston. Also shown is a cross- sectional view of portion of a pump element which operates in conjunction with the external fluid displacing piston.
  • the components of the pump piston force modulator as shown in Figure 1 are a fluid displacing piston (1) in a housing (2) which acts as a primary guide for the piston (1).
  • a fluid displacing piston (1) in a housing (2) which acts as a primary guide for the piston (1).
  • At the top of piston (1) is shown part of a pump element having a pump barrel (10) for precise location of the piston (1), part of pump element housing (9) and pump non return valve (8).
  • the housing (2) may be produced from a suitable material such as a heat treatable carbon steel.
  • the housing (2) is configured to house the internal components of the mechanism as well as provide mounting means (3) for mounting the assembly to the pump mechanism. This may be a threaded mounting to allow for the assembly to be attached to the pumping mechanism.
  • the principle of operation allows for the positive displacement piston (1) of the pumping system to slide through the housing (2) of the assembly when excessive force is generated on the piston (1) by the action of pumping.
  • the piston (1) is fixed to a piston holder (6) also housed in the housing (2).
  • the piston holder (6) is configured to allow for the piston (2) to be attached by means of a suitable security screw (4).
  • the piston holder (6) interfaces on to an internal spring mechanism (5).
  • the spring mechanism (5) is a stack of Belleville washers which restrict the movement of the piston (1 ) when the force on the piston (1) from the pumping action is not in excess of an initial preload set on the spring mechanism (5).
  • the initial preload of the spring mechanism (5) is such that it only allows movement of the piston (1) within the housing (2) when the force exerted on the piston (1) is in excess of the calculated maximum force that can be generated by the mechanical and electrical components of the pump at a specified duty cycle of 100%.
  • the force/displacement characteristics of the spring mechanism (5) must be such that the maximum force at full allowable displacement of the spring mechanism (5) preferably does not exceed a magnitude of double the magnitude of the preload characteristics of the spring mechanism (5).
  • the spring mechanism (5) is held in place by suitable means such as a securing spring clip or circlip (7).
  • the magnitude of displacement of the pump piston force modulator can be varied to suit the stroke of the positive displacement pump mechanism by increasing or decreasing the length of the housing (2) and suitably configuring the spring mechanism (5) to suit the configuration of the pumping system to which the system is to be fitted.
  • the life and reliability of the pumping system can be significantly increased by employing such a pump piston force modulator which restricts the magnitude of forces on the electrical and mechanical components.
  • the pump piston force modulator is a device which is designed to limit the stresses and forces exerted upon electrical and mechanical components by means of utilising a device such as but not restricted to a metal spring or gas spring, which acts upon the mechanism in such a manner as to allow itself to be compressed when forces exceeding a specified level are exerted onto it.
  • the specified level of force is determined by means of calculating the force that the driving mechanism can generate onto the working components by means such as but not restricted to electrical motors or hydraulic motors, both either with or without reduction gearboxes being employed in the design. These calculations are determined at 100% duty cycle conditions.
  • the resultant action of the pump piston force modulator is to reduce the volume output of the positive displacement piston pump. This occurs due to the piston stroke being limited by the compression of the modulator mechanism.
  • the back pressure of the fluid being pumped is the factor which causes the pump piston force modulator to interact with the pumping action.
  • the pump piston force modulator can take many different forms.
  • the spring assembly may be equipped with a conventional steel spring, a stack of Belleville washers or a gas spring or some other spring arrangement.
  • the word spring assembly shall be understood to include any arrangement that carries out the function of a spring .
  • the modulator can be mounted not at the end of piston (1) but on the pump element or the reciprocating mechanism. All these alternatives and others are variations within the scope of the invention.
  • the invention has Industrial Application in that it will be applied to high pressure pumps used for pumping lubricating fluid into lubricating systems for heavy duty machinery such as earth moving equipment.

Landscapes

  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Details Of Reciprocating Pumps (AREA)

Abstract

A pump piston force modulator comprises a predetermined preloaded spring assembly having a spring (5), a housing (2), and a piston holder (6) holding a piston (1). The spring assembly is adapted for use in conjunction with a positive displacement reciprocating pump having a pump element housing (9), non return valve (8) and a pump barrel (10). The spring assembly acts to modulate the force applied to the piston (1) during pumping by allowing reverse piston displacement relative to the pump barrel (10) when the force on the piston (1) exceeds the predetermined preload force in the spring assembly.

Description

PUMP PISTON FORCE MODULATOR
Technical Field
This invention relates to positive displacement piston pumps and in particular to a force modulating device, which limits the forces exerted on the mechanical and electrical components within a pump.
Background Art
Currently high pressure positive displacement pumps are driven by means of either electrical or hydraulic motors, which operate either cam and crank type mechanisms. Such mechanisms are designed to provide the motive forces for the reciprocation pumping action within the pump and generate specified maximum torque values, which are the basis for generating the fundamental reciprocating pumping forces within the pump. The back pressures generated during the pumping action, give rise to the generation of resistive forces on the drive mechanism, which may be in excess of the recommended allowable forces as specified for that drive mechanism. This excess causes over exertion of mechanical and electrical components, which in turn leads to premature failures of the pump. The object of this invention is to provide a solution to this problem.
Disclosure of Invention
A pump piston force modulator according to the invention comprises a predetermined preloaded spring assembly adapted for use in conjunction with a positive displacement reciprocating pump mechanism having a piston and a cylinder, the arrangement being such that the spring assembly acts to modulate the force applied to the piston during pumping by allowing reverse piston displacement relative to the pump cylinder when the force on the piston exceeds the predetermined preload force in the spring assembly. In one embodiment of a pump piston force modulator the spring assembly is mounted on the non fluid displacing end of the piston.
In another embodiment of a pump piston force modulator the spring assembly is mounted on the cylinder. In yet another embodiment of a pump piston force modulator the spring assembly is mounted on the reciprocating mechanism.
Further in a pump piston force modulator the spring assembly comprises a housing which acts as a primary guide for the piston, a piston holder secured to the non fluid displacing end of the piston, said holder acting as an interface with a spring also contained in the housing, and retaining means for retaining the spring in a predetermined preloaded condition.
The spring in one form of the invention is a stack of Belleville washers.
The retaining means to secure the spring under a preload force within the housing is a circlip. The invention is also directed to a method of pumping fluid which includes using a positive displacement reciprocating pump equipped with a pump piston force modulator as described in the preceding paragraphs.
The invention is also directed to a positive displacement reciprocating pump mechanism which has associated with it a force modulator as described in the preceding paragraphs.
Brief Description of the drawings
Figure 1 : is a cross-sectional view of one example of a force modulator assembly indicating all the internal components as well as the external fluid displacing piston. Also shown is a cross- sectional view of portion of a pump element which operates in conjunction with the external fluid displacing piston.
Best Mode for Carrying Out the Invention
The components of the pump piston force modulator as shown in Figure 1 are a fluid displacing piston (1) in a housing (2) which acts as a primary guide for the piston (1). At the top of piston (1) is shown part of a pump element having a pump barrel (10) for precise location of the piston (1), part of pump element housing (9) and pump non return valve (8).
The housing (2) may be produced from a suitable material such as a heat treatable carbon steel. The housing (2) is configured to house the internal components of the mechanism as well as provide mounting means (3) for mounting the assembly to the pump mechanism. This may be a threaded mounting to allow for the assembly to be attached to the pumping mechanism. The principle of operation allows for the positive displacement piston (1) of the pumping system to slide through the housing (2) of the assembly when excessive force is generated on the piston (1) by the action of pumping. The piston (1) is fixed to a piston holder (6) also housed in the housing (2). The piston holder (6) is configured to allow for the piston (2) to be attached by means of a suitable security screw (4). The piston holder (6) interfaces on to an internal spring mechanism (5). Preferably the spring mechanism (5) is a stack of Belleville washers which restrict the movement of the piston (1 ) when the force on the piston (1) from the pumping action is not in excess of an initial preload set on the spring mechanism (5). The initial preload of the spring mechanism (5) is such that it only allows movement of the piston (1) within the housing (2) when the force exerted on the piston (1) is in excess of the calculated maximum force that can be generated by the mechanical and electrical components of the pump at a specified duty cycle of 100%. The force/displacement characteristics of the spring mechanism (5) must be such that the maximum force at full allowable displacement of the spring mechanism (5) preferably does not exceed a magnitude of double the magnitude of the preload characteristics of the spring mechanism (5). The spring mechanism (5) is held in place by suitable means such as a securing spring clip or circlip (7). The magnitude of displacement of the pump piston force modulator can be varied to suit the stroke of the positive displacement pump mechanism by increasing or decreasing the length of the housing (2) and suitably configuring the spring mechanism (5) to suit the configuration of the pumping system to which the system is to be fitted. The life and reliability of the pumping system can be significantly increased by employing such a pump piston force modulator which restricts the magnitude of forces on the electrical and mechanical components.
The pump piston force modulator is a device which is designed to limit the stresses and forces exerted upon electrical and mechanical components by means of utilising a device such as but not restricted to a metal spring or gas spring, which acts upon the mechanism in such a manner as to allow itself to be compressed when forces exceeding a specified level are exerted onto it. The specified level of force is determined by means of calculating the force that the driving mechanism can generate onto the working components by means such as but not restricted to electrical motors or hydraulic motors, both either with or without reduction gearboxes being employed in the design. These calculations are determined at 100% duty cycle conditions.
The resultant action of the pump piston force modulator is to reduce the volume output of the positive displacement piston pump. This occurs due to the piston stroke being limited by the compression of the modulator mechanism. The back pressure of the fluid being pumped is the factor which causes the pump piston force modulator to interact with the pumping action.
Due to the cyclic action of the reciprocating pump, which is achieved by means such as a crank or cam type action, the potential forces generated by such a mechanical action, follow a sinusoidal curve and increase as the reciprocator reaches top and bottom dead centre. This increase is the factor that allows the pump piston force modulator to be effective.
It is to be noted that the pump piston force modulator can take many different forms. For example the spring assembly may be equipped with a conventional steel spring, a stack of Belleville washers or a gas spring or some other spring arrangement. In this specification the word spring assembly shall be understood to include any arrangement that carries out the function of a spring . Also the modulator can be mounted not at the end of piston (1) but on the pump element or the reciprocating mechanism. All these alternatives and others are variations within the scope of the invention. Industrial Application
The invention has Industrial Application in that it will be applied to high pressure pumps used for pumping lubricating fluid into lubricating systems for heavy duty machinery such as earth moving equipment.

Claims

CLAIMS: 1. A pump piston force modulator comprising a predetermined preloaded spring assembly adapted for use in conjunction with a positive displacement reciprocating pump mechanism having a piston and a cylinder, the arrangement being such that the spring assembly acts to modulate the force applied to the piston during pumping by allowing reverse piston displacement relative to the pump cylinder when the force on the piston exceeds the predetermined preload force in the spring assembly. 2. A pump piston force modulator as claimed in claim 1 in which the spring assembly is mounted on the non fluid displacing end of the piston. 3. A pump piston force modulator as claimed in claim 1 in which the spring assembly is mounted on the cylinder. 4. A pump piston force modulator as claimed in claim 1 in which the spring assembly is mounted on the reciprocating mechanism. 5. A pump piston force modulator as claimed in claim 2 in which the spring assembly comprises a housing which acts as a primary guide for the piston, a piston holder secured to the non fluid displacing end of the piston, said holder acting as an interface with a spring also contained in the housing, and retaining means for retaining the spring in a predetermined preloaded condition. 6. A pump piston force modulator according to any of the preceding claims in which the spring is a stack of Belleville washers. 7. A pump piston force modulator according to claim 6 in which the retaining means to secure the spring under a preload force within the housing is a circlip. 8. A method of pumping fluid which includes using a positive displacement reciprocating pump equipped with a pump piston force modulator according to any of the preceding claims. 9. A positive displacement reciprocating pump mechanism which has associated with it a force modulator as claimed in any of claims 1 to 7.
PCT/ZA2004/000107 2003-09-15 2004-09-13 Pump piston force modulator WO2005026551A1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
ZA200307197 2003-09-15
ZA2003/7197 2003-09-15

Publications (1)

Publication Number Publication Date
WO2005026551A1 true WO2005026551A1 (en) 2005-03-24

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ID=34314319

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/ZA2004/000107 WO2005026551A1 (en) 2003-09-15 2004-09-13 Pump piston force modulator

Country Status (1)

Country Link
WO (1) WO2005026551A1 (en)

Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1369915A (en) * 1919-01-13 1921-03-01 Packard Motor Car Co Motor-vehicle
US1922121A (en) * 1931-05-29 1933-08-15 Amal Ltd Reciprocating pump
DE914667C (en) * 1953-01-03 1954-07-08 Rudolf Soeding Dipl Ing Piston compressor without stuffing box with a moveable cylinder
US3186343A (en) * 1963-03-25 1965-06-01 Charles R Schneider Pumps and compressors
GB1128161A (en) * 1965-01-11 1968-09-25 Lucas Industries Ltd Reciprocating liquid pumps
DE2812076A1 (en) * 1978-03-20 1979-10-04 Ekkehard Schuppe Reducing pulsation in high-pressure liquid pumps - using chamber of variable capacity pref fitted with elastic PTFE or vinylidene! fluoride-hexa:fluoro:propylene copolymer

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1369915A (en) * 1919-01-13 1921-03-01 Packard Motor Car Co Motor-vehicle
US1922121A (en) * 1931-05-29 1933-08-15 Amal Ltd Reciprocating pump
DE914667C (en) * 1953-01-03 1954-07-08 Rudolf Soeding Dipl Ing Piston compressor without stuffing box with a moveable cylinder
US3186343A (en) * 1963-03-25 1965-06-01 Charles R Schneider Pumps and compressors
GB1128161A (en) * 1965-01-11 1968-09-25 Lucas Industries Ltd Reciprocating liquid pumps
DE2812076A1 (en) * 1978-03-20 1979-10-04 Ekkehard Schuppe Reducing pulsation in high-pressure liquid pumps - using chamber of variable capacity pref fitted with elastic PTFE or vinylidene! fluoride-hexa:fluoro:propylene copolymer

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