IES990890A2 - Fluid Pump - Google Patents

Abstract

A fluid pump for use with a vibratory apparatus comprises a cylindrical housing (10) having an inlet (14) and an outlet (16). A piston (20) is reciprocally mounted in the housing between the inlet and outlet and has a fluid passageway (22) extending between its opposite ends. Valve means (26,28) and (30,32) allow fluid to pass through the passageway substantially only in the direction from the inlet to the outlet so that as the piston moves to and fro in response to mechanical vibration of the housing fluid is pumped from the inlet to the outlet. <Figure 1>

Description

FLUID PUMP This invention relates to a fluid pump for use with an apparatus which is subject to regular and continuous vibration in use.

One example of such an apparatus is a vibratory • compactor, called a rammer, which is typically used in • roadworks for compacting and consolidating a hardcore l base. :5 ! ΐ ' Rammers are commonly driven by a two-stroke engine, which uses a mixture of oil and petrol. Advanced two-: stroke engines have individual pumps to pump the oil : and petrol. However, existing pumps are electrically . jdriven and relatively expensive, which prohibits their 1 iase on low cost engines such as those used, for example, on rammers.

It is object of the invention to provide a fluid pump which can be used, inter alia, for pumping oil in two-stroke engines> although the invention is not limited to that application.

According to the present invention there is provided a fluid pump comprising a housing defining a fluid chamber having an inlet and an outlet, and a mechanism for pumping fluid from the inlet to the outlet of the chamber in response to mechanical vibration of the housing.

Preferably the pumping mechanism comprises a piston reciprocally mounted in the chamber between the inlet and outlet and having a fluid passageway extending between its opposite ends, the mechanism further including a first one-way valve associated with the inlet to allow fluid to be drawn into the chamber through the inlet upon movement of the piston towards the outlet, and a second one-way valve associated with the piston passageway to allow fluid to pass through the passageway upon movement of the piston towards the inlet.

An embodiment of the invention will now be described, by way of example, with reference to the accompanying drawings, in which: Fig. 1 is a cross-sectional view of a fluid pump according to an embodiment of the invention; Fig. 2 is a cross-sectional view of the fluid pump with the piston at one end of its stroke; and Fig. 3 is a cross-sectional view of the fluid pump with the piston at the other end of its stroke.

Referring to Fig. 1 of the drawings, a fluid pump comprises a housing 10 defining a cylindrical chamber 12 having a fluid inlet 14 and a fluid outlet 16. The fluid inlet 14 is provided on a removable end cap 18 which allows access to the chamber 12 to service the parts therein.

A piston 20 is reciprocally mounted in the chamber 12 between the inlet 14 and outlet 16 and has a through bore 22 extending axially between its opposite ends. A • pair of compression springs 24 are disposed in the chamber, each acting between a respective end -of the / chamber 12 and the corresponding end of the piston 20. The springs 24, when the housing 10 is at rest, maintain the piston in a rest position in the chamber 12 intermediate the inlet 14 and the outlet 16.

A first one-way valve, comprising a ball 26 biased by a spring 28, is located in an enlarged portion of the inlet 14 where it opens into the chamber 12. The valve 26, 28 allows fluid to enter the chamber 12 through the inlet 14 but substantially prevents the flow of fluid in the reverse direction. A second one-way valve, likewise comprising a ball 30 biased by a spring 32, is located in an enlarged portion of the bore 22 where it opens into the outlet side of the chamber 12. The valve 30, 32 allows fluid to pass through the bore 22 in the direction from the inlet 14 to the outlet 16 but substantially prevents the flow of fluid in the reverse direction.

Finally, the pump includes a bracket 34 which allows the housing 10 to be secured by bolts 36 to a vibratory apparatus such as a rammer.

The pump operates as follows. At rest, Fig. 1, the piston 20 occupies a position midway between the inlet 14 and outlet 16, being held here by the springs 24. However, when the housing 10 is vibrated with a si gnifjcant component of vibration in the axial direction of the chamber 12, for example, if the pump were attached with the correct orientation to a vibratory apparatus such as a rammer, the inertia of the piston 20 causes it to reciprocate to and fro from one end of the chamber 12 to the other, alternately compressing one spring 24 and the other.

When the piston 20 moves towards the inlet 14, Fig. 2, the valve 26, 28 closes and forces fluid in the inlet side of the chamber 12 through the bore 22, opening the valve 30, 32. Then, when the piston 20 moves towards the outlet 16, Fig. 3, the valve 30, 32 closes so that fluid in the outlet side of the chamber 12 is forced through the outlet 16. At the same time, fluid is drawn into the chamber through the inlet 14, opening the valve 26, 28. This repeats for each cycle of vibration, leading to a net transfer of fluid from the inlet 14 to the outlet 16.

The volume/sec of fluid pumped depends on the following parameters: - Diameter & mass of piston 20 - Diameter of inlet 14 & outlet 16 - Diameter of bore 22 - Strength of springs 24 - Vibration amplitude & frequency - Density/viscosity of fluid By a suitable choice of these parameters the volume/sec of fluid pumped can be varied within wide limits. The volume/sec pumped can also be varied by providing a damper between the vibratory apparatus and the pump, or by feeding back a proportion of the pumped fluid from the outlet back to the inlet.

The invention is not limited to the embodiments described herein which may be modified or varied without departing from the scope of the invention.

F. R. KELLY & CO.

Agents for the Applicants