AU2005100567A4 - Improvements in the Displacement of Fluids - Google Patents

Description

-1- IMPROVEMENTS IN THE DISPLACEMENT OF FLUIDS FIELD OF INVENTION This invention relates to an improved method and apparatus for a fluid displacer.

In particular, the invention relates to an improved means of compressing air, particularly where there is a requirement for a small compressor powered from an electrical battery source.

BACKGROUND ART In the aerosol appliance industry it is commonplace to use a chlorofluorocarbon propellant in a spray can to provide the energy to atomise and transport a fluid in the process of the delivery of a finely atomised aerosol spray. More recently, hydrocarbon and hydrofluoroalkane propellants have been developed as a substitute, given the increasingly stringent legislative requirements governing gases which are known to damage the earth's atmospheric ozone layer. All such propellants are known to be harmful to some degree in this respect.

There are a number of aerosol-producing inventions using pumped air as a propellant. Commonly, these developments have employed manually powered air pumps.

There are a number of disadvantages in the known art employing pumped air.

These include poor performance in many exacting applications due to the limits imposed by the physical effort expended by the operator and, generally, such -2apparatus has commonly been inconvenient to the user to the extent that such devices are not in common use due to poor acceptance by consumers.

This invention provides a displacer which may be economically produced and has the performance necessary to compress air in a manner convenient for the operator. An air compressor based on this displacer invention may be small in size and may be powered electrically from a battery source.

SUMMARY OF INVENTION The invention is defined in the following statements:- A displacer is provided which is formed from a cylindrical pumping chamber, a unitary member cooperating within the cylindrical bore of the pumping chamber, such unitary member comprising of a cylindrical piston at one end within the bore and a circular bearing shell at the other end of the elongated axis of the piston which is adapted to receive the eccentric journal of a crank member which may rotate about an axis of rotation, the mid portion between the two features of piston and bearing shell being flexible to the extent of allowing the bearing shell to be rotated off the normally straight elongated axis of the cylinder and piston so that the circular motion of the eccentric journal is converted into reciprocating motion of the piston.

It is a further object of the present invention to provide a fluid displacer adapted to pump fluid:- -3- A displacer is provided as described as above which provides a fluid pump which may be driven by a motor with a circular drive to an eccentric journal which orbits around the drive axis of the motor, the eccentric journal being engaged within the bearing shell as described above so as to provide a pumping action for the piston as described above, a pumping chamber being formed between the crown of the piston and the bore of the cylindrical pump body, the chamber being closed at one end and within this closed end within the pump body there is formed a discharge port for a working fluid, this port being controlled by a spring-loaded sealing member which will allow fluid to pass from the pumping chamber when the pressure within the pumping chamber is sufficiently greater than the downstream zone from the discharge port, such that the spring force on the springloaded sealing member is overcome, fluid being blocked with respect to flow in the reverse direction.

There is provided a unitary member comprising of a cylindrical piston at one end of its length and a circular bearing shell forming a pivot at the other extremity along its axial length which receives a journal of an eccentric, between these two features being a selectively flexible columnar section which allows flexure of the unitary member so as to allow the bearing shell to move off the axis defined by the motion of the piston, the flexible member being substantially non-flexible in a direction perpendicular to the plane defined by the orbit of the eccentric journal, so as to restrain the bearing shell within a plane of orbit of the eccentric by virtue of the -4attachment of the bearing shell to the piston which maintains a concentric relationship within the cylinder bore, the piston being adapted to control the working fluid flow as follows:- A cylindrical piston forming one end of the elongated unitary member is defined which has a groove formed on the cylindrical surface near the extremity of the piston, said groove being around an axis of revolution substantially common with the piston axis and being defined within the zone of common engagement of the piston with the cylindrical bore defined within the pump body, such groove within the bore containing on four sides a flexible sealing ring within the groove which has sectional dimensions less than any comparable dimension defined within the groove, such groove defining four working lands with respect to the flexible sealing ring cooperating within the groove, such sealing ring having an axis of symmetry substantially coincident with the axis of the piston, so that the flexible sealing ring is:always in contact with the land defined by the cylinder bore, and always out of contact with the land defined by the minor diameter of the piston along the axial length of the piston within the groove, and in axial sealing contact with that land of the groove which will normally bear axially on the sealing ring as the piston is moved into increased engagement with the pumping chamber body, this direction being defined as the first direction, and in axial non-sealing contact with that land of the groove which will normally bear axially on the sealing ring as the piston moves in a direction defining less engagement of the piston in an axial direction with respect to the cylindrical bore of the pumping chamber, this direction being defined as the second direction.

With the above features, there is defined a piston which provides means to block the flow of fluid over the external surface of the piston and to contain the fluid ahead of the piston while the piston moves in said first direction, so that fluid within the pumping chamber is prevented from escaping past the piston, and, there is defined a piston which provides the aforementioned means to allow the flow of fluid past the piston, across the external surface of the piston in such clearance as is defined between the piston surface and the bore within the pump body, so as to allow fluid to flow into the pumping chamber as the piston moves in the said second direction.

-6- It is a further object of the present invention to provide means to allow the highest possible volumetric efficiency when pumping compressible fluids. For this purpose, there is defined a pump as described above having a unitary member as defined above, but with the following additional means:a unitary member as defined above, forming a fluid pump, but with a flexible portion between the piston and bearing shell features, defined by an arcuate flexible connection between the two features which is not only flexible with respect to motion of the bearing shell as it orbits with the eccentric journal, out of the axis of the cylinder of the pump body, but is also only partially resilient to substantially columnar forces acting between the piston at one extremity and the bearing shell at the other extremity so as to allow the crown of the piston to make contact with the closed axial end of the pumping chamber prior to the eccentric reaching the full extent of its throw in this direction where the piston increases its engagement in the bore of the pump body, partial flexibility being provided by the arcuate shape of the flexible portion of the unitary member in response to columnar stresses developed by virtue of the contact of the piston crown with the closed end of the pumping chamber, said columnar flexibility allowing the drive shaft to rotate, the eccentricity of the arcuate flexible portion of the unitary member relative to the elongation and sectional dimensions being adapted to provide sufficient force to overcome the fluid forces acting alone, in the absence of the contact of the piston with the closed end of the bore of the pumping chamber.

-7- It may be appreciated that the latter features allow less stringent manufacturing accuracy whilst providing the maximum possible compression ratio for the displacer. Alternatively stated, the latter aspect of the invention allows the minimum possible clearance volume in a pumping chamber so defined, whilst allowing some relative and absolute variation in the axial distance between the shaft at the centreline of a motor and the closed end at one extremity of the bore in the pump body whilst allowing some variation in the length of the unitary member between the piston crown and the bearing shell.

BRIEF DESCRIPTION OF THE DRAWINGS The invention will now be described with reference to the accompanying drawings, which illustrate several embodiments of a fluid pumping means formed in accordance with the invention.

In the drawings:- Figure 1 is an illustration of the preferred fluid pumping means formed in accordance with the present invention; Figure 2 shows more detailed views of parts of an embodiment adapted for use as an air pump, particularly of the unitary piston member, and, Figure 3 shows an alternative embodiment of the invention shown in Figure 2.

-8- BEST MODE OF CARRYING OUT THE INVENTION Referring now to figure 1, a displacer is defined which is formed from a cylindrical pumping chamber in a pump body within which there is a cylindrical bore which receives a unitary piston member the unitary piston member comprising of a substantially cylindrical piston at that end within the cylindrical bore and having a circular bearing shell at the other end of the elongated axis of the member the bearing shell being adapted to receive a journal of a crank member which may rotate about a shaft The flexible mid portion (11) of the unitary piston member allows the bearing shell to follow the eccentric journal as it moves off the normally straight axis of the unitary piston member as the shaft (10) rotates so that the circular motion of the shaft (10) is converted to reciprocating motion of the unitary piston member The flexibility of the mid portion (11) of the unitary member is achieved by the thin material section (dimension A in figure 2) in the relevant sense of allowing the bearing shell to follow the eccentric journal while in the alternative sense of flexure with respect to the bearing shell moving out of the plane defined by the circular path of the bearing shell rotating about the shaft the flexible mid section (11) of the unitary member is defined with a relatively large dimension (dimension W of figure 2) so as to resist such flexure and maintain the bearing shell within the aforementioned plane of rotation due to the restraint provided by the integral piston within the bore of the pump body -9- A fluid pump is defined when the shaft (10) is driven by a motor (12) and the pumping chamber varies in volume due to the reciprocating action of the piston within the bore a discharge port (13) being defined within the closed end (14) of the pumping chamber the discharge port (13) being controlled by a sealing member (15) acted upon by a spring (16) so as to normally restrict flow from the pumping chamber through the discharge port (13) until the pressure within the pumping chamber rises sufficiently to overcome the force exerted by the spring (16) on the sealing member Flow from the downstream zone (17) to the pumping chamber is always positively restrained by the checking action of the sealing member (15) on the sealing land (18) just downstream of the discharge port in the well-known manner of a check valve or spring-loaded relief valve.

The piston is defined with features to control the flow of fluid into the pumping chamber the flow path into the pumping chamber being generally from an upstream zone (19) outside of the pumping chamber and past the clearances as generally defined between the exterior surface of the piston and the bore of the pump body With particular reference to figure 2, for the purpose of controlling the flow of a working fluid across the piston there is defined a valve member (21) which is formed within the piston defined by a circular groove (22) formed in the outer surface of the piston into which groove (22) there is fitted a circular sealing ring (23) which has sectional dimensions less than those of the surrounding groove but with a circumferential line of sealing contact (24) always maintained between the sealing ring (23) and the circular bore of the pump body The circumferential line of sealing contact (24) defines, in a sectional view of the groove a so-called primary land (24) which is always in sealing relationship with the flexible sealing ring (23).

A so-called secondary land (26) of the groove defined as the surface of the minor diameter formed along the axis of the groove, is always out of contact with the sealing ring (23).

A so-called tertiary land (27) of the groove (22) bears in axial sealing relationship with the flexible sealing ring (23) only when the piston moves in a defined first axial direction where the piston is moving into increased engagement within the cylindrical bore this contact being urged by the frictional forces on the primary sealing land (24) and the forces produced on the sealing ring (23) by the fluid pressure developed within the pumping chamber A so-called fourth land (28) of the groove (22) bears in axial contact with the sealing ring (23) for the purposes of drawing the sealing ring (23) along with the unitary member as the piston moves in a defined second axial direction so as to decrease the degree of engagement of the piston within the cylindrical bore Sealing relationship of the fourth land (28) with the sealing ring (23) is avoided by the provision of non-sealing surface irregularities on the fourth land (28) and the provision of at least one flow port (29) which allows the flow of fluid across the fourth land by the provision of a bypass flow and the interruption of the -11 circumferential line of contact by the ports said circumferential line of contact being defined by the contact of the fourth land (28) with the sealing ring (23).

With the above means as defined, when the unitary member moves in the said first direction, the piston is sealed with respect to fluid flow past the surface of the piston in the clearances (20) relative to the cylindrical bore and the working fluid is forced into the decreasing volume of the pumping chamber with the result that the fluid pressure within the pumping chamber rises until the pressure is sufficient to discharge fluid from the discharge port (13) in the manner previously described.

When the unitary member moves in the said second direction, the piston is unsealed with respect to the aforementioned flow of fluid across the piston and the working fluid may pass from the low pressure region (19) across the piston surface (20) and the surface features of the flats (25) on the piston to increase the cross-sectional area open to flow, and past the fourth land (28) into the pumping chamber due to the pressure conditions created due to the increasing volume of the pumping chamber as the piston moves in the said second direction.

Fluid flow from the downstream zone (17) into the pumping chamber is prevented by the action of the sealing member (15) acting on the sealing seat (18) due to the action of the spring (16) and the forces due to elevated pressure in the downstream zone (17) acting on the sealing element The above describes an effective fluid pump which is particularly effective in pumping air and other low viscosity fluids, particularly for applications requiring -12electrical drive from a battery source.

In such applications, the generally low power supply which is available dictates that the pump has a small piston stroke, while the compressible nature of gases result in a tendency for poor volumetric efficiency if there is a large unswept volume.

The invention described here avoids a large unswept volume caused by mechanical lash in known pumps with connecting rods and piston gudgeons, while the control of the gas flow by the piston results effective sealing and porting, even at very high rates of pumping.

In this respect, known art typically utilises a spring-loaded valve in the fixed pump body to control the inlet flow of fluid into a displacer, which is in the same proximity with a discharge valve. At high rates of pumping, such pumps suffer problems with the inertial lag of the moving parts, whereas in the invention described here the valve (21) in the unitary member is positively enhanced in operation by the inertial, frictional and pressure forces acting in unison. In addition, sufficient space is provided for more optimum design of the relatively conventional discharge valve sealed by the sealing member The unitary piston member is easily manufactured by convenient and economical production methods such as plastic moulding and the assembly is conveniently provided for under conditions of mass production.

-13- The invention may also be embodied in a form to enhance the ease of production whilst maintaining pumping performance as a pump to compress gases.

In figure 3 there is shown an embodiment with all aforementioned means of providing a fluid pump, but with an arcuate flexible portion (30) of a unitary member all other aspects being provided as described above.

The arcuate flexible portion (30) of the unitary member is adapted to provide a resilient connection between the bearing shell and the piston but with flexibility with respect to columnar forces with the directions shown in figure 3 exerted on the piston at one extremity and the bearing shell at the other extremity. In this embodiment the piston crown (31) may make contact with the closed end (14) of the pumping chamber when the unitary member moves in a said first direction, just prior to the maximum throw produced by the eccentric journal During the event that contact of the crown (31) and closed end (14) occurs, the arcuate flexible portion (30) of the unitary member is adapted to flex under the action of the columnar forces so as to allow the eccentric journal to continue to rotate about the shaft (10) and to store strain energy in the arcuate flexible portion (30) during that motion in the said first direction, such strain energy being substantially returned to the eccentric journal during that portion of the contact event during the motion of the unitary member and piston in the said second direction.

The arcuate flexible portion (30) of the unitary member is adapted to resist the action of normal fluid forces in the general direction indicated by the arrows of -14figure 3, by virtue of the magnitude of the dimension and the dimension in relation to the eccentricity of the arcuate flexible portion (30) and the length (L) over which the dimension and dimension dominate the respective flexibility of the member so defined.

It may be appreciated that the latter features allow less stringent manufacturing accuracy whilst providing the maximum possible compression ratio for the displacer. Alternatively stated, the latter aspect of the invention allows the minimum possible clearance volume in a pumping chamber so defined, whilst allowing some relative and absolute variation in, the axial distance between the shaft (10) at the centreline of the motor (12) and the closed end (14) at one extremity of the bore in the pump body and, the length of the unitary member between the piston crown (31) and the bearing shell Modifications and variations as would be known to the skilled addressee are considered to be within the scope of this invention.

Claims (4)

1. A fluid displacer comprising a cylindrical pumping chamber, a unitary member cooperating within a cylindrical bore of the pumping chamber, such unitary member comprising of a cylindrical piston at one end within the bore and a circular bearing shell at the other end of the elongated axis of the piston which is adapted to receive an eccentric journal of a crank member which is rotatable about an axis of rotation, the mid portion between the two features of piston and bearing shell being flexible such as to permit the bearing shell to be rotated off the normally straight elongated axis of the cylinder and piston so that the circular motion of the eccentric journal is converted into reciprocating motion of the piston.

2. A fluid displacer as claimed in claim 1 wherein the displacer is in the form of a fluid pump which may be driven by a motor with a circular drive to an eccentric journal which orbits around the drive axis of the motor, the eccentric journal being engaged within the bearing shell so as to provide a pumping action for the piston, a pumping chamber being formed between the crown of the piston and the bore of the cylindrical pump body, the chamber being closed at one end and within this closed end within the pump body there is formed a discharge port for a working fluid, such port being controlled by a spring-loaded sealing member which will allow fluid to pass from the pumping chamber when the pressure within the pumping chamber is sufficiently greater than the downstream zone from the discharge port, such that the spring force on the spring-loaded sealing member is overcome, fluid being blocked with respect to flow in the reverse direction. -16-

3. A fluid displacer as claimed in claim 1 or 2 including a unitary member comprising of a cylindrical piston at one end of its length and a circular bearing shell forming a pivot at the other extremity along its axial length which receives a journal of an eccentric, between these two features being a selectively flexible columnar section which allows flexure of the unitary member so as to allow the bearing shell to move off the axis defined by the motion of the piston, the flexible member being substantially non-flexible in a direction perpendicular to the plane defined by the orbit of the eccentric journal, so as to restrain the bearing shell within a plane of orbit of the eccentric by virtue of the attachment of the bearing shell to the piston which maintains a concentric relationship within the cylinder bore. DATED this 13 1h day of July 2005 ORBITAL AUSTRALIA PTY LTD

4 WHIPPLE STREET BALCATTA WA 6021 AUSTRALIA