Pumps – Motor driven – Fluid motor
Patent
1996-08-14
1998-06-30
Thorpe, Timothy
Pumps
Motor driven
Fluid motor
417395, 92220, F04B 4300, F04B 43073
Patent
active
057724121
DESCRIPTION:
BRIEF SUMMARY
This application is a 371 of PCT/GB 94/02560 filed Nov. 22, 1994.
The invention relates to a pump particularly, but not exclusively, to a diaphragm pump suitable for pumping liquids.
Diaphragm pumps have been in use in industry for some years. In such pumps, piston are caused to move in a reciprocating manner within a chamber and sealing means are provided between the interior wall of the chamber and the moving piston. Sealed portions of the chamber are thereby created between the ends of the chamber and the relevant face of the appropriate piston. Any movement of the piston within the chamber therefore causes the pressure within that sealed portion of the chamber to change. Commonly, venting means are provided to allow the pressure within that portion of the chamber to return to ambient pressure at appropriate intervals during the operating cycle.
In certain instances, this venting can cause problems. For example, pumps of this type can be designed to transport liquids having internal pressures in the order of 18-28 psi created by internal carbonisation. Carbon dioxide or other gas or gas mixture supplied at a pressure of, for example, 60 psi, is introduced into the relevant portion of the chamber in order to move the appropriate piston from one operating position to another. When the reciprocal motion is to take place, the carbon dioxide or other gas at 60 psi is vented to atmosphere. This causes a pressure differential across the sealing means located between the piston and the interior wall of the chamber. Repeated pressure differences of this type can cause deterioration of the sealing means which must then be regularly inspected and, if necessary, replaced.
It is an object of the invention to provide a pump which does not have the aforementioned disadvantage and which therefore has an extended working life and reduced maintenance costs.
The invention provides a pump as set out in claim 1 of the appended claims. The invention also provides a pumping system as set out in claim 9 of the appended claims and a method of pumping a liquid as set out in claim 11 of the appended claims. Preferred features of the various aspects of the invention are set out in the subsidiary claims.
Embodiments of a pump according to the invention will now be described with reference to the accompanying drawings wherein:
FIG. 1 is a schematic cross-section taken through the longitudinal axis of a pump according to a first embodiment of the invention in a first operation position;
FIG. 2 is a schematic cross-sectional view of the pump of FIG. 1 shown in a second operating position; and
FIG. 3 is an enlarged cross sectional detail of part of a pump according to a second embodiment of the invention.
The pump shown in FIGS. 1 and 2 consists of a housing 10 which incorporates an elongate chamber 12 and a transverse through chamber 14 for the passage of pumped liquid. The through chamber 14 has an inlet 16 and an outlet 18, between which are two parallel channels 20,22 which can be opened and closed by means of valves 24a,24b,24c and 24d. The channels 20,22 are variable in volume in their central sections by means of the movement of pistons 26,28 which are rigidly connected by connecting member 30. Seals 32a and 32b form liquid-tight connections between the pistons 26,28 and the interior wall of the chamber 12.
Pistons 26 and 28 are arranged so as to be reciprocatingly movable within the chamber 12. The movement takes place along the longitudinal axis of chamber 12 and is controlled by means not shown in detail in the accompanying drawings. Furthermore, gas introduction means 34 are provided to allow the introduction of compressed gas into the chamber either to the left of piston 26 or to the right of piston 28 as desired. Venting means 36 allowing venting of these portions of the piston 12 are also provided.
The apparatus described thus far is known. However, the venting means 36 are attached to pressure regulating means in the form of a pressure valve 40. The pressure valve 40 incorporates control means and/or sensing means design
REFERENCES:
patent: 4386888 (1983-06-01), Verley
patent: 4624628 (1986-11-01), Marchant
patent: 4708827 (1987-11-01), McMillin
Kim Ted
Shurflo Limited
Thorpe Timothy
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