The present invention relates to pumps generally and more particularly to pumps for viscous fluids.

There are known a great variety of pumps. One type of pump, here described as a displacement pump, provides a pumping action as the result of displacement of a reciprocating member against fluid material to be pumped. Commonly, displacement pumps employ piston and cylinder combinations. The relative movement of the piston and cylinder produces shear forces on the material to be pumped. Certain materials, such as viscous resins, are sensitive to the shear forces and thus cannot be pumped in this way.

The present invention seeks to provide an improved pump which does not exert substantial shear forces on material being pumped. There is thus provided in accordance with a preferred embodiment of the present invention a pump including a chamber containing a fluid to be pumped and having an inlet and an outlet and reciprocating apparatus for displacing part of the fluid in the chamber and causing it to flow out of the chamber through the outlet, generally without applying shear forces thereto. In accordance with one embodiment of the invention, the apparatus for displacing includes a body of a second fluid which is separated from the fluid to be pumped by a diaphragm and linear actuator apparatus for displacing part of the second fluid, producing corresponding displacement of the diaphragm and a flow of a corresponding volume of the fluid to be pumped out of the chamber through the outlet. In accordance with an alternative embodiment of the present invention, the apparatus for displacing includes a reciprocatingly extendible and retractable bellows and linear actuator apparatus for producing reciprocating extension and retraction of the bellows, thus providing displacement of fluid out of the chamber through the outlet upon extension and displacement of fluid into the chamber through the inlet upon re- traction. Finally, in accordance with the present invention, the fluid is a viscous fluid, such as a resin. Typically, the fluid is at room temperature.

The present invention will be understood and appreciated more fully from the following detailed description, taken in conjunction with the drawings in which: Figs. 1A and IB are simplified illustrations of a pump constructed and operative in accordance with a preferred embodiment of the present invention in respective first and second operative orientations; and Figs. 2A and 2B are simplified illustrations of a pump constructed and operative in accordance with another preferred embodiment of the present invention in respective first and second operative orientations.

Reference is now made to Figs. 1A and IB which schematically illustrate a pump constructed and operative in accordance with a preferred embodiment of the invention. The pump includes a chamber 10 which is formed with barrier 12 forming first and second sub- chambers 14 and 16 therewithin which are separated thereby from each other. Subchamber 14 is filled with a ^" substantially non-compressible liquid, such as oil or hydraulic fluid and is associated with a linear actuator 18, having an extendible piston or rod 20 which may be extended into subchamber 14 by a precisely determinable amount, thus providing displacement of a precisely determinable amount of oil or hydraulic fluid. Subchamber 16 is filled with a viscous fluid to be pumped, such as a resin, which is sensitive to shear forces. Subchamber 16 communicates with a fluid inlet 22 and a fluid outlet 24, which are provided with respective one way valves 26 and 28, directed in appropriate directions. In accordance with a preferred embodiment of the invention, barrier 12 is formed with a flexible portion 30, which is preferably disposed at a location spaced from the sides of chamber 10. When piston or shaft 20 is in a relative retracted orientation as seen in Fig. 1A, the flexible portion 30 of barrier 12 may be oriented as shown in Fig. 1A, thus drawing in fluid to subchamber 16 from inlet 22 via valve 26. When piston or shaft 20 is in a relative extended orientation as seen in Fig. IB, the flexible portion 30 of barrier 12 may be oriented as shown in Fig. IB, thus displacing fluid from subchamber 16 to outlet 24 via valve 28. It is a particular feature of the invention that the movement of flexible portion 30, due to its location relative to the side walls of chamber 10, or

by any other suitable constructional feature thereof, provides very little if any shear force to the viscous fluid contained in subchamber 16. It will be appreciated that the pump of the present invention is operative to spread the viscous fluid when the viscous fluid is at room temperature. Furthermore, the pump controls the flow of the viscous fluid such that precise amounts of fluid can be released. Reference is now made to Figs. 2A and 2B which schematically illustrate a pump constructed and operative in accordance with an alternative preferred embodiment of the invention. The pump includes a chamber 40 which is formed with a bellows type barrier 42 forming first and second sub-chambers 44 and 46 therewithin which are separated thereby from each other. The bellows-type barrier 42 is typically comprised of a relatively large number of folds 47. Subchamber 44 may be filled with air and is associated with a linear actuator 48, having an extendible piston or rod 50 which may be extended by a precisely determinable amount, thus extending the barrier 42 by a precisely determinable amount and therefore providing displacement of a precisely determinable amount of viscous fluid which fills subchamber 46. Subchamber 46 communicates with a fluid inlet 52 and a fluid outlet 54, which are provided with respective one way valves 56 and 58, directed in appropriate directions. In accordance with a preferred embodiment of the invention, barrier 42 is preferably disposed at a location spaced from the sides of chamber 40. When piston or shaft 50 is in a relative retracted orientation as seen in Fig. 2A, fluid is drawn into chamber 46 from inlet 52 via valve 56. When piston or shaft 50 is in a relative extended orientation as seen in Fig. 2B, fluid is

displaced from subchamber 46 to outlet 54 via valve 58. It will be appreciated that the bellows-type barrier 42 can withstand external pressure caused when liquid in subchamber 46 is compressed. Furthermore, the relatively large number of folds 47 in the barrier 42 acts to reduce the relative displacement of any portion of the viscous fluid in subchamber 46, thereby reducing the stress on the fluid. It is a particular feature of the invention that the movement of barrier 42, due to- its location relative to the side walls of chamber 40, or by any other suitable constructional feature thereof, provides very little if any shear force to the viscous fluid contained in subchamber 46.

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