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Plunger Design for No-Leak Hydraulic Reciprocating Pumps for Use in Medical Devices Disclosure Number: IPCOM000182840D
Publication Date: 2009-May-07
Document File: 5 page(s) / 2M

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A design for an exemplary leak-free hydraulic pump and a method for manufacturing the exemplary leak-free hydraulic pump are presented.

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Plunger Design for No-Leak Hydraulic Reciprocating Pumps for Use in Medical Devices


[0001]             The invention relates generally to hydraulic pumps, and more particularly to hydraulic pumps configured for use in medical devices.   

[0002]             As will be appreciated, hydraulic pumps are extensively used in the various industrial applications for boosting the pressure of liquid to perform mechanical work.  Oil seals in hydraulic pumps play a vital role in preventing the oil leak.  Furthermore, if hydraulic pumps are used in medical equipment, it is highly desirable to ensure that even small traces of oil do not escape from the oil seals.  Hence, it is desirable to understand the physics of behavior of movable components in the hydraulic pumps and their interaction with oil seals.  Very tiny particles as small as one tenth of a milligram in weight, if generated as bur in the oil circuits, may lead to slits/cracks of micro levels and may eventually pave way for traces of oils to escape from the system. 

[0003]             Theoretically the plunger has to travel in the axis of its movement. However, if the pump is used in horizontal position, as the plunger moves inward, plunger will deflect downwards due to gravity and the probability of an end of the plunger touching the cylinder inner wall, during its inward movement to build hydraulic pressure is very high.  Consequently, an end of a conventional plunger rod tends to score the walls of cylinder and generate micro level of bur.  These micro-sized burs/chips travel in the hydraulic circuitry and cause a micro cracks in seals leading to traces of oil escape. 

[0004]             Furthermore, oil leaks in hydraulic pumps is a common affair in all industrial applications.  However, as will be appreciated, even traces of oil cannot be allowed to escape when the hydraulic pumps are used in medical industry.  These hydraulic pumps typically use oil seals for prevention of oil leaks.  It is a general practice to build an oil well to collect the oil droplets and these droplets are returned to a reservoir.  However, this collection and return of the leaked oil droplets is not feasible in medical equipment, because the medical equipment is generally operated in a sterile environment of a hospital.

[0005]             Moreover, manufacturing processes leave a very minute asperity in the ends of a piston in the pumps.  The motion of the piston against the inner walls of the pumps leading to “scoring”, which in turn leads to the generation of micro-sized chips or burs. These micro-sized burs or chips enter the oil circuitry and damage the seals. 

[0006]             It may therefore be desirable to study the physics of failure and develop a robust design of a leak-free hydraulic pump and a method of manufacturing the leak-free hydraulic pump configured to ensure that no traces of oil are ever allowed to...