Pumps – Expansible chamber type – Valved piston
Reexamination Certificate
1999-06-21
2001-06-05
Freay, Charles G. (Department: 3746)
Pumps
Expansible chamber type
Valved piston
C417S570000
Reexamination Certificate
active
06241491
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to A device for supplying an apportioned minimum amount of fluid, especially oil for lubricating pneumatically actuated systems.
BACKGROUND OF THE INVENTION
The device of the present invention has a positive-displacement chamber, a tappetlike positive-displacement member displaceable therein, and a feeding channel discharging into the positive-displacement chamber; A check valve for the hydraulic disconnection of a portion of the positive-displacement chamber that is at pumping pressure from a feeding channel is provided, and a discharge channel, leading away from the positive-displacement chamber and discharging into a drop opening; The discharge channel can be closed off sealingly from the positive-displacement chamber by a valve prestressed in the closing direction and counter to the pump direction, and the tappetlike positive-displacement member is movable by a pulse-controlled actuating device in the positive-displacement chamber, as a result of which fluid is pumped from the feeding channel to the discharge channel. A valve body of the valve is embodied as a structural component which is separate from the positive-displacement member and is subject to spring tension, and can be lifted from its valve seat without being touched by the positive-displacement member as the positive-displacement member moves into the positive-displacement chamber, so that during this process a fluid volume equivalent to the positively displaced volume is pumped past the valve body into the discharge channel, and once a terminal position of the positive-displacement member is reached the valve body is again pressed against its valve seat.
From German Patent a DE 43 19 098 A1, an oil pump for supplying lubricant to an internal combustion engine is known whose fundamental design is equivalent to that described above. However, in such oil pumps, much larger quantities of fluid are pumped.
From German Patent, DE 195 32 566 C1, and European Patent, EP 0 246 178 A2, devices for apportioned pumping of a minimum quantity of oil for lubricating pneumatically actuated systems are known. However, these devices have the disadvantage that when the positive-displacement member moves, a hydraulic communication or pressure communication exists between the feeding channel, acted upon by pumping pressure, and the discharge channel that leads to a drip opening. The oil quantity required therefore depends on instantaneous pressure conditions, and the replicability or settability of the desired pumping quantity is not satisfactory.
SUMMARY OF THE PRESENT INVENTION
According to the present invention therefore during the intake stroke of the positive-displacement member, the discharge channel is closed off sealingly from the positive-displacement chamber by the valve that is prestressed counter to the feeding direction. During the supply stroke of the positive-displacement member, the valve that disconnects the positive-displacement chamber from the discharge channel is opened, without the positive-displacement member touching the valve body of the valve.
Between the pumping pulses, that is, when the positive-displacement member is in its terminal position, the aforementioned valve is closed whenever the pressure prevailing on the drip side, that is, in the flow channel, plus the spring pressure of the valve is greater than the pilot pressure prevailing on the feeding side. Pressure fluctuations in the flow channel, however, can cause the valve body, prestressed in the closing direction, to be lifted from its valve seat, so that during that time there is an undesired pressure communication between the feeding side and the discharge side, with the consequence of undefined states. It is, therefore, an object of the present invention to improve device of the type defined at the outset in such a way that the above disadvantages do not occur, and that the minimal quantity to be pumped can be specified or set in a precisely defined way.
In a device of this type, this object is attained according to the present invention in that the positive-displacement member, in its terminal position, can be pressed sealingly against an axial stop inside the positive-displacement chamber.
Because the positive-displacement member, in its terminal position is in sealing contact, secure sealing off of the positive-displacement chamber or feeding side from the discharge channel is assured even if there are pressure fluctuations in the flow channel, that is, on the discharge side. Furthermore, by the contact of the face end of the positive-displacement member with the axial stop, the minimal volume pumped per supply stroke can be set still more precisely than was previously the case.
To prevent impact or seating of the positivedisplacement displacement member onto or on the axial stop from causing irritating noise, the axial stop, or a face of the positive-displacement member, includes a nonmetallic noise-damping material. In each case it is assured that the positive-displacement member and the axial stop are embodied in complementary fashion to one another, so that in this terminal position of the positive-displacement member in contact with the stop secure sealing off of the positive-displacement chamber from the discharge channel is assured.
In a preferred embodiment of the present invention, the axial stop is formed by an element which also forms the valve seat of the valve that closes off the positive-displacement chamber from the discharge channel. The production and assembly costs are accordingly not increased by this provision according to the present invention.
The axial stop could be formed by an intrinsically arbitrary sealing seat in the broadest sense. It proves to be especially advantageous, and simple from a production standpoint, if the axial stop is made by an O-ring of an elastomeric sealing material. The O-ring can rest on an encompassing shoulder in a graduated opening, which defines the positive-displacement chamber.
If the O-ring at the same time protrudes radially inward past the smaller-diameter boundary of the graduated opening, then the valve body of the aforementioned valve that closes off the positive-displacement chamber from the discharge channel can be pressed against the O-ring as a sealing seat.
According to a further concept of the present invention, the O-ring is pressed against the encompassing shoulder by a bushing for the positive-displacement member, the bushing defining the positive-displacement chamber, and is thus kept in an installed position.
It is also proposed that the stroke height of the positive-displacement member relative to the axial stop inside the positive-displacement chamber be made settable, which can advantageously be attained by a stop means, which is adjustable in the axial direction, in the pulse-controlled actuating device.
If the check valve, which seals off a portion of the positive-displacement chamber that is at pumping pressure from the feeding side, is located relatively far away from the positive-displacement chamber, as is the case in known devices of the generic type in question, trapped air in the volume between the check valve and the positive-displacement chamber has a very negative effect and makes the pumping device harder to control and use. It thus proves to be advantageous if in accordance with a further concept of the present invention, which intrinsically has independent significance, the check valve is provided inside the positive-displacement chamber. As a result, the volume between the check valve and the positive-displacement chamber is reduced virtually to zero. The device of the present invention is simpler to control and use, because disruptive trapped air can no longer form between the positive-displacement chamber and the check valve, air that could be compressed and thus make the device more difficult to start up because the device would first have to be ventilated in a complicated way.
It is also proposed that the check valve be provided as a seal between the positive-displacement member and one wal
Freay Charles G.
Gartenberg Ehud
J. Lorch Gesellschaft & Co. GmbH Gesellschaft fur Maschinen und
Jones Tullar & Cooper P.C.
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