GB2149015A

GB2149015A - Manually actuable hydraulic piston pump

Info

Publication number: GB2149015A
Application number: GB08425673A
Authority: GB
Inventors: Jurgen Korth
Original assignee: Rentrop Hubbert & Wagner
Current assignee: Rentrop Hubbert & Wagner
Priority date: 1983-10-31
Filing date: 1984-10-11
Publication date: 1985-06-05
Also published as: DE3339455A1; BR8405518A; KR850003937A; ES8506864A1; IT1181580B; FR2554175B1; GB2149015B; IT8485647A0; ES536511A0; SE8405138L; FR2554175A1; GB8425673D0; ZA848453B; JPS60129408A; SE8405138D0

Abstract

A manually actuable hydraulic piston pump, e.g. for raising a vehicle seat, comprises an actuating piston (2) and a cylinder divided 14 into front (4) and rear (5) chambers containing hydraulic fluid. A pump piston (6) and cylinder operable by a handle (22) pumps fluid into the front chamber (4), and from the rear chamber (5) via a duct (11). To prevent complete emptying, and thereby the sucking of atmospheric air into the rear chamber (5) when the actuating piston (2) is in its rear dead centre position, a stop (27) is disposed on the front surface of the actuating piston facing the rear chamber. <IMAGE>

Description

SPECIFICATION Manually actuable hydraulic piston pump The invention relates to a manually actuable hydraulic piston pump, for example a pump for raising and lowering a vehicle seat.

The invention provides a manually actuable hydraulic piston pump, comprising a casing; an actuating piston slidably guided in a cylinder within the pump casing which piston divides the cylinder into a front and a rear chamber each containing hydraulic fluid; a piston rod attached to the actuating piston and adapted to act on an external load; a pump piston movable in a further cylinder within the pump casing, urging, as it is actuated, pressurised hydraulic fluid via an outlet valve and a pressure duct into the front chamber, the pressurised fluid prsent in the rear chamber being at the same time supplied to the further cylinder via an inlet valve; a manually actuable valve for emptying the front chamber; and a stop which prevents complete emptying of the rear chamber when the actuating piston is situated in its rear dead centre position.

The stop prevents, in a particularly simple and operationally-reliable manner, the suction of atmospheric air into the rear chamber. The stop may be disposed on the front surface of the actuating piston facing the rear chamber, or else on the front face of the cylinder of the actuating piston facing the rear chamber.

An example of an hydraulic piston pump according to the invention is illustrated hereinunder in greater detail, with reference to the accompanying diagrammatic drawings, in which: Figures 1 to 3 are vertical cross-sections through the hydraulic piston pump according to the preferred embodiment, in various working positions; Figure 5 is a side view from arrow A of the arrangement shown in Fig. 1; and Figures 5 and 6 are partial cross-sections to an enlarged scale of the arrangement shown in Figs. 1 to 3.

A manually-actuable hydraulic piston pump has a housing 1 in which a cylinder is provided to receive slidingly an actuating piston 2. The actuating piston 2 is connected by means of the piston rod 3 to a conventional device (not shown) for raising or lowering a motor vehicle seat.

The actuating piston 2 divides the cylinder into a front chamber 4 and a rear chamber 5.

In housing 1 a further cylinder is provided in which a pump piston 6 is slidingly guided, being connected by means of a piston rod 7 to an actuating device which will be described in greater detail hereinunder.

A spring-loaded outlet valve 8 as well as a spring-loaded inlet valve 9 are associated with the piston 6. The outlet valve 8 is situated in a pressure duct 10 along which the front chamber 4 is supplied with pressurised oil as the hydraulic working fluid. On the other hand, the inlet valve 9 is disposed in a duct 11 which communicates by means of springloaded valves 12, 1 3 (Figs. 5 and 6) with the rear chamber 5.

The front chamber 4 can be emptied by means of a spring-loaded manually-actuable valve 14. The switching of valve 14 over to the emptying position is effected by means of a stem 1 5 which is connected to a slidably guided rod 16, which is manually actuable.

Provision is further made for a stop which prevents the complete emptying of the rear chamber 5 when the actuating piston 2 is in its rear dead centre position, and thus fully to the right in the drawings.

In the embodiment represented, the stop 27 is mounted on the front surface of the actuating piston 2 facing the rear chamber 5.

Alternatively, the stop could be disposed on the front surface of the cylinder of the actuating piston 2 facing the rear chamber 5. The diameter d of the stop is smaller than the diameter D of the actuating piston 2, or of the front face of the cylinder of the actuating piston 2, as the case may be. The arrangement, construction and size of the stop is dependent upon the particular circumstances and is moreover a matter for the specialist.

Mounted on the housing 1, and separated from each other, are two brackets 1 7 in which a fork is pivotably mounted by two arms 1 8.

In the two arms of the fork as well as in the two brackets 17, longitudinal slits 1 9 are provided through which a cross-bolt 20 is passed and which goes through a head 21 with flattened lateral sections mounted on the rod 16. This head 21 rests by means of a spring 23 against the casing 1 of the pump.

The fork with the two arms 1 8 can be actuated by means of a handle 22.

The piston rod 7 also carries at one end a head 24 with flattened lateral sections through which a pin 25 passes, the two ends of the pin engaging in the ends of the two arms 1 8 of the fork.

The hydraulic piston pump operates as follows: Fig. 1 shows the actuating piston 2 in its forward dead centre position. In this position, the vehicle seat, the actuating device of which is connected by means of the piston rod 3 with the actuating piston 2, should be in its starting position. Now, if it is desired to raise the vehicle seat, the handle 22 will be moved to and fro between two end positions with the result that the piston 6 of the pump performs to and fro movements. As a result, the two valves 8 and 9 open and close alternately in such a manner that, via the outlet valve 8 and the pressure duct 10, pressurised oil is supplied to the front chamber 4, as a consequence of which the actuating piston 2 and the piston rod connected with it move to the right of the drawing.As a consequence of this movement the actuation device for the vehicle seat is set in motion, thus, e.g. the vehicle seat is raised.

At the same time pressurised oil passes out of the rear chamber 5 via the spring-loaded valve 1 2 (Fig. 5) and the duct 11, and via the inlet valve 9 which opens rhythmically, into the space situated in front of the pump piston 6. The longitudinal slits 1 9 in the two arms 1 8 of the fork as well as the two brackets 1 7 allow the pump piston 6 to run freely in its cylinder.

In the case of the pivoting movement of the handle 22 the actuating piston 2 reaches the position represented in Fig. 2 and then the dead centre (rear) position in which the stop 27 applies against the rear front surface of the cylinder in which the actuating piston 2 is lodged. By this means it is ensured that the rear chamber 5 is not in any event fully emptied. The rear chamber is still filled with pressurised oil so that on the emptying of the front chamber no atmospheric air can enter the rear chamber.

The stem 1 5 should have such a length that, as a result of the oscillating movement of the handle 22 between its two end positions, the spring-loaded valve 14 will not in any event be moved into its open position.

If the vehicle seat has now reached its uppermost position and if it is desired to lower it back to its starting position, the handle 22 will be swung over its foremost end position against the force of the spring 23-in the drawing to the left-i.e. in the direction of the pump casing 1 in such a manner that the stem 1 5 can move the spring-loaded valve 14 into its open position, as a result of which the front chamber 4 is emptied via the pressure duct 10 as well as the connecting duct 26 controlled by valve 1 4. The actuating piston 2 and the piston rod 3 are in this arrangement subjected to the influence of the force in the loaded vehicle seat. The pressurised oil closes the valve 9 but is still able to flow via the duct 11 and the open valve 1 3 into the rear chamber 5.

Valve 12, moreover, also has the task, in the event of an accident to the vehicle equipped with the seat, to close abruptly the highly pressurised rear chamber 5. This is achieved by the valve 1 2 overcoming the force of the spring associated with it and applying in a seal-tight manner against its seat surface.

Claims

1. A manually actuable hydraulic piston pump, comprising a casing; an actuating piston slidably guided in a cylinder within the pump casing which piston divides the cylinder into a front and a rear chamber each containing hydraulic fluid; a piston rod attached to the actuating piston and adapted to act on an external load; a pump piston movable in a further cylinder within the pump casing, urging, as it is actuated, pressurised hydraulic fluid via an outlet valve and a pressure duct into the front chamber, the pressurised fluid present in the rear chamber being at the same time supplied to the further cylinder via an inlet valve; a manually actuable valve for emptying the front chamber; and a stop which prevents complete emptying of the rear chamber when the actuating piston is situated in its rear dead centre position.

2. A piston pump according to claim 1, wherein the stop is arranged on the front surface of the actuating piston facing the rear chamber.

3. A piston pump according to claim 1, wherein the stop is arranged on the front surface of the cylinder of the actuating piston facing the rear chamber.

4. A piston pump according to claim 2, wherein the diameter of the stop is smaller than the diameter of the actuating piston.

5. A piston pump according to claim 3, wherein the diameter of the stop is smaller than the diameter of the front surface of the cylinder of the actuating piston.

6. A manually actuable hydraulic piston pump substantially as described herein with reference to the accompanying drawings.