Motors: expansible chamber type – Cyclically operable – Working member controlled motive fluid for distributor motor
Reexamination Certificate
1997-08-06
2001-10-02
Lopez, F. Daniel (Department: 3745)
Motors: expansible chamber type
Cyclically operable
Working member controlled motive fluid for distributor motor
C417S403000
Reexamination Certificate
active
06295914
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a pressure intensifier for fluids, particularly for hydraulic liquids. The pressure intensifier includes a piston/cylinder arrangement with a low pressure side provided with a low pressure connection and a high pressure side provided with a low pressure connection and a supply connection, as well as an intensifier piston constructed as a double diameter piston arranged between the low pressure side and the high pressure side. The pressure intensifier further includes a valve slide member which alternatingly connects the low pressure connection to a pressure source and a negative pressure source, wherein the control valve is connected through a control line to the piston/cylinder arrangement, so that the pressure in the control line acts on one side of the valve slide member.
2. Description of the Related Art
Pressure intensifiers of the above-described type have the purpose of increasing the pressure in a fluid above the pressure of a pressure source. The following explanation will be with respect to hydraulic liquids. However, the principle is basically also applicable to other fluids.
A pressure intensifier of the above-described type is known from German application 40 26 005 A1. As is the case in the present invention, the known pressure intensifier is provided with a double diameter piston which acts as an intensifier piston. The intensifier includes a low pressure piston which is arranged in a low pressure cylinder and a high pressure piston which is arranged in a high pressure cylinder. Both pistons are rigidly connected to each other through a piston rod. The low pressure piston has a substantially greater cross-section than the high pressure piston. The pressure intensification between the low pressure side and the high pressure side then takes place in accordance with the ratio of the piston cross-sections. In this case as well as in the following description, the terms “low pressure” and “high pressure” are only used for distinguishing the two sides. The terms do not reflect absolute pressure values, but only relative relationships.
Hydraulic liquid is frequently removed from the high pressure side, wherein the hydraulic liquid must be replenished with the appropriate pressure. For this purpose, the high pressure cylinder, i.e., the pressure space acted upon by the high pressure piston, is filled with hydraulic liquid which is supplied from the pressure source. This causes the high pressure piston, and with it the low pressure piston, to be pushed back. The low pressure piston then displaces the hydraulic liquid out of the pressure space to the tank. Once the high pressure piston has been pushed back by a certain distance, the high pressure piston releases the opening of the control line, so that the pressure of the pressure source can act on the slide member of the control valve. The control valve is constructed as a three-way valve. When the appropriate pressure has been applied, the connection between the low pressure cylinder and the tank is interrupted and a connection between the pressure source and the low pressure cylinder is effected instead. The low pressure piston, and with it the high pressure piston, are then pushed back in the direction toward the high pressure side, so that the hydraulic liquid can be discharged through the high pressure connection at the appropriately high pressure.
In the known arrangement, the valve slide member is acted upon on one side by the pressure of the control line and on the other side by the force of a spring.
When more hydraulic liquid is to be taken out at the high pressure connection, the frequency increases at which the intensifier piston, on the one hand, and the valve slide member, on the other hand, must be moved back and forth. An increase in size of the piston/cylinder unit is possible only to a limited extent. On the one hand, this would mean that the time required for filling the high pressure side is longer. On the other hand, the mass increases, so that a fast reciprocating movement of the intensifier piston becomes more difficult. This means that the quantity that can be discharged is limited. In an embodiment of the pressure intensifier known from German patent application 40 26 005 A1, the maximum discharged quantity on the high pressure side was about 2.5 l/min, which corresponds to a maximum supplied quantity of about 10 l/min and which required a frequency of 30 Hz.
SUMMARY OF THE INVENTION
Therefore, it is the primary object of the present invention to provide a pressure intensifier of the above-described type in which the limitations described above are overcome.
In accordance with the present invention, in a pressure intensifier of the above-described type, a constant force acts on the other side of the valve slide member.
As a result of the configuration according to the present invention, the tendency of the valve slide member to reciprocate is reduced. The danger is reduced that a resonance occurs which makes a further increase of the reciprocation frequency more difficult. This makes it possible, for example, to increase the discharged quantity of hydraulic liquid at the high pressure side. Surprisingly, the structural configuration of the pressure intensifier can also be simplified. Even though the output is improved, the pressure intensifier can be manufactured less expensively.
This particularly is the case if the valve slide member is constructed as a double diameter piston which on its other side is acted upon with constant pressure. Accordingly, the double diameter piston is acted upon on one side by the pressure from the control line and on the other side with a constant pressure. The constant pressure acts on a slightly smaller surface than the pressure from the control line. Since the pressure from the control line is not present from time to time depending on the position of the intensifier piston, the valve slide member is alternatingly acted upon by a force difference in one direction and by a force difference in the opposite direction. These force differences are independent of the travel distance, i.e., they act practically over the entire travel distance of the valve slide member. The production of a force by means of a pressure can be easily realized by having the fluid act with the appropriate pressure on the end face of the valve slide member. Since the force difference is kept constant practically over the entire travel distance, relatively high accelerations can be achieved. This makes it possible to reduce the travel times. It is possible to select higher frequencies at which the pressure intensifier operates. Consequently, it is also possible to increase the discharged quantity of the high pressure fluid.
In accordance with a preferred feature, the other side of the valve slide member is acted upon by the pressure of the pressure source. This pressure is available anyhow. It is constant to a sufficient extent. Additional measures are not required.
The control line is advantageously connected to the high pressure side of the piston/cylinder arrangement in the travel range of the intensifier piston, wherein the intensifier piston closes the control line at the beginning of its movement toward the high pressure connection. This causes the pressure in the control line to be limited essentially to the pressure of the pressure source. By appropriately dimensioning the two end faces of the valve slide member, it is then possible to adjust to the desired values the force difference across the valve slide member which is necessary for moving the slide member. Accordingly, it is possible to achieve the desired pattern of movement.
The valve slide member is advantageously arranged in a valve housing so as to form an annular space to which a tank line and a pump line as well as a cylinder line between the tank line and the pump line are connected, wherein the valve slide member includes a control disk which divides the annular space and which, depending on the position of the valve slide member, is l
Iversen Hydraulics ApS
Kueffner Friedrich
Lopez F. Daniel
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