Expansible chamber devices – Displacement control of plural cylinders arranged in... – Parallel cylinders
Reexamination Certificate
2000-05-11
2001-11-06
Lopez, F. Daniel (Department: 3745)
Expansible chamber devices
Displacement control of plural cylinders arranged in...
Parallel cylinders
Reexamination Certificate
active
06311607
ABSTRACT:
In hydrostatic machines which are adjustable in respect of their displacement volume, more particularly axial piston machines, a zero position setting is required both in machines in which the adjustment member is adjustable from its zero position into a position of maximum displacement volume and back again and in machines in which the adjustment member is adjustable beyond its zero position, since it is scarcely possible to predetermine the zero position in a fixed manner on account of the manufacturing tolerances which are present in the adjustment mechanism.
A known measure of setting the zero position consists, for example, in the case of an adjustment member in the form of a pivot lever mounted on a shaft, in slotting the bearing eye of the pivot lever and, by means of a clamping screw penetrating the slot, constructing the pivot lever as a clamping device. In this design, which has long been known, the zero position can be set manually by releasing the clamping screw of the pivot lever, adjusting the adjustment mechanism into the exact zero position and then tightening the clamping screw, so that the pivot lever is securely connected to the shaft. In this known device, there is a danger of the clamping device working loose in the long term. In addition, the zero position setting is difficult since it is scarcely possible to carry out a controlled adjustment movement when manually pivoting the pivot lever on the shaft. There is also a danger, either before or during the locking of the pivot lever on the groove by tightening the clamping screw, of the setting being accidentally changed again.
In a device described in DE-OS 23 33 083 for adjusting the displacement volume of a hydrostatic machine, an adjustment member in the form of a pivot lever is provided, which is pivotably mounted independently of two bearing journals of a so-called tapered washer and is drivably connected to the tapered washer by a lever mechanism. In this known design, a zero position setting device is formed by a locking mechanism with a radial groove, which is arranged on an end face of the bearing shaft of the pivot lever and into which a resiliently mounted ball can lock, which is arranged eccentrically in a rotatably mounted bush relative to the pivoting axis of the pivot lever. In this known design, it is necessary when adjusting the displacement volume to overcome a locking point, which disturbs the adjustment movement.
A device of the initially described type is described in DE 26 20 524 C2 for adjusting the displacement volume of an axial piston machine with an external adjustment lever, on whose pivoting shaft an inner restoring lever is rigidly secured, which comprises a driving journal, which projects parallel to the pivoting shaft and is centered between two spring limbs of a helical spring, which engage around the driving journal and an abutment journal fixedly arranged on the housing, so that the driving journal and therefore the pivoting lever is also elastically centered between the spring limbs. In this known device, a setting device for setting the zero position in the region of the pivoting lever is not provided. Nor it is ensured that the centering is free of clearance.
It is the object of the invention to develop a device of the initially stated type in such a manner that a setting of the zero position is possible whilst ensuring a simple construction.
In the device according to the invention a setting device is provided, which is fitted into the connection between the spring limb and the adjustment member. In this manner, not only is a simple arrangement and reliable function ensured, but also a simple design and good accessibility, which results in cost-effective manufacture and easy handling during setting of the zero position. In addition, the design according to the invention, which is of small construction, can be easily integrated into the device.
In the case of an adjustment which is pivotable about a pivoting axis, a helical spring is suitable as a spring, a spring limb projecting from one end and a different spring limb projecting from the other end of the helical spring and acting between an abutment element fixed to the housing and the pivotable adjustment member. A spring of this type is particularly suitable for centered positioning of the adjustment member in its zero position, the abutment element being clamped between the limbs, so that the centering is ensured.
Within the framework of the invention, it is possible to construct the setting device with an adjustment member which can be adjusted over a path extending in the adjustment device either manually or by means of an adjustment gearing. The latter design also allows for the arrangement of a step-down gearing, so that not only simple handling during setting is possible as a result of the presence of the gearing, but also a fine setting as a result of the step-down gearing. A rotatable eccentric, for example, which forcibly effects the setting movement of the setting member when manually rotated, is suitable as a step-down gearing. For the restoring movement of the setting member, the tension of the spring can be exploited.
It is also advantageous to arrange the setting device in protected fashion between the hydrostatic machine and the adjustment member and to provide a setting mechanism, which is accessible from the outside of the adjustment member. This allows for ease of handling during the setting of the zero position.
A particularly simple development of the invention consists in arranging the setting member in a guide groove extending transversely to the associated spring limb in an adjustable and selectively lockable manner, e.g. by means of a clamping device. Both this embodiment and the embodiment with the eccentric described above allow for continuously variable setting of the zero position.
REFERENCES:
patent: 4934252 (1990-06-01), Giere
patent: 5142940 (1992-09-01), Hasegawa
patent: 5622051 (1997-04-01), Iida et al.
patent: 1528808 (1970-02-01), None
patent: 2333083 (1975-01-01), None
patent: 2620524C2 (1997-12-01), None
patent: 0386738A2 (1990-09-01), None
Brueninghaus Hydromatik GmbH
Lopez F. Daniel
Scully Scott Murphy & Presser
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