Caterpillar Inc.

Caterpillar Tractor Co.

Robert J Huebner

William K Engel

Carman P Lynnes

Donald H Sherman

Guy C Carlson, Jr

Ralph Anthony Matzelle

Richard L Sears

An apparatus for providing a hydraulic pressure differential proportional to a downstream pressure. The apparatus includes a first chamber having a first cross section area, a main chamber portion, a first end, and a second end; a first spool portion located in the first chamber, the first spool portion having a first end and a second end, the first end of the first spool portion being located at the location of the downstream pressure; a second chamber having a second cross section area, a first end, and a second end; and a second spool portion located in the second chamber, the second spool portion having a first end and a second end, the first end of the second spool portion being located generally adjacent the second end of the first spool portion and the second end of the second spool portion being located at the location of the upstream pressure.

Valve providing pressure differential proportional to downstream pressure

In many hydraulic systems, fluid borne noise is generated during operation due to the effects of the hydraulic pump. This fluid borne noise is many times transmitted to the hydraulic valves, hydraulic lines, and other structures that valves and lines are mounted on. The structure then emits vibrations that create the largest portion of the system air borne noise. In the subject invention, an apparatus is provided for the attenuation of fluid borne noise in a hydraulic system. The apparatus includes a fluid vessel having a volumetric space of a predetermined size located in the system generally adjacent a pump and a flow restrictor located in the system downstream of the fluid vessel. In the subject arrangement, the flow restrictor may be adjustable in response to various system parameters so that the fluid borne noise is effectively controlled over wide ranges of system pressures, pump drive speeds, and pump displacements. By reducing the fluid borne noise in the hydraulic system, the associated air borne noise that is created by various components that are associated with the hydraulic system is further attenuated.

Attenuation of fluid borne noise

In many hydraulic systems, fluid borne noise is generated during operation due to the effects of the hydraulic piston pump. This fluid borne noise is transmitted to various structures of the hydraulic system which emit vibrations that create the largest portion of the system air borne noise. In the subject invention, an apparatus is provided for the attenuation of fluid borne noise. The apparatus includes a sensor arrangement operative to sense operating system parameters and deliver signals representative thereof to a microprocessor, a porting arrangement within the hydraulic piston pump that includes a secondary port, a fluid chamber, and first and second passageways interconnecting the secondary port, the fluid chamber, and a discharge passage. The microprocessor receives the signals from the sensor arrangement and directs electrical command signals to an electrically controlled valve mechanism disposed in the first and second passageways. The microprocessor and the valve mechanism operate to control fluid flow between the discharge passage, the fluid chamber, and the secondary port. By pressurizing fluid in the fluid chamber which in turn pre-pressurizes the piston port through the secondary port prior to the piston port entering the discharge passage, the flow required to pressurize the piston port prior to the piston port entering the discharge passage is spread over a larger range of piston port rotation.

Attenuation of fluid borne noise from hydraulic piston pumps

Axial piston fluid translating units commonly experience undesirable shaft deflections and barrel tilting during operation. A fluid translating unit includes a barrel plate interposed the end of a barrel and a porting surface defined within a housing thereof. The barrel plate is axially spaced from an end of the barrel and is in face sealing engagement with the porting surface. The barrel plate defines a plurality of fluid ports, each communicating between one of a plurality of barrel cylinder bores and the porting surface. In one aspect a plurality of counterbores are provided in the barrel in surrounding relation to the fluid ports. A plurality of seal rings having a sealing end defining an annular seal face of a predetermined width for face sealing engagement with the barrel plate. The seal rings are each disposed in one of the counterbores in circumferential sealing relation of a predetermined length which is no greater than the width of the sealing face. A plurality of annular springs are disposed in the counterbores for urging the seal rings into sealing engagement with the other of the barrel and the barrel plate. This arrangement permits tilting of the barrel without damaging contact or excessive leakage between the barrel plate and the porting surface.

Axial piston fluid translating unit with sealed barrel plate

In order to reduce noise within a hydraulic pump of a type having a cylinder barrel defining a plurality of piston bores with the cylinder barrel being rotatable relative to a cylinder head having a valve face for periodically communicating the piston bores with inlet and outlet ports, the valve face is designed to provide overlapping alignment of each piston bore with the inlet passage at a bottom dead center position, subsequent communication of the bore with the outlet port being initiated by a bleed slot. Additionally, the valve face is configured for developing increased clamping engagement between the cylinder barrel and cylinder head by selective communication of each bore with the outlet and inlet ports at a top dead center position. The valve face configuration improves lubrication of the pistons.

Method and valve face configuration for reducing noise in a hydraulic

A hydraulic fluid pressure energy translating machine is provided with hydrostatic pressure-balancing means which communicate with the primary port to balance hydrostatic forces acting on the barrel during operation of the machine to maintain an optimum bearing clearance between the head and barrel, thereby controlling fluid leakage and maintaining adequate lubrication and support at this interface.

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Peoria, IL, United States of America

Robert J Huebner