Hydrostatic-mechanical gear for driving a mixing drum

Details Hydrostatic-mechanical gear for driving a mixing drum Hydrostatic-mechanical gear for driving a mixing drum

1995-10-18

1998-05-05

Cooley, Charles E.

Agitating

Mortar mixer type

Movable mixing chamber

60456, 60464, 92 72, 92130R, F16D 3102, B28C 542

Patent

active

057465096

DESCRIPTION:

BRIEF SUMMARY
The invention relates generally to a hydrostatic-mechanical gear for driving a mixing drum. In particular, it refers to the driving of the mixing drum of a concrete mixer truck. The gear has a hydraulic pump connected by pipes with a hydraulic motor. The hydraulic pump is surrounded by a pump housing. A gear housing serves to accommodate the hydraulic motor and a planetary gear. The web of said planetary gear is in driving connection with an input flange of the mixing drum.


BACKGROUND OF THE INVENTION

DE-A-29 04 107 has disclosed a mixing drum drive for a mixer truck in which the hydraulic motor is situated, in within a gear housing. An oil tank surrounds the hydraulic motor in order to obtain a compact design and better facilitate the removal of heat.


SUMMARY OF THE INVENTION

This invention improves a gear for driving a mixing drum in the sense of better cooling the hydrostatic part of the motor. The gear, of the present invention, also especially stands out because of compact design and noise reduction. In addition rotation of the mixing drum after the motor has been switched off is prevented.
The problem on which the invention is based is solved by the fact that oil is constantly removed from the high-pressure circuit via a connecting pipe, and that in addition oil that has passed an oil cooler is constantly fed to the interior of the gear housing via a pipe, said pipe discharging at a place in the gear housing which immediately adjoins the hydraulic motor. In the proposed solution, the cooling consists of two separate systems. Part of the oil in the closed high-pressure circuit is constantly replaced by cooled oil. In addition, the cooled oil is passed into the interior of the gear housing, specifically in the immediate proximity of the hydraulic motor. This oil flows through the hydraulic motor which is preferably designed as a slow-speed radial piston motor. The pistons, the rollers, the cam and the cylinder block are hereby cooled. This prolongs the service life of said structural parts, especially the cam. The oil removed either reaches the interior of the pump housing for flushing the pump or is supplied, immediately bypassing the pump, to the pipe leading to the oil cooler.
The connecting pipes lead to a flushing slide valve which connects a pipe under high pressure, at the time, with a low-pressure side by a flushing valve. The flushing slide valve and the flushing valve are preferably situated in the gear housing.
An especially good cooling of the supply pump is obtained when oil is absorbed by the supply pump from the interior of the gear housing via a pipe and a filter.
A constructionally simple solution consists in making the flushing slide valve from a 3/3 directional valve and the flushing valve from a pressure-limiting valve.
An especially effective cooling of the hydraulic motor is obtained in a simple manner when the pipe discharges in the interior of the gear housing in immediate proximity of the hydraulic motor. In this case, the oil that flows out from the pipe flows in an axial direction by the cam, the rollers, the pistons and the cylinder block of the radial piston motor.
When the pipe discharges in immediate proximity of the hydraulic motor, the added advantage that the oil flowing out from the pipe and the leakage oil of the hydraulic motor become mixed can be obtained.
An essential feature consists in that each piston of the hydraulic motor is supported by spring elements of the cylinder block. The spring element ensures that the piston and the associated roller are constantly biased against the cam path. When reversing the direction of rotation, such as during the reswitching of the drum, the hydraulic motor acts as a pump and each piston is consecutively pressed inward away from the cam path. During operation, the hydraulic oil, which is located between the cylinder surface of each piston and the cylinder block, is placed under pressure so that any leakage oil overflows into the interior of the gear housing.
When the piston reaches its inner most point during reversal,

REFERENCES:
patent: 3080152 (1963-03-01), Lendved
patent: 3333415 (1967-08-01), Adams
patent: 3359727 (1967-12-01), Hann et al.
patent: 3969897 (1976-07-01), Humphreys et al.
patent: 4329064 (1982-05-01), Mann et al.
patent: 4542990 (1985-09-01), Fouquet

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