Machine element or mechanism – Control lever and linkage systems – Multiple controlled elements
Patent
1984-11-02
1986-10-28
Herrmann, Allan D.
Machine element or mechanism
Control lever and linkage systems
Multiple controlled elements
74360, 74745, G05G 510, G05G 912
Patent
active
046191534
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
This invention relates to vehicle transmissions and in particular to selector fork arrangements used to select the operative ratio of such transmissions.
There is a longstanding requirement for a simple and easily accessible selector fork arrangement suitable for the type of transmission which is used in agricultural and industrial tractors (or similar vehicles) and which has a multi-ratio main change speed gear set and a range change gear set in series.
DISCLOSURE OF THE INVENTION
It is an object of the present invention to provide a vehicle transmission of the above described type which has an improved selector fork arrangement.
Thus according to the present invention there is provided a vehicle transmission having a housing within which is disposed a multi-ratio main change speed gear set and a first range change gear set in series and in which the speed and range changes are effected by selector forks which are mounted on and axially movable relative to a single selector fork rail which is held stationary relative to the housing.
The transmission may have a second range change gear set operated by a further selector fork which is also mounted on and movable relative to the same selector fork rail.
Additionally the transmission may include a creeper gear facility which is operated by a still further selector fork which is also mounted on and movable relative to the same selector fork rail.
Preferably the housing is provided with an access aperture and said selector fork rail is releasably mounted in the housing in a manner which permits the rail to be axially slid within the housing after the release of rail fastening means to allow removal of the selector forks one by one from one end of the rail via said aperture. Such an arrangement enables the selector forks to be easily accessible and removable from the housing.
One of the range change selector forks may be moved axially relative to the rail by an hydraulic cylinder which surrounds the rail.
Preferably the hydraulic cylinder is double-acting and contains a differential area double-acting piston which surrounds the rail and divides the cylinder into two operating chambers, the arrangement being such that if both operating chambers are subjected to the same level of pressure the piston moves in a first direction and if only one chamber is pressurised the piston moves in the opposite direction.
The invention also provides a vehicle transmission having a housing within which is disposed a multi-ratio change speed gear set in which the speed changes are effected by selector forks which are mounted on and axially movable relative to a single selector fork rail which is held stationary relative to the housing, the housing being provided with an access aperture and the selector fork rail being releasably mounted in the housing in a manner which permits the rail to be axially slid within the housing after the release of the rail fastening means to allow removal of the selector forks one by one from one end of the rail via said aperture.
The invention also provides a selector fork arrangement for a vehicle transmission contained within a housing, the arrangement comprising a selector rail, selector rail fastening means for holding the rail stationary relative to the tansmission housing, and a plurality of selector forks axially movable relative to the rail to effect changes in the operative ratio of the transmission.
DESCRIPTION OF THE DRAWINGS
One embodiment of the present invention will now be described by way of example only, with reference to the accompanying drawings in which:
FIG. 1 is a side view of a tractor transmission which is controlled by the selector mechanism of the present invention;
FIG. 2 diagrammatically shows the gear wheel layout of the input gear Z of the transmission;
FIG. 3 is a plan view of the selector fork layout of the transmission;
FIG. 4 is an enlarged side view in the direction of Arrow IV of FIG. 3 of the hydraulic High/Low range actuating cylinder;
FIG. 5A is a scrap plan view in the direction of Arrow
REFERENCES:
patent: 2052042 (1936-08-01), Thompson
patent: 3301078 (1967-01-01), Michael
patent: 3596534 (1971-08-01), Logan
patent: 3899934 (1975-08-01), Froumajou
patent: 4335623 (1982-06-01), Kronstadt
patent: 4472868 (1984-09-01), Takahashi
Revue Technique, No. 101, Jan.-Feb., 1980, (Billancourt, France), "Les Nouvelles Boites de Vitesses ZF", Ecosplit, pp. 101-103.
Farris Robert L.
Herrmann Allan D.
Massey-Ferguson Services N.V.
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