Machine element or mechanism – Gearing – Interchangeably locked
Reexamination Certificate
1999-08-27
2001-07-10
Estremsky, Sherry (Department: 3681)
Machine element or mechanism
Gearing
Interchangeably locked
C074S331000, C074S333000
Reexamination Certificate
active
06257080
ABSTRACT:
FIELD OF THE INVENTION
The present invention is directed generally to a power-shifted transmission for industrial vehicles and more specifically to a power-shifted transmission of the type capable of establishing three different forward gear ratios and two different reverse gear ratios with the use of simple and efficiently operable transmission components.
BACKGROUND OF THE INVENTION
As is generally known in the art, such industrial vehicles as forklift trucks, hydraulic excavators and telescopic handlers make use of pressurized fluid to perform an intended task. The pressurized fluid is produced by means of a reversible hydraulic pump which in turn is drivingly connected to an engine. The power of the engine is also utilized to have the industrial vehicles go forwards and backwards at different speeds selected by the operator.
In order to enable the operator to change the speed and the direction of movement of the industrial vehicles, a variety of power-shifted transmissions have been employed, including: parallel shaft type transmissions; and planetary gear type transmissions. Most of the state-of-the-art parallel shaft type transmissions are so constructed as to establish three forward gear ratios and three reverse gear ratios depending on the operator's desire. These type of transmissions tend to require an increased number of gear shafts, bearings and hydraulically operated clutches, which may of course makes the transmissions structurally complicated, bulky and heavy weight. Another drawback of the conventional parallel shaft type transmissions is that the number of gears meshed and the number of clutches engaged for establishing an intended gear ratio would be necessarily increased, thus deteriorating operability and durability of the transmissions.
As a solution to the afore-mentioned shortcomings, use has been made of the planetary gear type power-shifted transmissions which is usually provided with a sun gear, planetary pinion gears, a ring gear, hydraulically operated clutches for causing these gears to be coupled together for rotation as a unit and hydraulically operated brakes for releasably securing these gears to a transmission casing against any rotation. Two or more forward gear ratios can be established by selectively actuating the clutches and the brakes through the use of pressurized fluid. Although the planetary gear type transmissions have compact structure as compared with the parallel shaft type transmissions, they are costly to fabricate and hard to diversify gear ratios, thus heavily restricting the freedom of design of the transmissions.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the invention to provide a power-shifted transmission for industrial vehicles which can substantially eliminate the deficiencies inherent in the prior art transmissions.
Another object of the invention is to provide a power-shifted transmission for industrial vehicles which can be fabricated with ease and at diversified gear ratios, while enjoying improved operability and durability.
With these objects in view, the present invention provides a power-shifted transmission for industrial vehicles capable of accomplishing first through third forward gear ratios and first and second reverse gear ratios, comprising: a transmission casing; an input shaft rotatably mounted on said transmission casing and having a drive gear for unitary rotation therewith; a forward shaft assembly including a forward shaft rotatably mounted on said transmission casing, first and second forward gears rotatably fitted to the forward shaft, a forward clutch cylinder rotatable about the forward shaft and having a cylinder gear in meshing engagement with the drive gear of said input shaft, and first and second forward clutches selectively operable to couple one of the first and second forward gears with the forward clutch cylinder; a reverse shaft assembly including a reverse shaft rotatably mounted on said transmission casing, first and second reverse gears rotatably fitted to the reverse shaft, a reverse clutch cylinder rotatable about the reverse shaft and having a cylinder gear in meshing engagement with the cylinder gear of the forward clutch cylinder, and first and second reverse clutches selectively operable to couple one of the first and second reverse gears with the reverse clutch cylinder; an intermediate shaft assembly including an intermediate shaft rotatably mounted on said transmission casing, a third forward gear rotatably fitted to the intermediate shaft, an intermediate clutch cylinder rotatable about the intermediate shaft and having a cylinder gear in meshing engagement with the cylinder gear of the reverse clutch cylinder, and a third forward clutch operable to couple the third forward gear with the intermediate clutch cylinder; and an output shaft rotatably mounted on said transmission casing and having first through third driven gears each fixedly attached to the output shaft for unitary rotation therewith, said first driven gear meshing with the first forward gear and the first reverse gear, said second driven gear meshing with the second forward gear and the second reverse gear, and said third driven gear meshing with the third forward gear.
REFERENCES:
patent: 4549443 (1985-10-01), White
patent: 5471892 (1995-12-01), Sherman
patent: 5557978 (1996-09-01), McAskill
patent: 5592853 (1997-01-01), Rebholz et al.
patent: 5715727 (1998-02-01), Janiszewski
patent: 5743142 (1998-04-01), Leber et al.
Daewoo Heavy Industries Ltd.
Estremsky Sherry
Lewis Tisha D.
Staas & Halsey , LLP
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