This invention relates to a hydrostatic transmission system. In particular, this invention relates to a hydrostatic transmission system for imparting a drive to the crane. This invention also relates to an oscillating rear axle for use in a crane.
Cranes presently known in the art comprise a main carriage and a cabin mounted on wheels and having a drive source for imparting a drive to said carriage. A boom is mounted on said main carriage, the distal end of said boom having a pulley block with a pulley hook, which can be raised or lowered. The boom has a pivotal movement.
The hydrostatic transmission system of the present invention has a particular application only for drive of the carriage, and not for imparting a movement to the boom.
A disadvantage associated with the rear axle of the known art is that in the instance of a traverse of the wheels of the carriage over an uneven road surface, one of the wheels may not in contact with the road surface, which could result in a dangerous traverse or movement of the crane.
An object of this invention is to propose a novel hydrostatic transmission system for imparting a drive to the main carriage of the
crane.
Another object of this invention is to propose a novel construction of an oscillating rear axle for use in a crane.
According to this invention there is provided a hydrostatic transmission system comprising a main carriage with a cabin, a boom mounted on said carriage, characterized in that a hydrostatic transmission means is provided for imparting a movement or displacement to said carriage, an oscillating rear axle with said carriage, said hydrostatic transmission means comprising a hydraulic pump connected to a hydraulic motor, a lever provided with said pump to allow a forward or reverse movement of said carriage, an intermediate gear box connected to said motor to provided a drive to the rear axle through a shaft.
Specifically, the present invention resides in the provision of a hydrostatic transmission means for driving the carriage of the crane and an oscillating rear axle so as to allow the rear wheels to be in contact with a road surface even in instance of an uneven surface.

The hydrostatic transmission comprises a hydraulic: pump having a first and second outlet port and such that either one of said ports is in flow communication with a hydraulic pump at any one operating instance,, depending as to whether a forward or reverse movement is required of the carriage. The hydraulic motor is connected to an intermediate gear box adapted to provide different speeds to the rear axle, a 1 e v e r p r o v i d e d w i. t h s aid g e a r ta o
The oscillating rear axle comprises a bracket having pads for holding the axle.
Further objects and advantages of this invention will be more apparent from the ensuing d e s c r i p t i o n w h e n r e a d i n c o n j u n c t i o n w i t. h t h e a c c o m p a n y i n q d r a w i n g s a n d w h e r e i. n s
Fig. 1 & 2 show the hydrostatic transmission of the p i" e s e n t invention.,
F i. g „ 3s h o w s t h e a r r" a n g e m e n t f o r t h e o s c i. 11 a t i n g
rear a x1e.
Referring to the drawings,, the hydrostatic transmission for use as a drive for a crane comprises a hydraulic fluid tank T having an inlet. 1 for introduction of hydraulic fluid and a vent 2,, Tank T
has a window 3 for display of the hydraulic fluid within tank T,, Such features of a hydraulic tank are known in the art and do not form a concept of the present invention .,
S p e c i f i. c a 1 1 y , t h e p r e s e n t i n v e n t i o n r e s i d e s in the provision of a hydraulic pump 21 having a return port 17 connected to return port 22 of tank T through a hose 18,, Pump 21 has a suction port 19a connected to suction port 19 of tank T through hose 20., Pump 21 has a first port 13 and a second port 13a, any one of said ports being an outlet and the other an inlet depending upon the direction of movement of the main carriage. Thus, and if a forward movement is considered,, port 13 may be the discharge port and port 13a be the inlet port of pump 21,, If a reverse movement of the carriage is considered,, port 13 may be the inlet port and port 13a be the discharge port,, Such a working position of the ports is controlled by a lever 8 adapted to be actuated by the driver through an actuator &„
Ports 13 and 13a are connected to corresponding ports 12 and 16 of a hydraulic motor 7 through hoses Hi and H2 respectively. The out put shaft of hydraulic motor 7 is coupled to an intermediate gear box 4 adapted to provide different fixed speeds to shaft SI,,
Shaft SI drives rear axle A. for providing a drive to the rear wheels.
Reference is made to the rear axle., In the known systems the rear axle is supported by the main chassis throuqh leaf springs,, A disadvantage associated with such a system is that one of the wheels may not be in co fit act with the road surface,, when traversing over a n u n even s u rf ac e„
Such a disadvantage is obviated by the oscillating axle system of the present invention. For this purpose,, reference is made to Fig. 3, and wherein a bracket B is provided for mounting of axle A Brackets B is welded to the chassis of the carriage. Pads P are held to brackets B on either side of axle A so as to allow an oscillating movement of the axle.

WE CLAIM:
1. A hydrostatic transmission system comprising a main carriage
with a cabin, a boom mounted on said carriage, characterized in
that a hydrostatic transmission means is provided for imparting a
movement or displacement to said carriage, an oscillating rear axle
with said carriage, said hydrostatic transmission means
comprising a hydraulic pump connected to a hydraulic motor, a
lever provided with said pump to allow a forward or reverse
movement of said carriage, an intermediate gear box connected to
said motor to provided a drive to the rear axle through a shaft.
2. A hydrostatic transmission system as claimed in claim 1 wherein
said pump is connected to a hydraulic tank, said tank having a
suction port connected to a suction port of said pump, a return
port of the motor connected to the return port of said tank.
3. A hydrostatic transmission system as claimed in claim 2 wherein
said pump has a first and second ports connected to first and
second ports of said motor, said first and second ports being an
inlet or out port at any one working status.
4. A hydrostatic transmission system as claimed in claim 2 & 3
comprising a lever provided with said pump, said lever allowing
said first or second port to be in inlet or outlet status.
5. A hydrostatic transmission system as claimed in claim 1
comprising brackets held to the chassis of said carriage, said axle
held to said brackets through pads.
6. A hydrostatic transmission system substantially as herein
described & illustrated.