Hydraulic circuit with a cooling device

A hydraulic circuit with a cooling device including mainly two hydraulic cylinders, a cooling device in the form of a rectangular structure having two oil channels each for connecting to a hydraulic cylinder and a spare tiny passage to keep on connecting to the oil channels, a control valve to close and open the oil channels, a plurality of cooling fins formed perpendicular to a side of the cooling device, and a fan for fast cooling effect whereby the hydraulic cylinders can be driven for reciprocating movements in two opposite directions.

BACKGROUND OF THE INVENTION 
(a) Field of the Invention 
The present invention related to a hydraulic circuit with a cooling device 
including mainly two hydraulic cylinders, a cooling device in the form of 
a rectangular structure having two oil channels each for connecting to a 
hydraulic cylinder and a spare tiny passage to keep on connecting to the 
oil channels, a control valve to close and open the oil channels, a 
plurality of cooling fins formed perpendicular to a side of the cooling 
device, and a fan for fast cooling effect whereby the hydraulic cylinders 
can be driven for reciprocating movements in two opposite directions with 
controllable load for use in, for example, exercise equipment such as 
walking exercise machine, boat rower, or indoor bicycle. 
(b) Description of the Prior Art 
Conventionally each exercise equipment, such as walking exercise machine, 
boat rower, or indoor bicycle, uses two hydraulic cylinders connecting to 
pedals or oars to provide load for stepping or rowing by a control on 
hydraulic load. However, for each adjustment of hydraulic load, the 
hydraulic cylinders must be adjusted respectively. Moreover, the frequent 
operation of pistons results in rising of hydraulic oil temperature and 
consequently damages oil seals, and forcefully stepping or rowing without 
prior adjustment when their control valves are closed will result in 
damage to the hydraulic cylinders. 
SUMMARY OF THE INVENTION 
The main object of the present invention is to provide a hydraulic circuit 
with a cooling device including mainly two hydraulic cylinders, a cooling 
device in the form of a rectangular structure having two oil channels each 
for connecting to a hydraulic cylinder and a spare tiny passage to keep on 
connecting to the oil channels, and a control valve to close and open the 
oil channels so as to provide a precise control on hydraulic load of both 
the hydraulic cylinders simultaneously and the load of both the hydraulic 
cylinders can be easily adjusted by turning of a single control valve. 
Another object of the present invention is to provide a hydraulic circuit 
with a cooling device having a plurality of cooling fins formed 
perpendicular to a side of the cooling device, and a fan installed at an 
end of the cooling device for fast cooling effect when hydraulic oil 
temperature is rising in the oil channels in order to protect oil seals in 
the hydraulic cylinders from high temperature and to assure proper 
operation of the hydraulic cylinders. 
Another object of the present invention is to provide a hydraulic circuit 
with a cooling device having an appropriate tiny passage formed between 
the channels as a spare oil passage to keep on connecting to the channels 
even when the control valve is completely closed in order to maintain a 
thoroughly connection between the oil channels to assure that the 
cylinders will not burst when improper external force is applied to the 
cylinders.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
As shown in FIGS. 1 and 2, the present invention includes mainly a cooling 
device (1) for connecting to two hydraulic cylinders (2 and 2') via two 
hydraulic hoses (3 and 3'). These hydraulic hoses (3 and 3') are for 
flowing of hydraulic oil through the cooling device (1) to drive the 
hydraulic cylinders (2 and 2') for reciprocating movements in two opposite 
directions. The hydraulic cylinders (2 and 2') are substantially same with 
the conventional hydraulic cylinder, each of them has an oil outlet (21 or 
21') at a side of its wall, to which an elbow (22 or 22') is connected for 
connection of a hydraulic hose (3 or 3'). The present invention is mainly 
characterized by the provision of the cooling device (1), through which 
the said hydraulic hoses (3 and 3') are connected to an oil tank for 
operation of the hydraulic cylinders (2 and 2'). 
The cooling device (1) is in the form of an appropriate rectangular 
structure having two longitudinal oil channel (11 and 11'), one at each 
lateral side. A threaded bushing (111 or 111') is placed in the lower end 
of each of the oil channels (11 and 11') for fitting of a connector (31 or 
31') connecting to each of the hydraulic hoses (3 and 3'). The upper ends 
of both oil channels (11 and 11') are closed, but each of them has a hole 
(12 or 12') to connect to the other so that the two oil channels (11 and 
11') are connecting to each other via the holes (12 and 12'). A threaded 
cavity (13) is formed at a side of the cooling device (1) to connect to 
the holes (12 and 12'). A control valve (14) is installed in the threaded 
cavity (13) to control flowing of oil between the oil channels (11 and 
11') through the holes (12 and 12') in order to adjust hydraulic oil flow 
rate, and consequently adjust load applied to the respective hydraulic 
cylinders (2 and 2'). 
Following the operations of the hydraulic cylinders, the temperature of 
hydraulic oil flowing between the oil channels (11 and 11') is rising. 
Therefore, the cooling device (1) is preferably made of material having 
good heat dissipation property, and has a plurality of cooling fins (15) 
formed perpendicular to the body of the cooling device (1) and a cooling 
fan (16) driven by a motor (161) at an end of the cooling device (1) to 
provide a good cooling effect. 
To prevent from bursting of cylinders (2 and 2') due to wrong operation 
when the control valve (14) is completely closed, an appropriate tiny 
passage (17) is formed between the channels (11 and 11') as a spare oil 
passage to keep on connecting to the channels (11 and 11') regardless of 
whether the control valve (14) is opened or closed, as shown in FIG. 3. 
The tiny passage (17) is designed to maintain a thoroughly connection 
between the oil channels (11 and 11') to assure that the cylinders (2 and 
2') will not burst when improper external force is applied to the 
cylinders (2 and 2'). 
The hydraulic circuit with a cooling device described above is mainly used 
in sporting equipment, such as walking exercise machine, boat rower, 
indoor bicycle, and the like, in which two cylinders are used for pedals 
or oars to provide a certain load for the pedals or oars to perform a 
regular vertically reciprocating movement. As shown in FIG. 4 which shows 
an application of the present invention in walking exercise machine, the 
cooling device (1) is installed by fitting the motor (161) to a frame (5) 
of the walking exercise machine by means of a fixing element (4). The 
control valve (14) is fixed at the frame (5) for adjustment of flow rate. 
The control valve (14) has an appropriate thread (141) on its body which 
has an appropriate tapered front end for fixing into the threaded cavity 
(13) at the cooling device (1) with an oil seal (142). By turning of the 
valve body in normal or reverse direction, the load between the oil 
channels (11 and 11') can be adjusted. An appropriate adapter (143) and 
knob (143) are incorporated with the valve body for adjustment of load by 
turning the knob (144) directly.