Fluid handling – Self-proportioning or correlating systems – Self-controlled branched flow systems
Reexamination Certificate
2000-02-28
2002-04-16
Chambers, A. Michael (Department: 3753)
Fluid handling
Self-proportioning or correlating systems
Self-controlled branched flow systems
C137S119010, C137S119080
Reexamination Certificate
active
06371150
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a flow dividing valve. More specifically, the invention relates to a flow dividing valve capable of freely setting the ratio of flow rates for dividing the fluid in an inlet port into a plurality of outlet ports.
BACKGROUND ART
A flow dividing valve is capable of dividing the fluid in an inlet port into a plurality of outlet ports at a predetermined ratio of flow rates irrespective of the pressures in the outlet ports. This enables, accordingly, a stable flow rate to be fed to the hydraulic actuators in a plurality of systems by using a single oil hydraulic pump, making it possible to simplify the circuit and to decrease the cost of the apparatus. This flow dividing valve is used for actuating an operation apparatus equipped with hydraulic actuators and for actuating an attachment fitted to the operation apparatus in, for example, a construction machine by the fluid discharged from a single hydraulic pump.
With reference to
FIG. 3
, the flow dividing valve generally designated at a numeral
20
includes a flow rate control spool
24
inserted in a valve body
22
, and a needle
26
provided in a flow passage communicated with an inlet port P of the valve body
22
to form a throttle. The flow rate control spool
24
is inserted in a spool slide hole
22
a formed in the valve body
22
to freely slide therein, and is pushed, by a compression spring
25
arranged on one end side (left end side in
FIG. 3
) of the low rate control spool
24
, against the side of the other end thereof. The spool slide hole
22
a
communicates with the inlet port P, an outlet port A and an outlet port B. Part of the fluid in the inlet port P flows into the outlet port B through the needle
26
and the flow rate control spool
24
, and the remainder thereof flows into the outlet port A through the flow rate control spool
24
. Due to the throttle effect, there is produced a pressure difference between the upstream side of the needle
26
and the downstream side thereof. The pressure on the downstream side is guided to an end where the compression spring
25
of the flow rate control spool
24
is arranged, and the pressure on the upstream side is guided to the other end of the flow rate control spool
24
. The needle
26
is attached to the valve body
22
via its external thread
26
a
. The extent (opening degree) of the throttle is controlled by adjusting the screw-in amount of the needle
26
. The needle
26
that has been adjusted for its screw-in amount is secured by a lock nut
26
b.
The flow rate control spool
24
slides in the spool slide hole
22
a
due to a pressure difference between the upstream side and the downstream side, which is determined by the opening degree of the needle
26
, whereby the openings to the outlet port A and to the outlet port B are adjusted and accordingly, the flow is adjusted and divided. When the pressures change in the outlet port A and in the outlet port B, the flow rates to these ports through the flow rate control spool
24
undergo a change depending on a change in the pressure difference before and after passing through the flow rate control spool
24
. Consequently, the flow rate of the fluid flowing into the needle
26
changes to cause a change in the pressure difference between the upstream side and the downstream side of the needle
26
. According to this change in the difference in the pressure, the flow rate control spool
24
so slides as to maintain a predetermined ratio of flow rates despite of changes in the pressures in the outlet port A and in the outlet port B. Accordingly, the ratio of flow rates in the outlet port A and in the outlet port B is determined by the throttle opening degree of the needle
26
.
DISCLOSURE OF THE INVENTION
The above-mentioned conventional flow dividing valve involves the following problem that must be solved. That is, the ratio of flow rates is manually set by adjusting the opening degree of the needle, making it difficult to instantaneously and arbitrarily accomplish the setting in accordance with the operating amount of the operation lever as desired by an operator. It has therefore been desired to provide a flow dividing valve capable of instantaneously changing the ratio of flow rates.
The present invention has been accomplished in view of the above-mentioned fact, and its technical subject is to provide a flow dividing valve which enables the ratio of flow rates to be instantaneously and continuously set so that the fluid in the inlet port can be divided at a predetermined ratio of flow rates to a plurality of outlet ports.
In order to solve the above-mentioned technical problem according to the present invention, there is provided a flow dividing valve for dividing the fluid in an inlet port into a plurality of outlet ports irrespective of the pressures in the outlet ports, comprising:
a flow rate control spool for dividing the flow rate of the fluid in said inlet port into a predetermined ratio of flow rates, and
a flow rate ratio-setting spool for setting said ratio of flow rates to control said flow rate control spool, said flow rate ratio-setting spool being operated by a control signal from an external unit.
The ratio of flow rates is set by operating, by means of a control signal, the flow rate ratio-setting spool that controls the flow rate control spool.
In a preferred embodiment, the ratio of flow rates can be continuously set to an arbitrary value. A pilot hydraulic pressure is used as said control signal. The flow rate ratio-setting spool is provided with a variable throttle that is adjusted by said control signal.
The ratio of flow rates is instantaneously and continuously set to an arbitrary value by the control signal. The ratio of flow rates is instantaneously set in accordance with the magnitude of the pilot hydraulic pressure that is the control signal. Further, the ratio of flow rates is set depending on the throttle opening degree of the variable throttle that is adjusted by the control signal.
REFERENCES:
patent: 2868217 (1959-01-01), Faisandier
patent: 3730206 (1973-05-01), Sirek
patent: 3788339 (1974-01-01), Denker
patent: 4216702 (1980-08-01), Brundidge et al.
patent: 4285268 (1981-08-01), Deckler
patent: 4616671 (1986-10-01), Steinkuhl et al.
patent: 4712649 (1987-12-01), Saam
patent: 4921072 (1990-05-01), Divisi
patent: 5509391 (1996-04-01), DeGroot
patent: 54-74523 (1979-06-01), None
patent: 63-139302 (1988-09-01), None
patent: 5-44704 (1993-02-01), None
English Abstract of JP 63-139302.
Chambers A. Michael
Millen White Zelano & Branigan P.C.
Shin Caterpillar Mitsubishi Ltd.
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