Fluid-pressure and analogous brake systems – With pump – Pressure control
Patent
1997-05-28
1999-03-23
Graham, Matthew C.
Fluid-pressure and analogous brake systems
With pump
Pressure control
303 2, F15B 1100
Patent
active
058849840
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a hydraulic braking apparatus which where a hydraulic motor is used as a motor for driving a construction machine or the like and tends to continue a pumping action due to the inertia of a load when an operating valve is returned to its neutral position to stop the motor, is adapted to limit a flow of high pressure fluid that is discharged from the hydraulic motor and to apply a braking force thereto.
BACKGROUND ART
There has hitherto been known a hydraulic braking apparatus as disclosed in Japanese Unexamined Utility Model Publication No. Hei 4-133003.
According to this prior art, a first and a second main circuit 3 and 4 which are included to connect a hydraulic motor 1 to an operating valve 2 are provided with a pair of check valves 5 and 5 and a braking valve 6. When the said hydraulic motor 1 is to be stopped upon returning the said operating valve 2 to its neutral position N, the said braking valve 6 will be brought into its blocking position so that it may limit a flow of the high pressure fluid that is discharged by the said hydraulic motor 1 with its pumping action to apply a braking force thereon. The said apparatus further includes a bi-directionally operating safety valve 7 provided on a short circuit path 8 which bridge a pair of portions 3a and 4a which are located in the said first and second main circuits 3 and 4, respectively, between the said hydraulic motor 1 and the said braking valve 6.
The above mentioned safety valve 7 will be held in a closed state by a spring 14, and it will be thrusted in an opening direction under a pressure of a first, a second pressure receiving portion 15, 16. It has a construction in which the said spring 14 is retained by a piston 17 that is adapted to slide by a predetermined distance and the said piston 17 has a pressure receiving chamber 18 which is connected to a pipe conduit 9, thus being capable of being provided with a high pressure fluid. The said safety valve 7 will be held in a low pressure set state when the said pressure receiving chamber 18 is not provided with the said high pressure fluid, and will be turned to a high pressure set state when the said pressure receiving chamber is provided with the said high pressure fluid to push the said spring 14 with the said piston 17.
This being the case, it can be seen that the said safety valve 7 has the two possible pressure stages, the first with a low pressure that is determined by the spring 14 alone and the second with a high pressure that develops when the said spring 14 is thrusted by the said piston 17.
The above mentioned pipe conduit 9 is connected to an internal passageway 10 of the said braking valve 6. For this reason, when the said operating valve 2 is set by a lever 13 in its neutral position N to allow a fluid that is discharged from a hydraulic pump 12 to flow into a reservoir 11, the above mentioned pressure receiving chamber 18 will not be supplied with a high pressure fluid. Also, when the said operating valve 2 is set to take a first position A or a second position B, the fluid discharged from the said hydraulic pump 12 will be supplied into the said pressure receiving chamber 18.
With such a hydraulic braking apparatus, a said safety valve 7 in the state in which a said operating valve 2 is in its neutral position N will have a relief initiation pressure that is reduced, thus capable of lowering the pressure in a said main circuit at the high pressure side while a said hydraulic motor 1 is performing a pumping action. This will allow any shock at the time of stopping the said hydraulic motor 1 to be reduced. On the other hand, the said safety valve 7 in the state in which the said operating valve 2 is set to take a said first position A or a said second position B will have a relief initiation pressure that is increased, thus capable of increasing the drive output of the said hydraulic motor 1.
With a hydraulic braking apparatus as constructed as mentioned above, however, it has been noted that due to the fact that the relief init
REFERENCES:
patent: 5312175 (1994-05-01), Ando et al.
patent: 5320419 (1994-06-01), Inagawa
patent: 5711582 (1998-07-01), Koike
patent: 5779328 (1998-07-01), Mergenthaler et al.
Arai Mitsuru
Hayashi Seita
Kado Hideki
Nunotani Sadao
Oshiro Mitsuru
Graham Matthew C.
Komatsu Ltd.
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