Travel control device for excavators
First Claim
1. A travel control device for excavators, comprising:
- at least one main fluid pump (1, 2) and an auxiliary pump (4) each for discharging a hydraulic flow;
left and right travel motors (12, 14) driven by the hydraulic flow of the main fluid pump (1, 2) and respectively provided with speed changing mechanisms (13, 15);
travel control spools (16, 18) for controlling the hydraulic flow to the left and right travel motors (12, 14);
manual travel control devices (20, 22) for receiving the hydraulic flow from the auxiliary pump (4) and supplying a travel control signal pressure to the travel control spools (16, 18);
a high speed shifting valve (26) provided on a high speed signal line (24) interconnecting the auxiliary pump (4) and the speed changing mechanisms (13, 15) for cutting off or transmitting a high speed signal pressure to the speed changing mechanisms (13, 15);
a travel signal detection means (32) for detecting the travel control signal pressure outputted from the manual travel control devices (20, 22); and
a shutoff valve (28) provided on the high speed signal line (24) in a serial relationship with the high speed shifting valve (26) for closing the high speed signal line (24) to keep the speed changing mechanisms (13, 15) in a low speed condition if the travel control signal pressure supplied from the travel signal detection means (32) is no greater than a predetermined pressure value and for opening the high speed signal line (24) to keep the speed changing mechanisms (13, 15) in a high speed condition if the travel control signal pressure supplied from the travel signal detection means (32) exceeds the predetermined pressure value.
1 Assignment
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Accused Products
Abstract
A travel control device enables a crawler type hydraulic excavator to start slowly regardless of the preset speed ratio whenever the manipulation amount of a manual travel control device is small. The travel control device includes left and right travel motors respectively provided with speed changing mechanisms, a high speed shifting valve provided on a high speed signal line for cutting off or transmitting a high speed signal pressure to the speed changing mechanisms, a travel signal detection means for detecting a travel control signal pressure outputted from manual travel control devices. A shutoff valve is provided on the high speed signal line for closing or opening the high speed signal line to keep the speed changing mechanisms in a low speed condition or a high speed condition depending on the magnitude of the travel control signal pressure supplied from the travel signal detection means.
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Citations
5 Claims
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1. A travel control device for excavators, comprising:
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at least one main fluid pump (1, 2) and an auxiliary pump (4) each for discharging a hydraulic flow;
left and right travel motors (12, 14) driven by the hydraulic flow of the main fluid pump (1, 2) and respectively provided with speed changing mechanisms (13, 15);
travel control spools (16, 18) for controlling the hydraulic flow to the left and right travel motors (12, 14);
manual travel control devices (20, 22) for receiving the hydraulic flow from the auxiliary pump (4) and supplying a travel control signal pressure to the travel control spools (16, 18);
a high speed shifting valve (26) provided on a high speed signal line (24) interconnecting the auxiliary pump (4) and the speed changing mechanisms (13, 15) for cutting off or transmitting a high speed signal pressure to the speed changing mechanisms (13, 15);
a travel signal detection means (32) for detecting the travel control signal pressure outputted from the manual travel control devices (20, 22); and
a shutoff valve (28) provided on the high speed signal line (24) in a serial relationship with the high speed shifting valve (26) for closing the high speed signal line (24) to keep the speed changing mechanisms (13, 15) in a low speed condition if the travel control signal pressure supplied from the travel signal detection means (32) is no greater than a predetermined pressure value and for opening the high speed signal line (24) to keep the speed changing mechanisms (13, 15) in a high speed condition if the travel control signal pressure supplied from the travel signal detection means (32) exceeds the predetermined pressure value. - View Dependent Claims (2, 3, 4)
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5. A travel control device for excavators, comprising:
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at least one main fluid pump (1, 2) and an auxiliary pump (4) each for discharging a hydraulic flow;
left and right travel motors (12, 14) driven by the hydraulic flow of the main fluid pump (1, 2) and respectively provided with speed changing mechanisms (13, 15);
travel control spools (16, 18) for controlling the hydraulic flow to the left and right travel motors (12, 14);
electric travel control devices (20, 22) for generating an electric current in proportion to the amount of displacement thereof;
a high speed shifting valve (26) provided on a high speed signal line (24) interconnecting the auxiliary pump (4) and the speed changing mechanisms (13, 15) for cutting off or transmitting a high speed signal pressure to the speed changing mechanisms (13, 15);
a travel signal detection means (32) for detecting the magnitude of the electric current outputted from the electric travel control devices (20, 22); and
a solenoid-operated shutoff valve (28) provided on the high speed signal line (24) in a serial relationship with the high speed shifting valve (26) for closing the high speed signal line (24) to keep the speed changing mechanisms (13, 15) in a low speed condition if the electric current detected by the travel signal detection means (32) is no greater than a predetermined current value and for opening the high speed signal line (24) to keep the speed changing mechanisms (13, 15) in a high speed condition if the electric current detected by the travel signal detection means (32) exceeds the predetermined current value.
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Specification