Control system of industrial truck and controlling method of the same

• US 7,278,508 B2
• Filed: 05/28/2004
• Issued: 10/09/2007
• Est. Priority Date: 05/30/2003
• Status: Expired due to Fees

• Current Assignee: Mitsubishi Heavy Industries, Ltd., New Market Solutions LLC, Nissan Motor Co., Ltd.
• Original Assignee: Mitsubishi Heavy Industries, Ltd., Nissan Motor Co., Ltd.
• Inventors: Saito, Toru, Ueda, Katsumi, Nakada, Takuya
• Primary Examiner(s): Ellis; Christopher P.
• Assistant Examiner(s): WALTERS, JOHN DANIEL
• Application Number:
  US10/855,442
• Publication Number:
  US 20040261609A1
• Time in Patent Office: 1,229 Days
• Field of Search: 180/305, 180/306, 180/307, 180/308
• US Class Current: 180/305
• CPC Class Codes: B66F 9/20 Means for actuating or controlling masts, platforms, or forks power take-off from vehicle transmissions, combined with vehicle propulsion systems B60K

Abstract

A control system of an industrial truck includes a first switch, a second switch and a hydraulic circuit. The first switch detects whether an operator sits on a seat, and carries out a first operation based on the result. The second switch detects whether a device for operating an actuator is operated, and carries out a second operation based on the result. The hydraulic circuit is used for operating the actuator. It a control valve, a first circulating line, a hydraulic line and a drive lock valve. The control valve includes a spool whose position is changed by the device. The first circulating line includes the control valve, through which the hydraulic fluid circulates. The hydraulic line connects the spool with the actuator. The drive lock valve is provided for the hydraulic line and blocks the hydraulic line, based on the first operation and/or the second operation.

Claims

1. A control system of an industrial truck, comprising:

a first switch for an industrial truck body, said first switch being operable to detect whether or not an operator sits down on a seat and to carry out a first operation based upon a detection result by said first switch;

a second switch for the industrial truck body, said second switch being operable to detect whether or not a device for operating an actuator is being operated and to carry out a second operation based upon a detection result by said second switch; and

a hydraulic circuit which is usable for operating the actuator, said hydraulic circuit containing hydraulic fluid, and said hydraulic circuit including;

a control valve including a spool whose position is changeable by the device for operating the actuator,

a first circulating line that includes said control valve, the hydraulic fluid being able to circulate through said first circulating line,

a hydraulic line usable to connect said spool with the actuator, the hydraulic fluid being able to pass through the hydraulic line,

a drive lock valve provided for said hydraulic line,

a second circulating line connected in parallel with said first circulating line, said second circulating line not including said control valve, wherein the hydraulic fluid can bypass said control valve through said second circulating line, and

an unloading valve operable in response to said first operation and included in said second circulating line,

wherein said drive lock valve is operable to block said hydraulic line based on one of said first operation and said first and second operations, and

wherein said unloading valve is operable to open to connect a point upstream of said unloading valve directly with a hydraulic fluid tank based on one of said first operation and said first and second operations.

2. The control system of claim 1, wherein said drive lock valve is operable to block said hydraulic valve in a closed position thereon when said first switch does not carry out the first operation.

3. The control system of claim 1, wherein the first operation comprises outputting a first signal indicating that the operator sits down on the seat and the second operation comprises outputting a second signal indicating that the device for operating an actuator is being operated.

4. The control system of claim 1, wherein the first operation is carried out when a predetermined time period has passed after a first status changes to a second status, said first status indicating that said first switch detects that the operator sits down on the seat, and said second status indicating that the operator does not sit down on the seat.

5. The control system of claim 1, wherein said unloading valve is structured and arranged to open to directly connect a point upstream of said unloading valve with said hydraulic fluid tank when said first switch does not carry out the first operation.

6. The control system of claim 1, further comprising a controller which is operable to control said drive lock valve and said unloading valve based on the one of said first operation and said first and second operations.

7. The control system of claim 1, wherein said second switch is operable to output an electric signal corresponding to operational positions of said device.

8. The control system of claim 1, wherein said actuator is operated using gravity against a machine element.

9. The control system of claim 8, wherein said machine element is one of a crane arm of a truck crane, a shovel of a shovel type excavator, a fork of a forklift truck, a ladder of a fire-fighting vehicle, a hatch of a refuse collector and a ramp of a car carrier.

10. A control method of an industrial truck, said industrial truck including:

a first switch for a body of the industrial truck,

a second switch for the body, and

a hydraulic circuit that is usable for operating an actuator of the industrial truck and that includes hydraulic fluid, the hydraulic circuit including;

a control valve including a spool whose position is changeable,

a first circulating line that includes the control valve, the hydraulic fluid being able to circulate through said first circulating line,

a hydraulic line usable to connect said spool with the actuator, the hydraulic fluid being able to pass through the hydraulic line,

a drive lock valve provided for the hydraulic line,

a second circulating line connected in parallel with the first circulating line, the second circulating line not including the control valve, wherein the hydraulic fluid can bypass the control valve through the second circulating line, and

an unloading valve included in the second circulating line said control method comprising;

(a) detecting with the first switch whether or not an operator sits down on a seat of the industrial truck and carrying out a first operation based upon a detection result of said detecting with the first switch;

(b) detecting with the second switch whether or not a device for operating the actuator is being operated and carrying out a second operation based upon a detection result of said detecting with the second switch;

(c) blocking the hydraulic line using the drive lock valve based on one of the first operation and the first and second operations; and

(d) opening the unloading valve to directly connect a point upstream of the unloading valve with a hydraulic fluid tank based on the one of the first operation and the first and second operations.

11. The control method of an industrial truck of claim 10, wherein said step (c) includes closing the drive lock valve to block the hydraulic line when the first switch does not carry out the first operation.

12. The control method of claim 10, wherein the first operation comprises outputting a first signal indicating that the operator sits on a seat of the industrial truck and the second operation comprises outputting a second signal indicating that the device for operating the actuator is being operated.

13. The control method of claim 10, wherein said step (a) includes:

(a1) detecting a first status in which the operator sits on the seat;

(a2) detecting a second status in which the operator does not sit on the seat; and

(a3) carrying out the first operation when a predetermined time period passes after the first status changes to the second status.

14. The control method of claim 10, wherein the first operation takes priority over the second operation in said step (c).

15. The control method of claim 10, wherein said actuator is operated by using gravity against a machine element.

16. The control method of claim 10, wherein said step (b) includes:

(b1) detecting whether or not the device for operating the actuator is being operated in a predetermined direction, and

(b2) carrying out the second operation when the device is being operated in the predetermined direction.

17. The control method of claim 10, wherein said step (d) includes opening the unloading valve to directly connect a point upstream of the unloading valve with the hydraulic fluid tank when the first switch does not carry out the first operation.