Control systems for the lifting moment of vehicle mounted booms

• US 5,538,149 A
• Filed: 10/26/1994
• Issued: 07/23/1996
• Est. Priority Date: 08/09/1993
• Status: Expired due to Term

• Current Assignee: Altec Industries Incorporated (Avon Protection Plc)
• Original Assignee: Altec Industries Incorporated (Avon Protection Plc)
• Inventors: Martin, Jay D.
• Primary Examiner(s): Merritt, Karen B.
• Assistant Examiner(s): Brahan, Thomas J.
• Application Number:
  US08/329,497
• Time in Patent Office: 636 Days
• Field of Search: 212/153, 212/155, 212/278, 212/280, 212/276, 212/270, 60/420, 60/459
• US Class Current: 212/278
• CPC Class Codes: B66C 23/54 with pneumatic or hydraulic motors, e.g. for actuating jib-cranes on tractors
• CPC Class Codes: B66C 23/905 electrical

Abstract

In a vehicle mounted digger derrick or crane, the moment applied to the boom by a lift cylinder is controlled in a customized manner to more fully utilize the structural strength of the machine at different working positions of the boom. In one embodiment, the moment is controlled by controlling the moment arm through a pivot link which carries the base end of the lift cylinder and which is pivoted by an auxiliary cylinder. In another embodiment, the force component of the moment is controlled in response to changes in the boom angle or moment sensed by a linear position transducer or other sensor.

Claims

1. In a machine having an elongated boom mounted on a rotational turntable for up and down pivotal movement to vary the angular orientation of the boom about a boom pivot axis, the improvement comprising:

a power cylinder connected between said turntable and boom, said cylinder having a piston subjected to fluid pressure on opposite sides to extend and retract the cylinder for raising and lowering the boom about said boom pivot axis;

means for sensing a quantity indicative of the distance component of the lifting moment applied by said cylinder to the boom about the boom pivot axis; and

means for varying the fluid pressure to which said piston is subjected to a plurality of different pressures in response to changes in said distance component to control the lifting moment applied to the boom by said cylinder.

2. The improvement of claim 1, wherein said varying means is effective to maintain the lifting moment at a substantially constant value as the angular orientation of the boom changes.

3. A method of controlling the moment load applied to an elongated boom mounted on a rotational turntable for pivotal movement about a boom pivot axis and raised and lowered through a working arc about the boom pivot axis by a power cylinder which is connected between the turntable and boom and which has a piston subjected to fluid pressure on opposite sides to extend and retract the cylinder, said method comprising the steps of:

sensing a quantity indicative of the distance component of the moment load applied by the cylinder to the boom about the boom pivot axis; and

controlling the fluid pressure applied to the piston in accordance with said distance component in a manner to maintain the lifting moment applied to the boom by the cylinder at a substantially constant level through a substantial portion of said working arc as the boom is pivoted up and down about the boom pivot axis.

4. In a machine having an elongated boom mounted on a rotational turntable for up and down pivotal movement to vary the angular orientation of the boom about a boom pivot axis, the improvement comprising:

a power cylinder connected between said turntable and boom, said cylinder having a piston subjected to fluid pressure on opposite sides to extend and retract the cylinder for raising and lowering the boom about said boom pivot axis;

means for sensing a quantity indicative of the distance component of the lifting moment applied by said cylinder to the boom about the boom pivot axis;

means for using said quantity to determine said distance component; and

means for varying the fluid pressure to which said piston is subjected to a plurality of different pressures in response to changes in said distance component to control the lifting moment applied to the boom by said cylinder.

5. A method of controlling the moment load applied to an elongated boom mounted on a rotational turntable for pivotal movement about a boom pivot axis and raised and lowered through a working arc about the boom pivot axis by a power cylinder which is connected between the turntable and boom and which has a piston subjected to fluid pressure on opposite sides to extend and retract the cylinder, said method comprising the steps of:

sensing a quantity which is indicative of the distance component of the moment load applied by the cylinder to the boom about the boom pivot axis;

determining said distance component from said quantity; and

controlling the fluid pressure applied to the piston in accordance with said distance component in a manner to maintain the lifting moment applied to the boom by the cylinder at a substantially constant level through a substantial portion of said working arc as the boom is pivoted up and down about the boom pivot axis.

6. In a machine having an elongated boom mounted on a rotational turntable for up and down pivotal movement to vary the angular orientation of the boom about a boom pivot axis, the improvement comprising:

a power cylinder connected between said turntable and boom, said cylinder having a piston subjected to fluid pressure on opposite sides to extend and retract the cylinder for raising and lowering the boom about said boom pivot axis;

means for sensing the angular orientation of the boom about said boom pivot axis; and

means responsive to the angular orientation of the boom for varying the fluid pressure to which said piston is subjected to a plurality of different pressures, thereby controlling the lifting moment applied to the boom by said cylinder.

7. The improvement of claim 6, wherein said varying means is effective to maintain the lifting moment at a substantially constant value as the angular orientation of the boom changes.

8. A method of controlling the moment load applied to an elongated boom mounted on a rotational turntable for pivotal movement about a boom pivot axis and raised and lowered through a working arc about the boom pivot axis by a power cylinder which is connected between the turntable and boom and which has a piston subjected to fluid pressure on opposite sides to extend and retract the cylinder, said method comprising the steps of:

sensing the angular orientation of the boom about said boom pivot axis; and

controlling the fluid pressure applied to the piston in accordance with said angular orientation in a manner to maintain the lifting moment applied to the boom by the cylinder at a substantially constant level throughout a substantial portion of the working arc as the boom is pivoted up and down about the boom pivot axis.

9. In a machine having an elongated boom mounted on a rotational turntable for up and down pivotal movement to vary the angular orientation of the boom about a boom pivot axis, the improvement comprising:

a power cylinder connected between said turntable and boom, said cylinder being subjected to fluid applied force in opposite directions to extend and retract the cylinder for raising and lowering the boom about said boom pivot axis;

means for sensing a quantity indicative of the distance component of the lifting moment applied by said cylinder to the boom about the boom pivot axis; and

means for varying the force to which said power cylinder is subjected to a plurality of different forces in response to changes in said quantity to control the lifting moment applied to the boom by said cylinder in a preselected way.