Clamping attachment with regenerative hydraulic circuit

1. A load handling clamp for a vehicle, said clamp comprising:

(a) a frame arranged for engagement with said vehicle;

(b) a clamp arm movably attached to said frame;

(c) an actuator arranged to move said clamp arm relative to said frame when fluid under pressure flows into a first actuator volume; and

(d) a modulator valve arranged to enable fluid to flow from a second actuator volume to said first actuator volume when fluid in said first actuator volume and fluid in said second actuator volume is pressurized and said second actuator volume is not connected to a source of pressurized fluid.

2. The load handling clamp of claim 1 further comprising a load check valve arranged to prevent a flow of fluid from said first actuator volume unless said fluid in said second actuator volume is pressurized.

3. The load handling clamp of claim 1 further comprising:

(a) a second check valve blocking a flow of fluid from said first actuator volume unless said second actuator volume is in fluid communication with said source of pressurized fluid; and

(b) a third check valve blocking fluid flow from said second actuator volume to a reservoir.

4. The load handling clamp of claim 3 further comprising a load check valve arranged to prevent a flow of fluid from said first actuator volume unless said fluid in said second actuator volume is pressurized.

5. The load handling clamp of claim 1 wherein said modulator valve blocks fluid flow between said second actuator volume and said first actuator volume when either one of said fluid pressure in said second actuator volume is less than said fluid pressure in said first actuator volume and said second actuator volume is in fluid communication with said source of pressurized fluid.

6. The load handling clamp of claim 5 further comprising a load check valve arranged to prevent a flow of fluid from said first actuator volume unless said fluid in said second actuator volume is pressurized.

7. The load handling clamp of claim 5 further comprising:

(a) a second check valve blocking a flow of fluid from said first actuator volume unless said second actuator volume is in fluid communication with said source of pressurized fluid; and

(b) a third check valve blocking fluid flow from said second actuator volume to a reservoir.

8. The load handling clamp of claim 7 further comprising a load check valve arranged to prevent a flow of fluid from said first actuator volume unless said fluid in said second actuator volume is pressurized.

9. A load handling clamp for a vehicle, said clamp comprising:

(a) a frame arranged to engage said vehicle;

(b) a clamp arm movably attached to said frame;

(c) a linear hydraulic actuator comprising:

(i) an actuator body attached to one of said frame and said clamp arm and having an interior volume;

(ii) an actuator rod attached proximate a first end to the other of said frame and said clamp arm;

(iii) a piston having a first end affixed to said actuator rod and a second end, a first portion of said interior volume of said actuator body and said second end of said piston defining a piston end volume of said actuator and a second portion of said interior volume of said actuator body, a portion of said rod and a portion of said first end of said piston defining a rod end volume of said actuator, said piston and said actuator rod slidable in said actuator body to move said clamp arm relative to said frame when a fluid under pressure flows into one of said piston end volume and said rod end volume and fluid flows out of the respective other of said rod end volume and said piston end volume in response to movement of said piston in said interior volume of said actuator; and

(d) a first check valve to block a flow of fluid from said rod end volume unless said rod end volume is connected to a source of pressurized fluid; and

(e) a modulator valve arranged to enable a flow of fluid from said rod end volume to said piston end volume only if said rod end volume is not connected to a source of pressurized fluid and a pressure of said fluid in said rod end volume is at least equal to a pressure of said fluid in said piston end volume.

10. The load clamping attachment of claim 9 further comprising a load check valve arranged to block a flow of fluid from said piston end volume unless said rod end volume is connected to a source of pressurized fluid.