Head valve system for air spring power tool
A power tool includes an air spring cylinder. A piston is movably positioned within the cylinder. A head valve assembly of the power tool includes a flapper valve configured to seal the air spring cylinder from an air accumulator when the flapper valve is in a non-firing position.
1. A power tool, comprising:
an air spring cylinder;
a piston located within the air spring cylinder;
an air accumulator; and
a head valve assembly including a flapper valve configured to seal the air spring cylinder from the air accumulator when the flapper valve is in a non-firing position.
2. The power tool of claim 1 , further comprising:
a cap defining a headspace configured to fluidically connect the air accumulator and the air spring cylinder, wherein
the flapper valve is configured to seal the air spring cylinder from the headspace in the non-firing position.
3. The power tool of claim 2 , wherein the head valve assembly further comprises:
a pivot including a pivot pin received within a pivot bore of the flapper valve, wherein the flapper valve is movable with respect to the pivot pin.
4. The power tool of claim 3 , wherein:
the air spring cylinder defines a drive axis;
the pivot pin has a circular cross section;
the pivot bore has an oval cross section; and
a major axis of the pivot bore extends along the drive axis.
5. The power tool of claim 3 , wherein the head valve assembly further comprises:
a plunger operably coupled with the flapper valve and configured to move the flapper valve from the non-firing position to a firing position.
6. The power tool of claim 5 , wherein the plunger is further configured to move the flapper valve from the firing position to the non-firing position.
7. The power tool of claim 6 , wherein:
the air spring cylinder defines a drive axis extending upwardly and downwardly;
the plunger includes a neck positioned between fingers of the flapper valve;
the plunger is configured to move the flapper valve from the non-firing position to the firing position using a first shoulder portion of the plunger located beneath the fingers; and
the plunger is configured to move the flapper valve from the firing position to the non-firing position using a head of the plunger located above the fingers.
8. The power tool of claim 5 , further comprising:
a work contact element (WCE) assembly including a bearing portion aligned with a shaft of the plunger, the WCE assembly configured to move the plunger upwardly along a drive axis defined by the air spring cylinder when the power tool is pressed downwardly with the WCE assembly in contact with a workpiece.
9. The power tool of claim 8 , the WCE assembly further comprising a WCE spring configured to bias the WCE bearing portion downwardly along the drive axis, wherein:
the WCE spring has a spring constant selected to provide about 50% of a WCE actuation counter-force when the flapper valve is at the firing position; and
the plunger is configured to provide about 50% of the WCE actuation counter-force when the flapper valve is at the firing position.
10. A method of operating a power tool, comprising:
moving a flapper valve, of a head valve assembly, configured to seal an air spring cylinder from an air accumulator when the flapper valve is in a non-firing position, to a firing position;
disengaging a lifter gear from a rack fixedly attached to a piston positioned in the air spring cylinder; and
moving the piston within the air spring cylinder upon disengagement of the lifter gear from the rack using compressed air from the air accumulator thereby driving a fastener with a driver blade fixedly attached to the piston.
11. The method of claim 10 , wherein moving the flapper valve further comprises:
moving the flapper valve into a headspace defined by a cap, the headspace configured to fluidically connect the air accumulator and the air spring cylinder.
12. The method of claim 11 , wherein
the flapper valve is configured to seal the air spring cylinder from the headspace in the non-firing position.
13. The method of claim 11 , wherein moving the flapper valve further comprises:
pivoting the flapper valve using a pivot including a pivot pin received within a pivot bore of the flapper valve.
14. The method of claim 13 , wherein:
the air spring cylinder defines a drive axis;
the pivot pin has a circular cross section;
the pivot bore has an oval cross section;
a major axis of the pivot bore extends along the drive axis; and
pivoting the flapper valve comprises pivoting the pivot bore with the oval cross section about the pivot pin.
15. The method of claim 13 , further comprising:
moving the flapper valve to the firing position using a plunger operably coupled with the flapper valve.
16. The method of claim 15 , further comprising:
moving the flapper valve from the firing position to a non-firing position using the plunger after moving the piston within the air spring cylinder.
17. The method of claim 16 , wherein:
the air spring cylinder defines a drive axis extending upwardly and downwardly;
the plunger includes a neck positioned between fingers of the flapper valve;
moving the flapper valve to the firing position comprises moving the flapper valve to the firing position using a first shoulder portion of the plunger located beneath the fingers; and
moving the flapper valve from the firing position to the non-firing position comprises moving the flapper valve from the firing position to the non-firing position using a head of the plunger located above the fingers.
18. The method of claim 15 , further comprising:
pressing the power tool downwardly along a drive axis, defined by the air spring cylinder, while a work contact element (WCE) assembly is in contact with a workpiece; and
moving the plunger upwardly along the drive axis with a bearing portion of the WCE assembly contacting a shaft of the plunger to move the flapper valve to the firing position.
19. The method of claim 18 , further comprising:
providing about 50% of a WCE actuation counter-force when the flapper valve is at the firing position with a WCE spring of the WCE assembly, the WCE spring configured to bias the WCE assembly downwardly along the drive axis; and
providing about 50% of the WCE actuation counter-force when the flapper valve is at the firing position with the plunger.
20. The power tool of claim 1 wherein:
the head valve assembly further comprises a pivot including a pivot pin defining a pivot axis;
the air spring cylinder defines a drive axis; and
the pivot axis is not parallel to the drive axis.