Rotary knife with improved drive transmission

1. A rotary knife operable from a source of high pressure air, comprising:

a) a tubular handle assembly;

b) an annular blade having a blade edge at a first axial end and gear teeth formed around a perimeter of a second axial end;

c) a blade housing coupled to the tubular handle assembly that supports the annular blade for rotation about a central axis;

d) a pneumatic motor assembly supported by the handle assembly for driving the blade;

e) a connector assembly coupled to the pneumatic motor, the connector assembly including:

i) a first clamping member with an inner surface of axially decreasing extent;

ii) a second clamping member having an exterior surface of axially decreasing extent for engaging the inner surface of said first clamping member and further including a clamping surface, wherein axially pressing the second member into the first clamping member reduces the size of the clamping surface;

f) a drive shaft clamped in the clamping the surface of the connector assembly by axially pressing the second clamping member into the first clamping member; and

g) a pinion gear fixed to the drive shaft which meshes with the annular blade gear teeth to drive the annular blade upon rotation by the pneumatic motor assembly.

2. The rotary knife of claim 1 wherein the inner surface of axially decreasing extent is a conical surface.

3. The rotary knife of claim 1 wherein the outer surface of axially decreasing extent is a conical surface.

4. The rotary knife of claim 1 wherein the second clamping member is axially pressed into the first clamping member by tightening of a nut having internal threads that engage external threads of the first clamping member.

5. The rotary knife of claim 4 wherein the drive shaft extends through a central opening in the nut and the second clamping member is pressed into the first clamping member by an interior surface of the nut that surrounds the central opening.

6. A rotary knife operable from a source of high pressure air, comprising:

a) a tubular handle assembly;

b) an annular blade having a blade edge at a first axial end and gear teeth formed around a perimeter of a second axial end;

c) a blade housing coupled to the tubular handle assembly that supports the annular blade for rotation about a central axis;

d) a pneumatic motor assembly supported by the handle assembly for driving the blade;

e) a drive transmission assembly for transmitting drive from the motor to the annular blade, the drive transmission assembly comprising:

i) a connector having a first end coupled an output shaft of the pneumatic motor and a second end with a concavity having an inner surface of axially decreasing extent;

ii) a clamping member having an exterior surface of axially decreasing extent for engaging the inner surface of said connector and further including a clamping surface wherein axially pressing the clamping member into the concavity reduces the size of the inner surface;

iii) a drive shaft clamped against the clamping surface of the clamping member by axially pressing the clamping member into the concavity; and

iv) a pinion gear fixed to the drive shaft which meshes with the annular blade gear teeth to drive the annular blade upon rotation by the pneumatic motor assembly.

7. The rotary knife of claim 6 wherein the concavity of axially, decreasing extent is a conical concavity.

8. The rotary knife of claim 6 wherein the clamping member has a conical outer surface.

9. The rotary knife of claim 6 wherein the clamping member is axially pressed into the conical concavity by tightening of a nut having internal threads that engage external threads of the connector second end.

10. The rotary knife of claim 9 wherein the drive shaft extends through a central opening in the nut and the clamping member is pressed into the conical concavity by an interior surface of the nut that surrounds the central opening.

11. A rotary knife operable from a source of high pressure air, comprising:

a) a tubular handle assembly;

b) an annular blade having a blade edge at a first axial end and gear teeth formed around a perimeter of a second axial end;

c) a blade housing coupled to the tubular handle assembly that supports the annular blade for rotation about a central axis;

d) a pneumatic motor assembly supported by the handle assembly for driving the blade;

e) a drive transmission assembly for transmitting drive from the motor to the annular blade, the drive transmission assembly comprising:

i) a connector having a first end connected to an output shaft of the pneumatic motor and a second end with an inner conical surface;

ii) a clamping member having a conical exterior surface for engaging the conical surface and further including a clamping surface, wherein axially pressing the clamping member into the conical concavity reduces the size of the cylindrical inner surface;

iii) a drive shaft clamped in the clamping member by axially pressing the clamping member into the connector; and

iv) a pinion gear fixed to the drive shaft, the pinion gear meshes with the annular blade gear teeth to drive the annular blade upon rotation by the pneumatic motor assembly.

12. The rotary knife of claim 11 wherein the clamping member is axially pressed into the connector by tightening of a nut having internal threads that engage external threads of the connector second end.

13. The rotary knife of claim 12 wherein the drive shaft extends through a central opening in the nut and the clamping member is pressed into the conical concavity by an interior surface of the nut that surrounds the central opening.

14. A method of coupling a pinion gear to a rotary knife pneumatic motor, comprising:

a) inserting a drive shaft of the pinion gear into an opening in a clamping member having an exterior surface of axially decreasing extent;

b) inserting the clamping member into a concavity of axially decreasing extent defined in a member that rotates upon actuation of the pneumatic motor;

c) axially pressing the clamping member into the concavity to reduce the size of the opening in the clamping member to cause frictional engagement between the clamping member and the drive shaft to couple the pinion gear to the rotary knife pneumatic motor.

15. A method of coupling a pinion gear to a rotary knife pneumatic motor, comprising:

a) connecting a first end of a connector to a pneumatic motor drive motor;

b) inserting a drive shaft of the pinion gear through an opening in a clamping nut;

c) inserting the drive shaft into an opening in a collet;

d) inserting the collet into a conical opening in the second end of the connector;

e) tightening the clamping nut onto threads on an outer surface of the connector second end to axially press the collet axially into the conical opening to cause frictional engagement between the collet and the drive shaft to couple the pinion gear to the rotary knife pneumatic motor.