Drive arrangement in a pneumatic power tool

Patent metadata

Field	Value
Publication number	US-9751177-B2
Application number	US-201214356094-A
Country	US
Kind code	B2
Filing date	Oct 25, 2012
Priority date	Nov 4, 2011
Publication date	Sep 5, 2017
Grant date	Sep 5, 2017

Abstract

A drive arrangement in a pneumatic power tool includes a pneumatic motor with an output shaft, and a spindle for mounting a cutting element and which externally includes both a thread and an axial groove. A drive rotation of the spindle is driven by a drive gear that is engaged with the axial groove on the spindle and that is drivingly connected to the output shaft so as to rotate at a constant speed with respect to the output shaft. A feed gear is threaded upon the spindle and may be rotated with respect to the spindle in order to advance and retract the spindle. The feed gear is driven by one intermediate feed gear which is interchangeably drivingly connectable to the output shaft via a first and a second gear connection, respectively, so as to advance or retract the spindle.

First claim

The invention claimed is:

1. A drive arrangement in a pneumatic power tool which includes a pneumatic motor, said drive arrangement comprising:
a spindle for mounting a cutting element, said spindle being drivingly connected to said pneumatic motor and said spindle externally including a thread and an axial groove;
a drive gear for driving a drive rotation of said spindle, said drive gear being engaged with the axial groove on said spindle and being drivingly connected to the pneumatic motor so as to rotate at a constant rotational speed with respect to a motor output shaft; and
a feed gear threaded upon said spindle, said feed gear being rotatable with respect to the spindle to advance and retract said spindle, and said feed gear being driven by an intermediate feed gear which is interchangeably drivingly connectable to the pneumatic motor via a first and a second gear connection, respectively;
wherein the intermediate feed gear is arranged to drive the feed gear at a slightly higher rotational speed than the constant rotational speed of the drive gear so as to advance the spindle with respect to the feed gear in the first gear connection, and to drive the feed gear at a lower rotational speed than the constant rotational speed of the drive gear so as to retract the spindle with respect to the feed gear in the second gear connection, and
wherein an intermediate drive gear is drivingly connected to the pneumatic motor and journalled around a first gear shaft to rotate freely with respect to the first gear shaft, said intermediate drive gear being in toothed engagement with the drive gear, and said intermediate feed gear being in toothed engagement with the feed gear and lodged to slide coaxially along said first gear shaft between a first gear position in which it is engaged to the first gear shaft and a second gear position in which it is engaged to the intermediate drive gear, and wherein the first and second gear position of the intermediate feed gear correspond to the first and second gear connection, respectively.

2. The drive arrangement according to claim 1 , wherein a second gear shaft is arranged to drive the intermediate drive gear via a direct engagement, and to drive the first gear shaft via separate coupling parts, and wherein the first gear shaft is arranged to rotate at a higher rotational speed than the intermediate drive gear.

3. The drive arrangement according to claim 2 , wherein the separate coupling parts comprise a clutch sleeve which is rotationally engaged to the second gear shaft and lodged to slide coaxially along the second gear shaft, wherein the clutch sleeve is spring loaded by a torque limiting spring with a spring action (F A ) towards a smoothly toothed engagement with a second coupling that, in turn, is drivingly engaged with a first coupling of the first gear shaft, and wherein said smoothly toothed engagement is broken if a torque (T) acting between the clutch sleeve and the second coupling exceeds a value of a threshold torque (T A ) defined by the spring action (F A ) on the clutch sleeve.

4. The drive arrangement according to claim 3 , wherein the driving engagement between the first coupling and the second coupling is achieved by an exchangeable feed cassette including a primary feed cassette gear and an interconnected secondary feed cassette gear, and wherein a first gear ratio may be achieved by engaging the primary feed cassette gear to the first coupling and the secondary feed cassette gear to the second coupling, and a second different gear ratio may be achieved by engaging the primary feed cassette gear to the second coupling and the secondary feed cassette gear to the first coupling.

5. The drive arrangement according to claim 3 , wherein a retraction spring is arranged to push the intermediate feed gear into the second gear position in which it is engaged with the intermediate drive gear, and wherein a pneumatic pressure is arranged in a sealed chamber to act in an opposite direction on the intermediate feed gear to push the intermediate feed gear into the second first gear position in which the intermediate feed gear is engaged with the first gear shaft and not with the intermediate drive gear, said pneumatic pressure being adapted to override the action of the retraction spring when applied.

6. The drive arrangement according to claim 5 , wherein the clutch sleeve is pneumatically connected to the sealed chamber in such a way that a movement of the clutch sleeve when it slides against the action of the torque limiting spring and its smoothly toothed engagement with the second coupling part is broken, will release the pressure in the sealed chamber, whereby the intermediate feed gear will slide out of the first gear position in which it is engaged with the first gear shaft and into the second gear position in which it is engaged with the intermediate drive gear.

7. The drive arrangement according to claim 6 , wherein the intermediate feed gear is axially connected to a cylinder via a bearing, said cylinder being lodged to slide coaxially along the first gear shaft and is acted on by the retraction spring and in an opposite direction by the pressure in the sealed chamber, and wherein an axial position of the intermediate feed gear is directly governed by a position of the cylinder and indirectly by the action of the retraction spring and the pressure in the sealed chamber acting on the cylinder.

8. The drive arrangement according to claim 7 , wherein the engagement between the intermediate feed gear and the intermediate drive gear is achieved by a smoothly toothed engagement which is held together by the action of the retraction spring.

9. The drive arrangement according to claim 8 , wherein a retaining mechanism is arranged to restrict the intermediate feed gear from moving out of the engagement to the intermediate drive gear during an initial phase of the retraction of the spindle.

10. The drive arrangement according to claim 8 , wherein the position of the cylinder is pneumatically connected to a control unit of the tool, and wherein the cylinder produces a pneumatic signal to the control unit to interrupt an operation when the smoothly toothed engagement between the intermediate feed gear and the intermediate drive gear is broken and the cylinder slides against the action of the retraction spring.

11. The drive arrangement according to claim 10 , wherein the control unit sends a signal to close a main valve of the tool in response to an order to interrupt the operation.

12. The drive arrangement according to claim 1 , wherein a retraction spring is arranged to push the intermediate feed gear into the second gear position in which it is engaged with the intermediate drive gear, and wherein a pneumatic pressure is arranged in a sealed chamber to act in an opposite direction on the intermediate feed gear to push the intermediate feed gear into the first gear position in which the intermediate feed gear is engaged with the first gear shaft and not with the intermediate drive gear, said pneumatic pressure being adapted to override the action of the retraction spring when applied.

13. A pneumatic power tool, comprising a pneumatic motor and the drive arrangement according claim 1 .

Assignees

• Atlas Copco Ind Technique Ab

Inventors

• Eriksson Ulf Mikael
• Georgsson Wilhelm Mattias

Classifications

• B23Q5/402

  in which screw or nut can both be driven · CPC title

• F16H25/205

  comprising alternate power paths, e.g. for fail safe back-up · CPC title

• F16H25/2018

  with both screw and nut being driven, i.e. screw and nut are both rotating · CPC title

• B23Q5/326 Primary

  screw-operated · CPC title

• B23Q5/348

  by means of clutches · CPC title