GB2375983A

GB2375983A - A hand tool machine with cutout clutch

Info

Publication number: GB2375983A
Application number: GB0210904A
Authority: GB
Inventors: Joachin Schmezer
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 2001-05-25
Filing date: 2002-05-13
Publication date: 2002-12-04
Anticipated expiration: 2022-05-13
Also published as: SE0201433D0; GB2375983B; GB0210904D0; SE0201433L; DE10125641A1; DE10125641C2; SE524130C2

Abstract

A hand tool machine, such as a pneumatically operable screwdriver, with which a tool may be rotated, comprises a cutout clutch 10 and a spring-loaded locking pin 14. The locking pin is held in its operating position by at least one locking element 18,20,22,24. For interrupting a drive connection when a torque is exceeded, the at least one locking element is deflectable counter to a spring force of a clutch spring 30, and the locking pin is displaceable into a bore 34 of the locking pin. The clutch spring is elastically deflectable in the direction of motion 32 of the locking element.

Description

Hand coral machine Background art

The invention proceeds from a hand tool machine according to the preamble of claim 1.

In pneumatically operable offset screwdrivers it is known to limit the torque with a cutout clutch and to interrupt a drive connection by means of the cutout clutch. In a collar of a drive shaft drivable by a motor axial bores are introduced, in which driving balls are supported. Supported on the drive shaft at a side of the collar of the drive shaft directed towards the motor is a cutout ring, which is spring-loaded in the direction of the collar and presses the driving balls axially through the axial bores into recesses of a cam surface, which is directed axially towards the collar, of a clutch part of the cutout clutch' which clutch part is supported on the drive shaft at the side of the collar remote from the motor. A torque of the drive shaft is transmitted via the driving balls to the clutch part and from the clutch part to a bevel wheel of a right-angle gear of the offset screwdriver.

In the drive shaft in the form of a hollow shaft a locking pin of the cutout clutch is supported? which is loaded in motor direction by means of a at the side directed towards the clutch part and remote from the motor by means of a helical compression spring. Introduced in clutch part direction into the locking pin at the side directed towards the motor is an axial blind hole bore, which opens in a radial through-bore of the locking pin. The axial blind hole bore is closed at the side directed towards the motor by means of a threaded pin,

adjacent to which is a straight pin, which is in communication with a cutout valve. Disposed in the axial blind hole bore of the locking pin is a reversing ball, which is loaded in the direction of the radial bore by means of a clutch spring, which is aligned in axial direction and supported against the threaded pin.

Disposed in the radial bore are inner locking balls, which project radially inwards into the axial bore and radially out beyond the locking pin into radial bores of the drive shaft and are supported against outer balls. The outer balls project radially out beyond the radial bores of the drive shaft and are supported against the cutout ring. By means of the locking balls the locking pin is held in its operating position.

If a predetermined torque is exceeded, the driving balls are displaced by means of the cam surface of the clutch part and the driving balls displace the cutout ring axially in the direction remote from the clutch part. The cutout ring acts with a radially inner cone surface upon the outer balls and displaces the outer and the inner balls radially inwards against the reversing ball, wherein the reversing ball is displaced axially relative to the motor against the clutch spring in the locking pin, and namely up to the point where the inner locking balls are fully retracted in the radial bore of the locking pin. The locking pin is then displaced in clutch part direction by compressed air present at the cutout valve and by a tension force of a valve spring of the cutout valve via the straight pin counter to the helical compression spring directed towards the clutch part, the cutout valve is closed and the air supply to the motor is interrupted.

When the transmitted torque drops, the driving balls are pressed by the spring-

loaded cutout ring in a positionally stable manner back into the recesses of the cam surface of the clutch part. The air pressure at the cutout valve drops, and

the locking pin is displaced back into its starting position in the direction remote from the clutch part by means of the helical compression spring directed towards the clutch part. The cutout valve is opened, and the inner locking halls are pressed radially out of the locking pin into their locking position by means of the clutch spring disposed in the locking pin and via the reversing ball.

To prevent rotation of the locking pin in the drive shaft, there is formed on the locking pin on the side directed towards the clutch part a hexagon insert bit, which engages into a hexagon socket formed on the drive shaft. Furthermore, there is introduced into the drive shaft at the side directed towards the motor a radial bore, in which a pin is introduced' which projects into the drive shaft in the form of a hollow shaft and which forms a stop for the locking pin and holds the latter, in the disassembled state of the drive shaft, in an axially loss-

protected manner in the drive shaft.

Advantages of the invention The invention proceeds from a hand tool machine, in particular a pneumatically operable screwdriver, with which a tool may be set in rotation, and having a cutout clutch, which comprises a spring-loaded locking pin, which is held in its operating position by means of at least one locking element, wherein for interrupting a drive connection when a torque is exceeded the locking element is deflectable counter to a spring force of a clutch spring and the locking pin is displaceable into its cutout position.

it is proposed that the clutch spring is elastically deflectable in the direction of motion of the locking element. A reversing means and an axial bore in the locking pin as well as a means of closing Me axial bore may be avoided and additional components, assembly effort and weight may be saved. In particular,

it is moreover possible to achieve a locking; pin, which is easy to manufacture and inexpensive.

The clutch spring may act via an intermediate component, em via an intermediate component forming a spring support, or advantageously directly upon the locking element.

When the locking element is guided in a radial channel in the locking pin and when the clutch spring is disposed in the radial channel, it is possible to achieve a simple design, which substantially allows recourse to already known standard components. In principle, however, other designs deemed meaningful by the person skilled in the art are also conceivable, such as e.g. a design with channels extending obliquely relative to the locking pin etc. If the channel is closed at one end, locking elements may be spared, and with few locking elements an advantageous function is achievable. The manufacturing outlay of the locking pin may moreover be reduced. Re-working of a second opening at the outer periphery of the locking pin may no longer apply. In addition, a space-saving cutout clutch particularly suitable for small hand tool machines may be achieved. Although the channel may be introduced into the locking pin by various methods, it is introduced in a particularly inexpensive manner by a drilling method and is preferably formed by a blind hole bore.

The clutch spring may moreover be formed by various springs, which appear meaningful to the person skilled in the art and are made of different materials such as e.g. rubber or spring steel etc., and have various structural shapes, e.g a leaf spring etc. However, if the spring is formed by a helical compression

spring, this advantageously allows recourse to inexpensive standard components. In a further refinement of the invention it is proposed that an axial stop element of the locking pin is constructed integrally with an anti-rotation element of the locking pin. Additional components may be spared and it is possible to avoid a cost-intensive external contour of the locking pin and a contour, corresponding with said external contour, of a bearing component of the locking pin' in particular of a drive shaft. The stop element is in said case advantageously formed by a pin' which engages into a longitudinal groove of the locking pin.

The solution according to the invention may be used with all hand tool machines deemed suitable for said purpose by the person skilled in the art, e.g. the locking pin may be used to interrupt a power supply of an electric motor.

Preferably, however, the solution according to the invention is applicable to pneumatically operated hand tool machines' such as e.g. pneumatically operated offset screwdrivers, in which the locking pin may be used in a particularly advantageous manner to operate a pneumatic cutout valve.

Drawings Furler advantages arise from the following description of the drawings. In the

drawings embodiments of the invention are illustrated. The drawings, the description and the claims contain numerous features in combination. The

person skilled in the art will expediently consider the features also individually and combine them into meaningful further combinations.

The drawings show: Fig. I a side View Offal. ollset screwdriver, Fig. 2 an enlarged cutout II from Fig. 1 and Fig. 3 an alternative cutout clutch to Fig. 2, Description of the embodiments

Fig. 1 shows a side view of a pneumatically operated offset screwdriver. The offset screwdriver has in a housing part 46 a drive shaft 44 (Fig. 2), which is driven via a rotor (not shown in detail) and wa a planet carrier 42 of a planetary gear. The planet carrier 42 engages with a shaft portion, on which a hexagon insert bit is formed, into the drive shaft 44 in the form of a hollow shaft at an end of the latter directed towards the motor and is non-rotatably connected by the hexagon insert bit in a non-rotatable manner to a hexagon socket formed on the drive shaft.

A torque transmissible by the offset screwdriver is determined by a cutout clutch 10 which, when a set torque is exceeded, interrupts a drive connection between the drive shaft 44 and a shaft 5Q' which is nonrotatably connected to a bevel wheel, of a right-angle gear of the offset screwdriver.

Introduced in a collar 48 of the drive shaft 44 are axial bores 52, in which driving balls 54 are supported. Supported on the drive shaft 44 at a side of the collar 48 of the drive shaft 44 directed towards the motor is a Cutout ring 58, which is spring-loaded in the direction of the collar 48 by a helical compression spring 56 and which presses the driving balls 54 axially through the axial bores 52 into recesses 60 of a cam surface 62, which is directed axially towards the

collar 48, of a clutch part 64 of the cutout clutch 10, which clutch part is supported on the drive shaft 44 at the side of the collar 48 remote from the motor. In axial direction the clutch part 64 is secured by detent balls 86 on the drive shaft 44. The detent balls 86 are disposed radially between the clutch part 64 and the drive shall 44 and engage radially inwards into a peripheral groove 88 disposed at the outer periphery of the drive shaft 44 and radially outwards into a peripheral groove 90 disposed at the inner periphery of the clutch part 64.

During assembly, after the clutch part 64 has been slipped onto the drive shah 44, the detent balls 86 are introduced via a radial bore 92 into the peripheral grooves 88, 90. Then the radial bore 92 is closed by means of the cover 94.

A torque is transmitted from the drive shaft 44 via the driving balls 54 to the clutch part 64 and Mom the clutch part 64 to the shaft 50 of the bevel wheel.

The shalt 50 is inserted into an axial bore of the clutch part 64, and the shaft 50 and the clutch part 64 are non-rotatably connected to one another by a hexagon insert bit 68 formed on the shaft 50 and by a hexagon socket 66 formed on the clutch part 64.

In the drive shaft 44 in the form of a hollow shaft a locking pin 14 of the cutout clutch 10 is supported? which is loaded axially in motor direction and/or in the direction remote from the clutch part 64 by means of a at the side directed towards the clutch part 64 and/or remote from the motor by means of a helical compression spring 70.

Introduced into the locking pin 14 is a radial bore 34, in which a clutch spring 30 in the form of a helical compression spring is disposed, which acts in a radially outward direction with its ends in each case directly upon an inner

locking ball 20, 22 guided in the radial bore 34. The radially inner locking balls 20, 22 project radially out beyond the locking pin 14 into radial bores 72, 74 of the Lie she* 44 alla ale supported in a radially outward direction in each case against an outer ball 18, 24. The radially outer balls 18, 24 project radially out beyond the drive shaft 44 and are supported in a radially outward direction against the inner periphery of the cutout ring 58. The locking pin 14 is held in its operating position by the locking balls 20, 22.

If a predetermined torque is exceeded, the driving balls 54 are displaced by the cam surface 62 of the clutch part 64 and the driving balls 54 displace the cutout ring 58 axially in motor direction and counter to the spring force of the helical compression spring 56 The cutout ring 58 acts with a radially inner cone surface 76 upon the outer balls l 8, 24 and displaces the outer balls 18, 24 and the inner locking balls 20, 22 radially inwards against the clutch spring 30, which is deflectable in the direction of motion 32 of the locking balls 20, 22, and namely up to the point where the inner locking balls 20, 22 are fully retracted in the radial bore 34 of the locking pin I4. The locking pin 14 is then displaced by compressed air present at a diagrammatically illustrated cutout valve 8Q and by a tension force of a valve spring 82 of the cutout valve 80 via a straight pin 78 in the direction of clutch part 64 counter to the helical compression sprmg 70, the cutout valve 80 is closed and the air supply to the motor is interrupted. Adjustment of the cutout valve 80 and tolerance compensation are effected by means of straight pins of differing length and/or by means of interchangeable pins.

When the torque drops, the driving balls 54 are pressed by the springloaded cutout ring 58 in a positionally stable manner back into the recesses 60 of the cam surface 62 of the clutch part 64. The locking pin 14 is displaced back into its starting position and/or operating position in the direction remote from the

clutch part 64 by the helical compression spring 70, the cutout valve 80 is opened? and the inner locking balls 20, 22 are displaced by the clutch spring 30 disposed in the locking pin 14 radially out of the locking pin 14 into their locking position.

The locking pin 14 is restricted in its movement axially in the direction remote from the clutch part 64 by a stop element 38 formed by a pin and, in the disassembled state of the drive shaft 44, is held in the axial direction remote from the clutch part 64 in a loss-protected manner in the drive shaft 44 by the stop element 38. The stop element 38 is held by an interference fit in a radial bore 84 of the drive shaft 64 and projects radially inwards into a longitudinal groove 40 of the locking pin 14, the length of which groove is limited in the direction of the clutch part 64. The stop element 38 therefore simultaneously forms an anti-rotation element of the locking pin 14 in the drive shaft 44 and/or is constructed integrally with an anti-rotation element of the locking pin 14.

Disregarding the longitudinal groove 40 and the radial bore 34, the locking pin 14 has a constantly round cross-sectional area and is therefore particularly inexpensive to manufacture.

In Fig. 3 an alternative cutout clutch 12 with a locking pin 16 is shown.

Components' which remain substantially identical, are basically provided with the same reference characters. Furthermore, with regard to Unctions and features, which remain identical, reference may be made to the description of

the embodiment in Figs. l and 2.

Instead of a radial through-bore the locking pin 16 has a radial blind hole bore 36. Disposed in the blind hole bore 36 is a clutch spring 30, which is supported against the base of the blind hole bore 36 and acts in a radially outward

direction upon an inner locking ball 28. The inner locking ball 28 is guided in the blind hole bore 36 and projects radially outwards into a radial bore 72 of a dove she* Ad. In a radially old direction the inner iocicing ball 28 is supported against a radially outer ball 26, which projects radially out beyond the drive shaft 44 and is supported in a radially outward direction against an inner periphery of a cutout ring 58.

If a predetermined torque is exceeded, the balls 26, 28 are displaced in a manner corresponding to the balls 18, 19, 22, 24 radially inwards against the clutch spring 30, which is deflectable in the direction of motion 32 of the locking ball 28.

Reference characters 1Q cutout clutch 56 helical compression spring 12 cutout clutch 58 cutout ring 14 locking pin 60 recess 16 locking pin 62 cam surface 18 ball 64 clutch part 2Q locking element 66 hexagon socket 22 locking element 68 hexagon insert bit 24 ball 70 helical compression spring 26 ball 72 radial bore 28 locking element 74 radial bore 30 clutch spring 76 cone surface 32 direction of motion 78 straight pin 34 channel 80 cutout valve 36 channel 82 valve spring 3X stop element X4 radial bore 40 longitudinal groove 86 detent ball 42 planet carrier 88 peripheral groove 44 drive shaft 90 peripheral groove 46 housing part 92 radial bore 48 collar 94 cover 50 shaft 52 axial bore 54 driving ball

Claims

(claims 1. Hand too! m ach".e, m p.iculal a pne-Lul.atically operable

screwdriver, with which a tool may be set in rotation, and having a cutout clutch (10, 12), which comprises a spring-loaded locking pin (14, 16), which is held in its operating position by at least one locking element (20, 227 28), wherein for interrupting a drive connection when a torque is exceeded the locking element (2O, 22, 28) is deflectable counter to a spring force of a clutch spring (30) and the locking pin (14, 16) is displaceable into its cutout position? characterized in that the clutch spring (30) is elastically deflectable in the direction of motion (32) of the locking element (18, 20, 22, 24, 26, 28).
2. Hand tom machine according to claim 1, characterized in that the clutch spring (30) acts directly upon the locking element (20? 22, 28).
3. Hand tool machine according to claim 1 or 2, characterized in that the locking element (20? 22, 28) is guided in a radial channel (34, 36) in the locking pin (14, 16) and the clutch spring (30) is disposed in the radial charnel (34, 36).
4 Hand tool machine according to claim 3, characterized in that the channel (36) is closed at one side.
5. Hand tool machine according to claim 4, characterized in that the channel (36) is formed by a blind hole bore.
6 Hand tom machine according to one of the preceding claims, characterized in that the clutch spring (30) is formed by a helical compression spring.
7. Hand tool machine according to one of the preceding claims, characterized in that an axial stop element (38) of the locking pin (14, 16) is constructed integrally with an anti-rotation element of the locking pin (14, 16).
8. Hand tool machine according to claim 7, characterized in that the stop element (38) is formed by a pint which engages into a longitudinal groove (40) of the locking pin (14, 16).
9. A hand machine tool substantially as herein described with reference to Figures I and 2 or Figures I and 3 of the accompanying drawings.