GB2322324A

GB2322324A - Hand machine tool with spindle locking device

Info

Publication number: GB2322324A
Application number: GB9802647A
Authority: GB
Inventors: Peter Holzer; Robert Simm; Rinaldo Zuber
Original assignee: Scintilla AG
Current assignee: Scintilla AG
Priority date: 1997-02-20
Filing date: 1998-02-06
Publication date: 1998-08-26
Anticipated expiration: 2018-02-06
Also published as: GB2322324B; ITMI980251A1; CN1191170A; DE19706671A1; GB9802647D0; IT1298219B1; CN1071174C

Abstract

A hand machine tool, in particular a drilling or impact drilling machine, has an arresting device 21 for a workspindle 11 drivable in a rotating and/or percussive manner. The arresting device 21 comprises a locking element 26, which is housing-fixed in the direction of rotation of the workspindle 11 and is positively engageable into a locking element receiver 25 non-rotatably connected to the workspindle 11. The locking element receiver 25 is disposed with an offset (v Fig 2) relative to an annular groove 41 rotating with the workspindle 11. The at least one locking element 26, when spindle arresting is initiated, dips into the annular groove 41 and, while the workspindle 11 is rotating, is prevented from engaging into the locking element receiver 25.

Description

1 Hand machine tool

Background art

2322324 The invention proceeds from a hand machine tool according to the preamble of claim 1.

A hand machine tool is already known (DE 43 05 967 A1), which is provided with means of arresting the workspindle. The arresting means comprise a locking element for positive engagement into a part which is non-rotatably connected to the workspindle. The locking element is extended into the electrical operating region of a drive motor of the hand machine tool and is operable only when the drive motor is de-energized. Thus, operation of the spindle arresting device is prevented while the drive motor is switched on. What is however not prevented is engagement of the locking element during de-energized running down of the drive motor, in which case, because of the centrifugal mass, obtrusive operating noises and damage of the parts to be engaged may arise. The operating device for monitoring the de-energized state and for preventing engagement of the locking element is relatively expensive.

Advantages of the invention 1 In contrast, the hand machine tool according to the invention having the features of claim 1 has the advantage that engagement of the locking element is possible only when the workspindle is stationary or rotating slowly. When the workspindle is rotating quickly, such as is the case, for example, when the drive motor is switched on, 2 engagement of the locking element is not possible with the result that inadvertent arresting of the workspindle, with the resultant drawbacks, is avoided. An expensive operating device is not needed for said purpose.

Advantageous developments and improvements of the hand machine tool according to the invention are possible by virtue of the measures outlined in the dependent claims. It is particularly advantageous when annular groove and engagement opening are slightly radially offset. The locking element is then prevented particularly effectively from engaging into the engagement opening.

It is also particularly advantageous when a rounded-off is engagement journal is disposed on the locking element at the engagement end. As a result of the rounding-off, while the workspindle is rotating the locking element is pushed out of the engagement opening if it engages slightly into the engagement opening.

Drawings An embodiment of the invention is illustrated in the drawings and described in detail below. Figure 1 shows in a cutout manner a longitudinal section of an impact drilling machine, Figure 2 in a cutout manner a side view of an arresting gear wheel of the impact drilling machine, Figure 3 a view of an arresting device with a rotating workspindle and Figure 4 a view of the arresting device 30 with a stationary workspindle.

Description of the embodiment

In Figure 1, 9 denotes an electric impact drilling machine as an example of a hand machine tool which comprises a housing 10, in which a workspindle 11 is supported in rolling-contact bearings 13, 14 so as to be rotatable and, 3 to a limited extent, axially displaceable. The workspindle 11 is rotatably drivable by a drive motor (not shown in detail) via a gear wheel 12. The gear wheel 12 is seated, for said purpose, non-rotatably on the workspindle 11.

During rotation the workspindle 11 may additionally be periodically impulsively displaced in axial direction by means of a selectively connectable impact mechanism 15, thereby enabling so-called impact drilling. The impact mechanism 15 in the form of a latching impact mechanism acts upon the workspindle 11 via two rims having frontally opposing detent cams or detent bevels 16, 17 uniformly distributed in a peripheral direction. A rim with detent bevels 16 is disposed in a housing-fixed manner on a ring 16b in an end bracket 18. A second rim with detent bevels 17 is provided frontally on the gear wheel 12, which is axially displaceable with the workspindle 11. During impact drilling, the two detent bevel rims 16, 17 are brought into engagement with one another counter to the action of a compression spring 19 by the tool contact pressure of the operator. The compression spring 19 is supported, on the one hand, via a disc 20 against the ring 16b and the end bracket 18 and, on the other hand, against a shoulder of the workspindle 11. The detent bevels 16, 17, which slide along one another as the workspindle 11 rotates, in a known manner generate the axial displacement impulses of the workspindle 11.

The <gear wheel 12 is provided with a spur gearing 24. To enable the workspindle 11 to be locked in a housind-fixed manner, the hand machine tool 9 is equipped with an arresting device 21. At its end face 23 directed towards the bearing bush 18, the gear wheel 12 has a locking element receiver 25 for the positive engagement of a locking element 26 in the form of a locking pin. The locking element 26 is supported in an axially displaceable manner in a stepped bearing bore 22a of a bearing bush 22.

4 The bearing bush 22 is in turn pressed into a bore 27 in the end bracket 18.

The end 32 of the locking element 26 remote from the gear wheel 12 projects from the bearing bore 22a and forms a cylindrical journal 28, which is rounded off at one end. Situated in an opening 29 in the housing 10 is a button 30 which is displaceable radially inwards counter to the action of a spiral spring 31. Fastened to a projection 34 of the button 30 is a leaf spring 35, which has a free spring end 36 bent at an angle. The leaf spring 35 extends in a substantially U-shaped manner around the projection 34 and lies with its free spring end 36 partially against a radial cam 33 on the button 30. The radial cam 33 extends at an angle to a longitudinal axis 44 of the locking element 26. The locking element 26 is loaded by the pressure of a spring 38 in the direction of the radial cam 33 and lies against the leaf spring 35, which serves as wear protection for the radial cam 33. The spring 38 is supported, on the one hand, against the bearing bush 22 and, on the other hand, against a stop ring 39 pressed onto the journal 28.

When the button 30 is pressed by the operator in the direction of an arrow 45 radially in towards the longitudinal axis 44, the radial cam 33 with the leaf spring 35 moves inwards and slides on the rounded-off tip of the journal 28. In the process, the locking element 26 is displaced axially counter to the spring force 38 in the direction of the locking element receiver 2S (see also Figures 3 and 4).

The locking element receiver 25 is formed by engagement openings 25a, which are at least partially cut by a circumferential annular groove 41, which is open towards the locking element 26. In the present example, the engagement openings 25a are formed by six blind holes uniformly distributed in a peripheral direction on the end face 23 of the gear wheel 12. The blind holes 25a have a slightly greater diameter than a corresponding engagement journal 40 on the locking element 26. The blind holes 25a are slightly radially offset relative to the annular groove 41. Between a centre line 42 of the annular groove 41 and centre lines 43 of the blind holes 25a there is a radial offset v (Fig. 2).

Figure 3 shows a cutout of the arresting device 21 when the workspindle 11 is rotating. The button 30 is pressed radially inwards by the operator and the locking element 26 is displaced by the leaf spring 35 and the radial cam 33 axially in the direction of the locking element receiver 25 is in the gear wheel 12. The locking element 26 has, relative to the bore 22a, a distinct play (not shown in the drawings) enabling the locking element 26 to swivel with its longitudinal axis 44 slightly relative to a longitudinal axis 44b of the bore 22a. Because of said play, it is possible for the locking element 26 to dip into the annular groove 41 and be guided therein while the workspindle 11 is rotating. In said case, the locking element 26 lies with an oblique surface 40a of the engagement journal 40 against an outer flank 41a of the annular groove 41. In the region of the blind holes 25a only an inner flank 41b of the annular groove 41 is interrupted (Figure 2). The locking element, given a rotary position of the gear wheel 12 aligned with the blind holes 25a, then continues to be supported against the outer flank 41a.

When the rotational speed of the workspindle 11 drops to a specific value or the workspindle 11 stops, the locking element 26 may slide with the surface 40a axially along the outer flank 41a and is guided radially inwards to engage axially into the blind hole receiver 25a in the manner 6 shown in Figure 4. In said case, the button 30 is pressed even further radially inwards by the operator.

Figure 4 shows a cutout of the arresting device 21 with the locking element 26 engaging into the locking element receiver 25. In said position, the gear wheel 24 and hence also the workspindle 11 are positively locked in direction of rotation relative to the housing 10. The centre line 43 of the blind hole 25a is, in said case, aligned substantially radially with the longitudinal axis 44 of the bearing bore 22a so that longitudinal axis 44 of the locking element 26 and longitudinal axis 44b coincide. The centre line 43 may however also be slightly offset relative to the longitudinal axis 44, which would be compensated by the play of the locking element 26 in the bore 22.

The rotational speed, from which an engagement of the locking element 26 into the locking element receiver 25 becomes possible, is dependent upon various factors. An important factor is the si ze ratio of locking element diameter, groove width and opening cross section of the blind holes 25a. However, the contact pressure of the operator via the button 30 as well as other geometric proportions, e.g. the angles of lead-in slopes, also play a part. Given a relatively low opening cross section of the blind holes 25a, an engagement is possible only when the workspindle 11 is stationary. If the ratio of opening cross section to locking element diameter is greater, engagement of the locking element 26 is possible also when the workspindle 11 is rotating slowly. By virtue of the hemispherical rounding-off of the tip of the engagement journal 40 illustrated in the present example, an engagement of the locking pin 26 into one of the blind holes 25b may be totally prevented also while the workspindle 11 is rotating slowly. The locking pin 26, despite engagement into the blind hole 25b, is as a result of the rounding-off then displaced axially backwards 7 counter to the contact pressure by the operator. The operator, in said case, is additionally alerted to the fact that the workspindle 11 is rotating by the engagement noises which then arise.

The invention is not restricted to the illustrated embodiment. Thus, it is alternatively possible to provide in the gear wheel 12 fewer or more than six engagement openings 25a for the locking element 26, which openings naturally need not necessarily take the form of a blind hole but may take the form of any desired location opening, e.g. a through-hole or recess. The locking element receiver 25 may alternatively be disposed at a different point in the gear wheel 12 rather than at the end face 23, e.g. at the outer periphery of the gear wheel 12 for a radial engagement of the locking element. The workspindle 11 with arresting device 21 may alternatively be provided on a countershaft which is non-rotatably coupled to the output shaft of the impact drilling machine.

8

Claims

Claims

1. Hand machine tool, in particular a drilling or impact drilling machine, having a housing (10) accommodating a workspindle (11) for driving a tool in a rotating and/or percussive manner and having an arresting device (21) for the workspindle (11) comprising at least one locking element (26), which is housing-fixed in the direction of rotation of the workspindle (11) and, for locking the workspindle (11) against rotation, is positively engageable into a locking element receiver (25) rotationally connected to the workspindle (11), characterized in that the locking element receiver (25) comprises at least one engagement opening (25a) which is at least partially cut by a circumferential annular groove (41), which is open towards the locking element (26).

Hand machine tool according to claim 1, characterized in that the locking element receiver (25) comprises six engagement openings (25a) uniformly distributed in a peripheral direction.

3.

Hand machine tool according to claim 1 or 2, characterized in that the locking element receiver (25) is disposed on a gear wheel (12) which is seated non-rotatably on the workspindle (11).

Hand machine tool according to claim 3, characterized in that the locking element receiver (25) is disposed on an end face (23) of the gear wheel (12).

9 5. Hand machine tool according to one of the preceding claims, characterized in that the at least one locking element (26) is supported in an axially displaceable manner in a bearing bore (22a) of a bearing bush (22).

Hand machine tool according to claim 5, characterized in that the at least one locking element (26) is accommodated with such play in the bearing bore (22a) that a longitudinal axis (44) of the locking element (26) may swivel slightly about a longitudinal axis (44b) of the bearing bore (22a).

Hand machine tool according to claim 6, characterized in that the annular groove (41) has a centre line (42) which is disposed with an offset (v) relative to a centre line (43) of the at least one locking element receiver (25).

8. Hand machine tool according to one of the preceding claims, characterized in that movably supported in an opening (29) in the housing (10) is a button (30), upon pressing of which the at least one locking element (26) is loaded by a force in the direction of its position of engagement with the at least one locking element receiver (25).

9. Hand machine tool according to claim 8, characterized in that firmly connected to the button (30) is a radial cam (33) which extends at an angle to a longitudinal axis (44) of the at least one loCking element (26).

10. Hand machine tool according to claim 9, characterized in that the at least one locking element (26) is loaded by a spring force (38) in the direction of the radial cam (33).

11. Hand machine tool according to claim 10, characterized in that the radial cam (33) is covered by a leaf spring (35).

12. Hand machine tool according to one of the preceding claims, characterized in that a rounded-off engagement journal (40) is formed on the at least one locking element (26) at the engagement end.

13. A hand machine tool substantially as herein described with reference to the accompanying drawings.