GB2338205A

GB2338205A - Quick-action chuck for a hand tool machine

Info

Publication number: GB2338205A
Application number: GB9909593A
Authority: GB
Inventors: Raymond Brantschen; Andreas Christ
Original assignee: Scintilla AG
Current assignee: Scintilla AG
Priority date: 1998-04-30
Filing date: 1999-04-26
Publication date: 1999-12-15
Anticipated expiration: 2019-04-26
Also published as: GB9909593D0; DE19819528A1; CH693372A5; GB2338205B

Abstract

In a hand tool machine having an electric motor-operable drive element (14) for a tool (16) and a quick-action chuck (15) disposed on the drive element (14) for clamping the tool (16), which quick-action chuck comprises a clamping sleeve (18) held rotatably on the free end of the drive element (14) and clamping means coupled to the clamping sleeve (18) for automatically clamping the tool upon rotation of the clamping sleeve (18), a torsion spring (19) for rotating the clamping sleeve (18), as well as a tool ejector (22) which simultaneously holds the quick-action chuck (15) in its open position, for the purpose of reliable centring and bracing of the tool shank (161) in the quick-action chuck (15), the clamping means take the form of clamping jaws (20, 21), which lie diametrically opposite one another and are guided in a radially displaceable manner in the guide sleeve (17) and coupled for their displacement movement to the clamping sleeve (18).

Description

2338205 1 Hand tool machine The invention proceeds from a hand tool

machine of the type defined in the preamble of claim 1.

With such a hand tool machine, tool changing is possible very quickly and by single-handed operation. When the quick-action chuck holds no tool, the tool ejector ensures that the quick-action chuck is automatically held open so that a new tool may be introduced without any prior manipulation of the quick- action chuck and without the use of auxiliary means. By virtue of insertion of the tool shank into the quick-action chuck, the tool ejector is displaced counter to the action of an ejection spring and hence releases the quick- action chuck for automatic locking of the tool. As soon as the tool ejector has been moved out of its blocking position, the tensioned torsion spring rotates the clamping sleeve with clamping disc and the tool is clamped firmly between drive element and clamping disc. When the tool is to be changed, the clamping sleeve has to be rotated by hand counter to the action of the torsion spring. The tool is therefore released, and the tool ejector loaded by the ejection spring pushes the tool out of the chuck and finally arrives back in its arresting position, in which the quick-action chuck is held open.

For realizing such a quick-action chuck for a hand-held jig saw machine, it has already been proposed to fix the clamp Mig disc, which is provided with a slot-type opening, on a cap which is held rotatably on an annular flange at the free end of a hollow-cylindrical lifting rod forming the drive element. The unit comprising cap and clamping disc is enclosed by a collar and non-rotatably connected to the latter. The torsion spring acts, on the one hand, upon the collar and, on the other hand, upon the lifting rod. The clamping disc on its disc face facing the lifting rod end carries two ramps which, upon rotation of the collar with 2 unit comprising cap and clamping disc, run up onto the bottom edge of the clamping straps on the saw blade and hence brace the saw blade, which is supported against the end face of the lifting rod, towards the lifting rod end. For centring the saw blade, the annular lifting rod end is provided with a diametrical, V-shaped groove, into which the clamping straps on the saw blade shank are pressed. The tool ejector, which is used simultaneously to hold the quick-action chuck open, is guided inside the lifting rod in vertical grooves in the rod inner wall so as to be locked against rotation. On the bottom end of the tool ejector a pair of limbs is formed in such a way that the limbs in the open position of the quick- action chuck are aligned with arresting holes in the clamping disc and under the action of an ejection spring engage at one end into said arresting holes and hence prevent the clamping disc from being rotated by the tensioned torsion spring.

The hand tool machine according to the invention having the features of claim 1 has the advantage that the tool is not only braced and centred in axial direction but also clamped and centred laterally. As a result, an absolutely correct seating of the tool in the quick-action chuck is guaranteed and a rotation of the tool during operation, even in the event of substantial transverse moments, is reliably ruled out. When the tool takes the form of a saw blade for a hand-held jig saw machine, the centring is additionally improved by providing V- shaped grooves both in the front end of the drive element designed as a hollow- cylindrical lifting rod and also in the clamping jaws, with the result that even saw blades of differing thickness.are centred extremely well in the quick-acfion chuck.

Advantageous developments and improvements of the hand tool machine indicated 'm claim 1 are possible by virtue of the measures outlined in the further claims.

There now follows a detailed description of an embodiment of the invention which is illustrated in the drawings. The drawings show:

3 Figure 1 a side view of a hand-held jig saw, partially diagrammatically illustrated; Figure 2 an enlarged view of the cutout H in Figure 1 'm longitudinal section; Figure 3 a section along the line III-III Mi Figure 2; Figure 4 a perspective view of clamping jaws in the quick-action chuck according to Figures 2 and 3; Figure 5 a diagrammatic plan view of the clamping jaws in Figure 4 in their state of coupling to a clamping sleeve of the quick-action chuck.

The hand-held jig saw, which is diagrammatically illustrated as an example of a hand tool machine in side view in Figure 1, comprises a machine housing 10, on which a handle 11 for guiding the hand-held jig saw is formed, wherein the hand-held jig saw is placed with a supporting plate 12 onto a workpiece to be sawn. Projecting from the underside of the handle 11 is an is operating button 13, which cooperates with an electrical switch disposed mi the circuit of an electric motor. The electric motor, which is accommodated in the machine housing 10, via a gear unit comprising an eccentric drive sets a lifting rod 14, which is guided in an axially displaceable manner in the machine housing 10, into a reciprocating lifting motion. A quick- action chuck 15 for clamping a saw 20 blade 16 is disposed on the free end of the lifting rod 14 projecting out of the machine housing 10. As is evident from the enlarged view of Figs. 2 and 3, the saw blade 16 comprises two clamping straps 162, 163 protruding transversely from the saw blade shank 161 for clamping the saw blade 16 in the quick-action chuck 15.

The quick-action chuck 15 is so designed that the saw blade 16 may be inserted without additional manipulation or additional aids into the quick-action chuck 15 and, after insertion of the saw blade 16, the saw blade 16 is automatically firmly clamped. For changing the saw blade 16, the quick- 4 action chuck 15 is to be operated single-handedly, wherein the saw blade 16 is automatically ejected and the quick-action chuck 15 is held in its open position until a new saw blade is introduced.

For said purpose, the quick-action chuck 15 specifically comprises a guide sleeve 17, a clamping sleeve 18, a torsion spring 19, two identically designed clamping jaws 20, 2 1, an ejector 22 and an ejection spring 23. Theguide sleeve 19 is slipped onto the end of the hoflow-cylindrical lifting rod 14 and firmly connected to the latter, e.g. by welding or soldering. The clamping sleeve 28 is fastened in a rotatable and axially non-displaceable manner on the guide sleeve 17 by means of a snap or spreader ring 24. The spreader ring 24 is held in a circumferential groove 35 worked in the circumference of the guide sleeve 17.

The torsion spring 19 acts, on the one hand, upon the clamping sleeve 18 and, on the other hand, upon the guide rod 14. The clamping jaws 20, 2 1, a perspective view of which is shown in Figure 2, are disposed diametrically opposite one is another and accommodated in a radially displaceable manner in the guide sleeve 17. They are coupled to the clamping sleeve 18 in such a way that upon rotation of the clamping sleeve 18, they execute a radial displacement movement in the guide sleeve 17 which is directed either towards or away from one another depending on whether the clamping sleeve 18 is being rotated in the one or the other direction of rotation. For coupling the clamping jaws 20, 21 to the clamping sleeve 18, each clamping jaw 20 or 21 carries a transversely projecting, axially extending guide pin 25, and worked in the clamping sleeve 18 are two diametrically opposed, curved slot-type recesses 26, 27, into which the guide pins 25 project. The depth of the slot-type recesses 26, 27 is greater than the axial length of the guide pins 25, and the slot width is slightly greater than the outside diameter of the guide pins 25. The two slot-type recesses 26, 27 are disposed in such a way that their two centres of curvature 28, 29 (i.e. the centres of their radii of curvature) are offset in opposite directions by an identical extent of eccentricity "e" from the diameter line of the clamping sleeve 18 (Figure 5). When the clamping sleeve 18 is moved - in Figure 5 - in clockwise direction, the clamping jaws 20, 21 are displaced radially outwards and, when the clamping sleeve 18 is moved in anti-clockwise direction, the clamping jaws 20, 21 move towards one another.

On faces directed towards one another the clamping jaws 20,21 have in each case a fork-shaped opening 30 (Figure 4), the opening width of which is slightly greater than the shank thickness of the thickest saw blade 16 intended for use in the qwick-action chuck 15. Introduced 'm the fork base of each opening 30 is a V-shaped groove 3 1, the groove flanks 3 11 and 312 of which extend from the top surface of the clamping jaw 20 or 21 facing the lifting rod 14 obliquely down towards the fork opening 30. A V-shaped groove 32 of an identical type is worked diametrically into the annular front end of the lifting rod 14 facing the clamping jaws 20, 21 (Figure 2). The two fork- shaped openings 30 in the two clampingjaws 20, 21 lying diametrically opposite one another in the guide sleeve 17 form a slot-like insertion opening for introduction of the saw blade shank 16 1. In the open state of the quick-action chuck 15, i.e. when the two clamping jaws 20, 21 are spaced the maximum distance apart by the clamping sleeve 18, the length of the insertion opening is greater than the sum of the width of the saw blade shank 161 and the height of the two clamping straps 162 and 163 protruding from the saw blade shank 16 1. By rotating the clamping sleeve 18, the length of the insertion opening is shortened to the width of the saw blade shank 16 1. The clear inside diameter of the lifting rod 14 is made slightly larger than the width of the saw blade shank 161 so that the inner wall of the lifting rod 14 also performs a guiding flinction for the saw blade shank 16 1.

The ejector 22 loaded by the ejection spring 23 is guided in an axially displaceable manner inside the lifting rod 14, wherein the ejection spring 23 in the form of a compression spring is supported on the one hand against the 6 end face of the ejector 22 and on the other hand in the lifting rod 14. In the open state of the quick-action chuck 15, the ejector 22 engages between the two clamping jaws 20, 21 and is supported axially against a stop formed inside the guide sleeve 17. The ejector 22 has a diametrical, slot-shaped recess 33, which is congruent with the insertion opening formed by the openings 30 of the two clampingjaws 20, 21 and in the base of which a V-shaped groove 34 is formed for receiving the front end of the saw blade shank 16 1.

The mode of operation of the quick-action chuck 15 described above is as follows:

In the open state of the quick-action chuck 15, the saw blade 16 is introduced by its saw blade shank 161 into the insertion opening formed by the two fork-shaped openings 30 of the two clamping jaws 20, 2 1. In the process, the front end of the saw blade shank 161 lying 'm the recess 33 of the ejector 22 pushes into the V-shaped groove 34 at the base of the recess 33. As a result of further insertion of the saw blade 16, the ejector 22 is displaced counter to the action of the ejection spring 23 into the lifting rod 14 until the ejector 22 clears the two clampingjaws 20, 21. The tensioned torsion spring 19 then comes into eSect and rotates the clamping sleeve 18 in such a way that the two clamping jaws 20, 2 1 move towards one another. The groove flanks 3 11 and 3 12 of the two V-shaped groove 31 in the clampingjaws 20, 21 engage under the bottom edge of the clamping straps 162, 163 on the saw blade shank 161 and press the saw blade 16 upwards, with the result that the top edges of the clamping straps 162, 163 are pushed into the V-shaped groove 32 at the end face of the lifting rod 14. The saw blade 16 is therefore braced by its clamping straps 162, 163 between the lifting rod 14 and the clamping jaws 20, 23, wherein the V-shaped grooves 3 1, 3 2 provide for a centring of the saw blade 16. In addition, the ejector 22 under the action of the ejection spring 23 presses upon the end face of the saw blade shank 7 161 and, here too, the V-shaped groove 34 provides for a centring of the shank end of the saw blade 16.

When the saw blade 16 is to be changed, the quick-action chuck 15 has to be opened, for which purpose the clamping sleeve 18 has to be rotated single-handedly, simultaneously tensioning the torsion spring 19. By virtue of said rotation of the clamping sleeve 18, the pin-and-slot connections 25, 26 and 25, 27 of the clamping jaws 20, 21 to the clamping sleeve 18 cause the clamping jaws 20, 21 to be moved radially outwards so that the clamping jaws 20, 21 progressively release the clamping straps 162, 163. As soon as the clamping jaws 20, 21 have been pulled sufficiently far apart, the ejector 22 pushes the saw blade 16 out and simultaneously moves in between the opposing fork ends of the two clamping jaws 20, 2 1, with the result that the clamping jaws 20, 2 1, when the clamping sleeve 18 is let go, are arrested and prevented from moving back again. The'quick-action chuck 15 is situated in its open position and a new saw blade may be introduced in the described manner into the quick-action chuck 15 without requiring any prior manipulation of the quick-action chuck 15. After upward movement of the saw blade 16, the latter is then likewise automatically and reliably centred and clamped 'm the quick-action chuck 15 without any kind of manipulation by the operator.

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Claims

1. Hand tool machine having an electric motor-operable and, at least at its free end, hollow-cylmdrical drive element (14) for a tool (16), having a quick-action chuck (15) seated on the free end of the drive element (14) for clamping the tool (16), which has clamping straps (162, 163) protruding transversely from the tool shank (161), which quick-action chuck comprises clamping means (17, 20, 2 1) having an insertion opening for the tool shank (16 1), a clamping sleeve (18) which is held rotatably on the free end of the drive element (14) and through rotation braces the tool shank (161) between the drive element end and the clamping means, a torsion spring (19) acting on the one hand upon the drive element (14) and on the other hand upon the clamping sleeve (18), and a tool ejector (22) which is guided non-rotatably in the drive element end and simultaneously Mi the open state of the quick- action chuck (15) arrests the clamping sleeve (18) against rotation by the tensioned torsion spring (22) and by means of its axial displacement effected upon insertion of the tool shank ( 16 1) mito the insertion opening cancels the arresting action, characterized in that the clamping means comprise a guide sleeve (17), which is fastened to the drive element (14), and two clamping jaws (20, 2 1), which lie diametrically opposite one another in the guide sleeve (17) and are guided in a radially displaceable manner in the guide sleeve (17) and coupled for their displacement movement to the clamping sleeve (18).

2. Machine according to claim 1, characterized in that the coupling between clamping sleeve (18) and clamping jaws (20, 2 1) takes the form of a pin and-slot guide.

9

3. Machine according to claim 2, characterized in that from each clamping jaw (20, 2 1) a guide pin (25) projects at right angles to the direction of displacement and the clamping sleeve (18) has two diametrically opposed, curved slot-type recesses (26, 27), which are disposed in such a way that their centres of curvature (28, 29) are offset in opposite directions by an identical extent of eccentricity (e) from the diameter line of the clamping sleeve (18).

4. Machine according to one of claims 1 - 3, characterized in that the clear diameter of the guide sleeve (17) is slightly greater than the sum of the diameter of the tool shank (161) and the width of the clamping straps (162, 163) protruding transversely at a diametrical side of the tool shank (161).

5.

Machine according to one of claims 1 - 4, characterized in that the guide sleeve (17) is slipped onto the drive element end and rigidly connected, e.g.

welded, soldered or the like, to the latter.

6. Machine according to one of claims 1 - 5, characterized in that the clarnpm"g sleeve (18) is fastened rotatably on the guide sleeve (17).

7. Machine according to claim 6, characterized in that the rotatable fastening of the clamping sleeve (18) on the guide sleeve (17) is effected by means of a snap or spreader ring (24), which is situated in an axially non- displaceable manner in a groove (35) in the guide sleeve (17).

8. Machine according to one of claims 1 - 7, characterized mi that the tool ejector (22), which is loaded by an ejection spring (23), in the open state of the quick-action chuck (15) lies against a stop formed on the guide sleeve and in so doing engages between the clamping jaws (20, 2 1), preventing the latter from moving towards one another.

9. Machine according to one of claims 1 - 8, characterized in that the 5 drive element is a lifting rod (14) and the tool is a saw blade (16) and that introduced into the annular free front end of the lifting rod (14) is a diametrical Vshaped groove (32) for supporting the clamping straps (162, 163) protrudmig transversely from the saw blade shank (16 1).

10. Machine according to claim 9, characterized in that the clamping jaws (20, 2 1) on surfaces directed towards one another have in each case a forkshaped opening (30), the opening width of which is greater than the shank thickness of a saw blade (16) to be received in the quick-action chuck (15), and that introduced in the opening base of the fork-shaped opening (30) is a V-shaped groove (3 1), the groove flanks (3 11, 3 12) of which extend from the top surface of the clamping jaws (20, 21) facing the lifting rod (14) obliquely down towards the fork opening.

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