FR2696964A1 - Clamping device for a hand-held machine tool working the metal, for example a motorized file. - Google Patents

Abstract

a) Clamping device for a hand-held machine tool that works metal, in particular a motorized file. b) A clamping sleeve (71) is disposed on a reciprocating drive plate (25), with a hollow housing profile to receive the flat end of the tool, a clamp screw (73) locks it end of the tool on the drive plate (25), and can be screwed into the clamping sleeve (71), a clamping lever (77) being able to pivot about a pivot axis integral with the housing of the machine.

Description

"Clamping device for a hand-held machine tool working the metal,

  for example a motorized file "state of the art

  The invention relates to a clamping device

  age for a hand-machine tool working the metal, in particular a motorized file, for clamping and loosening the tool working the metal, and

especially the lime blade.

  In the case of the known clamping device of this type (WO 89/08524) for a jigsaw, which is also designed as the clamping device

  according to the invention, without a separate tightening wrench, the

  the saw blade's flat end is provided with laterally protruding bayonet lips, which are adapted to a bayonet lock attached to the end of a moving drive rod.

  The bayonet closure has a cap attached to the end of the drive rod and carries a pair of slots in the bottom of the cha-20 skin, being diametrically screwed to -vis, serving the passage of the lips of the bayonet-

  as well as two grooves arranged diametrically on the inner face of the bottom of the cap and turned at 900 relative to the windows, grooves in which

  the bayonet lips can be wedged by their lower edge The bayonet closure further has a roller-shaped locking member which is axially slidably guided within the drive shaft and is supported by a coil spring against the bottom of the cap The locking member carries an axial longitudinal slot which opens on the front side to receive the end of the blade.

  saw with the lips of the bayonet, whose length

  axial distance determines the driving depth of the saw blade in the clamping device To clamp the saw blade it is pressed by its end and the lips of the bayonet are there through an opening in the bottom of the cap , the lips

  of the bayonet passing through the slots and the ex-

  end of the saw blade dipping into the longitudinal slot of the locking member, until it abuts by its end face on the bottom of the longitudinal slot After which the saw blade of 90 is rotated by a slight axial pressure by means of which is lifted the clamping member of the bottom of the hat, until the lips

  the bayonet come in coincidence with the reasons

  After releasing the saw blade, the blocking member under the action of the coil spring presses the bayonet lips into the grooves and the saw blade is securely tightened without being able to

  turn in the bayonet lock.

  This known clamping device has, in addition to its wrench-free design, the advantage of an integrated overload protection, which in the case of extremely heavy saw blades

  hard or fitted to the waist, it prevents damage to

  If, for example, the blade of

  saw is stuck in the room being used, the organization

  blocking is pushed up by the blade of

  saw blocked against the coil spring during lifting

  the drive rod, so that the travel of the drive rod can not be transmitted to the saw blade The cost of construction and manufacture of the known clamping device is

  not negligible Moreover, this construction of the

  The clamping device does not allow for the universal use of saw blades from different fabrications. Advantages of the invention The clamping device according to the invention is characterized in that a clamping sleeve

  placed on a drive plate going and ve-

  with a hollow housing profile to receive

  the flat end of the tool, a screw

  the clamping sleeve for locking the end of the tool housed therein on the drive plate, screw which can be screwed into the clamping sleeve, a clamping lever pivotable about a pivot axis integral with the housing of the machine, serving

  to turn the clamping screw, and an actuator

  coupling arranged between the clamping lever and the clamping screw, being able to move radially with at least two recesses oriented at right angles to each other and radially, an axial driver of the clamping screw engaging in one of the recesses, and in the other recess engaging an axial driver connected to the clamping lever

in training.

  The clamping device according to the invention has

  the advantage that, as in the case of the

  known clamping tool, the tool can be blocked or

  changed by hand without using a separate wrench

  The clamping device has a low overall height and is suitable for metalworking hand tools in which the drive or lifting plate disposed in the head of the machine tool housing is not freely accessible In this case, the workpiece can be pressed and quickly locked in any lifting position of the drive plate in the clamping device which can not be seen until it reaches the lever

  and which can only be accessed through an opening

  tool in the housing head.

  Other advantageous developments and improvements of the clamping device according to the invention as indicated above can be obtained thanks to the

  makes that one of the axial coaches of the service screw

  rabies is arranged on a head, disc-shaped, of

the clamping screw.

  The coupling is constituted in the form

  a friction clutch operating by adhering

  this and / or by positive engagement, such as a

tooth coupling.

  The rotating member on one side

  axial projections and axial recesses.

  The projections and the axial recesses of

  the rotation member are contained in a

  in the form of a truncated cone,

  the rotating member and preferably form a

conical inner graining.

  The coupling has a training device

  It can be actuated in rotation by means of the clamping lever, which member has projections and axial recesses associated on one axial face with the axial projections and recesses of the actuating member.

  rotation and in this way protrusions and

  axial elements can be engaged for

  plement. The projections and the axial recesses of the drive member form a conical outer gear.

  The driving member is coupled to the

  tightening by positive engagement in the peripheral direction so as to be relatively slidable

in the axial direction.

  The coupling has a coupling spring

  with an axially oriented elastic force, which

  keeps in contact with each other the two meshes

  conical gears, and the bevel gears and the elastic force of the coupling spring are adjusted to one another so that in the case of a

  predefined torque on the drive member

  the external gear is disengaged from the internal gear in the axial direction against the force

  spring of the coupling spring.

  The rotation member is connected so

  lidar in rotation, at the clamping lever.

  The clamping sleeve is held in its driving position on the drive plate at

by means of a spring clip.

  The spring clip is constituted as a

  spring blade folded several times, which is

  quetée by elastic tabs on the drive plate and rests on the underside of the

clamping sleeve.

  Between the screw head of the clamping screw and

  the upper face of the clamping sleeve,

  a dust cover integral with the machine housing, with a longitudinal slot

  the direction of travel of the drive plate,

  te whose length corresponds at least to the longitudinal stroke of the drive plate, and the clamping screw passes through the longitudinal slot through

its threaded rod.

  The threaded rod of the clamping rod penetrates

  be in an indentation on the terminal side of the face

  top of the drive plate.

  The threaded rod of the clamping screw penetrates through a slightly larger diameter hole of the drive plate and presses on the terminal side

on the end of the tool.

  In one embodiment of the invention,

  the coupling member is constituted in the form of a disc and the recesses are constituted in the form of slits, oblong holes, groove or the like. The coach may be designed in the form of a disc.

  fingers, balls, bars or the like which slide

  feel in the direction of the length in the recesses.

  In a preferred embodiment of the invention, one of the axial drivers is provided on a rotational member, connected in drive to

clamping lever.

  In an advantageous embodiment of the invention, the drive connection is made between the rotation member and the clamping lever by

  a coupling which limits the tightening torque of the

  This coupling with torque limitation has the advantage that the tool is always fixed

  with the same constant force in the serration sleeve

  age, and that in this way it is possible to avoid any damage

  the clamping device when tightening the tool Furthermore this coupling also allows that,

  in the case where the flat ends of the tools are

  in the clamping bushing have different thicknesses

  in the case of a different adjustment stroke

  resulting in the clamping screw, it is always possible to orient a set of a trainer and recesses engaging with each other in the direction of the race of the

drive plate.

  According to a preferred embodiment of

  the invention, the end of the rod of the screw

  In this way the clamping screw, when the clamping device is in the open position, comes out of the thread into the clamping sleeve, but remains positioned

  by the coupling device and the protective disc

  1.0 dust in such a way that the external threads of

  the screw shank can be screwed back into the

  threading of the clamping bush during the movement

  Adjustment of the clamping lever Thanks to this

  removal of the screwing by the clamping sleeve and the clamping screw when the clamping device is in

  open position, so when there is no tool

  guaranteed, a blockage of the drive plate is

  which would lead to damage during the

  starting the hand-held machine tool.

  According to an advantageous embodiment of the invention, one still forms between the head of the

  screw and the stem of the clamping screw an annular shoulder

  The outer diameter of the annular shoulder is in this case maintained smaller than the transverse dimension of the longitudinal slot in the disk.

  dust cover, so that the annular shoulder

  can get through the disk

  dust cover The axial height of the shoulder should be

  nular has a dimension a little larger than

  the thickness of the dust cover With this disc

  position of construction it is prevented that the clamping sleeve is pressed against the dust disc held without sliding in the housing of the machine, which would also cause damage during

  the start of the hand-held machine tool.

  Drawings The invention will be explained in more detail

  in the description which follows from the examples

  ples of realization shown in the drawings:

  Figure 1 is a side view fragmen-

  Fig. 2 is a perspective view of a clamping device in the motorized file of Fig. 1 in an exploded view;

  FIG. 3 is a fragmentary representation

  similar to that of Figure 2, a provision

  clamping device slightly modified according to another

exemplary embodiment.

  Description of the embodiments

  The electric motorized file shown in Figure 1 in a fragmentary manner, according to a view of

  side and partly in section, serving as an example of

  China-hand tool for machining by removal of

  pieces, has a plastic casing

  tick 10 with two shells, formed in its section

  Like a handle 101, and formed in its next seamless anterior section, like a housing head 102 In the housing head 102 the drive unit 11 of a blade has been substantially integrated.

  12 protruding from the head of the housing

  tier 102 and is set in permanent reciprocating motion

  back and forth by the drive unit 11 The

  electric motor forming part of the driving unit

  11 is housed in the front part,

  cording directly to the housing head 102, the handle 101, and is connected or disconnected by means of a switch plunger 14 projecting from the underside of the handle 101 of the electric motor can only be seen in the figure 1 that the output shaft 16 and a fan wheel 17 wedged on it

  solidarily in rotation, a wheel that sucks on the

  The fresh air entering through the ventilation slots inside the plastic housing 10 is electrically powered. In the sectional representation of FIG. 1, details of the drive unit can be seen

  11 on which one will extend here only briefly.

  1.0 The output shaft 16 of the electric motor engages, by a drive gear 19, with a drive shaft 20, disposed at right angles to the

  the output shaft 16 and mounted so as to be able to

  into the housing head 102 by means of a roller

  ball bearing 21 and a needle bearing

  the lower ones 22 On the drive shaft 20 is integrally mounted in rotation an eccentric 24 provided with an upper appendage 241 serving to drive a lifting or driving plate 25 mounted

  way to slide axially, and an appendix

  this lower 242 serving to drive a plate of

  counterweight 26 The latter serves to reduce the

  brations in the machine during the filing process.

  The counterweight plate 26 is mounted, with interpolation

  sition of a thin wedging plate 27, on a support plate 23 connected to the housing head 142, while

  that the drive plate 25 rests interposi-

  spacer washers 28, 29 on the plate

  counterweight 26, the two plates 25, 26 are guided by

  designed to slide axially in the long-term direction

  longitudinal by means of two guides 30 and 35 formed

  by means of slotted-rod assemblies The driving plate

  25 is bent in the anterior area so that the anterior section is approximately in the plane of the counterweight plate 26 In the anterior end zone, the drive plate 25 carries a housing for the tool or a clamping device 42 by which the blade of the file 12 is

  rigidly fixed to the drive plate 25.

  The clamping device 42 that can be seen in section in FIG. 1 and in a view

  exploded in perspective in Figure 2, serving the

  exchangeable rage of the file blade 12, has a clamping sleeve 71 hollow housing profile, a clamping screw 7 can be screwed into a threaded hole 72 of the clamping sleeve 71, with a screw head 731 in the form of disc and a screw rod 732, which is called a joint Oldham 74 which consists of

  the screw head 731, of a coupling member 75 and

  if that of a rotational member 76, as well as a lever

  77 connected in drive to the organ of rotation

  76, a lever whose axis of rotation is coaxial with the axis of rotation of the rotational member 76.

  clamping sleeve 74 is formed of a flat strip re-

  folded, the two terminal branches of the flat band

  lying one above the other while being

  The clamping bushing 71 is threaded onto the drive plate 25 from the front, the threaded hole 72 coinciding with an indentation 78 on the upper face of the drive plate 25 in this position. the clamping bushing 71 is held by a spring clip 79. The spring clip 79 is formed by a spring blade 80 bent several times, which engages with two resilient tongues 801 and 802 in two lateral recesses 81, 82 of the drive plate 25, and thus fixes the spring clip so that it can not slide on the drive plate 25 The spring blade 80 rests with its anterior end on the underside of the clamping sleeve 71 and he

  tendency to exert upwards pressure in

  of the drive plate 25.

  The clamping screw 73 is threaded through its threaded rod 732 through a slot 83, lengthwise, into a dust washer and is screwed into the threaded hole 72 of the clamping sleeve 71. the longitudinal slot 83 corresponds at least to the maximum movement of the

  as the training plate race 25

  out of the sectional representation of Figure 1, we

  hold the dust cover 84 securely

  in the screw head 102 of the housing 10 As can be seen in Figure 2 and also in Figure 3, there is formed on the underside of the head of

  screw 731 of the clamping screw 73, an annular shoulder

  733 projecting radially on the rod of

  the screw 732 The outer diameter of the shoulder

  nular 733 is smaller than the transverse dimension

  dirty of the longitudinal slot 83 in the puck

  dust, 84 so that the annular shoulder

  733 also passes through the longitudinal slot.

  The axial height of the annular shoulder 733 is a little larger than the axial thickness of

the dust cover 84.

  The Oldham seal, known per se, 74 presents

  here two spring and groove guides oriented to

  FIG. 5 is a straight section, relative to each other, between the coupling member 75 and the rotational member 76 drivingly connected to the clamping lever 77, on the one hand, and to the clamping screw 73, On the other hand For this the coupling member 75 formed in the form

  of a disc, carries two transverse diametrical grooves

  sales 85, 86 turned relative to each other

  go ", which are formed on the faces being vis-à-

  In each of the transverse grooves, 86 engages a resilient bar that can slide. In this case, the elastic bar 87 is formed directly on the head of the screw 731, whereas the other elastic bar 88 is constituted on the face. lower part of the rotation member 76. As can be seen from the figure

  1, the rotational member 76 is mounted so as to

  see turning in the head 102 of the housing 10 It pre-

  on its axial side turned away from the coupling member 75, a trunk-shaped depression 98

  of cone, in which axial projections and

  The furrows form a conical internal toothing 90 which can engage a drive member 92.

  with external toothing 91, also of conical shape

  The drive member 92 connected to the clamping lever 77 with its external toothing 91 and the rotator 76 with its internal toothing together form with a coupling spring formed as a coil spring. 93, a safety coupling 89 limiting the tightening torque of the clamping lever

  77, coupling which makes it possible to screw the locking screw

  With the aid of the clamping lever 77, only the maximum predefined torque is achieved. The coil spring 93 in this case is supported on the rear face of the drive member 92 situated opposite the external toothing 91 and inside the clamping lever 77 being received by a hollow end 94 formed

  on the underside of the coaxial clamping lever 77

  the coil spring 93

  surrounds in this case an axis 95 which is depressed by

  positive engagement in the drive member 92 or integrally formed therewith The axle 95 and the hollow end 94 engage one into the other

  by positive engagement after the assembly of the

  clamping member 42, so that the engaging member 42

  92 drag is integral in rotation but slides

  axially with the clamping lever 77.

  As is apparent from the sectional representation of FIG. 1, the coil spring 93, when the clamping device 42 is assembled, compresses the external toothing 91 of the drive member 92 in the internal toothing 90 of the body Its elastic bar 88 rests axially in the transverse groove 86 where it slides axially, while the elastic bar 87 formed on the screw head 731

  clamping screw 73 slides into the transverse groove

  Versale 85 of the coupling member 75 The final stem

  732 of the clamping screw 73 passes together with the annular shoulder 733, through the length slot 83 of the dust cover 84 and is screwed into the threaded hole 72 of the clamping sleeve 71. When the clamping device 42 is open, the handle 77 is oriented forward on the head 102 of the housing 10 and extends in the direction of its length. The flat end of the file blade

  12 (Figure 1) is then threaded along the inside

  bottom of the drive plate 25 in the bushing

  the tightening clamp 71 Then the lever of

  tightening 1800 in the direction of the needles of a

  The lever pivoting and entering a recess of the housing head 102 By the pivoting of the lever

  clamp 77 is rotated by means of the coupling

  89 and the Oldham 74 joint, the clamping screw 73 on the right, its front end

  in the indentation 78 of the drive plate 75.

  The clamping sleeve 71 is pulled in this way towards

  the top and press the end of the lime blade

  be the lower face of the drive plate 25.

  Thanks to an appropriate design of the coupling of

  safety 89 with the coil spring 93, it is possible to

  use a clamping lever 77 with a maximum torque of 1 Nm to the tightening screw 73 Si

  this torque is exceeded, the actuator

  92 is then raised by its external toothing 91 against the elastic force of the coil spring

  93 out of the internal toothing 90 of the rotational member

In addition to the adhesion it is possible to

  between the drive plate 25 and the file blade 12, positive engagement in a manner such as on the underside of the drive plate 25, preferably coaxially with the indentation 78 of the upper face of the drive plate 25, there is provided an axial projection engaging (Figure 1) in a recess or a corresponding hole 97 of the

lime blade 12.

  To change the blade of lime 12 we make

  turn the handle 77 anti-clockwise 1800 forward until it extends in the direction of the length of the blade of

  In this way, the clamping screw 73

  Threaded hole 72, clamping sleeve 71

  being pushed down thanks to the support of the

  the screw rod against the upper face of the drive plate 25, so that the blade of the

  lime 21 is released and can be changed.

  To prevent the opening of the

  positive tightening 42 for the purpose of changing the

  12, the clamping sleeve 71 is not

  downwardly by too much pivoting of the clamping lever 77, so much so that it clamps the drive plate 25 into its reciprocating position, which could lead to damage, when in

  motorized file in the training unit.

  11 is made, without threading, according to a modification

  shown in Figure 3 of the clamping device

  ge 42, the end 734 of the rod 732 of the screw

  This has the consequence that at the end of

  of the clamping lever in the direction of opening

  ture, the external thread of screw rod 732 is no longer engaged with the internal thread of the threaded hole

  72, and that the clamping screw 73 is thus unscrewed

  the threaded sleeve 72, of the clamping sleeve 71. In this case the clamping sleeve 71

  can not be tightened on the drive plate 25.

  However, the clamping screw 73 is positioned unmodified, after as before, by the coupling member 75 of the dust washer 84, so that it has the possibility of screwing itself again without any problem in the hole threaded 72 during the

  adjusting movement of the clamping lever 77.

  The annular shoulder 733 between the screw head 71 and the screw rod 732 gives the assurance that in the case where the clamping device 42 is closed, and hence the file blade 12 is clamped, the clamping sleeve 71 can not be mounted on the face

  bottom of the dust cover 84 and this-

  close to it, which would also lead to

  damage in the training unit 12 when

  the start of the motorized file

  re, the clamping sleeve 71 rests on the shoulder

  733 and, because of its axial axial height

  relatively larger than the thickness of the dust washer 84, there remains between the clamping sleeve 71 and the dust washer 84 a slot

of movement.

  As an alternative to the clamping device described 42 can be provided in the drive plate 25 a bore passing therethrough instead of inden-

  The stem 732 of the clamping screw 73 passes

  then through the piercing and relies by its

  directly on the end of the lime blade.

  The invention is not limited to the exemplary embodiments which have been described above. Thus, it is possible to use in various ways what is known as the Oldham seal 74. In place of the transverse grooves 85, 8 may for example provide radial slots or radial oblong holes in the coupling member 75 and instead of the elastic bars 87, 88 of the fingers or balls on the head of the screw 731 or on the rotation member 76 In this case for example, two fingers respectively engage, on the head of the screw 731, in two radial slots coinciding with each other in the coupling member 75 and two fingers formed on the body

  of rotation 76 engage in two other

  your radials coinciding with each other in the or-

  coupling shaft 75, slits which are rotated 90

  compared to the first two radial slots.

  In addition, it is possible to make the safety coupling 89, constituted in the form of a coupling

  friction operated by adhesion and engagement

  Positively positive, with a frontal toothing instead of a conical toothing 90, 91 In the case of a less comfortable clamping device it is possible to completely abandon the safety coupling 89 In this case the rotation member 76 is then directly connected to the lever

  clamping 77 and integral in rotation thereof.

Claims (18)

R E V E N D I C A T IO N S   1) Clamping device for a machine-   hand tool working the metal, in particular a motorized file, for tightening and loosening the chip removal tool, and in particular the file blade, a clamping device characterized in that   clamping sleeve (71) disposed on an electrode plate   coming and going (25), with a profile of   hollow housing for receiving the flat end of the   a clamping screw (73) screwing the clamping sleeve (71) to block the end of the tool housed therein on the drive plate (25), screw (73) which can be screwed into the bushing of clamping (71), a clamping lever (77) pivotable about an axis   pivoting device attached to the machine casing,   to turn the clamping screw (73), and an or-   coupling (75) arranged between the lever of   (77) and the clamping screw (73) can be   radially, with at least two recesses (85, 86) oriented at right angles to one another and radially, an axial driver (87) of the clamping screw (73) engaging in one recesses (85) and in the other recess (86) engaging an axial driver (88) connected to the clamping lever (17) in training.   2) Clamping device according to the claim   1, characterized in that the recesses   tifs (85, 86) are constituted in the form of slits,   oblong holes, grooves or the like.   3) Clamping device according to the claim   1 or 2, characterized in that the respective coaches (87, 88) are formed in the form of   fingers, balls, bars or the like.   4) Clamping device according to one of the   Claims 1 to 3, characterized in that the coupling member (75) is in the form of a disc. ) Clamping device according to one of the   Claims 1 to 4, characterized in that one of the   axial stretcher (87) of the clamping screw (73) is arranged on a disk-shaped head (731) of the tightening screw (73).   6) Clamping device according to one of the   Claims 1 to 5, characterized in that the other   axial stretcher (88) is arranged on a rotational member   (76) connected in drive to the clamping lever (77).   7) Clamping device according to one of the   Claims 1 to 6, characterized in that the rotation member (76) is drivably connected to the clamping lever (77) by means of a coupling limiting the   tightening torque of the clamping lever (77).   8) Clamping device according to the claim   7, characterized in that the coupling (89) is in the form of a friction coupling   operating by adhesion and / or positive engagement   tif, such as a toothed coupling.   9) Clamping device according to one of the   Claims 1 to 8, characterized in that the organ of   rotation (76) has, on an axial face, lees and axial recesses.   ) Clamping device according to the   9, characterized in that the projections and the axial recesses of the rotational member (76) are contained in a recess (98), approximately in the form of a truncated cone, of the rotational member (76)   and preferably form a contiguous internal gear that (90).   11) Clamping device according to one of   Claims 7 to 10, characterized in that the   (89) has a drive member (92) which can be rotated by means of the clamping lever (77), which member (92) has associated axial projections and recesses on axial face with axial projections and recesses. of the rotation member (76), and in this way projections and axial recesses can be engaged for coupling.   12) Clamping device according to the   10 and 11, characterized in that the projections and the axial recesses of the drive member   (92) form a conical outer gear (91).   13) Clamping device according to the claims   It or 12, characterized in that the   drag (92) is coupled to the clamping lever (77) by positive engagement in the peripheral direction so as to be relatively slidable in the axial direction.   14) Device according to claims 12   or 13, characterized in that the coupling (89) has   a coupling spring (93) with an elastic force   axially oriented, which holds the two bevel gears (90, 91) and the bevel gears (90, 91) and the elastic force of the coupling spring (93) in engagement with each other are adjusted to one another. other such that, in the case of a predefined torque on the drive member   (92), the outer gear (91) is released from the gear   internal swim (19) in the axial direction against   the elastic force of the coupling spring (93).   ) Clamping device according to one of   Claims 1 to 6, characterized in that the   rotation (76) is integrally connected in rotation to the clamping lever (77).   16) Clamping device according to any one   shell of claims 1 to 15, characterized in that   that the clamping sleeve (71) is held in its position.   driving position on the drive plate   (25) by means of a spring clip (79).   17) A clamping device according to claim 16, characterized in that the spring clip (79) is formed as a folded leaf spring   several times (80), which is snapped on by   elastic gates (801, 802) on the drive plate -   ment (25) and rests on the underside of the clamping sleeve (71).   18) Clamping device according to one of   Claims 1 to 17, characterized in that between the   screw head (731) of the clamping screw (73) and the upper face of the clamping sleeve (71), a dust washer (84) secured to the housing is provided.   of the machine, with a longitudinal slot (83)   in the direction of the race of the training plate   (25), which slot corresponds at least to the longitudinal travel of the drive plate (25), and the clamping screw (73) passes through the   longitudinal slot (83) by its threaded rod (732).   19) Clamping device according to one of   Claims 1 to 18, characterized in that the rod   threaded thread (732) of the clamping rod (73)   an indentation (78) on the terminal side of the upper face   the drive plate (25).   ) Clamping device according to one of   Claims 1 to 18, characterized in that the rod   threaded thread (732) of the clamping screw (73) penetrates   to a slightly larger diameter drilling the   drive plate (25) and presses on the on the end of the tool.   21) Clamping device according to one of   Claims 1 to 20, characterized in that the   the stem of the clamping screw (73) is free threading.   22) Clamping device according to one of   claims 18 to 21, characterized in that between the   screw head (731) and rod (732) of the clamping screw (73) forming an annular shoulder (733) projecting radially on the screw shaft (732), the outer diameter member of which is more   small as the transverse dimension of the longitudinal slot   tudinal (83) in the dust washer (84) and whose axial height is greater than the thickness   the dust cover (84).