EP1621290B1 - Machine tool with intermittent angular momentum - Google Patents

Description

The invention relates to a hand tool with a drive spindle, which can be acted upon by a motor with a drive torque. In addition, the hand tool device has a tool spindle which serves to drive a tool bit in one direction of rotation. For this purpose, the tool spindle on the one hand with the drive spindle can be coupled and on the other hand rotatably connected to a tool holder, to which the tool bit is attachable. Furthermore, the hand tool device has a rotary pulse generator which, when a threshold value is reached with respect to a resistance moment occurring at the tool spindle, which is directed counter to the drive torque, subjects the latter to a recurring angular momentum.

During operation, such hand tool devices enable a change from a continuous to an intermittent rotary movement as soon as the braking forces occurring on the tool spindle and the tool holder produce a resistance moment which reaches the threshold value. In the case of the intermittent rotary motion, the tool spindle is subjected to very high recurring angular momenta, by which the moment of resistance can be more easily overcome and the work progress can be increased significantly.

From the DE 43 28 599 is a rotary impact tool in the form of a rotary impact wrench known. This has a hammer element, which is engaged via balls with the drive spindle, which are guided both in the hammer element and on the drive spindle in oblique grooves. Furthermore, the hammer element on projections which can be applied in the rotational direction of projections of the tool spindle in order to transmit a torque from the drive spindle to the tool spindle. As soon as the moment of resistance, which is delivered by the screw to be screwed to the tool spindle, reaches a certain threshold when screwing, the hammer element is moved away from the tool spindle via the oblique grooves relative to the drive spindle until the projections of the hammer element out of engagement with the projections come the tool spindle and be moved past each other. It increases on the one hand by the lack of resistance to the projections, the rotational speed of the hammer element. In addition, the hammer element is accelerated by a tension spring acting on it in the direction of the tool spindle as soon as the projections have passed each other in the direction of rotation. In this way, the hammer element generates on the one hand on the tool spindle an axial contact pressure. On the other hand, the hammer element exerts blows on the tool spindle in the direction of rotation.

By this known approach, it is possible screwing screws against high resistance moments in a workpiece, since the blows against the projections of the tool spindle very high torques are generated.

DE 43 44 849 shows a machine tool that switches over a certain moment of resistance from a quasi-continuous rotary motion with relatively low drive torque to a discontinuous rotary motion with relatively high recurring angular momentum both when screwing and core drilling. For this purpose, the machine tool has an oscillating drive, which is coupled via a freewheel with the tool holder.

A disadvantage of the known hand tools is that they can not be used in a comfortable way for holes in the metal, at least. The resistance moments occurring in the drilling area are namely not sufficient in normal operation to trigger the respective rotary pulse generator recurrently. Only by very strong pressing of the rotary impact tool against the metal to be processed, the threshold value of the resistance moment can be exceeded. This can be achieved in the metal drilling applications only by strong pressing of the hand tool by the operator a significantly increased Bohrvortrieb.

US 2,947,283 shows a pneumatic wrench with a cup-shaped output element, projects from an anvil element. This is repeatedly applied during operation by a hammer mechanism in the direction of rotation. In this case, the output element is mounted with the interposition of a sliding bearing in a housing.

EP 1 182 010 describes a vibration generating motorized wrench. This has two mutually offset flywheels, one of which is rotatable about a tool spindle and acted upon by a braking device.

The present invention has for its object to avoid the disadvantages mentioned in a hand tool with rotary pulse generator and to allow a comfortable production of a metal hole.

According to the invention the object is achieved in that on the tool spindle, a braking force generator is arranged, via which the tool spindle can be acted upon by a braking force acting counter to the direction of rotation. This makes it possible to raise the moment of resistance on the tool spindle without or with only a small external moment of resistance to the threshold. Thus, the rotary pulse generator can be activated without or with only a slight frictional resistance between the tool bit and a workpiece to be machined. In this way, a better Bohrvortrieb can be generated in a comfortable manner, ie especially without increased pressure, especially when drilling in metal.

In a particularly preferred embodiment, the tool spindle can additionally be acted upon by the angular momentum generator with an axial force pulse. In this way, by the braking force generator automatically a recurrent pulse-like impact or contact force can be generated in the axial direction of the tool spindle, which occurs together with the angular momentum. As a result, the angular momentum transmitted to the tool bit, which is preferably designed as a metal drill, and which serves for shaving into the workpiece, is superimposed with a particularly high axial contact pressure. This results in a particularly good cutting of the drill into the workpiece, without the device must be pressed by the operator against the workpiece. In this case, predominantly short metal chips, which are separated with each angular momentum of the workpiece to be machined, are relatively quickly transported from the work area and thus cause only low braking forces on the tool bit. As a result, a particularly good Bohrvortrieb in metal is possible.

In addition, it is particularly advantageous if the braking force generator is optionally switched on and off. As a result, the hand tool can be used as needed for either Tangentialschlagschrauben or metal hammer drilling. In this way, metal impact drilling can be provided as an additional, optionally switchable operating function on a Tangentialschlagschraubgerät.

Preferably, the braking force generator has a sleeve-shaped carrier body, which is penetrated by the tool spindle. As a result, the braking force can be applied circumferentially to the tool spindle, whereby a relatively large and uniform braking force can be generated.

Advantageously, in the direction of rotation, a prestressed form friction fit can be produced between the carrier body and the tool spindle. By prestressed positive frictional engagement this means a frictional connection achieved by prestressing an element against a surface, which is reinforced by a quasi-form fit between the element and the surface. However, because of the shape of the element and the surface, this quasi-form closure only acts up to a certain holding force. In this way, it is possible to reliably apply a relatively high braking force to the tool spindle while at the same time reducing the wear on the braking force generator.

It is advantageous if the mold friction is produced by a arranged between the carrier body and the tool spindle locking device. This stores a locking body radially displaceable on one of the elements of the tool spindle and carrier body. The latching body is biased against the respective other element, wherein at least one corresponding latching recess is recessed for receiving the latching body. In this way, a permanently constant braking force can be provided at a low manufacturing cost of the braking force generator.

Advantageously, the latching recess is formed by a groove extending transversely to the direction of rotation, whereby the latching device can be produced in a particularly simple and cost-effective manner.

Alternatively, the latching recess is advantageously formed by a Rampenausnehmung having a spiral-shaped cross-section, wherein the depth of the Rampenausnehmung in the direction of rotation increases steadily up to a paragraph, which acts as a stop for the locking body. As a result, the latching body is initially pressed almost completely in the transverse bore when jumping from a first to a second latching position and gradually moved out of the transverse bore until the next stop position. By this movement of the detent body unnecessary noise can be avoided.

In a further preferred embodiment, the latching recess is formed by a circular arc-shaped in cross section around the axis A, which has a constant depth in the direction of rotation over its length. As a result, the locking body is over the entire angular range between the ribs or in a consistently maximally disengaged position relative to the transverse bore. As a result, the contact pressure of the radial spring in this transition region is minimal, whereby the friction losses when jumping from one locking position to the next can be significantly reduced.

In this case, the carrier body between a braking position, in which the locking body is disposed at the axial height of the recesses, and a free-running position is advantageously displaceable, in which the locking body is arranged at the height of a rotating circumferential direction in the annular groove. As a result, the latching device can be switched on and off in a simple manner. As a result, the braking force generator can be switched on and off, depending on whether the hand tool is to be used as a tangential impact driver or as a percussion drill.

Alternatively or additionally, a frictional engagement can advantageously be produced between the carrier body and the tool spindle. As a result, the braking force generator can be produced in a particularly cost-effective manner or its braking force can be increased without major effort.

It is advantageous if the carrier body is formed by an elastic friction ring. As a result, the braking force generator can be produced in a particularly cost-effective manner.

Advantageously, the threshold is in the range of 1 to 5 Nm. This torque range has been found to be particularly suitable, since on the one hand ensures good performance of the rotary pulse generator and can be safely adjusted to the tool spindle with the above-mentioned braking force generators. On the other hand, this value can certainly be surpassed by the drive torque of most tangential impact wrenches so that tangential impact wrenches with additional percussion drilling capability can be manufactured based on a production series of conventional tangential impact drills.

Fig. 1

eine teilweise geschnittene Ansicht eines erfindungsgemässen Handwerkzeuggerätes,

Fig. 2

einen Längsschnitt durch einen Drehimpulserzeuger und einen Bremskrafterzeuger des Handwerkzeuggerätes nach Fig. 1 in einer Freilaufstellung,

Fig. 3

einen Längsschnitt durch den Drehimpulserzeuger und den Bremskrafterzeuger nach Fig. 2 in einer Bremsstellung,

Fig. 4

eine Diagramm-Darstellung des Momenten-und-Axialkraftverlaufes bei Generierung eines Drehimpulses durch den Drehimpulserzeuger,

Fig. 5a bis 5c

jeweils einen Querschnitt durch den Bremskrafterzeuger in drei Ausführungsformen und

Fig. 6

eine Explosionsdarstellung des Drehimpulserzeugers und einem reibschlüssig wirkenden Bremskrafterzeuger.

The invention will be explained in more detail below with reference to an embodiment. Show it:

Fig. 1

a partially sectioned view of a hand tool according to the invention,

Fig. 2

a longitudinal section through an angular momentum generator and a braking force generator of the power tool after Fig. 1 in a freewheeling position,

Fig. 3

a longitudinal section through the rotary pulse generator and the braking force generator after Fig. 2 in a braking position,

Fig. 4

a diagram of the torque and axial force curve when generating an angular momentum by the angular momentum generator,

Fig. 5a to 5c

in each case a cross section through the braking force generator in three embodiments and

Fig. 6

an exploded view of the rotary pulse generator and a frictionally acting braking force generator.

Fig. 1 shows a hand tool 2 in the form of a Tangentialschlagschraubers having a housing 4, in which a universal motor 6 is housed. The universal motor 6 drives a drive spindle 10 in the direction of rotation D about an axis A via a motor pinion 8.

The drive spindle 10 can be rotationally coupled to a tool spindle 14 via a rotary pulse generator, designated in its entirety by 12. The tool spindle 14 is in turn rotatably connected to a tool holder 16 to which a tool bit 18, for example in the form of a screwdriver bit or a drill, in particular a metal drill, can be attached.

Further, on the tool spindle 14, a braking force generator designated generally by 20 is provided, via which the tool spindle 14 can be acted upon by a braking force counter to the direction of rotation D. The braking force generator 20 has a sleeve-shaped carrier body 22, which is penetrated by the tool spindle 14.

As in particular from Fig. 2 can be seen, the carrier body 22 is displaceable in the axial direction but rotatably mounted in the housing 4. In this case, on an inner side 24 of the carrier body 22 a transverse to the axis A around the tool spindle 14 around circumferential annular groove 26 and two parallel to the axis A aligned recesses 28 are inserted, which open into the annular groove 26.

In the in Fig. 2 illustrated position of the braking force generator 20 projects into a transverse bore 30 of the tool spindle 14 radially displaceable, spherical detent body 32 in the annular groove 26. The detent body 20 is biased by a radial spring 34 against the inner side 24 of the support body 22 and forms together with the recesses 28 and the annular groove 26 a total of 35 designated and disconnectable latching device.

As further out Fig. 2 can be seen, the rotary pulse generator 12 on a racket element 36 on which two racket projections 38 are formed, which protrude in the direction of the axis A. The Schlagervorsprünge 38 are applied in the direction of rotation D to spindle projections 40 which project in the radial direction of the tool spindle 14, as indicated by dashed lines.

The racket element 36 is biased in the direction of the tool spindle 14 by means of an axial spring 42, which is supported on a bearing ring 44 fixedly connected to the drive spindle 10. For this purpose, the axial spring has a spring stiffness of 10 ³ to 10 ⁵ N / m. In this case, the beater element 36 is in contact with the drive spindle 10 via ball-shaped rotary drivers 46. For this purpose, the rotary drivers 46 are guided on the one hand in a zigzag-shaped, circumferential cam groove 48, which is embedded in the drive spindle 10. Alternatively, for each Drehitnehmer 46 also own, only partially circumferential cam 48 are provided. At the same time, the rotary drivers 46 project partially into control recesses 50, which are embedded in an axial bore 52 of the racket element 36.

When turning on the universal motor 6 in this position, a drive torque M _{A is delivered} from the drive spindle 10 to the rotary driver 46, which are pressed by the axial spring 42 both against the control groove 48 and against the respective control recess 50 initially in a fixed position. In this position, the rotational drivers initially remain upon rotation of the drive spindle 10 and in this way transmit the drive torque M _A to the racket element 36. From this, the drive torque M _A on the Schlierervorsge 38 and the spindle projections 40 on the tool spindle 14 and from there to the Transfer tool holder 16.

Here, the locking body 32 runs freely in the annular groove 26, so that no significant braking force acts on the tool spindle 14 of the braking force generator 20. The braking force generator 20 is located in Fig. 2 thus in a freewheeling position, which are particularly suitable for driving screws and bolts, not shown, into a workpiece.

In such a screwing-in process, a resistance moment M _B on the tool spindle 14, which is opposite to the drive torque M _A , is generated via the tool bit 18 and the tool receptacle 16 which engage with the screw or the bolt. Once this resistance moment M _{B reaches} a threshold which is in a range of 1 to 5 Nm, the rotary drivers 46 can no longer be held in their fixed position, but move along with the racket element 36 along the cam 48 away from the tool spindle 14 , Here, the stroke of the bat member 36 is between 5 and 20mm. In this way, the racquet projections 38 come out of engagement with the spindle projections 40, so that they are moved in the direction of rotation D past each other. At the same time, the action of the resistance moment M _B on the racket element 36 is interrupted.

As soon as the beater projections 38 have passed the respective spindle projection 40 on which they were previously in contact, the remaining beater element 36 is pressed by the axial spring 42 in the axial direction against the spindle projections 40. At the same time, the beater element 36 is accelerated along the control groove 48 in the direction of rotation D, so that the beater projections 38 are now beaten against the respective other spindle projection 40.

In this way, a recurring angular momentum is transmitted to the tool spindle 14 by the rotary pulse generator 12, through which the screw to be screwed or the bolt is subjected to an intermittent torque of 5 to 300 Nm. Thus, screws and bolts can be turned on or turned off counter to high resistance torques M _B with this hand tool.

Fig. 3 shows the hand tool 2 in a Schlagbohrstellung, which is particularly suitable for drilling metal, such as steel. In this position, the support body 22 is displaced in the axial direction relative to the housing 4, that the locking body 32 is now biased at the level of the two recesses 28 against the inside 24.

When switching on the universal motor 6, in this position, in turn, the drive torque is transmitted from the drive spindle 10 via the rotary pulse generator 12 to the tool spindle 14. Here, the locking body 32, as shown, comes into engagement with one of the recesses 28. The braking force generator 20 is located in Fig. 3 thus in a braking position, which is particularly suitable for drilling in metal.

In this braking position, the positive engagement between the latching body 32 and the respective latching recess 28 generates a braking force opposing the direction of rotation D, resulting in a resistance moment M _B of from 1 to 5 Nm on the tool spindle 14. The resistance element M _{B is} sufficient to enable the angular momentum generator 12 to be in the beating state described above independently of the external forces acting on the tool bit 18.

The beater element 36 causes by the movement in the axial direction a pressing of the tool bit 18, which is used for this purpose in the form of a metal drill, against the respective workpiece to be machined. During this pressing operation, the beater element 36 also strikes with the beater projections 38 in the direction of rotation D against the spindle projections 40. As is apparent from the diagram Fig. 4 is apparent thereby in the direction of rotation D reaches an intermittent torque M of 300 Nm with a simultaneous short contact pressure F of about 1 kN. As a result, the tool bit 18 can cut particularly well into the workpiece without a person operating the hand tool 2 having to exert an increased contact pressure.

The Fig. 5a to 5c show a cross section through the braking force generator 20 for three different embodiments of the recesses 28a-c. The positive engagement of the locking body 32 in the respective recess 28 is overcome only by the angular momentum generated by the rotary pulse generator 12. Here, the engagement body 32 is pressed against the radial spring 34 in the transverse bore 30 and the positive engagement repealed. The locking body 32 thus jumps in operation with each angular momentum in the direction of rotation of the one locking recess 28 to the other.

In the embodiment according to Fig. 5a the recesses 28a are formed by two opposing grooves 28a recessed into the inside 24, which are aligned parallel to the axis A. At these grooves, the locking body 32 in the direction of rotation D in operation produce a positive engagement with the rotationally fixed carrier body 22. When the locking body 32 is moved from one groove 28a to the other, it is almost completely pushed into the transverse bore 30 between two locking positions.

In the embodiment according to Fig. 5b the locking recesses 28 are formed by two recessed into the inside 24 and in cross-section spiral ramp recesses 28b formed only in the direction of rotation D a paragraph 58 as a stop for the locking body 32. When jumping between the locking positions of the locking body is thus along the Rampenausnehmungen 28b gradually moved from the indented into the transverse bore 30 position in the disengaged engagement position on the next paragraph 58.

In the embodiment according to Fig. 5c the recesses 28 are formed by two in the inside 24 sunken and in cross-section arcuate recesses 28c. These form in the direction of rotation between two stop ribs 60, which act stop for the locking body 32. In this embodiment, it is ensured that the latching body 32 is pressed against the carrier body 22 with as little force as possible during the transition from the stop on the one stop rib 60 to the stop on the other stop rib 60.

In all three embodiments, the rotational strength of the carrier body 22 relative to the housing 4 is achieved by a rib 54 which engages in a corresponding receptacle 56 on the housing 4.

Fig. 6 shows the rotary pulse generator 12 together with another embodiment of the braking force generator 20 in an exploded view. In this braking force generator 20, the carrier body 20 is formed by an elastic friction ring, for example made of rubber or plastic. This friction ring is rotatably mounted in the housing 4 according to the above-mentioned carrier bodies 20 and generated by friction on the surface of the tool spindle 14, the necessary moment of resistance M _B to trigger the rotary pulse generator 12.

In addition to the braking force generators 20 described above, other embodiments are conceivable. For example, could be made between the tool spindle 14 and the housing 4 a positive connection via a controlled locking member or a frictional connection via a controlled clamping member. The control of the locking member or the clamping member could be carried out, for example, electromagnetic, piezoelectric, electrostrictive or magnetostrictive.

Claims (13)

1. Hand-held machine tool (2) comprising a drive spindle (10) which can have a drive moment (M_A) applied to it by a motor (6), a tool spindle (14) which can be coupled to the drive spindle (10) to drive a tool bit (18) in a direction of rotation (D) and is linked in twistproof manner to a tool receptacle (16) on which the tool bit (18) can be mounted, and a rotary impulse generator (12) which, on reaching a threshold value with regard to a moment of resistance (M_B) acting on the tool spindle (14), applies a rotary impulse to said tool spindle, characterised in that arranged on the tool spindle (14) is a braking force generator (20), via which a braking force acting against the direction of rotation (D) can be applied to the tool spindle (14), and that the moment of resistance (M_B) of the tool spindle (14) can be increased independently of an external moment of resistance.
2. Hand-held machine tool according to claim 1, characterised in that the tool spindle (14) can have an axial force impulse applied to it via the rotary impulse generator (12).
3. Hand-held machine tool according to claim 1 or 2, characterised in that the braking force generator (20) can be optionally switched on and off.
4. Hand-held machine tool according to one of the claims 1 to 3, characterised in that the braking force generator (20) has a support member (22) which is mounted in twistproof manner and through which the tool spindle (14) extends.
5. Hand-held machine tool according to claim 4, characterised in that pre-tensioned positive frictional locking can be created between the support member (22) and the tool spindle (14).
6. Hand-held machine tool according to claim 5, characterised in that the positive frictional locking can be created by means of a locking apparatus (35) arranged between the support member (22) and the tool spindle (14), said locking apparatus (35) carrying a locking member (32) radially displaceably on an element comprising the tool spindle (14) and the support member (22), said locking member (32) being pre-tensioned against the respective other element in which at least one suitable locking recess (28) is created for accommodating the locking member (32).
7. Hand-held machine tool according to claim 6, characterised in that the locking recess (28) is formed by a groove (28a) extending transversely to the direction of rotation (D).
8. Hand-held machine tool according to claim 6, characterised in that the locking recess (28) is formed by a ramped recess (28b) which has a spiral-shaped cross-section wherein the depth of the ramped recess (28b) increases continuously in the direction of rotation (D) as far as a shoulder (58).
9. Hand-held machine tool according to claim 6, characterised in that the locking recess (28) is formed by a depression (28c) about the axis A which is circular segment-shaped in cross-section and has a constant depth over its length.
10. Hand-held machine tool according to one of the claims 6 to 9, characterised in that the support member (22) is displaceable between a braking position in which the locking member (32) is arranged at the axial height of the locking recesses (28) and a free-running position in which the locking member (32) is arranged at the height of an annular groove (26) which extends peripherally in the direction of rotation (D).
11. Hand-held machine tool according to one of the claims 4 to 10, characterised in that frictional locking can be created between the support member (22) and the tool spindle (14).
12. Hand-held machine tool according to claim 11, characterised in that the support member (22) is formed by means of an elastic friction ring.
13. Hand-held machine tool according to one of the claims 1 to 12, characterised in that the threshold moment lies in the range of 1 Nm to 5 Nm.

Images