EP1391269B1 - Hand tool, especially screwdriver - Google Patents

Description

The invention relates to a power tool, such as screwdriver, with a machine engine and a drive from a drive motor to a rotational movement drivable, connectable with a tool drive shaft, the transmission contains at least one epicyclic gear with a rolling off in operation on the internal ring gear of a ring gear Getrieberädanördnung and wherein the ring gear is associated with a safety device which loaded by spring force to the ring gear, movably mounted detent balls which are in Verrastungseihgriff the occurrence of with respect to a turn-off torque smaller torques on the ring gear with the ring gear and hold it against rotation and upon reaching the Shut-off torque from the ring gear against the spring force are displaced from its engaged position, so that the ring gear can vorberehschen the locking balls ring gear is enclosed by a machine-mounted bearing ring, which on the Umfan g arranged distributed, in the radial direction through bearing recesses for receiving in each case a detent ball, wherein the wall thickness of the bearing ring is smaller than the diameter of the detent balls, that the detent balls associated detent recesses are arranged on the outer circumference of the ring gear. Such a hand tool machine, according to the preamble of claim 1, is disclosed in DE 3636301.

For example, in the case of a screwdriver, with which a screw is screwed into a workpiece, the screw-in to avoid overloading only up to a certain torque on the screw attack at

the screw is securely tightened. For this purpose, a safety device of the type mentioned can be provided, which operates depending on the torque. The torque required for screwing is transmitted to the drive shaft by supporting the gear wheel arrangement on the ring gear. In this case, the ring gear is held against rotation by the locking balls latched to it. Upon reaching the turn-off torque exerted by the ring gear on the detent balls force is so large that the detent balls back against the spring force, so that the ring gear is no longer held but driven by the gear assembly to a rotary motion.

It goes without saying that it can also be any other hand tool machine instead of a screwdriver, in which a torque-dependent shutdown makes sense.

The present invention has for its object, the backup device as simple and inexpensive and in such a way to design that the turn-off torque can be adjusted by the user in handling simple manner and adapted to the particular application.

This object is achieved according to the invention that the bearing ring is enclosed by a support ring movable in the axial direction, which is loaded by the spring force in the axial direction and held by an oblique surface arrangement against the detent recesses protruding from the other and the ring gear resting balls, that the support ring rotatable from the outside to the power tool is arranged and that the inclined surface arrangement of distributed over the circumference, each associated with a detent ball and extending in the circumferential direction inclined surface areas is formed, within which viewed in cross-section oblique surface slope changes in the circumferential direction, so that depending on the rotational position of the support ring, the inclined surface areas with a rest on the rest of the detent balls.

At the inclined surface areas, the spring force exerted in the axial direction on the support ring is deflected so that the detent balls resting against the inclined surface areas are acted upon inwardly toward the ring gear. In addition to the spring force, the inclined surface pitch determines the force exerted on the detent balls. Therefore, the detent balls are held depending on the rotational position of the support ring with a different force against the ring gear. In this way, the turn-off torque can be changed and adapted to the particular application. The handling is very simple, since the support ring only has to be twisted.

Advantageous embodiments of the invention are specified in the subclaims.

Figur 1

eine Handwerkzeugmaschine in Gestalt eines Schraubers in schematischer Seitenansicht,

Figur 2

eine Umlaufgetriebestufe des Schraubers nach Figur 1 mit der zugehörigen Sicherungseinrichtung in gesonderter Darstellung in axialer Richtung gemäß Pfeil II in Figur 1 gesehen,

Figur 3

die Anordnung nach Figur 2 im zur Zeichenebene der Figur 1 parallelen Halbschnitt gemäß der Schnittlinie III-III in Figur 2, wobei die innerhalb des Hohlrades angeordnete Getrieberadanordnung der Übersichtlichkeit wegen weggelassen ist und die Rastkugeln am Hohlrad eingerastet sind,

Figur 4

die Anordnung nach Figur 3, wobei das auf das Hohlrad einwirkende Drehmoment das Abschalt-Drehmoment erreicht hat, so dass die Rastkugeln aus den Rastausnehmungen des Hohlrads ausgetreten sind,

Figur 5

den Stützring der Sicherungseinrichtung nach den Figuren 2 und 4 in gesonderter Darstellung im den Figuren 3 und 4 entsprechenden Schnitt,

Figuren 6, 7 und 8

die Stützringwandung in Umfangsrichtung mit Abstand zueinander angeordneten Schnitten, wobei die Schnittebene der Figur 6 der Schnittebene der Figur 5 entspricht und die Schnitte gemäß den Figuren 7 und 8 etwa bei den Schnittlinien gemäß den Pfeilen VII-VII und VIII-VIII gelegt sind,

Figur 9

eine der Figur 3 entsprechende Darstellung einer variierten Sicherungseinrichtung, bei der der Stützring anschließend an die Schrägflächenbereiche jeweils einen Neigungsbereich größerer Steigung aufweist und

Figur 10

die gleiche Variante in der Figur 4 entsprechender Darstellung.

An embodiment of the invention will be explained with reference to the drawing. Show it:

FIG. 1

a hand tool in the form of a screwdriver in a schematic side view,

FIG. 2

an epicyclic gear stage of the screwdriver of Figure 1 with the associated safety device in a separate representation in the axial direction as indicated by arrow II in Figure 1,

FIG. 3

the arrangement according to FIG. 2 in the half-section parallel to the plane of the drawing according to the section line III-III in FIG. 2, wherein the gear wheel arrangement arranged within the ring gear has been omitted for reasons of clarity and the locking balls are engaged on the ring gear,

FIG. 4

the arrangement of Figure 3, wherein the torque acting on the ring gear has reached the turn-off torque, so that the locking balls have exited from the locking recesses of the ring gear,

FIG. 5

the support ring of the safety device according to Figures 2 and 4 in a separate representation in the figures 3 and 4 corresponding section,

FIGS. 6, 7 and 8

the support ring wall in the circumferential direction with spaced-apart sections, wherein the sectional plane of Figure 6 corresponds to the sectional plane of Figure 5 and the sections are placed according to the figures 7 and 8 approximately at the section lines according to the arrows VII-VII and VIII-VIII,

FIG. 9

3 shows a representation corresponding to a varied safety device, in which the support ring then has an inclination range of greater pitch, following the oblique surface areas, and

FIG. 10

the same variant in Figure 4 corresponding representation.

In the resulting from Figure 1 hand tool 1 is a screwdriver. However, it could also be, for example, a drill or other machine, with which a tool is driven to a rotational movement.

The power tool 1 includes a machine engine, not shown, and a drive shaft 2 drivable by the engine via a gear, which can be rotatably connected to a tool, not shown, for example, a screw-in tool in the form of a bit. During operation, the drive shaft 2 performs a rotational movement with the tool about the axis of rotation of the drive shaft 2 corresponding Rotationsachslinie 3 from.

The transmission includes an epicyclic gear stage 4 (there may be a plurality of gear stages connected in series), which is formed by a planetary gear with a central sun gear 5, three planet gears 6 distributed over the circumference and a ring gear 8 having an internal ring gear 7. In the sun gear 5 and the planetary gears 6, the respective external gears are not shown for simplicity, so that these wheels are drawn only as circles. The sun gear 5 is non-rotatably mounted on the motor shaft 9 or another shaft driven by the machine motor and meshes with the planetary gears 6 arranged around the sun gear 5, which roll on the radially inner ring gear 7 of the ring gear 8. The Planetenradachsen 10 are components of the otherwise not shown web of the planetary gear, via which the subsequent gear stage or the drive shaft 2 is driven. The design and operation of such a planetary gear is well known, so that a further description is unnecessary. It is merely noted that in normal operation, the planetary gears 6, depending on the direction of rotation of the drive shaft 2, for example, in the direction of arrow 11 revolve around the sun gear 11. In this case, the transmitted via the Planetenradachsen 10 and the web of the planetary gear torque is absorbed by the ring gear 8.

During normal operation, when the torque acting on the ring gear 8 is less than a turn-off torque, the ring gear 8 is arranged rotationally fixed. However, if the torque reaches the value of the turn-off torque, the rotationally fixed stop of the ring gear 8 is released, so that the ring gear 8 is driven via the planet gears 6 to a rotational movement in the direction indicated by arrow 12. In this way, the drive shaft 2 or the tool connected to this work only with torques that are smaller than the turn-off torque.

To achieve this, the ring gear 8 is associated with a safety device. This safety device has a machine-mounted, the ring gear 8 enclosing bearing ring 13, which distributed over the circumference, arranged in the radial direction bearing recesses 14 includes, each receiving a detent ball 15 movable in the radial direction. In this case, the wall thickness of the bearing ring 13 is smaller than the diameter of the detent ball 15. The detent balls 15 are in normal operation below the turn-off torque with the ring gear 8 in latching engagement, so that the ring gear 8 is held against rotation (Figures 2, 3 and 9) , For this Verrastungseingriff distributed over the circumference locking recesses 16 are arranged on the outer circumference of the ring gear 8. Each detent ball 15 is associated with such a recess 16. In FIG. 2, the ring gear 8 has six bearing recesses 16. In contrast, only three locking balls 15 are present, so that only three locking recesses 16 are occupied by a detent ball 15.

The locking between the locking balls 15 and the recesses 16 is formed so that the ring gear 8 exerts an outwardly directed force on the locking balls 15. For this purpose, in the embodiment, the circumferentially opposite flanks 17, 18 of the recesses 16 are inclined accordingly.

The detent balls 15 are loaded by means of a spring force to the ring gear 8, so that they protrude when the machine and during normal operation under the spring force at the ring gear 8 facing inside of the bearing ring 13 from the bearing recesses 14 and engage in the recesses 16. The spring force does not act directly but via a support ring 19 on the locking balls 15. The support ring 19 surrounds the bearing ring 13 and is arranged to be movable in the axial direction. In this case, the support ring 19 is acted upon in the axial direction by the spring force. The support ring 19 further has a locking balls 15 facing inclined surface arrangement 20, with which the support ring 19 abuts against the bearing balls 15. When the machine is switched off and in normal operation below the turn-off torque, the locking balls 15 are not only inside but also outside of the recesses 16, so that the inclined surface 20 can rest under the spring force in the axial direction of the locking balls 15. In this case, a force deflection takes place on the inclined surface arrangement 20, so that a radially directed force component acts on the locking balls 15.

Reaches the torque on the ring gear 8, the value of the turn-off torque, 16 of the respective flanks 17 and 18 of the recesses 16 exerted so strong force from the inside on the locking balls 15 that they move outward and thereby on the inclined surface arrangement 20 displace the support ring 19 against the spring force in the axial direction (see Figures 4 and 10). The locking balls 15 are thus displaced from the ring gear against the spring force from its engaged position when reaching the turn-off torque, so that the ring gear 8 is released and can rotate. It rattles past the locking balls 15.

In this way, no greater torque than the turn-off torque can be transmitted to the drive shaft 2.

The force with which the support ring 19 acts on the locking balls 15 and thus determines the turn-off torque depends not only on the spring force but also on the in cross-section (Figures 3 to 10) seen slope of the inclined surface arrangement.

In the hand tool according to the invention, the turn-off torque is adjustable. For this purpose, the support ring 19 is rotatably arranged on the hand tool 1 from the outside. Furthermore, the oblique surface arrangement of distributed over the circumference, each associated with a detent ball 15 and extending in the circumferential direction inclined surface regions 21, 22, 23 are formed, within which in the circumferential direction seen in cross-section inclined surface pitch changed. This can be seen in particular from Figures 6 to 8, which show the support ring 19 at three within the same inclined surface region 21 at a distance in the circumferential direction to each other arranged locations. The three inclined surface regions 21, 22, 23 are identical. Thus, the inclined surface portions 21, 22, 23 depending on the rotational position of the support ring 19 with a different pitch on the locking balls 15. Accordingly, depending on the rotational position of the support ring 19, a different turn-off torque is required, in which the locking balls 15 move under axial displacement of the support ring 19 from the recesses 16.

In the illustrated embodiment, the support ring 19 is rotationally fixed, but it is connected in the axial direction movable with a surrounding him adjusting ring 24, which is arranged accessible from the outside to the machine tool, as can be seen from Figure 1. In this case, the adjusting ring 24 is rotatable and fixedly mounted in the axial direction on the machine housing. The non-rotatable and thereby axially displaceable connection of the support ring 19 and the adjusting ring 24 with each other can be prepared, for example, that distributed on the outside of the support ring 19 distributed over the circumference, axially directed guide grooves 25 and the adjusting ring 24 in the guide grooves 25 engaging guide ribs 26. Of course, it would also be possible to provide the guide grooves inside the adjusting ring and the guide ribs on the support ring.

The spring force holding the support ring 19 against the detent balls 15 is generated by a spring arrangement formed in the embodiment of several distributed over the circumference coil springs 27, which is supported in the axial direction on the one hand on the adjusting ring 24 and on the other hand on the support ring 19. For this purpose, the adjusting ring 24 has a radially inwardly directed annular portion 28 on which the coil springs 27 are supported.

There are applications in which the safety device, i. the torque shutdown, should be ineffective. In order to achieve this, a retaining part 29 protruding toward the bearing ring 13 is arranged on the inner circumference of the support ring 19 between the inclined surface regions 21, 22, 23 in each case. Does the support ring 19 such a rotational position, in which the retaining parts 29 are above the locking balls 15, the retaining portions 29 prevent leakage of the locking balls 15 from the recesses 16 of the ring gear 8, so that the locking balls 15 regardless of the torque occurring on the ring gear 8 be held in their latched with the ring gear position.

Switching off when the shutdown torque is reached should be as fast as possible. Therefore, the support ring 19 should move so fast as far in the axial direction that over the detent balls 15 sufficient space for their exit from the recesses 16 is created. However, the path of movement of the support ring 19 is from the slope of the inclined surface arrangement measured with respect to the axial direction 20 dependent. The smaller this slope is, the longer is the path of movement of the support ring 19. A smaller pitch corresponds to a larger turn-off torque. Therefore, a safety device designed for larger turn-off torques, if no further measures are provided, switches more slowly than a safety device designed for smaller turn-off torques.

In order to obtain a fast shutdown despite a relatively small pitch, is provided in the variant of Figures 9 and 10 that in the axial direction of the inclined surface areas 21, 22, 23 each in the circumferential direction of the respective inclined surface area, for example, the inclined surface area 21, along extending slope surface region 30 connects, which has a greater slope than the adjacent inclined surface region 21. In this way, the support ring 19 must move only a short distance until the locking balls 15 so to speak over the flattened between the flatter inclined surface areas 21, 22, 23 and the steeper slope surface areas 30 each edge 31 tilt and thus can quickly reach the outside.

Finally, it is apparent from the drawing that the support ring 19 in the axial direction subsequent to the inclined surface regions 21, 22, 23 (Figures 2 to 7) and the inclination surface regions 30 (Figures 9 and 10) projecting in the axial direction of a ring portion 32 as Failure for the detent balls 15 has. The ring section 32 covers radially outside the receiving space 33, in which the locking recesses 16 of the ring gear 8 displaced from the locking recesses 15 pass.

In the described embodiment, the planetary gear on three planet gears. It is understood that a different number of planetary gears could be present.

Furthermore, instead of six bearing recesses 16 and three locking balls 15, more or fewer bearing recesses or detent balls are also possible.

Claims (6)

1. Hand-operated power tool, for example a screwdriver, with a machine motor and a drive shaft, connectable to a tool, which may be driven by the machine motor via a gear to make a rotary movement, wherein the gear has at least one planetary gear step with a gearwheel assembly rolling off the internal gear rim of a ring gear in operation, and wherein the ring gear is assigned a safety device with movably supported locating balls biased towards the ring gear by spring force and which, on the occurrence of a lower torque at the ring gear than a tripping torque, make locking engagement with the ring gear and keep it non-rotatable and, when the ring gear reaches the tripping torque, are forced against the spring force out of their engaged position, so that the ring gear can ratchet past the locating balls, wherein the ring gear (8) is encompassed by a bearing ring (13) fixed to the machine and which has bearing recesses (14) distributed over the periphery and continuous in the radial direction, each holding one locating ball (15), wherein the wall thickness of the bearing ring (13) is less than the diameter of the locating balls (15), that on the outer periphery of the ring gear (8) are arranged locating recesses (16) assigned to the locating balls (15), characterised in that the bearing ring (13) is encompassed by a support ring (19) movable in the axial direction and biased by the spring force in the axial direction and held via an inclined surface arrangement (20) against the locating balls (15) protruding from the locating recesses (16) and at the other end fitting up against the ring gear (8), that the support ring (19) is mounted on the hand-operated power tool so as to be rotatable from the outside, and that the inclined surface arrangement (20) is formed by inclined surface areas (21, 22, 23) distributed over the periphery, each assigned a locating ball (15) and extending in the peripheral direction, and within which the inclined surface gradient, viewed in cross-section, changes in the peripheral direction, so that depending on the rotary position of the support ring (19), the inclined surface areas (21, 22, 23) are able to fit up against the locating balls (15) at a different pitch.
2. Hand-operated power tool according to claim 1, characterised in that a sloping surface area (30), extending along the relevant inclined surface area in the peripheral direction, adjoins each of the inclined surface areas (21, 22, 23) in the axial direction, wherein the sloping surface areas (30) have a gradient which is greater than the inclined surface areas (21, 22, 23), with reference to the axial direction.
3. Hand-operated power tool according to claim 1 or 2, characterised in that the support ring (19), in the axial direction adjacent to the inclined surface areas (21, 22, 23) or to the sloping surface area (30), has a ring section (32) extending in the axial direction to prevent the locating balls (15) from falling out.
4. Hand-operated power tool according to any of claims 1 to 3, characterised in that on the inner periphery of the support ring (19) in the peripheral direction between the inclined surface areas (21, 22, 23) there is provided in each case a retaining section (29) extending towards the bearing ring (13), so that with the retaining sections (29) rotated over the locating balls (15), the locating balls (15) are held in the locating recesses (16) of the ring gear (8), irrespective of the torque occurring at the ring gear (8).
5. Hand-operated power tool according to any of claims 1 to 4, characterised in that the support ring (19) is connected non-rotatably, but axially movable, to a rotatable and axially fixed adjusting ring (24) which surrounds it and is accessible from the outside, wherein a spring assembly (27) generating the spring force rests in the axial direction at one end on the adjusting ring (24) and at the other end on the support ring (19).
6. Hand-operated power tool according to claim 5, characterised in that there are provided on the outside of the support ring (19) or on the inside of the adjusting ring, distributed over the periphery, axially aligned guide slots (25), and on the adjusting ring (24) or on the support ring, guide ribs (26) engaging in the guide slots (25).

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