EP1258321A2 - Power driven screwdriver with torque limiting clutch - Google Patents

Abstract

The power screwdriver has a torque limiting coupling with first part (96) and second part (90), a spring element and at least one roll body (104). Both the coupling parts have locking elements (109, 196) on them, by which the two coupling parts are directly locked to each other when the screwdriver is being rotated in the unscrewing direction.

Description

The invention relates to a power screwdriver Screwing in and loosening screws, with a torque dependent triggering torque limiting clutch, which is a first clutch part, a second coupling part, a spring element for axial bracing of the first coupling part against the second Coupling part and at least one between the two coupling parts has rolling elements over which the two Coupling parts when driving the screwdriver in one first direction of rotation (working direction) until a preset trigger torque are coupled together.

Such a screwdriver is known from WO 99/16858.

Power driven screwdriver for screwing in and loosening screws have traditional hand screwdrivers increasing in the past replaced. In the commercial sector, predominantly power-driven screwdriver with a torque-dependent trigger Torque limiting clutch used because there are screws usually screwed in with precisely defined tightening torques should be. Screws are the broadest here Senses all types of threaded fasteners understood, especially screw nuts.

Torque limit clutches are in a powertrain between a drive of the screwdriver and a tool holder arranged. The torque limiting clutch interrupts the connection between the drive and the tool holder, as soon as a screwed-in screw with the desired force in a thread receiving the screw is clamped. The Torque with which the screwdriver is then driven to the a stuck screw acts as the release torque and can usually be set on the torque limiting clutch become. So that the drive does not release the torque limiting clutch idle, the torque limiting clutch works usually on an additional switch, at the Actuation of the drive is switched off. With a change the direction of rotation, i.e. To loosen screws, a higher one must be used Torque than be applied when screwing in, so for this suitable torque limiting clutches are often asymmetrical Show trigger behavior.

For example, DE 34 32 376 A1 describes a power-driven one Known screwdriver, its torque limiting clutch two clutch disks braced against each other by means of a compression spring includes. The clutch discs have spur gears whose teeth each have two different inclinations Have flanks. If the trigger torque is exceeded, slide the two spur gears on the less inclined Contrary to the action of the compression spring, flanks separate and arrive eventually disengaged, causing the torque limiting clutch opens. When loosening a screw that given by the spring tension and the slope of the flank Release torque higher than when screwing in, since the flanks then are steeper. This known torque limiting clutch has however, a relatively short service life, because on the teeth of the Spur gears when opening and closing the torque limiting clutch large shear forces act gradually lead to removal of the tooth edges.

A screwdriver is known from WO 99/16858 mentioned at the beginning, its torque-dependent clutch, which triggers as a function of torque not between two sections of a drive spindle, but between a housing of the screwdriver and one Ring gear of a planetary gear is arranged. The Ring gear takes a reaction torque of the planetary gear the drive spindle and is rotatably accommodated in the housing. In addition to the rotatable ring gear, the torque limiting clutch has an axially displaceable ring gear, which is clamped against the ring gear with the help of a compression spring. Are on a face of the ring gear facing the ring gear three recesses in which balls are captive are held. On the ring gear itself is on the ring gear facing end face formed a tread on the three cams are arranged at equal angular distances.

When screws are screwed in, i.e. if a drive of the The drive spindle in a first direction of rotation (Working direction) drives, the balls are each on the Cam on and thereby transmit a torque between the Ring gear and the ring gear. The preset trigger torque however exceeded, the ring gear rotates with its cams under the balls of the ring gear. This leads to one Loosen the torque limiting clutch because the ring gear and thus the planetary gear no longer rotatably in the housing the screwdriver is fixed. It also shifts the ring gear axially opposite the ring gear, actuates one Switches and in this way switches the drive of the screwdriver from.

Torque limiting clutches in which the torque transmitting Surfaces of coupling parts over balls with each other are subject to less wear than Torque limit clutches where these surfaces are immediate slide on each other. A disadvantage of torque limiting clutches with balls, however, is that with a loosening Often screws do not have a sufficiently high torque either is available or an increased wear of the Torque limiting clutch must be accepted. He follows namely a different definition of the maximum transferable torques with the help of asymmetrically trained Cams on coupling parts, this always leads to that the balls when screwing a screw relative "slow" when releasing the torque limiting clutch via the less inclined leading edge of the cam can then run however, due to the steeper trailing edge of the cam suddenly roll down again, or what's even more unfavorable is sliding down. The resulting blow leads to signs of wear on the rolling elements and possibly also on the the coupling parts trained cams.

It is therefore an object of the invention to provide a power driven To improve screwdrivers of the type mentioned in such a way that the wear of the torque limiting clutch at the same time high operational reliability is reduced.

The invention solves this problem with a screwdriver at the beginning mentioned type in that on the two coupling parts Locking elements are formed, via which when the In a second direction of rotation (release direction) engage the two coupling parts immediately.

Due to the immediate locking of the two coupling parts when loosening a screw, very high torques can occur are transmitted between the two coupling parts, namely even without participation of the at least one rolling element. There this means the high torques when loosening a screw does not need to be transferred, a significantly lower total occurs Wear of the at least one rolling element as this with the previously known torque limiting clutches the case is. The same applies to the coupling parts trained cams, teeth, protrusions or steps on which the at least one rolling element when the torque limiting clutch is closed attacks. Under a latch here, moreover, every establishment of a positive connection understood between the two coupling parts. Preferably the locking elements of the coupling parts come during the positive locking flat in plant, so that even larger ones are free of deformation Allow torques to be transmitted between the coupling parts.

Due to the instant latching of the two according to the invention Coupling parts are therefore deliberately omitted, even when Loosen a screw using the torque limiting clutch to be able to perform a torque-dependent triggering. The lack of such a trigger option is from a safety point of view safe; should still be one Torque-dependent triggering also desirable when loosening screws can be, for example, a second according to the invention Torque limiting clutch connected in series that are only reversed at a higher torque Direction opens.

Since the coupling when loosening screws according to the invention the immediate locking between the two coupling parts treads formed on the coupling parts, on which the at least one rolling element runs, so executed be that the two coupling parts after one Exceeding the trigger torque when screwing in screws not suddenly, but now in any way you can specify to move towards each other again. This makes an overall essential Quieter coupling behavior achieved.

The two coupling parts can be locked in such a way that this is only manual, i.e. for example by a relative movement caused by an operator between the two coupling parts can be lifted again.

However, latching by reversing the direction of rotation is preferred of the screwdriver can be canceled.

In this way, the latching is automatic again canceled as soon as after loosening a screw the direction of rotation is reversed to screw in a screw. As long as however, the direction of rotation is maintained, the latching remains received so that any number of screws in a row can be released without additional coupling movements. On such automatic release of the latching can for example achieve that the locking elements only in one Direction of rotation get into the system and if the Can remove the direction of rotation from each other.

In a preferred embodiment of the invention are on each other end faces of the two coupling parts facing each other assigned sliding surfaces formed over which the two Coupling parts together at predetermined relative angular positions issue.

In this way it is achieved that the at least one rolling element completely or at least partially at certain angular positions is relieved, which further reduces wear becomes. These particular angular positions preferably include at least those where the coupling between the two coupling parts do not have at least one rolling element he follows. The forces then between the coupling parts act, then essentially go back only to the spring element, so that the at least one rolling element little or possibly is not charged at all.

This measure also allows the locking elements on the sliding surfaces train.

The at least one rolling element and areas of the coupling parts, on which the rolling element runs, are thus by the Training of the locking elements is not affected.

In a preferred development of this embodiment the sliding surface of a coupling part through an end face and protrusions formed axially therefrom. The sliding surface the other coupling part is formed by steps, which are each limited by paragraphs on which the projections can strike in the second direction of rotation.

In this way, one can be designed in a particularly simple manner Achieve locking between the two coupling parts. It is then only to ensure that through a relative rotation between the two coupling parts the projections of the coupling part on the shoulders of the other coupling part can strike and thus effect the locking.

In another preferred embodiment of the invention on the second coupling part a circumferential direction Cam track formed from several, preferably three, identical track sections.

This measure, which is known per se, enables the coupling behavior the torque limiting clutch to be structurally simple Be influenced by the formation of the cam track.

The cam track is preferably outside and concentric arranged to the sliding surface of the second coupling part.

An external cam track enables a relative large range of motion for the rolling element and thus a favorable Leverage for torque transmission via the rolling element.

It is further preferred in this embodiment if each path section has a cam, the flanks of which a run-up side and an outlet side for the at least one rolling element form. It is particularly preferred if the run-up side is steeper than the drain side.

If the run-up side is the side of the cam on which the at least one rolling element when screwing in a screw System, so this configuration leads to the fact that at least a rolling element slowly over the flatter outlet side rolls down, causing a sudden movement of the Coupling parts prevented after exceeding the release torque becomes. The ability to make the drain side flatter than that Executing on the run-up side is possible on the basis of the invention Locking possibility, because the coupling when loosening Screws no longer over the rolling element, but over the Latching is effected.

In a preferred development of this embodiment the slope of the discharge side with increasing distance from the Upstream side smaller.

This leads to the fact that the two coupling parts increasingly move more slowly towards each other. This allows the to slowly formed after both coupling parts if the trigger torque is exceeded, so that with an appropriate arrangement of the sliding surfaces a quasi-continuous Transition from a rolling movement with participation of the at least one rolling element for a sliding movement between the sliding surfaces is made possible. Also through this Wear and tear on the parts of the measure Torque limiting clutch reduced and an overall quiet Coupling behavior achieved.

In an additional development, the cam track has between the cam each on a section that is not of the is touched at least one rolling element.

In this way it is achieved that when the clutch between the two coupling parts do not have at least one Rolling takes place, this from that of the spring element exerted pressure is relieved. During this time the compressive force is then only absorbed by the sliding surfaces.

In another preferred development of this embodiment the sliding surfaces are arranged in relation to the cam track, that when driving the screwdriver in the first Direction of rotation (working direction) and closed torque limiting clutch the at least one rolling element with the run-up side a cam is in the system and at the same time first coupling part on the second coupling part in axial Direction supported on the sliding surfaces.

Such an arrangement means that the at least one Rolling elements not or only partially when screwing in a screw is loaded in the axial direction. This measure bears thus also to reduce wear on the at least one Rolling elements at.

The at least one rolling element can be, for example around a free-running ball or in a recess act as is known from the prior art.

However, the at least one rolling element is preferably in the form of a roller educated.

This has the advantage that the point contact that occurs when using of balls on their surface, by a linear touch is replaced. Distribute this way the forces acting on the at least one rolling element over a significantly larger area, causing wear to continue is reduced. The role can e.g. in a hollow cylindrical Be guided in the recess on the front side of the two coupling parts is formed.

However, the roller is preferably on one of the first coupling part held axis rotatably mounted.

Such guidance of the role allows a much more friction and thus the wear on the roller with less wear of the two coupling parts. The bearing formed on the axle can e.g. be designed as a needle bearing, which high Loads with low friction values.

In a preferred development of this embodiment the axis of rotation of the roll defined by the axis to a Longitudinal axis of the first coupling part spaced apart.

The axis of rotation of the roller therefore does not run through a radius of the first coupling part, but at an angle to it. Accordingly, the running direction of the roller is not tangential, but fixed at an angle to the tangent. This leads to the fact that in one of the two possible directions of rotation, which is preferably the direction of work, the role performs a self-centering movement. The role Therefore, it does not migrate outwards when it rolls and can thus do not dig into the surrounding housing parts.

In a further development of this embodiment, it is therefore preferred if the roller is floating on the axle.

This flying storage, which is due to the self-centering of the Role due to the not through the longitudinal axis of the first coupling part extending axis of rotation is simplified the bearing of the roller on the axis and reduces the size, since fastening parts are omitted.

Overall, it is also preferred if one of the two Coupling parts rotatably with a housing of the screwdriver and the other coupling part rotatably with a reaction torque towards a spindle and towards the housing freely rotatable reaction part of a transmission is connected.

Compared to torque limiting clutches that are directly between two sections of a drive train are arranged, this has the advantage that there is no rotational movement of the two coupling parts when the torque limiting clutch is closed. As a result, none act on the at least one rolling element significant centrifugal forces that contribute to its wear.

The reaction part is preferably one of several Ring gear receiving planetary gear of a planetary gear.

Planetary gears are special due to their distribution of forces reliable and durable and are therefore particularly suitable for power-driven screwdrivers in the commercial sector.

It is particularly preferred if that with the housing of the Screwdriver's torsionally connected coupling part in the axial direction is slidably arranged.

In this way, the axial displaceability and the rotatability divided into different coupling parts, whereby their fixing in the screwdriver housing is simplified.

It is also preferred if a switch for switching off the Screwdriver is provided by the in the axial direction slidably arranged coupling part is actuated.

This prevents the screwdriver from being driven after loosening the torque limiting clutch the coupling parts act and thus continue to circulate of the at least one rolling element between the two coupling parts leads.

It is understood that the above and those below Features to be explained not only in each case specified combination, but also in other combinations or can be used alone, without the scope of to leave the present invention.

Fig. 1

einen erfindungsgemäßen Schrauber in einer Seitenansicht;

Fig. 2

einen vorderen Abschnitt des in Fig. 1 gezeigten Schraubers, wobei durch einen Gehäuseausschnitt schematisch angedeutete Teile im Inneren des Schraubers erkennbar sind;

Fig. 3

einen axialen Schnitt durch einen Abschnitt eines Antriebsstrangs des in den Fig. 1 und 2 dargestellten Schraubers, in dem ein Planetenradgetriebe und eine Drehmomentbegrenzungskupplung in teilgeschnittener Darstellung erkennbar sind;

Fig. 4

eine in dem Schrauber nach den Fig. 1 bis 3 verwendete Spielkupplung in einer perspektivischen Darstellung;

Fig. 5

einen Schaltring der in Fig. 3 gezeigten Drehmomentbegrenzungskupplung in einer perspektivischen Darstellung;

Fig. 6

eine Draufsicht auf den Schaltring aus Fig. 5, bei der zusätzlich an dem Schaltring gelagerte Rollen dargestellt sind;

Fig. 7

eine schematische Darstellung der Anordnung der Achsen, um die die Rollen des in Fig. 6 gezeigten Schaltrings drehbar gelagert sind;

Fig. 8

einen Nockenring der in Fig. 3 gezeigten Drehmomentbegrenzungskupplung in einer perspektivischen Darstellung;

Fig. 9

eine Draufsicht auf den in Fig. 8 gezeigten Nokkenring;

Fig. 10a-h

jeweils einen Ausschnitt aus einer Abwicklung des in den Fig. 8 und 9 gezeigten Nockenrings mit verschiedenen Relativpositionen zwischen dem Nokkenring und dem Schaltring.

Further advantages and features of the invention result from the following description of an embodiment of the invention with reference to the drawing. In it show:

Fig. 1

a screwdriver according to the invention in a side view;

Fig. 2

2 shows a front section of the screwdriver shown in FIG. 1, parts schematically indicated in the interior of the screwdriver being recognizable by a housing cutout;

Fig. 3

an axial section through a portion of a drive train of the screwdriver shown in Figures 1 and 2, in which a planetary gear and a torque limiting clutch can be seen in a partially sectioned representation.

Fig. 4

a game coupling used in the screwdriver according to Figures 1 to 3 in a perspective view.

Fig. 5

a switching ring of the torque limiting clutch shown in Figure 3 in a perspective view.

Fig. 6

a plan view of the switching ring of Figure 5, in which additionally mounted rollers are shown on the switching ring.

Fig. 7

is a schematic representation of the arrangement of the axes about which the rollers of the shift ring shown in Figure 6 are rotatably mounted.

Fig. 8

a cam ring of the torque limiting clutch shown in Figure 3 in a perspective view.

Fig. 9

a plan view of the cam ring shown in Fig. 8;

10a-h

each a section of a development of the cam ring shown in FIGS. 8 and 9 with different relative positions between the cam ring and the switching ring.

In Fig. 1 is a screwdriver according to the invention in a side view shown and designated overall by 10. The Screwdriver 10 has a housing 11 with a main housing part 12 on which a handle portion 16 is formed. From there a main switch 18 can be operated conveniently by an operator. At the front end of the main housing part 12 is rotatable an angle head housing 19 attached to an angle head 20, of which is perpendicular to a longitudinal axis of the screwdriver 10 Tool holder 22 protrudes. Such screwdrivers are usually also called and have an angle screwdriver the advantage over conventional power-driven screwdrivers that the reaction torque recorded by the screwdriver at Screwing in screws does not turn the screwdriver around its longitudinal axis, but to pivot the screwdriver around the right-angled one, through the tool holder 22 defined axis leads. Such pivotal movements are easier for an operator to pick up than rotations the screwdriver around its longitudinal axis.

At the transition between the angle head housing 19 and the Main housing part 12 is a rotating ring 28 rotatable relative to the main housing part 12 is arranged. By brought in Slits 30, of which only the one facing the viewer in FIG. 1 A tool can be inserted into the screwdriver 10 with which the trigger torque of the screwdriver 10 in can be set in more detail to be explained.

Fig. 2 shows part of the screwdriver shown in Fig. 1 10 with partially removed housing parts. The through the Parts of the screwdriver 10 that can be seen through the housing opening are only indicated schematically.

The screwdriver 10 has, for example, an electric motor executed drive 32 on the opposite to one another the main housing part 12 fixed support sleeve 34 attached is. The drive 32 drives via an intermediate shaft 36 Reduction gear in the form of a planetary gear 38 which sets a spindle 40 in rotation on the output side. The Spindle 40 drives via an arranged in the angle head 20 Bevel gear toothing 46 on a tool spindle 44 on its free end carries the tool holder 22.

2 is a torque limiting clutch 50 shown schematically, which is a reaction moment against the spindle 40 receiving reaction part of the planetary gear 38 couples with an adjusting sleeve 52. The adjusting sleeve 52 is formed in one piece with an angle head housing 19 or connected non-rotatably to it via one or more intermediate parts. To twist the angle head 20, e.g. in the in Fig. 2 position shown in dashed lines, the entire angle head 20, i.e. the angle head housing 19 with housed therein Bearings 55 and 56 for the spindles 40 and 44 and the adjusting sleeve 52, opposite to the housing-fixed support sleeve 34 an adjustment device designed here as a screw connection 58 twisted. With torque limiting clutch 50 closed is also the reaction part of the planetary gear 38 with respect to the angular head 20 and fixed via the Adjustment device 58 coupled to the drive 32.

This definition of the planetary gear 38 on the angle head 20 with simultaneous coupling to the drive 32 via the adjustment device 58 has compared to the conventional definition on the main housing part 12 significant advantages, such as the following considerations.

It is assumed here that the spindle 40 is fixed by a tightened screw is blocked, so that the drive 32nd Torque generated entirely by the housing parts of the angle screwdriver 10 must be included. On the intermediate shaft 36 acts between the drive 32 and the planetary gear 38 then the torque generated by the drive 32. A corresponding one Counter torque of the same size is closed - at as assumed torque limiting clutch 50 - from the housing parts, namely the carrier sleeve 34 and the adjusting sleeve 52, added. This torque is around the reduction factor of the planetary gear 38 smaller than the torque that between the planetary gear 38 and the angle head housing 19 acts. The adjusting device 58 can therefore be simple Screw connection to be carried out, the additional locking mechanism can have. For torque transmission reasons such a locking mechanism is not required. If nevertheless such a locking mechanism known per se is desired, it can also be very simple and easy be built up because it only absorb small torques needs.

Corresponding considerations naturally also apply to screwdrivers, in which the reaction part of the planetary gear 38 is not via the torque limiting clutch 50, but directly on the adjusting sleeve 52 or another rotatably on the angle head 20 fixed part is attached.

3 shows in an axial section details of in FIG. 2 only schematically shown parts inside the screwdriver 10th

On a rotor socket 60 of hexagonal cross section in Fig. 3 only indicated drive 32 is an intermediate shaft 62 rotatably pushed on, in one piece with a first sun gear 64 of the two-stage planetary gear 38 is trained. The first sun gear 64 meshes with three first ones Planetary gears 66 of a first planetary gear stage, of which in Fig. 3 only two are recognizable. The first planet gears 66 are rotatably attached to a first planet carrier 68 and Comb at the same time with a ring gear 70, which over the entire axial length of the planetary gear 38 extends. The first planet gear carrier 68 has a second sun gear 72 integrally formed or non-rotatably connected, which with second planet gears 74 meshes. The second planet gears 74 are in turn rotatable on a second planet carrier 76 stored and mesh with the ring gear 70. Planetary axles 82 on which the second planet gears 74 are guided are enforcing the second planet carrier 76 and form connecting piece 80 on its side facing away from the transmission attack on wings of a driving wheel 84, which is called the hexagon executed spindle 40 drives and in the axial direction is supported on a ring 87 held by a snap ring 85. The connecting piece 80 and the driving wheel 84 form together one explained in more detail below with reference to FIG. 4 Game clutch 86.

The ring gear 70, which is opposite the intermediate shaft 62 and the Spindle 40 takes over a reaction moment and thus the reaction part of the planetary gear 38 is over a Bearing 88 rotatable in the support sleeve screwed to the drive 32 34 and the associated via the adjusting device 58 Adjustment sleeve 52 added. The ring gear 70 is on the Adjusting sleeve 52 (or a part connected to it in a rotationally fixed manner) the torque limiting clutch 50 set. This includes a cam ring 90 screwed non-rotatably into the ring gear 70, whose shoulder 92 protrudes over the ring gear 70 is also supported on the adjusting sleeve 52 via the bearing 88, as well as a switching ring 96 which against a compression spring 94 the cam ring 90 is clamped. The switching ring 96 is axial, i.e. in the longitudinal direction 95 of the spindle 40, displaceable, however rotatably in an intermediate sleeve connected to the adjusting sleeve 52 98 added. The non-rotatable, but axially movable Arrangement of the switching ring 96 is with the help of first and second longitudinal grooves 100 achieved on a circumferential surface of the Switching rings 96 or arranged on the inside on the intermediate sleeve 98 are and cooperate with guide balls 102. About the rolling in the first and second longitudinal grooves 100 and 101, respectively Guide balls 102 can the switching ring 96 and the intermediate sleeve 98 to each other in the axial direction, wherein a snap ring 105 inserted into the intermediate sleeve 98 Falling out of the guide balls 102 prevented.

On the side of the switching ring 96 facing the cam ring 90 are circumferentially three rollers 104 rotatably mounted on axes 106. The rollers 104 can roll on a cam track 108, that on an end face facing the switching ring 96 of the cam ring 90 is formed. At the cam ring 90 facing end of the switching ring 96 are also three Protrusions 109 are formed, the function of which is shown in FIG. 5 to 10 will be explained in more detail.

The compression spring 94 is supported on the back of a tensioning disk 110 from which can be moved in the axial direction in the intermediate sleeve 98 is included. Act on the spring washer 110 four clamping bolts 112 evenly distributed over the circumference, that in bores 114 that in a shoulder of the intermediate sleeve 98 are attached, are guided and on a collar Support 116. The collar 116 can be on an outside the intermediate sleeve 98 applied thread section 118 in the Shift longitudinal direction 95 by twisting. A longitudinal shift of the collar 116 on the threaded portion 118 of the Intermediate sleeve 98 is on the clamping bolt 112 and the clamping washer 110 transferred to the compression spring 94, so that on this Way the preload between the switching ring 96 and the cam ring 90 can be changed. For actuating the adjusting ring 116 a tool, e.g. a screwdriver, through one of the slots 30 in the rotating ring 28 (see FIG. 1 through in one of several sockets formed on the adjusting ring 116 122 introduced. Then the collar 116 together with the rotating ring 28 until the desired one Bracing the compression spring 94 and thus the triggering moment Torque limiting clutch 50 is reached.

The rollers 104 abut while a screw is being screwed in formed on the cam track 108 so that the reaction torque exerted on the ring gear 70 via the cams, the rollers 104 and the switching ring 96 on the intermediate sleeve 98 and thereby to the adjusting sleeve 52 connected to it in a rotationally fixed manner is transmitted so that the ring gear 70 during the screwing one screw rests. If the torque increases, it grows Torque acting on the cam ring 90 until there is Finally, the cam ring 90 begins to rotate and thereby the rollers 104 and thus the switching ring 96 counter to its cams the force of the compression spring 94 increases. With further rotation the cam ring runs with its cams under the rollers 104 away, so that the rollers 104 with the switching ring 96th finally lower again under the pressure of the compression spring 94.

During rotation of the cam ring 90 and the associated one Ring gear 70, the planetary gear 38 is no longer rotationally fixed set so that the drive 32 on the spindle 40th applied torque is practically reduced to zero. In which Lifting the switching ring 96 against the force of the compression spring 94 the switching ring 96 triggers a switch 124 which through the Intermediate sleeve 98 in a remaining above the switching ring 96 Free space 128 protrudes. Switch 124 interrupts the power supply for the drive 32 and thus provides sure that after the triggering torque is exceeded Do not turn cam ring 90 several times under switching ring 96.

Before further details on the torque limiting clutch 50 is received, should first be based on the following 4 shows the play coupling 86 provided for the screwdriver 10 between the planetary gear 38 and the spindle 40 described become.

In Fig. 4, the game clutch 86 is between the output of the Planetary gear 38 and the spindle 40 shown in perspective. The game coupling comprises the three nozzles 80, the the planet gear axles passing through the second planet gear carrier 76 82 are formed, and the driving wheel 84, which in one central recess of the second planet carrier 76 is rotatably guided. The driving wheel 84 has a central, designed as a hexagon passage 130 in which in assembled state one end of the also hexagonal in cross section Spindle 40 is inserted. From the middle of the Driving wheel 84 radially extends three wings 132 outside, to the extent that it is in contact with the socket 80 can reach. When a screw is screwed in, the Stub 80 with the second planetary gear receiving this 76 about the longitudinal axis 95 of the spindle 40 and engage the Wings 132 of the driving wheel 84. In this way, the im Driving wheel 84 guided spindle 40 to the output of the planetary gear 38 coupled.

If now the rotation limiting clutch is reached when the tripping torque is reached 50 releases, so causes the pressure spring 94 exerted Force that the socket 80 reverse their direction of rotation. at this movement in the direction indicated by an arrow 134 the sockets 80 are not in contact with the wings 132 of the drive wheel 84 so that no torque on the spindle 40th is transmitted. Because the through the torque limiting clutch 50 caused movement of the nozzle 80 is short, they remain stand in an intermediate position between the wings 132. at the play clutch 86 couples in a subsequent screwing operation therefore with a short delay.

5 shows the switching ring 96 in a perspective view. The switching ring 96 is in three sections 136, 138 and 140 different diameters. At first Section 136 with the largest diameter are on the circumference the longitudinal grooves 100 distributed at uniform angular intervals. About these longitudinal grooves 100, the switching ring 96 in the axial Movable in the direction, but non-rotatable with the help of the guide balls 102 held on the intermediate sleeve 98. The first section 136 closes the second section 138 and on the third section 140. This third section is 140 Provided on the circumference with three holes 142 that the recording serve the axes 106 and of which only those for the viewer in FIG. 5 pointing hole is recognizable. The mouths of the holes 142 surrounding area of the second section 138 and third section 140 is just milled to a bearing surface to create for the rolls 104.

On the one facing the cam ring 90 when assembled Face 143 of the switching ring 96 is a flat End face 144, which forms a sliding surface of the switching ring 96. The three projections 109 protrude from the end face 144, which also form sliding surfaces of the switching ring 96. By the entire switching ring 96 extends centrally a bore 148, by the spindle 40 freely rotatable in the assembled state runs.

FIG. 6 shows a top view of the end face 143 of the in Fig. 5 shown switching rings 96. In this illustration are also shown rollers 104 attached to the shift ring 96. Further 6 are the longitudinal grooves 100 and the Projections 109 can be seen. They are indicated by dashed lines the position of the axes 106 predetermined axes of rotation 152 of the rollers 104. As can be clearly seen in FIG. 6, the axes of rotation run 152 spaced from the perpendicular to the face 144 Longitudinal axis of the switching ring 96. The axes of rotation 152 therefore do not meet at a common point on this Longitudinal axis, but are offset to the circumference and the radius connecting the longitudinal axis.

The effect of this offset of the axes of rotation 152 is now based on the schematic representation of FIG. 7 explained. Through a The longitudinal axis 154 of the switching ring 96 is indicated crosswise. Between an axis of rotation shown in solid line in FIG. 7 152 and the longitudinal axis 154 remains one by two arrows indicated distance 156, which is between 5% and 15%, preferably between 9% and 11% of the distance between those marked with 158 Center of a roller rotating about the axis of rotation 152 and the longitudinal axis is 154. It is vertical with an arrow to the axis of rotation 152 running direction 160 indicated a role.

7 shows a vectorial decomposition direction 160 into a tangential motion component 163 and a radially inward motion component 164. The tangential motion component corresponds to 163 the running direction of a roller, the axis of which is not spaced apart to the longitudinal axis 154, but runs through it. With such a running direction, there would therefore be no radial movement component available.

In the new screwdriver, however, the distance is 156 between the Axis of rotation 152 and the longitudinal axis 154 and thus also the radial inward motion component 164 other than zero, which leads to self-centering of the rollers 104. The inward motion component 164 works with others Words that the rollers 104 when the cam ring 90 is under moved away, not radially or not at all wander outside and thus not into the surrounding carrier sleeve 34 buried. Therefore, the rollers 104 can be used without additional Means for fixation are overhung on the axes 106. At the same time there are signs of wear on the rollers 104 and the surrounding carrier sleeve 34 reduced and a safe Function guaranteed as problems caused by friction are avoided become.

8 and 9, the cam ring 90 is in a perspective Representation or in a plan view of a mounted State shown for the end face 165 facing the switching ring 96. An external thread 166 can first be seen in FIG. with which the cam ring 90 is screwed into the ring gear 70. There are three cams 168 on the outer cam track 108 formed, each a steeper ramp side 170 and one have flatter discharge side 172. The cam track 108 is thus based on three equally trained Track sections together, their limits due to the periodic Arrangement can of course be determined arbitrarily. In Fig. 9, these limits are set so that they match those of Cam 168 opposite ends of the run-up sides 170 coincide and thereby a first, a second and a third Form path section 176, 178 and 180, respectively.

The cam track 108 encloses three spaced apart arranged steps 184 on one side of paragraphs 196 and on opposite sides of the ones there over the entire ring width extending sides 170 of the Cams 168 are limited. Levels 184 arise sliding surfaces of the cam ring extending in a radial plane 90, on which the switching ring 96 with its end face 144 or its protrusions 109 abut and along can slide. Through the paragraphs 196 also locking elements formed on which when the face 144 on the steps 184 rests, the protrusions 109 with a relative rotation between can strike the cam ring 90 and the switching ring 96. In this way there will be a latching between the cam ring 90 and the switching ring 96 achieved a further relative movement prevented in this direction of rotation.

The when screwing in and loosening screws between the cam ring 90 and the switching ring 96 taking place in the following explained in more detail with reference to FIGS. 10a to 10h.

There are approximations on the lower side two web sections extending development of the cam ring 90 shown. The solid line corresponds to thereby the contour of the cam track 108, while the The dashed line indicates the contour of the steps 184, those of intermediate depressions 192 from each other are separated. To make a comparison with the top view To facilitate Fig. 9, there are three reference lines in each of the two figures 186, 188 and 190 shown. The reference line 186 identifies the apexes of the cams 168 and the reference line 188, the paragraphs 196. With the reference line 190 is the end of the expiration pages 172, to which there is connect the depressions 192 that seamlessly into the upstream sides Pass over 170 of the following cam.

Furthermore, a section from the Switch ring 96 shown, in which one of the rollers 104 and one the projections 109 can be seen below the end face 144 are. Since the arrangement of the rollers 104 and protrusions 109 repeated periodically in the same way as the contour of the cam track 108, is only one of the rollers on the switching ring 96 104 and one of the projections 109 reproduced. Besides, is the relative movement shown in FIGS. 10a to 10h between the switching ring 96 and the cam track 108 for the sake of better Intelligibility presented as if the Switching ring 96 over the fixed cam track 108. In fact, as already explained above, it moves the cam ring 90 under the switching ring 96. If in the following e.g. it is said that the roles 104 move over the cam 168, so it is actually meant that the cam 168 among the fixed Move rollers 104 away.

10a shows the mutual arrangement of the cam ring 90 and the shift ring 96 at a time when the torque limiting clutch 50 has just been released so that the roles 104 have already rolled over the cams 168. The Rollers 104 lie on the outlet sides 172 of the cams 168 while both the face 144 and the protrusions 109 spaced apart from the steps 184 below move the cam ring 90 away.

After a further movement (Fig. 10b) in the direction of an arrow 194, the rollers 104 run on the drain pages 172, whereby the switching ring 96 approaches the cam ring 90. The tabs 109 follow this movement until, as in 10c is shown, finally with its end faces on steps 184 slide up. At this point the roles 104 relieved, this relief process due to the relatively flat slope of the discharge sides 172 quasi-continuously he follows. 10c delimit two further reference lines 195a and 195b a section 197 of the cam track 108, which is never touched by the rollers 104. The Switch ring 96 then lies on the steps 184 of the cam ring 90 exclusively with its end face 144 or its projections 109 at.

In Fig. 10d it can be seen that the rollers 104 are already from have lifted the cam track 108 so that the switching ring 96 only with the projections 109 on the steps 184 of the Cam ring rests. With further movement towards the Arrow 194 the projections 109 slide over the transition between the stages 184 and the subsections 192 forming depressions 196, whereby the switching ring 96 is slightly opposite the cam ring 90 lowers, so that now the switching ring 96 with respect to the cam ring 90 on its end face 144 supports the steps 184 (Fig. 10e).

This state is retained even if you continue to move forward (Fig. 10f) until finally the rollers 104 on the run-up sides Hit 170 of the next cam 168 and ready for screwing in another screw (Fig. 10g). At this moment, the torque limiting clutch 50 closed again, because now a torque transfer between the cam ring 90 and the switching ring 96 over the rollers 104 can take place along the run-up sides 170. While the Rollers 104 bear against the run-up sides 170 of the cams 168 a torque between the cam ring when screwing in screws 90 and to transmit the switching ring 96, the is based Switch ring simultaneously in the axial direction over its end face 144 from levels 184 onwards. This creates a double burden of the rollers 104 by that exerted by the compression spring 94 Compressive force and by the torque exerted by the drive 32 avoided.

Has during the release of the torque limiting clutch 50 the shift ring 96 has shifted so far in the axial direction, that the switch 124 is actuated and thus the drive 32 of the Screwdriver 10 was switched off. So at the time the rollers 104 hit the run-up sides 170 again the drive 32 is already de-energized, so that nothing worth mentioning More torque between the cam ring 90 and the switching ring 96 acts until the drive 32 switches on again by the operator becomes.

If the operator does not screw in any more screws would like, but a reversal of the direction of rotation of the screwdriver 10 causes, there is an opposite relative movement between the cam ring 90 and the switching ring 96, the is indicated by an arrow 198 in Fig. 10h. The Switch ring 96 then moves back again, whereby it still rests with its end face 144 on the steps 184. However, before the rollers 104 return the runout pages 172 touch, the projections 109 with the paragraphs 196 in System, whereby the above-mentioned latching between the cam ring 90 and the switching ring 96 is achieved.

A torque transfer can now be carried out via this latching the drive 32 and the spindle 40 take place, the significantly higher Can take values as the torque transfer between the rollers 104 and the run-up sides 170 of the cams 168 possible is. In this way, an asymmetrical trigger behavior achieved.

The locking between the projections 109 and the paragraphs 196 leads to a considerable reduction in wear between the parts of the torque limiting clutch 50 since the higher torques required when loosening screws need not be picked up by the rollers 104. Since the Protrusions 109 lie flat against the paragraphs 196, kick no punctual pressure peaks even at higher torques that lead to deformation or significant abrasion of the interacting parts.

Claims (20)

Power-driven screwdriver (10) for screwing in and loosening screws, with a torque-dependent clutch (50) that triggers a torque, which has a first coupling part (96), a second coupling part (90), a spring element (94) for axially bracing the first coupling part (96) against the second coupling part (90) and at least one rolling element (104) running between the two coupling parts (90, 96), via which the two coupling parts (90, 96) drive the screwdriver (10) in a first direction of rotation (working direction ) are coupled to one another until a preset tripping torque is reached, characterized in that latching elements (109, 196) are formed on the two coupling parts (90, 96), via which, when the screwdriver (10) is driven, in a second direction of rotation (release direction) lock the two coupling parts (90, 96) directly together. Screwdriver according to claim 1, characterized in that the locking can be canceled by reversing the direction of rotation of the screwdriver (10). Screwdriver according to Claim 1 or 2, characterized in that sliding surfaces (144, 184), which are associated with one another , are formed on the end faces (165, 143) of the two coupling parts (90, 96) facing one another, via which the two coupling parts (90, 96) abut each other at predetermined relative angular positions. Screwdriver according to claim 3, characterized in that the latching elements (109, 196) are formed on the sliding surfaces (144, 184). Screwdriver according to claim 4, characterized in that the sliding surface of one coupling part (96) is formed by an end face (144) and projections (109) axially projecting therefrom, and in that the sliding surface (184) of the other coupling part is formed by steps (184) is, which are each limited by paragraphs (196) on which the projections (109) can strike in the second direction of rotation. Screwdriver according to one of the preceding claims, characterized in that a cam track (108) extending in the circumferential direction is formed on the second coupling part (90) and is composed of several, preferably three, identical track sections (176, 178, 180). Screwdriver according to one of claims 3 to 5 and according to claim 6, characterized in that the cam track (108) is arranged outside and concentric to the sliding surface (184) of the second coupling part (90). Screwdriver according to claim 6 or 7, characterized in that each track section (176, 178, 180) has a cam (168), the flanks of which form a run-up side (170) and a run-off side (172) for the at least one rolling element (104). Screwdriver according to claim 8, characterized in that the upstream side (170) is steeper than the downstream side (172). Screwdriver according to claim 8 or 9, characterized in that the inclination of the outlet side (172) becomes smaller with increasing distance from the inlet side (170). Screwdriver according to claim 9 or 10, characterized in that the cam track (108) between the cams (168) each has a section (197) which is not touched by the at least one rolling element (104). Screwdriver according to claim 11, characterized in that the sliding surfaces (144, 184) are arranged in relation to the cam track (108) in such a way that when the screwdriver (10) is driven in the first direction of rotation (working direction) and the torque limiting clutch (50) is closed, at least a rolling element (104) is in contact with the run-up side (170) of a cam (168) and at the same time the first coupling part (96) is supported on the second coupling part (90) in the axial direction via the sliding surfaces (144, 184). Screwdriver according to one of the preceding claims, characterized in that the at least one rolling element is designed as a roller (104). Screwdriver according to claim 13, characterized in that the roller (104) is rotatably mounted on an axis (106) held on the first coupling part (96). Screwdriver according to claim 14, characterized in that the axis of rotation (152) of the roller (104) defined by the axis (106) is arranged at a distance from a longitudinal axis (154) of the first coupling part (96). Screwdriver according to claim 15, characterized in that the roller (104) is overhung on the axis (106). Screwdriver according to one of the preceding claims, characterized in that one of the two coupling parts (96) rotatably with a housing (11) of the screwdriver (10) and the other coupling part (90) rotatably with a reaction torque to a spindle (40) and relative to the housing (11) freely rotatable reaction part (70) of a gear (38) is connected. Screwdriver according to claim 17, characterized in that the reaction part is a ring gear (70) of a planetary gear (38) receiving several planet gears (66, 74). Screwdriver according to claim 17 or 18, characterized in that the coupling part (96) which is connected to the housing (11) of the screwdriver (10) in a rotationally fixed manner is arranged to be displaceable in the axial direction (95). Screwdriver according to claim 19, characterized by a switch (124) for switching off the screwdriver (10) which can be actuated by the coupling part (96) which is displaceable in the axial direction.

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