DE10131220C1 - Electric handtool with overload coupling reducing torque transmitted between drive shaft of electric drive motor and driven stage when tool is blocked - Google Patents

Abstract

Electric hand tool with a drive motor, a drive shaft for transmitting the drive power, an output part that can be coupled with a tool and a clutch that is arranged between the drive shaft and the output part and that serves to transmit rotation from the drive shaft to the output part, the clutch being designed as an overload clutch , to lower the torque when the driven part is blocked, the rotary drive taking place via latching bodies which are resiliently mounted between the drive shaft and the driven part, and the driven part slipping over the latching body when the driven part is blocked and the latching bodies engaging in axially extending grooves of the driven part, in order to ensure the rotational entrainment, the grooves being designed to be increasingly deeper over their axial course, and so the torque which causes the latching bodies to snap over can be adjusted by axially displacing the latching bodies in the grooves.

Description

The invention relates to an electric hand tool with a Drive motor, a drive shaft for the transmission of the Drive power, an output part that at one end can be coupled with a tool and a clutch that is arranged between the drive shaft and the driven part and for Rotation transmission from the drive shaft to the driven part serves, the clutch being designed as an overload clutch is to interrupt the torque transmission or to Lowering the torque when the output part is blocked,  where the rotational driving takes place via locking bodies, which in radial direction resilient between the drive shaft and Output part are mounted and the locking body at Block the stripping section via the stripping section slip.

Such electric hand tools with a safety clutch are from a variety of documents from the state of the Technology known.

When using drilling equipment, such as drills, rotary hammers, but also angle grinders etc. can be caused by the High torques occur underground. The maximum allowable Torque for a machine type of the type mentioned can be define relatively precisely. The effect of the torque on the Machine on the one hand and especially with hand-held devices on the other hand, however, on the user can be very different his. If the user stands on a ladder and operates it If possible with only one hand, it will bring less Counter moment on as if he was standing on the ground with the whole body against the drill. With a tough one The torque obviously increases more slowly underground than when hitting an extremely hard one Underground. In unfavorable application and stand situations can have a very small change in torque, especially a reaction moment to serious accidents to lead.  

To protect against excessive torque, it is known Use slip or snap-in clutches, their design There is a compromise between user and machine protection. This However, compromise is always unsatisfactory.

So the designer sets a critical torque, the machines shortly before reaching this torque activate a safety clutch, causing it to slip or engaging the clutch. However, one poses the critical torque so that it is also when working in critical positions, e.g. B. on ladders and scaffolding etc., safely prevents the machine from swinging out, if z. B. the drill hooked, so the machine would set that they are good even in critical situations is controllable, that would be under optimal or less torque to be achieved in critical working conditions low.

DE 38 32 202 C1 describes a hand tool, in particular a rotary hammer, known in various Use cases different torques from the Operator must be kept. To one if possible To enable low-stress working The triggering torque of the safety clutch is therefore adjustable his. For this purpose it should be provided that the Safety clutch is multi-stage.  

The disadvantage here is that only three stages can be switched on, it being one of the Switching stages to a complete blocking and thus too a cancellation of the effect of the clutch comes.

In addition, the design described is proportional consuming.

Furthermore, the safety clutches described above known for example from DE 43 02 083 A1, the a power tool, in particular an electric tool discloses radially against the spring body against a spring force can be moved, and thus a snapping of the same possible so that if the drill jams, for example no further torque transmission takes place. About that in addition to the safety function in this coupling also the function of switching between drilling and pure Hammer operation can be guaranteed.

A similar safety clutch is described in DE 199 29 833 A1, which also discloses an overload clutch in which a Dig the locking area into the counter surface of the Locking pocket is prevented by the locking elements on a pivoted single-arm lever are articulated.

Finally, EP 0 133 645 B1 describes this Angle grinder known, also a  Safety clutch included.

Finally, EP 0 694 706 A1 tries to solve the problem To take into account that the biasing spring with increasing Driving torque stronger against one with the output side Presses shaft part connected locking body. This is supposed to be achieved that by this adaptive slip clutch Bias of the spring is controlled so that the Trigger torque of the slip clutch in adaptation to the Shaft part requested torque is set. This can the trigger torque of the slip clutch the torque of the Electric hand tools are tracked and only at a spontaneous increase in torque, as in a Interlocking of the tool, for example "Iron hit" occurs, the slip clutch is triggered and engage the locking elements.

For tracking is z. B. a scenery tour provided that automatically sets the triggering torque. In general, however, such an adaptive coupling is quite right elaborately designed because the spring preload is adjusted guaranteed and still a certain damping moment must be present in order to trigger the overload clutch guarantee.

So-called "torque clutches" are also known which a shutdown torque can be preselected at  the machine switches off to mechanical or electronic Wise. The known solutions are based on the principle that spring-loaded elements from a certain point transmitted torque can lock. By choosing the Spring preload can preset this switch-off torque or be determined constructively. adjustable Shutdown clutches are in one with screwdrivers Torque range far below the maximum possible Torque adjustable or on rigid drive (without Switch-off) switchable. Switching off or snapping briefly below the maximum possible torque is at known solutions not adjustable.

The invention is therefore an object Electric hand tool with an overload clutch provide at which the trigger torque adjustable is to adapt it to different operating situations and with a simple constructive design is included.

The invention solves this problem by providing one Electric hand tool, in which the locking body in axial engage extending grooves of the stripping section so as to To ensure rotational driving, with the grooves over their axial course are increasingly deeper and so that a snapping of the locking body causing torque axial displacement of the locking body is adjustable.  

Such an embodiment offers the advantage that axial displacement of the locking body in the axial grooves and the different depth of the grooves over their axial course a more or less deep groove for locking the locking body must be overcome, d. that is, the locking body must depend on their axial position in the groove more or less far in radial direction against the biasing force of the spring moves to snap. In this way it can be special simply vary the force that is necessary to get one Trigger click. For every application there is different from an adaptive slip clutch Tripping torque preselected. So z. B. the user of one appropriate hand tool as soon as it starts with the hand tool climbs onto a ladder, a lower triggering moment adjust because he is on such a surface when leading with possibly only one hand only a lower counter moment can muster. The design is therefore opposite adaptive coupling with automatic torque tracking significantly simplified.

By such a safety clutch, in which different Tripping torques are adjustable, the one User safety increases, but at the same time the maximum possible torque utilization improved. So can For example, people with less strength have less Select the triggering moment to avoid the dangers of a deflection  Minimize machine.

It can be provided that the biasing force of the Springs against the locking body for the purpose of turning presses the driven part, even with an axial displacement of the Locking body remains essentially constant.

This can e.g. B. can be achieved in that the bottom of the groove runs approximately axially parallel over their axial course. D. that is, the distance of the bottom of the groove from the axis remains the entire course of the groove constant. This will achieved that even when moving the locking body Compression or expansion of the spring elements, i.e. deformation the spring elements, is made so that the biasing force the spring elements always remains constant. That the depth of the groove still varies, then z. B. can be achieved that the lateral flanks of the groove over their axial course be designed in the radial direction of different lengths, so that a groove with different depths across its axial Course arises. The torque that must then be applied to the shoulders or side flanks of the groove over the Pushing the latching body away is then the greater the longer the shoulder or flank of the groove is formed. That is, each the deeper the groove, the greater the critical Tripping torque, and the better the maximum Torque can be exploited.  

This configuration is particularly advantageous because it only low actuation forces when adjusting the clutch become necessary as there is no increase in the spring preload entry. This means that the adjustment is not operated against the spring preload. In addition, this will the springs over the life of the machine only relatively low burden.

Alternatively, the grooves can be designed so that the bottom the groove is not parallel to the axis, but the flanks of the Groove have an axially parallel course. Adjusted here but then at the same time the biasing force of the spring, so that two components have an influence on the trigger torque own, namely on the one hand the decreasing Preload force of the spring, but in return in return a higher force must be applied to the higher To overcome side flanks. The first mentioned design has advantages over it, because here when setting the triggering torque only one size, namely depth of Nut, is changed.

It can be provided that the grooves are conical are trained.

In particular, if rollers are used as the latching body it may be useful to step the grooves in the axial direction train so that the locking body over their entire  Longitudinal extension in the axial direction against a straight surface of the groove bottom or the entire locking body of one straight flank is locked over the entire roll Distribute load and the locking body not early or wear irregularly.

Alternatively, especially if balls are used as the latching body are used, the grooves continuously in the axial direction run.

As already stated, roles as rollers or Serve balls that are spring-supported. alternative corresponding elastic elements can also be used such as bent spring wire, in which the Function of the rollers through a curved arc is taken over.

As springs for loading the locking elements towards the The output shaft can be leaf springs or disc spring assemblies are used, the spring assemblies can be on the Drive shaft be mounted, for. B. in a hub with the Wave interacts. It is important that a there is sufficient space for the deformation of the spring elements, to allow it to click into place.

It can be provided that the electric hand tool comprises an operating lever with which the locking body in  are axially displaceable. The shift can this is done together with the preloading springs. The The lever for actuating the locking body is in operation unloaded, since the locking elements do not move performed during the operation of the electric hand tool becomes. This significantly reduces wear.

Further designs and features as well as advantages of Invention result from the remaining documents. The In the following, the invention is intended to be based on exemplary embodiments are explained in more detail, showing:

Fig. 1 shows a first embodiment of an overload coupling according to the invention in two views,

Fig. 2 shows a second embodiment of an overload clutch according to the invention in two views

Fig. 3 shows a third embodiment according to the present invention.

Fig. 1 shows a first embodiment of the invention in two views, the view A shows a longitudinal section through an overload clutch in an inventive hand-held tool and the representation B a corresponding cross section. The overload clutch, which is provided in its entirety with the reference numeral 10 , is mounted on a drive shaft 12 which, for the purpose of rotational driving, comprises webs 14 which run in the axial direction. On the drive shaft 12 , the overload clutch 10 is arranged, which is connected on the one hand to the drive shaft 12 and on the other hand to the driven part 16 , and transmits the torque from the drive shaft 12 to the driven part 16 and ultimately to the tool.

The overload clutch 10 comprises a hub 18 which has corresponding recesses and is connected to the drive shaft 12 via a groove / web ( 14 ) connection in a rotationally fixed connection.

The hub 18 has receptacles for leaf springs 20 which are fixed in the hub 18 with their ends 22 and with their central parts 24 are free in the hub 18 and can thus be subjected to certain elastic deformations.

The middle parts 24 of the leaf springs 20 have bulges 26 in which locking bodies 28 , which here have a roll shape, are mounted. The leaf springs 20 and the latching body 28 are fixed in the axial direction on the one hand by a flange 30 of the hub 18 and by a fixing disk 32 , which is used to fix the flange 30 .

Furthermore, the overload clutch 10 comprises an actuating element 34 , via which the overload clutch 10 can be displaced in the axial direction by the arrow path 36 .

The latching bodies 28 are guided in grooves 38 , the bottom 40 of the groove 38 being at the same distance from the axis 42 over the entire axial length of the groove 38 . In the axial direction, however, the groove 38 has a different depth, which increases over its axial course in the direction of the arrow 44 , since the flanks of the groove 38 are stepped and have an increasingly smaller distance from the axis 42 in the direction of the arrow. The stepped formation is formed over the entire inner surface 46 of the spur gear (driven part 16 ), so that the grooves 38 only have to be cut into the inner surface 46 of the spur gear. This significantly simplifies the manufacture of the spur gear.

In normal operation, the drive torque is transmitted from the drive shaft 12 via the latching bodies 28 , which are positively guided in the grooves 38 , to the spur gear and, via this, to a tool spindle and the tool.

If an overload occurs, in particular by the tool, e.g. B. a drill, blocked and so the tool spindle comes to a stop, then engage the locking body 28, the spur gear from a certain triggering torque, which then deform the leaf springs 20 such that they are bent towards the center of the axis. The latching bodies 28 can then also move radially in the direction of the axis 42 and the latching bodies 28 then run over the spur gear. In this case, filming is no longer carried out.

By adjusting the overload clutch 10 in the direction of the arrow path 36 , the triggering torque can be selected at which the latching bodies 28 engage the spur gear. This is achieved in that the groove 38 is designed to be of different depths over its axial course and a force of different magnitude has to be applied in order to engage, since the latching bodies 28 then cover a different distance and act against a different force of the leaf springs 20 have to.

In other words, the release torque increases from right to left (arrow direction 44 ) in the drawing. For example, a setting on the far right can be selected if a weaker person is operating the tool or, for example, the operator is standing on a poor surface or only has one hand free to guide the electric hand tool.

A setting on the far left in illustration A of FIG. 1 can be selected if either the operator is strong or is on a stable surface and can guide the electric hand tool with both hands. The maximum possible torque of the electric hand tool can then be used particularly well.

In particular, it is advantageous that the biasing force of the leaf springs 20 remains constant over the entire adjustment path, since the depth of the groove 38 is not varied by the fact that its bottom is inclined to the axis 42 , but the walls of the flanks of the groove 38 . This enables a precise prediction of the triggering torque to be made in a particularly simple manner. Wear is also reduced. A deformation of the leaf springs 20 to different degrees only takes place when triggered.

FIG. 2 now shows another embodiment of the overload clutch 10 , the electric hand tool also comprising a drive shaft 12 and a spur gear, which serves as an output part 16 . The stripping part 16 is in turn stepped on its inner surface 46 and, like the illustration shown in FIG. 1, has grooves 38 for receiving latching bodies 28 , which are also designed here as rollers. In particular when using rollers, the stepped configuration of the flanks of the grooves 38 makes sense, since then the roller with its cylindrical outer surface is loaded evenly when it is snapped on and is not tilted, since a surface running parallel to the axis 42 also slides over it.

The latching bodies 28 are mounted on the hub side in a latching body disk 48 , the latching body disk 48 being supported against a plate spring assembly 50 .

Here, too, the overload clutch 10 together with the hub 18 can be displaced in the direction of the arrow path 36 in order to generate a different triggering moment for the latching bodies 28 to be latched.

The actuation takes place here by means of the actuating means 34 , which can be adjusted from the outside by the operator.

In this case, 1 and 2, the setting of the minimum triggering time is shown on the far right in the picture in the lower half of the axle 42 in Preparation A in Figs., And the end position on the far left in the upper half.

FIG. 3 once again essentially shows an overload clutch 10 according to FIG. 2 in an enlarged view, wherein the toothing 51 with which the driven part 16 is in contact with the tool spindle or an intermediate shaft can be seen here. Here, too, the locking body 28 is held in a locking body disk 48 . The contact pressure in the groove 38 is also applied via a plate spring assembly 50 , whereby the locking body 28 is pressed into the groove 38 in the direction of arrow 52 . The stepped flank 40 of the groove, which runs from right to left in the illustration in the direction of the axis 42, can be clearly recognized. That is, the distance of the flank 40 from the axis 42 decreases from right to left in the illustration in FIG. 3.

In addition, the snapping and turning take place in Operation as described above.

The use of such an overload clutch 10 offers the following advantages:

• - An adjustability of the trigger torque depending on Operating case and thereby increased security maximum possible torque at the same time (best Torque utilization)
• - Only slight actuation forces are necessary when adjusting the overload clutch 10 , since the adjustment does not act against the spring forces of the spring that presses the latching body 28 into the groove 38 .
• - Only a small spring load due to relative constant switch-off torques over the service life.
• - The actuating means 34 for adjusting the slip or overload clutch 10 is unloaded during operation.

Claims (13)

1. Electric hand tool with a drive motor, a drive shaft ( 12 ) for transmitting the drive power, an output part ( 16 ) which can be coupled with a tool and a coupling which is arranged between the drive shaft ( 12 ) and output part ( 16 ) and for the rotation transmission of the drive shaft ( 12 ) serves on the driven part ( 16 ), the coupling being designed as an overload clutch ( 10 ), for interrupting the torque transmission or for lowering the torque when the driven part ( 16 ) is blocked, the rotational entrainment being carried out via latching bodies ( 28 ) takes place, which are resiliently mounted between the drive shaft ( 12 ) and the driven part ( 16 ), and the locking bodies ( 28 ) slip through the driven part ( 16 ) when the driven part ( 16 ) is blocked, the locking bodies ( 28 ) moving in axially extending grooves ( 38 ) of the driven part ( 16 ) so as to ensure the rotational entrainment, and the grooves ( 38 ) over their axial course Referring are formed deeper and so the a locking action of the locking body (28) causing torque is adjustable by axial displacement of the locking body (28) in the grooves (38). 2. Electric hand tool according to claim 1, characterized in that the biasing force of the spring acting on the locking body ( 28 ) with axial displacement of the locking body ( 28 ) remains substantially the same. 3. Electric hand tool according to claim 1 or 2, characterized in that the bottom of the groove ( 38 ) extends axially parallel over its axial course. 4. Electric hand tool according to one of claims 1 to 3, characterized in that the grooves ( 38 ) are conical. 5. Electric hand tool according to one of claims 1 to 4, characterized in that the grooves ( 38 ) extend continuously in the axial direction. 6. Electric hand tool according to one of claims 1 to 4, characterized in that the grooves ( 38 ) are stepped in the axial direction. 7. Electric hand tool according to one of claims 1 to 6, characterized in that rollers or balls serve as the latching body ( 28 ). 8. Electric hand tool according to one of claims 1 to 6, characterized in that bent as a locking body Spring wire is used.   9. Electric hand tool according to one of claims 1 to 8, characterized in that leaf springs ( 20 ) or plate spring assemblies ( 50 ) serve as springs. 10. Electric hand tool according to one of claims 1 to 9, characterized in that the overload clutch ( 10 ) is a slip clutch. 11. Electric hand tool according to one of claims 1 to 10, characterized in that the electric hand tool comprises an actuating means ( 34 ) with which the locking body ( 28 ) are displaceable in the axial direction. 12. Electric hand tool according to one of claims 1 to 11, characterized in that the actuating means ( 34 ) is unloaded during operation. 13. Electric hand tool according to one of claims 1 to 12, characterized in that the drive shaft ( 12 ) and the driven part ( 16 ) are arranged coaxially to one another.