EP2848368A1 - Device for limiting a torque that can be transferred by a screwing tool - Google Patents

Abstract

The invention relates to a device for limiting a torque that can be transmitted by a screwing tool, comprising a switching arrangement (21) and a clutch (22) transmitting the torque by means of the switching arrangement (21) to a tool shaft (12), wherein the coupling (22) rotates comprising a first tooth arrangement (23) connected to the switching arrangement (21), which can be subjected to a clamping force in a clamping direction (V) of the switching arrangement (21) by means of a tension spring (24) and with a second tooth arrangement connected non-rotatably to the tool shaft (12) (25) is in torque-locking engagement, wherein the first tooth arrangement (23) is pressed when a limit torque is exceeded against the clamping force of the tension spring (24) out of engagement. The clamping direction (V) of the switching arrangement (21) and a shank axis (S) of the tool shank (12) are angled at an angle ± to one another. In addition, a screwing tool is provided with a device for limiting a torque transmittable by the screwing tool (10).

Description

The invention relates to a device for limiting a transmissible torque of a screwing tool according to the preamble of patent claim 1 and a corresponding screwing tool according to the preamble of patent claim 10.

Generally screwing tools are known which comprise a torque limiting device for a during a screwing operation of a manually operable handle (drive body) to be transmitted to a tool shaft torque, wherein the tool shank with a working end with a screw to be rotated or the like engages. The torque transmitted from the drive body to the tool shank in this case can be limited by switching a clutch which decouples the drive when a predefined limit torque is exceeded. It is thus on the one hand ensures a reliable hold of the screw or the screw thus produced and on the other hand prevents overuse and damage of the screw receiving thread.

From the DE 195 07 558 A1 An embodiment of a screwing tool with a torque limiter is known in which a clutch is also provided between a manually operable by a user handle (drive body) and a shaft (driven part) of a screwdriver blade. This coupling has coupling balls on, the spring-loaded engage in locking recesses of a rotatably connected to the output member driver plate. When the torque transmitted via the clutch from the drive part to the driven part exceeds a limit torque, the clutch balls are pressed against the spring load from the detent recesses, so that the clutch is disengaged and the output part is no longer driven.

There are also other embodiments with elongated Schraubwerkzeugen known with a handle and a coupling for transmitting torque from the handle on a coaxially arranged tool shank, which interrupts the torque transmission when the limit torque is exceeded. For this purpose, the clutch has a drive pulley and an output pulley axially connected thereto in torque-engaging engagement, the engagement being provided by means of a respective frontal toothing of the pulleys. A required contact pressure of the drive and driven pulley is usually ensured by means of a coil spring.

The acting as a drive body handle such screwing is usually elongated extends in extension of the tool shaft, so that the screwing tool has a large axial length. However, this makes the screwing tools for many purposes unwieldy or simply not usable due to limited space and also requires a high expenditure of force of the user to generate the desired torque.

The object of the invention is therefore to provide a device for torque limiting for a screwing, on the one hand has a compact design and on the other hand provides the user the most comfortable use with less effort available, which also allows greater accuracy in setting the desired torque ,

This object is achieved by a device for limiting a torque transmitted by a screwing tool having the features of patent claim 1, as well as by a correspondingly configured screwing tool having the features of patent claim 10. Advantageous embodiments and further developments can be taken from the respective dependent claims.

Accordingly, a device for limiting a torque that can be transmitted by a screwing tool (hereinafter also referred to as "torque limiting device") is proposed, comprising a switching arrangement and a coupling which transmits the torque to a tool shank by means of the switching arrangement, wherein the coupling comprises a first tooth arrangement connected in a rotationally fixed manner to the switching arrangement which is acted upon in a clamping direction of the switching arrangement by means of a tensioning spring with a clamping force and with a rotatably connected to the tool shank second tooth arrangement is in torque-locking engagement, wherein the first tooth arrangement is pressed at a limit torque is exceeded against the clamping force of the tension spring out of engagement.

In addition, the clamping direction of the switching arrangement and a shaft axis of the tool shank are arranged at an angle α angled to each other.

The described torque limiting device is thus suitable for use in a screwing tool and has a coupling which connects the tool shaft and the switching arrangement in a torque-transmitting manner via the first and second tooth arrangements which mesh with each other. In other words, when using the screwing tool, a torque can be transmitted to the tool shank with the aid of the switching arrangement.

Preferably, the tool shank having a tool blade integrally formed therewith or a receiving device for the removable recording of separate tool bits.

The switching arrangement is designed such that it can exert a clamping force on the first tooth arrangement in the clamping direction and thus holds it in engagement with the second tooth arrangement, as long as the limit torque has not yet been reached. If there is a torque exceeding the limit torque, the first tooth arrangement is lifted out of engagement with the second tooth arrangement against the clamping force of the switching arrangement, since the first tooth arrangement can only escape in the clamping direction of the switching arrangement.

In this case, the torque transmitted by the tool shank is smaller than the torque counteracted by the workpiece, for example a screw or the like. This allows the tool shank to rotate relative to the workpiece without increasing the torque.

The clamping force of the tension spring can either act on the first tooth arrangement only when it is pressed out of engagement with the second tooth arrangement and thus against the adjacent tension spring. However, it is also possible to design the clamping arrangement in such a way that the tension spring also exerts a clamping force on it during the existing engagement of the first tooth arrangement, ie in a non-deflected state of the first tooth arrangement, and thus sets the first tooth arrangement under constant prestressing.

The device has the special feature that the shaft axis and the clamping direction are arranged angled to each other. The angle α is to be understood as an angle between the extension of the tool shank and the clamping device and is in Fig. 1 pictured. In this way, a particularly compact design for such a device, but also for a herewith equipped screwing be provided.

For example, the angle α can be selected from a range between 0 ° <α ≦ 90 °, in particular between 10 ° ≦ α ≦ 80 °, particularly preferably between 30 ° ≦ α ≦ 60 °. If the angle α selected from the above areas, so there is a particularly advantageous bending of the torque limiting device, which allows a particularly compact design of a corresponding screwing.

The bend also allows a particularly advantageous torque generation for the user due to the achievable leverage. In a preferred embodiment of the invention it is provided that the radially extending upper edge of a tooth of the first tooth arrangement is arranged at an angle Y to the clamping direction V, while the radially extending upper edge of a tooth of the second tooth arrangement is arranged at an angle Y to the shaft axis S, in particular: X + Y = 180 ° - α. If the angle X is equal to the angle Y, there is a power transmission in the ratio 1: 1. If the angle X is smaller than the angle Y, the force is converted by the clamping direction in a larger force about the shaft axis S. If the angle X is greater than the angle Y, the force is converted by the clamping direction in a smaller force about the shaft axis S. By appropriate choice of the ratio of the angle X and Y thus a desired power transmission can be achieved.

Preferably, the ratio X: Y is in the range of 1: 5 to 5: 1, in particular in the range of 1: 3 to 3: 1, and is for example about 2: 1.

Preferably, the second tooth arrangement comprises a cam wheel with a number of cams. The cams of the cam wheel are distributed uniformly in the circumferential direction over the cam wheel, so that each cam is a tooth-shaped elevation, wherein between each two adjacent cams one sink is defined. In each of these depressions, the at least one first tooth arrangement can intervene, to provide the torque-locking engagement.

According to a further embodiment, the cams are extended in the axial and / or radial direction of the cam wheel. This means that the cams are arranged either on a peripheral surface of the cam wheel, ie analogous to a spur gear with cams on its radially outer circumferential surface. Alternatively or additionally, the cams can be arranged on a side surface of the cam wheel, so that the cam wheel can be designed accordingly as a bevel gear.

Preferably, the first tooth arrangement comprises at least one switching cam, which is designed for selective engagement in the second tooth arrangement. Accordingly, the first tooth arrangement may comprise a single or a plurality of cams, which are engageable by means of the switching arrangement in engagement with the cam wheel. As soon as the applied torque is greater than the clamping force of the switching arrangement, the cam wheel switches to the next gap by the switching cam jumps from a first gap in the next gap.

In order to ensure the best possible engagement with the cam wheel, the at least one switching cam is designed to be complementary to the second gear arrangement, for example a mirror image of the cams of the cam wheel. This means that each of the cams of the cam wheel and the switching cams have the same shape, wherein the sink is formed between each two adjacent cams corresponding complementary for receiving the switching cam.

Thus, for example, if the second gear arrangement is designed as a cam wheel in the form of a bevel gear, then the first tooth arrangement can be embodied correspondingly engaging with the one or more switching cams, in particular also in the form of a bevel gear or at least a subsegment thereof comprising one or more teeth. Accordingly, associated pitch angle of both bevel gears or sub-segments can be selected and thus the clutch can be designed such that with the lowest possible spring force of the tension spring the highest possible torque is achieved before the two tooth arrangements get out of engagement.

Furthermore, the first and / or the second tooth arrangement may comprise a symmetrical or an asymmetrical toothing. This means that a shape of the teeth of the respective tooth arrangement is designed to be mirror-symmetrical with respect to both sides facing the adjacent teeth. Consequently, the teeth each have mirror-symmetrical tooth flanks and thus in both directions of rotation a symmetrical slope, so that in both directions of rotation, left and right rotation, the same limit torque results, in which the switching arrangement switches and the cam disengage by triggering the clutch.

On the other hand, if the teeth are designed asymmetrically, the two tooth flanks of the respective tooth differ from one another. This means that the left tooth flank has a greater or lesser slope than the corresponding right flank of the respective tooth flank Tooth. This causes a maximum transmittable limit torque for the left turn to differ from the right turn limit torque and disengage the clutch either sooner or later.

Thanks to the angled shape of the device, by suitable design of the slope, the coupling of the torque limiting device can be designed to the required torque forces. In particular, the respective edge steepness can be selected such that with low spring forces of the tension spring a particularly high torque can be achieved before the two tooth arrangements are disengaged.

In general, the steeper the tooth flank is configured, the higher the required limit torque in order to disengage the toothing. It can also be taken on the design of the teeth, in particular the edge steepness, an influence on the power transmission and the tripping behavior of the entire clutch.

This makes it possible to provide different limit torques for a left turn and a right turn. For example, a torque limit for screwing in a screw to protect the female thread and the screw may be defined lower than a limit torque for unscrewing stuck screws for which the highest possible torque is desired.

According to a further embodiment, a clamping force of the tension spring of the switching arrangement by means of a Adjustment can be varied. For example, this may be provided an adjusting screw, via which a voltage of the tension spring can be adjusted by the tension spring is compressed or relaxed by an adjustable distance.

Furthermore, a screwing tool is provided with a device for limiting a torque that can be transmitted by the screwing tool, with a handle and a tool shank, wherein the device is designed according to the description.

Preferably, in this case, the switching arrangement is associated with the handle. This means that the switching arrangement is arranged inside the handle, in particular enclosed by the handle.

Accordingly, the screwing tool is designed, for example, as a screwdriver with a handle portion of the handle which is angled by the angle α, in which the switching arrangement is integrated. As already stated, the angling allows a particularly advantageous compact design as well as a variable by the angle setting a einleitbaren on the screw torque.

For this purpose, the handle can preferably be designed in a substantially Y- or T-shaped, in particular pistol or cross-grip shape, for actuating the screwing tool.

Fig. 1

ein Schraubwerkzeug mit einer Vorrichtung zur Begrenzung eines von dem Schraubwerkzeug übertragbaren Drehmoments gemäß der Beschreibung in geschnittener Seitenansicht, und

Fig. 2

eine Kupplung des Schraubwerkzeugs aus Fig. 1 in einer Detailansicht A.

In the following the invention will be explained in more detail with reference to an embodiment shown in the drawings. Showing:

Fig. 1

a screwing tool with a device for limiting a transmissible torque from the screwing tool according to the description in a sectional side view, and

Fig. 2

a clutch of the screwing Fig. 1 in a detail view A.

The Fig. 1 shows a screwing tool 10 with a device 20 for limiting a transmissible by the screwing tool 10 torque. The screwing tool 10 is designed as a manually operable screwdriver and comprises a handle 11 and a tool shank 12. By manually rotating the handle 11 about a shank axis S, the tool shank 12 is acted upon by a torque, which by means of a blade (not shown), for example, a screw or the like is transmitted. The blade is not shown for the sake of clarity, but can either be integrally formed with the tool shank 12, or be provided via a provided on the tool shank 12 receptacle for replaceable tool bits.

The torque transmission to the tool shaft 12 by means of the device 20 for limiting a transmissible by a screwing torque, in short: torque limiting device. This includes a switching arrangement 21 and a clutch 22. The clutch 22 comprises a rotatably connected to the switching arrangement 21 first tooth arrangement 23, which is acted upon by means of a tension spring 24 in a clamping direction V of the switching arrangement 21 with a clamping force.

By means of the switching arrangement 21 and the tension spring 24, the first tooth arrangement 23 is in torque-locking engagement with the second tooth arrangement 25. The torque limiting device 20 is thus configured such that the first tooth arrangement 23 is pressed when a limit torque is exceeded against the clamping force of the tension spring 24 out of engagement with the second tooth arrangement 25.

As in particular from Fig. 2 can be seen, the clamping direction V of the switching assembly 21 and the shaft axis S of the tool shank 12 at an angle α are arranged angled to each other.

The angle α is selected in the illustrated embodiment, for example only about 60 °. However, the angle can be selected from a range between 0 ° <α ≦ 90 °, in particular between 10 ° ≦ α ≦ 80 °, particularly preferably between 30 ° ≦ α ≦ 60 °.

The angling on the one hand enables the switching arrangement 21 to be assigned to the handle 11 or to integrate the switching arrangement 21 into a gripping section of the handle 11 and thus to dispense with a handle of the screwing tool extending along the shaft axis S, since the angled handle portion is also angled α by the angle. Thus, by way of example for the illustrated angle α, a substantially T-shaped housing shape of the screwing tool, which may also be referred to as a pistol mold, results.

In this way, a particularly compact design for such a screwing with appropriate torque limiting device can be provided. On the other hand, the angling allows a particularly advantageous torque generation for the user due to the achievable leverage. The user can thus make a more sensitive dosage thanks to a reduced effort.

An upper edge of a tooth of the second tooth arrangement 25 runs at an angle X to the shaft axis S. The tooth arrangement 25 can be designed, for example, as a bevel wheel. An upper edge of a tooth of the first tooth arrangement 23 extends at an angle Y to the clamping direction V. In particular, X + Y = 180 ° -α.

In one embodiment, the angle X may correspond to the angle Y. In this case, the force exerted on the handle 11 is transmitted to the tool shank 12 in a ratio of 1: 1. By varying the ratio of the angles X to Y, the power transmission can be varied. For example, the ratio X: Y ranges from 1: 3 to 3: 1. For example, the angle X may be about 80 °, while the angle Y is in the range of about 40 °.

The second tooth arrangement 25 is designed as a cam wheel with a number of cams, wherein the cams are extended substantially in the axial direction of the cam wheel (not shown).

In addition, the first tooth arrangement 23 is designed with a switching cam which engages in the cam wheel of the second tooth arrangement 25.

It is possible to carry out the first and / or the second tooth arrangement with a symmetrical or an asymmetric toothing. The symmetrical toothing offers the possibility that a maximum torque transmitted by means of the two tooth arrangements or the entire clutch, ie the limit torque, is the same for both directions of rotation.

In the case of asymmetric gearing, on the other hand, a limit torque for a first direction of rotation may be made higher than for a second direction of rotation. Which direction of rotation should have the higher limit torque, can be done in coordination with the intended use of the screwing. Thus, a lower torque may be provided for tightening screws, as for the provided for releasing stuck screws opposite direction.

Only optionally, can a clamping force of the tension spring 24 of the switching arrangement 21 be variable by means of an adjustment arrangement 26. In the illustrated embodiment, it is thus possible to change a compression of the tension spring 24 to change the clamping force.

Claims (13)

Device for limiting a torque that can be transmitted by a screwing tool, having a switching arrangement (21) and a coupling (22) which transmits the torque to a tool shaft (12) by means of the switching arrangement (21), wherein the coupling (22) is non-rotatable with the switching arrangement ( 21) connected first tooth arrangement (23) which in a clamping direction (V) of the switching arrangement (21) by means of a tension spring (24) can be acted upon with a clamping force and with a rotatably connected to the tool shank (12) second tooth arrangement (25) in torque-locking engagement is, wherein the first tooth arrangement (23) is pressed when a limit torque is exceeded against the clamping force of the tension spring (24) out of engagement,
characterized in that
the clamping direction (V) of the switching arrangement (21) and a shaft axis (S) of the tool shank (12) are arranged angled at an angle α to one another. Apparatus according to claim 1, characterized in that the angle α from a range between 0 ° <α ≤ 90 °, in particular between 10 ° ≤ α ≤ 80 °, especially preferably between 30 ° ≤ α ≤ 60 °, is selected. Apparatus according to claim 1 or 2, characterized in that the radially extending upper edge of a tooth of the first tooth arrangement (23) is arranged at an angle Y to the clamping direction (V) and that the radially extending upper edge of a tooth of the second tooth arrangement (25) in one Angle Y is arranged to the shaft axis (S), wherein in particular: X + Y = 180 ° - α. Apparatus according to claim 3, characterized in that the ratio X: Y in the range of 1: 5 to 5: 1, in particular in the range of 1: 3 to 3: 1, is located. Apparatus according to claim 1 to 4, characterized in that the second tooth arrangement (25) comprises a cam wheel with a number of cams. Apparatus according to claim 5, characterized in that the cams are extended in the axial and / or radial direction of the cam wheel. Device according to one of claims 1 to 6, characterized in that the first tooth arrangement (23) comprises at least one switching cam, which is designed for selective engagement in the second tooth arrangement (25). Device according to one of claims 1 to 7, characterized in that the first (23) and / or the second tooth arrangement (25) comprise a symmetrical or an asymmetrical toothing. Device according to one of claims 1 to 8, characterized in that a clamping force of the tension spring (24) of the switching arrangement (21) by means of an adjusting arrangement (26) is variable. A screwing tool having a device for limiting a torque that can be transmitted by the screwing tool (10), having a handle (11) and a tool shank (12), characterized in that the device (20) is designed according to one of claims 1 to 9. Screwing tool according to claim 10, characterized in that the switching arrangement (21) is associated with the handle (11). Screwing tool according to claim 10 or 11, characterized in that the screwing tool (10) is designed as a screwdriver with a angled by the angle α grip portion of the handle (11), in which the switching arrangement is integrated. Screwing tool according to one of claims 10 to 12, characterized in that the handle (11) is substantially Y- or T-shaped, in particular pistol or Quergriffförmig, for actuating the screwing tool (10) is formed.

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