Rotary tool, especially screwing device

Abstract

The rotating tool, in particular a screw device (2) for screwing a screw element into a component, comprises a tool holder (16) for a screw tool (18), an axially fixed rotary drive (4) for generating a rotary motion and a torque, a feed drive (14) for generating a feed motion, and a telescopic transmission unit (10) with two components that are axially displaceable relative to each other (A), namely a profile shaft (6) and a hub (8) displaceable along this shaft with an internal profile corresponding to the profile shaft (6), wherein one component is connected to the rotary drive (4) and the other component is connected to the feed drive (14) and the tool holder (16), and the rotary motion generated by the rotary drive (4) is transmitted from one component to the other.To at least partially compensate for an axial frictional force (FRax) generated in this process which opposes the feed motion, the profile shaft (6) and the hub (8) are interlocked via a profile toothing (22) oriented obliquely to an axial direction (A).

Description

[0001] The invention relates to a rotating tool which extends in an axial direction and serves for machining a component. In particular, it is a screw device for screwing a screw element into a component with the features of the preamble of claim 1.

[0002] Such a screw device can be found, for example, in DE 10 2022 106 710 A1.

[0003] These types of screwdriving devices are primarily stationary devices in which screwdriving operations are performed automatically. Generally, a rotary motion and a feed motion are transferred to a tool holder in which a processing tool, such as a bit or a blade, is held during operation.

[0004] The stationary screwdriving tools discussed here feature a fixed rotary drive, to which the tool holder is offset axially during the feed movement. Simultaneously, the rotary motion and torque generated by the drive are transmitted to the tool holder via a telescopic transmission unit.

[0005] In the known screw device, this was achieved using a shaft-hub unit in which the shaft is designed as a profiled shaft along which the hub can be displaced axially. The hub is moved axially by means of a feed drive to generate the feed motion. As the torque transmitted between the shaft and hub increases, the frictional force also increases, thus inhibiting the feed motion. The known screw device distinguishes between different torque load ranges. At high torque loads, a compensating clutch is activated, allowing axial compensating movement so that the shaft can move along with the hub, thereby preventing wear between the hub and the drive shaft at high torques.

[0006] Based on this, the invention aims to provide an improved rotating tool, in particular a screw device, in which the problems caused by friction between the hub and the profile shaft are reduced.

[0007] The problem is solved according to the invention by a rotating tool for machining a component, in particular by a screw device for screwing a screw element into a component, wherein the tool extends in an axial direction. The tool has a tool holder for a machining tool, in particular for a screw tool, such as a bit or a blade, which engages the screw element during operation to transmit a rotary motion. The tool is generally designed to transmit a rotary motion as well as a feed motion to the tool holder.

[0008] The tool features an axially fixed rotary drive to generate the rotary motion, which is transmitted to the tool holder during operation. The rotary drive is preferably an electric drive and therefore includes an electric drive motor that generates the rotary motion and the desired torque. Alternatively, the rotary drive can also be a pneumatic or hydraulic drive.

[0009] When referring to an axially fixed rotary drive, this means that the tool holder is axially adjusted relative to the rotary drive during operation and machining, particularly screwing. Preferably, the rotary drive is stationary and does not move during machining. Preferably, the screwing device is, for example, fixed within a machining station, and the rotary drive is, for example, attached to a fixed frame.

[0010] Furthermore, the tool features a feed drive to generate the feed motion, which is transmitted to the tool holder during operation. This is either an electric feed drive or, alternatively, a pneumatic or hydraulic feed drive.

[0011] The machining process, in particular the screwing process, is preferably carried out automatically or fully automatically. The tool has a correspondingly configured control unit for this purpose. Here, the torque and / or feed force are typically controlled according to predefined process parameters in order to carry out the desired screwing operations according to a predefined, defined screwing process.

[0012] The tool further features a telescopic transmission unit with two components that are axially displaceable relative to each other: a profile shaft and a hub that is displaceable along this profile shaft and has an inner profile corresponding to the profile shaft. The hub is therefore generally a sleeve-shaped component with an inner profile that engages with a corresponding outer profile of the profile shaft, forming a toothed connection.

[0013] One component is connected to the rotary drive and is set into rotation by it during operation. The other component is connected to the feed motor and the tool holder, typically being fixed to the tool holder in a rotationally stable manner and being moved axially by the feed drive. The rotary motion and corresponding torque transmitted from the rotary drive to one component are then transferred to the other component.

[0014] The component driven by the rotary drive is, in particular, the profile shaft. This is formed, for example, by a motor shaft of a drive motor or is at least coupled to one. Alternatively, the rotary drive can also drive the hub, and the profile shaft is moved axially by the feed drive.

[0015] According to the invention, the profile shaft and the hub are interlocked via a profile toothing oriented obliquely to the axial direction. The profile toothing can therefore be considered to be at least partially helical (helical) profile toothing. Due to the oblique profile toothing, the inner and outer profiles each have interlocking profile flanks oriented obliquely at an angle to the axial direction. Both the inner and outer profiles each have at least one obliquely oriented profile flank.

[0016] Unlike a conventional profile gear with an outer and inner profile running parallel to the axial direction, the profile flank oriented obliquely to the axial direction offers the particular advantage that an axial feed force is generated during rotation and torque transmission between the two components. With a suitable design of the profile gear, this force can counteract the axial frictional force generated during torque transmission between the two components. This axial frictional force opposes and inhibits the feed motion generated by the feed drive. This effect is referred to here as feed inhibition.

[0017] The tilting position can therefore, for example, relieve the load on the feed drive.

[0018] In typical screwdriving applications, feed forces are transmitted to the tool holder when the screw element is tightened, often in the range of 150 N. Even with a torque of just 4 Nm, the resulting feed resistance due to friction can also be of this magnitude in conventional designs, for example, 150 N. Therefore, when high torques are transmitted, the feed drive in a conventional design must be correspondingly large. This leads to increased installation space requirements and higher costs. The inventive concept described here, with its inclined profile gearing, allows for a more compact and cost-effective feed drive compared to a conventional axially parallel profile gearing.

[0019] In a practical design, no bearing elements such as rollers, cylinders, needles, etc., are arranged between the profile shaft and the hub. While such (rolling) bearings would, in principle, reduce friction between the profile shaft and the hub, they require more installation space, which is often undesirable. They also entail higher costs. Therefore, preferably, only a plain bearing is used between the profile shaft and the hub, in which the inner and outer profiles simply slide against each other.

[0020] In a suitable embodiment, the helix angle of at least one profile flank of the outer profile of the profile shaft and correspondingly also of at least one profile flank of the inner profile of the hub lies in the range between 2° and 30° and preferably in the range between 5° and 15°.

[0021] The magnitude of the axial frictional force generated by the transmission of torque depends on the coefficient of friction of the mating between the profile shaft and the hub. This coefficient of friction is typically in the range of 0.08 to 0.25. The axial frictional force also depends on the normal force, which in turn depends on the circumferential force generated by the rotary drive and thus on the torque. The specified values ​​for the helix angle have proven to be particularly advantageous.

[0022] As mentioned above, the inclined position of the profile flanks during operation transmits an axial feed force from the component connected to the rotary drive (in particular, the profile shaft) to the component connected to the feed drive (in particular, the hub). Simultaneously, an axial frictional force is generated that counteracts this axial feed force. The axial feed force generated by the inclined position during operation, on the one hand, and the axial frictional force, on the other, each depend on the selected helix angle.

[0023] In a preferred embodiment, the helix angle is generally selected such that the feed resistance is reduced. Feed resistance, as already stated above, refers to the effect that the axial friction force inhibits the feed motion generated by the feed drive, thus reducing the feed force generated by the feed drive and transmitted to the component connected to it (in particular, the hub).

[0024] According to a preferred variant, the feed resistance is merely reduced, without being fully compensated.

[0025] In a preferred embodiment, the helix angle is selected such that the feed resistance during operation is compensated. This means that the helix angle is chosen so that the axial feed force generated by the helix and the axial friction force mutually cancel each other out. This is understood to mean that the magnitude of the generated axial feed force—given a predetermined or determined (measured) coefficient of friction (e.g., mean coefficient of friction)—is equal to, or at least substantially equal to, the magnitude of the axial friction force.

[0026] This measure therefore ensures in particular that no opposing axial frictional force has to be overcome via the feed drive.

[0027] In a further advantageous development, the helix angle is preferably selected such that – for a given or determined (measured) coefficient of friction (e.g., mean coefficient of friction) – the generated axial feed force is greater in magnitude than the axial frictional force. This measure offers the particular advantage that an additional feed component is generated via the rotary drive, thereby supporting the feed drive. In this case, the feed resistance is not only compensated but even overcompensated. The generated axial feed force is, in particular, at least 10% and more preferably at least 15% greater than the axial frictional force. The helix angle is therefore deliberately chosen to be somewhat larger than would be required for compensation based on a given or measured (mean) coefficient of friction.

[0028] In a practical embodiment, several profile flanks are arranged around the circumference of the profile shaft, in particular 4-12 profile flanks. These are preferably arranged in an even distribution. The profile has profile grooves and profile webs (profile flanks) that alternate around the circumference. Preferably, the profile grooves and profile flanks have the same (angular) width. The same applies to the inner profile of the hub.

[0029] The outer profile of the profile shaft has a profile height measured in the radial direction, which corresponds, for example, to 7% to 15% of the profile shaft's outer radius. The profile height is the radial distance between the bottom of a profile groove and the outermost radial area of ​​a profile web.

[0030] In a preferred embodiment, the tool is designed to exert a screw-in torque of up to 500 newton meters, in particular up to 150 newton meters and preferably up to 50 newton meters, on the tool holder.

[0031] In typical screw applications, the screw-in torques usually range from 0.05 Newton meters to 500 Newton meters, and usually preferably from 0.5 Newton meters to 50 Newton meters, depending on the application.

[0032] Screw-in torques are defined as the torques exerted during the tightening of the screw element into the component, before the screw element reaches a point where it makes contact with the component. Once the screw head is in contact with the component, the torques typically increase sharply, which usually leads to the control system shutting down the screwing process.

[0033] High screw-in torques are achieved particularly with so-called self-tapping or self-tapping screws, where the screw-in torque is, for example, at least 5 Nm, at least 10 Nm, or even at least 20 Nm or higher. High screw-in torques are also achieved with wood screws, plastic screws, and screws with thread-locking compound. The screw-driving device is therefore specifically designed for driving such screws. In operation, these types of screws are primarily used to drive the screw-driving device into components.

[0034] During operation, the rotary drive is controlled in such a way that the screw-in torques specified above are generated while the screw element is being tightened. For this purpose, the tool has the aforementioned control unit.

[0035] In a preferred embodiment, the tool is designed to generate a feed force at the tool holder in the range of 1 N to 3000 N, and particularly in the range of 10 N to 300 N. This feed force is set during the screwing process until the head contact is reached. Preferably, such a feed force is generated during operation by the feed drive. The control unit is also configured accordingly for this purpose.

[0036] An embodiment of the invention is explained in more detail below with reference to the figures. These show: FIG 1 a screw device partially in longitudinal section, FIG 2 an enlarged partial sectional view of the screw device according to FIG 1 in the area of ​​a telescopic transmission unit according to the section line C - C in FIG 3 , FIG 3 a cross-section through the telescopic transmission unit according to the section line B - B according to FIG 2 FIG. 4 shows an enlarged partial view of the cross-section according to the area marked A in FIG 3 as well as FIG 5 a force diagram to explain the mode of action of the inclined profile gearing.

[0037] One in FIG 1 The illustrated screw device 2 extends along a screw axis S in an axial direction A. In the exemplary embodiment, it has a rotary drive 4 in a rear region, which is designed to generate a rotary motion and a torque. The rotary drive 4 drives a profile shaft 6, which is, for example, designed as the motor shaft of a drive motor of the rotary drive 4 or is non-rotatably connected to such a shaft. The screw axis S defines an axis of rotation of the profile shaft 6, about which it rotates during operation.

[0038] The profile shaft 6 engages in a hub 8. This hub, at least in a partial section, is designed as a sleeve with an inner profile that corresponds to an outer profile of the profile shaft 6. The profile shaft 6 and the hub 8 form a telescopic transmission unit 10. The profile shaft 6 and the hub 8 are arranged in a guide tube 12. The hub 8 can move within the guide tube 12 in and against the axial direction A and, in doing so, move relative to the axially fixed profile shaft 6.

[0039] The screw device 2 also has a feed drive 14, which in the exemplary embodiment is arranged parallel to and next to the guide tube 12.

[0040] In this embodiment, it is designed as a pneumatic drive. However, it can also be designed as an electric or hydraulic drive. As an alternative to the parallel arrangement shown, it can also be arranged obliquely to the axial direction or coaxially to the screw axis S.

[0041] The feed drive 14 is connected to the hub 8 in the axial direction A, in particular by a positive locking connection, and moves the hub in the axial direction A during operation. In the exemplary embodiment, the hub 8 has a coupling pin at its end, which is connected to a coupling ring of the feed drive 14. A drive rod, in particular a piston rod of the feed drive, moves the coupling ring and, via the coupling pin, the hub 8 in and against the axial direction A. The hub 8 and the feed drive 14 thus form a feed unit. The coupling pin is rotatably arranged within the coupling ring. At its end, the coupling pin, which rotates together with the rest of the hub 8 during operation, is non-rotatably connected to the tool holder 16 for the transmission of the rotary motion and the torque.At its front end a tool holder 16 is arranged, into which a processing tool, in the exemplary embodiment a screw tool 18, is inserted and held.

[0042] The screwing device 2 also has a feeding unit 20 in its front area, through which screw elements are fed. During operation, these are typically successively placed into a staging area, then gripped and / or carried along by the screwing tool 18 and moved forward in the axial direction A. When the screw element is screwed into a component (not shown in detail here), the rotary drive 4, and thus the torque, as well as the feed drive 14, and thus the axial feed movement and the feed force generated by the feed drive 14, are appropriately controlled according to a predefined screwing program. A control unit (not shown in detail here) is provided for this purpose.

[0043] The screw element is in particular a screw or, alternatively, a nut.

[0044] Based on the enlarged view in FIG 2 especially also in combination with the representations according to FIG 3 und FIG 4 The structure of the telescopic transmission unit 10 is clearly visible.

[0045] In particular, it can be seen that the profile shaft 6 and the hub 8 are interlocked via a profile toothing 22 oriented obliquely to the axial direction A. The outer profile of the profile shaft 6 and the inner profile of the hub 8 each have several profile flanks 24 distributed around the circumference, designed as webs, with profile grooves arranged between them, each oriented at an angle α with respect to the axial direction A and the screw axis S.

[0046] The profile flanks 24 of the profile shaft 6 and the hub 8 interlock reciprocally. In the exemplary embodiment, each of these two components has eight profile flanks 24.

[0047] In the exemplary embodiment, the profile shaft 6 is designed as a solid shaft. Alternatively, it can also be designed as a hollow shaft.

[0048] During operation, the rotary motion and torque are transmitted from the rotary drive 4 to the profile shaft 6. The profile teeth 22 then transmit the rotary motion and torque from the profile shaft 6 to the hub 8. Simultaneously, the hub is moved axially in direction A by the feed drive 14 with a feed force exerted by it.

[0049] The inclined profile teeth 22 result in a force distribution of the circumferential force Fu generated by the applied torque, as can be seen from the FIG 5 will be explained in more detail.

[0050] The circumferential force Fu generated by the rotary drive 4, acting in the circumferential direction, exerts a normal force FN on the inclined profile flank 24. Due to a predetermined coefficient of friction acting between the two components, profile shaft 6 and hub 8, a frictional force FR is generated acting in the direction of the profile flank 24. This force has an axial component, which is referred to as the axial frictional force F Rax. Simultaneously, the normal force FN also generates an axial feed force F Nax that counteracts this axial frictional force F Rax.

[0051] During operation, the applied torque on the hub 8 therefore induces the axial frictional force FRax and the axial feed force FNax. The axial frictional force FRax opposes and inhibits the feed force generated by the feed drive 4. In contrast, the axial feed force FNax assists the feed movement.

[0052] As shown in the force diagram according to FIG 5 As can be seen, in the illustrated embodiment, the helix angle α (for a given coefficient of friction) is selected such that the two axial forces FRax and FNax are equal in magnitude, thus mutually compensating for each other. With this preferred setting, the feed resistance exerted by the generated frictional force FR is therefore compensated, and the feed drive 14 only needs to exert the desired feed force for the axial infeed movement, without having to additionally overcome the axial frictional force FRax.

[0053] How based FIG 5As is immediately apparent, varying the helix angle α can alter the force distribution between the two axial forces FRax and FNax, so that they do not necessarily have to cancel each other out. Thus, by appropriately selecting the helix angle α, the axial feed force FNax (in magnitude) is adjusted to be greater or less than the axial friction force FRax. In the exemplary embodiment, the axial feed force FNax increases with increasing helix angle α.

[0054] The force distribution is independent of the magnitude of the transmitted torques, since both the axial frictional force FRax and the opposing axial feed force FNax depend equally on the torque and thus on the circumferential force FU. Overall, the resulting axial forces FRax and FNax are proportional to the torque. The ratio of the two axial forces FRax and FNax is independent of the torque.

[0055] This inventive design with the inclined profile teeth 22 offers the following advantages in particular: In conventional designs with parallel profile teeth, the feed resistance would have to be compensated for by a correspondingly stronger feed drive 14. This would result in the profile shaft 14 being pulled out of the rotary drive 4 with a correspondingly high force, which would have to be compensated for by a corresponding counter-holding force from the rotary drive 4, for which, however, the rotary drive 4 may not be designed.

[0056] By compensating for or at least reducing the feed resistance, the feed drive can be designed to be more compact and cost-effective compared to a conventional design.

[0057] The advantage of the inclined profile teeth 22 is not only evident when screwing in, but also when loosening and unscrewing screw elements from a component. Here too, the problem of feed resistance exists, only in the opposite direction, which is at least reduced by the inclined profile teeth 22.

[0058] For the principle described here, the specific design of the gear profiles, i.e., the profile of the individual teeth or flanks, is not crucial. The profiled shaft 6, for example, is designed as a so-called toothed shaft, alternatively as a so-called splined shaft, or even as a shaft with a differently shaped profile, such as square, hexagonal, or polygonal. The splined shaft is the preferred variant.

[0059] The invention described here has been explained using screw device 2 as an example. In principle, the invention can also be applied to other tools that generate a rotary and a feed motion and that incorporate a telescopic transmission unit. Reference symbol list

[0060] 2 Screw device 4 Rotary drive 6 Profile shaft 8 Hub 10 Telescopic transmission unit 12 Guide tube 14 Feed drive 16 Tool holder 18 Screw tool 20 Feed unit 22 Profile toothing 24 Profile flank S Screw axis A Axial direction α Inclination angle Fu Circumferential force FR Frictional force FN Normal force F Rax Axial frictional force F Nax Axial feed force

Claims

1. Rotating tool extending in an axial direction (A) for machining a component, in particular a screw device (2) for screwing a screw element into a component, comprising: - a tool holder (16) for a machining tool, in particular for a screw tool (18); - an axially fixed rotary drive (4) for generating a rotary motion and a torque; - a feed drive (14) for generating a feed motion which is transmitted to the tool holder (16) during operation; - a telescopic transmission unit (10) with two components movable relative to each other in the axial direction (A), namely a profile shaft (6) and a hub (8) movable along this shaft with an internal profile corresponding to the profile shaft (6).wherein one component is connected to the rotary drive (4) and the other component to the feed drive (14) and the tool holder (16), and the rotary motion generated by the rotary drive (4) is transferred from one component to the other, characterized by the fact that - the profile shaft (6) and the hub (8) are interlocked via a profile toothing (22) oriented obliquely to the axial direction (A).

2. Tool according to the preceding claim, characterized by the fact that No bearing elements are arranged between the profile shaft (6) and the hub (8).

3. Tool according to one of the preceding claims, characterized by the fact that the profile wave (6) has at least one profile flank (24) which is oriented obliquely to the axial direction (A) at an angle of inclination (α).

4. Tool according to the preceding claim, characterized by the fact that the inclination angle (α) is in the range of 2° to 30° and preferably in the range of 5° to 15°.

5. Tool according to one of the two preceding claims, characterized by the fact that through the inclined profile toothing (22) an axial feed force (F) is generated during operation Nax ) as well as one of these axial feed forces (F Nax ) opposing axial frictional force (F Rax ) and thus a feed inhibition is created, whereby the helix angle (α) is chosen such that the feed inhibition is at least reduced.

6. Tool according to the preceding claim, characterized by the fact that the helix angle (α) is chosen such that the feed resistance is compensated during operation.

7. Tool according to claim 5, characterized by the fact that the helix angle (α) is chosen such that the generated axial feed force (F) Nax ) greater than the opposing axial frictional force (F Rax ) is.

8. Tool according to one of the preceding claims, characterized by the fact thatSeveral profile flanks (24) are arranged around the circumference of the profile shaft (6), in particular 4 to 12 profile flanks.

9. Tool according to one of the preceding claims, characterized by the fact that it is designed to exert a screw-in torque of up to 500 Nm, in particular up to 150 Nm and preferably up to 50 Nm, applied to the tool holder (16).

10. Tool according to one of the preceding claims, characterized by the fact that it is designed to exert a feed force on the tool holder (16) in the range between 1 N and 3000 N and in particular in the range between 10 N and 300 N.

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