EP4005735B1 - Machine tool with thread spindle drive - Google Patents

Description

The invention relates to a machine tool, in particular a pipe press, comprising a drive, an output shaft, a threaded spindle drive and a linear actuator, wherein a torque generated by the drive can be transmitted to the linear actuator via the output shaft and the threaded spindle drive connected to the output shaft.

Different machine tools for forming and cutting processes are known from the state of the art. With the help of these special machine tools, for example, reinforcing iron can be cut, pipes can be mechanically connected or hose clamps can be pressed on. The tasks of mechanical connection also include crimping, flanging and squeezing.

From the disclosure document EN 10 2018 124646 A1 a hand-held power tool according to the preamble of claim 1 with a planetary roller screw drive is known. From the published application EN 10 2018 115788 A1 A screw drive with rod-shaped rolling elements designed as friction rolling elements is known. From the non-patent document article " Backlash-free roller screw drive", F&M Feinwerktechnik Mikrotechnik Messtechnik, Hanser, Munich, DE, Vol. 103, No. 5, 01.05.1995, p. 255 A roller screw drive with a multi-start spindle and lengths of up to 7 meters is known.

In order to achieve the high pressing forces required for crimping steel pipes, for example, the forming machines available on the market have a pressing head driven by a pressing cylinder. The pressing cylinder is often driven hydraulically to move the pressing head. An electric motor in turn drives a hydraulic pump, which drives the linear movement of the pressing cylinder. Alternatively, mechanical pressing/cutting and crimping machine tools are also known which generate the pressing pressure via a threaded spindle drive in combination with an electric motor instead of hydraulics. The rotational movement of the electric motor is transformed into a linear movement via a threaded spindle. These machine tools often contain a gear connected between the spindle and the electric motor to reduce the required motor torque and thus enable the motor to be dimensioned smaller.

However, the machine tools with hydraulically driven linear actuators known from the state of the art tend to be too complex to develop and too large or too long, inefficient and too heavy to handle. Furthermore, the machine tools with hydraulically driven linear actuators known from the state of the art require a relatively long time for a single work cycle, where a work cycle can be a forming or cutting cycle, for example.

The threaded spindle drives previously used in such machine tools also lead to high friction losses. Attempts to minimize these friction losses have also led to very complex and therefore costly designs.

The object of the present invention is therefore to offer a machine tool of the type described above which is particularly cost-effective and offers high efficiency while still having a very high load-bearing capacity.

The object is achieved by a machine tool, in particular a pipe press, comprising a drive, an output shaft, a threaded spindle drive and a linear actuator, wherein a torque generated by the drive can be transmitted to the linear actuator via the output shaft and the threaded spindle drive connected to the output shaft, wherein the threaded spindle drive has an inner threaded spindle part with an external thread and an outer threaded spindle part with an internal thread, wherein the internal thread interacts with the external thread via at least one bearing roller and the at least one bearing roller has at least one radially circumferential groove with which the bearing roller engages in the external thread and in the internal thread.

According to the invention, the at least one bearing roller has one or more radially encircling grooves. Due to the at least one groove, no screw thread is formed on the bearing roller. The bearing roller is thus structurally very simple and can be manufactured inexpensively. When the inner threaded spindle part rotates relative to the outer threaded spindle part, the bearing roller can roll on the inner and outer threads. The bearing roller thus forms a roller bearing, which can have a particularly low rolling friction compared to, for example, sliding friction. The threaded spindle drive can therefore only have low friction losses and thus a particularly favorable efficiency in converting the rotary movement into a translation, in particular parallel to an axial direction of the threaded spindle drive. The more radially encircling grooves the bearing roller has, the higher Loads can be transmitted and/or generated along the axial direction of the lead screw drive.

The machine tool can preferably be a mobile machine tool, for example a hand-held power tool or a mobile construction robot, in particular for work in building construction and/or civil engineering, for example for installation work. The machine tool can be a pressing device, a cutting device, for example a cutting shear, and/or a crimping device.

Preferred embodiments of the invention can have several bearing rollers, in particular 3, 4, 6, 8, 10, 12 or 13 bearing rollers. The bearing rollers can be arranged evenly distributed over the circumference of the inner threaded spindle part.

Preferably, the internal thread and/or the external thread are single-start.

Simple assembly, in particular partial pre-assembly, is possible if the at least one bearing roller is accommodated in a cage. If several bearing rollers are provided, a cage can particularly facilitate an evenly distributed arrangement of the bearing rollers along the circumference of the inner threaded spindle part.

The cage and/or the rollers can have a translational degree of freedom, in particular parallel to the axial direction, relative to the rest of the threaded spindle drive. A translation of the cage and/or the rollers can thus be possible, in particular parallel to the longitudinal axis of the threaded spindle drive. In particular, it can be arranged that when the inner threaded spindle part rotates relative to the outer threaded spindle part, the cage together with the rollers, or in the case of dispensing with a cage, the rollers alone, are displaced along the axial direction relative to the inner threaded spindle part and/or relative to the outer threaded spindle part.

The outer threaded spindle part can be fixed in a rotationally fixed and/or displacement-fixed manner relative to a housing of the machine tool. The relative rotation can thus lead to a translation of the inner threaded spindle part relative to the housing.

If the inner threaded spindle part is connected to the linear actuator, the linear actuator can be and/or be actuated by the inner threaded spindle part, in particular by relative rotation.

The outer threaded spindle part can also be longer than the at least one bearing roller. Alternatively or additionally, the outer threaded spindle part can be longer than the cage. The bearing rollers and/or, if present, the cage can thus be displaced at least over a certain distance in the axial direction without leaving the area of the outer threaded spindle part. Particularly preferably, the outer threaded spindle part can be at least twice as long as the at least one bearing roller and/or, if present, the cage.

In one class of embodiments of the invention, the linear actuator is mounted on the inner threaded spindle part so as to be rotatable along the longitudinal axis of the inner threaded spindle part, so that the linear actuator can be decoupled and/or is decoupled from rotations of the inner threaded spindle part, in particular relative to the housing. For this purpose, a ball bearing and/or a roller bearing can be arranged between the inner threaded spindle part and the linear actuator.

In particularly preferred embodiments of the invention, the threaded spindle drive, preferably the inner threaded spindle part, can be driven by the drive via a telescopic shaft device, so that the torque from the drive can be transmitted to the threaded spindle drive, in particular to the inner threaded spindle part, even when the inner threaded spindle part is translated in the axial direction. The output shaft can be designed as a telescopic shaft device. Alternatively or additionally, the telescopic shaft device can be designed as part of the output shaft. The telescopic shaft device can have a groove element provided with one or more longitudinal grooves, on which a fitting piece can preferably be guided.

If the drive is designed as a brushless motor, the machine tool can have a particularly long service life, which in turn can improve the cost efficiency of the machine tool over its service life.

The torque can be transmitted via a gear device, in particular via a reduction gear, particularly preferably via an eccentric gear device, to the Threaded spindle drive can be and/or are transmitted. Preferably, a reduction by a factor in the range from 10 to 1000, in particular in the range from 10 to 100, for example 20, can be provided.

Thus, the machine tool can contain an eccentric gear device for torque adjustment between the drive and the threaded spindle drive, wherein the eccentric gear device contains a drive eccentric drivable by the drive, an eccentric gear drivable by the drive eccentric, a compensating coupling drivable by the eccentric gear for transmitting torque from the eccentric gear to the output shaft.

For further details on possible designs of the eccentric gear device, reference is expressly made to the European patent application file number EP20210196, filing date 27.11.2020 , the description, claims and drawings of which are hereby incorporated by reference in their entirety.

Further advantages also emerge from the following figure description.

The figures show various embodiments of the present invention.

The figures, the description and the patent claims contain numerous features in combination. The person skilled in the art will also expediently consider the features individually and combine them into further meaningful combinations.

In the figures, identical and similar components and assemblies are numbered with the same reference symbols.

Figur 1

eine seitliche Ansicht auf eine Werkzeugmaschine in Ausgestaltung einer Rohrpresse;

Figur 2

eine seitliche Schnittansicht auf die beispielhaft als Rohrpresse ausgestaltete Werkzeugmaschine mit einem Antrieb, einer Abtriebswelle, einem Gewindespindeltrieb, einem Linearaktuator und einer Exzentergetriebevorrichtung;

Figur 3

eine perspektivische Schnittansicht auf die beispielhaft als Rohrpresse ausgestaltete Werkzeugmaschine mit dem Antrieb, der Abtriebswelle, dem Gewindespindeltrieb, dem Linearaktuator und der Exzentergetriebevorrichtung;

Figur 4 bis Figur 6

perspektivische Schnittansichten auf den Gewindespindeltrieb mit einem inneren Gewindespindelteil, einem äußeren Gewindespindelteil und einem Käfig mit Lagerrollen in unterschiedlichen Zuständen und

Figur 7

eine perspektivische Schnittansicht des Gewindespindeltriebs.

Show it:

Figure 1

a side view of a machine tool in the form of a pipe press;

Figure 2

a side sectional view of the machine tool, designed as a pipe press by way of example, with a drive, an output shaft, a threaded spindle drive, a linear actuator and an eccentric gear device;

Figure 3

a perspective sectional view of the machine tool, designed as a pipe press by way of example, with the drive, the output shaft, the threaded spindle drive, the linear actuator and the eccentric gear device;

Figure 4 to Figure 6

perspective sectional views of the threaded spindle drive with an inner threaded spindle part, an outer threaded spindle part and a cage with bearing rollers in different states and

Figure 7

a perspective sectional view of the threaded spindle drive.

Detailed description of the invention:

In Figure 1 to 3 a machine tool 1 according to the invention is shown in an exemplary embodiment as a pipe press. Instead of being designed as a pipe press, the machine tool 1 can also be designed as any other cutting or forming tool. In particular, it is also possible for the machine tool 1 according to the invention to be designed as a squeezing device for chemical substances, such as adhesive or dowel compound. Such squeezing devices can also be referred to as dispensers.

As in Figure 1 As can be seen, the machine tool 1 designed as a pipe press essentially has a housing 2, a tool holder 3 and a power supply 4.

The housing 2 of the machine tool 1 is essentially cylindrical and contains a front end 2a, a rear end 2b, a left side surface 2c, a right side surface 2d, a top side 2e and a bottom side 2f. A middle part 2g of the housing 2 serves as a handle for holding or guiding the machine tool 1. In the Figures 1 to 3 only the left side surface 2c is shown. The housing 2 merges into a preferably metallic housing section 52.

The energy supply 4 is positioned at the rear end 2b of the housing 2 of the machine tool 1. In the present embodiment, the energy supply 4 is designed as an accumulator (also called a battery), preferably as a lithium-based accumulator. The energy supply 4 designed as an accumulator can be re-detachably connected via an interface 5 to the rear end 2b of the housing 2 of the machine tool 1. With the help of the accumulator 4, the machine tool 1 or the electrical consumers of the machine tool 1 are supplied with electrical energy.

According to an alternative embodiment of the present invention, the power supply 4 of the machine tool 1 can also be designed as a power cable for connecting the machine tool 1 to a power source (i.e. socket).

The tool holder 3 is positioned at the front end 2a of the housing 2 of the machine tool 1 for releasably receiving and holding a tool 6. In the present embodiment, a tool 6 in the form of a forming tool is positioned on the tool holder 3. In the present embodiment, the forming tool 6 is designed as a so-called press head. The forming tool 6 designed as a press head is used essentially for processing and in particular for forming lines, i.e. pipes and tubes. The lines are not shown in the figures.

An activation switch 7 is positioned on the underside 2f of the housing 2 of the machine tool 1. The machine tool 1 can be started and stopped using the activation switch 7.

A drive 8, a drive shaft 9, an eccentric gear device 10, an output shaft 11, a threaded spindle drive 12 and a linear actuator 13 are essentially positioned inside the housing 2 of the machine tool 1. In the present embodiment, the drive 8 is designed as a brushless electric motor.

As can be seen from the Figures 2 and 3 As can be seen, the drive 8, which is designed as a brushless electric motor, is connected to the eccentric gear device 10 via the drive shaft 9. Through the connection to the drive shaft 9, a torque generated in the drive 8 is transmitted from the drive 8 to the eccentric gear device 10.

With the help of the eccentric gear device 10, a speed transmission from the drive 8 to the output shaft 11 can be generated.

The output shaft 11 is adjacent to the threaded spindle drive 12. The threaded spindle drive 12 is connected to the output shaft 11. The threaded spindle drive 12 can convert the rotary motion of the output shaft 11 into a linear motion.

The output shaft 11 is designed as a telescopic shaft device. Its length is therefore variable. For this purpose, it has a groove element 54 provided with one or more longitudinal grooves, on which a fitting piece 56 is guided in an axially displaceable manner. In the sectional view according to Figure 3 One of the longitudinal grooves 58 can be seen as an example. The groove element 54 is driven in rotation by the eccentric gear device 10, which in turn drives the fitting piece 56 guided in the groove element 54 and thus drives it. The fitting piece 56 is in turn connected in a rotationally fixed manner, in particular via a splined shaft connection, to a part of the threaded spindle drive 12 via an axially arranged shaft section 60.

Like the Figures 2 and 3 can be seen, the threaded spindle drive 12 is connected to the linear actuator 13, in particular by means of an inner threaded spindle part 42, which will be explained in more detail, and a ball bearing 62. The ball bearing 62 decouples the linear actuator 13 in terms of rotation from the threaded spindle drive 12 and thus also from the output shaft 11, so that it can carry out purely translational movements.

The linear actuator 13 essentially contains a compression spring 25 and a push rod 26. The compression spring 25 acts as a return spring for the linear actuator 13.

A force flow deflection device 27 is provided on the linear actuator 13. With the help of the linear actuator 13 and the force flow deflection device 27, the linear force of the linear actuator 13 is transmitted to the tool holder 3 in such a way that the tool 6 designed as a press head can be moved between an open and closed position.

The drive 8 designed as an electric motor can be set up to rotate at a maximum extension and retraction speed of the linear actuator 13 at a speed value between 10,000 and 30,000 rpm. In particular, a speed value between 15,000 and 25,000 rpm is provided for the drive 8.

Figures 4 to 6 show partially sectioned, perspective views of the threaded spindle drive 12 in different states.

The threaded spindle drive 12 has an outer threaded spindle part 40, in which the inner threaded spindle part 42 is displaceable by means of bearing rollers 44, one of which is shown by way of example in Figure 4 is provided with a reference number. The two threaded spindle parts 40, 42 are cylindrical or at least essentially cylindrical. The outer threaded spindle part 40 and the inner threaded spindle part 42 are made of a metal.

As will be explained in more detail, the inner threaded spindle part 42 is movable along an axial direction A of the threaded spindle drive 12, in particular along its longitudinal direction.

For this purpose, the outer threaded spindle part 40 has an internal thread 48 and the inner threaded spindle part 42 has an external thread 50. To simplify the illustration, the internal thread 48 and the external thread 50 are only shown in Figure 4 marked with a reference symbol. The threads 48, 50 are matched to one another. In particular, their pitches correspond. The threads 48, 50 can preferably have pitch angles in the range of 0.4 to 4°, for example 2°.

The bearing rollers 44 are rod-shaped, in particular fully cylindrical. Their diameters preferably correspond essentially to half the difference between the diameters of the two threaded spindle parts 40, 42. The bearing rollers 44 have a plurality of circumferential, closed grooves on the circumference, of which Fig.4 For example, a groove 53 is marked. The grooves 53 run parallel to each other. Their distance from each other is matched to the threads 48, 50.

The bearing rollers 44 are arranged in a cage 46. The cage 46 is made of a plastic, alternatively it can also be made of a metal.

The outer threaded spindle part 40 is attached to the housing section 52 (see Figure 3 ) is fixed in a rotationally fixed and displacement-proof manner. The outer threaded spindle part 40 is thus stationary relative to the rest of the machine tool 1 (see also Figure 3 ).

As can be seen from the summary of Figures 4 to 6 As can be seen, a rotation of the inner threaded spindle part 42 relative to the outer threaded spindle part 40 leads to a translation of the inner threaded spindle part 42 along the axial direction A relative to the outer threaded spindle part 40, which is stationary relative to the rest of the machine tool 1. During the rotation, the cage 46 together with the bearing rollers 44 also migrates within the outer threaded spindle part 40. In particular, the inner threaded spindle part 42 is displaced along the axial direction A at twice the speed as the cage 46 or the bearing rollers 44. Accordingly, the amplitude stroke of the displacement movement of the inner threaded spindle part 42 is also twice as large as that of the cage 46 or the bearing rollers 44. In order to ensure that the cage 46 and the bearing rollers 44 always move within the outer threaded spindle part 40 despite a sufficient amplitude stroke of the inner threaded spindle part 42 and thus to ensure optimal load transfer, the outer threaded spindle part 40 is twice as long as the cage 46.

Figure 7 shows the threaded spindle drive 12 in a perspective, partially sectioned view. It can be seen in particular that the inner threaded spindle part 42 is at one end, in particular at the output shaft 11 ( Figure 3 ) facing end, a splined shaft section 64 for connection to the shaft section 60 ( Figure 3 ) having.

From the overview of the Figures 3 and 7 This means that the rotating output shaft 11 causes the inner threaded spindle part 42 to rotate, whereby the latter moves forwards, i.e. in the direction of the tool 6 ( Figure 3 ), or backwards, i.e. in the direction of the drive 8 ( Figure 3 ) along the axial direction A. This in turn causes the linear actuator 13 ( Figure 3 ) so that, depending on the direction of rotation, the tool 6, which is designed, for example, as a forming tool, opens or closes or increases or reduces a contact pressure.

The threaded spindle drive 12, in particular in conjunction with the drive 8, can be designed to exert a maximum shear pressure in the range from 7 N/mm ² to 14 N/mm ² , preferably 14 N/mm ² , on the linear actuator 13. Alternatively or additionally, it can be designed to drive the linear actuator with a maximum peripheral speed in the range from 5 m/s to 100 m/s, in particular 60 m/s.

List of reference symbols

1

Machine tool

2

Housing

2a

front end 2a of the housing

2 B

rear end of the housing

2c

left side of the housing

2d

right side of the housing

2e

Top of the case

2f

Bottom of the case

3

Tool holder

4

power supply

5

interface

6

Tool

7

Activation switch

8th

drive

9

drive shaft

10

Eccentric gear device

11

Output shaft

12

Threaded spindle drive

13

Linear actuator

25

Compression spring

26

Push rod

27

Power flow diversion device

30

camp

40

outer threaded spindle part

42

inner threaded spindle part

44

Bearing roller

46

Cage

48

inner thread

50

External thread

52

Housing section

53

groove

54

Groove element

56

Fitting

58

Longitudinal groove

60

Wave section

62

ball-bearing

64

Spline section

A

Axial direction

THERE

Diameter of a recess

DK

Diameter of a coupling element

DH

Inner diameter of the hollow gear

E

Eccentricity of the eccentric gear

Claims (10)

1. Power tool (1), in particular a pipe press, comprising a drive (8), an output shaft (11), a threaded spindle drive (12) and a linear actuator (13), wherein a torque generated by the drive (8) is transmissible via the output shaft (11), and the threaded spindle drive (12) connected to the output shaft (11), to the linear actuator (13),
   characterized
   in that the threaded spindle drive (12) has an inner threaded spindle part (42) with an external thread (50) and an outer threaded spindle part (40) with an internal thread (48), wherein the internal thread (48) interacts with the external thread (50) via at least one bearing roller (44), and the at least one bearing roller (44) has at least one radially encircling channel (53) by means of which the bearing roller (44) engages in each case into the external thread (50) and into the internal thread (48).
2. Power tool according to the preceding claim, characterized in that the at least one bearing roller (44) is received in a cage (46).
3. Power tool according to Claim 2, characterized in that the cage (46) and/or the at least one roller (44) have a translational degree of freedom relative to the rest of the threaded spindle drive (12).
4. Power tool according to any one of the preceding claims, characterized in that the outer threaded spindle part (40) is fixed so as to be non-rotatable and/or non-displaceable relative to a housing (2) of the power tool (1).
5. Power tool according to any one of the preceding claims, characterized in that the length of the outer threaded spindle part (40) is longer than the at least one bearing roller (44).
6. Power tool according to any one of the preceding claims, characterized in that the length of the outer threaded spindle part (40) is at least twice as long as the shortest bearing roller (44).
7. Power tool according to any one of the preceding claims, characterized in that the linear actuator (13) is mounted on the inner threaded spindle part (42) so as to be rotatable along the longitudinal axis of the inner threaded spindle part (42).
8. Power tool according to any one of the preceding claims, characterized in that the threaded spindle drive (12), preferably the inner threaded spindle part (42), is drivable by the drive (8) via a telescopic shaft device.
9. Power tool according to any one of the preceding claims, characterized in that the drive (8) is a brushless motor.
10. Power tool according to any one of the preceding claims, characterized in that the torque is transmissible and/or transmitted via a transmission device, in particular a reduction transmission, particularly preferably via an eccentric transmission device (10), to the threaded spindle drive (12).

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