POWER TOOL HAVING A FIRST GEAR STAGE AND A BELT DRIVE

Abstract

A power tool includes a motor, a rotary disk, a belt drive connecting the motor to the rotary disk, and a reduction gear stage between the motor and the belt drive. A power tool with a ratio of an outer diameter of the drive pulley and an outer diameter of the output pulley being 0.75 to 1.33 is also provided as is a method of operating a power tool.

Claims

1. A power tool comprising: a motor; a rotary disk; a belt drive connecting the motor to the rotary disk; and a reduction gear stage between the motor and the belt drive.

2. The power tool as recited in claim 1 further comprising an intermediate shaft between the reduction gear stage and the belt drive and connecting the reduction gear stage to the belt drive.

3. The power tool as recited in claim 1 wherein the motor has an output shaft and the reduction gear stage has a first gear and a second gear, the first gear being arranged on the output shaft of the motor and the second gear being arranged on the intermediate shaft

4. The power tool as recited in claim 1 wherein the belt drive includes a drive pulley, an output pulley and a belt passing around the drive and output pulleys.

5. The power tool as recited in claim 4 wherein the drive and output pulleys have an outer diameter of 10 to 100 mm.

6. The power tool as recited in claim 5 wherein the outer diameter is 25 to 50 mm.

7. The power tool as recited in claim 4 wherein the belt is a V-ribbed belt.

8. The power tool as recited in claim 7 wherein the V-ribbed belt has five to fifteen ribs.

9. The power tool as recited in claim 4 wherein the drive pulley is arranged on the intermediate shaft.

10. The power tool as recited in claim 9 wherein the motor has an output shaft and the reduction gear stage has a first gear and a second gear, the first gear being arranged on the output shaft of the motor and the second gear being arranged on the intermediate shaft.

11. The power tool as recited in claim 1 wherein the motor is rated to have an operational rotational speed in a range from 10 000 rpm to 30 000 rpm.

12. The power tool as recited in claim 1 wherein a speed reduction ratio of the reduction gear stage is between 2 and 4.

13. The power tool as recited in claim 1 wherein the reduction gear stage has spur gears.

14. The power tool as recited in claim 4 wherein a ratio between an outer diameter of the output pulley and an outer diameter of the rotary disk is in a range from 1/30 to 1/3.

15. The power tool as recited in claim 1 wherein a ratio between a rated operational rotational speed of the motor and a maximum rotational speed of the rotary disk is in a range from 1.97 to 5.91.

16. The power tool as recited in claim 1 wherein the rotary disk is a grinding wheel or saw.

17. The power tool as recited in claim 1 further comprising a handle, the power tool being a handheld power tool.

18. The power tool as recited in claim 1 wherein the motor is an electric motor and further comprising a rechargeable battery for driving the electric motor.

19. A power tool comprising: a motor; a rotary disk; and a belt drive including a drive pulley driven by the motor, an output pulley connected to the rotary disk and a belt passing around the drive and output pulleys, a ratio of an outer diameter of the drive pulley and an outer diameter of the output pulley being 0.75 to 1.33.

20. A method for operating a power tool having a motor, a rotary disk, and a belt drive including a drive pulley driven by the motor, an output pulley connected to the rotary disk and a belt passing around the drive and output pulleys, the method comprising: operating the motor at a speed between 10,000 rpm to 30,000 rpm; reducing the motor speed during the operating with a gear stage to drive the drive pulley at a speed less than 10,000 rpm; and driving the rotary disk with the output pulley at less than 10,000 rpm.

21. The power tool as recited in claim 1 wherein the reduction gear drive has two interacting toothed gears.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0035] In the figures, identical and similar components are denoted by the same reference signs.

[0036] In the figures:

[0037] FIG. 1 shows a plan view of a preferred embodiment of the power tool of the present invention;

[0038] FIG. 2 shows a sectional illustration of the preferred embodiment of the power tool of the present invention.

DETAILED DESCRIPTION

[0039] FIG. 1 shows a plan view of individual components of a preferred embodiment of a power tool 10 according to the present invention. In particular, power tool 10 has a reduction gear stage 18 and a belt drive 16, wherein reduction gear stage 18 and belt drive 16 are connected functionally together via an intermediate shaft 20. Power tool 10 has a motor 12, wherein a rotary movement of the motor 12 is transmitted to the first gear stage 18 via an output shaft 26 of the motor 12. Motor 12 preferably is a brushless electric motor driven rechargeable by two batteries 13, shown schematically. Reduction gear stage 18 has a first gear 22 and a second gear 24, configured as gearwheels. In this case, gear 22 has preferably a smaller diameter than second gear 24, in order to ensure a suitable reduction between the motor 12 and the belt drive 26. Gears 22, 24 have teeth 36, which can be configured in a straight manner in a preferred configuration of the invention; in other words, the first gear stage 18 can be configured with spur teeth. As a result, a direction of rotation of the motor 12 or the movement in the first gear stage 18 can be reversed particularly easily. The first gear stage 18 can be configured in particular as spur gearing.

[0040] Movement of motor 12 of power tool 10 is transmitted to the belt drive 16 via the first gear stage 18. This is achieved advantageously in that the first gear 22 of gear stage 18 is arranged on output shaft 26 of the motor 12 and thus picks up a movement of the motor 12. Second gear 24 of gear stage 18 engages first gear 22 and picks up the rotary movement of first gear 22. Second gear 24 of gear stage 18 is arranged on intermediate shaft 20, such that the intermediate shaft 20 is driven by movement of second gear 24 of gear stage 18. A first pulley 28 is also arranged on intermediate shaft 20. Pulley 28 is the drive pulley of the belt drive 16. Drive pulley 28 of the belt drive 16 is connected to a second pulley 30 of the belt drive 16 via a belt 32. According to the embodiment, pulley 28 and pulley have substantially identical or similar diameters, such that reduction work in the power tool 10 is carried out substantially in reduction gear stage 18.

[0041] Belt 32 of belt drive 16 is configured as a V-ribbed belt and has ribs 34. Preferably, the belt 32 has ten ribs 34 and a PJ profile. Second pulley 30 of the power tool 10 is present on a driveshaft 38 for rotary disk 14 of the power tool 10. Rotary disk 14 can preferably be a cut-off wheel, which has for example a diameter in the region of 300 mm. Other diameters of rotary disk 14 are also conceivable, however. Driveshaft 38 for rotary disk 14 is driven by second pulley 30, wherein rotary movement of driveshaft 38 is transmitted to rotary disk 14. The belt drive 16 is present in this embodiment in the region of a cutting arm 40 of the power tool 10, wherein the rotary disk 14 is arranged on the cutting arm 40. Cutting arm 40 connects preferably a main body of the power tool 10 to rotary disk 14.

[0042] FIG. 2 shows a sectional illustration of the preferred embodiment of power tool 10. In particular, FIG. 2 shows a section through the cutting arm 40 of the power tool 10. Illustrated on the left-hand side of FIG. 2 are the motor 12 and the first gear stage 18 of the proposed power tool 10. A rotary movement of the motor 12 can be transmitted to gear 22 of gear stage 18 by an output shaft 26. This is achieved in that gear 22 is arranged on the output shaft 26 such that gear 22 is made to move in rotation by rotation of motor output shaft 26. Second gear 24 of the first gear stage 18 engages first gear 22 and picks up the movement of the first gear 22. Gears 22, 24 are configured preferably as gearwheels of different sizes. Gears 22, 24 have teeth 36, which, in this embodiment, are configured in a straight manner in order to allow the direction of rotation to be reversed.

[0043] As a result of the movement of second gear 24, intermediate shaft 20 is driven, which for its part is connected to first pulley 28 of belt drive 16. First pulley 28 is driven by the intermediate shaft 20 and made to move in rotation. This rotary movement of first pulley 28 of belt drive 16 is transmitted to second pulley 30 by belt 32. The belt 32 can preferably be a V-ribbed belt with for example ten ribs 34, shown in FIG. 1. The rotation of output pulley 30 30 is transmitted to rotary disk 14 of the power tool 10 via a driveshaft 38.

[0044] Tool 10 can be a handheld and thus a handle 15, shown schematically, is also provided.

LIST OF REFERENCE SIGNS

[0045] 10 Power tool

[0046] 12 Motor

[0047] 13 Batteries

[0048] 14 Rotary disk

[0049] 15 Handle

[0050] 16 Belt drive

[0051] 18 Gear stage

[0052] 20 Intermediate shaft

[0053] 22 First gear

[0054] 24 Second gear

[0055] 26 Output shaft

[0056] 28 Drive pulley of the belt drive

[0057] 30 Output of the belt drive

[0058] 32 Belt

[0059] 34 Ribs

[0060] 36 Teeth of the gearwheels

[0061] 38 Driveshaft for the rotary disk

[0062] 40 Cutting arm