Material Cutting Device

Abstract

A material cutting device includes a rotatably mounted tool holder configured to carry a cutting tool and a drive for rotating the tool holder. The drive includes an electric motor with a rotor and a stator. The axis of rotation of the rotor of the electric motor and the axis of rotation of the tool holder are arranged coaxially. The stator encloses the rotor over an angle of less than 360 degrees.

Claims

1. A material cutting device, comprising: a rotatably mounted tool holder configured to carry a cutting tool; and a drive for rotating the tool holder; wherein the drive comprises an electric motor including a rotor and a stator; wherein an axis of rotation of the rotor of the electric motor and an axis of rotation of the tool holder are arranged coaxially; and wherein the stator encloses the rotor over an angle of less than 360 degrees.

2. The material cutting device according to claim 1, wherein the stator encloses the rotor over an angle of 270° or less.

3. The material cutting device according to claim 1, wherein the stator extends over an angle which is dimensioned such that the stator extends exclusively on one side of a boundary surface; and wherein the boundary surface is defined as a virtual tangential surface on an outer side of the tool holder.

4. The material cutting device according to claim 3, wherein the boundary surface is a virtual horizontal plane defined as a tangential surface on an underside of the tool holder when the material cutting device is in an intended working position.

5. The material cutting device according to claim 1, wherein the tool holder is configured to be substantially rotationally symmetrical; the tool holder has a maximum radius; and wherein the stator does not extend in a downward direction and in a forward direction beyond the maximum radius of the tool holder when the material cutting device is in an intended working position.

6. The material cutting device according to claim 1, wherein the material cutting device is a joint cutting device, comprising a chassis; and at least one running gear for moving the chassis; wherein the electric motor and the tool holder are arranged in a forward area of the chassis, as seen in a main direction of travel; and wherein an electric energy storage device is provided for supplying the electric motor with electric energy.

7. The material cutting device according to claim 6, wherein a center of gravity of the electrical energy storage device is arranged above the axis of rotation of the tool holder.

8. The material cutting device according to claim 6, wherein a battery receptacle is provided for receiving the electrical energy storage device; and wherein the electrical energy storage device is replaceable.

9. The material cutting device according to claim 6, wherein the chassis, with respect to an intended working position, has a lower area at a level of the electric motor and the tool holder; and wherein the chassis has an upper area arranged above the lower area and spaced away from the lower area by at least 400 mm.

10. The material cutting device according to claim 9, wherein a converter device is provided in the upper area or in the lower area, the converter device being configured to convert an electric direct current from the electric energy storage device into a current suitable for operating the electric motor.

11. The material cutting device according to claim 1, wherein the electric motor has a single rotor and a single stator.

12. The material cutting device according to claim 2, wherein the stator encloses the rotor over an angle of 180° or less.

13. The material cutting device according to claim 2, wherein the stator encloses the rotor over an angle of 120° or less.

14. The material cutting device according to claim 2, wherein the stator encloses the rotor over an angle of 90° or less.

15. The material cutting device according to claim 1, wherein the material cutting device comprises one of a joint cutter, an angle grinder, a chop saw, and a circular saw, and wherein the cutting tool comprises a cutting disc or a sawing disc.

16. A joint cutting device, comprising: a chassis; at least one running gear for moving the chassis; a rotatably mounted tool holder configured to carry a cutting tool; and a drive for rotating the tool holder, the drive comprising an electric motor including a rotor and a stator; wherein the electric motor and the tool holder are arranged in a forward area of the chassis, as seen in a main direction of travel; wherein an axis of rotation of the rotor of the electric motor and an axis of rotation of the tool holder are arranged coaxially; and wherein the stator encloses the rotor over an angle of less than 360 degrees.

17. The joint cutting device according to claim 16, further comprising an electric energy storage device that is configured to supply the electric motor with electric energy.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0036] These and other advantages and features of the invention are elucidated in more detail below by means of examples with the aid of the accompanying figures, in which:

[0037] FIG. 1 shows a side view of a material cutting device according to the invention as a joint cutter;

[0038] FIG. 2 shows a detail enlargement of the electric motor used in the joint cutter of FIG. 1;

[0039] FIG. 3 shows a bottom view of the joint cutter of FIG. 1;

[0040] FIG. 4 shows a rear view of the joint cutter of FIG. 1;

[0041] FIG. 5 shows a variant of the joint cutter of FIG. 1;

[0042] FIG. 6 shows a bottom view of the joint cutter of FIG. 5;

[0043] FIG. 7 shows a rear view of the joint cutter of FIG. 5; and

[0044] FIG. 8 shows a schematic representation of a circular saw as a further embodiment of a material cutting device according to the invention.

DETAILED DESCRIPTION

[0045] FIG. 1 to FIG. 4 show a first variant of a joint cutter serving as a material cutting device according to the invention.

[0046] The joint cutter has a chassis 1 with a chassis frame 2 and a running gear 3. Two front wheels 4 and two rear wheels 5 are provided on the running gear 3, which wheels are each arranged on an axle 6 (FIG. 3).

[0047] A guide handle 7 is attached in a manner that it can be swiveled in height in the upper area of the chassis 1 or alternatively of the chassis frame 2, by means of which guide handle an operator can guide or alternatively push or move the joint cutter.

[0048] Depending on the embodiment, the running gear 3 may be covered by a cover such that the upper and side surfaces are smooth, as shown, for example, in FIG. 1.

[0049] In the upper area of the chassis 1, a height adjustment 8 is also provided, which in the example shown is configured as a crank and with which an operator can adjust the lowering of a cutting device 9 relative to the rest of the chassis 1 in a manner known per se.

[0050] The cutting device 9 has a cutting disc 10 serving as a cutting tool, which is rotatably held in a clamping fixture 11 serving as a tool holder. The cutting disc 10 can be replaced if required, which is the reason for which the clamping fixture 11 can be easily opened and closed.

[0051] Coaxial to the clamping fixture 11, an electric motor 12 serving as a drive is provided, with a rotor 13 and a stator 14. A rotor shaft 15 of the rotor 13 extends to the clamping fixture 11 and can be directly driven in rotation by the rotor 13.

[0052] In conventional electric drives, the stator 14 would completely enclose the rotor 13 in a circular ring-like manner. In the material cutting device according to the invention, on the other hand, the electric motor 12 is configured as a segment motor, wherein the stator 14 extends only over a limited angular range smaller than 360°. In the example shown in FIG. 1 and — as a detail enlargement — FIG. 2, it can be seen that the stator only extends around the rotor 13 over an angular range (segment) of approx. 180°.

[0053] Rotor 13 and stator 14 are also enclosed by a housing 16. It can be clearly seen that the housing 16 can be very compact, due to the small size of the stator 14 which only extends over one segment.

[0054] It can, in particular, be seen in FIG. 2 that the stator 14 does not extend further downward than the rotor 13. In the case of a conventional electric motor with a ringshaped stator, the stator would even take up considerable installation space below the rotor 13. This is not the case with the solution shown in FIG. 1 and FIG. 2. In particular, towards the bottom, the installation space is limited to the diameter of the rotor 13 (and the enclosing housing 16). More installation space is not taken up towards the bottom.

[0055] If the rotor diameter (inclusive of the housing 16) is smaller, or at least not larger, than the diameter of the tool holder or clamping fixture 11, the diameter of the clamping fixture 11 alone is the limiting factor for the cutting depth. The cutting disc 10 can thus penetrate very deeply into the material to be separated. The penetration depth is limited only by the diameter of the clamping fixture 11. The design of the electric motor 12 does not require any limitation of the penetration depth or alternatively cutting depth.

[0056] This correlation is also shown in FIG. 4. There, the clamping fixture 11 and the electric motor 12 can be seen side by side in the rear view. It can, in particular, be seen that the electric motor 12 and thus the stator 14 inclusive of the housing 16 do not extend downward beyond a boundary surface which, in this embodiment, is a virtual horizontal plane which is tangentially defined on the underside of the tool holder 11 and which extends perpendicular to the drawing plane. In so doing, the electric motor 12 does not reduce the possible downwards penetration depth of the cutting disc 10.

[0057] In the lower area of the chassis 1, a rechargeable battery 18 is arranged as an electrical energy storage device. The rechargeable battery 18 can, in particular, be replaceably mounted in a corresponding rechargeable battery holder so that it can be quickly replaced with a fresh rechargeable battery 18 if required.

[0058] A converter 19 is arranged in the upper area of the chassis 1, which serves to convert the direct current obtained from the battery 18 into a suitable current for the electric motor 12. This is, in particular, necessary if the electric motor 12 is a reluctance motor, in particular a synchronous reluctance machine with a segmented stator.

[0059] FIG. 5 to FIG. 7 show a variant for a joint cutter as a material cutting device.

[0060] The joint cutter shown there is substantially consistent with the joint cutter of FIG. 1 to FIG. 4. However, in the example shown, the battery 18 is fixedly installed. In addition, the converter 19 is also arranged in the lower area of the chassis 1.

[0061] The design of the electric motor 12, on the other hand, is identical to that of FIG. 1 to FIG. 4.

[0062] The arrangement of the battery 18 above the clamping fixture 11 and the rotor 13 arranged coaxially thereto causes the mass of the battery 18, in particular, to press the cutting disc 10 downward into the material to be cut during operation of the joint cutter. The cutting disc 10 itself causes an upward tendency due to the rotary motion of the cutting disc (direction of the arrow in FIG. 5) and friction against the material to be cut. This upward movement is counteracted by the weight of the battery 18 and also of the converter 19.

[0063] FIG. 8 shows a schematic representation of a circular saw as another example of a material cutting device.

[0064] The circular saw has a saw table 30 in which a saw disc 31 serving as a cutting tool is rotatably held by means of a tool holder (disc holder) that is not shown.

[0065] The tool holder is rotationally driven directly by an electric motor arranged coaxially to the tool holder, which motor has a rotor 13 and a stator 14.

[0066] In this example as well, the stator 14 is configured as a segmented stator 14 and encloses the rotor 13 over an angle of less than 360°. In the example shown in FIG. 8, the stator 33 extends over an angle of about 180°, analogous to the stator of FIG. 1 and FIG. 2.

[0067] In this embodiment, too, it is thus ensured that the tool holder with the saw disk 31 can be directly driven coaxially by a motor without the electric motor impairing or reducing the usable cutting height (obstacle free area of the saw disk 31 above the saw table 30).