HANDHELD, HAND-GUIDED CUTTING-OFF MACHINE

Abstract

A handheld, hand-guided cutting-off machine, which includes a rotating cutting-off wheel, a supporting housing part (36), an output shaft (20), which is rotatably supported around an output axis (40), a drive motor, a transmission mechanism (19), which connects the drive motor to the output shaft (20), a flange (41) and a safety guard (24), which covers the cutting-off wheel over a covering area (25). The cutting-off wheel is rotatably fixedly mounted on the output shaft (20) with the aid of the flange (41) and surrounded by the safety guard (24). The safety guard (24) is pivotable around a pivot axis, and the pivot axis is displaced by a distance from the output axis (40) of the output shaft (20).

Claims

1-9. (canceled)

10: A handheld, hand-guided cutting-off machine comprising: a supporting housing part; a cutting-off wheel having a wheel diameter; an output shaft rotatably supported around an output axis on the housing part with the aid of a bearing element; a drive motor and a transmission mechanism connecting the drive motor to the output shaft, the transmission mechanism being situated on the housing part; a flange having a flange diameter, the cutting-off wheel being rotatably fixedly situatable on the output shaft with the aid of the flange; and a safety guard having a covering area at least partially covering the cutting-off wheel, and a machining area exposing the cutting-off wheel, the safety guard being pivotably supported around a pivot axis on the housing part; the pivot axis of the safety guard being displaced by a distance from the output axis of the output shaft.

11: The cutting-off machine as recited in claim 10 wherein the pivot axis is displaced with respect to the output axis into the covering area of the safety guard.

12: The cutting-off machine as recited in claim 11 wherein the safety guard includes a fastening flange having a diameter (d.sub.x), and the distance between the pivot axis and the output axis is greater than or equal to half the difference between the diameter (d.sub.x) of the fastening flange and the flange diameter.

13: The cutting-off machine as recited in claim 11 wherein the safety guard, having a first maximum distance (b.sub.1), the supporting housing part having a second maximum distance (b.sub.2) and the transmission mechanism has a third maximum distance (b.sub.3) from the output axis over an outcut angle, wherein the first, second and third maximum distances (b.sub.1, b.sub.2, b.sub.3) are less than half the flange diameter or equal to half the flange diameter.

14: The cutting-off machine as recited in claim 13 wherein the transmission mechanism includes an output disk situated on the output shaft, and a transmission element transmitting a movement of the drive motor to the output disk, the output disk having a fourth maximum distance (b.sub.4) and the transmission element having a fifth maximum distance (b.sub.5) from the output axis over the outcut angle, wherein the fourth and fifth maximum distances (b.sub.4, b.sub.5) are less than half the flange diameter or equal to half the flange diameter.

15: The cutting-off machine as recited in claim 14 wherein the transmission mechanism includes a cover, the cover having a sixth maximum distance (b.sub.6) from the output axis over the outcut angle less than half the flange diameter or equal to half the flange diameter.

16: The cutting-off machine as recited in claim 10 wherein the flange diameter of the flange corresponds to a minimum flange diameter (d.sub.min).

17: The cutting-off machine as recited in claim 16 wherein the drive motor is a combustion motor, and the cutting-off wheel is designed as a diamond cutting-off wheel or as an abrasive cutting-off wheel.

18: The cutting-off machine as recited in claim 16 wherein the drive motor is an electric motor, and the cutting-off wheel is designed as a diamond cutting-off wheel or as a bound, reinforced cutting-off wheel.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Exemplary embodiments of the present invention are described below on the basis of the drawing. The latter is not necessarily intended to represent the exemplary embodiments true to scale but rather the drawing is presented in a schematic and/or slightly distorted form where useful for the purpose of explanation. It should be taken into account that a variety of modifications and changes relating to the form and detail of a specific embodiment may be undertaken without deviating from the general idea of the present invention. The general idea of the present invention is not limited to the exact form or the detail of the preferred specific embodiment illustrated and described below, nor is it limited to an object which would be limited in comparison to the object claimed in the claims. In given measurement ranges, values within the specified limits are also to be disclosed as limiting values and be able to be arbitrarily used and claimed. For the sake of simplicity, the same reference numerals are used below for identical or similar parts or for parts having identical or similar functions.

[0023] FIGS. 1A, 1B show a handheld, hand-guided cutting-off machine, including a cutting-off wheel;

[0024] FIGS. 2A, 2B show a safety guard and a belt drive of the cutting-off machine illustrated in FIGS. 1A, 1B, including a cover (FIG. 2A) and without a cover (FIG. 2B);

[0025] FIGS. 3A through 3C show the cutting-off wheel and the safety guard of the cutting-off machine in FIG. 1A in a side view (FIG. 3A) as well as in a section along section line A-A (FIG. 3B) and in a second section along section line B-B (FIG. 3C);

[0026] FIG. 4 shows an enlarged detail of the second section in FIG. 3C; and

[0027] FIG. 5 shows the safety guard and a supporting arm housing of the belt drive, the cutting depth corresponding to the maximum cutting depth over an outcut angle.

DETAILED DESCRIPTION

[0028] FIGS. 1A, 1B show a handheld, hand-guided power tool 10 according to the present invention, which is designed in the form of a cutting-off machine. Cutting-off machine 10 includes a machining tool designed as a cutting-off wheel 11, which is driven by a drive unit 12 in a rotation direction 13 around a rotation axis 14. All drive components for cutting-off wheel 11 are combined as drive unit 12. In cutting-off machine 10 illustrated in FIG. 1B, a cover 15 was removed, so that at least some drive components of drive unit 12 are visible. Cover 15 may have a single-part or multi-part design and is fastened to cutting-off machine 10 by screws.

[0029] Drive unit 12 includes a drive motor 17 situated in a motor housing 16, a transmission mechanism situated in a supporting arm 18 and designed as a belt drive 19, and an output shaft 20, on which cutting-off wheel 11 is mounted. Additional transmission components are connectable as needed between drive motor 17 and belt drive 19. A centrifugal clutch may be situated between drive motor 17 and belt drive 19, which ensures that cutting-off wheel 11 does not rotate at low rotational speeds, such as when idling or when starting cutting-off machine 10. The centrifugal clutch includes a clutch bell, against which the centrifugal weights are pressed outwardly during operation, due to the centrifugal force. Drive motor 17 drives a drive shaft 21 around a drive axis 22. The clutch bell of the centrifugal clutch is rotatably fixedly connected to a drive disk 23, which is rotatably supported on drive shaft 21.

[0030] Combustion motors or electric motors are used as drive motors 17 for cutting-off machine 10. All drive motors for motor-operated electric power tools are combined under the term electric motor; the electric power tools may be cable-bound with a direct connection to the grid or wireless without a direct connection to the grid. Cutting-off machines which include a combustion motor, may be used with different types of cutting-off wheels 11diamond cutting-off wheels and abrasive cutting-off wheelsthe cutting-off wheels including abrasive cutting-off bodies made of bound abrasive materials and/or grinding tools having diamond and CBN abrasive materials. Cutting-off machines which include an electric motor may be used with different types of cutting-off wheels 11: diamond cutting-off wheels and bound, reinforced cutting-off wheels of type 41 or 42.

[0031] Cutting-off wheel 11 is surrounded by a safety guard 24, which is used to protect the operator against flying dust particles and also reduces the risk of injury by the operator reaching into rotating cutting-off wheel 11 during the operation of cutting-off machine 10. Safety guard 24 is fastened in a hub area of cutting-off wheel 11 and is made up of a covering area 25, which covers cutting-off wheel 11 over a covering angle of approximately 200, and a machining area 26, which exposes cutting-off wheel 11 over a machining angle of 160 for machining a workpiece. Safety guard 24 is designed to be pivotable and may be pivoted around a pivot axis 27 (FIGS. 2A, 2B) into a desired pivot position. To set the pivot position, a hand grip element 28 is fastened to safety guard 24, which may be used to apply the necessary forces to pivot safety guard 24 around pivot axis 27.

[0032] A first handle 31, which has an operating unit 32 and is designed as a top handle, is provided for operating cutting-off machine 10. A handle which is situated above motor housing 16 is referred to as a top handle. Alternatively, the first handle may be designed as a rear handle, which is situated on the side of motor housing 16 facing away from cutting-off wheel 11. In addition to first handle 31, a second handle 33, which is situated between cutting-off wheel 11 and first handle 31, is provided for guiding cutting-off machine 10. In the exemplary embodiment shown in FIGS. 1A, 1B, second handle 33 is designed as a separate gripping tube, or it may be alternatively designed as a single piece with motor housing 16 or another housing part.

[0033] FIGS. 2A, 2B show an enlarged representation of safety guard 24 and belt drive 19 of cutting-off machine 10 from FIGS. 1A, 1B. Belt drive 19 is situated in a supporting arm housing 35, which includes a stationary, supporting housing part 36 and cover 15. FIG. 2A shows belt drive 19, including mounted cover 15, and FIG. 2B shows belt drive 19 without cover 15.

[0034] The drive of cutting-off wheel 11 takes place via drive motor 17, belt drive 19 and output shaft 20. Drive motor 17 may be designed as a combustion motor or as an electric motor. Drive motor 17 drives drive shaft 21 and drive disk 23 around drive axis 22. A transmission element 38 designed as a drive belt is guided via drive disk 23 and an output disk 39 supported on output shaft 20. Output shaft 20 is rotatable around an output axis 40, which coincides with rotation axis 14 of cutting-off wheel 11. Drive disk 23, drive belt 38 and output disk 39 form belt drive 19. Alternatively, transmission mechanism 19 may be designed, for example, in the form of a chain drive, in which the transmission element between drive disk 23 and output disk 39 is designed as a chain. Cutting-off wheel 11 is situated on output shaft 20 with the aid of a flange 41 and is rotatably fixedly connected to output shaft 20. Flange 41 and cutting-off wheel 11 are mounted on output shaft 20, and cutting-off wheel 11 is situated between two flange halves of flange 41.

[0035] A workpiece is machined with the aid of cutting-off machine 10 in the area of cutting-off wheel 11 situated in machining area 26 of safety guard 24. Safety guard 24 includes a fastening flange 42 in the hub area of cutting-off wheel 11, which, in the exemplary embodiment, is designed as a single piece with a side wall 43 of safety guard 24; alternatively, the fastening flange may also be designed as a separate part and connected to safety guard 24. Fastening flange 42 is mounted on a matching counter-contour 44 of the stationary housing part 36 and is designed to be adjustable with respect to counter-contour 44 of housing part 36. Safety guard 24 is designed to be pivotable around pivot axis 27 between a front pivot position and a rear pivot position. The pivot range of safety guard 24 is limited to an angle range of approximately 60.

[0036] FIGS. 3A through 3C show an enlarged representation of cutting-off wheel 11 and safety guard 24 of cutting-off machine 10 from FIG. 1A. FIG. 3A shows the arrangement of cutting-off wheel 11 and safety guard 24 in a side view; FIG. 3B shows a section along section line A-A in FIG. 3A; and FIG. 3C shows a section along section line B-B in FIG. 3A. Cutting-off wheel 11 is fastened to output shaft 20 with the aid of flange 41 and is designed to be rotatable around rotation axis 14. The movement of drive motor 17 is transmitted to output shaft 20 via drive belt 38 and output disk 39, which is rotatably fixedly supported on output shaft 20.

[0037] Safety guard 24 is made up of the covering area 25, which covers cutting-off wheel 11, and machining area 26, which exposes cutting-off wheel 11 for machining a workpiece. The full angle of cutting-off wheel 11 of 360 is divided by safety guard 24 into a covering angle and a machining angle. Covering area 25 of safety guard 24 determines the covering angle, and machining area 26 of safety guard 24 determines the machining angle. In the exemplary embodiment, the covering angle is approximately 200, and the machining angle is approximately 160.

[0038] Output shaft 20 is supported on stationary housing part 36 via a bearing element 45. Safety guard 24 is fastened to stationary housing part 36. Fastening flange 42 of safety guard 24 is mounted on counter-contour 44 of housing part 36 and designed to be pivotable around pivot axis 27 relative to stationary housing part 36. To facilitate the pivoting movement of safety guard 24, a sliding element 46 is provided between fastening flange 42 and counter-contour 44, which reduces friction and is designed, for example, as a Teflon ring.

[0039] FIG. 3C shows pivot axis 27 of safety guard 24, which is different than output axis 40 of output shaft 20. Pivot axis 27 is displaced with respect to output axis 40 into covering area 25 of safety guard 24. In the exemplary embodiment, distance A between pivot axis 27 and output axis 40 is greater than half of diameter d of output shaft 20.

[0040] FIG. 4 shows an enlarged detail of the second section along section line B-B in FIG. 3A illustrated in FIG. 3C. The detail shows output shaft 20 and flange 41, with the aid of which cutting-off wheel 11 is fastened on output shaft 20.

[0041] Flange 41 has a multi-part design and includes a first flange part 51, a second flange part 52 and a tool screw 53. To assemble cutting-off wheel 11, first flange part 51 is mounted on or screwed to output shaft 20, cutting-off wheel 11 is mounted on first flange part 51, and second flange part 52 is mounted. Cutting-off wheel 11 is clamped between first and second flange halves 51, 52 with the aid of tool screw 53.

[0042] For gas-powered cutting-off machines, the European standard EN ISO 19432:2012, the U.S. standard ANSI B175.4-2013 and corresponding standards in other countries define a minimum flange diameter d.sub.min for flange 41, depending on the type of cutting-off wheel 11 (diamond cutting-off wheel or abrasive cutting-off wheel) and on wheel diameter D of cutting-off wheel 11 (D250 mm, 250 mm<D300 mm, 300 mm<D350 mm and 350 mm<D). For diamond cutting-off wheels, minimum flange diameter d.sub.min is: d.sub.min 37.5 mm for D250 mm, d.sub.min=45 mm for 250 mm<D<300 mm, d.sub.min=52.5 mm for 300 mm<D350 mm and d.sub.min=60 mm for 350 mm<D. For abrasive cutting-off wheels, minimum flange diameter d.sub.min is: d.sub.min 63.5 mm for D250 mm, d.sub.min=75 mm for 250 mm<D300 mm, d.sub.min=87.5 mm for 300 mm<D350 mm and d.sub.min=100 mm for 350 mm<D.

[0043] Maximum cutting depth t.sub.max achievable by cutting-off wheel 11 in a workpiece is then achieved if flange diameter d.sub.f of flange 41 corresponds to minimum flange diameter d.sub.min and no components of cutting-off machine 10 additionally limit the cutting depth. Maximum cutting depth t.sub.max is defined by half the difference between wheel diameter D of cutting-off wheel 11 and minimum flange diameter d.sub.min of flange 41: t.sub.max=*(Dd.sub.min). In gas-powered cutting-off machines 10 and a diamond cutting-off wheel, maximum cutting depth t.sub.max is: t.sub.max=106.25 mm for D=250 mm, t.sub.max=127.5 mm for D=300 mm, t.sub.max=148.75 mm for D=350 mm and t.sub.max=170 mm for D=400 mm. In gas-powered cutting-off machines and an abrasive cutting-off wheel, maximum cutting depth t.sub.max is: t.sub.max=93.25 mm for D=250 mm, t.sub.max=112.5 mm for D=300 mm, t.sub.max=131.25 mm for D=350 mm and t.sub.max=150 mm for D=400 mm.

[0044] In addition to flange diameter d.sub.f of flange 41, cutting depth t of cutting-off wheel 11 is defined by the outer contours of the components of cutting-off machine 10 in machining area 26 of safety guard 24. The outer contours include a first outer contour 54 of safety guard 24, a second outer contour 55 of supporting housing part 36 and a third outer contour 56 of belt drive 19. Outer contours 54, 55, 56 are designed in such a way that their maximum distances b from output axis 40 are at an outcut angle less than or equal to half of minimum flange diameter d.sub.min. First outer contour 54 of safety guard 24 has a first maximum distance b.sub.1 from output axis 40 in the outcut angle; second outer contour 55 of supporting housing 36 has a second maximum distance b.sub.2 from output axis 40 in the outcut angle; and third outer contour 56 of belt drive 19 has a third maximum distance b.sub.3 from output axis 40 in the outcut angle. The maximum distance of the outer contour from output axis 40 in outcut angle is defined as maximum distance b of a component.

[0045] The condition that maximum distance b.sub.3 of belt drive 19 from output axis 40 is less than or equal to half of minimum flange diameter d.sub.min must apply to all subcomponents of belt drive 19 in outcut angle . Belt drive 19 is made up of output disk 39, drive belt 38 and cover 15 in the area of output shaft 20. Output disk 39 has a fourth maximum distance b.sub.4 from output axis 40 in outcut angle ; drive belt 38 has a fifth maximum distance b.sub.5 from output axis 40 in outcut angle ; and cover 15 has a sixth maximum distance b.sub.6 from output axis 40 in outcut angle .

[0046] Since drive belt 38 is situated on output disk 39 and, in the exemplary embodiment, output disk 39 does not project over drive belt 38, fourth maximum distance b.sub.4 of output disk 39 from output axis 40 in the outcut angle is less than fifth maximum distance b.sub.5 of drive belt 38. If the condition that the maximum distance in outcut angle is less than or equal to half of minimum flange diameter d.sub.min is met for drive belt 38, the condition is also met for output disk 39. In an arbitrary design of output disk 39 and drive belt 38, the condition that the maximum distance in outcut angle is less than or equal to half of minimum flange diameter d.sub.min must be met for output disk 39 and drive belt 38.

[0047] Cover 15 performs the function of covering belt drive 19, and it covers output disk 39 and drive belt 38 in the area of output shaft 20. In the exemplary embodiment, output disk 39 and drive belt 38 are completely covered by cover 15. If the condition that the maximum distance in outcut angle is less than or equal to half of minimum flange diameter d.sub.min is met for cover 15, the condition is also met for output disk 39 and drive belt 38. In the exemplary embodiment, third maximum distance b.sub.3 of belt drive 19 from output axis 40 corresponds to sixth maximum distance b.sub.6 of cover 15 from output axis 40. In an arbitrary design of output disk 39, drive belt 38 and cover 15, the condition that the maximum distance in outcut angle is less than or equal to half of minimum flange diameter d.sub.min must be met for cover 15, output disk 39 and drive belt 38.

[0048] FIG. 5 shows safety guard 24 of cutting-off machine 10 without a cutting-off wheel 11 in a pivot position, which corresponds to the pivot position of safety guard 24 in FIG. 3A. Safety guard 24 is pivotably supported around pivot axis 27 with the aid of fastening flange 42 on stationary housing part 36. Fastening flange 42 has a circular design and a diameter d.sub.x. Diameter d.sub.x of fastening flange 42 is a variable which is essentially defined by the size and weight of safety guard 24.

[0049] Pivot axis 27 of safety guard 24 is different than output axis 40 of output shaft 20. Pivot axis 27 is displaced with respect to output axis 40 into covering area 25 of safety guard 24. The full angle of cutting-off wheel 11 of 360 is divided by safety guard 24 into the covering angle and the machining angle, the covering angle being approximately 200 and the machining angle being approximately 160. Outcut angle is situated within the machining angle of cutting-off wheel 11 and, in the exemplary embodiment, is approximately 70.

[0050] The support of safety guard 24 in outcut angle is particularly critical, due to the limited receiving area. Safety guard 24 includes fastening flange 42, which is mounted on counter-contour 44 of supporting housing part 36. If pivot axis 27 of safety guard 24 coincides with output axis 40 of output shaft 20, diameter d.sub.x of fastening flange 42 is limited by flange diameter d.sub.f. The smaller the flange diameter d.sub.f is selected, the smaller is the receiving area for arranging and supporting the components. If flange diameter d.sub.f of flange 41 corresponds to minimum flange diameter d.sub.min, the smallest receiving area is available for arranging and supporting the components.

[0051] Due to the displacement of pivot axis 27 into covering area 25 of safety guard 24, diameter d.sub.x of fastening flange 42 may be selected to be larger than flange diameter d.sub.f of flange 41 used. Distance between pivot axis 27 and output axis 40 is selected to be greater than or equal to half the difference between diameter d.sub.x of fastening flange 42 and flange diameter d.sub.f. In this case, fastening flange 42 of safety guard 24 is situated in the receiving area, which is defined by flange diameter d.sub.f.