MACHINE TOOL

Description

[0001] The present invention relates to a machine tool, in particular an angle grinder, with a spindle which can be driven about a rotational axis according to the type described in more detail in the preamble of patent claim 1.

[0002] In handheld angle grinders, it is common practice to secure a disk that can be slipped over the spindle using a nut. Particularly during sharp acceleration or deceleration of the spindle, this can cause the nut to loosen, causing the disk to detach from the spindle.

[0003] WO 19030058 A1 discloses a quick-clamping device for an angle grinder. Grinding wheels specifically adapted to the angle grinder are securely attached to the spindle by means of a clamping device.

[0004] However, with this design, only specifically designed and therefore expensive to produce grinding wheels can be attached to the spindle.

[0005] From US 5,577,872 A and from EP 3 202 533 A1 a machine tool according to the preamble of claim 1 is known.

[0006] It is an object of the present invention to provide a machine tool, in particular an angle grinder, with a spindle which can be driven about a rotational axis and in which grinding wheels which can be produced cost-effectively can be securely fixed to the spindle during operation of the machine tool.

[0007] The problem is solved with a machine tool according to patent claim 1.

[0008] Thus, a particularly hand-held machine tool, in particular an angle grinder, with a spindle drivable about a rotational axis is proposed, wherein a device is provided that can be secured to the spindle by means of a rotary joint. According to the invention, a separate securing device is provided that is operatively connected to the spindle, is arranged at least partially on the output side of the device, and has, at least during operation of the machine tool, an outer diameter that is at least partially larger with respect to the rotational axis than an outer diameter of the spindle.

[0009] In a machine tool designed according to the invention, it can be ensured in a simple and cost-effective manner that the device that can be brought into operative connection with the spindle cannot become detached from the spindle during operation of the machine tool. This is achieved in particular by providing a separate element on the machine tool side, which prevents the device from becoming detached from the spindle by the separate element having, at least in some regions, a larger outer diameter than the outer diameter of the spindle, at least during operation of the machine tool. This reliably prevents injury to a user. Furthermore, in the machine tool according to the invention, various types of machining elements, such as grinding wheels, cutting wheels, brushes or the like, can advantageously be used without their own requirements with regard to a safety device, so that they can be implemented simply and cost-effectively.

[0010] The solution according to the invention has the further advantage that it can be used regardless of the type and size of the device used, so that the securing device can secure devices with different extensions in the longitudinal direction of the spindle. The solution according to the invention reliably prevents the device or tool from becoming loose from the spindle during operation, even in the event of incorrect use by the user when securing the device.

[0011] The locking device can also have a non-circular outer edge region, so that the locking device is not rotationally symmetrical to the spindle's axis of rotation. In this case, the outer diameter of the locking device is defined as twice the maximum distance of a region of the locking device facing away from the spindle's axis of rotation from the spindle's axis of rotation.

[0012] The device is designed as a tool or machining element with an internal thread that can be brought into operative connection with an external thread of the spindle. The tool or machining element can be designed, for example, as a disk, grinding disk, cutting disk, brush or the like, wherein the tool itself is connected to the spindle. Alternatively, the device can be designed as a fastening nut with an internal thread that can be brought into operative connection with an external thread of the spindle for securing a tool or machining element. In this case, the fastening nut is preferably designed to secure a disk, grinding disk, cutting disk or the like without an internal thread, wherein the tool can be slipped onto the spindle, for example.

[0013] In a simple and cost-effective design of a machine tool, not part of the invention, the securing device has a threaded region with an external thread, with which the securing device can be brought into operative connection with a region of the spindle having an internal thread, in particular running in the longitudinal direction of the spindle and arranged concentrically to the axis of rotation, wherein a pitch of the thread of the securing device is smaller than a pitch of a thread of the device. Due to the smaller pitch of the thread of the securing device compared to the pitch of the thread of the device, loosening of the device from the spindle is reliably prevented even if the device is rotated relative to the spindle. The securing device preferably has a plate-shaped region which is arranged on one end of the spindle.The securing device is preferably arranged concentrically to the axis of rotation of the spindle.

[0014] In order to reliably prevent the device from becoming detached from the spindle, according to the invention the securing device is designed as a spring ring which is arranged in a groove of the spindle, in particular running perpendicular to the axis of rotation, wherein the spring ring is displaceable between a preloaded position in which an outer diameter of the spring ring is less than or equal to the outer diameter of the spindle, and a relaxed position in which the outer diameter of the spring ring is larger than the outer diameter of the spindle. The spring ring can have a continuous slot, in particular in the circumferential direction, which allows a reduction in the outer diameter of the spring ring. In order to enable the device to be arranged on the spindle and removed from the spindle against the spring force of the spring ring, the device can have chamfers, preferably on both sides, in particular on an inner diameter viewed in the longitudinal direction of the spindle.The spring force of the spring ring is selected in such a way that it is greater than the force acting on the spring ring during operation due to a loosened device.

[0015] Detachment of the device from the spindle can be easily prevented if the securing device is designed as a lever pivotally connected to the spindle, which can be displaced, in particular under the influence of centrifugal force, into a deflected position in which the lever has an outer diameter that is at least partially larger than the outer diameter of the spindle. In particular, if the lever is designed such that it is displaced into its deflected position solely by a centrifugal force acting during operation of the machine tool, fastening and detaching the device when the machine tool is in the non-actuated state is easily possible. This embodiment is not part of the invention as defined in claim 1.

[0016] The lever is preferably pivotably mounted on the spindle about an axis transverse to the spindle's rotational axis, with the lever being arranged in particular in a recess of the spindle. The lever can thus be easily pivoted between the use position and the non-use position, with the lever enabling the device to be arranged on the spindle in the non-use position, and the lever is thus preferably arranged entirely within an envelope geometry predetermined by the outer diameter of the spindle.

[0017] A spring device can be provided that applies a force preloading the lever into its deflected position. This ensures that, in all operating states, the lever has a larger outer diameter than the spindle, at least in some areas, and the device is thus securely held on the spindle. To remove or replace the device, the lever can be manually moved, for example, against the spring force of the spring device, into a non-use position, in which the device can be removed from the spindle or arranged on the spindle.

[0018] The lever can have an end region on either side of a pivot point, wherein each of the end regions can be pivoted into the deflected position, in which the respective end region has an outer diameter that is at least partially larger than the outer diameter of the spindle. This design has the advantage that both devices with a large extension in the longitudinal direction of the spindle and devices with a small extension in the longitudinal direction of the spindle can be securely held on the spindle. In order to ensure advantageous run-off protection, two spring devices can be provided which hold the lever in a balance. Preferably, a distance between the two end regions of the lever in the longitudinal direction of the spindle is greater than an extension of the device in the longitudinal direction of the spindle. The lever can, for example, be U-shaped or curved.In order to be able to ensure the safety function of the lever in a safe manner, a thickness of the device in the longitudinal direction of the spindle is preferably smaller than a distance of the end regions of the lever in the longitudinal direction of the spindle.

[0019] It can be provided that the securing device is designed as a plate-shaped element, in particular, which is arranged in a recess in the spindle and can be displaced via a guide device, in particular transversely to the axis of rotation. The plate-shaped element can be designed such that it is transferred into the deflected position due to the centrifugal force acting during operation of the machine tool and securely holds the device on the spindle. The recess runs, for example, substantially in the longitudinal direction of the spindle or substantially transversely to the longitudinal direction of the spindle, with the plate-shaped element being arranged accordingly substantially in the longitudinal direction or transverse direction of the spindle. This embodiment is not part of the invention as defined in claim 1.

[0020] If the element has an oblique edge on an outer side facing away from the axis of rotation, the edge being at a greater distance from the axis of rotation in a region facing the spindle end than in a region facing away from the spindle end, the device can be in contact with the element regardless of its extension in the longitudinal direction of the spindle and can be held without play in the longitudinal direction of the spindle during operation of the machine tool.

[0021] To ensure the device is held securely in place under all operating conditions, a spring device can be provided that applies a force to the element acting outward relative to the spindle's rotational axis. To attach a device to the spindle or to detach it from the spindle, the element can be moved, for example, manually or by means of a tool, against the spring force of the spring device into its non-use position.

[0022] Easy accessibility of the element, particularly for transferring it from the use position to the non-use position, can be achieved if the element is arranged at an output-side end of the spindle. The element can, for example, have an engagement element or an engagement opening for a tool, by means of which the element can be transferred from the use position to the non-use position. The recess can run essentially transversely to the longitudinal direction of the spindle. Further advantages will become apparent from the following description of the figures.

[0023] In the figures, identical and similar components are numbered with the same reference numerals. They show: Fig. 1a a simplified representation of a hand-held machine tool designed as an angle grinder, wherein a grinding wheel is arranged on a spindle by means of a fastening nut; Fig. 1b a highly simplified representation of the angle grinder according to Fig. 1a ; Fig. 2 a section of an end region of the spindle of the machine tool according to Fig. 1a and 1b, wherein a securing device is arranged on the spindle; This embodiment is not part of the invention as defined in claim 1. Fig. 3 a section of an alternatively designed end region of the spindle with a groove running perpendicular to a longitudinal direction of the spindle, in which groove a spring ring is arranged; Fig. 4 a section of a further alternatively designed end region of the spindle, wherein a lever is pivotally mounted in a recess in the spindle; This embodiment is not part of the invention as defined in claim 1. Fig. 5 a section of a further alternatively designed end region of the spindle, wherein a lever designed with two end regions is pivotally mounted in a recess in the spindle; This embodiment is not part of the invention as defined in claim 1. Fig.6 shows a section of another alternatively designed end region of the spindle, wherein an element displaceable perpendicular to the longitudinal direction is arranged in a longitudinally extending recess of the spindle; this embodiment is not part of the invention as defined in claim 1. Fig. 7 shows a sectional view of the spindle according to . Fig.6 along the line VII-VII; Fig. 8 a section of another alternatively designed end region of the spindle, wherein an element displaceable perpendicular to the longitudinal direction is arranged in a recess extending perpendicular to the longitudinal direction of the spindle and is visible in a use position; This embodiment is not part of the invention as defined in claim 1. Fig. 9 a Fig. 8 corresponding section, wherein the displaceable element is shown in a non-use position; and Fig. 10 a plan view of the spindle according to Fig. 8 and Fig. 9, where a guide groove for moving the element is visible. Examples of implementation:

[0024] Fig. 1 shows a highly simplified view of a particularly hand-held machine tool 1, designed here as an angle grinder. The machine tool 1 contains a housing 3, a battery 4 connected to the housing 3 as a power supply, a head 5 with a tool holder 6. The tool holder 6 contains a flange 7, a spindle 8, and a device 9. The device 9, designed here as a clamping element or fastening nut, has an internal thread 10, by means of which the device 9 can be arranged on an external thread 11 of the spindle 8 defining an external diameter 14 of the spindle 8 and can be displaced in the longitudinal direction L of the spindle 8. The spindle 8 serves to arrange a tool 12, for example a grinding or cutting wheel, and to transmit torque from an electric motor 2 to the tool 12.

[0025] The tool 12 has a central through-bore 13, wherein the tool can be placed onto the spindle 8 by means of the through-bore 13 and secured by means of the device 9. The spindle 8 is connected to the head 5 of the machine tool 2 by means of a flange 7 and is mounted for rotation about the longitudinal axis L. The flange 7 is positioned below the spindle 8 on the head 5 of the machine tool 2 with respect to the longitudinal direction L of the spindle 8.

[0026] The following shows various designs of a securing device, each of which is arranged partially or completely on a side of the tool 12 and / or the fastening nut 9 facing away from the head 5 of the machine tool 1 and which, at least in the operating state of the machine tool 1 with the spindle 8 rotating, reliably prevents the tool 12 and / or the fastening nut 9 from becoming loose from the spindle 8 by virtue of the fact that, during operation of the machine tool 1, the respective securing device assumes a use position on a side of the device 9 facing away from the head 5, in which an outer diameter of the securing device is at least partially larger than the outer diameter 14 of the spindle 8. It can be provided that a region of the respective securing device facing away from the longitudinal axis L is at a greater distance from the longitudinal axis L than the spindle 8 in at least one circumferential region of the longitudinal axis L.Such a case is also described below in that an outer diameter of the respective securing device has a larger outer diameter than the spindle 8. The non-use position is referred to as a position of the securing device in which the respective securing device is arranged completely within an envelope geometry of the spindle 8 and the device 9 can thus be screwed onto the spindle 8 without hindrance by the securing device.

[0027] Fig. 2shows, in a highly simplified manner, an end region of the spindle 8, wherein, starting from an end 15 of the spindle 8 facing away from the head 5 of the machine tool 2, an internal thread 16 extends concentrically to the spindle 8 in the longitudinal direction L of the spindle 8. In operative connection with the internal thread 16 is a securing device 17 which has a pin-like region 18 with an external thread 19, by means of which the securing device 17 interacts with the internal thread 16 of the spindle 8. Connected to the pin-like region 18 of the securing device 17 is a plate-shaped region 20 which is circular here and has a larger external diameter 21 than the spindle 8.

[0028] The thread pair 16, 19 has a smaller pitch than the external thread 11 of the spindle 8. If, during operation of the machine tool 1, the fastening nut 9 becomes loose relative to the spindle 8 and comes into contact with the plate-shaped area 20 of the securing device 17, a different axial rotational offset with a resulting inhibition occurs through the appropriate selection of the pitches of the threads 16, 19, 11, 10, so that a release of the securing device 17 from the spindle 8 and thus of the tool 12 from the spindle 8 is reliably prevented. Depending on the design of the tool 12 used, it can be provided that, in the mounted state of the tool 12, the securing device 17 rests against the tool 12 in the longitudinal direction L or is spaced from it.

[0029] When executed according to Fig. 3In an area spaced from the end 15 of the spindle 8, a groove 25 running perpendicular to the longitudinal direction L is arranged, in which a securing device 26, here a spring device 26 designed as a spring ring, is arranged. The spring ring 26 has a recess 27 in the circumferential direction U, so that the spring ring 26 can be displaced under the action of force between a use position, in which an outer diameter 28 of the spring ring 26 is larger than the outer diameter 14 of the spindle 8, and a preloaded position, in which the outer diameter 28 of the spring ring 26 is smaller than or equal to the outer diameter 14 of the spindle 8.

[0030] In Fig. 31 shows a section of the fastening nut 9, wherein it can be seen that the fastening nut 9 is designed with a chamfer 31, 32 in each of its axial end regions in the region of its internal thread 10, so that the fastening nut 9 can be screwed onto or removed from the spindle 8 via the spring ring 26 by applying a defined force in the longitudinal direction L. The force required for this is in particular coordinated with the spring force of the spring ring 26 in such a way that it is greater than the forces occurring during operation of the machine tool 1 and acting on the spring ring 26.

[0031] In this solution too, depending on the tool 12 used, it can be provided that the tool 12 or the fastening nut 9 rests against the spring ring 26 in the longitudinal direction L in the assembled state or that there is a distance between them.

[0032] Another version is in Fig. 4shown. The spindle 8 has a recess 35 extending in the longitudinal direction L from the end 15, in which recess a securing device designed as a lever 36 is mounted so as to be pivotable about a pivot axis 37 running perpendicular to the longitudinal direction L. The lever 36 is mounted in such a way that, during operation of the machine tool 1 and rotation of the spindle 8 about the longitudinal axis L, the centrifugal force acting thereon displaces it into a use position in which a region of a first end region 38 of the lever 36 facing away from the axis of rotation L is in some regions at a greater distance 41 from the axis of rotation L than an outer side of the spindle 8. An outer diameter of the lever 36 is thus larger than the outer diameter 14 of the spindle 8. As a result, when the tool 12 and fastening nut 9 are mounted, loosening of the fastening nut 9 and the tool 12 is reliably prevented.

[0033] To ensure that the lever 36 is securely transferred into the use position, a spring device 40 is provided in the present case, which applies a force pressing the lever 36 in the direction of the use position. In the embodiment shown, the lever 36 has a second end region 39 arranged on a side of the pivot axis 37 facing away from the first end region 38, which extends beyond the end 15 of the spindle 8 in the longitudinal direction L. By means of the second end region 39, the lever 36 can be easily displaced from the use position into a release position, particularly for assembling or disassembling a tool 12, in which the lever 36 is arranged entirely within an envelope geometry of the spindle 8 and thus does not extend beyond the outer diameter 14 of the spindle 8.

[0034] Fig. 5shows an alternative embodiment of a securing device 44, which here is designed as a curved lever 44 mounted on the spindle 8 so as to be rotatable about the pivot axis 37. By means of the lever 44, even when using a tool 12 and a fastening nut 9 with a total of a large extension in the longitudinal direction L of the spindle or when using a tool 12 itself connected to the spindle 8 by a thread with a large extension in the longitudinal direction L of the spindle 8, a run-off protection is ensured and a loosening of the fastening nut 9 or the tool 12 from the spindle 8 is reliably prevented.

[0035] The lever 44 in turn has two end regions 38 and 39, wherein both end regions 38, 39 can each be displaced into a use position in which the respective end region 38, 39 protrudes beyond the envelope geometry of the spindle 8 and a region of the respective end region 38, 39 facing away from the axis of rotation L thus has a greater distance 41 from the axis of rotation L in some regions than an outer contour of the spindle 8. The end region 39 further away from the head 5 is also arranged in such a way that it reliably prevents the tool 12 and / or the fastening nut 9 from becoming loose from the spindle 8. The end region 39 is particularly effective when an extension of the tool 12 and / or the fastening nut 9 in the longitudinal direction L of the spindle 8 is so great that they press the other end region 38 into the non-use position.

[0036] An outer diameter of the lever 44 is thus larger than the outer diameter 14 of the spindle 8. A distance 47 of the end regions 38, 39 in the longitudinal direction L of the spindle 8 is greater than an extension 48 of the fastening nut 9 or the tool 12 in the longitudinal direction L of the spindle 8, wherein the lever 44 is held in balance by two spring devices 45, 46.

[0037] A further embodiment of a safety device 52 is shown in Fig. 6 shown, wherein the securing device 52 is designed here as a plate-shaped securing element which is arranged in a Fig. 7which can be seen in more detail and runs in the longitudinal direction L of the spindle 8. The securing element 52 in the present case has two elongated holes 54, 55, in which pins 56, 57 arranged on the spindle 8 are guided. The securing element 52 can thus be displaced perpendicular to the longitudinal direction L relative to the spindle 8, wherein the securing element 52 is pressed outwards as far as possible with respect to the longitudinal axis L during operation of the machine tool 1 due to the acting centrifugal force. In addition, a spring device can also be provided if necessary, which applies a force to the securing element 52 in the use position, ie in the position pressed outwards.

[0038] In the Fig. 6 and Fig. 7In the use position shown, a distance of a side of the securing element 52 facing away from the longitudinal axis L in a circumferential region of the axis of rotation is greater than a distance of the outer contour of the spindle 8, so that an outer diameter of the securing element 52 is greater than the outer diameter 14 of the spindle 8.

[0039] The securing element 52 is designed such that it can be displaced from the use position into the non-use position, wherein the securing element 52 does not protrude beyond an envelope geometry of the spindle 8 in the non-use position and a tool 12 and / or the fastening nut 9 can be mounted or dismounted without being hindered by the securing element 52.

[0040] A side limit 58 of the securing element 52 facing away from the longitudinal axis L of the spindle 8 is in this case designed to be oblique, i.e. the side limit 58 forms an angle 59 with the longitudinal direction L, wherein an end of the securing element 52 facing the end 15 of the spindle 8 is at a greater distance from the longitudinal axis L of the spindle 8 than an end of the securing element 52 facing away from the end 15 of the spindle 8. This design of the securing element 52 has the advantage that, in the case of various tools 12 that can be brought into operative connection with the spindle 8, the securing element 52 is in contact with the tool 12 or the fastening nut 9 in the mounted state, the tool 12 or the fastening nut 9 is thereby clamped in the mounted position due to the self-locking mechanism and loosening is thus reliably prevented.

[0041] A further embodiment of a safety device 65 is shown in Fig. 8 to Fig. 10shown. The securing device 65 is again designed as a securing element, which is arranged in a recess 66 of the spindle 8. Fig. 8 and Fig. 9 show sectional views through an area of ​​the spindle 8 in which the securing element 65 is arranged.

[0042] The securing element 65 is in Fig. 9 shown in the use position, in which the securing element 65 projects beyond the envelope geometry of the spindle 8 in the radial direction and a distance 73 of a region of the securing element 65 facing away from the longitudinal axis L is greater than a distance of the outer contour of the spindle 8 from the longitudinal axis L. The securing element 65 thus has, at least in some regions, a larger outer diameter than the outer diameter 14 of the spindle 8. The securing element 65 is pressed into the position shown by means of a spring device 69 and is supported in this position on flanks 67, 68 of the recess 66.

[0043] In Fig. 8the securing element 65 is shown in the non-use position, in which the securing element 65 is completely arranged in an envelope geometry of the spindle 8 and thus does not protrude beyond the outer diameter 14 of the spindle 8.

[0044] The securing element 65 has a recess 71 designed to cooperate with a tool, wherein the securing element can be displaced into the non-use position by means of the tool against the spring force of the spring device 69. As in Fig. 10 As can be seen, the spindle 8 has a guide device in the form of a guide curve 70 arranged at its end 15, wherein the securing element 65 can be displaced from the use position to the non-use position by means of a tool which can be brought into engagement with the securing element 65 by means of the guide curve 70.

[0045] The guide curve 70 is designed such that, during such a displacement, the securing element 65 undergoes not only a translational movement in the direction of a central axis of the spindle 8 but also a rotational movement. The flanks 67, 68 of the recess 66 are designed such that, in the non-use position, the securing element 65 assumes a locked position in which the spring force of the spring device 69 does not displace the securing element 65 into the use position when the spindle 8 is stationary. In this state, the tool 12 and / or the fastening nut 9 can be mounted or dismounted.

[0046] When the machine tool 1 is transferred into an operating state and thus when the spindle 8 is subjected to a rotational movement according to the arrow 72, the securing element 65 is released from the locking position without further actuation and is transferred into the use position.

[0047] The securing devices designed according to the invention are suitable both for the use of a tool 12 fixed to the spindle 8 via a fastening nut 9 and for the use of a tool 12 which can be fixed to the spindle 8 and has an internal thread.

Claims

1. Machine tool (1), in particular angle grinder, comprising a spindle (8) that can be driven about an axis of rotation (L), a device (9) being provided which can be fixed to the spindle (8) by means of a rotary connection, a separate securing device (26) being provided which is operatively connected to the spindle (8) and which, at least when the device is in the mounted state, is arranged in regions on the output side of the device (9), and, at least during operation of the machine tool (1), in a region facing away from the axis of rotation (L) in at least one peripheral region of the axis of rotation (L), has a greater distance from the longitudinal axis (L) than the spindle (8), and the securing device (26) having an outer diameter (28) that is at least in some regions larger than an outer diameter (14) of the spindle (8) with respect to the axis of rotation (L), characterized in that the securing device (26) is designed as a spring ring which is arranged in a groove (25) of the spindle (8), which groove runs in particular perpendicular to the axis of rotation (L), the spring ring (26) being movable between a prestressed position in which an outer diameter (28) of the spring ring (26) is less than or equal to the outer diameter (14) of the spindle (8), and a relaxed position in which the outer diameter (28) of the spring ring (26) is greater than the outer diameter (14) of the spindle (8), the device (9) being designed as a tool (12) or machining element which is designed with an internal thread and which can be brought into operative connection with an external thread (11) of the spindle (8), or in that the device (9) is designed as a fastening nut (9) which is designed with an internal thread (10) and which can be brought into operative connection with an external thread (11) of the spindle (8) in order to fix a machining element.