hole saw

Abstract

Hole saw with a drive shaft (1) which can be driven in rotation about an axis of rotation (D), a holding member (2) which has radial guides (3) and an adjusting member (4) which can be rotated relative to the holding member (2) for adjusting the hole diameter and which has a spiral slot (9) open to the holding member (2), wherein a fastening element (5) is guided and can be fastened in each of the radial guides (3), which fastening element is connected to a saw element (7) and a control extension (8) which engages in the spiral slot (9), wherein the spiral slot (9) is also open to a free space (10) of the adjusting member (4) which is opposite the holding member (2), characterized by a circumferential limitation of the free space (10) which has at least one window (11).

Description

field of technology

[0001] The invention relates to a hole saw with a drive shaft that can be driven in rotation about a rotation axis, a holding member that has radial guides and an adjusting member that can be rotated relative to the holding member to adjust the hole diameter, wherein a fastening element is guided and fastenable in each of the radial guides, which fastening element is connected to a saw element and a control extension that engages in a spiral slot of an adjusting disk of the adjusting member that is open to the holding member, wherein the control slot (9) is also open to a free space (10) of the adjusting member (4) that is opposite the holding member (2). State of the art

[0002] WO 2014 / 146319 A1 describes a hole saw with a hood-shaped adjustment element having a bottom wall and a peripheral wall. On the bottom wall of the hood part is an adjustment disc with spiral slots, into which control extensions of fastening elements engage. These fastening elements are located in radial slots in a retaining disc. Each fastening element supports a saw element. The hole width of the hole saw can be adjusted by rotating the hood part relative to the retaining disc.

[0003] The hole saw disclosed in US Pat. No. 3,771,895 A has a holding disk forming radial guides, each of which guides a fastening element connected to a saw element and a control extension. The movement of the fastening element is limited by limiting elements running parallel to the radial guides. The adjusting disk also has spiral slots open to a holding element and to a free space of the adjusting element opposite the holding element.

[0004] US 2,803,153 A discloses a hole saw with a hood-like adjusting element, to the underside of which an adjusting disc with spiral slots is fixed, into which a control projection connected to a fastening element engages. A saw element is fixed to each fastening element with a screw. The fastening elements are guided in radial guides formed by a holding element.

[0005] Hole saws of the type described above are used primarily in drywall construction to cut large, circular holes in plasterboard for electrical outlets or switches. The fine plaster dust can clog the spiral adjustment slots. Summary of the invention

[0006] The invention is based on the object of further developing the generic hole saw in a manner that is advantageous for use.

[0007] The problem is solved by the invention specified in the claims, whereby each claim represents an independent solution to the problem.

[0008] Firstly and essentially, it is proposed that the spiral slots be open on both sides of the adjusting disc. The broad side surface of the adjusting disc opposite the holding member borders on a free space. The gypsum dust generated when processing a plasterboard can enter this free space. This leads to a reduced tendency for the spiral slots to become clogged. The free space is preferably delimited by a rear wall. The rear wall can be a wall of a hood part of the adjusting member. The free space is then delimited by the broad side surface of the wall of the hood part and the broad side surface of the adjusting disc. The free space preferably extends to the outermost edge of the adjusting disc and has a height that approximately corresponds to the material thickness of the adjusting disc. The hood part preferably has a cup-shaped opening surrounded by a peripheral wall. Windows can be arranged in this peripheral wall.These windows form radially outward-facing openings through which gypsum dust that has entered the free space can escape. Spacer elements can be provided in the free space. The spacer elements can be formed by webs arranged on spiral lines. If the gypsum dust passes through the spiral slots into the free space, the spacer elements cause the gypsum dust to be entrained in rotation. The centrifugal force acting on the gypsum dust transports the gypsum dust to the windows through which the gypsum dust can exit the free space. The adjusting member, which is formed by the hood part and the adjusting disk that is connected to the hood part in a rotationally fixed manner, is preferably rotatable relative to the drive shaft.The spiral slots rotate relative to the radial guides, which are also slots, so that the fastening elements arranged in the radial guides, which each engage in a spiral slot with a control extension, can be adjusted in the radial direction. While the adjusting disk and the hood part can be made of plastic, the holding member and the fastening elements are made of metal. The radial guide is preferably formed by a radial slot which has a cross-section with several slot sections that differ in terms of their slot width and are arranged offset from one another in the axial direction relative to the axis of rotation. A square section of the fastening element is located in a first slot section with a large slot width. The square section holds the fastening element in the radial guide in a rotationally secured manner.Round sections extend from both sides of the square section, one of which forms the control extension that engages in the spiral slot. The axial length of the control extension is greater than the axial slot height of the spiral slot, so that the free end of the control extension projects into the free space. A round section opposite the control extension engages in a second slot section that has a smaller slot width. This second slot section is followed by a third slot section with a larger slot width than the second slot section. A fastening bracket for the saw element is located in the third slot section. The width of the fastening bracket corresponds to the slot width of the third slot section, so that the fastening bracket is non-rotatable in the third slot section.A fastening screw is provided, the head of which rests on the mounting bracket and the shaft of which is screwed into an internal thread of the fastening element. The internal thread preferably extends over the entire axial length of the fastening element, i.e., through the two round sections of the fastening element. The square section and the mounting bracket form facing surfaces. These surfaces form clamping surfaces that rest on the bottom of the first and third slot sections. The screw can be used to generate a clamping force that holds the fastening elements and the saw elements in place. Short description of the drawings

[0009] An embodiment of the invention is explained below with reference to the accompanying drawings. They show: Fig. 1 a side view of a hole saw, Fig. 2 a bottom view of the hole saw on the holding member 2, Fig. 3 the section along the line III-III in Fig. 2, Fig. 4 the section along line IV-IV in Fig. 2, Fig. 5 the section along the line VV in Fig. 3, Fig. 6 a first perspective view, Fig. 7 a second perspective view and Fig. 8 an exploded view of the elements of the hole saw. Description of the embodiments

[0010] A drive section 1 defines an axis of rotation D around which the hole saw can be driven in rotation. For this purpose, the drive shaft 1 is clamped into the chuck of a drill. The drive shaft 1 supports a pilot drill 12. For this purpose, the drive shaft 1 has a bore coaxial with the axis of rotation D for receiving the shaft of the pilot drill 12. A threaded section of a first part of the drive shaft 1 is screwed into a threaded section of a restraining element 24 of the drive shaft 1. The restraining element 24 has an external thread that is screwed into a threaded bore 25 of a holding member 2. The restraining element 24 engages with a collar over a passage opening of an adjusting member 4, so that the adjusting member 4 is axially restrained to the holding member 2.

[0011] The retaining member 2 consists of a circular disc made of metal, which has three radial slots, each with a cross-section comprising three slot sections 17, 18, 19. The radial slots each form a radial guide 3.

[0012] Each of the three radial guides 3 accommodates a metal fastening element 5. The fastening element 5 has a square section 15 that is non-rotatably but radially displaceably located in a first slotted section 17 of the radial guide 3. Opposite polygonal edges of the square section are in contact with the wall of the first slotted section 17. A sliding surface section of the square section 15 rests on the bottom of the slotted section 17.

[0013] A round section 16 of the fastening element 15 projects through a second slot section 18, the slot width of which is smaller than the slot width of the first slot section 17. While the first slot section 17 is open to a first broad side surface of the holding member 2, a third slot section 19 is open to a second broad side surface of the holding member 2. A fastening angle 7' of a saw element 7 having saw teeth is mounted in the third slot section 19. The width of the fastening angle 7' corresponds to the width of the third slot section 19, which approximately corresponds to the width of the first slot section 17. A surface section of the fastening angle 7' is supported on the bottom of the third slot section 19. The fastening angle 7' has peripheral edges that bear against the two mutually parallel walls of the slot section 19, such that the fastening angle 7' is non-rotatably fastened in the radial guide 3.

[0014] The fastening bracket 7' has a bore through which a fastening screw 20 extends, which is screwed into an internal thread 14 of the fastening element 5. The screw 20 exerts a clamping effect with which the fastening element 5 and the saw element 7 fastened thereto can be fixed to the holding member 2. The clamping force is transferred from the fastening bracket 7' into the bottom of the slotted section 19. While the fastening bracket 7' lies in the surface extension plane of the holding member 2, a working section of the saw element 7, which has a saw toothing at its free end, protrudes from the broad side surface of the holding member 2 in the direction of the surface normal.

[0015] The adjusting member 4 is made of plastic and essentially comprises a hood part 13 with a wall 13' extending parallel to the holding member 2 and a peripheral wall 13" surrounding at least a portion of the circumference of the holding member 2.

[0016] Spacer ribs 21 protrude from the wall 13' of the hood part 13 into the cavity of the hood part 13. An adjusting disc 6 rests on the spacer ribs 21 and is non-rotatably secured to the hood part 13. For this purpose, adjusting projections 23 protruding from the wall 13' engage in adjusting holes 22 of the adjusting disc 6.

[0017] The focusing disc 6 has a total of three spiral slots 9 arranged on spiral curves, which are open to each of the two mutually facing broad side surfaces of the focusing disc 6. The spacer ribs 21 are spaced apart from one another and arranged on spiral lines such that they are arranged along an edge of each spiral slot 9. They thus extend in the spiral space between two adjacent spiral slots 9 and hold the focusing disc 6 at a defined distance from the wall 13', which approximately corresponds to the material thickness of the focusing disc 6.

[0018] In the peripheral wall 13", several windows 11 are provided, arranged at a uniform angular distribution. The windows 11 form radially outer openings of the free space 10.

[0019] A control extension 8 protruding from the fastening element 5 engages in the spiral slot 9. The axial length of the control extension 8 is greater than the material thickness of the adjusting disc 6, so that the free end of the control extension 8 extends into the free space 10. The hole saw works as follows:

[0020] With the screws 20 loosened, the fastening elements 5 can be moved within the radial guides 3. To do this, the adjusting element 4 must be rotated relative to the holding element 2. Since the drive section 1 is connected to the holding element 2 in a rotationally fixed manner, the adjusting element 4 can be rotated relative to the drive section 1. The control extensions 8 slide in their associated spiral slots 9 and the square sections 15 in the radial guides 3. By rotating the adjusting element 4 relative to the holding element 2 relative to the radial guides 3, the radial distances of all saw elements 7 can be adjusted synchronously. Once the desired hole diameter has been set, the screws 20 are tightened so that the fastening elements 5 are clamped in the radial guides 3 with the assistance of the fastening angles 7'.

[0021] When sawing holes, a pilot hole is first drilled using the pilot drill 12, the tip of which projects radially beyond the saw teeth of the saw elements 7. The saw teeth of the saw element 7 then engage the workpiece. When drilling plasterboard walls, fine gypsum dust is created, which can enter the spiral slots 9 through the slot sections 17 to 19 of the radial guides 3. Since the spiral slots 9 are open on both sides, the gypsum dust can enter the free space 10. The spacer ribs 21 entrain the gypsum dust in their direction of rotation, so that a centrifugal force acts on the gypsum dust, driving it radially outwards, where it can leave the free space 10 through the windows 11. The invention thus counteracts the problem of clogging of the spiral slots 9.

[0022] The above statements serve to explain the inventions covered by the application as a whole, which also independently develop the state of the art at least through the following combinations of features, namely:

[0023] A hole saw characterized in that the control slot 9 is also open to a free space 10 of the adjusting member 4 opposite the holding member 2.

[0024] A hole saw, which is characterized in that the adjusting member 4 has a wall 13' delimiting the free space 10.

[0025] A hole saw characterized in that the adjusting member 4 is a hood part 13 with a wall 13' extending parallel to the adjusting disc 6.

[0026] A hole saw characterized by a peripheral limitation of the free space 10 having at least one window 11.

[0027] A hole saw, which is characterized in that the circumferential boundary of the free space 10 is formed by a circumferential wall 13" of the hood part 13.

[0028] A hole saw, which is characterized in that spacer elements 21 originate from the wall 13' of the hood part 13, on which a broad side surface of the adjusting disc 6 is supported.

[0029] A hole saw, which is characterized in that the radial guide 3 is formed by a radial slot, the cross-section of which has slot sections 17, 18, 19 with different slot widths, wherein a square section 15 of the fastening element 5 is non-rotatably inserted in a first slot section 17, a second slot section 18 with a smaller slot width is connected to the first slot section 17 and a third slot section 19 with a larger slot width is connected to the second slot section 18, in which a fastening angle 7' of the saw element is non-rotatably inserted, which is fixed in a clamp fit relative to the square section 15 by means of a fastening screw 20 which is screwed into an internal thread 14 of the fastening element 5.

[0030] A hole saw, which is characterized in that a round section 8, 16 is connected to the square section 15 of the fastening element 5 on both sides, through which the internal thread 14 extends, wherein a round section 8 forms the control extension 8 engaging in the spiral slot 9.

[0031] A hole saw characterized in that the control extension 8 projects through the spiral slot 9 into the free space 10.

[0032] All disclosed features are essential to the invention (individually, but also in combination with one another). The disclosure of the application hereby fully incorporates the disclosure content of the associated / attached priority documents (copy of the prior application), also for the purpose of incorporating features of these documents into the claims of the present application. The subclaims, with their features, characterize independent inventive developments of the prior art, in particular for filing divisional applications based on these claims. List of reference symbols 1 drive shaft 2 holding link 3 Radial guide 4 Adjusting element 5 Fastening element 6 Adjusting disc 7 saw element 7' mounting bracket 8 Tax extension 9 spiral slot 10 Free space 11 windows 12 pilot drills 13 Hood part 13' wall 13" perimeter wall 14 internal threads 15 square section 16 circular sections 17 first slot section 18 second slot section 19 third slot section 20 screw 21 Spacer rib 22 Adjustment hole 23 Adjustment projection 24 Restraint element 25 threaded hole D axis of rotation

Claims

[1] Hole saw with a drive shaft (1) which can be driven in rotation about an axis of rotation (D), a holding member (2) which has radial guides (3) and an adjusting member (4) which can be rotated relative to the holding member (2) for adjusting the hole diameter and which has a spiral slot (9) open to the holding member (2), wherein a fastening element (5) is guided and fastenable in each of the radial guides (3), which fastening element is connected to a saw element (7) and a control extension (8) which engages in the spiral slot (9), wherein the spiral slot (9) is also open to a free space (10) of the adjusting member (4) opposite the holding member (2), characterized by a peripheral boundary of the free space (10) having at least one window (11). [2] Hole saw according to claim 1, characterized by that the peripheral boundary forms a peripheral wall (13") and the windows (11) are arranged in a uniform angular distribution [3] Hole saw according to claim 2, characterized bythat the windows (11) are radially outer openings of the free space (1) delimited by a wall (13') extending parallel to an adjusting disc (6) forming the adjusting member (4). [4] Hole saw with a drive shaft (1) which can be driven in rotation about an axis of rotation (D) and which is connected to a holding member (2) which has radial guides (3), wherein a square section (15) of a fastening element (5) is non-rotatably inserted in each of the radial guides (3), to which fastening element a saw element (7) is fastened by means of a fastening screw (20), wherein a control extension (8) is connected to the square section (15), which control extension engages in a spiral slot (9) of an adjusting member (4) which can be rotated relative to the holding member (2) for adjusting the hole diameter and through which the threaded shaft of the fastening screw (20) can extend. [5] Hole saw according to one of the preceding claims, characterized byin that the radial guide (3) is formed by a radial slot, the cross-section of which has slot sections (17, 18, 19) with different slot widths, wherein a square section (15) of the fastening element (5) lies non-rotatably in a first slot section (17), a second slot section (18) with a smaller slot width adjoins the first slot section (17), and a third slot section (19) with a larger slot width adjoins the second slot section (18), in which a fastening angle (7') of the saw element lies non-rotatably, which is fixed in a clamp fit relative to the square section (15) by means of the fastening screw (20) which is screwed into an internal thread (14) of the fastening element (5). [6] Hole saw according to claim 5, characterized bythat a round section (8, 16) is connected to the square section (15) of the fastening element (5) on both sides, through which the internal thread (14) extends, wherein a round section (8) forms the control extension (8) engaging in the spiral slot (9). [7] Hole saw according to one of the preceding claims, characterized by that the control extension (8) projects through the spiral slot (9) into a free space (10). [8] Hole saw according to one of claims 5 to 7, characterized by that an extension of the bore forming the internal thread (14) extending through the control extension (8) is open on the front side of the control extension (8). [9] Hole saw according to one of the preceding claims, characterized by that the axial length of the control extension (8) is greater than the axial slot height of the spiral slot (9). [10] Hole saw according to one of the preceding claims, characterized byspaced-apart spacer elements (21) arranged along an edge of each spiral slot (9), the spacer elements (21) holding the adjusting disc (6) of the adjusting member (4) at a defined distance from the wall (13').

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