Hole saw assembly

Abstract

A device for more efficient coupling and de-coupling of a hole saw to an arbor. A hole saw has a bottom wall with a central threaded hole. The arbor's clamping device has first and second thread-engaging parts for engaging the internal thread in the hole saw's bottom hole. The thread-engaging parts are moveable with respect to one another perpendicular to the longitudinal direction of the hole saw. When the thread-engaging parts are in a first, disengaged position, the clamping device allows retraction from or insertion into the hole saw's bottom hole substantially longitudinally. When the thread-engaging parts are in a second or engaged position having a larger circumference, the clamping device engages the internal thread in the hole saw's bottom hole for clamping the clamping device in the hole. The clamping device used in the hole saw provides a quick-coupling for mounting a hole saw on an arbor.

Claims

1. A hole saw assembly comprising a hole saw and an arbor for coupling said hole saw to a driving tool, said hole saw comprising a bottom wall provided with a hole with internal thread having a major and a minor thread diameter, and said arbor comprising a clamping device having a first and a second thread-engaging part, said first thread-engaging part extending in a longitudinal direction and having a first external surface for in use engaging the internal thread; said second thread-engaging part extending in said longitudinal direction and having a second external surface for in use engaging the internal thread; said first and second thread-engaging parts moveable with respect to one another with a component in a direction perpendicular to said longitudinal direction, allowing said first and second thread-engaging parts to displace between a first or disengaged position with respect to one another for together providing a first circumference allowing retraction from or insertion in said hole in a substantially longitudinal direction, and a second or engaged position having a second circumference that is larger than the first circumference, and in said second position said first and second external surfaces engaging said internal thread for clamping said clamping device in said hole.

2. The hole saw assembly of claim 1, wherein said clamping device comprises a blocking part for blocking said first and second thread-engaging parts in said second position.

3. The hole saw assembly of claim 1, wherein said first and second thread-engaging parts are biased away from one another.

4. The hole saw assembly of claim 1, wherein said external surface of said first and second thread-engaging parts comprise external thread parts corresponding to said internal thread.

5. The hole saw assembly of claim 1, wherein said first and second thread-engaging parts are longitudinal cylinder segments.

6. The hole saw assembly according to claim 1, wherein said first and second thread-engaging parts have a spacing of at least two times the difference between the major and minor thread diameter of the internal thread.

7. The hole saw assembly of claim 1, wherein said thread-engaging parts in said second position have a diameter for engaging the internal thread and blocking removal of said clamping device from said internal thread by displacing said clamping device in longitudinal direction of said internal thread, and in said first position a diameter for staying clear from said internal thread for allowing removing said clamping device from said internal thread by displacing the clamping device in longitudinal direct of said internal thread.

8. The hole saw assembly of claim 1, wherein said first and second thread-engaging parts are spaced apart in said second position, wherein in particular said spacing providing a clearance that measures at least a twice a difference between an major internal thread diameter and a minor internal thread diameter of said internal thread of said hole.

9. The hole saw assembly of claim 1, wherein said first and second thread-engaging parts are biased away from one another at least to said second position, for allowing the first and second thread to be brought into said first position under elevation of said biasing force.

10. The hole saw assembly of claim 1, wherein said first and second thread-engaging parts form part of a threaded end with an external thread, said thread-engaging parts in an embodiment forming circle cylinder segments having a clearance allowing the thread-engaging parts to be displaced between the first and second position, in particular said thread-engaging parts in said second position forming part of a circle cylinder, and for displacing between said first and second position, said thread-engaging parts displace in functionally, in particular substantially a radial direction of said circle cylinder.

11. The hole saw assembly of claim 1, wherein said first and second thread-engaging parts are spaced apart in said second position, wherein in particular said spacing providing a clearance that measures at least a difference between a major internal thread diameter and a minor internal thread diameter of a given internal thread into which said clamping device is designed to clamp.

12. The hole saw assembly of claim 1, wherein said first and second thread-engaging parts are biased away from one another at least to said second position, for allowing the first and second thread to be brought into said first position under elevation of said biasing force.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Embodiments of the invention will now be described, by way of example only, with reference to the accompanying schematic drawing in which corresponding reference symbols indicate corresponding parts, showing in:

(2) FIG. 1 shows an application of the clamping device on an arbor for holding a hole saw;

(3) FIG. 2 shows a longitudinal cross section of FIG. 1;

(4) FIG. 3 shows the embodiment of FIG. 2, partly in cross section and partly exploded;

(5) FIG. 4 shows the embodiment of FIGS. 1-3 with the clamping device of the arbor in its first or releasing position;

(6) FIG. 5 shows the embodiment of FIGS. 1-3 with the clamping device of the arbor in its second or clamping position;

(7) FIGS. 6A and 6B show a working principle of the clamping of a hole saw, with FIG. 6A the first or releasing position, and FIG. 6B the second or clamping position;

(8) FIGS. 7 to 10 show a further embodiment of the clamping device, in which FIG. 7 shows a perspective view, FIG. 8 a top view and FIGS. 9 and 10 cross sections as indicated.

(9) The drawings are not necessarily on scale.

DESCRIPTION OF PREFERRED EMBODIMENT

(10) The drawings show features that may be combined as described. In FIG. 1, an embodiment of a clamping device 1 is shown, showing an application of the clamping device 1 on an arbor 2 for holding a hole saw 3. FIG. 2 shows a longitudinal cross section of FIG. 1.

(11) The hole saw 3 is cylinder-shaped with a cylinder wall 4, at one end closed by a bottom wall 5 and at its opposite wall end provided with saw teeth 6.

(12) The bottom wall 5 of the hole saw is here provided with drive holes 7. The arbor 2 is provided with extended drive pins 8 that reach into the drive holes 7 when with the arbor 2 positioned on the hole saw 3, as illustrated. These drive pins 8 are part of an embodiment of a hole saw torque engagement part that transfers torque that is to be transferred from the arbor 2 to the hole saw 3. The drive pins 8 are positioned such that in use the internal thread of the hole saw 3 does not completely locks on the external thread of the arbor 2. Other embodiments of the torque engagement means are possible, but in hole saw design, the drive pins 8 are currently generally accepted. These drive pins 8 usually cooperate with corresponding drive holes 7 in the bottom wall 5 of the hole saw. The drive pins 8 and drive holes 7 are an example of a torque engagement part that further in use block rotation of the hole saw 3 with respect to the arbor 2.

(13) The arbor 2 here holds a twist drill 9 centred in the hole saw 3. The twist drill 9 is usually included in order to allow the hole saw 3 to provide its hole around a pre-defined centre.

(14) The bottom wall 5 of the hole saw 3 is furthermore provided with a centred hole 10 that has an internal screw thread or shortly internal thread 11. The internal thread 11 has a thread form, a pitch between the crests of adjacent threads, and a lead, usually equal to the pitch. Furthermore, the internal thread 11 has a major diameter, a minor diameter, and a pitch diameter.

(15) The major diameter of the internal thread 11 is the larger of two extreme diameters delimiting the height of a thread profile, as a cross-sectional view is taken in a plane containing the axis of the thread.

(16) The minor diameter is the lower extreme diameter of the internal thread 11. Major diameter minus minor diameter, divided by two, equals a height of the thread. The minor diameter of the internal thread 11 is its inside diameter.

(17) The pitch diameter of the internal thread 11 is the diameter of a cylindrical surface that is axially concentric to the internal thread. The cylindrical surface intersects thread flanks at equidistant points, when viewed in a cross-sectional plane containing the axis of the thread. The distance between these points is exactly one half the pitch distance. Equivalently, a line running parallel to the axis and a distance away from it, slices the sharp-V form of the thread at exactly 50% of its height, assuming that the flanks have the proper shape, angle, and pitch for a specified thread standard. The pitch diameter is generally unrelated to the major and minor diameters, especially if the crest and root truncations of the sharp-V form at these diameters are unknown.

(18) FIG. 3 shows the embodiment of FIG. 2, partly in cross section and partly exploded. It more clearly shows parts of the clamping device 1.

(19) The clamping device in this embodiment has a first thread-engaging part 12 and a second thread-engaging part 13. Both thread-engaging parts 12, 13 extend in longitudinal direction. At their outer surfaces, the thread-engaging parts 12, 13 have sections of external thread 14 that matches the internal thread 11 of the centred hole 11. The first and second thread-engaging parts 12, 13 can move with respect to one another, in this current embodiment in radial direction Ra. In the currently discussed embodiment, the first thread-engaging part 12 is stationary with respect to the arbor 2, and the second thread-engaging part 13 can move in the radial direction Ra with respect to the first thread-engaging part 12. This construction of two thread-engaging parts 12, 13, and one stationary with respect to the arbor, is relatively simple in construction. Other embodiments, with more than two thread-engaging parts can be engineered. Other directions of movement may also be possible.

(20) In the embodiment illustrated in FIG. 3, the second thread-engaging part 13 is mounted on, or here integrally formed as one piece with, a sledge part 15. The first thread-engaging part is here mounted on, or here integrally formed as one piece with, a mounting part 16. The mounting part 16 can be attached to the arbor 2. Mounting part 16 comprises a slide provision 17. The sledge part can be mounted into the slide provision 17 to allow the sledge part 15 to slide back and for the in radial direction Ra on the mounting part 16. Thus, the mounting part 16 with the first thread-engaging part 12 is here stationary with respect to the arbor 2. The sledge part 15 with the second thread-engaging part 13 can displace with respect to the longitudinal axis of the arbor 2. The sledge part 15 is further biased, here spring-biased, via spring 18. The second thread-engaging part 13 is in this way biased away from the longitudinal direction of the arbor 2. The mounting part 16 provides a first abutment for the sledge part 15 with the second thread-engaging part 13 in the first position in which the first and second thread-engaging parts 12, 13 can be inserted in the centred hole 10. The mounting part 16 furthermore in this embodiment has a second abutment for the sledge part 15 in which the second thread-engaging part 13 is at least at the second position. Note that the second abutment may also block the second thread-engaging part 13 at a position in which the second thread-engaging part 13 is further removed from the longitudinal axis of the arbor 2 than in the second position.

(21) The outer surface of the thread-engaging parts 12, 13 here has an external thread that matches the internal thread 11. In this way, the first and second thread-engaging parts 12, 13 can simply and securely engage the internal thread 11 of centred hole 10. There may, however, also be other external surfaces that allow the thread-engaging parts 12, 13 to engage with the internal thread 11 in such a way that the first and second thread-engaging parts can work together to hold and clamp the hole saw 3 onto the arbor 2. In particular, hold and clamp the hole saw 3 in such a way that it will not fall off the arbor 2. An external thread 14 matching the internal thread is a secure and safe choice for the thread-engaging surfaces.

(22) The first and second thread-engaging parts 12, 13 can assume a first position with respect to one another and a second position. This is illustrated in FIGS. 4 and 5.

(23) FIG. 4 shows the embodiment of FIGS. 1-3 with the clamping device 1 of the arbor 2 in its first or releasing position, FIG. 5 shows the embodiment of FIGS. 1-3 with the clamping device 1 in its second or clamping position.

(24) In the embodiment of FIGS. 4 and 5, it is illustrated that in the first position of FIG. 4, the circumference of the thread-engaging parts 12, 13 is such that they can be inserted in the insertion direction 1. Any diameter of the circumference of the thread-engaging parts 12, 13 is smaller that the minor diameter of the internal thread 11 of the centred hole 10, allowing easy insertion of the thread-engaging parts 12, 13 into the centred hole 10.

(25) With the first and second thread-engaging portions 12, 13 in the second position, the first and second thread-engaging portions are here spaced apart.

(26) FIGS. 6A and 6B show a working principle of an embodiment of the clamping device, with FIG. 6A the first or releasing position, and FIG. 6B the second or clamping position. In the clamping position, the thread-engaging parts 12, 13 form part of a cylinder, here with an external thread 14. These thread-engaging parts 12, 13 can engage with an internal thread 11 of the internal hole 10. When used for clamping other parts, the central part 9, in case of the hole saw application, may not be present. In these embodiments, a spacing between thread-engaging parts 12, 13 can be selected such that that it allows displacing these parts 12, 13 from their first position to their second position and vice versa.

(27) In the drawings 6A and 6B, diameter D5 is the major diameter of the internal thread 11, diameter Dm is the minor diameter of an internal thread 11 of a hole 10. Diameter D2 is the largest diameter of the thread-engaging parts in their first position. In order to be able to remove the clamping device 1 from the centred hole 10 (pull it out of the centred hole 10, parallel to the longitudinal direction), diameter D2 should be smaller than diameter Dm. In that way, a quick-release coupling can be provided.

(28) The radius of curvature of the thread-engaging parts corresponds here to the radius of curvature of the hole 10. In case the hole 10 is provided with an internal thread 11 and the thread-engaging parts 12, 13 are provided with (parts of) external thread 14, the radii of curvature of the threads correspond, see FIG. 6B, where the dotted lines almost overlap. In a definition, both the internal thread and the external thread have a pitch diameter. For matching threads, these pitch diameters will substantially match.

(29) In case of the hole saw, the extending twist drill 9 having a diameter complicates the design and dimensioning of the thread-engaging parts. In the embodiment of FIGS. 6A and 6B, the second thread-engaging part 13 has a recess that provides enough clearance for the second thread-engaging part 13 with respect to both the first thread-engaging part 12 and to the twist drill 9 to allow the first and second thread-engaging parts to be displaced back and forth between the first and the second position.

(30) In the embodiment shown in FIGS. 6A and 6B, the first and second thread-engaging parts 12, 13 are horizontal cylinder segments. These thread-engaging parts 12, 13 have parallel longitudinal faces. Both parts have a recess for the central twist drill that usually is part of a hole saw. The recesses are taken out of the longitudinal faces.

(31) In this shown embodiment, part of the thread-engagement parts 12, 13 have been clipped off in order to reduce the maximum diameter D2 of the thread-engaging parts 12, 13. There are several options for making the thread-engaging parts 12, 13 such that their external surface is disengaged from the thread of the hole. The options below are not limiting but illustrate some options available.

(32) One option is to make one (the largest) thread engaging part 12 a half cylinder. The other thread-engaging part 13 should then have a longitudinal face at least 2.Math.(D5Dm) removed from the longitudinal axis L. Furthermore, a part of the largest thread-engaging part 12 should be clipped as is shown in FIGS. 6A and 6B in order to obtain a largest diameter D2 that is smaller than Dm. The clipping at both ends should reduce the diameter D2 to less than Dm.

(33) Another option is to select both thread-engaging parts 12, 13 with a longitudinal face at a distance from the longitudinal axis. This is done in the embodiment of FIGS. 6A and 6B. The space D4 between both thread-engaging parts 12, 13 in their second or engaged position (or between their longitudinal faces) then is larger than 2.Math.(D5Dm). In this embodiment, the space D4 is less than a third of diameter D5. Again, when that spacing D4 is close to 2.Math.(D5Dm), additionally, one or both thread-engaging parts should be clipped as shown in the FIGS. 6A and 6B, in such a way that again the largest diameter D2 is smaller than Dm.

(34) The different options presented above, combinations thereof, and other options that are possibly make it difficult to provide a general mathematical equation for all possible options.

(35) When for instance the thread-engaging part, for instance part 12, is cut along a straight line parallel (solid line) to, but at a distance from, the longitudinal axis, (i.e., having a longitudinal face) creating in fact a horizontal cylinder segments, or in-plate with radial lines of the centred hole, the largest diameter can be calculated via:
D2=2.Math.(R.sup.2d.sup.2), or
D2=2.Math.R.Math.sin().

(36) In any way, D2 is smaller than Dm.

(37) The clamping device may comprise more than two thread-engaging parts, although this may increase complexity. In order to make production easy, the thread-engaging parts can be horizontal cylinder segments, but other cylinder types parts or segments may also be devised.

(38) In an embodiment, as shown in FIGS. 1-6B, the thread-engaging parts 12, 13 are horizontal cylinder sections that have the external thread 14. These cylinder sections are part of an engagement cylinder. From the horizontal cylinder sections, a centre part has been removes, to provide a recess to take up the twist drill of a hole saw assembly. Usually, the recess is in the form of a cylinder. The engagement cylinder has a circumference. Usually, the thread-engaging parts each have less than 40% of the engagement cylinder circumference. In the embodiment shown in the drawings, the thread-engaging part indicated with reference number 12 is stationary and rests against the twist drill. The thread-engaging part with reference number 13 in this embodiment defines a smaller part of the engagement cylinder circumference that the thread-engagement part 12. It in FIGS. 1-5 is placed on the sledge part 15 and in use moves here in radial direction. In an embodiment, the larger thread-engaging part 12 has between 30-40% of the engagement cylinder circumference. The smaller thread-engaging part 13 in an embodiment has between 20-30% of the engagement cylinder circumference.

(39) In the embodiment of FIGS. 1-5, the thread-engaging part 13, or in fact the sledge part 15, is spring-biased in radial outward direction. Usually, the sledge-part 15 has a thread-engaging parts blocking, not indicated. Such a thread-engaging parts blocking can block or fix or lock the position of the thread-engaging parts 12, 13 with respect to one another at or beyond the second or engaging position. In particular, the thread-engaging parts blocking fixes the thread-engaging parts 12, 13 with respect to one another in the second or engaging position. In this way, the clamping device provides the same or almost the same fixing as a regular set of threaded parts with an internal and external thread, respectively, like a bolt and nut. Thus, a hole saw can be mounted and demounted from an arbor 2 swiftly.

(40) The clamping device 1 may be integrated on an arbor 2. Alternatively, the clamping device 1 may be provided as a separate part that can be installed on the arbor 1 after which the arbor is used as a quick-coupling for a hole saw 3.

(41) FIGS. 7-10 show a further embodiment of the clamping device 1. In this embodiment, the first and second thread-engaging part 12, 13 are both moveable. The first and second thread-engaging parts 12, 13 are biased away from one another, here spring-biased via (two) springs 18. Two compression coil springs are here provided parallel at opposite sides of the hole 10. Upon applying pressure, the first and second thread-engaging parts 12, 13 can be pressed towards one another. When pressed together, the thread-engaging parts 12, 13 can be brought into the first position for allowing a tool with internal thread to be removed from or passed onto the clamping part 1. When released, the thread-engaging parts 12, 13 move away from one another. When moving away from one another, the thread-engaging parts 12, 13 move to or even passed the second or engaged position. The combined spring-biasing forces of the springs 18 thus result in opposite, radially working forces on the thread-engaging parts 12, 13.

(42) In the embodiment of FIGS. 7-10, both thread-engaging parts are provided on a sledge part 15 that allows the thread-engaging parts to slide in the mounting part 16. In this embodiment, the thread-engaging parts 12, 13 displace in a substantially and/or functionally parallel, opposite direction. Furthermore, the thread-engaging parts displace while remaining functionally parallel. In this embodiment, the thread-engaging parts can be identical, making the clamping device easier to produce. The mounting part 16 has a central hole that can hold a centring drill 9 that can be used for the hole saw, see also FIGS. 1 and 2. In this embodiment, the hole 10 does not pass through the mounting part 16. A locking bolt 22 may be provided for holding the drill 9.

(43) In the embodiment of FIGS. 8-10, the mounting part 16 and sledge parts 15 have a slide provision 17 for providing a linear motion (i.e., along a straight line) when the first and second thread-engaging parts 12, 13 moves between the first and second positions. In this embodiment, the sledges 15 each have a slotted hole. And a pin 8 extending through the slot and fixed into the mounting part. The pin and slotted hole may also be reversed, providing the mounting part 16 with slots and the sledge parts 15 with a pin.

(44) In an alternative embodiment, one or more rails and corresponding runners may be provided on the mounting part 16 and the tread-engaging parts 15, respectively, for providing the linear motion.

(45) In the embodiment of FIGS. 8 and 9, the sledge parts 15 have a lower surface that slide over an upper surface of the mounting part 16 when the sledge parts 15 slide between the first and second positions. In the current embodiment, in order to make the thread of the first and second thread-engaging parts 12, 13 come into engagement with the thread of the part-to-be-engaged 11, 11, the sledge parts 15 further displace under an angle of between 3 and 10 degrees with respect to the radial direction Ra. In particular, the angle is between 4 and 6 degrees. Here, the angle is about 5 degrees.

(46) In order to prevent a possible rotation of a clamped part 5 with respect to the clamping device 1, the clamping device 1 may additionally be provided with a rotation-blocking that engages the clamped part 5. The clamping device 1 is here provided with one or more rotation-blocking members. Such a rotation-blocking member engages a tool, for instance the hole saw bottom wall 5. The one or more rotation-blocking members may comprise one or more pins 8 mounted on the mounting part 16 that is provided to engage a hole in a clamped part 3. In an embodiment, such one or more pins extend functionally parallel to the first and second thread-engaging parts 12, 13. Here, the rotation-blocking pins also provide a motion-guiding for the thread-engaging parts 12, 13, by extending through the slotted holes in the sledges 15 as discussed above.

(47) In the embodiment of FIGS. 7-10, a holding plate 21 is mounted on the mounting part 16 to hold the sledges and thus the thread-engaging parts on the mounting part 16. Here a (radial) length of the slotted hole in each sledge 15 limits the radial motion of the sledges 15. Thus, one end nearest to the longitudinal axis L defines the first position and the opposite end remote from the longitudinal axis L defines the second or engaged position. The holding plate 21 holds the sledges on the mounting part 16, allowing them to slide radially or substantially radially.

(48) It will also be clear that the above description and drawings are included to illustrate some embodiments of the invention, and not to limit the scope of protection. Starting from this disclosure, many more embodiments will be evident to a skilled person. These embodiments are within the scope of protection and the essence of this invention and are obvious combinations of prior art techniques and the disclosure of this patent.

LIST OF REFERENCE NUMBERS

(49) 1 clamping device 2 arbor 3 hole saw 4 cylinder wall 5 bottom wall 6 saw teeth 7 drive holes 8 drive pins 9 twist drill 10 centred hole 11 internal thread 12 first thread-engaging part 13 second thread-engaging part 14 external thread 15 sledge part 16 mounting part 17 slide provision 18 spring for application of a spring-biased force 21 holding plate 22 locking for holding a (centering) drill Ra Radial direction P direction of applied force to overcome biasing force I insert direction of insertion of arbor into hole saw L Longitudinal direction F direction of (spring) biasing force D1 smallest minor diameter of the external thread of the clamping device D2 largest major diameter of the external thread of the thread-engaging part in the first or disengaged position D3 largest minor diameter of the external thread of the clamping device D4 maximum clearance between the second thread-engaging part 13 and the central twist drill 9 D4 maximum clearance between the first and second thread-engaging parts 12, 13 D5 major diameter of the internal thread 11 Dm minor diameter of the internal thread 11.