Abstract
Quick-change hole saw mandrel (10) for a hole saw (18); includes drive shank (14) extending along a central axis (C); and mounting end (16) detachable connected to mounting aperture (26) of hole saw (18) and including drive pin (30) for engagement with drive pin aperture (28) of the hole saw (18). The mandrel (10) includes a gripping arrangement (32) insertable through the mounting aperture (26) for gripping the hole saw base (20). In a normally expanded configuration the gripping arrangement (32) grips the base (20). The gripping arrangement is selectively movable to a contracted configuration in which it can be inserted into or removed from the mounting aperture (26). A pilot bit lock selector (44) for selecting between an unlocked mode permitting quick removal and quick insertion of the pilot bit (12) and a locked mode in which the pilot bit (12) is locked against removal.
Claims
1. A quick-change hole saw mandrel for a hole saw having a base with a central circular mounting aperture and a drive pin aperture, the mandrel including: a drive shank extending along a central axis of the mandrel for releasable engagement with a rotary tool; a mounting end opposite to the drive shank and configured for detachable connection with the mounting aperture of the hole saw and including a drive pin for engagement with the drive pin aperture of the hole saw; a gripping arrangement disposed at the mounting end and insertable through the mounting aperture for gripping the hole saw base, the gripping arrangement having a normally expanded configuration in which the gripping arrangement grips the base against movement along the central axis and is selectively movable to a contracted configuration in which the gripping arrangement is insertable into or removable from the mounting aperture; and a quick-release pilot bit connection arrangement for coupling a quick-release pilot bit to the mandrel, the connection arrangement configured for receiving the pilot bit through a pilot bit aperture extending centrally through the gripping arrangement and the pilot bit connection arrangement including a pilot bit lock selector for selecting between an unlocked mode permitting quick removal and quick insertion of the pilot bit and a locked mode in which the pilot bit is locked against removal from the pilot bit connection arrangement
2. A mandrel according to claim 1, wherein the lock selector comprises a locking collar rotatable about the central axis between an unlocked position corresponding to the unlocked mode and a locked position corresponding to the locked mode.
3. A mandrel according to claim 2, wherein the pilot bit connection arrangement is configured for use with a ball-detent hex shank pilot bit and includes a ball detent arrangement including a ball locatable in the ball detent of the hex shank for locking the shank against removal.
4. A mandrel according to claim 3, wherein the locking collar includes an internal abutment which, in the locked position, retains the ball in the ball detent of the hex shank.
5. A mandrel according to claim 1, further including an adjustable spacer disposed at the mounting end and configured to facilitate use of the mandrel with hole saws of different base thicknesses.
6. A mandrel according to claim 5, wherein the spacer is movable along the central axis relative to the gripping arrangement to accommodate various hole saw base thicknesses.
7. A mandrel according to claim 6, wherein the spacer is configured to contact an underside of the hole saw base and to clamp the hole saw base between the spacer and a portion of the gripping arrangement.
8. A mandrel according to claim 1, including a sliding collar manually movable along the central axis for selectively moving the gripping arrangement to the contracted configuration.
9. A mandrel according to claim 8, wherein movement of the sliding collar toward the drive shank actuates movement of the gripping arrangement to the contracted configuration.
10. A mandrel according to claims 8, wherein the gripping arrangement includes pair of grippers, each gripper including a distal end protruding from the mounting end and having a catch for engaging the base of the hole saw.
11. A mandrel according to claim 10, wherein the catch of each gripper is generally semi-circular and wherein, in the contracted configuration, the pair of catches forms an approximately circular configuration.
12. A mandrel according to claim 10, wherein the pair of catches is configured to contact a topside of the hole saw base and to clamp the hole saw base between the mounting end and the catches.
13. A mandrel according to claim 10, wherein the grippers of the pair of grippers are spaced apart from each other in the expanded configuration and moved toward each other in the contracted configuration.
14. A mandrel according to claim 13, wherein the grippers are movable in a direction perpendicular to the central axis.
15. A mandrel according to claim 10, wherein each gripper includes an outwardly-facing ramped surface in contact with an inwardly-facing corresponding ramped surface on the sliding collar and wherein movement of the inwardly-facing ramped surface of the sliding collar toward the drive shank urges the outwardly-facing ramped surfaces of the grippers toward the central axis and into the contracted configuration.
16. A mandrel according to claim 15, further comprising an angle plate having a pair of ramped surfaces in contact with corresponding ramped surfaces on an underside of the grippers and wherein contact between the ramped surfaces of the gripper undersides and the ramped surfaces of the angle plate promotes movement of the grippers toward the contracted configuration.
17. A mandrel according to claim 1, wherein the gripping arrangement includes a biasing arrangement urging the gripping arrangement toward the expanded configuration.
18. A mandrel according to claim 17, wherein the biasing arrangement includes including a pair of helical springs positioned between the pair of grippers.
19. A mandrel according to claim 1, further comprising a pair of drive pins configured for engagement with a pair of drive pin apertures in a hole saw, the pair of drive pins being located on opposite sides of the gripping arrangement.
20. A hole saw assembly, comprising: a hole saw having a base and an annular wall extending from the base with a toothed cutting edge, the base including a central circular mounting aperture and at least one drive pin aperture; a quick-release pilot bit comprising a ball-detent hex shank drill bit; a quick change hole saw mandrel, including a drive shank extending along a central axis of the mandrel for releasable engagement with a rotary tool; a mounting end opposite to the drive shank detachably connected with the mounting aperture of the hole saw and including a drive pin in engagement with the drive pin aperture of the hole saw; a gripping arrangement at the mounting end which is inserted in the mounting aperture and gripping the hole saw base, the gripping arrangement having a normally expanded configuration in which the gripping arrangement grips the base against movement along the central axis and is selectively movable to a contracted configuration in which the gripping arrangement can be removed from the mounting aperture; and a quick-release pilot bit connection arrangement coupling the quick-release pilot bit to the mandrel, the pilot bit connection arrangement receiving the pilot bit through a pilot bit aperture extending centrally through the gripping arrangement and the pilot bit connection arrangement including a pilot bit lock selector for selecting between an unlocked mode permitting quick removal and quick insertion of the pilot bit and a locked mode in which the pilot bit is locked against removal from the connection arrangement
Description
BRIEF DESCRIPTION OF DRAWINGS
[0042] In order that the invention may be more fully understood, some embodiments will now be described with reference to the figures in which:
[0043] FIG. 1 is a front perspective view of a hole saw mandrel according to an embodiment of the present invention and with a pilot bit coupled to the mandrel;
[0044] FIG. 2 is a perspective top view of a conventional hole saw having a central mounting aperture and drive pin apertures;
[0045] FIG. 2a is a perspective underside view of the hole saw of FIG. 2;
[0046] FIG. 3 is a perspective view of the hole saw of FIG. 2 detachably connected to the mandrel of FIG. 1;
[0047] FIG. 4 is a rear perspective view of the mandrel of FIG. 1;
[0048] FIG. 5 is an exploded view of the mandrel shown in FIG. 1;
[0049] FIG. 6 is a side view of the mandrel of FIG. 1;
[0050] FIG. 7 is a cross-sectional view of FIG. 6;
[0051] FIGS. 8 and 9 are side and top perspective views of a body portion of the mandrel of FIG. 1;
[0052] FIG. 10 is a perspective view of a base collar of the mandrel of FIG. 1;
[0053] FIG. 11 is a perspective view of a locking collar of the embodiment in FIG. 1;
[0054] FIGS. 12 and 13 are perspective and side sectional views of an angle plate of the mandrel of FIG. 1;
[0055] FIG. 14 is a perspective view of an adjustable spacer of the mandrel of FIG. 1;
[0056] FIG. 15 is a perspective view of a spacer-adjustable collar of the mandrel of FIG. 1;
[0057] FIGS. 16 and 17 are perspective and side sectional views of a sliding collar of the mandrel of FIG. 1;
[0058] FIGS. 18 and 19 are perspective and side sectional views of a gripper of the mandrel of FIG. 1;
[0059] FIGS. 20 and 21 are perspective and side sectional views of a top plate of the mandrel of FIG. 1;
[0060] FIG. 22 is a cross-sectional view of a hole saw assembly comprising the mandrel of FIG. 1 with a thick-based hole saw connected to the mandrel and a pilot bit coupled to the mandrel;
[0061] FIG. 23 is a cross-sectional view of a hole saw assembly comprising the mandrel of FIG. 21 with a thin-based hole saw connected to the mandrel and a pilot bit coupled to the mandrel;
[0062] FIG. 24 is a view of the hole saw assembly of FIG. 8 with a sliding collar retracted and a gripping arrangement moved to a contracted position; and
[0063] FIG. 25 is a cross-sectional view of a hole saw assembly according to an embodiment of the invention with the pilot bit decoupled and partially removed from the mandrel.
DETAILED DESCRIPTION
[0064] FIG. 1 illustrates an embodiment of a quick-change hole saw mandrel 10 according to the present invention. Mandrel 10 is coupled with a pilot bit 12. Mandrel 10 includes a drive shank 14 extending along a central axis C of the mandrel. The drive shank 14 has a conventional quick-release hex shank ball-detent configuration for engagement with a rotary tool such as a power drill.
[0065] Mandrel 10 includes a mounting end 16 configured for detachable connection with a hole saw 18 that is illustrated in FIGS. 2 and 2a. The hole saw 18 includes an annular base 20 and an annular wall 22 extending from the base 20 having a toothed cutting edge 24 for cutting a hole in a workpiece. The base 20 includes a central circular mounting aperture 26 and a pair of drive pin apertures 28 located on opposite sides of the mounting aperture 26. The hole saw base 20 includes a topside 21 visible and labelled in FIG. 2 and an underside 23 visible and labelled in FIG. 2a.
[0066] The configuration of hole saw 18 is considered a conventional hole saw design which is used by most manufacturers and is compatible for use with a variety of different hole saw mandrels and arbors. In this regard, the central mounting aperture 26 includes an internally threaded surface 27 for engaging with an externally threaded mount on conventional hole saw mandrels.
[0067] A pair of drive pins 30 (only one of which is visible in FIG. 1) are provided at the mounting end 16 of mandrel 10 for engagement with the corresponding drive pin apertures 28 in the hole saw 18. A gripping arrangement 32 is located at the mounting end 16 and which is insertable through the mounting aperture 26 of the hole saw 18. FIG. 3 illustrates the hole saw 18 detachable connected to the mounting end 16 of the mandrel 10. When the hole saw 18 is connected to mandrel 10 as shown in FIG. 3, it will be appreciated that the underside 23 of the hole saw base 18 is placed into contact with the mounting end 16 of the mandrel 10.
[0068] Still referring to FIG. 1, the mandrel 10 has a central axis C and which hereinafter will be referred to as a reference point for the location and movement of various components of the mandrel 10. As illustrated in FIG. 1, pilot bit 12 and drive shank 14 are approximately collinear with the central axis C.
[0069] The mounting end 16 further includes an adjustable spacer 34 having an annular disc profile and which is illustrated in isolation in FIG. 14. The adjustable spacer 34 includes a central opening 36 and a pair of drive pin openings 38 on opposite sides of the central opening 36. As shown in FIG. 1, the gripping arrangement 32 and pilot bit 12 extend through the central opening of the spacer 34. Similarly, the drive pins 30 extend through the drive pin openings 38 in the spacer 34.
[0070] The mandrel 10 further includes a spacer-adjustment collar 40 which is illustrated in isolation in FIG. 15. The collar 40 is rotatable about the central axis C and configured to allow positional adjustment of the spacer 34 along the central axis C. Referring to FIGS. 14 and 15, the annular wall 35 of the spacer 34 is externally threaded for engaging with a corresponding internally threaded surface 41 of the spacer-adjustment collar 40 illustrated in FIG. 15. The exterior of the spacer-adjustment collar 40 has a fluted configuration to facilitate gripping with a user's fingers. The spacer-adjustment collar 40 includes an annular shoulder 43 received by a corresponding shoulder groove 84 in the top plate 80 and which is best illustrated in FIG. 21.
[0071] Returning to FIG. 1, adjacent to the spacer-adjustment collar 40 is a sliding collar 42 configured to be manually slid by a user's hand along the central axis C in order to move the gripping arrangement 32 from an expanded configuration for gripping the hole saw 18 to a contracted configuration for allowing hole saw removal or interchange. The operation of the sliding collar 42 will subsequently be described in further detail.
[0072] Turning to FIG. 4 which provides a rear perspective of the mandrel 10, the mandrel 10 further includes a pilot bit lock selector comprising a locking collar 44 enabling a user to select between an unlocked mode permitting quick removal and quick insertion of the pilot bit 12 and a locked mode in which the pilot bit 12 is locked against removal. The locking collar 44 is rotatable about the central axis C between a locked position corresponding to the locked mode and an unlocked position corresponding to the unlocked mode.
[0073] The locking collar 44 includes an indicating protrusion comprising a raised rib 46 on its exterior surface which the user can rotate between locked indicia 48 and unlocked indicia 50 provided on a base collar 76 which will be discussed subsequently in further detail. In FIG. 4, the raised rib 46 is positioned at the locked indicia 48 which corresponds to the locked position indicating to the user that the pilot bit 12 is locked against removal.
[0074] Turning to FIG. 5, an exploded view of the mandrel 10 is provided. The components of the exploded view will be described in sequence to inform subsequent discussion of the components.
[0075] Beginning at the bottom left of FIG. 5, is the hex shank quick-release pilot bit 12 which is received through the central opening 36 in the adjustable spacer 34. The pilot bit 12 includes a hexagonal base portion 101 that includes a ball detent 13. The pilot bit 12 will be recognised by a person skilled in the art as a conventional quick-release hex shank pilot bit of the type that is produced by most manufacturers and which is compatible with most quick-release drill bit chucks and connectors.
[0076] A pair of bolts 39 extend through corresponding openings 81 in a top plate 80 which includes the pair of drive pins 30 which extend through drive pin openings 38 in the spacer 34. An O-ring seal 82 locates in a corresponding groove 78 in the circumferential surface of top plate 80. The O-ring seal 82 is provided to limit leakage of grease or other lubricant which may be used to reduce friction on moving components of the mandrel 10. The top plate 80 is surrounded by the spacer-adjustment collar 40. An externally threaded annular wall 35 of the spacer 34 is located between the circumferential surface of the top plate 80 and the spacer-adjustment collar 40 which includes an internally threaded surface 41 engaged with the external thread of the annular wall 35.
[0077] Adjacent to the spacer-adjustment collar 40 is the sliding collar 42 which includes exterior indentures 64 facilitating manual gripping by the user. The sliding collar surrounds several components including part of the gripping arrangement which includes a pair of grippers 52 each having a base portion 56, a neck 60 and a lip 54. The base portion 56 of each gripper 52 includes an outwardly-facing ramped surface 58 which contacts corresponding inwardly-facing ramped surfaces 62 on the interior of the sliding collar 42. A pair of helical springs 86 are located between the grippers 52 which urge the grippers 52 to an expanded configuration in which the grippers 52 are spaced apart from one another. Adjacent to the gripper base portions 56 is an angled plate 88 with a pair of ramped surfaces 90 which contact an underside of the gripper base portions 58. The angled plate 88 seats on a mandrel body 70 having a pair of protrusions 71 each having an internally threaded bolt opening 73 for engaging with the bolts 39.
[0078] The mandrel 10 further includes a pilot bit connection arrangement which, in the illustrated embodiment is a ball detent connection arrangement 75. The ball detent connection arrangement 75 includes a stem 91 provided on the mandrel body 70 having a ball opening 92. The ball detent connection arrangement 75 further includes a ball 93 received in the ball opening 92 and a spring collar 94 for securing the ball 93 in the ball opening 92 to form a ball assembly. The drive shank 14 extends from the body stem 91. The body stem 91, and ball assembly is located within a base collar 76. The locking collar 44 surrounds a stem portion 77 of the base collar 76.
[0079] FIGS. 6 and 7 respectively provide side and side cross-sectional views of the mandrel 10. The gripping arrangement 32 comprises a pair of identical grippers 52 which are generally elongate in shape and arranged on opposite sides of the central axis C. Each gripper 52 includes a catch comprising a semi-circular lip 54 extending from a distal end of the gripper 52 in a direction radially outwardly with respect to the central axis C. Each lip 54 forms a recess 55 between the lip 54 and the spacer 34 which is configured to receive an edge of the mounting aperture 26. FIG. 7 also illustrates a pilot bit aperture 57 extending centrally through the gripping arrangement 32 and, in particular, extending between the grippers 52. The pilot bit aperture 57 (also labelled in FIG. 22) extends along the central axis C and receives the pilot bit 12 therethrough.
[0080] Turning to FIGS. 18 and 19, one of the grippers 52 is illustrated in isolation for convenience of description. The gripper 52 includes a base portion 56 which includes a ramped surface 58 that is inclined with respect to the central axis C. The ramped surface 58 of each gripper 52 is orientated radially outwardly with respect to the central axis C and is therefore termed an outwardly-facing ramped surface 58. The gripper 52 further includes a semi-circular neck 60 extending from the base portion 56 in an orientation parallel with the central axis C. Atop the neck 60 is the semi-circular lip 54 which extends radially outwardly with respect to central axis C.
[0081] As shown in FIG. 19, the outwardly-facing ramped surface 58 is inclined at approximately 30 with respect to the central axis C. An underside of the base portion 56 of each gripper 52 comprises a underside ramped surface 59 which is angled at 95 from the central axis C (i.e. 5 from an axis perpendicular to the central axis C).
[0082] Returning to FIG. 7, the outwardly-facing ramped surfaces 58 of the grippers 52 contact corresponding inwardly-facing ramped surfaces 62 on an interior the sliding collar 42. Turning to FIGS. 16 and 17, the sliding collar 42 is illustrated in isolation for convenience of description. The sliding collar 42 has a generally annular configuration with an exterior having a pair of indentures 64 on opposite sides of the collar 42 to facilitate gripping of the collar by a user's fingers. An interior of the sliding collar 42 includes a pair of opposing ribs 66 which are configured for receipt and sliding engagement with a pair of corresponding grooves 68 in an outwardly-facing surface of the mandrel body 70 which is illustrated in FIGS. 8 and 9.
[0083] Still referring to FIGS. 16 and 17, the interior of the sliding collar 42 also includes a pair of opposing grooves 72 which receive a pair of corresponding outwardly-facing connection flanges 74 on the base collar 76 and which are illustrated in FIG. 10. As best shown in FIG. 17, the interior of the sliding collar 42 includes the pair of inwardly-facing ramped surfaces 62 on opposite sides of the collar interior and which face generally inwardly with respect to the central axis C. As shown in FIG. 17, the inwardly-facing ramped surfaces 62 are inclined at approximately 30 to the central axis C. Returning then to FIG. 7, it will be appreciated that the outwardly-facing ramped surfaces 58 of the grippers are parallel with and in contact with the inwardly-facing ramped surfaces 52 of the collar 42.
[0084] FIG. 7 also illustrates that the underside ramped surfaces 59 of the grippers 52 are parallel with and in contact with ramped surfaces 90 of the angle plate 88. Turning to FIGS. 12 and 13, the angle plate 88 is illustrated in isolation for convenience of description. The angle plate 88 is symmetrical about the central axis C and generally saddle shaped with a pair of ramped surfaces 90 angled at 85 with respect to the central axis. The pair of ramped surfaces 90 are angled from opposite sides of the central axis C such that the interior angle between the ramped surfaces is 170. As shown in FIG. 12, the angle plate 88 includes a central opening 89 through which the pilot bit 12 extends and a pair of rounded bolt notches 87 through which bolts 39 extend. The angle plate 88 further includes a central rounded protuberance 85 on its underside and through which the central opening 89 extends.
[0085] Returning to FIG. 7, the angle plate 88 is seated on the mandrel body 70 which is illustrated in FIGS. 8 and 9 in isolation for convenience of description. The mandrel body 70 includes the drive shank 14, a cradle portion 95 including a pair of upstanding protrusions 71 orientated parallel with the central axis and including internally threaded bolt openings 73 on their top surfaces for engaging with the bolts 39.
[0086] The mandrel body 70 further includes a hollow stem 91 between the drive shank 14 and the cradle portion 95. The interior 97 of the hollow stem 91 is elongate and includes a hexagonal portion 101 (shown in FIG. 25) which corresponds and engages with the hexagonal base portion 102 (shown in FIG. 2) of the hex-shank pilot bit 12. In use, the hex-shank pilot bit 12 is correspondingly fitted within the hexagonal portion of the stem interior 97 such that rotation of the body 70 by a rotary power tool drives rotation of the pilot bit 12. The elongate stem interior 97 is aligned with the central axis C and with the pilot bit aperture 57 extending through the gripping arrangement 32. The elongate stem interior 57 and pilot bit aperture 57 are aligned with the central opening 89 in the angle plate 88. The pilot bit 12 therefore extends through each of the pilot bit aperture 57, the angle plate central opening 89 and the elongate stem interior 97. The mouth 96 of the stem interior 97 is located in the cradle portion 95 and (as best shown in FIG. 7) is provided with a countersink which receives the central rounded protuberance 85 on the underside of the angle plate 88. In this way, the angle plate 88 is securely seated in the cradle portion 95 with the protuberance 85 engaged with the countersunk mouth 96 of the elongate interior 97 of the stem 91.
[0087] The mandrel body 70 further includes a pair of blind holes 65 (only one of which is visible in FIG. 9) on opposite sides of the mouth 96. The holes 65 provide receptacles for debris which may enter the mechanism during use. For example, plaster dust which might accumulate inside the mechanism during repeated hole sawing of plaster sheeting.
[0088] Referring to FIG. 8, the stem 91 includes a ball opening 92 which extends from outside the stem 91 to the stem interior 97 into which the hex shank pilot bit 12 is received. The ball opening 92 has a slightly smaller diameter than the diameter of the ball 93 shown in FIGS. 5 and 7 such that the ball 93 can seat in the ball opening 92 with a portion of the ball 93 extending into the stem interior 97 and whilst preventing the ball 93 from passing completely through the ball opening 92 and falling into the stem interior 97. As was illustrated in FIG. 5, a flexibly resilient steel spring collar 94 is fitted around the stem 92 which retains the ball 93 in or against the ball opening 92.
[0089] As shown in FIG. 7, when the pilot bit 12 is fully inserted into the stem interior 97, the ball detent 13 in the pilot bit 12 is aligned with the ball opening 92 such that the portion of the ball 93 which extends into the stem interior becomes seated in the ball detent 13. Turning to FIG. 25, when the pilot bit 12 is withdrawn from the interior 97 of the stem 91, the ball 93 is urged out of the ball detent 13 through the ball opening 92 in a direction radially outward from the central axis C.
[0090] When the lock selector 44 is in the unlocked position, the ball 93 is permitted to move out of the stem interior 97 and into an unoccupied volume at the interior of the locking collar 44. When the locking collar 44 is at the locked position the ball 93 is prevented from moving radially outward and is retained in the ball detent 13 by an internal abutment of the locking collar 44.
[0091] Turning to 11, the locking collar 44 is illustrated in isolation for convenience of description. The locking collar 44 is comprises an annular wall 45 with a fluted exterior surface facilitating gripping by a user's fingers. The annular wall 45 includes an external indicating protrusion comprising a raised rib 46. An internal abutment comprising an internal radial protrusion 98 is located on the opposite side of the wall 45 from the raised rib 46. To the sides of the radial protrusion 98 there is an unoccupied volume 99 at the interior of the locking collar 44.
[0092] Returning to FIG. 7, the locking collar 44 is shown in the locked position corresponding to a locked mode in which the abutment 98 is aligned with the ball opening 92 so as to retain the ball in the ball detent 13 and thereby lock the pilot bit 12 against removal. In FIG. 25, the locking collar 44 is shown in the unlocked position corresponding to an unlocked mode and in which the abutment 98 is not aligned with the ball opening 92. In the unlocked mode, the ball 93 can therefore be urged out of the ball detent 13 through the ball opening 92 and into the unoccupied volume 99 within the locking collar 44 and thereby allowing the pilot bit 12 to be withdrawn from the stem interior 97.
[0093] The locking collar 44 surrounds a stem portion 77 of the base collar 76 which is best illustrated in FIG. 10. As previously noted, the underside of the base collar 76 includes locked indicia 48 and unlocked indicia 50. In the illustrated embodiment the indicia 48, 50 consist of the words Lock and Unlock respectively but it is to be appreciated that other indicia may be used such as a locked or unlocked symbol or pictographic.
[0094] A first notch 49 is adjacent to the locked indicia 48 and a second notch 51 is adjacent to the unlocked indicia 51. The notches 49, 51 provide visual indicators to which the user can align the raised rib 46. For example, the locking collar 44 may be turned to the first notch 49 adjacent the locked indicia 48 which indicates to the user that the locking collar 44 (and therefore the pilot bit connection arrangement) is in the locked mode.
[0095] The stem portion 77 of the base collar 76 includes a locking collar retention arrangement comprising a triangular rib 69 connected to the stem portion 77 via a flexibly resilient web 79 which permits resilient movement of the rib 69 in a radial direction with respect to the central axis C. The web 79 may therefore provide a plastic spring which is temporarily deformable and capable of resiliently returning to a normal position. The web 79 may be formed from a resilient polymer such as nylon or other suitable resilient material.
[0096] The rib 69 corresponds with a pair of triangular grooves 67a, 67b in the interior surface of the locking collar 44 and illustrated in FIG. 11. Each of the grooves 67a, 67b is associated with one of the locked and unlocked positions. With the locking collar in the locked position, the rib 69 is engaged with the groove 67b so as to retain the locking collar in that selected position. When rotated clockwise, the resilience of the web 79 is overcome and the rub 69 urged radially during rotation of the locking collar 44 and with the resilience of the web 79 urging the rib 69 radially outwardly against the interior of the locking collar. Once the locking collar 44 arrives at the unlocked position the rib 69 snaps into the triangular groove 67a so as to retain the locking collar in the unlocked position against inadvertent rotation.
[0097] The stem portion 77 further includes a circumferential slot 100 extending approximately 90 about the circumference of the stem portion 77. The slot includes a pair of opposite end faces 100a and 100b which are contacted by the internal radial protrusion 98 of the locking collar 44 when the locking collar is in either the locked or unlocked position. This prevents the locking collar 44 from 360 rotation about the central axis and limits rotation of the locking collar 44 to 90 of rotation between the locked and unlocked positions.
[0098] FIG. 22 illustrates the mandrel 10 fitted with a hole saw 118 having a relatively thick base 120. The thickness B1 of base 120 is labelled in FIG. 22. To accommodate use with the relatively thick base 120, the adjustable spacer 34 has been withdrawn into the spacer-adjustment collar 40 via manual rotation of the spacer-adjustment collar 40 which is in threaded engagement with the spacer 34. The spacer 34 is approximately flush with (or protrudes only very slightly beyond) the edge of the spacer-adjustment collar 40.
[0099] FIG. 23 illustrates the same mandrel 10 in use with a hole saw 18 having a thinner base than that of hole saw 118. The hole saw 18 has a base 20 of thickness B2 which is less than B1. To accommodate the thinner base 20, the adjustable spacer 34 has been selectively extended until contact with the underside 23 of the hole saw 18 and to press the base 20 against the gripper lips 54 in contact with the topside 21 of the base 20. In this manner, the hole saw base 20 is clamped between the gripper lips 54 and the adjustable spacer 34 providing a secure and stable connection during use of the mandrel 10 with a rotary tool.
[0100] It will therefore be appreciated that via operation of the spacer-adjustment collar 40, the mandrel 10 is securely connectable with hole saws of different base thickness and such that the mandrel 10 is compatible with a larger variety of hole saws.
[0101] FIG. 23 illustrates hole saw 18 detachably connected to the mandrel 10 and wherein the drive pins 30 are located within the drive pin apertures 28 and with the grippers 52 extended through the central mounting aperture 26. The grippers 52 are shown in the expanded configuration wherein the grippers 52 are spaced apart from another so that the expanded distance DE between an outer edge of the gripper lips 54 is larger than the diameter DA of the mounting aperture 26. In this configuration, the gripper lips overlap the topside 21 of the hole base 20 and thereby gripping the hole saw 18 against the mandrel 10. The grippers 52 are maintained in the normally expanded configuration under bias from the helical springs 86 (shown in FIG. 5) which urge the grippers 52 apart from one another.
[0102] FIG. 24 illustrates the same componentry of FIG. 23 but with the gripping arrangement moved to the contracted configuration to allow disconnection and removal of hole saw 18 from mandrel 10. The sliding collar 42 has been manually slid along the central axis C in a downward direction (i.e. toward drive shank 14) and to the position shown in FIG. 23. The movement of sliding collar 42 has simultaneously shifted the base collar 76 along the central axis due to the connection between the base collar connection flanges 74 and the sliding collar grooves 72. The locking collar 44 is similarly shifted along the central axis by virtue of being fitted around the stem 77 of the base collar 76.
[0103] The movement of inwardly-facing ramp surfaces 62 apply a force onto the outwardly-facing ramp surfaces 58 of the grippers 52 which is normal to the plane of the ramp surfaces 62, 58 and which comprises a force component in the radially inward direction. This force overcomes the outwardly urging bias of the springs 86 causing the grippers 52 to move radially inward. This movement is guided and facilitated also by engagement between the underside ramped surfaces 59 of the grippers 52 and the angle plate ramped surfaces 90 which limit or prevents movement of the grippers in the direction of the central axis and directs movement of the grippers 52 radially inward.
[0104] The grippers 52 are thereby moved to the contracted configuration shown in FIG. 24 in which the grippers are brought into contact with one another and in which the contracted distance Dc between outer edges of the gripper lips 54 is approximately equal to or slightly less than the diameter DA of the central mounting aperture 26. The gripper lips 52 therefore no longer contact the topside 21 of the hole saw base 20 and the hole saw 18 is no longer secured to the mandrel 10 and can be manually removed by lifting the hole saw 18 off the drive pins 30.
[0105] Upon manual release of the sliding collar 42 the arrangement returns to the configuration shown in FIG. 23 under influence of the springs 86 which urge the grippers 52 apart and thereby draw the sliding collar 42 back along the central axis to its normal position which corresponds to the expanded configuration of the gripping arrangement 32.
[0106] Componentry of the mandrel 10 may formed from a variety of suitable materials. Components of the mandrel 10 subject to high load or contact with a hole saw (which are typically steel) may themselves be formed from steel. For example, the body 70, top plate 80 including drive pins 30 and the spacer 34 may be formed of a steel such as 40cr steel. Other components such as the sliding collar 42 and base collar 76 may be formed from a polymer such as nylon. The locking collar 44 may be formed of a thermoplastic such as acetal (Polyoxymethylene). Components such as the angle plate 88 and grippers 52 which are configured for repeated sliding movement against one another may be formed of a ferro nickel alloy. A person skilled in the art will appreciate that alternative suitable materials could be appropriate.
[0107] Those skilled in the art will appreciate that the invention described herein is susceptible to variations and modifications other than those specifically described. It is understood that the invention includes all such variations and modifications which fall within the spirit and scope of the present invention.
[0108] Where any or all of the terms comprise, comprises, comprised or comprising are used in this specification (including the claims) they are to be interpreted as specifying the presence of the stated features, integers, steps or components, but not precluding the presence of one or more other features, integers, steps or components.
