Abstract
The present invention seeks to provide a simple, easily realisable and inexpensive solution to the problems discussed above. The present invention further seeks to provide a hole-saw device which enables rapid changes of hole saw. The present invention also seeks to provide a simple device for enlarging apertures which is simple, cost effective and can be used with standard drills of corded and battery types as well as manual types.
Claims
1. A rotary hole saw for the creation of a hole in a work-piece, the tool comprising: a generally cylindrical boss having a shaft at a proximal end for fitment to a chuck of a drill tool and rotation therewith about a central axis; and a hole saw for cutting a substantially circular hole in a work-piece; wherein the boss comprises a mandrel and a screw-threaded portion, wherein the mandrel is operable to axially slide between a proximal release position and a distal locking position, between the proximal end and the screw-threaded portion at a distal end of the boss, the mandrel having at least one elongate member extending in a distal direction coaxial with the central axis; wherein the hole-saw element comprises a generally cup-shaped cutting element, having a base and a circularly cylindrical annular wall element extending therefrom with a distal edge at a distance L1 from the base, wherein the base has a central screw-threaded portion for coupling with the boss and at least one aperture through which the at least one elongate member of the mandrel can extend; the mandrel having a bias to the distal locking position, such that once the hole saw is screw-threadedly associated with the boss and the mandrel faces the base of the hole saw and the at least one elongate member of the mandrel extends into the bases of the hole saw the boss and the hole saw become axially and radially fixed with respect to each other.
2. A rotary hole saw according to claim 1, operable for the enlargement of a pre-existing hole in a work-piece, the tool further comprising: a guide element; wherein the guide element has a base and a circularly cylindrical annular wall element, wherein the base of the guide element has a central screw-threaded portion for coupling with the boss and at least one aperture through which the at least one member of the mandrel can extend, the annular wall element having a distal edge arranged at a distance L2 from the boss, wherein in use, the guide element can be inserted into the pre-existing hole to provide support in centralizing the rotary saw therewith, the guide element extending a distance L2L1, beyond the hole saw; the mandrel having a bias to the distal locking position, such that when the hole saw and the guide are screw-threadedly associated with the boss, the mandrel faces the bases of the hole saw and the guide and the at least one elongate member of the mandrel extends into the bases of the hole saw and the guide whereby to axially and radially fix the same.
3. A rotary hole saw according to claim 1, wherein the mandrel is provided with elongate members, which locate and abut with respect to two apertures associated with the base of the of the hole saw and the base of any guide.
4. A rotary hole saw according to claim 3, wherein the mandrel abuts the base of the hole saw element, when axially and radially fixed with respect to the boss.
5. A rotary hole saw according to claim 4, wherein the mandrel is associated with the boss element about a substantially cylindrical section of the boss, the movement between mandrel and the boss being determined by at least one of friction, detent means and resilient biasing to the locked position.
6. A rotary hole saw according to claim 2, wherein the guide element is fabricated as a pressed steel element.
7. A rotary hole saw according to claim 2, wherein the guide element is a generally cup-shaped element and a distal edge of the guide element is serrated.
8. A rotary hole saw according to claim 2, wherein the base of the guide has a screw-threaded portion for screw-threaded coupling with the boss fastened to the boss and having an annular wall element, the outside wall surface being generally smooth.
9. A rotary hole saw according to claim 2, wherein the guide element is fabricated from an engineering plastics material, as one of a molded or machined element.
10. A rotary hole saw according to claim 9, wherein the guide element is manufactured form a plastics material and has a centrally placed metallic insert having an internal screw-thread.
11. A rotary hole saw according to claim 1, wherein the distal end of the boss is provided with an aperture for placement of a guide drill bit.
12. A rotary hole saw according to claim 10, wherein with respect to the aperture placement of a guide drill bit, there is provided a radially directed internally threaded aperture and a screw-threaded member, whereby to enable securement of a drill bit therein.
13. A rotary hole saw according to claim 2, wherein a low friction paint is applied to an outside surface of the guide element.
14. A rotary hole saw according to claim 2, wherein the guide element has a slight frusto-conical shape, reducing in diameter at a distal end with respect to the boss.
15. A rotary hole saw according to claim 2, wherein a distal portion of the guide element is mounted for rotation with respect to the base of the guide element.
16. A rotary hole saw according to claim 2, wherein a distal portion of the guide element is resiliently and telescopically mounted with respect to the base, whereby the distance L2 can decrease in the event further axial progress by the guide element is prevented.
17. A hole saw according to claim 2, wherein the guide element can be placed about a twist drill bit when fastened to the boss.
18. A hole saw according to claim 1, further comprising a twist drill element that can be operably fastened by a chuck element having a base, wherein the chuck element base has an internally threaded aperture and at least one aperture through which the at least one member of the mandrel can extend, whereby to secure the twist drill element in place of a guide element.
Description
BRIEF DESCRIPTION OF THE DRAWING FIGURES
[0021] The accompanying drawings illustrate several aspects and, together with the description, serve to explain the principles of the invention according to the aspects. It will be appreciated by one skilled in the art that the particular arrangements illustrated in the drawings are merely exemplary, and are not to be considered as limiting of the scope of the invention or the claims herein in any way.
[0022] FIG. 1 shows a perspective view of a known hole saw.
[0023] FIG. 2 shows a perspective view of a first embodiment of the invention.
[0024] FIG. 3A shows a perspective view of a boss in accordance with the invention
[0025] FIG. 3B shows a side view of a boss in accordance with the invention.
[0026] FIG. 4A shows a side view of a boss with hole saw and guide elements in spaced apart fashion.
[0027] FIG. 4B shows another side view of a boss with hole saw and guide elements in spaced apart fashion.
[0028] FIG. 5A shows a plan view of the invention.
[0029] FIG. 5B shows another plan view of the invention.
[0030] FIG. 5C shows another plan view of the invention.
[0031] FIG. 5D shows a perspective view of the invention.
[0032] FIG. 6A shows a side view of a boss.
[0033] FIG. 6B shows another side view of a boss.
[0034] FIG. 7 shows an embodiment of the invention in spaced-apart fashion.
[0035] FIG. 8A shows an embodiment of the invention.
[0036] FIG. 8B shows a further embodiment of the invention.
[0037] FIG. 9A shows a view of an embodiment of the invention, detailing operation.
[0038] FIG. 9B shows another view of an embodiment of the invention, detailing operation.
[0039] FIG. 9C shows another view of an embodiment of the invention, detailing operation.
[0040] FIG. 9D shows another view of an embodiment of the invention, detailing operation.
[0041] FIG. 9E shows another view of an embodiment of the invention, detailing operation.
[0042] FIG. 10 shows a hole saw and two guide elements in perspective, dis-assembled views.
[0043] FIG. 11A shows a boss in a pre-engagement mode.
[0044] FIG. 11B shows a boss with a hole saw in an engagement mode.
[0045] FIG. 11C shows a boss with optional central drill bit in position.
[0046] FIG. 12A shows another embodiment of the invention.
[0047] FIG. 12B shows another embodiment of the invention.
[0048] FIG. 12C shows another embodiment of the invention.
[0049] FIG. 12D shows another embodiment of the invention.
[0050] FIG. 12E shows the arrangement of a specific embodiment.
[0051] FIG. 13A shows how a guide element engages with a mandrel.
[0052] FIG. 13B shows how a guide element engages with a mandrel.
[0053] FIG. 13C shows how a guide element engages with a mandrel.
[0054] FIG. 13D shows how a guide element need not be fully screwed-in with respect to the arbor, yet remains securely fastened.
[0055] FIG. 14 shows a simple range of products that can be available in accordance with the invention.
DETAILED DESCRIPTION
[0056] There will now be described, by way of example only, the best mode contemplated by the inventor for carrying out the present invention. In the following description, numerous specific details are set out in order to provide a complete understanding to the present invention. It will be apparent to those skilled in the art, that the present invention may be put into practice with variations of the specific.
[0057] FIG. 1 shows a perspective view of a known hole saw, showing a central twist-drill bit 11 mounted upon a boss 12 having a shaft 13 for fitment to a chuck of a drill. A hole saw element 14 comprising a general circular bucket shape, with parallel walls 15 and a base 16. The base is provided with a bore (not shown) to allow passage of an externally threaded portion of the boss 12 (not shown) and fastened to the boss by way of a screw-fastening element (also not shown). The base is conveniently formed from tool-grade steel which can be formed by pressing, together with teeth 18, which can be formed and then hardened. In the alternative, the hole saw element can be manufactured from two types of steel, the first type being capable of easily press-formed, the upstanding walls of which are welded to harder steel to enable the teeth to remain sharp, the diameter of the annular wall corresponds in size to the size of a desired hole. The walls of the hole saw are provided with diagonal slots, whereby to assist in the removal of swarf and to enable cooler operation of the saw.
[0058] Referring now to FIG. 2, there is shown a first embodiment of a hole saw 20 in accordance with the invention, shown in perspective view. This embodiment details not only a hole saw but also a guide, as employed to enlarge an existing hole, to enable the full utility of the invention to be explained simply and in detail, noting that both FIGS. 1 and 2 show a twist drill 11 as employed to steady the hole saw, when in use. The hole saw 20 has a shaft 13 for insertion and fastening with respect to the chuck of a rotary tool, as is known. A mandrel 12 is provided which is slidably mounted upon the shaft. The mandrel 12 is provided with a resilient element such as a coil spring (not shown) such that in its rest position it is as far away from the proximal shaft portion as is possible and the mandrel 12 is urged against the force of the resilient element as the hole saw element 14 is rotated towards the proximal end; the hole saw being fastened when the elongate members can be inserted within the apertures of the base of the hole saw. Ideally, the hole saw is rotated along the screw-thread such that the base of the hole saw abuts the distal face of the mandrel, but it has been found that it is not strictly necessary for the hole saw to be maximally threaded onto the boss, although it will be appreciated that the further the hole saw is threaded onto the boss, the greater amount of screw-thread is available for any subsequent guide to be placed upon the boss if one is enlarging a pre-existing hole. Mounted upon the boss is a hole saw 14, of a general open tin can shape, comprising a base 21 with a screw-threaded bore 22 defined therethrough and having an annular wall 23 depending from the base, with a distal portion terminating with teeth 18, the diameter of the annular wall corresponds in size to the size of a desired hole. The invention provides a further element, a guide element 24, also corresponding to a general open tin can shape, but which guide element is provided neither with teeth nor any apertures for swarf removal associated with its annular wall 25, which annular wall depends from a base 26 having a bore 27 whereby the guide element can fit about a threaded shaft 28 extending distally from the boss with respect to the input shaft, the diameter of the annular wall corresponding to the size of a prior hole. Conveniently, a low friction paint, such as a Teflon paint, is applied to an outside surface of the inner annular wall, whereby to ensure that the tool is not urged off axis in use. With regard to manufacture of the boss and components, especially the spigots or elongate elements, tool steel is employedtool steel, as is known, being the term used to cover a variety of carbon and alloy steels that are particularly well-suited to be made into tools, arising from their hardness, resistance to abrasion and deformation and their ability to hold a cutting edge at elevated temperatures.
[0059] In use, a boss is fitted with a hole saw element 14, with the threaded element 28 of the boss being screw-threadingly inserted through the bore 27 of the hole saw element. Conveniently, the hole saw 14 is provided with two further diametrically opposite spaced apertures 29, through which spigots 31, as shown with reference to boss 12 in FIGS. 3A and 3B, which show, respectively perspective and side views of the boss, without further elements being associated therewith. The FIGS. 4A and 4B show the hole saw element 14 and guide element 24 being placed in alignment with the spigots 31, with the mandrel retracted in the second, unstable position (i.e. against the forces of the resilient element) in side view, being rotated approximately 90 one view with respect to the other. In the alternative, the mandrel may be biased against movement by way of a friction fit, so instead of the mandrel being retracted against a resilient member, the mandrel is urged towards the proximal end of the boss merely by overcoming the friction grip, as provided by a polymeric element against the boss, for example. In the alternative the mandrel may be provided with a friction element or a ball-detent locking system as is known in the art, and may have a detent locking in the engagement position only or in the engagement and retracted positions. In any event, the mandrel does not rotate with respect to the boss, so that when the hole saw has received the elongate element(s), the hole saw cannot rotate about the boss.
[0060] FIG. 5A shows a plan view of an inside of the hole saw 14 when seated against the mandrel upon boss, and the threaded element 28 is shown centrally extending through the central bore of the hole saw, with spigots 31 extending through the corresponding apertures 29 of the hole saw. FIG. 5B shows a plan view of a nested guide element 24 placed within the hole saw 14, together with drill bit 11: in this case two spigots 31 are upstanding from the base 21 of the guide element, the central bore 52 being provided with an internal thread, whereby the base 21 of the guide engages with the threaded element 28 of the boss, whereby to ensure that, in use, the hole saw does not rotate by slippage with respect to the boss. It will be appreciated that the boss may alternatively be provided with a threaded element with a flat axial wall, with the bore having corresponding dimensions to prevent slippage. When the threaded element 28 extends through a threaded bore 27, a tool 55 can extend within the guide element 24 to assist in placement of the guide, especially when the distal edge is provided with teeth as shown in FIG. 5D. In the alternative, if the inside floor of the guide element is provided with an upstanding hexagonal drive, having an internally threaded screw-thread are employed, then a suitable wrench can be employed with a corresponding hexagonal socket to fastened the assembly. A spacer 53 can be fitted, to ensure that they are easily separable. The guide element 24 is selected such that, in use, the diameter of the annular element corresponds in size to the pre-existing hole. FIG. 5C shows a distal view of the shaft 13, mandrel 12 and hole saw element 14.
[0061] In a further alternative, the guide element 24 can be provided with a bore having an internal screw-thread complementary to the external screw-thread of the threaded shaft 28, the guide element being provided with drive means such as hexagonal drive faces coaxially arranged about the bore upstanding from the base of the guide element, whereby a tool can engage with such hexagonal faces to allow the elements to be screw-fastened together. It will be appreciated that other fastening systems can be employed, although fastening systems including a screw associated with the guide element which can be directed towards the axis would need to be driven through a wall of the first and second coaxial walls whereby apertures though such members would need to be provided, which may act cause unwanted vibration through intermittent contact of the wall against the sides of the hole being created or the pre-existing hole.
[0062] In a still further embodiment, it has been found that the guide element can be provided in a plastics material, such as a polyamide-imide e.g. Torlon which has considerable thermal stability. Such class of plastics have an extremely low coefficient of linear thermal expansion and provide excellent dimensional stability. Polyamide-imide plastics are known as amorphous materials with a Tg (glass transition temperature) of 537 F. (280 C.). Polyamide-imide plastics can be extruded or compression molded with glass-fiber reinforcement. Parts machined from Torlon stock shapes provide greater compressive strength and higher impact resistance than most advanced engineering plastics and can therefore be provided as an alternative to tool steels for use in a guiding, non-cutting function. Indeed, engineering thermoplastic polymers are lighter and stronger than aluminum, magnesium alloy, aluminum alloy and other metals, so they offer a reduced weight advantagewhich can assist in when operating hand-held tools. Indeed, there are other types of plastics materials, such as Acetal, which is actually a polyacetal of formaldehyde, with DuPont having a trade name of Delrin. This is an exemplary high density plastic that is considered as an aluminum substitute. Acetal is dimensionally stable, high tensile strength, wear resistant, and fairly impact resistant; it is commonly used to make bearings, pulleys, and wheels. It will be appreciated that it is necessary to have a guide, when made of such materials, to receive 6-10 turns of the thread within its tapped hole, to ensure that the screw-thread is not damaged in use; equally, if the material of the guide was similar to the hole saw, e.g. of a pressed steel, then in normal use, since the spigots do not extend beyond the threaded section of the boss, the guide will be secure after engagement, typically 2-6 turns, as it passes through metal of a thickness of typically of the order of 1.5-3 mm.
[0063] Another advantage in the use of engineering thermoplastics for replacement of metallic components is that they are simpler to produce; where die-casting and sheet metal construction techniques typically comprise a six-step process, thermoplastics can be transformed from granules to a finished part in a three-step process. Accordingly they can be cheaper to manufactureand to replace if needed. More importantly, by having an engineering plastics with a degree of resilience, in the event that a tool is employed sufficiently off axis that the tool becomes jammed and, for example, the drill is left hanging within the aperture, then the tool is likely to resiliently give rather than become deformed, whereby any further use would mean that the guide would become unbalanced and therefore need to be replaced.
[0064] FIGS. 6A and 6B show side views of the mandrel 12 in a retracted position, with the axis horizontal, the two views showing the boss arranged approximately 90 rotated one with respect to the other. FIG. 6A shows a grub screw 61, which is inserted into passage 62 having a corresponding internal screw-thread, which leads into a channel 63 which opens out at a distal end of the threaded shaft 28. A distal end of the grub screw, in operation, acts against a surface of a shaft of a drill bit, as shown with reference to FIG. 7. It will be appreciated that a set of hole saws, together with guide elements in accordance with the invention may well be sold as a set with various sizes of hole saws and guide elements, although it is expected that a single central twist drill bit 71, having a shank diameter of dimensions to slide fit with respect to channel 63, which will be sufficient to cater for the events where there is no pre-existing hole.
[0065] Referring now to FIG. 8A, it has been found that the guide element can be formed such that it defines a narrow angle frusto-conical element 81, such that the guide element engages with the annular element that is cut out from the work-piece, the frusto-conical element ensuring that the annular member does not fall out of hole saw element 14 and is contained within an interior diameter D1, the frusto-conical element being provided with a rotatable section 82, whereby the frusto-conical element remains stationary at its distal end, with respect to the annular member. FIG. 8B shows a further variation, the frusto-conical element being provided with a telescoping section 83, wherein the frusto-conical member 81 is both resiliently and telescopically mounted with respect to the base of the guide element. This enables the frusto-conical element to approach the boss as the cutting ensues, when the annular member cannot creep along the frusto-conical member and enables a greater depth to be achieved.
[0066] FIG. 9A shows a further embodiment of the invention wherein the boss 90 comprises a mandrel 12 that supports two engagement spigots 31. The boss is movably mounted upon shank 13 for engagement between a decoupled position (as shown), the shank 13 having a drive part of hexagonal sectionfor convenient coupling with a power tooland an output section having a screw-threaded distal part 92 and an axial indent 93 on a plain shank portion 94, into which indent a resilient detent mechanism (not shown) associated with an inside surface of the bush can engage. In this embodiment, there is no central aperture for fitment of a central twist drill bit. FIG. 9B shows how hole saw member 14 can be screw-threadingly engaged with the screw-threaded distal part 92. This embodiment does not have an aperture for placement of a twist-drill bit for pilot drilling, where no pre-existing hole exists.
[0067] FIG. 9C shows how guide element 24 can be screw-threadingly engaged with respect to the screw-threaded distal part 92 of the shank 13. Boss 12 is in its decoupled position. In FIG. 9D, the boss 12 is shown in the second coupled position; the spigots 31 have been received within both the apertures 29 of the hole saw and the apertures 51 of the guide element. Detent means can be provided so as to enable axial alignment, if desired, although a simple visual check is otherwise all that is required. FIG. 9E shows a further perspective view of a guide element position within a hole saw assembly. It will be appreciated that there are several factors to be taken in to account in the design of the assembly. This embodiment, for example, does not have a central axial twist drill bit, which has been found to be more advantageous, in use, since the twist drill can remain in an operating configuration, irrespective of the presence if the guide element 24, which can be changed to suit a pre-existing hole or be removed where no pre-existing hole exists.
[0068] FIG. 10 shows a hole saw element 14 manufactured from tool steel and is provided with a central aperture 27 and alignment apertures 29 for association with spigots 31 of the mandrel 12, together with first and second guide elements 24. Each of these exemplary guide elements 24 is manufactured from Acetal and is provided with a central screw-threaded aperture 28 having apertures 56 radially arranged about the central aperture for association with spigots 31 of the mandrel 12. It has been found, in use, that tolerances of a few degrees of axial movement are permissible since once rotational movement has begun, the spigots act against an inside face of the hole saw and guide element apertures, 29, 56. When the guide element is manufactured from a plastics such as Acetal, it is prudent to have the threaded section 93 extend for at least a centimeter or so whereby over-tightening will not result in a stripping of the thread of the guide element. In the alternative, a threaded metallic bush element may be inserted in an aperture, whereby to provide a more rugged threaded element for the guide element. It should also be noted that the exemplary guide elements are shown as being solid cylinders; this is not mandatory; indeed it is beneficial for the guide elements to be machined or otherwise formed so that they do not represent a solid mass, which has implication in tool handling and can comprise an overall shape not dissimilar to a hole saw; a heavy guide element will be more difficult to manage in use.
[0069] FIGS. 11A and 11B detail, respectively the bossin a part-dismantled position, (where collar 58 per FIG. 11B is removed) wherein first and second annular indents 93 are shown on shank 94. FIG. 11B shows how the boss 12 abuts the base of hole saw 14 when in the second position. In an alternative, further embodiment, there is a twist-drill bit 71 protruding from the distal part 92 of the shank. FIG. 11C shows a boss with optional central drill bit 71 in position.
[0070] With reference to FIGS. 12A and 12B, the present invention is shown, respectively, with the mandrel in a first screw-thread-fastened yet non-spigot-engaged position and with the mandrel in a second screw-thread-fastened and radially-fastened spigot-engaged position. FIGS. 12C and 12D show the invention, respectively, with one and two hole saw elements, with the inner hole saw element of FIG. 12D acting as a guide element. FIG. 12E shows some holes 34 which are present in guide element 24 to reduce weight and rotating mass; the screw-thread 33 of the guide element being clearly shown. With reference to the following figures, the hole saw element is absent, to clearly show how guide element can be fastened; in FIG. 13A, the guide element is shown as being substantially fully screw-threadedly engaged with respect to the threaded shank 28, yet the mandrel is disengaged; in FIG. 13B, the mandrel is in an engaged position: in FIG. 13C, the guide element is not fully substantially screw-threadedly engaged with respect to the threaded shank 28, yet, surprisingly, is still secureaccordingly, the present invention provides a simple and reliable connection yet forgiving with regard complete engagement of the hole saw and guide member and, most importantly, providing a systems that, by way of spigot engagement elements prevents the mandrel/screw-threaded shaft, the hole saw and the guide elements from becoming screw-threadingly locked together, given that radial fixing of the parts is determined by the axially moving spigots. FIG. 13D, for example, shows how a hole saw, and guide element is securely fastened with respect to each other, both axially and radially, despite the gap G being present. FIG. 14 shows a simple range of sizes (non-limiting) of hole saw elements 14, guide elements 24 for a mandrelboss assembly that can be provided for a workman which are easily and simply exchanged as between each other, depending upon the nature of an installation job.
[0071] Accordingly, the present invention provides a hole saw arrangement that enables the simple creation of holes, with a simple to operate hole saw change system and which enables pre-existing holes in plasterboard, cavity walls, block board and other wall/ceiling building divisional walls etc. to be enlarged with a tool comprising a hole saw and guide that can enable a pre-existing holeof various effective diametersto be enlarged with the same basic tool. Indeed, the invention, in a preferred embodiment can be employed to cut a pilot hole when the guide element is removed. It will be appreciated that simple alternatives are possible: for example, the may exist two elongate elements extending from the mandrel which locate through the base of the hole saw, yet only one extends though the base of the guide element, or that the elongate element engage external parts of the guide element. The screw-thread about the boss with which the hole saw and the guide member could be distinct for each element, but are conveniently the same, to simplify manufacture and use.
[0072] While particular embodiments of this invention have been shown in the drawings and described above, it will be apparent, that many changes may be made in the form, arrangement and positioning of the various elements of the combination. In consideration thereof, it should be understood that preferred embodiments of this invention disclosed herein are intended to be illustrative only and not intended to limit the scope of the invention.
