Abstract:
A hole saw having a blade portion separable into two parts which when separated form a base portion and a tip portion. The base and the tip have correspondingly shaped apertures and lugs that co-operate together to hold the blade tip in place. A locking means further assists in ensuring that the blade tip remains locked to the base and includes a sliding latch that engages an aperture in the blade and the base and is itself locked in place to thereby lock the blade to the base. An intermediate portion also allows for the hole saw to drill through different depths.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation-in-part of U.S. patent application Ser. No. 12/514,902, which is a National Stage of International Application No. PCT/AU2007/001748 filed Nov. 14, 2007, which claims priority to AU 2006906340 filed Nov. 14, 2006; the disclosures of which are incorporated herein by reference. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to a hole saw with interchangeable cutting or drilling blades. In particular, a hole saw adapted to receive a plurality of cutting blades of different cutting configurations. 
     BACKGROUND OF THE INVENTION 
     Hole saws are a very widely used tool for many applications. Typically a hole saw includes a flat solid base that is locked by a drill, the base providing support for the hole saw. Some bases include multiple diameter grooves adapted to accommodate hole saws of different diameters. Typically these bases, with a plurality of concentric grooves, are of a diameter greater than the hole saw blade and as a result drilling depth is limited to the length of the hole saw body portion. This limitation restricts the possible uses of the hole saw and possible surfaces able to be drilled. 
     Other hole saws are single sized, overcoming the abovementioned problem of a larger diameter base but requiring the user to change the entire hole saw for each application. A user with a single sized hole saw needs to replace the hole saw for each surface being drilled as well as for each different diameter hole. The removal and installation of hole saw bodies for each new application or following the failure of a hole saw blade is troublesome, labour intensive, and time consuming. 
     Holes saw blades use different cutter materials and configurations to more effectively cut the surface being drilled. For example, serrated carbide tipped hole saws are generally used to drill harder and more abrasive surfaces than is possible with a regular steel blade. Some composite woods are more effectively cut with a different blade configuration and are best cut with a single tooth carbide tipped cutting element. Abrasive materials such as glass, ceramics, stone, asbestos and some plastic surfaces also require different cutting materials and configuration of the hole saw blade. A diamond or carbide grit encrusted blade is typically used in these applications. As each application may require a different hole saw blade configuration, the user is required to maintain an inventory of different hole saws for each surface to be drilled and each diameter of hole, inclusive of back up hole saw bodies in the event of blade failure. Such a large inventory is both cumbersome and expensive. 
     In addition where different depth holes need to be drilled the user has to have an extensive hole saw inventory with hole saws of different lengths that can drill through different depths. When the hole saw wears out the whole hole saw has to be replaced at great expense. 
     It is therefore an object of the present invention to overcome the aforementioned problems and to provide the public with a useful alternative. 
     SUMMARY OF THE INVENTION 
     Therefore in one form of the invention there is proposed a hole saw including a base and a blade extending from the base and adapted to engage an arbor, the blade including a cylindrical skirt extending longitudinally from the base, the skirt divided into two parts along the longitudinal axis, the parts releasably lockable to each other, the first part coupled to the base and the second part having a cutting means. 
     In a preferred embodiment there is proposed a hole saw including a base adapted to engage an arbor and extending therefrom a cylindrical blade having at one end a cutting face, said cylindrical blade further comprising a radial slit about its circumference, said radial slit extending through the blade and separable into two main sections, the first section being a cutting tip cylinder and the second being a support cylinder that is attached to said base. 
     Preferably said hole saw further includes a releasable locking means to releasably lock the cutting tip cylinder to the support cylinder. 
     Preferably said locking means includes at least one locking member moveable from a first unlocked position to a second locked position whereby in said first position said cutting tip cylinder may be removed from the support cylinder and when in said second position said support cylinder and said cutting tip cylinder are lockingly engaged. 
     Preferably said support cylinder and locking member inner and outer circumferences do not protrude radially from the inner and outer circumferences of the cutting tip cylinder. 
     Preferably said locking member is a lug adapted to extend from the support cylinder into a correspondingly shaped locking cavity in the cutting tip cylinder. 
     Preferably said support cylinder includes a number of circumferential teeth adapted to engage correspondingly shaped cavities in the cutting tip cylinder, the teeth adapted to engage the cavities upon rotational movement between the two cylinders whereupon said lug is then in a position to engage the locking cavity. 
     An advantage of such an interchangeable hole saw blade arrangement is that a hole saw blade may be rapidly removed and reattached. 
     Still a further advantage is that by utilising such a removably attachable hole saw blade portion a user requires less room to store a plurality of hole saw blades for different applications. 
     Still a further advantage is that said hole saw body can be used with commonly available hole saw mandrels. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate several implementations of the invention and, together with the description, serve to explain the advantages and principles of the invention. In the drawings: 
         FIG. 1 a    illustrates a perspective view of a hole saw body and a hole saw blade in a disengaged position; 
         FIG. 1 b    illustrates a perspective view of a hole saw body and a hole saw blade in an inserted position; 
         FIG. 1 c    illustrates a perspective view of a hole saw body and a hole saw blade in a locked position; 
         FIG. 2  illustrates a cross sectional view of a hole saw body and a hole saw blade in a locked position; 
         FIG. 3  illustrates a top view of a hole saw body and a hole saw blade in a locked position; 
         FIG. 4  illustrates a perspective view of a hole saw body and a further locking means of the hole saw blade; 
         FIG. 5  illustrates the locking means of  FIG. 4  without a hole saw blade; 
         FIG. 6  illustrates the locking means of  FIG. 5  with a steel hole saw blade attached and locked thereto; 
         FIG. 7  illustrates the locking means of  FIG. 5  with a concrete saw blade attached and locked thereto; and 
         FIG. 8  illustrates the locking means of  FIG. 5  with a timber hole saw blade attached and locked thereto. 
         FIG. 9  is a perspective view of a further embodiment of hole saw assembly including a body, intermediate member and a hole saw blade in a disengaged position according to the present invention; 
         FIG. 10  is a perspective view of the hole saw assembly of  FIG. 9  when in an assembled position; and 
         FIG. 11  is a side view of the hole saw assembly illustrated in  FIG. 10 . 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The following detailed description of the invention refers to the accompanying drawings. Although the description includes exemplary embodiments, other embodiments are possible, and changes may be made to the embodiments described without departing from the spirit and scope of the invention. 
       FIGS. 1 a , 1 b  and 1 c    illustrate an embodiment of the present invention. The present invention includes a hole saw  10  there being means of retaining the hole saw blade portion  12  to the hole saw body portion  14 . In this embodiment the hole saw blade portion  12  includes at one end at least one cutting element  16  and at the other end an engagement means by which the blade is attached to the hole saw body  14 . 
     The engagement means on the hole saw blade  12  further includes at least one engagement lug  48  extending longitudinally from the flat edge  50  of the hole saw blade portion  12 . Shown in this figure is a plurality of repeating teeth shaped engagement lugs  48  whereby the lug projects at an acute angle from the hole saw blade portion  12  with the angle of the leading edge of the lug  48  being greater than the angle of the trailing edge. The hole saw blade portion  12  further includes at least one substantially rectangular recession  52  with an angular depression  54  approximately about half way up the side wall of the rectangular recession. The attachment means on the hole saw body  14  is adapted to receive the abovementioned engagement means in a rotatable manner. The attachment means comprises of a plurality of engagement lugs  56 , extending longitudinally from the end of the hole saw body  14 , and adapted to be received in the space between the extending hole saw blade lugs  48 . 
     To further retain the hole saw blade  12  to the hole saw body  14 , the present embodiment utilises at least one retention clip  60  longitudinally slideable from a first to a second position. This additional retention device safeguards against the blade unintentionally being removed through misuse or rough handling. The retention clip includes a tab  62  which a user asserts force upon to slidably move the retention clip from a first to a second position. In doing so the extension strip  64  is moved up into the recess  52  provided in the hole saw blade  12 . A projection  66  is adapted to be received by a depression  54  and ensures that the clip is retained in the second and locking position. 
       FIGS. 1 b  and 1 c    show the hole saw blade  12  and hole saw body  14  rotatably attached with the retention clip  60  in the first and second positions. The first position of the retention clip  60  allows the hole saw blade portion  12  to be inserted and removed from the hole saw body portion  14 . In the second position the retention clip extends into the hole saw blade portion recess  52  thereby locking the hole saw blade to the hole saw body. 
     The retention clip  60  slides along longitudinally extending rails  68 . These rails are formed by pressing the steel about the slot used to house the retention clip  60  in order to create a reduced thickness of the rails when compared with the thickness of the hole saw body  14 . The reduced thickness of the rails allows the retention clip to be the same thickness as the body and as a result it does not protrude radially from the hole saw body  14 . Thus allowing through-drilling applications and does not prevent drilling depth to be limited to only the depth of the hole saw blade portion  12 . 
       FIG. 2  illustrates a cross sectional view of the hole saw body portion  14  and the hole saw blade portion  12  locked together with the retention clip  60  in the second and locked position.  FIG. 3  illustrates the same arrangement in a top view. Also not shown in this figure is the means of fixing the hole saw body to a mandrel or base. 
     It is important to understand that the present invention teaches a removable hole saw blade that is adapted to be removably attached to a hole saw body. The advantages of this is that the user only needs to have one hole saw body and several blades to be able to cut through a range of materials. Not only is this more space effective and cheaper but it has the result that once a hole saw blade has worn out it can be simply replaced and used with the original hole saw body. This has the effect on saving on materials and thus cost. 
     One particular type of locking means is illustrated in  FIG. 4 . Here a slidable lug whose thickness is the same as the hole saw body  124  includes internally facing grooves  126  that engage a correspondingly shaped protrusion  128  of the hole saw body. The lug is thus restrained in place and can only move up or down to lock and unlock the hole saw blade  130 , the lug sliding within aperture  132  defined both by the hole saw body and the hole saw blade. To ensure that once the lug has slid up and engaged blade  130  it remains in place and does not slide down a press stud  134  may be used that engages correspondingly shaped aperture  136  in the hole saw body and prevents the lug from sliding. To unlock the blade from the body the stud  134  may be depressed and then the lug slid down to unlock the blade from the body. Once the hole saw blade is attached to the body the configuration of the various lugs  129  that have non-parallel surfaces to the longitudinal axis of the hole saw body and blade ensures that the blade is firmly locked to the body and cannot disengage itself. Given that the various lugs are typically not symmetrical nor equally spaced around the blade a marker may be used on both the blade and the body (not shown) to assist in the user correctly positioning the blade on the body. 
     Yet other ways of locking the lug in place may be used including an embodiment where a groove may engage protruding pins and so on. It is not intended to limit the invention to a particular way of causing the locking to occur. 
       FIG. 5  through to  8  illustrate the adaptation of different type of cutting blades  FIG. 5  illustrating the hole saw body  138  with the locking mechanism  122  of  FIG. 4 ,  FIG. 6  illustrating a metal hole saw blade  140  attached to the body,  FIG. 7  illustrating a concrete drilling blade  142  attached to the body  138  and  FIG. 8  illustrating a timber drilling blade  144  attached to the body. 
       FIGS. 9-11  illustrate a further embodiment of the present invention. Shown in the figures is a hole saw assembly  210  including a hole saw body  212 , intermediate portion (extension piece)  214  and hole saw blade  216 . The hole saw blade  216  includes a cylindrical body  218  with cutting teeth  220  at one end thereof. The arrangement of the cutting teeth differs for each application and in this embodiment shown is a hole saw blade  216  with a plurality of cutting teeth  220 . However it is to be understood that the blade may have different cutting arrangements and teeth for different materials. 
     At the opposite end of the hole saw blade  216  is an engagement means by which the blade  216  can be attached to the intermediate portion  214 . The engagement means is wave shaped including peaks  218  and troughs  220  in the blade that engage correspondingly shaped troughs  222  and peaks  224  in one end  226  of the intermediate portion  214 . The peaks extend over the troughs so to connect the blade to the intermediate portion they have to be rotated with respect to each other. Once in that position the blade and the intermediate portion are locked to each other and can only be disengaged by rotating them relative to each other in the opposite direction. 
     In a similar manner the intermediate portion  214  can be attached at the other end  228  to the hole saw body  212 . In case where the hole to be drilled is not deep at all, the intermediate portion can be dispensed with and the blade  216  directly attached to body  212 . 
     In order to prevent the pieces form rotating with respect to each other locking means  229  are provided both in the body  212  and the end  226  of the intermediate portion  214 . Typically there are two locking means in the blade and two in the intermediate portion. The locking means consists of a retention clip  230  longitudinally slideable from a first to a second position, illustrated in the first position in  FIG. 9  and in the second position in  FIGS. 10 and 11  where in the second position the clip  230  engages a recess  232  in the intermediate piece  214  or the blade  216 . This prevents relative rotation of the intermediate portion to the body and relative rotation also of the blade to the intermediate portion. The clip  230  includes grooves on its sides that engage tapered rails on the side of the recess to prevent them from moving outwardly. However other arrangements may well be used. A tab  233  is attached to the clip  230  through a hinge  234  allowing the tab  233  to sit on the surface of the body in the first position. When the clip  230  is slid into the recess, the tab  233  is then pushed and clicked into the body  212  to prevent the clip  230  from sliding back. Obviously the size of the tab and the space in the body  212  that it is clicked into is such to allow such a snap-fit arrangement. 
     To assist in removing the tab  233  from the body  212 , a small cut out  236  is employed so that the tab  233  may be prised out of engagement with the body  212  and then lifted to allow the clip  230  to be slid back. 
     The tab is securely attached to the clip through a plastic extension  38  that locks into a space (not shown) in the clip  230 . Again it is to be understood that other ways of attaching the tab to the clip may equally well be employed. 
     It is important to understand that the present embodiment teaches a removable hole saw blade that is adapted to be removably attached to a hole saw body and whose length can also be increased by using an intermediate piece. The advantages of this is that the user only needs to have one hole saw body, one intermediate piece and several blades to be able to cut through a range of materials and of varying depths. 
     Not only is this more space effective and cheaper but it has the result that once a hole saw blade has worn out it can be simply replaced and used with the original hole saw body. This has the effect of saving on materials and thus cost. 
     The locking mechanism that locks the pieces to each other to the hole saw body is contained within the footprint of the piece, that is, does not protrude in any direction, enabling the hole saw to be used for deep drilling. 
     Further advantages and improvements may very well be made to the present invention without deviating from its scope. Although the invention has been shown and described in what is conceived to be the most practical and preferred embodiment, it is recognized that departures may be made therefrom within the scope and spirit of the invention, which is not to be limited to the details disclosed herein but is to be accorded the full scope of the claims so as to embrace any and all equivalent devices and apparatus. 
     In any claims that follow and in the summary of the invention, except where the context requires otherwise due to express language or necessary implication, the word “comprising” is used in the sense of “including”, i.e. the features specified may be associated with further features in various embodiments of the invention.