Abstract:
A convertible miter/table saw comprises a base frame supporting a lower, miter saw table rotatable about a vertical axis. A circular saw assembly, namely a saw blade and motor, is mounted on a rear pedestal of the table and pivotable about a horizontal axis, the miter saw table providing a turntable and having a lower saw slot for receiving the saw blade. In miter saw mode, the swivel position of the miter saw table is adjusted and the circular saw blade moved downwards into the lower saw slot. In table saw mode, an upper saw table connected to the rear of the base frame is pivoted about a horizontal axis from a raised, generally vertical position to a lowered, generally horizontal position in which a slot in the upper saw table accommodates the circular saw blade when the latter is aligned therewith.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
   The present application claims the benefit of U.S. Provisional Patent Application Ser. No. 60/845,220 filed Sep. 18, 2006, the contents of which are hereby incorporated by reference in its entirety. 

   STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
   Not applicable. 
   REFERENCE TO A “SEQUENCE LISTING” 
   Not applicable. 
   FIELD OF INVENTION 
   The present invention relates to convertible circular saw apparatus and, in particular, to circular saw apparatus that can be readily converted to function as either a miter saw or a table saw. 
   BACKGROUND 
   Contractors doing construction or renovation work, such as installing kitchen cabinets, usually need both a miter saw for making accurate angled cuts across workpieces, and a table saw for performing straight cuts along large workpieces. Two saws clutter up the workplace, especially if it is confined. Also, it is a nuisance to transport two saws from site to site. Furthermore, professional quality saws are quite expensive. It is therefore desirable to have a saw which can perform both functions. 
   The prior art contains various examples of convertible saws which may be used in a first mode as a miter saw, or sometimes as a simple chop saw for making perpendicular cuts across workpieces, and in a second mode as a table saw. An early example, U.S. Pat. No. 1,924,672, issued Aug. 29, 1933 to Zachara, shows a type of convertible saw, which, to my knowledge has not been commercially adopted. This is a complex saw which provides mitering, cutting off, squaring, dadoing of convex or concave surfaces, tenoning, grinding or ripping, all saw operations being performed with a single circular saw blade. It includes abase unit having rails along which upper parts carrying the saw can run to perform cutting off. On this base unit is mounted an upper base unit having a vertical axis swivel carrying a horizontal axis pivot about which an arm carrying the saw and motor combination is mounted; this provides the miter cutting. Above this arm and saw/motor combination is a saw table, which is pivotally mounted so that it can be lifted up to allow mitering and other operations without interference, and can be lowered to a horizontal position, when the saw is suitably aligned to protrude through a slot in the table, in which position the saw can operate as a table saw. 
   In the Zachara design, the saw is belt-driven by a motor which is behind the swivel axis of the saw arm, while the back guides against which workpieces are held for miter cutting are well in front of the swivel axis. With this design it would seem that the miter angles which could be cut would be rather restricted. A further disadvantage is that, because the saw is intended to be used in so many different ways, including use as what amounts to a radial arm saw, it is very complicated and would not be particularly portable. Consequently, it would be of little or no use to a contractor who wished to use a single miter/table saw to do construction or renovation work at a customer&#39;s premises. 
   Present day miter saw designs differ considerably from Zachara&#39;s design in that they have compact gear drives, and swivel tables of the turntable type. Convertible versions of these saws may conveniently be described as “flip-over” saws, which have a base frame which pivotally supports the combination of a circular saw assembly and saw table, this combination being capable of being flipped over through 180°. In a first orientation, the saw assembly is above the table and has a handle by which it may be pressed down towards a slot in the table to perform chop or miter cuts. In the second orientation, the saw assembly lies below the table and can be fixed in position under the table to protrude through the slot, and so is usable as a table saw. “Flip-over” saws of this kind are represented by the following U.S. patents:
         U.S. Pat. No. 5,960,691, issued Oct. 5, 1999 to Garuglieri;   U.S. Pat. No. 5,787,779, issued Aug. 4, 1998 to “ ”;   U.S. Pat. No. 5,570,641, issued Nov. 5, 1996 to “”;   U.S. Pat. No. 5,513,548, issued May 7, 1996 to “ ”;   U.S. Pat. No. 5,189,937, issued Mar. 2, 1993 to it ”;   U.S. Pat. No. 4,531,441, issued Jul. 30, 1985 to Bergler;   U.S. Pat. No. 3,570,564, issued Mar. 16, 1971 to “ ”;   U.S. Pat. No. 2,851,068, issued Sep. 9, 1958 to Goodlet.       

   The “flip-over” design has some drawbacks. Firstly, the base frame has to be fairly large to provide space which allows the table and motor-saw blade combination to flip over through 180°, so such designs tend to be somewhat cumbersome. Also, the motor-saw blade combination is heavy, so the pivot mechanism must be robust and the user may find it awkward to switch from one mode to the other. 
   Another problem is that some of the most desirable miter saws are not adaptable to the flip-over design, since the saw table is in the form of a turntable having the required saw slot. This turntable also has structure below the slot, used for mounting or moving the turntable, which structure would not allow the miter saw to be inverted and used as a table saw. Such miter saws include those manufactured by Makita Corporation, for example that shown in U.S. Pat. No. 4,638,700, issued Jan. 27, 1987, which is otherwise a desirable type of miter saw for professional work. The turntable structure shown in  FIG. 2  of that patent would not allow the saw blade to project through the turntable, so it would be unsuitable for use in a “flip-over” convertible saw design. 
   SUMMARY OF THE INVENTION 
   An object of the present invention is to overcome or at least mitigate the disadvantages of such known convertible saws, or at least provide an alternative. In accordance with one aspect of the present invention, circular saw apparatus usable as either a miter saw or a table saw, comprises:
         a base frame;   a mounting pedestal to the rear of the base frame;   a lower, miter saw table rotatably mounted on the base frame for swivelling movement about a vertical axis, the miter saw table having a lower saw slot for receiving a circular saw blade;   a circular saw assembly having a saw blade and motor combination pivotally mounted on the rear mounting pedestal for pivoting relative thereto about a horizontal axis, whereby the miter table provides a turntable for the circular saw assembly;   handle means for adjusting the swivel position of the miter saw table and for moving the circular saw about the horizontal axis so that the saw blade can move into and out of the lower saw slot;   a workpiece back guide fixedly mounted on the base frame for positioning a workpiece on the miter saw table and located behind the vertical axis of the miter saw table so that the circular saw can be used in miter saw mode, upon adjustment of the swivel position of the miter saw table, by downwards movement of the circular saw blade into the lower saw slot by manipulation of the handle means;   an upper saw table pivotally connected to a rear portion of the base frame for movement about a horizontal axis between a raised position and a lowered, generally horizontal position, the upper saw table when in the raised position being clear of the circular saw assembly when the saw assembly is being used in miter saw mode, the upper saw table having an upper saw slot which accommodates the circular saw blade when the latter is aligned therewith and when the upper saw table is in the lowered position.       

   This circular saw apparatus may further comprise movable posts which support the front of the upper saw table above the base frame when the upper saw table is in its lowered position, these posts being movable clear of the space between the upper saw table and the base frame when the upper saw table is raised. The posts may be pivotally attached to either the base frame or the upper saw table. 
   Preferably, the miter saw will have a guard which will prevent the upper part of the saw blade protruding through the upper saw table slot, and accordingly this guard will be partially or wholly removed when the saw assembly is to be used as a table saw. In the preferred embodiment, this guard includes a lower portion which protects a lower front portion of the circular saw blade at all times, and a removable upper portion adapted to be removed when the upper saw table is to be lowered over the saw blade to allow the saw blade to project through the upper saw slot. 
   The handle means may include a handle projecting forwardly from the miter saw table and usable to adjust and lock the swivel position of the miter saw table. 
   Embodiments of the invention also may be provided in the form of a conversion kit for converting a circular miter saw into a combination saw which is additionally useable as a table saw, in which the circular miter saw is of the kind having a base frame, a turntable with a saw slot mounted on the base frame for swivelling motion about a vertical axis, a pedestal at the rear of the turntable and having a saw arm mounted thereon about a horizontal pivot; a circular saw assembly including a saw blade and motor mounted on the saw arm, handle means for operating the saw arm, and a workpiece back guide fixedly mounted on the base frame, and having a guard for the blade. This is a type of miter saw much used by professionals, as manufactured for example by Makita Corporation (see, for example, the above-mentioned U.S. Pat. No. 4,638,700), and which usually has structure under the turntable which would prevent it being used in the “flip-over” manner. A suitable conversion kit for such a miter saw includes;
         a) an upper saw table and pivot means for connecting the upper saw table to a rear portion of the miter saw base frame for movement about a horizontal axis between a raised and a lowered, generally horizontal position, the pivot means being such that the upper saw table, when in the raised position, is clear of the circular saw when the saw is being used in miter saw mode, the upper saw table having an upper saw slot which accommodates the circular saw blade when the latter is aligned therewith and when the upper saw table is in the lowered position,   b) means for supporting the front of the upper saw table above the miter saw base
 
frame when the upper saw table is in its lowered position, and
   c) means replacing the saw blade guard with a guard which is, at least in part, readily removable to allow the saw blade to project through the slot in the upper saw table.       

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     A preferred embodiment of the invention will now be described by way of example only with reference to the accompanying drawings, in which; 
       FIG. 1  is a perspective view of a convertible saw embodying this invention in the table saw mode; 
       FIG. 2  is a side view of the same saw in the process of being converted to its miter saw mode; 
       FIG. 3  shows a side view of the saw in the table saw mode; 
       FIG. 4  shows a front view of the saw in the table saw mode; 
       FIG. 5  shows a rear view of the saw in the table saw mode; 
       FIG. 6  shows a detail of a catch used to secure the upper saw table in the lowered position; 
       FIG. 7  shows a detail of the locking means for holding the saw assembly arm in the table saw position, and 
       FIGS. 8   a  and  8   b  show further views of the locking means for the saw assembly arm. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
     FIGS. 1 and 2  illustrate the general arrangement of the convertible saw in its two different modes, with the upper saw table  10  respectively in its lowered position over the miter saw components to provide the table saw, and in its raised position allowing normal usage of the miter saw. 
   As indicated, the basis of the convertible saw is a miter saw of the kind made by Makita Corporation, and is similar to that described in afore-mentioned U.S. Pat. No. 4,638,700. It has a base frame  12  having a raised, rectangular, planar portion  12   a  supported by four feet  12   b . The base portion has a central enlargement including a protruding, part-circular front portion  12   c , and this enlargement is provided with a concentric, circular, open-bottomed recess  12   d . This recess accommodates a disc-like turntable  14  having a lower saw slot  16  extending along a part of its diameter. The rotational position of the turntable  14  can be adjusted by means of a handle bracket  18  fixed to the bottom of the turntable  14  and movable in the open bottom of recess  12   d , this bracket extending forwards of the base frame and including a raised front lug  18   a  which has a threaded bore to receive the threaded shaft of a turntable handle  20 . The rear end of this threaded shaft can be locked onto the outer side of the part-circular front portion  12   c , to fix the angular position of the turntable, by twisting handle  20 . 
   The rear of the turntable  14  carries a rear mounting pedestal  22 , best seen in  FIG. 2 , and the upper end of this pedestal has a horizontal pivot  24  carrying an arm  26  which supports a circular saw assembly including a saw blade  28  and an electric drive motor  30  that drives the blade through a gear train. The arm  26  is urged upwardly by spring means (not shown), and is manipulated by a handle  32  at the front end of the arm, this handle having an on/off switch  34  ( FIG. 2 ) on its underside for use when the saw is in the miter cutting mode. 
   A workpiece guide or fence  38  extends across the rear portion of the turntable  14 , being fixed to outer side areas of the base frame  12 , this fence having a central aperture or recess to accommodate the saw blade  28 . 
   The items so far described are conventional for miter saws, and similar parts are shown for example in the Makita Corporation &#39;700 patent referred to above. As is also usual for miter saws, the upper portion of blade  28  is covered by a guard  40 . Here, however, the guard is modified by having a fixed lower portion  40   a  which covers a lower front part of the blade at all times, but leaves uncovered an upper part, perhaps ⅓ or ¼, of the blade  28 . The upper blade part may be covered by a removable upper guard portion  40   b , shown in  FIG. 2 , having guide plates  42  extending into the top cavity of the portion  40   a  and also having spring clips  44  extending from its lower sides, by which it can be removably attached to the lower portion  40   a  when the saw is used in the miter saw mode. 
   The other additions to the miter saw, which make it convertible for use as a table saw, will now be described. 
   At the rear corners of the base frame are provided pivot brackets  50 , each bracket being formed by a pair of upstanding lugs  52  fixed to the rear of an elongate base plate  53  which extends forwardly under the feet  12   b  of the base frame and is attached thereto. Each pair of lugs supports a horizontal pivot  54  which mounts a back support post  56  fixed to a rear corner of the upper saw table  10 . The rear sides of the support posts  56  are provided with rearwardly protruding legs  57  by which the table  10  is supported, by the contact of legs  57  with a support surface, when the upper saw table  10  is in the vertical position shown in  FIG. 2 . In addition, each pivot  54  has a screw threaded portion and a knurled knob  58  for locking the leg  56  relative to the bracket  50 . 
   In its lowered, horizontal position, the front of upper saw table  10  is supported by two movable posts  60 . These posts have their lower ends pivotally held by brackets  62  fixed to the front of the base frame  12  at the sides of the enlarged portion  12   c . When the upper saw table is lowered, the posts  60  are placed vertically and are located in position by locking clips  64  (see  FIG. 6 ) pivoted to the underside of the table  10  at the front. As shown in  FIG. 6 , each clip  64  is pushed by a spring plate  65  into a locking position wherein a shoulder  67  of the clip  64  engages a stop face  68  in a complementary recess  69  in leg  60 . When the user wishes to lift the upper saw table  10  to the  FIG. 2  position, the locking clips  64  can be disengaged from the recesses  69  and the posts  60  can be swung out sideways and laid horizontal (see  FIG. 2 ) so as not to interfere with miter saw operations. The use of recesses  69  presumes that the legs  60  are solid, which is preferred. If the legs were tubular, of course, an alternative locking arrangement could be used, as appropriate. 
   The upper saw table  10  has a fore-and-aft extending upper saw slot  70  which can receive an upper part of saw blade  28  when the saw arm  26  is in a generally horizontal position and aligned with the slot  70 , when the upper guard portion  40   b  has been removed, and when the table  10  is in the lowered position. The saw slot  70  then generally overlies the lower saw slot  16  of the turntable, and also overlies the swivel axis of the turntable  14 . The Upper saw table  10  may have the usual accessories of a table saw, including an adjustable side guide  72  controlled by a handle  74 . Also, the upper saw table  10  carries control buttons  76  which are used to control the saw motor when the saw is being used in table saw mode. 
     FIGS. 7 ,  8   a  and  8   b  show details of an adjustment mechanism  80  for fixing the position of the saw arm  26  ( FIG. 2 ) when operating in the table saw mode; this mechanism is disengaged when operating in the miter saw mode. The mechanism includes a lug  26   a  extending from the rear end of the saw support arm  26 , behind pivot  24 , and this lug  26   a  carries a threaded sleeve  82  in which is mounted a threaded shaft  83  rotatable by knob  84  at one end thereof. As seen in  FIG. 8   a , the outer end of shaft  83  has a reduced diameter portion  83   a  at its opposite end which can engage in a recess  86   a  ( FIG. 8   a ) in a locking plate  86  shown in  FIG. 8   a . This plate  86  is pivotally attached to a lug  88  held by an upper end portion of the pedestal  22  and urged into engagement with the shaft  83  by a leaf spring  89 . 
   When the saw is being used as a table saw, the plate  86  engages the shaft  83  as described, and rotation of the knob  84  can adjust the height of the arm  26  and therefore of the saw blade  28 ; and can thus adjust its amount of protrusion through the upper table slot  70 . When the saw is used as a miter saw, the user urges plate  86  against the spring  89  and disengages it from the shaft  83 , allowing the saw blade and motor to be raised and lowered. 
   It will be understood that, in operation as a miter saw, the upper table  10  will be raised to the vertical position of  FIG. 2 , and held there by tightening of the knobs  58  to secure the rear pivots  54 . Also, the front support posts  60  are pivoted outwards to lie horizontally, so as not to interfere with miter saw operations. The top portion  40   b  of the saw guard is put in place, and the plate  86  is pivoted to release recess  86   a  from the shaft  83 . The saw can then be used as a conventional miter saw, the motor being controlled by switch  34 . 
   For use as a table saw, upper guard portion  40   b  is removed, the turntable is adjusted by handle  20  so that the saw blade  28  is aligned with the saw slot  70  in the upper saw table  10 , the plate  86  is engaged with the recess  83   a  in shaft  83 , and the knob  84  adjusted to the required height for the saw blade. The posts  60  are swung into the vertical position, and the upper table is lowered into the horizontal position of  FIGS. 1 ,  3 ,  4 , and  5 . The saw is then used as a table saw, under the control of buttons  76 . 
   Some known miter saws have a gearbox between the saw blade and the motor drive shaft and the saw blade is offset downwardly relative to the motor drive shaft by as much as 1.5 inches. While this may be acceptable for a miter saw which has no other function, it is preferable for embodiments of the present invention to have the saw blade  28  and motor drive shaft either coaxial, as in the above-described preferred embodiment, or offset (say by way of a gearbox) so that the axis of the saw blade  28  is offset upwards relative to the axis of the drive shaft of motor  30 . Either of the latter two arrangements may allow the saw blade to protrude as much as 2.5 inches above the upper table  10 , especially if a 12 inch diameter saw blade is used, and thus enable thicker lumber to be sawn. 
   Embodiments of the invention can also be considered, and sold, as a kit of parts for transforming a miter saw of the type described into a convertible miter/table saw. The kit of parts would include the upper table top assembly comprising the pivot brackets  50  held by base plates  53 , the latter being suitable for fixing under the feet of the base frame  12  of the miter saw, and the rear legs  56  and upper table  10 , with parts carried thereby. The kit would also include the brackets  62  for attachment to the front of the base frame, with the pivotally attached posts  60 . Also, the kit would include the two-part blade guard  40 , and the components of the blade height adjustment mechanism  80 . 
   The contents of the various patents identified hereinbefore are incorporated herein by reference. 
   It will be appreciated by those skilled in the art that changes and modifications may be made thereto without departing from the invention in its broader aspects and as set forth in the following claims.