Note: Descriptions are shown in the official language in which they were submitted.
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~ITLE OF THE INVENTION
COMBINATION MITRE AND TABLE SAW
BACRGROUND OF THE INVENTION
This invention relates to chop saws and ~
5particularly to a combination mitre and table saw, ~ -
otherwise known as a flip-over saw. In particular, the
invention relates to such a saw which is capable of
making bevel cuts in both its table saw mode and mitre
saw mode.
Mitre saws usually, and table saws always, require
a slot to be provided in the workpiece support or
table, through which the saw blade will pass. In a
mitre saw, the saw blade passes through the slot in the
workpiece support once it has cut through the
15workpiece; in a table saw, the saw blade is mounted
below the workpiece support and passes through the slot
so as to present a cutting edge above the workpiece
support, to which the workpiece may be presented. In
order to keep to a minimum any damage which is done to
20the side of the workpiece which is adjacent the
workpiece support as the saw blade emerges from the
workpiece, the slot in the workpiece support is -~
generally to be kept as narrow as possible. ~-
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When a saw, whether it be a mitre saw or a table
25saw, i5 capable of making bevel cuts at a variety of
different bevel angles, the slot in the workpiece
support must be capable of accommodating the saw blade
at any one of that variety of angles. Since the
critical width of the slot in the workpiece support is
30its width at the surface of the workpiece support which
is actually supporting the workpiece, namely the upper
surface, the requirement for minimal damage to the
workpiece has led to the axis about which the saw blade
pivots, in order to alter the bevel angle at which it
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is cutting, being arranged to coincide with the upper
surface of the workpiece support. An example of a
mitre saw which includes such an arrangement is
described and illustrated in US-A-4537105. In that
5saw, the workpiece support includes a bearing block
having a part circular guide slot. The saw blade
mounting includes a similar bearing block and the two
bearing blocks co-operate to allow relative arcuate
movement about the centre of curvature of the guide
IOslot. The centre of curvature of the guide slot
coincides with the top of the slot in the workpiece
support.
US-A-4531441 illustrates and describes a
combination table and mitre saw, i.e. a flip-over saw,
l5which utilizes a similar bevel pivot arrangement. In
this saw, the bevel axis of the saw blade is arranged
to coincide with the upper surface of the workpiece
support when the saw is operating as a table saw.
Consequently, when the saw is operating as a mitre saw,
2()the bevel pivot axis coincides with the lower surface
of the workpiece support. Accordingly, when operating
as a mitre saw, this saw gives relatively poor
protection to the workpiece against damage caused by
emergence of the saw blade. If the bevel angle is
25adjustable between + 45 from the vertical, this will
require that the slot in the workpiece support, when --
the saw is operating as a mitre saw, being at least ~-
twice as wide as the workpiece support is thick. - ~-
A further problem with the type of bevel pivot
30exemplified by the above two documents is that there is
a tendency, owing to the inevitable tolerances in the
mating surfaces of the part circular or part
cylindrical bearing parts, for there to be a certain
amount of play in the pivot. This results in the bevel
35pivot axis not being well-defined, which in turn means
that the slot in the workpiece support must be widened
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somewhat to take this into account, not to mention the
inaccuracies that this results in the cutting of the -~
workpiece.
, :
The above problem ~has been recognized, and a
5solution proposed in the context of mitre saws, in -~
US-A-4934233. In the saw illustrated and described in ~ -
this document, the bevel pivot arrangement described
above has been replaced with a pair of cylindrlcal
parts of identical diameter, the end surfaces of which
10are abutted together and which are permitted to rotate
relative to one another about a central spindle. The ` ~
use of a central spindle enables the bevel pivot axis ~ -
to be well-defined, the axis being positioned to ~ -
coincide with the upper surface of the workpiece
l5support, and the radial extent of the cylinders reduces -~
substantially the amount of play in the pivot.
However, since the use of the cylindrical parts
inevitably means that there will be projections both
above and below the workpiece support, such an ~ -~
20arrangement is unsuitable for use with a bench saw and
consequently unsuitable for use with a flip-over saw.
BRIEF SUMMARY OF THE INVENTION
It is an object of the present invention to
provide a saw having a bevel pivot of improved
25stability.
Accordingly, the present invention provides a saw
comprising a frame, a table mounted in the frame having - -
first and second substantially planar parallel opposed
table surfaces, the table being pivotable in the frame
3()between two positions, a pivot block mounted on said
first surface, a pivot member pivotally mounted on said
pivot block for pivoting about a first axis
substantially parallel and within the confines of said
first and second surfaces, a saw assembly mounted on
35said pivot member and comprising a saw blade lying in a
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plane containing said first axis, a slot in the table ~;
adapted to receive said blade to enable cutting of
workpieces supported on either surface of the table,
and clamp means to clamp said pivot member and block
5together, wherein said first axis is defined by first
and second opposed arcuate pivot surfaces between said
pivot member and one or both of said table and pivot
block, at least the first pivot surface being defined
between said first and second table surfaces.
Said pivot surfaces may comprise a bore in a
projection of said pivot member and a pin spanning a
slot in the table, said projection being received in
said slot.
Alternatively and preferably said first pivot
15surface is defined by a part substantially cylindrical
surface of a projection of said pivot member and a part
substantially cylindrical surface of a recess formed in
said table, said projection being received in said
slot.
In this event said second pivot surface may
comprise another part substantially cylindrical surface
on said projection and a part substantially cylindrical
surface on said pivot block above said first surface.
In this way two conflicting requirements are met.
25Firstly there is no projection beyond said second
surface, which in use forms the working surface of the
saw in bench saw mode of operation of the saw and which
requires a flat unencumbered surface for efficient
operation. Secondly, the pivot axis of the pivot
30member is securely positioned and has little or no
opportunity to float which would otherwise give rise to
positional error of the blade.
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Preferably said pivot axis is intermediate said
first and second surfaces and most preferably centrally
between them so that the slot entrance at either
surface can be minimised. ~; ~
5 Preferably said part substantially cylindrical -
surface of the recess subtends an angle of 180 less
the angle of pivot required of the pivot member about
said first axis.
Preferably said projection is supported axially
I()against movement thereof. Said axial support may
comprise a radial surface with respect to said first
axis being formed in said recess. Adjustment means may "
be provided to adjust axially said radial surface.
îSaid adjustment means may comprise a wedge section
15received in said table at the end of said recess and
forming said first radial surface, and screw means
received in said wedge section and adapted to draw said
section axially with respect to said first axis.
As with US-A-4531441 and US-A-4537105, the pivot ~ -~
20block preferably also co-operates with the pivot member
to allow sliding arcuate relative motion of the pivot
block and the pivot support about the first axis. For ~ ~ -
convenience, it is preferred that said clamp means
comprises the pivot block having an arcuate slot and ; -
25the pivot member having a locating pin, such as a
releasable bolt which is operable to secure the pivot
member to the pivot block.
Preferably, said pivot member further comprises a
pivot guida mounted on the pivot block on the side ~
3~thereof remote from the pivot member and between which ~: -
the pivot block is clamped when said releasable bolt is
tightened. Said pivot guide serves, inter alia, to -
-` 212988~ ~ close the arcuate slot in the pivot block and prevent
the ingress of dust.
For reasons which will be apparent, it is also
preferred that the pivot member includes stop surfaces
5adapted to abut the table to limit the relative
rotation of one with respect to the other in both
directions.
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF TNE DRAWINGS
The present invention will now be described by way
10of example with reference to the accompanying drawings,
wherein~
Figure 1 is a side view of the saw;
Figure 2a is a side view in greater detail of a
first bevel pivot arrangement; - -
Figure 2b is a side view of a second and preferred
bevel pivot arrangement;
Figure 3a is a front view of the bevel pivot
arrangement of Figure 2a; and
Figure 3b is a similar view of the preferred
20arrangement.
DETAILED DESCRIPTION -
In Figure 1, a saw 10 comprises a saw assembly 20
mounted on a workpiece support or table 16. The -~
mounting is such as to allow pivotal motion of the saw
25assembly 20 relative to the table 16 about two spaced, --~
orthogonal axes 28,92. A pivot support 26 is pivotally
mounted on the workpiece support or table 16 about an
axis 92 which is parallel to the upper and lower
surfaces of the workpiece support 16 and coincident
30with the plane of the saw blade, in a manner which will
be more particularly described with reference to
Figures 2 and 3. The saw assembly 20 is itself
pivotally mounted on the pivot support 26 about a ;~
second axis 28 which is perpendicular both to the first -
35axis 92 and to the plane of the saw blade. Pivoting
7 212988~
about the second axis 28 enables the saw assembly 20 to
be raised and lowered and to allow a saw blade under a ~ ;
lower guard 36 to engage and cut a workpiece supported ;~
on the table 16 against a fence 17.
To enable the saw 10 to perform mitre cuts when
operating as a mitre saw, a circular portion of the
table 16 is rotatable about a vertical axis with
respect to the remainder of the table. The saw
assembly 20 rotates with the circular portion of the
IOtable 16. The fence 17 is fixed in position on the
remainder of the table 16.
The saw can be rendered a table saw by plunging
the blade into a slot (not shown) in the table and
locking the saw assembly in this position. The table
1516 is then pivoted by means (not shown) through 180 so
that the undersurface of the table is then uppermost -~
and the saw blade protrudes from beneath. Such a saw
was first described in DE-A-1628992, although a
preferred pivot arrangement for the table 16 is
20described in our copending British application number
9218363.1.
Pivoting of the saw assembly 20 about the first
axis 92 enables the saw 10 to make bevel cuts when
acting as a mitre saw or when acting as a table saw.
25As can more clearly be seen from Figures 2 and 3,
pivoting of the pivot support 26, and hence of the saw .
assembly 20, about the first axis 92, is controlled by ~
two concentric opposing pivot surfaces (described ! ~ ".
further below) centred on the pivot axis 92. The use
30Of dual concentric pivot surfaces reduces substantially
the likelihood of any unwanted floating of the bevel ~ -~
axis.
A pivot block 27, which is rigidly affixed to the
circular, rotatable portion of the table 16, ;;-
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co-operates with the pivot support 26 so as to allow ~ ; -
sliding arcuate relative motion of the two. The pivot
member 26 has a bolt 17 passing through it and this
bolt 170 is received within an arcuate slot 173 in the
Spivot block 27. The bolt 170 is adapted to secure the
pivot support 26 to the pivot block 27, and is
releasable. To this end, the bolt 170 is provided with
a handle 172 and co-operates with a captive nut or
other captive thread in known manner. In particular,
IOthe bolt 170 may be such as is described in our British
Patent Application No. 9218366.4.
In a first alternative arrangement, said
concentric opposing pivot surfaces are formed by a pin
or spindle 92' which is recessed into the rotatable
lSportion of the workpiece support or table 16 and which
laterally spans a semicircular recess 90 therein. The
pivot support 28 has a corresponding lug or projection
88 which is received in the semicircular recess 90, and
through which the spindle 92' passes. Thus relative
20rotation of the pivot support 26 with respect to the ~ ~-
workpiece support or table 16 occurs about the spindle
92'. This arrangement provides for stable pivoting,
and also locates the first axis 92 between the surfaces
of the workpiece support 16, in this case centrally
25between the surfaces, so as to enable the width of the - -~
slot (not shown) in the workpiece support 16, which is
necessary for passage of the saw blade, to be kept to a
minimum. -
A further degree of stability for the bevel pivot
30is afforded by the fact that the lug 88 of the pivot
support 26 is tightly received within the semicircular
recess 90, thereby preventing unwanted axial movement. ~;~
However, a perceived potential problem with this ;
arrangement is seen in that, if the clamp formed by the
35bolt 170 is loosened more than necessary, extreme
2129884
bending forces about an axis parallel the axis 28 may
be imposed on the pin 92' by the weight of the saw
assembly (at least in table saw mode) so that there is
a danger of the pin and/or table in that region bending
Sand causing significant damage to the saw.
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Consequently, Figures. 2b and 3b illustrate a
second and preferred bevel pivot arrangement. In this
case, there is no pin or spindle; the pivot lug 88 is
simply received in a correspondingly shaped,
lOsemicircular recess 90 in the rotatable portion of the
table 16. In addition, the pivot block 27 and the
pivot lug 88 each support a part-cylindrical surface
130,132, the surface 130 carried by the pivot block
being press-formed on a plate 134 attached thereto.
15The surface 130 carried by the pivot block 27 faces -
towards the first axis 92; the other surface 132 faces
away. With the saw operating as a chop saw, load is
borne by the lug 88 and recess 9o. However, when the
saw is in its table mode, it is the part-cylindrical
20surfaces 130,132 which do this job. Both the lug 88 and
recess 90 arrangement and the pair of part-cylindrical
surfaces 130,132 provide for pivoting about the first
axis 92 and co-operate to provide a stable pivot axis.
The lug 88 is axially supported against movement ~
25by the ends of the recess 90. Towards the pivot block ~ ~ `
27 there is a small clearance between the lug 88 and
end 91 of the recess which is not taken up when the
clamp bolt 170 is tightened. However, the lug may abut
that end when the saw is in its bench saw mode and the -
3()bolt 170 is overly loosened. However the flexibility
in the plate 134 in the region of its surface 130 can
accommodate torsion loads without permanent damage to ~ `~
the table or lug being caused. At the other end, a
nylon or like material wedge 180 is secured by a screw -~
35 182. Tightening the screw draws the plug 180 -~
downwardly and axially against the lug 88 and thereby ~--
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supports the lug when the bolt 170 is loosened when the
saw is in its chop saw mode. If the bolt 170 is overly
loosened in this position only small forces act on the
plug through the pivot support 26 attempting to pivot
Sabout an axis more or less passing through the bolt 170
but lying parallel the pivot axis 28. If the forces
are sufficient to damage the wedge 180 then this
component is easily replaced.
The pivot support 26 is also provided with a pair
IOof stop surfaces 174,176 which respectively limit ~ -
movement of the pivot support by abutting the table 16
when the pivot support 26 is vertical and inclined at
an angle of 45 with respect to the table or workpiece
support 16.
Thus the advantage gained by both embodiments of
the invention is that a precise location of the bevel --~
axis is achieved, much like that achieved in
US-A-4934233, but, on the other hand, the lower pivot
surface (when in mitre saw mode) does not extend below
20the level of the bottom surface 16b of the table. - --~
Hence it will not encumber this surface with
protuberances which would hinder efficient use of the ~
saw when it is switched to bench saw mode. ~ ~ ;
It will of course be understood that the above --
25description has been given purely by way of example and
that modifications of detail may be made without
departing from the scope of the invention.
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