[0001] The present invention relates to a power tool arranged to perform a plurality of
operations and has particular, although not exclusive, relevance to a power tool which
is interchangeable between the two tasks of sanding and planing a workpiece.
[0002] The general concepts of a power tool having interchangeable operative parts are known.
For example, UK patent number GB 1515390 discloses a power tool which is said to be
of modular construction. The tool comprises a battery unit which is adapted to accept
any one of a plurality of operative parts, such as a hedge clipper or a screwdriver.
Each of the operative parts has its own motor and an arrangement for converting the
output of the motor (usually a rotating spindle) into the type of drive necessary
for that particular tool. For example, a linear reciprocating drive is needed for
the hedge clipper, whereas a low rotational velocity, high torque drive is needed
for the screwdriver.
[0003] This known device therefore suffers from the disadvantage that the only common part
to all the tools is the battery. Also as each operative part must include a motor
and the necessary drive train/gear system to allow it to carry out its function, the
element which makes up the components for the tool can become very expensive and bulky.
[0004] In EP-A-698449 there is disclosed a modular power tool having separate motor and
drive mechanisms. The two mechanisms are brought into operative engagement by sliding
and rotating the motor relative to the transmission. This device is limited in that
the transmission may only be used as a drill/driver and is not able to function in
any other mode.
One aspect of the present invention is based on the recognition that the two operations
of sanding and of planing a workpiece are discrete, yet clearly related. Generally
planing is used to remove a larger amount of stock from a workpiece than sanding.
Also, sanding is used to provide a smoother or finer finish to a workpiece than planing.
Or for the removal of previously applied surface coatings. Furthermore, in all of
the prior art which discusses modular tools, none appears to offer the facility of
a tool which can be readily changed from operating as in a sanding mode to operating
in a planing mode (or vice versa) despite the advantages that such an operation could
achieve.
[0005] The present invention also, however, recognises that one of the most efficient forms
of sanding is belt sanding. This utilises a continuous loop of sandpaper being driven
around two displaced rollers, as is known in the art. However, to employ a continuous
loop of sandpaper in a modular tool (where one of the other modules is planer - which
essentially comprises only a single rotating cylinder or cutting device) could well
take up a great deal of space. Thus a modular tool which is able to offer modules
capable of both belt sanding and planing is a difficult challenge to achieve, not
least because of the different space requirements between tools to achieve each function.
[0006] It is thus an object of the present invention to at least alleviate the above shortcomings.
Accordingly, the present invention provides a power tool arranged to perform a plurality
of operations, the operations including belt sanding and planing, wherein the tool
comprises: a housing; a motor within the housing for providing drive to an output
shaft; and a plurality of cartridges, each of which cartridges may be coupled to the
housing and to the drive shaft to enable performance of a respective operation, wherein
one cartridge performs belt sanding and another cartridge performs planing. Not only
is the provision of a modular tool capable of belt sanding and planing particularly
advantageous, but also the provision of interchangeable cartridges to accommodate
each tool, despite the clear differences in the respective features of each tool,
offers significant advantages.
[0007] Preferably the drive shaft projects out of the housing and each cartridge includes
a recess for coupling with the drive shaft. Also the drive shaft may rotate under
the drive of the motor. Further, the motor may be coupled directly to the drive shaft.
[0008] In a preferred embodiment there is provided an interlock formed on the housing for
retaining a cartridge presented for coupling to the housing. Further, each cartridge
may include an interlock mechanism co-operable with the interlock formed on the housing.
[0009] Advantageously, each cartridge may be presented to the body in a predetermined orientation
in order to couple the cartridge with the body.
[0010] The present invention will now be described, by way of example only, and with reference
to the following drawings of which:-
Figure 1 shows a perspective view from below of a tool housing of one embodiment in
accordance with one aspect of the present invention;
Figure 2 shows the same perspective view as Figure 1, but also shows the coupling
of a cartridge according to another aspect of the present invention being coupled
to the housing;
Figure 3 shows a perspective view from below of the coupled housing and cartridge
of Figure 2;
Figure 4 shows a perspective view from above of the embodiment of Figure 3;
Figure 5 shows a perspective view from above of a housing in accordance with one aspect
of the present invention coupled to an alternative cartridge according to another
aspect of the present invention;
Figure 6 shows a perspective view from below of the embodiment of Figure 5;
Figure 7 shows a schematic view of a cartridge in accordance with one aspect of the
present invention;
Figure 8 shows a sectional view taken along the line X-X of Figure 7, and
Figure 9 shows a schematic illustration of another cartridge for use with a power
tool according to an aspect of the present invention.
[0011] Referring now to Figure 1, a housing for a power tool is shown generally as 2. The
housing comprises a handle (4) and a main body (6) in use of the device a user may
hold both the main body (6) and the handle (4) in order to guide the power tool against
a workpiece.
[0012] The underside portion (8) of the housing is shaped to accept a cartridge (described
further below) presented thereto. In order for such a cartridge to be accepted the
underside (8) defines an abutment (10) formed by the two side walls (12 and 14).
[0013] In the side wall (12) is formed an interlock member (16) for co-operable engagement
with a cartridge presented to the housing (2), as will be described below. The side
wall (12) also includes a recess (18) for stock removal/ dust extraction when the
power tool is in use.
[0014] Within the main body (6) is housed a motor (not shown). The motor is a conventional
electric motor and is described with reference to Figures 7 and 9 in more detail.
The motor is coupled to an output shaft (20) for providing drive to a cartridge presented
thereto.
[0015] Referring now also to Figure 2 a cartridge, shown generally as 22, has been presented
to the main body (6) for coupling thereto. In the example of Figure 2, the cartridge
comprises a belt sander module for incorporation with the main body (6) so that the
entire tool (2) (when the main body (6) and the cartridge (22) are coupled operatively
together) operates as a belt sander.
[0016] The cartridge (22) includes a first cylinder (24) and a further cylinder (26). The
cylinders (24 and 26) are surrounded by a continuous loop of sandpaper (28) thereby
forming a belt sander. Those skilled in the art will appreciate that the cylinders
(24, 26) need to be resiliently biassed so as to keep the loop of sandpaper (28) under
sufficient tension so that it may perform efficaciously as a belt sander.
[0017] It can also be seen from Figure 2 that the cartridge (22) includes a further interlock
member (30) which is co-operable with the interlock member (16) on the main body (6)
so as to retain the cartridge (22) in rigid engagement with the main body (6) in operation
of the tool.
[0018] In order to couple the cartridge (22) with the main body (6), the cartridge (22)
must be held relative to the main body (6) in a predetermined disposition. The cylinder
(24) includes a recess (not shown in Figure 2) for co-operating with the output shaft
(20). The first operation necessary to couple the cartridge (22) to the body (6) is
that of mating the recess in the cylinder (24) with the output shaft (20). This is
shown from the large arrow "A" in Figure 2. The cartridge (22) is then pivoted about
the axis of the cylinder (24) (because the cylinder (24) is now operatively coupled
to the output shaft (20)) and the interlock members (16 and 30) are coupled together.
This pivoting movement is shown by the arrow "B" in the figure.
[0019] Figure 3 shows the cartridge (22) when operatively coupled to the main body (6).
[0020] From Figures 2 and 3 it can be seen that the main body (6) includes an arcuate portion
(32). The cartridge (22) includes a correspondingly shaped arcuate portion (34). The
purpose of the arcuate portions (32, 34) is to ensure unimpeded motion when pivoting
the cartridge (22) to its final operative position.
[0021] Referring now to Figures 5 and 6, there is shown a power tool whose main body (6)
is operatively coupled to a cartridge (36). The cartridge (36) is an alternative to
that (22) with reference to Figures 1 to 4. In Figures 5 and 6, the cartridge (36)
is that of a planer, rather than a belt sander.
[0022] It can be seen particularly from Figure 6 that the cartridge (36) includes a cylinder
(38) which, in common with the cylinder (24) has a recess formed therein to mate with
the output shaft (20). Indeed, the operation of coupling the cartridge (36) to the
main body (6) is exactly the same as that with respect to cartridge (24). The main
differences between the two cartridges (22 and 36) is that the cartridge (22) is a
belt sander whereas the cartridge (36) is a planer. This means, that the cartridge
(36) does not require a rear roller and therefore only cylinder (38) is present. Those
skilled in the art will appreciate that the cylinder (38) is that of a planer and
therefore includes the common characteristics of the planer, such as a radial projection
(cutting blade) and depth of cut adjustment means as shown by reference numeral 40.
However, as these features are not germane to the present invention, they will not
be discussed any further herein, although they are clearly apparent to those skilled
in the art.
[0023] It would be apparent, therefore, with reference to Figures 1 to 6, that the power
tool (2) has a main body (6) which can be operatively coupled to any one of a plurality
of cartridges, of which two illustrative embodiments (22, 36) are shown. It will be
further apparent that further cartridges are possible and these are clearly within
the scope of those skilled in the art, although they are not described herein. For
example, an alternative cartridge could achieve orbital sanding or polishing tasks
or the like.
[0024] Referring now to Figures 7 and 8, the operation of the cartridge (22) will be described
in more detail. From these figures it can be seen that the cartridge (22) is operatively
coupled to a motor (42) by a belt drive mechanism (44). The output of the motor (42)
is coupled by rotating shaft (46) to a drive cog (48). The drive cog (48), in this
example, rotates at around 30,000 revolutions per minute. The belt drive (44) is coupled
to a driven cog (50) which is coupled to the output shaft (20) via a drive shaft (52).
[0025] The driven cog (50) has generally a greater number of teeth than the drive cog (48).
Therefore there is a speed reduction between the drive cog (48) and driven cog (50)
which results in the driven cog (50) (and therefore the drive shaft (52) and therefore
the output shaft (20)) rotating at around 16,000 revolutions per minute.
[0026] Whilst the rotational rate of the output shaft (20) is 16,000 revolutions per minute,
it will be apparent from Figure 7 that the belt sander cartridge (22) needs to rotate
in the sense shown by the arrow "C" yet the driving cogs (48 and 50) are rotating
in the opposite sense shown by arrows "D".
[0027] It will be understood that the belt sander cartridge (28) needs to have the drive
roller (24) rotating in the opposite sense to that of the planer cylinder (38) of
the planer cartridge (36).
[0028] Referring now also to Figure 8, it can be seen how the reversal of the sense of rotation
as between the output shaft (20) and the sense of rotation of the cylinder (24) is
achieved. Figure 8 shows a section taken along the line X-X of the cylinder (24) in
Figure 7. The output shaft (20) terminates in a sun gear (54) which is at the centre
of the cylinder (24). The sun gear rotates in a first sense, say, clockwise as shown
in Figure 8. A plurality of planet gears (56), in this example 3, are fixed in position
relative to the sun gear (54). Although the planet gears are fixed, they are free
to rotate about their respective central axis. This means, that when the sun gear
(54) rotates in a clockwise position, each planet gear (56) rotates about its own
axis in an anti-clockwise sense.
[0029] Surrounding the planet gears (56) is a rotatable ring gear (58) which is rigidly
coupled to the outer periphery of the cylinder (24). The inner periphery of the ring
gear (58) carries a plurality of teeth which co-operatively engage with the gearing
teeth of the planet gears (56). This means, therefore, that the ring gear (58) (and
therefore the cylinder (24)) rotate in an anti-clockwise sense as shown by the outermost
arrow of Figure 8.
[0030] In this manner, therefore, there is a reversal between the sense of the drive of
the output shaft (20) and the sense of rotation of the cylinder (24). In addition,
there is a gear reduction of around 8:1 in this example. This means that because the
output shaft is rotating at around 16,000 revolutions per minute, the speed of rotation
of the cylinder (24) is around 2,000 revolutions per minute. This is suitable for
belt sanding.
[0031] Referring now to Figure 9, there is shown a representation of the planer cartridge
(36). In Figure 9, similar components are numbered correspondingly with those of Figure
7, because the motor (42) and the belt drive (44) and the output shaft (20) are all
common with that of the housing (6) of Figure 7. Because of this, further description
of the mechanism up to and including the output shaft (20) will not be given herein.
[0032] However, as has been previously discussed, there is no need to reverse the sense
of rotation of the cylinder (38) compared to the output shaft (20). Because the driven
cog (50) is rotating at around 16,000 revolutions per minute, this in itself is suitable
for planing. It can be seen, therefore, from the arrows shown in the figure that all
rotating parts rotate in the same sense, that is as shown by the arrows marked "D".
[0033] Those skilled in the art will appreciate that various changes may be made to the
embodiments which are illustrated above whilst still remaining within the scope of
the invention. For example, any number of planet gears (56) may be employed rather
than just the three which are shown.
[0034] Additionally, any suitable cartridge may be coupled with the body (6) in order to
achieve the desired operative result.
1. A power tool arranged to perform a plurality of operations, the operations including
belt sanding and planing, wherein the tool comprises:
a housing;
a motor within the housing for providing drive to an output shaft; and
a plurality of cartridges, each of which cartridges may be coupled to the housing
and to the drive shaft to enable performance of a respective operation, wherein one
cartridge performs belt sanding and another cartridge performs planing.
2. A power tool according to claim 1, wherein the drive shaft projects out of the housing
and each cartridge includes a recess for coupling with the drive shaft.
3. A power tool according to either claim 1 or claim 2, wherein the drive shaft rotates
under the drive of the motor.
4. A power tool according to any one of the preceding claims, wherein the motor is coupled
directly to the drive shaft.
5. A power tool according to any one of the preceding claims, including an interlock
formed on the housing for retaining a cartridge presented for coupling to the housing.
6. A power tool according to claim 5, wherein each cartridge includes an interlock mechanism
co-operable with the interlock formed on the housing.
7. A power tool according to any one of the preceding claims, wherein each cartridge
must be presented to the body in a predetermined orientation in order to couple the
cartridge with the body.