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Title:
POWER TOOL
Document Type and Number:
WIPO Patent Application WO/2008/125795
Kind Code:
A1
Abstract:
The invention provides a power tool comprising a motor (30), a cutting bit holder (12) which is driven by the motor to rotate about an axis and a base plate (34) held apart from the motor in a plane which does not include said axis and in a manner permitting movement along said axis so as to vary the distance between the cutting bit holder and the base plate. In the preferred arrangement: the base plate (34) is adjustably mounted such that it is moveable in the plane thereof relative to said axis; the base plate only partially surrounds said axis in the plane of the plate; the motor is mounted to the base plate by supports (40) which are off-set out-of-line to the axis of rotation of the cutting bit holder; the motor is mounted perpendicular to the axis of rotation of the cutting bit holder; the base plate has retractable guide pins (60) which extend perpendicularly to the plane of the base plate; and the base plate includes a straight guide edge (38), said straight edge including a notch (34) through which the axis of rotation of the cutting bit holder extends.

Inventors:
BLAKE BRIAN JAMES (GB)
Application Number:
PCT/GB2008/000873
Publication Date:
October 23, 2008
Filing Date:
March 12, 2008
Export Citation:
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Assignee:
BLAKE BRIAN JAMES (GB)
International Classes:
B27F5/12; B23Q9/00; B27C5/10
Domestic Patent References:
WO2000003848A12000-01-27
Foreign References:
FR1074433A1954-10-05
US2726690A1955-12-13
DE1889195U1964-03-12
EP0049548A11982-04-14
DE10105147A12002-02-21
DE8803086U11988-04-21
US1566824A1925-12-22
US4763707A1988-08-16
Attorney, Agent or Firm:
STURT, Clifford, Mark (Unit 4 Bridge Farm,Botley Road,Curbridge, Southampton SO30 2HB, GB)
Download PDF:
Claims:
Claims

1. A power tool comprising a motor, a cutting bit holder which is driven by the motor to rotate about an axis and a base plate held apart from the motor in a plane which does not include said axis and in a manner permitting movement along said axis so as to vary the distance between the cutting bit holder and the base plate wherein the base plate is adjustably mounted such that it is moveable in the plane thereof relative to said axis.

2. A power tool as claimed in claim 1 wherein the base plate only partially surrounds said axis in the plane of the plate.

3. A power tool as claimed in claim 1 or claim 2 wherein the motor is mounted to the base plate by supports which are off-set out-of-line to the axis of rotation of the cutting bit holder.

4. . A power tool as claimed in any preceding claim wherein the motor is mounted perpendicular to the axis of rotation of the cutting bit holder.

5. A power tool as claimed in any preceding claim wherein the base plate has retractable guide pins which extend perpendicularly to the plane of the base plate.

6. A power tool as claimed in any preceding claim wherein the base plate includes a straight guide edge, said straight edge including a notch through which the axis of rotation of the cutting bit holder extends.

7. A power tool comprising a motor, a cutting bit holder which is driven by the motor to rotate about an axis and a base plate held apart from the motor in a plane which does not include said axis and in a manner permitting movement along said axis so as to vary the distance between the cutting bit holder and the base plate wherein the base plate only partially surrounds said axis in the plane of the plate.

8. A power tool comprising a motor, a cutting bit holder which is driven by the motor to rotate about an axis and a base plate held apart from the motor in a plane which does not include said axis and in a manner permitting movement along said axis so as to vary the

distance between the cutting bit holder and the base plate wherein the motor is mounted to the base plate by supports which are off-set out-of-line to the axis of rotation of the cutting bit holder.

9. A power tool comprising a motor, a cutting bit holder which is driven by the motor to rotate about an axis and a base plate held apart from the motor in a plane which does not include said axis and in a manner permitting movement along said axis so as to vary the distance between the cutting bit holder and the base plate wherein the motor is mounted perpendicular to the axis of rotation of the cutting bit holder.

10. A power tool comprising a motor, a cutting bit holder which is driven by the motor to rotate about an axis and a base plate held apart from the motor in a plane which does not include said axis and in a manner permitting movement along said axis so as to vary the distance between the cutting bit holder and the base plate wherein the base plate has retractable guide pins which extend perpendicularly to the plane of the base plate.

11. A power tool comprising a motor, a cutting bit holder which is driven by the motor to rotate about an axis and a base plate held apart from the motor in a plane which does not include said axis and in a manner permitting movement along said axis so as to vary the distance between the cutting bit holder and the base plate wherein the base plate includes a straight guide edge, said straight edge including a notch through which the axis of rotation of the cutting bit holder extends.

Description:

Power Tool

The present invention relates to power tools and in particular power tools suitable for cutting wood.

Power tools have, of course, now been available for very many years. In relation to carpentry in particular, although most tasks can be performed using one form of power tool or another some tasks are still often performed by hand. One such task is the cutting of recess to house the securing plates of hinges. It is possible to cut such recess using a conventional router power tool. However, the set-up of a conventional router for this task is somewhat time consuming, is not the most convenient to operate and can be subject to reduced precision due to the fundamental design of such a power tool.

Although not limited to such an application, it is an object of the present invention to provide a power tool useful in the cutting of wood and particularly suited to the cutting of recess to house the securing plates of hinges.

According to the present invention there is provided a power tool comprising a motor, a cutting bit holder which is driven by the motor to rotate about an axis and a base plate held apart from the motor in a plane which does not include said axis and in a manner permitting movement along said axis so as to vary the distance between the cutting bit holder and the base plate wherein the base plate is adjustably mounted such that it is moveable in the plane thereof relative to said axis.

Embodiments of the present invention will now be described by way of further example only and with reference to the accompanying drawings, in which :-

Figure 1 is a schematic illustration of a conventional power tool,

Figure 2 is a schematic illustration of a guide fence for use with the conventional power tool of figure 1,

Figure 3 is partial perspective view of a hinge recess cut in to a simple door or window frame,

Figure 4 is partial perspective view of a hinge recess cut in to a door frame which includes a door stop,

Figure 5 is partial perspective view of a hinge recess cut in to a door frame which has an architrave,

Figure 6 is a partial schematic view of an embodiment according to the present invention, and

Figure 7 is partial schematic view better illustrating the lower portion of the embodiment shown in figure 6.

Figure 1 is a stylised sketch of a conventional router power tool. The main components of the power tool are the motor 10, cutting bit holder 12 and base plate 14. The cutting bit holder 12 is driven by the motor 10 to rotate about an axis. The base plate 14 is connected to the motor 10 by two cutting depth shafts 16 which are secured perpendicularly to one face of the base plate 14. The shafts 16 are slidingly received in respective apertures in a carriage 18 which is rigidly secured to the motor 10. Thus the base plate 14 may be moved along the said rotation axis so as to vary the distance between the cutting bit holder 12 and the base plate 14. That is, with a cutting bit held in the holder 12 the distance by which the cutting bit projects beyond the base plate 14, and hence the depth of cutting, is varied by the shafts 16 sliding in their respective apertures. Locking screws 20, threadedly engaged with the carriage 18, are tightened against the shafts 16 once the required cutting depth has been set. As illustrated, these locking screws 20 are also configured so as to act as handles for guiding the power tool as cutting takes place.

The base plate 14 has an aperture through which the cutting bit extends. In some, but not all, cases the periphery of the base plate 14 includes a straight edge. This edge of the base plate 14 can be used to guide the movement of the tool when a piece of wood is being worked. Often a guide baton is lightly tacked on to the wood at the position required to guide the cutting by the power tool as required. An alternative form of guide, or fence as they are known, is illustrated in figure 2. Two parallel fence shafts 23 extend perpendicularly from one face of a rectangular bar 24. The shafts 23 ■ are received in and slide in respective housings 22 on the upper surface of the base plate 14. Thus, with the base plate horizontal, the shafts 23 extend horizontally and the bar 24 is held vertically. The extent to which the bar 24 projects horizontally from the base plate 14 is set by sliding the shafts 23, which are then held in position by tightening locking screws (not shown). The bar 24 is brought into contact with a side edge of the wood perpendicular to the surface 27 of the wood to be worked. The desired cutting location is thus established.

The conventional power tool described above is an extremely useful and successful product. However, it is not well suited to the task of cutting hinge recesses in rebated or stepped frames.

Figure 3 illustrates the most simple arrangement of a hinge recess 26 cut in to a square section door post or the like. Often a door post (or jamb) will be provided with a door stop 28, either pre-formed in the solid timber or formed by a baton on the jamb. A typical example

of this is illustrated in figure 4, showing a hinge recess 26 cut in to the door jamb. Another frequent variation is for the door jamb to be provided with a decorative architrave 29. A * typical example of this is illustrated in figure 5, again showing a hinge recess cut in to the jamb.

With the conventional power tool, cutting a hinge recess 26 as shown in figure 3 is possible - subject to various drawbacks as will be discussed below. Cutting a recess 26 as shown in figure 4, with the conventional power tool, is often quite troublesome. Even if the base plate 14 has a straight edge it is likely that the distance between the straight edge and the cutting bit will be greater than the distance between the "back" edge of the recess 26 and the door stop 28. This problem is sometimes overcome by securing a temporary baton to the "front" face of the door post, extending out beyond the surface 27 to be cut to a level equal to that of the door stop 28. The base plate 14 then rests on the door stop 28 and temporary baton, with the depth of the cutting bit adjusted accordingly. With the conventional power tool, cutting a hinge recess 26 as shown in figure 5 is possible - although difficulties may be encountered depending upon how the "depth" of the guide or fence 24 (shown in figure 2) compares with the size and shape of the architrave 29.

In cutting any of the recess shown in figures 1 to 3 with the conventional power tool various general drawbacks arise, in addition to those mentioned in the preceding paragraph. In particular it is found in practise that it takes quite some effort to achieve a precise cut, because it is not easy to control precisely movement of the tool, just as a consequence of it's general configuration, and because it is not easy to view a marked-out area to be cut. Adjusting the tool to cut recess in the door frame and then re-setting it to cut recess in the door is relatively time consuming. Often adjustments also have to be made between cutting, for example, the upper recess in the door frame and the lower recess - due to the door post being "out-of-square", not precisely vertical or the like. These considerations are often such that the craftsman will resort to cutting the recess using a hammer and chisel rather than spend the time setting and re-setting the power tool to do the job.

Figure 6 illustrates an embodiment of the present invention which mitigates the above mentioned disadvantages. There are a number of fundamental differences between the power tool of figure 6 and the conventional power tool as illustrated in figures 1 and 2. Probably the most readily apparent difference is that instead of the motor 30 being aligned with the axis of rotation of the cutting bit holder 32, in Hie embodiment it is set perpendicular thereto. Also readily apparent is the fact that the base plate 34 does not surround the cutting bit 33. Instead, the cutting bit 33 projects through a notch 36 which is open to the straight edge 38 of the base

plate 34. Closer examination reveals that the depth setting shafts 40 which slide in the motor carriage 42 are not secured directly to the base plate 34. Instead they are fixed to a mounting block 44 which slidingly abuts the base plate 34. The rear of the base plate 34, opposite to the straight edge 38 having. the cutting bit receiving notch 36, has a raised block 46 from which projects two guide shafts 48 (see figure 7). These shafts 48 are parallel to each other and are parallel to, and spaced apart from, the upper surface of the base plate 34. The shafts 48 are slidingly received in respective apertures in the mounting block 44. An adjustment shaft 50 is threadedly received in the mounting block 44 and is captivated in the raised block 46. Thus the base plate 34 can be moved adjustably in it's plane, perpendicularly relative to the rotational axis of the cutting bit. The effect is relative movement of the cutting bit 33 backwards and forwards in the base plate notch 36, towards and away from the straight "guide" edge 38 of the base plate 34. Once the base plate 34 has been adjusted to the desired position, in it's plane, relative to the rotational axis of the cutting bit 33, the position of the shafts 48 is locked using the locking screws 52.

The cutting depth of the bit 33 is set by the depth setting shafts 40 sliding in respective apertures in the motor carriage 42. The sliding motion is controlled by a control shaft 56 threadedly retained in a top brace 54, to which the upper ends of the shafts 40 are secured. The upper end of the control shaft 56 is provided with a thumb wheel 58 for ease of operation and the lower end of the control shaft 56 bears on the gearbox 31. Coil springs (not shown act between the mounting block 44 and the motor carriage 42 so as to bias the gearbox against the lower end of the control shaft 56.

A further distinction between the embodiment and the conventional power tool should be noted. Specifically, the cutting depth shafts 40 in the embodiment are not in line with the rotational axis of the cutting bit 33, as they are in the conventional tool. In the present embodiment the shafts 40 are off-set behind the rotational axis of the cutting bit 33, that is behind the cutting bit 33 with respect to the guide edge 38 of the base plate 34 - which is in front of the cutting bit 33. A further significant difference between the embodiment and the conventional power tool relates to the provision of a guide fence. With the conventional tool, as will be recalled from figure 2, the guide fence 24 is adjusted "horizontally" with respect to the base plate 14 - by the sliding adjustment of shafts 23 in housings 22 on the base plate 14. In the present embodiment the function of a guide fence is provided by two guide pins 60 (see figure 6) which extend perpendicularly, i.e. "vertically", with respect to the base plate 34. The guide pins 60 are slidingly received in respective collars 62 secured to the upper face of the base plate 34. The depth to which each pin 60 projects beneath the base plate 34 is

adjusted by the sliding motion in it's collar, and then locking it in place by a respective locking screw (not shown). Of course, the pins 60 may be locked in a position in which they do not project beneath the base plate 34.

It is found that the precision of movement of the illustrated embodiment when cutting a hinge recess 26 appears significantly enhanced in comparison to the conventional power tool. It is considered that the perpendicular orientation of the motor 30 to the rotational axis of the cutting bit 33 adds significantly to this effect. It is also considered that having the depth setting shafts 40 off-set "behind" the cutting bit 33, rather than in-line with it, adds to this effect. Certainly the off-set of the depth setting shafts 40 provides significantly increased viewing of the cutting area. This increased viewing is also assisted by the perpendicular orientation of the motor 30 to the rotational axis of the cutting bit 33.

The orientation of the motor and the length of the motor housing makes this the intuitive handle of the tool. The length of this handle gives far more precision than is usually obtained by clasping the normal handles/knobs of the conventional tool.

The fact that the cutting bit 33 can be moved right to the edge of the base plate 34, using the sliding adjustment of the base plate 34 relative to the cutting bit 33, means that there is no restriction in how close the "back" of the hinge recess 26 can be cut relative to a door stop 28. This very substantially increases the ease of use when cutting hinge recess 26 in door posts having door stops 28 and is to be compared with the above described situation of sometimes having to employ a temporary baton. Thus, both the lateral movement of the base plate 34 relative to the rotational axis of the cutting bit 33 and the open notch 36 of the base plate 34 add considerably to the functionality of the power tool.

When cutting a recess 26 of the type shown in figure 5 with the power tool illustrated embodiment of the present invention, the guide pins 60 are set to abut a convenient portion of the architrave 29. With the conventional power tool the "depth" of the fence 24, and hence the point of abutment against the architrave 29 is pre-set. With the illustrated embodiment the "depth" of the guide pins 60 is adjustable - which can critically affect how precise a guide can be obtained from the architrave 29.