GB2302057A - Hand-held circular saw - Google Patents

Abstract

The saw includes a base plate (24) comprising first and second plates (26, 28). The plates (26, 28) pivot about mutually orthogonal axes to adjust the depth of cut and bevel angle of the saw respectively. Adjustment of the angles of the plates (26, 28) is affected by means of rotatable actuators (34, 36). Each actuator (34, 36) comprises a rack and pinion mechanism and a lockable clamp (44, 42). Each actuator (34, 36) is operable by one hand of the user. The saw includes a motor (6) whose axis of rotation is in line with the plane of rotation of the saw blade (10). A handle (18) extends between a region adjacent the saw blade (10) and the motor (2).

Description

HAND-HELD CIRCULAR SAW The present invention relates to a hand-held circular saw and has particular, although not exclusive relevance to a circular saw as maybe used by professional workmen for cutting wood.

Conventional circular saws comprise an electric motor having an output spindle which is directly coupled to a circular saw blade.

When the electric motor is energised the circular saw blade rotates and this may be pushed into engagement with a workpiece to be cut.

The circular saw also comprises a blade guard which generally surrounds the blade such that the user is not in danger of either being cut by the blade or by being in the path of debris by the workpiece during use of the blade. The blade is positioned relative to the workpiece by means of a shoe or base plate connected to the body of the circular saw.

In use of the device the user will rest the base plate against the workpiece and push this along the workpiece such that the saw blade bites into the workpiece thereby achieving cutting.

In such conventional saw blades it is known to provide adjustment means whereby the angle of the plane of the blade with respect to the plane of the workpiece (known in the art as bevel) maybe altered. Such adjustment means generally comprises a pivot point on the base plate and a release mechanism. When the release mechanism is undone the base plate may pivot about the point thereby to alter the bevel angle of the saw blade. Such release mechanisms however, tend to be difficult to operate because the user needs to have two hands free. One hand needs to release the clamping mechanism which prevents pivoting of the base plate and the other hand of the user then needs to move the base plate about the pivot point to the desired angular position. Such complicated movements add time to the sawing operation and are also inconvenient for the user.

In such known saws there is generally also a mechanism for adjusting the depth of cut of the saw blade. This mechanism also includes a pivot point on the base plate whereby the amount of the saw blade which protrudes beyond the base plate into the workpiece is altered. The mechanism for achieving this alteration or depth of cut is similar to that described above for altering bevel angle in that a releasable catch needs to be undone in order to enable the user then to move the saw blade about the pivot point on the base plate in order to adjust the depth of cut. This too requires two handed operation and is generally inconvenient for the user.

Conventional circular saws also tend to be rather cumbersome to use because the axis of rotation of the motor for driving the saw blade is orthogonal to the plane of rotation of the saw blade itself. This means that when in use the saw blade is not particularly well balanced about its mid-point. Generally the handle for operating the saw blade is about the mid-point and so a degree of imbalance occurs. Furthermore, because the motor is arranged orthogonal to the plane of rotation of the saw blade the handle for using the circular saw tends to be rather small and therefore can often present problems with grip for the user.

It is therefore an object of the present invention to provide a circular saw which offers certain advantages to the user which will become apparent here below.

According to the present invention there is provided a hand-held circular saw comprising a housing accommodating a motor for driving a saw blade, a first plate pivotally connected to the housing about a first axis, a second plate pivotally connected to the first plate about a second axis substantially perpendicular to the first axis and means for holding the plates in chosen positions such that the depth of cut and the angle of cut of the saw blade can be defined. This provides the advantage that adjustment to the circular saw about 2 orthogonal axes is possible from an integral base plate unit without the need for separate mechanisms to achieve both these requirements.

Preferably the angle of one of the plates relative to the housing defines the depth of cut of the saw blade and the angle of the other plates relative to the housing defines the angle of cut of the saw blade. Additionally or alternatively the first axis may be substantially perpendicular to the plane of the saw blade.

maintained at the same attitude with respect to the rest of the users arm and therefore a more comfortable user position is obtained.

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 side view of a circular saw according to the present invention Figure 2 shows a side view of a circular saw according to the present invention from the opposite side to that of figure 1; Figure 3 shows a front view of the bevelling arrangement with a minimum depth of cut for a circular saw in accordance with the present invention; Figure 4 illustrates schematically a partially dismantled actuator in accordance with the present invention and; Figure 5 shows a schematic view of the motor and drive mechanism for a circular saw in accordance with the present invention.

Referring firstly to figures 1 and 2, it will be seen that a circular saw shown generally as 1 in accordance with the present invention comprises a housing (2), in this case clamshell arrangement (4) within which housing is mounted a motor (6) effective to drive a drive spindle (8) upon which a circular saw blade (10) may be an output which is a rotatable shaft (12) which shaft (12) lies in the plane of rotation of the saw blade (10) mounted on the drive spindle (8). This "in-line" arrangement of the motor with the rotated saw blade means that the circular saw in accordance with the present invention is well-balanced in use. Furthermore, this means that the clamshell (4) may be formed from only two portions (14, 16) which are brought together to form the single clamshell unit (4) within which are encased the motor (6), the rotatable shaft (12) and the drive spindle (10).By enabling such a clamshell arrangement to occur, this in-line motor and saw blade system means that construction of the saw is generally cheaper than with conventional units wherein more than 2 half portions are necessary to encapsulate all the working mechanisms of the device.

Furthermore, this in-line arrangement permits the clamshell (4) to define a handle (18) which extends from the region adjacent to the motor (6) to a region adjacent to the spindle (8), the handle extending parallel to the plane of rotation of the saw blade (10). The handle therefore is of much longer length than with conventional circular saws wherein the motor is adjacent the rotating saw blade, this providing a great deal of stability for the user of the circular saw.

As can be seen particularly from figures 1 and 2 the handle (18) forms an arc. This means that, regardless of the attitude of the circular saw to the work piece when the depth of cut is altered the user may maintain the same attitude of his wrist or hand regardless of the attitude of the saw for the selected depth of cut.

As can be seen from figure 1 the clamshell (4) is formed so as to define a blade guard (20). Forming the guard from the clamshell itself obviates the need to have a separate blade guard. Furthermore, the blade guard includes a window (22) formed of transparent plastics material. This enables the user of the saw to be able to accurately see where on the work piece the sawblade (10) will cut.

Referring now particularly to figures 2 and 3 it can be seen that the saw (2) includes a base plate (24) for adjusting the depth of cut and the bevel angle of the saw (2). The base plate (24) comprises a first plate (26) for adjusting the depth of cut and a second plate (28) for adjusting the bevel angle. The first plate (26) is pivotally connected to the housing (2) via pivot point (30) and the second plate (28) is pivotally connected to the first plate (26) via a pivot point (32).

It can be seen that the axes of the respective pivot (30 and 32) are substantially perpendicular. This allows the first pivot (30) and its corresponding plate (26) to enable depth of cut to be adjusted and the second pivot (32) and its corresponding plate (28) to enable bevel angle to be adjusted.

It can be seem from the drawings that the adjustment of the angular position of the component plates (26, 28) of the base plate (24) are controlled by means of respective actuators (34, 36). The actuators in this example comprise a rotatable pinion (or tooth gear) mechanism which co-operates with a respective rack mechanism.

Rotation of the actuator causes relative movement between itself and its respective rack thereby to move either of the plates (26 or 28) in order to adjust their angular position with respect to the housing (2).

For example figure 3 illustrates the maximum bevel angle being achieved by actuator (36) causing its rack (38) to be fully extended whereas the actuator (34) controlling the depth of cut is at the very other extreme of its rack (40) travel thereby achieving maximum depth of cut (because the saw blade (10) protrudes through the base plate (24) to its maximum possible depth).

Formed co-axial with each of the actuators (34 and 36) and having a screw thread passing all the way therethrough are respective clamps (42 and 44). Each of the clamps is rotatable to either prevent further rotation of the actuator or release the actuator for rotation. This operation is achieved because the screw thread of the respective clamp (42 or 44) tends to draw the clamp towards the actuator and restrain it between the clamp and the respective mount (46, 48) on which the actuator is held.

Figure 4 shows more clearly the actuator and clamp mechanism. It can be seen that the actuator (36) carries a toothed ring (pinion, 50) and through the centre axis of the actuator passes a screw thread (52) of the clamp (42), which screw thread engages with a corresponding screw thread hole (54) in the mount (46). When the clamp is not fully tightened the actuator (36) may be turned thereby to cause the teeth of the pinion (50) to engage with teeth in its respective rack (38) thereby to move the plate (28) about its pivot point (32) in order to alter the bevel angle of the saw blade (10).

However, when the clamp (42) is fully tightened the actuator (36) is held between the clamp (42) and the mount (46) thereby to lock the base plate at whatever angle it is at that time.

It will be appreciated that the present actuator mechanism enables adjustment of either of the plates (26, 28) with only one hand of the user This provides significant advantage over hitherto known circular saw adjustment mechanisms.

Considering now figure 5 it can be seen that the motor (6), which is housed within the clamshell (4), has an output which is a rotatable shaft (12). The rotatable shaft (12) co-operates with a gear mechanism. The gear mechanism includes a gear shaft (56) coupled to the rotatable shaft (12) via an electrically insulated belt (58). The end of the gear shaft (56) remote from the motor (6) carries a first bevel gear (60). It can be seen that the gear shaft (56) is axially parallel with, although displaced from, the axis of the rotatable shaft (12). The first bevel gear (60) on the gear shaft (56) co-operates with a corresponding bevel gear (62) formed on the drive spindle (8).

It can also be seen that the axis of the drive spindle (8) is orthogonal to the axis of both the gear shaft (56) and the rotatable shaft (12).

It will also be seen from figure 5 that the gear shaft (12) carries a fan (64). The fan is arranged to draw air (and therefore any material caught up in the air flow such as debris from the workpiece being cut) from the end of the gear shaft (56) adjacent the saw blade (10).

Such drawn material may then be ejected from the saw (2) via a port (not shown) in the clamshell (4). This facility allows for dust removal and will be apparent to those skilled in the art and so not firther described herein.

It will be understood by those skilled in the art that the housing (2) may be formed integrally with the plastics material of the clamshell (4) or both the housing (2) and the clamshell (4) maybe separate items.

It will be seen from the above and the enclosed drawings that in this example the rack mechanisms are contrate, but this is not imperative, as any rack mechanism will suffice.

Claims (16)

1. A hand-held circular saw comprising a housing accommodating a motor for driving a saw blade, a first plate pivotally connected to the housing about a first axis, a second plate pivotally connected to the first plate about a second axis substantially perpendicular to the first axis and means for holding the plates in chosen positions such that the depth of cut and the angle of cut of the saw blade can be defined.

2. A saw as claimed in claim 1, wherein the angle of one of the plates relative to the housing defines the depth of cut of the saw blade and the angle of the other of the plates relative to the housing defines the angle of cut of the saw blade.

3. A saw as claimed in any preceding claim, wherein the first axis is substantially perpendicular to the plane of the saw blade.

4. A saw as claimed in any preceding claim, wherein the first axis is positioned to the rear of the saw blade.

5. A saw as claimed in any preceding claim, wherein the second axis is substantially in the plane of the saw blade.

6. A saw as claimed in any preceding claim, wherein the first plate abuts the second plate when a cut normal to a work piece at maximum depth is to be made.

7. A saw as claimed in any preceding claim, wherein the holding means comprise at least one rack and pinion mechanism.

8. A saw as claimed in any preceding claim, wherein both the first and second plates are held in position by rack and pinion mechanisms.

9. A saw as claimed in claim 8, wherein one of the racks is mounted on the housing and the other of the racks is mounted on the second plate.

10. A saw as claimed in claim 9, wherein the rack of the second plate is a contrate gear.

11. A saw as claimed in any one ofclaims 7 to 10, wherein a releasable clamp grips the pinion to prevent motion of the pinion along the rack.

12. A saw as claimed in claim 11, wherein the releasable clamp comprises a knob and a mounting block, the pinion being gripped therebetween.

13. A saw as claimed in claim 12, wherein the mounting block is fixed to the first plate and moves therewith.

14. A saw as claimed in any preceding claim, wherein a viewing window of the housing exposes the front of the saw blade.

15. A saw as claimed in any preceding claim, wherein the motor is positioned in line with the plane of the saw blade.

16. A hand-held circular saw substantially as hereinbefore described with reference to and as shown in the accompanying drawings.