EP2185324A1

EP2185324A1 - Cam operated power tool

Info

Publication number: EP2185324A1
Application number: EP08788390A
Authority: EP
Inventors: Hugh Edward Fisher
Original assignee: Individual
Current assignee: Individual
Priority date: 2007-08-23
Filing date: 2008-08-20
Publication date: 2010-05-19
Also published as: GB0716503D0; WO2009024786A1

Abstract

There is disclosed cam operated power tool (5). The invention provides a tool (5) comprising a cam track (A) and cam follower means (B), wherein the cam track (A) has first and second opposing walls (D, E) ' and at least the first wall (D) has a plurality of spaced first teeth (TD). The second wall (E) has a plurality of spaced second teeth (TE). The cam track (A) is circumferentially provided on a cam cylinder (F). The/each second tooth (TE) is provided circumf erentially offset from or between respective adjacent first teeth (TD). Each first and/or second tooth (TD, TE) has a cam follower acceleration or throw portion, and between adjacent first and/or second teeth (TO, TE) there is provided a cam follower deceleration or catch portion (H).

Description

CAM OPERATED POWER TOOL

FIELD OF INVENTION This invention is concerned with improvements in and relating to tools. The invention also relates to cam operated devices or cam operated power tools, and more particularly to tools or power tools with reciprocating tool bits driven by rotary drive means or tools or power tools with rotary tool bits driven by reciprocating drive means .

The invention is also concerned with power tools, particularly, though not exclusively, relatively lightweight or handheld power tools, e.g. for the do-it- yourself (DIY) and professional/trade markets such as the marine field. The invention is also concerned with downhole tools, e.g. for use in drilling of wells or boreholes .

BACKGROUND TO INVENTION

A number of types of reciprocating power tools are in use for various tasks, e.g. scrapers, saws, hammers or the like. Commonly such tools are hydraulically or pneumatically powered; however, such powering necessitates use of a noisy and bulky compressor or the like in conjunction with the tool itself, resulting in a limited range of utility for such tools. Further, such tools cannot easily or efficiently attain high speeds of reciprocation . An alternative arrangement is to convert rotary movement provided by, for example, an electric motor into reciprocating movement of the tool bit. One means for achieving this conversion is to use the motor to drive the rotation of a cam bearing a cam track, and to provide the tool bit with a pair of cam followers, which are a close fit within the cam track. As the cam rotates the cam followers are driven forward and backward along the cam track, which is typically a sinusoidal cam track, so driving the tool bit forward and backward. Such arrangements are described in GB 2 219 958 A and WO 93/11910 by the same Inventor, the contents of which are incorporated herein by reference. WO 01/60564 also by the same Inventor, the content of which is incorporated herein by reference, discloses a portable power tool, such as a hand-held marine growth removal scraper tool comprising a housing, a drive means and a mounting arrangement for a tool bit, wherein there is provided within the housing an output arrangement adapted to drive an output shaft in a reciprocal axial movement to drive the tool bit, and wherein the drive means is substantially sealed from external of the tool.

WO 02/14028 also by the same Inventor, the content of which is incorporated herein by reference, discloses a power tool comprising a housing, a rotary drive means, a cylinder cam having a cam track extending around a circumferential surface thereof, cam follower means adapted to run in said cam track, and a mounting arrangement for a tool bit, one of the cam and the cam follower means being driven by the drive means, and the mounting arrangement being associated with one of the cam and the cam follower means, such that actuation of the rotary drive means drives reciprocal movement of the mounting arrangement; and wherein at least part of the cam track is in the form of a wave having an amplitude and a wavelength, the wave providing a forward throw section and a rearward throw section which in use drive the mounting arrangement respectively forward and rearward, at least one of the forward throw section or rearward throw section imparting a greater forward or rearward acceleration respectively to the mounting arrangement than that imparted by a sinusoidal cam track of equivalent amplitude and wavelength.

A number of problems have been identified in the prior art. For example, when a tool is operated in particularly robust uses, e.g. marine hull scraping, it has been found desirable to seek to provide an improved tool . This is required in order to seek to ensure appropriate efficient functionality of the tool, e.g. removal of marine debris or encrustations, preferably without damaging the underlying substrate, e.g. hull. It is an object of at least one embodiment of at least one aspect of the present invention to obviate or at least mitigate one or more problems and/or disadvantages in the prior art.

It is an object of at least one embodiment of at least one aspect of the present invention to provide an improved tool, e.g. a power tool, hand-held power tool, and/or scraper tool, e.g. marine tool such as an anti- fouling tool.

SUMMARY OF INVENTION

According to a first aspect of the present invention there is provided a tool comprising a cam track and cam follower means, wherein the cam track has first and second opposing walls and at least the first wall has a plurality of spaced first teeth.

Preferably the second wall has a plurality of spaced second teeth. Preferably the cam track is circumferentially provided on a cam cylinder.

Preferably the/each second tooth is provided circumferentially offset from or between respective adjacent first teeth.

Preferably each first and/or second tooth has a cam follower acceleration or throw portion.

Preferably between adjacent first and/or second teeth there is provided a cam follower deceleration or catch portion.

Preferably each first and/or second tooth comprises a ramp portion, which may comprise a front portion of the tooth.

The ramp portion may be inclined at an angle to the cam track, e.g. of between around 30° and 60°, e.g. around 45°.

Preferably each first and/or second tooth comprises a top portion, e.g. a curved top portion.

Preferably each first and/or second tooth comprises a wall portion, which may comprise a rear portion of the tooth.

Preferably the wall portion is substantially perpendicular to the cam track.

Preferably the wall portion is substantially parallel to a longitudinal axis of the cam cylinder.

The/each tooth may be described as substantially wedge shaped.

Between adjacent first teeth there may be provided a flat portion. The flat portion may be substantially parallel to the cam track.

The/each wall portion may meet with an adjacent flat portion at an angle, preferably around 90°. Preferably a top portion of a first/second tooth is provided opposite a flat portion on the second/first wall .

The first and/or second tooth may be described as being of a "dog tooth" arrangement.

A ramp portion may meet with an adjacent flat portion, e.g. at a curved portion of the ramp portion.

The ramp portion may comprise a/the curve portion and optionally a straight portion. Preferably teeth of the first/second wall do not longitudinally overlap with teeth of the second/first wall.

Preferably there is provided a longitudinal gap between adjacent teeth on opposing walls. Preferably the cam track and cam follower means are rotatable relative to one another in one direction but not an opposing direction.

In a preferred embodiment there may be provided rotary drive means for rotarily driving the cam track. In such instance the rotary motion of the cam track may be converted into reciprocal (longitudinal) motion of the cam follower means.

Alternatively there may be provided rotary drive means for rotarily driving the cam follower means. In such instance the rotary motion of the cam follower means may be converted into reciprocal (longitudinal) motion of the cam track.

Alternatively there may be provided reciprocal (longitudinal) drive means for reciprocally driving the cam track.

In such instance the reciprocal motion of the cam track may be converted into rotary motion of the cam follower means. Alternatively there may be provided reciprocal (longitudinal) drive means for reciprocally driving the cam follower means.

In such instance the longitudinal motion of the cam follower means may be converted into rotary motion of the cam track.

The cam follower means may comprise at least one member, and preferably at least one pair of opposing members . The/each member may have a substantially circular cross-section.

The/each member may comprise a substantially cylindrical member.

The cam track/cam cylinder may be made from a metallic material, e.g. phosphor bronze.

The cam follower means may be made from a metallic material .

Advantageously a width of at least a portion of the cam track is greater than a width of the cam follower means.

The cam follower means and cam track may therefore be a loose fit relative to one another. This is in contradistinction to the prior art wherein the cam follower means was a close or tight fit within the cam track.

Preferably the cam track and cam follower means are engaged with one another.

Preferably the cam follower means is engaged within, or located in the cam track. The cam follower means may be adapted to run in the cam track, e.g. move around the cam track and be thrown between opposing walls of the cam track. The width of the cam follower means may be less than 90%, 80%, 70%, 60%, or 50% of the width of the at least a portion of the cam track.

The width of the cam follower means may be in the region of 10% to 90%, or 40% to 80% of the width of the at least a portion of the cam track.

In use, when not placed against a work surface (unloaded) , the cam follower means may follow a path dictated substantially only by the cam track. The cam track and cam follower means may be such that, in use, when not placed against a work surface the cam follower means travels in a path from one portion (tooth) on one wall of the cam track to another portion on another wall of the cam track, preferably without intermediately striking the walls of the track.

In use, when placed against a work surface (loaded) , the cam follower means may follow a path dictated by the cam track and by ricochet of the tool off the work surface and/or the cam follower means off walls of the cam track.

In the latter case the cam follower means therefore has two degrees of motion, a first degree of motion defined by the cam track, and a second degree of motion defined by ricochet between opposing walls of the cam track.

The first degree of motion may have a frequency defined by the cam track.

The second degree of motion may have a higher frequency than the frequency of the first degree of motion. The frequency of the second degree of motion may vary dependent upon the work surface to which the tool is presented. The first degree of motion may cause a substantially- longitudinal throw of a tool bit of the tool .

The second degree of motion may cause a substantially longitudinal vibration or chatter of the tool bit of the tool .

The width of the cam follower means may be less than the width of the entire cam track.

The cam track may comprise a closed (circular) track, and may be provided on a cam cylinder. The cam follower means may comprise at least one pin, and preferably at least one pair of opposing pins.

The width of the cam track may be constant or may vary around the length thereof .

In one embodiment the width of the cam track is less or reduced between a top portion of a tooth on one wall and an opposing portion of the other wall .

Preferably the cam track may be recessed, and the cam follower means received therein. Alternatively the cam follower means may be recessed or comprise at least first and second spaced members or portions, and the cam track received therein. In the latter case there may be provided at least two pairs of opposing first and second members .

The cam track may comprise a waveform. The tool may advantageously be a power tool or handheld tool, e.g. a hand-held power tool.

The tool may be powered by an external electrical supply, e.g. mains electricity (e.g. 110V/240V) , which may be alternating current (AC) or advantageously by a low voltage supply (e.g. 12V), which may be direct current (DC), e.g. from a motor vehicle or vessel/boat. Alternatively, the tool may be battery powered. The cam track or the cam follower means may be rotationally driven by rotational drive means, e.g. an electric motor.

In a particularly advantageous embodiment the tool may comprise a marine growth removal or anti-fouling tool, e.g. barnacle scraper.

In such embodiment the tool may comprise a housing, a drive means and a mounting arrangement for a tool bit, wherein there is provided within the housing an output arrangement adapted to drive an output shaft in a reciprocal axial movement to drive the tool bit, and the drive means may be substantially sealed (e.g. against fluid ingress) from external of the tool. This arrangement allows the tool to be used underwater or in wet/moist environments.

In alternative advantageous embodiments the tool may comprise a handyman's or tradesman's tool.

The tool may comprise a scraper, paint stripper, wallpaper stripper, chisel, cold chisel, power spade, hammer or the like.

In a further alternative embodiment the tool may comprise a downhole tool.

The tool may comprise one or more of: a housing; a rotary drive means, e.g. electric motor; a cylinder cam having the cam track extending around a circumferential surface thereof; a mounting arrangement for (releasably holding) a tool bit, one of the cam track and cam follower means being driven by the drive means; the mounting arrangement being associated with one of the cam track and the cam follower means, such that actuation of the rotary drive means drives reciprocal movement of the mounting arrangement; at least part of the cam track being in the form of a wave having an amplitude and a wavelength, the wave having a forward throw section, and a rearward throw section, which, in use, drive the mounting arrangement respectively forward and rearward.

There may be provided a plurality of interchangeable tool bits. According to a second aspect of the present invention there is provided a tool comprising a cam track and a cam follower means, wherein the cam track comprises a first wall having at least one first means for throwing the cam follower means towards a second wall of the cam track, in use, when the cam track and cam follower means are rotated relative to one another.

The second wall may have at least one second means for throwing the cam follower means towards the first wall of the cam track, in use, when the cam track and cam follower means are rotated relative to one another.

The first means for throwing may comprise at least one first tooth.

The second means for throwing may comprise at least one second tooth. The features of the first aspect of the invention hereinbefore recited may be provided in the tool of the second aspect either separately or in combination.

BRIEF DESCRIPTION OF DRAWINGS Embodiments of the invention will now be described by way of example only, and with reference to the accompanying drawings, which are: Figure 1 a cam track and cam follower arrangement of a tool according to the prior art;

Figure 2 a perspective view from the front and to one side of a tool according to an embodiment of the present invention;

Figure 3 an exploded perspective view from the front and to one side of the tool of

Figure 2 ;

Figure 4 a cam track and cam follower arrangement comprising part of the tool of Figure 2 ;

Figure 5 (a) a perspective view from one side and one end of a first alternative cam track and cam follower arrangement according to the present invention;

Figure 5 (b) a side view of the first alternative cam track and cam follower arrangement of

Figure 5 (a) ;

Figure 5 (c) another side view of the first alternative cam track and cam follower arrangement of

Figure 5 (a) ;

Figure 6 (a) a perspective view from one side and one end of a second alternative cam track and cam follower arrangement according to the present invention;

Figure 6 (b) a side view of the second alternative cam track and cam follower arrangement of

Figure 6 (a) ;

Figure 6 (c) another side view of the second alternative cam track and cam follower arrangement of Figure 6 (a) ;

Figure 7 (a) an exploded perspective view from one side and one end of a third alternative cam track and cam follower arrangement according to the present invention; and

Figure 7 (b) a side view from one side of the third alternative cam track and cam follower arrangement of Figure 7 (a) .

DETAILED DESCRIPTION OF DRAWINGS

Referring initially to Figure 1, there is shown a cam track A and cam follower means B arrangement of a tool according to the prior art. This arrangement is disclosed in the prior art by the same Inventor hereinbefore mentioned.

As can be seen from Figure 1, the cam follower means B is a snug fit in the cam track A, a width W_B of the cam follower means B being substantially the same as the width W_A of the cam track A, such that there is little or no play between the cam follower means B and the cam track A. Thus, in use, the cam follower means B follows the track C shown, having only one degree of freedom of movement. The cam track has walls D, E. Although a tool according to the prior art providing such an arrangement was found to be an improvement over the previous art, further improvement is desirable, particularly in using such a tool in robust uses, e.g. as a marine scraper.

Figure 1 shows a parallel sided cam track A or wave or cam slot cut around a revolving cam drum F. The circular cam follower means B shown engaging the cam track A are near the same in diameter as the width of the cam track A. When the cam drum F revolves, the cam follower means B follows the wave shape precisely as there is no other alternative open to them. The track or path C is shown in Figure 1 by a dotted line central to the width of the cam track A.

Referring now to Figures 2 to 5 (c) , there is shown a tool, generally designated 5, according to an embodiment of the present invention having a cam track A and cam follower B arrangement. The tool 5 comprises cam track A and cam follower B means adapted to run in the cam track A, following a path C (not shown) .

The cam track A has first and second opposing walls D, E, and at least the first wall D has a plurality of spaced first teeth T_D. The second wall E also has a plurality of spaced second teeth T_E. The cam track A is circumferentially provided on a cam cylinder F. The/each second tooth T_E is provided circumferentially offset from or between respective adjacent first teeth T_D.

Each first and/or second tooth T_D, T_E has a cam follower acceleration or throw portion G. Between adjacent first and/or second teeth T_D, T_E there is provided a cam follower deceleration or catch portion H. Each first and/or second tooth T₀, T_E comprise a ramp portion I, which comprises a front portion J of the tooth T_D, T_E. The ramp portion I is inclined at an angle to the cam track A, e.g. of between around 30° and 60°, e.g. around 45°. Each first and/or second tooth T_n, T_E comprises a top portion K, e.g. a curved top portion. Each first and/or second tooth T_D, T_E comprises a wall portion L, which comprises a rear portion of the tooth T_D/ T_E. The wall portion L is substantially perpendicular to the cam track A. The wall portion L is substantially parallel to a longitudinal axis M of the cam cylinder F.

Between adjacent first teeth T_D there is provided a flat portion N. The/each flat portion N is substantially parallel to the cam track A. The/each wall portion L meets with an adjacent flat portion N advantageously at an angle around 90°. A top portion K of a first/second tooth T_D, T_E is provided opposite a flat portion N on the second/first wall E, D.

The first and/or second tooth T_D, T_E can be described as being substantially wedge shaped or of a "dog tooth" arrangement .

A ramp portion I meets with an adjacent flat portion N, e.g. at a curved portion P of the ramp portion I. The ramp portion I comprises a/the curve portion P and optionally a straight portion Q.

Teeth T_D/ T_E of the first/second wall D, E do not longitudinally overlap with teeth TD, TE of the second/first wall E, D. There is therefore provided a longitudinal gap R between adjacent teeth T_D, T_E on opposing walls D, E.

The cam track A and cam follower means are rotatable relative to one another in one direction S but not in an opposing direction due to the shape teeth T_D, T_E. The arrangement can therefore be described as providing a

"ratchet" mechanism.

There are provided rotary drive means for rotary driving the cam track A. In such instance the rotary motion of the cam track A is, in use, converted into reciprocal (longitudinal) motion of the cam follower means B .

Alternatively there can be provided rotary drive means for rotarily driving the cam follower means B. In such instance the rotary motion of the cam follower means

B is converted into reciprocal (longitudinal) motion of the cam track A. Alternatively there can be provided reciprocal

(longitudinal) drive means for reciprocally driving the cam track A. In such instance the reciprocal motion of the cam track A can be converted into rotary motion of the cam follower means B.

Alternatively there may be provided reciprocal

(longitudinal) drive means for reciprocally driving the cam follower means B. In such instance the longitudinal motion of the cam follower means B can be converted into rotary motion of the cam track A.

The cam follower mans B comprises at least one member W, and in this embodiment at least one pair of opposing members. The/each member W has a substantially circular cross-section. The/each member W comprises a substantially cylindrical member X.

The cam track A and/or cam cylinder F are, in this embodiment, made from a metallic material, e.g. phosphor bronze. The cam follower means B can also be made from a metallic material. The cam follower means B comprises at least one pin, and in this embodiment at least one pair of opposing pins V. In this embodiment the cam track A is recessed, and the cam follower means B received therein. Alternatively, in a modification the cam follower means can be recessed, and the cam track received therein.

The tool 5 is adapted for use as a power tool or hand-held tool, e.g. a hand-held power tool. The tool 5 can be powered by an external electricity supply, which can be an alternating current (AC) or direct current (DC) supply, e.g. mains electricity (e.g. 110V/240V) or by a low voltage supply (e.g. 12V), e.g. from a motor vehicle or vessel/boat. Alternatively, the tool may be battery powered. In a particularly advantageous implementation the tool comprises a marine growth or fouling removal tool, e.g. barnacle scraper.

As will hereinafter be described in greater detail, the tool 5 comprises a housing, a drive means and a mounting arrangement for a tool bit 10, wherein there is provided within the housing an output arrangement adapted to drive an output shaft in a reciprocal axial movement to drive the tool bit 10, and the drive means can be substantially sealed (e.g. against fluid ingress) from external of the tool 5. This allows the tool 5 to be used underwater or in wet/moist environments.

In alternative advantageous embodiments the tool 5 comprises a handyman's or tradesman's tool. The tool 5 can comprise a scraper, paint stripper, wall paper stripper, chisel, cold chisel, power spade, hammer or the like. In further alternative embodiments the tool can be adapted for use downhole and comprises a downhole tool.

The tool 5 comprises one or more of: a housing; a rotary drive means; cylinder cam F having the cam track A extending around a circumferential surface thereof; a mounting arrangement for (releasably holding) a tool bit 10, one of the cam track A and cam follower means B being driven by the drive means; the mounting arrangement being associated with one of the cam track A and the cam follower means B, such that actuation of the rotary drive means drives reciprocal movement of the mounting arrangement; at least part of the cam track A being in the form of a wave having an amplitude and a wavelength, the wave having a forward throw section, and a rearward throw section, which, in use, drive the mounting arrangement respectively forward and rearward.

The tool 5 comprises a plastics housing 20 and tool bit 10 in the form of a scraper blade 25. The blade 25 is mounted on a reciprocating shaft 30, which is powered by an internal motor (described below) . One end of a power cable 35 enters the casing 20, while another end leads to a power supply (not shown) , for example, a battery located on a boat. The casing 20 also includes an activating button or trigger mechanism 40, which can optionally provide a "dead-man's handle" safety feature, and a hand guard 45, located so as to protect a user's fingers when holding the tool 5.

Internal components of the tool 5 are shown in the exploded view of Figure 3. The power cable 35 leads to a low power rotary motor 45, which drives a rotatable output shaft 50. The motor 45 is "low power" in the sense that a typical motor as used in the present invention run at 12 -24V on 2-4A, as opposed to conventional motors for existing reciprocating power tools, which run at no less than a few hundred watts.

Mounted on the rotary output shaft 50 is a cylinder cam 55 with circumferentially arranged cam track A. Received in the cam track A are cam follower means B comprising a pair of pins or studs 15, which are connected via a frame 60 to an output shaft 65. Mounted on the output shaft 65 are a number of parts 70 and a cover 75, which serve to secure the scraper blade 25 to the shaft 65. The tool 5 also comprises a blade holder 76. In certain embodiments of the present invention, a plurality of interchangeable blades 70 can be provided, in order to adapt the tool 5 for use in different applications . In use, electric rotary motor 45 drives rotary- output shaft 50, which in turn rotates cam 55, which bears cam track A. Pins or studs 15 act as cam follower means B, and are driven in an axially reciprocating motion by the rotational motion of the cam 55, the pins or studs 15 in turn being mounted in frame 60, which is itself connected to tool blade 15 via output shaft 65. The rotary motor 45 is typically capable of driving an axially reciprocating blade 15 at up to 14,000 cycles per minute with relatively little waste heat generated, compared to conventional reciprocal motors.

Thus, the present invention provides a tool 5, which can be sealed from moisture or other hazardous environments, and therefore is suitable for use as a marine growth remover, among other applications, the drive means requiring no cooling my means of slots or vents in the housing. Sealing means can be provided as described in WO 01/60594.

Referring now to Figure 4, in use, the cam follower means B are catapulted from teeth T_D, T_E towards opposing wall E, D. The cam follower means B can then describe a path C controlled or defined by the teeth TD, TE of the cam track A.

The tool 5 therefore comprises a cam track A and a cam follower means B, wherein the cam track A comprises a first wall D having at least one first means for throwing the cam follower means B towards a second wall E of the cam track A, in use, when the cam track and cam follower means B are rotated relative to one another. The second wall E has at least one second means for throwing the cam follower means B towards the first wall D of the cam track A, in use, when the cam track A and cam follower means B are rotated relative to one another. The first means for throwing comprises at least one first tooth T_D/ while the second means for throwing comprises at least one second tooth T_E.

The width of at least a portion of the cam track A is greater than a width of the cam follower means B. This can, in use, result in a second degree of motion or "chatter" of the cam follower means B.

Referring now to Figures 5 (a) to (c) , there is shown a first alternative cam track A and cam follower means B. The arrangement is similar to the arrangement of Figures

2 to 4, like parts being designated by like letters and numerals .

In this implementation the first and second teeth have a flat top portion. A shaft and yoke 113 has pins 114 set into the extremities of the yoke 113. The pins

114 engage a shaped slot 107 cut into cam drum 105. The slot 107 has ramps or wedges to each side of the slot 107 wall arranged in alternate sequence so as to throw the pins 114 and therefore the shaft and yoke assembly 113 back and forth when the cam drum 115 is rotated but retrained from lateral movement. Note that the cam drum

115 can rotate in one direction only as the shape of the slot 107 ramps or wedges preclude reverse rotation of the cam drum 115. Referring now to Figures 6 (a) to (c) , there is shown a second alternative cam track A and cam follower means B arrangement. The arrangement is similar to the arrangements of Figures 2 to 4 or Figures 5 (a) to 5 (c) , like parts being designated by like letters and numerals, but suffixed "a".

The shaped slot 107a in the cam drum 105a is engaged by two shaft, yoke and pin assemblies set at 9Oo to one another. The shaft and yokes 113a are arranged to move in a co-axial manner through an integrated bearing 118) .

Referring now to Figures 7 (a) to (c) , there is shown a third alternative cam track A and cam follower means B arrangement. The arrangement is similar to the arrangements of Figures 2 to 4 or Figures 5 (a) to 5 (c) , like parts being designated by like letters and numerals, but suffixed "b" .

The shaped slot 107b is contained within the cam drum and is not external to the drum as shown in drawings the previous embodiments. The cam drum is split into two parts whereby the ramps or wedges on either side of the slot 107b and 103b are arranged to be alternate to each other in order to provide a path for the drive pins 104b which are fixed to, or integral parts of, the shaft 105b.

The two parts of the cam drum are secured together in position by fixings 109b and 110b.

The shaft 105b is prevented from rotation by the flats 106b cut into the shaft 105b which engage with the matching receptor cut into the fixed bearing 112b. The shaft 105b is led through the forward fixed bearing 111b and so, as the cam drum is arranged to rotate only and is restrained from lateral movement, the shaft 105b must reciprocate on rotation of the cam drum. The cam drum is shown with an integrally cut gear 102b, which engages with a drive shaft, and matching gear 101b.

It will be appreciated that the embodiments of the present invention hereinbefore described are given by way of example only, and are not meant to be limiting to the scope of the invention. As a non- limiting example the first degree of motion (longitudinal throw) of a tool bit of a tool of the present invention may typically operate at a frequency of the order of 5,000 to 10,000 cycles per minute. The second degree of motion (chatter) - if present - of the cam follower means and therefore the tool bit typically may be of the order of 10 to 20 times the frequency of the first degree of motion.

Claims

1. A tool comprising a cam track and cam follower means, wherein the cam track has first and second opposing walls and at least the first wall has a plurality of spaced first teeth.

2. A tool as claimed in claim 1, wherein the second wall has a plurality of spaced second teeth.

3. A tool as claimed in either of claims 1 or 2 , wherein the cam track is circumferentially provided on a cam cylinder.

4. A tool as claimed in any preceding claim, wherein the/each second tooth is provided circumferentially offset from or between respective adjacent first teeth.

5. A tool as claimed in any preceding claim, wherein each first and/or second tooth has a cam follower acceleration or throw portion.

6. A tool as claimed in any preceding claim, wherein between adjacent first and/or second teeth there is provided a cam follower deceleration or catch portion.

7. A tool as claimed in any preceding claim, wherein each first and/or second tooth comprises a ramp portion, which optionally comprises a front portion of the tooth.

8. A tool as claimed in claim 7, wherein the ramp portion is inclined at an angle to the cam track, optionally of between around 30° and 60°, or around 45°

9. A tool as claimed in any preceding claim, wherein each first and/or second tooth comprises a top portion, optionally a curved top portion.

10. A tool as claimed in any preceding claim, wherein each first and/or second tooth comprises a wall portion, which optionally comprises a rear portion of the tooth.

11. A tool as claimed in any preceding claim, wherein the wall portion is substantially perpendicular to the cam track.

12. A tool as claimed in either of claims 10 or 11 when dependent upon claim 3, wherein the wall portion is substantially parallel to a longitudinal axis of the cam cylinder.

13. A tool as claimed any preceding claim, wherein the/each tooth is substantially wedge shaped.

14. A tool as claimed in any preceding claim, wherein between adjacent first teeth there is provided a flat portion.

15. A tool as claimed in claim 14, wherein the flat portion is substantially parallel to the cam track.

16. A tool as claimed in either of claims 14 or 15 when dependent upon any of claims 10 to 12, wherein the/each wall portion meets with an adjacent flat portion at an angle, optionally around 90°.

17. A tool as claimed in any preceding claim, wherein a top portion of a first/second tooth is provided opposite a flat portion on the second/first wall .

18. A tool as claimed in any preceding claim, wherein the/each first and/or second tooth is a dog tooth.

19. A tool as claimed in any preceding claim, wherein a ramp portion meets with an adjacent flat portion, optionally at a curved portion of the ramp portion.

20. A tool as claimed in any preceding claim, wherein the ramp portion comprises a/the curve portion and optionally a straight portion.

21. A tool as claimed in any preceding claim, wherein teeth of the first/second wall do not longitudinally overlap with teeth of the second/first wall.

22. A tool as claimed in any preceding claim, wherein there is provided a longitudinal gap between adjacent teeth on opposing walls.

23. A tool as claimed in any preceding claim, wherein the cam track and cam follower means are rotatable relative to one another in one direction, but not an opposing direction.

24. A tool as claimed in any preceding claim, wherein there is provided rotary drive means for rotarily driving the cam track.

25. A tool as claimed in claim 24, wherein the rotary- motion of the cam track is, in use, converted into reciprocal or longitudinal motion of the cam follower means .

26. A tool as claimed in any of claims 1 to 23, wherein there is provided rotary drive means for rotarily driving the cam follower means.

27. A tool as claimed in claim 26, wherein the rotary motion of the cam follower means is converted into reciprocal or longitudinal motion of the cam track.

28. A tool as claimed in claim any of claims 1 to 23, wherein there is provided reciprocal or longitudinal drive means for reciprocally driving the cam track.

29. A tool as claimed in claim 28, wherein the reciprocal motion of the cam track is converted into rotary motion of the cam follower means.

30. A tool as claimed in any of claims 1 to 23, wherein there is provided reciprocal longitudinal drive means for reciprocally driving the cam follower means.

31. A tool as claimed in claim 30, wherein the longitudinal motion of the cam follower means is converted into rotary motion of the cam track.

32. A tool as claimed in any preceding claim, wherein the cam follower means comprises at least one member, and optionally at least one pair of opposing members.

33. A tool as claimed in claim 32, wherein the each/member has a substantially circular cross-section.

34. A tool as claimed in either of claims 32 or 33, wherein the/each member comprises a substantially cylindrical member.

35. A tool as claimed in any preceding claim, wherein the cam track/cam cylinder is made from a metallic material, such as phosphor bronze.

36. A tool as claimed in any preceding claim, wherein the cam follower means is made from a metallic material.

37. A tool as claimed in any preceding claim, wherein a width of at least a portion of the cam track is greater than a width of the cam follower means.

38. A tool as claimed in any preceding claim, wherein the cam follower means and cam track is a loose fit relative to one another.

39. A tool as claimed in any preceding claim, wherein the cam track and cam follower means are engaged with one another.

40. A tool as claimed in any preceding claim, wherein the cam follower means is engaged within or located in the cam track.

41. A tool as claimed in any preceding claim, wherein the cam follower means is adapted to run in the cam track, so as to optionally, in use, move around the cam track and be thrown between opposing walls of the cam track.

42. A tool as claimed in any preceding claim, wherein the width of the cam follower means is less than 90%,

80%, 70%, 60%, or 50% of the width of the at least a portion of the cam track.

43. A tool as claimed in any preceding claim, wherein the width of the cam follower means is in the region of

10% to 90%, or 40% to 80% of the width of the at least a portion of the cam track.

44. A tool as claimed in any preceding claim, wherein in use, when placed against a work surface, the cam follower means follows a path dictated substantially only by the cam track.

45. A tool as claimed in any preceding claim, wherein the cam track and follower means is such that, in use, when not placed against a work surface the cam follower means travels in a path from one portion or tooth on one wall of the cam track to another portion on another wall of the cam track, optionally without intermediately striking the walls of the track.

46. A tool as claimed in any preceding claim, wherein in use, when placed against a work surface the cam follower means follows a path dictated by the cam track and by ricochet of the tool off the work surface and/or the cam follower means off walls of the cam track.

47. A tool as claimed in claim 46, wherein the cam follower means has two degrees of motion, a first degree of motion defined by the cam track, and a second degree of motion defined by ricochet between opposing walls of the cam track.

48. A tool as claimed in any preceding claim, wherein the first degree of motion has a frequency defined by the cam track.

49. A tool as claimed in either of claims 47 or 48, wherein the second degree of motion has a higher frequency than the frequency of the first degree of motion, the frequency of the second degree of motion optionally varying, dependent upon the work surface to which the tool is presented.

50. A tool as claimed in any of claims 47 to 49, wherein the first degree of motion causes a substantially longitudinal throw of a tool bit of the tool.

51. A tool as claimed in any of claims 47 to 50, wherein the second degree of motion causes a substantially longitudinal vibration or chatter of the tool bit of the tool.

52. A tool as claimed in any preceding claim, wherein the width of the cam follower means is less than the width of the entire cam track.

53. A tool as claimed in any preceding claim, wherein the cam track comprises a closed or circular track and is optionally provided on a cam cylinder.

54. A tool as claimed in any preceding claim, wherein the cam follower means comprises at least one pin, optionally at least one pair of opposing pins.

55. A tool as claimed in any preceding claim, wherein the width of the cam track is constant or varies around the length thereof.

56. A tool as claimed in any preceding claim, wherein the width of the cam track is less or reduced between a top portion of a tooth on one wall and an opposing portion of the other wall .

57. A tool as claimed in any preceding claim, wherein the cam track is recessed, and the cam follower means received therein.

58. A tool as claimed in any of claims 1 to 56, wherein the cam follower means is recessed or comprise at least first and second spaced members or portions, and the cam track received therein, and optionally there are provided at least two pairs of opposing first and second members.

59. A tool as claimed in any preceding claim, wherein the cam track comprises a waveform.

60. A tool as claimed in any preceding claim, wherein the tool is a power tool, a hand-held tool, or a handheld power tool .

61. A tool as claimed in any preceding claim, wherein the tool is powered by an external electrical supply, mains electricity or by a low voltage supply, optionally from a motor vehicle or vessel/boat.

62. A tool as claimed in any preceding claim, wherein the cam track or the cam follower means is rotationally driven by rotational drive means, such as an electric motor .

63. A tool as claimed in any preceding claim, wherein the tool comprises a marine growth removal or anti- fouling tool, such as a barnacle scraper.

64. A tool as claimed in any preceding claim, wherein the tool comprises a housing, a drive means and a mounting arrangement for a tool bit, wherein there is provided within the housing an output arrangement adapted to drive an output shaft in a reciprocal axial movement to drive the tool bit, and the drive means may be substantially sealed from external of the tool.

65. A tool as claimed in any preceding claim, wherein the tool comprises a scraper, paint stripper, wallpaper stripper, chisel, cold chisel, power spade, or hammer.

66. A tool as claimed in any preceding claim, wherein the tool comprises a downhole tool, the tool comprises one or more of: a housing; a rotary drive means, such as an electric motor; a cylinder cam having the cam track extending around a circumferential surface thereof; a mounting arrangement for a tool bit, one of the cam track and cam follower means being driven by the drive means; the mounting arrangement being associated with one of the cam track and the cam follower means, such that actuation of the rotary drive means drives reciprocal movement of the mounting arrangement; at least part of the cam track being in the form of a wave having an amplitude and a wavelength, the wave having a forward throw section, and a rearward throw section, which, in use, drive the mounting arrangement respectively forward and rearward.

67. A tool as claimed in any preceding claim, wherein there are provided a plurality of interchangeable tool bits.

68. A tool comprising a cam track and a cam follower means, wherein the cam track comprises a first wall having at least one first means for throwing the cam follower means towards a second wall of the cam track, in use, when the cam track and cam follower means are rotated relative to one another.

69. A tool as claimed in claim 68, wherein the second wall has at least one second means for throwing the cam follower means towards the first wall of the cam track, in use, when the cam track and cam follower means are rotated relative to one another.

70. A tool as claimed in either of claims 68 or 69, wherein the first means for throwing comprises at least one first tooth.

71. A tool as claimed in either of claims 68 to 70, wherein the second means for throwing comprises at least one second tooth.

72. A tool as hereinbefore described with reference to the accompanying drawings.