WO2013142920A1

WO2013142920A1 - Levelling indicator

Info

Publication number: WO2013142920A1
Application number: PCT/AU2013/000336
Authority: WO
Inventors: Timothy Peter Wilhelm FROLICH; Luke MCVEIGH
Original assignee: Beyond Purple Pty Ltd
Priority date: 2012-03-29
Filing date: 2013-04-02
Publication date: 2013-10-03

Abstract

A levelling aid (63) has a curved closed tubular space 80 filled with a fluid containing a trapped visible air bubble, with indicators which enable the rotational angle about an axis to be indicated.

Description

LEVELLING INDICATOR

FIELD OF THE INVENTION

This invention relates to a levelling indicator which indicates the angle of rotation about an axis, and more specifically to a levelling aid for a chainsaw so that accuracy of cuts and angles can be monitored.

BACKGROUND TO THE INVENTION

[0001] It will be noted that felling trees with chainsaws is a very risky occupation which has very high costs in obtaining adequate insurance cover. Such insurance may also have associated therewith initial excess charges which encourage tree felling contractors to lodge insurance claims only for major or more serious accidents that may occur, and discourage minor claims. Such accidents can take place when the contractor has not achieved complete control over the direction of fall of the tree after it has been cut. This can result in the tree falling onto the operator and causing severe bodily harm. A slight deviation from proven or traditional methods can result in catastrophic errors that range in consequence from blunt chains, which occur from the saw tip contacting the ground during trimming of stumps, to damaged

infrastructure or death of the saw operator or civilian bystanders.

[0002] Prior art chainsaw levelling indicators are difficult to use and do not provide information as to the angle of the cutting plane or axis.

SUMMARY OF THE INVENTION

Levelling aid which indicates rotation about an axis

[0003] In one broad aspect, this invention provides a levelling aid comprising means for indicating the amount of rotation about a first axis, wherein the levelling aid includes a housing enclosing a curved closed tubular space filled with a fluid containing a trapped visible air bubble.

[0004] The curved closed tubular space may be of circular cross-section.

[0005] The volume of the air bubble is preferably small relative to the volume of the curved closed tubular space.

[0006] The curved closed tubular space may form a toroid or a segment of a toroid.

[0007] The curved closed tubular space may form a torus or a segment of a torus.

[0008] The means for indicating the amount of rotation may be a series of one or more angle indications which indicate the amount of rotation about the first axis.

[0009] The series of one or more angle indications may be markings on the housing.

[0010] The closed tubular space may lie in a plane and the size of the air bubble relative to the cross sectional area of the closed tubular space may be such that when the plane is inclined at an angle to the vertical, the indicated angle remains substantially the same as indicated when the plane is vertical.

[0011] The ratio of the diameter of the cross-sectional area of the closed tubular space to the largest dimension of the closed tubular space may be in the range 0.1 to 0.3.

[0012] The closed tubular space may be a torus with outside diameter about 65mm and cross sectional diameter about 15mm.

[0013] The closed tubular space may have dimensions substantially equivalent to those of a torus with outside diameter about 65mm and cross sectional diameter about 15mm. Levelling aid for a chainsaw

[001 ] In another broad aspect, this invention provides a levelling aid adapted to be attached directly or indirectly to a chainsaw, comprising means for indicating the amount of rotation about a first axis from either or both a horizontal or vertical orientation, wherein the levelling aid can be used to assist in making an angled cut using a chainsaw.

[0015] The levelling aid may include a housing enclosing a curved closed tubular housing space filled with a fluid containing a trapped visible air bubble.

[0016] The curved closed tubular space may be of circular cross-section.

[0017] The volume of the air bubble is preferably small relative to the volume of the curved closed tubular space.

[0018] The curved closed tubular housing space may form a toroid or a segment of a toroid.

[0019] The curved closed tubular housing space may form a torus or a segment of a torus.

[0020] The levelling aid may include a bar spirit level having a longitudinal axis.

[0021] The longitudinal axis of the bar spirit level may be substantially parallel to the first axis.

[0022] The longitudinal axis of the bar spirit level may be non-coplanar with the plane of the curved closed tubular space.

[0023] The means for indicating the amount of rotation may be a series of one or more angle indications which indicate the amount of rotation about the first axis. [0024] The series of one or more angle indications may be markings on the housing.

[0025] The closed tubular space may lie in a plane, and the size of the air bubble relative to the cross sectional area of the closed tubular space may be such that when the plane is inclined at an angle to the vertical, the indicated angle remains substantially the same as indicated when the plane is vertical.

[0026] The ratio of the diameter of the cross-sectional area of the closed tubular space to the largest dimension of the closed tubular space may be in the range 0.1 to 0.3.

[0027] The closed tubular space may be a torus with outside diameter about 65mm and cross sectional diameter about 15mm.

[0028] The closed tubular space may have dimensions substantially equivalent to those of a torus with outside diameter about 65mm and cross sectional diameter about 15mm.

Chainsaw with levelling aid

[0029] A further aspect of this invention provides a chainsaw with an improved levelling aid which is simple to operate. By being simpler to operate, improved safety procedures in accordance with workplace health and safety

requirements can be more easily put in place.

[0030] Preferably,the levelling aid indicates to the chainsaw operator the angle at which the chainsaw is held.

[0031] In a broad aspect, this invention provides a chainsaw with at least one levelling aid comprising means for indicating the amount of rotation about a first axis from either or both a horizontal or vertical orientation, wherein the levelling aid can be used to assist in making an angled cut using the chainsaw, and wherein the angled cut is in a plane which is neither horizontal nor vertical.

[0032] The first axis may be substantially parallel to a longitudinal axis of the chainsaw cutting bar.

[0033] The at least one levelling aid may include a housing enclosing a curved closed tubular space filled with a fluid containing a trapped visible air bubble.

[0034] The curved closed tubular space may be of circular cross-section.

[0035] The volume of the air bubble is preferably small relative to the volume of the curved closed tubular space.

[0036] The at least one curved tubular space may be attached in a plane which is not substantially parallel to the chainsaw cutting bar.

[0037] The at least one curved tubular space may be attached in a plane which is substantially orthogonal to the plane formed by the chainsaw cutting bar.

[0038] The curved closed tubular space may form a toroid or a segment of a toroid.

[0039] The curved closed tubular space may form a torus or a segment of a torus.

[0040] The chainsaw may include at least one bar spirit level having a longitudinal axis.

[0041] The longitudinal axis of the bar level may be substantially parallel to the first axis.

[0042] The longitudinal axis of the bar spirit level may be non-coplanar with the plane of the curved tubular space. [0043] The means for indicating the amount of rotation may be a series of one or more angle indications which indicate the amount of rotation about the first axis.

[0044] The series of one or more angle indications may be markings on the housing.

[0045] The closed tubular space may lie in a plane and the size of the air bubble relative to the cross sectional area of the closed tubular space may be such that when the plane is inclined at an angle to the vertical, the indicated angle remains substantially the same as indicated when the plane is vertical.

[0046] The ratio of the diameter of the cross-sectional area of the closed tubular space to the largest dimension of the closed tubular space may be in the range 0.1 to 0.3.

[0047] The closed tubular space may be a torus with outside diameter about 65mm and cross sectional diameter about 15mm.

[0048] The closed tubular space may have dimensions substantially equivalent to those of a torus with outside diameter about 65mm and cross sectional diameter about 15mm.

[0049] This invention provides a levelling aid for a chainsaw which has an air bubble located in a liquid in a housing attached to the chainsaw.

[0050] The housing may be provided with a screw threaded shank for attachment to a mounting aperture in a body of a chainsaw or may be provided with a screw threaded part for attachment to a fastener assembly or coupling having a screw threaded shank for attachment to the mounting aperture.

[0051] The levelling aid may have one or more indicator lines marked on a transparent face of the housing. The indicator lines may alternatively be marked on the chainsaw. [0052] The levelling aid may comprise a spirit level, and/or a toroidal level, and/or an angle gauge.

[0053] The levelling aid may comprise a digital level and/or a digital angle gauge.

[0054] The invention also extends to a chain saw including the levelling aid or aids described above.

[0055] The invention in another aspect provides a chainsaw with one or more levelling aids which is or are attached to one but more preferably a pair of substantially planar side surfaces of the chainsaw so that in use the levelling aid(s) are located in a plane that is coplanar or is substantially parallel with a plane defined by a cutting bar of the chainsaw when making a cut in use.

[0056] The chainsaw may also be provided with an angle gauge located and a further levelling device so that the chainsaw may also be proficient in making an angled cut. In another more preferred embodiment the angle gauge may be combined with the levelling aid which preferably is as described above.

[0057] It is highly desirable that the chainsaw levelling aid of the invention will directly correlate to a cutting axis of the cutting bar of the chainsaw. It may therefore depict not only horizontal and vertical planes but also once deemed level in either of these planes will be able to then also depict a range of angles for oblique or angled cuts.

[0058] The angle gauge may indicate an angle that is in the range of zero to 360 degrees, or may indicate a lesser range of angles. The angle gauge may be particularly useful for making an angled top cut of a scarf when felling a tree.

[0059] It is preferred that a pair of levelling aids with an inbuilt-angle gauge are used wherein a respective levelling aid is attached to an adjacent side surface of the chainsaw. This has the advantage that the chainsaw of the invention may be used in multiple orientations rather than a single orientation if only one levelling aid was used. [0060] The invention in a furtgher aspect provides a chainsaw including an angle gauge mounted thereon and visually observable to the chain saw user wherein the angle gauge can be used by a user to assist them in making an angled cut.

[0061] The angle gauge may be mounted to any surface of the chainsaw visible to the user when in use.

[0062] The angle gauge and the levelling aid may include any one or more of the features of the angle gauge and levelling aid defined above in the preceding aspect of the invention.

Method of operation of chainsaw with levelling aid

[0063] The invention further provides a method of operation of a chainsaw with at least one levelling aid which includes the steps of:

(i) aligning a cutting bar of the chainsaw by use of the at least one levelling aid such that a longitudinal axis of the chainsaw cutting bar is substantially horizontal, and

(ii) carrying out a cutting operation and maintaining the chainsaw

cutting bar at a desired rotational angle by use of the at least one levelling aid

while maintaining the longitudinal axis of the chainsaw cutting bar in an substantially horizontal orientation by use of the at least one levelling aid.

[0064] The invention also provides a method of operation of a chainsaw having a levelling aid as well as an angle gauge attached thereto which includes the steps of:

(i) aligning a cutting bar of the chainsaw in a horizontal or oblique plane, and (ii) carrying out a cutting operation and maintaining the cutting bar in the horizontal or oblique plane by use of the levelling aid and angle gauge respectively.

BRIEF DESCRIPTION OF THE DRAWINGS

[0065] A chain saw and a levelling aid in accordance with this invention may manifest itself in a variety of forms. It will be convenient to hereinafter describe at least one/ several embodiments of the invention in detail with reference to the accompanying drawings. The purpose of providing this detailed description is to instruct persons having an interest in the subject matter of the invention how to carry the invention into practical effect.

However it is to be clearly understood that the specific nature of this detailed description does not supersede the generality of the preceding broad description. In the drawings:

[0066] FIGS 1 -2 are views showing a side view and plan view of correct use of a chainsaw;

[0067] FIGS 3-6 are views illustrating incorrect use of a chainsaw;

[0068] FIG 7 shows a perspective view in relation to making a bottom cut using a chainsaw, using the levelling aid shown in plan view in FIG7a;

[0069] FIG 8 shows a perspective view in relation to making an angled cut or top cut using a chainsaw;

[0070] FIG 9 shows use of a chainsaw constructed in accordance with the invention showing incorporation of a spirit level device;

[0071] FIG 10 shows incorporation of the spirit level device in two alternative locations on the chainsaw;

[0072] FIG 11 shows calibration of correct installation of the spirit level device to a chainsaw; [0073] FIG 12 shows one method of attachment of the spirit level device to a chainsaw;

[0074] FIGS 13-14 show a sectional view and a perspective view respectively of another method of attachment of the spirit level device to the chainsaw;

[0075] FIGS 15-16 show yet another method of attachment of the spirit level to the chainsaw wherein FIG 15 is a plan view of the spirit level mounting assembly and FIG 16 shows a side view; and

[0076] FIGS 17, 18 , 19 show use of an alternative type of combined spirit level and angle gauge for use in the invention.

[0077] FIGS 20 and 21 are further views illustrating incorrect use of a chainsaw.

[0078] FIGS 22 and 23 illustrate plan and elevation views of a chain saw air box with an alternative implementation of the invention using a toroidal level and a bar level.

[0079] FIG 24 illustrates a levelling aid of the invention.

[0080] FIG 25 shows a perspective view of a levelling aid of the invention.

[0081] FIG 26 shows a cross-sectional view of the levelling aid of FIG 25 at line A-A.

DETAILED DESCRIPTION OF PREFERRED AND OTHER EMBODIMENTS

[0082] Figures 25 and 26 show a perspective view and a cross-sectional view at line A-A of an embodiment of the levelling aid of the invention. Levelling aid 63 is a torus-shaped spirit level. Angle markings 70 and indicator lines 72 are indicated on the housing of the levelling aid. Angle markings of 30°, 60°, 90° are indicated, though it will be appreciated that any set of angle markings may be indicated, and that the markings need not indicate angles in degrees. The angle markings and indicator lines are not shown in the cross sectional view of Figure 26.

[0083] In use, the levelling aid 63 is held with the plane of the level in a first plane which is not horizontal. When rotated within the first plane, about an axis of the level which is perpendicular to the first plane, the air bubble enclosed within levelling aid 63 indicates the amount of rotation within the plane.

[0084] The housing of the levelling aid is substantially torus shaped, and is comprised of a first portion 74 and a second portion 76 joined at joint 78. Joint 78 may comprise a matching tongue and groove to correctly position the first and second portions with respect to each other. When joined, first portion 74 and second portion 76 enclose a hollow enclosed curved tubular space 80 which is filled with a liquid containing a visible air bubble (not shown). The hollow enclosed curved tubular space 80 is shown to be circular in cross section, though it will be appreciated that other closed cross-sectional shapes are possible.

[0085] The second portion 76 has an attached base 77 which facilitates attachment to a chainsaw or other object. It will be appreciated that the base 77 is not essential to the operation of the invention.

[0086] While the described embodiment of the levelling aid is substantially torus shaped, it will be appreciated that other shapes are possible. In its broadest form, the shape of the hollow enclosed curved tubular space may be any curved closed shape. For example, the shape in plan view may be elliptical or oval, or some other curved or piecewise linear shape, for example an octagonal shape. The shape may also be a segment of any one of these shapes; for example a 180 degree segment of a toroid will indicate the amount of angular rotation with a 180 degree limitation. These alternative shapes provide different degrees of sensitivity in the indicating of the amount of rotation about the axis of the levelling aid. [0087] It will be further appreciated that it is the shape of the hollow enclosed curved tubular space 80 which determines the operation of the levelling aid. The external housing may be of arbitrary shape and configuration, provided that the air bubble contained within the internal hollow enclosed curved tubular space 80 is visible to a user when in use.

[0088] The size of enclosed the air bubble relative to the cross sectional area of the closed tubular space is such that when the plane of the levelling aid is inclined at an angle to the vertical, the indicated angle remains substantially the same as indicated when vertical, so that the levelling aid operates correctly whether or not the plane formed by the levelling aid is vertical.

[0089] In a preferred embodiment, the levelling aid has largest external diameter of about 70mm, with largest dimension of the enclosed space 80 about 65mm, and cross sectional diameter of the enclosed space about 15mm.

Chainsaw Levelling Aid

[0090] In the drawings in FIGS 1 -2 there is a shown how a chainsaw can be correctly used in felling a tree so that after the relevant cuts are made the tree is arranged to fall according to relevant codes of practice and in a certain direction that will not cause any damage or injury. For example the tree should fall away from the operator using the chainsaw. Thus in FIGS 1 -2 the general and correct technique is to produce a "scarf" 9 which includes an angled cut or top cut 10 to tree 11 and a bottom or horizontal cut 12 to tree 11. There is also produced a "hinge" 13 shown in phantom in FIGS 1 -2 which is formed when another cut or back cut 1 is made to tree 11 which is located at a correct distance above bottom cut 12 as shown. This also facilitates breaking any holding wood. The top cut 10 should be from 30-45° to bottom cut 12.

[0091] Incorrect use of a chainsaw in a felling operation is shown in FIGS 3-6, 20 and 21 where cut 14 is aligned with bottom cut 12 in FIGS 3 and 5 or where cut 14 is located adjacent to a top part of cut 14 in FIG 4 or where cut 14 is located slightly below bottom cut 12 in FIG 6. It will be noted in these instances that the tree 11 is likely to fall in any direction which may not be anticipated and that this will be dangerous to the operator of the chainsaw and others.

[0092] In FIG 7 there is shown a chainsaw 15 which has a spirit level 16 attached thereto. Spirit level 16 is shown in plan view in FIG 7a. Spirit level 16 has an inbuilt angle gauge shown by angle lines 57 and 58 which indicate inclinations of 15° and 30°. The angle lines may show inclinations other than 15° or 30°. More than two angle lines may be provided. It will be noted that use of the spirit level 16 facilitates the obtaining of a bottom cut 12 which is not only straight but is on a constant horizontal plane as is necessary for correct use of chainsaw 15. This is achieved by cutting with bubble 56 being located within angle line 57. There is also shown the use of chainsaw sight line 17 shown schematically in FIG 7 A which extends at right angles to the longitudinal axis of cutting bar 23 and which extends around the periphery of chainsaw 15. There is also shown operator 19 holding chainsaw 15 by front handle 20 and rear handle 21 adjacent guard 22. The operator has a helmet, safety glasses and earmuffs.

[0093] FIG 8 shows the correct technique when making an angled cut or top cut 10 using spirit level 16 or angle gauge 62 shown hereinafter in FIGS 17-19. The spirit level 16 is shown on each side surface 8A and 8B of chainsaw 15.

[0094] In FIG 9 there is shown correct use of chainsaw 15 with the tree 1 1 omitted for convenience. The cutting bar 23 with saw chain 24 movably attached thereto is maintained at a constant horizontal plane by use of spirit level 16. The arrows A and B show the horizontal plane that is required for a safe and correct procedure for carrying out a bottom cut 12 or backcut 14. The arrows C and D show that once the saw is aligned in the A-B plane it may then be tilted through to the C-D plane to allow an angled cut 14.

[0095] FIG 10 shows chainsaw 15 with grille 25 and engine 26 and shows spirit level 16 attached to body 27. There is also shown fuel tank 28, cap 29 and fasteners 30, 32, 32 and 33 attaching front or main handle 21 to body 27 while spirit level 16 is shown attached to body 27 by a screw threaded bolt as shown hereinafter in FIGS 12-16. It will be appreciated that spirit level 16 can be attached to chainsaw 15 by the removal of existing fasteners 30, 31 , 32 and 33. There is also shown spirit level 16A shown in phantom in an alternative location attached to air cover filter 28 by adhesive or bonding agent if appropriate but preferably moulded into an after market version of air cover filter 28. There is also shown sprocket chain 34 having links (not shown) with cutting teeth 35 and 36 attached to each link.

[0096] In FIG 11 there is shown another type of chainsaw 15A which does not have a rear handle to which are attached spirit levels 16 and 16A which are in alternative locations as is the case with FIG 10. In chainsaw 15A there is shown guard and chain brake 22A, handle 21A, fuel tank cap 29A, oil tank cap 38, pull start handle 39, and air filter cover 20A. There is a further spirit level 16B shown temporarily placed on cutting bar 23 for the purpose of calibration of spirit levels 16 or 16A when being attached to chainsaw 15A.

[0097] In FIG 12 there is shown one method of attachment of spirit level 16 to chainsaw 15 wherein there is provided a spirit level assembly 47 having spirit level 16 and housing 16A and screw threaded body portion 40 which engages with a collar 41 having an internal screw thread 42. There is also provided a bolt 43 having aperture 44 for engagement into an Allen key or similar tool and screw threaded shank 44 which passes through bottom aperture 45 of collar 41 so as to attach collar 41 to a screw threaded aperture 46 of body 27 of chainsaw 15.

[0098] In FIGS 13-14 there is shown another method of attachment of spirit level 16 to aperture 46 of body 27 of chainsaw 15. In this embodiment spirit level mounting assembly 48 is provided with spirit level 16 having housing 16A which is supported in block 49 which is also provided with a screw threaded internal passage 49A which engages with fastener assembly 50 having a depending screw threaded shank 51 which engages in aperture 46 of body 27. The fastener assembly 50 also has screw thread 50A for engagement with mating passage 49A. The mounting assembly 48 may replace an existing bolt of chainsaw 15 as described in FIG 10. [0099] In another variation as shown in FIG 15-16 there is shown spirit level mounting assembly 51 having spirit level 16, hexagonal housing 16B, support body 52, bevel 53 and depending part 54 having depending bolt 55. Support body 52, bevel 53 and part 54 may engage in a recess of corresponding shape (not shown) in body 27 which has a screw threaded passage for engagement with bolt 55 or alternatively bolt 55 may engage with screw threaded aperture 46 in body 27. FIG 15 also shows that bubble 56 has moved from within sight line 57 to enter angle line 58 showing the angle of the cut being made.

[0100] In FIGS 17-19 there is shown use of an arcuate angle gauge 62 used in place of spirit level 16 which is attached to each side surface 8A and 8B of chainsaw 15 so that chainsaw 15 may be used in different positions so that either surface 8A or surface 8B is uppermost and thereby visible to the eye of the operator. In regard to angle gauge 62 there is shown in FIGS 18-19 an air bubble 63 at the 0° position and lines corresponding to angles 45°, 60° or 70° on either side of bubble 63.

[0101] The angle gauge may be a curved sight tube.

[0102] It will also be appreciated that a combined spirit level and angle gauge may be used. The angle gauge may be a digital angle meter which can be used on any surface of chainsaw 15 or 15A. It will also be appreciated that the spirit level or angle gauge can be placed on any surface of the chainsaw 15 or 15A.

[0103] FIGS 22 and 23 show a chainsaw air box 65 including an attached bar level 64 and an attached toroidal spirit level 63. The toroidal spirit level comprises a transparent or translucent toroidal housing filled with a liquid containing a trapped air bubble. The toroidal housing is preferably torus shaped, but may take some other toroidal shape. The combination of toroidal level 63 and bar level 64 in a dual plane configuration provides a levelling aid which is easy to construct and easy to use. It will be understood that provision of a housing which is a segment of a toroid (e.g. 180 degree segment or 270 degree segment) rather than a full toroid would allow measurement of a restricted range of rotational angles. [0104] The bar level 64 is a straight level, and contains trapped air bubble 66a. The toroidal level 63 is shown in FIG 24 attached to the air box 65.

Indicator lines to indicate, for example, angles of 0°, 30°, 60° and 90°, are marked on the air box, and are visible through the toroidal level. The indicator lines may alternatively be marked on the housing of the toroidal level such that they are visible to a user. The toroidal level 63 includes a trapped air bubble 66b which indicates the degree of rotation. The toroidal level 63, used in combination with the indicator lines on the air box, and with the bar level 64, allow the chainsaw to be held at the correct angle. The bar level is aligned parallel to the longitudinal axis of the chainsaw cutting bar, while the toroidal level lies in a plane orthogonal to the plane formed by the chainsaw cutting bar, forming an angle with the plane formed by the chainsaw cutting bar. In use, the bar level is first aligned such that a longitudinal axis of the chainsaw cutting bar is horizontal by use of bar level 64 with trapped air bubble 66a, and then while maintaining that level, the rotational angle of the chainsaw about the longitudinal axis is adjusted, with the angle of rotation indicated by the position of the air bubble 66b within the toroidal level 63. The sensitivity of the angle indication is determined by the angle between the bar level 64 and the plane of the toroidal level 63. Preferably, the angle is in the range 45 degrees to 75 degrees.

[0105] In regard to operation of the chainsaw 15 of the invention with incorporated spirit level 16, or with incorporated bar spirit level 64 and toroidal spirit level 63, it will be appreciated that safety and efficiency can be enhanced by:

(i) improving accuracy when attempting to direct a scarf cut towards the desired direction of fall;

(ii) reducing the chances of overcutting top or bottom cuts;

(iii) ensuring a minimum scarf cut opening of 45 degrees;

(iv) intersecting top and bottom cuts at the rear of the scarf cut along one intersecting line to act as a hazard control measure; and (v) ensuring that the backcut is level to allow the step between the intersecting scarf cut and backcut heights to act as a hazard control measure.

[0106] The chainsaw of the invention may have sight line(s) 17 as described above. These lines 17 are standard safety features on most chainsaws and are usually perpendicular to the longitudinal axis of cutting bar 23. The chainsaw 15 may also have "dog teeth" which are a standard component that stabilizes the chainsaw against the tree while cutting.

[0107] Spirit level 16 is mounted correctly on both sides 8A and 8B of the body 27 with the following features:

(a) bubble sight line 57 that lines up with the chainsaw sight line(s) 17 and indicates the desired direction of fall;

(b) bubble sight line 57 that indicates when the bar is horizontal from side to side; and

(c) bubble 45 degree tilt line shown in FIGS 18 and 19 that indicate when the bar 23 is tilted at 45 degrees from side to side.

Cutting Procedures using the levels of Figs 7, 8, 10-16

[0108] In making a top cut 10, the following procedure should be followed:

(i) Rest the chainsaw bar 23 against the tree 11 and use the bubble 56 to align the bar 23 using the following positioning requirements:

(a) chainsaw sight lines 17 and bubble sight line 57 are directed at the felling target; and

(b) bubble 56 is located directly under the intersection of the bubble sight line 57 and the bubble 45 degree tilt line; and

(ii) The top cut 10 may be completed when the depth of the cut

penetrates through 25-30% of the tree trunk or stem diameter. [0109] In making a bottom cut 12, the following procedure should be followed:

(i) rest the chainsaw bar 23 against the tree stem with the bottom set of dog teeth engaged alongside the finish of the top cut 10;

(ii) ensure that bubble 56 is located directly under the intersection of sight line 17 and level line 57. It will be noted that sight line 17 will not point towards the felling target when the bottom cut 10 is initiated. The chainsaw bar 23 should be horizontal to and alongside the finish of top cut 10; and

(iii) the bottom cut 12 is completed when the intersection with top cut 10 is achieved. The progress of bottom cut 12 should be monitored by looking down the top cut 10 to avoid overcutting.

[0110] In making a scarf cut, the following procedure should be followed:

(i) remove the scarf; and

(ii) rest the chainsaw bar 23 along the intersecting line at the rear of the scarf cut and check that the following requirements are in place:

(a) sight line(s) 17 and level line 57 are directed at the felling target;

(b) bubble 56 is located directly under the intersection of sight line 17 and level line 57; and both top cut 10 and bottom cuts 12 have intersected along clean line at the back of the scarf cut without overcutting.

[0111] In making back cut 14, the following procedure should be adopted:

(i) rest the chainsaw 15 against the tree behind the position of the scarf cut and use the spirit level 16 to align the chainsaw bar 23 using the following positioning requirements: (a) chainsaw sight lines 17 and bubble level line 57 are directed at the felling target; and

(b) bubble 56 is located directly under the intersection of sight line 17 and the level line 57; and

(c) the level of the chainsaw bar is approximately 10 percent of the tree's diameter above the level of the intersecting scarf cut; and

(ii) finish back cut 14 at a point that allows a hinge of intact fibres to control the fall of the tree. The minimum width of hinge fibres should be approximately 10 percent of the tree's diameter.

Cutting Procedures using the level of Figs 22-24

[0112] In making a top cut 10, the following procedure should be followed:

(i) Rest the chainsaw bar 23 against the tree 11 and use the bubble 66a to align the bar 23 to be horizontal;

(ii) Rotate the chainsaw about a longitudinal axis so that the desired angle of rotation is indicated by air bubble 66b;

(iii) The top cut 10 may be completed when the depth of the cut

penetrates through 25-30% of the tree trunk or stem diameter.

[0113] In making a bottom cut 12, the following procedure should be followed:

(i) Rest the chainsaw bar 23 against the tree stem with the bottom set of dog teeth engaged alongside the finish of the top cut 10, and use the bubble 66a to align the bar 23 to be horizontal;

(ii) Rotate the chainsaw about a longitudinal axis so that the desired air bubble 66b indicates that the chainsaw bar is horizontal, ensuring that bubble 66a remains in the position which indicates the bar 23 to be horizontal; (iii) the bottom cut 12 is completed when the intersection with top cut 10 is achieved. The progress of bottom cut 12 should be monitored by looking down the top cut 10 to avoid overcutting.

[0114] In making back cut 14, the following procedure should be adopted:

(i) rest the chainsaw 15 against the tree behind the position of the

scarf cut and use the bubble 66a to align the bar 23 to be horizontal, such that the level of the chainsaw bar is approximately 10 percent of the tree's diameter above the level of the intersecting scarf cut;

(ii) Rotate the chainsaw about a longitudinal axis so that the desired air bubble 66b indicates that the chainsaw bar is horizontal, ensuring that bubble 66a remains in the position which indicates the bar 23 to be horizontal;

(iii) finish back cut 14 at a point that allows a hinge of intact fibres to control the fall of the tree. The minimum width of hinge fibres should be approximately 10 percent of the tree's diameter.

[0115] It will of course be realized that the above has been given only by way of illustrative example of the invention and that all such modifications and variations thereto, as would be apparent to persons skilled in the art, are deemed to fall within the broad scope and ambit of the invention as is herein set forth.

Claims

The claims defining the invention are as follows:

1. A levelling aid comprising means for indicating the amount of rotation about a first axis, wherein the levelling aid includes a housing enclosing a curved closed tubular space filled with a fluid containing a trapped visible air bubble.

2. The levelling aid of claim 1 wherein the curved closed tubular space is of circular cross-section.

3. The levelling aid of claim 1 or claim 2 wherein the volume of the air bubble is small relative to the volume of the curved closed tubular space.

4. The levelling aid of any one of the previous claims in which the curved closed tubular space forms a toroid or a segment of a toroid.

5. The levelling aid of any one of the previous claims in which the curved closed tubular space forms a torus or a segment of a torus.

6. The levelling aid of any one of the previous claims in which the means for indicating the amount of rotation is a series of one or more angle indications which indicate the amount of rotation about the first axis.

7. The levelling aid of claim 6 wherein the series of one or more angle indications are markings on the housing.

8. The levelling aid of any one of the previous claims wherein the closed tubular space lies in a plane and the size of the air bubble relative to the cross sectional area of the closed tubular space is such that when the plane is inclined at an angle to the vertical, the indicated angle remains substantially the same as indicated when the plane is vertical.

9. The levelling aid of any one of the previous claims wherein the ratio of the diameter of the cross-sectional area of the closed tubular space to the largest dimension of the closed tubular space is in the range 0.1 to 0.3.

10. The levelling aid of any one of the previous claims wherein the closed tubular space is a torus with outside diameter about 65mm and cross sectional diameter about 15mm.

11. A levelling aid adapted to be attached directly or indirectly to a chainsaw, comprising means for indicating the amount of rotation about a first axis from either or both a horizontal or vertical orientation, wherein the levelling aid can be used to assist in making an angled cut using a chainsaw.

12. The levelling aid of claim 11 which includes a housing enclosing a curved closed tubular space filled with a fluid containing a trapped visible air bubble.

13. The levelling aid of claim 12 wherein the curved closed tubular space is of circular cross-section.

14. The levelling aid of any one of claims 12 to 13 wherein the volume of the air bubble is small relative to the volume of the curved closed tubular space.

15. The levelling aid of any one of claims 12 to 1 in which the curved closed tubular space forms a toroid or a segment of a toroid.

16. The levelling aid of any one of claims 12 to15 in which the curved closed tubular space forms a torus or a segment of a torus.

17. The levelling aid of any one of claims 11 to 16 which includes a bar spirit level having a longitudinal axis.

18. The levelling aid of claim 17 wherein the longitudinal axis of the bar spirit level is substantially parallel to the first axis.

19. The levelling aid of any one of claims 17 to 18 when dependent on any one of claims 12 to 16 wherein the longitudinal axis of the bar spirit level is non-coplanar with the plane of the curved closed tubular space.

20. The levelling aid of any one of claims 11 to 19 in which the means for indicating the amount of rotation is a series of one or more angle indications which indicate the amount of rotation about the first axis.

21. The levelling aid of claim 20 when dependent on any one of claims 12 to 16 wherein the series of one or more angle indications are markings on the housing.

22. The levelling aid of any one of claims 12 to 21 wherein the closed tubular space lies in a plane, and the size of the air bubble relative to the cross sectional area of the closed tubular space is such that when the plane is inclined at an angle to the vertical, the indicated angle remains substantially the same as indicated when the plane is vertical.

23. The levelling aid of any one of claims 12 to 22 wherein the ratio of the diameter of the cross-sectional area of the closed tubular space to the largest dimension of the closed tubular space is in the range 0.1 to 0.3.

24. The levelling aid of any one of claims 12 to 23 wherein the closed tubular space is a torus with outside diameter about 65mm and cross sectional diameter about 15mm.

25. A chainsaw with at least one levelling aid comprising means for indicating the amount of rotation about a first axis from either or both a horizontal or vertical orientation, wherein the levelling aid can be used to assist in making an angled cut using the chainsaw, and wherein the angled cut is in a plane which is neither horizontal nor vertical.

26. The chainsaw of claim 25 wherein the first axis is substantially parallel to a longitudinal axis of the chainsaw cutting bar.

27. The chainsaw of claim 25 or claim 26 in which the at least one levelling aid includes a housing enclosing a curved closed tubular space filled with a fluid containing a trapped visible air bubble.

28. The levelling aid of claim 27 wherein the curved closed tubular space is of circular cross-section.

29. The levelling aid of claim 27 or claim 28 wherein the volume of the air bubble is small relative to the volume of the curved closed tubular space.

30. The chainsaw of any one of claims 27 to 29 wherein the at least one curved tubular space is attached in a plane which is not substantially parallel to the chainsaw cutting bar.

31. The chainsaw of claims 27 to 30 wherein the at least one curved tubular space is attached in a plane which is substantially orthogonal to the plane formed by the chainsaw cutting bar.

32. The chainsaw of any one of claims 27 to 31 in which the curved closed tubular space forms a toroid or a segment of a toroid.

33. The chainsaw of any one of claims 27 to 32 in which the curved closed tubular space forms a torus or a segment of a torus.

34. The chainsaw of any one of claims 25 to 33 which includes at least one bar spirit level having a longitudinal axis.

35. The chainsaw of claim 34 wherein the longitudinal axis of the bar level is substantially parallel to the first axis.

36. The chainsaw of claim 34 or claim 35 when dependent on any one of claims 27 to 33 wherein the longitudinal axis of the bar spirit level is non- coplanar with the plane of the curved tubular space.

37. The chainsaw of any one of claims 25 to 36 in which the means for indicating the amount of rotation is a series of one or more angle indications which indicate the amount of rotation about the first axis.

38. The chainsaw of claim 37 when dependent on any one of claims 27 to 33 wherein the series of one or more angle indications are markings on the housing.

39. The levelling aid of any one claims 26 to 38 wherein the closed tubular space lies in a plane and the size of the air bubble relative to the cross sectional area of the closed tubular space is such that when the plane is inclined at an angle to the vertical, the indicated angle remains substantially the same as indicated when the plane is vertical.

40. The levelling aid of any one of claims 26 to 39 wherein the ratio of the diameter of the cross-sectional area of the closed tubular space to the largest dimension of the closed tubular space is in the range 0.1 to 0.3.

41. The levelling aid of any one of claims 26 to 40 wherein the closed tubular space is a torus with outside diameter about 65mm and cross sectional diameter about 15mm.

42. A method of operation of a chainsaw with at least one levelling aid of any one of claims 25 to 41 which includes the steps of:

(iii) aligning a cutting bar of the chainsaw by use of the at least one levelling aid such that a longitudinal axis of the chainsaw cutting bar is substantially horizontal, and

(iv) carrying out a cutting operation and maintaining the chainsaw