WO1997042806A1

WO1997042806A1 - Pruning saw

Info

Publication number: WO1997042806A1
Application number: PCT/AU1997/000292
Authority: WO
Inventors: Robert Gregory Forage; Colin COUCH
Original assignee: CURTIS, Susanne, Jean; COUCH, Ian, John
Priority date: 1996-05-09
Filing date: 1997-05-09
Publication date: 1997-11-20

Abstract

A pruning saw or similar cutting tool (1) provided with the following features: a saw blade frame (2) having spaced apart mounting means projecting laterally of the frame between which a saw blade (3) is adapted to be mounted to the frame (2), retaining means (4) disposed transversely of the blade when mounted to the frame said retaining means being adapted to engage or contact a branch or other object to be cut (5), while it is being cut, and an elongate shaft (6) to be rigidly attached to the saw blade frame to enable the saw to be remotely positioned against the object to be cut and to facilitate a cutting operation, wherein the retaining means (4) and the frame (2) are relatively moveable during a cutting stroke such that a return mechanism (12, 14) is operatively activated by that relative movement to assist return of the frame to an initial cutting position at the end of each cutting stroke.

Description

PRUNING SAW

Technical Field The present invention concerns a pruning saw, but is also applicable to any similar manually operated cutting tool where remote operation is required.

Background Art The most commonly known pruning saw involves a curved saw blade bolted or strapped to the top of a wooden pole. The wooden pole provides reach to enable an operator to stand on the ground and saw small branches from trees. The operator pushes the pole backwards and forwards, and the curved shape of the blade, together with the overall weight of the pruning saw. enables the teeth of the blade to cut on both the forward and backward strokes, even though the operator is not able to apply a proper sawing motion to the blade. Use of this type of pruning saw is restricted to relatively small and easily cut branches, because of the difficulty in manipulating it and the flexure and flimsiness of the blade.

A very large number of attempts to improve the arrangement of remote cutting have been proposed. However, none has proved sufficiently robust, reliable, easy to use or inexpensive, to provide an attractive replacement for the simple arrangement described above.

Disclosure of the Invention The invention, as currently envisaged, contemplates a pruning saw or similar cutting tool provided with the following features: a saw blade frame having spaced apart mounting means projecting laterally of the frame between which a saw blade is adapted to be mounted to the frame, retaining means disposed transversely of the blade when mounted to the frame said retaining means being adapted to engage or contact a branch or other object to be cut, while it is being cut, and an elongate shaft to be rigidly attached to the saw blade frame to enable the saw to be remotely positioned against the object to be cut and to facilitate a cutting operation, wherein the retaining means and the frame are relatively movable during a cutting stroke such that a return mechanism is operatively activated by that relative movement to assist return of the frame to an initial cutting position at the end of each cutting stroke. The saw blade itself is an inessential part of the saw of the invention as such, and will be replaced as it wears, or exchanged for other blades having a cutting profile and temper suitable for the object to be cut.

The blade mounting means or brackets will usually engage the ends of the blade and with one bracket being adjustable to apply tension to stiffen the blade and improve its cutting performance. The tension may be adjustable in any known manner, such as by means of the engagement of one end of the blade by a hook having a threaded shaft, and a tensioning nut. Advantageously, the blade is arranged in the saw so that cutting is effected by a downstroke, that is pulling the shaft towards the operator. This is found to make operation easier especially when the object to be cut is above the operator, such as may be the case when cutting a branch from a tree.

In one embodiment the return mechanism which assists in returning the saw to its start position after a cutting stroke is formed as a slidable arrangement to which is mounted the retaining means or arms.

In another embodiment the retaining arm extends laterally of and on both sides of the blade in order to ensure that it engages that part of the branch which remains attached to the tree after cutting. This prevents the saw from falling together with the cut branch at the conclusion of a cutting operation thus providing greater safety for the operator.

In a further embodiment the saw blade frame comprises a straight portion having a saw blade mounting bracket at each end. The retaining arm in this embodiment is attached to a carriage adapted to reciprocate back and forth along the shaft. When the retaining arm has a U-shaped configuration, it may extend from opposite sides of the carriage in a loop encompassing the blade. The retaining arm would generally intercept the blade at about 90°. The retaining arm may be curved to improve its retention against a branch during use. Yet another embodiment has a generally U-shaped retaining arm mounted to a plate which is slidable on the frame. Preferably, the plate comprises multiple positions for fitting the free ends of the U-shaped retaining arm so that the arm can be tilted relative to the plane of the saw's blade so that the angle of the cut of the blade can be varied relative to the axis of the object to be cut. In a still further embodiment a spring is connected between the retaining arm carriage and the saw blade frame in order to assist the upstroke during use. For instance, an extension spring may be connected between the retaining arm carriage and the lowermost, in use, blade mounting means so that the spring is tensioned during the downstroke. Another embodiment employs a compression spring between the carriage and the uppermost, in use, blade mounting means so that it will be compressed during each cutting down stroke. The spring, in each case, will then be ready to assist in the upstroke as it contracts or expands, respectively. Ideally, the spring will provide all the energy required for the upstroke under normal operation.

The retaining arm carriage may be keyed to the straight portion of the blade mounting frame to prevent rotation of the retaining arm carriage about the straight portion. Keying may be achieved in any convenient way, such as by a rectangular key on the carriage side and a keyway in the straight portion. Alternatively both may be of oval or rectangular section and thereby self- centering.

Another embodiment of the invention provides a saw frame having a pair of fixedly mounted laterally extending mounting means in the form of arms or spreader with eyes or runners at the free ends of the arms. In this version an elasticised cord is mounted to retaining means through each runner and extension of the elasticised cord as the saw undergoes a cutting stroke causes biasing of the saw to its initial position where the retaining means are engaged with an object to be cut.

The saw blade is generally angled with respect to the straight portion of the saw blade frame. Ideally the blade is angled between 5° and 15° from the vertical when in use so that on the downstroke, as the saw blade frame is pulled downward, the saw blade will bite into the branch, and on the upstroke, will be withdrawn from the cut surface. The blade will usually be straight, and the angle of rake may be variable. The elongate holding shaft may be arranged parallel with the frame or may be angled backwards to be approximately parallel with the saw blade. It may have a variable connection with one of the blade mounting brackets, but it is preferred to have a rigid connection between the two. Brief Description of the Drawing An example of the invention will now be described by way of example with reference to the accompanying drawings in which:-

Fig. 1 is a side view of a first embodiment of a saw in accord with the invention;

Fig. 2 is the same view of a second embodiment being a modification of the embodiment of Fig. 1;

Fig. 3 is a side view of another embodiment of the present invention; Fig. 4 is a rear view of a modified saw of the form of Fig. 3; Fig. 5 is a rear view of the saw of Fig. 3 with part of the saw omitted;

Fig. 6 is a schematic view of a third embodiment of the invention; Fig. 7 is a plan view of the retaining arm of an embodiment; Fig. 8 is a section view V-V of the arm of Fig. 4; Fig. 9 is a side elevation of a further embodiment of the invention; Fig. 10 is a plan view of the embodiment of Fig. 9;

Fig. 11 is a plan view of a running eye of the spreader in the embodiment of Figs. 9 and 10; and

Fig. 12 is a side view of a mating lug adapted to fit the running eye of the embodiment of Fig. 11. Best Modes for Carrying Out the Invention

The pruning saw 1 of Fig. 1 comprises a saw blade frame 2 having the form and appearance of a modified bow saw. The frame 2 has an upper blade mounting bracket 8 and a lower blade mounting bracket 9, between which, in use, saw blade 3 is located. The saw also comprises a retaining arm 4 extending in a direction transverse to blade 3 to engage the branch 5 to be cut, and remaining in engagement with branch 5 while being cut. In addition, the saw incorporates an elongate holding shaft 6 which is attached to bracket 9 of blade frame 2.

In more detail the saw blade frame 2 comprises a straight portion 7 having a first blade mounting bracket 8 at its upper end, and a second blade mounting bracket 9 at its lower end, a rectangular keyway 10 extends along the lengths of the portion 7. The portion 7 is angled with respect to blade 3 by an angle α which is about 15°.

The removable blade 3 is mounted to the blade mounting brackets 8 and 9 in the same manner as a hacksaw blade or bowsaw blade is mounted.

When mounted blade 3 is under tension, and the tension may be adjustable by means of adjustment mechanism indicated schematically at 11 in a manner which is well known. The blade 3 is arranged to cut on the downstroke.

The laterally extending retaining arm 4 is in the form of a loop which extends from both sides of a carriage 12 mounted on portion 7. The loop 4 extends on either side of blade 3, and is angled to intersect the blade at approximately a right angle. The loop 4 has a curve in its arms to enable it to effectively hook over branch 5.

The carriage 12 to which the retaining arm 4 is connected is able to reciprocate longitudinally along portion 7. A key 13 extending from the carriage rides in keyway 10 to prevent rotational movement of the carriage, and therefore retaining arm 4, with respect to portion 7.

A spring 14 connects carriage 12 with the lower mounting bracket 9. The shaft 6 is telescopic, and may have additional lengths added to it as the user requires. It is angled with respect to the axis of portion 7 by an angle β which is about 10°. Preferably, β < α.

In use the user manipulates shaft 6 to hook retaining arm 4 over the branch to be cut 5. The retaining arm then carries the weight of the cutter and holds it in place. Initially spring 14 retains carriage 12 adjacent lower bracket 9 and the lower part of saw blade 3 is used to effect the starting cut.

A starting cut is made by moving blade 3 downwards by a small amount as a result of a small manipulation at the end of shaft 6. Once the starting cut has been made, the full action can be employed by pulling down firmly on shaft 6 to move the blade 3 and the blade frame 2 downwards with respect to the branch and retaining arm 4.

As the cutting stroke proceeds downward, carriage 12 moves, relative to the remainder of the saw, upwards along portion 7 extending spring 14 (in fact the carriage 12 and retaining arm 4 are relatively stationary to the object being cut, and it is the remainder of the apparatus that moves downward). At the end of the downstroke extension of spring 14 assists in the upstroke, returning the apparatus to its starting position with contraction of the spring. When the branch has been cut through, it drops down, but the cutter is retained on the stump of the branch by one side of the U-shaped stabilising rest or retaining arm 4. The operator is able to select a position out of the way of the falling branch, but if necessary, he or she can step quickly out of the way while retaining a light hold on the lower end of shaft 6. The embodiments of Figs 3-5 are similar to those of Figs 1 and 2 except that the saw blade frame is purpose built rather than an adaptation of a bow saw. As a result of the similarities between Figs 3-5 and 1 and 2 the same reference numerals are used to refer to like parts. The Fig 4 embodiment employs a compression spring 14 like that of

Fig 2 while Figs 3 and 5 show an extension spring 14 like that of Fig 1.

As shown in Fig 6 plate 40 for mounts retaining means 30 of the form shown in Fig. 3. The arcuate slots 41 with wave shaped outer edges 42 enables retaining means 30 to be oriented at an incline/decline relative to the axis of the saw blade frame 3 or blade 3.

The schematic representation of Fig. 6 shows a saw blade frame 20 which is mounted with a saw blade 21. Frame 20 is connected to elongate handle 22 while an additional blade holder 23 with cutting edge 24 is pivotally mounted to handle 22 with a biasing spring 25 joining blade holder 23 to frame 20. A control line 26 is connected adjacent the free end of blade holder 23 so that blade holder 23 can be pivoted out of and into contact with the underside of article 27. When blade holder 23 is in the position shown in Fig. 3 and action of the saw is effected then not only does blade 21 cut article 27 but undercutting blade 24 scores the underside of article 27. After blade 24 has sufficiently scored the underside of article 27 in alignment with the cut of blade 21, blade holder 23 can be pivoted out of contact with article 27 to a rest position against handle 22 as spring 25 is moved through an over- centre position. After blade 24 is pivoted out of contact with article 27 the cutting action of blade 21 can be continued to completely sever article 27. The undercutting effected by blade 24 aids in the formation of a clean cut without tearing as particularly occurs where article 27 is cantilevered from a stable support as exemplified by the limb of a tree.

The U-shaped retaining means 30 of Fig. 7 is similar in form to that shown in the embodiment of Figs. 1-5 while the cross-sectional shape the arms of the retaining means are depicted in Fig. 8 which shows the section as having a lowermost edge 31 of smaller radius of curvature than its uppermost edge. That inverted tear-drop shape assists the lateral stability of the saw during its cutting action when cutting a relatively soft surface material such as timber or the like. Figs. 9 and 10 are views of a device in accord with another embodiment of the invention comprising frame 60 holding a blade 61. Spreader bar 62 is mounted to extend laterally of frame 60 and may be mounted on either the frame or pole 65.

At each free end of spreader bar 62 there is a running eye 63 through which is fed an elasticised cord 64. Elasticised cord 64 is looped around one of a plurality of tensioning lugs 67 while at each free end the cord 64 is joined to a rigid hook 66.

The depictions show the manner of use of this embodiment with hooks 66 fitted around a tree branch section 70. Hooks 66 retain a hold on branch section 70 as blade 61 is drawn down across the branch to effect cutting. The downward movement of blade 61 via handle 62 extends elasticised cord 64 which then provides the restoring force for the return stroke of blade 61 ready for its next downward cutting stroke.

To ensure the correct orientation of hooks 66 relative to frame 60 and blade 61 each running eye 63 of the spreader bar 61 is shaped to be a complementary single orientation fit with a lug 68 at the base of each hook

66 where it is mounted to elasticised cord 64.

Although the invention has been described with reference to a particular embodiments, it should be appreciated that it may be embodied in many other forms. For instance, the angle α of the saw blade 3 relative to portion 7 may be varied between wide limits as may the angle β of the elongate shaft 6 with respect to the portion 7. Furthermore, the saw blade frame need not comprise a straight portion, but a slight curvature will be acceptable provided the curvature permits travel of the retaining arm carriage 12 along it. The retaining arm itself need not have a loop configuration, and the point of attachment of the arms on either side of carriage 12, need not be level. A non-level arrangement as exemplified by Figs 4 and 5 will allow the saw to be operated vertically even when the branch is not horizontal, by matching the offset in the arm to the angle of the branch. It is envisaged that many parts of the cutter could be fabricated from synthetic materials such as fibre reinforced resins instead of from metals, which would provide a light weight product. Such materials may be particularly suited to the embodiment of Figs 9-11.

It should also be appreciated that the retaining arm need not be attached to the blade frame, but could be attached to the elongate shaft 6 or any other extension from it, provided it is arranged in a way that allows movement to keep the saw blade in contact with the branch while it is being cut.

The pruning saw may also incorporate an upwards cutting blade to make a small cut in the underside of the branch before it is sawn through as exemplified by Fig 6, That small cut prevents the branch from breaking away and damaging the stump as the saw nears the end of the cut, and assists in finishing the sawing cleanly. For best results the saw cut should intersect with the small cut on the underside of the branch when it nears the end of its cut. It will be appreciated by persons skilled in the art that numerous variations and/or modifications may be made to the invention as shown in the specific embodiments without departing from the spirit or scope of the invention as broadly described. The present embodiments are, therefore, to be considered in all respects as illustrative and not restrictive.

Claims

CLAIMS:

1. A pruning saw or similar cutting tool provided with the following features: a saw blade frame having spaced apart mounting means projecting laterally of the frame between which a saw blade is adapted to be mounted to the frame, retaining means disposed transversely of the blade when mounted to the frame said retaining means being adapted to engage or contact a branch or other object to be cut, while it is being cut. and an elongate shaft to be rigidly attached to the saw blade frame to enable the saw to be remotely positioned against the object to be cut and to facilitate a cutting operation, wherein the retaining means and the frame are relatively movable during a cutting stroke such that a return mechanism is operatively activated by that relative movement to assist return of the frame to an initial cutting position at the end of each cutting stroke.

2. A saw as claimed in claim 1 wherein the blade mounting means has a saw blade tensioning means.

3. A saw as claimed in claim 1 or 2 wherein the retaining means comprises an arm movable relative to the frame.

4. A saw as claimed in any one of claims 1 to 3 wherein the return mechanism comprises a carriage slidably mounted to the frame with spring bias means mounted between the carriage and the frame.

5. A saw as claimed in claim 4 wherein the retaining arm is fixedly mounted to the carriage.

6. A saw as claimed in any one of the preceding claims wherein the retaining arm has a U-shaped configuration which envelopes the saw blade when mounted to the frame.

7. A saw as claimed in claim 6 wherein the U-shaped arm is adjustable between a plurality of positions to vary the angle of cut applied to the article to be cut.

8. A saw as claimed in any one of the preceding claims wherein the retaining means, when engaged with the object to be cut, intercepts a blade at about 90°, when the blade is mounted to the frame.

9. A saw as claimed in claim 4 or 5 wherein the carriage is keyed to the frame to prevent rotation of the carriage relative to the frame.

10. A saw as claimed in claim 4 or 5 wherein the cross-sections of adjacent surfaces of the carriage and frame are non-circular.

11. A saw as claimed in any one of the preceding claims wherein the saw comprises an additional blade which is positionable to provide a cut substantially coplanar with that of the blade but to an underside of an object to be cut.

12. A saw as claimed in claims 1, 2 or 3 wherein the mechanism comprises a spreader extending laterally of the frame and having a running eye at each of two spread apart locations of the spreader, one eye on each side of the frame; elasticised cord means passing through each eye and tensioned relative to the frame, said elasticised cord means also being connected to the retaining means which are adapted to hook over an article to be cut.