EP0330689A1

EP0330689A1 - Chain saw for pruning trees and shrubs

Info

Publication number: EP0330689A1
Application number: EP88907167A
Authority: EP
Inventors: John Matey
Original assignee: Individual
Current assignee: Individual
Priority date: 1987-07-29
Filing date: 1988-07-29
Publication date: 1989-09-06
Also published as: WO1989000806A1; JPH02500246A; EP0330689A4

Abstract

A tree pruner comprising a small chain saw (35) attached to one end of an elongate tubular guide bar (12) which has a motor (10) attached to the other end thereof. A belt drive (19,20) extends between a pulley (11) on the motor and a pul ley (32) at the chain saw to drive the cutting chain (36) and the belt is enclosed within the guide bar. A flywheel (33) is in cluded on a common shaft with the chain saw pulley (32) and has a mass sufficient at full speed to store enough energy to cause the saw to cut through smaller branches whereby the motor and the belt drive can be of reduced power capability and only sufficient to spin the flywheel to maximum speed within a short space of time under a no load condition. A tur bine drive between motor and chain saw is also disclosed as is a guard member (38) for the saw blade. The guard member (38) also has guide portions (39) for guiding the cutting chain over a branch to be severed.

Description

CHAIN SAW FOR PRUNING TREES AND SHRUBS

This invention relates to portable chain saws and more particularly to chain saws, or attachments for chain saws. which facilitate use of the saw for tree pruning whereby the user is able to stand at ground level and cut branches which would normally be out of reach. Apparatus of the general kind in question is known and examples can be found in U.S. patents 4,341,017 and 4,654,971 , for example. The U.S. patent 4,341 ,017 to Janczak discloses a guide bar supporting a chain saw at one end and being suitable for holding by the user at the other end whereby it can extend upwardly to reach branches which would normally only be accessible by the user being in an elevated position. An internal combustion engine and hydraulic pump are strapped to the user and the chain saw is driven by hydraulic fluid pumped to the saw via hydraulic lines which pass along the guide bar. A major disadvantage of the Janczak apparatus is that the hydraulic lines, when full of fluid, become quite heavy and it is difficult for the user to hold the chain saw in an upward or raised orientation for any length of time. Furthermore, since an oil cooler is required and since the motor must be relatively large in power to provide sufficient power at the chain saw, the apparatus strapped to the user is neavy and cumbersome. The U.S. patent 4,654,971 which has been assigned t o Hudd Enterprises uses a hand-held electric or gasoline driven engine to drive a remote chain saw. In this case a drive shaft extends between the motor and saw and the main feature of the Hudd patent is to provide extension and retraction of the drive shaft and housing by a unique telescoping arrangement. Again, however, a drive shaft capable of transmitting sufficient power witnout too much flexing of the shaft becomes somewhat heavy and also requires expensive bevel gears at the remote or chain saw end in order t o convert the drive through It will be appreciated that it is necessary to provide sufficient powe r to the saw to avoi d stal ling of the cutting chain when the chain catches on a knotty or particularly hard piece of timber, and thus the prior art arrangements provide considerable power at the motor as well as drive arrangements which are capable of transmitting that power to the remote chain saw. The result is apparatus which is heavy or cumbersome and thus incapable of use over continuous extended periods.

A further problem which exists with the known apparatus concerns the difficulty in accurately guiding the cutting chain onto a branch to be severed particularly because the cutting chain is at a height well above the user which makes accurate vision and control of the cutting chain difficult. It is desirable to avoid jumping of the blade from an initial position or re-starting a cut in another position on a branch, particularly if the cuts caused by a false start remain on the tree or shrub since this causes damage thereto.

Accordingly. it is an object of this invention to provide an improved chain saw which overcomes or reduces the aforementioned disadvantages of known apparatus.

Thus the invention provides a chain saw for pruning trees and shrubs wherein a guide bar extends from a motor to a remote chain saw and incorporates drive means whereby said motor is able to drive the cutting chain of said chain saw, characterized in that, a flywheel is provided on said drive means at said remote chain saw. said flywheel having a mass sufficient to provide sufficient inertia when said flywheel is rotating at full speed to enable the cutting chain to cut through a relatively small branch of a said tree or shrub.

In order that the invention may be more readily understood, one particular embodiment will now be described with reference to the accompanying drawings wherein:

Figure 1 is a schematic perspective view showing a chain saw apparatus according to the invention, being held in position for use in a pruning operation.

Figure 2 is a perspective side view o f a motor. shown schematical i y , forming p art of the apparatus.

Figure 3 is a side view of part of the motor if Figure 2 and showing a sectional view of one end of a guide bar and belt drive connected to the motor,

Figure 4 is a section taken on the line 4-4 of Figure 3,

Figure 5 is a side view of the chain saw end of the apparatus including a sectional view of the other end of the guide bar and belt drive, and

Figure 6 is a section taken on the line 6-6 of Figure 5.

Referring now to the drawings, the chain saw apparatus according to this particular embodiment is shown to c omp r i s e a motor 10 represented schematically and being in the form of a conventional small internal combustion engine of the kind used to drive a conventional small chain saw or brush cutter, for example. The motor may have a capacity of about 15cc - 18cc maximum in order to provide a very light-weight apparatus but of course in some circumstances a motor of larger capacity may be used. The motor 10 is provided with a pulley 11 which is connected to the output shaft of the motor. A mounting bracket 13 formed of aluminium is connected to the side of the motor 10 adjacent the pulley 11 by means of bolts 14. The mounting bracket has spaced substantially circular boss members 15 and 16 arranged thereon for supporting one end of a tubular guide bar 11 which extends to a chain saw arranged at the other end of the guide bar 12. The circular boss members 15 and 16 are each formed in two parts with a space therebetween to form cavities 17 and 18 (see Figure 4) enabling passage of drive belts 19 and 20 along the tubular guide bar 12. An oil feed line 21 also enters the tubular guide bar 12 and passes via one of the cavities.

The tubular guide bar 12 fits snuggly over the boss members 15 and 16 and terminates adjacent the motor 10. The guide bar 12 has l ongitudinal slots (not shown diametrically opposed and adjacent the end of the bar 12 t o enable it to clamped on to the boss members 15 and 16 by tightening of clamps 22 and 23. As is evident in Figure 21 a handle 21 is clam ped o r otherwise attached to the out of bar 12 a short distance from the motor 10. Of course another handle 25 is provided on the motor 10 in a manner known per se and would normally have a throttle control lever (not shown) attached thereto. By gripping the respective handles the user is able to control the device despite the fact that the chain saw end is considerably remote from the user.

Referring now to Figures 5 and 6 the other end of the guide bar 12 is shown in more detail. The other end refers to the remote or chain saw end of the guide bar 12. As is evident in Figure 6 the tubular guide bar 12 is cut away at its remote end and is attached to a further mounting bracket 26. The further mounting bracket 26 is affixed to the guide bar 12 by screws (not shown) which pass through the wall of the tubular guide bar 12 and into respective semi-circular boss members 27 and 28 on the bracket 26. Spaced plates 29 and 30 of the bracket 26 support a shaft 31 mounted in bearings in the respective plates 29 and 30. A multiple groove V-belt pulley 32 is mounted on the shaft 31 between the plates 29 and 30 and a flywheel 33 is mounted on the outer end of the shaft 31. The flywheel has a gear 34 attached to the inside thereof for the purpose of driving a cutt ing chain 36 which moves on a chain saw bar 35. The chain saw bar 35 is affixed to the mounting bracket 26 by a bal t 37 which passes through a slot in the chain saw bar 35. The sl ot of the chain saw bar is not evident in the drawings. The bolt 37 passes through the plate 29 and on the opposite side of the plate 29 to the bar 35 there is a nut which clamps a guard member 38 to the plate 29. As is evident in Figure 5. the guard member 38 passes around the cutting chain 36 in close proximity thereto for the purpose of preventing contact with the cutting chain along the extent of the guard member 38 when the apparatus is in use. It will be seen that the guard member leaves one elongated side of the cutting chain exposed for the purpose of performing a cutting operation. The guard member 35 has depending guide portions 39 wnizn extend away from the exposed elongated side of the cutting chain. The guide portions 39 in combination with the chain define a bight for accommodating a branch to be severed by the pruning apparatus.

In use the cutting head, that is, the cutting chain 36 and guard member 38 may be located above a branch to be severed with the points of the guide portions 39 against the trunk of the tree or shrub. By sliding the guide portions 39 down the trunk until the cutting chain contacts the branch to be severed, it is ensured that the cutting chain does not jump to several different starting points when it contacts the branch and thus damaged caused by false starts to the cutting operation is avoided. Alternatively, the guide portion 39 at the free end of the apparatus may be hooked over a branch to be severed whereby the inclined surface 41 is used to guide the branch onto the cutting chain 36. The oil line 21 which extends from the motor inside the tubular guide bar 12 provides oil to the cutting chain 36 in a manner known per se.

A pair of like poly V-belts of type section J extend between the pulley 32 at the remote end of the guide bar 12 and the pulley 11 mounted on the motor output shaft. The pulley 11 has similar multiple grooves to the pulley 32. The belts pass inside the tubular guide bar 12 as previously mentioned. Additionally, a guard 40 is provided over the f lywheel 33 to protect the flywheel against inadvertent contact with branches of the tree or shrub during a pruning operation. The guard 40 is affixed to the guard member 38 by screws (not shown).

According to a further form of the invention, the belt drive is replaced by a turbo drive. In this instance the output shaft of the motor 10 drives an impeller which is arranged within a tubular guide bar which extends to the remote end in a similar manner to the guide bar 12. The f lywheel shaf t 31 incorporates a rotor which receives compressed air passing up the tubular guide bar thus rotating the flywheel and thereby rotating the cutting chain 36. In this embodiment the need f or a transmissing bel t passing inside the guide bar 12 is obviated. I t is necessary however, to have a gear reduction between the rotor and the flywheel since the turbo drive is not capable of transmitting large torque at slow speed. Thus, by using a reduction gearing arrangement the rotor may be spun at speeds up to about 25,000 r.p.m. in order to drive the flywheel at a speed of about 10,000 r.p.m. and thus there is sufficient torque to accelerate the flywheel back up to speed in the required short time after a cutting operation.

It should be evident from the description above that the present invention provides a light-weight pruner apparatus which is convenient to use and which overcomes some or all of the aforementioned disadvantages of prior art apparatus. Whilst the transmission medium between the motor and chain saw is not capable of transmitting high power, the unique arrangement of a flywheel at the remote chain saw end of the apparatus enables use of a smaller capacity motor which is capable of spinning the flywheel to a relatively high speed (8000 - 10000 r.p.m.) in a short space of time, say 2 - 3 seconds, under no load conditions. The energy stored In the flywheel 33 is sufficient to enable the cutting chain 36 to cut through small branches and limbs before the energy is dissipated. The flywheel has a mass of about 200 gm. During the time in which the operator moves the cutting chain to another branch or limb, the motor is able to accelerate the flywheel back to full speed. Thus the use of a smaller motor and a relatively low power drive means, results in an extremely light-weight apparatus. The use of aluminium in the guide bar 12 and brackets 13 and 26 also contributes to the light weight.

Whilst a twin V-beit drive has been shown it is clear that a single belt drive or a tripple belt drive could be utilized depending on the particular power to be transmitted.

Whilst the apparatus described utilizes a guide bar 12 having a length of approximately 1.2 metres, it will be evident that a longer guide bar 12 may be provided. In the case of a guide bar of 1.2 metres in length, an operator is able to reach 3 to 3.5 metres in height depending of course on the height of the operator, for the purpose of lopping a branch. According to another embodiment of the invention, the guide bar 12 has a length of about 3.5 metres which is achieved by having 3 cascaded belt drive arrangements. In other words, because of the difficulty in obtaining longer V-belts, intermediate pulley arrangements are spaced along the length of the guide bar 12 to extend the belt drive in 3 stages. Of course, it may be possible to use a single longer belt to extend the full 3.5 metres in which case intermediate pulleys would not be required.

It is envisaged that a contractor engaged in the task of pruning a forest of trees may require two of the apparatus according to the invention, namely, a first apparatus using a shorter guide bar 12 and a second apparatus using the aforementioned longer guide bar 12. In such an instance, the contractor would first prune trees to a height which can be reached using the shorter apparatus and would subsequently prune the trees using the longer apparatus which would allow pruning up to 5 - 6 metres. Alternatively, the apparatus may be constructed in a way which allows interchanging of guide bars 12 between a long bar and a short bar utilizing the same motor.

Whilst the embodiments described above utilize either a V-belt drive or a turbine drive, it will be apparent that other low power light-weight drives could be used to transmit power between the motor 10 and the f lywheel 33. Whatever type of drive means is used it must be capable of some degree of flexing particularly in the case of a long guide bar 12 and it must be of a light weight.

Claims

CLAIMS 1. A chain saw for pruning trees and shrubs wherein a guide bar (12) extends from a motor (10) to a remote chain saw and incorporates drive means whereby said motor is able to drive the cutting chain (36) of said chain saw, characterized in that, a flywheel (33) is provided on said drive means at said remote chain saw, said flywheel having a mass sufficient to provide sufficient inertia when said flywheel is rotating at full speed to enable the cutting chain to cut through a relatively small branch of a said tree or shrub. 2. A chain saw as defined in claim 1, characterized in that, said drive means is capable of transmitting sufficient power to rotate said flywheel to maximum speed in a short time when said saw is not engaged in a cutting operation but not sufficient power to maintain rotational speed of said flywheel during a cutting operation. 3. A chain saw as defined in claim 1 or 2, characterized in that, said drive means comprises a belt drive arrangement (19.20) extending between a first pulley (11) arranged at said motor and a second pulley (32) arranged on a common shaft (31) with said flywheel, said guide bar is a tube and said belt drive passes inside said tube. 4. A chain saw as defined in claim 3. characterized in that, said belt drive is a twin V-belt drive. 5. A chain saw as defined in claim 1 or 2, characterized in that, said guide bar is a tube and said drive means comprises a turbine including a rotor arranged on a common shaft with said flywheel and driven by compressed air in said tube generated by an impeller on said motor. 6. A chain saw as defined in any one of the preceding claims wherein the saw is a typical endless chain having a configuration of substantially parallel elongate side chain portions and end return chain portions, characterized in that, a guard member (38) is provided on said chain saw, said guard member extends along one said elongate side chain portion and over said end return chain portions to prevent contact with the blades along the extent of the guard member, whereby only one of the elongate side chain portions is exposed for a cutting operation. 7. A chain saw as defined in claim 6, characterized in that, said guard member has depending guide portions (39) which extend away from said exposed elongate side chain portion substantially in the plane of said endless chain whereby said guide portions and said exposed side chain portion combine to define a bight for receiving a branch to be cut. 8. A chain saw as defined in claim 3 or 4, characterized in that, said flywheel has a mass of about 200 gm and said motor is capable of rotating said flywheel up to a speed of about 8000 - 10000 r.p.m. in about 2 - 3 seconds. 9. A chain saw as defined in any one of the preceding claims, characterized in that, a guard (40) is provided at least substantially over said flywheel, and said chain is driven by a sprocket (34) on said common shaft. 10. A chain saw as defined in any one of the preceding claims, characterized in that, said guide bar has a handle (24) thereon adjacent said motor, and said motor has a handle (25) thereon whereby the user is able to grasp the respective handles, one in each hand, in order to operate the apparatus for pruning a tree or shrub.