EP0063147A1

EP0063147A1 - Delimbing unit for manual power saw

Info

Publication number: EP0063147A1
Application number: EP19810902949
Authority: EP
Inventors: Knut Kullberg
Original assignee: Individual
Current assignee: Individual
Priority date: 1980-10-28
Filing date: 1981-10-27
Publication date: 1982-10-27
Also published as: WO1982001503A1; SE8007555L

Abstract

Unite d'elagage pour tronconneuse comprenant une scie articulee (3, 4) et un guide de scie articule (2) pouvant etre fixe sur le boitier (1) d'une tronconneuse. Le dispositif de guidage de la scie articulee s'avance depuis le boitier de la tronconneuse et comprend une section a nez plie (22', 23', 24) qui guide la scie articulee sur un chemin sensiblement semi-circulaire sur un plan transversal par rapport a la direction d'avancement, les dents de la scie etant orientees sensiblement vers l'avant. Pendant l'operation d'elagage la forme semi-circulaire de la section de nez est maintenue contre la peripherie ronde du tronc et deplacee vers l'avant le long de celui-ci. L'unite d'elagage facilite et accelere considerablement le demembrement, tout en reduisant les dangers d'accident et permettant une position de travail nettement amelioree.Pruning unit for chainsaw comprising an articulated saw (3, 4) and an articulated saw guide (2) which can be fixed on the casing (1) of a chainsaw. The hinged saw guide device advances from the chain saw housing and comprises a bent nose section (22 ', 23', 24) which guides the hinged saw on a substantially semi-circular path on a transverse plane by relative to the direction of advance, the teeth of the saw being oriented substantially forward. During the pruning operation the semicircular shape of the nose section is held against the round periphery of the trunk and moved forward along it. The pruning unit considerably facilitates and accelerates dismembering, while reducing the danger of accidents and allowing a significantly improved working position.

Description

Delimbing unit for manual power saw

The present invention relates to a delimbing unit for a manual power saw comprising a saw chain and a chain guide attached to the power saw, with a longitudinal guide groove for guiding the saw chain which can he driven by means of the chain sprocket of the power saw.

In modern forestry manual power saws play an essential role. Nowadays timber cutting is largely carried out by hand, with the aid of such power saws.

The working process associated with tree cutting by means of a manual power saw can substantially be subdivided into three operational phases, i.e. cutting the tree, delimbing by sawing off branches and cross-cutting of the trunk into suitable lengths. Of these operations none is more time-consuming than delimbing. Experience has shown that roughly 50 per cent of the cutting tine is used for delimbing. That so much time has to be expended on delimbing is partly due to the fact that the design of a conventional power saw is not appropriate to this particular operational phase.

A power saw of conventional design is provided with a level, longitudinal chain guide projecting straight from the saw, i.e. the bar. The saw chain is guided in a track leading from the driving chain sprocket along the lateral edges of the bar back to the driving chain sprocket. During the sawing operation one of the lateral edges of the bar is pressed against the sawing point. Sawing is accordingly effected across the bar, in the plane of the bar. During the delimbing phase the bar must be moved from branch to branch and at the same time to different points around the trunk. Normally delimbing is effected from a position at the side of the tree, with the bar substantially directed across the trunk. During the sawing operation the bar is kept pressed against the limb or branch. Depending en the position of each branch on the trunk the pressing-on force is provided to a larger or smaller extent by the person who handles the power saw twisting his body. Especially as regards the branches en the underside of the tree, which may cause jamming of the bar, this entails a working position which from the ergonomic point of view is definitely unsuitable and tiring.

As already stated, delimbing is a time-consuming operation, and this fact often leads to an especially high working speed during this operational phase. The higher speed and the inconvenient working position contribute to increasing the danger of accidents during the delimbing phase.

The above shows clearly that for delimbing a tool is required which has none of the disadvantages of a conventional power saw, and it is the object of the invention to provide an aid for delimbing which will meet this requirement and enable more rapid and simpler delimbing from a working position which, from an ergonomic point of view, is definitely improved.

The object of the invention is achieved by a delimbing unit of the type described above, characterised in that the chain guide extends forward from the casing of the power saw in the same way as a bar-shaped chain guide of conventional design and in that a nose section of the chain guide facing away from the casing has a laterally bent shape, as a result of which the saw chain is guided along a substantially semicircular track in a plane transverse to the forward direction, whereas the saw teeth of the saw chain are, along the nose section of the chain guide, pointing substantially forward.

By means of the delimbing unit in accordance with the invention delimbing is considerably facilitated, inasmuch as the semicircular nose section of the chain guide is held against the trunk of the tree. During this process the semicircular shape substantially encompasses half the periphery of the trunk. Thus the saw chain teeth, which point substantially forward along the nose section, simultaneously remove branches along half the periphery of the trunk as the power saw is moved along the trunk. By turning the power saw at the same time towards both sides by substantially 90° also the branches on the "lower" half of the periphery of the trunk are reached and sawn off. This further accelerates and simplifies the delimbing operation. Since the semicircular shape of the nose section partly encompasses the trunk, sudden jerks of the saw during the delimbing process are prevented, thus largely eliminating any danger cf accidents during this operational phase. As the power saw is pressed forward against the sawing points from a working position next to or astride the trunk stresses due to twisting of the body are substantially eliminated and a clearly improved working position is achieved.

Known technology with a view to attaining corresponding objects is represented by such designs as described in the NO Patent Specification 100.803, the SE Patent Specification 77529 and the US Patent Specification 1.043.502. However, the designs described in these patent specifications are of a type quite different from the unit in accordance with the invention and cannot be applied to a manual power saw, inter alia because none of the known designs comprises any chain guide of the type required to this end. Other characteristics of the delimbing unit in accordance with the invention will be found in the claims.

The invention is described in greater detail below with reference to a specimen embodiment shown in the drawing, where fig. 1 is a side view of a delimbing unit in accordance with the invention attached to a schematically drawn power saw casing, fig. 2 shows the unit represented in fig. 1 as seen from above, fig. 3 gives a schematic view from the front of the unit represented in fig. 1 and fig. 4 shows a saw chain for use in the unit in longitudinal section as well as a cross-section of the combination. saw chain/ chain guide. Fig. 1 shows, in schematic form, a power saw casing 1 with roughly outlined, conventional handles 101, 102. A delimbing unit in accordance with the invention is attached to the saw casing. The unit comprises a chain guide 2 and a saw chain 3, 4 guided thereby. The saw chain runs in a closed circuit from the driving chain sprocket 11 of the power saw along an edge of the chair, guide and back to the driving chain sprocket. Links 3 of the saw chain are provided with a guide lug 6 moving within a guide groove 2; marked by a dashed line along the edge of the chain guide. Every other link 3 bears a saw tooth 10 and a chip ejector 10' located, in the driving direction, after the tooth. The chain, links are held together by steel rods 4 (see also fig. 4). The saw chain is driven by the driving chain sprocket in the direction of the arrow.

Chain guide 2 consists of a substantially flat rail extending, in the shape of two legs 22, 23 from the power saw casing in the forward direction, which is marked by an arrow in the drawing, and thereupon obliquely downward and outward (see fig. 2). At its lower end each leg passes into a section 22' or 23', respectively, bent in a substantially circular way both upward and inward towards one another. The sections 22' and 23' meet transversely to the forward direction in section 24.

The sections 22', 25' and 24 constitute a nose section of the unit. As can be seen in fig.3 the nose section is, viewed from the front, substantially semicircular. During the delimbing process this semicircular shape is held against the round periphery of the tree trunk, the saw being moved forward in the direction of the arrow.

Along the nose section guide groove 21 of the chain guide faces substantially forward, as a result of which also teeth 10 of the saw chain point forward. Along section 24 teeth 10 are facing straight forward, along sections 22' , 23' forward and obliquely downward, and at the lowest points of sections 22', 25' downward. Due to the shape of the chain guide as described the saw accordingly acts along the entire nose section, as it is moved forward. The nose section of the chain guide is so dimensioned that its semicircular shape corresponds substantially to half the periphery of trees of such size as normally cut.

Fig. 1 shows also how the unit is attached to casing 1 of the power saw. Legs 22 and 23 of the chain guide are connected in the same plane by means of a retaining plate 26 with fastening devices 27, 28, 29, 30 appropriately adapted to chain guide fastening devices on a power saw casing of conventional design. With the aid of the screwing devices 27, 26 plate 26 is secured to a movable part of the power saw (not shown) as is the case with a conventional chain guide. By means of an adjusting screw (not shown the movable part with the chain guide can be adjusted in known manner along slot 30 using pin 29 by way of control element. Thanks to this feature the saw chain can be tensioned as required. Plate 26 is provided with a lubricating point 31 connected via a duct 32 in plate 26 with that part of the guide track which extends along the lower edge of plate 26.

In fig. 2 the power saw illustrated in fig. 1 is shown schematically as seen from above. The figure shows that also legs 22, 23 are in relation to the forward direction somewhat bent. This shape is due to the fact that a smooth and as a result frictionless transition is required, on the one hand, to the plane of the driving chain sprocket 11, and, cn the other hand, to chain guide sections 22', 23'. The bent shape is also required inasmuch as the tree trunk shall be able to pass freely when the saw is moved forward along the trunk. Th e figure shows the twist by 180° of the rail within legs 22, which is illustrated by a chain link 3 with saw teeth 10 directed in a horizontal plane substantially halfway between the driving chain sprocket 11 and the transition between leg 22 and section 22'.

Fig. 3 shows a protective device 25 enclosing the saw chain along leg 23 of the chain guide. A corresponding protective device is provided for section 22. The protective device 25 eliminates any risk of direct contact with the saw chain along the corresponding section of the chain guide.

The schematic view of the chain guide in fig. 3 is primarily intended to illustrate the semicircular shape of the nose section of the chain guide . For this reason both the saw chain and l egs 22 , 23 have been omitted and power saw casing 1 has only been marked by dashed lines. Guide track 21 along the edge of the chain guide is marked by a dashed line. In this connection it is pointed cut that the saw chain is not loaded as it passes along leg 22, this being due to the direction in which it. is driven forward (see fig. 1). It will be appreciated that a saw chain to be able to run along chain guide 2 must be capable of being turned in all lateral directions and about its own longitudinal axis. Such a saw chain is known from the German laid open print 2758380. In this specification saw chains are described, the links of which are held together by means of ball and socket joints.

A saw chain of this basic design is shown in fig. 4. The figure shows on the left the saw chain in longitudinal section and on the right in cross-section along line I-I, including also a cross-section of chain guide 2. Links 3 are held together by steel rods 4 both ends of which are rotatably fixed by means of ball and socket joints 5 in the corresponding links. Every other link bears a saw tooth 10 and a chip ejector 10 arranged next to it. The cross-sectional view shows guide track 21 in rail 2 of the chain guide. The inner shape of the guide track matches the outer shape of guide lugs 6 thus achieving a suitable sliding fit. So as to prevent the saw chain from sliding out of the guide track each guide lug 6 is provided with a link pin 8 projecting sideways. The side walls of guide track 21 are provided with longitudinal recesses, with the guide pins engaging the said recesses. The chain guide has a T-shape tapering from the chain links, which counteracts jamming of the chain guide during the sawing operation.

Claims

1. A delimbing unit for a manual power saw comprising a saw chain (3, 4) and a chain guide (2) capable of attachment to casing (l) of a power saw, with a longitudinal guide track (21 ) for guiding the saw chain, which can be driven by driving chain sprocket (11) of the power saw, c h ar a c t e r i s e d in that the chain guide extends forward from the casing of the power saw in the same way as a forward-extending chain guide of ordinary design pertaining to a manual power saw and in that a nose section of the chain guide facing away from casing (1) has a laterally bent shape, by means of which the saw chain is guided in a track which viewed in a plane transverse to the forward direction is substantially semicircular, whereby the said track can be made to follow the round periphery of a tree trunk, the guide track of the chain guide causing saw teeth 10 of the saw chain to point substantially forward along the nose section.

2. A delimbing unit in accordance with claim 1, c h a r a c t e r i s e d in that chain links (3) forming part of saw chain (3, 4) are provided with a guide lug (6) which, when the saw chain moves, slides in guide track(21) and in that the guide lug has a laterally projecting link pin (5) engaging a longitudinal recess (7) in the side walls of the guide track, as a result of which the saw chain is prevented from sliding out of the guide track.

3. A delimbing unit in accordance with claim 1 or 2, c h a r a c t e r i s e d in that saw chain links (3) are so designed that the saw chain can be driven by the driving chain sprocket (11) of a manual power saw of conventional design.

4. Application of a delimbing unit in accordance with any of the above claims as part of a manual power saw for delimbing felled trees.