EP0724938A1 - Tool with parallel wedges for splitting wood - Google Patents

Abstract

The tool for splitting wood comprises "n" parallel wedges activated successively in a movement to penetrate into the wood. It comprises a system with "n" primary parallel wedges (3a,3b,3c,....3n) which activate successively in an alternate movement advancing and receding so that when one wedge advances, the "n-1" other wedges are immobile between them. The device may have two groups with parallel primary wedges mounted with respect to the axis of symmetry of the tool. In this case the primary wedges may advance in pairs.

Description

The present invention relates to a tool for splitting logs of firewood and a wood splitter equipped with this tool.

The logs, cut in length of one meter and whose diameter is greater than 15-20 cm, are systematically split longitudinally to facilitate their handling, accelerate their subsequent drying, promote their combustion.

In 80 to 90% of cases, the splitting is carried out manually, that is to say using wedges, masses and merlins.

In the 10 to 20% of the remaining cases, the splitting is mechanized, either by a conical screw system, or by a hydraulic wedge system.

• par moteur électrique, mais ce type est peu répendu car le fendage ne s'effectue pas en forêt et les performances sont médiocres.
• par moteur thermique, mais ces systèmes ont un prix beaucoup trop élevé.
• par système accouplé sur un attelage "trois points" d'un tracteur ou sur sa prise hydraulique. Les performances de ce système sont bonnes mais un tracteur puissant est nécessaire.

For each of these systems, we can use different types of drive:

• by electric motor, but this type is not widely used because the splitting is not done in the forest and the performances are poor.
• by thermal engine, but these systems are far too expensive.
• by system coupled to a "three point" hitch of a tractor or to its hydraulic outlet. The performance of this system is good but a powerful tractor is necessary.

In fact, at present, only owners of agricultural tractors use mechanical splitters, conical screw splitters being the most widespread and the least expensive, for example that described in the document FR 2 462 979.

Hence the idea of designing a machine of a completely new type, which is intended for the vast majority of loggers, amateurs or semi-professionals, who still split their wood manually.

• utilisation comme source d'énergie d'une tronçonneuse thermique déjà largement répandue par les utilisateurs potentiels ou de toute autre machine portable,
• adaptation facile sur la machine,
• portabilité, avec poids de l'adaptation inférieur à 4 kg,
• performances correctes, même dans le bois dur et de gros diamètre,
• prix de vente public modéré.

To achieve this objective, the machine according to the invention must meet the following specifications:

• use as an energy source of a thermal chainsaw already widely used by potential users or any other portable machine,
• easy adaptation on the machine,
• portability, with adaptation weight less than 4 kg,
• correct performance, even in hard and large diameter wood,
• moderate public selling price.

The objectives are achieved thanks to the invention which consists of a tool for splitting wood, characterized in that it comprises at least one system with parallel elementary corners, successively animated by an alternating movement of advance and retreat such that, when a corner advances, the other corners are immobile with each other.

Preferably, the tool is characterized in that it comprises two systems with parallel elementary corners, mounted symmetrically with respect to the axis of symmetry of the tool and in that the elementary corners advance in pairs.

In addition, this tool is designed to be adaptable to any portable machine of the chainsaw or other type, the power transmission being effected for example by means of a chain.

• figure 1 : vue d'ensemble d'une fendeuse selon l'invention.
• figure 2 : croquis montrant le système à coins parallèles.
• figure 3 : graphique illustrant les déplacements des coins pour un système à trois coins parallèles.
• figure 4 : détail du montage du système à coins parallèles.

The invention will be better understood using the description below made with reference to the following appended figures:

• Figure 1 : overview of a log splitter according to the invention.
• figure 2 : sketch showing the system with parallel corners.
• figure 3 : graph illustrating the displacements of the corners for a system with three parallel corners.
• figure 4: detail of the assembly of the system with parallel corners.

A log splitter according to the invention is composed of an engine assembly (1) and a system with parallel corners (2) adaptable to the engine assembly (1).

The wedge system according to the invention is formed by a plurality of elementary wedges (3a, 3b, 3c, ... 3n) capable of moving parallel to each other alternately in the direction of penetration into the wood ( see figure 2).

The inventive idea consists in exploiting the theory of friction of the corner.

• . P = effort pour enfoncer le coin dans la bûche
• . R = effort pour extraire le coin
• . a = ½ angle du coin
• . f = angle de frottement coin/bois

Yes :

• . P = effort to push the wedge into the log
• . R = effort to extract the wedge
• . a = ½ corner angle
• . f = corner / wood friction angle

We have: $$\text{P / R =}\frac{\text{tg (a + f)}}{\text{tg (f + a)}}$$

The friction angle f is variable depending on the species of wood, their degree of humidity and the speed of movement of the corner.

The angle a results from the geometry of the corner. It must not be less than a certain value to preserve the mechanical strength of the corner.

Experience has shown us that the P / R ratio varies between 2 and 5 depending on the case.

We can therefore imagine a system formed by n parallel corners, successively animated with a movement such that, when a corner advances, the n-1 other corners are immobile with each other. If n-1> P / R, the system is self-penetrating.

As an example, Figure 3 illustrates the movements of three elementary corners (3a, 3b, 3c) for n = 3. At each instant, two corners are motionless between them while the third enters the wood.

FIG. 4 shows by way of nonlimiting example a means of coupling the system with parallel corners (2) with the motor assembly (2) of the chainsaw.

The displacement of the corners (3n) is ensured by a camshaft (4) driven by the chain (6) of the chainsaw which engages on a drive pinion of the camshaft.

Each cam (4) will have a profile such that on 1 / n turn, the corresponding corner advances by a distance d and, on the (n-1) n / remaining turn, moves back by the same distance.

The n cams (4) will be offset by 1 / n turn.

The camshaft-wedge contact is ensured by n independent springs (5).

The inversion of the pressure of the springs (5) for example by a lever allows the extraction of the corners if the log is not exploded.

Bearings ensure frictionless contact between the camshaft and corners.

The wedge system described adapts to any portable motor comprising a rotary PTO.

Other corner actuation systems, for example hydraulic, connecting rods or percussion are possible, the essential characteristic being that the system comprises n parallel corners successively animated by a movement of penetration into the wood.

The elastic and reversible means capable of pushing or removing the corners are not limited to the example shown, it is also possible for example to use a stack of leaf springs or Belleville washers, or an elastomer block.

Furthermore, the shape, the width, the angle of a corner may be different from those presented without going beyond the ambit of the invention.

The number of corners is preferably greater than three and of the order of ten.

According to an embodiment not shown, the tool is formed of two systems of symmetrical corners, that is to say that the corners advance in pairs, symmetrically arranged with respect to the axis of symmetry of the tool so as to distribute the forces evenly on each corner.

• légèreté,
• adaptation facile,
• grande sécurité,
• opération de fendage plus rapide, moins pénible, moins dangereuse qu'à la main,
• dégagement automatique par inversion du système,
• performances staisfaisantes pour un prix de vente modéré.

The performances and advantages of the invention are numerous and in particular:

• lightness,
• easy adaptation,
• great security,
• faster, less tedious, less dangerous splitting operation than by hand,
• automatic release by reversing the system,
• staisfaisantes performances for a moderate sale price.

Claims (7)

Tool for splitting wood, characterized in that it has n parallel corners successively driven by a movement of penetration into the wood. Tool according to Claim 1, characterized in that it comprises at least one system with n elementary corners (3a, 3b, 3c, ... 3n) parallel, successively driven by an alternating movement of advance and retreat such that, when a corner advances, the n-1 other corners are immobile with each other. Tool according to one of the preceding claims, characterized in that it comprises two systems with parallel elementary corners systematically mounted with respect to the axis of symmetry of the tool and in that the elementary corners advance in pairs. Tool according to one of the preceding claims, characterized in that it comprises a camshaft (4) driven by a chain (6) of a machine on which the tool is adapted, each cam having a profile such as on 1 / n turn, the corresponding corner advances by a distance d and on (n-1) / n remaining turn, it moves back by the same distance, the n cams being offset by 1 / n turn. Tool according to Claim 4, characterized in that the camshaft-wedge contact is ensured by elastic and reversible means. Wood splitter characterized in that it is formed by a portable machine on which the tool according to the main claim is adapted. Wood splitter according to claim 6 characterized in that the portable machine is a chainsaw.

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