WO1993016853A1

WO1993016853A1 - A support arrangement for round timber in a round timber lathe

Info

Publication number: WO1993016853A1
Application number: PCT/FI1993/000070
Authority: WO
Inventors: Eero Paski
Original assignee: Pohmako Ky
Priority date: 1992-02-27
Filing date: 1993-02-26
Publication date: 1993-09-02
Also published as: FI920869A; FI94734C; FI94734B; FI920869A0

Abstract

The invention relates to a support arrangement for round timber in a round timber lathe, comprising a feeder, such as a roller conveyor (7), feeding raw timber to a set (1) of lathe tools for being worked into round timber. For supporting the round timber and for preventing its vibration during working, a number of rollers (4) arranged in a circle are positioned in the round timber lathe immediately after the set (1) of lathe tools, which rollers receive and support from different directions the round timber turned into a nominal diameter. A tubular guide (2) is positioned in the lathe immediately after the rollers, through which guide the turned timber is guided to pass by means of the rollers (4).

Description

A support arrangement for round timber in a round timber lathe

The invention relates to a support arrangement for round timber in a round timber lathe, comprising a feeder, such as a roller conveyor, feeding raw wood to a set of lathe tools for being worked into round timber.

Round timber is used as basic wood for building villas and saunas. Round timber lathes used at pre¬ sent are of such a construction that the raw wood must be exactly straight and close to the dimensions of the final product, otherwise the raw wood must first be sawn square and straight in order that straight round timber with dimensional accuracy can be provided.

About 20 % of the timber available can be turn¬ ed round by the present methods without pretreatment. About 30 % of the timber intended for papermaking can be turned into round timber, after it has at first been shaped into square timber.

On account of these needs for pretreatment and of the tool types selected, cuttings from present round timber lathes are not suitable as industrial wood chips and neither can sawings be sold further as such.

Because only straight or sawn timber is used in the lathes used at present, roller feed can be used for feeding the timber. If it is desirable to use knotty timber or timber with an otherwise uneven sur¬ face, the position of the timber in the roller feeder changes during feeding and the finished round timber will not be straight.

When timber is fed to round timber lathes used at present, the end of the timber begins to vibrate when it hits the tools. Due to this fact, the first end of the timber will be surfaced thinner along a distance required for the end of the wood to calm down on the receiving rollers. If an avoidance of this dimensional inaccuracy is desired, the feeding must take place very slowly, which has a decisive influence on the output to be obtained.

The lathes in use have tools of two types. One is a normal cutting blade with a negative cutting angle and a small clearance angle, which blade shall be rotated rapidly in order not to cause cracks in the wood. The other type of tools consists of a round sharpened tube, which cuts off fibres well, and with which no cracks will occur within its normal range of rotation speed. A problem with this type of tool is that it becomes rapidly dull and is difficult to sharpe .

In the lathes in use, the feeding of wood takes place either by means of rollers or along conduits. A problem with each of these types is that the wood ro¬ tates together with the blade, if the cutting depth or a knot increases the cutting power.

A further problem with the present lathe types is a vibration of the wood, which is caused by the fact that the supporting and fastening points of the wood are situated far from the blades in a turning situation, whereby the cutting angle of the blades and variations in the cutting power cause bending and vibration of the wood. The object of the invention is to provide such a support arrangement for round timber in a round timber lathe which has none of the above-mentioned drawbacks. To provide this, the support arrangement for round timber according to the invention is char- acterized in what is presented later in the claims. The invention will be described in the follow¬ ing in greater detail by means of an embodiment with reference to the enclosed drawings, in which

Figure 1 shows a round timber lathe provided with a support arrangement for round timber according to the invention,

Figure 2 shows a set of tools of the round tim¬ ber lathe according to Figure 1 seen from the end,

Figure 3 shows the round timber lathe of Figure 1 in operation, and

Figure 4 shows the support arrangement for round timber according to Figure 1 on an enlarged scale.

By means of a device according to the inven- tion, 80 % of all available paperwood and saw logs meeting the size requirements can be used as raw timber. According to Figure 1, the feeding of the timber takes place on a roller conveyor 7, on which one grip holds the timber during the whole feeding procedure, due to which the position of the timber does not change. The roller conveyor is driven e.g. by means of a hydraulic motor. A roller is con¬ structed in such a way that the wood cannot roll thereon. To effect this, the lathe has been provided with such a feeding device that centralizes and feeds the timber in one position along the whole feeding distance. The feeding device extends very close to the blades. The centralization of the wood takes place by means of hydraulic compression springs 6 and a mechanical centralizer. The centralizer can also be operated electronically.

In order for the feed speed of timber to be high along the whole length of the timber, the end of the timber must be prevented from vibrating and bend- ing when it hits the blades. For this reason, a knife framework 1 is provided with rollers 4, between which the end of the timber goes immediately after the knives 5, stopping the vibration which has possibly begun. After these rollers the wood passes to a fixed guide 2 and further to a roller conveyor 3 of the re¬ ceiving side. The inner diameter of the guide is as little as only about 2 mm larger than the nominal outer dimension of the worked timber. The fixed tubu¬ lar guide 2 is preferably so long that it extends nearly to the removing roller conveyor 3. Thus the length of the free unsupported wood remains very short and it has no possibility of bending or vibrat¬ ing, and the invariability of the timber feeder line is secured at the same time. The round lathe of the invention has a knife framework 1 e.g. according to Figure 2, comprising a pre-knife structure consisting of an amount of pre- knives 8, 9, 10 (e.g. 3 in number) cutting off fibres, the cutting power of which pre-knives is di- rected to the centre of the timber to be fed and the cutting angle of which is axial and small, due to which the track of cutting is thread-like on the sur¬ face of the timber. A finishing blade 11 is a broad hard metal blade and cuts wood like a veneer knife. The breadth of the finishing blade is considerably larger than the feed distance of one turn. By means of this blade assembly, the feeding velocity of tim¬ ber can be made so high that the cuttings from the timber meet the requirements for chips defined by the industry (the length of the chips should be in fibre direction at least 7 mm). The outer periphery of a drum is formed by a blower, which throws the chips on a transport platform reserved for it. Figure 2 also shows the rollers 4 according to the invention, which support a round timber 12 from three different direc- tions, as well as the fixed tubular guide 2.

The operating principle of the device appears from Figure 3, in which raw timber 13 is turned into a round timber by means of a round timber lathe ac- cording to Figure 1.

Figure 4 shows the support arrangement for round timber according to the invention shown in Fig¬ ure 1 on an enlarged scale. The arrangement is posi¬ tioned in a round timber lathe immediately after the knife framework and comprises a number of rollers 14 positioned in a circle, which rollers receive and support from different directions the round timber turned into a nominal diameter. Immediately after the rollers is positioned a tubular guide 15, through which the turned timber is guided to pass by means of the rollers 14 in a direction indicated by an arrow.

Claims

Claims :

1. A support arrangement for round timber in a round timber lathe, comprising a feeder, such as a roller conveyor (17), feeding raw timber (13) to a set (1) of lathe tools for being worked into round timber, c h a r a c t e r i z e d in that, for sup¬ porting the round timber (12) and for preventing its vibration during working, a number of rollers (4; 14) arranged in a circle are positioned in the round tim¬ ber lathe immediately after the set (1) of lathe tools, which, rollers receive and support from differ¬ ent directions the round timber (12) turned into a nominal diameter, and that a tubular guide (2; 15) is positioned in the lathe immediately after the rol¬ lers, through which guide the turned timber (12) is guided to pass by means of the rollers (4; 14).

2. A support arrangement for round timber ac¬ cording to claim 1, c h a r a c t e r i z e d in that the inner diameter (2; 15) of the tubular guide is only slightly larger than the nominal outer dimen¬ sion of the worked timber (12).

3. A support arrangement for round timber ac¬ cording to claim 1 or 2, c h a r a c t e r i z e d in that the tubular guide (2; 15) extends to a timber removing device (3) .