WO1996016774A1

WO1996016774A1 - Sawing machine

Info

Publication number: WO1996016774A1
Application number: PCT/SE1995/001410
Authority: WO
Inventors: Kurt Janson
Original assignee: AK Eriksson AB
Current assignee: AK Eriksson AB
Priority date: 1994-11-29
Filing date: 1995-11-24
Publication date: 1996-06-06
Anticipated expiration: 1997-05-29
Also published as: AU4126796A; SE505309C2; SE9404137D0; SE9404137L

Abstract

A circular saw for re-sawing or ripping wood, timber and the like, such as logs, blocks, cants and boards, into thinner pieces, wherein the saw includes to this end a plurality of saw blades (21, 22) which are mounted on two mutually parallel and vertically spaced saw axles (9, 10), and wherein means are provided for feeding the wood towards those parts of the blades that are located between the axles, such that both sets of blades will saw one and the same piece of wood from opposite sides thereof. The saw axles (9, 10) are each journalled in a respective stand unit (12, 13), wherein the stand units are vertically movable relative to one another so as to be able to saw through wood of large dimensions with the use of pairs of mutually opposing blades (21, 22) for sawing each cut, and wherein the blades are displaceably mounted on respective saw axles (9, 10) so that each blade of the two sets of blades is able to produce its own through-penetrating cut when cutting wood of smaller dimensions.

Description

SAWING MACHINE

The present invention relates to a circular saw for re-sawing or ripping lumber or timber and like wood, such as logs, blocks, cants, boards and the like, hereinafter simply referred to as wood, into thinner pieces, wherein the saw includes to this end a plurality of saw blades which are mounted on two mutually parallel and vertically spaced saw axles, and wherein means are provided for feeding pieces of wood towards those parts of the blades located between said axles, so that both sets of saw blades will saw the same piece of wood from mutually opposite sides thereof.

Present-day requirements with regard to high production rates, thin cuts, large depths of cut and smooth, even cut surfaces place high demands on the stability of both the sawing machine itself and the saw blades. The stiffness of a saw blade is dependent, among other things, on the thick¬ ness and radius of the blade. The natural resonance frequency of a circular saw blade, and therewith its critical speed of rotation _ncritf is a function of saw geometry, which is defined as t/R², where t is the thickness of the blade and R is its outer radius. The saw blade should preferably work in the subcritical speed range, a suitable speed being n = 0.85 n_crit.

In order to achieve the best possible yield, the saw cuts will also be as thin as possible. This requires the use of thin saw blades and it is necessary to give the blades the smallest possible outer radius so as to obtain a high natural resonance index. However, it is not always possible to work with small saw blades, since there are occasions when the sawing machine is required to saw wood of larger sizes that require the use of a larger saw blade. Consequently, the mill is normally forced to work with an excessively large and therewith thick saw blade during the major part of its production, resulting in thick cuts and therewith poor yield. The yield loss increases by about 2 percentage units with each millimeter of increase in the width of a saw cut. A small blade not only reduces losses due to the width of the cut but also reduces the extent to which the wood needs to be oversized, because the wood is cut to size more accurately with smaller and thinner blades. In order to saw wood of different sizes to an optimum yield, it is thus necessary to use saw blades of mutually different diameters.

The main object of the present invention is to provide a circular saw with which wood of both large and small dimen¬ sions can be sawn effectively with the use of relatively thin saw blades of small radius.

The invention is based on the belief that this object can be achieved with the use of two sets of saw blades, wherein when sawing wood of large dimensions the saw blades are caused to work in pairs to produce a through-penetrating saw cut, whereas when sawing wood of smaller dimensions, each saw blade is caused to effect its own through-penetrating saw cut.

In accordance with the present invention, a circular saw of the kind defined in the first paragraph of this document is characterized by the combination wherein the saw axles are each joumalled in a respective stand unit which are dis- placeable relative to one another in a vertical direction so as to enable large pieces of wood to be sawn through with the aid of a pair of mutually opposing blades for sawing each cut, and wherein the saw blades are displaceably mounted on respective saw axles so that when sawing smaller pieces of wood, each blade in the two sets of blades will produce its own through-penetrating cut.

This enables saw blades of equal thinness to be used when sawing wood of both large and small dimensions. According to one embodiment of the invention, the two sets of saw blades can be moved synchronously towards and away from each other. The cutting forces and power consumption will therewith be distributed evenly over the two saw axles.

In order to enable the saw blades to be easily replaced or exchanged, for instance to change to saw blades that are suitable for the dimensions of the wood to be sawn or for the purpose of sharpening the blades, the outer ends of the axles that carry the saw blades are preferably mounted in bearing means that can be displaced axially to enable the ends of respective axles to be released in conjunction with a blade change.

Other features of the invention will be apparent from the following Claims.

The invention will now be described in more detail with reference to an exemplifying embodiment thereof and also with reference to the accompanying drawings, in which

Fig. 1 is a front view of an inventive saw, i.e. shows the saw in the direction of wood feed;

Fig. 2 shows the saw of Fig. 1 from above;

Fig. 3 illustrates the saw-axle drive means;

Fig. 4 illustrates an arrangement for adjusting the positions of the saw blades in accordance with the invention;

Fig. 5 illustrates the pair-wise coaction of the saw blades when sawing wood of large dimensions;

Fig. 6 is a side view of the arrangement shown in Fig. 5;

Fig. 7 illustrates part of the saw shown in Fig. 1, with the saw blades set for sawing wood of relatively small dimen¬ sions;

Fig. 8 illustrates the relative positions of the saw blades in a blade-setting according to Fig. 7; and

Figs. 9 and 10 illustrate the journalling of the outer end of respective saw axles.

The sawing machine shown in Fig. 1 includes a motor 1 whose output shaft 2 is connected to a drive wheel 3 (see Fig. 3) which drives a ribbed belt 4. The belt 4 drives, in turn, two wheels 5, 6, each of which drive a respective saw axle 9 and 10 through the medium of a respective universal drive shaft 7, 8. The speed at which the saw axles rotate can be altered readily, by exchanging the installed drive wheel 3 for a wheel of different diameter.

Each of the saw axles 9 , 10 is carried by a respective pair of arms 12, 13 which project out from a stand 11 (see Fig.

2) and which can be raised and lowered in relation to one another along guides 18, 19, the outer ends of which are guided by thinner guides 16, as indicated in Fig. 4. The arms are raised and lowered with the aid of setting devices mounted adjacent the stand 11, for instance motorized screw jacks 14 or hydraulic devices and synchronizing shafts 17.

When the arms 12, 13 have been vertically adjusted, the arms can be locked mechanically to the guides 16, 18 and 19, for instance by means of pressure-medium controlled clamps, so as to compensate for any play that may occur.

Thus, the inventive sawing machine includes two vertically spaced saw axles 9, 10, each of which carries a respective set of saw blades 21 and 22 which are dogged by the axles as they rotate, for instance by using spline couplings or profiled axles which fit into holes of corresponding shape in the blades. The saw blades 21, 22 are loose in other respects, i.e. freely mounted on respective axles so as to be readily movable in the longitudinal direction of said axles.

With the machine in its illustrated operational state, one set of saw blades will work against the direction in which wood is fed into the machine and the other set of saw blades will work in the direction of wood feed. This will balance- out those forces that strive to "throw" the wood in one direction or the other.

In this regard, the blades are held in their respective positions, determined by the saw-blade set-up concerned, with the aid of blade guides which each include a fixed part 23 and parts 24 which are pivotally connected to said fixed part, see Figs. 5 and 6. The pivotal parts define therebe¬ tween a slot in which a respective saw blade is received and guided on both sides thereof. The reference numeral 15 identifies hose connections through which an air-water coolant is delivered to the blade guides. When carrying out a blade change, the pivotal parts 24 of respective blade guides are lifted in the direction of the arrow A in Fig. 6 and the blades then removed from their respective axles.

Each of the fixed parts 23 of the blade guides is fixedly mounted on one of a plurality of mutually telescopic tubes 25-27, see Figs. 4 and 5. The tubes are adjusted positionally with the aid of servo-controlled hydraulic piston-cylinder devices 28-30 or with the aid of some other type of setting device, for instance screw jacks, each coacting with the tube ends that project outwardly from the arms 12-13 through the medium of an associated piston rod 31-32.

In the case of the illustrated embodiment, each saw axle carries six saw blades 21, 22 and the blade guides are controlled in groups of three with the aid of setting devices

28-30 mounted on each arm. These groups of setting devices thus enable the positions of the blade guides 23, 24, and therewith the positions of all saw blades 21, 22, to be set with a high degree of accuracy in accordance with a desired saw-blade set-up.

In the Fig. 1 illustration, the saw blades on respective axles 9, 10 are set so as to be located pair-wise in precise¬ ly one and the same vertical plane. The saw axles 9, 10 are conveniently displaced slightly in the feed direction of the wood 34 to be cut; see Fig. 5 in this regard. The saw blades in each blade pair may therewith overlap each other slightly in a vertical direction, as shown in Fig. 6.

When the saw blades are located in pairs in one and the same vertical plane, as shown in Fig. 1, the saw can be used to saw wood of large dimensions with the use of blades 21, 22 that have a relatively small radius, i.e. can be used to saw round wood whose radius is almost twice the radius of the saw blades. This means that relatively thin saw blades which produce only a small amount of sawdust or cuttings can also be used when sawing large pieces of wood. When the saw blades are disposed in the manner illustrated in Fig. 6, the wood will be sawn through completely with a maximum thickness corresponding to the distance B in Fig. 6. The saw-blade set- up can be varied as desired, necessitating the blades in each blade pair to be displaced to precisely the same extent as the other. This can be achieved by coordinating adjustment of respective blade guides with the aid of associated setting devices.

When wood of smaller dimensions is to be sawn, i.e. round wood whose radius is smaller than the radius of the saw blades 21, 22, the blades are moved axially in relation to one another (see Figs. 7 and 8) so as to be located between each other for sawing a respective saw cur with the maximum saw depth C. In this case, it is necessary to move the arms 12, 13 carrying the saw axles 9, 10 vertically towards each other, so that each blade will be able to cut through wood that is fed-in between the saw axles.

Thus, it is possible to obtain twice the number of saw cuts with the same number of saw blades as that shown in Fig. 1 and with a fully flexible saw-blade set-up when setting the blades in accordance with Fig. 7, since each blade can be set individually in the case of this embodiment.

Thus, the aforedescribed sawing machine enables wood of both thick and thin dimensions to be cut with blades of relatively small diameter, which can therewith also be relatively thin. This results in a high yield of sawn wood. The saw con¬ struction is less critical than in the case of earlier known constructions, because it need not be dimensioned for use with blades of large diameters.

The inventive sawing machine may include a down-pressing roll for coaction with wood fed into and out of the saw. The roll may be suspended from a structure which accompanies movements of the upper saw axle. The position of the roll in accordance with block height can therewith be finely adjusted with the aid of a pneumatic piston-cylinder device that has a very short piston stroke, for instance.

In order to enable saw blades to be easily exchanged or replaced, the outer end of respective saw axles 9, 10 is secured in a bearing device 35 which is movably mounted on the underside of respective arms 12-13, for instance with the aid of a dovetail joint as illustrated in Fig. 9.

Fig. 10 illustrates in full lines a position in which the bearing device 35 has been moved to a position in which the axle trunnion 36 is free. After having swung down the pivotal parts of respective blade guides, the blades can be withdrawn from the axle and replaced with other blades. When changing to blades of another radius, it may also be necessary to change the speed at which the blades rotate. This can be readily achieved by replacing the belt-drive wheel 3 with a wheel of commensurate diameter.

Although the invention has been described in the aforegoing with reference to a preferred embodiment of a circular saw, it will be understood that modifications can be made within the scope of the following Claims. For instance, the saw axles may be driven with the aid of hydraulic motors or with the aid of frequency-controlled electric motors. In the case of motor powers in the order of 200-450 kW combined with requisite high blade speeds, such solutions are relatively expensive. The means used to set the positions of the saw blades may also be varied, provided that said means will provide the blade settings shown in Figs. 1 and 7.

Claims

1. A circular saw for re-sawing or ripping lumber, timber and like wood, such as logs, blocks, cants and boards, into thinner pieces, wherein the saw includes to this end a plurality of saw blades (21, 22) which are mounted on two mutually parallel and vertically spaced saw axles (9, 10), and wherein means are provided for feeding the wood towards those parts of said blades that are located between said axles, such that both sets of blades will saw one and the same piece of wood from opposite sides thereof, characterized by the combination wherein the saw axles (9, 10) are each joumalled in a respective stand unit (12, 13); wherein the stand units are vertically movable relative to one another so as to be able to saw through wood of large dimensions with the use of pairs of mutually opposing blades (21, 22) for sawing each cut; and wherein the blades are displaceably mounted on respective saw axles (9, 10) so that each blade of the two sets of blades is able to produce its own through- penetrating cut when cutting wood of smaller dimensions.

2. A circular saw according to Claim 1, characterized by means (14, 17) which function to move the two sets of blades (21, 22) synchronously towards and away from each other.

3. A circular saw according to Claim 1 or Claim 2, charac¬ terized in that the two saw axles (9, 10) are joumalled in support bearings (35) carried by guided arms (12, 13).

4. A circular saw according to Claim 3, characterized by means for locking said arms (12, 13) in desired positions relative to one another.

5. A circular saw according to any one of Claims 1-4, characterized in that the saw axles (9, 10) are driven by means of axle sections connected through the medium of universal joints.

6. A circular saw according to any one of Claims 1-5, characterized in that the outer ends of respective saw axles (9, 10) are joumalled in bearing means (35) that can be displaced axially so as to release said axle ends in conjunc¬ tion with a blade change.