AU735551B2 - Portable sawmill arrangements - Google Patents

Description

WO 97/35697 PCTINZ97/00038 PORTABLE SAWMILL ARRANGEMENTS This invention relates to a portable sawmill and in particular to a sawmill in which a carriage, that carries a saw, is arranged to travel along a track defined by track runners.

A portable sawmill in which a saw, including a circular saw blade is supported in a carriage that is arranged for operation along a pair of spaced apart track runners is well known. For example, my United Kingdom Patent Application GB-A-2212101 illustrates such an arrangement. In that arrangement the carriage is arranged for movement along the tracks and the saw is also supported for movement within the carriage, both transversely of the tracks and upwardly and downwardly relative to the carriage. The saw is arranged for movement between two cutting positions, a first in which the circular saw blade is held in a substantially vertical orientation and a second in which the saw blade is held in a substantially horizontal orientation. The portable sawmill can be assembled in any desired location and enables on-site sawing of timber. A modification of the type of sawmill shown in GB-A-2212101 is described in my New Zealand Patent No. 248548/250983. In this modified portable sawmill, one of the track runners is arranged to be supported in an elevated position and the carriage includes runners or wheels adapted to cooperate with the elevated track to provide for smooth movement.

Both of these portable sawmill arrangements have been very successful. However, both suffer from disadvantages. In particular, they may be difficult or complicated to assemble and disassemble for packaging. In particular, the adjustment mechanisms, which usually involve a combination of wires and chains can be difficult to assemble, reliably.

It is an object of the present invention to provide a portable sawmill that at least mitigates the problems associated with prior arrangements.

In its broadest aspect, the invention provides a carriage for a portable sawmill, the carriage comprising spaced apart end frames, a carriage deck that is adapted to support a saw for movement therealong, means for connecting the carriage deck with uprights of WO 97/35697 PCTNZ97/00038 the end frames and means for adjustably supporting the carriage deck for upward and downward movement relative to the uprights, a separate supporting means being associated with each end frame, each supporting means being held in position on the respective end frame when the sawmill is disassembled for transportation.

Preferably, a single actuator, for operating the adjustable support means is provided on one of the end frames, a removable shaft connecting the actuator on one frame with the adjustable support means on the other frame to allow for synchronous movement.

Preferably each support means comprises a chain or cable, or combination of both, arranged to cooperate with a pulley wheel, roller or toothed sprocket arrangement.

Most preferably, at least a portion of the adjustment means comprises a chain element that cooperates with a toothed sprocket, means being provided so that the chain connects with mounting means for the carriage deck on opposite sides of the end frame so that a uniform adjustment of the carriage deck relative to the tracks may be achieved.

In one arrangement, in which the carriage is adapted to run on track runners positioned close to the ground, the track runners are supported on skids to displace the track runners slightly above the level of the ground. This arrangement facilitates set up of the sawmill on uneven ground and reduces interference that may be caused by collection of saw dusts during operation.

Another disadvantage associated with present portable sawmills arises from the limitation of blade size. In particular the larger the blade used, the wider the teeth required (saw kerf) and hence the more waste saw dust produced and the more horse power required to produce a cut (or alternatively the longer time taken for each cut). In order to reduce saw kerf on a given diameter blade a thinner blade plate must be used and a larger diameter supportive collar is therefore required. This, however, leads to a reduction in the maximum capacity cut.

WO 97/35697 PCT/NZ97/00038 Thus, the inventor has also produced a system by which two different diameter collars can be interchanged on the same mill. In this arrangement, a small collar and thick blade can be used to saw up to 10 inch boards, for example. The small collar can be replaced with a larger collar and the thicker blade replaced with a thinner one to saw boards of, for example, six inches and under with greater speed, accuracy and efficiency. This is important as most of such a mill's production involves six inch cuts or less.

In order that the invention may be more readily understood, and so that further features thereof may be appreciated, an embodiment of the invention will now be described, by way of example, with reference to the accompanying drawings, in which: Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Fiaure 6 Figure 7 Figure 8 Figure 9 Figure 10 Figures 11 to 14 is a perspective view of a carriage for a sawmill in accordance with the invention, with parts thereof omitted for clarity; is a side elevational view of the carriage of figure 1; is an enlargement of a part of figure 1; illustrates a split collar blade mounting arrangement that may be used with a sawmill; is a schematic illustration of a saw body and mounting plate with one possible mounting arrangement; is a schematic view of a saw body and mounting plate with an alternative mounting arrangement; is a schematic view of a saw body and mounting plate with a further alternative mounting arrangement; is a schematic view of a saw body and mounting plate with yet a further alternative mounting arrangement; is a schematic view of a saw body and mounting plate with a still further mounting arrangement; is a schematic view of a saw body and mounting plate with a still further mounting arrangement; and illustrate a novel locking arrangement.

WO 97/35697 PCT/NZ97/00038 Referring to figure 1, a carriage for a sawmill is generally indicated at 1. The carriage 1 is arranged to be supported upon spaced apart track runners 2, 3, the track runners 2, 3 being profiled, at 4, to cooperate with wheels or rollers 5 mounted at the base of the carriage 1. The track runners 2 may be supported on skids 6 and held in place by retaining means 7. Only one skid 6 is illustrated. However, any suitable number may be provided.

The carriage 1 comprises two spaced apart end frames 8. For the purpose of illustration, one of the end frames is illustrated in full and the other illustrates only an adjustment mechanism 9, which will be described in more detail below. Each frame comprises a pair of spaced apart tubular uprights 10 connected by an upper cross member 11 and a lower cross member 12 to form a substantially rectangular end frame. A flange 13 projects from a lower end of each of the uprights 10. Each flange 13 carries one of the wheels or rollers 5 and a guide means 14. Guide means 15a, 15b are mounted at the upper end of one of each pair of uprights 10 and a drive mechanism 16a, 16b is mounted at the upper end of the other of each of said pair of uprights.

A carriage deck 17, that extends, in use, between the end plates 8, 9, is located for upward and downward movement relative to the upright 10. The carriage deck 17 is substantially rectangular in shape and carries a bushing 18a, 18b at each corner thereof that is sized to be received over the tubular uprights 10 to allow relative upward and downward movement of the carriage when in position for use.

The bushings are shown in greater detail in figure 3. Each bushing 18 comprises an annular portion 19, an outer flange portion 20 and an inner flange portion 21. The annular portion 19 fits closely about the periphery of the upright 10, but with sufficient clearance to allow free movement axially along the upright 10. The outer flange 20 has an upper securement aperture 22 and a lower securement aperture 23 for cooperation with the adjustment means 9 (as will be discussed further hereinbelow). The flange 21 receives a bolt 24 to secure the bushing 18 to a cross member 25 of the carriage deck 17.

WO 97/35697 PCT/NZ97/00038 The carriage deck 17 carries means for mounting the saw arrangement (not shown).

Suitable means are described in detail in GB-A-2212101 and NZ 248548/250983 and full disclosure of these documents is included herein by reference.

Each adjustment means 9 comprises a chain or chain and cable combination that cooperates with the drive mechanism 16.

As best illustrated in figure 1 each of the drive mechanisms 16 comprises a pair of toothed sprockets 16a, 16b arranged for co-axial movement and which cooperate with drive elements 26, 27, respectively. Considering one of the end plates, the drive element 26 comprises a length of chain 26a connected with a length of cable 26b via a connector 26c. The free end 26d of the chain 26a is attached to the upper securement aperture 26 of the bushing 18. The chain 26a extends upwardly about the toothed sprocket 16a and then downwardly towards the lower guide means 14. The cable 26b then passes about the guide means 14 and extends upwardly to be connected to the bushing 18a at the lower securement aperture 23. Thus, it will be appreciated that movement of the drive elements 26 in one direction will produce an upward movement of the carriage deck 17, on which the bushings 18 are mounted, and movement in the reverse direction will produce a downward movement of the carriage deck.

The drive element 27 is arranged to provide a simultaneous lifting effect to the bushing on the opposite upright of the end frame. The drive element 27 comprises a chain length 27a that connects, at each end, with a length of cable 27b, 27c. The chain length 27a is positioned to cooperate with the toothed sprocket 16b, one end of the chain/cable 27a, 27b extending towards and passing about the guide means 15a, and then downwardly to engage the upper securement aperture of the bushing 18b. The other end of the chain/cable 27a, 27c extends, towards and over, guide means 15b and then downwardly to pass about the guide means 14 at the base of the upright and return for engagement on the lower securement aperture of the bushing 18b.

WO 97/35697 PCTNZ97/00038 The toothed sprockets 16a, 16b are arranged to be driven simultaneously so that a corresponding lifting/lowering force may be applied to each corner of the carriage deck 17. The connection of one end of each of the drive elements to upper and lower parts of the bushings 18 allows a positive push pull effect for each lowering/lifting of the carriage deck.

An operating means 31, in the form of a reduction gear or crank handle arrangement connects with the drive mechanism 16a of one of the end plates. A releasable shaft 32 is adapted to be connected with the drive mechanism 16a, 16b of each of the end plates so that actuation of the operating means 31 will cause corresponding movement of the adjustment means 9 on the opposite end frame. Thus, it will be seen that movement of the operating means in a first direction may cause upward movement of the carriage deck 17 and movement of the operating means in the opposite direction causes downward movement. The operating means 31 and releasable shaft 32 may be mounted at the top of the carriage (as shown) or may be mounted for movement with the carriage deck, the shaft 32 extending alongside the carriage deck.

It will also be appreciated that the adjustment means 9 of each end plate is entirely separate and forms a single unit with the end plate. This facilitates assembly and disassembly of the carriage. In the embodiment illustrated the end frame 8 can be disconnected from the carriage deck 17 by removal of the bolts 24. In this way, the portable sawmill can be disassembled, but with the adjustment means retained in a position ready for use.

In an alternative arrangement, not shown, the bushings 18 may be mounted for connection to the side members 33 of the carriage deck 17. In this arrangement loosening of the connecting bolts 24 will allow pivoting movement of the frame down into a position resting on top of the carriage deck for easier transportation and packaging.

Although illustrated in use with tracks laid on or close to the ground, the invention is equally applicable to a high-low track arrangement or to a dual high track arrangement.

WO 97/35697 PCT/NZ97/00038 Figure 4 illustrates a split collar attachment mechanism to facilitate the mounting of different circular saw blades to the apparatus. In the mounting arrangement, a shaft that is driven by the saw motor mechanism (not shown), carries an integral collar 51.

A spigot 52 extends outwardly of the collar 51. The collar 51 includes screw holes for receiving screws for mounting a removable collar 53 or 54 that supports the saw blade.

Two alternative removable collars are provided. A small collar 54 may be used to support a blade for large cuts having wide teeth. The mill is also provided with a supplementary larger diameter collar 53 that is adapted to be connected directly to the shaft collar 51, using countersunk screws and then to receive a blade mounted over those screws, using additional countersunk screws. This blade can be thinner and with reduced kerf to reduce sawdust waste, increase recovery efficiency and increase cutting speed on smaller cuts.

It is preferable that the spigot extends sufficiently through the small or large collar (which ever is being used) to mount the blade in the appropriate position for cutting. This technique can also be used to adapt an existing single swinging blade mill to receive a larger diameter blade and thus to achieve a greater cut capacity or a better cutting efficiency.

The previously described aspects of the invention can also be used in connection with an apparatus for mounting a saw body, that supports a circular saw blade, in a saw mill.

In particular, with such apparatus wherein the saw body and blade are arranged to swing between a first position, in which a horizontal cut can be made, and a second position in which a vertical cut can be made.

It is well known that a saw mill can be constructed with a single swinging blade to cut horizontally in one direction and vertically when the blade is moved in the opposite direction. In such an arrangement, the point about which the saw body pivots is known as the axis swing point or ASP.

WO 97/35697 PCT/NZ97/00038 In order for the two cuts to meet and intersect properly, the ASP must be located at a point distant from the blade equal to the radius of the blade.

In all previously known arrangements, as the blade swings about the ASP, the tip, or leading edge, of the blade dips by a significant percentage of the diameter of the blade.

This creates the dangerous possibility of the swinging blade striking loose timber, stones, dirt or other equipment and flinging this towards the operator or forward towards an operator's assistant or other bystanders. Although this potential danger arises only near the bottom of a log being cut, it is present on every log that is cut. To avoid this problem, it has been known to raise the log above the surface of the ground by distance sufficient to ensure that, at its lowest cut position, the blade does not swing into or close to the ground. With larger logs, such a manoeuvre is very difficult and the saw mill itself retains the potential for accident if safety procedures are not initiated.

The inventor's new arrangement provides apparatus for mounting a saw body that supports a circular saw blade, the-apparatus comprising a mounting plate that receives pivot means about which the saw body and blade can swing, so that the blade can move from a substantially vertical cutting position to a substantially horizontal cutting position, the pivot means defining a swing axis point that is fixed in relation to the saw body, the mounting plate including guide means to allow the pivot means to move upwardly so that the access swing point can be moved upwardly away from a cutting position, the saw body carrying secondary support means that cooperates with guide means on the mounting plate to support the saw body during movement from the vertical cutting position to the horizontal cutting position, the arrangement being such that when the body is moved from one cutting position to the other, the swing access point is constrained to move upwardly by distance sufficient to ensure that the saw blade does not dip below a horizontal cut datum during the swinging movement.

Thus, this arrangement provides a means by which the blade is prevented from swinging below the horizontal cut datum and in fact swings above that datum. This allows for more worry-free sawing and provides a saw mill with a capacity to safely mill to a point WO 97/35697 PCT/NZ97/00038 much closer to the ground, eliminating the need to lift or chock-up logs in order to achieve high recovery.

Preferably, the access swing point incorporates a bearing which is encapsulated in a linear raceway raising upwards to an extent necessary to raise the trailing edge of the blade above the cut datum. The bearing returns to its lowermost, or starting, point when the saw body reaches the desired cutting position. This is true for both the horizontal and vertical cutting positions ensuring that proper cut intersection is achieved.

Attached to the swinging portion of the saw body, at a fixed position thereon, a second bearing, that is spaced from the first bearing, is located on the saw body and constrained to pass along a second encapsulating raceway. Respective ends of the second raceway locate the second bearing, and therefore the saw body and saw blade, in the respective first and second cutting positions, the second bearing moving along the raceway during a movement of the saw body between positions. The second raceway is shaped so that as the second bearing is constrained to follow that raceway, the first bearing is forced to move upwardly in the first raceway and thus the saw blade is moved upwardly during swinging movement. The second raceway may be of any convenient shape, the shape controlling the actual path movement of the blade. The end portions of the second raceway locate the second bearings such that the axial centre of the bearing in each of the end positions and the axial centre of the first bearing in the cutting position define an angle that is substantially 900, the axial centre of the first bearing providing the corner point of the right angle.

The actual amount of blade rise is determined by the amount of upward movement of the first bearing and that bearing can also move either left or right without jeopardising the desired end result. The second bearing can be fixed at an infinite number of positions.

Some positions will reduce the total cut size possibilities and some will cause the blade to rise perhaps into the saw guard. Other positions may be selected to allow easy manufacture or easier access for maintenance.

In alternative arrangements, adoption of an arrangement for simultaneously lifting and WO 97/35697 PCTINZ97/00038 swinging the blade allows the addition of locking means for stabilising the blade in a position other than the usual vertical and horizontal cutting positions. This enables the saw to be at selected angles off-set from the vertical, for example to form boards for use as outside cladding (weather boards) or to allow for creative cutting, for example to achieve cut boards with a parallelogram or trapezoidal cross section, as desired.

Figures 5 to 10 illustrate a number of alternative arrangements for mounting a saw body on a mounting plate to achieve the aims of the invention. In the arrangements illustrated, a saw body 61, carrying a circular saw blade 62 is supported by a mounting arrangement in a mounting plate 63. The mounting plate 63 is adapted to be located in the carriage (not shown) of a saw mill, the carriage being supported in a frame work for upward and downward movement, to adjust the height of a cut and for longitudinal movement, along the length of a log to be cut. The invention is particularly suitable for use carriages as described earlier and indeed in sawmills such as described in my United Kingdom Patent Application GB-A-2212101 or in my New Zealand Patent No. 248548/250983 and the disclosure of each of these is incorporated herein by reference.

A bearing 64 extends outwardly from a fixed point on the side of the saw body 61 and is received within a raceway 65 of the mounting plate 63. The bearing 64 defines the access swing point ASP about which the saw body pivots during swinging of the saw blade 62 from its vertical cutting position, shown in bold lines in figure 5, to its horizontal cutting position, shown in dotted lines in figure 5. As shown by the arrow 66, the bearing 64 is able to move upwardly within the raceway 65. Locking means, not shown, are provided to lock the bearing 64 in the lowermost, cutting, position, the locking means being releasable to allow upward movement during swinging between cutting operations. A second bearing 67 mounted on a flange 68 that extends from the body 61 of the saw is received within a second raceway 69 of the mounting plate 63.

One end of the raceway 69a defines a position in which the bearing 62 is retained with the saw body in the first (in this case) vertical cutting position and a second end of the raceway 69b defines the location of the bearing 67 in the second (in this case) horizontal cutting position of the saw body 61.

WO 97/35697 PCT/NZ97/00038 The raceway 69 extends in a complex arc between the positions 69a and 69b, the arc being shaped to constrain the bearing 67 to follow the desired path and to cause the bearing 64 to move upwardly in the raceway 65 during swinging movement. Thus, when the saw body is moved from the vertical cutting position, by exertion of a force on the direction change handle 70, the bearing 62 is forced to follow the pathway defined by the raceway 69 and the bearing 64 is forced to move upwardly in the raceway 65. Thus, the swing access of the saw blade during movement is moved upwardly and the leading edge of the blade 62 is lifted clear of the horizontal cut datum during movement. When the saw body passes the midpoint of the movement from the first to the second cutting position, the bearing 64 moves downwardly towards the cutting position.

Thus, in this first embodiment movement of the blade leading or trailing edge occurs substantially across the horizontal cut datum, substantially continually intersecting the horizontal cut datum. At the same time the arrangement provides a bearing position which does not interfere with the capability to cut maximum size square sections from the log. The complex curved shape of fhe raceway provides that the vertical movement slot rests on the line which equally divides the starting and finishing positions of the curved slot. Provided that this arrangement is kept, the curved raceway could be symmetrical regardless of the upward angle of the vertical raceway. By using this system of dual encapsulated raceway a large variety of options for shape and installation can be provided.

As shown in figures 6 to 10, a similar effect can be achieved by using a linkage arm mechanism in place of the curved raceway.

Thus, referring to figure 6, a bearing 64 that defines the ASP is constrained to move within a substantially vertical raceway 65. However, the bearing 67 is replaced by a fixed linkage pin 71 that is mounted on the flange 68 of the saw body and projects into a short slotted raceway 72 of the mounting plate 63. A linkage arm 73 is rotatably mounted about the fixed linkage pin 71 at one end and about a separate fixed linkage pin 73 positioned on the mounting plate 63. For ease of description, the fixed linkage point WO 97/35697 PCT/NZ97/00038 73 is noted as FLP1 the fixed linkage point 71 as FLP2 and the uppermost extent of the raceway 65 defines the access swing position at its maximum height (ASPM).

The three points FLP1, FLP2 and ASPM can be rotated equally around the ASP in either direction to achieve a similar effect in lifting the saw body and blade during swinging of the blade. The distance between the ASP and the ASPM (shown A in the drawing) can be enlarged to accommodate a larger blade and the subsequent depth of blade swing. The distance A, between the ASP and ASPM, is the same as the distance between the ASP and FLP2.

Thus, on movement of the operating handle 70 the bearing 64 moves upwardly in the raceway from the ASP4 to the ASPM.

Thus, when the handle 70 is moved upwardly the bearing 64 moves upwardly in the raceway 65 and the linkage arm pivots about the fixed point FLP1 whilst FLP2 is maintained in the slotted raceway of the linkage arm and moves upwardly with the flange 68 so that the saw body 63 and body 62 are lifted in a controlled manner. AThe linkage arm returns to a second position, shown in dotted lines in figure 6, when the blade 62 reaches the horizontal cutting position.

Figure 7 shows how the same lifting effect can be obtained using two linkage arms 76. The first linkage arm 75 is identical with the linkage arm described in connection with figure 6 and includes a raceway 77 that cooperates with the fixed linkage pin 71 (FLP2). The other end of the linkage arm 75 is mounted at the fixed linkage point 73 (FLP1) to the mounting plate 63.

The second linkage arm 76 has one end mounted to move with the bearing 64 at the ASP and a second end mounted via a fixed linkage point (FLP4) 78 to a top part of the body 61. By using a slotted raceway FLP1 can be positioned at any point along a substantially vertical line 79. The fixed linkage point 71 (FLP2) is determined by the intersect of a perpendicular from the specific (FLP1) on line 1. The ASPM is determined by extending WO 97/35697 PCT/NZ97/00038 line 1 through the ASP by a distance A as before. The FLP4 is determined by a line perpendicular to line 1 that bisects line 1 between the ASP and ASPM. As FLP4 can be located at any convenient point along line 3, each selected point defines a slightly different path of movement for the saw body and blade.

It should be emphasised that these figures by no means convey all possible configurations which may be used to lift the blade while changing its position. However, an arrangement should provide that a fixed point, the ASP, is raised during change-over to allow blade clearance of the horizontal cut datum. A second fixed point is transferred to a position about equal distance from and substantially 900 to a line between its first position and the ASP to effect a 90* blade change-over. Other curve effects and any motion devices can be used to achieve this effect. In figures 6 and 7 the ASPM can be moved parallel with the line shown (in the vertical position) without altering the blade lift height. In this case, line 3 continues to bisect the line between ASP andASPM at right angles and the linkage arm 75 would be lengthened to achieve the necessary extra linear movement of the ASP.

Figure 8 illustrates a further alternative arrangement in which a gas strut or spring mechanism 79 which has one end attached to the mounting plate 63, at a point along a line 1 that passes through the ASP and the other end attached, at a fixed linkage point 62 on the saw body 63. In this arrangement the bearing 64 is constrained to pass through a slightly arcuate raceway from the ASP to the ASPM. The FLP2 could be a bearing as in figure 5. It will be appreciated that in this arrangement there are an infinite number of methods and positions which could utilize the general principle.

Figures 9 and 10 illustrate further alternative arrangements.

WO 97/35697 PCT/NZ97/00038 It may also be desirable to provide a locking device for use in a portable sawmill which incorporates a single swinging circular saw blade. The locking means should be so designed to better accomplish the following desirable ends: 1. simple and economical to construct 2. simple, smooth, easy to use 3. positive and safe locking in both positions 4. provides simple, easy to use, and easy to understand blade adjustment.

Figures 11 to 14 illustrate a novel locking arrangement.

Referring to figures 11 to 14, it can be seen that in operation, the operator lifts up locking handle 85, draws 85 to the left during which bearing 82 can roll smoothly over bearing race 81 and locks 82 behind locking face 89 by pulling the handle 85 towards himself. This sequence changes blade position from horizontal to vertical position.

Reversing the sequence from left to right achieves change from vertical to horizontal position.

Tension spring 91 ensures locking handle 85 and bearing 82 do not vibrate loose during operation. Adjustable locking plate can be moved from side to side to change the exact cutting angle of both vertical and horizontal blades, at the same time ensuring that the blade intersect remains more or less constant in any position. Locking tension between roller bearing 82 and each respective locking face 89, 90 can be adjusted at adjustable horizontal stopper 88 for the horizontal position, and at adjustable vertical stopper 87 for the vertical position. The adjustable stoppers can be located either on the mill portion that carries the swinging blade, or on the stationary frame within which the swinging frame is mounted. The adjustable extension spring 98, although fully extended in the horizontal, exerts no upwards pressure, as it is mounted crossin the swinging axis point Once the blade is released lightly from the horizontal lock position, the spring exerts a positive lifting force assisting the operator in raising the blade to the vertical position.

This spring also prevents the blade from crashing down from the vertical position which WO 97/35697 PCT/NZ97/00038 could cause damage to some part of the mill. The curve shape of the bearing race also permits the use of a removable bearing stopper which can be placed at any point along the bearing race 81 to provide one or more alternate locking positions to facilitate the sawing of timber shapes/angles other than vertical and horizontal, i.e. 450 angle cuts.

This novel locking arrangement provides an effective and cost effective locking means for utilizing the advantages of a single swinging blade. It provides a positive and safe locking mechanism. It requires only a simple operator movement which is natural and smooth. This movement requires very little force with little chance for error, injury or damage during operation. It also offers the opportunity of boards at any number of different angles, if so desired. In addition, it reduces the number of adjustable points for blade adjustment down to three, a reduction from previous art. In many cases, blade adjustments can be accomplished by altering either one of the adjustable stoppers 87, 88, or perhaps both. Once properly set, the adjustable locking plate 83 would rarely need further adjustment.

Thus, embodiments of the invention are intended to provide the following features: 1. A lever type locking arm which swivels down into one or two or more locking positions to hold the blade in the desired cutting position.

2. A raceway which joins the locking positions and upon which a roller bearing or low friction composite material slides to prevent the locking arm prematurely dropping into a locking position.

3. A joined raceway and base plate which ensures that the blade intersect remains constant regardless of adjustment position.

4. A roller bearing or low friction material which permits the locking arm to slide smoothly and easily from one locking position to the other.

WO 97/35697 PCTNZ97/00038 A tension spring which tends to hold the locking arm in a locked position until removed with light positive pressure.

6. An extension spring which assists in raising the blade into the vertical position, and prevents the blade from dropping down too rapidly.

7. A facility (not shown) for locking the blade in alternate angled positions across the bearing raceway.

Claims (1)

1. 23-MAY-01 WED 09:59 COLLISON AND CO FAX NO. 61 8 82123988 P 03/06 THE CLAIMS DEFINING THE INVENTION ARE AS FOLLOWS: 1. A carriage for a portable sawmill, the carriage comprising spaced apart end frames, a carriage deck that is adapted to support a saw for movement therealong, means for connecting the carriage deck with uprights of the end frames and means for adjustably supporting the carriage deck for upward and downward movement relative to the uprights, a separate supporting means being associated with each end frame, each supporting means being held in position on the respective end frame when the sawmill is disassembled for transportation, and wherein a single actuator, for operating the adjustable support means is 1i provided on one of the end frames, a removable shaft connecting the actuator on one frame with the adjustable support means on the other frame to allow for -synchronous movement. 2. A carriage according to claim 1, wherein each support means comprises a chain or cable, or combination of both, arranged to co-operate with a pulley 15 wheel, roller or toothed sprocket arrangement. o A carriage according to claim 2, wherein at least a portion of the adjustment means comprises a chain element that co-operates with a toothed sprocket, means being provided so that the chain connects with mounting means for the carriage deck on opposite sides of the end frame so that a uniform adjustment of the carriage deck relative to the tracks may be achieved. 17 23/05 '01 WED 10:26 [TX/RX NO 9762] 23-MAY-01 WED 09:59 COLLISON AND CO FAX NO, 61 8 82123988 P.04/06 4. A carriage according to any one of claims 1 to 3, wherein the carriage is adapted to run on track runners positioned close to the ground, the track runners being supported on skids to displace the track runners slightly above the level of the ground. 5. A portable sawmill arrangement including a carriage according to any one of claims 1 to 4. 6. A portable sawmill arrangement according to claim 5 which incorporates an arrangement by which two different diameter collars can be interchanged on the same mill. 0 7. A portable sawmill arrangement according to claim 6, wherein a small collar and thick blade can be used to saw up to 10 inch boards and the small collar can be replaced with a larger collar and the thicker blade replaced with a thinner one to saw boards of, for example, six inches and under. 8. A portable sawmill arrangement substantially as hereinbefore described Is with reference to the accompanying drawings. Dated this 23rd day of May 2001 e PETERSON PORTABLE SAWING SYSTEMS LIMITED By their Patent Attorneys COLLISON CO R 18 23/05 '01 WED 10:26 [TX/RX NO 9762]