The present invention relates to a portable sawmill assembly to enable a chainsaw to be used to mill logs and other pieces of wood.

Portable chainsaw mills are known which enable a chainsaw to be used as a cutting implement to mill logs, for example to form planks of wood from logs or tree trunks. However, such known chainsaw mills suffer from several drawbacks.

US8479628 describes a portable sawmill which uses a ladder as a pair of guide rails along which the sawmill can be advanced to cut into a log. This apparatus suffers from the drawback that the ladder must be mounted securely to two base portions to enable the sawmill to function. Furthermore, the handle is remote from the chainsaw blade which means that the force applied by the user is not effectively transferred to the blade which can flex causing uneven cutting. Another

disadvantage of this apparatus is that the log must be lifted into guides to be cut. This provides an upper limit to the size of the log or tree trunk that can be cut. Furthermore, the chainsaw is only clamped to one side of the wood causing distortion during cutting and allowing the chainsaw bar to jump as the cut finishes.

US20120037276 describes a portable chainsaw mill which also suffers from the drawback that a log or tree trunk must be lifted into the assembly to be cut. This provides a limit on the upper size of log or tree trunk that can be cut.

Furthermore, this apparatus also suffers from the

disadvantage that the point of application of force by the user is remote from the chainsaw blade which reduces the applicable force and enables the blade to flex causing uneven cutting .

A preferred embodiment of the present invention seeks to overcome the above disadvantages of the prior art.

According to the present invention, there is provided a portable sawmill assembly comprising: a frame assembly comprising first and second guide rails; and a chainsaw guide assembly comprising: first and second guide bar clamp members to clamp to respective first and second positions on a guide bar of a chainsaw in use; and first and second guide members to slidably engage said respective first and second guide rails of said frame assembly, wherein said first and second guide members each engage both the upper surface and underside of said

respective first and second guide rails.

This provides the advantage of a portable sawmill which enables a chainsaw to be used to reliably and repeatedly cut a piece of wood such as a log or tree trunk. By providing a chainsaw guide assembly having first and second guide bar clamp members to clamp to respective first and second

positions on a guide bar of a chainsaw in use, this prevents flexing of the chainsaw guide bar and therefore prevents uneven cutting. By providing first and second guide members which each engage both the upper surface and underside of said respective first and second guide rails, this provides the advantage of preventing the chainsaw moving in and out of the plane being cut to prevent an uneven surface. In many known chainsaw mills, the saw guide members simply rest on a surface which allows the chainsaw to jump during cutting.

Said first and second guide members may comprise C-shaped members .

This provides the advantage of a guide member shape which ensures that the chainsaw blade can be held in the plane of cutting and be prevented from moving vertically relative to the cutting plane during operation.

In a preferred embodiment, said first and/or second guide member comprises a pivot member configured to engage a side of the respective first or second guide rail to enable pivoting of said chain saw guide bar in the plane of the cut during cutting.

This provides the advantage of allowing the chainsaw to pivot in the plane of the cut to enable a user to ease through the wood being cut in a see-saw motion. This also puts less stress on the chainsaw links at any one time by cutting less material at the same point in time. The links can also be cleared of shavings more quickly reducing the strain on the saw .

In a preferred embodiment, the assembly further comprises a handle assembly having at least one handle mounting arm projecting at an acute angle relative to the guide bar of a chainsaw in use.

This provides the advantage of positioning the user behind the cut to direct the force applied horizontally and evenly along the guide bar of the chainsaw. This prevents pivoting of the guide bar out of the plane of the cut to provide improved control and efficiency in the plane of the cut.

In a preferred embodiment, each said guide bar clamp member comprises upper and lower plates, the lowermost plate forming the upper part of the respective guide member.

This provides the advantage of ensuring that the point at which the chainsaw guide bar is clamped is as close as possible to the guide members to ensure maximum transmission of force and to provide improved control to the user.

In a preferred embodiment, each of said first and second guide bar clamp members comprises a handle mounting arm projecting at an acute angle from each said respective upper plate .

This provides the advantage of increasing transmission of force and providing improved control to the user.

In a preferred embodiment, the assembly further comprises log mounting means configured to hold a log between said first and second guide rails.

In a preferred embodiment, said log mounting means comprises at least one log engaging member disposed on an end of a first telescopically adjustable portion of said frame

assembly . This provides the advantage of enabling many different sizes of the logs or tree trunk to be mounted in the assembly for cutting .

Said at least one log engaging member may comprise at least one bolt configured to pierce an end of a log in use to enable rotation of said log on said at least one bolt.

This provides the advantage that the piece of wood being cut can be reoriented without having to be removed and remounted to be cut at a different angle.

In a preferred embodiment, the distance between said first and second guide rails and said first and second guide bar clamp members is adjustable.

This provides the advantage of facilitating the cutting of pieces of wood of different sizes.

The assembly may further comprise a base portion having a plurality of foldable legs.

This provides the advantage that if a particularly large piece of wood is to be mounted in the assembly, the legs can be folded and the assembly can inverted and mounted to the wood. The assembly can then be rolled over to enable cutting of the wood. This avoid heavy pieces of wood having to be lifted.

In a preferred embodiment, the distance between said first and second guide rails and the base portion is adjustable. This provides the advantage that multiple cuts at different heights can be performed on a log without having to move the log .

In a preferred embodiment, said first and second guide rails are removable and the assembly further comprises first and second cross brace members mountable between said first and second guide rails.

This provides the advantage that the assembly can be used to mill particularly large pieces of wood such as large tree trunks that cannot be lifted, by enabling the guide rails to be mounted to that piece of wood rather than the base member

Said first and second cross brace members may each comprise at least one log engaging member.

In a preferred embodiment, the assembly further comprises a tool support assembly comprising at least one perpendicular support rail mounted between third and fourth guide members configured to slidably engage said respective first and second guide rails of said frame assembly; a tool mounting bracket configured to hold one of a chainsaw or a router; and wherein said tool mounting bracket is slidable along said at least one perpendicular support rail.

This provides the advantage of enabling vertical cuts to be made into a log if a chainsaw is used in the tool mounting bracket and also enables a router to be used on the piece of wood being milled. A preferred embodiment of the present invention will now be described by way of example only, and not in any limitative sense, with reference to the accompanying drawings in which:

Figure 1 is a perspective view of a portable sawmill assembly embodying the present invention;

Figure 2 is a perspective view of the portable sawmill assembly of Figure 1 to which a chainsaw and log has been mounted;

Figure 3 is a perspective view of the portable sawmill assembly of Figures 1 and 2 in which the guide rails have been removed and mounted to cross brace members;

Figure 4 is a perspective view of the portable sawmill assembly in the configuration of Figure 3 mounted to a large log and also to which a tool support assembly has been mounted to the guide rails to enable use of a chainsaw in a vertical configuration;

Figure 5 is a perspective view of the portable sawmill assembly in the configuration of Figures 1 and 2 to which the tool support assembly has been mounted with a mounting bracket to enable use of a chainsaw in a vertical

configuration;

Figure 6 is perspective view of the portable sawmill assembly in the configuration of Figure 5 but with a tool mounting bracket for a router rather than a chainsaw; Figure 7a is a perspective view of a log mounting member that can be telescopically mounted to the assembly;

Figure 7b is a perspective view of an additional log mounting member;

Figure 8a is a perspective view of a first type of telescopic member that can be mounted to the assembly to enable the portable sawmill assembly to be used as a sawhorse; and

Figure 8b is a perspective view of a second type of modular sawhorse additional component that can be telescopically mounted to the portable sawmill assembly.

Referring to Figures 1 and 2, a portable sawmill assembly 2 comprises a first guide rail 4 and a second guide rail 6. A chainsaw guide assembly 8 comprises first and second guide bar clamp members 10 and 12 to clamp to respective first and second positions on a guide bar 14 of a chainsaw 16 in use. The guide bar clamp members comprise first and second guide members 18 and 20 to engage the respective first and second guide rails 4 and 6.

Each guide bar clamp member 10, 12 comprises upper and lower plates 10a and 10b, the lowermost plate 10b also forming the upper part of respective guide member 18 or 20. The first and second guide members 18 and 20 each engage both the upper surface and underside of said respective first and second guide rails 4 and 6. This enables guide members 18 and 20 to slide along the guide rails 4 and 6 but not be displaced vertically during sliding. The guide members 18 and 20 may therefore be C-shaped and are adjustable for larger guide bars . Plates 10a and 10b can be clamped together with nuts and bolts 22. A contact pad 24 is placed between plates 10a and 10b to grip the guide bar 14 of the chainsaw 16. A pivot member is located in the downwardly extending leg of the C- shaped guide members 18 and 20 to contact the sides of guide rails 4 and 6 to enable rocking in a see-saw motion in the plane of cut of chainsaw guide bar 14. The pivot member is a piece of metal or other material preventing the upright of the c-shaped guide member fully contacting the respective guide rail to enable pivoting.

A handle assembly 31 has at least one handle mounting arm 26, 28 projecting at an acute angle relative to the guide bar of a chainsaw in use. Preferably, this is accomplished by each guide bar clamp member comprising handle mounting arms 26 and 28 which project acute angles from the guide rails 4 and 6 when the chainsaw guide assembly 8 is mounted thereon. A handle 30 mounts telescopically through receiving portions 32 at the end of arms 26 and 28. The handle mounting arms 26 and 28 are connected to upper plates 10a of the guide bar clamp members 10 and 12.

It can be seen that the portable sawmill assembly 2 is generally formed from tubular metallic elements that

telescopically slide in respective guide portions such as handle guide portion 32. All of the telescopic sliding portions are tightened by thumbscrews 34.

Log mounting means comprises a log engaging member 36

disposed on an end of a telescopically adjustable member 38 which can be tightened by a thumbscrew 34. In Figures 1 and 2, log engagement means is shown as a plate through which screws can be threaded through holes 40 into the surface of log 42. Smaller logs 42 can also be mounted such that their longitudinal axis is a vertical between log engaging members 36. This enables cutting of log coins. Alternatively, referring to Figure 3, in this embodiment a log engaging means is shown as a pair of screws 44 which can be screwed into log 42. Securing screws 46 can be screwed into the log to prevent rotation.

Referring again to Figures 1 and 2, the distance between the first and second guide rails 4 and 6 is adjustable to enable accommodation of larger logs or tree trunks. Cross brackets 48 comprise slidably adjustable guides 50 which can slide towards or away from each other to change the distance between guide rails 4 and 6. To accommodate this motion, handle 30 slides in guides 32 and when the required

separation is set, thumbscrew 34 on guide 32 can be

tightened .

The portable sawmill assembly 2 also comprises a base portion 54 having foldable legs 56. This enables the legs to be folded up and the assembly 2 to be inverted and mounted on large pieces of wood. The height of the guide rails 4 and 6 above the base portion 54 can be adjusted by sliding rail support members 58 in respect of guides 60 and tightening thumbscrews on guides 60. By setting the height of the front pair of rail support members 58 to be different to the height of the rear pair of rail support members 58, this inclines the guide rails 4 and 6 relative to the piece of wood being cut. This enables the preparation of feather edge boards which are planks of wood varying in thickness across the width of the wood. Such feather edge boards are used to make the like of log cabins with overlapping boards. Referring to Figures 1 and 2, the operation of the portable sawmill assembly 2 to cut a log will now be described. Log 42 is lifted into the assembly and placed on base plates 92. If the operator wishes, screws can be screwed into the log through base plates 92 to hold the log in place. The log is then lifted to the desired height and base plate thumbscrews 94 tightened. Log engaging plates 36 are then moved into position and screwed into the ends of log 42.

Chainsaw 16 is mounted in the chainsaw guide bar clamp members 10 and 12 and the screws 22 tightened to clamp the chainsaw guide bar 14 at two positions. The chainsaw can then be actuated and the user can push handle 30 to advance the chainsaw guide bar 14 into the log to make a cut. As has been described, width and height adjustments are possible to accommodate different sizes of logs. The user can also slightly pivot the handle 30 in a see-saw motion such that the guide bar 14 pivots in the plane of the cut to aid cutting .

Referring to Figures 3 and 4, in order to use the assembly 2 on particularly large pieces of wood, the guide rails 4 and 6 can be removed and mounted between cross brace members 62. Each cross brace member 62 comprises a log engaging screw 44 which can be used to mount the assembly to a large piece of wood as shown in Figure 3. Chainsaw guide assembly 8 can then be used in the same manner as the embodiment of Figures 1 and 2.

Alternatively, a first tool mounting bracket 74 shown in Figure 4 enables mounting of a chainsaw in a vertical

configuration. First tool mounting bracket 74 comprisesthird and fourth guide members 70 an 72 which slidably engage rails 4 and 6. Tool mounting bracket 74 is also shown mounted to the assembly 2 in the configuration of Figures 1 and 2 in Figure 5. A second type of tool support bracket 76 for a router is shown in Figure 6.

Referring to Figures 7a and 7b, telescopically mountable log engaging members 78 and 80 comprise V-shaped plates 82.

Bolts can be screwed into a log such that they project out of the ends of the log to rest in V-shaped plates 82. The log can then be freely rotated. To secure the log, screws 84 are provided .

Referring to Figures 8a and 8b, telescopically mountable sawhorse members 86 and 88 are further modular additions to the portable sawhorse assembly 2. Each sawhorse member 86,

88 comprises a toothed V-shaped holding plate 90 for gripping a freely mountable log to be cut with a chainsaw in the manner of a sawhorse.

It will be appreciated by persons skilled in the art that the above embodiment has been described by way of example only and not in any limitative sense, and that various alterations and modifications are possible without departure from the scope of the invention as defined by the appended claims.