GB2153743A - Adjustable side fence for woodworking machines - Google Patents

Abstract

A woodworking machine has a side fence 5 comprising upper and lower fence elements 7,6 of which the lower fence element 6 is fast to a worktable 1 and the upper fence element may be raised and lowered on hardened steel shafts 8 by rams 9. Optional position sensors 13 control the optimum height of the side fence in relation to the thickness of timber being worked. <IMAGE>

Description

SPECIFICATION Adjustable side fence for woodworking machines The invention relates to woodworking machines in which timber is fed past one or more workstations in sliding abutment with a side fence which positions the timber relative to cutting heads operative at the workstations. The cutting heads may be planing heads, moulding heads or mortising heads as appropriate.

In such woodworking machines the side fence has hitherto been a fixed fence upstanding from a worktable over which the timber passes. For most woodworking operations it is important that the fence should not stand proud of the timber, so that such fences have in general been of limited height, providing lateral guidance only for the timber but little or no support to maintain the timber square to the worktable.

Some woodworking machines can be programmed to perform a series of different forming and finishing functions as a preset sequence on different pieces of timber fed therethrough. A typical example is a window-frame machining centre which can be programmed to produce, in succession, window frame sills, heads, jambs and sash members. If the different window frame elements are to be made of substantially different final sections and sectional sizes, as is the industry standard in some countries including Great Britain, then the fence height has in the past been limited to less than the height of the smallest timber pieces to be worked; in this case the sash members.This in turn has restricted the flexibility of the machining centre, as timber has always to be fed in a stable attitude, with a broad planar face abutting the worktable to provide virtually the whole of the resistance of the timber to tilting in cross-machining operations.

The invention provides an adjustable side fence for woodworking machines, comprising an elongate lower fence element fast to a worktable, defining a bottom guide edge for timber fed along the worktable, an elongate upper fence element mounted on vertical shafts passing through linear bearings in the lower fence element and/or the worktable, and means for raising and lowering the upper fence element so that a top guide edge thereof is always in vertical alignment with the bottom guide edge of the lower fence element.

The means for raising and lowering the upper fence element is preferably a fluid-activated means in which a ram acts vertically on one or more of the vertical shafts. For accurate control of longer fences at least, a number of such rams is desirable, acting near the ends of the upper fence element and optionally also at intermediate positions. All such rams may be operated in synchronism from the same fluid pressure source. The source of fluid pressure may be a source of superatmospheric or subatmospheric pneumatic pressure or a source of hydraulic pressure as appropriate.

The accuracy with which the upper and lower fence elements can be maintained in vertical alignment during and after movement of the upper fence element has proved sufficient for all woodworking operations. Moreover the stability imparted to the workpiece by virtue of raising the top guide edge of the side fence to a position near the top of the timber workpiece has improved the accuracy of some machining operations, particularly cross-machining operations involving a transverse movement of the cutter head relative to the direction of movement of the timber. A further advantage has become apparent when the ends of the timber is being or has been mortised. So-called break-out during mortising results in some wood fibres at the end of the stroke of the mortising cutting head being not completely severed but merely bent outwardly into the path of the fence.Prior to this invention there was always a tendency for such fibres to become completely folded back between the timber and the fence, thus pushing the timber away from the fence. In the case of the present invention the mortise may be positioned so that any break-out that does occur is accommodated in the vertical space between the upper and lower fence elements, so that the timber is not pushed away from the fence.

The movement of the upper fence element may be controlled in a variety of ways. The simplest control is a two-position control, with the upper fence element being moved merely between a fully raised position and a fully lowered position. Alternatively one or more intermediate positions may be defined, corresponding to popularly used intermediate timber sizes. The intermediate positions may if desired be identified by position sensors on the upper fence element, on one or more of the vertical shafts supporting the upper fence element or on the rams or other means for raising and lowering the upper fence element. Suitable position sensors include limit switches and photocells.

Advantageously the selection and control of the optimum ram extension is achieved automatically in response to sensing, by the woodworking machine, of the timber height being passed. In such a woodworking machine the ram extension and the corresponding height of the upper fence element is preferably a few millimetres less than the height of the worked timber.

Drawings Figure 7 is a vertical cross-section through a part of a worktable of a woodworking machine, showing in schematic elevation the control means for raising and lowering the upper fence element; and Figure 2 is a side elevation, partly in section, of the control means of Figure 1 viewed in the direction of arrow A of Figure 1.

In the drawings a worktable 1 of a woodworking machine supports a timber workpiece. Three such workpieces 2, 3 and 4 are shown in Figure 1, being the typical stock sizes for a British standard timber window frame. These three workpieces represent a sill 2, a head 3 and a sash element 4.

A side fence 5 of the woodworking machine comprises a lower fence element 6 fast to the worktable 1 and an upper fence element 7 which can be raised and lowered on vertical shafts 8. A number of such shafts 8 is arranged along the length of the side fence 5. Two of the shafts 8, preferably the end two, are connected at their lower ends to rams 9 which are double-acting rams powered by air or by hydraulic fluid pressure.

The shafts 8 are hardened steel shafts which pass through a linear ball race 10 fast beneath the worktable 1 and through a bushing 11 in the lower fence element 6. The upper fence element 7 is secured fast to the steel shafts 8 by means of grub screws 12.

As so far described, the adjustable side fence illustrated may be moved between the fully raised condition shown in chain-dotted lines and the fully lowered condition shown in solid lines. If desired, however, intermediate positions of the side fence may be established, for example by the optical sensing means 13 illustrated in Figure 2. As shown, a finger 14 mounted on the head of each ram 9 passes between a row of LED emitters and associated photoelectric sensors 15. In this way the ram 9 may be moved from any partially extended condition to any other partially extended condition, by means of electrical circuitry which actuates valve mechanisms in the fluid pressure circuit.

Suitable electrical circuitry and the valve mechanisms are both known in themselves and are not therefore illustrated in the drawings.

Claims (6)

1. An adjustable side fence for woodworking machines, comprising an elongate lower fence element fast to a worktable, defining a bottom guide edge for timber fed along the worktable, an elongate upper fence element mounted on vertical shafts passing through linear bearings in the lower fence element and/or the worktable, and means for raising and lowering the upper fence element so that a top guide edge thereof is always in vertical alignment with the bottom guide edge of the lower fence element.

2. An adjustable side fence according to claim 1, wherein the means for raising and lowering the upper fence element comprises a fluid-actuable means in which a ram acts vertically on one or more of the vertical shafts.

3. An adjustable side fence according to claim 2, wherein at least two such rams are used, one acting near each end of the upper fence element, the rams being operated in synchronism from the same fluid pressure source.

4. An adjustable side fence according to any preceding claim, wherein the means for raising and lowering the upper fence element comprises means for arresting the upper fence element in a fully raised position, a fully lowered position and one or more intermediate positions.

5. An adjustable side fence according to claim 4, wherein the means for arresting the upper fence element is responsive to sensing means for sensing the thickness of timber stock fed along the work- table.

6. An adjustable side fence for woodworking machines substantially as described herein with reference to the drawings.