US2094303A - Method and apparatus for bending wood - Google Patents

Description

Sept. 28, 1937.

c. v. ROWELL 2,094,303

METHOD AND APPARATUS FOR BENDING WOOD Filed May 8, 1935 F'IIIIIIIII 7 1.

- INVENTOR. %50W// m M NEYS.

Patented Sept. 28, 1937 .UNlTED STATES METHOD AND APPARATUS FOR BENDING WOOD Charles Victor Rowe-ll Burwood, near Sydney,"

New South Wales, Australia Application May 8,

1935, Serial No. 20,472

In Australia May 18, 1934 2 Claims.

' This invention is based on the fact, ascertained as a result of extensive experimental work, that natural wood in the form of thin boards, and also boards and laths fabricated from vegetable fibre, arecapable of being bent more or less sharply without fracture, provided that in the bending operation in a folding platen press end pressure is applied to compress the boards or laths towards the bend line so as thereby to cause what is in effect an endwise movement of the fibres which compensates the tendency they would otherwise display to pull apart at the salient face and develop a crack on the bend line.

For the manufacture of boxes, such as butter boxes and the like, 'a board of natural wood or fabricated fibre wood of appropriate dimensions is set in the bending press. Endwise pressure is applied in one or both leaves of this press tending to feed the board inward toward the hinge joint between these leaves where the bend is to be made in the board, and simultaneously folding up the leaves of the press to right angle position more or less to make a bend at the required angle up to 90; four 90 bends are thus made to constitute the four corners of a square box. The ends of the board are arranged to come together midway of two bends and the joint is closed and sealed; afterwards bottoms and covers are fitted and secured to the open end structure thus produced. The side joint is preferably a toothed or dovetailed joint formed by interlocking the previously complementarily shaped ends of the board to interfit and fixing them together in alignment preferably by gluing a strip of stout woven material on either or both sides of the interlocked joint thus made.

The method of bending and the essential elements of the bending press will be understood by reference to the accompanying drawing, in which: Fig. 1 is a top plan view with parts in section and others broken away to facilitate illustration, of the entire assembly of my device.

Fig. 2 is a horizontal sectional View, taken on the line 22 of Fig. 1.

Figs. 3, 4 and 5 are Views similar to Fig. 2 and showing the position of the parts at various progressive stages of the bending operation.

Fig. 6 is a side elevation of the board after the latter has been bent in accordance with my invention. I

As may be seen from the drawing, Figs. 2, 3, 4 and 5 are sectional views through portions of the press platens in the different stages of the bending operation on a board, while Fig. 6 shows an end view of a bent board, this view being taken across the bend, suggesting the way in which are caused to displace from the interior corner and crowd outwards to the salient corner to fill it. The press in all cases consists of a pair of platens A and B hingedly connected as indicated at T to fold bookwise from alignment up to right angle relation. Cover plates C and D are mounted on the members A and B respectively so as to grip the board E under them. In the particular arrangement illustrated, one of the platens or carrier members of the press is shown slotted at F and in this slot a shoe plate G is contained which is held in slidable alignment with the. platen with its top face H standing slightly above the level of the face of the platen. This shoe plate member G is tightly clamped to the top cover plate D to embrace the board E non-slidably between it and the shoe plate, .and the assembly (cover plate, board, and shoe plate) is slidable relative to the platen B endwise inward towards the hinge'joint by any appropriate mechanical contrivance. The clamping means for securing the assembly may be of any suitable construction, and for the purpose of illustrating the invention, I have shown the shoe plate G provided along its side edges with apertured studs Y adapted to project through slots arranged on the outer border of the cover plate D. Levers X, each provided with a cam surface, are connected to said studs and are adapted to bear upon the cover plate for clamping the board E between these two plates. Similar clamping means may be provided on the platen A and cover plate C for clamping these two elements together. The end compression should be applied so as to compress the wood in the region of the bend. It is undesirable to apply it at the outer ends of the board because that might result in buckling or splitting the board. The compressing device shown is an elementary design of device consisting of a threaded spindle L threaded at the outer end, with a heavy nut M running on the thread and a lever N formed on the nut to facilitate rotation of it on the threaded spindle L. The shoe plate G is clamped to the cover plate D, and the board E is tightly embraced between them, so that when the spindle L is rotated positively the whole assembly G-ED is slidable as a unit on the platen B towards the hinge joint about which the platens fold. Whilst the folding movement is taking place, inward movement is applied to the unit GE-D by revolving the arm N to turn the nut M, or by otherwise applying endwise pressure on the shoe plate and cover plate to slide the unit more or less towards the hinge joint, the range of movement bethe fibres ing proportioned in relation to the thickness of the board.

Fig. 3 indicates the effect of this endwise compressing of the boards, a bulge being produced between the adjacent ends of the platens. It will be noted that in this case a depression at the meeting point of the cover plates C and D is formed to accommodate the flow of the wood at the bend and allow the crowding out of the fibres as seen at 0.

Fig. 4 shows the condition during the bending of the board, and Fig. 5 shows the condition when a right angle bend has been completed. The section of the board processed as shown in Figs. 2, 3, 4 and 5 is shown in Fig. 6, the flow of the fibres being indicated by stippling. The flow varies somewhat according to the board thickness, the end pressure applied, and the nature of the material of the board. It is advantageous to place a slip of thin leather Q (see Figs. 2-4) as an underlay for the bend, as its presence appears to support fibres which tend to bulge outwards. Minimization of risk of making a burst at the corner is thus effected.

Bending of natural wood boards and fibre boards in thickness up to about is thus accomplished without any notable risk of fracture developing at the bends except in rare cases. The folding movement of the platens should be slow, very rapid movement being undesirable as thereby the natural tendency of the Wood to burst on the salient face of the bend might be increased. The rate of end feed applied to the boards in process of bending should be related to the rate at which the platens are folded, and this will vary according to the nature of the wood or fibre board and should be proved for each sample by putting through a test piece. It is desirable to make the area of the board on which the clamp acts as great as practicable as thereby the risk of damage is minimized. High clamping pressure spread only over a limited area is apt to leave a blemish on the board faces. The clamping surface, in order to ensure an effective gripping on the board surface, should be appropriately roughened or serrated, and should not be polished or quite smooth as in that case there would be a tendency for slippage to occur.

In the case of particularly fragile timbers, it may be sometimes found desirable to pre-soften the timber by steaming or soaking in the region of the joints, and in these cases it may also be found desirable to work the press hot. These are, however, exceptional cases.

What I claim as my invention and desire to secure by Letters Patent is:-

1. The process of angularly bending a natural or artificial wood board, which consists in clamping the board on the opposite faces of its end portions and leaving the middle portion free for bending and gradually folding the end portions of the board to produce the bend, and simultaneously gradually advancing one of said end portions in relation to the other to compress the fiber structure of the board across the bend line thereby to crowd the fibers so as to fill the bend without bursting the board structure on the outer surface of the bend.

2. Apparatus for bending natural and artificial Wood boards, comprising essentially a bookwise folding pair of platens for bending said boards, a shoe plate slidably mounted on one of said platens, a cover clamp plate mounted on the other of said platens for clamping one end portion of a board on said last mentioned platen, a second cover clamp plate mounted on said shoe plate for clamping the other end portion of said board on said shoe plate, said second cover plate being secured to said shoe plate and movable therewith, and means for moving said shoe plate and second cover plate endwise relatively tothe platens.

CHARLES VICTOR HOWELL.

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