The invention concerns cutting and like machines, and has more particular, though not exclusive , reference to a cut-off machine for severing discrete lengths of laminated rigid foam board during the production of continuous lengths thereof.

A conventional method of producing rigid foam boards for insulating and building purposes as a continuous process comprises spraying the appropriate foam-forming chemicals onto a moving v/eb of paper, and, when such chemicals have risen to an appropriate thickness (usually from one half to' four inches), applying a top paper to the foam, the resultant laminate then being passed through a curing conveyor of a length determined by the necessary curing time of the foam in relation to the speed of advancement of the conveyor, for compression and curing of the foam. In a typical installation the ccnveyor will be between twenty and thirty feet long.

The laminate iss,ues from the curing conveyor as a continuous board, a typical board being one inch thick and four feet wide, and comprising a rigid urethane foam of density between one and one half and three pounds per cubic foot having a kraft or bitumen impregnated paper or rigid sheet, which may be metal, at each side thereof.

As the continuous board issues from the conveyor, it is necessary to cut the same into discrete lengths, cut-off machines for severing such discrete lengths being known in the art.

One conventional cut-off machine includes a carriage for clamping to the board for movement therewith in t e direction of advance of the conveyor or mounted for movement

in synchronism with the advance of the conveyor, a circular saw being supported on the carriage and being movable on the carriage transversely of the board to make a cut therein, upon completion of the cut, the carriage is released from the hoard or is returned to its initial position, so as to be readied for a further cutting operation.

Whilst such cut-o f -machines are effective in operation problems arise with higher linear speeds of production of the laminate, particularly when wider laminates are involved, having regard to the time taken to effect the cut and to return the carriage to its initial position to effect the next successive cut, such problems being most acute when it is required to produce short boards of significant width.

The object of the invention is to provide an alternativ method and means for cutting discrete lengths of board during the continuous production thereof which allows of effecting of a more rapid cut than is possible with conventional cut-off machines.

According to the present invention, there is proposed a method of severing a length from an advancing continuous sheet material which includes the steps of providing rotary cutting elements at each of the opposed faces of such material and in closely spaced disposition relative thereto, moving the cutting elements at the respective opposed faces successively into cutting engagement with the face of the material whilst moving such elements in the feed direction of the sheet material from a datum position and in synchronism with the advance of such material, disengaging the cutting elements from the material, and returning such elements to the said datum position, the dimensions and disposition of the

cutting elements and the respective paths of movement thereof

- in moving to and from a position of cutting engagement with the material being such as to provide a continuous line of cut through the full transverse extent of the material. The invention also includes a cut-off machine characterised by spaced first and second rotary cutter elements movable into and out of cutting engagement with respective opposed faces of a sheet material located between the said

' first and second such elements, the dimensions and relative / dispositions of the cutting elements'and the respective paths of movement thereof in moving to and from a position of cutting engagement with the material providing a continuous line of cut in such material.

The invention will now be described further, by way of example only, with reference to the accompanying diagrammatic drawings illustrating one embodiment thereof and in which:-

Figure 1 is a front elevation of the individual circular saws of a cut-off machine constructed in accordance with the invention, and shows the relative dispositions of such saws; and

Figure 2 is a side elevation of the cut-off machine as shown in- Figure 1.

Referring now to the drawings, a cut-off machine constructed in accordance with the invention comprises three circular saws 11, 12, 1 arranged one above and two below the laminate 1i, the saws being mounted for translational motion towards and away from the plane of the laminate 11+, and perpendicular thereto. The individual blades 11', 12 ¹ , 13' of the respective saws 11, 12, 13 lie in a common plane perpendicular to and transversely of the laminate, and the diameters of the respective blades and their relative " dispositions are such that collectively the blades extend continuously from edge to edge of the laminate.

As can best be seen in Figure 1, the peripheries of the respective blades lie in closely spaced disposition relative to the upper or lower surface, as appropriate, of the laminate, and the upper blade 11', is symmetrically disposed in relation to the spaced lower blades 12', 13'.

The saws 11, 12, 13 are supported in a common support frame 15 arranged in generally vertical disposition, such frame 15 being mounted in guides 16 on a carriage movable parallel to the direction of laminate feed and in synchronism with such feed, the frame 15 being movable in the said guides in a plane perpendicular to the plane of the laminate and extending transversely thereof.

A suitable displacement means, not shown, is provided to effect adjustment of the frame 15 towards and away from the plane of the laminate, and a drive means, likev/ise not shown, is provided -to move the carriage 17 in synchronism with the advance of laminate, such drive means being adapted to return the carriage to its datum position upon completion of the cutting operation. ^• In practising the method of the invention, and with the carriage 17 initially at its datum position, the carriage 17 is moved in synchronism with the laminate M and the frame 1 is caused to effect a reciprocatory motion in the guides 16 to bring the blades 11', 12', 13' at the opposite sides of the laminate into successive cutting engagement with such laminate. upward movement of the frame 15 will bring the lower blades 12', 13' into the position shown in dotted lines in the lower part of Figure 1, whilst a subsequent downward movement will bring the upper blades 11 ' into the position shown in dotted line in the upper part of Figure 1.

As will be appreciated, the disposition and diameters of the blades as shown, in relation to the width of the laminate, will sever the laminate throughout its full transverse extent subject to a sufficient engagement of the blades with the laminate during the translational motion of such blades.

On completion of the reciprocation of the frame, motion of the carriage in synchronism with the advance of the laminate is interrupted, and the carriage is returned to its initial position. In an alternative arrangement, not shown, instead of moving the fr?ne linearly upwards and downwards relative to the laminate, which linear motion can be derived from a piston and cylinder arrangement or from a crank and connecting rod operating on a frame supported in a guide formation, such frame can be caused to execute a rotary motion in the plane of the frame such that the axis of each blade moves in a circle of small radius and in so doing brings the peripheries of the respective blades into cutting engagement with the laminate. As will be appreciated, the rotary motion as aforesaid can readily be effected by mounting the frame on the carriage via two cranks, driven, and interconnected, cranks. One advantage of the use of the gyratory motion suggested is that the effective cutting width of each blade is increased, with the possibility of reducing the blade diameter or of providing for the use of a given cut-off machine for cutting a range of widths of laminate.

In the embodiment illustrated the individual saws 11, 12, 13 are independaHtly driven from respective motors, _ and although such independent drive is to be preferred, a common drive can be used for the various saws.

The invention is not limited to the use of three sav/s, or to three saws arranged in the disposition shown, since other numbers and dispositions may be preferred in some instances.

The invention is of particular value for cutting rigid urethane foai- laminates and particularly such laminates faced on both sides with metal sheeting.