GB2074076A - Power operated guillotine - Google Patents

Abstract

A guillotine is provided with a back gauging stop 40 adjustable towards and away from the lower guillotine blade 14 and a rear support table 10 which is vertically adjustable. Prior to or during the shearing operation, the table 10 is lowered under the control of hydraulic rams 20, 28 in order to minimise distortion of the cut edge during shearing. Upon completion of the shearing operation, the support table 10 can either be tilted about pivots 16 to allow the cut sheet to slide to a stacking station or the table 10 may be returned to an upper position in which its edge immediately adjacent the guillotine is slightly above the level of the top edge of the blade 14. In this mode of operation, the back gauging stop 40 is used to transfer the cut sheet back to the front side of the guillotine for reorientation by the operator so as to enable a second cut to be made. <IMAGE>

Description

SPECIFICATION Power operated guillotine This invention relates to a power operated guil lotineforshear-cutting sheet materials, especially metal sheets such as mild steel and non-ferrous metals.

Known guillotines for shear cutting metal sheets comprise a pair of cutting blades one of which is fixed and the other of which is movable to effect the shearing operation in conjunction with the fixed blade. To facilitate cutting of sections of a selected length from a sheet, a so-called back gauge is located rearwardly of the cutting blades and is adjustable by means of a lead screw driven towards and away from the vertically disposed plane of shear cutting. In use, the back gauge is set to a selected position of adjustment such that the spacing between the cutting plane of the blades and the back gauge corresponds to the length of section to be cut off from a sheet. The sheet is then fed between the blades until its leading edge abuts the back gauge whereupon the blades are operated, e.g. by means of a foot operable control unit, to effect the shearing operation.Prior to or during the shearing operation, to minimise distortion at the cut edge, the support area supporting the sheet at the rear side of the guillotine is lowered and, if necessary, the area of the sheet at the front side of the guillotine is clamped.

The cut sheet is then collected on the lowered rear support area from which it is transferred to a stacking station. Thereafter the rear support area returns to its initial raised position.

Hitherto, where the cutoff sections are to be subjected to a further shearing operation, it has been necessary to collect each cut off section from the area to the rear of the blades and transport it either manually or by mechanical handling equipment back to the front for the next shearing operation.

Where a number of sections are to be produced to given dimensions by successive shear cutting operations, the cut off sections are usually accumulated after each has been subjected to the first shearing operation and then the stack of cut off sections is transferred from the rear to the front of the guillotine to enable the second shearing operation to be carried out on each section.

One attempt at simplifying the problem of transferring the cut sheet sections back to the operator's side of the guillotine is disclosed in British Patent No.

1438593. The solution proposed in this patent involves constructing the rear support area as an endless belt conveyor with a reversible drive so that the conveyor may be used both to convey the sheet material towards the back stop gauge assembly and to return cut sheet sections between the guillotine blades and hence back to the operator. Although such an arrangement facilitates return of the cut sheets considerably, it suffers from the drawbacks of being expensive to manufacture by virtue of the need for a reversible drive conveyor and complex electrical control circuitry.

The object of the present invention is to provide an improved power operated guillotine for shear cutting sheet material in which transfer of the cut off sections from the rearto the front of the guillotine for subsequent shearing operations is simplified and can be effected immediately without the need for expensive mechanical handling equipmentorthe risk of damage to the material.

According to the present invention we provide a power operated guillotine for shear cutting sheet material comprising shearing means operable to effect cutting of a sheet, support means located rearwardly of the shearing means for supporting the sheet material on that side of the shearing means and adjustable back gauge means located rearwardly of the shearing means to provide abutment means for cooperation with the leading edge of a sheet supported on said support means, characterised in that said support means is vertically movable between a lower collecting position for receiving a cross section of sheet material and an upper delivery position wherein a sheet supported thereon is presented towards the gap between and is clear of shearing means and in that the back gauge means is operable to return a sheet supported by the support means back through said gap while the support means is in said upper delivery position.

In this manner, the cut off section is made immediately available for the next cutting operation and because it is clear of the shearing means during transfer back through the gap, there is no risk of damage to the section as its passes over the lower blade of the shearing means. Thus, in contrast with the known forms of metal sheet cutting guillotines where the back gauge functions purely as a limiting stop, in the guillotine according to the present invention the back gauge is instrumental in transferring the cut off sections back to the operator. This, it will be noted, avoids the need for expensive conveying equipment such as that shown in British Patent No.

1438593.

In practice, a front support area will also be provided and the rear support area, in addition to the positions previously mentioned, may be movable also into an intermediate position in which it provides continuation of the front support area so that prior to the shearing operation, the sheet is supported by the front and rear support areas. Clamping means, for example, in the form of fluid powered jacks are conveniently located forwardly of the blades above the front support area to clamp the sheet firmly against the front support area. Thus, when the clamping means becomes operative the rear support area can be lowered to the collecting position leaving the leading section of the sheet extending in overhanging fashion above the rear support area.

Other features and advantages of the present invention will become apparent from the following description given with reference to the accompanying drawings, which illustrate diagrammatically a preferred form of guillotine in accordance with the present invention. In the drawings: Figure 1 is a side view showing the rear support table of the guillotine occupying the sheet supporting position and with the back stop gauge set to define predetermined width of cut; Figure 2 is a similarviewto Figure 1 but showing the reartable in its collecting position after cutting of the sheet has taken place; Figure 3 is a side view showing the support table tilted in order to allow the cut sheet section to slide into a stacking station;; Figure 4 is a side view illustrating the use of the rear support table and the back stop gauge to return a cut sheet section back to the front side of the guillotine; and Figure 5 is a side view showing use of the rear support table in rejection of scrap material.

The present invention is applicable to various known guillotines for cutting metal and other material such as plastics but will be described herein with reference to its application to the form of metal shearing guillotine which is currently available under the trade name SCIMITAR from Joseph Rhodes Manufacturing Limited of Wakefield, England. As this machine is commercially available, its construction and operation is already known and detailed description is unnecessary here. The machine comprises a fixed lower shearing blade with a straight generally horizontal cutting edge and 2 vertically movable upper shearing blade the cutting edge of which is arcuate. The vertical movement of the upper blade is effected in such a way that shearing occurs with a rolling action with only limited portions of the blades overlapped at any given time.

Referring now to the accompanying drawings, the sheet supporting assembly comprises a reartable 10 which may have a substantially plain top surface or may be provided wiih a series of idler rollers 12 to facilitate sliding of metal sheets and the like on the table top. The table 10 is located immediate adjacent the rear side of the lower fixed blade 14 of for example a SCIMITAR guillotine, the upper moving blade of which is not illustrated. A further supporting table (not shown) will normally be located in front of the guillotine and the top surface of the front and rear tables will normally be co-planar with the top edge of the lower blade 14 when the sheet material is being loaded and located in preparation for shearing.

At the end adjacent the guillotine, the rear table 10 is pivotally connected at 16 to a pair of vertically extending columns 18 located one at each lateral side of table 10. Adjacent its opposite end, the table 10 is pivotally connected at 21 to one or more double acting fluid operated rams 20 the cylinders of which are pivoted at 22 to a fixed anchorage 23. The rams 22 are operable to tilt the table 10 about the pivot 16 and to control lowering of the table 10, as explained hereinafter.

Each column 18 is generally channel-shaped and within each column 18 there is a pair of double acting fluid powered rams 26, 28 arranged in rigid endto-end relation with their piston rods 27,29 extend ing in opposite directions. The rods 27 and 29 engage respective fixed anchorages 30,31 and each column 18 is pivoted at 24 to a lateral arm 32 secured to the ram cylinder 28. Tilting of each column 18 about pivot 24 is controlled by a double acting fluid powered ram 34 whose cylinder is pivotally con nected at 35 to lugs 36 secured to the column 18 and whose piston rod extends into the interior of the column 18 and is pivotally connected to the assembly of the rams 26, 28.

Above the table 10, there is provided a back stop gauge assembly comprising a stop assembly 40 mounted on a pair of parallel lead screws 42 which are driven by a motor through suitable gearing so as to move the stop 40 towards and away from the gauge for the purpose of gauging the size of cut to be made. The stop 40 may comprise a number of transversely aligned, generally vertically extending plates movable along suitable openings in the top surface of the table 10.

In use,wfth the rear table located in the position shown in Figure 1, the back stop 40 is set to a predetermined position relative to the guillotine according to the size of the cut to be made. The sheet 44 to be cut is then loaded onto the front table and pushed through the gap between the guillotine blades until the leading edge of the sheet engages the back stop 40. At this stage, the sheet is supported by the front and rear tables. Next clamps (not shown) are operated to clamp the sheet to the front table, the stop 40 is retracted slightly (see Figure 2) and the cutting operation is initiated. Eitherpriorto, or during, the cutting operation, the rear table 10 is lowered to the position shown in Figure 2 under the control of the rams 20 and 26 whose piston rods are respectively extended and retracted.

The next step in the sequence depends upon whether the sheet section just cut is to be stacked or whether it is to be subjected to a second cutting operation before being stacked. If the cut sheet section is to be stacked, the ram 20 is operated again so as to retract its piston rod further and tilt the table about the pivot 16 thereby allowing the cut sheet to slide down the inclination into a stacking station as shown in Figure 3. On the other hand, if the sheet is to be cut back again before stacking, it must be transferred back to the operator on the front side of the guillotine.

In accordance with the present invention transfer of the cut sheet back to the front side is effected by means of the back stop 40 in conjunction with the table 10. When the machine is required to operate in this mode, the operator removes the sheet section supported by the front table and then operates a switch or the like causing the table 10 to rise again under the control of rams 20 and 26 until it returns to the position of Figure 1 whereupon the ram 28 is operated to raise that end of the table even further until, as shown in Figure 4, it projects slightly above the top edge of the blade 14 by typically approximately 3 mm. The stop 40 is now advanced towards the guillotine so that the cut sheet is returned to the front table via the gap between the guillotine blades.

Such return movement of the stop may be manually controlled by maintaining a switch operated until the desired amount of sheet has been fed back. Alternatively return movement may be a predetermined fixed amount which can be related to the width of the last cut made. The ram 28 is next retracted to bring the table 10 back to the horizontal position shown in Figure 1 and the stop 40 is reset (either under manual control or automatically) in preparation for the next size of cut to be made. Although as shown in the drawings, the table 10 is raised in order to lift the trailing edge of the sheet above the lower blade 14, in an alternative arrangement, means separate from the table 10 may be located rearwardly of the blade 14 in order to lift the trailing edge slightly over the blade 14 during return movement of the stop gauge.

In some circumstances, it is necessary to trim a certain amount of scrap from the sheet before cutting proper is effected and dispose of the scrap. This is achieved by means of the ram 40 in conjunction with ram 20 which are operated to tilt the columns 18 about their pivots so as to displace the table 10 rearwardly as shown in Figure 5 thereby creating a gap through which the cropped scrap 44a may fall for deflection by a deflector plate 48 into a scrap bin 50 which is not illustrated in other figures. The machine is described above may be pre-programmed so as to operate in any one of a number of selected modes, including those described above, so that the operator may select the desired programme before starting. Also, the back stop gauge may be preprogrammed with the settings it is required to occupy at different points in an operating sequence.

For example where two cuts are required before the sheet section is discharged to the stacking station the operator may select a mode in which the cut sheet is automatically returned by the back stop following completion of the first cut and the positions to which the back stop is moved for the first and second cuts may be preset.

Positioning of the back stop gauge is preferably controlled by means of a suitable encoder (not shown) so that a precise measurement of the position of the stop relative to the guillotine is available within the accuracy limits obtainable from the encoder. Thus, for example, the position measuring encoder may be in the form of a shaft encoder for sensing rotation of one or each of the lead screws employed to effect back stop adjustment. In this way, when a given position is keyed into the preprogrammable control unit by the operator, the con troi unit is effective to displace the stop through the agency of the lead screws until the encoder provides a reading corresponding, within the accuracy limits of the encoder and lead screw drive, to the desired position.

As described above, the back stop gauge in the present invention is employed not only to limit displacement of the sheet through the guillotine but also, in the appropriate mode of operation, to return the cut sheet back to the operator to enable a second cut to be made. This arrangement of the back stop gauge together with the use of an encoder to achieve precise positioning allows the machine to be used with advantage in cutting sheets of material provided with rows of pre-printed areas, e.g. in the production of plastic credit cards. Such cards are printed in rows and columns on a large sheet of plastic which must then be cut up to produce the individual cards.The conventional method of cutting up sheets by a power operated guillotine entails setting the back stop gauge according to a nominal width of each printed area and advancing the sheet until its leading edge abuts the back stop gauge, effecting shearing to remove the leading row of pre-printed areas, advancing the sheet again to abut with the back stop gauge and repeating the procedure. This suffers from the drawback that if the back stop gauge setting is not precise, the error will be compounded with each cut made and eventually, instead of being located between adjacent rows of pre-printed areas, the cut may encroach on the printed areas and thereby result in rejection of these rows. Periodic re-setting of the back gauge may therefore be necessary to correct for encroachment of the cut onto the preprinted areas.

According to a preferred aspect of the invention, cutting of sheets bearing pre-printed areas of uniform dimensions arranged in rows is effected by initially setting the back stop gauge at a position corresponding to the full width of the sheet less the row width, cutting off the first row at the trailing edge (with accompanying lowering of the table either prior to or during cutting as previously described), advancing the back stop gauge and hence the sheet towards the guillotine until the gauge reaches a position corresponding to the width of the sheet less twice the row width, cutting off the second row at the trailing edge of the sheet and so on, each time advancing the gauge (and hence the sheet) to a position corresponding to the sheet width less the appropriate multiple of row widths. In this manner, positioning of the sheet is effected by means of the back stop gauge (with the table located in said position previously described) and any compounding of the error in the gauge setting is eliminated thereby avoiding the need to correct for any mis-registration due to such compounding.

Claims (10)

1. A powered operated guillotine for shear cutting sheet material, comprising shearing means operable to effect cutting of a sheet, support means located rearwardly of the shearing means for supporting the sheet material on that side of the shearing means and adjustable back gauge means located rearwardly of the shearing means to provide abutment means for cooperation with the leading edge of the sheet supported on support means, characterised in that said support means is vertically movable between a lower collecting position for receiving a cut off section of sheet material and an upper delivery position wherein a sheet supported thereon is presented towards the gap between and is clear of the shearing means, and in that the back gauge means is operable to return a sheet supported by the support means back through said gap while the support means is in said upper delivery position.

2. A guillotine as claimed in Claim 1 characterised in that the back gauge means is operable under manual control as it returns the sheet through said gap to the front of the shearing means whereby the operator can determined the extent to which the sheet is returned.

3. A guillotine as claimed in Claim 2 characterised in that, in response to terminatation of said manual control, back gauge means automatically moves to a pre-set position corresponding to the next length to be cut.

4. A guillotine as claimed in Claim 1 characterised in that the back gauge means is operable to turn the sheet through the gap by a predetermined amount (which may be related to the length cut) and thereafter move automatically to a preset position corresponding to the next length to be cut.

5. A guillotine as claimed in any one of Claims 1 to 4 characterised in that the support means is movable into an intermediate position in which it forms a continuation of a support area located at the front of the shearing means and in that clamping means is provided to clamp a sheet against said front support area to enable the rear support means to be lowered to said collecting position.

6. A guillotine as claimed in any one of Claims 1 to 5 characterised in that the rear support means is tiltable selectively to enable a cut sheet supported thereby to slide into a stacking area and/orthe rear support means is operable selectively to move away from the shearing means to create a discharge opening through which scrap lengths cut from a sheet can be discharged.

7. A guillotine as claimed in Claim 1 characterised in that the rear support means comprises a support table with means for raising at least the end thereof adjacent the shearing means above the level of the lower blade of the shearing means.

8. A guillotine as claimed in Claim 1 characterised in that said supporting means comprises a support table and means operable to raise the trailing edge of a cut sheet above the level of the lower blade of said shearing means.

9. A guillotine as claimed in any one of claims 1 to 8 characterised in that setting of the back gauge means is controlled by position sensing means and in that, in one mode of operation of the guillotine, the back gauge means is controlled so as to move, in response to each operation of the shearing means, from an initial rearwardly located position towards the guillotine through a plurality of intermediate positions at each of which the shearing means is operated, each such position being measured from the same reference point so as to avoid any accumulative error in positioning of the back gauge means.

10. A method of operating a guillotine as claimed in any one of claims 1 to 9 characterised by locating the back gauge means in a pre-selected position, placing a sheet to be cut on said support means so that the leading edge of the sheet abuts the gauge means, operating the shearing means to cut the sheet, lowering said sheets support means prior to and/or during operation of the shearing means so that the cut sheet is supported by the rear support means in its lower collecting position, moving the rear support means to its upper delivery position and operating the back gauge means to return the cut sheet back to the front side of the shearing means.