Abstract:
Automatic hollow punch search device and relevant control, for die-cutting machines, particularly for footwear production, in which a mobile head is associated to means to move it to and fro, both horizontally and vertically, above a fixed faceplate on which the material to be cut is placed, together with a hollow cutting punch. The movement means are automatically piloted by a drive circuit interlocked to manual starting means which provides means to carry out a complete head movement operating sequence from its positioning above the hollow punch to its lowering and return to the starting point after cutting.

Description:
INTRODUCTION 
     This invention refers to an automatic hollow punch device and relevant control, for die-cutting machines, particularly for footwear production, in which a mobile head is associated with means to move it vertically and horizontally to and fro, above a fixed faceplate on which the material to be cut is placed, a hollow cutting punch being laid above this material, to be pushed down, in the cutting phase, by said mobile head. 
     The device of this invention is suitable both for flag type and bridge type die-cutting machines with mobile heads to cut material in any size sheet. 
     BACKGROUND OF THE INVENTION 
     In die-cutting machines presently in use, after the hollow punch is laid above the material to be cut, the mobile lead is hand-positioned above said hollow punch, and the command is then given to lower the head for cutting. To facilitate the operator&#39;s task, in some die-cutting machines at present in use, the horizontal head movement is motorized, by push-button or similar means. Once again, however, head positioning above the hollow punch must be directly operator-controlled, as the operator intervenes and stops this head moving horizontally when it has reached the desired position. This operator then commands head lowering for cutting and then its lifting to carry out a successive operating cycle. 
     As can be seen, therefore, the die-cutting machines of known type require continuous operator attention, making this type of work particularly tiring. Also, head centering on the hollow punch is entrusted to the operator&#39;s experience and keen eye, which does not always lead to completely satisfactory results and, at any rate, involves the assistance of particularly expert operators. 
     BRIEF SUMMARY OF THE INVENTION 
     The main purpose of this invention is to eliminate the abovementioned drawbacks found in presently used systems, constructing an automatic hollow punch search device and relevant control, for a die-cutting machine, which insures accurate working without the need for continuous operator assistance, the operator having only to arrange the hollow punches above the material to be cut and give the starting command. In this way, the die-cutting machine may be operated by non-specialized operators, which obviously yields a considerable reduction in production costs. 
     Another important purpose of this invention is to construct an automatic device for die-cutting machines, operating safely and accurately, to guarantee regular cutting even while working time is reduced to a minimum. 
     These and further purposes, which may appear clear from the following description, are achieved by the automatic hollow punch research device and relevant control, for die-cutting machines, according to the invention, where a mobile head is associated with means to move it horizontally and vertically to and fro, above a fixed faceplate on which the material to be cut is laid, the hollow cutting punch resting above this material, to be pushed down, in the cutting phase, by said mobile head. This control device is characterized by the fact that said movement means are piloted automatically by a drive circuit interlocked to the manual starting means, this drive circuit providing means to produce a complete head movement operating sequence, from its position above the hollow punch to lowering and subsequent return to the starting point after cutting. Said circuit comprises a sensitive element assembled on said head for automatic searching for the position of said hollow cutting punch laid on the material to be cut, and then stops the horizontal head movement automatically, when, in the initial phase of said operating sequence, it comes to rest above said hollow punch, in cutting position. 
     According to a further feature of this invention, the abovementioned sensitive element is composed of an inductive surface switch, prearranged on one side of said head and cooperating with said hollow punch to stop horizontal head movement automatically and to subsequently lower the head, after said inductive surface switch has passed over said hollow punch. 
     In order to always have the head centered on different sizes of hollow punches, according to a further invention feature, said drive circuit comprises an adjustable timer element connected to said inductive surface switch to delay stopping of the horizontal head movement and its subsequent downstroke, when said hollow punch laid on the material to be cut is relatively small. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Further features of this invention will be seen in the detailed description of a preferred but non-exclusive embodiment of an automatic hollow punch search device and relevant control, for die-cutting flag type machines, illustrated purely by way of example and not by way of limitation in the attached drawing, in which: 
     FIG. 1 is a perspective view of said die-cutting machine provided with the device of the invention; 
     FIG. 2 is a partial cutaway side view of the same die-cutting machine; 
     FIG. 3 is a horizontal cross section of the machine head movement unit; 
     FIG. 4 is a schematic diagram of the electronic control circuit. 
    
    
     DETAILED DESCRIPTION 
     In these figures, number 1 indicates a flag type die-cutting machine, provided with the automatic search device described in the invention. 
     The same device can also be applied to any other type of die-cutting machine, e.g. the bridge type with mobile head. 
     As shown in detail in FIGS. 1 and 2, the die-cutting machine in the example includes a base 2, the top of which constitutes a fixed horizontal faceplate 3, above which a flag-assembled mobile head 4 is prearranged, corresponding an upright 5 having a vertical axis. 
     At the foot of the head 4 is a horizontal plate, parallel to faceplate 3 and suitable, in cutting position, to push down a hollow steel cutting punch 6, laid on the sheet material 7 to be cut (FIG. 7), this material 7 being in turn arranged on the faceplate 3. 
     The head 4 may be horizontally and vertically moved to and fro, i.e. vertically, with lifting and lowering movements along the axis of the vertical upright 5, obtained by known control means (not shown), e.g. fluid dynamics. Horizontally, the head 4 may be angularly moved around the axis of the upright 5 by means of the mechanism shown in FIG. 3. This mechanism comprises a gear wheel 8 mounted on a vertical axis, keyed on vertical column 5, sliding axially within the upright 5 and supporting the head 4. A rack 9 is engaged with the gear wheel 8, mounted in a piston 10 on a horizontal axis, and sliding in a respective horizontal hydraulic cylinder 11. This cylinder defines, from one side of piston 10 and the other, two chambers 11a and 11b, connected alternatively to a pressurized oil feed and drain, not shown, to angularly move the head 4 via the rack 9 and gear wheel 8. 
     Naturally, an equivalent mechanism may be provided in place of that shown in FIG. 3, composed, for example, of an electric motor and a suitable linkage, or the like. 
     It is also anticipated that, in rest conditions, the head 4 can be in a side position, e.g. to the right in the figures, as shown by the solid and dashed lines in FIG. 2. In this position, the head 4 is also lifted a certain height (adjustable) from the faceplate 3. 
     In the operating cycle, the head 4 rotates clockwise around the axis of column 5 in continuous sequence, starting from the abovementioned rest position, until said head is above the hollow punch 6, after which the horizontal head movement stops and head 4 lowering starts for cutting. The head is then relifted on wheels, in the counter-clockwise direction, to reach its initial position and stop. This operational sequence is automatic and operator assistance is only required to start the cycle, as explained below. 
     Starting control of the operating cycle is carried out by the operator placing both hands on two sensitive control plates 12 and 13 provided, with a certain space between them, in the front part of the machine near the faceplate 3 (FIG. 1). This operation, for which the operator must use both hands for safety reasons, activates the drive circuit illustrated in FIG. 4. 
     Means are provided to automatically search for the hollow punch 6 and to stop horizontal movement of the head 4 thereat. To this end and an inductive bar surface switch 14 often called simply &#34;bar&#34; herein is provided, prearranged near the side edge of the head 4. The bar 14 is located on the lower surface of the plate 4a to detect the presence of the hollow metal punch 6, when it passes above it, later emitting a signal which is handled by the circuit in FIG. 4. This signal persists for the entire length of time in which the bar 14 remains superimposed on hollow punch 6 and stops when said bar passes over the hollow punch. 
     While the abovementioned signal is being emitted by the bar 14, two condensors 15 and 16 (FIG. 4) are simultaneously charged. The discharge time of the condensor 15 is determined by the features of said condensor, while the discharge time of the condensor 16 may be adjusted and extended as desired by means of a &#34;trimer&#34; timer 17. 
     When a relatively large hollow punch is placed on the work level, the signal emitted by the bar switch 14 is extended while the head moves horizontally, since a fairly long amount of time is required for the bar to pass over the relatively large hollow punch; when the signal stops, i.e. when the bar has pass over the hollow punch, the condensor 15 discharges and the power transistor 19 is made conductive, through transistor 18. This causes consequent pickup, and locking in by means of a contact 25, of the relay 20 which also operates the contacts 20a and 20b. In practice, the relay 20 is operated at the same amount at which the bar 14 passes the hollow punch. The normally closed contact 20a then opens (shown in FIG. 4), in which there is pickup of the solenoid valve 21, to make the head 4 rotate in the clockwise direction (operated by the mechanism in FIG. 3) to the opening position where the solenoid valve 21 pickup stops and the head 4 consequently stops rotating. 
     Since in the case considered a large hollow punch has been used (i.e. slightly narrower than the plate 4a), the head is suitably stopped when it is centred above the hollow punch. 
     When the contact 20a is opened, the normally open contact 20b is simultaneously closed, causing pickup of the solenoid valve 22 which controls head 4 lowering for cutting. At the end of this phase, an end of stroke switch (not illustrated) controls the return of the head to the lifted position and its subsequent counter-clockwise rotation until it comes to rest in the initial position (moved to the right). 
     The machine is thus preset to carry out a successive operating cycle which will start, similarly to what has been seen, as soon as the operator again places both hands on the two sensitive plates 12 and 13. 
     In the case of small or narrow hollow punches, the signal determined by the bar 14, while the head is moved horizontally, if brief, and therefore, in the absence of the condensor 16 and the &#34;trimer&#34; 17, the condensor would be discharged too soon, as the head 4 would be stopped and would descend as soon as the bar 14 has passed the hollow punch. Since, in the case in question, this is narrow, the head 4 would then be stopped in an off-center position to said hollow punch, thus making regular cutting impossible due to eccentric stress, which would determine an unfavourable head inclination. 
     With the presence of the condensor 16 and the &#34;trimer&#34; timer 17, this problem is overcome, by suitably delaying stopping of the clockwise movement of the head 4. In fact, while the condensor 15 is discharged immediately after the bar 14 has passed the hollow punch, the condensor 16 remains charged for a certain time, depending on adjustment of the &#34;trimer&#34; 17, so that clockwise head rotation may continue. By suitably adjusting the &#34;trimer&#34; timer 17, in relation to the hollow punch size, the condensor 16 will be discharged when the head is centered above the hollow punch. During discharge, similarly to the above, the relay 20 will intervene to stop clockwise head rotation and down stroke for cutting. Immediately after cutting, as seen above, the head will be lifted and moved in the counter-clockwise direction until it reaches the rest position. The die-cutting machine is therefore ready for a successive operating cycle. 
     From the above the operation of the control device in the invention appears evident. 
     The operator has only to deposit the hollow punch chosen above the material 7 to be cut, prearranged on the faceplate 3, after which he can start the operating cycle by simply placing both hands on the sensitive plates 12 and 13. As seen above, the operating cycle is fully automatic and requires no operator attention. In fact, the head 4 is moved first in clockwise direction, searching for the hollow punch automatically and stopping when it is centered above said hollow punch, independently of the size of the latter. Immediately afterwards, cutting is carried out, as the head is lowered and then lifted and returned towards its initial position, also automatically. When the head is in the side rest position, the operator can conveniently adjust the faceplate 3. 
     It should be noted that, when the operator raises his hands from the sensitive control plates 12 and 13, the machine stops automatically in its exact position at that moment. If the operator then replaces his hands on said plates, he will start the head 4 moving in the opposite direction, so that, when dealing with small hollow punches, the operator may also avoid the head making an entire forward and backward stroke, with a consequent reduction in operating time. 
     As is now evident, the device of the present invention insures almost complete automation of the cutting cycle, at least centering of the head above various sizes of hollow punches, considerably lightening the operator&#39;s task and guaranteeing top quality work products, even with non-specialized staff. Naturally, the invention is not limited to the type of structure described, but numerous modifications are possible within the invention. 
     For example, in the case of application to bridge type die-cutting machines, with a mobile trolley, it can be equipped on two opposite sides with two inductive bar switches, so that it can operate the hollow punch search automatically both in translation direction and the opposite direction.