GB2050913A

GB2050913A - Die-cutting machine

Info

Publication number: GB2050913A
Application number: GB8017386A
Authority: GB
Original assignee: Atom SpA
Current assignee: Atom SpA
Priority date: 1979-05-29
Filing date: 1980-05-28
Publication date: 1981-01-14
Also published as: ES491858A0; ES8102796A1; IT7921686V0; JPS55164497A

Abstract

A die-cutting machine 1, which may be used in footwear production, has a base 2 with a working surface 15 bearing a punch 18 and uprights 3 and 4 supporting a frame or bridge 5 on which runs a wheeled trolley 7 carrying a vertically movable pressing head 13 with a operative surface 14 which is centred over the punch by moving the trolley along the bridge. Trolley movement is effected by supplying hydraulic fluid to one or other single acting hydraulic cylinder 19 or 20 each containing a piston 21 or 22 with a piston rod 23 or 24 carrying a pulley 25 or 26 about which runs chain 27 or 28 attached at one end 27a or 28a to the base 2 and at the other end to the trolley after passing about high level guide pulley 33 or 34. <IMAGE>

Description

SPECIFICATION Die-cutting machine This invention concerns a die-cutting machine comprising a base from which rise two facing side uprights supporting a fixed frame or bridge having slides on which a trolley runs longitudinally, said trolley having an associated vertically movable head.

Such machines may be used in the production of foot wear.

At present, in bridge type die-cutting machines, the trolley supporting the head is either moved by drive from an electric motor or hydraulically. The trolleys operated by electric motor, or, more precisely, those driven by torque generator, have drawbacks, largely due to the trolley and head forming a heavy load. The continual starting and stopping of the trolley and high current required to move the trolley rapidly cause deterioration of relay contacts.

Also, since the motors normally used are selfbraking, during the trolley braking phase the kinetic energy of the trolley is entirely absorbed by the motor brake. This necessitates frequent maintenance and makes trolley positioning above a hollow punch on the machine less accurate. In fact, as the motor brake becomes worn, the trolley tends to run on excessively in the braking phase and the time between the instant braking starts and the instant the trolley comes to rest increases. As regards hydraulical ly-controlled trolloys, these are either moved by means of a hydraulic motor which rotates a threaded shaft engaged by a nut connected to the trolley moved to and fro by movement of the nut along the shaft, or by means of a cylinder arranged above a work level.The former type of hydraulic device has the drawback of requiring frequent maintenance caused by wear of the threaded shaftnut coupling. Also the trolley is only moved fairly slowly, so the times to carry out working operations are relatively long and detrimental to productivity and efficiency. The latter type of hydraulic device is very bulky, since its piston rod, which must emerge from the cylinder, requires, for the same trolley stroke, much more machine space than is occupied either by an electric motor or by other types of hydraulic device driving the trolley. Another problem with the known machine in which the trolley is moved by a hydraulic cylinder, is the loss of hydraulic fluid which can drip on the work level and spoil the material to be cut.Finally, there is the drawback, caused by the basic structure of a double acting hydraulic cylinder, of the reduced speed at which the piston rod re-enters the cylinder and pulls back the trolley after having pushed it forward at higher speed. An object of the invention is to eliminate or at least mitigate the abovementioned drawbacks by providing die-cutting machine which may be compact and is capable of being constructed so that the trolley can be moved faster, but a more reliable operation may be achieved.

According to the invention there is provided a die-cutting machine comprising a base, two facing side uprights rising from the base, said uprights supporting a fixed frame or bridge having slides on which a trolley runs longitudinally, a vertically movable head associated with the trolley, a substantially vertically arranged hydraulic cylinder corresponding to each upright, a respective piston arranged to slide in each cylinder, each piston having a piston rod carrying at its free end a pulley having a respective chain or cable extending around the pulley, one end of each chain or cable being attached to a fixed part of the machine and the other end of each chain or cable being attached to the trolley, and each chain or cable being provided with a respective transmission pulley located at substan tiallythe same level as an upper part of a said upright.

These hydraulic cylinders can be supplied with working fluid by a hydraulic pump controlled by an electric circuit operated by manual starting means, said cylinders being interconnected by a duct having constriction means to balance the pressures in the hydraulic cylinders.

A main advantage of the machine is the relatively high trolley movement speed, which makes it possible to move the trolley from the location to another quickly and thus reduce the time between cuts. This higher trolley speed is due to the pulley system which makes it possible to obtain a trolley movement of twice the distance moved by a said piston rod. Another advantage, deriving from using this technique to increase trolley speed, is the possibility of reducing the capacity of the pump. This capacity reduction also means that one can rely on having less noisy, safer pumps, since they undergo less stress.It should also be noted that the presence of the constriction means in the duct which interconnects the hydraulic cylinders makes it possible, by balancing the pressures in the respective cylinders, to carry out transitory trolley acceleration and braking phases in which knocking or shaking of the trolley is avoided or at least mitigated.

The invention will now be further described, by way of example, with reference to the accompanying drawings in which: Figure 1 is a fragmentary perspective view of a bridge type die-cutting machine formed according to the invention; Figure 2 is an enlarged view from the front and partially cut away, of the machine in Figure 1; Figure 3 is a side view, partly cut away of the machine in Figure 2, and Figure 4 is a schematic diagram of a hydraulic connection between hydraulic cylinders in the machine in Figures 1 to 3.

In thd drawings, there is indicated at 1 a bridge type die-cutting machine to cut sheet material, for example leather for footwear production. The diecutting machine 1 has a base 2, from which two facing side uprights 3 and 4 rise, supporting a fixed bridge or frame 5.

Slides 6 (Figure 2) are provided on the fixed frame 5. The slides 6 are engaged by a trolley 7 having at least two pairs of wheels 10 and 11 which can rotate freely about axles 8 and 9. These wheels run on the slides 6 permitting the trolley to move back and forth along the slides.

A hydraulic cylinder unit 12 is located inside the trolley 7. This unit has a piston rod mounted on a head 13 carrying a striking surface 14. The head 13, which is suspended above work level 15 on the base, can thus move vertically towards and away from the work level. Also in Figure 2, two bar type inductive surface switches 16 and 17 are provided on the sides of the head 13. Automatic centering of the head 13 on a hollow punch 18, previously arranged on the work level 15, is carried out by means of the inductive surface switches 16 and 17 which are arranged in line with the striking surface 14.

The trolley 7 is moved along the slides 6 by a device comprising vertically arranged hydraulic cylinders 19 and 20 each corresponding to a respective upright 3 and 4. Each of these cylinders contains a sliding piston 21 or 22 having a corresponding piston rod 23 or 24 carrying a pulley 25 or 26 at its free end. As shown in Figures 2 and 3, the hydraulic cylinders 19 and 20 are preferably incorporated in the respective uprights 3 and 4.

The pulleys 24 and 25 have circumferential grooves around which respective chains or cables 27 and 28 pass. Each chain or cable 27 or 28 is attached at one end 27a or 28a to a fixed part of the machine, for example a base of the upright 3 or 4, and is attached at its opposite end 27b or 28b to a side wall of the trolley 7. The chains 27 and 28 are provided with transmission pulleys 33 and 34 arranged level with the upper part of the uprights 3 and 4 respectively.

With reference to Figure 4, the hydraulic cylinders 19 and 20, which are single acting, are interconnected by a duct 29 having constriction 30. The function of the constriction 30 is to balance pressures inside the hydraulic cylinders 19 and 20 so that when the trolley 7 is in the acceleration or braking phase the entire structure is not shaken. The hydraulic cylinder and piston units 19,21 and 20,22 are operated by a hydraulic pump (not shown) which is controlled by an electric circuit (not shown) operated by manual starting means, preferably two sensitive spaced plates 31 and 32 (Figure 1), at the front of the machine.

Further details on the sensitive plates 31 and 32 and the electric circuit operated thereby and how the head 13 is automatically centred on the hollow punch 18, are set forth in our co-pending application number 11776.

The trolley 7 can be moved along the slides 6 by filling the cylinder 19 with working fluid, thus forcing the piston 19 downwards. There is a corresponding downward movement of the pulley 25. It will be understood that when the pulley 25 is lowered a certain distance, then due to the chain or cable 27 the trolley moves horizontally through twice that distance. While the hydraulic cylinder 19 is being filled with working fluid, working fluid is discharged from the hydraulic cylinder 20 due to the piston 22 being raised by the movement of the trolley 7 under the influence of the downwardly moving piston 21.

When the piston 21 has reached its minimum level, the trolley 7 is near the upright 3, while the piston 22 is at its maximum level inside the cylinder 20. At this point, the cylinder 20 is filled with fresh working fluid, leading to lowering of the piston 22 and the consequent movement of the trolley 7 towards the upright 4.

When the die-cutting machine is operated, the trolley 7 can be stopped in intermediate positions and moved back without having to carry out the entire backward and forward stroke from the upright 3 to the upright 4.

Claims

1. A die-cutting machine comprising a base, two facing side uprights rising from the base, said uprights supporting a fixed frame or bridge having slides on which a trolley runs longitudinally, a vertically movable head associated with the trolley, a substantially vertically arranged hydraulic cylinder corresponding to each upright, a respective piston arranged to slide in each cylinder, each piston having a piston rod carrying at its free end a pulley having a respective chain or cable extending around the pulley, one end of each chain or cable being attached to a fixed part of the machine and the other end of each chain or cable being attached to the trolley, and each chain or cable being provided with a respective transmission pulley located atsubstantially the same level as an upper part of a said upright.

2. A die-cutting machine as claimed in claim 1 in which the hydraulic cylinders are incorporated in the respective uprights.

3. A die-cutting machine as claimed in claim 1 or claim 2, in which said hydraulic cylinders are supplied with working fluid by means of a hydraulic pump controlled by an electric circuit operated by manual starting means, and said cylinders are interconnected by a duct having constriction means to balance pressures in the hydraulic cylinders.

4. A die-cutting machine substantially as hereinbefore described with reference to the accompanying drawings.