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(11) | EP 0 345 489 A2 |
| (12) | EUROPEAN PATENT APPLICATION |
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| (54) | Improvements in machines for producing expanded sheet metal |
| (57) The expanded sheet metal production machine comprises a toothed blade mobile in two
mutually orthogonal directions and cooperating with a backing blade which can retract
against the action of elastic means during the active movement of the toothed blade.
The improvements consist in the provision of a device for feeding the sheet metal
in such a manner as to obtain: a required distance between the holes in the sheet
metal, stretching limited to intermediate zones of a metal sheet, which therefore
has front and rear end portions free of stretch, and expanded metal sheets starting
from strip. |
[0001] This invention relates to improvements in expanded sheet metal production machines of the type comprising a surface along which the non-stretched sheet metal slides, a toothed blade mobile in two mutually orthogonal directions, one of which is away from and towards the sheet metal, and a backing blade which can retract against the action of elastic means during the active movement of the toothed blade.
[0002] Machines of this type are known, for example from Italian patent No. 896,425 and from the corresponding extensions in the United States (No. 3,667,055) and in the German Federal Republic (No. 2,109,216).
[0003] These known machines have certain limitations such that they are unable to produce metal sheets in which the front and rear end portions are free of stretch and the stretch is limited to an intermediate zone of the sheet, they are unable to accurately feed the sheet metal, and they are unable to cut expanded metal sheets to a required length starting from a strip unwinding from a roll. The main object of the present invention is therefore to provide improvements which enable machines of the indicated type to obtain the said results.
[0004] This and further objects which will be apparent from the detailed description given hereinafter are attained according to the invention by improvements characterised essentially in that with the slide surface for the sheet metal there is associated a pneumatic device for feeding the sheet metal along said surface. The invention will be more apparent from the detailed description of a preferred embodiment thereof given hereinafter by way of non-limiting example and illustrated on the accompanying drawing in which:
Figure 1 is a diagrammatic longitudinal section through a machine of the indicated type incorporating the pneumatic sheet metal feed device;
Figure 2 is a view on the line II-II of Figure 1, with certain parts omitted, sectioned or partly removed;
Figure 3 is a side view of the pneumatic feed device with part of the machine bed shown sectioned;
Figure 4 is a diagrammatic plan view of a particular metal sheet shown partly stretched.
[0005] In the figures, the reference numeral 1 indicates the bed of the expanded sheet metal production machine. The bed 1 has a surface 2 on which the sheet metal (L) slides. This surface terminates at the level of a backing blade 3. The backing blade 3 is mounted on a slide 4 horizontally slidable in the bed 2 through a distance which is limited at the end comprising the backing blade by a stop member 5. Rods 6 are fixed to the slide, these in practice constituting the rods of pneumatic cylinders 7 connected to a compressed air source, not shown. The cylinders in question are fixed to a cross-member 8 within the bed 1.
[0006] Under the thrust of the pneumatic cylinders 7 the backing blade 10 tends to abut against the stop member 5 rigid with the bed 1. The backing blade 3 is designed to cooperate with a toothed blade 20 mounted in a slide 21 which can be driven with reciprocating horizontal motion by known means, not shown, and described for example in the initially stated patents. The slide 21 is mounted in a ram 22 mobile vertically under the control of crank mechanisms 23, which are not shown or described. An example thereof is described in the initially cited patents. The toothed blade 20 is therefore able to undergo both vertical motion away from and towards the underlying backing blade 3, and horizontal motion.
[0007] The following are associated with the slide surface 2 or bed 1, starting from the backing blade 3:
a) a pneumatically controlled flattening device 11 for the sheet metal, its purpose being to flatten the sheet metal L, which may be distorted ie not flat;
b) a pneumatically controlled brake 12 which presses the sheet metal against the slide surface during the machine active (ie stretching) stage;
c) a feed device 13 for the sheet metal.
[0008] The feed device 13 comprises an upper cross-member 13a connecting together a pair of side members 13b. A second cross-member connects the two side members 13b together below the slide surface 2.
[0009] The second cross-member upperly carries a plate 13d for example consisting of or covered with a friction material, which penetrates into an aperture 2a in the surface 2 and has its upper face substantially in line with the slide surface 2. The second cross-member carries sleeves 13e in which bushes or ball bearings 13f are mounted to allow linear movement. Guide rods 13g pass through the sleeves 13e and are fixed to inner transverse walls 1a of the bed 1. On the upper cross-member 13a there is mounted a series of double-acting pneumatic cylinders 13h the rod 13i of which carries a slide block 131 provided or faced with material of high coefficient of friction. The threaded rod 13n of a double-acting pneumatic cylinder 13o is fixed to the base of each of the two side members 13b by a bracket 13m. The rod 13n is guided axially in supports 13p rigid with the bed 1, and between the two supports carries a threaded ring nut 13q for adjusting the feed stroke of the feed device 13, as described hereinafter. The brake 12, which acts on the sheet L alternately with the programmed feed device 13, comprises a brake shoe 12a of high coefficient of friction provided at the lower end of a plate 12b from which there rises a series of supports 12c. The supports 12c are mounted on a shaft 12d comprising cams 12e, the rotation of which enables the shoe 12a to be applied to the underlying sheet metal L or to be withdrawn from it. The shaft 12d carries two arms 12f at its two ends. Each arm is hinged to a double acting pneumatic cylinder 12g hinged at its based to the bed 1.
[0010] The sheet flattener 11 lowerly comprises a plate 11a rigid with supports 11b traversed by a camshaft 11c driven by gears 11d and a rack (not visible on the figures) by means of a double-acting pneumatic cylinder 11e. This cylinder controls the raising and lowering of the plate 11a from and towards the sheet metal L. The machine is provided with a control unit 40. The operator sets on said control unit the parameters of the expanded sheet metal to be obtained. Data representing the machine conditions are continuously fed to this unit. These data are compared with the preset parameters. When coincidence is verified, signals are emitted to modify the machine operating conditions. Said data are provided by sensors. For the purposes of the present invention it is sufficient to mention the presence of a first sensor S1 (see Figure 3) which senses when the front edge of the sheet metal L to be stretched is present at the backing blade, and a pair of end-of-travel sensors S2, S3 for the feed device 13. On the control unit 40 the operator sets, for example, the number of strokes which the feed device 13 must effect before a given event occurs.
[0012] It will be supposed that a metal sheet A of a given length is to be produced, such as that shown in Figure 4, ie having a front end portion A1 and a rear end portion A2 which are equal and without stretch, ie free of apertures 50. The stretching operation therefore concerns only the intermediate portion A3 of the sheet. It will also be supposed that the toothed blade 20 and the backing blade 3 mounted on the machine are correct for the particular processing to which the metal sheet A is to be subjected. The operator places the sheet A on the slide surface 2, which is such as to allow easy sliding of the sheet, for example because it carries a very light film of lubricant, because it is of suitable surface finish, or because it combines these two aspects. Based on the required stretch pitch, this pitch being indicated by P in Figure 4, he correctly positions the ring nuts 13q of the feed devices. The distance between these ring nuts and the left hand support 13p (Figure 3) of the devices 13 is equal to this pitch. If the front and rear end portions A1, A2 of the metal sheet correspond for example to five pitches P, the operator sets this parameter on the control unit 40. This means that the blade 20 must remain at rest and distant from the backing blade 3 through five initial feed pitch movements and five final feed pitch movements.
[0013] If the intermediate portion A3 corresponds to one hundred pitches, this value is also set on the control unit 40. This means that stretching of the metal sheet A commences after the five initial pitch movements (corresponding to the portion A1), this stretching ceasing when there are five final pitch movements to go (corresponding to the portion A2).
[0014] Having done this, the operator places the metal sheet on the slide surface 2 taking care that at least a given portion of the sheet lies within the feed device 13. On starting the machine, only this device operates. Its shoe locks the sheet A against the plate 13d by virtue of pressure being supplied to the double-acting cylinders 13h which control it. Pressure is then applied to the cylinders 13o so that the sheet A moves forward (arrow X of Figure 3) through one pitch towards the backing blade 3. When the ring nuts 13q encounter the left hand support 13p the sensor S2 positioned thereat transmits this information to the control unit 40 which causes the shoe 131 to rise and the device 13 to return to its initial position. Here, the other end-of-travel sensor S3 causes the sheet A to undergo a further forward movement. When the front edge A4 of the sheet A reaches the backing blade 3 the sensor S1 acts to cause the feed device to return to its initial position even if it has not effected a whole pitch movement. At this point, the feed device is enabled for five pitch movements (to obtain the portion A1) without the blade 20 being brought into operation, ie without being driven to produce the stretching effect by cooperation with the backing blade 3. On termination of the five pitch movements (which are sensed by said sensors S2, S3), the operating conditions are modified in the sense that the blade 20 is operated to produce the stretching stage lasting for the scheduled one hundred pitch movements. During this, the sheet A moves through one pitch at a time by the action of the device 13 in the manner described, the brake 12 is applied and the blade 20 lowered, followed by disengagement and return of the feed device 13. When the hundred pitch movements have been completed, the control unit releases the brake 12 and halts the blade 20 in a position distant from the backing blade 3 to commence a stage corrresponding to that described in relation to the portion A1, ie to obtain the rear end portion A2. When the rear edge of the sheet passes the sensor S1 the machine stops.
[0015] If totally stretched sheets are to be produced from continuous strip wound on a reel, the procedure is as follows:
[0016] The intitial part of the strip is passed under the feed device 13. The machine is started. The device feeds the strip as far as the backing blade 3 with the set pitch movement. Here, the sensor S1 activates the backing blade. The stretching operation thus begins. When the required set length, equal to a certain number of pitch movements, has been attained, the control unit 40 halts the feed movement and causes the brake to act, but keeps the toothed blade 20 moving for one more descent stroke. As this further descent takes place after the toothed blade 20 has undergone a horizontal movement, a totally stretched sheet is cut from the strip. Said operation then recommences. In this respect, by way of clarification it should be noted that in an expanded metal sheet (see Figure 4) the rows of apertures 50 are staggered, so that if the metal sheet remains at rest for two consecutive active movements of the blade 20, during the first of these the apertures are produced and during the second (as the blade has been moved horizontally to obtain the stagger) the expanded sheet is separated form the rest of the strip. It is apparent from the aforegoing description that the improvements of the invention lead to a level of results and performance unattainable with the known machines described in the initially cited patents.
[0017] The sensors S₁, S₂ and ₃ can be chosen from a large number of well known types such as of photoelectric cell or photodiode type or proximity sensors for example of magnetic, inductive, capacitive or other type. Their signals can be counted and compared with the preset data by using electronic circuits widely known in the control field. Based on the data received, the control unit 40 which comprises said circuits controls solenoid valves, for example of two or three-way and/or reversing type, for the feed and discharge of air to and from the pneumatic cylinders.
1. Improvements in expanded sheet metal production machines of the type comprising
a surface (2) along which the non-stretched sheet metal (L) slides, a toothed blade
(20) mobile in two mutually orthogonal directions, one of which is away from and towards
the sheet metal (L), and a backing blade (3) which can retract against the action
of elastic means (7) during the active movement of the toothed blade (20), characterised
in that with the slide surface (2) for the sheet metal (L) there is associated a pneumatic
device (13) for feeding the sheet metal along said surface (2).
2. Improvements as claimed in claim 1, characterised in that the pneumatic device
(13) is driven with reciprocating motion of adjustable stroke by pneumatic cylinders
(13o) and comprises a series of pneumatic cylinders (13h) for gripping the metal sheet
(L) to enable it to be fed.
3. Improvements as claimed in claim 2, characterised in that the stroke is adjusted
by means of manually operated locators (13q).
4. Improvements as claimed in claims 2 and 3, characterised in that the locators (13q)
are mounted on the rods (13n) of the pneumatic cylinders (13o).
5. Improvements as claimed in one or more of the preceding claims, characterised in
that a pneumatic device (12) for braking the metal sheet is associated with the feed
device (13) downstream thereof.
6. Improvements as claiemd in one or more of the preceding claims, characterised by
comprising a control unit (40) for programming the sheet metal feed, for controlling
the braking device (12) and for controlling the toothed blade (20).