Apparatus for shaping heated thermoplastic plates or sheets

The invention relates to a device for shaping heated plates or Film web sections of thermoplastic material according to the genre of the Main claim.

In such a device the heating means is moved horizontally between a heating position above the plate or the sheet section and a rest position. The heating position is either in the forming station, then the heater in this per cycle between rest position and Forming station process and / or a heating is preceded by the forming station, and a transport means used to transport the plate or Film web portion between the heating station and the forming station.

With respect to the heater movement, there are various requirements. So shall carried out the movement of the heater as soon as possible, because the journey time at specific machine designs directly influences the cycle time. Come in addition the so-called cross-over effect, that is, the heater moves from the rest position initially on the plate and again after heating back. It means that the longer heated one side of the plate, which passes over the heater first is defined as the side on which arrives the heating device at the end of the movement. On the way back it is reversed, ie the longer heated during the forward side will now turn more heated, because the heater this page last leaves. The could be only two rest positions - opposite - encounter, which is not possible from different reasons. result of this Driving is a different length heated plate, which effect more is stronger, the slower the speed. Another problem is through the use of grid-like arranged Radiators in the form of ceramic heaters, quartz lamps or halogen lamps, all of which are sensitive to vibration. Care must be taken so that the occurs approaching the end position gently and without shocks, which in turn not to high travel speeds allow.

A further problem with heating of the motion is that when failure of the Energy supply fire hazard, the heater on the plate should stand. The radiators have been saved so much heat that even when switching off its power supply initially further warming of Plate made, they thereby softens and falls to the bottom heater. A fire can be the result. It must be ensured so that at Power failure, the heater can still drive in rest position.

From DE 22 16 651 A1 it is known, the movement by means of a heating make pneumatic cylinder. Although this allows you to power failure yet a pneumatic movement of the heating in the rest position by known Providing a compressed air cushion, but the travel movement, because of the done-mentioned problems of fragility relatively slowly, which brings the problems of cross-over effect and the clock time adjustment with him.

By machine deliveries of the applicant, it is known electromotive Actuators for the movement of the heating device in the form of a crank mechanism use. While this brings a rapid movement of the heater with Soft start of the end positions by a sinusoidal motion. a but power failure must lavish funds - for energy storage this emergency - are met. This increases the cost of device considerably.

The invention has for its object to design the device so that the Moving the heater quickly and yet with a gentle start the end positions is carried out and when power failure in driving resting position to Avoid the risk of fire without consuming expensive measures can be made.

To achieve the object, the characteristic features are the Main claim proposed.

An embodiment of the invention and an advantageous development are reference to the schematic drawings of a device prefixed Disc magazine and one each heater in the mold station and in the closer loading station and with optional work of the film roll described.

It shows:<dl tsize="8"><dt>Figure 1:</dt><dd>a front view of the device.</dd><dt>Figure 2:</dt><dd>a plan view of the heater and its drive means.</dd><dt>figure 3</dt><dd>a variation of the drive of the heating means.</dd></dl>

The apparatus comprises a forming station 1 with two clamping frames 2, 3, from which the upper clamping frame 2 is vertically adjustable and both the Interaction a plate 4 or a sheet section of thermoplastic clamp. A heating device 5, arranged in the forming station 1 and / or in the feed station 6, takes place Heating the plate 4 or the film web section on Deformation temperature. By means of a height on the movable mold table 7 arranged mold 8 and by applying a vacuum, the plate 4 or the Sheet section deep drawn to form a molding. 9 This is supported Deep drawing, if necessary through a pre-stretch 10 provided with a drive means 11 is connected via a coupling 12th

Laterally the forming station 1 a feed station 6 is optionally arranged in the plates 4 are placed in a stack. 13 About a sucker plate 14 with at Vacuum suction cups that can be connected 15 is in each case the uppermost plate of the stack 4 13 is lifted and transferred to the transport device 19, both stations 6, 1 connects. The vertical movement of the suction plate 14 is carried on the Drive means 16. Drive means 16 and suction plate 14 are on the Clutch 17 is connected.

If the device does not operate from the plate stack 13, but Sheet sections deformed, is a film web 18 from a roll 21 by a transport device subtracted 19, a cross-cutting device 20 separates this film web sections starting and the transport device 19 it brings in the individual stations 6.1.

is in the forming station 1 and / or in the upstream feed station 6 a heating device 5 is arranged, the one of a top heater and optionally from Underheater is and is generally referred to as a heating device. 5 The horizontal movement of the heater 5 between a rest position 22 and the heating position is effected via a pneumatic cylinder 23 controlled by a valve 24, which is fed by a compressed air source 29th The supply lines 25 to the Pneumatic cylinder 23, one each in cross section continuously variable throttle 26 fitted which is designed so that its cross-section from a controller 27 from can be changed via a control line 28th For example, it may be act at the throttle 26 to a proportional valve whose cross-section is proportional to the applied voltage. Each heater 5 is with any commercially available measuring system 30 is provided, with the stated position of the heater 5 and a Control line 28 of the control is reported 27th In the simplest case, at this measuring system 30 to individual - preferably adjustable - Switches to a specific position of the heater reached the Control Report 27th

In the process of the heater between rest position 22 and heating position Now, the throttle 26 for supplying the compressed air for generating the movement fully open, the exhaust air side throttle 26 first also. The heater 5 moves very quickly. When approaching an end position - rest position or Heating position - there is a reduction of the cross section, preferably, the corresponding exhaust air side reactance 26 and thus throttling Driving speed in such a way that the movement just in end position to Standing comes without a jerky braking is. An additional Changing the cross-section of the supply air throttle 26 is possible.

Another possibility of the restriction of the travel movement of the heater 5 depending on their location is shown in FIG. 3 parallel to Pneumatic cylinder 23 is a damping cylinder 34 arranged with piston 38th The Piston rod 36 of the pneumatic cylinder 23 is of the piston rod 35 Damping cylinder 34 - or alternatively directly with the heater 5 - connected. The damping cylinder 34 is filled with oil and the oil passes over the Connecting line 37 between the two sides of the cylinder in order. In the Connecting line 37 incorporates a throttle 26, the through cross-section corresponding control via the controller 27 can be changed.

can Experiments and an appropriate parameterization of the controller 27 to the date of commencement of the restriction and the rate of Throttling identify uniquely through experiments and in the controller 27 deposit. It has in this way an optimal fast movement the heater 5 without risk of damaging their heating elements.

To the heater 5 in the event of power failure in the rest position 22 To go back is proposed in development of the invention, the Side of the pneumatic cylinder 23, which acts on the drive in rest position 22 must be to connect with a passage valve 31, the one with Pressure accumulator 32 is connected. This pressure accumulator 32 is on the Compressed air source 29 and a check valve 33 is fed. In operation, the Device is the passage valve closed 31, open at power failure and thus connects the one side of the pneumatic cylinder 23 to the Compressed air reservoir 32, thereby moving the heater 5 in rest position takes place 22nd