JPH0218969B2 - - Google Patents

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a sheet tensioning device for a cut sheet thermoforming machine, in which a cut sheet heated by a heating station and fed into a forming station is heated by a heating station, and the front and rear edges of the cut sheet are heated by a heating station and fed into a forming station. The first step is to shrink each central portion into a concave curved shape to reduce the moldable area.
An object of the present invention is to provide a device that prevents material loss by stretching back and forth in the direction of movement using a movable clamp device and a second movable clamp device.

(Prior art) In conventional resin cut sheet thermoforming, the cut sheet S fed into the molding station is heated by a heating station, but at this time, it has not been conventional to clamp the leading and trailing edges of the sheet separately from a clamp chain. It has been done. In this case, the square shape is maintained during heating, but as soon as it is fed into the forming station, the self-shrinkage of the sheet causes the first
As shown in Fig. 5, the center part hangs down due to its own weight, and the front and rear edges c, c in the direction of movement are contracted into a concave curved shape.

The reason for this is that the resin sheet extruded by an extruder is usually stretched in the extrusion direction, so if it is heated to an appropriate temperature suitable for molding in a heating station and then transferred to a molding station with a lower temperature, it will shrink to restore the stretching. However, since the edges of both ears are clamped by the clamp chain, they cannot contract, and the edges contract in a concave curved shape between the edges of both ears.

As a countermeasure to this problem, it is necessary to provide the molding station with a sheet tension device consisting of movable first and second movable clamp devices similar to the present invention, but there is no example of such a sheet tension device being implemented.

(Problem to be Solved by the Invention) The cut sheet S, which is clamped at the edge edges on both sides and fed into the forming station via the heating station, is thermally softened and its center part hangs down due to its own weight as described above. Edges c and c are contracted into a concave curved shape.

For this reason, when trying to mold the molded product b shown by the chain lines in Figures 5 to 7, thermoforming cannot be performed unless the length of the cut sheet S in the traveling direction is increased. If so, there will be material loss for that length.

The problem of the present invention is to prevent such material loss.

In addition, in the case of a model that performs width adjustment in which the edges a and a on both sides are brought closer to each other at the forming station in order to prevent deformation of patterns such as grain patterns formed on the cut sheet, wrinkles may occur around the molded product b. It is also important to prevent this.

(Means for Solving the Problems) The present invention aims to solve the problems mentioned in the previous section.The present invention is aimed at solving the problems described in the previous section.The cut sheet is gripped by the edge edges on both sides and sent to a molding station. In a thermoforming machine that performs molding, the molding station is provided with a first movable clamp device and a second movable clamp device that grip the concave curved portions c, c of the front and rear edges of the cut sheet S in the traveling direction, and the first and second movable clamps The devices are first and second movable clamp devices mounted on movable carts 8 and 28, respectively, which can move backward and forward in the direction of movement of the cut sheet, and grip the concave curved portions c and c of the cut sheet S before forming. The rear one 8 of each of the movable carts is moved rearward, and the front one is moved forward to pull the concave curved portions c, c, thereby increasing the moldable area of the cut sheet S. With regard to the sheet tension device of the cut sheet thermoforming machine, this configuration reduces the sheet loss mentioned in the previous section.
The generation of wrinkles, etc. can be effectively prevented.

A preferred implementation of the invention will now be described.

(Example) The attached drawings show an example of the present invention, and FIG. 1 is a vertical side view of a cut sheet thermoforming machine, and
The figure is a longitudinal side view showing the movement and sheet forming of the first movable clamp device and the second movable clamp device, and FIG. 3 is a back front view of the first movable clamp device seen from the direction of arrow A in FIG. 4 is a back front view of the second movable clamp device as seen from the direction of arrow B in FIG. 2, and FIGS. 5 to 7 are explanatory views of the cut sheet.

The cut sheet thermoforming machine 1 has a heating station and a forming station, and as shown in FIGS. A is grabbed and moved in the direction shown by the arrow,
It is heated at a heating station, and formed into a molded article S _-1 by a lower mold 3 and an upper mold 4 at a molding station, and is conveyed in the take-out direction. The above operations continue intermittently.

The forming station includes a first movable clamp device and a second movable clamp device for timely grasping the concave curved portions of the front and rear edges c, c between the clamp chains 2, 2 of the cut sheet S on the rear and front sides in the traveling direction. Clamp devices are provided on the movable carts 8 and 28, respectively. The movable carriages of both movable clamp devices each have tension cylinders 7, 27 fixed with their upper sides reversed on the carriages 5, 25, which are moved forward and rearward and positioned by adjustment screws 6, 26. Connect to rod.

The cut sheet S is a flat sheet without a molded product. The first movable clamp device is fixed to the movable cart 8 as described above, and the gate frame 9
Clipping piece 10 positioned above the cut sheet S
and a clipping piece 11 located on the lower side, and the lower clipping piece 11 is attached to a rod 13 of a vertically operating cylinder 12 mounted on a movable cart 8. The guide rods 14, 1 shown in FIGS. 3 and 4 are attached to the clip 11.
4 is installed vertically, and cylinder 1 of gate-shaped frame 9 is installed.
The guide rods 14, 14 are passed through guide tubes 16, 16 provided on the horizontal rod 15, which is fixed in position and extends above the rod 2.

The second movable clamp device shown in Fig. 4 is a molded object.
Since the rods ₃₁ , 31 of vertically operating cylinders 30, 30 are attached to support pillars 29, 29 erected on both sides of the moving carriage 28,
2, and an upper clipping piece 33 is provided on the bar,
Further, a lower clamping piece 36 is attached to the rod 35 of the vertically operating cylinder 34 attached to the moving cart 28. The guide rod 37 shown in FIG. 4 is attached to the clip 36,
37 is installed vertically, and the horizontal rod 38 is fixed by passing it over the cylinders 30, 30 above the cylinder 34.
The guide rods 37, 37 are passed through the guide tubes 39, 39.

In the embodiment described above, the adjustment screws 6 and 26 are used to position the carts 8 and 28 in front and behind the first and second movable clamp devices. Furthermore, at the timing of moving the cut sheet S, the lower mold 3 and the upper mold 4 are separated as shown in FIG. 1, and the first movable clamp device lowers the lower clamping piece 11 as shown in FIG. 2. In the movable clamp device, raise the upper clamping piece 33, lower the lower clamping piece 36,
The cut sheet S whose edge edges a, a are gripped by the pair of clamp chains 2, 2 is advanced and stopped between the first and second movable clamp devices. Cut sheet S
is softened by heating, the center part hangs down due to its own weight as mentioned above, and the front and rear edges c and c in the direction of travel are curved into a concave arc shape as shown in Figure 5. 1 In the movable clamp device, the lower clamping piece 11
, and in the second movable clamp device, lower the upper clamping piece 33 and raise the lower clamping piece 36 (first
(Dash-and-dash line in figure) Grasp the concave curved parts c and c shown in Fig. 5 as shown in Fig. 6, and move the first and second movable clamp devices in the front-rear direction of the sheet S by contraction of the cylinders 7 and 27. Then, as shown in FIG. 7, tension is applied to the sheet S to correct it into a wide-area flat plate shape and thermoform it. Once the molding is finished, the first and second
Return the movable clamp device to the non-tensioned position shown by the solid line in Figure 1.

(Function of the Invention) The present invention includes a first movable clamp device and a second movable clamp device that grip the concave curved portions c and c of the front and rear edges of the cut sheet S in the direction of movement in the forming station. A moving and stopping cut sheet S is grabbed by a first movable clamp device and a second movable clamp device at the concave curved portions formed on the front and rear edges c, c in the direction of travel, and the first and second movable clamp devices are used to hold the cut sheet S. Each movement of the first and second movable clamp devices mounted on movable carts 8 and 28, which move backward and forward in the moving direction, respectively, grips the concave curved portions c and c of the cut sheet S before forming. The structure is characterized in that the rear part of the cart is moved rearward, the front part is moved forward, and the concave curved parts c, c are pulled to increase the moldable area of the cut sheet S. , Due to this effect, the moldable area of the cut sheet S can be increased.

(Effects of the Invention) The device of the present invention grasps cut sheets from the front and back in the direction of movement of cut sheets that are distorted by heating and shrinking and then stopped after being transported to a forming station, and applies tension to correct thermal distortions, so that the cut sheet material is almost the same as before heating. Since it is possible to eliminate the loss of sheet material by stretching it over the same area, there is no need to use a cut sheet larger than necessary in anticipation of thermal distortion due to heating, and there are effects such as no wrinkles caused by forming. .

[Brief explanation of drawings]

The attached drawings show embodiments of the present invention, and the first
The figure is a longitudinal side view of the cut sheet thermoforming machine, Figure 2 is a longitudinal side view showing the movement and forming of the first movable clamp device and the second movable clamp device, and Figure 3 is the direction of arrow A in Figure 2. FIG. 4 is a back front view of the second movable clamp device as seen from the direction of arrow B in FIG. 2, and FIGS. 5 to 7 are illustrations of the cut sheet S. be. 1 → cut sheet thermoforming machine, → forming station, → first movable clamp device, → second movable clamp device, 7 → tension cylinder, 8 → moving trolley, 9 → portal frame, 10 → pinch piece, 11 → Clipping piece, 28 → moving trolley, 33 → clipping piece, 33 → clipping piece, S → cut sheet.

Claims (1)

[Scope of Claims] 1. In a thermoforming machine that grips the edge edges on both sides of a cut sheet and sends it to a forming station, and forms the cut sheet with a forming die in the station, the forming station has concave curved portions on the front and rear edges of the cut sheet S in the direction of travel. A first movable clamp device and a second movable clamp device are provided for gripping the cut sheet c, c, and the first and second movable clamp devices are mounted on movable carts 8 and 28, respectively, which can move backward and forward in the direction of movement of the cut sheet. Then, before forming, the rear parts of the movable carts of the first and second movable clamp devices that grip the concave curved parts c and c of the cut sheet S are moved rearward, and the front ones are moved forward. A sheet tension device for a cut sheet thermoforming machine, characterized in that the moldable area of the cut sheet S can be increased by pulling the concave curved portions c, c.