JPS5917646B2 - Manufacturing method and manufacturing device for concave articles - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION This invention relates generally to the manufacture of plastic articles of the type having a concave shape.

Articles of the type to which the invention relates, such as automotive mudguards, generally in the form of a part cylinder with a flange edge. However, it will be understood that the present invention hereinafter includes, for convenience, all concave-shaped articles, and is applicable to dish-shaped and other concave-shaped articles other than the mudguard. The main object of the invention is to provide a method for manufacturing concave articles in a simple and efficient manner.

As a feature of the present invention, the production of concave articles is accomplished by mounting a sheet of thermoplastic material on a machine, fixing its edges to each of a pair of track carriages that are movable toward each other on the machine; In order to soften the sheet, a heating device that can be lifted and moved in the horizontal direction is used to heat the sheet, and a forming tool is lifted to form the sheet into a desired concave shape, and by this lifting, the sheet is The track carriages are moved toward each other under the tension applied by the sheet, and the sheet is cooled by a cooling device installed above the sheet in order to harden the sheet to prevent further deformation; In addition to providing a method for manufacturing a concave article including a final step of removing it from the machine, another object of the invention is to provide a machine for carrying out the method.

Other aspects of the invention include a frame, a pair of horizontally movable track carriages having respective fasteners for engaging opposite ends of the plastic sheet to be processed, for deforming the sheet clamped to the track carriages; a forming tool having a device for raising and lowering across the horizontal plane of motion of the track car; a heating device arranged to heat evenly over at least a portion of the sheet being deformed by the forming tool; The present invention provides a machine including a cooling device for cooling the sheet after it is deformed.

Another object of the invention is to provide a concave plastic article produced by the method and machine described above.

In this aspect, the invention provides a concave thermoplastic article formed by the method described above and having a substantially uniform thickness throughout.

The present invention will be explained below with reference to the accompanying drawings.

As shown in FIGS. 1, 2 and 3, a machine according to the invention includes a frame 10 which preferably has a generally rectangular rigid aperture structure.

The frame consists of a box and angle-shaped members welded or joined thereto. The frame has two pairs of horizontally arranged substantially flat elongated rail strips 11, 12, 13 thereon.
, 14 are installed.

A respective track bogie 15, 16 is mounted on each rail assembly. Each groove sheave group 17 is provided to engage a respective rail for mounting the track bogie. Each groove wheel group (consisting of two sets placed above and below the rails, respectively).The track carts 15, 16 are mounted on the rails in order to move toward and away from the center of the machine in a horizontal plane. Each track truck has a movable clamping rod 18, 19 attached to it.

In this embodiment, this clamping bar is of angular profile and is arranged so as to be clamped to a respective cooperating flat bar 20, 21, each forming part of a track truck. A device is provided for hydraulically or mechanically attaching the clamping rods 18, 19 to the respective cooperating flat rods 20, 21 in a manner not shown in the figures. The track car includes a device for attaching additional weights, thereby adjusting the force required to move the track car along the rail. The frame 10 of the machine has a hydraulic or pneumatic piston-cylinder unit 22 mounted in its center, and the ram 23 of the device carries a forming tool 24 of a predetermined shape.

In this embodiment, the forming tool has the shape of a vehicle mudguard manufactured by this machine. However, it is clear that other forms of forming tools can be substituted to produce the desired concave article. The illustrated former has a semi-cylindrical configuration, the curved end of which is provided with a flange of equal width as can be seen. The former is coated with some material to prevent the thermoplastic from sticking to the surface.

A woolen coating is suitable for this. The forming tool 24 is made of a thin metal plate and has almost the same shape as the finished product, although it is slightly smaller. Suspended above the frame is a heating box 25 which can be raised and lowered (although the manner in which it is not shown).

The heating box 25 is rectangular and has a top wall, side walls, and end walls made of thin metal sheets. It is equipped with a heating element for uniform heat radiation over substantially its entire area in order to radiate heat downwardly. The heating box is further movable laterally relative to the frame to remove it from its normal heating position above the frame when it is not in use. A suspended cooling fan 26 is disposed above the frame and is available for use when the heating box 25 is removed from its position above the frame.

A switch panel 27 is provided on the frame 10.

The switch panel activates the hydraulic or pneumatic circuit so that the forming tool 24 is raised and lowered by its piston-cylinder unit 22, and also energizes the heater, the heating box motion controller, and also the cooling fan 26. let Figures 1, 2 and 3 show the machine at various stages of processing during the manufacture of a vehicle mudguard.

FIG. 1 shows the machine fitted with a sheet 28 of thermoplastic material. The sheet is rectangular and initially flat. Its narrow edge is attached to the clamping rod 1 on the track carriages 15 and 16 respectively.
8 and 19, respectively. Furthermore, the track vehicles are shown at the outer end of their transfer journey. When cold, the sheet has considerable rigidity, but when heated, it softens as described below. The heating box 25 is lowered from the illustrated position to a position very close to the seat 28 and the heater is energized.

Since the area of the heating box is approximately the same as the area of the sheet 28, the sheet is heated almost evenly. Once the sheet 28 has been softened to the desired degree, it is raised to the heating box 25 and then moved laterally so that the heating box is no longer located above the sheet 28.

The forming tool 24 is at this stage lifted by its piston-cylinder unit 22. This action deforms the sheet 28 so that it follows the shape of the forming tool 24. Figures 2 and 3 show intermediate and final stages of lifting the former. While the forming tool is being lifted, the sheet 28 applies tension to the clamping rods 18, 19, which are attached to the track carriages 15, 16, so that they tend to move towards each other. rails 11, 12, 13
, 14. This movement of the track bogie can be clearly understood from these three accompanying diagrams. Track bogies are made of thermoplastic plastic, although, as mentioned above, they are weighted to prevent their inward movement.
It is important that the sheet 28 move freely under tension only from the sheet 28. It is also important that the lifting speed of the forming tool 24 is controlled. If the thermoplastic sheet 28 is stretched too quickly, its thickness will be reduced in certain areas, whereas if it is stretched too slowly, the track car will not move inwardly, so that the sheet 28 will be stretched at the lowermost end of the former 24. You won't be able to wrap it tightly around it. When the forming tool 24 is lifted, the thermoplastic sheet 2 is formed as shown in the figure.
8 to assume the semi-cylindrical profile of the former, but at the same time form respective edge flanges similar to those of the former itself.

FIG. 3 shows the former in the fully lifted position.

This is the location where cooling of the thermoplastic sheet is carried out. For this purpose, the cooling fan 26 is energized to blow cool air to the sheet 28.
Spray onto the surface facing upwards. It is necessary to hold the ends of the two flanges formed in the sheet 28 inwardly relative to the corresponding flanges of the former 24 to prevent creep.

One means used for this purpose was to attach the ends of the same flange together using wire-bonded fasteners. However, mechanical components must be used to achieve this. However, the equipment used for this purpose must not expand or stretch the material when it is in its softened state, so as not to cause a reduction in the thickness of the material. Once sheet 28 has cooled to a substantially rigid temperature, it is removed from tool 24. Once the entire manufacturing process is complete,
The flange of the mudguard is larger than the flange of the former 24 and the additional material is cut by hand or by suitable automatically or semi-automatically operable equipment.

Similarly, the flanges formed on the ends of the mudguard, which are tightened by clamping rods 18 and 19, are also sized by hand or by suitable equipment. As a preferred device,
The two machines shown are arranged in parallel, and the heating box 25 is movable between positions aligned with each of the two machines.

Thus, while heating one sheet, cooling of another sheet is carried out on an adjacent machine, and vice versa. FIG. 4 shows a pneumatic control circuit for such a reciprocating machine.

The heating box 25 is mounted on the upper support structure and is laterally movable between aligned positions above each of the two machines. A pneumatically actuated double acting piston and cylinder unit 30 is provided for laterally moving the heating box 25. The heating box 25 can also be raised or lowered in either of the two positions and a further piston-cylinder unit 31 is provided to accompany this movement.
There is a pilot and main air or other fluid supply;
This is indicated at 32 and 33 respectively.

Two inputs from each of the above sources are shown and identified by subscripts a and b, respectively. Pilot supply 32 communicates with isolation valves 34 and 35, respectively, to which main supply 33 is also coupled. The main supply reaches these isolation valves 34, 35 via respective valves 36, 37, 38 and 39, 40, 41. Shutoff valves 34, 35
Air from there reaches one end of the lifting/lowering unit 31 through the respective non-return valves 42, 43. The main supply valve 33 also has respective adjustable restrictors 44, 45 used to adjust the speed of the lateral movement of the heating box.
via which both ends of the lateral control unit 30 can be reached.

The two sets of valves 36, 37, 38 and 39, 40, 41 are identical in function to each main supply line.

Valves 36, 39 are operated by the pilot air supply. These valves select the side of the system that is operated by the selected pilot source 32a or b. valve 37
and 40 are actuated by contact with the heating box support structure, and these valves are provided with respective contact rollers for this purpose. Valves 38 and 41 are plunger actuated and mounted on the heating box 25 so that the heating box contacts the support structure when it reaches its upper position. This cycle arrangement includes a feed pilot source from either source 32a or 32b to actuate valve 36 or valve 39.

Also, pilot air is supplied to a suitable shutoff valve 3.
4 or 35. This is done by means of a unit 31 which raises and lowers the heating box. When the valve 38 or 41 located at the top of the heating box is actuated, air from the main source is allowed to reach the appropriate end of the cylinder of the transverse movement unit 30.
To ensure this, the heating box remains in its lifted position during the lateral movement and air reaches the valve 34 or 35 from the main supply to keep the unit 31 in the upward position. When the heating box reaches its new position, valve 37 or 40 contacts the support structure and shuts off the main source of air.

The heating box is also cut off from the air supply to the unit 31 at this point. Opening of valve 38 or 41 places the system in a drain condition. The device is further automated by the cooperation of operating devices for loading and unloading the thermoplastic sheet, the cycles of the device being controlled by an electronic program control circuit.

The tightening device, the operation control device, the loading and unloading device are operated in a predetermined order. The plastic material is preferably, but not necessarily limited to, high density polyethylene and made from extruded sheets.

However, other materials such as polypropylene or acrylonitrile butidiene styrene can also be processed with the apparatus according to the invention. It has been found that it is possible to vary the thickness of the sheet within small limits and that this method tends to increase the thickness of the sheet very slightly over the entire area of the sheet.

While the material is in its softened state, there is no surface marking or contact with the surface, resulting in a very good surface finish. It has already been mentioned that this uses a woolen surface to prevent material from sticking to the former 24. The use of woolen fabrics has the advantage of being able to withstand high temperatures without significant deterioration. The clamping rod may further be provided with a highly polished surface to prevent adhesion, or alternatively a sheet of material to which the thermoplastic material does not easily adhere may be provided between the clamping rod and the material itself. Will be done〇

[Brief explanation of drawings]

1 is a perspective view of a machine constructed according to the invention shown in the installed state; FIG. 2 is a view similar to FIG. 1 showing the plastic sheet in a partially deformed state; FIG. FIG. 4 is a similar view showing the seat fully deformed and in the cooled position; FIG. In the figure; Code: 10... Frame; 11-14.
...Rail; 15,16...Track bogie;
17... Groove wheel; 18, 19... Movable tightening rod; 20, 21... Flat tightening rod: 22...
... Piston/cylinder unit; 23...
Ram; 24... one molding tool; 25... heating box;
26... Cooling fan; 27... Switch panel: 28... Seat; 30, 31... Piston/cylinder unit; 32... Pilot supply source; 33... Main supply source; 34, 35...
...Shutoff valve; 36-41...Valve; 42,4
3...Non-return valve; 44, 45...Adjustable restrictor.

Claims (1)

[Claims] 1. A sheet made of a thermoplastic material is placed on a machine, and both edges of the sheet are fixed to each of a pair of track carts that move toward each other on the machine. heating with a heating device capable of being lifted over the sheet to soften the sheet;
A forming tool for forming the sheet into the desired concave configuration is lifted across the horizontal plane of the carriage, then cooled by a cooling device provided above the sheet to harden the sheet, and finally A method of manufacturing a concave article comprising the step of removing the sheet from a machine. 2. A method as claimed in claim 1, in which the heating device is lowered into the heating position to heat the sheet and then lifted out of the heating position prior to lifting of the former. 3. A method according to claim 2, wherein the heating device is then moved laterally while being lifted into position on another machine on which the same method is carried out and lowered again into the heating position. . 4 A frame, a rail arranged horizontally on it,
A pair of track bogies mounted on the rails are equipped with fasteners for fixing both ends of a sheet made of a thermoplastic material to be processed, and the sheet with both end edges fixed by the fasteners is deformed. a heating device for uniformly heating the sheet, which is capable of being lifted and moved laterally above the sheet; and a cooling device disposed above the sheet to cool the sheet after forming with the forming tool. 5. The manufacturing apparatus according to claim 4, wherein the pair of track trucks are movable freely on rails provided on the frame. 6. The manufacturing apparatus according to claim 4 or 5, wherein the forming tool is movable up and down across the horizontal movement surface of the track truck by means of a fluid-operated piston-cylinder unit. 7. The manufacturing apparatus according to any one of claims 4 to 6, wherein the heating device is a heating box that is vertically movable between a heating position and a lifting limit position. 8. The manufacturing apparatus according to claim 1, wherein the heating device is laterally movable to a predetermined position offset from a heating position above the sheet. 9. The manufacturing apparatus of claim 8, wherein the heating box is laterally movable between positions so as to be aligned in a predetermined position on another frame located laterally. 10. A manufacturing apparatus according to claim 9, comprising a fluid control system for actuating a fluid actuation unit for vertically and horizontally moving the heating box according to a timed sequence. 11. The manufacturing apparatus according to any one of claims 4 to 10, wherein the surface of the forming tool is covered with woolen fabric. 12. Claim 4, wherein the heating device and the forming tool are operated according to an automatically controlled predetermined timing cycle.
The manufacturing apparatus according to any one of Items 1 to 11.