TECHNICAL FIELD

The present invention relates to forming of protective film-coated stainless-steel sheets in the production line, particularly facilitated by heating, to obtain the decorative panel of an oven.

BACKGROUND OF THE ART

In the production process of an oven, a protective film coated stainless steel decorative panel is adapted to the outside of the casing to provide an alternative design variant with a stainless-steel appearance. The decorative panel is supplied either as pre-cut PVC coated pieces or is cut from a stainless-steel coil. It is undesirable to have a trace, burr or visual defect on the visible surfaces of the stainless-steel sheets in the production lines utilized to produce decorative panels. In order to prevent the defect, the stainless steel sheet is covered with a protective film. The coated protective film is peeled off after production.

Stainless steel sheets are shaped by pressing lines in production facilities. Presses are fed with stainless steel sheet material by roll or manually piece by piece. In cases where the material is fed with a roller, the width of the roller is chosen the same as the width required for the part to be produced, the measure is called the slitting distance. The size of the other dimension of the part is adjusted by cutting with the help of blades positioned in front of the first station of the press. The process of shaping stainless-steel sheets with presses is not always at the desired level. In order to solve this problem, heating process is applied to the stainless-steel sheets before the press line.

CN110395021A describes a novel roller coating film-coated metal composite plate and a production process thereof. According to the production process, surface treatment is carried out on selected raw materials, namely an aluminum alloy plate and a stainless steel plate; film glue covering is carried out, specifically the aluminum alloy plate and the stainless steel plate are preheated, and then the inner side of the preheated aluminum alloy plate and the inner side of the preheated stainless steel plate are coated with a macromolecule damping adhesive film in a rolling mode through a film coating roller; novel hot-pressing roller coating is adopted for manufacturing a metal composite plate, specifically the aluminum alloy plate and the stainless steel plate are continuously heated as a whole, and are laminated together by adopting a hot-pressing roller hot laminating method to form a metal composite plate; and the metal composite plate is cooled and leveled. A bonding treatment method is adopted, the machining process is simple, operation is convenient, the method is suitable for manufacturing of aluminum alloy sheets and stainless-steel sheets, and the production cost is reduced.

BRIEF DESCRIPTION OF THE INVENTION

The object of the invention is to facilitate the shaping of the protective film-coated stainless- steel sheet in a production line that provides a decorative panel for the oven.

Another objective of the invention is to facilitate the peeling of a protective film on the stainless-steel sheet.

In order to achieve the aforementioned objectives, the invention relates to a production line control method comprising the steps of loading a stainless-steel sheet covered with a protective film of plastic polymer material onto a transport unit; cutting stainless-steel sheet covered with a protective film to obtain at least one workpiece with a long side at a predetermined slitting length and one short side at the width of the stainless-steel sheet covered with a protective film which is provided at an outlet of the transport unit; loading the workpiece into a feeding station and shaping by means of a press provided on the workpiece in a pressing station to obtain an intermediate piece in an progressive mold. The method further comprising the steps of heating the workpiece to a predetermined temperature by means of a heating station, transferring the heated workpiece directly to a pressing station, and the peeling off the protective film on the pressed workpiece. Formation of any scar, burrs or visual defects on the visible surfaces is prevented during the processes applied in the production line thanks to the protective plastic film on the workpiece. Friction force between the press and the workpiece decreases due to the heating of the workpiece thus the shaping process is facilitated. Additionally, after the production process is completed, the protective films on the workpiece are peeled off without leaving any traces. Moreover, thanks to the heating process in the heating station, the peeling strength value of the protective film on the workpiece increases and the rupture of the protective film is prevented. Thus, problems caused by rupture that may occur during production are prevented.

A preferred application of the invention comprises the process step of cutting the stainless- steel sheet covered with the protective film by means of a shear. Cutting with shears ensure adjustable lengths of the long and short sides of the workpiece obtained and cut marks are not visible on the long and short sides. In an alternative embodiment, a guillotine cut can be made instead of a shear cut. In another alternative application, laser cutting may be preferred.

A preferred application of the invention comprising the step of transferring the workpiece loaded into the feeding station directly to an inlet portion of the heating station by means of a conveyor belt. The conveyor belt transfers the workpiece directly inlet of the feeding station subsequent to the feeding station. The production line is faster and more compact due to the said application.

In a preferred application of the invention the workpiece heated in the heating station transferred by means of a carrier unit arranged to load from an outlet part of the heating station directly to the mold adjacent to an opening of the pressing station. Transfer with the carrier unit ensures that the heated feed part is transmitted directly to the pressing station without cooling. In this way, the workpiece is easily formed by pressing in the pressing station.

A preferred application of the invention comprises the step of cooling the pressed workpiece at an outlet of the pressing station to room temperature. Cooling to room temperature makes it easier to peel off the protective film on the workpiece. In this way, it is ensured that the problems that may occur during the peeling process of the protective film are prevented from breaking off and the remaining protective film sticks in the piece during peeling.

A preferred application of the invention comprises the step of the step of heating the workpiece by an electric heater disposed in the heating station. In an alternative embodiment, the heating operation can be performed with an infrared heater. In another alternative application, heating can be performed with the use of a fan heater.

In a preferred application of the invention, the workpiece is heated to reach a temperature range of 60°C to 70°C by means of the heating station. Thus, the protective film on the workpiece is prevented from breaking during the pressing process and thus, visual defects that may occur on the visible surface of the workpiece are prevented.

In a preferred application of the invention, the workpiece is heated to reach a temperature of 66°C by means of the heating station. In this way, both the forming process of the feeding sheet is facilitated, and it is ensured that the protective film is prevented from breaking over the workpiece. In a preferred application of the invention, the temperature value of the heating station is determined by a temperature measurement sensor. Mmelting of the protective film is prevented which may occur with the temperature rise during the heating process or excessive adhesion of the protective film on the workpiece.

In a preferred application of the invention, a volatile oil is applied on the workpiece. In this way, easy shaping of parts with high deep drawing amount is provided. In addition, due to the volatile nature of the volatile oil, it is facilitated to separate from the surface of the part.

In a preferred application of the invention, the workpiece is pressed by means of a single stroke press in the pressing station. Thanks to the single-stroke press, fast and reliable pressing is realized. In an alternative embodiment, pressing can be performed with a transfer press having more than one station.

BRIEF DESCRIPTION OF THE FIGURES

Figure 1 is a top view of the heating and pressing condition of a stainless-steel sheet at the feeding unit in a representative embodiment of a production line of the subject matter invention.

Figure 2 is a front view of the production line shown in Figure 1.

DETAILED DESCRIPTION OF THE INVENTION

In this detailed explanation, the subject matter invention is explained without any limitation and only with reference to examples to better explain the subject.

A top view of the production line of the subject matter invention is shown in Figure 1. At one end of the production line, a protective film (2) covered stainless-steel sheet (1) roll is disposed. The protective film (2) is made of a plastic polymer material and a PVC film is covered as on the stainless-steel sheet (1). The protective film (2) coated stainless steel sheet (1) is loaded onto a transport unit (20) from an inlet section (22) in a way that pulled from its outer end and brought into a plain and flat form. The transport unit (20) presses the protective film (2) covered stainless-steel sheet (1) with a bending cylinder (22) and turn into horizontal position. A lower part of the transport unit (20) is supported by a plurality of narrowly spaced rotating transport rollers (24). The protective film (2) covered stainless steel sheet (1) slides on the transport rollers (24). An outlet (26) has a support element (42) that extend closely with a feeding station (40) so that the protective film (2) coated stainless-steel sheet (1) not falls with its own weight. The outlet (26) is at the same height as the support member (42). In this way, the stainless-steel sheet (1) covered with the protective film (2) climbs straight onto the support element (42) without forming a slope. The support element (42) includes narrow and adjacent rotating rollers. A shear (30) extends transversely across the outlet part (25) of the transport unit (20). The shear (30) cut the stainless-steel sheet (1) coated with the protective film (2) by moving a slitting length (L) from the exit part (26) of the stainless-steel sheet (1) covered with the protective film (2). In this way, a workpiece (10) is obtained, which extends under a feeding device (46) located inside the feeding station (40) and on the support element (42). The resulting workpiece (10) includes a long side (12) equal to the slitting length (L) and a short side (14) having a sheet width (w). The workpiece 10 has a rectangular-like form. The feeding station (40) includes a carrier unit (44) at its lower end, which includes magnetic or vacuum grippers extending down from the lower corners of a table. The workpiece (10) rises by means of a carrier unit (44) of the feeding station (40). The conveyor unit (44) transfers the workpiece (10) at the feeding station (40) directly to an inlet (52) of a heating station (50). The workpiece (10) transferred to the heating station (50) is heated up to a temperature of 66°C by the multiple electric heaters (54) located in the heating station (50). During the heating process, the temperature inside the heating station (50) is measured by a temperature measurement sensor (56) and a warning is given by an audible warning unit (57) electrically connected with the temperature measurement sensor (56) in case the temperature exceeds the desired temperature value. With the increase in temperature, the deep drawing ability of the workpiece (10) is increased. The workpiece (10) that reaches the desired temperature is loaded onto a conveyor belt (70) from an outlet part (58) of the heating station (50). The conveyor belt (70) transfers the workpiece (10) directly to a die (63) adjacent to an opening (62) of a pressing station (60) without any cooling occurring. A long side (12) of the workpiece (10) in slitting length (L) is adjacent to the mold (63) from a mouth (62) part, whereas the short side (14) in sheet width (w) is in a vertical position. The pressing station (60) includes a single stroke press (61). The press (61) has a rectangular-like base (66) and four dies (referred to as dies) including the first die (64) perpendicular to the base (66) and at least one second die (65) in parallel following it in the direction of movement has been located. The short sides of the dies (63, 65) are located along the long side of the press (60). In contrast, the long sides of the dies (63, 65) are parallel to each other and to the short side of the press (60). The dies (63, 65) are identical to each other and are adjacent to each other with a distance between them.

Figure 2 shows the same production line from the front. The protective film (2) made of PVC coated stainless-steel sheet (1) in the form of a roll material is cut with shears (30) at the outlet (26) of the transport unit (20) with, with the protective film (2) on top. The workpiece (10) obtained in the feeding station (40) by the cutting process is moved with the carrier unit (44) in the direction of progress and is taken onto a heating mold (53) from the inlet (52) of the heating station (50). The heating die (53) is heated up to a temperature of 66 °C by the electric heaters (54) located in the heating station (50). The workpiece (10) discharged from the heated heating die (53) is transferred to the first pressing mold (65) located in the pressing station (60) with a conveyor belt (70) without any cooling. A movable jaw (63) in the upper jaw structure of the press (61) facing the base (66) descends and forms the workpiece (10) by compressing between a core (68) and the first press mold (64). Then it is opened by moving back up and is picked from the first press mold (64) as a first part (16) and placed in the second pressing mold (65) by being aligned. The workpiece (16) is adjusted approximately equally with the sheet width (w) and the short side of the first pressing mold (64), and the slitting length (L) and the long side perpendicular to it. All other molds are equally sized. The first part (16) is placed in the second pressing mold (65), while another newly arrived workpiece (10) is placed in the first pressing mold (64) that is discharged at the feeding station (40). The movable jaw (63) closes and the cores (68) form the sheet by pressing the corresponding dies (64, 65). The formed workpieces (10) taken from an outlet (69) of the pressing station (60) are cooled down to room temperature. The protective film (2) on the workpieces (10) that reaches room temperature is peeled off.

REFERENCE NUMBERS

1 Stainless steel 54 Electric heater

2 Protective film 56 Temperature measurement sensor 10 Feeders 57 Audible warning unit

12 Long side 58 Output part 14 Short side 60 Pressing station 16 First part 61 Press 20 Transport unit 62 Opening

22 Inlet 63 Movable jaw

23 Bending cylinder 64 First press mold

24 Transport roller 65 Second press mold 26 Outlet 66 Base

30 Shear 68 Core

40 Feeding station 69 Output part 42 Support element 70 Conveyor belt 44 Carrier unit L Slitting length Feeding assembly W Sheet width Heating stations Inlet Heating mold