GB2110157A

GB2110157A - Moulding bicycle mud-guards and similar curved objects

Info

Publication number: GB2110157A
Application number: GB08232926A
Authority: GB
Inventors: Jarkko Matti-Juhani Turpeinen
Original assignee: Parton Oy AB
Current assignee: Parton Oy AB
Priority date: 1981-11-25
Filing date: 1982-11-18
Publication date: 1983-06-15
Also published as: DE3242280C2; FI813784L; FI67507C; GB2110157B; DE3242280A1; FI67507B

Abstract

A band of mouldable material (t) from an extruder (2), having the width of the mud-guard or fender to be manufactured, is directed, at a suitable molding temperature, onto a rotating bending drum (5). The band of material moves, pulled by the bending drum (5), under tension, in close contact with the surface of the drum. The tension being produced by means of a velocity difference between the bending drum (5) and the band of material (1) and by means of friction produced by a pressing wheel (7). The cutting member (6) cuts a desired length of the bent band of material travelling on the drum. <IMAGE>

Description

SPECIFICATION A continuous method for the manufacture of fenders and similar curved objects from a moldable material, and an apparatus for carrying out the method The present invention relates to a continuous method for the manufacture of fenders and similar curved objects for example, bicycle mud-guards from a band of a thermally moldable material, for example thermoplast, and in particular to a method in which a band of material adjusted to the molding temperature is molded into a curved shape by means of a rotating bending member and is cut into the desired length by means of a cutting member at a point where the band material has cooled. The invention also relates to an apparatus for carrying out this method.

According to known methods, plastic fenders are manufactured today by the thermal method, the vacuum method, the compression method, or some similar method. The starting material in such a case is a prefabricated sheet which is fed into the machine, in which the sheet is first heated to a suitable treatment temperature, shaped and cooled, whereafter the shaped fender is removed from the machine, the excess edge material is trimmed off, and the edges are finished. Thus, one sheet at a time is fed into the machine, heated, shaped, cooled and taken out of the machine.

U.S. Patent US4,161,383 discloses a continuous method for molding a thermally moldable material into a curved shape, while pattern according to another mold is formed on its surface. The object is, thus, to obtain a pattern parallel to the longitudinal direction of the band on the surface of the object molded into a curved shape. This is achieved by directing a band of material, heated to the molding temperature, between the mantle surface of a drum and a resilient, endless belt which moves in close contact with the mantle surface. When moving between the mantle surface and the said moving belt, the band of material is molded according to the shape of the said opposite surfaces.A cutting member cuts the molded band of material at a suitable point after the molding stage, and from that point the molded piece moves forward, together with the molding drum, supported by support rollers which can be transferred aside, and falls thereafter at the reception point. However, this method does not involve the shaping of curved objects provided with bent edges, and the shaping of such objects would not be possible using the machines according to the U.S.Patent The present invention provides a method for the manufacture of a curved object from an elongate web of thermally moldable material, the method comprising the steps of disposing a length of the web around a rotatable bending member having a particular radius of curvature, the length being at a temperature at which it is moldable; applying tension to the length so as to dispose it in close contact around the bending member such that the length is molded according to the curved shape of the bending member, the width of the bending member substantially corresponding to the distance between the edges of the object to be manufactured, and cutting the web to a desired length by means of a cutting member at a point on the member at which the web has cooled so as to be not moldable.

An embodiment of the present invention will now be described by way of example with reference to the accompanying figures, in which: Figure 1 depicts a side view of the bending of a fender by a method and using an apparatus according to the invention; and Figure 2 depicts a vertical section through the apparatus shown in Figure 1 at 2-2.

The band of material emerges from an extruder 2 and passes via calender rollers 3 and a guide roller 4 onto the bending drum 5, which rotates clockwise.

The bending drum pulls the band of material clockwise, at its own velocity, from the guide roller by means of friction between the band of material and the mantle surface. Close to the cutting member 6 there is located a regulatable pressing wheel 7 by means of which the said friction is produced. The compressive force can be adjusted according to the circumstances. At the point at which the pressing wheel affects the band of material, the band has already solidified. The cutting member 6 cuts the band of material at the predetermined time. After the cutting, the completed fender 8 falls at the reception point and is transferred to the edge-trimming stage.

The new head of the band of material continues its travel clockwise on the bending drum until the head advantageously meets a rail, compressed-air nozzle or similar device, not shown, between the drum and the band of material, the band of material being detached from the drum under the effect of this device. At this stage the cutting device cuts the band of material. The control roll pair 9 has been fitted so as to work on the downwards bent edges of the band of material 1 at approximately the highest point of the drum. In this manner it is possible to adjust precisely the angle of the edges of the fender, which should preferably be 900. The rolls 9 of the control roll pair rotate on shafts radial in relation on the drum, in opposite directions, i.e. in the same direction as the travel direction of the band of material.

The devices for cooling or respectively heating the band of material are not shown in the figures, but they are of a known structure. A suitable molding temperature is about 100"C, which is an exceptionally low molding temperature. In known methods the sheet is heated to a temperature of about 150-180 C.

The band of material emerging from the extruder 2 is in the described case in the form of a straight mat and passes via calender rollers 3, which give a shine to the band. If the starting material is a band of material extruded into the shape of a profile, the calender rollers are omitted and the band of material is directed via suitable guide rollers and cooling devives onto the bending drum.

Whether the band used isa straight, non-profiled band or a profiled band, it is directed onto the bending drum in such a way that the drum is as close to the center of the band as possible. When the tensile force aimed at the band is adjusted to a suitable strength, the edge parts are bent in the former case to a right or nearly right angle in relation to the center area of the band. By means of a suitable tensile force aimed at the center area of the band of material, the edge parts bent downwards in advance are bent into a curved shape, without wrinkles being produced in the edge parts.

The method and device according to the invention have been described above in connection with the manufacture of a plastic fender. However, the same method can also be applied to other moldable and stretchable materials, for example metal.

Preferably the apparatus for carrying out the method according to the invention comprises a rotating bending member, i.e. a drum, onto which a continuous band of material is directed in order to be bent on it. The radius of the bending drum mainly corresponds to the radius of curvature of the fender to be manufactured. However, the magnitude of the tensile force affects the radius of curvature of the fender. When the tensile force increases, the radius of curvature of the fender decreases. The thickness of the material and the temperature also affect the radius of curvature. Thinning of the material reduces the radius, and an increase in temperature increases the radius, owing to the smaller tension requirement. The radius of a completed fender is about 02% smaller than the radius of the drum.The apparatus further includes temperature control members, by means of which the band of material is brought to a suitable temperature for the shaping and the cutting, and a cutting member, by means of which the bent band of material is cut in order to detach the fender. What is essential in the apparatus is the fact that the width of the mantle surface of the bending drum mainly corresponds to the distance between the edges of the fender, and thatthe surface velocity of the mantle surface is greater that the feeding velocity of the band of material, and that between the mantle surface and the band of material there is sufficient friction so that the mantle surface pulls the band of material at its own velocity and produces a state of tension in the band.The friction is produced advantageously by means of a pressing roll having an adjustable compressive force, which affects the bending drum and the band of material running on it. The apparatus further includes a preferably adjustable pair of control rolls, the rolls being located on each side of the bending member and rotating against the downwards bent edges of the band of material, the rotational direction being the same as the direction of the circumferantial motion of the edges. The task of the pair of control rolls is to make precise the angle of the downwards bent edges of the band of material in relation to the straight center area of the fender. The bending of the edges by means of the effect of tension is directly proportional to the thickness of the sheet.The thicker the band of material is, the more the bending angle deviates from 900. An angle of 90t3 was achieved in a trial run, when the thickness of the material was about 1 mm. The thickness of material being 2 mm, the greatest deviation of the angle has been 9% For the purpose of cutting the bent hand of material there is between the drum and the band a rail or a compressed-air nozzle, or some similar device, for detaching the sufficiently cooled band from the surface of the drum. The cutting is by sawing, grinding, slashing, by means of a thermal knife, or some similar method.The cutting device is locked to the drum for the duration of the cutting, or it otherwise closely follows the movement of the drum and the band in order that the cutting can be carried out perpendicularly or in some other desired and reproducible manner.

Preferred embodiments of the present invention provide a method which is speeded up with regard to the known manufacturing method and at the same time reduces the consumption of energy. This is achieved by making the method continuous-working and by combining the stage of shaping the starting material directly with the manufacture of the band of material, whereby the cooling of the band of material is eliminated and, above all, its reheating prior to the shaping stage is eliminated. This continuous method can also be applied to a prefabricated storec material in the form of a roll, in which case, however, it is necessary to reheat the band of material to the molding temperature, but the method is continuous-working.

According to a method according to preferred embodiments of the invention, the band of material to be molded, its width mainly corresponding to the total width of the fender to be manufactures, is guided onto a bending member having the desired radius of curvature, i.e. a drum, on which the band of material, subject to tension and in close contact with the drum mantle, is shaped according to the shape of the curved mantle surface of the drum. The width of the drum mantle corresponds to the distance between the edges ofthefenderto be manufactured.

What is effectively essential in the present method is the stretching which is to be produced in the band of material; under the effect of this stretching the edge parts of the band of material to be bent downwards are bent downwards, thereby producing the shape characteristic of a fender. Correspondingly, when the starting material is a band of material which has been profiled into a shape having edges, the band of material and, together with it, the downwards bent edges are molded into a curved shape without producing wrinkles in the edge parts. This results from the fact that the center area of the band is subjected to tension, whereas the edge parts are left untensioned.

The stretching of the band of material is advantageously achieved in such a way that the surface velocity of the bending drum is greater than the feeding velocity of the band of material, and the friction between the band of material and the mantle surface of the drum is such that the bending drum pulls the band of material forwards by its own velocity. The friction between the mantle surface of the drum and rhe band of material is produced advantageously by means of a pressing roll having an adjustable compressive strength which affects the surface of the band of material. The friction effect can be enhanced from inside the drum by means of suction affecting the mantle surface. The shrinkage in the plastic material in connection with cooling also promotes the adherence of the band to the roller.

When the starting material is a band of material in the form of a straight band, the distance between the downwards bent edges is advantageously made more precise by means of rotating rolls working on these edges.

It is possible, by methods known per Se, to form beams, perforations, holders, or the like in the center area of the band of material by means of molds in the mantle surface of the drum.

The most significant advantage of the method according to the invention is the fact that the shaping of the band of material is directly linked to the manufacture of the band of material. A band of material emerging from an extruder or the like is thus directed, possibly via pressing rollers and guide rollers, onto the bending drum. Depending on the production temperature of the said band of material and its moldable properties, its temperature is adjusted to a suitable level for the subsequent shaping. This has made it possible to eliminate the heating stage, necessary in known methods, prior to the shaping.

The energy required for the actual shaping is also considerably less than the energy required for the shaping of the prefabricated sheet. In addition to energy, also work and work space are saved, since the intermediate storing is eliminated.

Another noteworthy advantage is the savings in raw material. The fender detached from the bending drum is complete except for minor finishing of the edges. Only a small excess part is trimmed from the longitudinal edges, this part having a width of about 1-2 cm. This allowance is added to the width of the starting material for the reason that in the guiding of the band onto the bending drum there may occur an error of 1-2 cm in one direction or the other. Fully precise guiding of the band onto the drum would be more expensive than the said trimming of the edges and the resultant waste. In the methods used so far, a large amount of waste is produced which must be trimmed off and crushed into a suitable form of remelting. This requires machinery, energy and labour. In addition to the wasteto be trimmed off there is produced so called floor waste, which cannot be reused.

A third considerable advantage consists of the high manufacturing speed. By the method according to the invention it is possible to achieve an hourly rate of about 60 fenders, which is many times higher than the rate achieved by a known method.

The strength of thefender produced according to the invention is also greater than the strength of a fender produced by known methods, because the molecular structure of the plastic material is oriented during the tensioning, thus producing a greater strength.

When the starting material is a profile produced by extrusion, having a cross section which already closely corresponds to the cross section of the fender to be produced, the thickness of the material of the profile can be adjusted, for example, by reinforcing the edges or by forming in them a reinforcement edging or by forming longitudinal reinforcements in the profile. The reinforcements can be in the form of longitudinal surface stripes on either side or both sides of the band. The reinforcements may appear only in the bent edge parts, or the reinforcement may consist of a wave pattern formed in a band of even thickness.

When the manufacture starts from a profiled starting material emerging from an extruder, this material is directed onto the bending drum via a cooling apparatus. When the starting material is a non-profiled band of material emerging from an extruder, this material is fed advantageously via calender rollers in order to treat the surface of the fender so as to be shiny, and further via a guide roller or rollers onto the bending drum. If the temperature is not suitable when the band arrives at the bending drum, a suitable heat treatment is added. Between the molding stage and the cutting stage it is necessary to lower the temperature of the band to a level suitable for the subsequent cutting stage.

Claims

1. A method for the manufacture of a curved object from an elongate web of thermally moldable material, the method comprising the steps of disposing a length of the web around a rotatable bending member having a particular radius of curvature, the length being at a temperature at which it is moldable; applying tension to the length so as to dispose in in close contact around the bending member such that the length is molded according to the curved shape of the bending member, the width of the bending member substantially corresponding to the distance between the edges of the object to be manufactured, and cutting the web to a desired length, by means of a cutting member, at a point on the bending member at which the web has cooled so as to be not moldable.

2. A method according to claim 1, wherein the tensioning of the web of material is produced by a difference between the surface velocity of the rotatable bending member and the velocity of feed of the web of material to the bending member, resulting in friction between the bending member and the web of material.

3. A method according to claim 2, wherein the friction between the bending member and the web of material is produced by a roller which applies an adjustable compressive force to the web and urges the web against the surface of the bending member.

4. A method according to any preceding claim, wherein the contact between the web of material and the bending member can be enhanced by means of suction which is applied through that surface of the bending member which can contact the web.

5. A method according to any preceding claim wherein the web of material is formed by an extruder apparatus from which the web can be directed towards the bending member in the form of an elongate sheet, the web being directed by means of rollers, at least one pair of rotatable rollers being disposed one at a respective edge of the bending member, the axis of rotation of each of the rotatable rollers being inclined to that of the bending member, such that the web of material on the bending member is compressed between one rotatable roller and an edge surface of the bending member on either side of the web, such that each edge of the web has a portion which is inclined to the plane of the web.

6. A method according to any one of claims 1 to 4, in which the web of material has a profiled surface produced during extrusion of the web and has substantially the cross section of the material of the curved object to be manufactured, the web being fed either directly from an extruder apparatus or from a storage roll onto the bending member.

7. A method according to any preceding claim wherein, the central region of the length of the web stretches due to the tension in the length to a greater extent than do the edges of the length such that the edges are bent into a curved form together with the central region and are bent so as to be inclined thereto.

8. A method according to any preceding claim wherein the surface of the bending member is shaped so as to produce a corresponding shaped surface on the curved object.

9. An apparatus for the manufacutre of a curved object from an elongate web of a thermally molded able material, the apparatus comprising a rotating bending member having a particular radius of curvature, means for disposing a length of the web around the member, means for maintaining the web at a temperature at which it is moldable, means for applying tension to the length so as to dispose it in close contact around the bending member, the means producing friction between the surface of the bending member and the web of material, so as to produce tension in the central region of the web of material, and a cutting member by means of which the molded length of material can be separated from the web, the width of the surface of the bending member substantially corresponding to the distance between the edges of the object to be manufactured and the surface velocity of the bending member being higher than the velocity of feed of the web of material to the bending member.

10. An apparatus according to claim 9, further comprising a pressing roller which applies an adjustable compressive force to the web and urges the web against the surface of the bending member so as to produce friction at the surface of contact of the bending member and the web of material.

11. An apparatus according to claim 8 or 9, further comprising a control roll pair having an adjustable position, the axis of rotation of each roll being inclined to that of the bending member, each roll being situated on a respective edge of the bending member so as to urge a respective edge of the web to be inclined to the plane of the central region of the web, the rotational direction of each mll being the same as that of the circumferential motion of the respective edge of the bending member.

12. A method for the manufacture of a curved object from an elongate web of moldable material, 6 > e method comprising the steps of disposing a Glil2-11.cI-s7A 4 portion of the elongate web at least partly around a surface of rotation of a rotatable molding member, the temperature of the material of the portion of the elongate web to be used being, prior to molding the portion, at least that required to render the material moldable; aplying a tensile force to the portion so as to mold the portion against the surface of rotation and such that at least one elongate edge of the web moves under the action of the tensile force over an edge of the molding member so as to be inclined to the plane of the web, and cutting a desired length of the molded web so asto form the curved object.

13. Apparatus for the manufacture of a curved object from an elongate web of moldable material, the apparatus comprising a rotatable molding member, means for disposing a portion of the elongate web at least partly around a surface of rotation of the molding member, means for heating the material such that, prior to molding the portion, the temperature of the material of the portion of the elongate web to be used is at least that required to render the material moldable, means for applying a tensile force to the portion so as to mold the portion against the surface of rotation such that at least one elongate edge of the web moves under the action of the tensile force over an edge of the molding member so as to be inclined to the plane of the web and means for cutting a desired length of the molded web so as to form the curved object.

14. A method for the manufacture of a curved object from an elongate web of moldable material substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.

15. Apparatus for the manufacture of a curved object from an elongate web of moldable material substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.

16. Apparatus according to any one of claims 9, 10,11, 13 or 15 in combination with a web of moldable material.

17. A curved object when made by the method of any one of claims 1 to 7, 12 or 14.

18. Acurved objectwhen made bytheapparatus ofanyoneofclaims8,9,1O,11, 13 to 15 or 16.