System and method for rotational moulding

Abstract

A system for the production of an object from a material containing a hardenable base material by rotational moulding includes a die having die walls surrounding a cavity wherein an object is to be formed, the die being provided with a flow channel for conducting a heat exchange fluid and heating or cooling the die, a rotation device for rotating the die, for bringing melted base material into contact with the die walls surrounding the die cavity and forming the object by rotational moulding, and thermal assemblies comprising a heating assembly and a cooling assembly for promoting flow of heat exchange fluids through the flow channel.

Claims

1. A system for the production of an object from a material containing a hardenable base material by rotational moulding, the system comprising: a die having die walls surrounding a cavity wherein an object is to be formed, the die being provided with a flow channel for conducting a heat exchange fluid and heating or cooling the die, a rotation device for rotating the die, for bringing melted base material into contact with the die walls surrounding the die cavity and forming the object by rotational moulding, and thermal assemblies for promoting flow of heat exchange fluids through the flow channel, wherein the flow channel of each die has a first connection for supplying the heat exchange fluid and a second connection for draining off the heat exchange fluid, and wherein said thermal assemblies comprise: a heating assembly at a first position with respect to the rotation device and provided for promoting flow of a heating fluid through the flow channel and thereby heating the die, and a cooling assembly at a second position with respect to the rotation device and provided for promoting flow of a cooling fluid through the flow channel and thereby cooling the die.

2. The system according to claim 1, wherein each thermal assembly comprises a heat exchange fluid store for storing a supply of the respective heat exchange fluid.

3. The system according to claim 1, wherein the heating assembly and the cooling assembly are located on opposite sides of the rotation device.

4. The system according to claim 1, wherein each thermal assembly comprises a connector for connecting the respective thermal assembly to at least one of the first and second connections of the flow channel, wherein a fixed end of the connector is connected to a heat exchange fluid store and a movable end of the connector is equipped with coupling elements for connecting the connector to at least one of the first and second connections of the flow channel.

5. The system according to claim 4, wherein each thermal assembly further comprises a positioning device for positioning the coupling elements with respect to the respective connection of the flow channel.

6. The system according to claim 5, wherein the connector is telescopic and wherein the positioning device is provided for moving a telescopic part of the connector.

7. The system according to claim 5, wherein the positioning device is arranged to rotate the connector around a rotation point R located near the fixed end of the connector.

8. The system according to claim 7, wherein the positioning device is arranged to rotate the connector at a maximum over an angle of 25-500 towards a central axis (X) of the connector.

9. The system according to claim 4, wherein the coupling elements of the connector and the at least one of the first and second connections form a ball joint, wherein the coupling elements of the connector contain the ball of the ball joint, and wherein the at least one of the first and second connections has a complimentary ball recipient of the ball joint.

10. The system according to claim 1, wherein the first and second connections are arranged at one side of the die and wherein coupling elements for coupling the die to the rotation device are arranged at an opposite side of the die.

11. The system according to claim 1, wherein the rotation device is a robotic arm.

12. The system according to claim 1, wherein the die is one of multiple dies that are movably attached to the rotation device.

13. The system according to claim 12, wherein the dies are located on opposite sides of the rotation device.

14. A thermal assembly for promoting flow of a heat exchange fluid through a flow channel for heating or cooling of a die, the thermal assembly forming part of a system defined according to claim 1.

15. A method for the production of an object from a material containing a hardenable base material by rotational moulding using the system according to claim 1, the method comprising the steps of: filling the die cavity with the hardenable base material; moving the die to the first position and heating the material to a first predetermined temperature by promotion of the flow of the heating fluid through the flow channel; rotating the die by the rotation device in such a way that the object is moulded from the material; and moving the die to the second position and cooling the material to a second predetermined temperature by promotion of the flow of the cooling fluid through the flow channel.

16. The method according to claim 15, wherein the die is detached from the rotation device during the cooling step.

17. The method according to claim 15, comprising, prior to the step of filling the die cavity, preheating of the die to a third predetermined temperature lower than the first predetermined temperature.

18. The method according to claim 16, wherein the die is detached from the rotation device during the preheating step.

Description

SUMMARY DESCRIPTION OF THE FIGURES

[0018] The invention will be explained in more detail using a design shown in the figure.

[0019] FIG. 1 shows a simplified presentation in perspective of a system according to the state of the art of technology; and

[0020] FIGS. 2 and 3 show schematic cross sections of a system according to a first and second design of the current invention.

DETAILED DESCRIPTION OF THE FIGURES

[0021] The current invention will be described with regard to particular designs and with reference to certain figures, but the invention is not limited to these and is only determined by the claims. The figures described are only schematic and non-limiting. In the figures, the size of certain element is exaggerated an not drawn to scale for illustrative purposes. The dimensions and the relative dimensions are not necessarily consistent with actual practical designs of the invention.

[0022] In addition, the terms first, second, third and the like are used in the description an claims to differentiate between similar elements and not necessarily to describe a sequential or chronological sequence. The terms are interchangeable under fitting circumstances and the designs of the invention can be applied in sequences other than those described or illustrated here.

[0023] In addition, the terms, top, bottom, over, under an the like in the description and claims are used for illustrative purposes and not necessarily to describe relative positions. The terms used are interchangeable under fitting circumstances and the designs of the invention described can be applied in other orientations than described or illustrated here.

[0024] Furthermore, the various designs, even though called “preferred designs” must be considered rather as a manner of example of how the invention can be designed than as a limitation of the range of the invention.

[0025] The term “comprising”, used in the claims, must not be interpreted as being limited to the resources or steps listed after it. The term does not exclude other elements or steps. The term should be interpreted as specifying for the presence of the listed features, elements, steps or components which are referenced, but does not exclude the presence or addition of one or more other features, elements, steps or components or groups thereof. The range of the expression “a design comprising resources A and B” must thus not be limited to designs that consist only of A and B. The intention is that, with regard to the current invention, only the components A and B of the design are summarized, and the claim must be further interpreted as they also contain equivalents of these components.

[0026] The systems shown in the figures are rotational moulding systems or elements for these, to produce an item made of a material containing a hardenable base material using rotational moulding.

[0027] In the text below, a material referred to as containing a hardenable base material is plastic. However, it must be clear that a hardenable base material can be thermoplastics, thermoset resins, metal, chocolate, fat or any other material that can be moulded or attached using rotational moulding. In particular, composite or fibre reinforced plastic materials or materials consisting of combinations of thermoset materials and fibre materials, such as “short”, “long” or “prepreg” carbon fibres.

[0028] FIG. 1 shows a known system for rotational moulding. The system 1 shown contains multiple assemblies 2, 2′ for rotational moulding and a central control unit 5 for the controlling of the assemblies 2, 2′. Each assembly 2, 2′ includes a die 3, 3′ and a robot or robotic arm 4, 4′ to receive the die 2, 2′ on a free end.

[0029] The functionality of such a system includes in the first step the filling of the die cavity in the die with a pre-weighed quantity of base material, such as in powder form, after which the die is closed. In a subsequent second step, thee die filled with base material is heated to a desired temperature, such as a pre-determined melting temperature of the base material. While heating the die, the die is rotated around its vertical and/or horizontal axis so that the melting base material is brought into contact with the internal walls of the die surrounding the die cavity. The die continues to rotate until all of the base material in it is melted and evenly structured and distributed. In a subsequent third step, the die is cooled with air, water or a combination of the two. In this way, the die and the melted layer of base material are cooled, after which the die is opened and the moulded product removed. After this, the die can be filled again and the process started from the beginning.

[0030] FIGS. 2 and 3 display systems 10, 10′ for producing a plastic object using rotational moulding according to the designs of the invention. The systems displayed 10, 10′ include a robot 100 and a die 200 equipped with a flow channel 214 with an input connection on one end of the flow channel and a drain connection on the other end of the flow channel. The system 10, 10′ also include at least one thermal assembly 310, 320, 330 for input and drainage of a heat exchanging fluid, such as a coolant, on the connections of a flow channel in or around the die wall of the die 200.

[0031] The robot 100 shown includes a robotic arm 110 and a robotic foot 130 connected using a robot body 120. The robotic arm 110 is equipped for connection to at least one die 200.

[0032] The die 200 shown includes a defined cavity 220 through a die wall 210 and the flow channel 214. The die 200 is connected to the robotic arm 110 using coupling elements 111, 211. In the design shown, the coupling elements are designed as complementary coupling elements, with a first coupling elements 111 on the robotic arm 110 and a second coupling element 211 on the die 111.

[0033] Additional possible designs of the die 200 according to the invention are described in WO 2018;69459:A1, which is wholly included here as a reference.

[0034] The thermal assembly 310 shown in FIG. 2 includes a telescopic connector 311, 312 for input of a heat exchange liquid to the input connection of the flow channel 214 ad for draining a heat exchange liquid from the drain connection of the flow channel, and a booster 313 for promoting the flow of the heat exchange liquid through the connector 311, 312 and the flow channel 214. On the free end 318 of the connector 311, 312, there are coupling elements for connecting the connector 311, 312 to the input and drain connections of the flow channel 214.

[0035] The thermal assembly 310 shown here also has positioning elements 314, for example, actuators or (hydraulic) cylinders for positioning the connector on the die 200. The positioning elements 314 can be arranged to turn around the connector toward a rotation point R. In particular, it is possible to turn the connector 311, 312 over an angle of 25° on the XZ plane vertically on the Y axis and over an angle of 50° in the XY plane. The thermal assembly 310 shown also has a heat exchange liquid store 315 in fluid connection with the booster 313, the connector 311, 312 and the coupling elements.

[0036] The functionality of such an assembly includes in a first step the pulling out or extending the telescopic part 311 of the connector when the input and drain connections of the die 200 are within range. In a second step, the coupling elements are attached to the free end 318 of the connector 311, 312 with the connections, such as using a flexible ball coupling in which the free end 318 is equipped with the ball and the connection of a complementary recipient for receiving the ball.

[0037] The system 10′ shown in FIG. 3 according to a second design of the invention includes multiple thermal assemblies according to the invention in the form of a heating element 320 provided in a first position for the heating of the die 200 and a cooling system 330 in a second position for cooling the die 200. In particular, the first and second positions are on opposite sides to the robot 100′ as shown in FIG. 3. The robot 100′ is equipped with a robotic arm 110′ with multiple coupling elements 111 and connected with these to the 200 to form an object from a hardenable base material.

[0038] The thermal assemblies 310, 320, 330 shown can also include a cooling or heat source 337 for the direct or indirect cooling or heating off the heat exchange liquid using a heat exchanger 336.

[0039] In designs not shown, the system 10, 10′ may also include an input assembly to input the first material that contains a first plastic into the die cavity 200 of one or more dies 200 for moulding an object. The assembly may include two or more base material inputs, wherein a first input assembly is provided for the supply of the first die with a first base material and a second input assembly is provided for the supply of a second die with a second base material.

LIST WITH REFERENCE NUMBERS

[0040] 10. System for rotational moulding [0041] 100, 100′. Robot [0042] 110, 110′. Robotic arm [0043] 120. Robot body [0044] 130. Robot foot [0045] 200. Die [0046] 310, 320, 330. Thermal assembly [0047] 311, 321, 331. Telescopic part of the connector [0048] 312, 322, 332. Fixed part of the connector [0049] 313, 323, 333. Booster [0050] 314, 324, 334. Positioning elements [0051] 315, 325, 335. Heat exchange fluid store [0052] 336. Heat exchanger [0053] 337. Thermal source [0054] 318, 328. Free end of the connector