Triaxial rotary molding machine

Abstract

Rotary molding machine (1) comprising a fixed frame (2), a support arm (3) comprising a first portion (4) and a second portion (5) rigidly joined together, the support arm being rotationally fixed to the rotary frame (2) only at the first portion (4) to rotate about a first rotation axis (101) which is substantially horizontal, a movable frame (6) rotationally fixed to the support arm (3) to rotate about a second rotation axis (102) which is substantially perpendicular to the first rotation axis (101), the movable frame comprising a support portion (7) lying in a plane which is substantially perpendicular to the second rotation axis (102), an actuation system (8) rigidly fixed to the movable frame (6) at the support portion (7) and configured to fix a mold (20) and to rotate the mold (20) about a third rotation axis (103) which is substantially perpendicular to the second rotation axis (102).

Description

Technical Field

[0001] This disclosure relates to a three-axis rotary molding machine. Background Technology

[0002] Rotational molding is a molding technique commonly used to produce products, typically made of plastic materials. It involves either an open cavity (i.e., communicating with the external environment of the product) or a closed cavity (i.e., without such communication). Objects commonly produced using rotational molding include, for example: parts of motor vehicles (e.g., the roofs of trucks, tractors, etc.), boats (e.g., kayaks), containers / tanks (e.g., for fuel, water, etc.), boxes, vases, street furniture, toys, garden equipment, etc.

[0003] Rotational molding typically involves providing a mold with an internal cavity having a shape suitably opposite to the geometry of the product to be manufactured. The mold is loaded with plastic raw material, usually in powder form, and then closed. Once securely attached to the rotational molding machine, the mold rotates about two axes of rotation (usually perpendicular to each other) and is simultaneously subjected to a heating cycle (e.g., by means of an oven in which the mold is placed, by means of resistors arranged on the outer surface of the mold, by means of a heat transfer fluid flowing in suitable channels in the walls of the mold, etc.).

[0004] The rotation of the mold allows the plastic material, in fluid form (e.g., powder), to extend and distribute along the entire useful surface of the mold cavity, so as to cover the entire useful inner surface of the mold with at least one layer of polymer material. At the same time, the heating of the mold allows the polymer raw material to melt and sinter, thereby adhering to the inner surface of the mold and reproducing its shape.

[0005] Then, the mold is cooled and opened, and the product is extracted.

[0006] In the context of rotary molding processes, documents US188845B1, US5022838B1, and US4956135B1 describe rotary molding machines comprising three or more rotary die axes. Summary of the Invention

[0007] In the aforementioned context of the rotary molding process, the applicant believes it is necessary to produce manufactured products with complex geometries and / or extensive extensions along one or more corresponding extension directions in a single rotary molding process.

[0008] In this context, the applicant has recognized that known rotary molding machines have some drawbacks and / or can be improved in one or more aspects.

[0009] For example, the rotary molding machines described in US188845B1, US5022838B1, and US4956135B1 comprise multiple enclosed frames arranged in a series, one inside the other, which, for a given physical size of the entire machine, restrict the free internal volume intended to accommodate the mold. In fact, this free internal volume is primarily determined by the dimensions of the two innermost frames in the series, which must be appropriately sized to allow for the complete rotation of the mold.

[0010] Therefore, in order to use larger molds, it is necessary to increase the size of these frames, and thus the size of the corresponding rotary molding machines, resulting in higher manufacturing and / or operating and / or labor costs, which typically increase with the size of the machine itself (e.g., larger footprint, greater weight, greater energy consumption for machine operation).

[0011] Therefore, the applicant faces the challenge of being able to use molds on rotary molding machines with dimensions that vary over a wide range, while keeping the overall load on the machine constant and limited.

[0012] According to the applicant, the aforementioned problem is solved by a rotary molding machine having one or more of the following characteristics.

[0013] According to one aspect, the present invention relates to a rotary molding machine. The machine includes:

[0014] —Fixed frame;

[0015] —A support arm comprising a first portion and a second portion rigidly connected together, the support arm being rotatably fixed to the fixed frame only at the first portion to rotate about a (substantially) horizontal first axis of rotation, wherein the second portion extends and protrudes from the first portion (substantially) parallel to the first axis of rotation;

[0016] —A movable frame, which is rotatably fixed to the support arm at the second portion only, for rotating about a second rotation axis that is substantially perpendicular to the first rotation axis, the movable frame including a support portion located in a plane substantially perpendicular to the second rotation axis;

[0017] —An actuation system, which is rigidly fixed to the movable frame at the support portion, the actuation system being configured to fix the mold and rotate the mold about a third rotation axis that is (substantially) perpendicular to the second rotation axis.

[0018] According to the applicant, the support arm is rotatably fixed to the fixed frame only at its first portion to rotate about a substantially horizontal first axis of rotation, wherein a second portion extends and protrudes from the first portion substantially parallel to the first axis of rotation, allowing the second portion of the support arm to be cantilevered substantially relative to the fixed frame, in addition to providing the mold with a first degree of rotational freedom during use. Thus, the second portion allows a series of other components of the machine (i.e., the movable frame, the actuation system, and the mold in use) to be supported without simultaneously restricting the space intended for these other components.

[0019] In fact, since the second part protrudes from the first part, the support arm describes an open profile that allows other elements fixed thereto to protrude relative to the first and / or second parts in width and / or length and / or height, so that the overall size of these other elements is not limited by the size of the support arm, but rather allows them to be comparable to the support arm, if not larger than the support arm in general.

[0020] A movable frame, rotatably fixed to a support arm at a second portion, allows rotation about a second rotational axis perpendicular to the first axis of rotation, providing a second degree of rotational freedom for the mold in use. The support portion of the movable frame lies in a plane perpendicular to the second axis of rotation, allowing support for the actuation system and the mold without simultaneously introducing any structural limitations on the shape and / or dimensions of these elements due to the shape of the plane. For example, the planar support portion does not restrict the extension of the actuation system and / or the mold away from the support portion itself, i.e., its height, nor does it restrict the extension of the length and / or width of these elements, so they can protrude from the support portion.

[0021] Finally, the actuation system described above provides a third rotational degree of freedom for the mold during use.

[0022] Thus, three rotational degrees of freedom can be provided for the mold, while restricting the gradual reduction of the useful volume (in contrast to the gradual reduction of the concentric frame size shown in the aforementioned documents US188845B1, US5022838B1 and US4956135B1), and therefore the gradual reduction of the mold, as the rotational degrees of freedom increase, or even canceling this reduction (e.g., providing the machine with a mold whose size is at least equivalent to the size of the movable frame).

[0023] The terms "horizontal" and "vertical" refer to the directions parallel to and perpendicular to the plane supporting the machine under normal operating conditions, respectively.

[0024] By being “substantially horizontal / vertical” relative to the machine's components, it means that the components form an angle of 0°+ / -15° with the horizontal / vertical direction, preferably 0°+ / -10°.

[0025] By being “substantially perpendicular” to geometric elements (e.g., lines, planes, surfaces, etc.), it means that these elements form an angle of 90°+ / -15°, preferably 90°+ / -10°.

[0026] By being “substantially parallel” to the aforementioned geometric elements, it means that these elements form an angle of 0°+ / -15°, preferably 0°+ / -10°.

[0027] In one or more of the foregoing aspects, the present invention may have one or more of the following preferred features.

[0028] Preferably, the support arm has a generally L-shaped profile. Thus, the support arm has a simple shape that maintains the second portion protruding relative to the first portion.

[0029] The invention includes support arms of any shape, such as those in which the first and second portions are straight and connected to each other to form a right angle, or in which at least one portion (e.g., the second portion) has an arcuate shape or has continuous segments, without prejudice to the fact that the second portion extends and protrudes substantially parallel to the first axis of rotation from the first portion.

[0030] Preferably, in at least one configuration of the machine, the first and third rotation axes are (substantially) perpendicular to (and associated with) each other. Preferably, when the mold is fixed to the actuation system, all the first, second, and third rotation axes pass through each other at points located in the substantially central region of the mold. Thus, because each of the three rotation axes passes substantially through the center of the mold (i.e., the center of rotation of the mold about the three axes is located inside the mold), the rotation of the mold about each of the three axes is balanced.

[0031] Preferably, the support arm and / or the movable frame are rotatably fixed to perform any number of full rotations around a corresponding axis of rotation in the same direction of rotation. Preferably, the actuation system is configured to cause the mold to perform any number of full rotations around a third axis of rotation in the same direction of rotation.

[0032] The expression "any number of complete rotations" refers to the rotation of a component about its own axis of rotation. This means that the component can sweep through any angle given the same direction of rotation, and therefore the component can perform an infinite number of complete rotations (n). 360°). Preferably, the rotation of the support arm, the movable frame, and the mold is independent of each other. This allows these components to rotate in different ways, for example, all three components in their entirety (n... (360°) and simultaneous rotation, or only two of them, or the complete rotation of one element.

[0033] Preferably, the movable frame is rotatably fixed to the support arm on the same side of the second portion relative to the first portion. Thus, the first portion of the support arm faces the movable frame, and for example, it can support other components in the machine that must be associated with the mold during the rotary molding process (e.g., the active cooling system of the mold, which will be described better later).

[0034] Preferably, the movable frame is rotatably fixed to the support arm at the end of the second portion away from the first portion. This maximizes the available space of the movable frame relative to the support arm (this space is provided by the distance between the second axis of rotation and the first portion to allow rotation of the movable frame).

[0035] Preferably, the support portion is located at the distal portion of the second portion away from the support arm (for supporting the rotation system).

[0036] Preferably, the support portion, more preferably the entire movable frame, has central symmetry with respect to the second axis of rotation. Thus, the support portion (preferably the entire movable frame) is shaped in a reasonable manner to rotate about the second axis of rotation (e.g., without eccentricity to facilitate its own rotation, e.g., without generating imbalance during rotation and optimizing the overall load of rotation).

[0037] Preferably, the support portion has a circular or approximately circular shape in a plane, and is composed of polygonal shapes (e.g., hexagons, octagons, dodecagons, etc.) with at least six sides. This creates a large support surface for the rotating system.

[0038] In one embodiment, the support portion includes a main extension direction (e.g., it may be substantially rectangular or square). This limits the weight of the movable frame, making it easier to rotate.

[0039] Preferably, the circumferential radius inscribed in the support portion is substantially equal to the length of the useful portion of the second part of the support arm, which extends from the second axis of rotation to the first part of the support arm. This effectively utilizes the rotational space available for the movable frame. The expression "substantially equal" refers to the first quantity relative to the second quantity, meaning that the first quantity is equal to the second quantity plus / minus 15%, more preferably plus / minus 10%.

[0040] Preferably, the actuation system is detachably fixed to the movable frame. Preferably, the movable frame is configured to directly and detachably secure the mold (e.g., by removing the actuation system). This allows the machine to be adapted to different rotary molding production processes, for example, by directly fixing the mold to the movable frame and utilizing only two rotational degrees of freedom (first and second rotational axes).

[0041] Preferably, the actuation system is configured to detachably fix the mold. This allows for the replacement of the mold type depending on the object to be produced.

[0042] Preferably, the actuation system is configured to fix the mold only at its fundamental central portion. This further restricts the gradual reduction of usable volume as rotational freedom increases, because the mold can utilize its entire usable dimension perpendicular to the second axis of rotation, which is compatible with its own rotation about this axis (unlike, for example, an actuation system configured to fix the mold at corresponding ends, which would occupy usable space for the mold along this usable dimension perpendicular to the second axis of rotation). Furthermore, this keeps the ends of the mold free, allowing the extraction of the manufactured product (depending on the shape of the manufactured product, such as taking into account any undercut) given a mold equipped with at least one openable end.

[0043] Preferably, the actuation system includes a base structure that extends away from the support portion of the movable frame, and more preferably substantially parallel to the second axis of rotation. This base structure allows for support of the mold during machine operation.

[0044] Preferably, the base structure has central symmetry with respect to the second axis of rotation. Preferably, the actuation system, more preferably the base structure, is arranged at the basic central portion of the movable frame. Thus, the actuation system (base structure) is arranged in a reasonable manner to facilitate its own rotation about the second axis (e.g., by limiting rotational imbalance and / or inertia).

[0045] In one embodiment, the base structure includes first and second support portions arranged on opposite sides of the movable frame. Thus, for example, the mold can be supported at two separate, distinct areas of the mold.

[0046] Preferably, the actuation system includes a fixed element and a rotating element, the fixed element being rigidly fixed to (or integrated with) the base structure, and the rotating element being rotatably coupled to the fixed element to rotate relative to the fixed element about the third rotation axis and configured to rigidly (preferably detachably) fix the mold. Thus, when the mold is fixed to the rotating element, the rotating element causes the mold to rotate.

[0047] Preferably, the actuation system includes a motor rigidly fixed to the base structure and mechanically connected to the rotating element to rotate the rotating element about the third rotation axis. Thus, the actuation system for actuating the mold is reasonable.

[0048] Preferably, the fixing element has an annular shape around a (corresponding) axis that coincides with the third rotation axis and is shaped to surround the mold. Thus, the fixing element provides rotational guidance for the rotating element without interfering with the mold.

[0049] Preferably, the rotating element has an annular shape around a (corresponding) axis coinciding with the third axis of rotation and is shaped to surround the mold. Thus, the fixing points for the mold are arranged to be distributed around the mold itself (e.g., equidistantly) to facilitate its fixation. For example, the fixing element and the rotating element are two coaxial rings, with the rotating element rotatably fitted to the fixing element (e.g., the fixing element and the rotating element constitute two annular portions of a fifth wheel). Furthermore, the fixing element and the rotating element shaped to surround the mold allow the mold to be fixed to the rotating element while simultaneously extending on both sides relative to the two elements to achieve the aforementioned fixation only at the essentially central portion.

[0050] Preferably, the rotating element comprises a gear mechanically coupled to a pinion of the motor. This connection is thus simple.

[0051] Preferably, the base structure includes a through-hole having an extension substantially parallel to the third axis of rotation. Preferably, the rotating element is arranged at the through-hole, more preferably at the edge of the through-hole. Preferably, the through-hole is shaped to accommodate the rotating mold when the mold is rigidly fixed to the rotating element. Thus, the base structure supports the mold without hindering its extension.

[0052] Preferably, the machine includes a plurality of slip ring systems for transmitting electrical signals from the fixed frame to the mold when the mold is fixed to the actuation system.

[0053] Preferably, the machine includes a first slip ring system operatively inserted between the fixed frame and the support arm, more preferably at the fixed region from the first portion of the support arm to the fixed frame.

[0054] Preferably, the machine includes a second slip ring system operatively inserted between the support arm and the movable frame, more preferably at a fixed region between the movable frame and the second portion of the support arm.

[0055] Preferably, the machine includes a stationary portion of a third slip ring system, which is operatively inserted between the actuation system and the mold when the mold is fixed to the actuation system.

[0056] By referring to a "slip ring system," one means an electromechanical system comprising stationary and rotating parts electrically connected to each other, allowing electrical signals to be continuously transmitted from the stationary part to the rotating part, or vice versa, for any angular position of the rotating part relative to the stationary part. The transmitted electrical signals are typically used to deliver power and / or operating commands to one or more parts of a machine. For example, each slip ring system can be of the following types: with conductive blocks, with liquid metal, with brushes, or non-contact (wireless, utilizing a capacitive connection between two plates of a capacitor, or an inductive connection between two coils).

[0057] Preferably, the machine includes an active cooling system configured to cool the mold. This promotes mold cooling and reduces cycle time.

[0058] Preferably, the active cooling system is fixed to the first portion of the support arm. Preferably, the active cooling system includes a plurality of fans configured to direct corresponding air jets toward corresponding positions on the mold when the mold is fixed to the actuation system. Thus, the mold is cooled in a simple manner by forced convection, without contact or structural complexity of the mold and / or machine (e.g., pipes made on and / or in the mold to cool the mold's resistance by means of refrigerant fluid and / or by means of the Peltier effect arranged along the mold).

[0059] According to one aspect, the present invention relates to a combination including the rotary molding machine according to the invention and a mold fixed to the actuation system for rotating about the first, second and third rotation axes.

[0060] Preferably, the mold includes a fixing element (e.g., a flange) disposed at the substantially central portion of the mold and configured to (removably) fix the mold to the actuation system, more preferably to the rotating element. Thus, the mold is suitably shaped to allow the aforementioned fixation only at its substantially central position.

[0061] Preferably, the mold includes a main extension direction. For example, the mold has a generally cylindrical shape. These types of molds are often used in conjunction with rotary molding machines for making boxes and / or storage containers, such as for water or gas (e.g., the mold dimension along the main extension direction is much larger than the rest of the dimensions). Another example provides a mold for forming canoes and / or kayaks.

[0062] Preferably, as the mold is fixed to the actuation system, the main extension direction of the mold is parallel to the third rotation axis. This limits imbalance during rotation.

[0063] Preferably, the mold includes a rotating portion of a third slip ring system electrically connected to a stationary portion for implementing the third slip ring system. This allows electrical signals to be transmitted from the machine to the mold.

[0064] In one embodiment, the mold includes at least one corresponding openable end, more preferably corresponding openable ends arranged on opposite sides relative to the main extension direction. Thus, for example, the manufactured product can be removed from the mold by opening the end. Arbitrary inserts can also be arranged inside the mold via one or both openable ends, these inserts being co-molded with the manufactured product during the molding cycle. The rotary molding machine of the present invention, including an actuation system configured to fix the mold only at its fundamental central portion (as with molds including a fixing element at their fundamental central portion), is particularly useful when using molds including at least one openable end, because the opening and closing of the openable end and the extraction of the manufactured product are not hindered by the actuation system (e.g., compared to an actuation system configured to fix the mold at the corresponding end).

[0065] In one embodiment, the mold comprises a first half-mold and a second half-mold with separation planes distinct from each other along a direction parallel to the main extension direction. This type of mold is commonly used for constructing canoes and kayaks. In this case, the rotary molding machine according to the invention allows for the limitation (i.e., as described above, by limiting and / or eliminating the gradual reduction in usable volume with increasing rotational degrees of freedom) of geometric constraints relative to the mold length along the main extension direction, thus enabling the production of finished products with large dimensions in a simple and / or rapid manner. Attached Figure Description

[0066] Referring to the accompanying drawings, the features and advantages of the invention will be further illustrated by the following detailed description of some embodiments presented with the aid of non-limiting examples, in which:

[0067] — Figure 1 A perspective view is shown of a combination including a rotary molding machine and a mold according to the present invention;

[0068] — Figure 2 Show Figure 1 A side view of the combination;

[0069] — Figure 3 Show Figure 1 A front view of the combination;

[0070] — Figure 4 Show Figure 1 Details of the combination. Detailed Implementation

[0071] In the accompanying drawings, reference numeral 99 generally indicates a combination including a rotary molding machine 1 and a mold 20.

[0072] For example, machine 1 includes a fixed frame 2 that is stably fixed to a surface (not shown) supporting the machine.

[0073] For example, the machine includes a support arm 3 having a generally L-shaped profile, and the support arm 3 includes a first part 4 and a second part 5 rigidly connected together. Figure 2 ).

[0074] For example, the support arm 3 is rotatably fixed to the fixed frame 2 at only the first part 4 to rotate about a horizontal first axis of rotation 101, wherein the second part 5 extends substantially parallel to the first axis of rotation 101, protruding from the first part 4 and away from the fixed frame 2.

[0075] For example, the first part 4 is straight, while the second part 5 includes a first segment 51 inclined relative to the horizontal direction and a horizontally arranged second segment 52. Figure 2 ).

[0076] For example, the machine 1 includes a movable frame 6 that is fixed to the support arm 3 only at one end 53 of the second part 5 away from the first part 4, so as to rotate about a second rotation axis 102 that is perpendicular to the first rotation axis 101.

[0077] For example, the support arm 3 and the movable frame 6 are rotatably fixed so that, given the same direction of rotation, any number of complete rotations can be performed around the corresponding axis of rotation (i.e., an infinite number of consecutive rotations can be performed—n). 360° (around the corresponding axis of rotation). For example, the rotation of the support arm and the movable frame is independent of each other, and the direction of rotation can be any direction of rotation (e.g., clockwise-counterclockwise rotation can also be alternated).

[0078] For example, the movable frame 6 is rotatably fixed to the support arm 3 on the same side of the second part 5 relative to the first part 4.

[0079] For example, the movable frame 6 includes a support portion 7 located in a plane perpendicular to the second axis of rotation 102, and it is arranged at a distal position to the second portion 5 of the support arm 3 (i.e., at an extreme position where it moves away from the second portion).

[0080] For example, the entire movable frame 6 is centrally symmetric with respect to the second axis of rotation 102 to maintain balance during rotation and optimize the overall load of rotation, and the support portion 7 has a perimeter that approximates a polygonal shape with sixteen sides (hexagon) on the plane.

[0081] In one embodiment (not shown), the support portion includes a main extension direction, and may be substantially rectangular to limit the total weight of the movable frame and facilitate its rotation.

[0082] For example, the radius R of the circle inscribed within the support portion 7 ( Figure 3 The length L is substantially equal to the useful portion of the second part 5 of the support arm, which extends from the second axis of rotation 102 to the first part 4 of the support arm, in order to effectively utilize the rotational space available for the movable frame. Given the central symmetry of the support portion, this circumference is exemplarily centered on the second axis of rotation.

[0083] For example, the machine 1 includes an actuation system 8 rigidly fixed to a movable frame 6 at a support portion 7, the actuation system 8 being configured to fix the mold 20 and rotate the mold 20 about a third rotation axis 103 perpendicular to the second rotation axis 102.

[0084] Exemplary ( Figure 1 The first rotation axis 101 and the third rotation axis 103 are perpendicular to each other and related to each other in at least one configuration of the machine 1, and when the mold 20 is fixed to the actuation system 8, the first rotation axis 101, the second rotation axis 102 and the third rotation axis 103 all pass through the same point P arranged in the basic central region of the mold 20.

[0085] For example, the actuation system 8 is configured to cause the mold 20 to rotate any number of full rotations around the third rotation axis 103 given the same rotation direction.

[0086] For example, the actuation system 8 is detachably fixed to the movable frame 6, and the movable frame 6 is configured (not shown) to directly and detachably fix the mold 20 so that the machine can be adapted to different rotary molding production processes, such as using only two rotational degrees of freedom (first and second rotational axes).

[0087] In one embodiment (not shown), the actuation system is securely fixed to a movable frame (e.g., integrated with the movable frame) to simplify the structure of the machine.

[0088] For example, the actuation system 8 is configured to be detachable and located only at the basic central portion 21 of the mold. Figure 3 Fix the mold at position 20.

[0089] In one embodiment (not shown), the actuation system may be configured to fix the mold at a basic peripheral region of the mold (in other words, the mold cantilever is fixed to an actuation system that is asymmetrical relative to the actuation system itself).

[0090] Exemplary ( Figure 4 The actuation system 8 includes a support plane 91 and a base structure 9. The support plane 91 is arranged on a support portion 7 parallel to the support plane 91, and the base structure 9 extends from the support portion 7 parallel to the second rotation axis 102. Exemplarily, the base structure 9 is arranged at the basic central portion of the movable frame (exemplarily, the second rotation axis 102 passes through the base structure).

[0091] Exemplary ( Figure 4 The base structure 9 has central symmetry with respect to the second axis of rotation 102 and has an extension that is substantially planar (except for the paired support elements 92 arranged perpendicular to the base structure).

[0092] Exemplary ( Figure 4 The actuation system 8 includes a fixed element (not shown) rigidly fixed to the base structure 9 and a rotating element 10 rotatably coupled to the fixed element to rotate relative to the fixed element about a third rotation axis 103 and configured to rigidly and detachably fix the mold (e.g., by means of a plurality of attachment points, such as bolts, to which the mold is fixed).

[0093] Exemplarily, the stationary element and the rotating element 10 have annular shapes surrounding corresponding axes coinciding with the third rotation axis 103, and they are shaped to surround the mold 20. Exemplarily, the stationary element and the rotating element 10 constitute two annular portions of the fifth wheel (i.e., an axial support), while the rotating element 10 is exemplaryly mounted to the outside of the stationary element. The actuation system exemplaryly also includes (not shown) a plurality of rotating elements (e.g., spheres or cylinders, all having corresponding axes parallel to the third rotation axis), the plurality of rotating elements being arranged sequentially at the interface between the stationary element and the rotating element 10 to facilitate their rotation.

[0094] Exemplarily, the actuation system 8 includes a motor 11 rigidly fixed to the base structure 9 and mechanically connected to the rotating element 10 to rotate the rotating element 10 about a third rotation axis. Exemplarily, the rotating element 10 includes a gear 12 arranged at a radially outer position of the rotating element and mechanically coupled to a pinion (not shown) of the motor 11.

[0095] For example, the base structure 9 includes an extended through hole (occupied by the mold in the figure) that is substantially parallel to the third axis of rotation 103.

[0096] For example, the rotating element 10 is arranged at the edge of the through hole, and the through hole is shaped to accommodate (as shown) the rotating mold 20 when rigidly fixed to the rotating element, without hindering the extension of the mold.

[0097] Exemplarily, machine 1 includes a plurality of slip ring systems for transmitting electrical signals from fixed frame 2 to mold 20 when mold 20 is fixed to actuation system 8. More specifically, machine 1 exemplary includes a first slip ring system (not shown) operatively inserted between fixed frame 2 and support arm 3 at a fixed region from a first portion 4 of support arm 3 to fixed frame 2.

[0098] For example, machine 1 includes a second slip ring system (not shown) that is operatively inserted between the support arm 3 and the movable frame 6 at a fixed region from the movable frame 6 to the second part 5 of the support arm.

[0099] Exemplary ( Figure 4 The machine 1 includes a stationary portion 15 (shown schematically only) of a third slip ring system 14, which is operatively inserted between the actuation system 8 and the mold 20 when the mold 20 is fixed to the actuation system.

[0100] Exemplarily, machine 1 includes an active cooling system 16, which is fixed to a first portion 4 of support arm 3 and configured to cool the mold. Exemplarily, the active cooling system 16 includes a plurality of fans 17 (exemplarily six) configured to direct corresponding air jets toward corresponding positions of the mold when the mold is fixed to the actuation system.

[0101] Exemplarily, the mold 20 is fixed to the actuation system 8 (the rotating element 10 fixed to the actuation system 8) to rotate about a first rotation axis 101, a second rotation axis 102, and a third rotation axis 103. Exemplarily, the mold 20 includes a rotating portion 22 (e.g., a plurality of conductive tracks) of a third slip ring system 14 electrically connected to a stationary portion 15 to realize the third slip ring system 14 when the mold is fixed to the actuation system 8.

[0102] Exemplarily, the mold 20 includes a retaining element 23 (e.g., an annular flange) disposed at a substantially central portion 21 of the mold 20 and configured to detachably secure the mold to the rotating element 10. In the example shown, the flange is bolted to the rotating element along the entire annular extension.

[0103] Exemplary ( Figure 3 The mold 20 includes a main extension direction 104, which is arranged parallel to the third rotation axis 103 when the mold 20 is fixed to the actuation system 8.

[0104] Exemplary ( Figure 3 The mold includes a cylindrical central portion 24 having an axis parallel to the main extension direction 104 and corresponding openable ends 25 (shown schematically) having a spherical cap shape and arranged on opposite sides relative to the main extension direction. Exemplarily, the outer surface of the mold has central symmetry with respect to a third axis of rotation 103, on which the main extension direction 104 is located.

[0105] In use, assembly 99 exemplarily allows for a rotary molding process to be performed for the production of cylindrical tanks typically used for water. The openable end 25 of the mold allows for the placement of any inserts (such as metal reinforcing elements) within the mold, which are co-molded with the finished product during the molding cycle, and the finished product is removed at the end of the cycle (given that the tank has no undercut).

[0106] Fixing the mold to the actuation system only at the basic central part 21 of the mold does not impede the movement of the end parts, allowing them to open and close without moving the entire mold and / or other parts of the machine, and it allows the finished product to be extracted while leaving the mold in place (e.g., fixed to the actuation system) for the next molding cycle, thereby reducing cycle time.

[0107] Furthermore, the actuation system, configured to fix the mold only at the basic central portion 21, allows for further restriction of the reduction in usable volume as the rotational degrees of freedom granted to the mold increase. In effect, the mold can thus further utilize the entire usable dimension perpendicular to the second axis of rotation 102 (compatible with the mold's rotation about the second axis of rotation). This usable dimension is essentially equal to the diameter of the circumference inscribed with the support portion 7. Figure 3 ).

[0108] It should be noted that, referring to a comparative machine similar to the machine according to the invention (e.g., having similar dimensions and overall load) but without an actuation system (i.e., only having first and second axes of rotation), in order for the mold to rotate about the respective main extension direction, it is necessary to arrange the mold directly fixed to the support portion and to arrange the main extension direction substantially coincide with the second axis of rotation. In this configuration, because the mold must necessarily be included in the rotational load of the first portion of the support arm, the useful dimension usable by the mold along the second axis of rotation is substantially equal to the distance between the ends of the support portion and the first portion of the support arm (away from the second portion). Furthermore, if the mold includes two respective openable ends, this useful dimension parallel to the second axis of rotation is further reduced because it is necessary to clear the space near the support portion in order to open the end near the movable frame (thus the mold is spaced apart from the support portion). Thus, in the comparative machine, the useful length for the mold along the second axis of rotation 102 is less than the useful length for the mold along the third axis of rotation 103 according to the invention (see... Figure 3 Therefore, the machine according to the invention allows for rotations about three axes, but alternatively, the rotation axis 102 can be locked and a configuration can be assumed in which only rotations about axes 101 and 103 are used, which remain perpendicular to each other (e.g., a combination of back-and-forth oscillations about axis 101 and continuous rotations about axis 103, referred to in jargon as "rock and roll") is used, but with a longer die than the aforementioned comparative machine, which does not have axis 103 and in which the die must be arranged parallel to the rotation axis 102 to perform the aforementioned rock and roll.

Claims

1. Rotational molding machine (1), the machine (1) comprising: - a fixed frame (2); - a support arm (3) comprising a first portion (4) and a second portion (5) rigidly joined together, the support arm (3) being rotationally fixed to the fixed frame (2) only at the first portion (4) to rotate about a first rotation axis (101) which is horizontal, wherein the second portion (5) extends from the first portion (4) parallel to the first rotation axis (101); - a movable frame (6) rotationally fixed to the support arm (3) at the second portion (5) to rotate about a second rotation axis (102) which is perpendicular to the first rotation axis (101), the movable frame (6) comprising a support portion (7) lying in a plane perpendicular to the second rotation axis (102); - an actuation system (8) rigidly fixed to the movable frame (6) at the support portion (7), the actuation system (8) being configured to fix a mold (20) and to rotate the mold (20) about a third rotation axis (103) which is perpendicular to the second rotation axis (102), wherein the actuation system (8) is configured to fix the mold (20) with a main extension direction (104) of the mold (20) parallel to the third rotation axis (103), wherein the actuation system (8) comprises a base structure (9) which extends away from the support portion (7) of the movable frame (6); wherein the actuation system (8) comprises a fixed element rigidly fixed to the base structure (9) and a rotating element (10) rotationally coupled to the fixed element to rotate about the third rotation axis (103) with respect to the fixed element and configured to rigidly fix the mold (20); and wherein the fixed element has an annular shape about a respective axis which coincides with the third rotation axis (103) and it is shaped to surround the mold (20).

2. The machine (1) according to claim 1, characterized in that, The support arm (3) has an L-shaped profile, wherein, in at least one configuration of the machine, the first rotation axis (101) and the third rotation axis (103) are perpendicular to each other, and wherein, when the mold (20) is fixed to the actuation system (8), the first rotation axis (101), the second rotation axis (102) and the third rotation axis (103) pass through each other at a point (P) arranged in a central region of the mold (20).

3. The machine (1) according to claim 1 or 2, characterized in that, Said support arm (3) and / or said movable frame (6) are rotationally fixed to perform any number of complete rotations around the respective rotation axis (101, 102) given the same direction of rotation, wherein said actuation system (8) is configured to rotate said mold (20) in any number of complete rotations around said third rotation axis (103) given the same direction of rotation.

4. The machine (1) according to claim 1 or 2, characterized in that, Said movable frame (6) is rotationally fixed to said support arm (3) at the same side of said second portion (5) with respect to said first portion (4) and at the end (53) of said second portion (5) distanced from said first portion (4), wherein said support portion (7) is arranged at the distal portion of said second portion (5) distanced from said support arm, wherein said support portion (7) has a central symmetry with respect to said second rotation axis (102) and it has a circular shape or a polygonal shape with at least six sides in a plane, and wherein, wherein the radius (R) of the circumference having said support portion (7) inscribed is equal to the length (L) of the useful portion of said second portion (5) of said support arm (3) which extends from said second rotation axis (102) up to said first portion (4) of said support arm (3).

5. The machine (1) according to claim 1 or 2, characterized in that, Said actuation system (8) is removably fixed to said movable frame (6), wherein said actuation system (8) is arranged at a central portion of said movable frame (6), wherein said movable frame (6) is configured to directly and removably fix said mold (20), and wherein said actuation system (8) is configured to removably and only at a central portion (21) of said mold (20) fix said mold (20).

6. The machine (1) according to claim 1 or 2, characterized in that, Said base structure (9) has a central symmetry with respect to said second rotation axis (102), and wherein said actuation system (8) comprises a motor (11) rigidly fixed to said base structure (9) and mechanically connected to said rotating element (10) to rotate said rotating element (10) around said third rotation axis (103).

7. The machine (1) according to claim 6, characterized in that, Said rotating element (10) has an annular shape around a respective axis coinciding with said third rotation axis (103) and it is shaped to surround said mold (20), wherein said rotating element (10) comprises a gear (12) mechanically coupled to a pinion of said motor (11), wherein said base structure (9) comprises a through hole having an extension parallel to said third rotation axis (103), wherein said rotating element (10) is arranged at said through hole, and wherein said through hole is shaped to accommodate said mold (20) in rotation when said mold (20) is fixed to said rotating element (10).

8. The machine (1) according to claim 7, characterized in that, Said rotating element (10) is arranged at the edge of said through hole of said base structure (9). Said support arm (3) and / or said movable frame (6) are rotationally fixed to perform any number of complete rotations around the respective rotation axis (101, 102) given the same direction of rotation, wherein said actuation system (8) is configured to rotate said mold (20) in any number of complete rotations around said third rotation axis (103) given the same direction of rotation. Said movable frame (6) is rotationally fixed to said support arm (3) at the same side of said second portion (5) with respect to said first portion (4) and at the end (53) of said second portion (5) distanced from said first portion (4), wherein said support portion (7) is arranged at the distal portion of said second portion (5) distanced from said support arm, wherein said support portion (7) has a central symmetry with respect to said second rotation axis (102) and it has a circular shape or a polygonal shape with at least six sides in a plane, and wherein, wherein the radius (R) of the circumference having said support portion (7) inscribed is equal to the length (L) of the useful portion of said second portion (5) of said support arm (3) which extends from said second rotation axis (102) up to said first portion (4) of said support arm (3). Said actuation system (8) is removably fixed to said movable frame (6), wherein said actuation system (8) is arranged at a central portion of said movable frame (6), wherein said movable frame (6) is configured to directly and removably fix said mold (20), and wherein said actuation system (8) is configured to removably and only at a central portion (21) of said mold (20) fix said mold (20). Said base structure (9) has a central symmetry with respect to said second rotation axis (102), and wherein said actuation system (8) comprises a motor (11) rigidly fixed to said base structure (9) and mechanically connected to said rotating element (10) to rotate said rotating element (10) around said third rotation axis (103). Said rotating element (10) has an annular shape around a respective axis coinciding with said third rotation axis (103) and it is shaped to surround said mold (20), wherein said rotating element (10) comprises a gear (12) mechanically coupled to a pinion of said motor (11), wherein said base structure (9) comprises a through hole having an extension parallel to said third rotation axis (103), wherein said rotating element (10) is arranged at said through hole, and wherein said through hole is shaped to accommodate said mold (20) in rotation when said mold (20) is fixed to said rotating element (10). Said rotating element (10) is arranged at the edge of said through hole of said base structure (9).

9. The machine (1) according to claim 1 or 2, characterized in that, comprises a plurality of slip ring systems for transmitting electrical signals from the fixed frame (2) to the mold (20) when the mold (20) is fixed to the actuation system (8), wherein the machine (1) comprises stationary parts of a first slip ring system, of a second slip ring system and of a third slip ring system, the first slip ring system being operatively interposed between the fixed frame (2) and the support arm (3), the second slip ring system being operatively interposed between the support arm (3) and the movable frame (6), the third slip ring system being operatively interposed between the actuation system (8) and the mold (20) when the mold (20) is fixed to the actuation system (8), wherein the machine (1) comprises an active cooling system (16) fixed to the first portion (4) of the support arm (3) and configured to cool the mold (20), and wherein the active cooling system (16) comprises a plurality of fans (17) configured to direct respective air jets towards respective positions of the mold when the mold is fixed to the actuation system.

10. A combination (99) comprising a rotary molding machine (1) according to any preceding claim and the mold (20), the mold (20) being fixed to the actuation system (8) to rotate around the first rotation axis (101), the second rotation axis (102) and the third rotation axis (103).

11. The combination (99) according to claim 10, characterized in that The mold (20) comprises a fixing element (23) arranged at a central portion (21) of the mold (20) and configured to fix the mold (20) to the actuation system (8), wherein the mold (20) comprises the main direction of extension (104), wherein the main direction of extension (104) of the mold is parallel to the third rotation axis (103) when the mold (20) is fixed to the actuation system (8), wherein the mold comprises a rotating portion (22) of the third slip ring system (14) operatively interposed between the actuation system (8) and the mold (20), the rotating portion (22) being electrically connected to a stationary portion (15) of the third slip ring system (14) for implementing the third slip ring system (14), wherein the mold comprises at least one respective openable end portion (25), or wherein the mold comprises a first half-mold and a second half-mold different from each other along a separation plane parallel to the main direction of extension.

12. The combination (99) according to claim 11, characterized in that The at least one respective openable end portion (25) is a respective openable end portion (25) arranged at an opposite side with respect to the main direction of extension (104).

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