EP3842167B1

EP3842167B1 - Mold extraction device from mold string conveyor

Info

Publication number: EP3842167B1
Application number: EP19383209.4A
Authority: EP
Inventors: Pello Larrañaga
Original assignee: Castirgalu SA
Current assignee: Castirgalu SA
Priority date: 2019-12-27
Filing date: 2019-12-27
Publication date: 2022-08-17
Anticipated expiration: 2039-12-27
Also published as: EP3842167A1; PL3842167T3; PT3842167T; HUE060469T2; MX2022007938A; ES2930408T3; WO2021130297A1

Description

TECHNICAL FIELD

The present invention generally belongs to the field of casting production using breakable mold materials.
The object of the invention is a mold string conveyor having one or more gravity-driven mold extraction devices allowing for the extraction of molds in different positions along the conveyor.

STATE OF THE ART

Casting manufacture is often carried out using breakable molds produced in a mold station. The molds are then transported to a pouring station where each mold cavity, which usually corresponds to the space between two adjacent mold parts in a mold string, is filled with the melt for forming a part. Finally, after a cooling process taking place along a particular stretch of the mold string conveyor, the castings are extracted from within the molds at an end of the mold string conveyor. The molds are then transformed into mold raw material again for the subsequent production of new molds.
Throughout the whole process, the molds form a mold string and are advanced stepwise by means a mold string conveyor. The molding chamber, the pouring station, as well as any additional device provided along the mold string conveyor, operate intermittently in synchronism with the stepwise advancement of the molds along the mold string conveyor. During the stepwise forward movement of the mold string, mold integrity must be assured until the castings are sufficiently cooled for break-out from the molds. In particular, in the case of vertical parting surface molds, the mold string conveyor must ensure that no shifting, distortion or displacement of molds occurs.
Currently, for the first stretch of the mold string conveyor, a first high-precision type of transport system is employed. A less precise, lighter transport system is used for the second stretch of the mold string conveyor. High-precision transport systems are, e.g. movable longitudinal side rails and walking beam, while an example of a low-precision transport system is an endless belt conveyor. These transport systems are known in the art, see, e.g. document US 7,032,641 .
Sometimes, molds must be extracted before reaching the end the mold string conveyor, e.g. from a stretch of the conveyor between the pouring station and the extraction station where cooling of the castings takes place. Indeed, in certain cases it is interesting to extract molds before they are completely cool for research purposes in connection with the cooling process. Occasionally, faulty molds or molds containing faulty castings must be extracted from a specific position along the mold string. In any case, there are a number of systems specifically designed for extracting the castings from within the mold string.
Document US 4,082,135 discloses the removal of the castings from any location along the mold string conveyor using a gripping device. The gripping device penetrates the molds from above and grips the casting along with a lump of mold material adhered to said casting.
Document US 3,659,701 discloses different mold extraction locations via movable conveyors. The transport surface comprises spaced rails and movable conveyors are positioned in line by telescoping the corresponding rails at their ends. This system is compatible with the abovementioned high-precision, longitudinal side rail transport system.
Document EP 1,752,239 discloses a process for removing the casting from the mold by dissolving the binder in the mold.
Document US 6,092,585 discloses a method comprising two conveyors at different speeds. When the mold string transported by the low-speed conveyor reaches the high-speed conveyor, consecutive molds separate. A gripping device then extracts the exposed castings from within the separation gap between consecutive molds.
Patent documents FR 1486510 and JP S 5638304 B further disclose a mold string conveyor with a mold extraction device, wherein the mold extraction is provided with a trapdoor.
However, there is still a need in the art for a mold string conveyor having one or more simpler and more convenient extraction devices which allows the continuous extracting of the molds at certain locations.

DESCRIPTION OF THE INVENTION

The mold string conveyor of the present invention, which is disclosed in appended claim 1, solves the aforementioned drawbacks by comprising one or more mold extraction devices allowing for the extraction of particular molds or for the continuous extraction of molds at certain locations from the mold string. Indeed, a mold string conveyor is configured for providing support for a mold string while stepwise displacing said mold string forward along a displacement path. The mold string conveyor of the invention further comprises at least one extraction device, where the extraction device comprises an inferior trapdoor provided along the displacement path between a first stretch and an adjacent, second stretch of said mold string conveyor. Therefore, any mold located on the trapdoor falls down out of the mold string when said trapdoor is in open position. Besides, the mold extraction device further comprises trapdoor mold conveying means configured for stepwise displacing the portion of the mold string located on the trapdoor forward along the displacement path in synchronism with first mold string conveying means of the first stretch of the mold string conveyor and second mold string conveying means of the second stretch of the mold string conveyor.
In a preferred unclaimed embodiment of the invention, the trapdoor comprises a plate horizontally hinged to an end of the first stretch of the mold string conveyor in perpendicular to the direction of the displacement path. Therefore, the trapdoor alternates between a closed position where the plate is oriented horizontally for providing support to a portion of the mold string located on the trapdoor, and an open position where the plate is inclined downwards for allowing molds in the portion of the mold string located on the trapdoor to fall down.
In a further preferred embodiment, the trapdoor comprises a first horizontal portion providing support for the mold string in a gap between the end of the plate when in the horizontal position and the end of the second stretch of the mold string conveyor thus minimizing the gap between the end of the following stretch of the mold string conveyor and the trapdoor. This embodiment is advantageous in that the horizontal portions avoid any mold raw material from falling down through the gap between the trapdoor and the ends of the following stretch of the mold conveyor. Note that the molds are commonly made of small grain size particles, so in case no horizontal portions were present the mold raw material could fall through the gap distorting the layout of the mold with the risk of losing its integrity.
Preferably, the mold string conveyor of the invention comprises an actuation means causing the trapdoor to alternate between the open position and the closed position. In principle, the actuation means could be of any type, such as e.g. based on electric motors or the like. However, in a further preferred embodiment of the invention, the actuation means comprise pneumatic or hydraulic cylinders connected to the plate.
In a still further preferred embodiment of the invention, the mold string conveyor further comprises a shield plate extending essentially downwards from an end of the second stretch of the mold string conveyor for guiding the falling molds when the trapdoor is in the open position. The shield plate thus ensures that molds falling downwards through the trapdoor land on a predetermined desired position under the mold string conveyor. The shield plate further ensures that the falling molds do not hit any part of the mold string conveyor located below, such as support legs, beams, or endless belt rotating cylinders.
In a further preferred embodiment, the mold string conveyor further comprises a receiving chute situated under the trapdoor for receiving the falling molds when the trapdoor is in the open position. The receiving chute could be of any kind provided it receives the falling molds when the trapdoor opens. The chute may additionally comprise a vibrating horizontal grid for breaking up the molds into raw mold material, thus releasing castings embedded inside the molds. Thus, the falling molds land in the chute and the vibrating horizontal grid breaks up the molds and converts them into raw material, e.g. sand. The mold raw material falls down through the vibrating grid, while castings present inside the molds accumulate on the horizontal grid.
More preferably, the receiving chute is connected to a dedicated casting conveyor configured for transporting away the castings. Even more preferably, the mold string conveyor further comprises a lower conveyor situated under the receiving vibrating horizontal grid for receiving the raw mold material that drops down through the vibrating horizontal grid. The raw mold material, e.g. sand, can then be transported to a device where it is more thoroughly broken up for being subsequently converted into new molds again. Therefore, by means of these dedicated casting conveyor and lower mold raw material conveyor, the castings and the molds can be automatically separated and transported to respective stations.
In a still further preferred embodiment of the invention, although the trapdoor mold conveying means could be of any type, it preferably comprises movable longitudinal side rails mechanically synchronized with the first mold string conveying means and the second mold string conveying means.
In a particular embodiment where the first mold string conveying means are movable longitudinal side rails and the second mold string conveying means is an endless belt, the trapdoor movable longitudinal side rails are prolongations of the movable longitudinal side rails of the first mold string conveying means. That is, the trapdoor movable longitudinal side rails can be produced merely by providing longer movable longitudinal side rails in the first stretch of the mold string conveyor. Synchronization between them is thus guaranteed without needing to perform any additional mechanical connection.
In an alternative particular embodiment where the first conveying means is a different high precision transport system as walking beam, or where the first and second mold string conveying means are respective endless belts, the trapdoor movable longitudinal side rails comprise dedicated side rails. Therefore, in this embodiment an additional mechanism is provided for stepwise transporting forward the portion of the mold string situated on the trapdoor. This additional mechanism is mechanically connected to the mold string conveying means of the first and second stretch of the mold conveyor for ensuring a suitable synchronism therebetween.
Preferably, when the trapdoor movable longitudinal side rails are dedicated side rails, the mold string conveyor of the invention further comprises a second horizontal portion providing support for the mold string in a gap between the end of the first stretch of the mold string conveyor and the trapdoor. In the same way as the first horizontal portion of the trapdoor, this second horizontal portion ensures that no raw material, e.g. sand, falls down through the gap present between the trapdoor and the first stretch of the conveyor.
Finally, in still another preferred embodiment of the invention, the mold string conveyor comprises detection means configured for detecting the position of a particular mold along the mold string conveyor and control means configured for opening the trapdoor when said particular mold is located on the trapdoor.

BRIEF DESCRIPTION OF THE DRAWINGS

To complete the description and in order to provide for a better understanding of the invention, a set of drawings is provided. Said drawings form an integral part of the description and illustrate an embodiment of the invention, which should not be interpreted as restricting the scope of the invention, which is restricted by appended claims 1-14, but just as an example of how the invention can be carried out. The drawings comprise the following figures:

Fig. 1 shows a prior art mold string conveyor having a first stretch with movable longitudinal side rails and a second stretch with endless belt conveyor.
Fig. 2 shows a first example of the present invention with the trapdoor in the closed position.
Fig. 3 shows the first example of the present invention with the trapdoor in the open position.
Fig. 4 shows a second example of the present invention with the trapdoor in the closed position.
Fig. 5 shows the second example of the present invention with the trapdoor in the open position.

DESCRIPTION OF A WAY OF CARRYING OUT THE INVENTION

Figs. 1 shows a prior art mold string conveyor (200) having a first stretch with movable longitudinal side rails and a second stretch with endless belt conveyor.
The movable longitudinal side rails mechanism of the first stretch comprises a plurality of lower longitudinal plates (210) providing support for the mold string (300) along the displacement direction (DD). The mold string (300) thus slides on these plates (210) it is are forced to move forward towards the second stretch. Movable longitudinal side rails (220) are provided at both sides of the mold string (300) supported by the lower plates (210). The movable longitudinal side rails (220) sequentially grip the mold string (300), displaces the mold string (300) forward a predetermined distance, then releases the mold string (300), and finally returns to its original position. Fig. 1a shows a first situation where the movable longitudinal side rails (220), in a forward position, are still gripping the mold string (300) after having advanced the predetermined distance. Then, as shown in Fig. 1b, the movable longitudinal side rails (220) move outwards, i.e. horizontally in perpendicular to the displacement direction (DD). The mold string (300) is thus released. In a subsequent step shown in Fig. 1c, the movable longitudinal side rails (220) move backwards, i.e. in a direction opposite the displacement direction (DD), therefore returning to an original back position. Since the mold string (300) is not gripped by the movable longitudinal side rails (220), it remains in place during this step. Fig. 1d shows the movable longitudinal side rails (220) again moving horizontally inwards in perpendicular to the displacement direction (DD), thus gripping the mold string (300) again. Finally, as shown in Fig. 1e, the movable longitudinal side rails (220) move forward the predetermined distance. The mold string (300), gripped by the movable longitudinal side rails (220), is displaced forward the predetermined distance (in the figure the distance corresponding to twice the molds thickness) along the displacement direction (DD). This mechanism therefore ensures that the mold string (300) moves stepwise forward along the first stretch of the mold string conveyor (200).
The second stretch of the mold string conveyor (200) is based on an endless belt mechanism that moves stepwise in synchronization with the movable longitudinal side rail conveyor disclosed above. More particularly, the movable longitudinal side rails (220) of the first stretch are mechanically connected with side beams (230) of the second stretch by means of a connection bar (250) to assure full synchronism. The side beams (230) are provided in parallel to the displacement direction (DD) at both sides of an endless belt (240) providing support for the mold string (300). The side beams (230) of the second stretch, driven by the movable longitudinal side rails (220), alternatively move forward and backward. However, unlike the movable longitudinal side rails (220) of the first stretch, the side beams (230) do not move outwards or inwards in perpendicular to the displacement direction (DD). A known mechanism allows for the side beams (230) to selectively grip the side portions of the endless belt (240). When the side beams (230) move forward, as shown in Fig. 1e, they grip the endless belt (240) causing it to advance the predetermined direction disclosed above. When the side beams (230) move backwards, as shown in Fig. 1c, they do not grip the endless belt (240), and therefore it remains in place.

First example

Figs. 2 and 3 show a first example of the mold string conveyor (1) of the present invention. The mold string conveyor (1) is formed by a first stretch (11) having first mold string conveying means based on movable longitudinal side rails (111) and a second stretch (12) having second mold string conveying means based on an endless belt (121). The actuation and synchronization mechanism driving these mold conveying means is similar to that disclosed above in connection with Fig. 1.
In the first stretch (11) of the mold string conveyor (1), movable longitudinal side rails (111) are provided at both sides of the mold string (300) in parallel to the displacement direction (DD). The movable longitudinal side rails (111) are driven by a mechanism comprising a pneumatic cylinder (112) that causes them to follow the movement cycle disclosed above in connection with Fig. 1: the movable longitudinal side rails (111) grip the mold string (300), then move forward the predetermined direction, then open outwards for releasing the mold string (300), and finally return back to the initial position. Particularly, in Fig. 2 the movable longitudinal side rails (111) are gripping the mold string (300) while in the back position (as in the situation shown in Fig. 1d).
In the second stretch (12) of the mold string conveyor (1), the mold string (300) is resting on an endless belt (121). Side beams (122) are provided at both sides of the endless belt (121). The side beams (122) are mechanically connected to the movable longitudinal side rails (111), such that the movable longitudinal side rails (111) cause the side beams (122) to move alternatively forward and backward along the displacement direction (DD). A known mechanism allows for the side beams (122) to selectively grip the side portion of the endless belt (121). When the movable longitudinal side rails (111) move forward, the side beams (122) are caused to also move forward while gripping the endless belt (121). The mold string (300) thus synchronously moves forward the predetermined direction both in the first stretch (11) and in the second stretch (12) of the conveyor (1). When the movable longitudinal side rails (111) move backwards, the side beams (122) are caused to also move backwards. However, the side beams (122) do not grip the endless belt (121) during the backward displacement. The mold string (300) thus does not move during this step.
This conveyor (1) further comprises an extraction device comprising a trapdoor (2). The trapdoor (2) is provided between the first stretch (11) and the second stretch (12). The trapdoor (2) comprises a plate (21) hinged to an end of the first stretch (11) of the conveyor (1) along a horizontal direction in perpendicular to the displacement direction (DD). The plate (21) can therefore adopt a closed position where it is horizontal, as shown in Fig. 2, and an open position where it is oriented essentially downwards, as shown in Fig. 3. In the closed position, the plate (21) is flush with the lower horizontal plates (not shown in Figs 2-3, but disclosed in connection with Fig. 1) providing support to the mold string (300) in the first stretch (11) and with the endless belt (121) providing support to the mold string (300) in the second stretch (12). Therefore, the mold string (300) moves normally supported by the plate (21) when in the horizontal position. When the trapdoor (2) opens, the plate (21) opens downwards, and any mold (310) resting on the plate (21) when in the horizontal position will fall down. The trapdoor (2) opens and closes driven by a pneumatic cylinder (22) having an actuation end connected to the plate (21) and a fixed end connected to a portion of the structural support of the conveyor (1) or to the floor.
The mold extraction device further comprises mold string conveying means for ensuring that molds (310) resting on the plate (21) when in the horizontal position move normally forward along with the rest of the mold string (300). In this first example, the trapdoor mold string conveying means comprises movable longitudinal side rails (6). These trapdoor movable longitudinal side rails (6) are merely a prolongation of the movable longitudinal side rails (111) of the first stretch (11) of the conveyor (1). Therefore, synchronization between them is ensured without the need to implement any additional synchronization mechanism.
The conveyor (1) additionally comprises a shield plate (3) extending essentially downwards from an end of the second stretch (12) of the conveyor (1). When the molds (310) fall through the trapdoor (2), the shield plate (3) ensures that they don't hit any of the cylinders of the endless belt (121). The shield plate (3) further directs the falling molds (310) towards a receiving chute (4). The trapdoor (2) further comprises an first horizontal portion (31) closing a gap between an end of the endless belt (121) of the second stretch (11) and a free end of the plate (21), thus avoiding deformations in the molds (see Fig. 6).
The receiving chute (4) is configured as a container for collecting the molds (310) extracted from the mold string (300) through the trapdoor (2). The base of the receiving chute (4) comprises a vibrating horizontal grid (not shown) that causes the molds (310) to break up, thus turning into mold raw material. The mold raw material falls through the grid and is collected by a lower conveyor (5) situated under the receiving chute (4). The lower conveyor (5) is parallel to the mold string conveyor (1), ending in a machine where the mold raw material along with mold raw material from the mold string (300) are thoroughly broken up into small grain size mold raw material for the subsequent production of new molds. On the other hand, a dedicated casting conveyor (not shown) is provided for extracting castings released from the molds inside the receiving chute (4) and for transporting them towards a subsequent station.

Second example

Figs. 4 and 5 show a second example of the mold string conveyor (1) of the present invention where the first and second mold string conveying means of the first stretch (11) and the second stretch (12) of the conveyor (1) comprise endless belts (121). The mold extraction device comprises a trapdoor (2) provided between the first stretch (11) and the second stretch (12) of the conveyor (1). As in the first example, when the plate (21) of the trapdoor (2) opens downwards driven by the pneumatic cylinder (22), any mold (310) resting on said plate (21) when in the horizontal position falls down through the trapdoor (2) towards a receiving chute (4). A shield plate (3) directs the falling molds (310) towards the receiving chute (4) and ensures that no cylinder of the endless belt (121) is hit. The trapdoor (2) further comprises a first horizontal portion (31) closing a gap between the end of the second stretch (12) of the conveyor (1) and the free end of the trapdoor plate (21). A vibrating grid provided at the bottom of the receiving chute (4) breaks up the molds (310) into mold raw material, thus releasing the castings. A dedicated conveyor transports the castings away. A lower conveyor (5) provided under the receiving chute (4) transports the mold raw material away. When the plate (21) of the trapdoor (2) is in the horizontal position, it is flush with both endless belts (121), and therefore the mold string (300) advances normally along the conveyor (1) as a whole.
Now, the main difference between the conveyor (1) of the first example and the conveyor (1) of the second example is that, in the second example, the first and second mold string conveying means of both the first stretch (11) and the second stretch (12) of the conveyor (1) are based on respective endless belts (121). Each endless belt (121) is driven by respective side beams (122) according to the selectable grip mechanism disclosed earlier in the present document. However, unlike in the first example, the mold extraction device here comprises a trapdoor mold conveying means based on dedicated movable longitudinal side rails (6).
Indeed, the trapdoor (2) of the second example comprises dedicated movable longitudinal side rails (6) extending substantially along the length of the trapdoor (2). A pneumatic cylinder (61) drives the trapdoor movable longitudinal side rails (6) according to the sequence disclosed above in the present document: the movable longitudinal side rails (6) grip the portion of the mold string (300) resting on the trapdoor (2), then move forward the predetermined distance, then open outwards for releasing the portion of the mold string (300) resting on the trapdoor (2), and finally return back to the initial position. These movable longitudinal side rails (6) are mechanically connected with the side beams (122) of the first stretch (11) and the second stretch (12) of the conveyor (1), thus ensuring a synchronized movement of the mold string (300) throughout the whole conveyor (1).
The mold string conveyor (1) of the second example further comprises a second horizontal portion (7) provided in a gap between the trapdoor (2) and the first stretch (11) of the mold conveyor (1). The first horizontal portion (7) is flush with the horizontal plate (21) of the trapdoor and with the endless belt (121) of the first stretch (11) of the mold conveyor (1) and ensures that no mold raw material falls through the gap.

Claims

Mold string conveyor (1) with mold extraction device, where the mold string conveyor (1) is configured for providing support for a mold string (300) while stepwise displacing said mold string (300) forward along a displacement path, wherein the mold string conveyor (1) comprises a first stretch (11) and an adjacent second stretch (12) and the mold extraction device comprises an inferior trapdoor (2) located along the displacement path between the first stretch (11) and the second stretch (12), characterized in that the mold extraction device further comprises trapdoor mold conveying means configured for stepwise displacing the portion of the mold string (300) located on the trapdoor (2) forward along the displacement path in synchronism with first mold string conveying means of the first stretch (11) of the mold string conveyor (1) and second mold string conveying means of the second stretch (12) of the mold string conveyor (1).
Mold string conveyor (1) according to claim 1, where the trapdoor (2) comprises a hinged plate (21) and where the trapdoor (2) is configured to alternate between a closed position where the plate (21) is oriented horizontally for providing support to a portion of the mold string (300) located on the trapdoor (2), and an open position where the plate (21) is inclined downwards for allowing molds (310) in the portion of the mold string (300) located on the trapdoor (2) to fall down.
Mold string conveyor (1) according to claim 2, further comprising actuation means configured to cause the trapdoor (2) to alternate between the open position and the closed position.
Mold string conveyor (1) according to any of claims 1-3, further comprising a shield plate (3) extending downwardly from an end of the second stretch (12) of the mold string conveyor (1) and being configured for guiding the falling molds (310) when the trapdoor (2) is in the open position.
Mold string conveyor (1) according to claim 4, where the trapdoor (2) comprises a first horizontal portion (31) providing support for the mold string (300) in a gap between the end of the plate (21) when in the horizontal position and the end of the second stretch (12) of the mold string conveyor (1).
Mold string conveyor (1) according to any of the previous claims, further comprising a receiving chute (4) situated under the trapdoor (2) that is configured for receiving the falling molds (310) when the trapdoor (2) is in the open position and wherein the receiving chute (4) comprises a vibrating horizontal grid configured for breaking up the molds (310) into raw mold material, thus releasing castings embedded inside the molds (310).
Mold string conveyor (1) according to claim 6, where the receiving chute (4) is connected to a dedicated casting conveyor configured for transporting away the castings.
Mold string conveyor (1) according to any of claims 6-7, further comprising a lower conveyor (5) situated under the receiving vibrating horizontal grid configured for receiving the mold raw material that drops down through the vibrating horizontal grid.
Mold string conveyor (1) according to claim 1, where the trapdoor mold conveying means comprises movable longitudinal side rails (6) mechanically synchronized with the first mold string conveying means and the second mold string conveying means.
Mold string conveyor (1) according to any of claims 1 or 9, where the first mold string conveying means comprise movable longitudinal side rails (111), and the second mold string conveying means comprise an endless belt (121), and where the trapdoor movable longitudinal side rails (6) are prolongations of the horizontal side rails (111) of the first mold string conveying means.
Mold string conveyor (1) according to any of claims 1 or 9, where the first mold string conveying means comprise a walking beam and the second mold string conveying means comprise an endless belt (121), and where the trapdoor movable longitudinal side rails (6) are dedicated side rails.
Mold string conveyor (1) according to any of claims 1 or 9, where the first and second mold string conveying means comprise respective endless belts (121), and where the trapdoor movable longitudinal side rails (6) are dedicated side rails.
Mold string conveyor (1) according to claim 12, further comprising a second horizontal portion (7) providing support for the mold string in a gap between an end of the trapdoor (2) and the end of the first stretch (11) of the mold string conveyor (1).
Mold string conveyor (1) according to any of the previous claims, further comprising detection means configured for detecting the position of a particular mold (310) along the mold string conveyor (1) and control means configured for opening the trapdoor (2) when said particular mold (310) is located on the trapdoor (2).