Low-pressure die casting plant and method for operating the same

Abstract: The present invention relates to a low-pressure die-casting plant with improved production capacity, which comprises a first furnace and a second furnace with mutually independent operating pressures and metal levels. A station for unloading the cast parts and for performing graphitization of the dies is arranged between the furnaces. The furnaces can be selectively connected to respective dies which are associated with handling units which can be mutually detachably coupled for a synchronous translatory motion between the casting position and the unloading position and/or viceversa.

Description: The present invention relates to a low-pressure die-casting plant with improved production capacity. Conventional low-pressure die-casting plants are usually constituted by a casting furnace in which a tube is immersed in order to dispense, by supplying pressure to the furnace, the liquid metal into a die which is connected to the metal drawing tube. A handling unit is generally provided at the furnace and allows to perform the various operations for handling the die, to load the cores, unload the cast part, and perform the graphitization and cooling of the dies. With these applications, if the production capacity is to be increased it is necessary to radically modify the furnaces, with considerable constructive complexities and very high power allocations. Another typical problem of conventional plants is constituted by the fact that they are difficult to automate and furthermore do not allow to quickly modify the type of metal being cast. An apparatus with features as comprised in the preamble of claim 1, is known from the document US-A-3 804 152. The aim of the present invention is to solve the above problems, by providing a low-pressure die-casting plant which has a high production capacity despite having furnaces with relatively low power allocations. Within the scope of this aim, a particular object of the invention is to provide a casting plant in which all downtimes are optimized, allowing to perform casting in one die whilst the cast part is unloaded from another die. Another object of the present invention is to provide a casting plant which can be fully automated and is also extremely versatile and practical in use. Another object of the present invention is to provide a die-casting plant which can be easily obtained starting from commonly commercially available elements and materials and is furthermore competitive from a merely economical point of view. This aim, these objects, and others which will become apparent hereinafter are achieved by a low-pressure die-casting plant with improved production capacity, according to the invention, as defined in the appended claims. Further characteristics and advantages will become apparent from the description of a preferred but not exclusive embodiment of a low-pressure die-casting plant with improved production capacity, illustrated only by way of non-limitative example in the accompanying drawings, wherein: figure 1 is a schematic view of the die-casting plant according to the invention with the first furnace in the casting step; figure 2 is a view of the casting plant with the second furnace in the casting step; figure 3 is a schematic view of the automatic control of the pressure inside the furnaces; figure 4 is a schematic plan view of the step for picking up the cast part, with movement towards the operator; figure 5 is a view of the step for handling the cast part to show it to the operator, who performs instantaneous visual inspection; figure 6 is a plan view of the step for unloading the cast part; figure 7 is a plan view of the step for removing the cast part and rotating it towards the operator to allow him to view the part; figure 8 is a view of the movement of the handling unit towards the transfer belt; figure 9 is a view of the step for unloading the part; figures 10, 11, and 12 are sequential views of the step for the spray graphitization of the die. With reference to the above figures, the low-pressure die-casting plant with improved production capacity, according to the invention, comprises a first furnace 1 and a second furnace 2 which can operate with different operating pressures and different metal levels, with the additional possibility of having two different alloys inside them. The furnaces 1 and 2 are arranged to the side of an unloading station which is generally designated by the reference numeral 3 and performs, as will become apparent hereinafter, the unloading of the cast parts and the graphitization of the dies. At the supporting frame of the plant there are provided two handling units 5 and 6 which can be mutually detachably coupled and can move along guides, generally designated by the reference numeral 7, to be arranged selectively with a translatory motion at a furnace and at the unloading station 3 and/or viceversa. In greater detail, the furnaces 1 and 2, which have standard dimensions and a consequent relatively limited power allocation, are controlled, as shown by the diagram of figure 3, by a computerized central unit 10, which drives a converter 11 to which a pressure transducer 12 is connected which detects the pressure inside of each furnace 1 or 2. The converter drives a proportional valve 14, which in turn controls a large-capacity pressure valve 15 which is interposed along the line 16 which controls the pressure inside the furnace. Load cells 17 are also provided, which have the purpose of detecting the presence of material so as to adjust the curve of the pressures which can be obtained. When performing the castings, it is necessary to be able to feed the material according to the various operating steps by performing controlled pressurization of the furnace. The computerized control of the plant allows to provide any kind of pressure curve, so that it is possible to always obtain an optimized casting step throughout the execution of the process. The load cells for the level of the metal in the furnace also allow to automatically vary the pressure in order to always reach the threshold set in the pressurization process, regardless of the variation of the level of the metal in the furnace; the same result can be achieved by replacing the load cells with laser detectors which use a laser beam which reflects off the surface, or with graphite floaters connected to an instrument which produces an analog output. As shown in figures 4 to 9, the handling units 5 and 6 have the purpose of alternately performing casting in the dies, at one of the furnaces, whilst the other handling unit performs unloading at the unloading station. In particular, there is provided a removal unit, designated by the reference numeral 30, which removes the cast part and, after moving it forwards (figure 4), turns it (figure 5) so as to show it to the operator, who can immediately detect any defects. Correspondingly, a tray 35 is arranged above the graphitization tanks 40 so as to retain any part which might slip down. After the part has been inspected by the operator, the removal unit retracts and, after overturning, as shown in figures 8 and 9, unloads the part onto an unloading belt 41. Then the handling unit introduces the dies in the graphitization tanks 40 to treat the dies and cool them. Optionally, the graphitization step, as shown in figures 10 to 12, can be performed by spray-coating with a spray nozzle 43 which is arranged frontally with respect to the apparatus, so as to treat the dies which are arranged in front of said nozzle. It should be added to the above that during the normal production steps there are provided means for vertically lifting the furnaces to apply them to the die, or optionally there are provided means for the descent of the handling unit, so as to couple the casting tube to the die. With the above-described arrangement, therefore, whilst one of the dies is in the casting step, the other die is in the step for unloading the part and for preparing the dies for subsequent casting and for core insertion. Once the various operations have been completed, the cycle resumes with a translatory motion of the handling unit, which places the previously unloaded die at the furnace in order to fill it, whilst the other die in which casting had been performed is arranged at the unloading unit. It should be added to the above that it is optionally possible to mutually uncouple the handling units, so as to block the operation of one handling unit, when it is sufficient to use a single furnace or, for example, when the corresponding furnace is undergoing maintenance. From the above description it is thus evident that the invention achieves the intended aim and objects, and in particular the fact is stressed that an automatic casting plant is provided which is capable of considerably simplifying all the casting operations, achieving a very high hourly production rate with a reduced power allocation and with the possibility of having a single operator who controls both furnaces. The invention thus conceived is susceptible of numerous modifications and variations, all of which are within the scope of the claims. All the details may furthermore be replaced with other technically equivalent elements. In practice, the materials employed, as well as the contingent shapes and dimensions, may be any according to requirements. Where technical features mentioned in any claim are followed by reference signs, those reference signs have been included for the sole purpose of increasing the intelligibility of the claims and accordingly, such reference signs do not have any limiting effect on the interpretation of each element identified by way of example by such reference signs.

Claims: A low-pressure die-casting plant with improved production capacity, comprising a first furnace (1) and a second furnace (2), and handling units (5, 6) said furnaces (1, 2) being selectively connectable to respective dies which are associated with said handling units (5, 6), characterized in that it further comprises a station (3), arranged between the furnaces (1, 2) for unloading the cast parts and for performing graphitization of the dies, in that said furnaces (1, 2) have mutually independent operating pressures and metal levels, and in that said handling units (5, 6) are mutually detachably coupled for moving synchronously by translatory motion between the casting position and the unloading position and/or viceversa. A casting plant according to claim 1, characterized in that it comprises a computerized central unit (10) which drives a conversion device (11) which is connected to a pressure transducer (12) which detects the pressure inside each one of said furnaces (1, 2), said conversion device driving a proportional valve (14) which controls a high-capacity pressure valve (15) which is interposed along the line (16) for feeding pressure into each one of said furnaces (1, 2). A casting plant according to the preceding claims, characterized in that it comprises load cells (17) which act at each furnace to detect the presence of material in order to adjust the curve of the pressures which can be fed into each one of said furnaces (1, 2). A casting plant according to one or more of the preceding claims, characterized in that each one of said handling units (5, 6) is provided with a removal unit (30) for removing the cast part, said removal unit (30) being adapted to move the cast part towards the operator and to rotate it so as to show it to said operator, and being connected to motion actuating means in order to place the cast part on an unloading belt (41). A casting plant according to one or more of the preceding claims, characterized in that it comprises a tray (35) which can be arranged above graphitization tanks (40) during the removal of the cast part. A casting plant according to one or more of the preceding claims, characterized in that said handling units (5, 6) are adapted to place said dies in the graphitization tanks (40). A casting plant according to one or more of the preceding claims, characterized in that it comprises spray nozzles (43) for the spray graphitization of said dies. A casting plant according to one or more of the preceding claims, characterized in that it comprises means for vertically lifting said furnaces (1, 2) to connect the casting tube to the die. A casting plant according to one or more of the preceding claims, characterized in that it comprises means for the descent of said handling units (5, 6) in order to couple the casting tube to the die. A casting plant according to one or more of the preceding claims, characterized in that said handling units (5, 6) can be uncoupled in order to use a single furnace. A method for operating a low-pressure die-casting plant comprising a first (1) and a second (2) furnaces with mutually independent operating pressures and metal levels, an unloading station (3), arranged between said furnaces, and handling units (5, 6), the method comprising the steps of: detachably coupling with each other and synchronously moving by translatory motion said handling units (5, 6) to locate one of said handling units (5, 6) at one of said furnaces (1, 2) in a casting position while locating the other handling unit at the unloading station (3) and/or viceversa; selectively connecting said furnaces (1, 2) to respective dies which are associated with said handling units (5, 6) located in said casting position; unloading the cast parts at said unloading station (3); and performing graphitization of the dies.

Inventors: GIOLO FABIO, GIOLO, FABIO
Applicants: IMR S P A, IMR S.P.A.
Application year: 1997
Main classification: B22D18
IPC codes: B22D18