TEMPERATURE-ADJUSTING DEVICE FOR PLASTICS MATERIAL EXTRUDING, INJECTING AND DRAWING MACHINES AND CYLINDERS

Abstract: The present invention relates to a temperature adjusting device, particularly designed for processing cylinders of ex­ truding, injecting, drawing and the like machines for pro­ cessing plastics materials in general, which comprises a flex­ ible body, of sleeve shape, which may be arranged on the outside of the plastics material processing machine: the body is housed in an outer duct, for conveying and discharging air in a substantially transversal direction with respect to the body itself.

Description: BACKGROUND OF THE INVENTION The present invention relates to a temperature adjusting device, particularly designed for extruding, injecting and drawing machine cylinders, for processing plastics material in general. As is known, for processing plastics materials and elastomeric materials in general, there are used machines which are provided with a plasticizing cylinder including heating systems which are controlled by automatic temperature adjusting means, provided for holding at a set value the temperature, in order to process in the most suitable way the plastics materials. In these machines, as the temperature rises above the set thermal levels, it is necessary to stop the operation of the machine, with a consequent yield reduction and increase of the production cost. The presently used devices for stabilizing the operation temperatures in these machines are not generally able of solving the above mentioned problem since they are rather complex and of difficult assembling. Moreover, the known devices are not able of providing a constant operation and require frequently maintenance operations. The document EP-A-0 122 887 in the name of the same applicant discloses an electric thermal unit for adjusting the temperature of cylinders of plastics material extruding machine having the features of the preamble of the main claim. SUMMARY OF THE INVENTION Thus, the main object of the present invention is to overcome the above mentioned drawbacks, by providing a temperature adjusting device, specifically designed for plastics material extruding cylinders, injection machines, drawing machines and plastics material processing machines in general, which affords the possibility of holding the operation temperature constant, under all of the operation conditions. Another object of the present invention is to provide such a temperature adjusting device which may be quickly and simply installed on any types of plastics material processing cylinders, while affording the possibility of quickly controlling the machine with reduced maintenance requirements. Yet another object of the present invention is to provide a temperature adjusting device of very simplified structure, which is very reliable and safe in operation. Yet another object of the present invention is to provide such a temperature adjusting device, particularly designed for cylinders of plastics material extruding machines, injecting machines, drawing machines and machines for processing plastics material in general, which may be easily made starting from easily commercially available elements and materials and which, moreover, is competitive from a mere economic standpoint. According to one aspect of the present invention, the above mentioned objects, as well as yet other objects, which will become more apparent thereinafter, are achieved by a temperature adjusting device, particularly designed for plastics material extruding, injecting and drawing machines having the features of the main claim. BRIEF DESCTIPTION OF THE DRAWINGS Further advantages of the invention will become more apparent thereinafter from the following detailed description of a preferred though not exclusive embodiment of a temperature adjusting device, particularly designed for plastics material processing cylinders, which is illustrated by way of an indicative but not limitative example in the accompanying drawings, where: Figure 1 is a cross-sectional view illustrating the temperature adjusting device according to the invention; Figure 2 illustrates a longitudinal cross-sectional view of the temperature adjusting device applied to an extruding machine cylinder; Figure 3 illustrates a heating electric resistance which forms a part of the flexible body, with air cooling; Figs. 4 and 5 illustrate two different embodiments of the heat exchanger finned assemblies; Figures 6 and 7 illustrates two different embodiments of strip members, devoid of fins; and Figure 8 is a side view illustrating a strip member devoid of fins. DESCRIPTION OF THE PREFERRED EMBODIMENTS With reference to the drawings, the temperature adjusting device, particularly designed for cylinders of plastics material processing machines in general, such as extruding, injecting and drawing machines, according to the invention, comprises a flexible body which substantially consists of heating assemblies 1 and heat exchanger assemblies 2, which, advantageously, are mutually intercalated and coupled along an axial direction. Moreover, a not finned heating assembly 3 arranged at one end is provided. The assemblies 1, 2 and 3 are axially applied on the outside of a plastics material plasticizing cylinder, indicated at 4. More specifically, these assemblies are made starting from strip members, which are clearly illustrated in Figures 4 to 8, and which may be adjoined one another according to the most suitable arrangements. The strip members illustrated in Figures 4 and 5 are provided with outer fins and hollows 8 at the end portions thereof contacting the plastics material processing cylinder 4. The strip members indicated at 5' have a like shape, with the difference that they are not provided with fine. All of the strip members are formed with throughgoing holes 7 for introducing thereinto electric heating resistances, indicated at 8, and are so constructed as to allow for cooling air to pass therethrough, as it will be illustrated in a more detailed way thereinafter. As is cleraly shown in the end elevation view of Figure 8, the strip members are provided, on a side, with a recess 5a, with substantially circular shape, and, on the other side, with a projection 5b, also of substantially circular shape, so as to provide a coupling able of causing the adjoining strip members to assume a nearly circular shape. The not finned heating assembly 3, which is specifically shown in Figure 3, consists of two assemblies, arranged to define a semicylindrical shape, which are separated by a base strip member 9 and a bottom strip member 10, having respective mating shapes. On the outside they are coated by a thermally insulating material layer 11 which is restrained, jointly to the two semicylindrical assemblies, by an overcoating tight band 12 which is locked by a tierod 13 and supports insulating small blocks 14 thereat end the power supply wires 15 and ground wires 16. The heating assemblies 1, heat exchanger assemblies 2 and not finned heating assemblies 3 are protected by a thermally insulated carter, including a fixed portion 17 and a removable portion 18. The fixed portion consists of a base metal sheet, which is made rigid with the extruding cylinder 4 by means of flanges 19 and supporting small blocks 20. The base metal sheet is provided with intermediate slots 21, therethrough the forced cooling air is caused to pass, and is provided, at the transversal end portions thereof, upwardly curved, with a thermally insulating material layer 22 which is coated, on a side, by a corrugated metal sheet 23 adapted for operating as a reflecting mirror element and, on the top, by a flat metal sheet 24 providing a resting abutment. An outer casing 40, made of stainless steel, is further provided for defining a forced ventilation path, which ventilation path is controlled by an electric motor operating a double fan so as to generate an air flow which is transversely moved of the axial extension of the flexible body and is provided with a discharging outlet which is diametrically arranged of the inlet region. The removable portion 18 of the carter or casing is advantageously made of a shaped metal sheet having vertically extending walls which are provided with aerating slots 25, and a top horizontally extending wall in which there is formed an air discharging stack 26 for discharging the air conveyed through the outer envelope or casing 40. The vertical walls are provided with closure hook members 27 engaging with corresponding hook members 28 provided on the fixed portion of the carter or casing and which are intercoupled, at their end portions, by shaped perpendicular walls 29 for closing the carter at the front and rear thereof. The carter further supports, in its inside and in the longitudinal direction, two corrugated metal sheets 30, which have a substantially semicylindrical arrangement and operate as reflecting mirror elements, and encompass the heating and heat exchanger structure, so as to form, thereabout,continuous gaps 21 for the passage of the cooling air which contributes to the temperature adjusting of the system. To the mentioned corrugated metal sheets there is coupled a thermally insulating material layer 32 which is enclosed and protected by an outer holding metal sheet 33, which defines, with the carter outer walls, a further gap 34 communicating to the outside through the aerating slots 25. Thus, a portion of the cooling airflow, by directly entering through the slots 21, contacts the plastics material processing cylinder and passes through the offset hollows 6 of the strip members 5 and 5' so as to adjust to the set value the temperature of said cylinder and prevent the temperature from undesirable increasing. A portion of the airflow flows through the gaps 21 thereby cooling the outer portion, possibly finned, of the strip members 5 and 5'. Accordingly, the carter or casing is constantly held at a comparatively low temperature, thereby it does not represent a danger source for the operators. By acting on the hook members 27, the removable portion 18 of the carter or casing may be easily removed, jointly to the thermally insulating structure coupled thereto, thereby affording the possibility of visually controlling the heat exchanger and heating assemblies. In order to more accurately control the temperature, inside the carter or casing there is provided at least a thermocouple 35 for controlling the power supplying of the electric resistances 8. From the above disclosure it should be apparent that the invention fully achieves the intended objects. While the invention has been disclosed with reference to preferred embodiments thereof, it should be apparent that it is susceptible to several modifications and variations all of which come within the scope of the appended claims.

Claims: A temperature adjusting device, particularly designed for cylinders (4) of plastics material extruding machines, injecting machines, drawing machines and machines for processing plastics material in general, comprising a flexible body including a plurality of ceramic strip members (5, 5') coupled together and restraining heating electric resistances (8), said body being adapted to be mounted, as a sleeve member, on the outside of the machine cylinder (4) and being housed inside an outer casing, for conveying and discharging air along a substantially transversal direction of said body, characterized in that said plurality of ceramic strip members (5, 5') define heating assemblies (1) and heat exchanger assemblies (2), arranged in an intercalated way and axially aligned, a not finned heating assembly (3) being provided at one end. A temperature adjusting device according to Claim 1, characterized in that said ceramic strip members (5, 5') are of substantially semicircular shape and are arranged in an adjoining relationship, at the cylinder (4) resting inner side there being provided alternating hollows (6) adapted for creating a cooling air passage path. A temperature adjusting device according to Claims 1 and 2, characterized in that at least some of said strip members (5) are provided with a perimetrical fin arrangement. A temperature adjusting device according to one or more of the preceding claims, characterized in that said strip members (5, 5') are provided with throughgoing holes (7) for housing electric resistances (8), said holes (7) defining cooling air passage paths. A temperature adjusting device according to one or more of the preceding claims, characterized in that the not finned heating assembly (3) is provided with semicylindrical shape portions which are separated by a separating base strip member (9) and a bottom strip member (10), said not finned heating assembly (3) being coated by an insulating material layer (11) and overcoated by a tightness band (12), coupling to one another said semicylindrical portions, said band supporting insulating small blocks (14) for coupling power supply and ground cables. A temperature adjusting device according to one or more of the preceding claims, characterized in that it comprises a thermally insulated casing (17, 18) having a fixed portion (17) and a removable portion (18), said fixed portion (17) consisting of a base metal sheet, made rigid with said machine cylinder (4) by means of flanges (19) and supporting small blocks (20), said base metal sheet being provided with intermediate slots (21) for allowing the forced cooling air to pass therethrough, at the transversal end portions there being provided an insulating material layer (22) which is coated on a side by a corrugated metal sheet (23) adapted for operating as a reflecting mirror element and, at the top, by a flat metal sheet (24) providing a resting abutment. A temperature adjusting device according to claim 6, characterized in that said removable casing portion (18) comprises a shaped metal sheet, having slotted (25) vertical walls and a top horizontal wall, longitudinally of which there is defined a stack (26) for discharging air, said vertical walls being provided with closure hook members (27) adapted for engaging with corresponding hook members (28) applied on the edges of said fixed portion (17), said side walls being coupled, at their ends, by perpendicular walls for closing said casing at the front and rear. A temperature adjusting device according to one or more of the preceding claims, characterized in that it comprises two corrigated metal sheets (20), longitudinally extending with substantially semicylindrical shape, adapted for providing reflecting mirror like elements encompassing said heating and heat exchanging assemblies, said sheet metals being provided with continuous gaps (31) for the passage of the cooling air, to said corrugated sheet metals and insulating material layer (32) being applied which is enclosed and protected by a holding outer metal sheet (33) defining, with the outer walls of said casing, a gap (34) communicating to the outside through aerating slots (25). A temperature adjusting device according to one or more of the preceding claims, characterized in that it comprises, inside said casing, at least a thermocouple (35) for controlling the temperature of said cylinder (4) and controlling the power supply to said electric resistance (8).

Inventors: PIAZZOLA, GAETANO
Applicants: PIAZZOLA, GAETANO
Application year: 1987
Main classification: B29C47
IPC codes: H05B3, B29C47, B29C35, B29C45