SU994274A1 - Apparatus for pneumatic-vacuum moulding of articles of sheet thermoplastic materials - Google Patents

Description

The invention relates to the field of processing thermoplastic sheet materials into products and can be used to manufacture, in particular, thin-walled products of the chemical industry.

A device is known for forming a product using a pneumatic vacuum method using thermoplastic materials by heating a sheet thermoplastic billet to TV molding and subsequent negative vacuum pneumatic molding under the action of a pressure difference from two sides of the forming sheet, which contains a form, an air distribution plate, an infrared heater, a clamp, an apparatus and an infrared heater. compressed air supply l.

The disadvantages of this device are unevenness of the molded product (the ratio of the difference between the maximum and minimum thickness to the average thickness of the product in%), reaching 100% or more, the uneven distribution of internal stresses, causing distortion of the product and reducing its service life, as well as small drawing depth (the ratio of the height of the product to the nominal diameter

products) - not more than 0.5 in case of pneumatic vacuum foto

The closest in technical essence and achieved result is that the invention is a device that contains evacuation channels connected with a drive of its vertical movement, a clamping device, an air distribution plate 10 and a pneumatic cylinder NDH connected to an air supply system under constant pressure of 21.

The product is shaped using the device in the following way.

15

A thermoplastic sheet preliminarily heated with an infrared heater is fixed by a clamping device on a plate, the shape of which is pre-driven upward.

Claims (2)

20 Then, the mold is lowered, clamping a sheet of thermoplastic between and the plate, in the pneumatic cylinder, the gas distribution system creates a pressure of 5, atm, and then the air supply stops. At the same time, a vacuum is created in the foria cavity. Under the influence of the resulting pressure, the thermoplastic sheet is formed. The pressure in the cylinder during the forming process 30 is provided by the displacement. the piston in a pneumatic cylinder, driven by a hydraulic cylinder. At the end of the molding process, the mold is lifted and the product is removed from the mold. However, in this device, the unevenness of the product reaches 900-100%, the stresses are unevenly distributed, the product is distorted, and the degree of stretching of the sheet of thermoplast does not exceed 0.5. The purpose of the invention is to improve the quality of the product by reducing its thickness variation and increasing the degree of stretch. The goal is achieved by the fact that in a device for pneumatic vacuuming, containing a form with channels for vacuuming, associated with a drive of its vertical movement, a clamping device, an air distribution plate and a pneumatic cylinder connected to an air supply system under steady pressure, the pneumatic cylinder is equipped with a vibrator, The air distribution plate is made with an internal cavity communicated with the full capacity of the pneumatic cylinder. The drawing shows a general view of the device. The device comprises a form 1 with channels for evacuation associated with a vertical displacement drive 2, an air distribution plate 3, an air cylinder 4, an infrared heater 5, a clamping attachment b, an air supply system 7 under a constant pressure in the pneumatic cylinder 4 and the mechanical vibrator 8 connected to the pneumatic cylinder 4 ohm. The air distributor plate 3 is made with an internal cavity 9 communicated by the hole 10 with the cavity of the pneumatic cylinder 4. The device works as follows time .. thermoplastic sheet 11 is fixed on the air distribution plate 3 and the clamping device 6 is heated by infrared heater 5 to the molding temperature. Then the heater 5 is retracted, the form 1 is lowered by means of the actuator 2 until it comes in contact with the clamping device 6. Then a vacuum is created in the form 1, and a pressure of 5 bar is created in the pneumatic cylinder 4 with the help of the compressed air supply system 7 in the process of forming the thermoplastic sheet 11. At the same time, the mechanical vibrator 8 creates in the pneumatic cylinder 4 oscillations that are close to harmonic with a frequency of 5-20 Hz. The total pressure in the pneumatic cylinder 4 is transferred to the surface of the sheet 11 of the thermoplastic through the hole 10 connecting the cavity of the pneumatic cylinder and the air diffusing of the separating plate. In this case, the thermoplastic sheet 11 is molded under the action of a pressure difference on both sides of the sheet and variable pulsations in the cavity 9 of the plate 3. During the molding process, the thermoplastic sheet is subjected to vibration. due to the pulsating pressure, it partially slips down, which leads to a decrease in thickness variation and an increase in the degree of stretching of the product. The presence of the cavity 9 allows the compressed gas to be applied to the entire sheet of thermoplastic, which contributes to a better reduction of Hss in the sheet 11 of the thermoplastic, increases the degree of stretching and reduces the thickness difference of the finished product. After the molding process is completed, the mold 1 is disconnected from the vacuum, the actuator 2 rises up and the product is removed from the mold 1. The proposed device allows to improve the quality of the products, because due to the vibration that the thermoplastic cH n ci undergoes in contact with the walls of the mold, it partially slides down, which leads to a decrease in the thickness variation of the product to. 45-50%, while the product obtained by standard pneumatic vacuum molding, the thickness difference reaches 90-100%. Since the thermoplastic sheet is subjected to additional dynamic loading during vibration and also due to a decrease in the effective elastic modulus of the thermoplastic sheet, the thermoplastic sheet is formed with a stretching ratio of up to 0.58 (with the standard method the stretching ratio does not exceed 0.5). An installation, D 24 30, manufactured at the Gidropress plant in the city of Orenburg, is used for the basic object. Thus, the proposed installation allowed us to obtain products with a lower thickness variation (up to 45-50% versus 90-100%) and with a greater draw depth (up to 0.58 versus 0.50). Apparatus of the Invention A device for pneumatic vacuum forming of products from sheet thermoplastic materials, comprising a mold with evacuation channels connected with a drive of its vertical movement, a fixture, an air distribution plate, a pneumatic cylinder connected to an air supply system under a constant pressure, is different the fact that, in order to improve the quality of the product by reducing its thickness variation and increasing the degree of stretching, the pneumatic cylinder is equipped with a vibrator, and the air distribution the plate is made with an internal cavity communicated by an opening with a cavity of the pneumatic cylinder. Information sources. hp ppch i lchatsi 1, taken into account during the examination 1, Zavgbrodniy V.K. Equipment for processing plastics. M., Mashinostroenie, 1976, p. 262. 2.Patent of England 1516163,. CATT ENGLAND 151 cl. B5A, 1979 (prototype).