JPS61280907A - Exothermic body of heating apparatus for high polymer plasticized material - Google Patents

Abstract

PURPOSE:To average the output of heat of conical cylindrical exothermic bodies, by changing the thicknesses of the electrical resistance materials of the heating bodies continuously or stepwise from the end surfaces of larger hole diameter to the end surfaces of smaller hole diameter of the heating bodies. CONSTITUTION:The thicknesses of exothermic bodies 28, 29 become larger continuously or stepwise from the end surfaces 28a, 29a of larger hole diameter to the end surfaces 28b, 29b of smaller hole diameters. The electrical resistance is inversely proportional to the thickness, i.e. the cross-sectional area of the conductor and is proportional to the hole diameter. As the joule heat is propor tional to I<2>R, the calorific value becomes small with decrease in the hole diame ter. Overheat of the parts close to the end surfaces with the smaller hole diameters of exothermic bodies 28, 29 where overheating tends to occur can be thereby avoided and no shortage of the total summed calorific value occurs.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a heating element for a device that heats a polymeric ear-shaped fluid as a raw material during injection molding, transfer molding, extrusion molding, or the like.

Conventionally, in injection molding, transfer molding, extrusion molding, etc.
As a device that rapidly heats raw material ear-shaped fluid such as rubber or synthetic resin just before the die, it is equipped with a conical protrusion formed at the tip of the raw material passage and a cylinder head assembled to the tip. The gap between the formed conical concave portion and the conical concave portion can be freely adjusted, and a so-called megaphone-like structure is provided on each surface of the conical convex portion forming the gap and the conical concave portion via an electrical insulating layer. By attaching a conical cylindrical heating element and passing the raw material through the opposing gap between the two heating elements as a heating passage, the Joule heat generated in the heating element and passing through the narrow gap. There is a method that uses the generated frictional heat to heat the raw material and raise its temperature.

As a heating device for the plasticized fluid in the above-mentioned conventional injection molding machine, there is one shown in FIG. 1, in which the plasticized raw material is stored in the raw material storage chamber 3 in the cylinder 1, Upon receiving an injection instruction, the raw material is forced out from the storage chamber 3 and enters the heating passage 3b through the raw material 3a that is open in the flange 15a of the conical convex portion 15. The heating passage 3b includes an electrically insulating layer 19
A conical cylindrical heating element 20 made of a thin metal resistance material is fixed to the conical convex part 15 via an electric insulating layer 21, and a conical cylindrical heat generating element 20 is fixed to the conical concave part 17 via an electrical insulating layer 21. Since the gap faces the heating element 22, by turning the screw 17a'i of the conical recess in either direction, the gap can be widened or narrowed on the same central axis as the conical protrusion 15. is also free. The sliding surface 5a of the cylinder head 5 has a conical convex portion 15 and a conical concave portion 1.
7t-1 Always keep it correctly concentric. The double nut 18 fixes the gap between the heating passages 3b at a desired position. Insulating layer 2
3.24.25.26 often uses an electrically insulating backing material, but ceramic or other inorganic or organic insulating materials may be used, for example, by thermal spraying or painting. 4 b, 1
7b is a contact that electrically connects both metals by welding, brazing, etc., and 27 is a conductive plate that is a good electrical conductor. Now, the electric current supplied from the connecting piece 11 passes through the conductive plate 27 to the conical cylindrical heating element 20 made of a plate-shaped electrically resistive material such as nichrome, stainless steel, etc. It enters the conical convex part 15, then leads to the conductive shaft 16 with good conductivity, is heated by the conical cylindrical heating element 22t from the collar 16a of the conductive shaft, reaches the conical concave part 17 through the contact 17b, and then reaches the cylinder head. 5'@: Passes through and returns to the power supply from the connection piece 12.

The raw material heated in the heating passage 3b is transferred to the flange 16a of the conductive shaft.
It passes through the hole drilled in , gathers at 3c, and advances from the nozzle 6 in the direction of the gun.

The conventional heating elements 20 and 22 described above have the following drawbacks. In other words, the heating element is formed into a megaphone shape (conical shape) by a relatively thin electrically resistive material with uniform wall thickness.
The aperture of one end face of the megaphone is large, and the aperture of the other end face is smaller than the aperture, or almost forms the apex of a cone.The current travels straight between the two end faces, and the resistance is opposite to the cross-sectional area of the conductor. Since they are proportional, the electrical resistance within the heating element is different by tK, and the resistances of both diameter portions are inversely proportional to their diameters. Therefore, Joule heat is I”
Since it is proportional to H, the calorific value is also inversely proportional to the aperture, and the smaller the aperture, the greater the calorific value of the core. Furthermore, as above, the watts inside the heating element! [When compared by t-position, it can be seen that the ratio of watt densities is inversely proportional to the 12° power of the aperture at which it is located. In other words, the small-diameter portion of the heating element generates more heat per unit area than the large-diameter portion. As a result of the above results, in the conventional heating element, the portion close to the small-diameter end face of the heating element tends to overheat, and if an attempt is made to avoid the above-mentioned overheating, the total amount of heat generated is insufficient.

In addition, from the point of view of heating control and heating efficiency, extreme differences in watt density as shown in the above example are not preferable.

In order to eliminate the drawbacks of the above-mentioned conventional device and to obtain practical convenience, this invention aims at the end surface of a conical cylindrical heating element made of an electrically resistive material from the end surface with a large diameter to the end surface with a small diameter. By changing the thickness of the resistive material gradually or stepwise, the Joule heat generated through the electric current between the two end faces can be arbitrarily controlled. To give an example, the diameter of one side of the conical cylindrical heating element is 130 m, the diameter of the other side is 15 m, and the wall thickness of the heating element is, for example, 0.15 m at the end face of the large diameter. If the end face of a small diameter is 0.3 m, the thermal output generated in the heating element by energization can be averaged without changing due to the difference in diameter of the heating element.

FIG. 2 is an enlarged sectional view showing an embodiment of the conical cylindrical heating element of the present invention. There are various examples of heating devices attached to this heating element, but basically they are not much different from the one shown in Figure 1, and in order to clarify the explanation of the shape of the heating element. , here K indicates only the heating element, and the heating device to which it is attached is omitted. 28.29 is a conical cylindrical heating element (of this invention), 3a is a raw material inlet, 3
b is a heating passage, 28a * 29a is a large diameter end face, 2
8b and 29b are small-diameter end faces, and 30 is a collar, respectively. The conical and cylindrical heating elements 28 and 29 are made of nichrome or other metal resistance material, stainless steel, low expansion alloy, etc. thin plates, tubes, etc., and are manufactured by methods such as welding, polishing, turning, etc. It can also be manufactured from the above materials by so-called squeezing processing. The wall thickness of the heating element 28, 29 shown in the figure is the large diameter end face 28a.
, 29a to small diameter end faces 28b, 29b, respectively.
It gradually becomes thicker towards , but the slope rate of the thickness mentioned above (
gradient) is not necessarily directly and inversely proportional to the aperture ratio, as in the previous example. The thickness of the heating element and the gradient of the thickness are arbitrarily determined from the viewpoints of desired heat output, desired heating control, etc.

It is also possible to eliminate the gradient of the wall thickness above the father and replace it with one in which the wall thickness varies in stages.

Furthermore, in exceptional cases, if the conical slope of the heating element 28, 29 is very gentle, or for reasons of heating control, the entire wall thickness of the large diameter section is usually directed toward the small diameter section. In some cases, the thickness may be made uniform after gradually increasing the thickness, or the thickness may be reversed and the thickness of the small diameter portion may be made thinner than the thickness of the large diameter portion. Now, the collar 30 is a filler for the gap that is created when adjusting the interval between the heating passages 3b of the conical cylindrical heating element, and whether it is conductive or insulating is determined by the current circuit. .

Collars 30 of various thicknesses are prepared in advance and used by being replaced depending on the desired spacing of the heating passages 3b.

The present invention is not limited to the use of two conical cylindrical heating elements in combination as in the above example, but all of the above heating elements may be used alone. The heated object that is heated by passing through the surface of the heating element is not limited to polymer molding fluids, but may also include polymeric compounds that are liquid at room temperature, ceramics, powder molding raw materials, etc. There are a wide variety of materials, including powder fluids, water, oil and other liquids, and gases.

The heating element of the present invention is firstly suitable for performing high-output heating in a narrow space. Second, it is easy to adjust the entire cross-sectional area of the heating passage. Thirdly, since the fluid to be heated is heated little by little as it passes through while touching the heating element, a large heating temperature can be achieved in a short period of time, and the thermal efficiency is high. Fourthly, since the heat capacity of the heating section can be extremely small, the heating response is very rapid, which is an advantage in adapting to intermittent heating. Fifth, by narrowing the heating passage, there is a pressure loss (pressure drop) t-thermal energy of the fluid passing through. It has the above excellent effects.

[Brief explanation of drawings]

FIG. 1 is an example showing a cross section of the main part of a conventional polymer ear shaped compound heating device. FIG. 2 is a sectional view of one embodiment of the conical cylindrical heating element of the present invention. 3b...Heating passage 5...Cylinder head 5a...Sliding surface 15...Conical convex portion 17...Conical recess 17a. ...
...Screw 20.22...Conical cylindrical heating element 28
．． 29... Conical cylindrical heating element (of this invention)

Claims (1)

[Claims] (1) The thickness of the resistive material is gradually or stepwise changed from the end face with a larger diameter to the end face with a smaller diameter of a conical cylindrical heating element made of an electrically resistive material, and the thickness of the resistive material is gradually or stepwise changed between the two end faces. A heating element for a polymer plastic heating device in which the Joule heat generated through electric current can be arbitrarily controlled.