JPS5936864B2 - Intermittent heating device for plasticized fluid in injection molding or transfer molding, etc. - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides an intermittent method of heating the raw material plasticizing fluid to be press-fitted into a molding cavity in injection molding, transfer molding, etc., one injection amount at a time, during the flow immediately before the raw material plasticizing fluid is press-fitted into the molding cavity. The invention relates to a heating device.

In conventional injection molding, transfer molding, etc., the time from injecting the raw material into the molding cavity to removing the molded product is not constant depending on the size of the molded product and other factors. It is within 10 seconds,
Similarly, molding of rubbers and the like that involves a thermal crosslinking reaction requires at least 120 seconds or more.

The reason for the difference in time between the two is that the latter requires time for crosslinking (vulcanization) to proceed within the molding cavity.

The present invention mainly relates to a heating device for shortening the crosslinking time of raw rubber, etc. in a molding cavity.

Note that detailed explanation will be given below using rubber as an example.

First, some examples of the heat-related properties of rubbers will be given.

Phenomena such as scorch and vulcanization of rubber progress according to thermal history with temperature and time as factor variables (parameters).

The vulcanization rate of rubber during molding and vulcanization is sensitive to temperature; for example, a 10° C. temperature increase will shorten the vulcanization time to approximately 1/2.

Due to this property, the vulcanization time in the molding cavity is, for example, 1
It has been found that in order to shorten the time to around 5 seconds, the temperature of the plasticized fluid, for example, from 80° C. to 180° C., can be increased and the temperature of the plasticized fluid is then press-fitted into the molding cavity.

That is, in order to improve the shortcoming of the long molding time of conventional molding equipment, it is sufficient to increase the temperature of the raw material that is press-fitted into the mold.

However, rubber exhibits a more rapid vulcanization reaction at higher temperatures, and once vulcanized (scorched) rubber irreversibly loses its previous plasticity and fluidity, it becomes unable to flow.

In order to prevent this scorch from occurring in the flow path, conventional equipment cannot raise the raw material to a sufficiently high temperature before putting it into the mold. It takes a long time (usually about 120 seconds or more) to heat up and add mud after entering the tank.

The first object of the invention is to eliminate the disadvantage of the long time required for molding of conventional devices.

That is, in this invention, the temperature of the raw material is raised to the same high temperature as the mold temperature (for example, 170 to 180°C) immediately before being press-fitted into the mold, and then the raw material is press-fitted into the mold. The first feature of the present invention is that the molding time is shortened by eliminating the need to wait for the molding process to take place.

Even in conventional devices, attempts have been made to raise the temperature of the raw material as much as possible just before it is poured into the mold.

However, when we look at the heating (including cooling) method of raw materials in conventional injection molding machines, transfer molding machines, etc., the raw materials go through various processes such as compression kneading, heat softening, storage injection, and fluidization in mechanical equipment before being press-fitted into molds. Until then, it is common to use a method of heating via the structures of the above-mentioned parts.

In other words, heating can be done by pressing a heater or the like against the outer surface of the wall of the structure (mainly thick steel), or by providing a flow path for a heat medium in the wall of the structure and heating (or (cooling) and also heat generation due to friction of the raw material itself, thereby maintaining the temperature of the raw material immediately before the mold at a predetermined temperature, for example, any constant temperature within the range of 75 to 120 ° C. ing.

As described above, in conventional heating devices, heat transfer is performed using a thick structure as a medium as described above, so the heating response between the heating element and the heated object (raw material) is often insensitive.
It was almost impossible to raise the temperature of the raw material to a large extent just before the mold.

Therefore, the second feature of the present invention is that by using a heating element with a small heat capacity and reducing the amount of raw material heated at one time, it is possible to significantly raise the temperature of the raw material just before the mold. It is a special feature.

Furthermore, injection molding is performed intermittently for a fixed amount, but as mentioned above, in conventional equipment, the heat capacity of the heating device is large and the amount of raw material heated at one time is large, so the amount of raw material heated and The drawback is that it takes a relatively long time to establish thermal equilibrium with the heating section of the device.

In other words, for one injection molding, the heating method is different for the raw material heated initially and the raw material heated later.
There was a drawback that the degree of vulcanization varied, resulting in unevenness in the finished product.

In the present invention, by reducing the heat capacity of the heating device and reducing the amount of raw material heated at one time, thermal equilibrium is established between the raw material to be heated and the heating section of the device in a short time, and the material is heated. The third feature is that the heating of the raw material can be maintained uniformly within one injection amount.

In other words, in the present invention, the raw material present in the heating section at one time is about 10% or less of the amount of one injection, and the temperature of the raw material is raised while flowing through the heating section, and the amount of heat generated in the heating section and the raw material flowing through the heating section are increased. The amount of heat removed is equal to the amount of heat removed, and since the time required to reach a thermal steady state is short, most of the raw material flows into the mold in a uniformly heated state.

Also, rubber is a poor conductor of heat, and is more like an insulator.
The numerical values described below are not constant depending on the component content of the rubber raw materials blended, but for example, the thermal conductivity is 1150% of that of iron.
0, 115 times that of water, and 6 times that of air.

Note that the specific heat of rubber is more than four times that of iron.

The second drawback of the conventional equipment described above, which arises from the characteristics of this rubber, is that it takes time to conduct heat from the time it is injected into the mold to the time when the raw material is heated from the surroundings and then vulcanized inside, resulting in molded products. The problem is that uneven vulcanization tends to occur inside and outside.

The uneven vulcanization is a serious drawback that tends to occur when molding thick-walled molded products or molded products with uneven wall thickness.

In the present invention, the raw material is heated to the required temperature immediately before entering the mold, so regardless of the shape of the mold,
A feature of this method is that it does not cause uneven vulcanization unlike conventional equipment.

In view of the causes of the drawbacks of the conventional apparatuses mentioned above, the present invention has been developed to inject the raw material to be injected into the molding cavity at a rate of about 10% or less of the injection amount per unit at a time, while the raw material is flowing, just before the molding cavity of the mold. The material is heated, raised to the above-mentioned high temperature, and continuously press-fitted into the molding cavity in that high-temperature state, and heated one pair at a time, so that the influence of the above-mentioned heating is not exerted on the raw material to be injected from the next time onward. It features something like no other.

That is, in an injection molding machine or a transfer molding machine, etc., the flow of raw material in a raw material passage that connects a mold and a device that intermittently discharges raw material plasticizing fluid (including liquid raw material) by -injection amount (variable) A heating passage is a narrow passage whose cross section perpendicular to the direction is made up of a narrow gap (slit) or a small diameter hole (respectively plural or single holes), and an electric resistance is set in the heating passage so that Joule heat can be generated. A heating element is arranged, and the raw material fluid is brought into direct contact with the surface of the heating element, or passes through a film-like thin layer while touching it, and is press-fitted into the mold.

In this case, the volume of the flow path of the raw material fluid in the heating passage is set to be less than or equal to the above-mentioned injection amount (volume), preferably about 10% or less of the above-mentioned injection amount.

Therefore, a variable power source that can intermittently apply power to the resistance heating element from outside the structure of the heating passage is connected, and the electricity is applied to the resistance heating element in response to the intermittent flow of the raw material fluid. The electric power is applied intermittently to the body, that is, the electric power is generally cut off during the flow of the raw material fluid, and the electric power is cut off when the raw material fluid is stopped, and the Joule heat generated in the resistance heating element is used to heat all of the raw material at once. Approximately 10% or less of the injection amount is heated to a desired temperature during its flow, and the heated raw material is continuously press-fitted into the mold as it is, so that one injection amount is heated at a time.

An embodiment of the present invention will be described in detail below with reference to the drawings.

FIG. 1 is an elevational view, partially in cross section, showing the main parts of the entire injection molding apparatus to which an example of the intermittent heating device of the present invention is applied.

In the figure, reference numeral 1 denotes a plasticizing cylinder, which has a cylindrical shape and houses a rotating screw shaft 2 for kneading and transferring raw materials therein.

3 is raw rubber, which is sent to cylinder 1 via hopper 3'.
supplied within.

A heating fluid passage 4 is provided in the wall of the plasticizing cylinder 1, through which heating fluid at an appropriate temperature is passed to control the plasticizing temperature of the raw material in the cylinder 1 to a constant temperature.

The base of the screw shaft is connected to a hydraulically actuated piston, so that the entire screw shaft 2 can reciprocate.

The plasticized raw rubber 3 is stored in front of the screw shaft 2.

Then, the plasticized raw rubber 3 is transferred from the storage chamber to the nozzle 5 by the fluid pressure-operated piston that responds to the injection instruction.
After that, it is forced forward by -injection amount.

Reference numeral 6 indicates a movable mold, and 7 indicates a fixed mold.

Both of the molds 6 and 7 are clamped to form a molding cavity 8 inside.

A fluid at an appropriate temperature is passed through heating medium passages 9a and the like provided in both molds 6 and 7 to maintain the molds 6 and 7 at the above-mentioned vulcanization temperature.

The intermittent heating device of the present invention includes the nozzle 5 and the mold 6.
, 7, and a heating passage 10 communicating therebetween.

That is, a hole communicating from one side to the other is bored in the structure 9 of the heating passage 10, and the bush 11 is attached to one part of the hole, which is the opening on the nozzle 5 side, and the connecting end 12 is attached to the other opening. The nozzle 5 and the bushing 11, the opening communicating with the molding cavity 8 in the molds 6 and 7, and the connecting end 12.
are brought into close contact with each other to form a consistent raw material passage throughout the entire structure, so that the raw material fluid extruded from the nozzle 5 can be press-fitted into the molding cavity 8 without leaking.

The close contact between the nozzle 5 and the bush 11 or the opening of the mold and the connecting end 12, etc. is achieved when the raw material stops flowing.
They may be made so that they can be released from each other and separated from each other.

Now, inside the heating passage 10, there is a heat-resistant electrical insulating layer 14.
, 14' apart from each other in a thin plate shape (for example, thickness 0.I
(within Tn7IL) electric resistance heating elements 13°13' are arranged.

Therefore, the electrodes 15, 16:15' are connected to almost both ends of the electrical resistance heating elements 13, 13' and penetrate through the structure 9.
, 16' are provided, respectively, and the electrodes 15, 15': 16, 16
conductive screws 15'' protruding from the outside of the structure 9, respectively.
, 16", 15"'.

16", electrically insulating the heating part from the structure 9,
Fix it to it.

However, the conductive screws 15", 16", 15"', 16"
' from a variable power source (not shown) provided outside the structure 9, intermittently in response to the intermittent flow of the raw material.
That is, while the raw material is almost flowing, electric power is transferred to the resistor 13,
13'.

Resistance heating elements 13, 13 in the heating passage 10
'The opposing gap is the flow path 10 through which the raw material fluid passes.
/becomes.

Incidentally, the above-mentioned gap or flow path 10' is usually not relatively narrow (for example, about 1 mm), so that the raw material passing therethrough can be efficiently heated.

Generally, the narrower the gap in the flow path 10', the narrower the gap in the flow path 10'
The longer the length of the flow path 10' in the raw material flow direction, the better the heating effect will be, but the pressure drop of the raw material fluid passing through the flow path 10' must not exceed its allowable range.

Furthermore, the total volume of the flow path 10' in the heating passage is less than or equal to the above-mentioned injection amount, preferably 1 of the above-mentioned injection amount.
It is necessary to keep it below 0%.

Note that for the heating passage structure 9, a plurality of medium passages 17,
17', 1B, and 1B' are provided, and one of the medium passages 17
, 17' is made equal to the raw material temperature (e.g. 90°C) to be extruded from the nozzle 5, and the temperature leading to the other side of the medium passage i s , i s' is made equal to the mold temperature (e.g. 170°C). A temperature gradient is applied to the structure 9 along the direction in which the raw material passes.

Within a short period of time before and after the moment when the rubber raw material fluid flows out from the nozzle 5 and enters the flow path 1σ, the electric resistance heating element 1
The above electric power is applied to 3 and 13', and the rubber raw material becomes
The Joule heat generated in the resistance heating elements 13, 13' heats the material to a desired temperature that allows vulcanization in a short time, and sends it to the mold in that state.

(Then, the power is cut off within a short period of time before and after the moment when the raw material rubber has passed by the injection amount, that is, when the molding cavity 8 is filled with the raw material at the desired temperature.

As described above, by intermittent heating power corresponding to the intermittent flow of the raw material rubber, the raw material fluid press-fitted into the molding cavity 8 can be heated to a desired approximately constant temperature.

Note that the power applied above is usually low voltage and large current (for example, IO
V or less, 300 to 3000 A) is desirable.

The electric power applied to the electric resistance heating elements 13, 13' is such an excessive current that the resistance heating elements 13, 13' can become scorched within a few seconds, for example in air. Since it flows into the flow path 10' at an appropriate timing and quickly flows away while directly touching the resistance heating elements 13 and 13', most of the Joule heat generated in the heating elements 13 and 13' is transferred to the flowing raw material. As a result, the resistance heating elements 13, 13' are maintained at an appropriate temperature, and the raw rubber can be heated all at once to the desired vulcanization temperature without the risk of deterioration due to overheating.

When repeating the above molding process, if necessary, make a so-called hot water pool (not shown) in the mold slightly thicker, stagnate the unnecessary portion of the residual rubber in the hot water pool, and remove it from the molded product. It can also be removed.

In addition to reducing the unnecessary portion of the remaining raw material, the flow path 1
It is necessary that the total volume of 0' be smaller than the raw material volume of the above injection amount, preferably about 10% or less of the above raw material volume.

Next, the heat-resistant electrical insulating layers 14 and 14' formed in the heating passage 10 will be explained.

These layers 14, 14' are heat-resistant electrically insulating coating layers obtained by casting or coating heat-resistant electrically insulating varnishes such as polyamide-imide varnish, modified polyester varnish, silicone varnish, and others.

Alternatively, it may be a heat-resistant electrically insulating layer such as a ceramic coating, enamel, or glass lining.

Alternatively, the heat-resistant electrical insulating layer 14° 14' is coated with a separately molded silicone compound or the like.
You can also change it to

Next, the electric resistance heating elements 13 and 13' will be described.

These include, for example, nickel-chromium alloy, iron-chromium alloy,
Aluminum alloy and other commercially available electric heating resistance materials are mainly used in the form of thin plates.

In addition to the above, general metal materials that are not normally used as electrical heating resistance materials, such as iron (steel) and stainless steel, can also be used.

The above-mentioned material is arranged in the heating passage 10 in the shape of a thin plate, a line, a tube, etc. to form a resistance heating element, and the raw material fluid passes through the heating element 13, 13' in direct contact with the surface thereof. Use it as you see fit.

Apart from this, on the surface of the resistance heating elements 13 and 13',
For example, a thin layer may be formed by coating with fluororesin, silicone resin, polyamide, or ceramic, and the raw material passing through the thin layer may be heated.

The thin layer provides electrical insulation, reduces resistance during flow of the raw material fluid, and also improves mold releasability (non-adhesiveness) when removing raw material residues. have

FIG. 2 is a partially cutaway side view of another embodiment of the heating device of the present invention.

That is, in this example, the structure 9 of the heating passage 10 is divided into an upper structure q and a lower structure 9'' with the flow path 10/ as a boundary.
If the structure is divided into two parts and both structures γ and 9" are opened and closed, and both are closed, the above-mentioned high-pressure intermittent fluid can be press-fitted into the molding cavity without leaking, as in the example shown in Fig. 1. Similarly, when opened, the inner surface of the flow path 10' can be exposed to the outside.

In the example shown in FIG. 2, the lower structure 9 is fixed, and the upper structure 9' is connected to a device for raising and lowering the movable mold 6 shown in FIG. It is constructed so that it can be opened and closed in conjunction with the direction of the arrow a, and the other parts are the same as those explained with reference to FIG.

In the example shown in FIG. 2, the inner surface of the flow path 10' where the raw rubber repeatedly flows and stops can be exposed as necessary.
This is convenient for removing unusable raw material rubber and the like in the flow path 10' each time molding is performed or as needed.

Moreover, by doing as described above, it becomes possible to form the flow path 10' into even more diverse shapes.

FIG. 3 is a sectional view showing essential parts of still another embodiment of the present invention.

In the figure, an electric resistance heating tube 13'' is a relatively thin circular tube made of the same material as the electric resistance heating element, replacing the heating passage structure 9 and the electric resistance heating elements 13, 13', etc. described above. A bushing 11 is attached to one end and a connecting end 12 is attached to the other end, and the raw rubber extruded from the nozzle 5 is transferred to the resistance heating tube 13''. It is made so that it can be passed through the pipe and fed under pressure to the mold side.

Connect terminals 15'' and 16'' to the bushing 11 and the fixed mold 7, for example, as shown in the figure, at any position of another structure that is electrically closely connected to both ends of the resistance heating tube 13''.
are attached respectively, and the terminals l 5//// and l 6//
The variable power source is connected to //, the Joule heat is generated in the resistance heating tube 13'', and the raw rubber passing intermittently through the tube is heated as described above and sent to the mold.

Alternatively, a tube with a smaller diameter may be inserted into a tube with a larger diameter, and the gaps between the plurality of tubes and/or the inside of the limb tube may be used as the flow path 10' for the raw material fluid.

In order to make the heating response as quick as possible and further improve the heating efficiency, the electrical resistance heating tube 13'' has a small diameter of the limb tube, a thin wall thickness of the tube, and is used in a plurality of tubes arranged side by side. This is desirable.

According to the example, 50 stainless steel pipes (seamless pipes) with an inner diameter of 1.5 x outer diameter of 2.0 mm were used as the resistance heating tube 13'', and raw rubber was press-fitted into the mold at an injection pressure of 2500 kg/crtf. , the above molding could be carried out.

The raw material rubber flows in its entirety without adhering to the inner wall of the exothermic tube 13'', thereby preventing scorch from occurring within the tube (during continuous injection, the raw material rubber is flowed at a constant flow rate (flow rate) at the desired rate). It can be heated to a high temperature and passed through a mold.

Note that the resistance heating tube 13 can also push out and remove rubber that is vulcanized inside the tube due to erroneous operation or the like by using the injection pressure.

Since the resistance heating tube 13'' does not normally require reinforcement by other structures, the resistance heating tube 13'' can be constructed only from the tube itself.

Therefore, the structure is simple and can be manufactured at low cost.

As a result, the thick hollow structures 9' and 9'' described above as well as the resistance heating element 1 disposed inside them
3, 13', etc., compared to the total weight of resistance heating tube 1 of this example.
3" is extremely lightweight, and when comparing the two from the standpoint of heat transfer, there are significant differences in the amount of heat storage, temperature rise rate, cooling rate, etc. between the two.

That is, when using the resistance heating tube 13'', electric power is applied in response to the inflow of the raw material fluid to raise the temperature of the raw material to a desired temperature while flowing, or the application of power is stopped and the raw material is heated to a desired temperature. Regarding the speed of heating response when stopping temperature rise, etc., the resistance heating tube 13'' of this example is much faster and more accurate than the above-mentioned examples of the hollow structures 9' and 9''.

This is particularly important in cases where it is desired to heat only one injection amount of raw material injected into the mold to the desired vulcanization temperature and not have any effect of heat on subsequent raw materials. be.

In this example, due to the speed of the heating response, for example, in the resistance heating tube 13'', by stopping the application of the electric power immediately before the moment when the flow of the raw material stops, for example, within one second immediately before, the resistance is increased. While heating the remaining flowing raw material to an appropriate temperature with the heat held by the heating element 13'', the heating element is cooled by the flowing raw material, and the raw material that remains in the pipe is stopped from being scorched (vulcanized). In other words, it can be left unvulcanized and used as a raw material for the next molding.

Therefore, it is not necessary to provide a special cooling device to prevent the raw material remaining in the flow path from scorching.

Furthermore, at the start of the next molding, immediately before the moment when the raw material in the pipe starts to flow, for example, within one second immediately before,
By applying the electric power to the resistance heating tube 13 in advance, the -injection amount of raw material, including the raw material remaining in the tube, can be heated to a desired temperature and sent into the mold.

In this way, almost all of the rubber raw material can be used for molding.

Moreover, the entire injection amount of raw material can be heated almost uniformly, and a high-quality product can be obtained.

Note that the resistance heating element 13'' is not limited to a circular tube,
Of course, it is possible to use a deformed tube, and furthermore, a tube of a smaller diameter is inserted into the tube of the same diameter, and the gaps between the respective tubes and/or the inside of the tube are used as flow paths for the raw material to pass through. (It is also possible to raise the temperature by heating.

Furthermore, if the pressure resistance of the resistance heating tube 13'' cannot withstand the injection pressure, a heat-resistant electrical insulating layer is formed on the outer periphery of the limb tube, and the limb tube is reinforced from the outside through the insulating layer. It is also easy to use.

Furthermore, apart from the above, when molding liquid thermosetting resin etc.
It is also easy to attach a rod corresponding to the inner diameter of the tube so that it can be inserted and removed, and to push out the raw material remaining inside the tube with the rod whenever necessary.

FIG. 4 is an example of a system diagram regarding heating and injection instructions of the intermittent heating device of the present invention.
1, limit switches 22 and 23 each indicate a bar that can move the position of the limit switch in the horizontal direction as seen in the paper.The limit switch 20 can be adjusted by moving on the bar 22, for example, to adjust the position of the limit switch to the tip of the screw shaft 2. The limit switch 21 is actuated when the screw reaches a position where it cannot move forward any further, and the limit switch 21 is moved, for example, by 2ru in the direction of the base of the screw shaft from the position of the limit switch 20.
It is installed so that it operates at a position of nH degrees.

The operating protrusion 24 is fixed to the base of the screw shaft 20 and moves forward and backward together with the screw shaft to respectively operate the contacts of the two limit switches.

The actuation of the contact means, for example, that the normally closed contact of a circuit (normally closed circuit) in which current always flows within the limit switch is separated so that no current flows.

25 is a snap switch for instructing injection, 26 is a time relay (timer) that can arbitrarily adjust the delay time, 27 is an injection drive device that gives injection motion to the screw shaft 2, 28 is an external commercial power source, 29 is a power switch, 30 is a magnet switch, 31 is a slide transformer, and 32 is a step-down transformer.

Now, referring to FIG. 4, an example of instructing an injection command using a current will be explained. First, the injection command current emitted from the snap switch 25 is transmitted to the limit switch 25.
0 and 21, the former current reaches the time relay 26 through the respective normally closed circuits, and the injection command is sent to the injection drive device 27 after a delay time set by the time relay (for example, 0.5 seconds). tell.

Therefore, the injection by the screw shaft 2 is actually started with a delay of, for example, 0.5 seconds from the injection instruction.

However, after the start of injection, when an arbitrary amount of raw material is injected and the tip of the screw shaft 2 reaches the abutting position, the limit switch 20 is activated as described above, the injection instruction current is cut off, and the injection drive device is stopped. .

Next, the current passing through the latter IJ and S switch 21 enters the electromagnetic coil of the magnet switch 30 that connects and disconnects the commercial power supply 28 to the slide transformer 31, energizes the electromagnetic coil, and closes the magnet switch 30.

As a result, a voltage arbitrarily adjusted by the slide transformer 31 is immediately generated on the secondary side of the slide transformer 31, and this voltage is further stepped down to a desired low voltage, for example, IOV or lower, by the step-down transformer 32, and the voltage is lowered to the resistive heating tube of the load. 13 or the above-mentioned resistance heating elements 13, 13', etc., usually with a large current.

Therefore, the electric power is applied to the resistance heating tube 1γ at the same time as the injection instruction, and the electric power is applied to the resistance heating tube 1γ at the same time as the injection instruction.
Injection flow of the raw material is started after a delay of 5 seconds.

The injection flow continues until one injection amount has passed, and during this time, the raw material is heated at once to a desired temperature, for example, a temperature that reaches vulcanization in about 15 seconds, while passing through the resistance heating tube 13''. It heats up and is sent toward the mold, where it enters the cavity in its high temperature state.

As the screw shaft 2 moves forward, the IJ Mitswitch 21 operates as described above at a position immediately before, for example, 2 mm before the end of the screw shaft 2 reaches the end, thereby cutting off the heating current sent to the resistance heating tube.

Even after the heating current is cut off, the screw shaft continues to move forward and the raw material continues to be discharged from the tip of the nozzle 5 until the screw shaft reaches the end.By changing the position of the limit switch 20, the raw material can be continued to be discharged. It is possible to freely change the amount to be more or less, and furthermore, by operating the two limit switches at the same time, the amount of raw material that continues to be discharged can be reduced to almost zero.Similarly, the time of the time relay 26 can be changed. The settings can be arbitrarily adjusted, and the delay time can be freely adjusted, for example, from zero to an arbitrary number of seconds.

The reason why the timing of injection start and heating, or the timing of injection end and heating stop, etc. is adjusted within a short time as described above is that by doing so, when performing injection molding continuously, for example, resistance It becomes possible to heat and raise the temperature of the raw material stopped in the exothermic tube 13'' waiting for the next flow from the beginning of the flow to almost the desired temperature, and also allows the injection amount of raw material to pass through. By cutting off the heating current just before the heating is finished, the raw material stopped in the tube can be kept in an unvulcanized state.

In addition, contrary to the above, the heating current continues to be sent for a short period of time after the injection flow has stopped, and thereby, for example, the flow path 10 of the raw material fluid in the pipe or the upper cavity is heated.
It is also possible to add mud to the rubber remaining on / etc., making it easier to remove as scrap.

However, although the method of passing the instruction current in this case is different from that shown in FIG. 4, the implementation method can be easily inferred from the above explanation.

Intermittent heating by the heating device of the present invention corresponds to the intermittent flow of the raw material fluid, and applies electric power to the resistance heating element only during the approximate flow time, and does not apply the electric power at all during other times. The present invention is not limited to intermittent heating in which no voltage is applied, but during the other times mentioned above, a small amount of electric power can be applied to maintain the flow path 10' through which the raw material fluid passes at a desired constant temperature to correspond to the start of injection. Then, the upper ybt-power may be switched to an appropriate high power and applied.

Furthermore, the intermittent heating of the present invention is not limited to intermittent heating in which electric power is applied only while the injection continues, that is, from approximately the beginning of the flow of the raw material to the stop of the injection; During the process, it is also possible to optionally switch off and on the electrical power, thereby creating a temperature difference in the injection quantity of the raw material fluid and forcing it into the molding cavity.

By doing this, it is possible to obtain, for example, a molded product whose skin and core have different physical properties.

The intermittent heating device of the present invention is applicable not only to the rubbers mentioned above, but also to various thermosetting resins that undergo a thermal crosslinking reaction during molding. It can be similarly used in the production of foam molded products using resin.

By adjusting the above-mentioned mold temperature appropriately, the present invention can be similarly used for a wide range of thermoplastic resins, such as thermoplastic resins mixed with thermally crosslinkable components, and other general thermoplastic resins.

The present invention uses a simple device to reduce the vulcanization (hardening) time in injection molding or transfer molding of rubber and other materials.
It can be shortened to about 10 seconds.

However, the above-mentioned molding can be continued stably, and as a result, the molding cycle can be greatly shortened compared to the conventional method, and not only can injection vulcanization be realized immediately, but also the wall thickness of the molded product can be reduced. ,
Regardless of size, the entire molded product can be vulcanized uniformly, and there is no risk of scrap generation (quality can be improved).

The intermittent heating device of the present invention is an advantageous invention that can be used for a variety of applications other than those described above because of its rapid and efficient heating.

[Brief explanation of drawings]

FIG. 1 is a partially sectional side view showing the main parts of the entire injection molding apparatus to which an example of the intermittent heating device of the present invention is applied, and FIG. 2 is a part of another example of the heating device of the present invention. FIG. 3 is a cross-sectional view showing the essential parts of still another example of the heating device of the present invention, and FIG. 4 is an intermittent heating device of the present invention and a system of rows related to injection instructions. It is a diagram. 1... Plasticizing cylinder, 2... Rotating screw shaft, 3... Raw material rubber, 31...
Hopper, 4... Heating fluid passage, 5... Tuzzle, 6... Movable mold, 7... Fixed mold, 8... Molding cavity, 9... structure,
9'... Upper structure, r... Lower structure, 9a... Heating medium passage, 10...
Heating passage, 10'-□...Flow path, 11...
...Button, 12...Connection end, 13, 13
'... Electric resistance heating element, 13... Electric resistance heating tube, 14, 14'... Heat resistant electrical insulating layer, 15, 15'... electrode, 15〃,15
'll... Conductive screw, 15////...
・Connection terminal, 16, 16'... Electrode, 16"
, 16”... Conductive screw, 16tut...
...Connection terminal, 17, 17'. i s, i s'...media path, 19...
...Thread, 20゜21...Limit switch, 22,23...Bar, 24...
Operating projection, 25...Snap switch, 26
...Time relay, 27 ... Injection drive device, 28 ... Power supply, 29 ... Power switch, 30 ... Magnet switch ,3
1...Slide transformer, 32...
Step-down transformer.

Claims (1)

[Claims] 1. During molding, plasticizing raw materials such as rubbers and synthetic resins that involve reactions such as vulcanization, crosslinking, and foaming are controlled intermittently to a temperature range where the acceleration of the reaction can be ignored. a discharge device for discharging to;
The raw material from the dispensing device is transferred to a plurality of relatively thin walls,
In addition, electricity is applied to the electric resistance heating tube that flows through the small diameter tube and sends it to the mold, and generates Joule heat, and the raw material passing through the tube is rapidly brought to a high temperature just before reaction. In conjunction with the heating passage configured to heat the material and the discharge device, heating power is started to be applied to the resistance heating tube within a short period of time immediately before the flow of the raw material starts, or at the same time as the flow of the raw material starts, and the flow of the raw material is started. Either the heating power is cut off within a short period of time before the flow stops, or at the same time as the flow stops.
or a control circuit that reduces the amount of electric power supplied.