JPH0356886B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a molding machine for liquid injection molded articles, and in particular to a molding machine for liquid injection molded silicone articles.

In recent years, liquid silicones have been formulated as materials for liquid injection molding machines. Compared to most conventional organic elastomers, silicone compositions cure quickly, are easy to pump, are immiscible, release easily from molded surfaces, and often No trimming or deburring required. Because of this unique handling and curing properties, silicone materials are easier to liquid injection mold than other materials. Generally, the shaping of elastomers requires several different operations: rolling, sheeting or extrusion compaction, transfer or injection molding, and subsequent deburring of the finished product. Liquid silicones only require actual injection molding, allowing for much shorter cycle times than other elastomers. The liquid nature of the silicone eliminates the need for rolling, sheeting or extrusion operations, and its liquid nature allows for precise metering and dispensing with conventional pump delivery systems. Since the pressure in the mold cavity is low and the material is hardenable, deburring is also eliminated. As a result, significant savings in labor, administrative costs, and materials can be achieved by switching from conventional molding methods to liquid injection molding. In fact, for large production volumes and small part dimensions, liquid silicones are more than competitive in terms of cost with cheaper organic materials. This is not surprising given that the cost of conventional molding and deburring processes depends mostly on the number of parts and not on the amount of material used. In contrast, with liquid injection molding, the cost per part depends essentially on the amount of material used. Liquid injection molding is also characterized by low capital investment ($20,000 to $50,000 for most applications). This is because the mold cavity pressure is low and the cycle time is short, so a small injection press can produce a large amount of molded products annually.

Special silicone compositions manufactured for liquid injection molding applications are addition-curable room temperature vulcanizable silicone rubber compositions (referred to hereinafter as RTV).
It is. Therefore, one type of composition that is manufactured or formulated for liquid injection molding applications is the addition cure type.
RTV composition. Such compositions are one-part or two-part compositions containing a basic component such as a vinyl polysiloxane, a hydrogenated siloxane as a crosslinking agent, and a platinum catalyst. Other additives may also be present in the composition, such as vinyl resins, suitable amounts of fillers and various types of vinyl-containing polymers. Generally, such formulated compositions combine the platinum catalyst with either the crosslinker, the vinyl siloxane, or the vinyl-containing siloxane, and keep the hydrogenated siloxane separate from the vinyl-containing polysiloxane. That is, there is no package containing vinyl siloxane, platinum catalyst, and hydrogenated siloxane, and if they are contained together, the composition will react and crosslink. If such a composition is to be cured especially in an injection molding machine,
A mixing device is used to mix one package with the other, thus coexisting the vinyl siloxane, hydrogenated siloxane, and platinum catalyst in a single mixture. This composition crosslinks and cures at room temperature to form a silicone elastomer. The composition crosslinks and cures in about 1 to 48 hours at room temperature. However, it is applied at high temperatures in liquid injection molding presses. i.e. the composition at 100℃
It can be cured in a few seconds by heating to a temperature above, especially about 150°C.

Compositions such as those described above are also prepared in one-component forms. Recently, the addition of effective inhibitors to the compositions has made these compositions one-component, i.e.
It is a package composition. An example of this type of composition containing an effective inhibitor is the composition disclosed in William J. Bobear, US Pat. No. 4,061,609. This patent discloses the use of hydroperoxy compounds as inhibitors in addition-curable compositions, which hydroperoxy compounds inhibit the curing of the compositions at room temperature for extended periods of time, such as from 6 months to over 1 year. It is prohibited to pass, but
Allows the composition to cure rapidly at elevated temperatures, ie, temperatures above 100°C. Other types of inhibitors that can be used in such compositions are dialkenyl maleates. Such dimaleate is disclosed in U.S. Patent Application No. 1, filed by R. Eckberg, assigned to the present applicant.
No. 40015 "Solvent-free mold release composition, manufacturing method, and article" (filed May 17, 1979).
The use of such inhibitors allows the composition to be one-component. The composition can then be submitted as is to a processor who applies the one-component composition to a liquid injection molding machine and molds silicone elastomer moldings from the composition.

When you want to mold a composition or silicone elastomer molded article with outstanding solvent resistance,
Fluorosilicone addition-curable compositions can be used. Thus, using the same SiH olefin platinum catalyst-containing compositions as described above, fluorosilicone elastomers with particularly high solvent resistance can be obtained. Fluorosilicone addition cure compositions consist of a vinyl-containing polysiloxane with fluoroalkyl substituents, a hydrogenated polysiloxane optionally with fluoroalkyl substituents, a platinum catalyst, and various types of additives. An inhibitor is used to render such a composition into a one-component form. In particular, the inhibitors disclosed in the Bovea US patent and the Ekberg US patent application mentioned above are used. The composition cures into a silicone elastomer in a liquid injection molding machine when heated at high temperatures, and the cured molded article exhibits unique solvent resistance. An example of a fluorosilicone addition cure composition particularly suitable for liquid injection molding machines is disclosed in Jeram, U.S. Pat.
See No. 4041101 and No. 4029629.

These silicone compositions are particularly suitable for use in plunger-type reciprocating screw devices for forming silicone molded articles. However, the present invention concerns a reciprocating screw injection molding machine. In conventional molding machines, the organic plastic material is a solid plastic material in the form of pellets, which is introduced into the molding machine through a hopper and forced into a forward position in the molding barrel by the machine's screw threads. When the screw thread pushes the organic plastic pellet forward into the molding barrel to inject it into the mold, the pellet liquefies into a liquid under the pressure of being pushed forward. Therefore, the pellets are liquid only in the front section of the reciprocating screw machine. Therefore, there is no problem of the liquid organic material extruding itself out of the rear end of the molding barrel of the reciprocating screw molding machine. In addition, since the pellets are fed from the hopper to the screw in the molding barrel of the reciprocating screw type injection molding machine, as far as the pressure when introducing the liquefied organic plastic pellets into the mold is concerned, the front end of the screw of the reciprocating screw type injection molding machine There were no problems with fluctuations in the pressure of the liquid. However, when using liquefied or liquid raw materials in a reciprocating screw molding machine, the same molding machine used to form molded articles from organic plastic pellets cannot be used without further modifications.

A molding machine configured according to the present invention for forming a liquid injection molded article from a liquid molding material includes: a frame; a drive means attached to the frame; a support means attached to the frame and supporting the drive means. and; a molding barrel mounted on said support means and having a large longitudinal bore and having a front opening through which liquid molding material passes and a rear opening adjacent said drive means; a screw extrusion means configured to move within the lumen; coupled to and supported by the drive means;
link means for driving said screw extrusion means; and sealing means mounted on a rear opening of said forming barrel.

A molding machine for forming a silicone liquid injection molded article from a liquid silicone injection molding composition constructed in accordance with another aspect of the invention comprises: a frame; a drive means mounted on the frame; a drive means mounted on the frame; support means for supporting said drive means; a molding barrel mounted on said support means and having a longitudinal bore and having a front opening through which a liquid silicone molding composition passes and a rear opening adjacent said drive means; a screw extrusion means configured to move within a longitudinal lumen of the forming barrel; an extrusion head mounted at the forward end of the forming barrel and having a longitudinal lumen; coupled to the drive means. and supported by it,
a link means for driving the screw extrusion means; a supply means mounted on the molding barrel for supplying the liquid molding composition to the molding barrel; a link means mounted on the supply means for supplying the liquid molding composition to the molding barrel when the molding machine is extruding the composition; A supply means and a supply valve means for isolating the liquid pressure from the liquid pressure within the forming barrel.

In a preferred embodiment, the rear opening of the molding barrel is provided with a rear sealing means and the first valve means is arranged in the feed means to the molding barrel in the same molding machine.

Next, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a plan view showing the molding barrel, screw, and motor of the reciprocating screw injection molding machine of the present invention, with the barrel portion shown in cross section. It should be noted that the present invention is an improvement over the invention relating only to reciprocating screw injection molding machines. The present invention does not involve plunger-type molding machines. Before going into the explanation of the improved structure of the reciprocating screw injection molding machine, especially the improved sealing structure, it is necessary to explain a little about the device shown in Figure 1 in order to understand how the device works. . Briefly, a silicone composition is delivered to the device through flexible conduit 10 and into passageway 14. The passageway 14 can be molded integrally with the molded barrel 18. Cylindrical tube 20 constituting the molded barrel 18 of the device
is bored with a longitudinal lumen 22 and has a front opening 24 and a rear opening 28 . Portion of the front opening 24 of the forming barrel 18 is a threaded opening 30 into which a forming head 32 is screwed. The forming head 32 has a rear threaded section 34 which connects the forming barrel 18.
screw into the screw opening 30 of. Molding head 32
is perforated with a vertical hole 36 and has a front nozzle 38.
A threaded portion 34 of the forming head 32 threadably engages a threaded opening 30 in the forming barrel 18.

As shown, thermocouple temperature measurement probes 40 and 42 are provided. These thermocouples do not form any part of the present invention and will not be described in detail. The shaped barrel 18 is supported by supports 50 (shown in phantom), cross-sectional supports 52, 54, and longitudinal supports 56. The molded barrel 18 has a steel cooling jacket 6 with an opening 62 drilled therein.
0 is also provided, through which cooling water is circulated to cool the forming barrel 18 to a desired temperature. Molded barrel 18
A cylindrical shaft 70 passes through the longitudinal bore 22 of. The cylindrical shaft 70 has a front forming head 72 that fits into the rear opening of the forming head 32 and a forward shank 74 followed by a central shank 76 having threads 80 on its outer periphery and a smooth rear shank 82. continues. A smooth rear shaft 82 extends out of the opening 28 of the molded barrel 18 and is connected to a flange 86 . Motor 90 moves the shaft longitudinally through linkage 92 and flange 86 . Movement of the flange 86 is guided by a shaft 98 attached to the support surface 100 and a motor 90. Bracket 86 has limit switch 1.
A switch support member 102 to which 04 is attached is supported or attached. A support member 108 is also attached to the support surface 100, and a cam 110 is mounted thereon. A threaded portion 112 supports the cam 110 on the bracket 108. During movement of flange 86 and thus switch support member 102, limit switch activator 104 hits cam 110, shutting off the valve in the feeder as described below, and causing the pressure in the feeder to match the pressure in forming barrel 18. prevent it from affecting However, for the purposes of the present invention,
Suffice it to say that: The silicone composition enters the forming barrel passageway (or channel) 14 via the supply conduit 10 and is delivered to the forward portion of the longitudinal lumen 22 by the screw 80 of the shaft 70. While this is in progress, the screw shaft 70 is retracted away from the ram head 32 and the forward end of the bore 22 is filled with liquid material by the propelling action of the screw 80 of the shaft 70. When the cam 110 triggers the activator switch 104, the supply valve leading to the supply conduit 10 of the supply device is shut off by another mechanism, not shown, and the motor 9
0, the entire molding barrel apparatus including the support member 100, the molding barrel 18 and the head 32 is moved, and the head 32, especially its nozzle 38, is moved into the mold (not shown).
contact with the opening of The mold logic control system is not shown as it does not form any part of the invention. The motor 90 moves the flange 86 and thus the shaft 70 straight forward so that the control ram head 72 forces any liquid silicone composition in front of it out of the nozzle 38 through the longitudinal hole 36 of the extrusion head 32. Move into the cavity of the mold. The logic control system and screw rotation control system (not shown) are again activated to prevent ram head 72 from moving beyond the position shown in FIG. 1 within longitudinal lumen 22 by means not shown. Once all of the silicone composition, the proper amount of silicone composition, has been pumped into the mold, as determined by the forward stroke of the conical ram head 72 within the bore 22, the molding barrel 1
8. The entire ram head 32, motor 90 and support 100 are moved away from the mold;
Motor 90 is energized to pull screw shaft 70 back out of longitudinal lumen 22 in rotational motion. When this happens, the motor 90 on the support member 100 is activated, i.e. the shaft 70 and therefore the screw 8
0, the supply valve to the conduit 10 is opened and the silicone composition is reintroduced and directed forward into the longitudinal lumen 22 by the screw 80 in the central shaft 76. That is, the screw 80 transfers the silicone composition to the front end of the screw shaft 70 and the conical head 7.
Promote before 2.

The present invention is an improvement of the standard reciprocating screw type injection molding machine shown in FIG.
shown in the rear opening 28 of the second, third and fourth
It is shown in detail in the figure. Without the improvements of the present invention, when the silicone composition is fed into the forming barrel 18 through the screw 80 of the shaft 70, the pressure generated within the longitudinal bore 22 causes the silicone composition to flow into the forming barrel 18. was pushed out from the rear opening 28 of. Thus, the exact amount of silicone composition fed into the screw shaft 70 is equal to the exact amount forced into the mold by the shaft 70 minus the longitudinal bore 3 of the molding head 32.
6 and the amount that remains in the nozzle 38.
The logic device controlling the supply valve becomes inaccurate. According to a first aspect of the invention, the molded barrel 1
A sealing device is provided at the rear end of the rear opening 28 of 8. In FIG. 2, such a seal comprises two plates 120 and 122 that are split in half and joined together to form a single plate. plate 120
and 122 have semicircular openings 124 and 126, which together define a circular opening through which the shaft rear portion passes. plates 120 and 122
is secured to the rear end of the molded barrel 18 at the rear opening 28 by a threaded bolt 130. The fixing structure of the plate is clearly shown in FIG. Plates 120 and 122 are provided with beveled portions 140 and 142 at the locations where the plates contact rear shaft portion 82 to facilitate contact between rear shaft portion 82 and openings 124, 126 in plates 120, 122. to minimize wear. In a different embodiment of the invention shown in FIG.
22 and the rear end of the molded barrel 18 at the location of the rear opening 28. The plastic disc 150 thus actually performs a sealing function. The advantage of using a plastic disc is that it not only performs a proper sealing function, but also that it can be easily and inexpensively replaced when it wears out. The plastic disk can be provided in two parts, like the plates 120, 122, or it can be a single piece. The same applies to plates 120, 122, which can also be manufactured as a single unit. but,
A two-part construction, as shown in FIG. 2, is cheaper and much easier to attach the sealing device to the molding equipment. It should also be appreciated that a seal can be formed integrally with the molded barrel 18 at the rear opening 28. However, welding or integrally molding the seal to the rear end of the molded barrel 18 makes it difficult to replace when it wears out, and also makes it extremely difficult to adapt existing equipment to include such a seal. It's expensive. With the sealing device of this example, existing reciprocating injection molding machines can be adapted to include such a sealing device, allowing the use of silicone compositions or any other liquid molding composition as opposed to the use of pellets. It is possible to make things usable. Therefore, in a broad sense, the present invention provides a molded barrel 1
8 consists in applying a sealing device to the rear opening 28 of the molded barrel 18 to prevent the liquid material present in the longitudinal lumen 22 of the molded barrel 18 from leaking out.

Next, a second improved example of the reciprocating screw type injection molding machine of the present invention, shown in FIGS. 5 to 7 in a form attached to FIG. 1, will be described. In FIG. 5, the conduit 10 is connected to a molded barrel 18 (partially shown in FIGS. 5 and 7), which is then connected to a ball valve 162 by a suitable nut-sleeve connection 160. Ball valve 162 is connected to conduit 170 by a suitable nut-sleeve connection 166. Conduit 170 leads to a pressurized container of liquid silicone composition such that the liquid silicone composition is delivered to conduit 170 under pressure. The pressurized container of liquid material will likely be equipped with a valve, which will remain open during use of the device and will prevent the forming barrel 18 of the liquid material from forming.
The supply to is controlled by a ball valve 162. Ball valve 162 includes an inlet tube 174, an outlet tube 172, and a ball 178 having a longitudinal bore 180.

When the vertical hole 180 is aligned with the supply conduits 174 and 172, the liquid material flows from the supply conduit 170 to the conduit 10.
and can flow into the forming barrel 18. As shown in FIG.
2, liquid molding material will not flow to valve 162. Ball 178 is connected to pneumatic motor 192
It is rotated by a shaft 190 propelled by. The pneumatic motor 192 includes a flange 196, and is configured to rotate the flange 196 in one direction or the opposite direction by air arriving at a lower side 200 or an upper side 202 of the pneumatic motor 192. Three-way air valve 20 operated by electric solenoid 208
6 delivers air to the upper side 202 of the pneumatic motor 192 via the air line 204. Three-way air valve 222 controlled by electric solenoid 224
air is introduced into the underside 200 of the pneumatic motor 192 via the air line 220. Solenoid 224 is supplied with electrical pulses via electrical line 226 . Solenoid 208 is connected to electrical line 228
It is energized through . Lines 226 and 228 are connected to logic controller 260, which will be described below. Solenoids 208,2 are controlled by logic controller 260.
24 to allow air to enter and flow through the appropriate side of the pneumatic motor 192 through either of the three-way air valves 206 and 222, thus rotating the flange 196 from one position to the other. and opens and closes ball valve 162 to allow or prevent liquid silicone composition from entering mold barrel 18. Additionally, when the ball 178 is on its side as shown in FIG. 5, the liquid silicone composition supply tank pressure is isolated from the pressure within the molding barrel 18. Pneumatic motor 192 and air valve 2
For a more detailed explanation of the operation of 06,222, reference should be made to FIGS. 1 and 6 as well as FIGS. 5 and 7. Bracket 86 is motor 9
0 and the switch activator 104 is triggered by the cam 110, a sufficient amount of liquid silicone composition is deposited into the screw shaft 7.
0 into the front end of the longitudinal lumen 22.
Therefore, at this time, the logic controller 260 is energized via the limit switch, which causes the solenoids 208, 2 to be activated via the electrical lines 228, 226.
24 is energized. Specifically, solenoid 208 is energized via line 228 to connect air valve passage 240 of three-way valve 206 to passage 242 . As a result, the air supply pressure is reduced to the passage 242 of the three-way valve 206.
The passageway 240 is connected to the passageway 240 and bypasses the passageway 250. Simultaneously, logic controller 260 energizes solenoid 224 via electrical line 226, thereby isolating passage 262 of three-way valve 222 from both passages 270 and 272. Air pressure thus communicates from passage 272 to passage 270 and through conduit 220 to the underside 200 of pneumatic motor 192 to pivot flange 196 . As a result, ball 178 is rotated sideways so that hole 180 is oriented laterally as shown in FIG. Logical controller 260
then operates motor 90, thereby pushing flange 86 and screw shaft 70 forward. After the forming barrel 18, motor 90, flange 86, and support surface 100 have moved forward to bring the forming head 32 into contact with an opening in a mold (not shown), the motor 90 moves the flange 86 under control of the logic controller 260. It is forced rapidly forward with the screw shaft 70, thus causing the conical head 72 to force the liquid silicone composition out of the longitudinal bore 22 of the molding barrel 18 and into the mold.

After the molding material has been introduced into the mold, a screw rotation control device 280 (not forming any part of the present invention and shown diagrammatically in FIG. 6) operates to rotate the entire molding barrel assembly. Once removed from the mold, both the screw shaft 70 and the forming barrel 18 are retracted and the ball valve 162 is simultaneously opened so that the liquid material again flows under pressure into the forming barrel 18. However, the manner in which the screw shaft 70 is actuated to move the entire forming barrel 18 and motor 90 and support 108 away from the mold differs from molding machine to molding machine, depending on the type of screw rotation control and the type of logic control. Similarly, three-way valve 20
6,222 is selectively communicated by the solenoid, the screw shaft 70 is retracted, and the flange 196 is rotated to open the ball valve 162, ie, to bring the bore 180 into line with the conduit 170. Since the control devices do not constitute any part of the present invention, a detailed description thereof will be omitted. A feature of the invention is the valve arrangement 162 on the supply conduit 10. Although this valve device is illustrated as a ball type valve device, any type of valve device can be used as long as it operates effectively in accordance with the present invention. The illustrated ball valve device 162 has been found to be effective and suitable for use. Other types of valve devices that can be used are:

Globe valve Butterfly valve Plug valve Needle valve Stop valve Lift check valve Swash plate check valve Gate valve Swing check valve Foot valve Cock valve In addition, the ball valve device can be actuated by means other than a pneumatic motor, for example by suitable electrical means, hydraulic means, springs or check valves. The particular pneumatic motor itself does not form any part of the invention. Broadly speaking, the present invention relates to supply conduit 1
A valve arrangement is used at 0 to regulate the flow of pressurized liquid material through the supply conduit 170, thus introducing the proper amount of material into the forming barrel 18, and once the proper amount has entered the forming barrel, the valve controls the supply. The flow of liquid material into the forming barrel 18 via conduit 10 is stopped and conduit 1
70 is isolated from the pressure within the forming barrel 18, such that the pressure exerted on the liquid material within the forming barrel 18, and in particular its longitudinal lumen 22, is determined solely by the screw shaft 70, particularly its forward end. Do it like this. Otherwise, conduit 170
The pressurized liquid molding material inside passes through the molding barrel 1.
Screw shaft 70 within longitudinal lumen 22 of 8
The liquid material in front of the forming conical head 72 may be under too high a pressure, resulting in wasted material and possible damage to the molded part.

Thus, in a broad sense, the present invention comprises an effective valve arrangement actuated by any means on the supply conduit 10 described above and located at the rear opening 28 of the molding barrel 18, such that liquid molding material is supplied to the rear opening 28 of the molding barrel. and an effective seal to prevent leakage from 28.
The present invention is suitable for reciprocating screw injection molding machines, particularly for molding machines that use liquid or pasty molding materials. If the molding machine receives solid pellets or particles in the feed conduit, the improved construction of the present invention is not necessary, but if the material is a liquid molding compound, a reciprocating screw injection molding machine will produce a suitable injection molded product. The improved structure of the present invention is needed to form a . Therefore, for use in such molding machines, silicone molding compositions such as 100 parts by weight of a vinyl-containing polysiloxane, 0.1 to 50 parts by weight of a monofunctional siloxy, as disclosed in the aforementioned Povea US patent, may be used. hydride-containing silicone resins consisting of units and tetrafunctional siloxy units, or hydride resins consisting of monofunctional siloxy units, tetrafunctional siloxy units and difunctional siloxy units,
and a platinum catalyst are preferred. In addition to hydride resin, as a crosslinking agent,
A hydride-containing linear polysiloxane having a viscosity of 1 to 1000 centipoise may be included. The vinyl-containing polysiloxane polymer can be a polymer having a viscosity of 100 to 200,000 centipoise at 25°C. The required third component is a platinum catalyst. As mentioned above, the composition can be a two-component system or, through the use of a suitable inhibitor, a one-component system. The various additives disclosed in the patents cited in the most part of this specification may be added to the above-described base composition, or any other type of additive may be used to prepare suitable silicone molding compositions. can manufacture things. Use 0.1-500 ppm platinum catalyst for the total composition. The platinum catalyst is charcoal or γ-
Although it can be solid platinum deposited on alumina, solubilized platinum catalysts, such as those disclosed in the aforementioned US patent applications, are more preferred. However, not only these silicone compositions, but also other liquid molding compositions or silicone molding compositions that may be developed in the future can be used in the reciprocating screw injection molding machine having the improved structure of the present invention.
The improved structure of the screw molding machine constituting the present invention is as follows:
The particular type of molding material used is irrelevant as long as the molding material is a liquid molding material. The apparatus of the present invention can be used with any type of liquid silicone molding composition, and in general with any liquid molding composition.

[Brief explanation of drawings]

FIG. 1 is a partially sectional plan view of the reciprocating screw type injection molding machine of the present invention, and FIG.
An end view of the sealing means seen in the two-line direction, FIG.
Sectional view of the sealing means taken in the direction of line 3-3 in the figure, No. 4
The figure is a sectional view showing another example of the sealing means as seen in the direction of line 3-3 in Fig. 2, Fig. 5 is a partially cutaway perspective view showing the valve means for monitoring the supply means, and Fig. 6 is Fifth
FIG. 7 is the same perspective view as FIG. 5 showing the ball hole aligned with the conduit. 10... Supply conduit, 14... Passage, 18... Barrel,
22...Longitudinal lumen, 24...Front opening, 28...Rear opening, 32... Ram head, 36... Head hole, 3
8... Nozzle, 50, 52, 54, 56... Support, 70... Shaft, 72... Molding head, 74...
Front shaft part, 76... Central shaft part, 80... Screw, 8
2... Rear shaft section, 86... Flange, 90... Motor,
92... Link mechanism, 100... Support surface, 104...
Limit switch, 110...Cam, 120, 12
2... Plate, 124, 126... Opening, 150...
Plastic disc, 162...Ball valve, 170...
Supply conduit, 178... Ball, 192... Electric pressure motor, 206, 222... Three-way valve, 208, 224...
Solenoid, 260...logic control device.

Claims (1)

[Claims] 1: a frame; a drive device 90 attached to the frame; a support 100 attached to the frame and supporting the drive device; attached to supports 50, 52, 54, 56;
a molding barrel 18 having a longitudinal cavity 22 and a front opening 24 through which liquid molding material passes and a rear opening 28 adjacent the drive device; and configured to move within the cavity of the molding barrel. an extrusion screw 70 connected to and supported by the drive device;
and link means 92 for driving said extrusion screw, wherein sealing means are mounted in said rear opening of said molding barrel, said sealing means sealing said rear opening relative to said rear part of said molding barrel. sealing plates 120, 122 mounted adjacent to the extrusion screw and having openings 124, 126 therethrough through which the rear shaft 82 of the extrusion screw is in sealing contact; the sealing plate has an inclined surface at the rear of the point where the sealing plate contacts the rear shaft; For forming liquid injection molded parts from liquid silicone molding compositions, characterized in that cutouts 140, 142 are provided to minimize contact and thus wear between the rear shaft and the opening of the sealing plate. Injection molding machine. 2. A front head as the extrusion screw;
A threaded central cylindrical shaft is connected to a smooth rear cylindrical shaft of smaller diameter than the diameter of the central cylindrical shaft, and such rear cylindrical shaft is connected to and supported by the link means. The injection molding machine according to item 1. 3. The sealing plate is comprised of two plates, each plate forming one half of the opening through which the rear shaft passes, and both plates are thus provided adjacent to the rear opening of the molded barrel so that the rear shaft An injection molding machine according to claim 1, wherein a circular opening is defined therethrough. 4. Said sealing plate is made of metal, and a plastic or elastomer plate sealing means is arranged between said metal sealing plate and the rear opening of said molded barrel, said plastic or elastomeric plate sealing means forming the actual seal. An injection molding machine according to claim 1, which operates as follows. 5. Said sealing plate is made of metal, and a plastic plate sealing means is arranged between said metal sealing plate and a rear opening of said molded barrel, said plastic plate sealing means being in a cavity of said molded barrel. 4. An injection molding machine as claimed in claim 3, which comprises two plates, which act as the actual seal for the liquid silicone molding composition and are made of metal, similar to said sealing plate. 6. An injection molding machine according to claim 5, wherein said plastic is a fluorinated plastic. 7. The molding machine of claim 1, wherein an extrusion head is disposed in the front opening of the molding barrel, and the silicone molding composition is extruded from the extrusion head. 8. An extrusion head located at the front opening of the molding barrel is provided with a longitudinal aperture, the molding barrel having a supply for supplying a liquid silicone molding composition to the molding barrel. means are attached to the supply means, and first valve means are attached to the supply means for isolating the supply means from pressurized liquid silicone molding composition when the injection molding machine is extruding. Claim 1
Injection molding machine as described in section. 9. A mold according to claim 8, wherein the frame is fitted with a mold into which liquid silicone molding composition is introduced by the extrusion head in accordance with operation of the injection molding machine. Injection molding machine. 10. Claim 9, wherein said supply means comprises a container containing a liquid silicone molding composition under pressure, said container being connected to said molding barrel through a conduit with said first valve means disposed therebetween. The injection molding machine described. 11 said first valve means has a ball with a cylindrical hole passing through the diameter of the ball, said liquid silicone molding composition being able to pass through said cylindrical hole when said cylindrical hole coincides with an opening in a conduit; 11. The injection molding machine of claim 10, wherein the ball cannot pass through the cylindrical hole when the hole is perpendicular to the opening of the conduit, and the ball is actuated by a pneumatic motor. 12 The pneumatic motor is operated by two three-way valves, and the three-way valves are driven by a solenoid;
12. The injection molding machine according to claim 11, wherein said solenoid is energized or deenergized by a logic control device and a screw rotation control device. 13. The injection molding machine of claim 12, wherein said logic control device for energizing said solenoid is triggered by a limit switch mounted on said link means and engaged with a cam mounted on said support means. 14 The extrusion screw connects the front head, a threaded central cylindrical shaft, and a smooth rear cylindrical shaft having a diameter smaller than the diameter of the central cylindrical shaft, and connects the rear shaft to the link means. 14. A molding machine according to claim 13, which is connected and supported thereby.