RU94903U1 - PRESS FORM FOR PRESSURE CASTING - Google Patents

Abstract

 1. A mold for injection molding containing detachable parts, in one of which a forming cavity is made and an ejector is located, and in the other a nozzle is made, characterized in that the forming cavity is made with a variable volume by means of a moving sign in the form of a piston, simultaneously being an ejector. ! 2. The mold according to claim 1, characterized in that at least one form-forming sign is passed through the piston. ! 3. The mold according to claim 1, characterized in that the shape of the piston surface and the surface of the forming cavity mating with it are different from the cylindrical one.

Description

The utility model relates to foundry for the production of products, mainly from thermoplastic polymer injection molding, mainly thick-walled products. The technical solution of the invention can also extend to the receipt of products from other materials.

Known mold [1] for injection molding, containing detachable parts, in one of which a nozzle is made, and in the other a forming cavity.

However, such a device has a low universality of its application, since it can be used to produce products of only small thickness.

The mold for injection molding [2], adopted as a prototype, is more universal, containing detachable parts, in one of which a forming cavity is made and an ejector is located, and the nozzle is made in the other.

However, the disadvantage of the prototype [2] is that using such a mold it is not possible to obtain thick-walled products of good quality without sinks, without gas and shrinkage porosity. The fact is that with the help of a casting machine, the material is melt through the nozzle of the mold, which determines its laminar (jet) flow when filling the forming cavity (in the case of casting thick-walled products). As a result, the negative effect of the “free stream” is formed, “cold junctions” appear in boundary flows close to the surface of the forming cavity, and the likelihood of formation of gas and shrinkage porosity and shells increases. In addition, a negative “diesel effect” may also occur, accompanied by an explosion of a mixture of melt vapor and displaced air in the forming cavity to produce an unwanted burn in the manufactured product and on the surface of the forming cavity. All this reduces the efficiency of the mold.

The objective of the utility model is to increase the efficiency of the use of injection molds.

The problem is solved in that the injection mold containing detachable parts, in one of which a forming cavity is made and an ejector is located, and in the other a nozzle is made, has distinctive features: the forming cavity is made with a variable volume using a movable sign in the form of a piston, which is also an ejector.

This embodiment of the forming cavity and the use of a movable sign for this purpose is aimed at providing the possibility of creating a kind of initial barrier (movable partition) for the formed laminar stream of the melt supplied through the nozzle, in order to prevent the spread of negative effects formed in the case of the use of the mold according to the prototype [ 2].

Performing as a sign of the piston with its location in the forming cavity will contribute to the gradual filling of the resulting variable volume of such a cavity with a melt, which will further enhance the aforementioned effect of the first distinctive features of the device.

Mold Options:

- at least one form-forming sign is passed through the piston.

- the shape of the piston surface and the surface of the forming cavity mating with it are different from the cylindrical one.

The essence of the utility model is illustrated by illustrations. Figure 1 shows the General scheme of the mold for injection molding of products without a Central hole. In Fig.2 - the same as in Fig.1, but for injection molding of products with a Central hole.

The mold for injection molding contains detachable parts 1 and 2. The detachable part 1 is movable (dashed lines with two points show the contour 1 of the detachable part 1a in the displaced position). Such mobility can be ensured by the closing-opening unit of the injection machine (its movable and fixed plates 3, 3a are shown). In the detachable part 1, a forming cavity 4 is made and an ejector 5 is located, provided with a movable sign in the form of a piston 6 located in the forming cavity 4 to change its volume.

The lateral surface of the piston 6 may be non-cylindrical, for example, in the form of a profile of a curved cam surface (not shown). To obtain parts with a Central hole in the mold design introduced (figure 2) form-forming sign 7, also located in the forming cavity 4 and mounted on the detachable part 1.

The pusher 5 is moved by the power cylinder 8 of the injection machine (not shown). The dashed lines show the contour 5a of the ejector 5 in the displaced position together with the piston 6 (the dashed lines of its contour 6a).

The detachable part 2 is stationary and a nozzle 9 is made in it, to which the output part of the injection machine (not shown) is supplied for supplying the melt. The piston 6 or the end part of the sign and the nozzle 9 are located relative to each other with a gap Δ, forming the element of hydraulic resistance "nozzle-flapper"

The detachable part 1 is equipped with a brake mechanism designed to create the necessary pressure in the mold cavity by slowing down the speed of movement of the piston under the influence of the melt flow on it. Such a mechanism consists, for example, of friction pads 10 located near the extendable parts of the ejector 5, and rods 11, for example, coil springs (not shown) or brake chambers (not shown), used to move the friction pads 10.

The forming cavity 4 is formed in the insert 13 of the detachable part provided with the cooling jacket 12. Inside the forming sign 7, a cooling cavity 14 is made (Fig. 2). A cavity or cooling jacket (not shown) can also be made in the detachable part 2.

Injection molding is carried out using a mold as follows.

In the initial position on the injection machine (not shown), the releasable parts 1 and 2 of the mold are closed and under pressure, and the ejector 5 together with the piston 6 are in the extreme right position (as shown by solid lines).

Depending on the casting mode, the braking of the displacement of the ejector 5 is preliminarily controlled by acting on the rods 11, for example, by tightening - loosening coil springs or by using hydraulic brake chambers (not shown).

Then, the injection unit of the injection machine (not shown) is brought to the inlet of the mold, with which the melt is fed through the nozzle 9 under pressure. Overcoming the hydraulic resistance "nozzle-damper" created by the mutual arrangement with the gap Δ of the nozzle 9 and the piston 6, the laminar stream of the melt entering the gap Δ hits the end face of the piston 6, dramatically changing its direction along this end. Therefore, together with the displacement of the piston with the ejector 5 under the action of the melt pressure, the melt particles are mixed (its turbulent motion), which helps to eliminate the negative effects of a “free stream”, “cold junctions” in the boundary melt flows close to the surface when the melt is filling in the forming cavity 4 the forming cavity 4, which are present in the mold of analogues [1, 2].

Reducing the speed of movement of the ejector 5 contributes to the above-mentioned preset braking mechanism. It is used to adjust the pouring pressure inside the forming cavity 4. This happens automatically depending on the mode of filling with the melt of the forming cavity 4 by changing the braking value of the displacement of the ejector 5 by acting on the rods 11, for example by tightening - loosening screw springs or using brake hydraulics cameras (not shown).

In this case, the thermal casting is controlled by the supply of coolant (not shown) to the cooling jacket 12, to the cooling cavity 14 of the shape-forming sign 7 (Fig. 2) and around the fixed part of the mold 2.

In the extreme left position of the ejector 5 (circuit 5a), the piston 6 also occupies the extreme left position (circuit 6a), forming the necessary volume of the forming cavity 4, in which the hot melt will be located.

After that, the flow of the melt through the nozzle 9. is stopped. The melt cools down, hardening and forming a part (not shown) in the forming cavity. Due to the previously obtained effect of turbulence of the melt flow, in which the above-mentioned negative effects are eliminated, cold junctions are not formed inside the obtained part, gas and shrinkage porosities, shells are significantly reduced, and on its outer surface and inner surface (in the case of the formative sign 7 of FIG. .2), as well as on the surface of the forming cavity 4, no soot is formed.

To remove the molded part on an injection molding machine (not shown), the detachable parts 1 and 2 are separated from each other and the detachable part 1 occupies the leftmost position (circuit 1a). After that, the fluid is supplied under pressure into the rodless cavity 8a of the cylinder of the ejector 8, moving the ejector 5 together with the piston 6 from the extreme left positions (circuits 5a and 6a) to the right, pushing the finished part (not shown) from the forming cavity 4 into the tray ( not shown). In this case, in the case of application of the design of the mold according to figure 2 receive a part with a Central hole.

Then, the detachable parts 1 and 2 are closed, and are under pressure. Next, the mold cycle is repeated.

Thanks to the introduction of the original connection of the elements into the utility model and the support of their interaction using the schemes shown in figures 1 and 2, it is possible to increase the efficiency of injection molding and the operation of the mold for the manufacture of parts of various configurations and sizes with and without a central hole.

Information sources:

1. Patent RU 2284913, IPC В29С 45/12, priority from 2002.04.17, publ. 2006.10.10.

2. Patent RU 2010667, IPC B22D 17/22, priority from 1990.12.13, publ. 1994.04.15 / prototype /.

Claims (3)

1. A mold for injection molding containing detachable parts, in one of which a forming cavity is made and an ejector is located, and in the other a nozzle is made, characterized in that the forming cavity is made with a variable volume by means of a movable sign in the form of a piston, simultaneously being an ejector. 2. The mold according to claim 1, characterized in that at least one form-forming sign is passed through the piston. 3. The mold according to claim 1, characterized in that the shape of the surface of the piston and the mating surface of the forming cavity are different from cylindrical.