GB2579766A

GB2579766A - Improvements to injection moulding machines

Info

Publication number: GB2579766A
Application number: GB1817122.3A
Authority: GB
Inventors: Cooper Thompson Samuel
Original assignee: Pancake Machine Ltd
Current assignee: Pancake Machine Ltd
Priority date: 2018-10-20
Filing date: 2018-10-20
Publication date: 2020-07-08
Also published as: GB201817122D0

Abstract

An injection moulding machine comprises a barrel (2, fig 1) and a piston (1, fig. 1). A portion 6 of the outer surface 10 of the piston abuts a portion 6 of the inner surface 11 of the barrel at all times in use. An opening 7 is provided when the piston is sufficiently withdrawn (figure 2) from the barrel to permit moulding material to be inserted into the barrel. The opening not is not present when the piston is fully inserted into the barrel (figure 3).

Description

Improvements to injection moulding machines

Field of the Invention

The invention relates generally to injection moulding machines and, more specifically, desktop injection moulding machines.

Background to the Invention

Desktop injection moulding machines are small, simple-to-use machines for making small quantities of prototypes in thermoplastics and other moulding materials. They are useful to the hobbyist and seasoned inventor, as well as being a helpful tool in the education of the basic concepts of injection moulding.

Popular and well-known prior art involve a barrel which contains the moulding material and a piston which is inserted into the barrel and channels the moulding material through an opening in the barrel, into a mould in which the moulding material sets. Some of the prior art arrangements are designed to secure onto a tower drill or bench drill, with the piston being attached into the opening for the drill bit, and being offered into the barrel by a hand-or electrically-operated lever. In such arrangements the tower drill or bench drill provides the structural framework for the machine, as well as a straight-line motion for the piston to be inserted into with the barrel. Other arrangements of the prior art are designed with a fully integrated framework and support, and are standalone machines that do not require a tower drill or bench drill to provide the structural framework and/or the means by which the piston is inserted into the barrel.

The problem with the prior art arrangements, particularly those which involve a tower drill or bench drill, is that the alignment of the piston and barrel is difficult to maintain when there is a need to refill the barrel with the moulding material between injection moulds. Often the piston will need to be withdrawn fully from the barrel, to avail an opening to refill the barrel with the moulding material. This means that the piston and the barrel become disconnected and lose their alignment relative to one another and to the direction of travel. Realigning the piston and barrel between injection moulds is a time-consuming and awkward process, and since the parts are often very hot, the process is made dangerous and difficult for the user. During this process the temperatures can change and this can require even further time to allow the parts to heat up or cool down to the required temperatures for moulding.

It is therefore an object of the current invention to alleviate at least these problems.

Summary of the Invention

A barrel and piston that interact in such a way as to keep in alignment at all times, and yet to provide the opportunity to refill the barrel with moulding material between moulds. The arrangement provides an opening between the barrel and piston when the piston is sufficiently withdrawn from the barrel, and in this withdrawn position a portion of the piston's outer surface abuts a portion of the barrel's inner surface, to keep the two parts in alignment. When the piston is inserted further into the barrel, the opening is closed by the outer surface of the piston, which means that moulding material is not permitted to escape to escape out of the opening but is instead channelled through another opening into the mould. This means that the piston and barrel are always connected and therefore are at no risk of coming out of alignment with one another, and yet provides the user with the ability to refill the barrel with moulding material.

This is advantageous as it speeds up the injection moulding process, since no time is incurred realigning the parts or waiting for cooling or heating following this process. It is also safer than other arrangements which require handling the piston and barrel when they are out of alignment and very hot, and it is also easier to use.

Preferably, the barrel is formed with a portion of its inner surface being circular in cross-section, with the piston likewise having a portion of its outer surface being circular in cross-section. The portion of the inner surface of the barrel which is circular in cross-section is preferably of the same diameter as that of the portion of the outer surface of the piston which is circular in cross-section, or is slightly larger. Alternatively, the inner surface of the barrel and outer surface of the piston may have a differently shaped cross-sections, or not be uniform in their cross-sections but instead have tapering or twisting cross sections across their lengths or portions of their lengths.

The arrangement provides an opening to allow refilling of the barrel with moulding material between injection moulds when the piston is sufficiently withdrawn from the barrel. This is preferably availed by a slit in the end of the barrel near to where the piston and barrel meet, which forms a break in the otherwise preferably circular cross-section of the barrel's inner surface, such that the cross-section of the portion of the inner surface of the barrel along the slit is not a full circle but nearly a full circle. In this preferred arrangement, the required opening is availed when the piston is sufficiently withdrawn from the barrel, and starts to be exposed when the end of the piston reaches the beginning of the portion of the inner surface of the barrel which is not fully circular in cross-section. Once fully withdrawn, the opening is provided by the sides of the slit and the end of the piston. In a preferred arrangement, the a slit is straight-edged, however it may alternatively be tapered or curved, or be of a different shape depending on the cross-section of the inner surface of the barrel. There may alternatively be no slit at all but rather a hole in the side of the barrel serving the same purpose in availing an opening to insert moulding material into the barrel when the piston is sufficiently withdrawn.

Preferably, the barrel is made of a single piece, and the piston of a single piece, with no other parts being required to keep the two parts in alignment with one another.

Brief Description of the Drawings

In the drawings: Figure 1 shows a perspective view of the two parts, the piston 1 and the barrel 2.

Figure 2 shows a perspective view of the piston 1 and barrel 2 in the withdrawn configuration 3.

Figure 3 shows a perspective view of the piston 1 and the barrel 2 in the closed configuration 4.

Detailed Description of the Embodiment

An improved arrangement shows the piston 1 and the barrel 2 in Figures 1, and Figures 2 and 3 show the piston 1 and the barrel 2 in different configurations. In the withdrawn configuration 3, there is an opening 7 provided between the end 5 of the piston 1, the sides 13 and the base 8 of a slit in barrel 2. In the withdrawn position 3, a portion 6 of the outer surface 10 of the piston 1 abuts a portion 6 of the inner surface 11 of the barrel 2, keeping the two parts in alignment. In the closed configuration 4, the opening 7 is no longer available as a result of the piston 1 being fully inserted into the barrel 2. This prevents material from exiting the barrel through the opening 7 when the piston is inserted into the barrel. A portion of the outer surface 10 of the piston 1 always abuts a portion of the inner surface 11 of the barrel 2.

In the withdrawn configuration 3, the portion 6 of the outer surface 10 of the piston 1 that abuts the portion 6 of the inner surface 11 of the barrel 2 is sufficient to ensure that the two parts remain closely connected and in alignment relative to each other and to the direction of travel of the piston 1 into the barrel 2. The cross-section of a portion of the outer surface 10 of the piston 1 is preferably circular, and likewise the cross-section of a portion of the inner surface 11 of the barrel 2 is preferably circular, with its diameter the same or slightly larger than the diameter of that of the equivalent portion of the outer surface 10 of the piston 1. The cross-sections of the outer surface 10 and inner surface 11 may, alternatively, be of different shapes or be non-uniform across their length or a portion of their length.

There is preferably a slit in the barrel 2 between the inner surface 11 and the outer surface 12 which extends from a base 8 to the end 9 of the barrel 2. In the withdrawn configuration 3, the opening 7 is provided between base 8 and sides 13 of the slit and end 5 of the piston 1. The opening 7 may, alternatively, be provided by a hole in the side of the barrel 2 or by other means.