THIS INVENTION relates to moulding of synthetic polymeric moulding material. It relates more specifically to a method of charging, and to a charging device for charging synthetic polymeric moulding material into a mould.

In accordance with a first aspect of this invention, there is provided a method of charging synthetic polymeric moulding material into a mould, including positioning a holding chamber in stationary relationship in flow communication with the mould; filling a measuring cavity of predetermined volume with a charge of the synthetic polymeric moulding material in plastisized state; transferring the charge of plastisized synthetic polymeric moulding material from the measuring cavity into the holding chamber;

charging the charge of plastisized synthetic polymeric moulding material under pressure from the holding chamber into the mould.

The measuring cavity may be provided in a measuring chamber which is adjustable in respect of its volume, the method including controlling the volume of the measuring chamber to a predetermined volume when it is filled.

The measuring chamber may be cylindrical, one end thereof being defined by an end of a plunger which is reciprocal in the cylindrical measuring chamber, controlling the volume of the measuring chamber then being effected by appropriately positioning the plunger in the cylindrical measuring chamber, and transferring the charge of moulding material from the measuring chamber then being effected by driving the plunger along the measuring chamber.

One method may include conducting the charge of moulding material from the measuring chamber via a conduit into the holding chamber.

In another method, the measuring chamber may be generally in series alignment with the holding chamber, the holding chamber may be cylindrical, one end of the holding chamber may be defined by a leading end of a moulding plunger which is reciprocal in the cylindrical holding chamber, the measuring chamber may be defined intermediate a trailing end opposite said leading end of

the moulding plunger, and said plunger which is in the form of a measuring plunger defining said end of the measuring chamber.

The method may include controlling a volume of the holding chamber commensurately with controlling the volume of the measuring chamber by appropriately positioning the moulding plunger and the measuring plunger in relation to an end of the holding chamber proximate the mould and in relation to each other.

The method may include driving the moulding plunger and the measuring plunger respectively along the holding chamber and the measuring chamber by means of respective plunger drive means under control.

Said control may be programmed logic control or computerized control.

The invention extends to charging apparatus for charging a plastisized synthetic polymeric moulding material into a mould, the charging apparatus including a stationary holding chamber including an outlet and locating formations for locating the outlet in stationary relationship in flow communication with the mould;

a measuring cavity of predetermined volume for receiving a charge of plastisized synthetic polymeric moulding material; a communication passage for communicating the holding chamber and the measuring cavity; a transfer means for transferring the charge of plastisized synthetic polymeric moulding material from the measuring cavity to the holding chamber; a charging means for charging the charge of plastisized synthetic polymeric moulding material under pressure from the moulding chamber into the mould.

The holding chamber may be cylindrical and the charging means may include a moulding plunger reciprocal within the cylindrical holding chamber and a drive for reciprocating the plunger along the cylindrical holding chamber, the moulding plunger defining an end of the holding chamber.

The measuring cavity may be in the form of a measuring chamber which is adjustable in respect of its volume. The measuring chamber may be cylindrical and the transfer means may include a measuring plunger which is reciprocal within the measuring chamber and a drive for reciprocating the measuring plunger along the measuring chamber, adjustment of the measuring chamber being effected by appropriate positioning of the measuring plunger in the measuring chamber.

In one embodiment, the communication passage may be external of the measuring chamber and the holding chamber.

In another embodiment the measuring chamber and the holding chamber may be in generally series alignment, the moulding plunger forming a reciprocal division between the holding chamber and the measuring chamber, the measuring plunger defining an end of the measuring chamber opposed to that end formed by the moulding plunger. Conveniently, the holding chamber, the measuring chamber, the holding plunger and the measuring plunger may be co- axial. The measuring plunger may be mounted via an outer tubular stem to the drive of the measuring plunger, and the moulding plunger may be mounted to the drive of the moulding plunger by means of an inner stem passing through the outer tubular stem with sliding clearance.

The communication passage may be a generally peripheral passage around the moulding plunger and a non-return valve arrangement may be provided in said generally peripheral passage.

The drive of the moulding plunger and the drive of the measuring plunger may be in the form of hydraulic plunger and cylinder arrangements.

The charging apparatus may include a control, in the form of programmed logic or computerized control, controlling the drives of respectively the moulding plunger and the measuring plunger.

The invention is now described by way of examples with reference to the accompanying diagrammatic drawings.

In the drawings; Figures 1 and 2 show, in axial sections, respectively two embodiments of charging apparatus in accordance with this invention.

With reference to Figure 1 of the drawings, a first embodiment of charging apparatus in accordance with the invention is generally indicated by reference numeral 10. The charging apparatus 10, in use, charges synthetic polymeric moulding material into a mould fragmentally shown in the drawings, indicated by reference numeral 12. The portion of the mould shown is an inlet portion having a receiving cavity 14 and a plurality of runners 16 extending from the receiving cavity 14.

In other embodiments, the moulding material may be charged directly into a moulding cavity. Then, if desired, the face of the plunger (to be described below), may have markings, e. g. wording, logo, or the like, which will be moulded into a corresponding face of the moulded article.

The charging apparatus 10, in this embodiment, includes two main components, namely a charging device generally indicated by reference numeral 20 and a measuring device generally indicated by reference numeral 40. In the embodiment shown in Figure 2, described hereinbelow, the charging device and measuring device are integrated.

With reference again to Figure 1, the charging device 20 has a hollow generally cylindrical body 22 having, at one end thereof, a flange 26. The flange 26 is provided to locate or position the charging device 20 stationarily in relation to the mould 12, for example by means of a camping arrangement schematically indicated by reference numeral 24.

At one end of the cylindrical body 22, proximate the flange 26, a holding chamber 30 is defined within the cylindrical body 22. One end of the holding chamber 30, which end will for convenience be referred to as the downstream end, and which coincides with the end of the flange 26, is open, the holding chamber thus being effectively bounded by a wall defining the receiving cavity 14 of the mould 12.

An opposed end of the holding chamber 30 is defined by an end of a plunger 32 which is reciprocal within the hollow cylindrical body 22 i. e. within the holding chamber 30. The plunger 32 is mounted on a stem 34 which is connected to a drive 36 for reciprocally driving the plunger 32. In this

embodiment, the drive 36 is hydraulic. In other embodiments, the drive may be mechanical, for example a cam/lever arrangement, a cranked arrangement, or the like. Instead, the drive may be electrical.

If desired, the face of the plunger, around the periphery, may be bevelled, and the moulding chamber, at its periphery at its downstream end, may have a complemental formation to act as a stop for the plunger and to enhance emptying of the moulding material from the chamber.

The holding chamber 30 has a lateral inlet 38 spaced below the downstream end. The inlet 38 is exposed when the plunger 32 is withdrawn i. e. when the volume of the holding chamber is large, and is covered when the plunger 32 is extended, i. e. when the volume of the holding chamber is small.

The measuring device 40 includes a hollow generally cylindrical body 42 having an end wall 46 at one end, which will be a downstream end, of the body 42. An outlet 44 is provided in the end wall 46.

At one side of the body 42, spaced a small distance from the top 46, there is provided a lateral inlet 48.

The measuring device 40 includes a measuring plunger 52 reciprocal within the cylindrical body 42. A measuring chamber 50 is defined intermediate an end of the measuring plunger 52 and the end wall 46. The measuring plunger 52 is mounted on a stem 54 via which the measuring plunger 52 is reciprocally driven by means of a drive 56, which, in this embodiment, is hydraulic. Similarly to the drive 36 of the charging device, in other embodiments, the drive may be 5 mechanical, such as a cam/lever arrangement, a cranked system, or electric such as by means of an electric motor, or the like.

Partially along one side of the measuring plunger 52, it has a slot 58 which is closed at one end which will be a bottom or upstream end of the measuring plunger 52, the slot being open along a radialky outer side of the 10 plunger and at the top or downstream end of the plunger 52. The drive 56 is adapted also to pivot the measuring plunger 52 respectively to bring the slot 58 into alignment with the inlet 48 thus to open the inlet, and out of alignment with the inlet 48 to close the inlet 48. When the slot 58 and the inlet 48 are aligned, the slot 48 also provides communication with the measuring chamber 50.

15 A conduit 60 communicates the outlet 44 of the measuring device 40 and the inlet 38 of the charging device 20.

The drives 36 and 56 are controlled by programmed logic or computerized control schematically indicated by reference numeral 62. The control 62 is connected to the drive 36 by means of a connection 64 and with

the drive 56 by means of a connection 66 such as to control operation of the drives 36,56.

In use, synthetic polymeric moulding material which has been plastisized is introduced into the measuring chamber 50 via the inlet 48 and the slot 58. The measuring plunger 52 is positioned at a predetermined axial position by means of the control 62 to render the measuring chamber 50 of a predetermined volume. When it has been filled with a charge of predetermined volume of plastisized synthetic polymeric moulding material, the drive 56 pivots the measuring plunger 52 to close the inlet 48 and then drives the measuring plunger 52 toward the top 46 to transfer the charge of moulding material via the conduit 60 into the holding chamber 30. By means of the drive 46 and the control 62, the plunger 32 is positioned such as to render the inlet 38 open and the holding chamber of a volume commensurate with the predetermined volume charged into the measuring chamber and being transferred from the measuring chamber to the holding chamber 30.

When the measuring chamber has been charged, the drive 36 drives the plunger 32 to decrease the volume of the holding chamber 30 and thus to expel or discharge the moulding material from the holding chamber 30 under pressure into the receiving cavity 40 and thus via the runners 16 into the moulding cavities of the mould 12.

The above procedure is repeated cyclically under operation of the control 62.

A second embodiment of charging apparatus in accordance with the invention is now described by. way of example with reference to Figure 2. The charging apparatus of Figure 2 is generally indicated by reference numeral 110.

The charging apparatus 110 is similar in many respects to the charging apparatus 10 of Figure 1. Thus, like components or features are numbered similarly and all of the features or components are not again described in detail.

The charging apparatus 110 is formed of two main components, namely a charging device 120 and a measuring device 140. In this embodiment, the charging device 120 and the measuring device 140 are integrated and are generally in axially aligned series relation.

The charging device 120 includes a generally cylindrical, hollow body 122 which is shared also by the measuring device 140. The body 122 includes a flange 126 at one end by means of which it is positioned in stationary relation and in flow communication with a mould 112 having a receiving cavity 114 and runners 116 extending to moulding cavities. Mechanical fasteners, schematically indicated by reference numerals 124, secure the body 122 to the mould 112.

A holding chamber 130 is defined within the hollow body 122 at one end thereof proximate the mould 112. A plunger 132 is reciprocal within the cylindrical holding chamber 130. The plunger 132 is connected via an inner stem 134 to a hydraulic drive 136.

The body 122 defines a measuring chamber 150 below the plunger 132, co-axially aligned with, and, in this embodiment, at a slightly larger diameter than, the holding chamber 130. In another embodiment, the diameters may be equal. An upper or downstream end of the measuring chamber 150 is defined by a trailing or bottom end of the plunger 132.

Also reciprocal within the measuring chamber 150, there is provided a measuring plunger 152 connected via an outer tubular stem 154 to a drive 156.

The inner stem 134 of the plunger 132 is received with slidable clearance within the outer tubular stem 1 54. Also, there is provided a sliding passage for the stem 134 through the plunger 152. However, although relative motion is allowed, the plunger 152 is sealed against the stem 134 to prevent passage of moulding material.

A lateral inlet 148 leads through a wall of the body 122 into the measuring chamber 150.

A communication passage 160 is provided peripherally around the plunger 132. A non-return device is provided in the passage 160. More specifically, the plunger 132 includes a peripheral groove 132.1. Below the peripheral groove 132.1, an outer periphery of the plunger 132 is of small diameter compared to the diameter of the wall of the holding chamber 130 such as to allow passage of moulding material into the groove. Above the groove 132.1, a crown of the plunger 132 includes a plurality of circumferentially spaced peripheral passages 132.4, spiderfashion. In the groove 132.1, there is provided a ring 132.3 which is slidingly sealingly engaged with the wall of the holding chamber 130 and which has clearance to pass moulding material relative to the bottom of the groove 132.1. Operation of the passage 160 and the non return device will be described below.

A predetermined amount of synthetic polymeric moulding material in plastisized state is to be charged into the mould 112. Thus, by means of a control 162 controlling, via a connection 164, operation of the drive 136 for the plunger 132, and, via a connection 166, the drive 156 of the plunger 152, the plunger 132 is positioned such that the holding chamber 130 is of predetermined volume. Similarly, the plunger 152 is appropriately positioned such that the measuring chamber 150 defined between the plunger 152 and the plunger 132 is of predetermined volume.

Synthetic polymeric moulding material in plastisized state is introduced via the inlet 148 into the measuring chamber 150. When it has been filled, the plunger 152 is driven forwardly or upwardly to decrease the volume of the measuring chamber 150, thus transferring the moulding material via the passage 160 into the holding chamber 130.

The ring 132.3 is forced against the crown of the plunger 132 thus allowing moulding material to move into the groove 132.1, underneath the ring 132.3 and through the circumferentially spaced passages 132.4 into the holding chamber 130.

When the holding chamber 130 has been filled, the plunger 132 is driven forwardly or upwardly to discharge the synthetic polymeric moulding material from the holding chamber 130 into the receiving cavity 114 of the mould 112 and then via the runners 116 to moulding cavities.

When the holding chamber 130 is pressurized, back pressure of the moulding material via the passages 132.4 displaces the ring 132.3 to seal against a lower rim of the groove 132.1, thus acting as a one way valve.

It is to be appreciated that the volume of the measuring chamber 150 can be kept constant even though the plunger 132 and 152 move, generally in unison. In an embodiment where the diameter of the measuring chamber 150

is equal to the diameter of the holding chamber 130, movement of the plungers in unison will not influence the volume of the measuring cavity 150. In the embodiment of Figure 2, slight relative movement of the plungers is required to cancel the effect of the difference in diameters of the measuring chamber immediately above the measuring plunger 152 and the portion immediately below the plunger 132. Such relative motion can be controlled by means of the control 162.

Thus, for example, when the plunger 132 is in its uppermost position, the measuring chamber 150 can be charged by withdrawing or driving the plunger 152 downwardly. Even when the plunger 132 is driven downwardly, the measuring chamber can still be enlarged by driving the plunger 152 downwardly at the same rate (bearing in mind the difference in diameters) or at a slightly faster rate. Thus, although operation of the apparatus 110 was described above as if the plungers are stationary when filling of the measuring chamber takes place and the like, the process can be effected dynamically under the control 162.

It is a first advantage of the invention that the moulding material is not plastisized generally in the same operation as and by the charging device for charging the mould. Thus, plastisizing can be effected in any convenient manner.

For example, it can be effected more or less conventionally by means of a plastisizing screw in combination with heat, but such screw can be merely rotary,

i. e. it need not have translation capability. This advantage also allows the charging device to be simpler than in conventional injection moulding apparatus as plastisizing of the moulding material is done elsewhere.

It is an advantage that the holding chamber is stationary relative to the mould or mould inlet which is an advantage over another kind of injection moulding known to the Applicant in which a holding chamber is filled with moulding material and is then moved to come into alignment with a plunger and a mould opening. The holding chamber and positioning it in relation to the mould is thus simple, as it is stationary and not dynamic.

It is yet a further advantage that moulding material can be measured to a selected volume to cater for different moulded articles to be manufactured, and the like.

It is yet a further advantage that, by means of the control 62,162, small adjustments in the volume of the moulding material can be effected, for example to cater for small changes in compounding of the moulding material, compressibility, and the like.