WO2000067978A1

WO2000067978A1 - Method of and apparatus for charging plasticized polymeric moulding material into a mould

Info

Publication number: WO2000067978A1
Application number: PCT/IB2000/000591
Authority: WO
Inventors: Manuel Filipe Viana Teotonio Pereira; Jeremias Daniel Wilkins; Willem Jacobus Louw
Original assignee: Csir
Priority date: 1999-05-07
Filing date: 2000-05-08
Publication date: 2000-11-16
Also published as: AU4138300A

Abstract

Charging apparatus (10, 110) for charging plasticized moulding material into a mould (12, 112) includes a measuring cavity or chamber (50, 150) and a measuring plunger reciprocal within the chamber (50, 150) for adjusting the volume of the chamber (50, 150) and discharging the moulding material from the chamber (50, 150). The apparatus further includes a holding chamber (30, 130) in communication with the measuring chamber (50, 150) for receiving moulding material, and a moulding plunger (32, 132) reciprocal within the holding chamber (30, 130) for adjusting the volume and for discharging moulding material from the holding chamber into the mould (12, 112). The plungers (32, 52, 132, 152) may be computer controlled. The measuring and holding chambers (50, 30) may be in communication via an external conduit (60). Instead, they may be in a common body (122), arranged in series and divided by the moulding plunger (132), communication being via a passage (160) through or around the moulding plunger (132).

Description

METHOD OF AND APPARATUS FOR CHARGING PLASTICIZED POLYMERIC MOULDING MATERIAL INTO A MOULD

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;

CONFIRMATION COPT 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 1 0. The charging apparatus 1 0, in use, charges synthetic

polymeric moulding material into a mould fragmentally shown in the drawings,

indicated by reference numeral 1 2. The portion of the mould shown is an inlet

portion having a receiving cavity 14 and a plurality of runners 1 6 extending from

the receiving cavity 1 4.

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 1 0, 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 stationaπly in

relation to the mould 1 2, for example by means of a clamping 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 1 2.

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

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 radially outer side of the

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.

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 1 6 into the

moulding cavities of the mould 1 2 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 1 1 0.

The charging apparatus 1 1 0 is similar in many respects to the charging apparatus

1 0 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 1 1 0 is formed of two main components,

namely a charging device 1 20 and a measuring device 140. In this embodiment,

the charging device 1 20 and the measuring device 1 40 are integrated and are

generally in axially aligned series relation.

The charging device 1 20 includes a generally cylindrical, hollow body

1 22 which is shared also by the measuring device 1 40. The body 1 22 includes

a flange 1 26 at one end by means of which it is positioned in stationary relation

and in flow communication with a mould 1 1 2 having a receiving cavity 1 1 4 and

runners 1 1 6 extending to moulding cavities. Mechanical fasteners, schematically

indicated by reference numerals 1 24, secure the body 1 22 to the mould 1 1 2. A holding chamber 1 30 is defined within the hollow body 1 22 at one end thereof proximate the mould 1 1 2. A plunger 1 32 is reciprocal within the

cylindrical holding chamber 1 30 The plunger 1 32 is connected via an inner stem

1 34 to a hydraulic drive 1 36

The body 1 22 defines a measuring chamber 1 50 below the plunger

1 32, co-axially aligned with, and, in this embodiment, at a slightly larger diameter

than, the holding chamber 1 30 In another embodiment, the diameters may be

equal. An upper or downstream end of the measuring chamber 1 50 is defined by

a trailing or bottom end of the plunger 1 32.

Also reciprocal within the measuring chamber 1 50, there is provided

a measuring plunger 1 52 connected via an outer tubular stem 1 54 to a drive 1 56.

The inner stem 1 34 of the plunger 1 32 is received with slidable clearance within

the outer tubular stem 1 54. Also, there is provided a sliding passage for the stem

1 34 through the plunger 1 52 However, although relative motion is allowed, the

plunger 1 52 is sealed against the stem 1 34 to prevent passage of moulding

material.

A lateral inlet 1 48 leads through a wall of the body 1 22 into the

measuring chamber 1 50. A communication passage 1 60 is provided peripherally around the plunger 1 32. A non-return device is provided in the passage 1 60. More

specifically, the plunger 1 32 includes a peripheral groove 1 32.1 . Below the

peripheral groove 1 32.1 , an outer periphery of the plunger 1 32 is of small

diameter compared to the diameter of the wall of the holding chamber 1 30 such

as to allow passage of moulding material into the groove. Above the groove

1 32.1 , a crown of the plunger 1 32 includes a plurality of circumferentially spaced

peripheral passages 1 32.4, spider fashion . In the groove 1 32.1 , there is provided

a ring 1 32.3 which is slidingly sealingly engaged with the wall of the holding

chamber 1 30 and which has clearance to pass moulding material relative to the

bottom of the groove 1 32. 1 . Operation of the passage 1 60 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 1 1 2. Thus, by means of a

control 1 62 controlling, via a connection 1 64, operation of the drive 1 36 for the

plunger 1 32, and, via a connection 1 66, the drive 1 56 of the plunger 1 52, the

plunger 1 32 is positioned such that the holding chamber 1 30 is of predetermined

volume. Similarly, the plunger 1 52 is appropriately positioned such that the

measuring chamber 1 50 defined between the plunger 1 52 and the plunger 1 32

is of predetermined volume. Synthetic polymeric moulding material in plastisized state is

introduced via the inlet 1 48 into the measuring chamber 1 50. When it has been

filled, the plunger 1 52 is driven forwardly or upwardly to decrease the volume of

the measuring chamber 1 50, thus transferring the moulding material via the

passage 1 60 into the holding chamber 1 30.

The ring 1 32.3 is forced against the crown of the plunger 1 32 thus allowing moulding material to move into the groove 1 32.1 , underneath the ring

1 32.3 and through the circumferentially spaced passages 1 32.4 into the holding chamber 1 30.

When the holding chamber 1 30 has been filled, the plunger 1 32 is

driven forwardly or upwardly to discharge the synthetic polymeric moulding

material from the holding chamber 1 30 into the receiving cavity 1 1 4 of the mould

1 1 2 and then via the runners 1 1 6 to moulding cavities.

When the holding chamber 1 30 is pressurized, back pressure of the

moulding material via the passages 1 32.4 displaces the ring 1 32.3 to seal against

a lower rim of the groove 1 32.1 , thus acting as a one way valve.

It is to be appreciated that the volume of the measuring chamber

1 50 can be kept constant even though the plunger 1 32 and 1 52 move, generally

in unison. In an embodiment where the diameter of the measuring chamber 1 50 is equal to the diameter of the holding chamber 1 30, movement of the plungers

in unison will not influence the volume of the measuring cavity 1 50. 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 1 52 and the portion immediately below

the plunger 1 32. Such relative motion can be controlled by means of the control

1 62.

Thus, for example, when the plunger 1 32 is in its uppermost

position, the measuring chamber 1 50 can be charged by withdrawing or driving

the plunger 1 52 downwardly. Even when the plunger 1 32 is driven downwardly,

the measuring chamber can still be enlarged by driving the plunger 1 52

downwardly at the same rate (bearing in mind the difference in diameters) or at

a slightly faster rate. Thus, although operation of the apparatus 1 10 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 1 62.

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, 1 62,

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.

Claims

1 . 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 .

2 A method as claimed in Claim 1 in which the measuring cavity is

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 .

3. A method as claimed in Claim 2 in which the measuring chamber is

cylindrical, one end thereof being defined by an end of a plunger which is

reciprocal in the cylindrical measuring chamber, and in which method controlling

the volume of the measuring chamber is by appropriately positioning the plunger

in the cylindrical measuring chamber, and in which method transferring the charge of moulding material from the measuring chamber is by driving the plunger along the measuring chamber.

4. A method as claimed in Claim 3 which includes conducting the

charge of moulding material from the measuring chamber via a conduit into the

holding chamber.

5 A method as claimed in Claim 3 in which the measuring chamber is

generally in series alignment with the holding chamber, in which the holding

chamber is cylindrical, one end of the holding chamber being defined by a leading

end of a moulding plunger which is reciprocal in the cylindrical holding chamber,

the measuring chamber being 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.

6 A method as claimed in Claim 5 which includes 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.

7. A method as claimed in Claim 6 which includes 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.

8. A method as claimed in Claim 7 in which said control is programmed logic control or computerized control.

9. 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

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 .

1 0. Charging apparatus as claimed in Claim 9 in which the holding

chamber is cylindrical and in which the charging means includes 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.

1 1 Charging apparatus as claimed in Claim 1 0 in which the measuring

cavity is in the form of a measuring chamber which is adjustable in respect of its

volume.

1 2. Charging apparatus as claimed in Claim 1 1 in which the measuring

chamber is cylindrical and in which the transfer means includes 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.

1 3. Charging apparatus as claimed in Claim 1 2 in which the

communication passage is external of the measuring chamber and the holding

chamber.

14. Charging apparatus as claimed in Claim 1 2 in which the measuring

chamber and the holding chamber are 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.

1 5. Charging apparatus as claimed in Claim 14 in which the holding

chamber, the measuring chamber, the holding plunger and the measuring plunger

are co-axial, in which the measuring plunger is mounted via an outer tubular stem

to the drive of the measuring plunger, and in which the moulding plunger is

mounted to the drive of the moulding plunger by means of an inner stem passing

through the outer tubular stem with sliding clearance.

1 6. Charging apparatus as claimed in Claim 1 5 in which the

communication passage is a generally peripheral passage around the moulding

plunger and in which a non-return valve arrangement is provided in said generally

peripheral passage.

1 7. Charging apparatus as claimed in Claim 1 5 or Claim 1 6 in which the

drive of the moulding plunger and the drive of the measuring plunger are in the

form of hydraulic plunger and cylinder arrangements.

1 8. Charging apparatus as claimed in any one of Claim 1 5, Claim 1 6 or

Claim 1 7 which includes a control, in the form of programmed logic or

computerized control, controlling the drives of respectively the moulding plunger

and the measuring plunger.