Apparatus for injection moulding

Injection moulding apparatus consists of a rotary carrier (11) which transports a number of mould sets (14,15) in turn through an injection station (46), cooling stations (35) and a mould opening station (27). The injection body (62) is upwardly arranged, and there is a positioning device (71-74) for adjusting the position of the injection head (60) when in an injection position and in a withdrawn position, and a further positioning device (65,66) for moving the injection head (60) relative to the injection body. The clamping device (47) at the injection station and the cooling device (36,37) at the cooling station can also be used as heat transfer devices. The sprue formed between the mould cavity (17) and the inlet (18) of the mould set can be severed while the mould set is closed. During transfer between the injection station and the opening station, tools (14) and (15) of the mould set are held in a closed condition by connectors (16) and retaining elements (21,22) which are part of the mould set. There are openings in the carrier that provide access for devices to operate on the mould set.

BACKGROUND AND SUMMARY OF THE INVENTION 
From one aspect, the present invention relates to injection moulding 
apparatus. As used herein, the term injection moulding apparatus embraces 
apparatus used for injecting a plastics moulding composition into a mould 
cavity and apparatus used for injecting molten metal into a mould cavity, 
commonly called die-casting apparatus. 
Apparatus which is commonly used for injection moulding comprises two 
platens, on which are fixed respective tools of a set of moulding tools. 
The apparatus also includes means for moving one of the platens relative 
to the other for opening and closing the set of tools. Means is provided 
for injecting a moulding composition through the tool on the stationary 
platen to the mould cavity, when the tools are closed. It is necessary to 
maintain the set of tools in a closed condition until the moulding has 
cooled sufficiently to acquire dimensional stability. A substantial 
proportion of the operating cycle of the apparatus is represented by a 
cooling time, during which the platens must be held stationary relative to 
each other. This is achieved by maintaining in operation throughout the 
cooling time hydraulic pumps used to establish the mould-closing pressure. 
One object of the present invention is to improve the efficiency of an 
injection moulding operation. Further objects include improving the 
efficiency of cooling of a set of mould tools. 
According to a first aspect of the present invention, there is provided 
injection moulding apparatus comprising a plurality of mould sets, an 
injection head, transport means for imparting relative movement to the 
mould sets and the injection head to bring the injection head into 
proximity with the mould sets in sequence, feed means for feeding a 
moulding composition through the injection head into a mould set when that 
mould set is in proximity with the injection head and clamping means for 
clamping in a closed condition at least one of said mould sets whilst the 
moulding composition is injected through the injection head into the mould 
set. 
In in accordance with the first aspect of the invention, after injection of 
the moulding composition into a first mould set, the injection head can be 
used to inject moulding composition into a second mould set before the 
moulding formed in the first mould sets has cooled sufficiently to permit 
removal of that moulding from the first mould set. The interval between 
successive injection operations does not depend upon the required cooling 
time. 
According to a second aspect of the invention, there is provided a method 
of moulding a composition wherein an injection head is used to inject the 
moulding composition into each of a plurality of mould sets in turn. 
According to a third aspect of the invention, there is provided an 
injection moulding tool set comprising first and second tool parts which 
collectively define a mould cavity and comprising retaining means for 
releasably retaining the tool parts in a closed condition. A tool set 
embodying the third aspect of the invention is especially suitable for use 
in a method according to the second aspect of the invention. 
Relative movement of the mould sets and the injection head may be achieved 
by maintaining the injection head at an injection station and moving the 
mould sets in turn into the injection station. Alternatively, the relative 
movement may be achieved by maintaining the mould sets in respective 
stations and moving the injection head to those stations in turn. 
The transport means used for imparting relative movement to the mould sets 
and the injection head may be adapted to locate each mould set in turn 
accurately in relation to the injection head. Alternatively, there may be 
provided, in addition to the transport means, locating means for locating 
each mould set in turn accurately relative to the injection head. The 
transport means may comprise a conveyor of generally known form for 
conveying the tool sets sequentially to the injection station. 
Alternatively, the transport means may comprise a track defining a path 
along which the mould sets move to the injection station and propulsion 
means for imparting motion to the mould sets which are on or in the track. 
The propulsion means may be adapted to drive the mould sets by means of 
air pressure, magnetic field or other known means. The mould sets may be 
guided along the track and/or supported in the path, at least when moving, 
by air pressure, magnetic field or other known means. In a case where the 
mould sets remain in respective stations and the injection head is moved 
from one mould set to another, the injection head may be transported by a 
conveyor of known kind or may be driven along a track by known propulsion 
means hereinbefore mentioned and supported by known means mentioned 
herein. Also in a case where the injection head is moved from one mould 
set to another, transport means for transporting the injection head may be 
adapted to establish accurately a predetermined position of the injection 
head relative to each mould set in turn or there may be provided in 
addition to the transport means locating means for establishing accurately 
the required position. 
In a case where either the mould sets or the injection head are or is moved 
along a track, guidance along the track may be achieved by known means 
which do not rely upon physical contact, for example guidance by means of 
electromagnetic radiation or by means of an electromagnetic field 
associated with a conductor buried in a floor. 
Means for performing operations additional to injection may be positioned 
at stations additional to an injection station or may be transported along 
the path along which the injection head is transported. 
Means for applying heat to or extracting heat from the mould sets may be 
moved to the mould sets in turn, either following a path which is followed 
by the injection head or following a different path. Means for opening the 
mould sets may be moved to each of the mould sets in turn, either 
following the path along which the injection head moves or following a 
different path. 
In a case where the mould sets are moved in turn into an injection station, 
the mould sets are preferably moved through additional stations including 
a heat transfer station and an opening station. 
There may be provided a plurality of injection heads through which 
respective moulding compositions are injected into the mould sets. These 
compositions may differ in respect of colour or in respect of other 
characteristics. In a case where respective moulding compositions are 
injected through a plurality of heads into each mould set, these may be 
injected into each mould set concurrently through respective inlet nozzles 
or sequentially. An injecting relation may be established between the 
mould set and the injection heads in turn. 
In a case where more than one injection head is provided, these may be 
moved along a common path from one mould set to another or may be disposed 
at respective injection stations through which the mould sets are 
transported. 
In a case where means additional to one injection head moves from one mould 
set to another, movement of the additional means may be independent of 
movement of the injection head. Alternatively, these may be mounted on a 
common carrier which carries them to the mould sets in turn. In a case 
where the mould sets are mounted on a common carrier and are moved through 
successive stations, a particular mould set may pass through one or more 
stations without any operation being performed on that particular mould 
set at that particular station or stations. Thus, the actions to which one 
mould set is subjected at successive stations may be selected 
independently of the actions to which another mould set is subjected 
during travel along the same path. 
According to a further aspect of the invention, injection moulding 
apparatus comprises a carrier for carrying a plurality of mould sets, an 
injection head, feed means for feeding a moulding composition through the 
injection head into a mould set and clamping means for clamping at least 
one of the mould sets in a closed condition whilst the moulding 
composition is injected through the injection head into that mould set, 
wherein the carrier is arranged for moving the mould sets, when carried on 
the carrier, around an orbital path, wherein the feed means is on the 
inside of said path and wherein the injection head extends from the feed 
means to said path. This arrangement has the advantage that a relatively 
compact apparatus can be achieved. Furthermore, there is at the outside of 
the orbital path space for accommodating the clamping means and this space 
is not restricted by the feed means and injection head. 
The feed means preferably includes a feed screw which is rotatable about an 
axis transverse to said path. Generally, the path along which the mould 
sets are moved by the carrier will be horizontal. In this case, the 
injection head is preferably disposed at a level above the feed screw and 
the feed screw is arranged to feed the moulding composition upwardly to 
the injection head. This arrangement has the advantage that gravity will 
tend to cause the moulding composition to move in a direction from the 
injection head towards the feed screw and the risk of moulding composition 
escaping from the injection head under the action of gravity in an 
uncontrolled manner is substantially eliminated. Furthermore, the 
arrangement provides the possibility of removing the injection head and 
replacing it with a fresh injection head whilst the moulding composition 
is supported by the feed screw and in a molten condition. 
Preferably, the moulding composition is moved upwards during melting and is 
injected downwards. 
The apparatus preferably includes a housing which substantially encloses 
the moving parts of the apparatus. The atmosphere within the housing may 
be monitored and/or may be controlled. There may be provided inside the 
housing a smoke-detector or a temperature-responsive device suitable for 
providing an alarm signal if a fire occurs inside the housing. In the 
event of a fire occurring inside the housing, the housing will restrict 
access of air to the fire and an inert gas or other fire-extinguishing 
medium may be discharged inside the housing to extinguish the fire. 
Operation of the apparatus is preferably controlled by a microprocessor. 
Information relating to mouldings to be produced by the apparatus and 
relating to mould sets present in the apparatus may be applied to the 
microprocessor through known input devices, for example a keyboard, a disc 
drive or a tape reader. The microprocessor may have an interface with 
other components of a control system of the apparatus which facilitates 
the transfer of information between the control system of one apparatus 
embodying the invention and the control system of further apparatus. Thus, 
if a programme suitable for controlling operation of the apparatus to 
produce certain mouldings is applied to the microprocessor of first 
apparatus, that programme may be transferred to further apparatus or the 
further apparatus may be controlled by the microprocessor of the first 
apparatus to cause the further apparatus to produce the same or similar 
mouldings. 
The clamping means may remain at the injection station in a case where the 
mould sets are moved through the injection station. Alternatively, the 
clamping means may move with the mould sets through the injection station 
and other stations. In a case where the injection head moves to the mould 
sets in turn, the clamping means also may be moved to each of the mould 
sets in turn. Alternatively, respective clamping means may be provided for 
each mould set, the clamping means remaining with the mould set when the 
injection head moves from one mould set to another. 
Preferred features of injection moulding apparatus in accordance with the 
first aspect of the invention and other aspects of the invention are 
defined in the claims appended hereto.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
The moulding apparatus illustrated in the accompanying drawings comprises a 
hollow body 10 which typically stands on a floor and does not move during 
use of the machine. There is used with the machine a number of mould sets 
which may be identical with one another or which may differ from one 
another. An example of a suitable mould set is illustrated in FIGS. 2, 3 
and 4. In the body 10, there is mounted transport means comprising a 
carrier 11 suitable for carrying a plurality of the mould sets and for 
moving the mould sets in turn along a orbital path through a number of 
stations. In the particular example illustrated, the carrier 11 is 
arranged for rotation relative to the body 10 about a carrier axis 12 and 
the carrier axis is upright. The carrier is adapted to support the mould 
sets in respective positions which are spaced substantially the same 
distance from the carrier axis 12. Conveniently, the carrier is circular 
and the mould sets are mounted adjacent to the periphery of the carrier 
and are spaced apart equally around the axis 12. A representative mould 
set is shown at 13 in FIG. 1. 
The carrier 11 is annular and is supported from the body 10 by a bearing 88 
shown in FIG. 10 and disposed adjacent to the inner periphery of the 
carrier and below the carrier. The bearing 88 is supported by support 
plate 89 incorporated in the body 10. This plate is substantially and is 
spaced downwardly a substantial distance from the carrier 11 so that the 
bearing 88 lies generally between the carrier and the support plate 89. An 
electric motor 90 and associated gear box 91 for driving the carrier 11 
relative to the body 10 are mounted in the body 10 beneath the support 
plate 89. A drive shaft 92 extends upwardly from the gear box 91 through 
an opening in the support plate 89 and carries a sprocket 93 which meshes 
with teeth formed on that part of the bearing 88 which is fixed with 
respect to the carrier 11. The motor 90 is capable of establishing a 
pre-determined angular position of the carrier 11 within a very small 
tolerance so that the motor and carrier are capable of carrying mould sets 
from station to station and also of locating each mould set accurately in 
a required position at each station. 
The mould set 13 is illustrated in greater detail in FIGS. 2, 3 and 4. The 
mould set comprises a first tool 14, a second tool 15 and a plurality of 
spaced connectors 16. Each connector is in the form of an elongated shaft 
having one end portion which is fixed with respect to the first tool 14 
and an opposite end portion which can slide in an opening in the second 
tool. Preferably, this opening extends completely through the second tool. 
The connectors 16 guide the first and second tools for relative movement 
along a rectilinear path between an open condition illustrated in FIG. 2, 
in which the tools are spaced apart, and a closed condition in which the 
tools are in mutual contact at an interface. At the interface, the tools 
14 and 15 collectively define a mould cavity 17 in which a moulding is to 
be formed. The mould cavity may be formed entirely in one or other of the 
tools or partly in each of the tools. 
The mould set further comprises a guide plate 86 which is rigidly secured 
to the tool 15 at the face thereof remote from the tool 14. As viewed in a 
direction along the axis 12, the guide plate 86 is considerably smaller 
than is the tool 15 and the guide plate is inset from the periphery of the 
tool. The guide plate is received in a complimentary opening formed in the 
carrier 11 and the tool 15 rests on the carrier adjacent to the opening. 
The tool 15 is located precisely in a predetermined position relative to 
the carrier 11 by means of dowels (not shown) and is secured to the 
carrier by bolts (not shown). The depth of the guide plate 86 may be 
somewhat greater than the depth of the carrier 11, so that the guide plate 
protrudes slightly at the underside of the carrier. 
An inlet for admitting a moulding composition to the mould set is formed in 
an inlet nozzle 18 which is mounted in the first tool 14 for limited 
movement relative thereto in a direction towards and away from the second 
tool 15. The inlet nozzle is guided for sliding movement in the first tool 
14 along a path which is offset from the mould cavity 17. A sprue element 
19 is mounted in the second tool 15 for sliding relative thereto along a 
path which is an extension of the path along which the inlet nozzle 18 
slides. The sprue element is biased towards the inlet nozzle 18 by a 
spring 20 acting between the sprue element and the second tool 15. The 
sprue element bears on the inlet nozzle 18 adjacent to the interface 
between the tools 14 and 15. Movement of the sprue element 19 and inlet 
nozzle 18 in a direction from the tool 15 towards the tool 14 is limited 
by engagement of a shoulder on the inlet nozzle 18 with a shoulder on the 
first tool 14. Movement in the opposite direction is limited by engagement 
of the sprue element 19 with a shoulder on the second tool 15. 
There is formed in one of the sprue element 19 and inlet nozzle 18 a sprue 
passage 94 which, when the sprue element 19 is in the charging position 
(not illustrated) in which it rests on the shoulder of the second tool 15, 
provides communication between the mould cavity 17 and the inlet defined 
by the nozzle 18. When the sprue element 19 is in the severing position 
illustrated in FIG. 3 and the inlet nozzle 18 bears on the shoulder of the 
first tool 14, the sprue passage is out of communication with the mould 
cavity 17 and any moulding composition occupying the sprue passage is 
therefore separated from a moulding formed in the cavity. 
There is provided in the second tool 15 holding means for retaining the 
connectors 16 in the fully inserted positions illustrated in FIG. 4, which 
correspond to the closed condition of the tool set. The holding means 
comprises a plurality of holding elements 21, one for each connector 16. 
Each holding element is in the form of a rectilinear rod and is slidably 
mounted in a corresponding bore formed in the second tool 15 with a 
longitudinal axis of the rod perpendicular to a longitudinal axis of the 
corresponding connector. Each holding element is slidable relative to the 
second tool 15 between the holding position illustrated in FIG. 4, in 
which an end portion of the holding element is seated in a complimentary 
recess formed in the corresponding connector 16, and a releasing position 
in which the holding element is withdrawn from the recess in the 
corresponding connector. When seated in the recess, the holding element 
restrains movement of the corresponding connector relative to the second 
tool 15 from the position shown in FIG. 4. The holding elements and the 
connectors thus constitute parts of retaining means for retaining the 
tools 14 and 15 in the closed position illustrated in FIG. 4. 
The retaining means further comprises a locking element 22 which is mounted 
in the second tool 15 for movement relative thereto along a path which is 
transverse to the paths of the holding elements 21. There is associated 
with the locking element a spring 23 which urges the locking element into 
the locking position shown in FIG. 4, in which the locking element 
obstructs movement of the holding elements 21 from their holding 
positions. There is in the second tool 15 sufficient space to permit 
movement of the locking element 22 against the action of the spring 23 
from the locking position into a releasing position in which the locking 
element permits movement of the holding elements 21 from their holding 
positions to their releasing positions. An end portion of the locking 
element 22 which is remote from the spring 23 is accessible along a bore 
24 in the second tool 15 to facilitate movement of the locking element 
from its releasing position to its locking position by the action of a 
finger 25 which can be inserted along the bore 24. The finger 25 is 
supported from the body 10 at a releasing station. 
When the finger 25 is withdrawn from the locking element 22, the spring 23 
urges the locking element onto the holding elements 21 so that these are 
driven by a camming action towards the connectors 16. There is sufficient 
clearance between the locking element 22 and the second tool 15 to permit 
sufficient movement of the locking element relative to the second tool in 
directions along the holding elements 21 to ensure that the pressure 
derived from the spring 23 is exerted substantially equally by the locking 
element 22 on the holding elements. This ensures that both holding 
elements are driven fully home into the recess of the corresponding 
connector 16. Furthermore, a tapered portion of the locking element 22 
lies between the holding elements and movement of the locking element into 
the locking position illustrated in FIG. 4 is limited only by engagement 
of the holding elements with the connectors 16. Accordingly, any wear of 
the components which occurs during the service life of the mould set does 
not impair the ability of the locking element 22 to seat both of the 
holding elements in their recesses in the connectors. Any wear which does 
occur merely permits the tapered portion of the locking element to move 
slightly further under the action of the spring 23. When the locking 
element has been driven by the spring into its locking position, there is 
no free-play between the connectors, the holding elements and the locking 
element, even after some wear has occurred. 
In place of the mechanical retaining means illustrated in the accompanying 
drawings, there may be provided electro-magnetic or electro-mechanical 
retaining means for retaining the tools 14 and 15 in the closed condition. 
Furthermore, the retaining means may include hydraulic components, for 
example pistons or diaphragms which are moved by hydraulic pressure to 
perform a locking function and an hydraulic accumulator to maintain the 
hydraulic pressure when the mould set is disconnected from a source of 
hydraulic pressure. At the releasing station, the tool set may be 
connected with the source of hydraulic pressure so that the pressure can 
be reduced to effect or permit unlocking and then re-established to 
re-lock the mould set. Similarly, in a case where the retaining means is 
electro-magnetic or electro-mechanical, the mould set may have an 
electrical circuit which is connected temporarily with a source of 
electrical power at the opening station or a magnetic circuit of the tool 
set may be connected temporarily with a magnetic circuit at the opening 
station. By a magnetic circuit, we mean a path of high magnetic 
permeability. 
There are also mounted in the second tool 15 a pair of ejector pins, one of 
which is shown at 26. The ejector pins 26 have respective end surfaces 
which form a part of the boundary of the mould cavity. Each ejector pin is 
spring loaded to a position in which this end surface of the pin is flush 
with an adjacent part of the boundary of the mould cavity. The ejector 
pins are arranged for movement relative to the second tool, when the tool 
set is in an open condition, to respective positions shown in FIG. 2 in 
which the ejector pins extend upwardly through that part of the mould 
cavity which is formed in the tool 15 to eject a moulding from that part 
of the cavity. 
There may be defined between the first and second tools 14 and 15 more than 
one mould cavity, in which case there would be formed at the interface 
between the inlet nozzle 18 and the sprue element 19 a corresponding 
number of sprue passages, one for each mould cavity. Furthermore, at least 
one ejector pin would be provided for each mould cavity. In a case where 
more than one mould cavity is defined between the tools 14 and 15, the 
sprue element 19 extends to each of these cavities so that when the sprue 
element moves to its severing position, the moulding composition occupying 
each of the sprue passages leading to the mould cavities is separated from 
the plastics composition in those mould cavities. The mouldings 
subsequently ejected from the mould cavities do not require de-spruing. 
At an opening station 27, there is mounted on the body 10 opening means 
shown in FIG. 3 for opening the tool set 14, 15. The opening means 
includes a slide 28 guided on guide bars, one of which is shown at 29, for 
reciprocation relative to the body 10 between the retracted position shown 
in FIG. 3 and an extended position in which plungers 30 mounted on the 
slide 28 extend through respective openings in a guide plate 31 and 
project from the guide plate into the second tool 15 of a set of tools at 
the opening station. In the projected position, the plungers 30 engage the 
ejector pins 26 and hold these in respective ejecting positions. 
The finger 25 is mounted on the slide 28 in a guide tube containing a 
spring which allows the stroke of the finger 25 to be shorter than that of 
the slide. 
There is also mounted on the slide 28 a number of pushers 32 corresponding 
to the number of connectors 16 in each tool set. When a tool set is at the 
opening station 27, each pusher 32 is aligned with a corresponding 
connector and when the slide 28 is moved along the guide bars 29, the 
pusher enters the corresponding bore in the second tool 15, engages the 
connector and drives the connector from or partly from the second tool 15. 
Since the connectors are fixed with respect to the first tool, this raises 
the first tool from the second tool, so establishing the open condition of 
the tool set. Complementary tapers on the pushers and connectors establish 
friction which inhibits movement of the connectors from the pushers whilst 
the tool set is open. It will be understood that the pushers raise the 
first tool from the second tool before the ejector pins are moved relative 
to the second tool. A lateral projection 85 on the sprue element 19 
cooperates with a pin mounted in the tool 15 to prevent the sprue element 
escaping from that tool. The pin also restrains rotation of the sprue 
element. 
For moving the slide 28 relative to the guide plate 31, there is provided 
an hydraulic piston and cylinder unit 33, the cylinder of which is fixed 
with respect to the guide plate 31 and the body 10. The guide plate 31 is 
mounted just below the carrier 11 so that portions of the carrier lying 
between adjacent tool sets move over the guide plate during rotation of 
the carrier. A pneumatic piston and cylinder unit or an electrically 
energised device may be substituted for the unit 33. The stroke of the 
slide 28 is selected according to the moulding produced. 
There is also provided at the opening station 27 a chute 34 for receiving 
ejected mouldings and means for delivering ejected mouldings to the shoot. 
The latter means may be a nozzle 81 for directing a jet of air between the 
tools 1 and 15 towards the chute. 
At a heat transfer station 35 spaced around the axis 12 from the opening 
station 27, there is provided at least one heat exchanger for engaging a 
tool set at the heat transfer station and transferring heat between the 
tool set and a head transfer fluid. Generally, heat will be transferred 
from the tool set to the heat transfer fluid, in order to avoid the 
temperature of the tools 14 and 15 rising to an unacceptable level. 
However, at start-up after a period during which the apparatus has been 
idle, heat may be transferred from the heat transfer fluid to a tool set, 
in order to avoid premature freezing of moulding composition which is 
injected into the mould cavity 17. 
In FIG. 8, there is shown a pair of heat exchangers 36 and 37 which are 
mounted on the body 10 at the heat transfer station 35. The heat 
exchangers are both mounted on a support 38 for sliding relative to the 
support towards and away from each other. The support guides the heat 
exchangers for movement along a common rectilinear path. The support 38 is 
fixed on the body 10 in any convenient manner. 
Adjustable stops 39 are provided on the support 38 for limiting the travel 
of the heat exchangers 36 and 37 in directions away from each other. 
Driving means is provided in the support 38 for moving the heat exchangers 
from their stops towards each other into pressure contact with a tool set 
at the heat transfer station 35. The driving means may be a piston and 
cylinder unit. It will be understood that, when the heat exchangers 36 and 
37 are withdrawn from each other into engagement with the stops 39, there 
is between them a gap sufficiently wide for the tool set, when in its 
closed condition, to pass through the gap without contact being made with 
the heat exchangers. 
The heat exchanger 36 comprises a block of copper or other metal which is a 
relative good conductor of heat. In this block, there is formed a passage 
96 for the flow of a heat transfer fluid through the heat exchanger 
between an inlet 40 and an outlet 41. The heat exchanger 36 further 
comprises a face plate 43 at that face of the heat exchanger which engages 
the tool set at the heat transfer station when the heat exchangers are 
moved towards each other. The face plate 43 is formed of steel or other 
relatively hard-wearing metal. The heat exchanger 37 is preferably 
identical with the heat exchanger 36 but is mounted with its face plate 
facing towards the heat exchanger 36. 
The inlet 40 and outlet 41 of both heat exchangers may be connected by 
flexible hoses (not shown) with a remote cooler 44 mounted in the body 10. 
The cooler may be a known heat exchanger adapted to facilitate the 
transfer of heat to air and a fan may be provided to blow air through the 
cooler. Additionally, there may be provided heating means for supplying 
heat to the heat transfer fluid during start-up. A pump 45 is provided to 
pump the heat transfer fluid through the cooler or the heater and through 
the heat exchangers. 
As shown in FIG. 1, there may be a plurality of heat transfer stations, 
each being equipped with heat exchangers corresponding to the heat 
exchangers 36 and 37. 
There may be formed in one or both of the tools 14 and 15 one or more 
passages through which a heat transfer medium can be conveyed whilst the 
mould set is at a heat transfer station A representative passage is shown 
in the tool 14 at 87 in FIG. 3. The coolant passage 87 incorporates valves 
(not shown) for closing the ends of the coolant passage whilst the mould 
set is out of the heat transfer station. The heat exchangers 36 and 37 
incorporate connectors controlled by respective valves (not shown) for 
communicating with the heat transfer passage 87 of a mould set at the heat 
transfer station. Movement of the heat exchangers 36 and 37 may be used to 
open the valves in the heat transfer passage 87 for flow of coolant 
through the tool, whilst the mould set is in the heat transfer station. 
At an injection station 46 which is spaced around the axis 12 from the 
opening station 27 and from all of the heat transfer stations, there is 
provided a clamping device 47 for clamping together the tools 14 and 15 of 
a tool set at the injection station. The clamping device is adapted to 
establish a relatively high contact pressure between the tools. Although 
the retaining means holds the tools in a closed condition, it does not 
maintain a high contact pressure between the tools. 
The clamping device 47 includes a support 48 which is fixed to the body 10 
in a convenient manner. On the support 48, there is provided a pair of 
jaws 49, 50. The support 48 includes a pair of rectilinear, parallel guide 
bars which are fixed to the jaw 49 and on which the jaw 50 slides. 
The clamping device 47 further comprises a reaction member 52 connected 
with the jaw 49 by a pair of threaded, rotatable shafts 53. These shafts 
engage female screw threads formed in the reaction member 52 and the 
reaction member can be moved towards and away from the jaw 49 by turning 
of the shafts 53. A hand wheel 54 on the jaw 49 is connected with the 
shafts by suitable gearing to facilitate turning of the shafts for setting 
of the position of the reaction member 52 relative to the jaw 49. The jaw 
50 lies between the jaw 49 and the reaction member 52. An end plate 57 is 
attached to the guide bars 51 at the ends thereof remote from the jaw 49 
and corresponding end portions of the threaded shafts 53 are rotatably 
mounted in the end plate. 
The clamping device 47 further comprises a toggle linkage 55 connected 
between the reaction member 52 and the jaw 50. A piston and cylinder unit 
56 is mounted on the support 48 and is connected with the toggle linkage 
for operating that linkage. 
The jaw 50 of the clamping device is connected with the support 48 by 
connecting means which permits limited movement of the jaw 50 relative to 
the support. The particular example of connecting means shown in FIG. 5 
comprises a pair of stepped bolts 58 which allow small movements of the 
jaw 50 relative to the support in a direction along the guide bars 51. The 
position of the jaw 50 relative to the support 48 is always such that the 
jaw 50 lies below the carrier 11. The jaw 50 may, however, move into 
engagement with the underside of the guide plate 86. The jaw 49 is spaced 
upwardly from the carrier 11 sufficiently for a tool set 14, 15 to be 
received between the jaws 49 and 50, when the tool set is in the closed 
condition. 
The clamping device 47 further comprises a pair of pre-stressing screws 59 
which are connected by suitable gearing with the handle wheel 54 to be 
turned when the threaded shafts 53 are turned. The screws 59 are arranged 
to subject the clamping device 47 to stress when the jaws 49 and 50 are 
out of contact with a tool set. When the toggle linkage is operated to 
drive the jaws 49 and 50 into pressure contact with the tool set, this 
pre-stress is relieved but there is no unacceptable distortion of the 
clamping device. 
There is also provided at the injection station 46 an injection head 60 
through which a moulding composition can be injected into a tool set at 
the injection station. The injection head is mounted on feed means 61 for 
feeding the moulding composition to the injection head. The feed means is 
disposed at the center of the carrier 11 and is intersected by the carrier 
axis 12. Thus, the feed means is nearer to the carrier axis than are the 
tool sets. 
The feed means 61 is shown in FIG. 7 isolated from other parts of the 
apparatus. The feed means includes a hollow injection body 62 which 
extends upwardly from a base 63 disposed below the level of the carrier 
11, through the central opening of the carrier, to a position above the 
level of the carrier. The injection head 60 is an elongated, hollow member 
which is mounted on the injection body 62 for pivoting relative thereto 
about a pivot axis 64 which is transverse to the carrier axis 12. The 
injection head and the axis 64 lie adjacent to an upper end of the body 
62. Accordingly, an end portion of the injection head remote from the 
injection body 62 is movable upwardly and downwardly relative to the 
carrier 11. The interior of the injection head 60 is in communication with 
the interior of the injection body 62 throughout pivoting movement of the 
injection head relative to the injection body. First positioning means is 
provided for adjusting the position of the injection body 62 relative to 
the body 10 and second positioning means is provided for moving the 
injection head relative to the injection body. 
The second positioning means comprises a piston and cylinder unit 65 which 
acts on the injection head through the intermediary of a toggle linkage 
66. The second positioning means is used for driving an outlet nozzle 67 
of the injection head onto the inlet nozzle 18 of a tool set at the 
injection station. The travel of the outlet nozzle 67 is sufficient to 
depress the inlet nozzle 18 into the first tool 14 and drive the sprue 
element 19 into the charging position. 
It will be noted that, in the example illustrated, the outlet nozzle 67 is 
above the inlet nozzle 18 and the injection head 60 pivots upwardly and 
downwardly relative to the injection body 62. By extending the piston and 
cylinder unit 65, the injection head can be pivoted upwardly to move the 
outlet nozzle 67 clear of the inlet nozzle 18. 
The injection head 60 contains a shut-off valve 68 for preventing flow of 
moulding composition from the injection head through the outlet nozzle 67. 
There is formed in the outlet nozzle an annular seat for receiving the 
shut-off valve. This seat is immediately adjacent to an orifice at a lower 
end of the outlet nozzle, through which orifice the moulding composition 
leaves the outlet nozzle to enter the inlet nozzle 18 of a mould set. As 
shown, the valve may have a small projection which extends into this 
orifice. The valve 68 is carried on a stem 69 which extends upwardly from 
the valve along the axis of the outlet nozzle 67, through a nozzle 
retainer 108 mounted in the injection head 60 and into a chamber 109. The 
chamber 109 is divided by a diaphragm 110 into upper and lower parts 
having respective inlets for admitting fluid under pressure. An upper end 
portion of the valve stem 69 is secured to the diaphragm at the middle of 
the diaphragm. 
Coolant passages 111 are formed in the nozzle retainer 108. Flow of coolant 
through these passages minimises the transmission of heat from the 
plastics composition in the outlet nozzle 67 to the diaphragm 110. The 
diaphragm may also be cooled by means of hydraulic fluid admitted to the 
chamber 109 during operation. If the diaphragm 110 is formed of a material 
which can withstand elevated temperatures without deterioration, then the 
coolant passages 111 could be omitted. 
The first positioning means comprises vertical shafts disposed inside cover 
tubes 70 on the injection body 62. These shafts are in screw-threaded 
engagement with the injection body and transmission means is provided for 
transmitting rotary movement from a hand wheel 71 to the screws to raise 
and lower the injection body 62 relative to the base 63. 
The base 63 is slidably mounted on horizontal guide bars 72 which are fixed 
to the body 10 by brackets 73. A screw and nut mechanism is provided for 
driving the base 63 along the guide bars 72 and a hand wheel 74 is 
provided for operating this screw and nut mechanism. The guide bars 72 are 
arranged with their lengths extending in the direction of length of the 
injection head 60. 
There is provided in the injection body 62 a feed inlet 75 for admitting a 
moulding composition to the feed body. An elevated feed hopper 79 is 
arranged to deliver granules of the moulding composition to the feed inlet 
75. This hopper is water-cooled. 
In the injection body 62, there is provided a feed and injection screw 97 
which is constructed, arranged and driven in a known manner. A motor 76 is 
provided on the body 10 for turning the injection screw, suitable 
transmitting means being provided for transmitting rotary motion from the 
motor 76 to the screw. A pair of piston and cylinder units 77 is provided 
for reciprocating the injection screw relative to the injection body 62 
along an axis of the screw. These piston and cylinder units are supported 
on the injection body 62 by a supporting structure 78. The screw axis is 
vertical. 
Electrical heating elements 112, 113 are provided in the injection body 62 
and in the injection head 60 for heating the moulding composition to the 
required temperature, by the time that composition reaches the outlet 
nozzle 67. An electrical heating element is preferably incorporated in the 
outlet nozzle 67 to raise the temperature of the moulding composition to 
the required value, the temperature of the moulding composition upstream 
of the outlet nozzle 67 being significantly lower than the injection 
temperature. It will be noted that the moulding composition is fed 
upwardly through the injection body 62 by the injection screw and then is 
fed at least approximately horizontally through the injection head 60 to 
the outlet nozzle 67. The heating elements are controlled by a control 
system which includes thermo-couples in the outlet nozzle 67, the 
injection head 60 and the injection body 62. 
The feed and injection screw 97 has a conical tip 98 and between the 
conical portion and the helical formation 99, there is a peripheral groove 
100 containing a ring 101. The ring surrounds a tapered neck 102 of the 
screw and has a correspondingly tapered inner periphery which seats on the 
tapered neck of the screw adjacent to one end of the neck, when the screw 
is driven upwards. The ring is a close fit inside the bore of the body 62 
so that it then operates as a piston on the moulding composition which 
lies within the bore of the body 62 and above the ring 101. When the screw 
is screwed downwards, a smaller diameter portion of the neck moves into 
the ring and this provides between the ring and the neck a clearance 
through which the moulding composition can flow under the action of the 
helical formation 99. This recharges the space between the screw tip 98 
and the complementary end portion of the bore of the body 62 with the 
moulding composition. 
An outlet from the bore of the body 62 is provided between the ends of that 
bore, at one side of the screw 97 and in the larger diameter portion of 
the conical surface of the bore which complements the tip 98. From this 
outlet, a rectilinear passage 103 leads upwardly through the body 62 to an 
annular transfer chamber 104. The passage 103 communicates with the 
transfer chamber near to one end thereof. The transfer chamber 104 
surrounds the pivot axis 64. One part of the outer periphery of the 
transfer chamber is defined by the injection body 62 and the other part of 
the outer periphery of the transfer chamber is defined by the injection 
head 60. A heating element 105 extends along the transfer chamber at the 
centre thereof. A passage 106 formed in the injection head 60 extends 
tangentially from the transfer chamber 104 adjacent to a second end 
thereof to the outlet nozzle 67. 
A heating element 107 is mounted in the injection head 60 and extends into 
the outlet nozzle 67 so that there is provided in the outlet nozzle an 
annular chamber for receiving the moulding composition from the passage 
106. This passage communicates with the annular chamber and approaches 
that chamber in a direction at right angles to a longitudinal axis of the 
outlet nozzle. 
There may be substituted for the shut-off valve 68 an alternative shut-off 
valve mounted in the injection body 62 for closing the passage 103 This 
alternative shut-off valve may, for example, comprise a rotatable plug 
which intersects the passage 103 and has a bore through which the moulding 
composition can flow when the valve is in an open position. 
The control system of the apparatus includes a microprocessor (not shown) 
having input means for receiving data relating to the mouldings to be 
produced, to the tools in which the mouldings are to be formed and the 
conditions under which the mouldings are to be produced, including the 
duration of successive stages of operation of the apparatus. The input 
means may include one or more known input devices, for example a keyboard, 
a disc drive and a tape-reader. The control system also includes sensing 
devices incorporated within the apparatus for providing information to the 
microprocessor. These sensing devices include the thermo-couples 
previously mentioned and proximity switches or other known devices for 
detecting the presence of and position of tools and other components. 
In preparation for use of the apparatus, a number of mould sets is mounted 
on the carrier 11 in respective predetermined positions. The mould sets 
may be substantially identical with one another. Alternatively, the mould 
sets may define different mould cavities, differing in size and/or shape. 
During mounting of the mould sets on the carrier, the carrier is indexed 
about the axis 12. Each mould set may be mounted on the carrier at a 
position between the unlocking and opening station 27 and the injection 
station 46. The mould sets are rigidly secured to the carrier. Respective 
inlet nozzles 18 of the mould sets lie in corresponding positions, that is 
to say at the same distance from the axis 12 and spaced apart equally 
around the axis, although the apparatus may be operated with a number of 
mould sets on the carrier less than the maximum number of mould sets which 
can be accommodated on the carrier. 
During an initial stage of operation, heated fluid may be passed through 
the heat exchangers at the heat transfer station 35 and other heat 
transfer stations to raise the temperature of the mould sets passing 
through the heat transfer stations. This initial stage may comprise more 
than one complete revolution of the carrier 11, in which case no moulding 
composition is introduced into the mould sets during the initial stage of 
operation. The mould sets are moved through all of the stations in turn 
until the temperature of each mould set has attained a sufficiently high 
value to avoid risk of the moulding composition freezing prematurely in a 
mould set and either preventing proper injection of the required amount of 
moulding composition or producing a defective moulding. 
After a mould set has moved into the injection station 46, the clamping 
device 47 is operated to clamp the tools 14 and 15 of the mould set 
together under relatively high pressure. The injection head 60 is then 
pivoted downwards by the piston and cylinder unit 65 into engagement with 
the inlet nozzle 18 and drives the inlet nozzle downwards to move the 
sprue element 19 into the charging position. The lower part of the chamber 
109 is pressurised to open the valve 68. It will be understood that the 
pressure in the injection nozzle 67 is not high when the screw 97 is not 
driven. The piston and cylinder units 77 are then actuated to inject a 
quantity of moulding composition downwards through the inlet nozzle 18 and 
the associated sprue passage into the mould cavity of the mould set. The 
upper part of the chamber 109 is then pressurised to close the shut-off 
valve 68 and the unit 65 is operated to raise the outlet nozzle 67 from 
the inlet nozzle 18 and to allow the sprue element 19 to move to the 
severing position. The clamping device 47 is then operated to release the 
mould set. It will be understood that the tools 14 and 15 are held in the 
closed position by the retaining means acting on the connectors 16. 
The shut-off valve 68 is closed and the outlet nozzle is raised from the 
inlet nozzle 18 immediately after the required amount of moulding 
composition has been injected into the mould cavity. Accordingly, the 
sprue plate is permitted to move to its severing position whilst the 
moulding composition in the sprue passage is in a molten or plastic 
composition. The moulding composition does not significantly obstruct 
movement of the sprue plate. Any moulding composition occupying the outlet 
orifice of the outlet nozzle 67 when that nozzle is raised from the inlet 
nozzle 18 remains with the moulding composition in the inlet nozzle. 
The carrier 11 is indexed to the next position, carrying the mould set from 
the injection station 46 to the heat transfer station 35. When the mould 
set has reached at least approximately the normal working temperature, the 
supply of a heated fluid to the heat exchangers 36 and 37 is terminated 
and a coolant is supplied to these heat exchangers. At the heat transfer 
station, the heat exchangers 36 and 37 are driven into firm contact with 
upwardly and downwardly facing surfaces of the mould set to establish a 
thermally transmitting relation therewith. This relation is maintained 
during the period when the next following mould set is clamped by the 
clamping device 47 at the injection station. When the following mould set 
is released by the clamping device, the heat exchangers 36 and 37 are 
moved out of engagement with the mould set at the heat transfer station so 
that the mould set can be moved by the carrier to successive heat transfer 
stations and then to the unlocking and opening station. 
When the tool set is positioned in the unlocking and opening station, the 
finger 25 is raised into engagement with the locking element 22 and drives 
the locking element upwardly to release the holding elements 21 for 
sliding towards each other. The piston and cylinder unit 33 is then 
extended further to cause the pushers 32 to engage the connectors 16 and 
drive the connectors upwardly out of the second tool 15 so that the mould 
set is opened. As the first tool 14 approaches a fully-raised position, 
the ejector pins are driven upwardly to eject the moulding from the mould 
cavity. A jet of air from an air nozzle 81 carries the moulding to the 
shoot 34. 
The plastics sprue also is removed from the mould set. This may be achieved 
mechanically, for example by means of a grab which advances to the sprue, 
grips the sprue and then retracts from the tool set, or by means of an air 
jet. The sprue is cut up and is returned to the hopper. 
In a case where additional cooling of the moulding is required before the 
moulding is removed from the mould set, the mould set may be permitted to 
travel through the unlocking and opening station 27 without operation of 
the piston and cylinder unit 33 to open the mould set. The mould set would 
then travel through the injection station 46 without operation of the 
piston and cylinder units 77 and so back to the heat transfer stations. In 
this way, one particular mould set or all of the mould sets may be cooled 
for a relatively long period before the moulding formed therein is 
removed. Furthermore, in order to prevent cooling of the moulding at an 
unacceptably high rate, one of the heat transfer stations may be used to 
impart heat to the mould set, in order to reduce the overall rate of 
cooling. Control of the piston and cylinder unit 33 and of the piston and 
cylinder units 77 by the microprocessor facilitates subjecting one mould 
set to a cooling cycle which differs from the cooling cycle to which 
another mould set on the carrier 11 is subjected. This is useful when 
significantly different mouldings are produced in respective mould sets on 
the carrier. 
It will be noted that, in a case where the control means is programmed to 
inject different amounts of moulding composition into successive tool 
sets, after the moulding composition has been injected into a first tool 
set, the screw motor 76 is operated for a period to feed only that 
quantity of moulding composition which is to be injected into the next 
mould set. This avoids premature heating of the moulding composition to 
the injection temperature and minimises the period for which the moulding 
composition is maintained at the injection temperature. This is important 
in cases where the moulding composition deteriorates at the injection 
temperature. 
Whilst the tool set is still positioned in the unlocking and opening 
station, the slide 28 is retracted from the tool set. The first tool 14 is 
moved by gravity towards and onto the second tool 15 to close the mould 
set. If the connectors 16 move fully home into the tool 15, then the 
holding elements 21 will be driven into respective recesses in the 
connectors by the camming action of the locking element 22. Alternatively, 
if the connectors do not move fully home into the second tool 15 at the 
unlocking and opening station, the connectors will be driven fully home 
when the mould set is in the injection station 46 and the clamping device 
47 acts on the mould set. If required, there may be provided at the 
unlocking and opening station or at an intermediate station means for 
exerting on the first tool 14 a force additional to the force of gravity 
to drive the connectors fully home into the second tool 15. 
During operation of the apparatus, the moulding composition in granular 
form is fed through the cooled, elevated hopper 79 to the inlet 75 and 
passes from that inlet into a heating chamber containing the injection 
screw. It will be noted that the screw is rotatable about a vertical axis 
within the injection body 62. The moulding composition is driven upwards 
intermittently by the screw and is melted in the injection body 62. 
The injection screw is rotated whilst the shut-off valve 68 is closed, in 
order to feed the required quantity of moulding composition to the 
downstream end of the screw. Pressure established in the moulding 
composition downstream of the screw helps to maintain the shut-off valve 
closed. The amount of composition delivered to the downstream end of the 
screw is determined by the duration of the period for which the screw is 
turned and this is controlled by the microprocessor according to the 
volume of the composition which is to be injected into the mould set. 
There may be on the carrier 11 mould sets which differ from one another 
and the volume of moulding composition to be injected may differ from one 
mould set to another. In this case, information concerning the required 
volumes of moulding composition for each mould set is entered into the 
microprocessor and the microprocessor controls energisation of the screw 
drive motor accordingly. 
The volume of the moulding composition which occupies the passage 103, the 
transfer chamber 104, the passage 106 and the outlet nozzle 67 is 
typically greater than the volume of moulding composition which is 
injected into one tool set to form one or more mouldings therein. 
Typically, the volume of moulding composition which is downstream of the 
feed and injection screw 97 is equivalent to three or four times the 
volume of moulding composition to be injected into a single tool set. 
Accordingly, the moulding composition is downstream of the feed and 
injection screw but retained in the injection body and injection head for 
a period which corresponds to the movement of three or more mould sets 
through the injection station. In consequence of the position of the 
outlet from the tapered end of the bore of the injection body 62, flow of 
the moulding composition from that bore into the passage 103 is severely 
turbulent. The flow of moulding composition through the transfer chamber 
104 is substantially along a spiral path, in consequence of the moulding 
composition approaching and leaving the transfer chamber along respective 
paths which are tangential to that chamber and are spaced apart along the 
chamber. Further severe turbulence of the moulding composition is caused 
as that composition flows from the passage 106 into the outlet nozzle 67. 
The turbulent flow and the period for which the moulding composition is 
retained in the passages 103 and 106, the transfer chamber 104 and the 
outlet nozzle 67 contribute to conditioning of the moulding composition to 
ensure that the temperature of the moulding composition is uniform before 
that composition is injected into a mould set. It will be noted that the 
length of the passage 103 is many times the width of that passage and the 
length of the passage 106 is many times the width of that passage. These 
passages are preferably cylindrical. 
It will be noted that the space adjacent to the outer periphery of the 
carrier 11 is not obstructed by the injection head 60, the injection body 
62 or associated parts of the apparatus. Accordingly, there is no 
significant restriction on the space available to accommodate the clamping 
device 47 which is disposed adjacent to the outer periphery of the 
carrier. A strong and powerful clamping device can be provided 
conveniently and this enables a high clamping force to be applied to the 
tools of each mould set at the injection station. 
The opening station 27 is well-spaced from the clamping device 47 and from 
the injection head 60 and the injection body 62. Access to the mould set 
at the opening station is not restricted significantly. Accordingly, there 
can be provided at the opening station a plurality of devices for 
disengaging mouldings from the tools of the mould set. For example, there 
may be provided two such devices at opposite sides of the mould set. This 
facilitates extraction from the tools of, for example, a moulding having 
respective threaded portions at opposite ends of the moulding. 
It will also be noted that the inlet nozzle 18 is mounted in the first tool 
14 at a position near to the or each mould cavity. The sprue passage 
formed in the sprue element 19 provides communication between the inlet 
and the or each mould cavity. There is no requirement for machining of the 
tools to provide passages additional to those defined by the sprue element 
and the inlet nozzle 18. It will also be noted that the inlet nozzle 18 is 
spaced inwardly from the periphery of the tool set, as viewed in a 
direction at right angles to the interface between the tools 14 and 15. It 
is not necessary to provide in the mould set passages for the flow of the 
moulded composition which extend to the periphery of the mould set. 
Accordingly, the amount of machining necessary to produce the tools 14 and 
15 is relatively small. The inlet nozzle 18 is accessible to the outlet 
nozzle 67 at an upwardly facing surface of the tool 14 and this surface is 
nearer to the second tool 15 than is the surface of the tool 14 on which 
the clamping device 47 bears. 
The apparatus includes a storage hopper 82 which is charged intermittently 
with the granular moulding composition. The storage hopper may also be 
cooled by means of water or air cooling, if required. A pneumatic conveyor 
83 is provided for conveying the moulding composition granules from a 
position within the storage hopper 82 and above the bottom of that hopper 
to the elevated hopper 79. The elevated hopper has a weir over which 
excess moulding composition can fall and return to the storage hopper 82 
along overflow duct 84. The moulding composition moves under the action of 
gravity from the elevated hopper 79 to the inlet 75. The duct leading to 
the inlet 75 preferably communicates with the elevated hopper at a level 
above the bottom of that hopper so that any foreign matter which enters 
the hopper and falls to the bottom of the hopper will not then be fed into 
the inlet 75. The top of the elevated hopper 79 is closed, except for an 
air outlet and the air outlet is closed by an air filter. The main hopper 
80 also is normally closed by a removable lid which prevents foreign 
matter entering the hopper. 
It will be noted that operation of the apparatus is a continuous, cyclical 
process. Each mould set travels along an endless path through each of the 
stations. Typically, each mould set dwells at each station for the same 
period. Whilst a moulding is being removed from a first mould set, a 
second mould set is being cooled and moulding composition is being 
injected into a third mould set. The first mould set is then advanced 
towards or into the injection station and further moulding composition is 
injected into the first mould set. The time required for a mould set to 
return to the injection station is determined by the number of stations, 
the dwell at each station and the time taken to travel between adjacent 
stations. 
In the example of apparatus illustrated in the accompanying drawings, the 
devices at the several stations, for example the injection head 60, the 
clamping device 47, the heat exchangers 36 and 37 and the pushers 32 and 
associated components are mounted on or in the body 10 which is stationary 
during use of the machine. Alternatively, the carrier 11 may be fixed on a 
stationary base which rests on the floor and the body 10 may be turned 
relative to the carrier by the drive means. With this arrangement, the 
several devices which operate on the mould sets would travel along a 
common path from one mould set to another. Alternatively, the devices for 
operating on the mould sets may travel along respective different paths 
and these paths may be defined by known guide means. In practice, there 
will generally be more than one mould set but the apparatus could be used 
to form mouldings in one mould set only, other mould sets being idle, and 
the invention may be used in a case where there is only a single mould 
set. 
In addition to or as an alternative to the provision to the microprocessor 
of information concerning the amount of moulding composition to be 
injected into each mould set by way of the input means, this and other 
information may be presented by the tool sets. Such information may be 
presented on a tool set by an adjustable indicator, the position of which 
relative to a reference position indicates the amount of moulding 
composition required by that tool set. For transferring such information 
to the microprocessor, there is provided a mechanical feeler for 
contacting the indicator of the tool set and a known transducer for 
providing to the microprocessor an electrical signal representing the 
position of the indicator. 
In the example of apparatus illustrated in the accompanying drawing, there 
is a single injection screw for feeding the moulding composition through 
the injection head 60. The apparatus may be modified by the provision of a 
plurality of injection screws, each operating in a respective heating 
chamber, and the heating chambers all communicating with the injection 
head. In this way, a larger volume of moulding composition can be injected 
into each mould set without the use of larger injection screws, which 
would increase the overall height of the apparatus. 
In a further alternative arrangement, there is provided a plurality of 
injection screws, each feeding the moulding composition through a 
respective injection head to the mould set either at a common injection 
station or at respective injection stations. Thus, respective moulding 
compositions which differ from each other, for example in respect of 
colour, may be injected into a single mould set. 
The features disclosed in the foregoing description, or the following 
claims, or the accompanying drawings, expressed in their specific forms or 
in terms of a means for performing the disclosed function, or a method or 
process for attaining the disclosed result, as appropriate, may, 
separately or in any combination of such features, be utilised for 
realising the invention in diverse forms thereof.