Plastic article or earthenware shaping or treating: apparatus – Female mold and charger to supply fluent stock under... – With means between charger and mold to cut off flow of...
Reexamination Certificate
2002-01-14
2004-06-22
Heitbrink, Tim (Department: 1722)
Plastic article or earthenware shaping or treating: apparatus
Female mold and charger to supply fluent stock under...
With means between charger and mold to cut off flow of...
C425S566000
Reexamination Certificate
active
06752617
ABSTRACT:
This is a Nailkona Stage Entry under 37 C.F.R. § 371 of PCT/EP00/04503, with an international filing date of May 18, 2000, the complete disclosure of which is incorporated herein by reference.
BACKGROUND OF THE INVENTION
The present invention relates to a unit for actuating the rod of a closure element in a mould for the injection-moulding of plastics material.
An injection-moulding mould provided with a conventional actuating unit is shown in partial section in
FIG. 1. A
heated nozzle
10
is mounted beneath a heated plate
11
in order to receive the molten plastics material from a supply duct
12
and to inject it into a moulding cavity
13
through an injection duct
14
and a lower injection hole
15
.
A closure rod
16
slides coaxially inside the injection duct
14
, the axial position of the rod
16
being controlled by an upper actuating unit, generally indicated
17
and housed in a cavity
18
formed in an upper plate
19
. The actuating unit
17
, which is pneumatically operated, comprises a cylinder
20
in which a piston
21
, to which the upper end
16
a
of the rod
16
is connected, can slide vertically.
The vertical movement of the piston
21
and of the rod
16
is brought about by sending an operating fluid (air) alternately through an inlet duct
22
and an inlet duct
23
which are formed in the upper plate
19
and communicate with the cavity
18
in upper and lower positions, respectively, in order to admit the operating fluid to the cylinder
20
through a duct
24
or a duct
25
, so as to raise or lower the piston
21
. As is known, in the lowered position (not shown), the lower end
16
b
of the rod
16
blocks the injection hole
15
whereas, in the raised position (as shown in FIG.
1
), the injection hole is open to allow plastics material which is injected from the duct
14
of the nozzle
10
to pass through to the moulding cavity
13
.
To prevent the injected material From reaching the actuating unit
17
, a tempered steel sealing bush
26
is provided and is housed in a cavity
27
in the hot plate
11
; the sealing bush
26
is fitted on the slidable rod
16
. A reaction ring
28
is interposed between the hot plate
11
and the upper plate
19
. A closure cover
29
is fixed to the upper plate
19
to restrain the actuating unit
17
at the top.
A conventional actuating unit of this type requires numerous seals; in addition to two seals
30
and
31
between the piston
21
and the cylinder
20
, there is a seal
32
between the cover
29
and the upper plate
19
, there are two seals
33
and
34
between the upper plate
19
and the stationary cylinder
20
, and there is a further seal
36
mounted on an enlarged element
37
acting as a stop for the rod
16
.
Injection moulds provided with actuating units configured as described above have a disadvantage of a practical nature when it is necessary to perform adjustment or maintenance operations on one or more closure rods, for example, when it is necessary to replace a worn rod or to clear an injection duct of accumulations of waste. For example, in order to gain access to an injection nozzle, it is necessary to remove the upper plate
19
and with it all of the closure units of the various injection nozzles of which there may be a considerable number (
48
or more) in cases in which the mould comprises several nozzles and numerous moulding cavities. During the removal of the upper plate
19
, all of the rods of the various closure units are thus removed.
Since an operation of this type is performed hot to enable the rods to be removed, the plastics material tends to rise through the sealing bushes
26
and thus to be deposited on surfaces which should, however, remain clean. Once the maintenance or adjustment operation has been performed on the nozzle or nozzles which required it, it is therefore necessary to clean the surfaces on which plastics material has been deposited during the operation, for all of the nozzles of the mould, before the upper plate with the respective rods and closure units is reassembled.
As will be understood, the removal of the upper plate, complete with closure units and rods, is a complex operation but, above all, careful cleaning at many points of the mould as referred to above requires long periods of inactivity of the apparatus and is therefore expensive.
SUMMARY OF THE INVENTION
Moreover, during the reassembly of the closure units, it is necessary to pay particular attention to the various seals, ensuring that they are positioned correctly before closing the mould again.
An object of the invention is to provide an actuating unit in which the piston can be released from its rod easily without requiring the latter to be removed from the nozzle.
An object of the present invention is to propose an actuating unit which is easy to install and to maintain, and which can prevent the problems of the prior art discussed above.
A further object of the present invention is to provide an actuating unit having an improved and simplified system for adjusting the travel of the closure rods; in particular, the adjustment of the travel and the removal of the rod of a particular actuating unit should be independent operations.
This further object is achieved, again according to the invention, by an actuating unit having the characteristics defined in claim
4
.
Yet another object of the invention is to mould products which do not bear obvious marks on their surfaces in the regions of the injection points when these points lie on surfaces which are not perpendicular to the closure rod.
REFERENCES:
patent: 4380426 (1983-04-01), Wiles
patent: 5511968 (1996-04-01), Guzzini et al.
patent: 5894025 (1999-04-01), Lee et al.
patent: 4300334 (1993-07-01), None
patent: 920970 (1999-06-01), None
patent: 98/56560 (1998-12-01), None
Heitbrink Tim
Sughrue & Mion, PLLC
Thermoplay S.p.A.
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