COMMANDE A CREMAILLERE ET PIGNON POUR MOULE EN EMPILADE

RACK AND PINION GEAR STACK MOLD CONTROL

Abrégé anglais

ABSTRACT OF THE DISCLOSURE
The present invention provides in a stack mold
comprising a center mold part, first and second outside
mold parts movable at both sides of the center mold part,
a rack and pinion gear arrangement to move the outside
mold parts. The rack and pinion gear arrangement
comprises a plurality of pinion gears located at the
center mold part and including a drive gear and first and
second follower gears driven off the drive gear. Also
provided are first and second free ended racks extending
in opposite directions from the first and second outside
mold parts respectively in engagement with the first and
second follower gears. These follower gears reach above
and below the drive gear and the first follower gear is
offset to the side of the drive gear opposite that to
which the free end of the first rack extends while the
second follower gear is offset to the side of the drive
gear opposite that to which the free end of the second
rack extends.

Revendications

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A rack and pinion gear arrangement for movement
of first and second outside mold parts relative to a
center mold part in a stack mold, said rack and pinion
gear arrangement comprising pinion gear means located at
said center mold part including a drive gear, first and
second follower gears driven off said drive gear and first
and second free ended racks extending in opposite
directions from said first and second outside mold parts
respectively and in engagement with said first and second
follower gears, said follower gears reaching above and
below said drive gear and said first follower gear being
offset to a first side of said drive gear opposite that to
which the free end of said first rack extends and said
second follower gear being offset to a second side of said
drive gear opposite that to which the free end of said
second rack extends for opening and closing said stack
mold.

2. A rack and pinion gear arrangement for opening
and closing a stack mold having a center mold part with
first and second outside mold parts to either side of said
center mold part with relative movement between all of
said mold parts, said rack and pinion gear arrangement
comprising a center pinion gear and upper and lower pinion
gears meshed with and off-set to either side of said
center pinion gear and first and second free ended racks
extending in opposite directions from said first and
second outside mold parts and in engagement with said
upper and lower pinion gear for opening and closing said
stack mold.

Description

13
FIELD OF THE INVENTION
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The present invention relates to a stack mold and
in particular a new and improved rack and pinion gear
arrangement for increased opening of the stack mold.
BACKGROUND OF THE INVENTION
As known stack molds include a center mold part,
generally the female part of the mold, and two outside
male mold parts which open and close relative to the
center mold part. Typically the opening and closing of
these stack molds is controlled through a rack and pinion
gear arrangement comprising individual racks from the twu
outside mold parts which are driven off ùne big pinion
gear located at the center mold part. The racks on the
outside mold parts extend across the center mold part only
as far as the outside surface of the opposite outside mold
part when the s-tack mold is closed. It is not desirable
to increase the length on the racks beyond this point
otherwise they interfere with the outside mounting
surfaces for the mold parts which would then require
special molding machine modifications to accomodate the
increased length of the racks.
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1 The required relatively limited length of the
racks in combination with a single pinion gear for
controlling rack movement results in a relatively limited
opening and sormewhat poor access to the stack mold which
may for example make it awkward to eject the molded pieces
even with the stack mold in the fully opened position.
SUMMARY OF THE PRESENT INVENTION
The present invention provides in a stack mold
comprising a center mold part, first and second ou-tside
mold parts movable at both sides of the center mold part,
a rack and pinion gear arrangement moving the first and
second outside mold parts. Accordin0 to the present
invention the rack and pinion gear arrangement comprises
pinion gear means located at the center mold par-t and
includiny a drive gear and first and second follower gears
driven off -the drive gear. Also provided are first and
second free ended racks extending in opposite directions
from the first and second outside mold parts respectively
and in engagernent with the first and second follower
gears. The two follower gears reach above and below the
drive gear and the first follower gear is offset to the
side of the drive gear opposite that to which the Free end
of the first rack extends while the second follower gear

5146A/0065A - 3 ~ 6~56
1 is offset to the side of the drive gear opposite that to
which the free end of the second rack extends. This
arrangement effectively increases the lengths of the racks
in contact with the pinion gear arrangement and provides
increased opening of the stack mold in comparison to
conventional stack molds.
BRIEF DISCUSSION OF THE DRAWINGS
The above as well as other advantages and
features of the present invention will be described in
greater detail according to the preferred embodiments of
the present invention in which;
Figure 1 is an exploded perspective view of a
stack mold showing the center female mold part and the two
outside male mold parts separated Frorn one another;
Figure 2 is an assembled view of the stack mold
of` figure 1 showing a prior art rack and pinion gear
arrangemen-t for opening and closing of the stack mold;
Figure 3 is an assembled perspective view of the
stack mold of figure 1 showing the rack and pinion gear
arrangement according to a preferred embodiment of the
present invention.

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1 DETAILED DESCRIPTION ACCORDING TO THE PREFERRED
EMBODIMENTS OF THE PRESENT INVENTION
Figure 1 shows in the exploded or open form a
stack mold comprising a center female mold part 1 with
first and second outside mold parts 3 and 7 respectively.
The two outside ~o~d parts open and close relative to the
center mold part during a molding operation which
comprises injecting a flowable material into the stack
mold while the mold sections are closed and thereafter
ejecting the pieces formed from the mold when the mold
parts are opened. Note in figure 2 the type of pieces
such as buckets B which are formed from the stack molds
shown in the drawings.
In order the ensure proper alignment of the
outside mold parts rslative to the center mold part the
stack mold Further includes a guide rod 11 as well as stud
and socket fittings 13 and 15 which place the male
projections of the outside mold part directly over the
female receptacles of the center mold part.

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1 Figure 2 is labelled PRIOR ART shows the
conventional rack and pinion gear arrangement which is
used to open and close the stack mold. This arrangement
comprises one large pinion gear indicated at PG in figure
2 located at the center mold part and first and second
racks 6 and 8 which extend forwardly From the first and
second outside mold parts 3 and 7 respectively. It is to
be noted in figure 2 that rack 6 extends only as far as
the back surface O of outside mold part 7 while rack 8
extends only as far as the back surface 5 of outside mold
part 3. It is not desired to extend these racks past
these positions since otherwise they tend to interfere
with other equipment around the mold which would then
require modifications to receive the extended length racks.
Staying with figure 2 it will be well appreciated
how the outside mold parts can only open to khe extent
that racks 6 and 8 maintain engagernent with the one large
pinion gear PG~ Therefore, the opening of the stack mold
is directly propor-tional to the length of rack extending
past the center point on the pinion gear, i.e. the
distance between the free end of the rack and the center
point on the pinion gear.

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1 The purpose of the present invention is to
increase the degree to which the outside mold parts can oe
opened relative to the center mold part for creating a
larger clearance area to gain access to the interior of
the mold and to provide greater clearance for piece
ejection from the mold. Figure 3 shows the novel rack and
pinion gearing arrangement of the present invention to
achieve this purpose.
More particularly, as will be seen in figure 3
the one large pinion PG is in accordance with the present
invention replaced by a plurality of pinion gears
comprising a center drive gear 17 as well as a pair of
follower gears 19 and 21 driven off drive gear 17. The
arrangement of the pinion gears is such that follower gear
19 reaches above and is located to the second outside mold
part side of the drive gear opposite the side to which the
free end of rack 8 extends. Follower gear 21 on the other
.hand reaches below and is located to the first outside
mold part side of drive gear 17 away from the free end of
rack 6. According to the arrangement shown the three
pinion gears are aligned along their center axis and the
two follower geas are of the same diameter with identical
teeth configuration for simultaneous and corresponding
opening of the two outside mold sections. Furthermore,

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1 because the two follower gears are controlled by one
common drive gear the two racks are always moved in
opposing directions consistent with the use of one large
pinion gear as shown in figure 2.
By using three pinion gears and by offsetting the
follower gears to the side of the drive gear away from the
free end of the first and second racks the effective
length of the racks for contact with thepinion gear drive
is increased thereby allowing increased opening of the two
outside mold parts. More specifically the effective
increased length of the two racks is the distance between
the center point on the drive gear and the center point on
the individual follower gears since the racks can now be
drawn back past the drive gear while maintaining contact
with the follower gears. The actual increased opening
space of the mold parts is directly proportionate to the
si~e of the gears and the diagonal on which the gears are
placed.
The description above relates to the two outside
mold parts moving relative to the center mold part through
the use of a triple pinion gear arrangement. It is to be

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1 appreciated that this same triple pinion gear arrangement
fittable to a pair of racks can equally as well be used
with a mold system in which one of the outside mold parts
remains stationary while the center and other end mold
parts are moved by the triple pinion gear and rack system
for opening and closing the mold.
Although various preferred embodiments of the
invention have been described herein in detail, it will be
appreciated by those skilled in the art that variationsa
may be made without departing from the spirit of the
invention or the scope of the appended claims.
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