Adjustable cam track for an injection molding machine

An adjustable cam track for an injection molding machine includes a set of guides coupled to a moveable platen for guiding the movement of space defining surfaces which are movably mounted to a stripper platen as it moves with respect to the movable platen. A set of cam followers coupled to the space defining surfaces cause relative movement of each pair of surfaces to release molded articles previously striped from the molds of the molding machine. A set of cam inserts engage the cam followers and are adjustably positionable with respect to the guides to adjust the point of release of the molded articles. Each guide includes a pair of guide walls forming a channel defining two limits of position of the cam follower engaged therein. Each cam insert is received between the guide walls and includes a pair of cam insert walls spaced apart by a distance about equal to the size of the cam follower engaged therein to define a path of movement for the cam follower between the two limits of position. Each cam insert includes a first toothed rack, while a second toothed rack is removably fixed to each guide and engages the first toothed rack to fix the position of each cam insert relative to each guide only at certain preselected locations to coordinate the operation of all the cam followers thereby avoiding any wear imbalance.

BACKGROUND OF THE INVENTION 
The present invention is directed generally to injection molding machines 
having a stripper for stripping molded articles from the mold core 
subsequent to removal of the article from the mold cavity, and 
particularly to means for adjusting the position and/or timing of release 
of the molded article from the stripper. 
Injection molding machines commonly include a fixed platen which is 
generally fixed at a specific location with respect to the base of the 
injection molding machine. This fixed platen can take the form of a mold 
base and can include the runner or manifold system coupled between the 
mold base and a plasticizing injector unit. The mold base and/or fixed 
platen generally includes one or more mold cavity units which, together 
with a core unit, defines a space into which molten plastic is injected to 
form one or more articles. The core units are movable with respect to the 
base and are generally mounted on a movable platen which reciprocates with 
respect to the fixed platen between a closed position where the core unit 
and cavity unit are engaged with each other to define the molding space 
and an open position where the plastic article can be removed from the 
molding machine. 
Molding machines also often include a stripper for stripping the molded 
articles from the core or cavity unit. In some instances, the stripper 
takes the form of some additional space defining surfaces which act 
together with the mold cavity and mold core to define the space receiving 
plastic material from the injection unit. The space defining surfaces on 
the stripper are generally designed to intimately engage the molded 
article so the article can be successfully removed from the core and 
cavity assemblies and additionally require some action to affirmatively 
cause release of the molded article from the space defining surfaces. The 
successful operation of this stripping and plastic part release has been 
the subject of some prior development. 
In order to have the space forming surfaces release the molded article once 
it has been successfully stripped from the core and cavity unit, the space 
defining surfaces have been coupled to an actuating means as shown in U.S. 
Pat. No. 4,497,624. The space defining surfaces are there disclosed to 
constitute thread splits for forming threads on a portion of each molded 
article with each of the thread splits being coupled to an actuator for 
causing relative movement of the thread splits. The actuator is in turn 
coupled to cam followers which ride within a track. The track includes an 
insert which defines a ramp or incline which, interacting with the cam 
followers, causes the actuator to move the thread splits engaging the 
molded article in such a way to release the article. In use, at least two, 
and typically four, such track inserts are employed and are adjustable in 
position with respect to the track to permit adjustment of the timing 
and/or point of release of the molded article. The adjustability of the 
position of the track inserts itself caused some difficulty in that it is 
difficult to position all four track inserts at the same relative position 
in the respective tracks to cause a balanced application of force to move 
the thread splits apart, the imbalance of force results in an unintended 
strain and wear on the equipment and led to unreliable part separation. 
The use of a single fixed position ramp or incline fails to permit the 
variability in operation of the mold unit thought to be desirable in that 
changes in the confirmation of the core and cavity unit can also require 
changes in the part release point. Thus, the use of single position ramps 
or inclines to activate the actuators by means of the cam followers is not 
a viable alternative. It was therefore desirable to develop apparatus 
interactive with a cam coupled to an actuator for causing release of parts 
from a molding machine which cam would be adjustable in position yet 
easily coordinated with other like cams on the same machine to avoid any 
unbalanced application of force and would improve part drop performance. 
SUMMARY OF THE INVENTION 
In accordance with the present invention, an adjustable cam track for an 
injection molding machine includes a set of guides which are coupled to 
the movable platen or core base of an injection molding machine. The 
guides act to guide the movement of space defining surfaces such as thread 
splits which are movably mounted on the stripper platen. A set of cam 
followers are coupled to the space defining surfaces by actuators to cause 
relative movement of the pair of surfaces to release molded articles 
previously stripped from the molds of the molding machine. A set of cam 
inserts engage the cam followers and are adjustably positioned with 
respect to the guides to adjust the point of release of the molded 
articles. Each guide includes a pair of guide walls forming a channel 
defining two limits of position of the cam follower engaged in the 
channel. Each cam insert is received within the guide walls and defines 
the path of movement for the cam follower between the two limits of 
position. The path of movement defined by the cam insert is a matter of 
choice of design and includes one or more inclined areas for guiding the 
cam follower from one position to another within the two limits of 
position defined by the guide walls. Each cam insert includes a first 
tooth rack while a second tooth rack is removably fixed to each guide. The 
two toothed racks interengage to fix the position of each cam insert 
relative to each guide only at certain pre-selected locations so that 
coordination of the position and therefore operation of all of the cam 
followers can occur, thereby avoiding any stress or wear in balance. 
One feature of the present invention is the presence of at least one index 
mark on one of the walls of the guide means and a plurality of graduation 
marks on one of the walls of the cam insert. This feature provides for an 
easy indication of the selected position of the cam insert with respect to 
the guide thereby enabling a simple coordination of the position of all of 
the cam inserts. 
Another feature of the invention is the inclusion of a cam insert extension 
secured to the cam insert to have one wall aligned with the surface 
defining the path of the cam follower. Such a cam insert extension has the 
advantage of lengthening the adjustability of the release point. 
Other features and advantages of the present invention will become apparent 
to those Skilled in the art upon consideration of the following 
description of the preferred embodiment. The description refers to the 
accompanying drawings which, together with the description, disclose the 
best mode of carrying out the invention as presently perceived.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
An injection molding machine 10 according to the present invention is shown 
generally in FIG. 1 to include a base 12 and a stationary platen 14 which 
is fixed with respect to base 12. The stationary platen 14 has a front 
face 16 facing a movable platen 18 which moves on guide means 20. The 
movement of the movable platen 18 is achieved by a first motive means 22 
which is illustrated in the form of a clamp toggle, but which could be any 
conventional mechanical, hydromechanical, or hydraulic clamping mechanism. 
Situated between the stationary platen 14 and the movable platen 18 is a 
stripper platen 24 which is also guided for movement on the guide means 20 
by means of bushings 26. The stripper platen 24 is moved with respect to 
the movable platen 18 by a second motive means 28 which is shown to be a 
hydraulic cylinder having a piston rod 30 extending through the movable 
platen 18 and secured to the stripper platen 24. Other motive means such 
as an air cylinder, rack and pinion gear, etc., could be employed for this 
same purpose. 
The plasticizing-injector unit 32 is coupled to the back face 34 of the 
fixed platen 14 by means of a manifold assembly 36. The manifold assembly 
36 directs the plastic material from the plasticating injector unit 32 to 
a mold cavity assembly 38 which includes a plurality of mold cavity units 
40. A mold core assembly including mold cores 42 are connected to the 
movable platen 18 such that the cavities 40 and cores 42 can be 
cooperatively engaged to one another to form a space for receiving plastic 
material from the plasticator unit 32 to form molded articles 44. 
The molded articles are shown in FIG. 1 as they are being ejected from the 
molding machine after being stripped from the cores 42. While the specific 
examples illustrated in the figures of injection molded parisons or 
preforms for the manufacture of blow molded plastic bottles and 
containers, this use is merely illustrative and is not intended to 
restrict the scope of utility of the invention described and claimed. 
The injection molding machine 10 is shown in FIG. 1 with the movable platen 
18 separated from the fixed platen 14 by a distance necessary to eject the 
molded articles 44. This ejection is achieved through the use of apparatus 
shown more fully in FIG. 2 which shows the face of the stripper platen 24 
confronting face 16 of the fixed platen 14. Mounted to the stripper platen 
24 are a plurality of pairs of space defining surfaces 46, commonly known 
in the trade as "thread splits". The thread splits cooperate with the core 
42 and cavity 40 to complete the definition of the space which receives 
the plastic forming article 44. The space defining surfaces hold the 
articles 44 as it is stripped from the core 42. Each half 46a and 46b of 
the thread split is mounted to a separate slide 50 or 52 by screws 54 
which secure the thread splits against seat 56. The slides 50 and 52 
reciprocate laterally within a channel defined by brackets 58 and 60. 
The slides 50 are secured together by tie members 62 while slides 52 are 
tied together by tie members 64 such that the lateral movement of all 
slides 50 or 52 is uniform and coordinated. The movement is caused by 
actuating rods 66 which extend through block 68 secured to the face of 
stripper platen 24. The actuating rods 66 are coupled to beams 70 which 
have at each end a roller 72 which comprises a cam follower situated in a 
cam track 74 which is fixed to movable platen 18. As the stripper platen 
24 is caused to move with respect to the movable platen 18 by means of 
motive means 28, the rollers 72 proceed along a channel defined by the cam 
track 74. 
At a desired location, the cam track 74 is configured to cause the beams 70 
to move from the position illustrated in FIG. 2 in solid lines outward to 
the position shown in phantom. This outward movement of beam 70 pulls the 
actuating rods 66 outward which in turn caused the slides 50 and 52 to 
move away from each other thereby separating the halves of the thread 
splits 46a and 46b from each other and releasing the part held by the 
thread split. 
In the upper left of FIG. 2, the cam track is shown in section to comprise 
generally a channel shaped guide having within it a cam insert 78 which 
are shown in greater detail in FIGS. 3 and 4. The guide means 76 comprises 
in cross-section a generally U-shaped channel, the channel having an open 
end 80 and a closed end 82. The closed end 82 includes a land 84 which 
constitutes the surface of the guide 76 which is attached to the movable 
platen 18. The land 84 spaces the lower surface 86 away from the side of 
the stripper platen 24 by a clearance distance. Fastening elements (not 
shown) extend through openings 88 in closed end 82 to secure the guide 76 
to the movable platen 18. 
The U-shaped channel of guide 76 is defined by two walls 90 and 92 which 
define the limits of position of the cam follower 72 within the channel. 
Each of the walls 90 and 92 includes an undercut 94 shown in FIG. 4. Wall 
90 also includes a stepped brake 96 for receiving a toothed rack 98 and 
retainer plate 100. The toothed rack 98 is secured to the retainer plate 
100 by fasteners 102 shown in phantom in FIG. 3 while the retainer plate 
100 is secured to wall 90 of the guide 76 by fasteners 104 which are 
received in openings 106 in wall 90. 
The cam insert 78 is received between the pair of walls 90 and 92 and 
includes outwardly extending flanges 108 which engage the undercuts 94 at 
the base of walls 90 and 92 and allow slidable movement of the insert 78 
with respect to the guide 76 in the direction A shown on FIG. 3. Depending 
on the position of the insert 78 in the guide 76, one end 110 of the 
insert 78 may project beyond the end 80 of guide 76 as shown in FIG. 3. 
The insert 78 includes a pair of walls 112 and 114 which define a path for 
the cam follower 72. It will be appreciated that the specific shape of the 
channel defined by walls 112 and 114 is a matter of choice of design and 
may be determined in part by the relative movement necessary to cause 
release of the molded article 44 from the thread splits 46a and 46b. 
The path of movement defined by the cam insert 78 generally includes one or 
more inclined areas defined by walls 112 and 114 for guiding the cam 
follower 72 from one position to another within the two limits of position 
defined by the guide walls 90 and 92. To insure the cam follower 72 has a 
sufficiently long operational path, a cam insert extension 124 can be 
added to the end of cam insert 78 nearest closed end 82 of the channel and 
secured in place by fasteners 126 in alignment with the surface of wall 
114 contacting cam follower 72. 
The outside face 116 of wall 112 includes graduation markings which, in 
cooperation with reference marks 118 on wall 92 of guide 76, can be 
employed to accurately position the insert 78 with respect to the guide 
76. Wall 114 also includes a tooth rack 120 secured in position by 
fasteners 122. The teeth of rack 120 and the teeth of rack 98 interengage 
when the retainer plate 100 is secured to wall 90. The interengagement of 
the teeth of the racks 98 and 120 fix the position of the insert 78 with 
respect to the guide 76 only at certain preselected locations defined by 
the pitch of the teeth on racks 98 and 120. 
The point of release of the molded articles 44 is determined by the 
longitudinal position of the inclined portion of the walls 112 and 114, 
The stepwise adjustment of the position of the walls through the use of 
the interengaging racks 98 and 120 insures that all four cam tracks 74 
will be similarly positioned at a selected location to coordinate the 
operation of all of the cam followers 72 causing simultaneous outward 
motion of beams 70 thereby avoiding undesired strains and wear in the 
molded part release mechanism. 
Although the invention has been described in detail with reference to the 
illustrated preferred embodiment, variations and modifications exist 
within the scope and spirit of the invention as described and as defined 
in the following claims.