Probe assembly for injection molding apparatus

A temperature and molding material pressure compensated probe for use in injection molding apparatus. The probe includes a two-part telescoping body with a molding material filled space therebetween. Longitudinal thermal expansion which formerly presented sealing problems only results in changes in the extent of telescoping overlap. Molding material pressure is applied equally to both probe parts tending to improve sealing. The molding material filled space has a greater transverse area than all outlets and passages.

BACKGROUND OF THE INVENTION 
In the field of injection molding, particularly in multi-cavity molds of as 
many as 128 cavities, there has risen a problem that is heretofore 
unrecognized. That is, the molding pressure applied from a manifold is 
multiplied many times by the areas of the probe, runners, gate, and 
outlets with many of these areas applying force which tends to separate 
the probe assembly from the mold. On occasion, the separation force 
exceeds the capacity of the molding apparatus. 
Additionally, it has been common practice to design a probe assembly with a 
large cavity adjacent to the mold gate. When this cavity is filled with 
molten molding material, the molding material exerts separating pressures 
which may exceed the holding strength off the molding machine fasteners or 
locking devices. Even if the molding apparatus is capable of retaining the 
assembly together, changes in temperature such as cooling after a molding 
operation can allow molding material to enter a seam line similar to flash 
in molding and then upon reheating, the material in the seam line acts as 
a block against precise, tight mold assembly. Repeated temperature cycling 
inherent in the molding process only aggravates the problem. 
Also, proper temperature compensation of probe assemblies has been 
difficult, if not impossible, to achieve using existing probe designs. The 
only solution has been to design probes with the front face acting as a 
reference so that the probe is free to expand and contract in a rearward 
direction away from the mold and toward the molding material manifold. 
BRIEF DESCRIPTION OF THE INVENTION 
I have faced this state of the art and this critical problem present in the 
use of multi-cavity injection molds and have solved each of these problems 
in my design of a new probe assembly. This invention involves a new probe 
assembly for use in single or multi-cavity injection molding and is useful 
wherever the force tending to separate the hot side of the mold from the 
injector plate can become excessive. The use of this invention is likewise 
desirable wherever thermal expansion of the probe due to thermal cycling 
throughout the normal molding operation so that longitudinal expansion of 
the probe can affect the mold injector plate joint integrity. While these 
problems are more likely to exist in multi-cavity molding operations, the 
features of this invention are, however, equally useful in single cavity 
molding systems, as well. 
The desirable effects of this invention are achieved by designing the path 
of the molding material from the manifold to the point of injection to 
provide for pressure balancing within the probe. 
Each of the foregoing highly desirable features or characteristics is 
accomplished in a two-part body probe with the parts overlapping or 
telescoping in a longitudinal direction with respect to the molding 
material flow from a supply manifold to the mold hot side. The telescoping 
parts of the probe body define an annular recess in the molding material 
passage from the molding material supplying manifold to the mold proper. 
The annular recess has a cross sectional area in a direction normal to the 
longitudinal axis of the probe assembly larger than any other of the 
molding pressure regions between the manifold and the mold proper. 
One feature of this invention resides in the presence of the cross 
sectional dimensional relationship to the runners, gates and an internal 
cavity which acts as an internal reservoir of molding material tending to 
balance molding forces within the probe. 
Another feature relates to the overlapping or telescoping form of the probe 
body whereby thermal expansion occurs within the probe body without change 
in the overall length of the probe despite dramatic changes of probe 
temperature. 
A further feature of the invention is the presence of the internal recess 
or reservoir between the telescoping parts to accommodate the change in 
volume of the probe due to thermal expansion without any change in the 
distance between the reference planes defined by the mold body and the 
molding material manifold. 
Another feature of this invention resides in the tapered contact region 
between the probe body parts which maintain good thermal transfer despite 
changes in probe body thermal expansion.

DETAILED DESCRIPTION OF THE INVENTION 
Reference is now made to FIGS. 1 through 4 of the drawing in combination 
with FIGS. 2 and 3, showing a probe assembly, generally designated 10, 
restrained between a front plate 11 and a rear plate 12 to provide molding 
material to a injection mold assembly 13 having a hot side 14 and an 
ejector side 15. The injection mold assembly 13, typically has a large 
number of cavities, for example, 128, two of which, 16a and 16b, appear in 
FIG. 1. The cavities, 16a, 16b, 16c, 16d are arranged in the hot side 14 
in groups such as four in number as depicted in FIG. 18, to be fed in the 
direction of the dashed arrows in FIGS. 1 and 4 with molding material MM 
from a common manifold, unshown in the drawing, but simulated by manifold 
assembly 21 via the probe assembly 10, a central passage 32, its internal 
runners 22, two of which may be seen in FIG. 1 and gates 23, one 
associated with each mold cavity. 
The plates 11 and 12 containing the major length of the probe assembly 10 
as well as the hot side plate 14 of the injection mold assembly 13 are 
aligned by guide pins such as pin 50 of FIG. 1. Plates 11 and 12 are 
secured together and are fixed within the injection molding machine by 
bolts, unshown. The ejector side 15 separates from the hot side 14 at the 
part line, P/L, for each mold cycle to allow ejection of the molded parts 
24, of FIG. 4, as is well known in the injection molding art. 
As is indicated above, there may be tremendous separating forces present 
due to the cross sectional area of mold material MM at or near the zero 
temperature line, ZTL, between the front plate 11 and hot side plate 14. 
The separation forces may be as high as fifteen to twenty times the normal 
or high molding pressure of only 2,000 psi. These separation forces have 
been known to cause a separation at the zero temperature line ZTL 
resulting in the destruction of prior design probes as well as the molded 
parts in process. This problem is solved by my new probe assembly 10 which 
is accompanied design without any change in the mold or molding machine 
design. 
FIG. 2 shows the hot side plate 14 of a typical mold assembly with four 
mold cavities 16a, 16b, 16c and 16d in a square array to be fed as shown 
in FIGS. 1 and 4 with molten molding material MM by a single probe 
assembly 10 through individual internal runners 22. Heater connectors 17 
are shown at the top of the mold hot side 14 as well as lift straps 18. 
Cooling water connections 19, guide pin bushings 49 and several fasteners 
are also shown. 
FIG. 3 shows the mating ejector side of the mold assembly 13 with the four 
cavities 16a, 16b, 16c and 16d, cooling water connections 19, guide pin 
bushings 49, and guide pins 50 used to insure alignment between the hot 
side 14 and the ejector side 15 as they come together for a molding cycle. 
Referring now specifically to FIG. 4 in combination with FIGS. 1 and 6-9, 
the probe assembly 10 comprises a two-part probe body, the probe outer 
body 34 and the probe inner body 35 with the inner body 35 telescoping 
into the outer body 34 at mating surfaces 30 and 31, respectively. Both 
the probe outer body 34 and probe inner body 35 are fabricated with a 
common central passage 32 which communicates with the manifold assembly 21 
and with the runners 22. The probe body parts 34 and 35 are preferably 
coaxially mounted withinwith the passage 32 extending along the 
longitudinal axis of the two body parts 35 and 35. Note that the passage 
32 also communicates with a washer shaped recess 33 between the forward 
end of the inner probe body part 35 and the bottom of the rear recess of 
the outer probe body 34. The probe body parts 34 and 35 are dimensioned so 
that the washer like recess 33 is present and filled with molding material 
MM at all molding temperatures and pressures. 
The front face 36 of probe assembly 10 is best seen in FIG. 8, but also 
appearing in FIGS. 1, 4, 5, 6, 16 and 17, is flat and has four orifices 40 
for the four runners 22 shown in dotted lines in FIG. 5 and communicating 
with the central passage 32 for supplying molten molding material MM to 
four gates 23 and four mold cavities 16a, 16b, 16c and 16d of FIGS. 1-3 in 
the mold hot side 14. Behind the face 36, as best seen in FIGS. 4-6, is a 
reduced diameter body length, L, which contains the passage 32 and is 
surrounded by a band heater 41 of FIGS. 1 and 4 in conventional probe 
design. The band heater 41 is located in an air space, AS, of FIGS. 1 and 
4. The rear or inner end 55 of the probe outer body part 34 is positioned 
by locator 38 within an opening in the rear plate 12. 
The locator 38 performs a number of important functions. First, it centers 
and precisely positions the probe assembly 10 within the opening, AS. 
Next, the locator 38 provides an annular bearing surface 38B for the probe 
inner body part 35. Thirdly, the locator 38 provides the mating tapered 
surface 38CS for the tapered outer end of the outer probe body 34. Upon 
expansion of the probe outer and inner parts 34 and 35, these tapered 
surfaces provide compressive forces for sealing the slip fit joint between 
the mating surfaces 30 and 31 of the probe body parts 34 and 35. This is 
all accomplished while allowing for thermal expansion of the inner and 
outer probe body parts 34 and 35 as the probe assembly 10 is heated from 
ambient outside temperature, e.g., 77 degrees F. (25 degrees C.) to 
typical molding temperatures of 340 to 540 degrees F. (177 to 288 degrees 
C.). 
The front face 36 of the probe assembly 10 is positioned within the front 
plate 11 by tubular housing member 42 of FIGS. 1, 4, 10 and 11. An annular 
groove 43 in the front face of the tubular housing member 42 engages an 
outer lip 36L on the front face 36 of the outer probe body 34 positioning 
the outlets or orifices 40 adjacent to gate tips 52. The male mold member 
46 in the ejector side and its associated molded part ejector 47 may be 
clearly seen in FIG. 1. 
Adjacent to the gate tips 52, within the female mold 45 are gate housings 
23 of FIG. 4. Just behind the gate housing 23 of each mold cavity 16a-d is 
a respective gate chamber 51a-d which is filled with molding material MM 
at all times during molding operations. Two mold cavities 16a and 16b of 
the four mold cavities 16a-d and two gate chambers 51a and 51b of the four 
gate chambers 51a-d appear in FIG. 4. Between mold shots, the molding 
material MM in the gate chambers 51, the outlets 40, the runners 22, the 
passage 32 and recess 33 will remain molten and with proper temperature 
control of the heater bands 41 and cooling through passages in the mold, 
remain at molding temperature without overheating or degradation. The 
balancing of temperatures is well known in the molding art; however, the 
probe assembly 10 of this invention facilitates temperature control as is 
described below. 
The gate housing 23 is closed by gate tip 52 which is shown in two 90 
degree different diametrical sections in FIGS. 14 and 15 with FIG. 15 
corresponding to the view in FIG. 4. The gate tips 52 have two ports which 
allow the flow of molding material MM from the orifice 40 to the mold 
cavities 16a,b. The gate tips 52 virtually closes off the actual molding 
orifice 53 between mold shots by absorbing the heat of the small amount of 
molding material MM at the mold orifice 53 and thereby allowing opening of 
the mold, removal of the molded part without any dripping of excess 
molding material MM from the molding orifice 53. 
TEMPERATURE COMPENSATION 
For an understanding of the temperature compensation features of this 
invention, reference is again made to FIGS. 1 and 4 which shows the base 
or zero temperature line ZTL located at the junction of the front plate 11 
and the hot side plate 14 of the mold 13. A rear reference line, RRL is 
located at the junction of the manifold assembly 21 and the rear face of 
the probe inner body 35. It is essential that the distance D between the 
zero temperature line ZTL and the rear reference line, RRL remain constant 
during all times particularly during heating for the first mold cycle and 
thereafter throughout the series of molding cycles or shifts as the 
molding operation continues. In the past, the lack of stability of this 
dimension, although not recognized by many molders, has been a problem 
which sometimes resulted in the loss of parts and, more important, by in 
damage to the probes or the molds. 
Various fasteners such as internally located machine bolts, unshown in the 
drawing, hold the front plate 11 and the rear plate 12 together and 
external clamps hold the front plate 11 and the rear plate 12 with as many 
as 32 probe assemblies 10 to the manifold 21 so that the distance D 
remains constant between the zero temperature line ZTL and the rear 
reference line RRL of the probe assembly 10. 
Maintaining this standard distance D is possible since the component of the 
entire assembly which undergoes the greatest temperature changes and 
cycling is the probe assembly 10. The probe outer body part 34 and the 
probe inner body part 35 telescope freely with temperature changes while 
the overall length of the probe assembly 10 does not change and 
essentially remains constant. A slip fit relationship is present between 
the cylindrical walls of the interfitting probe outer body part 34 and the 
probe inner body part 35 while a tapered compression fit seal exists 
between the probe outer wall 34 CS of the outer body part 34 at its rear 
end 55 which is depicted at the upper portion of FIG. 4 and the tapered 
inner wall 38 CS of the locator 38. As indicated above, the mating of 
these tapered walls 34CS and 38CS of the locator 38 also as shown in FIG. 
4 and the outer body part 34 by wedging together as the temperature rises 
in the probe assembly 10 produces a radial compression force between the 
telescoping surfaces 30 and 31 of the outer and inner body parts 34 and 
35, respectively, to seal the washer shaped recess 33 and to prevent any 
molding material MM from leaving the recess 33 via that seal. 
An indication, although somewhat exaggerated for purposes of illustration 
of the extent of thermal expansion is seen by comparing FIGS. 16 and 17 in 
which the size of the internal washer shaped reservoir 33 for molding 
material MM enlarges in thickness in FIG. 17 as compared with FIG. 16. 
Lengths L1 and L2 will grow with heating; however, distance D remains 
constant. 
INTERNAL PRESSURE COMPENSATION 
The washer shaped reservoir or recess 33 expands and contracts in thickness 
with temperature changes of the probe assembly 10. The diameter of the 
washer shaped reservoir or recess 33 remains constant and both faces, 
forward face 33F and rear face 33R are exposed to the same pressure. The 
rear face 33R exerts pressure against the inner probe body 35 and that 
pressure is applied against the manifold assembly 21. The same pressure is 
applied by the forward face 33F against the probe outer body 34 tending to 
balance the pressures which are exerted in the gate housings 23 and the 
cavities 16. This balancing of pressures in the direction of the 
longitudinal axis of the probe assembly 10 is a major advantage of this 
invention. 
The actual diameter of the washer shaped reservoir or recess 33 is defined 
by the sizes of the various other reservoirs from the manifold assembly 21 
to the actual mold gate chamber 51. This relative size relationship is 
proportionately illustrated by graphically representation in FIG. 18. 
There it may be seen that the cross sectional area of the reservoir or 
recess 33 minus the correctional area of combined passage 32 is larger 
than the combined cross sectional areas of the gate chambers 51a through 
51d. The principal separating force within the probe assembly 10 is the 
force which tends to maintain the probe assembly 10 in its stable 
condition and does not tend to separate the probe assembly 10 from the 
mold assembly 13 during normal and even abnormal, excess pressure or 
temperature conditions. 
The forgoing constitute my disclosure of the best mode known by me at the 
time of filing this patent application for carrying out this invention. 
The embodiment shown is, however, only illustrative and does not limit the 
scope of the inventive concept. It is recognized that one of skill in the 
molding art may produce an operative assembly which may have differences 
without departing from the true concept of this invention. Therefore, this 
invention is defined, not by the illustrative embodiment but rather by the 
following claims including the protection afforded by the Doctrine of 
Equivalents.