United States Patent [19]
`Lundquist
`
`[11]
`[45]
`
`4,452,420
`Jun, 5, 1984
`
`[54] COMPENSATING CORE PIN FOR PLASTIC
`INJECTION MOLDS
`[76] Inventor: Lynn Lundquist, 10833 NE. Russell
`St., Portland, Oreg. 97220
`[21] Appl. No.: 431,043
`[22] Filed:
`Sep. 30, 1982
`[51] Int. Cl* ................................................ B29C 1/06
`[52] U.S. Cl. ...................................... 249/175; 249/68;
`-
`249/142; 425/107; 425/577
`[58] Field of Search .................. 425/107,577; 249/68,
`249/142, 175
`
`[56]
`
`References Cited
`U.S. PATENT DOCUMENTS
`2,134,829 11/1938 McWane ......................... 249/142 X
`2,237,606 4/1941 McWane ..........
`... 249/142 X
`2,361,348 10/1944 Dickson et al. ......................... 18/30
`2,440,144 4/1948 Hosking .................................. 18/45
`2,508,865 5/1950 Lund ................................. 249/68 X
`2,607,080 8/1952 Stewart ................................. 249/68
`
`2,822,578 2/1958 Lobell ..................................... 18/42
`2,825,093 3/1958 High ........................................ 18/42
`3,060,509 10/1962 McCubbins, Jr. ...................... 18/42
`3,315,317 4/1967 Winkler .................................. 18/42
`Primary Examiner—Thomas P. Pavelko
`Attorney, Agent, or Firm—Glen A. Collett
`[57]
`ABSTRACT
`A core pin for use in a plastic injection mold for forming
`a hole through a part as it is formed in the mold. A shaft
`is longitudinally slidable in one of the base members of
`the mold and extends through the cavity of the mold
`and abuts the inner face of the opposing base member. A
`spring biases the shaft toward the second base member.
`When the mold is open the shaft has a small amount of
`positive clearance. When the mold closes the spring is
`compressed and the shaft has zero clearance against the
`inner face of the second base member, regardless of
`dimensional changes of the mold.
`
`15 Claims, 6 Drawing Figures
`
`
`
`PETITIONERS' EXHIBIT 1110
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`PAGE 1 OF 5
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`U.S. Patent
`US. Patent
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`Jun. 5, 1984
`Jun. 5, 1984
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`4,452,420
`4,452,420
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`COMPENSATING CORE PIN FOR PLASTIC
`INJECTION MOLDS
`BACKGROUND OF THE INVENTION
`This invention relates to plastic injection molding
`equipment, and in particular to a core pin for use in
`plastic injection molds for forming a hole through a part
`as it is formed in the mold.
`Conventional core pins are used in plastic injection
`dies when holes or small depressions are desired in the
`molded part. In order to accomplish this function the
`core pin projects into the cavity and prevents the plastic
`from filling the area occupied by the core pin. If a hole
`is desired completely through the molded part the core
`pin must seat tightly against the opposing face of the
`The core pin is the accepted means of accomplishing
`this task. However, inasmuch as the core pin is a fixed
`20
`length when mounted in the die there are certain limita
`tions, particularly when it is used to form a hole com
`pletely through the part. The fit of the core pin is criti
`cal. Excess length will damage the die and/or the core
`pin. On the other hand, excess clearance will cause
`flash, giving a poorly formed or entirely closed hole.
`Due to temperature changes within the die during
`operation, many dimensions and clearances change as
`the die reaches operating temperature. Not only can this
`cause flashing at full temperature, but it may damage
`the pin if the die is tightly clamped at ambient tempera
`30
`ture.
`All dies show slight dimensional change after long
`service from pressure and wear. This dimensional
`change frequently requires refitting or shimming the
`core pins to acceptable sealing functions.
`In some applications it is desirable to use a removable
`insert for accomplishing the function of readily chang
`ing a logo, or the like. When removable inserts are used
`which have a sealing core pin, the clearance may vary
`slightly from insert to insert or because of clearances
`allowed for installation of the insert sections.
`The usual result of these complications is that flashing
`occurs around the end of the intended hole. This flash
`ing must be removed, which task often requires a sec
`ondary machining operation.
`45
`It is the general object of the present invention to
`provide a compensating core pin which automatically
`compensates for dimensional changes due to wear, tem
`perature fluctuations, and variations in removable in
`50
`SertS.
`Another object is to provide a core pin which is not
`required to be fit at close tolerances, but rather will
`automatically adjust to zero clearance in use.
`Another object is to provide such a core pin in which
`the installation is simple and straightforward for the
`tool and die maker.
`A further object is to provide such a core pin requir
`ing only state of the art manufacturing skill.
`These and other objects and advantages of the pres
`ent invention, and the manner in which they are
`achieved, will become apparent in the following specifi
`cation and claims.
`SUMMARY OF THE INVENTION
`In its basic concept the present invention is a core pin
`for use in a plastic injection mold for forming a hole
`through a part as it is formed in the mold. The mold
`includes opposing first and second base members posi
`
`4,452,420
`2
`tionable in either an open position wherein the base
`members are separated or in a closed position wherein
`the base members are together and form an injection
`molding cavity between the inner faces thereof. The
`core pin includes a shaft mounted longitudinally slid
`ably in the first base member and extending through the
`cavity and abutting the inner face of the second base
`member when the base members are in the closed posi
`tion. Spring means biases the shaft toward the second
`base member. This assures that the core pin will always
`seat tightly against the opposing face, regardless of
`dimensional changes in the mold.
`BRIEF DESCRIPTION OF THE DRAWINGs
`FIG. 1 is a fragmentary sectional plan view of an
`injection molding die, illustrating a fragmentary portion
`of a cavity therein, and illustrating the first embodiment
`of the compensating core pin of the present invention.
`FIG. 2 is a fragmentary sectional plan view similar to
`FIG. 1 illustrating a second embodiment of the compen
`sating core pin.
`FIG. 3 is a fragmentary sectional plan view similar to
`FIGS. 1 and 2 illustrating a third embodiment of the
`compensating core pin which includes an indexing as
`sembly.
`FIG. 4 is a fragmentary section taken along the line
`4–4 of FIG. 3.
`FIG. 5 is a fragmentary section similar to FIG. 4
`illustrating a second embodiment of the indexing assem
`bly.
`-
`FIG. 6 is a top perspective view of the component
`parts of the second embodiment of the indexing means
`shown in FIG. 5.
`DESCRIPTION OF THE PREFERRED
`EMBODIMENTS
`The present invention is a spring-biased movable core
`pin used in plastic injection molds. This movement
`allows the pin to be fixed in the mold with a positive
`clearance to the mold face against which it is closing,
`By providing spring loading to the movable pin, the
`core pin will always close with zero clearance relative
`to the mold face opposite it. Thus, irrespective of mold
`wear or similarly caused dimensional changes, a plastic
`part using a core pin to form a hole will be assured of a
`flash-free opening.
`-
`As shown in FIG. 1, an injection molding die in
`cludes a first base member 10, and an opposing second
`base member 12. An injection molding cavity 14 is
`formed between the inner faces of base members 10 and
`12.
`In the first base member 10 a stepped hole is drilled
`having a guide portion 16, and an enlarged component
`section 18. The outside end of hole 18 is threaded. A
`shoulder 20 is formed by the end of the drill bit at the
`base of hole 18.
`The core pin includes a shaft 22 which is mounted in
`the first base member 10 and is longitudinally slidable in
`guide 16. A stop means, preferably a head 24, is pro
`vided on the shaft for engaging shoulder 20 of the base
`member to determine the limits of extension of the shaft.
`The shaft includes a circumferential groove 26 for re
`ceiving a packing or lubricating material to provide
`long-term lubrication between the shaft and guide 16.
`Spring means, preferably coil spring 28, is provided
`to bias the shaft toward the second base member.
`
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`Cap means, preferably comprising a threaded mem
`the end of the shaft as shown. This arrangement is ac
`ber 30 screws into the threads in hole 18. The cap pref.
`ceptable only so long as shaft 84 does not rotate.
`erably includes a hex socket for turning by an Allen
`Accordingly, an indexing means is provided as illus
`wrench. A projection 32 aligns spring 28 in the center of
`trated in FIGS. 3 and 4. A pin 92 is mounted in guide 78,
`and extends outwardly to engage head 86 of the shaft
`hole 18.
`throughout the range of its travel. This effectively se
`As shown in the drawing the mold is in its closed
`position. Head 24 is raised off of shoulder 20. This spac
`cures the shaft against rotation.
`ing is equal to the spacing that shaft 22 extends posi
`FIGS. 5 and 6 illustrate a second embodiment of the
`indexing means. Shaft 94 is provided with a lubricating
`tively when the mold is in its open position.
`groove 96 and a head 98. A guide 100 includes an up
`FIG. 2 shows a second embodiment of the compen
`10
`standing segment 102. The segment has an inwardly
`sating core pin of the present invention which is similar
`facing surface 104. Head 98 has a matching face 106
`to that shown in FIG. 1. First and second base members
`configured to slide against the segment. This particular
`34 and 36 correspond to base members 10 and 12 respec
`embodiment is useful where there is not sufficient room
`tively of FIG. 1. Between the base members the cavity
`on guide 78 to use a pin 92. However, it does have a
`38 is formed. A stepped hole is provided in first base
`drawback in that a larger area of the spring is not touch
`member 34. The stepped hole includes a lower portion
`ing the head. Accordingly, this design is useful for small
`40 and an enlarged upper portion 42 having threads at
`core pins while the design of FIGS. 3 and 4 is more
`the end thereof. A shoulder 44 is formed at the base of
`useful for larger core pins.
`the upper portion of the hole.
`In this embodiment of the core pin a cartridge design
`OPERATION
`is employed for guiding the shaft and confining the
`Installation of the compensating core pin of the pres
`spring. The guide 46 is mounted in the lower portion 40
`ent invention is very simple. A stepped hole with a short
`of the hole abutting shoulder 44. Preferably the guide is
`threaded area is machined into the mold base. The
`milled flat with the cavity face, however this is a matter
`guide, tube and shaft are machined to their proper
`of design since a larger secondary hole could be formed
`length.
`partway into the part by extending the guide further
`The shaft should be fitted so that it has a positive
`into the cavity.
`clearance when the mold is open. Preferably a clearance
`A tube 48 seats on guide 46, and both are secured into
`of plus 0.005 inch to plus 0.025 inch should be attained.
`place by a cap or threaded member 50 similar to cap 30
`This, of course, allows the die maker considerable lati
`30
`in the first embodiment. A hex socket 52 is provided in
`tude.
`the cap for tightening by an Allen wrench.
`With any positive clearance between zero and the
`Shaft 54 is similar to shaft 22 of the first embodiment.
`limits of the spring the core pin is assured of having zero
`Its rearward end terminates internally of base member
`clearance fit when the mold is closed.
`34 in a head 56. A lubricating channel 58 is provided on
`If the opposing face is not flat with respect to the
`35
`the shaft within guide 46 for providing lubrication be
`direction of the core pin, it is necessary to use an in
`tween the shaft and the guide. The end of shaft 54 is
`dexed core pin while the shaft has a slanted or con
`indented at 60 to increase the pressure at which the
`toured end. It is important that the seal between the end
`periphery of the shaft engages the opposing mold face.
`of the shaft and the opposing mold face be exact, since
`This assures a positive contact and prevents high cen
`if it were not plastic would work under the end of the
`tering.
`shaft and the dynamic pressure would lift the shaft
`A spring 62 similar to spring 28 of the first embodi
`away from the face.
`ment is provided within tube 48, between cap 50 and
`It can be seen that a core pin is provided which
`greatly simplifies the problem of forming a precision
`head 56.
`-
`In the second base member 36 an insert 64 is pro
`hole in an injection molded part. The embodiments
`45
`vided. It is particularly advantageous to provide an
`herein disclosed show particular applications and no
`insert made of steel for use in an aluminum mold in
`limitation is intended thereby.
`order to preserve the mold face against repeated open
`Having disclosed my invention in its preferred em
`ings and closings.
`bodiment, I claim:
`FIG. 3 illustrates a third embodiment of the inven
`1. A compensating core pin for use in a plastic injec
`50
`tion. Similar to the first two embodiments the first base
`tion mold for forming a hole through a part as it is
`member 66 and second base member 68 define a cavity
`formed in the mold, the mold including opposing first
`70 therebetween. A stepped hole is provided in the first
`and second base members positionable in either an open
`base member having a lower portion 72 and an enlarged
`position wherein the base members are separated or in a
`upper portion 74, with a shoulder 76 being formed at
`closed position wherein the base members are together
`the lower end of the upper portion. The guide 78 similar
`and form an injection molding cavity between the inner
`to guide 46 in the second embodiment is mounted in the
`faces thereof, the core pin comprising:
`lower portion of the hole abutting shoulder 76. A tube
`(a) a shaft mounted longitudinally slidably in the first
`80 is mounted on the guide and secured in place by a cap
`base member and extending through the cavity and
`82 similar to the previous embodiment.
`abutting and sealing against the inner face of the
`A shaft 84 similar to shaft 54 extends through the
`second base member when the base members are in
`mold cavity. A head 86 is provided on the shaft, as is
`the closed position, the shaft having constant di
`lubricating channel 88, similar to the previous embodi
`mension throughout the mold cavity; and
`ment. A spring 90 biases the shaft outwardly.
`(b) spring means biasing the shaft toward the second
`It will be noted that the opposing face member of
`base member.
`65
`2. The core pin of claim 1 further comprising stop
`second base member 68 is not flat with respect to the
`means attached to the shaft for engaging the first base
`direction of shaft 84. However, the shaft is still matted
`flush against the surface of the base member by slanting
`member to determine the limits of extension of the shaft.
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`3. The core pin of claim 2 wherein the first base mem
`(a) a guide configured to seat in the stepped hole and
`ber has a stepped hole therein forming a shoulder and
`having a hole therethrough configured and dimen
`wherein the stop means comprises a head on the shaft
`sioned to receive the shaft in longitudinal sliding
`relationship;
`configured to abut the shoulder and limit the forward
`(b) a tube extending from the guide and confining the
`travel of the shaft.
`4. The core pin of claim 2 wherein the spring means
`spring means; and
`biases the shaft forwardly so that when the mold is in
`(c) a cap mounted in the first base member for capti
`the open position and the stop means engages the first
`vating the guide, tube and spring means.
`base member the extension of the shaft is greater than
`10. The core pin of claim 9 wherein the shaft further
`the width of the cavity at the core pin location.
`comprises a head on the end thereof configured to abut
`5. The core pin of claim 2 wherein the limit of exten
`the guide to limit the forward travel of the shaft.
`sion of the shaft when the mold is in the open position
`11. The core pin of claim 10 further comprising in
`is between 0.005 inch and 0.025 inch greater than the
`dexing means engaging the guide and the head for pre
`distance between the opposing mold faces of the cavity
`venting rotation of the shaft.
`15
`at the core pin location.
`12. The core pin of claim 11 wherein the indexing
`6. The core pin of claim 1 wherein the first base mem
`means comprises a pin mounted in the guide parallel to
`ber includes a hole extending therethrough, the shaft
`the shaft, and a notch in the head configured and dimen
`being mounted in the hole with its rear end terminating
`sioned for engagement with the pin.
`within the hole, and further comprising cap means
`13. The core pin of claim 11 wherein the indexing
`means comprises a segment upstanding from the guide,
`mounted in the first base member at the rear of the hole, 20
`the spring means being captivated between the rear end
`and wherein the head includes a matching face config
`of the shaft and the cap means.
`ured to slide against the segment.
`7. The core pin of claim 1 wherein the shaft includes
`14. The core pin of claim 9 further comprising index
`a circumferential groove therein for receiving a packing
`ing means engaging the guide and the shaft for prevent
`of lubricating material to provide long-term lubrication 25
`ing rotation of the shaft.
`between the shaft and its guide.
`15. The core pin of claim 1 wherein the inner face of
`8. The core pin of claim 1 wherein the shaft includes
`the second base member is not flat with respect to the
`direction of the core pin, and wherein the periphery of
`an indentation on its end to increase the effectiveness of
`a seal against the opposing mold face.
`the end of the shaft is contoured to mate with and seal
`against the mold face, and further comprising indexing
`9. The core pin of claim 1 wherein the first base mem- 30
`ber includes a stepped hole extending therethrough, and
`means engaging the shaft and preventing any rotation
`wherein the core pin further comprises a cartridge com
`thereof which would cause the surfaces not to mate.
`prising:
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