US3897929A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Recessed sprue bushing for a three-plate mold set
Assignee: NAT TOOL AND MANUFACTURING CO
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Filing: 1974-08-12
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Granted: 1975-08-05
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Expires: 1994-08-12
Abstract
Abstract A sprue bushing for mold sets is described for use with injection molds employing three plates to permit easy stripping of runners and sprue portions from products molded therein. This nozzle sprue bushing is adapted to receive an injection nozzle while mounted in a first or top plate. This sprue bushing has an extending portion which mates and seats in a tapered recess in a second bushing carried by the second or stripper plate. The nozzle sprue bushing has a sprue passageway which terminates at the top plate of the mold. The extension nozzle of the injection press seats within a radiused portion formed in the recessed sprue bushing. The extension of the sprue bushing which seats in the runner plate bushing is preferably exactly the length of the stripper or runner plate bushing which is carried in the runner or stripper plate of a tri-plate mold set. The sprue is very short and, as reduced to practice, remains with the runner sprue which is usually separated from the molded piece during removal of the molded unit from the mold cavity.
Inventors
- 👤 James H Hartmann
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-28 23:25
CPC Classifications
B; B29; B29C; B29C45/00; B29C45/17; B29C45/40; B29C45/26; B29C45/27; B29C45/2701; Y; Y10; Y10S; Y10S425/00; Y10S425/051
Claims Analysis
Total Claims: 9
Claim 1
Independent Claim
376 words
In a tri-plate mold set as used in injection molding by and in a press using an extending sprue, said tri-plate mold set including a top plate which is associated with and aligned with a stripper plate by appropriate lost motion and guide means, said stripper plate also associated with a first mold plate and having aligning means and a lift means by which said first mold plate is lifted by the stripper plate at a determined time period during the mold opening action by the press mechanism after termination of the injection molding cycle and for use with this mold set a sprue bushing improvement including: (a) a recessed sprue bushing having a through sprue passageway and having its outer surface formed and sized for a compatible mounting in a precisely formed through aperture in a top plate of a three-plate mold set and including means for securing this bushing at a fixed position in the top plate, said bushing having a sprue receiving cavity which is formed with its inner and lower end at a selected taper providing a conical recess terminating at a spherically radiused socket, said sprue bushing having a lower portion which extends beyond the lower surface of the top plate in which it is to be mounted, said extending portion having at least its lower outer surface formed with a precise taper, and (b) a stripper plate bushing sized for a compatible and fixed mounting in a precisely formed through aperture in a stripper plate associated and aligned with said top plate, said stripper plate bushing including means for securing this bushing in a position in the stripper plate so that the axis of the stripper plate bushing and the recessed sprue bushing are in coincidence, said stripper plate bushing having a tapered aperture therethrough, this aperture having at least its lower portion sized for precisely receiving and engaging the precisely formed lower tapered extending end portion of the sprue bushing and when the top plate and the stripper plate are brought into a contiguous relationship the tapered end of the extending portion of the sprue bushing engages the receiving taper to provide a molten plastic shut-off at the lower surface of the sprue bushing and the stripper plate bushing.
Claim 2
Dependent Claim
376 words
In a tri-plate mold set as used in injection molding by and in a press using an extending sprue, said tri-plate mold set including a top plate which is associated with and aligned with a stripper plate by appropriate lost motion and guide means, said stripper plate also associated with a first mold plate and having aligning means and a lift means by which said first mold plate is lifted by the stripper plate at a determined time period during the mold opening action by the press mechanism after termination of the injection molding cycle and for use with this mold set a sprue bushing improvement including: (a) a recessed sprue bushing having a through sprue passageway and having its outer surface formed and sized for a compatible mounting in a precisely formed through aperture in a top plate of a three-plate mold set and including means for securing this bushing at a fixed position in the top plate, said bushing having a sprue receiving cavity which is formed with its inner and lower end at a selected taper providing a conical recess terminating at a spherically radiused socket, said sprue bushing having a lower portion which extends beyond the lower surface of the top plate in which it is to be mounted, said extending portion having at least its lower outer surface formed with a precise taper, and (b) a stripper plate bushing sized for a compatible and fixed mounting in a precisely formed through aperture in a stripper plate associated and aligned with said top plate, said stripper plate bushing including means for securing this bushing in a position in the stripper plate so that the axis of the stripper plate bushing and the recessed sprue bushing are in coincidence, said stripper plate bushing having a tapered aperture therethrough, this aperture having at least its lower portion sized for precisely receiving and engaging the precisely formed lower tapered extending end portion of the sprue bushing and when the top plate and the stripper plate are brought into a contiguous relationship the tapered end of the extending portion of the sprue bushing engages the receiving taper to provide a molten plastic shut-off at the lower surface of the sprue bushing and the stripper plate bushing.
Claim 3
Dependent Claim
32 words
A recessed sprue bushing in combination with a stripper plate bushing as in claim 1 and further including forming the spherical radius portion in the sprue bushing with a one-half inch radius.
Claim 4
Dependent Claim
32 words
A recessed sprue bushing in combination with a stripper plate bushing as in claim 1 and further including forming the spherical radius portion in the sprue bushing with a three-quarter inch radius.
Claim 5
Dependent Claim
53 words
A recessed sprue bushing in combination with a stripper plate bushing as in claim 1 and further including forming the stripper plate bushing so that when mounted in the stripper plate the underside surface of this bushing toward the first mold cavity plate is flush with the underside surface of the stripper plate.
Claim 6
Dependent Claim
59 words
A recessed sprue bushing in combination with a stripper plate bushing as in claim 4 which further includes forming the underside surface of the extension portion of the sprue bushing so that in a fully seated condition in the stripper plate bushing, said underside surface of the sprue bushing is also flush with the undersurface of the stripper plate.
Claim 7
Dependent Claim
46 words
A recessed sprue bushing in combination with a stripper plate bushing as in claim 1 which further includes forming the lower exterior taper of the extending portion of the sprue bushing and the mating taper recess in the stripper plate bushing with a 30* included angle.
Claim 8
Dependent Claim
51 words
A recessed sprue bushing in combination with a stripper plate bushing as in claim 1 which further includes forming both the recessed sprue bushing and the stripper plate bushing with flange portions adapted to seat in counterbored portions formed in the associated die set plates in which the bushing is mounted.
Claim 9
Dependent Claim
27 words
A recessed sprue bushing in combination with a stripper plate bushing as in claim 1 which further includes making both bushings of heat treated and treatable steel.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1978-08-04 | 1979-02-03 | 1979-08-05 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1982-08-04 | 1983-02-03 | 1983-08-05 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1986-08-04 | 1987-02-03 | 1987-08-05 | $7700.00 | Window Closed / Lapsed |