THE HISTORY OF INJECTION
SCREW DESIGN

BY: R. F. DRAY
R. B. GREGORY AND K. STROBLE

THIS HISTORICAL REPRESENTATION IS GENERATED FROM THE ACTUAL PATENTS. IN TECHNOLOGY ADVANCES THAT WERE NOT PATENTED, THE INFORMATION SHOWN WAS GIVEN BY PEOPLE WHO WERE DIRECTLY INVOLVED AT THE TIME.

THE DESCRIPTIONS SHOWN IN THE "UNIQUE AREAS" ARE BY THE AUTHOR, EDITED BY R. B. GREGORY, AND TAKEN FROM THE ACTUAL PATENTS.

THE ART DESCRIBED IN THE TOP (LARGER) DRAWINGS IS BEST DESCRIBED AS "BASIC". THAT IS, UNIQUE WITH NO PRECEDENT AND CANNOT BE DESCRIBED AS AN IMPROVEMENT. THE LOWER PATENTS CAN BE DESCRIBED AS "IMPROVEMENT PATENTS" AND ARE LINKED TO THE PRIOR ART. ANY INACCURACIES OR OMISSIONS THAT ARE OBSERVED, IF PRESENTED TO THE AUTHOR, WILL BE CHECKED AND, IFVALIDATED, EITHER CORRECTED OR INSERTED AS APPLICABLE IN THE NEXT SHOWING OR PUBLICATION THE INTENT IS TO PROVIDE THE GREATEST ACCURACY POSSIBLE

NOTE: THIS IS A FIRST VERSION OF THE HISTORY OF INJECTION SCREWDESIGN. FURTHER VERSIONS WILL FOLLOW.

NEW ADVANCES

1.) 20:1 LID
2.) SQUARE PITCH DESIGN
3.) VENTING
4.) TWO STAGE DESIGN
5.) BLISTERS FIRST DISPERSIVE MIXER
6.) LDPE BLOWN FILM RATE 3.5 - 20:1 L/D -150 PPH

 1950 - 1955
BASIC PATENT






NEW MATERIALS PROCESSED

1) ACRYLIC
2) SARAN

SQUARE PITCH SINGLE STAGE DESIGN
PRIMARY DEVELOPER
UNIQUE AREAS

P. SQUIRES

FIRST SQUARE I'ITCH DESIGN (LEAD DIAMETER). PREVIOUS DESIGNS WERE DERIVED FROM RUBBER AND USED FOR PI.ASTICS. THE SQUARE PITCh WAS EASIER TO MACHINE AND MORE EFFICIENT FOR PLASTICS PROCESSING.

Vented Extrusion
PRIMARY DEVELOPER

UNIQUE AREAS

A. KAUFMAN

FIRST COMMERCIAL TWO STAGE SINGLE SCREW DEVOLTIZINC IN AN EXTRUDER
DEVELOPED FOR PROCESSING PVC.

SQUARE PITCH TWO STAGE DESIGN
PRIMARY DEVELOPER

UNIQUE AREAS



R. B. GREGORY

TWO STAGE DESIGN USED FOR ADDITIONAl. MIXING AND LOWER MELT TEMPERATURES FOR SELECTED RESINS.

GREGORY MIXER
INVENTOR: R.B. GREGORY

ASSIGNED TO: G.K. SYSTEMS		 FILED: 12/06/1972

 PATENTED: 01/29/1974

PATENT NO.: 3,788,614


NOTE: THIS IS AN "IMPROVEMENT PATENT" DEVElOPED BY GREGORY AFTER LEAVING EGAN MACHINERY. THIS PATENT IS WIDELY USED TODAY IN BOTH INJECTION MOLDING AND EXTRUSION.


NEW ADVANCES
1.) PRECLOSE AND SLIDING CLOSURE 		1990-1995
BASIC PATENT


DRAY NON-RETURN VALVE
INVENTOR: R F DRAY
ASSIGNED TO: NOT ASSIGNED
FILED: 05/13/1991
PATENTED: 12/06/1972
PATENT# 3.151,262

UNIQUE AREAS: FIRST VAI.VE TO PRE-CLOSE BY PRESSURE UTII.IZING TWO DIFFERENT DIAMETERS ON THE PISTON TO CREATE FORCE FOR CLOSURE. THIS PATENT IS ALSO TI-IF FIRST NON-RETURN VALVE TO USE A SLIDING CLOSURE RATHER THAN A SEAT CLOSURE


NEW ADVANCES

1) OUTER PISTON DESIGN WITH PRECLOSE AND SLIDING CLOSURE

 1990-1995
BASIC PATENT


DRAY NON-RETURN VALVE
INVENTOR: R F DRAY
ASSIGNED TO: NOT ASSIGNED
FILED: 12/11/1991
PATENTED: 11/08/1993
PATENT# 9 3,236,158

UNIQUE AREAS: OUTER PISTON VERSION OF PATENT NO. 3,151,252 THIS IS TIlE FIRST VALVE TO PRE-CLOSE BY I'RESSURE UTILIZING TWO DIFFERENT DIAMETERS ON THE OUTER PISTON TO CREATE FORCE FOR CLOSURE. THIS PATENT IS AI.SO THE FIRST NON RETURN VALVE TO USE A SL.IDING CIOSURE RATTLER THAN A SEAT CIOSURE


NEW ADVANCES
1.) SLIDING CLOSURE 		1995-2000
BASIC PATENT


DRAY NON-RETURN VALVE
INVENTOR: R F DRAY
ASSIGNED TO: NOT ASSIGNED
FILED: 05/13/1997
 PATENTED: PENDING
PATENT# PENDING

UNIQUE AREAS: THlS PATENT IS AlSO THE FIRST NON-RETURN VALVE TO UTILIZE A SI.IDING CLOSURE WITH A SINGLE DIAMETER RING.

NEW ADVANCES
1.) PRECLOSE AND SLIDING CLOSURE 		1995-2000
BASIC PATENT


DRAY SHUTOFF NOZZLE
INVENTOR: R F DRAY
ASSIGNED TO: NOT ASSIGNED
FILED: 09/20/1996
 PATENTED: PENDING
PATENT# PENDING

UNIQUE AREAS: PNEUMATTCALLY ACTIVATED SHUTOFF NOZZLE WITH SLIDING CLOSURE

NEW ADVANCES
1.) SHOT CONTROL BY PRESSURE 		1995-2000
BASIC PATENT


DRAY PRESSURE CONTROL SYSTEM
INVENTOR: R F DRAY
ASSIGNED TO: NOT ASSIGNED
FILED: 08/31/1993
 PATENTED: 02/28/1995
PATENT# 5,470,514

UNIQUE AREAS:: THIS SYSTEM CONTROLS THE AMOUNT OF RESIN THAT IS INLET TO THE ACCUMULATION AREA AND ALSO CONTROLS RESIN PRESSURE INLET TO ACCUMULATION AREA.