# US 2014/0360018 A1 · Method for manufacturing a gear

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- Number: US 2014/0360018 A1
- Document ID: US20140360018A1
- Status: Published application
- Kind: A1
- Application number: 14/141,809
- Filed: 2013-12-27
- Published: 2014-12-11
- Earliest claimed: 2013-05-22
- Assignees: Cooper Industries Holdings (Ireland)
- Applicants: Cooper Industries Holdings (Ireland)
- Inventors: Bulent Chavdar; Michael Killian; Eric Nshimiye; Thomas Stoltz
- Web page: https://patentgrep.com/patent/US20140360018A1

## CPC

- B21K 1/30: with gear-teeth
- B23P 15/14: gear parts, e.g. gear wheels
- B21J 1/02: Preliminary treatment of metal stock without particular shaping, e.g. salvaging segregated zones, forging or pressing in the rough (modifying the physical properties by deformation C21D7/00, C22F1/00)
- B21J 5/025: {Closed die forging}
- Y10T 29/49474: Die-press shaping
- Y10T 29/4948: with specific gear material
- B21K: MAKING FORGED OR PRESSED METAL PRODUCTS, e.g. HORSE-SHOES, RIVETS, BOLTS OR WHEELS (making particular articles by working sheet metal without essentially removing material B21D; processing wire B21F; making pins, needles or nails B21G; making particular articles by rolling B21H; forging machines, pressing machines, hammering machines, in general B21J; making chains B21L; plating B23K)
- B23P: METAL-WORKING NOT OTHERWISE PROVIDED FOR; COMBINED OPERATIONS; UNIVERSAL MACHINE TOOLS (arrangements for copying or controlling B23Q)
- B21J: FORGING; HAMMERING; PRESSING METAL; RIVETING; FORGE FURNACES (rolling of metal B21B; making particular products by forging or pressing B21K; cladding or plating B23K; finishing surfaces by hammering B23P9/04; compacting surfaces by blasting with particulate material B24C1/10; general features of presses, presses for consolidating scrap B30B; furnaces in general F27)
- Y10T: TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION

## Abstract

A method for manufacturing a gear includes forming a bi-material billet from a steel cylinder having a cylindrical wall, a first end closed with a first steel cap, and an open second end distal to the first end. The method includes disposing a core material other than steel into the steel cylinder, welding a second steel cap onto the steel cylinder to form the bi-material billet, and heating the cylindrical wall. The method includes a first forging blow on the heated billet or on a disk-shaped rough forging forged from the heated billet with a first closed blocker die to produce a partial toothed preform, and a second forging blow on the preform with a second closed blocker die to produce a netshape gear. The first closed blocker die has a die cavity including gear tooth forms, and the partial toothed preform includes a plurality of spaced gear teeth.

## Claims

### Claim 1

A method for manufacturing a gear, comprising:
forming a bi-material billet by:
providing a steel cylinder having:
a cylindrical wall with a cylindrical wall thickness;
a first end closed with a first steel cap; and
a second end distal to the first end wherein the second end is an open end;
disposing a core material other than steel through the open end into the steel cylinder;
welding a second steel cap onto the second end of the steel cylinder to form the bi-material billet;
heating the cylindrical wall until a minimum temperature of a coolest portion of the cylindrical wall is at least about 1900 degrees F. and a maximum temperature of a hottest portion of the cylindrical wall is less than about 2300 degrees F.;
performing a first forging blow on the heated billet or on a disk-shaped rough forging forged from the heated billet with a first closed blocker die driven by a press to produce a partial toothed preform; and
performing a second forging blow on the partial toothed preform with a second closed blocker die driven by the press to produce a netshape gear wherein:
the first closed blocker die has a die cavity including gear tooth forms; and
the partial toothed preform includes a plurality of spaced gear teeth.

### Claim 2 (depends on 1)

The method as defined in claim 1, further comprising performing a rough forging blow on the heated billet with a closed buster die driven by the press to produce the disk-shaped rough forging after the heating and prior to the performing the first forging blow.

### Claim 3 (depends on 2)

The method as defined in claim 2 wherein the buster die, the first blocker die, and second blocker die comprise a multi-stage die set for simultaneous operation on a single press.

### Claim 4 (depends on 1)

The method as defined in claim 1 wherein the second cap is welded onto the second end of the steel cylinder by electron beam welding or by friction welding.

### Claim 5 (depends on 4)

The method as defined in claim 4 wherein the second steel cap includes:
a steel disk having a substantially flat base surface and center axis orthogonal to the base surface;
an annular wall projecting from the steel disk opposite to the base surface;
an open cavity defined by the annular wall and the disk, the open cavity having a mouth opposite the disk defined by the annular wall, the open cavity having a depth measured from a plane defined by an edge of a shortest side of the annular wall to the steel disk, the depth ranging from about 0.005 inch to about 0.015; and
an end surface defined on the annular wall distal to the steel disk;
wherein the end surface is substantially flat and perpendicular to the center axis, or the end surface is an annular bevel.

### Claim 6 (depends on 1)

The method as defined in claim 1 wherein the first forging blow and the second forging blow are performed on a single heat of the bi-material billet.

### Claim 7 (depends on 2)

The method as defined in claim 2 wherein the rough forging blow, the first forging blow and the second forging blow are performed on a single heat of the bi-material billet.

### Claim 8 (depends on 1)

The method as defined in claim 1 wherein:
the core material is composed of a single piece of aluminum or an aluminum alloy;
the core material is in a solid phase during the step of disposing the core material into the steel cylinder; and
the core material is maintained in the solid phase during the steps of:
welding the steel cap onto the second end of the steel cylinder;
heating the cylindrical wall with a high frequency induction heater;
performing the first forging blow; and
performing the second forging blow.

### Claim 9 (depends on 8)

The method as defined in claim 8 wherein the heating is performed via a high frequency induction heater operating on the cylindrical wall at an operating frequency from 9000 Hertz to 11000 Hertz and wherein the high frequency induction heater applies from 5000 Kilowatts to 7000 Kilowatts per square meter of an external surface of the steel cylinder.

### Claim 10 (depends on 8)

The method as defined in claim 8, further comprising induction hardening a gear tooth surface of the gear to a case depth of less than 1 millimeter.

### Claim 11 (depends on 1)

The method as defined in claim 1 wherein the core material is selected from the group consisting of clay, workable wet concrete, sand, ceramic powder, mineral powder, metal particles, and combinations thereof.

### Claim 12 (depends on 11)

The method as defined in claim 11 wherein the metal particles are non-sintering during the forging steps and have a lower density than steel.

### Claim 13 (depends on 1)

The method as defined in claim 1 wherein a ratio of a coefficient of thermal expansion of the core material to a coefficient of thermal expansion of the steel is from about 0.8 to about 1.2.

### Claim 14 (depends on 1)

The method as defined in claim 1 wherein at least 85 percent of the volume of the core material is in a liquid phase or a viscous glass phase during the steps of:
performing the first forging blow; and
performing the second forging blow.

### Claim 15 (depends on 14)

The method as defined in claim 14, further comprising:
during the first forging blow, operating the first blocker die to squeeze the core material from between a first central portion of a steel shell and a second central portion of the steel shell opposite the first central portion to collapse the first central portion and the second central portion into mutual contact thereby producing a steel web at a center of the partial toothed preform or the netshape gear.

### Claim 16 (depends on 15)

The method as defined in claim 15, further comprising:
transferring the partial toothed preform to a second blocker die cavity in a die;
aligning a center of the partial toothed preform with a center of the second blocker die cavity;
rotationally aligning a portion of the steel at a center of a top land of a tooth of the partial toothed preform with a center of a top land of the second blocker die cavity; and
performing the second forging blow on the partial toothed preform in the second blocker die cavity, thereby:
causing the portion of the steel at the center of the top land of the tooth of the partial toothed preform to be the center of the bottom land of a gear tooth of the netshape gear; and
forming an aperture completely through the web of the netshape gear.

### Claim 17 (depends on 14)

The method as defined in claim 14 wherein a minimum thickness of steel on the gear teeth is at least 50 percent of a maximum thickness of steel on the gear teeth.

### Claim 18 (depends on 17)

The method as defined in claim 17 wherein the minimum thickness of steel on the gear teeth is at least 2 millimeters.

### Claim 19 (depends on 15)

The method as defined in claim 15, further comprising:
transferring the partial toothed preform to a second blocker die cavity in a die;
aligning a center of the partial toothed preform with a center of the second blocker die cavity;
rotationally aligning a portion of the steel at a center of a top land of a tooth of the partial toothed preform with a center of a top land of the second blocker die cavity; and
performing the second forging blow on the partial toothed preform in the second blocker die cavity thereby causing the portion of the steel at the center of the top land of the tooth of the partial toothed preform to be the center of the bottom land of a gear tooth of the netshape gear.