# US 4,396,257 A · Zoom binocular with gear drive about central pivot axis

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- Number: US 4,396,257 A
- Document ID: US4396257A
- Status: Granted
- Kind: A
- Application number: 06/305,041
- Filed: 1981-09-23
- Granted: 1983-08-02
- Earliest claimed: 1981-09-23
- Assignees: Enshu Optical Co., Ltd.
- Inventors: Masakazu Nakamura
- Web page: https://patentgrep.com/patent/US4396257A

## CPC

- G02B 7/04: with mechanism for focusing or varying magnification
- G02B 7/12: Adjusting pupillary distance of binocular pairs
- G02B 23/18: for binocular arrangements {(focusing binocular pairs G02B7/06; adjusting pupillary distance of binocular pairs G02B7/12)}
- G02B: OPTICAL ELEMENTS, SYSTEMS OR APPARATUS

## Abstract

An improvement in zoom binoculars is disclosed which utilizes a small gear rotated by a larger drive gear connected to a pivotally mounted lever for transmitting rotation to one of two intermediate gears which are meshed to each other through free central gear. Each intermediate gear is meshed with a tube gear connected to a tube lens. Each intermediate gear with its meshed tube gear is rotatably mounted on one of a pair of binocular body portions which are pivotally mounted to each other. The pivotally mounted body portions can be pivoted with respect to each other to change the spacing between lens tubes. Due to the small size of the small gear, such pivoting of the body portions produces only a small differential rotation between the two intermediate gears, and thus a small differential and magnification throughout the entire range of magnification for the zoom binoculars.

## Claims

### Claim 1

In a zoom binocular having a body with a pair of body portions pivotally connected to each other and a lens tube with tube gear rotatably mounted to each body portion, an improvement comprising:
an operating lever pivotally mounted to the body;
a drive gear operatively connected to said operating lever for rotation of said drive gear with pivoting of said lever;
a small gear which is small with respect to said drive gear meshed with said drive gear;
an intermediate gear shaft connected to each body portion;
an intermediate gear mounted to each intermediate gear shaft, each meshed with one tube gear;
said small gear mounted on one of said intermediate gear shafts for rotation of an intermediate gear mounted on said one intermediate gear shaft with rotation of said small gear; and
a free central gear meshed with both said intermediate gears for transmitting rotation of one of said intermediate gears to the other of said intermediate gears.

### Claim 2 (depends on 1)

In a zoom binocular, an improvement according to claim 1, wherein said small gear is integrally connected to said one intermediate gear.

### Claim 3 (depends on 2)

In a zoom binocular, an improvement according to claim 2, wherein each of said intermediate gear shafts are rotatably mounted to a respective one of the body portions and each respective intermediate gear is fixed to its intermediate gear shaft.

### Claim 4 (depends on 1)

In a zoom binocular, an improvement according to claim 1, including a drive shaft connected to said drive gear, a pin extending radially from said drive shaft, said operating lever including a slot extending axially therein with respect to said drive shaft, said pin extending in said slot to transmit pivotal movement of said operating lever into rotational movement of said drive shaft and drive gear.

### Claim 5 (depends on 1)

In a zoom binocular, an improvement according to claim 1, wherein said free central gear is small with respect to said drive gear.