# US 5,704,455 A · Automatic brake booster

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- Number: US 5,704,455 A
- Document ID: US5704455A
- Status: Granted
- Kind: A
- Application number: 08/704,452
- Filed: 1996-08-27
- Granted: 1998-01-06
- Earliest claimed: 1995-09-29
- Assignees: Jidosha Kiki Co., Ltd.
- Inventors: Makoto Watanabe
- Web page: https://patentgrep.com/patent/US5704455A

## CPC

- B60T 13/72: in vacuum systems {or vacuum booster units}
- B60T 13/563: with multiple booster units, e.g. tandem booster units
- B60T 13/569: characterised by piston details, e.g. construction, mounting of diaphragm
- B60T: VEHICLE BRAKE CONTROL SYSTEMS OR PARTS THEREOF; BRAKE CONTROL SYSTEMS OR PARTS THEREOF, IN GENERAL (electrodynamic brake systems for vehicle, in general B60L; brakes per se, i.e. devices where braking effect occurs, including ultimate brake actuators, F16D); ARRANGEMENT OF BRAKING ELEMENTS ON VEHICLES IN GENERAL; PORTABLE DEVICES FOR PREVENTING UNWANTED MOVEMENT OF VEHICLES; VEHICLE MODIFICATIONS TO FACILITATE COOLING OF BRAKES

## Abstract

An automatic brake booster having the functioning of an automatic brake, or more specifically, an improvement of bellows contained in a shell thereof is disclosed. The bellows comprises a stepped tubular member having portions of different diameters, namely, a reduced diameter, a medium diameter and an increased diameter. By using a reinforcing ring having a rigidity in the step, an expansion to increase the diameter of the bellows when the atmosphere is introduced into the internal space of the bellows can be prevented. Different diameters of the portions of the bellows allows the likelihood to be minimized that an output loss of the brake booster may be caused by contact of bellows portions to each other as the bellows is axially shrunk. As compared with an accordion-like bellows, the stepped tubular bellows can utilize a simplified die assembly and manufacturing steps and thus can be manufactured inexpensively.

## Claims

### Claim 1

An automatic brake booster including a valve body slidably disposed in a shell, a power piston mounted on the valve body, a constant and a variable pressure chamber defined across the power piston, a tubular bellows disposed within the constant pressure chamber, and a valve mechanism received within the valve body for switching a fluid circuit between a constant pressure passage communicating with the internal space of the bellows and a variable pressure passage communicating to the variable pressure chamber, thus allowing either a negative pressure or the atmosphere to be selectively supplied to the internal space of the bellows, wherein the bellows comprises a stepped tubular member having a small diameter portion, a middle diameter portion and a large diameter portion, these portions being formed in the mentioned order, and a reinforcing ring being disposed in at least one radial step of the stepped tubular member.

### Claim 2 (depends on 1)

An automatic brake booster according to claim 1 in which the stepped tubular member is provided with a rear step and a front step, the small diameter portion being intermediate a rear end of the stepped tubular member and the rear step, the middle diameter portion being intermediate the rear step and the front step, the large diameter portion being intermediate between the front step and a front end of the stepped tubular member, and the front end of the stepped tubular member having a greater diameter than the rear end of the stepped tubular member.

### Claim 3 (depends on 2)

An automatic brake booster according to claim 2 in which the middle diameter portion has a rigidity which is less than the rigidity of the small diameter and large diameter portions.

### Claim 4 (depends on 1)

An automatic brake booster according to claim 1 in which a said reinforcing ring is disposed in each said radial step and said rings are adhesively bonded to the respective step of the stepped tubular member by vulcanization.

### Claim 5 (depends on 1)

An automatic brake booster according to claim 1, wherein the reinforcing ring is rigid sufficient to prevent expansion of the diameter of the bellows.

### Claim 6 (depends on 2)

An automatic brake booster according to claim 2, wherein a support member secures the front end of the stepped tubular member to an inner wall surface of the shell.

### Claim 7 (depends on 2)

An automatic brake booster according to claim 2, wherein one said reinforcing ring is disposed in each of said rear step and said front step .