Brakes – Operators – Electric
Reexamination Certificate
1999-04-01
2001-04-24
Oberleitner, Robert J. (Department: 3613)
Brakes
Operators
Electric
C188S164000
Reexamination Certificate
active
06220403
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to an eddy current reduction braking system, which increases both heat dissipation and braking torque.
In a magnet type eddy current reduction apparatus disclosed in Japanese Patent Publication No. 3-86,050 Publication or the like, a magnet supporting tube is reciprocated in an axial direction to switch between braking and non-braking conditions. Such apparatus has the inherent disadvantage of increasing space requirements in the axial direction.
In a magnet type eddy current reduction apparatus disclosed in Japanese Patent Publication No. 7-118,901, a movable magnet supporting tube is rotated to adjust the relative polarities of magnets axially adjacent in a pair of axially aligned magnet arrays to switch between braking and non-braking conditions. In such an apparatus, however, each pair of N and S-poles of each magnet are directed in a radial direction of the brake drum. It is therefore necessary to process outer and inner surfaces of the magnets into cylindrical or circular form so that an effective magnetic flux is applied to the brake drum via a ferromagnetic plate. The required magnet processing considerably increases cost. Furthermore, the ferromagnetic plates must be large so as to completely cover the magnets in the braking condition. Complete covering by the plates allows the magnets to apply a magnetic field to the brake drum without any substantial leakage. Magnetic flux density cannot be effectively increased to improve braking force therefor due to ferromagnetic plate limitations.
The object of the present invention, therefore, is to provide an eddy current reduction apparatus which is compact in its entirety, and in which braking performance is enhanced.
SUMMARY OF THE INVENTION
The present invention is an eddy current braking system including a guide tube formed of a non-magnetically permeable material coaxially disposed in a brake drum coupled to a rotational shaft, a support tube formed of a non-magnetically permeable material mounted for axial movement on the guide tube,and an array of permanent magnets supported at equal annular intervals on an outer peripheral wall of the magnet support tube. Also included are a pair of ferromagnetic pole piece members with proximal end surfaces adjacent to opposed magnetic pole surfaces at opposite ends of each magnet and extreme end surfaces supported in openings of a wall portion of the guide tube and closely adjacent to an inner peripheral surface of the brake drum. An actuator mechanism provides reciprocating movement of the magnet support tube between a braking position in which the magnetic pole surfaces at opposite ends of each permanent magnet are adjacent to the proximal surfaces of a pair of the ferromagnetic members and a non-braking position in which the magnetic pole surfaces of the permanent magnet are withdrawn from the proximal surfaces of the ferromagnetic members. The stationary ferromagnetic members can be mounted closely adjacent to the brake drum to establish a short magnetic circuit path.
According to another embodiment of the invention, a guide tube having a rectangular cross-section and formed of a non-magnetically permeable material is coaxially disposed in a brake drum coupled to a rotational shaft, a magnet support tube formed of a non-magnetically permeable material is mounted for axial movement on the guide tube, an array of permanent magnets are supported at equal annular intervals on an outer peripheral wall of the magnet support tube, and proximal surfaces of a pair of ferromagnetic pole piece members are coupled to opposite magnetic pole surfaces at opposite ends of each permanent magnet. Also included is an actuator mechanism for reciprocating the magnet support tube between a braking position in which the extreme end surfaces of the ferromagnetic members are juxtaposed to the inner surface of the brake drum and a non-braking position in which the ferromagnetic members are axially spaced from the inner surface of the brake drum. The ferromagnetic members shorten magnetic circuit paths to increase braking torque and coupling of their ends to the ends of the magnets simplifies construction of the braking system.
According to certain features of the magnetic north and south poles at opposite ends of each magnet are oriented annularly and each ferromagnetic member is curved with a proximal end coupled to one of the magnetic pole surfaces of a magnet and an extreme end extending in annularly and radially outwardly directions toward the inner surface of the brake drum. The features optimize magnetic circuit paths to enhance braking performance.
According to other features of the above embodiment, the guide tube has an outer wall having a magnetically permeable wall portion and an axially aligned non-magnetically permeable and extremely thin portion covering the extreme end surface of the ferromagnetic members when in a non-braking position. These features further enhance braking performance.
REFERENCES:
patent: 3601641 (1971-08-01), Baermann
patent: 3656815 (1972-04-01), Talebi et al.
patent: 3962595 (1976-06-01), Eddens
patent: 4122922 (1978-10-01), Baermann
patent: 4482034 (1984-11-01), Baermann
patent: 5023499 (1991-06-01), Kuwahara
patent: 5045739 (1991-09-01), Kuwahara
patent: 5050711 (1991-09-01), Sawato
patent: 5054587 (1991-10-01), Matsui et al.
patent: 5154623 (1992-10-01), Kuwahara
patent: 5206555 (1993-04-01), Morris et al.
patent: 5303802 (1994-04-01), Kuwahara
patent: 5465815 (1995-11-01), Ikegami
Kobayashi Shin
Narumi Yukitoshi
Isuzu Motors Limited
Jarcho Harold G.
Oberleitner Robert J.
Pezzlo Benjamin A.
Toupal John E.
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