US2670815A - Hydraulic brake - Google Patents

Description

P. N. WILSON 2,670,815

3 Sheets-Sheet 1' 5 Inventor .2 MHL LEO-Z21 HYDRAULIC BRAKE I III March 2, 1954 Filed Feb. 20, 1950 Filed Feb. 20, 1-950 3 Sheets-Sheet 2- P.1YffzLlsoru March 2, 1954 p, w Lso r 2,670,815

HYDRAULIC BRAKE Filed Feb. 20, 1950 3 Sheets-Sheet 3 are described in detail below.

Patented Mar. 2, 1954 HYDRAULIC BRAKE Paul Norman Wilson,v Kendal, England, asslgnor to Gilbert Gilkes & Gordon Limited, Kendal,-

England Application February 20, 1950,: Serial, No. 145,108

2 Claims. (01. 188:--90) This invention relates to hydraulic brakes for absorbing power generated by a prime mover and more especially an hydraulic turbine generating power.

In British specification N0. 22,909/47, there is described a plant incorporating an hydraulic brake which in effect is a Pelton wheel, the rotor of which is caused to rotate in opposition to a jet of liquid admitted to the casing in which the rotor is enclosed.

An hydraulic turbine of this type usedas a brake should have the characteristic that when it is absorbing power it shall absorb the maximumamount of power with the minimum supply of water or other liquid impinging on the rotor whilst when running free it should be so constructed that windage or other frictional losses are reduced.

The object of the present invention is to provide an hydraulic brake, the rotor of which in effect isa Pelton Wheel rotated in opposition to the jet of liquid introduced into its casing.

One feature of the invention consists in forming the rotor so that its opposite sides adjacent to its periphery conform with the surface of the side walls of the casing.

Further, and in some instances optional features and the purposes they are designed to serve In order that the maximum power may be absorbed the velocity of the rotor at the radius at which the jet strikes the buckets with which it is provided or formed must be maintained at the highest possible figure.

The mechanical strength of the rotor must therefore be great and to secure this result most satisfactorily the buckets or vanes are formed in the rim of the rotor and between the side walls of the rim and are provided with means allowing the braking liquid to escape through vents formed onv each side of the rotor.

ThuS the rotor may be a casting or forging. in whichv the buckets are integrally formed.

In order that frictional losses may be reduced to a minimum when the rotor is rotating freely and no braking effect is required, the side walls of the casing ar pr f rably ymmetrical as with an unsymmetrical casing similar to that employed to shield a Pel'ton wheel or similar free jet impulse turbine in which the. water falls away in the, lower portion of the casing, violent air snrges are set up causing relativelyllishi power absorption when the rotor revolves whether or not a braking effect is desired.

The buckets or vanes are formed in the rim of the rotor in such manner that they are concave when viewed along the axis of the entering jet or jets of liquid which strike against them to produce the braking effect and at this point it may be repeated that the rotor rotates towards the jet and not away'fro-m it'as inthe case of the conventional free jet impulseturbine of the Pelton or similar type. r v

7 Owing to the shape of the buckets or vanes in the rotor of an hydraulic brake in accordance with the invention, the dischargevelocity of the liquid is increased and may be several times the velocity of the entering liquid.

By this means a relatively small amount of liquid may be used to absorb arelatively large amount of power in thebrake.

Conveniently the'supply of liquid by way of the jet is controlled by the provision of a variable spear controlled noz zle valve and supply pipe.

This spear control may be operated by "hand. or by a speed governor;

Alternatively; a fixedsize nozzle may be substituted; a valve being provided in the supply line for operation by hand or by a speed governor.

In certain cases instead of varying the rate at which liquid enters the rotor chamber by the operation of a valve, a nozzle adapted to give a fixed supply of liquid may be used and a deflector introduced between the nozzle and the rotor to vary the volume of braking liquid striking the buckets in the rotor,

Alternatively, both a, variable spear control valve and a deflector control maybe provided.

In order to prevent air entering or liquid leaving the casing along the shafts, a labyrinth or thrower system or alternatively a gland system may be arranged where the shaft passes through the walls of the chamber in which the rotor revolves. I

The invention will be described further in detail and by way of example with reference to the accompanying drawings in which:

i re 1: a view in sectional elevation of a hydraulic brake in accordance with the invention";

Figure 2- is a planview thereof with the upper half of the casing removed;

Figure 3 is a diagrammatic representation illustrating the application of the braking mecha nism in connection with a water turbine driven electric, generator.

As will be seen fromthe drawings, the rotor I istorm'zd to provide. opposite faces 2 which con form with the surface of the sidewalls 3 of the" casing.

The mechanical strength of the rotor must be great and to secure this result the buckets or vanes 4 are formed on the rim 5 of the rotor which preferably is a casting or forging.

The side walls of the rim are provided with vents 6 formed on each side of the rotor to allow the braking liquid to escape from the buckets.

It will be noted that the casing in which the rotor rotates is symmetrical with the rotor in order that air surges shall not be set up causing a relatively high power of absorption when the rotor revolves, whether or not a braking effect is desired. a

The buckets, as will be seen, are concave along the axis of the entry jet I.

In the construction shown the jet is variable by the provision of a valve furnished with a spearhead control member 8 which is urged towards a nozzle 9 by a spring l0 engaged between a plate H and an abutment member 12, the stem [3 of the valve being furnished with an eye I4 for con.- necting it with the mechanism which will be described generally with reference to Figure 3.

. As shown in Figure 1, the lower half of the rotor is substantially surrounded by a line 15 in which is provided an aperture [6 through which the braking liquid may escape and enter a deflector I1.

The rotor shaft 18 is preferably furnished with a labyrinth or gland packing, not shown, in order to prevent air entering or liquid leaving the casing along the shaft.

As above indicated, the braking device is designed more particularly to be included in a plant as described in British specification No. 22,909/47 and such application of the device is illustrated purely diagrammatically in Figure 3 in which 20 is an hydraulic turbine of the Francis type in the lead 2! to which is included a valve 22 which will normally be agate valve connected with a governor 23 which is driven from the shaft 24 on which the rotor of the turbine is mounted and which is connected to the shaft of the armature of a generator 25 which in turn is connected with the shaft 26 of the hydraulic brake 21 to which is by-passed a portion of the liquid supplied by way of the pipe 28 through a nozzle 29 in which operates a spearhead valve connected through a bell crank lever and link 30 with the cylinder of a dashpot device 3| the pistonof which is connected by a system of links 32 with the governor.

It is therefore clear that the present invention provides a hydraulic brake mechanism that comprises a cylindrical casing having symmetrical facing side walls 3. The shaft to be braked is journalled for rotation in the casing and carries a rotor body. This shaft rotates at a high speed in a predetermined direction. The rotor body has opposite symmetrical side walls 2 conforming in symmetry to the facing side walls of the casing. The rotor body is of less diameter than the internal diameter of the casing and has less axial extent than the distance between the facing side walls of the casing so that space exists between all surfaces of the rotor body and the casing. Means are associated with the casing for directing at least one jet of liquid such as water, tangentially into the casing through the periphery thereof and in a direction opposite to the direction of rotation of the rotor. As hereinbefore set forth, the rotor body has its periphery shaped to define recessed buckets or vanes 4 that are located between the side walls of the rotor. The peripheral surfaces of these vanes are concave in a 4 circumferential direction as viewed along the axis of the jet. This presents arcuate surfaces to be impinged upon by the jet as the rotor rotates. The outlet l6 has its axis perpendicular to the axis of the jet and on the side of the axis of the jet opposite to the axis of the rotor so that the discharge velocity of liquid is increased and a' high relative velocity exists between the rotor periphery and the jet. This provides for a high power absorption at minimum liquid supply. As previously pointed out in the specification, the symmetrical arrangement of rotor and easing side walls minimize air surges within the casing. The side walls of the rotor body have liquid egress openings therein that provide communication between the buckets and the space between the rotor and casingsidewalls to allow braking liquid to vent or pass through these openings.

I claim:

1. A hydraulic brake mechanism comprising a cylindrical casing having symmetrical facing side walls, a rotor body journalled for rotation in the casing and adapted to rotate at a high speed in a predetermined direction, said rotor body having opposite symmetrical side walls conforming in symmetry to the facing side walls of the casing and having less diameter than the internal diameter of the casing, said rotor body further having less axial extent than the distance between the facing side walls of the casing so that space exists between all surfaces of the rotor and the casing, means for directing at least one jet of liquid, tangentially into the casing through the periphery thereof and in a direction opposite to the direction of rotation of the rotor, said rotor body having its periphery shaped to define recessed buckets constituting vanes located between the side walls of the rotor, the peripheral surfaces of the vanes being concave in a circumferential direction as viewed along the axis of the jet so as to present arcuate surfaces to be impinged upon by the jet as the rotor rotates, the periphery of the casing having an outlet opening therein, the axis of which is perpendicular to the axis of the jet and on the side of the axis of the jet opposite to the axis of the rotor body so that the discharge velocity of liquid is increased and a high relative velocity exists between the rotor periphery and the jet in order to provide for high power absorption at minimum liquid supply and the symmetrical arrangement of rotor and easing side walls minimizing air surges within the casing.

2. A hydraulic brake as defined in and by claim 1, in which the side walls of the rotor body have liquid egress openings therein providing communication between the buckets and the space between the rotor and casing side walls.

PAUL NORMAN WILSON.

References Cited in the file of this patent UNITED STATES PATENTS Switzerlandu" Dec. 1, 1930

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