A NEW GARRETT BOILER.
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A Résumé of Recently Published Patents.
THATTHE Garrett vertical bailer of the water-tube type is "something different " is apparent immediately upon glancing at the sectional •drawing which we reproduce this week from specification No. 196,173, which emanates from .Richard Garrett and Sons, Ltd., who, in company with M. G.
Plane, are responsible for this invention. • The firebox, it will be observed, is riveted to the boiler shell both at the top and at the bottom, not bolted, as is the custom in most boilers of this type. There is, therefore, no provision whatever for the 'separation of these two parts which has hitherto, in the majority of cases, been thought to be essential in order to enable the tubes to be cleaned. The last-named, in this design of boiler, are all parallel and run in one direction only. All the tubes are accessible at both ends .by the removal of two doors, one in front of and one behind the boiler.
As is well known, the usual arrangement of these tubes is, in several rows lying in two or more directions across the firebox, and this arrangement has the advantage that the tubes themselves afford additional stiffening means for the firebox shell. In this new Garrett design the lack of such support at right angles to the one nest of *tubes is compensated for by the provision of circumferential corrugations in the walls of the firebox. These-corrugations may be observed on reference to the illustration showmg the outside view of the boiler, on which they appear as dotted lines. It is also claimed for this innovation that the inwardly projecting portions of the corrugations improve the heating properties of the boiler by preventing the products of combustion from passing upwards without first impinging on the tubes.
This particular boiler is designed to be used either with or without a super-heater. If the latter is fitted it is conveniently supported near the inside of the tap of the firebox by a special type of header, so formed as to combine the functions of a cover for the smoke-box or flue, and a chimney base. it is formed, too; with an annular steam space connecting the ends of the super-heater tithes, to each of which access is had by means of small holes which are normally filled by screwed plugs.
Other Patents of Interest.
The main object of the invention which is described in specification No. 187,962, by C. Semx, is that of preventing the road wheels of a motor vehicle being skidded as the result of the application of a servo-motor brake. This object is attained by arranging that the servo-motor is operated by the road wheels themselves, so that, so soon as a wheel ceases to revolve, when it would in ordinary circumstances commence to skid, it ceases to operate the servo-motor; consequently, the brake is automatically released.
Entirely different methods of attaining the same object are illustrated in specifications Nos. 192,997 and 196,042, the former standing to the credit of R. Bosch and the latter to L. Bussereau. Both these inventors have in mind the diffi 848
culties which have arisen, in connection with the design of efficient contact breakers, as engine speed has gradually increased concurrently withadditions to the number of cylinders with which these same engines were fitted. So far as the contact breaker is concerned the difficulty is that of providing sufficient sparks per minute. The interruptions of the primary current which are necessary for producing these ;sparks must, in multi-cylinder high-speed engines follow one another with such extreme rapidity that vibration of the contact-breaker rocking arm is produced, to such an extent that that lever never actually comes entirely to rest between the closing and opening of the contacts' so that as a matter of fact perfect closing of the contacts does not take place. Various means of circumventing this difficulty have been tried from time to time with more or less success. The new Bosch construction provides for positive operation of the contact breaker arm in both directions, but leaves a slight clearance between the cam and rocker arm, which clearance is taken up by means of a spring. The cther inventor mounts his contact breaker so that it is operated by the engine camshaft, to which is keyed an electrically conductive disc, on the. face of which a segmental cam, is secured. A cylindrical casing, facing this disc, carries a requisite number of spring-pressed ball contacts. These are positively retained at a specific distance from the main face of the disc and make contact with the cam as it turns.
Semi-automatic clutch operation would appear to be attained by the employment of the device which is described in specification No. 196,053by A. G. Ionides. In addition to the usual clutch spring cansing engagement of the clutch, there is another which has the opposite effect. The latter is so controlled by a governor which is mounted on the engine shaft that it is the superior until a certain predetermined engine speed is reached, when ,the governor takes effect to put it out of action and allow the ordinary clutch-engaging spring free play. There is an additional provision in the, way of a quick thread screw on the connection between clutch shaft and the clutch sleeve which permits overrunning by the driven shaft and thus provides the equivalent of a free wheel. The clutoh pedal operates in the ordinary way subject to the control exercised by the governor.
The invention which is described in specification No. 196,009, by W. Sharpies and Co., Ltd., is of compara. tively wide application, being designed not only for use in retarding motor vehicles which might otherwise race downhill, but also for controlling steamship engines which are also apt
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to race in heavy seas when the propeller leaves the water_ The former of these uses is our particular concern. A curved arm or lever which is coupled to the brake gear has resting upon it a weight in the form of a ball,, roller, or other device which will perform the same function of moving along the lever in accordance with the inclination to the horizontal which that lever may from time to time assume. In cases where this invention is applied to a motor vehicle, this mechanism is so arranged that when the vehicle commences to descend a hill the lever is so inclined that the weight rolls to its outer end, which it depresses, thus applying the brake.
An improved method of supporting rubber shock absorbers is described in specification No. 196,154, by G. Spencer Moulton and Co., Ltd. The invention refers to the design of the cups between which the rubber buffers are held. They are of such a size that free annular space is allowed between the outer periphery of the block and the walls of the cups when the block is not compressed, but when compression takes place under load this annular space is taken up and affords support for the ends of the block.