Imágenes de páginas
PDF
EPUB

Sprague Electric Railway and Motor Company.
Lightest Weight Consistent with

Bearings Self Oiling
Highest Efficiency.

NON-SPARKING IN OPERATION. SIMPLE IN CONSTRUCTION.

Commutator Wear Reduced Not Liable to get out of Order.

to a Minimum.

[graphic]

16 and 18 BROAD STREET, NEW YORK.

THE

OMETHING NEW

IN BOTH

Life and Accident Insurance. A

* Life and Accident Insurance. American Bell Telephone

TEN-PAYMENT ACCIDENT POLICIES.-Insuring against Accident up to 70 years

of age, and if desired, returning amount of premiums to insured. ANNUITY LIFE POLICIES.- The only form issued wbuh su-nishes a regular income, and the lowest in premium rate.

Both Forms Copyrighted, and used exclusively by

COMPANY 95 MILK ST., BOSTON, MASS.

THE TRAVELERS

w

Agassiz Alex 18 Apr90

Jus Comp Zool

ller

IT

LARG CIBALIT SINESS

OF THE

ACCIDENT PREMIUMS, over $1,000,000. LIFE INSURANCE WRITTEN,

largely in excess of corresponding period of 1888. Assets, 810,992,000.- - Surplus, 82,248,000.

This Company owns the Letters Patent granted to Alexander Grabam Bell, March 7th, 1876, No.

174,465, and January 30, 1877, OF HARTFORD, CONN.

No. 186,787.

The Transmission of Speech by

all known forms of ELECTRIC blic think of them is shown by the

SPEAKING TELEPHONES infringes the right secured to this

Company by the above patents, and MONTHS.

renders each individual user of tel. ephones, not furnished by it or its licensees, responsible for such unlawful use, and all the consequences thereof and liable to suit

therefor. PAID POLICY-HOLDERS OVER $16,500,000.

rSTERBROOK'S

C STEEL PENS. JAMES G. BATTERSON, President,

RODNEY DENNIS, Secretary.
JOHN E. MORRIS, Assistant Secretary.

OP SUPERIOR AND STANDARD QUALITY.

Leading Nos.: 048, 14, 130, 135, 239, 333 Readers of Science

FOOD

For Sale by all Stationers. Corresponding with or visiting Advertisers, !

THE ESTERBROOK STEEL PEN CO., will confer a great favor by mentioning this paper. ADULTERATION

Works : Camden. N.J. 26 John St., New York. | And its Detection. With photomicrographic plates and Old and Rare Books. | a bibliographical appendix. By J. P. Battershall. 328

pages, 8vo, cloth. Price, $3.50. Circulars and Catalogues One Million Magazines. Back numbers, vols. I on application. E. & F. N. SPON,

12 Cortlandt St., New York.

PATENT and sets-old and new, Foreign and American.

IN THE WORLD
CATALOGUE UPON APPLICATION.

Schools.
A. S. CLARK,

CONNECTICUT, New Haven,
34 Park Row, New York City.
MRS. CADY'S SCHOOL FOR YOUNG LADIES.

Couoeiter Made
DACK NUMBERS and complete sets of leading Mag.
IV Prepares for Smith and Wellesley, and admits to

Used by thousands of first-class D azines. Rates low. AM. MAG. EXCHÅNGÉ, Vassar by Certificate. Circulars. Early application

mechanics and by such manufact. Schoharie, N.Y. necessary.

urers as Pullman Palace Car Co.,

Mason & Hamlin Organ and Piano
INDIANA, TERRE HAUTE.

Co., &c., &c.
REMOVAL.
ROSE POLYTECHNIC INSTITUTE.- A School

Repairs Everything. of Engineering. Well endowed well equipped departAfter Monday, July 1, 1889, my dental office will be at

Ils success has brought a lot of ments of Mechanical and Civil Engineering. Electricity,

imitators copying us in every way 6 Somerset Street (ist lest from Beacon), until further Chemistry, Drawing. Extensive Shops & Laboratories.

possible. Remed ber that THẾ notice. My Flesh-brushes will be for sale there. All inExpenses low. For catalogue address T.C. Mendenhall,

ONLY GENUINE L Page's Liquid formation in regard to the Flesh-brushes, also instruc

Glue is manufactured solely by the Pres. tions for using the same, can be obtained at the new

GLOUCESTER MASS.US

RUSSIA CEMENT CO. office, from 9 30 to 10.30 AM, and from 4 to 5 P.M.

MICHIGAN, HOUGHTON.

GLOUCESTER, MASS. Communications by mail promptly replied to. IGAN MINING SCHOOL, -For Catalogues

Send 100, and dealers' cand who BOSTON, MASS.

GEO. F. WATERS. Ivi address M. E. Wadsworth, A.M., Ph.D., Director. | Patent Pocket Can. No waste doesn't keep it in stock, for sample.

THE
TRONGFC
GLUE

[graphic]
[ocr errors]
[graphic][subsumed][subsumed][subsumed][ocr errors][subsumed][subsumed][subsumed][subsumed][subsumed][subsumed][subsumed][subsumed][subsumed]

FIG. 1.- STORAGE-BATTERY OF MUTUAL ELECTRIC MANUFACTURING COMPANY, KNOWLES PATENT. the several points at which it is to be used. At these points, in- one of the battery-plants being located at 187 Montague Street, stead of passing the current through the lamps, it is employed in the generating-station being on Graham Street, where will be found storage-batteries ; and from these storage-batteries the current for the necessary boilers, engines, dynamos, and regulators.

[graphic][subsumed][merged small][graphic][graphic][ocr errors][subsumed][subsumed][subsumed][subsumed][subsumed][subsumed][subsumed][ocr errors][merged small][merged small]

In charging a secondary battery from a dynamo, there is need of maintaining the charging current at a constant and suitable strength. For this purpose it will be seen in Fig. 2 that the dynamo is supplied with a clock-work arrangement, to one of the shafts of which the dynamo brushes are attached. Now, so long as the current strength is maintained, this clock-work remains

and has avoided the application of the active material as a paste. Fig. I shows the cell complete. The perforated plates of nonoxidizable alloy are made in two sheets, between which is held a layer of the active material, which is moulded to the right shape before being placed between the two halves of the retaining plates. When ready, the whole is assembled as shown in the illustration, flexible insulating-rods being passed through the hooks cast on the plates top and bottom.

In a later number we hope to give further details of this system, which is being introduced by the Mutual Electric Company of Brooklyn.

[graphic][subsumed][subsumed]

DESCRIPTION OF PERRET MOTORS AND DYNAMOS.

The chief distinctive feature of these machines, manufactured by The Elektron Manufacturing Company, Brooklyn, N.Y., is the method of constructing the field-magnet, whereby the well-known advantages due to lamination and to the best quality of iron are secured, while the cost, which has heretofore been a bar to the commercial use of such magnets, is reduced nearly to that of forgings. This method of construction is peculiarly adapted to machines of small size; and by its use their efficiency is greatly increased, as a test will show. It may also be used to advantage in machines up to io horse-power, and even higher; as, by the ingenious shape and arrangement of the plates, a magnet of large size may be built up of comparatively small plates, which are stamped from sheet iron, no other machine-work being necessary. Eight sizes are now on the market, and others will be soon brought out.

In the is, , and i horse-power sizes, a magnet of the ordinary U-shape is used, in which the plates are so formed and put together that the limbs may be swung apart and clamped to the face plate of a lathe for winding, after which they are swung back and bolted fast. Fig. I shows one of these motors complete. Fig. 2 shows the magnet before winding.

In machines of horse-power and upwards, the double horseshoe shape, with consequent poles, is used. These are shown in Fig. 3. Upon removing the two bolts which pass through the yoke, the top half of the magnet may be separated from the lower

[graphic][subsumed]

FIG. 4. — AUTOMATIC RHEOSTAT AND REGULATOR.

still; but upon any slight variation the contact-bar in the regulator (seen in the upper part of Fig. 3), consisting of a solenoid carrying a core with the contact-bar at its low end, closes a circuit passing through one or the other of the magnets of the dynamo clock-work, and causes this to move the brushes so as to increase or decrease the current, as need may be.

Again, to avoid the reversal of the polarity of the dynamo through an excessive fall in its current while charging the battery, which would allow of a reverse current passing through it from the storage-battery, the apparatus shown on the lower part of Fig. 3 is provided. On the occurrence of any sudden change, the lever shown near the bottom of the board would fall, breaking the main circuit, and causing the alarm-bell at the top to ring.

The practice of Mr. Knowles in charging is to start the dynamo on the resistances contained in the rheostat (Fig. 4), connecting the batteries when the due strength of current is reached, when, at the same time, the automatic contrivance shown on the top cuts out resistance in proportion.

The battery station in this Brooklyn plant is about half a mile from the dynamo station, but could be much farther away, it is maintained. Here the cells (Fig. I) are arranged in batteries, as shown in Fig. 5. These racks are of wood, covered with insulat. ing paint. Each cell rests on porcelain knobs, and the whole is again insulated from the floor.

In his secondary battery Mr. Knowles has several new features,

Fig. 1.

half. Each half is then attached to a lathe or other suitable machine, and wound by revolving it, after which they are put together and the bolts replaced, all these operations being very simple and very rapidly done.

One of the plates of which these magnets are built is shown in Fig. 4. Four of these are necessary to form the complete enclosure (see Fig. 5). It will be noticed that the plates interleave at the yoke, at which point their cross-section is enlarged, and they are clamped firmly together by bolts. Little or no magnetic polarity is found at the yoke, which shows that the joint is good.

An important feature is the extremely low resistance of the mag. netic circuit, which is due partly to superior quality of iron, the use of which is allowed by this construction, and partly to the smallness of the air-gap between the pole-pieces and the iron of the armature, which is of the drum type, with teeth. In the longi

not only on the internal resistance of the armature-coils, but also to an equal if not larger degree on the intensity of the field : in other words, the lower the internal resistance of the armature-coils and the lower the resistance of the magnetic circuit, the closer the regulation.

This is clearly demonstrated by recent experiments with a ta horse-power motor on a 110-volt circuit, which, with an armature without teeth (the air-gap being ie of an inch, and the internal resistance ii ohms), showed a variation in speed of 15 per cent be

[graphic][subsumed]
[merged small][ocr errors][merged small][merged small]

Fig. 2. tudinal recesses formed by these teeth the armature-coils are wound.

This construction increases the efficiency, allows a large reduction in armature speed, and improves the regulation. As showing this, reference is made to the 1-horse-power machine (Fig. 3), which weighs complete, with pulley, seventy pounds, and has a commercial efficiency of from 80 to 85 per cent. As a shuntwound dynamo, it will generate a current of 4 ampères at 110 volts when run at a speed of 1,800 revolutions per minute. The armature is wound with 7,000 inches of conductor, which is at the rate of about 64 inches per volt, at the remarkably low peripheral speed of 1,500 feet per minute. This showing is believed to be rarely equalled in machines of the largest size.

It may further be stated of the t-horse-power machine that the drop in electro-motive force when run as a dynamo, and the varia

[merged small][ocr errors][merged small][ocr errors][merged small][ocr errors][merged small][ocr errors][merged small][ocr errors][merged small][ocr errors][merged small][ocr errors][merged small]
[graphic]
[ocr errors][merged small][ocr errors][merged small][ocr errors][merged small][ocr errors][merged small][ocr errors][merged small][ocr errors][merged small]
[ocr errors]

It is of course not claimed that the use of toothed drum arma tures is new; but Mr. Perret finds that they possess some decided advantages over plain armatures, in addition to those already stated, as, for instance, positive driving of the coils, secured by winding them in the recesses. He also finds, that, when used with finely laminated field-magnets, they are free from some disadvantages experienced in other constructions. It is quite certain that such armatures, running in close proximity to solid pole-pieces, would produce heating effects therein which would be wasteful and very troublesome, to say the least. With laminated field-magnets, all trouble of this sort is avoided.

A strong point in favor of these machines is freedom from sparking at the commutator, provided this is kept in reasonably good condition ; and the brushes, having been once set at the nonsparking point, require no changing under extreme changes in load. A rocker arm for the brush-holders is therefore unnecessary, and the machine is by so much the simpler. The reason for this will be readily seen by electricians in the foregoing description, and lies in the fact that the magnetism of the field is so powerful relatively to that of the armature, that no distortion of the lines of force is produced, and consequently the line of commutation remains unchanged regardless of changes in load.

A prominent electrician connected with another motor company was heard to remark, after testing some of these machines, that they were “ harder to knock a spark out of than any he had ever seen.” It may be said, further, that these machines have been

Fig. 3. tion in speed as a motor, are less than 5 per cent between full load and no load (see details of Prony brake test). The motors are usually shunt-wound, and, on constant potential circuits, run at practically a constant speed, regardless of changes in load. In several instances parties requiring regulation so close that they believed compound winding absolutely necessary, have been induced to try the Perret shunt-wound machines, and have found them to fully meet the requirements.

This superior regulation is due to the fact, not always given its full weight, that the regulation of a shunt-wound machine depends

« AnteriorContinuar »