US1228405A - Process and apparatus for rectifying alternating currents of electricity. - Google Patents

Description

W. H. CHAPMAN.

PROCESS AND APPARATUS FOR RECTIFYING ALTERNATIN G CURRENTS 0F ELECTRICITY.

APPLICATION FILED SEPT. 29' I915.

1,228,405. Patented June 5,1917.

w five nt MAM 5, 4 Wm UNITED STATES PATENT OFFICE.

WILLIAM H. CHAPMAN, OF PORTLAND, MAINE.

:enocnss AND APPARATUS FOR nnc'rxryme ALTERNATING CURRENTS or ELECTRICITY.

Application filed September 29, 1915. Serial No. 53,198.

To all whom it may concern.

Be it known that I, WILLIAM H. CHAP- MAN, of Portland, in the county of Cumberland and State of Maine, have invented certain new and useful Improvements in Processes and Apparatus for Rectifying Alternating Currents of Electricity, of which the following is a specification.

My invention relates to the production of constant polarity, high tension charges such as are required for X-ray work and for the commercial deposition of solids from smoke.

Hitherto the production of such charges has been attended with great difficulty. The well known influence machines of Holtz, Toepler and Wimshurst give excellent results for these uses if constructed on a large scale with a multiplicity of glass plates to gain the quantity and voltage required. But all of these machines'are too fragile and too easily put out of commission by damp Weather to be of extensive practical use for these purposes.

Transformers on the other hand produce charges that are very stable in all weather conditions and the transformers themselves are naturally rugged machines.

Many devices have therefore come into use to rectify the charges to be obtained from the transformers. All such devices hitherto constructed make use of a suitably timed carrier to pick off the positive side of the alternating wave from a conductor having alternating charges in it. The direct charge so obtained is always of lower voltage than the alternating charge from which it originated and the charges are of a pulsating character.

My invention is designed to provide means for multiplying up the voltage and of maintainin a uniform supply not subject to the pulsations of former rectifiers, thus making the current equivalent in its steadiness to that of a Wimshurst or a Toepler machine while havin the quantity and stability characteristic of a transformer.

My invention consists essentially of delivering the negative ionsof the alternating charge through an intervening air space onto the surface of thin insulating material which forms the dielectric element of a condenser.

The invention is based on the fact which I have discovered that if a sheet of paper is laid down onto the surface of a grounded body of conducting material like metal and a pointed conductor having an alternating Specification of Letters Patent.

Patented June charge of several thousand Volts be brought near the paper but separated therefrom 'b'y an interve'mng air space for an instant as it is in contact with the the paper when moved from the surface of the conductor will show a very high negative charge of many times the voltage of the alternating charge. In fact a voltage of 100,000 volts may readily be produced in this manner by the use of an alternating charge of only 10,000 volts in the pointed conductor and the charge on the paper is invariably negative.

The explanation of this fact may be involved in the known fact that negative ions have a higher velocity than positive ions and more of them will therefore reach a given distant surface than of the positive ions during a single cycle of the alternating exciting charge.

Whatever the explanation may be, this principle has enabled me to construct an eflicient producer of constant polarity high potential charges operative under all weather conditions.

My invention may best be understood by reference to the accompanying drawing in which I have illustrated diagrammatically several different mechanisms by which my invention may be carried out.

Referring to the drawing:

Figure l is a diagram showing the elements of my apparatus in simple form,

Fig. 2 shows an arrangement for collecting the positive electricity,

Fig. 3 shows an arrangement of conductors for efi ecting a uniform distribution of the charge over the surface of the paper,

Fig. 4 is an elevation of a machine using a disk in place of the band used in the other forms shown and Fig. 5 is a section taken on the line as w of Fig. 6%.

In carrying out my invention I make use of a thin sheet of insulating material which is arranged to be brought repeatedly into contact or into close proximity to a conducting body discharging the alternating charge which is to be rectified onto the sheet through a comb pointed conductor whereby the air becomes ionized, the discharge taking place through a gaseous medium while the sheet is in contact with the conducting body. A negative charge of high potential will be generated on the surface of the sheet and is grounded conductor,

collected in the usual manner after the sheet separates from the conducting body.

In the preferable form of my apparatus I make use of a-pair of rolls of conducting material over which runs an endless band of paper or other insulating material.

' Referring to the form shown in Fig. 1, 6 represents a continuous web of thin paper which may be .005 inch in thickness arranged to run over two metal rollers a and I) like a belt over two pulleys.

Comb points or conductors c and d are loon the combs 0 and d.

The rolls which are preferably grounded may be driven by any desired motive power and as the paper travels around it carries negative charges from 0 and d to f and g and the direction of movement is immaterial.

An exciting alternating voltage at c and d of 10,000 will easily maintain a constant direct voltage of 100,000 volts at f and g and the quantity of negative electricity thus supplied is proportional to the surface of the paper presented to the rolls per minute.

If it is desired to produce positive electricity this is easily accomplished by means of the apparatus shown in Fig. 2. a

In this case the comb points f and 9 have extended surfaces or plates f and g located adjacent to the paper; The comb points j and k are located on the opposite-side of the paper from the plates f and g and are connected with each other. The comb points j and k are grou ded and the surfaces f" and g which are c arged with negative electricity induce positive charges in j and is. These positive charges in j and k are deliveredto the paper and are collected by comb points It and i. In this case where positive electricity is to be collected it is necessary to'have the rolls run in a pre-determined direction. When a single comb is used to deliver the negative charge to the paper as it runs over the roll, the charge is greater on some sections than on others, due to the fact that the section of paper that happens to be passing under the points during the positive alternation is receiving little if any charge. A greater uniformity of charge is secured when two or more combs are used and placed some fraction of a cycle apart.

For example, suppose we are using a 60 cycle alternating current to supply the exciting charge to the combs and suppose the paper is arranged to at a speed of 360 inches per second.

Then the paper moves six inches during the time of one cycle of the A. C. charge and if a single comb is used every alternate space. of three inches will receive a maximum negative charge and the intervening spaces a minimum charge. If now we place two combs three inches apart or nine inches apart measured along the eripheral surface of the roll, a greater uni ormity of charge will be secured because every inch of the paper will, during the passage over the roll come under one or the other of the combs during negative alternation of the exciting charge. I I

.In Fig. 3 I show the arrangement of two combs d and d for delivering the charge to the paper.

While the contact of the paper with the conductive surface is most desirable, my

process may becarried out without this contact. 7

Instead of abelt I may use a paper disk and have it run in very close proximity to a solid grounded surface instead of being in actual contact with it as in the forms already shown.

In Figs. 4 and 5 I show an arrangement where a paper disk is made to rotate closely adjacent to a grounded-m etal plate.

Referring to Figs. 4 and 5, Z represents a disk of paper or other insulating material mounted on a shaft a supported on suitable bearings and driven by a belt or other power. A grounded metal plate m of relatively large bulk as compared with the paper disk is set parallel to the disk and as close as possible to it without touching. A conductor 19 having comb points is located on the opposite side of the disk from the grounded metal plate and connected with a source of alternating current preferably of 4,000 volts or more. A conductor 1' having comb points is presented to the disk at a point where it is not backed by any solid material. The conductors r and p are supported by a standard t of insulated material.

The arrangement may be varied if desired by connecting the rolls to the alternating exciting charge while the combs 0 and d are connected with the ground. In this latter case the alternating charge on the rolls acts by induction on the grounded combs and causes them to deliver positive and negative ions to the intervening air.

The negative ions will arrive in greater abundance on the surface of the paper as is the case in the form shown in Fig. 1 and a negative charge will be collected on the collecting conductors as shown in dotted line in Fig. 1.

It is to be understood that while I have described specifically certain forms which my invention may take them are many other forms which may be developed as the principle of the invention comes to be understood and developed for various purposes.

It is understood that in the drawings an alternating source of electricity which consists of discharging said charges in the form of a glow discharge to a body of relatively thin non-conducting material backed by a body of conducting material whereby ions of one sign are delivered upon said thin material, se arating the materials from each-other and finally collecting the resulting charge.

2. The process of rectifying charges from an alternating source of electricity which consists of discharging said char es in the form of a glow discharge to a bo y of relatively thin non-conducting material backed by a body of conducting'material whereby.

ions of one sign are delivered upon said thin material separating the materials from each other and finally collecting the resulting charge from the thin material.

3. The process of rectifying charges from an alternating source of electricity which consists of discharging said charges in the form of a glow discharge to a body of paper, backed by a body of metal, then separating the paper and metal and finally collecting the rectified charge from the paper.

4. In an apparatus for rectifying alternating chargesof electricity the combination of a thin sheet of insulating material and a conducting body so movable with relation to each other that portions of the sheet'will repeatedly approach to a point adjacent to the conducting body and recede therefrom, a conductor having small discharging points or surfaces for delivering the alternating charge to the sheet while the same is adjacent to the conducting body and means for collecting the rectified charge from the sheet after it has receded from the conducting body.

5. In an apparatus for rectifying alternating charges of electricity the combination of a thin sheet of insulating material and a conducting body so movable with relation to each other that portions of the sheet will repeatedly contact with the conducting body and recede therefrom, a conductor having small discharging points or surfaces for delivering the alternate charge to the sheet while the same is in contact with the conducting body and means for collecting the rectified charge from the sheet after it has receded from the conducting body.

(3. In an apparatus for rectifying alternating charges of electricity the combination of a stationary conducting body, a movable sheet of insulatin material rotatin in such a position as to ring portionso its surface repeatedly adjacent to said conducting body, a conductor having small discharge points or surfaces for delivering the alternating charge to the sheet while ad'acent to the conducting body and means or collecting the rectified charge from the sheet when it is separated from the, conducting body.

7. In an apparatus for rectifying alternating charges of electricity the combination of a pair of rolls of conducting material, a thin band of insulating material running over said rolls, a conductor having fine points or surfaces for discharging the alternating charge onto said band while in contact with one of said rolls and means for collecting the rectified charge from said band while out of contact with said rolls.

8. In an apparatus for rectifying alternating charges of electricity the combination of a pair of metal rolls, a paper band running over said rolls, a conductor having fine points or surfaces for discharging the alternating charge onto said band whlle in contact with one of said rolls and means for collectin the rectified charge from said band while out of contact with said rolls.

' 9. In an apparatus for rectifying alternating charges of electricity the combination of a pair of rolls of conducting material, a band of insulating material running over said rolls, a conductor having fine points or surfaces for discharging the alternating charge onto said band while in con tact with one of said rolls, a collecting conductor for collecting the rectified charge from said band, a plate of conducting material connected with said collecting conductor and positioned near said band and a WILLIAM H. CHAPMAN.

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