US664086A - Regulator for electrically-actuated air-compressors. - Google Patents

Description

No. 664,086 Patented D80. 18, I900.

E. 'm. HEWLETT.

REGULATOR FOR ELEGTRIGALLY ACTUATED AIR GOMPRESSORS. (Application filed Nov. 7, 1898.)

(No Model.)

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UNITED STATES PATENT Orrics.

EDWARD M. HEWLFTT, OF SCHENECTADY, NEXV YORK, ASSIGNOR TO THE GENERAL ELECTRIC COMPANY, OF NEIV YORK.

REGULATOR FOR ELECTRICALLY-ACTUATED AlR-COMPRESSORS.

SPECIFICATION forming part of Letters Patent No. 664.086, dated December 18, 1900.

Application filed November '7, 1898. Serial No. 695,669. (No model.)

To aZZ whom it may concern:

Be it known that I, EDWARD M. HEWLETT, a citizen of the United States, residing at Schenectady, in the county of Schenectady and State of New York, have invented certain new and useful Improvements in Regulators for Electrically- Operated Air- Compressors, (Case No. 632,) of which the following is a specification.

My invention relates to electrically-operated aircompressors or similar machines in which fluid is pumped into a reservoir until a certain pressure is reached, at which time the operation of the electric motor is interrupted, usually by opening its circuit. These devices have maximum and minimum operating positions, the motor being thrown into action in the lower position or when the pressure reaches a certain determinate lower limit and its action being suspended when the upper limit is reached. Several different types have been devised, the problem of starting and stopping these devices being quite a different one from those involved in the use of other motive powers. One type with which I am familiar might be called an air-relay devicethat is, a small valve is actuated by the regulator and by its operation works a larger valve, which in turn admits the full pressure to actuate a switch of one form or another. The general type has been unsatisfactory because of the leakage in the air apparatus and because of the difficulty in keeping it in order and its general complication. There have been other types involving their own difficulties, to which it is unnecessary to refer. Some, at least, of these difficulties are overcome by the apparatus of my invention, which has in practice operated successfully. It consists in general in the form herein illustrated of a spring with a switch attached thereto, the switch having two positions of contact, in one of which, corresponding to the inferior pressure limit, it closes the circuit of the motor through a magnet-coil in the seriescircuit. The magnet-coil operates a shunting-contact through which the main current is delivered to the motor, the operation of the device being thus to shunt the starting-contact practically immediately after it has starting of the series-relay magnet, as I prefer to call it, and is carried through the magnetcoil in opposite directions, so that the two parts of the coil act differentially and the magnet-core is deenergized. A suitable spring then opens the main circuit of the motor. I also prefer to provide a blow-outmagnet for the main contacts, so that they may not be subjected to any damage from arcing. It is manifest that this arrangement differs from many preceding devices in that no attempt is made to use a shunt-coil. The motors which are commonly employed in this work are five-hundred-volt machines, since these devices are particularly useful in rail way-work and the winding of the shunt-coil for such potentials is expensive and the coil itself is liable to accident. I therefore avoid the difficulty by using the series coil in the way pointed out and avoid the difficulty of the large current required to start the motor by the relay action which I have already described in brief and which will be better un; derstood from the accompanying specification.

The scope of my invention will be pointed out in the attached claims.

The drawings show an apparatus embodying myinvention particularly adapted for furnishing the compressed air to operate an airbrake system.

Figure 1 is a front elevation; Fig. 2, a section on the line 2 2 of Fig. 1, showing some of the parts in side elevation; and Fig. 3 is a diagram of the circuits.

In the drawings, A is the frame of the ap- 9o interposed and is held in place by the screws B. A spring E is provided, and a plate D at the base of the spring reciprocates under the variations of pressure in such a way as to com- 100 K series-relay coil already referred to.

press the spring as the pressure rises, the upper limit of the plates motion being determined by the shoulder (Z on the case of the box containing the spring. A second plate D at the top of the spring is held in place by the screws 1) D by the adjustment of which the tension of the spring may be regulated. A core F, passing through the spring, is fastened to the plate D and is pivoted atf to an arm G. This arm is pivoted at g to a suitable part of the frame and carries a piece of insulation g, in which is set a strip of metal carrying the contact G, which reciprocates between the upper and lower contacts H H. These contacts are preferably of carbon, while the contact G is of metal, so that there will be no difficulty from arcing. In practice, as will be pointed out farther on, the circuit is not opened at these contacts in such a way as to cause any serious tendency to are.

M is the armature of a coil 1, which is the The armature M carries a pair of contacts K K, which are connected by a bar K and are secured to the piece of insulation M. A spring an opposes the motion of the armature. The contacts K K and the bar K bridge the contacts K K in the series circuit. A blow-out-magnet coilI energizes the pole-piece P, the magnetic circuit being so arranged as to blow the arcs out at the sides of the apparatus through suitable chutes L L, provided for this purpose, which chutes act to restrain the are and prevent damage to the metallic portions of the apparatus. The chutes, as is well understood, should be formed of some refractory insulating material, such as compressed fiber.

The circuits of the apparatus will be best understood from Fig. 3. In this figure, N is the motor, 0 is the compressor operated by the motor, P is the main reservoir, and P is the train-pipe, from which leads the pipe 0 to the apparatus A, already described. In the illustrated position the motor is just starting.

Current enters from the trolley T and passes to the lower contact H, the circuit of the upper contact H being open at this time. From here it passes to the contact G, through the magnet-coil l, and by the lead directly to the motor N. As the current thus passes through the coil 1, the armature M is attracted and closes the circuit of the contacts K K. The current then passes by these con tacts through the blow-out-magnet coil 1 and through part only of the coil 1 to the contact H, and thus directly to the motor, a part of the coil being sufficient to hold the armature attracted after the entire winding has overcome the increased reluctance due to the wide air-gaps when the armature is in the position shown in dotted lines. The contact G, assuming that it still remains touching the contact H, is thus practically short circuited, so that only a very small amount of current will pass through it, and it will be seen that the passage through it of the starting current to the motor, which,

if continuous or enduring for any length of time, would be destructive, is attended with no risk. This is the operation at starting. It manifestly occurs as soon as the contact G touches the contact H. When, however, the superior limit of pressure is approximated, the contact G rises until it touches the contact 1-1. It will be seen, as already indicated, that as the contact G moves from the contact H there is practically no current in its circuit, the armature M having shunted the current across the contacts K K, so that practically no are forms. When the contact G touches the contact H, a new circuit is established, the two halves of the coil I being now thrown in multiple and the current passing through them in opposite directions, so that the magnet is killed and the spring on (see Fig. 2) opens the circuit of the contacts K K by withdrawing the armature M. The circuit of the trolley is thus opened and the blow-out magnet 1 takes care of the are at these contacts, which, it will be seen, have a considerable range of movement. The contacts K have a wiping motion over the contacts K, so that they are kept clean and free.

In practice the apparatus has been found to operate successfully and to avoid the difficulties experienced with other devices with which I am acquainted. It is simple, substantial, and of moderate cost, there being no complication of circuits, and the expensive and unreliable shunt-coil is avoided in its construction.

What I claim as new, and desire to secure by Letters Patent of the United States, is-

1. In a fluid-pressLire-operated controller for an electric motor, the combination of a switch having two circuit-closing positions, means for causing the switch to assume one or the other position when the pressure reaches its superior and inferior limits, respectively, means for shunting the switch by a circuit of low resistance when in one position, and means for opening the shunt when the switch reaches the second position.

2. The combination in a regulator for an electrically actuated air pump, of a diaphragm actuated by the air-pressure against an opposing force, a switch the position of which is determined by the resultant of the two opposing forces, contacts for the switch corresponding respectively to the opening and closing of the motor-circuit, a relay in circuit with the motor-closing contact of the switch, and a shunt around the switch operated by the relay.

The combination in a regulator for an electrically actuated air pump, of a diaphragm actuated by the air-pressure against a spring, a switch the position of which is determined by the resultant of the two opposing forces, contacts for the switch correspond ing respectively to the opening and closing of the motor-circuit, a relay in circuit with the motor-closing contact of th switch, and connections operated by the other contact of the switch fordeenergizing the relay-magnet and opening the circuit.

4. The ml 'nation of a switch of moderate or small capacity with a shunt of large current capacity around its terminals, a contact corresponding to the inferior-pressure limit of a fluid-pressure system, which closes the motor-circuit through the switch, a relay device operated by the closing of the circuit for closing the shunt, a pressure-responsive device for opening the circuit at the switch as the pressure rises, thus leaving the shunt the only path to the motor, and meansin circuit with the other point of the switch corresponding to the superior-pressure limit, for opening the shunt when the switch makes the latter contact.

5. The combination of a two-point switch, an electromagnet'in circuit with one point of the switch, a shunt around the switch opened and closed by the action of the electromagnet, a lead from one of the contacts of the shunt to an intermediate point of the electromagnet-winding, and leads from the other point of the switch and its moving contact to the ends of the electromagnet-winding; whereby when the switch touches one point, a shunt is closed around its own contacts by the action of the magnet, and when it touches the other point, the magnet-coil acts differentially to deenergize the magnet and open the circuit.

6. In a controlling device for an electric motor driving an air-pump, the combination of a switch, a pressure-responsive device actuating the switch, a coil in series with the cont-act touched by the switch at the inferior limit of pressure, an armature operated by the coil, and contacts on the armature for shunting the switch as soon as current passes.

7. An antisparking device fora switch, comprising a shunt-circuit around the switch-contacts controlled by a coil in series with the contacts, said shunt-circuit including an armature controlled by said coil, sparloabsorbing contacts controlled by the armature, and means for holding said contacts closed until the switch-contacts have been ruptured, whereby the spark is absorbed by the auxiliary contacts.

3. The combination with a two-point switch, of a shunt in parallel to its movable and one of its fixed contacts, said shunt including auxiliary contacts of large current-carrying capacity, a coil controlling the closure of the shunt when the circuit is completed through the switch-contacts, and means for demagnetizing said coil when the movable switch-contact engages the other fixed contact.

9. As a means for starting an electric motor, the combination of a switch in the motorcircuit, a path of greater current capacity shunting the switch, and a quickly-responsive device operated by the completion of the m otor-circuit for closing the shunt as soon as the switch closes.

10. The combination of a switch of moderate or small size, with a shunt of large capacity around its terminals, and an electromagnet in the switch-circuit provided with a quickly-responsive armature for closing the shunt when the switch-contacts touch.

11. The combination of a two-pointswitch, a normally open shunt around the switch bridging its contacts, an electromagnet for closing the shunt actuated on closing the switch at one of its contacts, and means for opening the circuit when the switch engages its other contact.

12. The combination of a two-point switch, a shunt around the switch bridging its contact-s, an electromagnet in circuit with one point of the switch for closing the shunt, and means for passing current through the magnet-coil differentially when the switch touches the other point, thus opening the circuit.

13. In an electric switch mechanism, a contact operated by variations in fluid-pressure to close a circuit, a coil energized by said circuit, and a main switch controlling said coil.

14:. In an electric switch mechanism, a contact operated by variations in fluid-pressure to close a circuit, a coil energized by said circuit, a main switch controlling said coil and in shunt to the contact, and means for deenergizing said coil responsive to variations in the tiuid-pressure.

15. In an electric switch mechanism, a contact operated by variations in fluid-pressure to close a circuit, a coil energized by said circuit, a main switch controlled by said coil (and in shunt to the contact), and means for deenergizing said coil responsive to variations in the iiuid-pressu re, and a blow-out magnet for the switch.

In witness whereof I have hereunto set my hand this 5th day of November, 1898.

ED WVARD M. HEWVLETT.

Witnesses:

B. B. HULL, M. H. EMERSON.

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