US2156685A - Electrical relay - Google Patents

Description

May 2, 1939. N. c. SHAW ELECTRICAL RELAY Filed Dec. 30, 1937 2 Sheets-Sheet l N U BSR HIS ATTORNEY May 2 1939. N. c. SHAW ELECTRICAL RELAY 2 Sheets-Sheet 2 Filed Dec. 30, 1937 INVENTOR [V0 C1 Ska w Y E N R O T T A m Patented May 2, 1939 UNITED STATES PATENT OFFICE ELECTRICAL RELAY Noble 0. Shaw,

Penn Township,

Allegheny of Pennsylvania Application December 30, 1937, Serial No. 182,501

15 Claims.

My invention relates to electrical relays, and particularly to relays which are adapted for flashing danger signals on highway-railroad crossings upon the approach of a train.

More particularly, my present invention relates to flasher relays of the type described and claimed in an application for Letters Patent of the United States, Serial No. 182,506, filed by A. W. Fisher and B. Mishelevich, on December 30, 1937, for Electrical relays, and one object of my invention is to provide an improved relay of this type.

Other objects and characteristic features of my invention will appear as the description proceeds.

I shall describe two forms of relays embodying my invention, and shall then point out the novel features thereof in claims.

In the accompanying drawings, Fig. 1 is a view partly in end elevation and partly in section showing one form of relay embodying my invention. Fig. 2 is a view partly in front elevation and partly in section of the relay shown in Fig. 1. Fig. 3 is a top plan view of the relay illustrated in Fig. 1. Fig. 4 is a top plan view with the top plate removed of the relay illustrated in Fig. 1. Figs. 5 and 6 are detail views of parts of the relay shown in the preceding views. Fig. '7 is a fragmentary end view showing a modification of a portion of the relay illustrated in Figs. 1, 2, 3 and 4.

Similar reference characters refer to similar parts in each of the several views.

Referring to the drawings, the reference character A designates an insulating top plate, which top plate supports all of the operating parts of the relay. Suspended from the top plate A by means of hangers l is a cast rectangular frame 2, and journaled at its ends in ball bearings 3 mounted in bearing cups 3a secured to the frame 2 by means of bearing caps 20. is a rockshaft 4. This rockshaft is biased to one position by a compound pendulum P, and is arranged to be oscillated at a predetermined frequency which depends upon the proportioning and adjustment of the parts, by means of a suitable motor device M which I shall describe presently. The bearing cups 3a are preferably constructed in such manner that the bearing opening is eccentric with respect to the outside surface of the cup for a purpose which will appear hereinafter, and are provided with spring washers 6 which enclose and protect the ball bearings from dirt.

The compound pendulum P may have any suitable form, but in the form here shown, this pendulum comprises a cast U-shaped bracket 1 the upwardly extending arms la of which are pinned to the rockshaft 4 intermediate their ends, and are provided at their upper ends with enlarged portions lb to provide the desired mass. A threaded post 1c is secured at its upper end within a boss 1d formed on the underside of the yoke 1c of the bracket 1, and this post carries a counterweight 1] which is mounted eccentrically with respect to the post, and which serves both as a means for regulating the period of oscillation of the rockshaft within certain limits, and also as a means for varying the position to which the rockshaft is biased by means of the pendulum. The counterweight If is arranged to be locked in an adjusted position by means of nuts To which are screwed onto the post lc on opposite sides of the counterweight.

The previously referred to motor device M for oscillating the rockshaft 4 comprises an armature 8 which is pinned to the rockshaft, at one side of the bracket 1, and an electromagnet which 00- operates with the armature 8. This electromagnet may have any preferred construction, but in the form here shown, this electromagnet comprises a winding 9 mounted on a backstrap H) secured to the short arms Ila of L-shaped pole pieces II, the long arms Nb of which extend upwardly past the opposite sides of the armature 8 and are secured to depending lugs 21) formed on the frame 2. One lead 9a of the winding 9 is connected to a terminal post 30 mounted on the top plate A, and the other lead 9?) is connected to a connecting post 32 which is also mounted on the top plate A. The angular disposition of the armature 8 with respect to the rockshaft 4 is such that, when the rockshaft occupies the position to which it is biased by the pendulum P, the

longer axis of the armature will be inclined at an acute angle with the magnetic field which is set up between the pole pieces II when the winding 9 is energized. This acute angle may be varied between relatively large limits, but I have found that the best operating characteristics are obtained for most conditions of operation when this angle is approximately The relay also comprises a plurality of contacts, here shown as six in number and designated by the reference characters I2, I 3, I 4, l5, l6 and II, respectively. These contacts are of the well-known mercury type, and each comprises a pair of electrodes I8 and I9 disposed in an evacuated or gas filled bulb containing a quantity of mercury 20 which flows into or out of engagement with the electrodes to make or break a circuit passing through the electrodes. The contacts l2, l 3 and M1 are mounted in spring clips 2!, 22 and 23, respectively, which are secured to the lower side of the yoke 'le of the bracket 1 as viewed in Fig. l, by means of bolts 24, and the contacts is, it and ii are mounted in spring clips 25, 2S and 2t, respectively, which are secured to the other side of the yoke lie of the bracket 'i' by means of the bolts 26 in such manner that the contacts l2 and 65, the contacts I3 and i5, and the contacts l4 and H are directly opposite each other.

The two contacts l2 and 85 together control the supply of energy to the winding 9 of the motor device M, and to this end the two electrodes is of these contacts are connected together by a jumper ll, while the other electrodes is of these contacts are connected respectively, by means of flexible connectors 12 and t3 and conducting strips @201. and GM, to a terminal post 3! mounted on the top plate, and to the previously described connecting post 32. A source of electromotive force, here shown as a battery Ml is connected with the terminal posts 36 and Si through a switch It will thus be apparent that if the switch 45 is closed, winding 9 will be supplied with current when the contacts l2 and i5 are both closed, but that when either one of these contacts becomes opened due to the motion of the rockshaft, the supply of current to the winding 9 will be interrupted. The position of the rockshaft at which the contacts iii and l5 are adjusted to open will depend upon the angular position of the armature with respect to the rockshaft and the proportioning of the parts, but when the armature is secured to the rockshaft in the position shown, the contact l2 will preferably be so adjusted that it will break the operating circuit when the rockshaft swings approximately 7 in a clockwise direction, as viewed in Fig. 1, from the position to which it is biased by the pendulum, while the contact i5 will preferably be adjusted so that it will break the operating circuit when the rockshaft swings approximately 10 in a counterclockwise direction as viewed in Fig. 1 from the posi tion to which it is biased by the pendulum P. It should be particularly pointed out, however, that satisfactory operation of the relay can be obtained with a variation of several degrees in either direction from the above described adjustment of the contacts.

The remaining contacts l3, l4, l6 and ll may be 'used for controlling the flashing light of a highway crossing signal or any other signaling device, and are so adjusted that when the rockshaft i occupies the position to which it is biased by the pendulum P, these contacts will all be open, but that oscillation of the rockshaft through its intended amplitude will cause these contacts to become alternately opened and closed. To facilitate making electrical connections with these contacts, the two electrodes IQ of the contacts l3 and it are connected together by a jumper Q8, and are also connected to a terminal post 3 i mounted on the top plate A, by means of a flexible connector t"! and a conducting strip did, while the remaining electrodes [8 of these contacts are connected by means of flexible conductors 4S and and conducting strips 48a and Mia to terminal posts 35 and 33, respectively, mounted on the top plate A. In a similar manner, the two electrodes l8 of the contacts 54 and ll are connected together by a jumper 59 and to a terminal post 3'5 mounted on the top plate A by means of a flexible connector 5| and a conductingstrip 5w, while the electrodes [9 of these latter contacts are connected by means of flexible conductors 52 and 53 and conducting strips 52a and 53a to terminal posts 38 and 36 mounted on the top plate A.

It is desirable in order to minimize the stresses in the fiexible-conductors and the amount of torque required to flex them that these conductors should flex as little and as uniformly throughout their lengths as possible, and to this end I provide means for clamping the conductors adjacent their lower ends in positions close to the rockshaft. As here shown, these means comprise an insulating member 55 (see Fig. 5) which straddles the rockshaft t between the arms la of the bracket 1, and which is secured at its ends by means of machine screws 56 to inwardly extending lugs 'lh provided on the arms la. The member 55 is provided in its opposite sides with spaced notches ill which receive the flexible conductors 62, Q3, 58, 49, 4'5, M, 52 and 53, and with studs 58 and 59 by means of which clamping members fill (see Fig. 6) having projections 6011 which extend into the notches and grip the conductors are secured to the opposite sides of the member 55. These means also comprise insulating strips provided with holes through which the conductors extend, and which strips control both the manner in which the con-- ductors flex and the spacing between the conductors. It should be noted that the members 55 and til in addition to controlling the manner of flexing of the flexible conductors serve further as a means for preventing these members from coming into contact with any of the metal parts of the relay, thereby eliminating the possibility of short circuits.

Two metal stops 62 are secured to the opposite sides of the frame 2 directly opposite the one arm Id of the bracket 7, and these stops cooperate with the enlarged portion lb of this arm to limit the extreme position to which the rockshaft 4 is free to rotate.

With the relay constructed in the manner thus far described, when the switch ie-5 is open, as shown in the drawings, so that the winding 9 of the electromagnet is deenergized, the rockshaft d will occupy the position to which it is biased by the pendulum P, and under these conditions the contacts l2 and Iii will be closed, but the contacts l3, it, it and El will all be open. When, however, the switch 45 is closed, current will flow from battery i through switch 45, terminal post 31?, lead wire 91.! of winding 9, winding 53, lead wire 9b, connecting post 32, conducting strip eta, flexible connector 43, contact l5, jumper ll, contact 52, flexible connector 42, conducting strip 42a, and terminal post 3! back to battery M. The current in winding 9 will, of course, set up a magnetic field between the pole pieces H of the electromagnet, which field will cause the armature to turn in a clockwise direction as viewed in Fig. l in order to assume a position of minimum reluctance. This rotation of the armature will, of course, be transmitted to the rockshaft, and as soon as the rockshaft has been rotated to the position in which the contact i2 opens, winding 9 will become deenergized and will thus remove the torque tending to rotate the armature, but the shaft and armature will continue their motion beyond this position due to the momentum of the parts. After this momentum of the parts has been spent, however, the shaft will start to rotate in the opposite direction due to the action of gravity on the pendulum, and as soon as the pendulum returns to the position in which the contact 12 becomes closed, winding 9 will again become energized and will cause a retarding force to be exerted on the armature. This retarding force will be small, however, because the air gaps between the pole pieces and the armature will then be increasing rapidly, and also because as soon as the armature has rotated to the position in which the contact I 5 opens, winding 9 will again become deenergized. As a result, the rockshaft will swing in a counterclockwise direction to a position which is displaced from the position to which it is biased by the pendulum only a few degrees less than the previous clockwise displacement. As soon as the energy of the rotating parts has been spent in the counterclockwise direction, the action of gravity on the pendulum will cause a clockwise torque to be again exerted on the shaft, and as soon as the shaft is rotated in a clockwise direction to the position in which contact l5 closes, winding 9 will again become energized and will subsequently remain energized until therockshaft is swung to the position in which the contact I2 opens. The energization of winding 9 will cause a pulse of energy to be exerted on the rockshaft which assists the clockwise rotation of the rockshaft, and the parts are so proportioned that this pulse at normal operating voltages will be sufficient to supply to the rockshaft the loss of energy during each cycle caused by friction, and the retarding force of the magnet during the previous counterclockwise rotation of the rockshaft. It follows, therefore, that when switch 45 is closed the rockshaft will oscillate at substantially the natural period of the pendulum. This oscillation will cause the contacts l3, I4, I6 and I! to alternately open and close in an obvious manner.

The alternate opening and closing of the contacts l3, l4, l6 and I! may be utilized for controlling the fiashing lights of a highway crossing signal of the well-known type or for any other desired purpose. When the contacts are used to control the flashing lights of a highway crossing signal, it is sometimes desirable to effect the alternate flashing of the lights by alternately short circuiting the lamps, and when this is the case, it is preferable that the lamp control contacts l3, I4, I 6 and I! should be so arranged that when the relay is deenergized, the lamp contacts on one side of the rockshaft will be closed while those on the other side of the rockshaft will be open, but that when the relay is operating, there will not be any time during each oscillation of the rockshaft when the lamp contacts on both sides of the rockshaft are simultaneously closed. This result can be obtained by adjusting the contacts unsymmetrically with respect to the pendulum biased position of the rockshaft, but I have found that when the contacts are adjusted in this manner, the unsymmetrical contact adjustment tends to produce some difference in the timing of the contacts on opposite sides of the rockshaft. It is desirable that the timing of the contacts on opposite sides of the rockshaft should be uniform, and in accordance with one form of my present invention, I accomplish even contact timing and cause the contacts to be closed on one side of the rockshaft when the relay is deenergized without interfering with the symmetrical adjustment of the contacts as described hereinbefor'e', by means which I shall now describe.

As here illustrated, these means comprise a permanent magnet 63 which is adjustably supported above the armature 8 in such a position that when the relay is deenergized, this magnet will produce a counterclockwise torque, as viewed in Fig. 1, on the armature, of such magnitude that this torque will rotate the rockshaft 4 away from the position to which it is biased by the pendulum P just far enough to cause the contacts l3 and I4 to become closed. The permanent magnet may be supported in the desired position in any desired manner, but, as here shown, it is clamped to the underside of a supporting plate 64 of non-magnetizable material such as brass, by means of a non-magnetic clamping plate 65, and a plurality of screws 56. The screws 66 extend through spaced clearance holes provided in the clamping plate and are screwed into tapped holes 61 formed in the supporting plate.

At its opposite ends, the clamping plate 64 is provided with slotted lugs 68 which receive vertical supporting posts 69 with some clearance, and screwed onto the posts 69 on opposite sides of the lugs 68 are nuts 10 by means of which the clamping plate may be secured in different vertical positions with respect to the armature. The lower ends of the posts 69 are screwed through tapped holes provided in the enlarged heads of horizontally extending bolts H, and these latter bolts, in turn, are adjustably screwed through tapped holes provided in two of the hangers I, and are locked in adjusted positions by means of jam nuts 72.

I have found that when the permanent magnet is adjusted to produce the necessary torque to hold the contacts l3 and I4 closed when the relay is deenergized, it tends to balance the bias produced by the motor M when the relay is in operation, and that this balance is such that a stroke of practically the same length in either direction from the position to which the rockshaft is biased by the pendulum P alone, results, thus producing even contact timing. I have also found that under ordinary conditions the permanent magnet has only a very small effect on the speed of operation of therelay, there being a slight decrease in speed which decrease can be readily compensated for by adjusting the counterweight 7].

Referring now to Fig. '7, I have here shown a means which may be employed to obtain even contact timing when an unsymmetrical contact adjustment is employed to cause the contacts on one side of the rockshaft to be closed and those on the other side of the rockshaft to be open in the deenergized position of the relay. This means, in the embodiment illustrated, com-- prises a spring which is arranged to resist counterclockwise movement of the armature, as viewed in Fig. 1, from the position to which it is biased by the pendulum P. This spring is secured at one end to a threaded post 16 which is adjustably mounted in a support 11 secured by means of bolts 18 to the upper end of the one pole piece I l of the motor device M, and this spring cooperates at its inner end with an arm 19 secured to the armature. The spring is so adjusted that it will engage the arm 19 when the armature has rotated a short distance, for example 2 or 3, in a counterclockwise direction from the position to which it is biased by the pendulum P, and the contacts 13 and I4 are so adjusted that these contacts will be closed and the contacts I6 and I! will be open, when the armature occupies its pendulum biased position. The spring tends to shorten the stroke of the rockshaft in a counterclockwise direction, as viewed in Fig. 1, and it stores up energy which is given up to the armature in. the subsequent clockwise movement, thereby aiding the magnetic pull to produce a longer stroke from the deenergized position in this direction.

While I have shown the spring as a coil spring, it may be made in any convenient form as desired, and with or without a stop for initial pressure, depending upon the operating characteristics desired.

The operating mechanism of the relay may all be enclosed within a suitable casing 88 which in the form here shown is a box-like metal casting, three of the sides of which are provided with glass windows 8! through which the operating mechanism may be viewed. The casing is held in position against the underside of the top plate by means of screws 82 which pass through clearance holes provided in the bottom of the casing, and are screwed into tapped holes provided in the lower ends 01" depending legs 83, the upper ends of which are secured to the underside of the frame 2.

It should be pointed out that a relay embodying my invention can be made to oscillate without the use of the contact 15, but that this contact materially aids in controlling the stroke of the pendulum, and thereby insures smooth operation of the relay. This is due to the fact that this contact is closed over a rather wide angle of displacement of the shaft from its biased position, and this contact therefore maintains the control circuit closed through a longer portion of the total time of each operation, and in the proper section of the stroke, than would be possible with only one control contact, which fact helps in giving a satisfactorily long stroke, and in easing up the stroke in each direction. The armature passes through the energized position at a greater speed at higher voltages, and there is some cornpensation due to the contact l6 tending to limit the total stroke, although, of course, there is an increase in the length of the stroke in all cases with increases in voltage.

It should also be pointed out that since the bearing cups are eccentric, by rotating these bearing cups the rockshaft 4 can be moved laterally to positions in which the armature is properly centered between the pole pieces i I, thus providing an adjustment to take care of minor variations in manufacture.

It should still further be pointed out that the adjustment of the position of the operating contacts i2 and i is very important from the standpoint of emcient power consumption and proper and eflicient operation of the relay. The importance of the adjustment and arrangement of these contacts can be readily understood from the fact that starting voltage, pendulum stroke, power consumption, uniformity of timing and uniformity of swing, etc. depends upon this adjustment and arrangement.

One advantage of a relay embodying my invention is that the contacts are capable of carrying large current over a very large number of operations of the relay without deterioration or without material change in resistance.

Another advantage of a relay embodying my invention is that the contacts are uniformly operated thus providing uniform flashing of the light signals controlled by the relay.

A further advantage of a relay embodying my invention is that inasmuch as there are no parts subject to impact the life of the relay is exceptionally long.

Although I have herein shown and described only two forms of electrical relays embodying my invention, it is understood that various changes and modifications may be made therein within the scope of the appended claims without departing from the spirit and scope of my invention.

Having thus described my invention, what I claim is:

l. A relay comprising a rockshaft, a pendulum secured to said rockshaft, means for at times oscillating said rockshaft at substantially the natural period of said pendulum, a contact operated by the oscillation of said rockshaft and adjusted to occupy one position when said rockshait occupies the position to which it is biased by said pendulum, and magnetic means for exerting a force on said rockshaft which is efiective when said rockshaft is not oscillating to rotate said rockshaft to a position in which said contact occupies another position.

2. A relay comprising a rockshaft, a pendulum secured to said rockshaft, a first contact controlled in accordance with the position of said rockshaft, electromagnetic means controlled by said contact for oscillating said rockshaft at substantially the natural period of said pendulum, a second contact controlled by said rockshaft and arranged to occupy one position when said rockshaft occupies the position to which it is biased by said pendulum, and magnetic means for exerting a force on said rockshaft which is effective when said rockshait is not oscillating to rotate said rockshaft to a position in which said second contact occupies another position but which is ineifective when said rockshaft is oscillating to materially change its period of oscillation.

3. A relay comprising a rockshaft, a pendulum secured to said rockshaft, a first contact operated by said rockshaft, an armature secured to said rockshaft, an electromagnet cooperating with said armature and controlled by said first contact for oscillating said rockshaft at substantially the natural period of said pendulum, magnetic means effective when said electromagnet is deenergized for exerting a force on said rockshaft which moves said rockshaft away from the position to which it is biased by said pendulum, and other contacts controlled by the oscillation of said rockshaft.

4. A relay comprising a rockshaft, a pendulum secured to said rockshaft, means for at times oscillating said rockshaft at substantially the natural period of said pendulum, means effective when said rockshaft is not oscillating for exerting a force on said rockshaft which moves said rockshaft away from the position to which it is biased by said pendulum, and. contacts controlled by said rockshaft.

5. A relay comprising a rockshaft, a pendulum secured to said rockshaft, means for at times oscillating said rockshaft at substantially the natural period of said pendulum, means effective when said rockshaft is not oscillating for exerting a force on said rockshaft which moves said rockshaft away from the position to which it is biased by said pendulum, and a contact operated by said rockshait and adjusted to occupy one position when said rockshaft occupies the position to which it is biased by said pendulum and another position when said rockshaft occupies the position to which it is moved by said second mentioned means.

6. A relay comprising a rockshaft, a pendulum secured to said rockshaft, means for at times oscillating said rockshaft at substantially the natural period of said pendulum, means effective when said rockshaft is not oscillating for exerting a force on said rockshaft which moves said rockshaft away from the position to which it is biased by said pendulum, and a contact operated by said rockshaft in such manner that said contact will become alternately opened and closed for substantially uniform time intervals when said rockshaft is oscillating but will be open when said rockshaft occupies the position to which it is biased by said pendulum and will be closed when said rockshaft occupies the position to which it is moved by said means.

7. A relay comprising a rocksha-ft, a pendulum secured to said rockshaft, a first contact operated by said rockshaft, an armature secured to said rockshaft, an electromagnet cooperating with said armature and controlled by said first contact for oscillating said rockshaft at substantially the natural period of said pendulum, magnetic means eifective when said electromagnet is deenergized for exerting a force on said rockshaft which moves said rockshaft away from the position to which it is biased by said pendulum, and other contacts controlled by said rockshaft in such manner that said contacts will be alternately opened and closed for substantially equal time intervals when said rockshaft is oscillating but that some of said contacts will be closed and others opened when said electromagnet is deenergized.

8. A relay comprising a rockshaft, a pendulum, means for oscillating said rockshaft at substantially the natural period of said pendulum, contacts controlled by said rocks'haft and arranged in such manner that said contacts will become alternately opened and. closed when said rockshaft is oscillating but that some of said contacts will be closed and others opened when said rockshaft occupies the position to which it is biased by said pendulum, and means for con trolling the distance said rockshaft rotates in both directions from the position to which it is biased by said pendulum to cause said contacts to become alternately opened and closed for substantially equal time intervals.

9. A relay comprising a rockshaft, a pendulum secured to said rockshaft, a first contact operated by said rockshaft, an armature secured to said rockshaft, an electromagnet cooperating with said armature and controlled by said first contact for oscillating said rockshait at substantially the natural period of said pendulum, a second magnet associated with said armature and effective when said electromagnet is deenergized for exerting a force on said rockshaft which moves said rockshaft away from the position to which it is biased by said pendulum, and other contacts controlled by said rockshaft.

10. A relay comprising a rockshaft, a pendulum secured to said rockshaft, a first contact operated by said rockshaft, an armature secured to said rockshaft, an electromagnet cooperating with said armature and controlled by said first contact for oscillating said rocks'haft at substantially the natural period of said pendulum, a permanent magnet associated with said armature and effective when said electromagnet is deenergized for exerting a force on said rockshaft which moves said rockshaft away from the position to which it is biased by said pendulum, and other contacts controlled by said rockshaft.

11. A relay comprising an electromagnet provided with pole pieces, a movable armature mounted to rotate between said pole pieces, a pendulum operatively connected with said armature, a permanent magnet associated with said armature and effective when said electromagnet is deenergized for exerting a force on said armature which moves said pendulum away from its gravity biased position, a first tube secured to said pendulum, fiuid means within said tube adapted when the pendulum is swung to one position to close a circuit for said magnet and when the tube is swung to another position to open the circuit for said magnet, and a second tube carried by said pendulum and containing a pair of electrodes and a fluid which flows into and out of engagement with said electrodes to alternately open and close a contact in response to swinging movement of said pendulum between two extreme positions, said second tube being secured to said pendulum in such a position that said fluid will not engage said electrodes when said pendulum occupies its gravity biased position but will engage said electrodes when it is moved away from its gravity biased position by said permanent magnet.

12. A relay comprising an electromagnet provided with pole pieces, a movable armature mounted to rotate between said pole pieces, a pendulum operatively connected with said armature, a permanent magnet associated with said armature and efiective when said electromagnet is deenergized for exerting a force on said armature which moves said pendulum away from its gravity biased position, means for energizing said electromagnet in a manner to cause said pendulum to oscillate at substantially its natural period, and a tube carried by said pendulum and containing a pair of electrodes and a fluid which alternately flows into and out of engagement with said electrodes in response to oscillation of said pendulum, said tube being secured to said pendulum in such a position that said fluid will not engage said electrodes when said pendulum occupies its gravity biased position but will engage said electrodes when it is moved away from its gravity biased position by said permanent magnet.

13. A relay comprising an electromagnet provided with pole pieces, a movable armature mounted to rotate between said pole pieces, a pendulum operatively connected with said armature, means for energizing said electromagnet in a manner to cause said pendulum to oscillate at substantially its natural period, a pair of mercury contacts secured to said pendulum on opposite sides of its: pivotal axis and adjusted to both be open when said pendulum occupies its gravity biased position, and a permanent magnet associated with said armature and eifective when said electromagnet is deenergized to exert a force on said armature which rotates it away from its gravity biased position to a position in which one of said contacts becomes closed.

14. A relay comprising an electromagnet provided with pole pieces, a movable armature mounted to rotate between said pole pieces, a pendulum operatively connected with said armature, means for energizing said electromagnet in a manner to cause said pendulum to oscillate at substantially its natural period, mercury contacts secured to said pendulum on opposite sides of its pivotal axis and adjusted in such manner that one of said contacts will be open and the other will be closed when said pendulum occupies its gravity biased position, and spring means cooperating with said pendulum to resist rotation of said pendulum in the direction to close the normally closed contact.

15. A relay comprising an electromagnet provided with pole pieces, a movable armature mounted to rotate between said pole pieces, a pendulum operatively connected with said armature, means for energizing said electromagnet in a manner to cause said pendulum to oscillate at substantially its natural period, contacts secured to said pendulum on opposite sides of its pivotal axis and adjusted in such manner that one of said contacts is open and the other is closed when said pendulum occupies its gravity biased position, and spring means cooperating with said pendulum to shorten its stroke in one direction and lengthen it in the other to cause said two contacts to become alternately opened and closed for substantially equal time intervals when said 10 pendulum is oscillating.

NOBLE C. SHAW.

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