US2214599A - Inductor relay - Google Patents
Inductor relay Download PDFInfo
- Publication number
- US2214599A US2214599A US196938A US19693838A US2214599A US 2214599 A US2214599 A US 2214599A US 196938 A US196938 A US 196938A US 19693838 A US19693838 A US 19693838A US 2214599 A US2214599 A US 2214599A
- Authority
- US
- United States
- Prior art keywords
- arms
- magnetizable
- arm
- relay
- contact members
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Lifetime
Links
Images
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B66—HOISTING; LIFTING; HAULING
- B66B—ELEVATORS; ESCALATORS OR MOVING WALKWAYS
- B66B1/00—Control systems of elevators in general
- B66B1/34—Details, e.g. call counting devices, data transmission from car to control system, devices giving information to the control system
- B66B1/46—Adaptations of switches or switchgear
- B66B1/50—Adaptations of switches or switchgear with operating or control mechanisms mounted in the car or cage or in the lift well or hoistway
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01H—ELECTRIC SWITCHES; RELAYS; SELECTORS; EMERGENCY PROTECTIVE DEVICES
- H01H50/00—Details of electromagnetic relays
- H01H50/54—Contact arrangements
- H01H50/62—Co-operating movable contacts operated by separate electrical actuating means
Definitions
- Our invention relates to inductor relays such as are frequently utilized in elevator systems for controiling the operation of their cars, hatchway doors, etc.
- Fig. 3 is a View in iront elevation of the switching part of the inductor relay shown in Fig. 2 with the switching arms in their actuated position, broken lines being used to show them in their closed position and with the cover plate 10 removed;
- the relays may be utilized in systems for decelerating and stopping the car at iioors.
- the relays may be mounted on the car and have arms biased to unoperated positions by springs and the operators for the arms may be mounted on the walls of the hatchway.
- An inductor relay system in which the relays are mounted on the car and the operators on the wall of the hatchway is described in Patent 1,884,446, issued October 25, 1932 to Westinghouse Electric Elevator Company and reference may be had to thatpatent if more information regarding such a system is desired.
- the contact members such ill, 28 and 29 on the relay may be so mounted that they will be in either a closed position or an open position when the relay is ener-
- the trailing ngers will cause the arr-ns il and iii to move out of their operated position as the car leaves the floor and Will thereby provide for a safe operation of the contact members.
- An energizer for an inductor relay comprising a magnetizable fin of greater length than width, a non-magnetizable nger mounted on one end of the magnetizable fin with its free end 4extending into a plane beyond the plane of the side surface of the magnetizab'le nn, and a mounting plate for supporting the iin.
Landscapes
- Engineering & Computer Science (AREA)
- Automation & Control Theory (AREA)
- Physics & Mathematics (AREA)
- Electromagnetism (AREA)
- Computer Networks & Wireless Communication (AREA)
- Elevator Control (AREA)
Description
3 Sheets-Sheet 1 I Ir..
INDUCTOR RELAY Filed March 19, 1938 H W. WILLIAMS ET AL.
Sept. l0, 1940.
mma n ma WM5, TT. A @QB uw m WITNESSESI Sept. l0, 1940. HA w. WILLIAMS Er AL 2,214,599
` INDUcToR RELAY Filed March .19., 1938 3 Sheets-Sheet 2 WITNESSES:
SPt- 10, 1940. H. w. 'WILLIAMS ET AL 2,214,599
INVENITOR Haro/d W W//ams awa Oiga/cz /L/ a m ATTEY Patented Sept. 10, 1940 UNITED STATES PATENT OFFICE INDUCTOR RELAY Application March 19, 1938, Serial No. 196,938
Claims.
Our invention relates to inductor relays such as are frequently utilized in elevator systems for controiling the operation of their cars, hatchway doors, etc.
5 Where inductor relays of this kind are used for controlling the circuits of the hatchway door motors, one relay is usually mounted on the hatchway wall at each hatchway door and in position to be actuated by an energizer carried on the car when the car makes a stop at that door. Each relay comprises a plurality of contact members and a pair of magnetizable switching arms vfor opening and closing the contact members. The arms are pivotally mounted so the force of gravity will cause them to open the contact members when they are not under the iniuence of the energizer on the car. The energizer comprises a magnetizable member and a coil for energizing it. When the car makes a 53"" stop at a floor with the energizer adjacent to the relay, the coil is energized to induce a magnetic circuit through the energizer and the switching arms to magnetically move the arms intotheir i operated position, thereby closing the contact members.
When the coil is deenergized or the energizing member is moved away from the switching arms, gravity or biasing springs cause the switching arms to return the Contact members to their w normal open position.
In actual practice, it is found that the contact members oi an inductor relay will freeze or stick at times and remain closed or the arms will y fail to return to their unoperated position after the car moves the energizer away from the relay. When this happens, it causes trouble in the control circuit with which the Contact members of the relay are connected.
Hence, it is an object of our invention to proi 40 vide means for positively freeing and opening the closed Contact members of inductor relays after their energizers are deenergized and moved away from their switching arms to thereby insure accurate operation of the control circuits in which the relays are connected.
It is also an object of our invention to provide inductor relays and energizers therefor of more simple and durable construction than have been produced heretofore.
50 Other objects will be apparent from the following description taken in conjunction with the accompanying drawings, in which:
Figure 1 is an illustration of a plurality of inductor relays with their switching parts 5 mounted on the Wall of an elevator hatchway and a portion of an energizer to be moved past them by a car, as constructed in accordance with our invention;
Fig. 2 is a view in top elevation of the inductor relay shown at the second iioor in Fig. l; 5
Fig. 3 is a View in iront elevation of the switching part of the inductor relay shown in Fig. 2 with the switching arms in their actuated position, broken lines being used to show them in their closed position and with the cover plate 10 removed;
Fig. 4 is a view in side elevation on a slightly enlarged scale of the relay shown in Fig. 3;
Fig. 5 is a View in side elevation of the energizer for actuating the switching arms of the relay 15 shown in Fig. 3; and
Fig. 6 is a View in rear elevation of the energizer shown in Fig. 5.
Referring more particularly to the drawings, the relay and energizer therefor are of the kind y90 in which a plurality of relays I, 2 and 3 are mounted on a hatchway wall of an elevator hatchway to be operated by an energzer 6 mounted on the elevator car C as the car moves up and down the hatchway. When the car brings y the energizer adjacent to relay while it is energized for action, that relay is operated to control a circuit (not shown) for the car. rThe relays illustrated herein are such as are utilized for controlling the motors for operating ythe hatchway doors (not shown) at the landings and there will be one inductor relay mounted on the wall at or near each landing. ln other cases, the relays may be utilized in systems for decelerating and stopping the car at iioors. In such cases, the relays may be mounted on the car and have arms biased to unoperated positions by springs and the operators for the arms may be mounted on the walls of the hatchway. An inductor relay system in which the relays are mounted on the car and the operators on the wall of the hatchway is described in Patent 1,884,446, issued October 25, 1932 to Westinghouse Electric Elevator Company and reference may be had to thatpatent if more information regarding such a system is desired.
As shown in Figs. 2, 3 and 4, each of the inductor relays comprises a pair of magnetizable arms 9 and il! pivotally mounted and supported by a bolt or pin ll in a housing casting I2. The bolt is retained in position by a nut Ila. The housing is approximately rectangular in shape as indicated by the dotted line I2@ and is provided with flanged front face portion 12b (Fig. 3) upon which a cover plate l5 may be mounted by means of screws 15d to protect the working parts of the .55
relay. A pair of slotted projections or brackets i3 and Hl provide a means by which the housing may be securely fastened by a pair of bolts i@ to the hatchway wall fi at the point where the relay is to be located. The upper hinged portion l of the arm il is bifurcated with its divided parts supported upon the pin li and the is provided with a single hinged portion I3 that is mounted on the pin l i and between the bifurcated ends of the arm 9, in order to secure a rigid construction which will permit the arms to move outwardiy easily but prevent them from movin sideways when they are beine operated.
A pair ci rubber bumpers E9 and 2U are mounted upon adjustable screws 2l and 22 supported in the topmost portion of the casting l2 in such manner that they extend downwardly into position to be engaged by the upper shoulders on the arms $2 and il) when they are moved to their open position. The rubber bumpers may be adjusted to the desired height by rotating the screws 2l and 22 on which they are mounted. A pair of rubber bumpers 23 and 26 are mounted upon the sides of the casting i2 in position to be engaged by projections 25 and 2G on the arms 5 and l0 when the arms are released to move into their normal unoperated position. The provision or" the rubber bumpers for limiting the movements of the arms reduces the noise usually inherent to the operation of inductor relays of this character, thus reducing the amount of noise usually produced by the operation of an elevator system.
As shown in Fig. 3, the switching arm 9 is provided with an insulating block upon which a pair of contact members 21 and 28 are mounted by a screw 39 to be closed against cooperating contact members 27a and 28a by movement of that arm to its operated position, as shown in full lines in this gure. rThe operating arm fil is provided with an insulating block Sila secured by a pair of screws 52. A pair of contact members 29 and 3G are mounted on the block 3M by a bolt to be closed against cooperating contact members 25a and 35a (Fig. 4) by movement of that arm to its operated position, as shown by the full lines. The broken lines represent the unoperated positions of the arms and the open positions of the contact members when the arms are in their normal unoperated positions.
The cooperating contact member 28d is mounted upon a spring arm 3l in a mounting block 32 supported by a cross member 33 that is secured to the interior of the casting frame l2. A terminal post 3G is provided for connecting any suitable circuit to the spring arm Si. The supporting block 3?. is. provided with a stop arm 35i for limiting the movement of the spring arm when the contact members 28 and 28a are opened. Each of the contact members 27d, 23a, 29a and are mounted and supported by a spring arm in the same manner as the contact member 28a.
The casting l2 is provided with a lower outwardly extending chamber 3'! with the underside of which a pipe connection 3S is joined to provide an entrance for such conductors as are to be secured to the connecting posts 35 and the contact members 2l, 28 and 2S.
The energizer for operating the arms Q and IB is shown in Figs. 5 and 6 as comprising a base or supporting plate ll, a plurality of coils ill, ft2, /53 and fill, a plurality of cores di, d, il and Q8, and a pair o1" inductor plates or ns i9 and iii). The supporting plate Sil is provided with a horizontally bent portion 5l at its lower end that is adapted to be seated on the top portion of the arm lll.
elevator car C, only a small portion of which is shown. A plurality of bolts 53 may be used to hold the base plate in position. A bracing web Eficonnects the base portion 5i of the supporting plate with its vertical portion for the purpose oi giving it a greater degree of strength and solidity. The coil il is mounted upon the core and the coil i2 is mounted on the core lill, then a cover 5l is placed over them and secured to the cores by means of a plurality of screws 58. The two coils, their cores and the cover are then secured in vertical alinement on the front face and at one side of the supporting plate by means of a plurality of screws The coils t3 and lA, respectively, are mounted upon the cores 47 and 4B; a cover Bi? is then placed over them and they are mounted on the same side or" the plate GG as the other coils but close to its opposite edge by means of a plurality of crews 6l in the same manner as the coils 'il and are secured to the plate. The cores and the plate are made of magnetizable material so that the coils are, in eiect, mounted on the legs of a substantially U-shaped magnetizable structure. The outer ends of the cores t5 and S are connected vertically by the energizing n 49 of magnetizable material and the magnetizable iin is mounted on the free ends of the cores [il and IHS. A plurality of machine screws Sii are used to hold the fins in position on the ends of the cores.
The inductor relays mounted upon the hatchway wall by means of the bracket id and the energizer 6 mounted on the roof oi' the car at the edge adjacent the wall on which the inductor relays are mounted are disposed in such position that the ns "i9 and 59 will embrace, but not touch, the switching arms il and i5 as the car moves up and down the hatchway, as shown in the top plan view of Fig. 2. When the coils are energized as the energizer is brought adjacent to the relay, a magnetic circuit passes through the cores [i5 and 46, the supporting plate fill, the cores il and 48, the iin Ell, the arm lil, the arm El and the iin 49 to the cores 45 and fil-5. rIhis magnetic circuit causes the magnetizable arms and lil to move outwardly from their normal unoperated position as shown by the broken lines Glito their operated position as shown in lull lines toward the energizing fins 49 and as shown in Figs, 2 and 3. The outward action of the arms 9 and it? closes the Contact members E?, and 29 for operating the control circuit (not shown) in the manner for which the system may be designed.
In practice, it has been found that there are times when the contact members operated by the arms 9 and l'] will freeze or stick and thus remain closed after the energizer has been deenergized and moved away from the relay. In elevator systems, this is a serious matter. For instance. ii an inductor relay is being used ier controlling the opening and closing of a hatchway door the contact members freeze in a closed position, the hatchway door associated therewith may not close but remain open when the car bearing the energizer leaves the door at which the hatchway door is located. It may result in a serious accident to some passenger. Oi course, contact members on relays of this character do not stick or freeze very often to such an extent that the biasing weight or spring tension on the operating arms fails to open them. However, it is obvious that it is dangerous to take any risk in this direction. It is for this reason that we have provided a means for causing the operating arms to break the contact members loose from each other if they should happen to freeze or stick when the car leaves the oor. In order to accomplish this desirable result, we mount a plurality of non-magnetizable ngers 66, 61, 68 and 69 upon the free ends of the magnetizable ns to trail behind the iins and knock the arms toward their unaperated position if they remain in their operated position after the energizer is withdrawn from them.
rlhe linger 66 comprises a body portion of nonmagnetieable metal such as bronze, that is secured by a plurality of screws 1I to the upper end of the nn 49. The upper end of the ringer' is bifurcated to provide a fork 'I2 in which a rubber tired Wheel 13 is rotatably mounted by means of a pin ld. It is obvious that, in elevator service,the iingers must not touch the relay arms when they pass unless the arms are in their operated position and even then must merely free them from their operated position when they stick in that position. For this reason, the ringer 66 is bent or curved slightly inwardly so that the inner periphery of the wheel I3 travels in a plane S6 which overrides the plane 8l of thn arm in its operated position but does not touch the plane 82 of the arm in its unoperated position. These plane lines are indicated in 2. With the wheel mounted as described, it will impinge against the outer face of the arm 5 as the car leaves the iloor, if the arm 9 is still in its full operated position with its contact members 2'1 and 28 in their closed position. When the arm is in its full operated position and the wheel strikes it, it causes the arm to start toward its unoperated position, thus breaking open the contact members` 21 and 28. Once the contact members are freed, the force of gravity on de arm .fl will cause it to move in toward the body of the relay into its normal unoperated po. Jion. The position of the trailing nnger 66 is designed to cause the wheel 13 to start the arm toward its normal unoperated position if it sticks in its operating position, but not to press the all the way into its unoperated position and not to touch the arm if the arm is in its uneperated position while the energizer is moved past it. The trailing arm. H mounted on the up of the fin 50 is a duplicate of the arm (it is mounted to free the arm Ill if its Contact members 29 stick in their closed position. The trailing nngers 66 and 61 are disposed on the upper ends of the fins. for preventing the contact members on the relay from remaining closed after the car moves away from a floor while traveling in the down direction The trailing -lingers 68 and 69 are mounted on the lower ends of the i'lns to prevent the contact members on the relay from remaining closed when the car moves away from al floor while traveling in the up direction.
'it will be obvious that the contact members such ill, 28 and 29 on the relay may be so mounted that they will be in either a closed position or an open position when the relay is ener- In some cases, it is desirable to have a portion of a control circuit closed when the relay is energized but in another case it may be desirable to have a portion of a control circuit energized by the closing of the contact members on the relay when the relay is deenergized. In either case, the trailing ngers will cause the arr-ns il and iii to move out of their operated position as the car leaves the floor and Will thereby provide for a safe operation of the contact members.
From the foregoing, it will be seen that we have provided an inductor relay and an energizer therefor, in which any tendency of the contact members to freeze or stick will be eliminated and every contact member will be operated positively when the relay is deenergized and will thereby prevent any accidents due to the circuits being controlled in a wrong manner by a relay when the car leaves the floor at which that relay is located.
It will also be obvious that the mounting or the cores and the coils on the magnetizable plate in the energieer provides a substantially U- shaped magnetic structure easily manufactured and assembled and very -eiiicient in operation A.for causing the switch arms 9 and l0 to move outwardly. This simple construction also provides an energizer in which a plurality of coils may be used on the legs of the U-shaped magnets and then the U-shaped magnets may be connected vertically by the energizing ns and by the mounting plate which is also the main supporting element for the entire unit to provide a simple yet rugged construction.
We claim as our invention:
l. 'An energizer for an inductor relay comprising a magnetizable plate for magnetically operating' a movable member to an operated position, a non-magnetizable trailing finger, and means for supporting the magnetizable member and the non-rnagnetizable finger, with the finger extending beyond the working face of the magnetizable member.
2. An energizer for an inductor relay comprising a magnetizable fin of greater length than width, a non-magnetizable nger mounted on one end of the magnetizable fin with its free end 4extending into a plane beyond the plane of the side surface of the magnetizab'le nn, and a mounting plate for supporting the iin.
3. An energizer for an inductor relay comprising a supporting plate of magnetizable material having a substantially flat portion, a pair of magnetizable cores disposed on one side of the plate and near opposite edges thereof, a magnetizable fin disposed on the outer free end of each core, and an electrical coil disposed on each core for inducing a magnetic eld between the magnetizable ns.
4. An energiser for an inductor relay comprising a supporting plate of magnetizable material having a substantially iiat portion, a pair of magnetizable cores disposed on one side of the plate and near opposite edges thereof, a magnetizable fin disposed on the outer free end of each core, an electrical coil disposed on each core for inducing a magnetic eld between the magnetizable fins,.and a trailing finger of non-magnetizable material disposed on each end of each nn.
5. An energizer for an inductor relay comprising a supporting` plate of magnetizable material, two pairs of magnetizable cores mounted on one side of the plate, one pair of cores being disposed apart irom each other near one edge of the plate and the other pair of cores being disposed apart from each other but near the opposite edge of the plate, a magnetizable fin mounted on and bridging the free ends. of the two cores disposed near one edge of the plate, a second magnetizable fin mounted on and bridging the free ends of the two cores disposed near said opposite edge of the plate, and an electrical coil disposed on each core for causing a magnetic held to be induced between the ins.
6. An energizer for an inductor relay comprising a s'1pportin'r plate oi magnetizable material, two pairs ci magnetizable cores mounted on one side of the plate, one pair of cores being disposed apart from each other near one edge of the plate and the other pair oi cores being disposed apart from each other, but near the opposite edge of the plate, a magnetizable iin mounted on and bridging the i'ree ends or the two cores disposed near one edge of the plate, a second magnetizable fin mounted on and bridging the free ends of the two cores disposed near the opposite edge of the plate, an electrical coil disposed on each core for causing a magnetic field to be induced between the iins, an a trailing finger oi non-magnetizable materi dispose on each end of each iin with their ee ends extending within the planes defined by tne adjacent faces of the ns.
'7. electric reiay comprising a pair or" magnetizable arms, a pin for pivotally supporting the upper portions of the arms to permit their lower portions to close toward each other by gravity when no force is applied to move them outwardly, a plurality or" contact members associated with the upper portions o the arms to be opened and closed by movement of the arms, and an energizer for magnetically moving said arms outwardly, said energizer comprising a U-shaped einher of magnetiaa ie material, a magnetizable fin disposed on the outer end of each leg of the rl-Shaped member to position the arms between them when the energizer is brought into cooperative position with the switching arms, and an electrical coil mounted on each leg oi the U-shaped member i r inducing a magnetic circuit through the U-shaped member, the iins and the arms to magnetically move the arms outwardly and thereby operate the contact members.
3. An electric relay comprising a pair of magnetizable arms, a pin for pivotally supporting the upper portions of the arms to permit their1 lo ver portions to ciose toward each other by gravity when no force is applied to move them outwardly, a plurality of contact members associated with the upper portions of the arms to be opened closed by movement of the arms, and an energiser for magnetically :roving said arms outwardly, said energizer comp ing a U-shaped member oi magnet-liable material, a magnetizable iin disposed on the outer end of each leg of the U-shaped member to position the arms be tween them when the energizer is brought into cooperative position with the arms, an electric SYld Q,
coil mounted on each leg of the U-shaped member for inducing a magnetic circuit through the U-shaped member, the fins and the arms to magnetically move the arms outwardly and thereby operate the contact members, and a non-magnetizable finger mounted on the end of each iin in position to physically engage and knock the arm associated with that iin if that arm remains in its operated position upon removal of the energizer from its operative position adjacent to the arms.
9. An inductor relay for an elevator car operating in a hatchway comprising a magnetizable arm, means for pivotally mounting the arm on the wall of the hatchway, a plurality of contact members associated with the arm to be opened and closed thereby, an energizer comprising a magnetizable member, means for mounting the magnetizable member on the car whereby movenent of the car past the arm will move the energiaer into position adjacent to the arm, an electrical coil for inducting a magnetic circuit in the magnetizable member and the arm when they are adjacent to each other for magnetically moving the arm into an operated position, and a nonmagnetizable nger connected to one end of the magnetizable member and extending into a plane assing through the arm in its operated position whereby movement of the car and the magnetizable member away from the arm will cause the finger to knock the arm out of its operated position if it remains therein when the energizer leaves its position adjacent to the arm.
19. An inductor relay for an elevator car operating in a hatchway comprising a pair of contact members and a movable magnetizable arm for operating the contact members, an inductor plate, an electrical coil for causing a magnetic circuit through the arm and the plate when they are adjacent to each other to cause the arm to move from an unoperated position to an operated position, means for mounting the arm and the plate on the wall of the hatchway and the car whereby movement of the car in the hatchway will cause relative movement between the arm and the plate to bring them adjacent to each other when the car is at a predetermined position in the hatchway, and a non-magnetizable finger associated with the plate for starting the arm from its operated position to its unoperated position when there is a relative movement of the arm and the plate causing one to move away from the other.
HAROLD W. WILLIAMS. DONALD H. BAUM.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US196938A US2214599A (en) | 1938-03-19 | 1938-03-19 | Inductor relay |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US196938A US2214599A (en) | 1938-03-19 | 1938-03-19 | Inductor relay |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| US2214599A true US2214599A (en) | 1940-09-10 |
Family
ID=22727367
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| US196938A Expired - Lifetime US2214599A (en) | 1938-03-19 | 1938-03-19 | Inductor relay |
Country Status (1)
| Country | Link |
|---|---|
| US (1) | US2214599A (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US2666110A (en) * | 1949-11-26 | 1954-01-12 | Westinghouse Electric Corp | Elevator inductor switch |
-
1938
- 1938-03-19 US US196938A patent/US2214599A/en not_active Expired - Lifetime
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US2666110A (en) * | 1949-11-26 | 1954-01-12 | Westinghouse Electric Corp | Elevator inductor switch |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| US2996152A (en) | Magnetic retractable door roller for automatic elevators | |
| US2214599A (en) | Inductor relay | |
| US2749454A (en) | Electromagnetic flashing relay | |
| US2120751A (en) | Positive vehicle-storage automatic system | |
| US2189597A (en) | Electric inductor relay | |
| US3115847A (en) | Aerial tramways | |
| US2171365A (en) | Automatic holding and releasing device | |
| US2531025A (en) | Cushioned magnetic switch | |
| US3783978A (en) | Stop control for elevators | |
| US2385293A (en) | Device for overcoming effects of shocks | |
| US2081618A (en) | Switching mechanism | |
| US2843697A (en) | Magnetic leveling unit for elevators | |
| US2897316A (en) | Electromagnetic switch | |
| US1940027A (en) | Closure retaining mechanism | |
| US1902602A (en) | Relay | |
| US1934867A (en) | Elevator gate | |
| US2174969A (en) | Release box | |
| US1530963A (en) | Electromagnetic switch | |
| US1970140A (en) | Switch control system and apparatus | |
| US2542835A (en) | Electromagnetic contactor | |
| US2916677A (en) | Armature hold-down latch for electrical relays | |
| US2669620A (en) | Electromagnetic contactor | |
| US1639190A (en) | Apparatus for the control and operation of electric lifts and the like | |
| US1178305A (en) | Automatic train-stopping device. | |
| US1879919A (en) | Electrical means for operating or raising and lowering railway booms and the like |