US2792106A - Safety device for elevators and similar transporting means - Google Patents

Description

' May-14, 1957 1-, FREDH ETAL 2,792,106

SAFETY DEVICE FOR ELEVATORS AND SIMILAR TRANSPOR'iING MEANS Filed Sept. 13, 1954 Fig.1,

United States Patent SAFETY DEVICE FOR ELEVATORS. TRANSPORTINQME'ANS Tore Fredh, Stockholm, and Evert lil li arkemjohannes- I hov, Stockholm, Sweden, assigno'i's to Aktiebolaget Svenska Flaktfabriken, Stockholm, Sweden The present invention relates to a safety device for I elevators and similar transporting means provided with a driving device and equipped with magnetically conductive receptacles for the material to be conveyed or other regularly spaced parts of iron or the like.

In elevators and similar conveyQts-Where belts transport the material or carry a plurality of receptacles, for instance elevator buckets, the belt often tends to slip on the driving drum if overloaded or if interfering objects happen to come into the space between the conveyor and its casing. often the case as the elevators usually-are'rathe'r high and extend through several floors in for instance a magazine building-the slipping is allowed to continue for some time, this resulting in considerable disadvantageous re- 'sults: the belts are worn out quickly and there is a tremendous risk of fire caused by friction between the driving drum and the belt. This risk is especially serious if the material to be transported consists of grain or other inflammable material.

A primary object of the invention is to provide an electromagnetic safety device for eliminating these disadvantages by disconnecting the current to the driving motor of the elevator or stopping the elevator by mechanically disconnecting the conveyor from the driving means, when slipping occurs.

The present invention is mainly characterized by electric current inducing means mounted adjacent to the belt conveyor and consisting of a permanent magnet and a coil wound around an iron core, which coil via rectifying means and preferably an electronic amplifier is connected with a sensitive relay responsive to the voltage generated in accordance with changes in the current occurring when the buckets pass the inducing means, the core arm of said relay being arranged to disconnect to the driving motor of the conveyor or to actuate a device for mechanically disconnecting the conveyor from the driving means as well as to energize simultaneously an alarm system if the intervals between the changes in current exceed a predetermined value. The inducing means may suitably be enclosed in a shell of iron for directing the magnetic field of said means towards the conveyor.

A suitable modification within the scope of the invention is the addition of means for the adjusting of the response of the relay to ditferent values of the intervals between the changes in the current.

The invention will now be described more in detail with reference to the accompanying drawings in which,

Fig. 1 illustrates one embodiment of an electromagnetic safety device in accordance with the invention; and

Fig. 2 illustrates a second embodiment of the present invention.

In the embodiments illustrated in the drawings, the elevator is equipped with iron buckets for transporting the material, for instance grain .or similar material. The invention may, however, also be used in other belt conveyors, if the belt is provided with any regularly spaced If such slipping is not observed-which is 2,792,106 Patented May 14, 1957 ice 2 iron parts. Bolts, jointing irons or other iron parts may thus be attached to the belt for operating the safety device.

In the drawings, reference number 1 designates a coil arranged on an iron core 2, of a permanent magnet 2a, which together constitute an electric current inducing means 20. The permanent magnet 2a is aligned with the core at the rear end, and the assembly is provided with an iron shell 5. The function of this shell is to direct the magnetic field towards the coil and towards the path of the belt 17 driven by a pulley 16 and carrying buckets 18. In the illustrated embodiments, as the buckets 18 move past the iron core 2, a change of the electromagnetic field results, and an alternating current is induced in the coil 1. This current is rectified by means of rectifying means 4 for instance diodes of germanium. v The rectified current energizes in the embodiment illustrated in Fig. l, a polarized relay 6, the contacts of which control a motor relay connected between the electric source 12a and an electric motor 13 for the elevator belt or belts. An electronic amplifier may be provided between the rectifying means 4 and the motor relay 12.

The device may also be arranged as shown in Fig. 2 wherein the relay 6 controls a solenoid 14 of a clutch 15 for mechanically disconnecting an electric motor driving the elevator belts. The remaining elements of the circuitare identical to those shown in Fig. 1 and have beengiven identical reference numerals.

Reference number 11 in each figure designates an alarm bell responsive to the relays 6, 8, when the degree of slipping has reached a predetermined extent. Reference number 7 designates a condensor or capacitor shunted across the coil of the relay 6. By means of such a condensor an adjustment of the sensitivity of the relay can be made. Furthermore there are in the illustrated forms of the safety device a relay 8, a switch 9 and a transformer 10, all of designs prior known.

Within the scope of the invention is an apparatus having twin elevators, as shown in Fig. 1, there is inducing means 20 and 20a for each of the belts 17 and 17a. The two inducing means 20 and 20a are connected in series and are connected by the responsive relay 6 to the motor relay 12.

In the operation of the safety device the advance of the iron parts 18 of the conveyor past the current inducing means 20 creates a surge of current in the coil 1. The

I current is rectified by the rectifier 4 to provide a positive operating normally, the relay 6 is maintained energized constantly, whereas if the conveyor slows below a minimum speed, the capacitor 7 fails to maintain the relay energized, and causes its contacts to open.

When the relay 6 is energized, the contacts of the relay 6 energize the relay 8 which completes a circuit to either the relay 12 of Fig. l, or the electric actuator or solenoid 14 of the clutch 15 of Fig. 2. When the relay 6 is deenergized, the opening of the contacts of the relay deenergizes the relay 8, opening the circuit to the relay 12' or the clutch 14 and closing a circuit to the alarm bell 11. The push button switch 3 is provided to by-pass thelower contacts of the relay 8 to energize either the relay 12 or the electric clutch 14 for manual operation of theconveyor. Thus, when the conveyor is operating at or above the desired speed, the drive means for the conveyor is rendered operable, and when the speed of the conveyor falls below the desired speed, the drive means is rendered inoperable and an alarm is energized.

To adjust the safety device to be responsive to diiferent rates of advance of the belt 17, the capacitor 7 is ad justed. A meter M is provided to indicate the frequency of the current changes induced by the inducing means 20, thereby indicating the operation of the conveyor 17.

It is to be understood that the clutch 14, 15 of Fig. 2 may be employed with twin conveyors, as shown in Fig. l, and the relay 12 of Fig. 1 may be employed with a single conveyor as shown in Fig. 2. Thus while specific embodiments of the present invention have been herein illustrated and described, changes and modifications may be made within the scope of the following claims.

What is claimed is:

1. For elevators and similar endless conveyors provided with magnetically conductive receptacles for the material to be conveyed or other regularly interspaced parts of iron, said conveyor having selectively operable drive means, .a safety device characterized by an electric current inducing means mounted adjacent said conveyor and consisting of a permanent magnet, an iron core disposed between said magnet and said conveyor, and .a coil wound around said core, said current inducing means being operable upon advance of each of said parts of iron past said current-inducing means to generate a surge of current in said coil, circuit means including a sensitive relay electrically connected to said coil and energized by said surges, means in said circuit means maintaining said relay energized for a predetermined interval after each surge, a second circuit means including contacts of said relay and operable upon enrgization of said relay to maintain said drive means operative.

2. A safety device according to claim 1 wherein said selectively operable drive means comprises an electric motor and said second circuit means includes a relay actuatable to connect said motor to a source of current.

3. A safety device according to. claim 1 wherein selectively operable drive means comprises an electrically actuated clutch, and wherein further said second circuit means includes an actuator for said clutch actuatable to engage said clutch.

4. A safety device according to claim 1 including an alarm system in said second circuit energized upon deenergization of said relay to generate an alarm signal. I

5. A device according to claim 1 wherein said current inducing means includes a shell of iron surrounding said magnet and said core to direct the magnetic field of said magnet toward said conveyor.

6. A device according to claim 1 wherein said means for maintaining said relay energized for a predetermined interval is adjustable to change said predetermined intcrval.

7. A device according to claim 1 for a plurality of conveyors driven by said drive means including a current inducing means for each of said conveyors, said plurality of current inducing means being connected in series in said first circuit means to energize said relay. Y

8. A device according to claim 1 including meter means in said first circuit means responsive to the fro quency of said surges of current to thereby indicate the speed of operation of the conveyor.

References Cited in the file of this patent UNITED STATES PATENTS 2,503,812 Fath Apr. 11, 1950

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