US2828449A - Safety feature for electric watertight door systems - Google Patents

Description

March 25, 1958 l. 1.. KERPER SAFETY FEATURE FOR ELECTRIC WATERTIGHT DOOR SYSTEMS Filed 001:. 20. 1955 INVENTOR.

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mi. n 2 T Z 5* h a n M m 5N z I W a I. .mlllcl 4 8 0 mm wflar United States Patent SAFETY FEATURE FOR ELECTRIC WATERTIGHT DOOR SYSTEMS Irving L. Kerper, Flushing, N. Y.

Application October 20, 1953, Serial No. 387,333

1 Claim. (Cl. 317--137) (Granted under Title 35, U. S. Code (1952), sec. 266) The invention described herein may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor.

This invention relates to improvements in electric watertight door systems for use on merchant vessels and military sea transports and more particularly to a safety mechanism for preventing the accidental opening of such doors during emergencies.

At the present time a large percentage of the American merchant vessels and military transports are equipped with one form of power-operated watertight door system or another. The electrical circuitry of such systems are similar in many respects, differing only slightly. They are designed for local and/ or remote opening and closing of doors'by hydraulic means activated by electrical control equipment.

As a result of sinkings of merchant ships due to collisions or other factors, the United States Coast Guard has conducted numerous investigations to determine why these ships sank at such a rapid rate. In conducting the investigations, attention was focused on the particular electrical systems installed for maintaining the doors secure under flooding conditions. It was learned that entry of sea water into the local-control switches employed in the existing electrical systems would energize the open contactor coil of the electrical control circuit, thus unintentionally causing the doors to open. Such opening of doors under flood conditions would account for the ships sinking rapidly.

Several modifications to prevent the doors from being opened by salt water have been proposed and installed on merchant vessels but these modifications have not in all instances been successful. In one particular system, an auxiliary holding relay is inserted in parallel with the closing relay to maintain the doors closed until the localcontrol switch is thrown to the open position. While such a system can be designed to function properly, extra electrical power is required to maintain the holding relay energized. Another disadvantage of such a system is that additional equipment is required, increasing the cost of the installation. A further and more important disadvantage is that in the event the holding relay becomes open, as occurs when the relay burns out, the electrical system reverts back to the previous systems providing no protection when salt water floods the local-control switch.

A system contemplated for use consisted of providing a break on the opening contactor coil, which in effect, breaks both sides of the line when the opening coil is to be deenergized requiring both sides of the coil to be energized to cause the doors to open. It was thought that if water then entered the local-control switch, both sides of the circuit would be shorted out causng the fuse to blow because both sides of the circuit were located in the switch. However, it was found that the safety fuse in the line would not always blow prior to the doors opening because of the physical distribution of the contacts and the of separation of the circuit elements.

2,828,449 Patented Mar. 25, 1958 It is an object of this invention to provide fool-proof means for holding the doors of an electrical water tight door system in a closed position.

Another object of the present invention is to provide short-circuited means for maintaining a relay coil in a deenergized state although acted upon by other influences.

Other objects and many of the attendant advantages of this invention will be readily appreciated as the same becomes better understood by reference to the following detailed description of a specific embodiment, when read in conjunction with the accompanying drawings, in which:

Fig. l is a schematic wiring diagram of an electric watertight door control circuit including the invention.

Fig. 2 is a table denoting the operation of the localcontrol switches of Fig. 1.

Fig. 3 is a partial wiring diagram of an alternate form of the invention.

Essentially the invention consists of inserting bridge means in parallel with a relay to prevent such relay from being activated except under certain conditions which, hereinafter, will be more fully described. Fig. 1 shows one of the standard electrical circuits for power-driven door systems installed on merchant ships including the bridging means. Although such circuit is well known, a description of the circuit will be given to particularly point out the advantages gained by this invention.

The electrical circuit is supplied with a suitable source of direct current to operate the relays 11, 13, 15, howler 17, lights 19 and 21 and activate the armature 23 of a of the ship for use by the captain for remotely closing the doors. Local-control switches 31 and 31' suitably mounted on both sides of a bulkhead 32 at a convenient height near each door enables one to open or close the door Said switches are interconnected as shown and are standard four-circuit drum switches having three positions, namely, open, neutral and close with a spring return from the open to neutral position.

Open relay 15 has four contacts 33 associated therewith and similarly close relay 13 has four contacts 35. Said relays 13 and 15 are activated when switch 31 or 31' is thrown to open or close position depending on whether the doors are to be opened or closed. When switch 31 or 31 is in the neutral position the circuit is open and no current flows. Limit switches 36 and 37 of standard design stop rotation of the motor (not shown) associated with armature 23 when the doors travel to either fully closed and/ or open positions.

The circuit hereinbefore described is the basic circuit employed in most water tight door controllers except that instead of a three-circuit local-control drum switch there is shown a four-circuit drum switch in Fig. 1. The contact terminals labeled D and D make up the fourth circuit. As shown, an electrical connection 39 is made between two of the contact terminals (D and D) of switches 31 and 31. An electrical connection 41 is made between the other contact terminal D of switch 31 to one side of open relay 15. Another electrical connection 43 connects the other side of relay 15 to the second contact terminal D of switch 31. Thus, when the circuits D and D of switches 31 and 31' are closed, as when said switches are in the neutral or close" position (see Fig. 2) open relay 15 is effectively shorted and cannot be energized.

The sequence of operation of switches 31 and 31 is shown in Fig. 2. When either switch 31 or 31 is thrown to open position, contact terminals C or C respectively are closed thereby completing the power circuit to open relay Energizing relay 15 causes open contacts 33 to close and power is supplied to armature 23 (and correa) sponding field) causing the for opening the door. When the door reaches the fully open position a limit switch 36 is actuated causing the motor to stop. As mentioned hereinbefore local-control switches 31'; and 31'- are designed with spring-return action from Open to Neutral position; When said switches are returned to Neutral position, the circuit C -C is opened andfcircuits B-B and D D' are closed. In Neutral position no power flows to either relay 13 or 15.

When'local-control switch 31 or 31' is thrown to close position circuits A A, BB and DD are closed enabling current to How to close relay 13. When relay 13 is energized, said relay activates contacts 35 to .close and power is supplied to armature 23 (and corresponding field) of the motor (not shown) in a direction for closing the door. When the door reaches the fully closed position limit switch 37 is activated causing the motor to stop. 3 s i j It is obvious that when the local-control switch is in close position, relay 15 is effectively shorted out by the circuit composed of line 41, circuit D-D and line 43. Thus, when the local-control switch is in close and/or neutral position, open relay 15 cannot be accidently energized because of the shorting bridge across relay 15.

Instead of two local-control switches operating in conjunction with each other to either open or close the doors, one switch 45 similar to switches 31 and 31', having a shaft 46 extended through the bulkhead with a handle 47 to turn said switch to either open, neutral or close position can be employed in lieu of a second switch (see Fig. 3). Bridging means comprises line 41, circuit D and line 43' similar to bridging means consisting of line 41, circuit DD and line 43'.

Obviously many modifications and variations of the present invention are possible in the light of the above teachings. It is therefore to be understood that Within the scope of the appended claim the invention may be practiced otherwise than as specifically described.

motor to run in a direction" 7 4; -What is claimed:

A control device for preventing the premature activation of an electric watertight-door system under flooding conditions comprising a multi-circuit switch having a plurality of contact pairs, a first relay for energizing a motor for closing the watertight doors, a second relay for energizing such motor for opening the watertight doors, one side of said first relay connected to a contact of a first pair of normally closed contacts, one side of said second relay connected to a contact of a first pair of norniaiiy'c-pen contacts, a source of power, one side of said source of power connected to the other sides of said first and second relays, the other side of said source of power connected to the other contact of said first pair of normally open contacts and to a contact of a second pairof normally open contacts, a conductor connected between a contact of a second pair of normally closed contacts and one side of said second relay, a second conductor connected between the other contact of said second pair of normally closed contacts and the other side of said second relay, a third conductor connected between the other contact of said first pair of normally closed contacts and the other contact of said second pair of normally open contacts, and means connected across said contacts of said second pair of normally open contacts for remotely activating said first relay, said second relay remaining inactive when said first pair of normally open contacts are accidently connected electrically.

References Cited in the file of this patent UNITED STATES PATENTS 1,045,981 Jacobs Dec. 3, 1912 2,467,901 McArthur Apr. 19, 1949 2,507,976 Hull May 16, 1950 2,528,777 Persons Nov. 7, 1950 2,540,098 Cartmell Feb. 6, 1951 2,693,514 Smith.- Nov. 2, 1954

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