the present invention is an elevator levelling / hatch controller logic system for use with a weapons or equipment elevator aboard ship . the system operates the elevator and the hatch controllers to implement desirable safety conditions . the layout of the elevator , trunk , decks and hatches is illustrated in fig1 . fig2 is a block diagram of the invention , while fig3 is a circuit diagram of a preferred embodiment . referring now to the drawings , wherein like reference numerals designate identical or corresponding parts throughout the several views , and more particularly to fig1 thereof , a shipboard elevator system is depicted . the elevator system includes an elevator trunk 10 within which an elevator platform 12 travels . the elevator platform 12 is raised and lowered on guides 14 and operates to service the various decks and platforms including the main deck 16 , second deck 18 , third deck 20 , fourth deck 22 , first platform 24 , second platform forward 26 , second platform aft 27 , and hold 28 . a main deck hatch 30 is positioned to seal off the trunk 10 when closed . the main deck hatch 30 is controlled by a dual - hatch controller with main deck hatch open and close inputs . a third deck hatch 38 is controlled by the same dual - hatch controller , with third deck hatch open and close inputs . a hatch sequence level 44a is positioned between the main and third decks . fig2 is a block diagram of the invention . referring now to fig2 a control unit 50 is interconnected with a dispatch unit 52 including dispatch stations at the main deck hatch and at each door , a platform location sensing unit 54 , a motor controller 56 , and a dual - hatch controller 58 . the control unit 50 receives input signals indicating elevator destination , and elevator location . the control unit 50 utilizes this input information to generate control signals for the motor controller 56 and dual - hatch controller 58 . these control signals are generated in response to the various inputs received and insure safe operation of the elevator . the various safety features incorporated into the control unit are described in detail below . the hatch controller 58 and motor controller 56 are not part of the present invention . the hatch controller includes hatch close and hatch open inputs activated by relays controlled by the control unit 50 . the motor controller 56 includes up , down , high - speed and low - speed inputs for activating the coils of magnetic contactors in the master controller . these inputs are also activated by relays controlled by the control unit 50 . fig3 a - 3f represent a circuit diagram of a preferred embodiment of the present invention . before considering the details of fig3 a - 3f the following overview of the control requirements is presented for better understanding . generally , dispatch of the elevator is only possible from the level at which the elevator is stationed . certain exceptions are detailed later . during travel between lower decks , the third deck hatch is open and the main deck hatch is closed . if the elevator is dispatched from a lower deck to the main deck it first stops at the hatch sequence position between the main deck and third deck . next the third deck hatch is closed and the main deck hatch is opened . finally , the elevator proceeds to the main deck . similarly , when dispatched from the main deck , the elevator stops at hatch sequence while the main deck hatch closes and the third deck hatch opens . this hatch sequencing prevents objects or fluids which may cause a fire from falling into the lower decks of the ship since the main deck hatch and the third deck hatch are never simultaneously open . the circuits depicted in fig3 a - 3f include relays and switches . the dispatch switches and elevator proximity switches are depicted in fig3 a and 3c , respectfully . the relays have their coils identified by circles and their contacts identified by two parallel and spaced apart lines . a normally closed relay contact has an oblique line across the parallel lines and a normally open contact has no such oblique line . it should be noted that the coil and contacts associated with a particular relay are always separated from each other in the drawing symbols . each relay coil is wired in parallel with an indicator light that is on when the coil is activated . these indicator lights are identified by a small circle with four lines radiating therefrom . the relays used in an actual circuit are six pole double throw ( 6 pdt ) electromechanical relays . fig3 a - 3f are sections of a complete circuit diagram of the system . each figure includes several input and output terminals 100 labeled by capital letters . the complete circuit is formed by connecting the terminals labeled with the same letter . fig3 a is a circuit diagram of dispatch unit 52 , fig2 . a plurality of dispatch switches 101 - 158 and relay contacts 160 - 195 form a grid for selectively energising output terminals c - m at + 24 v . fig3 b is a diagram of the dispatch destination memory circuit of the control unit . note that the input terminals c - m are connected to the output terminals c - m of fig3 a . eleven relay coils 201 - 211 connect the inputs c - m to a power supply common line ( p -- com ) 212 . in addition the relay coils 201 - 211 are connected to a dispatch - set line 213 by a plurality of relay contacts 214 - 228 . note that hclm relay contact 230 connects input e to input f . fig3 c is a circuit diagram of the elevator location sensing unit 54 , fig2 . this unit comprises a plurality of proximity switches 231 - 248 and h and l relay coils 250 - 267 . each relay coil is directly connected to a p - com line and to a + 24 v line by a proximity switch . the proximity switches are normally closed so that the h and l relay coils are activated . when the elevator is at the proximity switch location the switch is open and the h or l relay coil connected to the switch is deactivated . these proximity switches are opened and closed by a metal target attached to the elevator platform 12 . in fig3 c the proximity switches are normally closed but are opened when the target is adjacent to the switch . thus , the h and l relay coils are activated unless the associated proximity switch is opened by the target . turning next to fig3 d , a circuit diagram of an elevator levelling circuit is presented . the circuit includes a godnm relay coil 270 and a goupm relay coil 272 connected by a first relay contacts chain 272a including up and dn relay contacts 304 , 324 and h and l contacts 305 - 323 . additionally , a dnhsm relay coil 271 is connected to a uphsm relay coil 273 by a second relay contact chain 273a including h and l relay contacts 333 - 351 . the two relay contact chains 272a , 273a are connected to each other by memory relay contacts 361 - 367 and are connected to an interlocked + 24 v line by memory relay contacts 361a - 367a . the contact chain 272a is connected directly to the interlocked + 24 v line by contacts 368 and 368a in series . if the number of elevator locations is greater than that illustrated in fig1 then a g3 relay or time - delay disp reg . relay 413 ( fig3 e ) is required because there are not enough contacts in the present circuit . next , fig3 e is a circuit diagram of the command circuit of the control unit including a plurality of relay coils 400 - 410 , 416a - 416d ( the command relays ) and relay contacts 420 - 492 . each command coil is directly connected to p - com and connected to an interlocked 24 v line by a circuit including several relay contacts interconnected in series and / or parallel . note that hatch signal relays 416a - 416d receive input signals from the dual - hatch controller indicating the hatch positions . finally , fig3 f depicts a circuit including 115 vac power supply 500 , a 24 vdc power supply 502 , a safety interlock circuit 504 , and upa , dna , hsa , and lsa relay contacts 506 , 508 , 510 and 512 for activating the up , dn , hs and ls motor contactors 514 , 516 , 518 and 520 , respectively . these contactors are large relays that interconnect the motor inputs to a 440 vac motor power supply ( not shown ). both the up and dn contactors include auxiliary contacts that function as the up and dn relay contacts 304 , 324 of the elevator levelling circuit of fig3 d . the p - com line is connected to the negative output of the 24 vdc power supply 502 . the + 24 vdc output is connected to terminals w and x . note that terminal x is connected to the power supply positive terminal by the safety interlock circuit 504 . this circuit interrupts power to the control unit thereby stopping the platform if platform over - travel , door interlock , slack cable , motor over temperature , motor over - load and other safety switches ( not shown ) are activated . a description of the operation of the circuit depicted in fig3 a - 3f follows . assume that the platform 12 is positioned at the hold level 28 with the third - deck hatch cover 38 open and the main - deck hatch cover 30 closed . closing of trunk doors and completion of safety permissive signals 504 ( fig3 f ) is outside the scope of this patent . next the push - button for dispatch to the main - deck 110 is actuated and the order is registered in the logic . the main - deck push - button activates the &# 34 ; hatch - clear memory &# 34 ; relay ( hclm ) 203 , and also via hclm contacts 230 , the &# 34 ; stow memory &# 34 ; relay ( 2m ) 204 . since the &# 34 ; dispatch registered &# 34 ; contacts 354 and 361 ( disp . reg .) and the &# 34 ; emergency - override memory &# 34 ; relay ( eorm ) contacts 355 are unactivated both the &# 34 ; up high - speed memory &# 34 ; relay ( uphsm ) 273 and the &# 34 ; down high - speed memory &# 34 ; relay ( dnhsm ) 271 are activated . since platform high and low leveling switches at the hold level 246 , 247 and 248 are activated , input switch relays 8h , 8hd and 8l 265 , 266 , and 267 are unactivated and relay contacts 8h and 8l 308 and 307 are open . this results in the &# 34 ; go - up memory &# 34 ; relay ( goupm ) 272 being activated via 2m contacts 367 and 367a , and the &# 34 ; go - down memory &# 34 ; relay ( godnm ) 270 being unactivated . when goupm is activated and godnm is unactivated with no emergency override condition , the &# 34 ; dispatch - registered &# 34 ; relay ( disp . reg .) 413 becomes activated . when disp . reg . 413 becomes activated two relays are locked in memory . these are hclm 203 so long as the &# 34 ; hatch - clear time - delay &# 34 ; relay ( hcl - td ) 409 is unactivated ( contact 219 closed ), and 2m 204 so long as one hatch is open as indicated by relay contacts &# 34 ; main - deck hatch closed &# 34 ; ( mdhc ) 220 and &# 34 ; third - deck hatch closed &# 34 ; ( 3dhc ) 221 . at this point the dispatch command has been registered and the main - deck push - button 110 can be released . actuation of the disp - reg . relay 413 results in the actuation of the &# 34 ; go &# 34 ; relays ( g1 and g2 ) 414 and 415 provided the third - deck hatch is open and the maindeck hatch is not opened or vice versa is indicated by relay contacts &# 34 ; main - deck hatch open &# 34 ; ( mdho ) 479 and 485 , and &# 34 ; third - deck hatch open &# 34 ; ( 3dho ) 480 and 486 . when the platform is at the hatch sequence level as indicated by relay &# 34 ; at hatch - sequence # 1 &# 34 ; ( at h . seq1 ) contacts 483 , the go relay remains activated even though both hatches may be closed . finally the &# 34 ; go &# 34 ; relay is interlocked through dispatch memory relay contacts as indicated by 1m 478 , 2m 481 and &# 34 ; low - deck command &# 34 ; ( lodk ) 484 . when the &# 34 ; go &# 34 ; relays switch , power is severed , via g1 relay contacts 420 , to the push - button stations of the dispatch unit 52 and the memory relay inputs are isolated . simutaneously , power is established via g1 relay contact 421 to permit platform or hatch movement ( relays 400 - 407 ) and prohibit redispatch unless memory relays 1m - 8m ( 202 , 204 , and 206 - 211 , respectively ) have dropped out . a further consequence of relay disp . reg . 413 switching is to deactivate &# 34 ; down high - speed memory &# 34 ; relay ( dnhsm ) 271 while &# 34 ; up high - speed memory &# 34 ; relay ( uphsm ) 273 remains activated via 2m memory relay contacts 367a , input switch l and h relay contacts 349 - 351 , and uphsm relay contact 353 . operation of the &# 34 ; go # 1 &# 34 ; relay &# 34 ; g1 &# 34 ; contacts 303 , 327 leaves the &# 34 ; go - down memory &# 34 ; relay ( godnm ) 270 unactaivated and the &# 34 ; go - up memory &# 34 ; relay ( goupm ) 272 activated in such a manner that any switch actuation above the destination level would cause goupm 272 to fall out and stay out until a new dispatch is made . with g1 contact 421 and goupm contact 444 activated and godnm contact 445 deactivated the &# 34 ; up auxiliary &# 34 ; solid - state relay ( upa ) 404 turns on . with goupm contact 449 and uphsm contact 450 activated and dnhsm contact 455 and 1m contact 448 deactivated , &# 34 ; high - speed auxiliary &# 34 ; solid - state relay ( hsa ) 406 turns on . the platform departs upward at high - speed to the hatch sequence level where the platform slows down by activation of proximity switches 234 or 235 which operate relays 2l or 2ld 253 or 254 . a short time later the platform comes to a full stop by operation of switches 232 or 233 which deactivate relays 2h or 2hd 251 or 252 . the third - deck hatch cover close command is now given . since relay lodk contact 436 is not activated and relay at h . seq1 contact 437 is activated , the hatch cover closes following activation of the &# 34 ; third - deck hatch close command &# 34 ; relay dh1 ( 3 close ) 402 . stopping the platform at the hatch sequence level and subsequent closing of the third - deck hatch cover only occurs when the platform is dispatched to the main - deck from any level including the second - deck . if the &# 34 ; hatch - clear &# 34 ; button 102 at the main - deck recessed control station has not been depressed by the main - deck station operator in the time allowed , the platform stays at hatch sequence with both hatches closed and the memory is cancelled . the &# 34 ; hatch clear &# 34 ; push - button 102 is enabled when relays at h . seq2 , hclm and 3dhc are activated and contacts 460 , 461 and 462 are closed . the hatch clear push - button 102 must be depressed during the &# 34 ; hatch clear time - delay &# 34 ; relay ( hcl - td ) 409 set - time , otherwise the relay times out and cancels memory relays hclm 203 and 2m 204 , and the dispatch is cancelled . if the &# 34 ; hatch - clear &# 34 ; permissive signal is received in the allotted time the next operation is to open the main - deck hatch cover 30 . when the hatch - clear push - button 102 is depressed , memory relay 1m 202 is set . this in turn activates &# 34 ; main - deck hatch open command &# 34 ; relay ( m open ) 401 since interlock relays 3dhc and at h . seq1 are activated , and contacts 431 and 432 closed . the dual - hatch controller provides signals from hatch position proximity siwtches to activate the coils of relays &# 34 ; main - deck hatch opened &# 34 ; mdho 416a , &# 34 ; main - deck hatch closed &# 34 ; mdhc 416b , &# 34 ; third - deck hatch opened &# 34 ; 3dho 416c , and &# 34 ; third - deck hatch closed &# 34 ; 3dhc 416d . for purposes of ensuring that the main - deck hatch is clear , an indicator light 408a and a momentary contact type push - button 102 are provided at the main - deck control station . the indicator light is energized when a dispatch is registered from any level to the main - deck but only after the platform has reached the hatch sequence level and the third - deck hatch cover has been closed . this light is to indicate that a &# 34 ; hatch - clear &# 34 ; permissive signal is required by means of the push - button furnished for the purpose . once the &# 34 ; hatch - clear &# 34 ; signal has been received by the logic it can be cancelled in case the hatch is no longer clear , and imminent danger exists , by actuation of the &# 34 ; emergency - override &# 34 ; push - button 101 . if , after arrival at the hatch sequence level , no &# 34 ; hatch - clear &# 34 ; signal has been received within the time allowed , the dispatch is cancelled and a new dispatch order will be required from the main control station at the second deck or it will be necessary to activate the &# 34 ; call to main - deck &# 34 ; push - button 103 at the main - deck recessed control station . actuation of the &# 34 ; hatch - clear &# 34 ; push - button 102 does not register a permissive signal to the controller unless a dispatch command to the main - deck has been received by relay 203 with subsequent operation of the indicator 408a requesting &# 34 ; hatch - clear &# 34 ; signal . the &# 34 ; stow &# 34 ; memory ( 2m ) 204 is cancelled when both the main - deck and third - deck hatches are closed unless there is a &# 34 ; hatch - clear - request &# 34 ;, in which case both &# 34 ; stow &# 34 ; and &# 34 ; hatch - clear - request &# 34 ; 203 memories are cancelled at the end of the hatch - clear time delay . a &# 34 ; main - deck &# 34 ; command sets both the &# 34 ; hatch - clear - request &# 34 ; memory ( hclm ) 203 and the &# 34 ; stow &# 34 ; memory ( 2m ) 204 . once the main - deck hatch cover 30 has been opened , the platform resumes its travel to its final destination at slow - speed upward from the hatch sequence position . travel away from the main - deck shall be the reverse ( except for speed ) for all levels below hatch sequence and no &# 34 ; hatch - clear &# 34 ; signal is needed . the platform leaves every level in either direction at high - speed except that it travels upwards from hatch - sequence to the main - deck all the way in slow speed . for travel to the second - deck the third - deck hatch cover remains open . only if subsequent travel to the main - deck is required , is this hatch closed but not before the platform has traveled the short distance to the hatch sequence level . when the platform is dispatched from the main - deck to a lower level , it first stops at hatch sequence to close the main - deck hatch cover and then open the third - deck hatch . only then does the platform resume its downward travel to its destination including the second - deck . when the platform approaches every destination exept the main - deck , the speed is transferred from high to low by means of a slow - switch installed in the trunk . after traveling a short distance in slow - speed the platform stops at its destination upon the actuation of a stop - switch . dispatch of the platform is possible only from the level at which the platform is stationed except that : a . at the main - deck recessed control station it is possible to call the platform to the main - deck from hatch sequence . b . at the master control station on the second - deck it is possible to ; i . call the platform to the second - deck from all levels including hatch sequence , but not from the main - deck , provided any platform leveling switch is activated . at &# 34 ; stow &# 34 ;, the platform must activate leveling switches 232 - 234 for the third - deck hatch to open . ii . dispatch the platform : from hatch sequence to the main - deck . this requires &# 34 ; hatch - clear - request &# 34 ; to be acknowledged . in this description a command to send the platform to &# 34 ; stow &# 34 ; is equivalent to sending the platform to &# 34 ; hatch - sequence &# 34 ;. the &# 34 ; emergency - override &# 34 ; ( eor ) push - button 101 at the main - deck station operates upon momentary actuation as follows : a . all dispatch orders are cancelled . relay disp . reg . 413 is deactived . b . the stowage level is entered as the destination , but only after a temporary delay permitting all contactors to drop out and the main drive motor or hatch to stop moving . this is via operation of the &# 34 ; emergency override time - delay &# 34 ; relay ( eor - td ) 410 which is activated via &# 34 ; emergency override memory &# 34 ; relay ( eorm ) contacts 463 . c . the platform then decends to the hatch - sequence level ( at high - speed unless a low - speed switch is activated ), and stops when switches 2l or 2ld 234 or 235 are activated . when switches 2h , 2hd and 2l 232 - 234 at the hatch - sequence level are actuated by the platform the main - deck hatch returns to the closed position . d . it is not possible to start the above sequence when the main - deck hatch is fully closed . this interlock is via normally - closed contacts of &# 34 ; main - deck hatch closed &# 34 ; relay ( mdhc ) 193 . e . when the main - deck hatch becomes fully closed it cancels both memory relays eorm 201 and 2m 204 . the platform is now ready for a new dispatch . except for relay switching times , when the controller is powered , there always is an activated open - or close - command for each hatch . circuitry to reverse commands to each hatch is interlocked through the &# 34 ; go # 1 &# 34 ; relay contacts 421 . a change in hatch command is possible only under the following circumstances : a . a change of command from third - deck hatch close to third - deck hatch open is possible only when the platform is at hatch - sequence ( at h . seq1 activated , contacts 443 closed ), dispatch is for a level below &# 34 ; stow &# 34 ; ( lodk 416 activated , contacts 441 closed ), and the main - deck hatch is closed ( relay mdhc 416b activated , contacts 442 closed ). b . a change of command from third - deck hatch open to third - deck hatch close is possible only when the platform is at hatch - sequence ( relay at h . seq1 411 activated , contacts 436 closed ) and the destination is either &# 34 ; stow &# 34 ; or &# 34 ; main - deck &# 34 ; ( relay lodk 416 deactivated , contacts 436 closed ). c . a change of command from main - deck hatch close to main - deck hatch open is possible only when the platform is at the hatch sequence level , ( relay at h . seq 1 411 activated , contacts 432 closed ), destination is to the main - deck ( relay 1m 202 activated , contacts 430 closed ), and the third - deck hatch is closed ( relay 3dhc 416d activated , contacts 431 closed ). d . a change of command from main - deck hatch open to main - deck hatch close is possible only when the platform is at the hatch - sequence level ( relay at h . seq 1 411 activated , contacts 426a closed ), and the destination is &# 34 ; stow &# 34 ; or levels below ( relay 1m 202 is unactivated , contacts 426 closed ). a safety interlock from proximity switch 231 prevents the main - deck hatch closing if the main - deck platform - leveling switch is activated ( relay 1h 250 must be activated and contacts 424 closed ). to reduce the number of relay parts to be stocked , and therefore influence the supply system the least , logic circuits are configured for the acceptance of time - delay relays which are all of the delay - on - operate type . a summary of time - delay relays used is as follows : d . if the number of levels does not require a g3 relay then disp . reg . relay 413 should be time - delay ; 0 . 3 - 0 . 4 seconds . a . the signal to the &# 34 ; go - up memory &# 34 ; ( goupm ) relay coil 272 goes through the &# 34 ; down &# 34 ; motor contactor auxiliary contacts ( dn ) 324 . similarly the signal to the &# 34 ; go - down memory &# 34 ; relay coil ( godnm ) 270 goes through the &# 34 ; up &# 34 ; motor contactor auxiliary contacts ( up ) 304 . b . only dispatch switches at command control stations from which dispatches are permissible are energized . this is via normally closed contacts 160 - 176 of the h and l relays . c . an unsafe signal from sensors consists of an input into the logic control which is open , grounded or power supply common . trunk mounted proximity switches 231 - 248 to sense platform motion have power supply high voltage output when the switch is not actuated by a device normally intended for that purpose . this causes the signal input relays ( h and l series ) to be activated for a safe condition and deactivated for an unsafe , slow or normal stop condition . d . dispatch orders consist of an input signal into the logic , m relays 202 - 211 , with a potential difference from ground , chassis or common . the circuitry of the logic is so designed that no potential difference from ground or common remains on any command input lead when not energized by a push - button . e . duplicate proximity switches are provided at the hatch - sequence level 233 and 235 , and at the lower extreme of travel 247 . the duplicate switches are used as back - up for the primary switches and interrupt logic signals to the auxiliary command relays insuring that platform travel shall proceed in slow - speed or stop . f . a safety provision is incorporated into the memory circuits which causes the cancellation of output signals to the main contactor solenoids should the high - speed contactor not drop out within a prescribed time of being commanded to do so . this circuit involves passing the logic power to the reset circuitry of the memory units through the normally - closed auxiliary contacts of the &# 34 ; high - speed &# 34 ; motor contactor ( hs ) 214 in parallel with normally - closed contacts of a &# 34 ; low - speed time - delay &# 34 ; relay ( ls - td ) 215 . the dispatch memory 202 - 211 will be caused to reset if the high - speed contactor fails to drop out and the &# 34 ; low - speed time - delay &# 34 ; relay ( ls - td ) 408 in parallel with the &# 34 ; low - speed auxiliary &# 34 ; command relay ( lsa ) 407 times out and energizes . this resetting of the dispatch memory deactivates godnm and goupm coils 275 , 272 because the m contacts 361 - 368 are opened . consequently , godnm and goupm contacts 446 and 444 are opened and upa and dna relay coils 404 and 405 are inactivated . the motor controller is wired so that both the hs contactor and an up or dn contactor must be activated for the platform to move . g . the elevator is permitted to start just once in high - speed on each dispatch ; except that there is an automatic high - speed reset at hatch - sequence when the platform is proceeding to levels below from a dispatch which originated at the main - deck . this safety feature is to prevent the logic from switching back into high - speed after the platform has been traveling in low - speed if , for example , a stop switch should fail and the platform travels to a section of the trunk clear of any leveling switches . it is accomplished by interlocking relays uphsm and dnhsm 273 and 271 as memory units via their own contacts 353 and 330 . h . when the platform is dispatched to an intermediate level , all slow - and stop - switches beyond the destination in the direction of travel act to slow the platform and bring it to a stop in case the switches at the intermediate level fail to do so . this is particularly important at the stowage level when the platform travels upward to prevent the platform from running into the closed maindeck hatch cover . this feature is achieved by the use of l and h relay contacts 305 - 323 and 332 - 351 in the input signals to relays goupm , uphsm , godnm and dnhsm 272 , 273 , 270 and 271 . in actual use , several modifications of the above - described circuit may be necessary due to varying system requirements . specifically : ( a ) if platform stopping levels are disposed so closely together that the high and low proximity switches associated with the respective platform levels overlap ( e . g . platform forward 26 and second platform aft 27 ) then the relay contact chains for goupm 272 and godnm 270 must be separated . this is to prevent the elevator platform , when going down for example , from stopping prematurely at the h switch for the level below that desired . ( b ) for reasons of standardization it has been required in some cases to use proximity switches in the location sensing unit that are closed by the target so that the associated h and l relays are normally unactivated . one particular embodiment utilizes duplicate switches that are opened by the target but utilizes switches that are closed by the target elsewhere . ( c ) the electromechanical relays described above may be replaced by all - solid - state relays . obviously , numerous ( additional ) modifications and variations of the present invention are possible in light of the above teachings . it is therefore to be understood that within the scope of the appended claims , the invention may be practiced otherwise than as described herein .