Air conditioning monitoring device
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to time monitoring devices and more particularly to such devices that make commonly used equipment available to one or more persons or entities for a predetermined schedule and to provide the flexibility of extending it. 
     2. Description of the Prior Art 
     It is usual to find agreements between the owner of a particular equipment with one or more entities for its use during a schedule that is agreed upon ahead of time. The most common example is a landlord that contracts with tenants, in a multiple unit, office building, to maintain adequate air conditioning from Monday to Friday, from 8:00 AM to 6:00 PM. It is not unusual that a particular tenant needs to extend its working hours beyond the contracted schedule, i.e., accountants near tax deadlines. The landlord usually needs to be notified ahead of time to make the proper arrangement. The present invention allows each individual tenant to switch on and off the use of the air conditioning system beyond the contracted schedule without giving notice to the landlord. The landlord only needs to read the elapsed time meter associated with each tenant and charge for this extra service accordingly. Also, the landlord may leave the air conditioning system off for the weekends, for example, and allowing any of the tenants to turn it on if needed. This would eliminate the compromise usually found in these situations which call for maybe one half of a day service on Saturdays, or the like. This arrangement saves energy. 
     Applicant believes that the closest reference corresponds to U.S. Pat. No. 3,995,686, issued to Herbert L. Laube. However, it differs from the present invention because this device measures the time that a compressor or heater is in operation and the present device measures the time of each person (tenant) individual use outside the predetermined schedule. 
     Other patents describing the closest subject matter provide for a number of more or less complicated features that fail to solve the problem in an efficient and economical way. None of these patents suggest the novel features of the present invention. 
     SUMMARY OF THE INVENTION 
     It is the main object of the present invention to provide a device that allows the building owner or operator to set a minimum operating schedule (a major energy conservation technique) while allowing the tenant or equipment user of the equipment that require overtime use of the equipment to do so with a minimum of complication to extend the time of its use beyond a predetermined schedule without requiring giving notice to the owner. 
     Another object of the present invention is to provide a device that may be used in a multiple office unit building and allow each tenant to obtain air conditioning service beyond the contracted schedule. 
     Further objects of the invention will be brought out in the following part of the specification, wherein detailed description is for the purpose of fully disclosing the invention without placing limitations thereon. 
    
    
     DESCRIPTION OF THE DRAWING 
     With the above and other related objects in view, the invention consists in the details of construction and combination of parts as will be more fully understood from the following description, when read in conjunction with the accompanying drawings in which: 
     FIG. 1 represents the circuit of the present invention using electro mechanical devices. 
     FIG. 2 is a schematic representation of a logical circuit that implements the functions of the circuit of FIG. 1. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring now to FIG. 1 where the present invention is referred to numeral 10 and the equipment being used is referred to with the letter E. The circuit of equipment E is interrupted at terminals 50 and 51 which are connected or disconnected by device 10, as it is described below. 
     Time monitoring device 10 is powered by an electric source S through protective circuit breaker B. A main timer 20 is energized by this electric source. Timer 20 includes a normally closed relay 21 and normally open relay 22 which are controlled simultaneously. Main timer 20 is set in the preferred embodiment so that normally open relay 22 closes during the contracted schedule for which equipment E will be made available to the user or users and during this time normally closed relay 21 will be open. Of course, relays 21 and 22 may be interchanged and the timer 20 programmed in reverse. In the preferred embodiment the equipment being shared by two users corresponds to an air conditioning system in a multiple tenant office building so timer 20 is programmed on a 7 days basis from 8:00 AM to 6:00 PM, Mondays through Fridays. The contacts of relay 22 are directly connected to terminals 50 and 51 so that if timer 20 is within the contracted time then equipment E is in operation. One of the contacts of relay 21 is connected to one of the poles of source S and the other contact is commonly connected to one end of the individual time monitoring circuits 30 and 30&#39;. The other end of circuits 30 and 30&#39;  are connected to the other pole of source S. In the preferred embodiment only two individual time monitoring circuits are shown corresponding to two individual users or tenants. However, it is understood that there are as many circuits like the 30 and 30&#39; circuits as tenants or users exist. Circuit 30 (and 30&#39;) includes elapsed time meter 35 which is connected in parallel with the coil of normally open relay 36. Switch 37 is connected in series with the relay 36 and elapsed time meter 35 combination. When normally open switch 37 is closed, the coil of relay 36 is activated which closes the contacts of relay 36. Normally open switches 37; 37&#39; etc. may be controlled through timers, computers or any other programmable means. These contacts are electrically connected to terminals 50 and 51 thereby activating equipment E. During this time, elapsed time meter 35 is activated thereby measuring the time that this particular user has caused equipment E to be energized outside the contracted time. Switch 37 could be a single pole switch or a timer switch that could be set to close for a predetermined time. Ideally, switch 37 would be placed in a secure location accessible only by the authorized agents of the tenant. 
     An alternative electronic embodiment is shown in FIG. 2 wherein a timer 20a controls normally open switch 21a which is connected on one end to ground which represents logic state &#34;0&#34;. The other end of switch 21a is connected through resistor 29a to supply voltage Vcc which represents logic state &#34;1&#34;. Also, there are two other connections to this other end of switch 21a. One of the connections is to the input of inverter 26a and the other connection is to a point where a plurality of commonly connected individual tenant switches 37a, 37&#39;a, etc. are connected. Normally open switches 37a are commonly connected on one end and the other end being connected to the enabling input of a quartz digital clock 35a, which is connected to ground through resistor 39a in order to avoid picking up noise, and also connected to one of the inputs of OR gate 40a. The other switches in parallel, 37a; etc. have similar connections. The output of inverter 26a is connected to one of the two inputs of OR gate 60a and the other input is connected to the output of gate 40a. The output of gate 60a activates relay 22a which closes the circuit that enables equipment E to operate. Relay 22a could be a plurality of relays and equipment rather than just one. 
     The operation of the circuit shown in FIG. 2 is as follows: during a predetermined time period for which equipment E must be on, timer 20a causes switch 21a to be closed which makes the output of inverter 26a a logic &#34;1&#34; which in turn is gated through OR gate 60a thereby activating relay 22a and enabling equipment E. Also, the ground level, or &#34;0&#34; state, transmitted through switch 21a is applied to the common end of the plurality of switches 37a; 37&#39;a; etc. thereby keeping a &#34;0&#34; level at the enabling input of clock 35a which will not make it run. Therefore, during this predetermined period it is inmaterial what the position is for any of the switches in the plurality of swtiches since they will not activate their associated clocks 35a; 35a; etc. When switch 21a is open, either manually or through timer 20 or any other programmable device, then pull-up resistor 29a connected to a logic &#34;1&#34; voltage brings the level up causing the output of inverter 26a to go to &#34;0&#34; thereby deactivating relay 22a. At this point, any of the plurality of switches 37a; 37&#39;a; etc. would, if closed, transmit a &#34;1&#34; that would activate its associated clocks 35a; 35&#39;a; etc. and this &#34;1&#34; would be gated through OR gates 40a and 50a thereby activating relay 22a and making equipment E operable. Each individual tenant would be charged for the time of equipment use and the location of switches 37a; 37&#39;a; etc. would be in secure places only accessible to a particular tenant or user assigned. 
     It is believed the foregoing description conveys the best understanding of the objects and advantages of the present invention. Different embodiments may be made of the inventive concept of this invention. It is to be understood that all matter disclosed herein is to be interpretted merely as illustrative, and not in a limiting sense, except as set forth in the following appended claims.