US3539818A - System for controlling the transfer of materials into or out of a reservoir - Google Patents

Description

Nov. 10, 1970 -r. c. COVILL- 3,539,313

SYSTEM FOR CONTROLLING THE TRANSFER OF MATERIALS INTO OR OUT OF A RESERVOIR Filed July 19, 1968 2 Sheets-Sheet 1 NOV. 1,1970 1-. c, cov 3,539,818

SYSTEM FOR CONTROLLING THE TRANSFER OF MATERIALS v v INTO OR OUT OF A RESERVOIR Filed July 19, 1968 2 Sheets-Sheet 2 FIG. 2.

US. Cl. 307-9 9 Claims ABSTRACT OF THE DISCLOSURE A system for controlling the transfer of material into or out of a mobile reservoir such as a fuel tank. A switch device associated with an electrical circuit interrupts said circuit when the amount of material in the reservoir falls outside a selected limit. The reservoir may be compartmentalized into a plurality of horizontally separated compartments which are separately controlled by the same electrical circuit.

The present invention relates to a system for controlling the transfer of material into or out of a reservoir for gases, liquids or particulate solids, and is particularly concerned with a means for filling and/or emptying the reservoir wherein the reservoir and the filling and/or emptying means are movable relative to each other.

It is often required during the filling and/or emptying of a reservoir that the amount of material stored in the reservoir should fall within one or more particular limits: i.e., the amount of material in the reservoir should not exceed a specified maximum quantity and/or should not fall below a specified minimum quantity. Common examples Where one or more of these requirements are to be met in the filling and/ or emptying of road tankers and marine tankers.

The present invention seeks to provide a system for ensuring that the maximum and/r minimum amount of material stored in the reservoir is automatically controlled.

The system in accordance with this invention comprises a switch device associated with the reservoir, fixedly located transfer means operable for transferring material into or out of the reservoir, and means for detachably interconnecting the switch device and the transfer means to form a circuit, the switch device being arranged to interrupt the circuit when the amount of material in the reservoir falls outside a selected limit, and the transfer means being operable only when the circuit is complete.

The circuit may be arranged for transmitting electrical, pneumatic or hydraulic signals.

Preferably, a part of the circuit when completed, provides a connection to earth from the reservoir. This is advantageous where the material to be transferred is inflammable since any accumulated static charge due to friction in the material can be discharged with substantially no risk of fire or explosion from this cause. Conveniently, the connection to earth may be through the fixedly-located part of the circuit so that the interconnection of the switch device and the transfer means concurrently earths the reservoir, and provides a definite indication that the reservoir is earthed. In the case where the circuit transmits electrical signals, the voltage and circuit would be, of course, quite small. The electrical energy may be supplied in the form of direct current or of alternating current, or rectified alternating current.

The transfer means may include a valve and/or a pump for the transfer of material, and a relay which United States Patent 0 3,539,818 Patented Nov. 10, 1970 operates when the circuit is complete to provide power, in operation, for the valve and/or pump.

The switch device may operate in accordance with either the level or the weight of material in the reservoir.

The invention also includes an installation comprising at least one reservoir in combination with the system as described in the preceding paragraphs.

There may be a plurality of reservoirs in the installa-' tion, there being a switch device for each reservoir, and the devices being all connected.

Preferably, the or each device is mounted on the, or a respective, reservoir.

The invention will now be described by Way of nonlimitative example only and with reference to the accompanying drawings, in which:

FIG. 1 depicts diagrammatically one form of an installation incorporating a system in accordance with the invention.

FIG. 2 illustrates a part of the installation of FIG. 1 to a greater scale.

FIG. 3 illustrates another part of the installation of FIG. 1 to a greater scale, and

FIG. 4 depicts an alternative part which may be used in place of the part shown in FIG. 2.

Referring first to FIG. 1, the installation generally indicated by reference numeral 10, comprises a reservoir or tank 11 forming the cargo-carrying part of a mobile road tanker 12 suitable for transporting a liquid such as petroleum spirit, or a dry, particulate solid such as sugar or flour. The tank 11 is divided into a number of horizontally separated compartments Ila-11c, each of which is required to be filled with cargo to a specified level.

Each compartment 11a-11e is provided with an electrical switch 13a-13e respectively which is responsive to the level of cargo in the corresponding compartment. The switches 1311-1312 are electrically connected in series by conducting wires 14. When the level of cargo in a compartment is below a specified maximum level, the switch 13 for that compartment is closed. If the specified maximum level in a compartment is exceeded, the corresponding switch is open.

It will be appreciated that when the maximum level of cargo for each compartment 11a-11e is not exceeded, all the switches 13a-13e will be closed and will form an uninterrupted electrical path. As depicted in FIG. 1, the specified maximum level of cargo in compartment He has been exceeded and switch 13e is open, thus interrupting the electrical path.

The switches 13a-13e are connected to a fixedly located intrinsically safe source of electrical energy generally indicated by reference 15, via a two pole detachable connecting plug 16 which is adapted to engage electrically with suitable contacts connected respectively to switch 13a and switch 13c. (An intrinsically safe source is a source which is certified by Her Majestys Factory Inspectorate of the Ministry of Labour as being incapable of producing sparks of sufficient energy to ignite stored materials or vapours emanating therefrom.) In this case, the source 15 comprises a step-down transformer 15a which is connected to an alternating mains supply 15b of 240 volts, and has a low-voltage output of, say 15 volts alternating current. The transformer output is connected to two contacts of a full-wave rectifier 15c and the two other con tacts of the rectifier are connected respectively to a high ohmic-valve resistor 15d, and the connecting plug 16. The source 15 thus provides full-wave rectified alternating current at 15 volts and a low current. The current may be of the order of 20 milliamps when the circuit is complete and functioning correctly.

A relay 17 is provided in series with the resistor 15d of source 15. The relay 17 serves to control the supply of electrical power to a fixedly located solenoid valve 18 for regulating the flow of cargo through a filling pipe 19 and a flexible filling hose (not shown) for transferring cargo into a desired compartment 11a11e.

The arrangement is such that when current flows through the relay 17, the relay 17 provides a path for electrical power to pass via lines and 21 to the valve 1 8. The valve 18 opens enabling cargo to pass through pipe 19 and the flexible hose (not shown) to the required compartment 11a-11e. This situation will result only when all of the switches 13a-13e are closed, i.e'. the specified maximum level of cargo for every compartment 11a- He has not been exceeded and when the detachable connecting plug 16 is in the position shown.

When the current through the relay 17 is interrupted, e.g. due to exceeding the specified cargo level in one of the compartments 11a-11e, or because the connecting plug 16 is not attached in its electrically-connecting location-the relay.-- 17 interrupts the electrical conduction path in line 20 causing the solenoid valve 18 to become inactivated and to close the passage for cargo in pipe 19. Thus, two conditions must be fulfilled in order that cargo can flow through pipe 19; these conditions are that the connecting plug 16 must be connected and that the maximum specified level of cargo in every one of the compartments 11a-11e must not have been exceeded.

In many instances, the movement of the cargo either in the tank 11 or through the pipe 19 generates static electrical charges which can be hazardous if allowed to accumulate. This is particularly the case when the cargo is inflammable, e.g. petroleum spirit, sugar or flour. In the embodiment of the invention depicted in FIG. 1, any static charges associated with the road tanker 12 are discharged to earth through an earthing strap 23 attached to one of the leads from the source 15. For convenience, it is preferred to arrange the earthing strap 23 as part of the fixedly-located part of the installation comprising, inter alia, the source 15, the relay 17 and the solenoid valve 18.

In the arrangement of FIG. 1, there is depicted a con necting plug 16a substantially identical with the connecting plug 16 but at a different location on the road tanker 12. The connecting plug 160: is connected into the aforedescribed electrical circuit in parallel with plug 16, but so that it functions in the same manner as plug 16 and may be used as an alternative thereto to suit the convenience of the operating personnel. Preferably, only one at a time of the plugs 16, 16a is employed, the choice being determined to suit the convenience of the personnel involved, The connecting electrical conductors are indicated by the dotted lines 14a.

, It is to be noted that the system in accordance with the invention is fail safe. That is to say that any break in the electrical connections will cause the solenoid valve 18 to become inoperative so that the loading operation is interrupted until the break is remedied.

The regulation of the quantity of material transferred into or out of each compartment of the tank 11 maybe effected by suitable measuring devices (not shown) upstream of the solenoid valve 18. If these measuring devices, or their control systems, break down, the system of the invention inactivates the material transfer system, thus avoiding troublesome, expensive or dangerous spillages of cargo. For example, during the filling of a road tanker with a measured quantity of petroleum, the tank of the tanker may initially contain some residual petroleum from its previous duty, and there will not be suflicient room in the tank to accomodate the measured quantity; in such circumstances, the system of the invention will prevent any overfilling of the tank and the consequential spillages. Alternatively, the system of the invention may be employed to regulate the transfer of material in the absence of other measuring devices.

FIG. 2 shows in greater detail a preferred form of switch which may be used as one of the switches l3a-13e, particularly for liquid cargoes.

The switch, generally designated by reference 25 comprises a flexible diaphragm 26 of polytetrafiuoroethylene exposed to the cargo space of the tank 11 via an electrically-insulating tube 27 of nylon or unplasticised polyvinyl chloride extending downwardly to just below the desired maximum height of cargo, and a micro-switch 28 having contacts (not shown) which are in electrical contact when the level of cargo in the tank is less than the desired maximum level (corresponding with the switches 13a-13d of FIG. 1) and which become separated in a manner hereinafter explained when the desired maximum level in the tank is exceeded (corresponding with switch 13e of FIG. ,1). The microswitch 28 has an operating arm 29 which is biassed to an inoperative position by a spring 30, the compression in the spring 30 being adjustable by an adjusting nut 31.

When the cargo in a compartment 11a-11e approaches the desired maximum level, it closes ofif the lower end of the tube, trapping air and/or vapour therein. If the level of the cargo continues to rise, the trapped air and/or vapour is compressed and the rise in pressure moves the diaphragm upwardly so that it pushes upwardly against an actuating member 32. The actuating member 32 is displayed upwardly into contact with the operating arm 29 which then is moved upwards to cause the contacts in the microswitch 25 to separate, so that the electrical circuit is interrupted. The effect of this interruption has already been explained by reference to the switches 13a-13e of 'FIG. 1. When the level of the cargo falls, the pressure in the tube 27 falls and eventually the corresponding movement of the diaphragm permits the microswitch to complete the electrical circuit.

Pressure switches are advantageous in that no electrical conductors need enter the cargo compartments Ila-11a.

Since the parts of the pressure switch which are exposed to the interior of the tank 11 (the tube and the diaphragm) are electrically non-conductive, the risk that static changes accumulating in the tank 11 will be discharged outside the tank 11 is almost negligible.

FIG. 4 shows in detail another form of switch which may be used in place of the switch shown in FIG. 2. This switch comprises two rigid electrical conductors a, 50 which are retained in a tube 51 extending downwardly from a retaining nut 52. The nut 52 retains the tube 51 and a connection housing 53 against the top of the tank 11. About half-way down the outside of the tube 51 is a fixed annular washer 54, and within the tube, just below the level of the washer 54, is a springy metal contact 55a which is supported by the conductor 50a, and extends downwardly therefrom and somewhat inwardly towards a similar springy metal contact 55b supported by the conductor 50. Both of the contacts 55a, 55b are of magnetisable metal, such as steel.

An annular float 56 of spongy polyvinyl chloride is arranged to travel up and down around the tube 51 when the surface of the cargo has risen above the floats lowest position as determined by an adjustable annular washer 57 resting on a cotter pin 58 extending through the tube 51.

Recessed into the top of the float 56 is an annular magnet 59.

When the level of the cargo is so high that the float 56 is disposed adjacent the Washer 54, and with the magnet 59 substantially surrounding the contacts 55a, 55b, the contacts are outwardly attracted away from e ch other by the annular magnet 59.

While the contacts 55a, 55b are touching, under the action of their inherent springiness, they provide an electrical path through the switch from the lead 14 on one side of the switch to the lead 14 on the other side thereof, in correspondence with the switches 13a-13d of FIG. 1. When the contacts 55a, 5512 are separated by the attraction of the annular magnet 59, the electrical path through the switch is interrupted, as in the case with the switch 1312 of FIG. 1. If the level of the cargo should fall so that the float moves downwardly away from the washer 54, the contacts 55a, 55b will spring back into their mutually contacting position thus providing an uninterrupted electrical path through the switch.

The invention may take forms other than that described for example, where the cargo is a particulate solid, it may be preferred to replace the above-described forms of switch by other means, such as a proximity probe. This latter comprises, in effect, a condenser including a downwardly protruding conductive electrode concentrically surrounded by an annular electrode. The cargo is able to rise into the space between the two electrodes thus increasing the capacitance of the condenser. When the capacitance attains a selected value, the circuit including the proximity probe is interrupted by a switch.

In another form, the switches 13a-13e may be replaced by means responsive to the weight of the cargo, e.g. strain gauges. When a selected weight of cargo is exceeded, the circuit is interrupted.

The invention may be modified for operations involving the discharge of cargo from tank 11. In this case, the switches 13a-13e, pressure switches float-operated switches, proximity probes or strain gauges are adapted to interrupt the electrical circuit when a specified minimum quantity of cargo remains in the tank 11 or a compartment thereof.

Various combinations of the features disclosed above may be employed without departing from the invention as defined by the appended claims.

What is claimed is:

1. A system for controlling the transfer of material into or out of a mobile reservoir comprising:

(a) a reservoir;

(b) a spring biased diaphragm switch disposed in said reservoir, responsive to the level in said reservoir;

(c) a fixedly-located transfer means operable for transferring material into said reservoir; and

(d) means for detachably interconnecting said diaphragm switch and said transfer means to form a circuit which is interrupted by said diaphragm valve when the amount of material insaid reservoir falls outside a selected limit thereby cutting off operation of said transfer means.

2. The system of claim 1 including a means for grounding said electrical circuit connected to said transfer means.

3. The system of claim 1 wherein said diaphragm switch comprises:

(a) an electrically insulated tube extending into said reservoir;

(b) an actuating member disposed inside said insulating tube, responsive to the level of material in said reservoir;

(c) an operating arm, responsive to said actuating 55 member, disposed above and in communication with said actuating member;

((1) a microswitch disposed above said actuating member, and in communication with said operating arm;

(e) a spring means connected to said actuating member and said operating arm, which biases said arm so that said switch is normally closed.

4. A system for controlling the transfer of material into or out of a mobile reservoir comprising:

(a) a reservoir;

(b) a switch comprising a magnetic activating means responsive to the level in said reservoir;

(c) a fixedly located transfer means operable for transferring material into said reservoir; and

(d) means for detachably interconnecting said switch and said transfer means to form a circuit, which is interrupted by said switch when the amount of material in the reservoir falls outside a selected limit, thereby cutting off operation of said transfer means.

5. The system of claim 4 including a means for grounding said circuit.

6. The system of claim 4 wherein said switch comprises:

(a) a tube, provided with a pair of annular constraints around said tube at two vertical levels, disposed in said reservoir;

(b) a pair of electrical conductors connected to said circuit and disposed in said tube, each of the ends of said conductors tipped with a magnetizable metal contact, said contact biased to touch each other below said upper annular constraint;

(c) a magnetized float disposed around said tube between said constraints providing the means for opening said circuit when said float reaches the level of said touching contacts.

7. A system for controlling the transfer of material into or out of a reservoir comprising:

(a) a reservoir comprising a plurality of horizontally separated compartments;

(b) a plurality of series connected switch devices, one said device disposed in each of said compartments;

() a fixedly-located transfer means operable for transferring material into any of said compartments;

((1) means for detachably interconnecting said plurality of switch devices and said transfer means to form a circuit which is interrupted when the amount of material in any of said compartments falls outside a selected limit, thereby cutting off operation of said transfer means.

8. The system of claim 7 wherein each of said switch devices comprises an actuating member responsive to the level of material in said compartment, disposed inside a tube, said actuating member activating an operating arm to disengage a microswitch, whereby said circuit is interrupted.

9. The system of claim 7 wherein said switch device comprises a magnetized float responsive to the level of material in said compartment, disposed around the tube in which a pair of electrical conductors, electrically connected to said circuit, are disposed with their ends in electrical communication by means of a pair of magnetizable metal contacts, whereby said float acts to break the circuit when the level in said compartment moves said float up to the point where said conductors are in electrical communication.

References Cited UNITED STATES PATENTS 2,380,884 7/1945 Von Stoeser et al 222-64 3,170,479 2/1965 Mueller 22264 X 3,339,578 9/1967 Smith 307118 X 0 FOREIGN PATENTS 938,473 2/ 195 6 Germany.

ROBERT K. SCHAEFER, Primary Examiner 5 T. B. I OIKE, Assistant Examiner US. Cl. X.R.

Images