Automatic Slowdown And Cutoff System

Abstract

A system for dispensing a precise quantity of a fluid. When power is applied to a motor, the motor drives a pump to dispense fluid at a relatively high rate. However, in response to an indication that a quantity of fluid, slightly less than the desired quantity, has been dispensed, power to the motor is substantially reduced. This slows the dispensing rate so that power may be removed from the motor and the pump stopped when precisely the desired quantity of fluid has been dispensed.

Description

BACKGROUND OF THE INVENTION

This invention relates generally to a system for controlling the dispensing of a fluid, and more particularly to a system for automatically reducing the rate at which the last bit of a selected quantity of fluid is dispensed so that cutoff may be effected at the precise quantity desired.

There are numerous applications in the sale of fluid substances and in industrial processes where a requirement exists to provide a precise quantity of a fluid. In the past, the fluid-dispensing operations for these applications have generally been manually controlled. However, the precision which can be obtained with manual operation is somewhat limited and, as labor costs increase, the tendency has been to automate such dispensing operations wherever possible.

An example of a partially automated fluid-dispensing system is provided in copending applications, Ser. No. 852,848 entitled "A system for Remotely Controlling and Monitoring Fuel Dispensing Pumps" filed on behalf of Charles R. Sauber on Aug. 25, 1969 and assigned to the assignee of the instant application. In this system an operator at a central station controls the turning on of a fluid-dispensing pump at a remote location, while the purchaser at the remote location controls the actual amount of fuel delivered. The pump is automatically turned off under control of the control station when the purchaser stops dispensing fuel. This system could be fully automated by requiring the purchaser to only place the nozzle of the fuel pump in his gas tank and specify the amount of fuel which he desires. The operator at the central station would then set the system to dispense the specified amount of fuel and turn the pump on. The pump would be turned off when the desired amount of fuel has been dispensed.

However, in this and most other practical applications, the pump runs at relatively high speed during most of the dispensing operation in order to permit the desired amount of fuel to be delivered within a reasonable time. However, with the pump running at this high speed, it is difficult to instantaneously stop the pump when it has delivered precisely the desired amount of fuel. In order to overcome this problem, some prior art systems have utilized a valve, such as a solenoid valve, in the fuel line. This valve is energized to slow down the flow of fuel when a predetermined amount of fuel, generally slightly less than the desired amount, has been dispensed. This permits the last small amount of the fuel to be dispensed at a slow rate so that cutoff may be had at precisely the desired quantity.

The above-described solution to the slowdown cuts problem accomplishes the desired result. However, it requires the use of relatively expensive valves which are subject to maintenance and replacement problems. Further, the installation of such a valve within the plumbing of the fuel dispenser is difficult and expensive.

A requirement therefore, exists for a fluid-dispensing system which permits the fluid to be dispensed at high speed until most of a desired amount of fluid has been dispensed, and that cuts down the dispensing speed for the last bit of fluid so that cutoff may be effected when precisely the desired amount of fluid has been dispensed. Such a system should be relatively easy and inexpensive to install, should be long lived, and should be relatively maintenance free. Since the above requirements cannot be met by a system utilizing electromechanical valves, these requirements would seem to dictate the use of a fully electronic system.

SUMMARY OF THE INVENTION

It is therefore, a primary object of this invention to provide an improved fluid-dispensing system.

A more specific object of this invention is to provide a system for dispensing a precise amount of fluid while permitting the dispensing operation to be completed within a reasonable time.

A still more specific object of this invention is to provide a dispensing system of the type indicated above which dispenses most of the fluid at a relatively high rate, but cuts back to a low dispensing rate for the last bit of fluid so that cutoff may be easily effected at precisely the desired amount.

Another object of this invention is to provide an automatic fluid-dispensing slowdown and cutoff system, of the type indicated above, which is relatively easy and inexpensive to install, operate and maintain.

In accordance with these objects this invention provides an electronic automatic slowdown and cutoff system which comprises a controlling module and at least one controlled module. At the controlled module there is a motor-driven device, such as a pump, for dispensing a fluid. The controlling module has a means responsive to the operation of the fluid-dispensing device for indicating a condition thereof such as, for example, the quantity or dollar value of the fluid dispensed. The system also includes a first means responsive to an indication of a first condition of the device from the indicating means for reducing the average power applied to the motor, thereby reducing the speed of the motor, and thus the rate at which fluid is dispensed; and a second means responsive to the indication of a second condition of the device, such as the dispensing of the desired amount of fluid, from the indicating means for terminating power to the motor, and thus terminating the fluid-dispensing operation.

BRIEF DESCRIPTION OF THE DRAWING

The foregoing and other objects, features and advantages of the invention will be apparent from the following more particular description of a preferred embodiment of the invention as illustrated in the accompanying solitary view which is a semiblock schematic diagram of an illustrative embodiment of the automatic slowdown and cutoff system according to the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring now to the drawing, it is seen that the system for the illustrative embodiment of the invention is a fuel-dispensing system of the general type shown and described in the before-mentioned copending patent application. The system of this invention includes three major units; a control module 10, an automatic slowdown module 12, and a pump station 14. One or more additional pump stations 14' may also be provided. The relative locations of the various units are not critical; however, in most applications, the control module and automatic slowdown module would be situated at a centralized point with the pump stations being remotely located.

In operation, a purchaser at a pump station contacts the operator at the control station module through an intercom system, or some other standard communications device, and specifies the amount of fuel which he desires. The particular means utilized to convey this information does not form part of the present invention. The amount of fuel specified by the purchaser may be in gallons, or some other unit of measure, but, more usually, it is specified as a dollar amount.

The operator at the control module adjusts dials 16A, 16B, and 16C on a control console to set the amount specified by the purchaser into counter stages 18A, 18B, and 18C respectively. Each counter stage includes a dial portion 20 having 10 conductive points, a conductive arm 22, and a counter stage control circuit 24. The control circuits may be of any standard type. For example, they may comprise a relay coil which is effective, each time it is energized, to step the corresponding arm 22 of the stage is positioned on the zero conductive point.

If control module 10 is being utilized to control more than one pump station, the operator would then set switches 30 and 32 to the appropriate position for the selected pump station and then close pump-on switch 34. For applications where modules 10 and 12 are at the same central control location, switches 30 and 32 may be ganged so that both switches are transferred in a single operation. The closing of switch 34 permits a low-voltage DC potential, for example +24 volts, to be applied from source terminal 36, through power-on indicator lamp 38, now-closed switch 34, line 39, normally closed contact 40' of relay coil 40, and relay coil 42 to ground. The energizing of coil 42 closes normally open contact 42'. This closes a circuit from AC potential source 44 through line 46, triac device 48, line 50, switch 32, and pump motor 52 to ground. Pump motor 52 is in this manner energized to drive pump 54 permitting the desired fuel-dispensing operation to be performed.

In addition to the path-containing triac device 48, there are also two high-impedance paths between lines 46 and 50. The first of these paths includes a small resistor 56 and a low-value capacitor 58. The function of this path is to serve as a surge suppressor. The second path includes a resistor 60 and a low-value capacitor 62 which are connected together through two parallel paths. One of these paths is through normally closed contact 64' of relay coil 64, and the other path is through potentiometer 66. When contact 64' is closed, potentiometer 66 is effectively shorted out of the circuit. Under this condition, the potential which is developed across capacitor 62 never reaches a level which is sufficient to trigger diode 68, and triac 48, therefore, remains conductive during the entire AC cycle. The power supplied to pump motor 52 under this condition of operation is sufficient to cause the motor to operate at a relatively high speed.

As each unit of fuel is pumped by pump 54, a standard telemeter device associated with the pump generates a pulse signal on line 70. If it is assumed that counter stages 18 are counting in units of 1 cent, then a pulse would appear on line 70 for each 1 cent's worth of fuel which is pumped. Each pulse on line 70 is applied through switch 30 and line 72 to energize units counter stage control 24A to step stage 18A down one unit. Every 10th pulse of line 72 is passed through control 24A and line 74 to decrement stage 18B. Similarly, every 10th pulse on line 74 is passed through control circuit 24B and line 76 to decrement counter stage 18C.

The above sequence of operations continue until counter stage 18C has been counted down to zero, counter stage 18B has been counted down to zero, and counter stage 18A has been counted down to a value of 5 cents. From the drawing, it is seen that, at this time, the positive voltage on line 39 is applied to a circuit which includes the zero contact point on dial 20C, arm 22C, line 78, the zero contact point on dial 20B, arm 22B, line 80, arm 22A, the five contact point on dial 20A, line 82, resistors 84 and 86, and relay coil 64 to ground. Since contact points 4, 3, 2 and 1 on dial 20A are also connected to line 82, coil 64 remains energized until precisely the desired amount of fuel has been dispensed. The energizing of relay coil 64 opens normally closed contact 64'. This removes the short circuit across potentiometer 66, increasing the total resistance of the path containing this element by an amount which is dependent on the setting of the potentiometer arm. This increase is effective to cause the potential developed across capacitor 62 to be sufficient to fire diode 68 at some predetermined point in each AC half cycle, thus causing triac 48 to be cut off for a portion of each AC cycle. Since only a portion of each AC half cycle is now applied to pump motor 52, the average power delivered to the motor is significantly reduced, causing the motor to run at a slower speed. This reduces the rate at which fuel is pumped so that cutoff may more easily be effected at precisely the desired quantity. The average power supplied to the motor in its slowed-down condition, and thus its speed, may be controlled by adjusting potentiometer 66.

When arm 22A reaches the zero contact point on dial 20A, the positive DC potential on line 80 is removed from line 82 and applied instead through relay coil 40 to ground. The energizing of relay coil 40 opens normally closed contact 40', thus cutting off power to relay coil 42. This releases normally opened contact 42', thus terminating power to both automatic slowdown module 12 and pump motor 52. At the reduced speed that the pump is operating, virtually no fuel is pumped between the time that the last pulse is generated by the telemeter device and the time the motor is cut off. A system for dispensing a precise quantity of fuel is thus provided. The operation is completed by the operator opening pump-on switch 34. This restores the system to its initial condition in preparation for the next fuel-dispensing request.

While in the drawing, control module 10 and slowdown module 12 have been shown as being shared by a number of pump stations 14, and 14', thus permitting only a single pump station to be operated at any given time, it is apparent that a separate control and slowdown module could be provided for each pump so as to permit the pumps to be operated simultaneously. Further, while it has been assumed that modules 10 and 12 are located physically remote from pumps 14, it is apparent that a system operator could be eliminated if a control module and slowdown module were provided at the pump, with the purchaser himself setting the desired amounts into counter stages 18, and operating pump-on switch 34 with a key, credit card reader, or other suitable security device. It is also apparent that the fluid being dispensed need not be fuel, but might instead be for example a chemical utilized in an industrial process. In such an application, counter stages 18 might be set under computer rather than under manual control. Other substitutions in the specific elements shown in the drawing, such as, for example, the use of electronic rather than electromechanical switches, might be also made while still remaining within the scope of the invention.

Thus, while the invention has been particularly shown and described with reference to a preferred embodiment thereof, it will be understood by those skilled in the art that the foregoing and other changes in form and details may be made therein without departing from the spirit and scope of the invention.

Claims

What is claimed is:

1. In a fluid-dispensing system having pump means driven by a motor and signaling means indicating the operation of the pump means: the improvement comprising an automatic slowdown and cutoff system including a control module having means for presetting a predetermined quantity of fluid to be dispensed from said pump means, means for providing power to said motor to pump fluid at a predetermined rate of flow, means responsive to signals from said pump means for indicating a first condition of said pump means, said first condition being the dispensing of a quantity of fluid which is less than said predetermined quantity by a precise amount, means for reducing the power to said motor to reduce the flow rate of said pump means when said first condition occurs, said means for reducing the power to said pump means including a cyclic power source, means responsive to the indication of said first condition for cutting off said power for a selected portion of each source cycle, and means responsive to a second condition of said pump means for terminating power thereto, said second condition being the dispensing of said predetermined quantity of fluid.

2. The structure of claim 1 in which said means for cutting off said power for a selected portion of each source cycle includes trigger means operative when fired to apply a cutoff bias to said power, means normally preventing the potential applied to said trigger means from exceeding its firing threshold, and means responsive to said first condition for permitting said trigger means to fire at a selected point of said source cycle.

3. The structure of claim 1 in which said condition-indicating means is a counter including means for presetting said counter to indicate a predetermined quantity of fluid to be dispensed, and means responsive to the dispensing of said fluid for decrementing said counter.

4. The structure of claim 3 in which said counter includes a plurality of stages, and means operative when said counter stages are set to indicate said first condition for passing a signal through said counter to energize said power-reducing means.

5. The structure of claim 4 including means operative when said counter stages are set to indicate all values between said first condition and zero for maintaining said power-reducing means energized.

6. The structure of claim 4 including means operative when all of said counter stages are reset to zero for passing a signal through said counter to energize said power-terminating means.