US2124018A - Conveyer control - Google Patents

Description

July 19, 1938 M. voGEL-JORGENSEN 2,124,018

CONVEYER CONTROL ATTORN EYS July 19, 1938. M. voGEL-JoRGENsEN 2,124,018

coNvx-:YER' CONTROL Filed Aug. 5, 1936 2 Sheets-Sheet 2 f5 @im lNVENTOR /ael Vogel-Jorgensen BY Y fm@ ,ww' MM; a www@ ATTORN EYS Patented July 19, 193s UNITED STATES 2,124,018 coNvEYER coN'raoL Mikael Vogel-Jorgensen, Frederiksberg, near Copenhagen, Denmark, assigner to F. L. Smidth t Company, New York, N. Y., a corporation of New Jersey Application August 3,

1936, Serial No. 94,112

In Great Britair` August 3, 1935 2 Claims.

This invention'relates to mechanism for controlling the conveyance of pulverulent or quasiliquid material to and from a container such as a tank. More speciiically, the invention is con- 5 cerned with improved means for controlling automatically the valves of such a tank in accordance with the height ci' the material therein.

In accordance with the invention the valves which control the charging of the tank with the material, and with compressed air, are actuated by 'electrical impulses produced when the material in the tank reaches a predetermined high, low or intermediate level. These impulses result when the change in level of the material varies the dielectric constant of an electric condenser or changes the illumination incident on a photoelectric cell. The preferred mechanism includes certain locking devices by which the valves are constrained to operate in the correct sequence.

Heretofore it has been customary to control the valves oi' storage tanks either directly through mechanical linkage or indirectly through electric or pneumatic mechanism operated by the movement of a iioat or lever which follows the level of the material in the tank. In some installations where electrically conductive materials were stored in the tanks the material has been caused to bridge electrical contacts at the low and high levels on rising and to break the circuits on falling, and in this way to actuate electrically controlled valves. If the control mechanism were actuated pneumatically, instead of electrically, diaphragm-operated valves were substituted for magnetically-operated valves.

These previously 'known mechanisms introduced several disadvantages some of which were due to the fact that the specific gravity of the material usually varies from day to day and therefore any control which depends on the specific gravity of the material is unreliable. Furtheremore if the material is inclined to adhere to the walls of the tank the float or lever which actuates the control mechanism will operate too late.

In systems in which the change of pressure in the tank is employedto operate the control, dust from the material to be conveyed usually lodges in the diaphragm valve causing sluggish movement and sometime even stopping the movement altogether, so that it does not shut off the compressed air at the right time. Furthermore, an accumulation of material in the conveying pipe causes the pressure in the tank to be not always the same for the same level of material, from which it follows that the operation of the controls will not be in strict accordance with the level of the material.

All of the foregoing, as well as additional disadvantages of prior control arrangements are avoided by the present invention which provides greatly increased accuracy and reliability of operation, because in accordance therewith the operation of the necessary valves is controlled entirely by the actual level of the material in the tank and is independent of the conductivity of the material and its physical characteristics. Furthermore, the operation is entirely independent of the pressure in the tank within the range customarily used.

In order that the invention may be more clearly understood and carried into effect, two examples of arrangements in accordance therewith will now be described with reference to the accompanying drawings, in which:

Fig. 1 illustrates an embodiment of the invention in which the controlling impulses are initiated by the change of dielectric constant and electrostatic capacity of condensers;

Fig. 2y shows details associated with the arrangement of Fig. 1;

Fig. 3 is a modification of Fig. 1 in which photoelectric cells are substituted for the condensers.

Referring rst to Fig: 1, the container comprising a tank I is provided with two pipes 35, I4 for conveying the required material to and from the tank. In operation the material may be fed to the tank through the pipe 35 under control of valve I0 until the tank is nearly full, when the valve I0 must be closed and the valve 3| opened. This allows compressed air to be introduced into the tank through pipe I2 forcing the material out through the delivery pipe I4.

The present invention contemplates the automatic control of the conveyance of material to and from the tank so that the tank will be lled to the proper height, then discharged and automatically relled again. In general, the mechanism controlling the valves to secure this operation is as follows: Rings I5 and I6 mounted on insulators I1 each form one electrode of electrostatic condensers, the metal tank I forming the other electrode. 'Ihese electrode rings may be of any suitable metal such as iron. When the material to be stored comes between the electrodes I5 and I6 and the tank, respectively. the dielectric constant of the condenser dielectric is changed and the relay circuits connected to the condensers are operated. Each of these condensers is con'- nected respectively in a series circuit comprising electromagnet I or 1' of relay I8 or I8' and an l alternating current il or II'. lI'hisconnature (such as the dielectric constant) of the materialinthetank. Itwillbeseenthatwhen the material enters or leaves the dielectric spaces between the ring electrodes II and II and the tank itself, the electrostatic capacity and therefore the capacitive reactance of the corresponding condensers will change, thus affecting the current flowing through the electromagnet 1 or I and causing the amature I or -I' of the relay to be attracted or released as the case may be. 'Ihe initial impulse thus established will therefore control the associated electromagnets to open and close the valves in the correct sequence.

'Ihe operation of the system is as follows: Upon closure of the main switch 22 the electric power supply II is connected to solenoids 2l, 2l energizing them and causing the latches 2l, II to be drawn clear of the detents III and I2 of the valves iii and Ii, respectively. If there is no material between the tank and the condenser rings il and i6 the current flowing through the windings of the relays I8, iI will be very small, allowing the springs Il, I1 to close contacts I, I, and I', I'. Closing of the contact I' permits the solenoid il to be energized so that the valve II is opened to permit the material to enter thev tank l through the supply pipe II. Under these conditions the simultaneous closing of the contact I would cause the solenoid I I to be energized `thus also opening the compressed air line valve Il, were it not that switch 2l is initially open.

Switch 2l should not be closed until a short time Vhas elapsed to insure that the valve II has fully opened and in so doing has opened the contact between 'amature 26 and the contact 2I of valve Athe tank`and^reaches electrode I5 the electrostatic capacity'of condenser l I increases. thereby causing relay II to attract amature I, breaking the circuit through contact I and releasing latches 2I and Il to be `'pressed forward by compression springs 21 and Il, respectively. As the material further accumulates in the tank it will finally reach condenser II changing the electrostatic capacity thereof and causing armature I of relay II' to be attracted, opening contact I. This deenergizes solenoid il, and valve II closes by gravity augmented by the pressure of the incoming material upon the upper surface of the valve. The detent II in passing the latch. 2I moves the latch to the right against the action of spring 21.

When valve II is fully closed and the contact 2I and armature 2I complete the circuit for solenoid II, valve Il opens, admitting compressed air to the tank.

It is evident that Awhen valve II has closed, solenoid I I will not be able to open the valve because detent II will bear upon latch 28. Similarly, valve Il cannot close because detent 32 bears upon latch Il which is urged against it by spring II.

Inlet valve II being locked closed, and air valve Il being locked open, the material in the tank is blown out through the pipe il. This Y Operation continues even below the condenser ring and Il are locked.

operating any switches or other manual controls.

Obviously if the supply of material is to be continuous, or nearly so, two or more tanks may be operated side by side, one or more being filled while one or more are being emptied and the level of material in one tank may be caused to control the valves of another.

'Ihe embodiment illustrated in Fig. 3 is similar to that Just described in connection with Figs. l and 2 except that in the system of Fig. 3 the initial impulse is not caused by a change in electrostatic capacity of a condenser. In this embodiment the initial impulse is effected by the diminution or interruption of light beams from light sources 4 and I which otherwise impinge upon photo-electric cells 2 and I, respectively. The circuits'from the photoelectrlc cells 2 and I control the relay circuits including windings 1 and 1' just as in the arrangement of Fig.l where the current in those windings is controlled by the change of reactance of the condensers II and II. In this case, howeventhe action of the relays must be reversed because the presence of material at the level of the photo-electric cells causes a decrease, rather than an increase, in the current through the electromagnets 1' and 1'.

In employing photo-electric cells for the present purpose, it has been found especially convenient to accommodate the cells and their associated lamps in protective tubes I. which permits removal of the photo-electric cells andthe lamps when required, without the necessity'of opening the tank.

l. In a system for conveying pulverulent material, a tank, nrst and second control relays, first and second stationary control means 'secured at 'upper and lower portions of said tank. respectively, sensitive to the level of material in said tank and connected to said control relays to operate the same upon change of said level, a material-inlet valve actuated in response to said first control relay connected to said first stationary control means, an electrically-operated airinlet valve actuated to open position in lresponse to the operation of said material-inlet valve so that said material-inlet valvecloses before said air-inlet valve opens. electrically-operated locking means associatedy with each of said valves serving to lock said material-inlet valve closed and said air-inlet valve open, and connections from said second control relay serving to release said locking means when the level of said material passes said second stationary control means.

2. A system according to claim l, wherein said stationary control means comprises a photoelectric cell located on said tank and a source of 'exterior of said tank.

MIKAEL VOGEL-JORGENBEN.

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