US2804520A - Circuit interrupters - Google Patents

Description

1957 w. D. KYLE, JR.. ET AL 2,804,520

CIRCUIT INTERRUPTERS 4 Sheets-Sheet 1 Original Filed Aug. '21., 1950 RN A R w H 5 OER N T m KV W mum n n M m mm M N LT lllflfl lnn m w m T m m W a l w Y m B lNsuLATu OIL LEVEL Aug. 27, 1957 w. D. KYLE, JR, ET AL 2,

. CIRCUIT INTERRUPTERS Original Filed Aug. 21, 1950 4 Sheets-Sheet 2 I I"I--' I= I I. 4 43 3 26 lo IO lnsuLm' ou i 25 l5 '5 22- INSULATI |4 l7 I? i 20 I3 9 M 3 9 23 INVENTOR WILLIAM D. KVLE,JR.

BY ANTHONY VAN RYAN A T TOR NEY Aug. 27, 1957 w. o. KYLE, JR. ETAL 2,

CIRCUIT INTERRUPTERS Original Filed Aug. 21. 1950 4 Sheets-Sheet 3 lHSULATlON b5 INVENTOR cmwlffciggfirg WILLIAM D. KYLE, JR

R 66 BY ANTHONY VAN RYAN ATTORNEY Aug. 27, 1957 w. D. KYLE, JR. ET AL 2,304,520

CIRCUIT INTERRUPTERS Original Filed Aug. 21. 1950 4 Sheets-Sheet 4 Jiilorny United States Patent CIRCUIT INTERRUPTERS William 1). Kyle, .lr., Milwaukee, Wis., and Anthony van Ryan, Ocean Springs, Miss., assignors to McGraw- Edison Company, a corporation of Delaware Continuation of application Serial No. 180,580, August 21, 1950. This application February 24, 1955, Serial No. 490,359

4 Claims. (Cl. 200-89) This invention relates to circuit interrupters.

This application is a continuation of our prior application, now abandoned, Serial No. 180,580, filed August 21, 1950, for Circuit Interrupters, which latter is a continuation-in-part of our application Serial No. 665,048, filed April 26, 1946, for Circuit Interrupters, and now abandoned.

Objects of this invention are to provide a circuit interrupter which is so constructed that it will open the circuit after an overload only when there is no current flowing, the circuit interrupter being designed to be used in cooperation with a reclosing circuit interrupter, the reclosing circuit interrupter being placed in the main line and the circuit interrupter forming the subject of this invention being placed in a branch line or a continuation of the main line.

In greater detail, further objects are to provide a circuit interrupter which may be called a counting, single shot circuit interrupter which has a counting means for tripping the circuit interrupter, in which the counting means is advanced towards tripping position in a step-by-step manner upon cessation of current following overloads, and in which the counting means is finally moved to a position to trip the circuit interrupter when there is no current flowing following the occurrence of the last overload of the series for which the device is adjusted.

Further objects are to provide a circuit interrupter of the character above set forth in which adjustable means are provided for adjusting or setting the device so that trip out of the circuit interrupter during a current zero will occur after any given number of overloads for which the interrupter is adjusted, provided the overloads recur in a sufficiently rapid sequence, means being provided whereby a gradual resetting of the count-ing means takes place either after trip out of the circuit interrupter or when there has been a lesser number of overloads than that for which the device is set, or when such overloads occur at widely spaced intervals.

Further objects are to provide a circuit interrupter in which the counting means which trips the circuit interrupter is operated by current responsive means when the current responsive means is returning to its initial position and which is not operated by the current responsive means when the current responsive means is being moved due to an overload, the construction thereby guarding against any violent shock to the counting means on heavy overload.

Further objects are to provide a circuit interrupter in which the counting means is not operated by pawl and ratchet mechanism with associated mechanical escapement mechanism for final return of the counting means to its initial position, but in which the counting means is actuated hydraulically by current responsive pumping means, the pumping action occurring on cessation of current fiow, provision being made for the gradual discharge of liquid from the counting means to provide for the final return of the counting means to its initial position.

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It has been found that where a magnetic pumping plunger is employed in an alternating current circuit interrupter, that it frequently happens that the minute vibrations of the pumping plunger due to the alternating current will cause an undesirable pumping of oil. This is particularly true as minimum trip value of current is approached.

This invention is designed to overcome the immediately above stated objections and a further object of this inventionis to so construct the magnetic plunger and its associated valve structure that their correlation prevents undesirable pumping of oil and only allows pumping of oil at the desired time for proper functioning of the circuit interrupter.

Embodiments of the invention are shown in the accompanying drawings, in which:

Figure 1 is a vertical sectional view partly broken away through the circuit interrupter.

Figure 2 is a sectional view on the line 22 of Figure 1.

Figure 3 is a fragmentary sectional detail of a further form of the invention.

Figure 4 is a view showing the distribution system in.

which the circuit interrupter is used.

Figure 5 is a fragmentary sectional detail view showing a further way in which the device may be constructed.

Figure 6 is a fragmentary sectional view of the intake valve of Figure 5.

Figure 7 is a side elevation, partly in section, of the impulse valve of Figure 5 showing such valve removed from the remainder of the apparatus.

Figure 8 is a bottom view of the impulse valve.

Referring to the drawings, it will be seen that the circuit interrupter is mounted within a tank or can 1 having closed bottom and side walls terminating in a beaded upper edge indicated at 2. The tank is closed by means of a top or cover 3 which has a gasket 4 resting upon the beaded edge 2 of the lower portion of the tank. The tank is provided with a bracket 5 of any suitable type, whereby it may be attached to a pole or other support in the usual manner. The top is held to the tank by any suitable means, as by means of the bolts 6 and nuts 7. Insulating bushings 8 extend downwardly into thhe tank and below the oil level as indicated and carry terminals, not shown, at their upper ends in accordance with the usual practice. The tank is preferably lined with a fiber lining 9.

The entire circuit interrupter is supported from the cover 3. Insulating tubular members 10, attached to the cover in any suitable manner, extend downwardly and receive the bolts 11 by means of which the insulating portion 12 of the contact assembly is held in place. This insulated section may take any suitable form. It is preferably provided with side walls 13 between which the movable and stationary contacts are positioned. The stationary contacts are indicated by the reference character 14 and the movable contacts by the reference character 15. The movable contacts are carried by metal arms or levers 16 which are pivoted at 17 and are provided with metal spacers 18 against which the ends of a U-shaped bronze or other metal conducting member 119 bears. The inner ends of the arms 16 are slotted as indicated at 20 and receive the pin 21 carried by the insulating slide rod 22. When the switch is in closed position, the parts are as shown in Figure 2. In order to open the switch, the slide rod 22 is pulled upwardly by means hereinafter described and suddenly separates the movable contacts from the stationary contacts and rocks the levers or arms 16 downwardly into contact with the insulating bushings or spacers 23 for the lower portion of the side walls 13,

and thus limits the upward travel of the slide rod 22 as well as the downward rocking motion of the movable contacts 15. A pair of tension springs 24 are connected to a transverse pin 25 at their lower ends and at their upper ends are anchored to the top 3 of the casing. These springs, therefore, constantly pull upwardly on the slide rod 22. The pin 25 serves to pivot the lower arm 26 of a toggle link mechanism, the upper arm of such toggle link mechanism being indicated at 27, the arms being pivotally joined together as indicated at 28. In reality, the arm 26 consists of a pair of links as shown most clearly in Figure 2 located on opposite sides of the slide bar 22. A small latch 29 is pivotally carried by the lower arm or arms 26 of the toggle link and normally latches a downwardly projecting extension 30 of the upper arm 27 of the toggle link mechanism. The latch 29 is spring urged as indicated at 31 in a counter-clockwise direction and is provided with an extension or trip engaging portion 32. The upper end of the arm 27 rigidly carries a pin 33 which is pivotally mounted in one of the arms 34 of a bell crank lever, the other arm of such bell crank lever being indicated by the reference character 35.

It is to be noted that the pin 33 is diametrically cutaway at one end and the remaining half of the pin bears against a shoulder 36 formed on a latch lever 37. The latch lever 37 is urged in a clockwise direction by means of the spring 38. It is provided with an extension or foot 39 at its lower end. The bell crank lever 34, 35 is provided with an upwardly projecting arm 40 which is connected to one end of a spring 41, such spring being anchored at its other end to the cover 3,'as shownin Figure l. The bell crank lever is, therefore, urged in a counterclockwise direction. The bell crank lever 34, 35 is loosely mounted.

on a rock shaft 42 journaled in any suitable manner in the cover 3 and projecting outwardly from one side of the cover. The shaft is provided with an external arm having a manipulating eyeleted arm 43 adapted to receive a switch stick. Normally, this arm is housed in a downwardly opening casing 44 carried by the cover 3 and may be reached by the hook end of a switch stick so that the arm may be pulled downwardly to manually open the circuit interrupter or pushed upwardly to reset the circuit interrupter. A lever or arm 45 is rigidly mounted on the rock shaft 42, see Figure l, and is connected by means of a spring 46 with the arm 35 of the bell crank lever heretofore described.

The spring 46' holds a foot or extension 47 of the lever 45 in engagement with the under side of the arm 35 of the bell crank lever. The lever or arm 45 is provided with an extension 46 which, when the rock arm or manipulating arm 43 is pulled downwardly, is adapted to engage the foot 39 of the latch lever 37 and move such latch lever to the right as viewed in Figure l to disengage the pin 33 from the shoulder 36, and allows the springs 24 to raise the slide bar 22 and thus suddenly open the circuit interrupter.

On the other hand, provision has been made for the automatic opening of the circuit interrupter as by manipulating the extension 32 of the latch 29 so thaton overload the latch 29 will be released and the toggle link mechanism will be allowed to collapse temporarily, thus allowing the springs 24 to suddenly open the switch. The toggle link will straighten itself out at the upper end of its stroke for it will be seen that the flattened face of the pin 33 will rock and will thus force the latch 37 clear of the pin and allow the arm 34 of the bell crank lever to rock upwardly under the influence of the spring 41 and will thus again straighten out the toggle link mechanism as up- When the circuit interrupter is opened either by automatic or manual operation, the arm 43, see Figure 2, rocks downwardly into a displayed position. In resetting, the lineman engages the arm 43 with the switch stick and forces the arm upwardly, thus rocking the rock shaft 42 in a clockwise direction. The arm or lever 45 rigid with such rock shaft engages the under side of the lever 35 and forces the lever 35 upwardly, thus depressing the arm 34 of the bell crank lever and moving the circuit interrupter back into closed position. Obviously, at any time during this closing motion, the automatic means hereinafter described can trip the latch 29 by engaging the extension 32in the event overload still persists.

The automatic means for tripping the circuit interrupter comprises a solenoid or magnet coil 48 wound about an insulating cylinder 49 which may be provided with end flanges, as shown, to provide a spool'like structure for the reception of the winding. The cylinder 49 is continued upwardly by means of a metal cylinder 50 whose lower edge is anchored in any suitable manner to the inner walls of the cylinder 49. The lower ends may be spun outwardly, as indicated in Figure l, to thus lock the cylinder 50 to the cylinder 49. The lower end of the cylinder 49 is closed by means of an apertured plug 51 which constitutes a valve seat adapted to be normally closed by means of a downwardly biased valve 52. The valve 52 may be slotted at its upper end and may be guided by a pin 53 which pin also limits the upward motion of the valve 52. The valve 52 is made cylindrical and is seated in a deep cylindrical aperture so that small vibrations of the plunger 55 will not cause it to open. Instead, considerable motion of the plunger 55 is required. This prevents pumping of oil due to vibration of the plunger just before minimum value of trip current is reached. it has been found that if no provision is made to prevent undue pumping of oil due to minute vibrations of the plunger, particularly as minimum value of trip current is approached, that the plunger will pump oil and cause tripping of the sectionalizer prior to its normal operation. However, by means of the construction hereinabove described, this serious defect is avoided. There is, therefore, a coaction between the intake valve 52 and the pumping plunger since the size of the pumping plunger and the length of its minute strokes just before the time minimum tripping current is reached, are so related to the size and the length of the opening stroke of the intake valve that the intake valve remains closed and prevents pumping while the plunger is making its minute strokes hereinabove described. The plug 51 continues upwardly and the upper end of the plug is slotted to lessen eddy currents.

It is preferable to form the plug 51 of magnetic material, whereas, the valve 52 is preferably formed of nonmagnetic material. A magnetic yoke 54 extends across the top and bottom and around the sides of the magnet coil 48 and a reduced extension 52 of the plug 51 may be swaged or riveted in an aperture formed in the lower portion of the yoke 54. The upper portion of the yoke 54 is apertured for the cylinder 53. Within the cylinder formed of the members 49 and 50 a magnetic plunger 55 is positioned. Thisrplunger has an aperture extending through it which is normally closed by a down wardly spring pressed ball valve 56. Preferably, the plunger 55 is slotted through a considerable portion of itsextent to reduce eddy currents. The magnetic plunger 55 is urged upwardly by means of a spring 57 seating against a shouldered portion on the plunger and loosely surrounding a reduced portion thereof. The lower end of the spring 57 rests on the upper part of the magnetic plug 51. The cylinder 50 carries a transverse pin 58 which limits the upper stroke of the plunger 55. This pin also limits the lowermost position of the counting pistension or reduced portion 60.

From the description thus far given, it is clear that the magnetic plunger 55 constitutes a pumping piston and when an overload occurs the plunger 55 will be drawn downwardly through the action of the coil 48. Oil will flow upwardly past the check valve 56. When the current flow ceases through the action of a repeating circuit interrupter hereinafter described, the plunger 55 rises and pumps oil upwardly into the space between the plunger or pumping piston 55 and the counting piston 59 and thus raises the counting piston 59. Successive actions of the plunger or pumping piston 55 will move the counting piston 59 upwardly in a step-by-step manner. The lower valve 52 is arranged to allow oil to pass into the space below the pumping piston 55 on the up stroke of such piston.

A tripping member 61 is pivoted as indicated at 62' and normally occupies the position shown in Figure 1. It is adapted to be rocked in a clockwise direction when the counting piston 59 arrives at a predetermined point. When the tripping member 61 is rocked to the right, its normal vertical arm 62 engages the extension 32 of the latch 29 and trips the latch and allows the circuit interrupter to suddenly open as previously described. The tripping member 61 is provided with an adjustable screw 63 and a lock nut to lock the screw in its adjusted position. The screw is threaded through the norrnal horizontal arm 64 of the tripping member and is adapted to be engaged by the extension 69 of the counting piston 59. Obviously, the number of strokes required before tripping of the circuit interrupter occurs is determined by the adjustment of the screw 63.

It is to be understood that the electrical circuit extends through the magnet coil 48 to one of the stationary contacts 14 through the arms 16 and the conductor 19 to the other stationary contact 14.

This circuit interrupter is intended to be used with a reclosing circuit interrupter of any suitable type. As shown in the diagrammatic view of Figure 4, the reclosing circuit interrupter is indicated by the reference character 65 and is placed between the supply transformer 66 and the line 67. Branch lines 68 extend outwardly from the line 67 and circuit interrupters of the type hereinabove described are placed in the branch lines 68. These circuit interrupters are indicated by the reference charactor 69.

The operation of the system is as follows:

Assume that an overload occurs on one of the branch lines 68. The magnetic plunger or pumping piston 55, see Figure l, of the circuit interrupter 69 is drawn downwardly, as the magnet coil 45 thereof is the ordinary series coil, and oil passes through it to a position below the counting piston 59. The repeating circuit interrupter 65 in the main line 67 opens and the load current ceases to flow through the magnet coil &8 of the circuit interrupter 69. Consequently, the pumping piston or plunger 55 rises and pumps oil upwardly beneath the counting piston 59 and thus moves the counting piston 59 upwardly one step. The upward motion of the piston :5 occurs only when there is no current flowing through the magnet coil 43, and, consequently, when there is no current iiowing through the contacts of the circuit breaker.

When the repeating circuit interrupter 65 closes, if the fault on the branch line 6% under consideration has disappeared, the counting piston will reset itself as hereinafter described. However, if the fault persists, the pumping action of the piston 59, see Figure l, is repeated for each reclosing of the reclosing circuit interrupter 65 and the counting piston 59 moves upwardly in a step-by-step manner and trips the circuit interrupter 69. The tripping of the circuit interrupter 69 occurs when there is no current flowing through the circuit interrupter. Consequently, there is no arcing at the contacts and a much simpler construction can be employed. After the circuit interrupter 6% in the line on which the fault exists has opened, the reclosing circuit interrupter 65 again closes and supplies power to the remaining branch lines, the defective branch line having been isolated from the system by the operation of the circuit interrupter 69 on such line.

Figure 3 shows a lfurther form of construction whereby a different means is provided for determining the adjustment for the counting piston; that is to say, for determining the point at which the counting piston will trip the circuit interrupter. Similar reference characters are employed as those used in Figure 1 wherever the parts are alike. The principal difierence between the two constructions resides in the fact that the counting piston 59' is provided with an adjustable screw 60 which may be adjusted upwardly or downwardly as required and which will determine the point at which it will engage the trip ping member indicated generally at 61.

A further difference in the construction shown in Figure 3 from that described is that the magnetic plug 51' is provided with a reduced portion around which the indicated generally by the reference character 72, is posi-- tioned. This valve structure is shown more clearly in Figure 6. It will be seen that it comprises a body portion 73 and a non-magnetic ball valve 74. The ball valve normally seats, 'as shown in Figure 6, and closely fits the cylindrical portion 75 and is located below the outlet ports or transverse openings 76. A slidable member 77 is positioned above the valve and has an upper flange 78 located above the body portion 73. It has a limited amount of longitudinal motion and is held against re moval from the body portion 73 by means of a limit screw 79 which is adapted to be engaged by the lower enlargement 89 of the member 77 when such member is drawn upwardly. The member 77 is non-magnetic and when the magnetic pumping plunger 7%), see Figure 6, is in its lowermost position, at approximately minimum trip current, the upper flange 78 of the member 77 rests against the upper portion of the body 73 and thus prevents the ball valve 74 from rising to a position where it would establish communication between the inlet port 81 and the outlet ports '76. This, it will be seen, prevents the valve from executing opening motion until the magnetic pumping piston 76 moves upwardly upon cessation of overload current. At this time the member 77 is free to move upwardly and the valve consequently is free to open and allow oil to be drawn into the lower end of the cylinder 32, see Figure 5.

Immediately above the pumping piston, an impulse valve assembly is positioned. This valve assembly is positioned within and is secured to the cylinder and forms a partition between the pumping piston 79 and the counting piston 83. The impulse valve assembly cornprises a body portion or partition proper 84 which is apertured as indicated at 85 and which is provided with a valve disk 86 on its lower side, spring pressed downwardly by means of the spring 87. The valve disk 86 is free to move upwardly when the pumping plunger 70 suddenly moves downwardly on overload and tends to project a jet of oil upwardly past its check valve 83. This protects the counting piston 83 from the jet of oil.

It will be seen from the structure described immediately above that the magnetic pumping piston 70 is drawn downwardly on overload against the action of the spring 71. Upon cessation of overload current, as hereinbefore described, the magnetic plunger is released and the spring 71 pushes it upwardly and causes it to pump oil beneath the counting piston 83 and thus raise the counting piston a predetermined amount. The number of strokes rcquired to cause tripping of the .sectionalizer is determined by the adjustment of the pin 89 carried by the trip lever 90. This pin is provided with a plurality of apertures through any one of which the pin 91 may be passed to thus secure it to the trip lever 90 in a selected adjusted position.

In the first forms of the invention, a slow leak is provided around the counting piston 59 or 59', see Figures 1 and 3, so that the counting piston slowly settles downwardly to its initial position. In the construction shown in Figure 5 a slow leak is provided around the counting piston 83. This leak is secured by the clearance between the counting pistons and their respective cylinders and is too small to show in the drawings. If a number of strokes of the pumping piston has occurred, less than that required to trip the circuit interrupter, and if the fault is thereafter cleared, it is apparent that the counting piston will settle downwardly, in all forms of the invention, to its initial position and will be ready for operation from its initial position for any subsequent fault or faults that may occur.

On the other hand, if the circuit interrupter has been tripped by a continuing fault with a predetermined number of operations of the pumping piston, thereafter the counting piston will slowly settle down to its initial position so that no thought is required on the part of the operator when he resets the circuit interrupter.

No claim is made to the specific details of the structure shown in Figures 6, 7, and 8.

It is to be noted that this invention provides a circuit interrupter which opens the circuit only when there is no current flowing. The pumping action takes place only when there is no current flowing. Consequently, the last pumping action which causes the counting piston to move to tripping position occurs when there is no current flowing.

Another feature which is to be noted is that there is no sudden violent shock to the counting piston. It is not driven upwardly when there is an overload. The only sudden shock of any part of the apparatus on overload, while the current is flowing, is that imparted to the pumping piston. This causes no damage whatsoever and no jar to the mechanism as the pumping piston is merely suddenly drawn downwardly without any shock being imparted to any part of the apparatus.

Although this invention has been described in considerable detail, it is to be understood that such description is intended as illustrative rather than limiting, as the invention may be variously embodied and is to be interpreted as claimed.

We claim:

1. In an oil immersed electric circuit sectionalizer includiing normally closed contact means, actuating means for opening said contact means, and releasable locking means normally holding said actuating means inactive, the combination with a trip element for releasing said locking means, of. an overload responsive assembly immersed in said oil and comprising a cylinder, a coil surrounding the cylinder, said cylinder being open at one end and closed at the other end by a closure member including a check valve movable a predetermined distance for admitting oil into said cylinder, a magnetic plunger in said cylinder movable toward said closure member in response to a predetermined overload current flow in said coil, a spring in said cylinder disposed between said closure member and magnetic plunger and urging said plunger from said closure member, said plunger having an axially disposed port extending therethrough and a check valve closing said port when said plunger moves from said closure member, movement of said plunger from said closure member also causing a predetermined movement of said check valve and drawing oil into said cylinder, means limiting the extent of movement of said plunger under the influence of said spring, the open end of said cylinder extending from said coil, a counting piston in said cylinder movable toward said trip element for operating said trip element, said plunger being disposed between said closure member and counting piston, said piston being arranged to release said locking means and being moved toward said trip element only on cessation of overload current, said valves permitting flow of oil through said cylinder only in the direction of said counting piston and only on cessation of overload, and adjustable means for determining the number of operations before tripping occurs.

2. In an alternating current circuit interrupter, normally closed contact means, normally ineffective opening means for opening said contact means, a coil energized by alternating current, a coil spool constituting a cylinder, an armature and plunger normally occupying an initial position and coacting with said coil spool and constituting a pumping plunger arranged to be drawn into said coil spool upon energization of said coil by overload current, means urging said plunger to execute a return stroke to its initial position, hydraulic counting means against which fluid is pumped by said plunger to move said hydraulic counting means in a step-by-step manner, said hydraulic counting means being arranged to render said opening means effective to open said contact means when said counting means arrives at a predetermined position, outlet valve means between said plunger and said hydraulic counting means and arranged to close on return stroke of said plunger, and intake valve means including a stationary member and a coacting movable member, said stationary member having an elongated passage therethrough and coacting with said movable member to maintain a seal between said stationary member and said movable member while said movable member executes an opening movement and moves along said passage, said movable member at the extreme limit of its opening movement allowing flow of oil through said passage, whereby pumping action of said piston due to vibrations from the cyclic variation of the alternating current is prevented and pumping action of said piston upon cessation of overload current is allowed.

3. An oil immersed alternating current tripping device comprising an overload responsive assembly having a cylinder, a coil surrounding the cylinder, said cylinder being open at one end and closed at the other end by a closure member including a check valve for admitting oil into said cylinder, said check valve including a valve seat and a movable member coacting with said valve seat, said valve seat being elongated and maintaining a seal with said movable member while said movable member moves through a predetermined distance with reference to said valve seat, a magnetic plunger in said cylinder movable toward said closure member in response to an alternating current flow in said coil of a predetermined value, a spring in said cylinder disposed between said closure member and magnetic plunger and urging said plunger from said closure member, said plunger having an axially disposed port extending therethrough and a check valve closing said port when said plunger moves from said closure member, means limiting the extent of movement of said plunger under the influence of said spring, the open end of said cylinder extending from said coil, and a counting piston in said cylinder, said plunger being disposed between said closure member and counting piston, said counting piston being advanced to operate as a tripping means only on cessation of current of said predetermined value, said valves permitting flow of oil through said cylinder only in the direction to advance said counting piston and only on cessation of alternating current of said predetermined value.

4. An alternating current tripping device adapted to be immersed in oil comprising a cylinder having a closed end, an inlet valve at the closed end of said cylinder, said inlet valve including two members one of which is stationary and provided with a passage therethrough and the other of which is movable and coacts with said passage, at least one of said members being elongated and maintaining a seal with the other of said members While relative movement between said members is taking place for a predetermined length of movement, a magnetic pumping plunger having a passage therethrough, a spring normally holding said plunger in an initial position spaced from said closed end, a coil surrounding said cylinder for drawing said magnetic plunger inwardly against said spring when energized by an alternating electric current of a predetermined value, an outlet valve carried by said magnetic plunger and opening to allow oil to pass through the passage in said magnetic plunger when said magnetic plunger is drawn towards the closed end of said cylinder and closing when said magnetic plunger is moved by said spring towards the other end of said cylinder, and a counting piston located in said cylinder and positioned between said magnetic pumping plunger and said other end of said cylinder and advanced in a step-by-step manner upon each pumping stroke of said magnetic pumping plunger.

References Cited in the file of this patent UNITED STATES PATENTS 1,737,649 Edsall Dec. 3, 1929 1,742,837 Wallace Jan. 7, 1930 1,805,082 Edsall May 12, 1931 1,982,986 Garlington Dec. 4, 1934 2,029,780 Mazer et a1. Feb. 4, 1936 2,452,233 Gerard et al. Oct. 26, 1948 2,515,530 Schindler July 18, 1950

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