US2474349A - Electromagnetic pump - Google Patents

Description

June 28, 194,

Filed Feb. 11, 1948 WITNESS J. W. DICKEY ETAL ELECTROMAGNETIC Fund? 2 Sheets-Shet 1 Ju e 28, 1949 J. w. mm ETAL 2,4?4349 ELECTROMAGNETIC PUMP 1 Filed Feb. 11, 1946 2 Sheets-Sheet 2 WITNESS Patented June 1949 UNITED STATES, PATENT oFFma nnncmomaonnrro rum John W. Dickey and Millard M. Henry, Elmira,

N. Y., assignors to Bendix Aviation Corporation, Elmira Heights, N. Y., a corporation of Delaware Application February 11, 1948, Serial No. 643.952

1 Claim.

. 1 y The present invention relates to electromagnetic pumps and more particularly to a piston Y pump of the type which is adapted to maintain vide a novel electromagnetic pump which is reliable, emcient and quiet in operation, simple in construction-and economical to manufacture.

It is another object to provide such a device which is designed to allow the fluid to flow straight through the pump with a minimum of deflection or constriction.

It is, a further object to provide such a device which is capable of priming itself even though located considerably above the sources of supply.

It is another object to provide such a device incorporating means to eliminate hammering or knocking at the ends of the piston stroke.

It is another object to provide such a device having means for reducing sparking at the control contacts.

Further objects and advantages will be apparent from the following description taken in connection with the accompanying drawing in which: I

Fig. 1 is a vertical substantially mid-sectional view of a preferred embodiment of the invention, the electrical connections being shown diagrammatically; 4 v

Fig. 2 is a section taken substantially on the line 2-2 of Fig. 1;

Fig. 3 is a sectional detail taken substantially on the line 33 of Fig. 2; and

F 4 is a sectional detail taken substantially on the line 4-4 of Fig. 2.

In Fig. 1 of the drawing there is illustrated a enerally cylindrical pump casing l of magnetic material having a can 2 suitably fixed on its upper end, and an annular pole piece 3 similarly fixed in its lower end. A cylinder 4 of nonmagnetic material such as brass or stainless steel is mounted in its upper end in the cap 2 and adjacent its lower end in the pole piece 3. All the joints of the members so far described are preferably made by .brazing or copper welding in order to provide an hermetically sealed annular space between the cylinder 4 and easing i.

A lower cap member 5 is attached to the pole piece 3 by suitable means such as the studs 9, i which may be welded on the pole piece, and is formed with an inlet fitting 8 adapted to receive a conduit communicating with a source of fluid supply. The upper end of the cylinder 6 is provided with an outlet fitting 9 fixedly attached therein as by brazing, and adapted to receive an outlet conduit communicating with a receptacle such as the carburetor of an internal combus tion engine to be supplied with fuel.

A cylindrical piston H of magnetic material is slidably mounted in the cylinder i and is provided with an axial passage l2 therethrough.

A valve mounting thimble I3 is fixedly attached to the upper end of the piston H as by crimping as illustrated at I4. The thimble I3 is constricted slightly as shown at i5 thereby providing an ex- .ternal annular shoulder l6 and an internal conical seat H. The portion of the thimble l3 above the constricted portion 15 is cut away so as to form three separated arms i8, i9 and 2| which are joined at their upper endsas shown at 22 in Fig. 2.

A check valve member 23 of non-magnetic material is mounted in the thimble l3 with freedom for vertical movement, and is urged in a downward direction by a light compression spring 24 seated at its lower end on a shoulder 25 of the valve member and at its upper end bearing on the end portion 22 of the thimble. An annular valve seat member 26 is also mounted in the thimble i3 and provided with an inner conical bearing surface 21 cooperating with the movable valve member 23 to form a check valve, and anextemal conical surface 28 adapted to engage the seat I! in the thimble l3 and forming therewith a secondary or relief valve which is normally held closed by a spring 29 bearing on a shoulder 3! formed in the interior of the piston II. The relief valve spring 29 is substantially stiffer than the check valve spring 24 so that the relief valve is held closed except at the thimble l3 and bearing against the outlet fitting 9. The stop member 33 is of non-magnetic material and is preferably formed of a cushioning material such as Bakelite to deaden the impact of the thimble. The piston spring 32 is so calibrated as to exert on the piston II the force required to maintain the fluid being pumped at the-desired pressure.

A strainer 30 of suitable material such as fine wire mesh is located in the lower end of the cylinder 4 and pressed against the inlet fitting B by the piston spring 32 so that the incoming fluid is required to flow through the strainer.

Electromagnetic means for retracting the piston I I, thereby compressing or cocking the piston spring 32 is provided comprising an electromagnet 34 surrounding the cylinder 4, having an upper pole piece 35 of magnetic material suitably fixed in the casing I, the member 3 providing the lower pole piece for the electromagnet.

Means for energizing the electromagnet are provided comprising a battery 36, one terminal of which is grounded at 31. and the opposite terminal connected by a manual switch 38 and a lead 39 to a bindin post 4'I mounted in the upper end of the casing I. A lead 42 connects the binding post to one terminal of the electromagnet 34, and a lead 43 connects the opposite terminal of the electromagnet to a fixed contact 44 mounted in the interior of the casing I but insulated therefrom as indicated at 45 (Fig. 3).

Means for periodically closing the circuit through the electromagnet 34 to cause reciprocation of the piston II is provided comprising a rocker member 46 of non-magnetic material pivotally mounted on the upper pole piece 35 by means of a bearing pin 41, as best shown in Figs. 2 and'4.-, A spring reed 48 is fixed at one end on the rocker member 46 as shown at 49 in Fig. 2, and carries on its free end a contact member I adapted to cooperate with the fixed contact 44. The ree'd 4B is rounded as indicated diagrammatically at 52 to complete the electrical circuit for the electromagnet 3 4. The free end of the reed 48 is preferably bent back on itself as shown at 53, and the rocker member 46 is formed with a portion 54 extending into the U- shaped end of the reed .48, with a slight clearance 55 therebetween. The reed is so tensioned as to normally bear firmly on the extension 54 of the rocker 46 so as to space the contact 5| slightly therefrom. This insures firm engagement of the contact 5| with the fixed contact 44' as best shown in Fig. 3.

In order to oscillate the rocker member 46 to open and close the contacts 5I, 44, a permanent ;magnet 56 is mounted in the arm 51 of the rocker 'member, being clamped between pole pieces 58 and Why suitable means such as rivets 6!, 62. The inner pole piece 58 is formed with a concave surface conforming to the exterior of the cylinder 4 with which it engages when the rocker member 46 is moved to position to close contacts 44, 5I as shown in Fig. 2. The outer pole piece 59 is formed with a convex surface having a curvature approximating that of the interior of the casing I, and a spacer 63 of non-magnetic material: such as rubber is suitably mounted thereon as by cementing, in order to prevent the pole piece 59 from coming into direct contact with the casing.

The annular space or chamber containing the electromagnet 34 and the actuating mechanism for contacts 44, 5| is preferably charged with an inert or non-oxidizing atmosphere such as nitrogen. In order to further eliminate sparking or erosion of contacts 4'4, 5 I a non-inductive resistor 64 is preferably connected across the terminals of the electromagnet 34, thereby providing a path for the inductive surge enerated by the coil when the contacts are opened. It has been found in practice that the resistor 64 may have an ohmic value many times that of the coil 34 while still serving to effectively control the tendency to produce sparking at the contacts.

In operation, starting with the parts in idle position as illustrated in Fig. 1, closure of the manual switch 38, which may be the ignition switch of an internal combustion engine, causes energization of the electromagnet 34 inasmuch as the upper end of the piston I I is at this time within the field of flux of the permanent magnet 56 which is accordingly attracted theretoas shown in Fig. 2. Energization of the electromagnet 34 causes the piston I I to be retracted downwardly against the force of the spring 32 until the piston has moved out of the zone of infiuence of the permanent magnet 56. At this time, the attraction of the permanent magnet for the magnetic material of the adjacent portion of the casing I causes the permanent magnet to swing the rocker member 46 in a counterclockwise direction around its pivot 41 until the spacer 63 engages the interior of the casing I, thus moving contact 5I out of engagement with the contact 44 and thereby deenergizing electromagnet 34. The piston spring 32 thereupon moves the piston I I upwardly toward its original position, and since at this time the check valve 23, 26 is closed by the spring 24, any fluid trapped above the check valve is ejected from the pump so as to be conducted to the desired receptacle. During this forward motion of the piston, a partial vacuum is formed beneath the check valve which causes fluid to enter the lower end of the cylinder from the supply container, under atmospheric pressure. It will be understood that the spring 29 is sufficiently stiff to hold the relief valve 26, I! closed during the forward stroke of the piston I I.

When the upper end of the piston again enters the zone of influence of the permanent magnet 56, the mutual attraction of the magnetic material of the piston and the permanent magnet causes the permanent magnet to move its inner pole piece 58 back into engagement with the cylinder 4, thereby closing contacts 44, 5| and reenergizin the electromagnet 34.

Where a liquid fuel such as gasoline is being pumped, the liquid acquires considerable momentum during the upward stroke of the piston and this momentum together with the momentum of the valve member 23 causes said member to continue its upward motion after the piston starts down under the influence of its electromagnet. The valve member 23 is thus unseated and moved up until the shoulder 25 thereof bears on the inwardly extending portions .65 of the spider arms I8, I9, 2I thus providing free passage for the liquid between said arms and out through the outlet fitting 9.

At the lower end of the piston stroke when the contacts 44, 5| open and the spring 32 starts the piston upwardly, the check valve member 23 may engage the said member 26 with considerable force due to the combined effect of its inertia, the spring 24, and the inertia of the liquid trapped above the check valve. In order to relieve this shock and prevent any noisy operation or water hammer, the spring 29 is arranged to yield slightly and permit the relief valve 26, I! to open sufiiciently to by-pass a small amount of liquid. This valve immediately recloses, however, after such excess pressure has been dissipated.

It will be seen that the pump is so designed that the liquid passes directly through from one end to the other of the cylinder 4 with very little constriction or lateral deflection, the only obstruction to such flow being the check valve 23, 28. This arrangement has been found in practice to cause the liquid to flow continuously through the pump both during the upward and downward movement of the piston l I whereby the volumetric efliciency of the pump is actually very substantially more than 100%. That is to say, the volume of fuel delivered by the pump is substantially greater than the piston displacement multiplied by the number of strokes taking place during a measured time interval.

Attention is called to the fact that the pump here disclosed utilizes the inertia of the fluid beneath the piston to obviate the necessity for a check valve below the piston. In other words, since the fluid is already moving upwardly, it will not immediately reverse its motion when the piston comes down but will continue its upward motion, although somewhat retarded, until the piston again rises and accelerates the flow of liquid. It has been found that this operation is entirely reliable throughout the entire range of delivery of the pump since the downward motion of the piston is always at high speed irrespective of the speed of the piston during its forward or delivery stroke.

Another advantage in the omission of the inlet check valve usually provided in reciprocating pumps is that with the present arrangement, this 1 pump is self-priming even though completely airbound at the start of its operation. This is caused by the fact that when the pump is operating even in an airbound condition, the inertia of the check valve member 23 is sufflcient to compress its valve spring 24 and unseat itself at the end of the upward stroke of the piston ll. During the downward stroke of the piston, there is therefore no obstruction whatever to the upward passage of the air through the piston II, and the air is thus raised and ejected through the pump without the necessity of building up any pressure to raise the check valve. It has been found by extended tests that this enables the pump to prime itself even though it be located a considerabledistanceabove the supply container.

6 4 Although but one embodiment of the invention has been shown and described in detail, it will be understood that changes may be made in the form and arrangement of the parts without departing from the spirit of the invention as defined in the claim appended hereto.

What is claimed is:

In an electromagnetic pump a non-magnetic cylinder, a piston of magnetic material slidable thereon having an axial passage therethrough,

means for controlling the flow 'of fluid through said passage including a. check valve member movably mounted on the piston, a relief valve member formed to provide a seat for the check valve member, movably mounted on the piston, said piston having a seat cooperating with the relief valve member, a comparatively light spring urging the check valve member toward its seat, a substantially stiifer spring holding the relief valve member on its seat, and means for reciprocating the piston including an electromagnet surrounding the cylinder adapted when energized to retract the piston, the mass of the check valve member being so related to the strength of the spring that the action of theelectromagnet unseats the check valve and opens a free passage through the pump, and a spring for actuating the piston to discharge fluid from the pump when the electromagnet is deenergized, said relief valve spring being arranged to yield .and permit the relief valve to open momentarily to cushion the shock occasioned by the reversal of the motion of the piston by the piston spring when the electromagnet is deenergized.

JOHN W. DICKEY. MILLARD M. HENRY.

REFERENCES orrnp The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 458,873 Van Depoele Sept. 1, 1891 1,402,218 Cushing Jan. 3, 1922 1,489,348 Hampton Apr. 8, 1924 1,598,792 Wallace Sept. 7, 1926 1,615,139 Rusdell Jan. 18, 1927 1,640,348 Wallace et al. Nov. 6, 1928 1,888,322 Lanclot'et al. .Nov. 22, 1932 2,179,925 Dilg Nov. 14, 1939 2,322,913 Best et al. June 29, 1943. 2,381,650

' Dick' Aug. '1, 1945;.

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