US1954831A - Electromagnetic pump - Google Patents

Description

, L.H.ROLLER' ELECTROMAGNETI C PUMP April 17, 1934.

5 Sheets-Sheet 1 Filed May 7. 1928 INVENTOR Lou/S h! flo/ler I N8 NR IQ... S Q

A ORNEY April 17, 1934. L. H. ROLLER ELECTROMAGNETIC PUMP Filed May 7, 1928 5 Sheets-Sheet 2 Q EEE Q I N wt INYENTOR A 011/: hf/Fol/err ATTORNEY April 17, 1934. H. ROLLER ELECTROMAGNETIC PUIP Filed May 7, 1928 5 Sheets-Sheet 3 I l I H. M 'I". IHIllllllllllllllllllllll bin" 3 INVENTOR Lou/3 l1. fial/er." Y

A ORNEY A ril 17, 1934. L. H; ROLLER ELECTROMAGNETIC PUIP Filed llay 7, 1928 5 Sheets-Sheet 4 April 17, 1934. ROLLER 1,954,831

ELECTROIAGNETIC PUIP Filed lay 7. 1928 5 Sheets-Sheet 5 INYENTOR Law: If flo/ler:

Patented Apr. 17, 1934 UNITED STATES PATENT orrics My invention relates to pumps adapted for use in pumping either liquids or gases and has for an object to provide such a pump in which all moving parts are completely encased, thereby preventing 6 leakage of fluids by avoiding the use of stumng boxes, packings, and like means.

With this object in view, I have invented an electromagnetically driven pump which, in general, employs the principles of an electric motor, having a stationary or stator element and a moving element or armature corresponding to a "rotor which, however. reciprocates instead of running continuously as in ordinary electric motors. In the preferred form of my invention, the armature has a rectilinear motion which may be considered as an angular motion about an infinitely distant center.

Another object of the invention is to provide an electric motor which is, in itself, a pump; that is, one in which the stator is in the form of a cylinder and, in fact, forms part of a pump cylinder, while the armature forms part of a plunger re ciprocating within the cylinder. Thus, instead of using a separate pump driven by a motor, the motor and pump are combined into a single integral machine.

The present invention is an improvement on that disclosed in my Patent No. 1,647,147, issued November 1st, 1927 and an object of the present invention is to provide an electromagnetic pump having a more eflicient motor portion.

A more specific object is to provide a straight line motor of the induction type, but in which the armature is constructed to have a higher electrical resistance and hence a higher force at the starting period of each stroke, thereby showing a higher efficiency.

Another object of the present invention is to provide an electro-magnetic pump of very long stroke with respect to the diameter of the cylinder, so that the armature may operate at desirable speeds from the point of view of the electromagnetic action without operating upon an excessive volume of fluid. Thus, I avoid using the ordinary reduction gearing employed between a motor and a reciprocating pump.

Another obiect of the present invention is to provide for automatically cutting off the electric power to the stator before the plunger has reached the'end of its stroke, thereby eflecting a saving in current consumption and utilizing the pressure built up in the fluid being pumped to arrest the plunger at the end of its stroke.

Another object of the invention is to store up a part of the energy of compression of the pump 14 Claims. (Cl. 173-240) and utilize this energy to overcome the inertia of the plunger on its return stroke.

Another object is to provide for internally cooling the motor portion of the pump by using a hollow plunger and extending a water-cooledtube from head to head of the cylinder through the plunger.

with these and other objects in view which will appear hereinafter, I shall now describe a preferred embodiment of my invention and shall as thereafter define the novelty and scope of my invention in the claims.

In the accompanying drawings,

Fig. 1 is a plan view of my improved electromagnetic pump;

Fig. 2 is a front elevation of the same;

Fig. 3 is an end view on a larger scale looking from the right hand end of Fig. 2;

Fig. 4 is a fragmentary detail view in longitudinal section of the stator and armature; Fig. 5 is a fragmentary view partly in section and showing the motor portion of the electromagnetic pump, the section being taken on the line 5-5 of Fig. 6;

Fig. 8 is a view in cross-section taken on the line 6-6 of Fig. 5 and viewed in the direction of the arrows;

Fig. 7 is a fragmentary detail view of a lamina used in the stator core of the motor;

Fig. 8 is a detail view of a lamina used to convey magnetic flux through a water jacket employed on the pump;

Fig. 9 is a view in cross section taken on the line 9-9 of Fig. 5;

Fig. 10 is a plan view of a transformer used in the pump;

Fig. 11 is a view in transverse section taken on the line 11-11 of Fig. 10;

Fig. 12 is a side view of the armature or plunger indicating the relative distribution of conductor rings thereon;

. Fig. 13 is a fragmentary side view partly in section of the right half of the plunger, and Fig. 14 is a similar view of the left half of the plunger;

Fig. 15 is a view in longitudinal section through a portion of the armature showing a means of cooling the same; and

Fig. 16 is a diagram of electrical connections.

The specific embodiment of my invention illustrated in the drawings is a machine particularly adapted for pumping liquid refrigerant such as ammonia. In general, the machine is a horizontal double-acting electromagnetic pmnp, and comprises a closed cylindrical casing in which 0 tween the brackets and the pipe 30, as shown in Fig. 3. Similarly a discharge pipe 32 connecting opposite ends of the pump is carried on the opposite side of the base, being supported on insulating blocks 33 carried by brackets 34 which are secured to the base 28. An inlet pipe 35 communicates with one end of the suction pipe, and a delivery pipe 36 leads from the center of the discharge pipe.

Motor section The motor section of the casing consists preferably of a thin steel tube reinforced, if necessary, with rings of some suitable insulating material. A fragment of the motor section is shown in Fig. 4. A steel tube is indicated at 40 and at suitable intervals thereon are reinforcing rings 41. The tube 40 'is preferably turned or otherwise formed with annular depressions 42, as shown, in which the rings 41 are embedded. The purpose of these depressions will be explained hereinafter. In practice, I find it advisable in forming this section of the casing, to place the steel tube on an arbor and then to wrap the tube with a continuous length of paper or cloth impregnated with a suitable phenolic compound. The cloth is of a width equal to the length of the tube, and the wrapping is continued until a thickness has been built which after subsequent treatment will provide the desired depth of reinforcing rings 41. Then the tube and its wrapping may be compressed in a mold and subjected to suflicient heat to permanently set the phenolic compound. The tube with its coating is then placed in a lathe, and the coating is cut away at intervals down to the steel, leaving the reinforcing rings 41. A portion of the coating is leftuncut at each end of the tube, as indicated at 43, Fig. 5, while the extreme ends of the steel tube are left bare. It will be understood that the tube is formed of very thin material and, in order to couple the motor section of the casing to the intermediate cylinder sections, sleeves 44 are sweated on or otherwise secured upon the bare ends of the steel tube 40. Each sleeve member 44 is threaded to screw into a tapped central bore of a spider 45. The spiders 45 provide means for anchoring the stator of the motor and also for coupling the motor section and the two intermediate cylinder sections, as will be explained hereinafter. The cylinder is bored true to receive the stator.

The stator The stator comprises a plurality of disk-shaped coils indicated in Fig. 5 at 50. These coils are preferably formed as described in my co-pending application, Serial No. 224,359, filed October 9, 1927, and consist of a continuous length of wire wound in two or more layers with the termini of each coil at the outer periphery of the coil. Two such double coils as indicated in Fig. 4, are fitted over each reinforcing ring 41. Fitted over the disk coils are-silicon steel cores 51 which are built up of comb-shaped lamina of silicon steel, as shown in Fig. 7, consisting of a back portion 51a and teeth 51b. The teeth of the core members pass between the coils 50 and the rings 41 and contact with the steel tube 40. Each core 51 is made up of a plurality of lamina, as clearly shown in the Figs. 6 and 9. The back 51a of each combshaped lamina is provided with perforations 52 so that, in assembling the lamina into a core, they may be pinned together with pins 53, preferably of non-conducting material (see Fig. 5).

The cores 51 are disposed radially about the tube 40 and are preferably machined at their inner ends to fit the curvature of the tube. In the particular embodiment illustrated, the cores are uniformly spaced 60 apart, but the number and spacing of the cores may be varied as desired. The backs 51a of each set of core lamina are fitted into a. recess in a yoke 54. The latter is made rigid by suitable reinforcing ribs 55. At suitable intervals along each yoke, there are opposed pairs of flanges 56 extending inwardly from opposite edges of the yoke, and through these flanges pass the pins 53 which secure the core members to the yokes. Wedges 57 are fitted respectively on opposite sides of the cores between the latter and the adjacent flanges 56 and screws 58 serve to draw the wedges radially outward. The wedges and flanges have co-acting tapered faces so that by tightening the screws the lamina of each core are tightly clamped together. The yokes 54 are connected at each end to annular flange members 59 by means of bolts. As shown in Fig. 5, the motor unit is preferably made up of two or more sections connected by bolts 60 which pass through adjoining flange members 59 and the adjacent ends of the yokes 54 while shorter bolts 61 connect the yokes to the outer flange members. The latter in turn are connected by bolts 62 to the spiders 45, sleeves 63 on the bolts serving to space the flange members from the spiders.-

For convenience in assembling the stator and dismantling it for inspection and repairs, the flange members 59 are diametrically split to form upper and lower halves. Thus,- the upper or lower half of any section of the stator may be removed by unbolting the corresponding flange members without disturbing the rest of the stator. The stator lamina are of unequal length so that alternate lamina will overlap at the center of the stator unit and knit together with the adjoining ends of the lamina of the other stator section. The flange members 59 are each formed with an inwardly projecting peripheral rim 64 and are preferably polyhedral instead of circular in proflle, so as to reduce bulk. Set screws 65 are threaded into the rims 64 and bear against the yokes 54. The bolt-holes in the flange members 59 through which the bolts 60 and 61 pass, are large enough to permit a certain amount of play, so that by tightening up the set screws 65 the yokes and the core members they carry may be adjusted relatively to the steel tube 40 and are preferably pressed tightly against said tube.

v The armature or plunger The armature or plunger of the motor unit consists of a hollow steel shaft 70 on which are mounted metal rings of high conductivity interspersed with metal rings of low electrical but high magnetic conductivity. The rings of high electrical conductivity 71 (Figs. 4, 13 and 14) are preferably of copper throughout the main body 5 of the plunger and are separated by rings 72 of say, silicon steel. The copper rings are approximately of twice the thickness of the steel rings and there are preferably two narrow steel rings between each pair of copper rings. A length of the plunger approximately equal to the stroke of the pump, is fitted with copper rings, while, at either end of the armature for a length equal to half that of the stator, the copper rings are .replaced with rings 73 of lead or some metal ofiering a muchhigher electrical resistance than copper. The relative arrangement of rings on the armature is indicated in Fig. 12. Owing to its length, the shaft 70 is preferably made in sections, each section having a tapped socket 74 at one end and threaded stem 75 at the other by means of which the sections may be screwed together. At the center joint each section is fitted with a steel ring 76 afiixed thereon and providing an abutment for the conductor rings and spacers. Against these abutments, the conductor rings are clamped by end sections '77 of the shaft which are threaded upon the outer stems of the center sections. Pins 78 serve to hold the sections from unscrewing. The end sections which are of a diameter equal to that of the rings, serve as pump plungers and are provided with piston rings 79 fitted in suitable ring grooves.

Pump sections 0/ the cylinder The two end portions 26 of the casing (Figs. 1 and 2), as well as the intermediate connecting sections 27, are made like the section 25, of a tube of thin steel 80 (Fig. 11) reinforced with a sleeve or rings. of some phenolic condensation product 81. The motor section and the intermediate sections of the casing are then bolted together with bearing or guide blocks 84, interposed therebetween. These bearing blocks support the sliding plunger '70 and are slightly eccentric so as to raise the axis of the plunger slightly above that of the tubes 40 and 80. Hence, in operation, the magnetic pull on the plunger will tend to lift the plunger against gravity, thus virtually reducing its weight and wear on its bearings.

Similarly, the end or pump sections of the easing are coupled to the intermediate sections with valve blocks 86 therebetween and at each end of the pump there is a cylinder block 89.

The suction pipe 30 (Figs. 2 and 3) is provided with two valves 91 from which pipes 92 lead into the two valve blocks 86 and with two valves 91A from which pipes 93 lead into the end or cylinder blocks 89. The discharge pipe 32 connects with the blocks 89 through a pair of discharge valves 94. Communicating with the interior of the pump cylinder at each end of the machine is a short vertical pipe 95 which is adapted to be filled with air or gas and serves as an air dome or gas chamber to store energy for starting the plunger in the reverse direction. Similarly, a pipe 96 is connected to the discharge pipe 32 adjacent each discharge valve 94 to serve as an air or gas chamber for smoothing out the pulsations of the pump.

Passing from end to end of the machine through the hollow plunger and armature shaft is a fixed pipe 105. The latter is sealed against leakage at each end of the cylinder. Water is circulated through this pipe to cool the pump internally. The plunger 70 runs freely on the pipe and to prevent transfer of fiuid from one end of the pump to the other through the bore of the plunger, piston rings 107 (Fig. 15) are seated on the pipe 105, near its middle, to engage and fit snugly against the plunger. The rings 107 are located within the motor section where most of the heat is generated, and provide a good path for the flow of heat into the water pipe 105. When the pump is operated on liquids rather than gases, internal cooling will not generally be needed, and the pipe 105 may be withdrawn, and the openings in the ends of the cylinder. as well as those in the plunger, may be plugged up. In addition to the internal cooling, I provide a water jacket 108 (Figs. 10 and 11) about each cylinder section of the pump, as will be described more fully below.

Transformers To control the reversal of the motor at the end of each stroke, I provide a pair of open core transformers T-1 and T-2 near the left-hand end of the machine, as viewed in Figs. 1 and 2. and a pair of similar transformers T3 and T4 near the right hand end of the machine. The transformers are clamped on the water jacket and two of them, T-l and T3, are located adjacent the intermediate blocks 88 and the other two adjacent the cylinder blocks 89. The construction of these transformers is shown in Figs. 10 and 11.

The water jacket 108 consists preferably in a thin tube of insulating material and, at the points where the transformers are applied, soft iron laminae 111 are fitted radially about the cylinder serving to space the jacket 108 from the cylinder. These lamina: are comb-shaped, as shown in Fig. 8, being provided with teeth 112 which fit between the rings 81 and contact with the thin steel tube 80. The laminae serve to provide a good magnetic path through the water jacket to the tube 81 while the water is free 'to circulam between the lamina: to carry offv the heat developed by the pump.

The core 114 of each transformer is built up of U-shaped soft iron lamina! which are clamped together between plates 115 by means of bolts 116. The free ends oi the core legs are shaped to fit snugly against the water jacket 108.

Clamping plates 117 secured to the top and bottom of each core leg embrace the water jacket and serve to clamp the core thereto, However, most of the weight of the transformer is carried by a bracket 118 which is secured to the base 28 of the machine. Around one leg of the transformer core is fitted a primary coil 120, and around the other a secondary coil 121. As will be explained more fully hereinafter, when the plunger 70 passes the core of a transformer, there is an increase in current induced in the secondary of the transformer and this current is employed to control the motor through suitable relays.

Electrical connections The motor shown in the drawings is adapted for three-phase alternating current. The coils 50 are arranged in three groups a. b and c which are Y-connected to three power mains A, B and C, as indicated in Fig. 16. A three-pole switch 140 serves to control the admission of power to the mains A, B and C. The motor is reversed in the usual manner, i. e., by alternately transposing the connections with the power mains of two of the Y-branches of the stator coils, thus varying the phase relation of successive windings and causing a change in the direction of travel of the arms.- ture. This reversal of the motor is effected by means of a switch 8 which, in turn, is operated by a relay R controlled by the transformers, as will now be explained. While the main A is permanently connected to the a coils of the motor stator and the valve stators, the mains B and C are connected with the other coils alternately in the order b-c and c-b. The main Bis connected to contact arms 141 and 142 and main C to contact arms 143 and 144 of the switch S. Arms 141 and 143 are insulated from each other and are mounted on a rock shaft 145 while the arms 142 and 144 are insulated from each other and mounted on a rock shaft 146. The rock shafts 145 and 146 bear armatures 147 and 148 respectively adapted to be actuated by electromagnets 149 and 150. When the armature 147 is actuated by electromagnet 149, the arms 141 and 143 make contact with the terminals 151 and 152 respectively which are connected to the windings c and b respectively and, when the armature 148 is attracted by electromagnet 150, the arms 142 and 144 make contact with terminals 153 and 154 respectively which are connected to the windings b and 0 respectively. Thus, energizing of magnet connects mains B and C to the b and c coils respectively, and while energizing magnet 149 reverses thefield by connecting the B and C mains to coils c and b respectively.

Mounted on the shaft 145 is a contact arm 155 which is adapted to engage a contact point 156 connected by a line 156a to a terminal of the primary winding P1 of the transformer of T1 when the electromagnet 149 is energized. Similarly, shaft 146 bears a contact arm 157 which engages a contact point 158 connected by wire 158a to a terminal of the primary winding P3 of transformer T-3. The opposite terminals of the primary coils P1 and P3 are connected together by a wire 159 which in turn is connected through a resistance or reactance 160 and by a line 161 to the main B. The contact arms 155 and 157 are connected together and to a terminal of the magnet 150 by a line 162, and the latter in turn is connected by a lead 1641) to the main A. A terminal of the magnet 149 is connected by a line 163 to the main A. Interposed in the lead 163 is an automatic switch 164 controlled by a thermostat. The automatic switch may be shunted by throwing a switch 16411 which leads through a hand switch 163a, whenever it is desired to substitute hand control for thermostatic control. I

Springs 165 serve to resist the pull of electromagnets 149 and 150 on armatures 147 and 148. Means are provided to prevent both arms 155 and 157 from swinging out of vertical position should both electromagnets 149 and 159 be energized simultaneously. Such means may consist of a bar 166 having pin and slot connection with the arms 147 and 148. When said electromagnets are unenergized, the arms 155 and 157 press against spring contact arms 167 and 168 respect vely, but are electrically insulated therefrom. The spring contact arms are thus pressed by the springs 165 against terminals of a connecting line 168a. The contact arm 167 is connected by a line 169 to one terminal of the primary coil P2 of the transformer T2, while contact arm 168 isconnected by the line 163 to the main A. The other terminal of the coil P2 is connected by line 170, through the primary P4 of transformer T4 and by lines 171 and 172 to the main B. Thus, when, and only when, both of the magnets 149 and 150 are de-energized (i. e., when no current is passing through primaries P1 and P--3) a path for the flow of current is established across 1,954,881 the lead 168a and through the primaries P2 and P4. When current is being fed through either one of the primaries P1 and P -3, it cannot pass through the other because of the bar 166 which interlocks the arms 155 and 157.

The electromagnets 149 and 150 are controlled by the relay R which has four solenoids M1, M2, M--3 and M4. These solenoids are respectively electrically connected to and energized by the secondaries S1, S2, S3 and 8-4 of the transformers T1, T2, T3 and T4. The solenoids are arranged in opposed pairs M4 and M1 constituting one pair and M--2 and M3. the other. Operated by the solenoids M-4 and M1 is a contact arm 175 which is electrically connected to a second arm 176 operated by the other pair of solenoids. The relay is of the type in which the contact arms cannot remain in a neutral position but are always either in one or the other extreme position. The contact arm 175 is adapted to engage a contact 177 when actuated by the solenoid M1 and a contact 178 when actuated by the solenoid M4. The contacts 177 and 180 are electrically connected to the line 172 and thence to the main B. Contact 178 is connected to a terminal of the electromagnet 149 and contact 179 to a terminal of the electromagnet 150. As explained above, the opposite terminals of the electromagnets 149 and 150, are connected by way of lines 163 and 164b respectively, to the main A.

Shunted across the contacts 153 and 154 is the solenoid 181 of a flutter relay. A plunger 182 is adapted to make contact with a pair of contact points 183 and 184 connected respectively to the contacts 177 and 178. The solenoid, when eneris adapted to make contact with a pair of contact points 183 and 184. When the solenoid is deenergized, the plunger moves comparatively slowly and after an appreciable time interval, which may be adjusted at will, it engages the con tact points 183 and 184 providing a path for current across the contacts 177 and 178. The part which the flutter relay plays in the operation of the electromagnetic pump will be explained hereinafter. Inserted in the line 15611 in series with the primary P1 is a relay coil 185, and an opposed relay coil 186 is inserted in the line 15811 in series with the primary P-3. These coils control a switch arm 187 which is connected to the line 170 and plays between a pair of contact points. One of the contact points is connected through a resistance 188 by way of a shunt line 189 to the primary P4 while the other is connected through a resistance 190 through a shunt line 191 to the primary P2. The purpose of these shunt lines will be explained hereinafter.

Operation of the pump In the control of the motor, the transformers T1 and T3 are used to cut off the current to the motor while the transformers T2 and T4 are used to reverse the motor field. In the diagram, Fig. 16, the plunger 70 is shown in full lines in its extreme left-hand position and the relay and switch parts are shown in the positions they occupy as the plunger starts to travel from left to right. A moment previously, the plunger, by bridging the core legs of the transformer T2, provided an increased magnetic flux through the core and hence induced an increased voltage in the secondary 8-2 which energized solenoid M2 and closed a circuit through the electromagnet 150. ,This circuit may be traced from the main A through the line 164b, magnet 150, thence by way of'line 179', contact 179, arm 176, arm 175,

'contact 177, and line 172 to main B. As soon that the am 157, by engaging contact 158, has

established a circuit through primary P3. This circuit may be traced as follows: from the main A, line 1641), line 162, arm 157, contact 158, line 158a, coil 186, to the primary P-3, thence by way of reactance 160 and lines 161, 171 and 172 to the main B. The parts are now in the position indicated in the diagram Fig. 16 with only one transformer primary energized (namely P-3), and the motor stator windings are so connected as to exert a force on the plunger 70, urging the latter toward the right.

In series with the primary P3 is the relay 186 so that the switch arm 187 is swung to the position shown in full lines when said primary is energized, thereby closing the line which shunts the primary of transformer T2. However, no current fiows through either of the transformers T-2 or T-4 until both spring arms 167 and 168 have been actuated to close the circuit through the line 1680.

After the plunger has traveled to the right sufficiently to enter the magnetic circuit of the transformer T3,'there will be a sudden increase of magnetic flux flowing through the transformer core with a corresponding increase of voltage induced in the secondary 8-3. The increased voltage will be sumcient for the solenoid 16-3 to attract the arm 176 to the position indicated by broken lines in the diagram. thereby interrupting the circuit through solenoid 150. Thereupon the spring 165, acting on armature 148. turns the shaft 146 withdrawing the switch arms 142 and 144 from contacts 153 and 154 respectively and breaking the circuit from mains B and C to wind:

ings b and c respectively. The stator is thus de- 1 energized and the plunger continues under its own momentum. At the same time, the arm 157 interrupts the circuit through the primary P-3 and, by pressing the arm 168 against the lead 168a re-establishes the circuit through the two primaries P-2 and P-4. Most of the current is by-passed through the shunt circuit around primary P2 and hence primary P-4 is more strongly energized than primary P-2. However, little power is consumed by the transformer T-4 until the plunger enters the magnetic field of primary P-4. Thereupon there will be a sudden increase of voltage induced in the secondary 8-4 which will cause the solenoid M.-4 to draw the arm 175 to the position shown by broken lines. In this position, a circuit is established through electromagnet 149 which may be traced as follows: from main A through switches 164a, thermostatic switch 164, line 163, electromagnet 149, contact 178, arms 175 and 176, contact 180 and line 172 to main B. The electromagnet 149 attracts the armature 147 turning the shaft 145 on its axis and moving the parts carried thereby to the positions indicated by broken lines. As soon as the arm 155 leaves the contact arm 167, the circuit through the primaries P-4 and 1'-'2 is broken In the new position of the shaft 145, the arms 141 and 143 engage contacts 151 and 152 respectively, so that the main B is now connected with the c coils and the main C with the b coils of the motor and valve stators. The stator fields are thus reversed and the plunger is moved in reverse direction or toward the left. Energizing .80 the electromagnet 149 also serves to swing the contact arm 155 into engagement with the contact 156 thereby closing the circuit of primary P-l, which may be traced from main A through lines 164D and 162, contact arm 155, contact 156, line 156a, relay 185, primary P-1, lines 159 and 161, reactance 160, and lines 171 and 172 to main B. Energizing of the relay 185 throws the switch 187 to the dotted line position shunting the primary P-4. Now, when the plunger enters the magnetic field of the transformer T-l, it causes an increase of induction in the secondary 8-1 which energizes solenoid 111-1 and attracts the arm 175 to the position shown by full lines in the diagram. The circuit through electromagnet 149 is thereby interrupted and the switch shaft 148 with the parts it carries returns to the position slown in the diagram, breaking the stator circuits through switch arms 143 and 144, while the arm 155 acting on contact arm 167, re-establishes 10 the circuit through the primaries P-2 and P-4, but relatively little current will pass through primary P4 because of the shunt circuit established by throwing the switch 187 to the left hand position.

The plunger now coasts to the end of its lefthand stroke and on entering the magnetic field of transformer T-2 causes an increase of voltage to be induced in the secondary 8-2 which-energizes solenoid M-2 and swings the contact arm 176 to the position shown by full lines. The parts are thus restored to their initial position and the cycle of operations is repeated as long as current is fed to the motor.

It will be observed that the shunt circuits controlled by the switch 187 serve to weaken the primary of the end transformer from which the plunger is moving.

The flutter relay shunted across the contacts 177 and 178 prevents the plunger from stalling in a position intermediate between one of the stopping transformers T1 or T-3 and the adjacent field reversing transformer T-2 or T-4. Thus, let us assume that the plunger had not sufilcient' momentum to reach the end of its stroke and that the parts have stopped with the right-hand end of theplunger located midway between transformers T--3 and T-4; The switch arms 142 and 144 will have swung open. interrupting current to the stator windingsfrom mains B and C. and simultaneously tie-energizing solenoid 181.- But the plunger-182 will move down comparatively slowly until it bridges the contacts 183 and 184. This will establish a momentary circuit through the electromagnet 149, 185 which may be traced as follows: from main A through line 163, electromagnet 149, contacts 184 and 183, and line 172 to main B. This will throw the switch arms 141 and 143 into closed position supplying the stator windings with current, but reversing the field so that the plunger will start backward or toward the left. But as soon as the stator windings are connected to the mains, the solenoid 181 will be energized, breaking the circuit through electromagnet 149 and interrupting the stator circuit. Thus, the flutter relay will continue to operate intermittently until the plunger has been drawn to the extreme left. when the transformer T-2 will act in the manner above described to close the relay switch arms 16o to best advantage.

142 and 144 and start the plunger on righthand stroke. The same restorative service will be performed by the flutter relay should the plunger stall on its left-hand stroke with its lefthand end midway between the transformers Tl and T2. The flutter relay will cause the plunger to be fed by steps toward leftuntil it reaches the reversing transformer T--2.

By using two sets of transformers, one to cut oil the stator current and the other to t en the current and simultaneously reverse the field, I efiect a considerable saving of power. The transformers T-1 and T--3 are placed where they will cut off the stator current at the proper moment to utilize the momentum of the plunger after the armature speeds up to normal. In the present machine, a resistance is provided, as in- I dicated above, by employing lead rings in place of copper ateach end of the armature section of the main plunger 70. The parts are so proportioned that/when the plunger is in its extreme position either to the right or left, half of that portion of the plunger which lies within the stator bears lead rings and the other copper rings. This proportion could be varied to suit different conditions, but I have found that equal parts of copper and lead in the armature at starting give a highly eflicient result. Thus, at the time when the greatest force is required, the greatest amount of electrical resistance is present in the armature and as the plunger moves, the resistance is proportionately cut down or removed from the influence of the stator field until it is all eliminated. The resistance forms a permanent part-of the armature and yet the latter,

because it reciprocates instead of rotating, itself introduces and withdraws the resistance as required, and the use of elaborate starting apparatus is avoided. The motor is so designedthat before the lead-ringed section at the opposite end of the plunger has entered the stator field, the current will be cut off from the stator and the plunger will coast under its own momentum to the end of its compression stroke.

By cutting down the thickness of the tube 40 at the points 42, resistance is offered to the passage of magnetic flux along the tube from tooth to tooth of the core members, and most of the flux passes through the armature at the same time the tube is reinforced at said points by the rings 41 and will withstand considerable internal pressure.

Having thus described my invention, and with the, understanding that I am at liberty to make such alterations, modifications and variations in details of construction and arrangements of parts as fall within the spirit and scope of my invention, what I claim and desire to protect by Letters Patent is:

1. A reciprocating electromagnetic motor comprising coils for producing a magnetic field. an armature actuated thereby, means electro-magnetically controlled by said armature-for automatically reversing the field at predetermined intervals to cause reciprocation of the armature and for interrupting the field during a part of each stroke of the armature.

2. A reciprocating electromagnetic motor, comprising coils for producing a magnetic field, an

armature actuated thereby, means electro-magnetically controlled by the armature for periodically reversing the field to cause reciprocation of the armature and for automatically interrupting the field at a predetermined interval prior to each reversal of the field.

3. A reciprocating electromagnetic motor, com prising coils for'producing a magnetic field, an armature actuated thereby, a reversing switch controlling the field, means electro-magnetically controlled by the armature for periodically operating the switch to reverse the fieldand the direction of motion or tne armature,and means electro-magnetically controlled by the armature for operating the switch to interrupt the field at a predetermined interval prior to each reversal of the field.

4. An electromagnetic pump comprising a cylinder, a plunger reciprocable therein, field coils adapted to produce a magnetic field for actuating the plunger, a reversing switch controlling the field, a pair of switch operating coils, the plunger being adapted to enter said coils respectively, near opposite ends of its stroke and thereby cause current variations in the coils for operating said switch to alternately reverse the field, a second pair of coils located intermediate the switch operating coils and also adapted to be alternately entered by the plunger to cause current variations therein, and means controlled by said last mentioned current variations for operating said switch to interrupt the field.

5. An induction motor comprising a stator and an armature adapted to be reciprocated thereby, the armature being provided with coils of higher electrical resistance at each end than in the middle in order to generate a higher starting force atthe beginning of each stroke of the armature.

6. A polyphase straight line motor comprising stator coils for producing a magnetic field, an armature actuated thereby, the armature being provided at each end thereof with coils of high electrical resistance and with intermediate coils of low electrical resistance, means controlled by the armature for interrupting the field before the high resistance armature coils have entered therein whereby the armature will continue under its own momentum, and means also controlled by the armature for re-establishing the field, after the high resistance armature coils have entered therein, but with the stator coils in reversed phase relation to exert a force in reverse direction on the armature.

7. An electromagnetic pump comprising a cylinder of magnetizable metal, a plunger reciprocable therein, a plurality of field coils surrounding the cylindencore members overlying the coils and formed with legs disposed between the coils and engaging the cylinder, the cylinder wall between the core legs being of reduced thickness, and rings of insulating material applied to the cylinder to reinforce the parts of reduced-thickness.

8. An electromagnetic pump comprising a cylinder, a hollow plunger reciprocable therein, field coils surrounding the cylinder and adapted to actuate the plunger, a fixed cooling pipe within the plunger and opening out of one end of the cylinder, and cylinder rings between the pipe and the hollow interior of the plunger.

9. A reciprocating electro-magnetic motor comprising coils for producing a magnetic field, an armature actuated thereby, means for automatically reversing the field at predetermined intervals to cause reciprocation of the armature, means for interrupting the field during a part of each stroke of the armature, and means for preventing stalling of the armature while the field is interrupted.

10. A reciprocating electro-magnetic motor comprising coils for producing a magnetic field, an armature actuated thereby, a pair of switches for reversely controlling said field whereby the field produced on closing one of the switches will be reversed with respect to the field produced on closing the other of the switches, means electro-magnetically controlled by said armature for alternately closing said switches, and means also controlled by the armature for opening each closed switch at a. predetermined time interval before the other switch is closed.

11. A reciprocating electro-magnetic motor comprising coils for producing a magnetic field, an armature actuated thereby, a pair of switches for reversely controlling said field whereby the field produced on closing one of the switches will be reversed with respect to the field produced on closing the other of the switches, means electromagnetically controlled by said armature for alternately closing said switches, means also controlled by the armature for opening each closed switch at a predetermined time interval before the other switch is closed, and means for preventing simultaneous closing of both switches.

12. An electro-magnetic motor comprising a cylinder, a plunger reciprocable therein, field coils adapted to produce a magnetic field for actuating the plunger, a pair of switches for reversely controlling said field whereby the field produced on closing one of the switches will be reversed with respect to the field produced on closing the other of the switches, means electromagnetically controlled by said plunger for alternately closing said switches, and means also electro-magnetically controlled by said plunger for opening each closed switch at a predetermined interval before the other switch is closed.

13. An electro-magnetic motor comprising a cylinder, a plunger reciprocable therein, field coils adapted to produce a magnetic field for actuating the plunger, 2. pair of switches for reversely controlling said field whereby the field produced on closing one of the switches will be reversed with respect to the field produced on closing the other of the switches, means electro-magnetically controlled by said plunger for alternately closing said switches, means also electro-magnetically controlled by said plunger for opening each closed switch at a predetermined interval before the other switch is closed, and means for preventing simultaneous closing of both switches.

14. A reciprocating electro-magnetic motor, comprising a cylinder, 9. plunger fitted therein, field coils adapted toproduce a magnetic field for actuating the plunger, means controlled by the plunger tor periodically reversing the field, whereby the plunger will be reciprocated in the cylinder, and means for retaining fiuid pressure in the cylinder at the end of each stroke to aid in overcoming inertia of the plunger upon the starting of the next stroke.

LOUIS H. ROLLER.

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