US2004751A - Low voltage generator - Google Patents

Description

June 11, 1935. H, G. FISCHER ET Al. 2,004,17 51 LOW VOLTAGE GENERATOR Filed March 2s, 1951 5 sheewsheet 1 @l A .l/Q10 .frm/mr r/me 6mm/wc gti. fix/aa Jig 14 Ir-g '13 'Y /Msnmvf 6u.

June ll, 19.35. V H. G. FISCHER rAL LOW VOLTAGE GENERATOR Filed March 25, 1931 5 Sheets- Sheet 2 RE.. Sula.

June 11, 1935.. H. G. FlscHR Erm. 2,004,751

LOW VOLTAGE GENERATOR y Filed March 23, 1931 5 Sheets-Sheet 5 June 11, 1935. H, G FlscHER Er AL 2,004,751

LOW VOLTAGE GENERATOR Filed March 23, 1951 I -5 sheets-sheet 4' gf/ ff A a June ll, 1935.l

Filed March 23, 1931 G. FISCHER El' AL OW VOLTAGE GENERATOR 5 Sheets-Sheet 5 J/ 4.9 Jg JZ x K/ 1: EC. GEN. :lil Home n.6. GEN. j

Patented June 11, 1935 LOW VOLTAGE GENERATOR.

Herman G. Fischer. Peter P. Musket, and Donald sigma E. Richardson. Chicago, Ill.,

tou. G.

Fischer Company, Chicago, Ill., a corporation of Illinois Application Match 23, 1931, Scrll'l No. 524,530

'9 Claim.. (Cl. lil-07) This invention relates in general to multi-current generators and while it has more particular reference to multi-current generators for generating electric current of varying wave form for the use in electro-physiotherapy, it will be readily apparent that the invention is capable of employing an apparatus for other and more general use.

A principal object of the present invention is the provision of an apparatus of simple construction and certain operation for producing the various currents desired in electro-physiotherapy, the particular current being provided by the apparatus through simple external controls so constructed and operating that the usual physician can employ the apparatus with certainty and with lminimum of directions.

Another important object of the invention is the provision of an apparatus of the character described, the parts of which will be of simple, sturdy construction, and unlikely to require frequent repair, replacement, or internal readjustment in use.

The invention contemplates the provision of a simple low voltage, multi-wave apparatus, for use in electro-physiotherapy, which will produce, at the option of the operator and through the manipulation of simple controls, currents designated as straight galvanic, pulsating galvanic, rapid alternating. galvanic surge, pulsating gal- -vanic surge, rapid alternating surge, slow sinusoidal, pulsating slow sinusoidal, rapid alternating in surges, and various modifications of these current wave forms to provide dwells and periods of rest.

Numerous other objects and advantages of the invention will be apparent as it is better understood from the following description, which, taken in connection with the accompanying drawings, discloses a preferred embodiment thereof.

Referring to the drawings:

Figures l to 15 inclusive are diagrammatic views illiltrtin graphically the wave forms of various current adapted for generation by the apparatus in which the present invention is embodied;

Fig. 18 is a front elevation of an apparatus embodying our present invention, the internal parts being shown in section;

Fig. 17 is an enlarged fragmentary elevation of the commutator and brush mechanism employed in the apparatus; l

Fig. 18 is an end view of the brush head and associated parts;

Fig. 19 is a transverse longitudinal section through the collector rings;

Fig. 20 is a section taken substantially on the line Il--ll of Fig. 19;

Fig. 2l is a front elevation of the commutator;

Fig. 22 is a side view thereof and Fig. 23 is a wiring diagram of the several cir- 5 cuits of the apparatus.

The apparatus shown on the drawings, and which constitutes the embodiment of the invention at present preferred, comprises generally, an outer housing Ii. in which is mounted a motor generator unit 32 having a shaft 33 adapted through suitable friction gearing, generally indicated at 34, to drive a shaft l5 upon which is mounted a set of collector rings 36 and which is provided at its ends with a brush head 31. The brush head 31 carries brushes generally -in dicatcd at 38, and which` will be presently more fully described. These brushes in their movement engage and move over a commutator 39 to which direct current is supplied by the gen- 20 erator unit 22. The control of the apparatus and the selection of the various wave forms to be produced is accomplished through two switches 4I and 42 which in cooperation with the circuit wiring, illustrated in Fig. 23, determine the 25 current characteristic of the apparatus at each treatment. A main switch 43 is arranged in the circuit as are also volt and ammcters 44 and 45. A rheostat, generally indicated at 4B, is provided and controlled by an external knob 41 and a polarity reversing switch 48 is or may be provided if desired.

A motor generator unit. as may be seen from Fig. 23, comprises an electric motor 49. a direct current generator il, and an alternating cur- 35 rent generator or current modulator 52. The motor 49 and the generators 5i and 52 are mounted upon a common shaft 5I which is rotated by the motor. This shaft is provided with a worm 84 which engages a worm gear 55 (Fig. i8) fixed for rotation with the friction disc 34. A friction wheel mounted to slide lengthwise of the shaft 35 may be moved by the hand nut il to impart rotation at desired speed to the shaft 35.

Referring more particularly to Figs. 17 to 22, it will be noted that the shaft l5 is provided at its lefthand end with a brush head 58 secured at 59 upon the end of the shaft. This brush head in the instant embodiment of the invention is provided with three sockets, identified by reference characters Il, 82 and 63, in which are mounted three brushes 64, and 66. The shaft ll is provided with four collector rings, indicated respectively at 61, 68,69 and 1|. These collector rings are mounted between collars 12 and 13 and are insulated from each other and from the surrounding structure at 14.

Wires 15 and 16 lead respectively from brushes 65 and 66 to collector rings 68 and 61. A wire 11 leads from brush 64 to collector ring 69. ,Viewing Fig. 20, it will be noted that collector ring 1| is divided into segments 18 and 19 insulated from each other at 8|. The segment 18 is electrically connected by a wire 82 with the brush 64 so that this brush is electrically connected to both the collector ring 69 and 1|. Suitable xed brushes 83 are provided for continuous engagement with the collector rings as they rotate, and these brushes deliver and receive the current from the stationary portion of the circuit wiring to be presently described.

A commutator or resistance element shown in Figs. 17, 21 and 22, is mounted for engagement by the brushes 64, 65 and 66 as they rotate with the shaft 35. This commutator is built up of a plurality of intermediate parallel bars 84 of relatively narrow sides edges. The bars 84 are insulated from each other at 85. Wider blocks or bars 86 are arranged at the ends or top and bottom of the commutator. The bars 84 and blocks 86 together with the interposed insulation 85 is tightly clamped into a single compact unit by bolts 81, with the presented edges or faces of these parts in a single plane for engagement with the brushes. 'I'he blocks 86 and the bars 84 are electrically connected to interposed resistance coils, which will now be described.

Each bar 84 is extended alternately at its end, as may be seen by comparing Figs. 17 and 21, to provide lugs 88 and 89, and on adjacent bars the position of the lugs is reversed, this arrangement providing room for wires 9| and 92 to be connected to the extended ends or lugs of the bars by soldering or in other suitable manner.

A resistance coil is arranged in the connection between each two successively arranged or adjacent bars 84. These coils, generally indicated at 93, are wound about a carrier 94 arranged back or to the left of the unit formed of the bars 84 and blocks 86. An inletterminal 95 is connected by a wire 96 with the bottommost bar 84, viewing Fig. 21. This bar is in electrical contact with thevbottom block 86. 'I'he wiring is such that current passing through the commutator and in at the terminal 95 flows first in and through the bottom bar 84 and block 86, thence serially through the successively arranged bars 84 and the interposed resistance coils 93 to the top bar 84 and top block 86. The last mentioned parts are connected by a wire 91 with a second terminal 98.

Wire connects one side ofthe direct current generator with a wire |02 connected in turn to terminal 95. A wire |03 connects terminal 98 with a wire |04 which in turn is connected to the movable element of the rheostat 46, this rheostat being in turn connected by wire |06 with the direct current generator.

The control and selection of the various circuits is accomplished by manipulation of the switches 4| and 42. The switch 4|, as indicated in Fig. 23, is a triple switch having three xed contacts F adapted to be connected by the usual arcuately swinging arm with contacts A, B, C, AD and E, a set of which is appropriately arranged for and about each contact F. The switch 42 is likewise a triple switch, having xed contacts 4 adapted for connection with the usual switch arm with similarly arranged sets of arcuately positioned contacts I, 2 and 3.

After thus describing the major mechanical parts and devices in the apparatus in which the invention is at present embodied, a full understanding of it, it is believed, can be easiest accomplished. by a description of the electrical circuits established to produce the current form illustrated in Figs. 1 to 15, and in describing these currents letter and numeral designation is employed in accordance with the switch positions of the switches 4| and 42, the letter designations referring to the contacts A, B, C, D and E of switch 4 I, and the numeral designations referring to the contacts 2 and 3 of switch 42. It may be mentioned in this connection that like letter and numeral designation of position is indicated upon index plates |01 and |08 arranged upon the front of the casing 3| to guide the physician or other user in the selection of his circuit. It will be understood that the switch 4| is a three arm switch, each arm of which pivots about a terminal F and into contact with the terminals or contacts A, B, C, D and E, lthe three arms moving together at each switch manipulation. The switch 42 similarly is comprised of three arms respectively movable about terminals or contacts 4 and simultaneously into engagement with 'the three contacts 2 and 3. Each arm in each switch is insulated froml other arms and completes its own independent portion of the circuit to be formed.

Circuit A-|, which is the circuit established when contact F is connected with contact A, and contact 4 with the contact provides thestraight galvanic current, Fig. 1 of the drawings. The circuit for this current is established as follows: Wire |0| from D. C. generator 5| leads to contact C, which in turn is connected to contact B to contact A. A wire |09 leads from com-. panion contact F to a wave filter (which is or may be provided to reduce or prevent rippling of the various wave forms of the currents provided in the operation of the apparatus). This wavek filter is not thought to need particular. description since its construction provides no part of the present invention. It may be mentioned, however, that it comprises reactance units ||2 and ||3 and condensers ||4 and ||5 suitably wired together. From the wave lterv a wire ||6 leads to contact points 2 and of the righthand unit of switch 42. From point the circuit continues through contact 4 to wire I1 (in which is or may be arranged the ammeter 45). Wire ||1 connects With terminal ||8 at the pole changing switch 4 8 and through the pole changing switch with one or the other of load terminals ||9 to which the electrodes delivering the current to the patient is connected. From the pole changing switch the circuit continues through terminal 2| to contact 4 over wire |22. From contact to contact 3 through wire |23 to intermediate terminal F of switch 4| to contact A of this switch and wires |24, |04 to rheostat 46 and thence to wire |06 to generator 5|.

A volt-meter 44 may be put across this circuit between contact F of the intermediate unit of switch 4| and contact of righthand unit of switch 42 by wires |25 and |26. A wire |21 leads from contact of lefthand unit of switch 42 to wire |28 to the middle of the condensers ||4 and ||5 onlter In tracing this circuit, it will be observed that the current passes without alteration through the load terminals ||9 and is only affected in its y is - and its wiring is as follows: wire IOI, wire |02 to the commutator and to the point B of lefthand unit of switch 4 I. One circuit is completed from the commutator by wire |03 through rheostat 46 and wire |06 back to D. C. generator 5I. The other circuit continues from B to F, wire |09 to filter, wire ||5 to contact I of righthand unit of switch 42, contact 4 to wire |I1, contact ||6, contact |2|, wire |22, contacts 4 to I of lefthand unit of switch 42, wire |23 to intermediate contact F of switch 4|, contact B, wire |29 to collector ring 91 and from this ring to brush 65 in engaging with the commutator. The circuit continues through terminal 93, wire |03, rheostat 46, and wire |06 Ato D. C. current generator. This circuit includes like connection to wire |23, |21 and wire |26 to intermediate portion oi.' condensers ||4 and I|5 on the filter III and the volt-meter 44 is included in the circuit as earlier described.

Direct current ilows through the circuits and the brush 65 in movingover the commutator causes the current to surge irom zero to a maximum and back to zero again, as may be observed in Fig. 4.

Current C-I (Fig. '7) provides a galvanic dwell with the surge and a quarter of the cycle as a rest period for the patient. In this circuit, the current flows from generator 5| as before to the commutator and to contact C oi' the leithand unit of switch 4|. From this contact to contact F, wire |09 to lter and thence as described in connection with the earlier circuits to wire`||6, contacts 2, I and 4, wire II1 to terminals ||3 and |2I at the pole chan-ging switch. From here the current flows to wire |22, contacts 4, I and 3 of lefthand unit of switch 42, and thence by wire |23 to intermediate contact F oi switch 4|. From here the circuit continues through wire I3| leading from contact C to colflector ring 69, and from collector ring 56 to brush 66 and from brush through commutator, wire |03, rheostat 46, and wire |06 to D. C. generator 5|.

It will be noted that brush 66 has travelled over the end blocks of the commutator and that when the patients current reaches a maximum, as

occurs when the brush engages the top block (viewing Fig. 23) a dwell is provided which gives the wave form shown in Fig. '1 of the drawings. At the opposite diameter oi! the movement, the brush 66 is in contact with the bottom block and through the bottom block directly with the wire |03, so that`no current flows through the load portion of the circuitor is received by the patient. This gives a rest dwell of zero current. As before, the volt-meter 44 is arranged across the circuit and connection is made with the middle of the filter.

Current D-I oi slow sinusoidal form, as shown in Fig. 10, is produced through the circuit to be now described: wire I0| to wire |02 to terminal of commutator; from commutator the circuit is completed through terminal 98, wire |03, wire |04, rheostat 46, wire |06`to generator. Brush 55 and collector ring 61 are connected by wire |29 to contacts B and D oiintermediate switch unit 4|. Contact F of this unit is connected by wire |23 to contacts 3 and of lefthand unit of switch 42 and the circuit continues through contact 4, wire |22, terminals |2| and ||9, wire |I1 to contacts 4, I and 2 of righthand switch unit 42, wire II6, alter III, wire |09 to contact F and D of lefthand unit of switch 4|, wire |32 connects this contact D with a collector ring 69 in turn connected with brush 64. It will be noted that the two brushes 64 and 60 travel continuously over the commutator bars 34 and impart modulated current of the true sign form shown in Fig. 10.

Current E-I (Fig. 10), which is a galvanic surge giving a two-thirds rest period, is provided through wiring as follows: The commutator is supplied with current as described in the immediately preceding circuits and, as before described, is returned to the generator. Brush 65 and coilector ring 61 are connected by wire |29, the contacts B, D and E ot the intermediate unit of switch 4I. Wire |23 connects contact F with contacts 3 and I ot lefthand unit oi switch 42. 'Ihe circuit continues through wire |22, contacts |2| ||6,'wire |I1 to contact 4 of righthand unit of switch 42; thence by contacts I and 2, wire ||6, iilter II|, wire |09, contact F of lefthand unit of switch 4 I, and thence by contact E, wire |33 to the active segment o! collector ring 1| and to brush 64 at the commutator. By reason of the idle period oi the collector ring 1| a two-thirds period of rest is provided in the resulting galvanic circuit.

Current A-2 is the pulsating galvanic current shown in Fig. 2. The circuit comprises wire IOI through contacts C, B and A of lefthand unit ot switch 4I, wire |09, illter I|I, wire II6, contacts 2 and 4 of righthand unit of switch 42, wire I|1, terminals ||9 and |2|, wire I 22 to contacts 4 and 2 of lefthand unit of switch 42, wire |34 and wire |35 to A. C. generator 52. The current thence flows by wire |36 to contacts and 3 of lefthand unit of switch 42, wire |23 to contacts F and A of intermediate unit of switch 4I, and then back to generator through wire |24, wire |04, movable contact |05, rheostat 46 and wire |06. In the A. C. generator, which is preferably an induction generator, an A. C. current is generated by induction and upon this a D. C. current is superimposed to give the wa've form shown in Fig. 2 of the drawings. The neld of the A. C. generator is excited by the circuit to be now described: wire |0| to contacts C, B, A, contact F, wire I 09 to contacts 4, 2, 3 of intermediate unit of switch 42, wire |31 to generator 52, wire |36 to contacts I and 3 of lefthand unit of switch 42, wire |23 to contact F of intermediate unit of switch 4|, contact A of this unit, wire |24, wire |04', rheostat 45, and wire |06 to D. C. generator. At the A. C. generator, wire |36 is provided to connect both to the I A galvanic to pulsating galvanic. The circuit comprises wire IOI to contacts C and B of lefthand unit of switch 4|, wire |09 of contact F to illter wire ||6 to contacts 2 and 4 of righthand unit of switch 42, wire I|1 to terminals ||6 and |2|, wire |22 to contacts 4 and 2 of lefthand unit of switch 42. The circuit then continues through wires |34 and |35 to A. C. generator, from the A. C. generator wires |36 and |21 connect contacts I and 3 o! lefthand unit of switch 42. Wire |23 leads from contact 3 to contact F of intermediate unit of switch 4| which is connected to contact B in turn connected by wire |29 to collector ring 61 of brush 65 in engagement with the commutator. The circuit is completed through terminal 96, wire |03, wire |04, rheostat 46 and wire generator is excited as just above described in connection with current A--2.

Current C-2 is the pulsating galvanic dwell surge with the one-quarter rest period shown in Fig. 8. This circuit comprises wire to the point C of the lefthand unit of switch 4|, Wire |09 to filter wire ||6 to contacts 2 and 4 of 'the righthand unit of switch 42, wire ||1, terminals ||8, |2|, wire |22 to contacts 4 and 2 of the lefthand unit of switch 42, wire |34, wire |35 to A. C. generator 52, wire |36 to contact points I and 3 of the lefthand unit of switch 42, wire |23 to contacts F and C of the intermediate unit of switch 4|, wire |3| to collector ring 68 and brush 66 in engagement with the commutator. From the commutator, the circuit is completed through terminal 98, wire 03, movable contact |05, rheostat 46 and wire |06 to D. C. generator 5|. rent and its circuit and the current and circuit of the galvanic dwell surge of Fig. 7. The field of the A. C. generator is excited as just above described in connection with current A-2.

Current D-2, which is the pulsating slow sinusoidal current of Fig. 11 is produced as follows: wire |0| leads to wire |02 and the terminal 95 of the commutator and an energizing circuit is completed from terminal 98, wire |03, wire |04, rheostat 46 and wire |06 back to D. C. generator 5|. Brush 65 in contact with this generator and its collector ring 61 are connectedby wire |29 to contacts B, D of intermediate unit of switch 4|. Wire |23 connects contact F of this unit with contacts 3 and of lefthand unit of switch 42 and wires |21 and |36 connect to A. C. generator 52. From the A. C. generator wire |35 and wire |34 lead to contacts 2 and 4 of leithand unit of switch 42 and the circuit continues to terminals |.2| and ||8, wire ||1, contacts 4 and 2 of right-y hand unit of switch 42, and wire ||6 to lter From the filter wire |09 leads to contacts F and D of lefthand unit of switch 4| and from contact D wire |32 leads to collector ring 69 of brush 64. The eld of the A. C. generator is excited as just above described in connection with current A-2.

Current E-2, which is the pulsating galvanic surge with the two-thirds rest period, and which is illustrated in Fig. 14, is produced as follows: The current, as earlier described, is caused to flow from the D. C. generator through the commutator and back to the generator. The circuit for supplying this current to the terminals ||8 and |2| is as follows: brush 65 andcollector ring 61 are connected by wire |29 to contacts B, D and E of intermediate unit of switch 4|. Contact F of this unit is connected by wire |23 to contacts 3 and of lefthand unit of switch 42. From the contact of this switch wires |21 and |36 lead to A. C. generator 52. From this generator, wire |35 and wire 34 lead to contacts 2 and 4 of lefthand unit of switch 42. The circuit continues in sequence as follows:Y wire 22,

-terminals |2| and ||8, wire ||1, contacts 4 and 2 of righthand unit of switch 42, wire |l6, filter wire |09, contacts F and E of lefthand unit of switch 4|, wire |33, active segment of col-A lector ring 1| and brush 64. The eld of the A. C. generator is excited as just above described in connection with current A Z.

Current A-3 is therapid alternating current illustrated in Fig. 3 of the drawings. The circuit for .it in sequence is as follows: Wire I 0I, contacts C, B and A of lefthand unit of switch 4|,

Comparison is suggested between this cur' contact F, wire |09 to contacts 4 and 3 of intermediate unit of switch 42, wire L31 to A. O. generator 52, wire |36, contacts and 3 of letthand yunit of switch 42wire |23 to contacts F and A of intermediate unit of switch, wire |24, wire |04, rheostat 46 and wire 06 to D. C. generator 5|. 'I'he circuit thus completed is a. generating or field circuit for the A. C. generator. From the A. C. generator a delivery circuit is formed as follows: wire |35, wire |30, contacts 3 and 4 of righthand unit of switch 42, wire ||1, terminals ||8 and |2|, Wire |22, terminals 4, 3 and of llefthand switch unit of switch 42, wire |21 and wire |36 back to A. C. generator.

Current B-4, which is the rapid alternating current in surges, is illustrated in Fig. 6, and is produced by creating a field or delivery circuit in the A. C. generator. Wire |0| leads to contacts C and B of lefthand unit of switch 4|, wire |09 leads to contact 4 of the intermediate unit of switch 42, and wire |31 connects contact 3 of this unit to the eld of the A. C. generator 52. From this eld, wires |36 and |21 lead to contacts and 3 of lefthand switch unit of switch 42, and wire |23 leads to contact F of the intermediate unit of switch 4|. The circuit continues: Contact B, wire |29, collector ring 61, brush 66 to the commutator and from the commutator by wires |03, |04 to rheostat 46 and wire |00 to the D. C. generator. The delivery circuit is the same as that already described for circuit A3.

Current C--3 is the rapid alternation in dwell surges with the quarter rest period as shown in Fig. 9. A eld circuit for the A. C. generator is provided as follows: Wire 0| to contacts C,

and F of lefthand unit of switch 4| wire |00 to contacts 3 and 4 of intermediate unit of switch 42, wire 31 to A. C. generator, wire |30 land wire |21, contacts and 3 of lefthand unit of switch 42, wire |23 to contacts F and C of intermediate unit of switch 4|, wire |3| to collector ring 68 and brush 66, to terminal 90, wire |03, wire |04, rheostat 46 and-wire |06 to D. C. generator. The delivery circuit is the same as that already described in connection with the immediately preceding circuit, series 3.

Current D-3 is the current of Fig. 12 producing rapid alternations in surges (see Fig. 6) Here the held circuit is energized as follows: Wire |0| from the A. C. generator 5| connects by wire |02 with terminal 95 of the commutator. The current iiows through the resistances of the commutator to terminal 98 and back through wire |03, wire |04, rheostat 46 to the D. C. generator 5|. Brush 05 and collector ring 61 are connected by wire |29 to contacts B, D, and F. The circuit continues in sequence as follows: wire |23, contacts 3 and of lefthand unit of switch 42, wire |21, wire |36, the field of A. C. generator 52, wire |31, contacts 3 and 4 of intermediate unit of switch 42, wire |09 to 'contacts F and D of lefthand unit of switch 4|, wire |32 to collector ring 69 and brush 64. 'I'he delivery circuit is that already described in connection with the circuit of the 3 series now being described.

circuit r'f-s, which is the rapid alternating circuit with the two-thirds rest period, shown in Fig.

15, is produced as follows: The current is caused field of A. C. generator 52. Wire |31 leads to contacts 3, l of intermediate unit of switch l2, and

wire |09 connects these contacts with contacts F.

lleading respectively fromtaps |43 and I at the commutator and connecting to terminals F and E of the righthand unit of switch 4i.

In all of the foregoing circuits. the volt meter 44 is connected as described in explanation of circuits A-I and B-i and similar wiring is provided to tap into the center of the filter, as earlier described.

It is thought that this invention and many of its attendant advantages will be understood from the foregoing description, and it is apparent that various changes may be made in the form, construction and arrangement of the parts without departing from the spirit and scope of the invention or sacrificing all of its material advantages, the form hereinbefore described being merely a preferred embodiment thereof.

l. An apparatus for generating currents of wave form for use in electro-physiotherapy and for other uses, comprising in combination, a series of contact bars arranged with their edges in a single plane, resistances interposed between and connected to said contact bars in electrical series, terminals at the ends of the series of bars, a direct current generator connected with said terminals, a brush having relative movement over said contact bars for variously receiving current therefrom, a source of alternating current, a pair of load terminals and selectively operable means for making, varying and breaking connections between said load terminals and said brush, and also between said load terminals and said source of alternating current to superimpose an alternating current upon the direct current passing between said load terminals.

2. An apparatus for generating current of wave form for use in electro-physiotherapy and for other uses, comprising in combination a direct current generator, an alternating current generator, a rotary commutator consisting of a plurality of axially alined rings, a plurality of brushes severally connected with said rings, said brushes being movable jointly with said rings, resistance elements over which said brushes are maintained in sliding engagement, said resistance elements being connected with the direct current generator, selectively operable means for altering the connection between said resistance elements and said generator, and selectively operable means for establishing connection between said alternating current generator and said brushes `to superimpose the alternating current of said alternating current generator upon the direct current, the selectively operable means interposed between the alternating current generator and the brushes being connected with load terminals for leading oil the modified current.

3. An apparatus for generating current of wave form for use in electro-physiotherapy and for other uses, comprising in combination, a series of contact bars arranged with their edges in a single plane, resistances interposed between and connected to said contact bars in electrical series. terminals at the two ends of the series of bars. a direct current generator connected with said terminals, a brush mechanism having relative movement on said contact bars for receiving current therefrom, said brush mechanism including a plurality of brushes, a pair of load terminals. a source of alternatingcurrent, and means for variously connecting'rrsaid brushes and said alternating current with said load terminals to superimpose an alternating current upon the direct current passing between said load terminals.

4. An apparatus for generating current of wave form for use in electro-physiotherapy and for other uses, comprising in combination, a series of contact bars arranged with their edges in a single plane, resistances interposed between and connected to said contact bars in electrical series, terminals at the two ends of the series of bars, a direct current generator connected with said terminals, a brush mechanism having relative movement on said contact bara for receiving current therefrom, said brush mechanism comprising three brushes, load terminals, a source of alternating current, and means for selectively connecting said brushes in pairs and said source of alternating current to said load terminals to superimpose an alternating current upon the direct current passing between said load terminals.

5. An apparatus for generating current of wave form for use in electro-physiotherapy and for other uses, comprising in combination, a series of contact bars arranged with their edges in a single plane, resistances interposed between and connected to said contact bars in electrical series,l terminals at the two ends. of the series of bars, a direct current generator connected with said terminals, a brush mechanism having relative movement on said contact bars for receiving current therefrom, said brush mechanism comprising three brushes, a source of alternating current, load terminals, and means for selectively connecting said brushes singly and in pairs to said load terminals and also for selectively connecting said source of alternating current to said load terminals to superimpose an alternating current upon the direct current passing between said load terminals.

6. An apparatus for generating current of wave form for use in electro-physiotherapy and for other uses, including an aggregate consisting of an alined motor, direct current generator and alternating current generator, a commutator. having a plurality of axially alined electrically insulated rings, said commutator being rotated by said motor, a plurality of brushes severally conductively connected with said rings and also rotated by said motor, a plurality of .alined resistance bars over which said brushes travel while successively engaging different bars, the resistance elements being connected with said direct current generator, a plurality of switches interposed between said direct current generator, and some of said brushes, and adapted to vary the electric connection between said commutator rings and said generator, and another plurality of switches interposed between said alternating current generator and said first named switches additionally to vary the relation of said brushes to said resistances and to superimpose an alternating current of selectively variable form upon the direct current of selectively variable form.

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