US3051806A

US3051806A - Switch assembly

Info

Publication number: US3051806A
Application number: US813736A
Authority: US
Inventors: Glenn A Reese
Original assignee: Magnavox Co
Current assignee: Philips North America LLC
Priority date: 1959-05-18
Filing date: 1959-05-18
Publication date: 1962-08-28
Anticipated expiration: 1979-08-28

Description

Aug, 28, 1962 Filed May 18, 1959 G. A. REESE SWITCH ASSEMBLY 4 Smeets-Shane?l 1 Nga;

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Aug- 28, 1962 G. A. REESE 3,051,806

SWITCH ASSEMBLY Filed May 18, 1959 4 Sheets-Shea?l 2 gy-gj Z6 f 22 24 g2 162 Aug. 28, 1962 G. A. REEsl-z 3,051,806

SWITCH ASSEMBLY Filed May 18. 1959vl 4 sheets-sheet s mmxwg "lll" 200 Aug- 28, 1962 G. A. REESE 3,051,806

SWITCH ASSEMBLY Filed May 18, 1959 Sheets-Sheet 4 7 l I far/7414);

United States Patent M 3,051,806 SWITCH ASSEMBLY Glenn A. Reese, Canoga Park, Calif., assigner to Magnavox Company, Los Angeles, Calif., a corporation of Delaware Filed May 18, 1959, Ser. No. 813,736 25 Claims. (Cl. 20G- 90) The invention relates to a switch assembly in which a plurality of magnetically `operated switches are mounted to extend into an annular air gap Iand to be swept by iiux in the air gap so as to provide -successive and periodic yoperations of the switches. The invention is more particularly directed to an improved switching assembly of (this `type which is capable of rapid and interference-free operation and which is also capable of providing a plurality of -ancillary signals having a controlled timing with respect to lthe `operation of the individual switches.

Switching lassemblies which Vare capable of operating at extremely high switching rates :at precisely timed intervals find wide utili-ty in the electronic and electric arts. However, is has proven diicult to construct a switching yassembly which will provide the desired high speed switching characteristics and which, at ythe same time, will be relatively free from the production of noise and interference signals in the switching circuits.

A switching assembly is disclosed, however, in copending application 652,968, led April 15, 1957, now Patent No. 2,945,931 in the name of the present inventor, which solves most of ythe problems outlined above. The switching assembly disclosed in the copending application includes a plurality of magnetically operated switches which are mounted to extend into an annular air gap. A magnetic ilux is produced in the annular air gap and slight distortions are introduced into the flux at predetermined angular positions around the gap. The components which form the annular air gap and which produce the ux in the -air gap are mounted on a rotor. The rotor, in turn, is rotated with respect to the magnetically operated switches and ythe switches Aare caused to be actuated in succession by the slight distortions in the flux every time that 1a `iiux distortion sweeps past corresponding ones of the switches.

The switches described in the copending application are extremely sensitive and may be actuated by slight distortions in the flux in the annular air gap. The use of annular air gap causes an essentially constant flux to link the individual switches at all times. This means that there is little tendency for the extraneous sign-als to be induced in the leads associated with each switch. Such induction would `occur if the switching ywere achieved, for example, by actually sweeping a magnetic pole past the respective swi-tches. The slight distortions in the ilux are suicient to :actuate the individual switches but are insufficient to induce any appreciable error signals in the associated switching circuitry.

A second copending application, namely application Serial No. 656,051, was tiled on April 30, 1957 in the name of the present inventor. The second assembly also included structure for further reducing :any noise signals that might be induced in the `switching circuitry associated with the individual switches of the switching assembly.

A third copending application on switching assemblies of the general type under discussion has also been led. The latter application, Serial No. 753,041 was filed August 4, 1958, now Patent No. 2,988,616, also in the name of the present inventor. The embodiments of the assembly disclosed -and claimed in the third copending applicaltion also served to reduce the production of noise signals to a minimum. ln the third copending application, the

3,051,806 Patented Aug. 28, 1962 lCe armature yof each individual magnetically-operated switch was insulated from the casing, and the fixed contacts of each switch were also insulated from the casing. This enabled the casing of each switch to function as a shield, even though error signals were produced on the assembly as the switches were swept by the linx in :the annular iair gaps, the error signals did not enter the switching circuits controlled by the switches to Iany appreciable extent.

The switching assembly of the present invention may incorporate individual low-noise magnetically operated switches such as `disclosed in the copending application 753,041 now Patent No. 2,988,616 and described in the preceding paragraph. The embodiment of the invention to be described includes two banks of such switches supported in coaxial relationship and activated by rotors mechanically coupled :to one `another and mounted on a common drive shaft. Each of the switches may be of the single-pole double-throw type disclosed in copending application Serial No. 753,041, now Patent No. 2,988,616 and pairs of switches from the -two banks are 'adapted to be connected to a common switching circuit.

The illustrated embodiment of the present invention is particularly useful in applications where the voltage developed across each of a multiplicity of elements is to be sampled without causing `any appreciable current ilow or without the production of error-creating noise voltages, and in which the sampled voltage is to be measured. One method of achieving this, as will be described, is to connect :an lassociated capacitor across a corresponding one .ofthe elements to cause the capacitor to assume -a charge corresponding to the voltage across that particular element, the capacitor being subsequently connected into a circuit capable `of measuring its voltage and which voltage corresponds to the voltage across the corresponding element.

The switching assembly of the present invention en tables the voltage developed across a plurality of elements, such as those menti-oued in the preceding paragraph, to be sampled and measured with extreme rapidity and accuracy. The assembly is also constructed so that the voltage across all the elements can be successively sampled and measured, `or the voltage across any selected one of the elements can -be so processed.

A feature of the improved switching assembly of the present invention is that the structure is so composed that any lead extending to an individual switch in the unit is adjacent its return lead. This causes any noise currents that may be induced in the switching leads to effectively cancel one another. This feature further reduces trou-blesome noise signals which might otherwise be induced into the switching circuits.

It is evident that for the constructed embodiment of ythe invention to perform the sampling and measuring function outlined above, the individual switches of each pair must be actuated at exactly the same time. achieved lby the improved structure of the present invention, as will be described, in the construotional details of the two banks of magnetically operated switches and by the manner in which these banks are mounted at precisely determined orientations with respect to one another.

The magnetized rotor of the switching assembly described in copending application Serial No. 753,041 now Patent No. 2,988,616 was provided with a plurality of axial inscriptions on its peripheral surface. One or more electro-magnetic transducer heads were then mounted in the housing to read the inscriptions as they were swept past by the rotation of the rotor. The resulting output signals from the transducer heads were then used to synchronize the operation of the switching units.

The illustrated embodiment of the invention also uses electro-magnetic transducer heads to develop control sig- This isnals synchronized with the actuation of the individual switches in the assembly. A shoulder is formed on the magnetized rotor of the illustrated switching assembly, and this shoulder is swept past an electro-magnetic transducer head in each revolution of the rotor to provide, for example, an origin pulse type of output signal.

The drive shaft of the illustrated embodiment of the invention has a plurality of discs of magnetizable material mounted on it. These discs may be replaceable, and each has a pattern of inscriptions on its peripheral surface. The inscriptions on the different discs may be in accordance, for example, with a binary code, or they may have any other suitable configuration. The inscriptions are read by a plurality of electro-magnetic read heads to provide output pulses of any desired timing which are synchronized with the actuations of the different switches in the assembly.

A movable electro-magnetic transducer head is also provided in the illustrated embodiment of the invention, and this latter head is magnetically coupled to a disc driven by the drive shaft of the unit. The latter disc may, for example, contain a single inscription, and the movable head may be manually adjusted to any predetermined calibrated angular position. In this manner, output pulses may be produced coincident with the actuation of any selected one of the pairs of switches referred to above. This enables the reading of any desired one of the elements referred to above to be carried out by appropriate electronic equipment.

Other features and advantages of the switching assembly of the invention will become apparent from the following description when taken in conjunction with the accompanying drawings, in which:

IFIGURE l is a perspective view of a magneticallyoperated switching assembly constructed in accordance with the invention, this view being taken from a first end of the assembly and showing the (manner in which the switch housing is secured to a motor housing, and this view also showing a plurality of leads extending from individual magnetic switches in the unit and through one end of the housing to a first group of terminals located on the peripheral surface of the housing, a similar group of leads extending through the other end of the housing to a second group of terminals on the peripheral surface;

FIGURE 2 is a second perspective view of the magnetically-operated switching assembly, this latter view being taken from the other end and showing a further housing which supports a plurality of electro-magnetic transducer heads which produce control signals synchronized with the actuation of individual switches in the assembly, this latter view also showing a manually controllable member which supports a further transducer head and which may be adjusted to a plurality of angular positions respectively corresponding to different pairs of the switches in the assembly;

FIGURE 3 is a side elevational view of the magnetically-operated switching assembly, partly in section, to reveal a pair of magnetic units which are mounted in back-to-back atiixed relationship on a common shaft and which serve to control corresponding groups of magnetically-operated switches, this latter view also showing an electro-magnetic transducer head which is disposed in magnetically coupled relationship with a shoulder on one of the magnetic units so as to produce a pulse indicating, for example, each revolution of the rotor of the assembly;

FIGURE 4 is a sectional view of the magneticallyoperated switching assembly taken along the lines 4 4 of FIGURE 3, showing the configuration of the pole pieces of one of the -magnetic rotors included in the switching assembly, which pole pieces dene an annular air gap having variations in the magnetic ux produced therein at selected positions in the gap to produce a desired actuation of each of the individual switches which are supported to extend into the air gap;

FIGURES 5a and 5b are schematic representations of the air gap formed by the rotor pole pieces of either one of the magnetic units of the switching assembly, these views illustrating the manner in which a movable contact in each of the individual magnetically-operated switches is brought into contact with a fixed contact in the switch as that particular switch is swept by a variation in the magnetic flux of the annular air gap;

FIGURE 6 is a side sectional view, on an enlarged scale, of a typical single-pole double-throw magneticallyoperated switch which is supported to extend into the air gaps of the above mentioned magnetic units;

FIGURE 7 is a schematic representation of the terminals and bus leads supported on the peripheral surface of the magnetically-operated switching assembly of FIG- URES l and 2, and FIGURE 7 also incorporating a circuit diagram representing the electrical connections to the different terminals; and

FIGURE 8 is a side elevational view, partly in section, of the transducer portion of the switching assembly, this view illustrating a plurality of discs of magnetizable material which are mounted on the drive shaft of the assembly, and also illustrating different tixed and adjustable electromagnetic transducer heads associated With these discs.

The magnetically-operated switching assembly of FIG- URES 1 and 2 includes a generally cylindrical switch housing 10. This switch housing includes a first disclike end support portion lf2 and a second disc-like end support portion 14. Each of these end support portions is provided with a doughnut-shaped cover, these covers being represented respectively as 16 and 18. The view in FIGURE l illustrates the switching assembly with the cover t6 removed. The covers are secured to the end portions by means of thumb screws, such as the screws 2,0.

A first plurality of axially-extending magnetically-operated switches are supported in the end portion l2 of the housing l0 at successive angular positions to extend into a lirst annular air gap. A second plurality of axially'- `extending magnetically-operated switches are supported in the end portion 14 at successive angular positions to extend into a second annular air gap. These switches, as mentioned above, may be of the single-pole double-throw type. Each of the switches has three leads extending from it, and these leads extend out through the end portions rllhe leads associated with the first group of switches extend out from the end portion l2 under the cover 16, and the leads associated with the second group of switches extend out from the end portion I4 under the cover E8. These leads are brought around the end portions and to a plurality of terminals which are supported on the outer peripheral surface of the housing fitti. These terminals are indicated, for example, as 22.

A iirst group of terminals 22 is provided on the peripheral surface of the housing l@ for the leads extending from the rst plurality of magnetically-operated switches.

A second plurality of the terminals 22 is provided for the switches of the second plurality, and extend into the second air gap inside the housing l0. A pair of ybus leads 24 and 26 also are supported on the peripheral surface of the housing 1t) in spaced mutually insulated positions. A lead from each of the switches of the rst plurality is connected to the buis lead 25 and a lead from each of the switches of the second plurality is connected to the vbus lead 24.

The housing lt? is supported on a mounting base 26 by means of a plurality of screws such as the screws 28 and by associated nuts such as the nuts 30. The mounting base 28 is equipped with a plurality of mounting holes 32 through which appropriate mounting bolts may extend. It 5will be appreciated that the mounting base 7.6 may be conveniently mounted on `any stationary surface so as to hold the housing 10 in a rigid stationary position.

A cylindrical-shaped drive shaft housing 36 is secured to the end portion i2 of the housing 1G in coaxial relationship with the housing 10. The housing 36 is fastened to the housing by means of a plurality of screws 30. The housing 36 surrounds a drive shaft which extends from a motor 40v into the interior of the switching assembly 10 to drive the switching assembly. The housing 36 is secured to the motor 40 by means of a plurality of screws 42. This enables the housing 10 to serve as a support for the motor 40, with the drive shaft of the motor extending through the housing 36- into the interior of the housing 10 in coupled relationship with the rotor of the magnetically-operated switch.

A second cylindrical-shaped housing 46 is secured to the other end portion 14 of the housing 10 by means of a plurality of screws 43 (FGURE 2). The cylindricaln shaped housing 46 also extends in coaxial relationship with the housing 10, and it is secured to `a further cylindrical housing 50 of increased diameter with respect to the housing 46. The housing 50 supports a plurality of electro-magnetic transducer heads 52 on its peripheral surface. These heads may have any suitable known construction, or they may Ibe constructed in a manner to be described in conjunction with FiGURE 8.

The drive shaft of the switching assembly supports a plurality of m'agnetizable discs within the housing 50, and these discs have a magnetic means, such as a permanent magnet, `disposed in coupled relationship with them so as to produce a magnetic ilux through the discs and through corresponding ones of the heads 52. The discs are provided with inscriptions, so that a variation in the -tlux through the corresponding transducer head occurs at selected angular positions of the drive shaft. These angular positions may be made to correspond with the actuation of diierent ones of the individual switches in the housing 10.

An annular knurled knob 56 is mounted on the remote end of the housing 50 in friction t with the housing. The knob 56 may be manually adjusted to predetermined angular positions. Suitable calibrations may be provided to assist in the setting of the knob 56 to its different predetermined angular positions. A transducer head 58 is supported on the knob 56. As will be described, the `lmob may be adjusted to any one of a plurality of angu lar positions, to cause the transducer 58 to generate a pulse at times corresponding to selected angular positions ofthe drive shaft of the switching assembly. These angula-r positions may be made to correspond, in turn, to the actuation of predetermined ones of the individual switches of the assembly.

As best shown in FIGURE 3, the drive shaft 100 of motor 40 is secured to a coupling '102 in the housing 36 by means, `for example, of a screw 104. The switching assembly 10 has a central shaft 106 which extends through the end support portion 12 into the housing 36. The shaft 106 is rotatably mounted in the

end portions

12 and 14 of the switching assembly by means of a pair of

bearings

108 and 110. The shaft F106 is also fastened to the coupling 102 in the housing 316, so that the drive shaft 100 of the motor may 'be mechanically coupled to the shaft 106 of the switching assembly.

The shaft 106 of the magnetic switching assembly is composed of a non-magnetic material, such as stainless steel. This shaft has a central threaded portion, such as illustrated at 112 which is disposed within the housing 10 of the magnetic switching assembly. The rotor of the switching assembly is mounted on the threaded portion of the shaft 112. This rotor includes a first magnetic unit which, in turn, includes an annular shaped permanent magnet 114. This magnet has a central aper* ture, and the threaded portion 112 of the shaft extends through the aperture so that the magnet 114 is positioned in coaxial relationship with the shaft 112. The permanent magnet 114 may be composed of any suitable material, and it is magnetized in -an axial direction. A bushing `116 is threaded onto the threaded portion 112 of the shaft 106, and this bushing is composed of a non-mag- 6 netic material such as stainless steel. The bushing serves to support a first pole piece at one of its ends, by means of a plurality of screws, such as the screw 120, and it supports Aa second pole piece 122 at its other end by means of a plurality of pins, such as the pin 124-.

The pole pieces `are composed of any suitable magnetizable material, such as iron. The pole piece 118 is disc-shaped, and it is supported by the screws 120 extending into the bushing 116 in coaxial relationship on the drive shaft 106. rllhe second pole piece 122 has a cylindrical shape, with the cylinder formed by the second pole piece having a closed end in facing spaced relationship with the pole piece 11S. The pole piece 122 is supported by the pin 124 in coaxial relationship on the drive shaft 106. The magnet 114 is held in position between the

pole pieces

118 and 122.

The pole pieces 11S and 122 form an annular air gap 126. This -annular air gap is disposed in facing relationship with the support `end portion 12 of the housing 10. A plurality of magnetically-operated switches, such `as the switch 120, are supported in the end portion 12 and extend into the air gap 126 at spaced angular positions around the air gap.

A second magnetic unit is supported on the shaft 106 adjacent the iirst unit. The second magnetic unit includes a pole piece 130 of magnetizable material and which is similar in configuration to the pole piece 122. The pole piece 130 is mounted on the shaft 106 in baci;- to-back relationship with the pole piece 122. A permanent magnet 132 which may be similar to the permanent magnet 114 is positioned on the shaft 106 between the pole piece 130 and a disc-like pole piece 134. The pole pieces 130 and 134- are held on a `bushing 136 by means of the pins, such as the pin 124.

The magnet 132 is ring-shaped, and it is positioned between the

pole pieces

130 and 134. This latter magnet is aiso magnetized in an axial direction. The Ibushing 136 is threaded Onto a threaded central portion, like the p0rtion 122, of the shaft 106. The

pole pieces

130 and 122, after being adjusted to predetermined relative angular positions on the shaft 106, are cemented together about their peripheries, as indicated at 138, by means of any suitable bonding cement. The pin 136 may also be bonded in place by any suitable cement.

The

pole pieces

130 and 134 are shaped to define an annular air gap 140 in facing relationship with the end portion 14 of the housing 10. A plurality of magnetically operated switches, such as the illustrated switch 142, are supported in the end portion 14 and extend into the annular gap 140. These latter switches are positioned at spaced angular positions around the annular air gap 140. The switches, such as the switch 142, are held in place in suitably tapered apertures in the end portion 14 by means of individual brackets such as the bracket 144 and individual screws such as the screw 146. Each of the screws 146 is threaded into the end portion 14, to hold the corresponding bracket 144 rmly against the end of the associated switch 142, so as to hold the switch in place. The portion of the switches ofthe first group, such as the switch 142, which extend outwardly from the end portion 14 are covered by the doughnut-shaped cover shield 18. Likewise, the portion of each of the switches of the second group, such as the switch 128, which extends outwardly from the end portion 12 are covered by the dough- J nut-shaped cover shield 16.

A iirst ring-shaped member 150 is supported about the shaft 106 on the end portion 14 by means of a plurality of screws such as the screw 152. This member is formed of magnetic material and it becomes magnetized and serves to prevent particles from entering the bearing 110. A similar member 154 is supported on the end portion 12 around the shaft 106 to prevent particles fromentering the bearing 108.

A first annular flange member is secured to the end portion 14 of the housing 10 by means of screws such as apetece the screw 161, and a similar ring-shaped member 162 is secured by similar screws to the end portion 12, These ring-shaped members support one end of the respective shields 16 and 1S, and they extend radially outwardly from the housing 10.

In the particular embodiment of the invention being described, the switches of the first group, such as the switch 128, which extend into the annular air gap 126, constitute a predetermined number of switches of the first plurality. Each of these switches is of the single-pole double-throw type, and each has three leads extending from it. The switches of the second group, such as the switch 142, which extend into the air gap 14d constitute the switches of the second plurality. Each of these latter switches also is of the single-pole double-throw type, and each has three leads extending from it.

The leads from the switches of the irst group, which extend into the air gap 126, are brought out through corresponding apertures in the ring-shaped member 162 to the terminals 22, and to the bus bar 2e on the periphery of the switching housing 1d, as described above. In like manner, the leads from the switches of the second group, which extend into the air gap 140, are brought out through the ring-shaped member 160 to the terminals 22 and to the bus leads 241, as described above.

For a particular application of the embodiment of the invention presently being described, an equal number of switches are mounted to extend into each of the

air gaps

126 and 140. These switches are precisely located, and their corresponding magnetic units are accurately oriented, so that corresponding pairs of the switches in each of the air gaps may be actuated exactly at the same time.

The pole piece 134 has a shoulder 166 formed at a par ticular angular position on its outer surface. An electro magnetic transducer head 168 is mounted in the end portion 14 of the housing 1@ in magnetically coupled relationship with the shoulder 166. The transducer head 168 is held in place by a `bracket 17@ which, in turn, is mounted on the end portion 14 by means of a screw 172. The transducer head 16S generates a pulse for each revolution of the rotor of the switching assembly, for exam ple, so as to provide an origin pulse for the system in which the switching assembly is incorporated.

rlhe

annular air gaps

126 and 146 may be identical in their configurations. The configuration of the air gap 14th is shown in FIGURE 4, together with the manner in which certain contours in the air gap cause the flux in the gap to react on the switches 142, this latter action being explained in FIGURES a and 5b. lt will be un* derstood that an identical con-figuration may be used for the air gap 126.

lt is evident that the axially magnetized permanent magnet 132 develops a magnetic ilux in the annular air gap 140 between the pole pieces 13) and 134. Because one of these pole pieces represents a north pole and the other a south pole, the lines of ux ilow generally in a radial direction and uniformly across the air gap 140. The air gap therefore has uniform characteristics at successive positions around the gap.

However, the pole piece 130 is provided with contours in the form, for example, of a pair of radially inwardly extending tongues 2110 and 202 positioned diametrically opposite one another. Likewise, the pole piece 134 is provided with contours in the form of a pair of inwardly extending radial grooves 294 and 206 positioned adjacent corresponding ones of the tongues. These contours dene displacements in the air gap which produce variations in the flux across the air gap 140 in their vicinity.

When a switch, such as the switch 142, is mounted on the end portion 14 of the switch housing to extend into the air gap, roation of the rotor ofthe switching assembly causes .the flux in the air gap to rotate. A magnetic armature included in the switch 142 moves as the switch is swept by the flux in the portion of the air gap corresponding to the tongue and

groove

200, 204; and when it is swept by the ux in the portion of the air gap corresponding to the tongue and

groove

202, 206. This action is shown in FIGURES 5a and 5b.

As shown in FGURE 5a, for example, as the rotor of the switching assembly rotates in a counterclockwise direction, the variations in the ux produced by the tongue 2G@ and the groove 204 approach the switch 142. As the switch moves into this area, and as shown in FIGURE 5b, a movable contact in the switch is drawn from one iixed contact to a second. This is due to the fact that the tongue portion 201B brings the pole piece 131B- into closer proximity to the `armature of the magnetically-operated switch than the pole piece 134. When the continued movement of the pole pieces and 134 brings the particular switch 142 out of the areabetween the tongue 20@ and the groove 204, the pole piece 134 is again closer to the armature than the pole piece 130, and the armature of the switch 142 is moved to draw the movable contact out of engagement with the second ixed cont-act and back into engagement with the first ixed contact.

Therefore, each time the tongue 200 and the groove 204, or the tongue 2112 and the groove 2&6, are swept past the switch 142, the lmovable contact of the switch is lirst drawn out of engagement with the iirst fixed contact and into engagement with the second lixed contact. The rnovable contact is subsequently returned into engagement with the lirst fixed Contact and out of engagement with the second fixed contact. This single-pole dou-ble-throw action or" each of the switches 142 is therefore positive, with the first set of contacts being normally held in engagement by the 4flux in the annular air gap, and with the movable contacts being moved into engagement with the second set of fixed contacts by the variations in the ilux twice for each revolution of the rotor of the switching assembly.

Each of the magnetically-operated switches 12S and 142 may lbe similar in their construction to the switches disclosed in the copending application 753,041 referred to above. Such a switch, namely the switch 142, is shown in FlGURE 6. The illustrated switch includes an upper tubular casing 2.26 and a lower tubular casing 22S. These casings are shown as being cylindrical, but they may also be elliptical with the major axis of the ellipse extending in the radial direction in FIGURE 3. The tubular casing 225 may be composed of brass, for example, and it serves as a magnetic shield for the internal components of the switch. This shield serves to prevent noise pulses from being induced magnetically into the inner active components of the switch, and it reduces any tendency for such pulses to find their way into the electrical circuitry associated with the switch.

As shown in FIGURE 6, the upper tubular casing 226 of the switching unit has a larger diameter than the lower casing 22%. The lower casing is mounted coaxially with the upper casing and is fitted into the upper casing, as illustrated. The lower casing is welded or soldered to the bottom of the upper casing, as at 229. The lower end of the lower tubular casing 223 of the switching unit is crimped as at 232, and this lower tubular casing is at least partially filled with a damping insulating tiuid, such as a light electrical grade oil. i

The switch lfurther includes a magnetic armature 224, which is preferably cylindrical in shape and which is adapted to be tted into the lower tubular casing 228. The armature 224 is composed of any suitable magnetic material, and the outer diameter of the armature is less than the inner diameter of the lower tubular casing. An insulating collar 234 is mounted on the lower end of the magnetic armature 2124 for pivotal movement with the armature. This insulating collar has an outer diameter which is slightly greater than that of the armature and less than the inner diameter of the lower tubular casing 228.

The oil in the lower tubular casing 228 forms a cushion for the magnetic armature 224, and a film of oil lforms between the insulating collar 234 and the inner surface Q of the tubular casing 228. This film of oil forms a dynamic pivot for the magnetic armature 224 and the collar 234 relative to the casing at the lower end of the tubular casing 228. This dynamic pivotal action occurs about the collar 234 as a fulcrum.

The switch includes a movable contact 220 which has a cup-shaped configuration. This movable contact includes a cylindrical end portion 236 of reduced diameter which is inserted in -press lit into the `free end of the magnetic armature 224. The cup-shaped movable contact 220 is therefore supported at the end of the magnetic arm-ature 224 in coaxial relationship with the magnetic armature and in substantial coaxial relationship with the longitudinal axis of the switching unit. In this way, the movable contact 220 is pivotable with the armature.

A tubular insulating member 238 is supported within the upper tubular casing 230. The upper end of the tubular insulating member 238 is open, and the lower end of this member is closed. A group of apertures are formed in the closed lower end of the tubular insulating member to receive a group of fixed

contacts

222, 222 and 222", and to receive a pilot tube 248. The pilot tube 248 is supported by the insulating member 238 on the longitudinal yaxis of the switching unit.

The pilot tube 248 has its lower end essentially ush with the lower end of the insulating member 238. The fixed

contacts

222, 222 and 222 each protrude lfrom the bottom of the insulating lmember 238 and are fiared outwardly to have respective flared

end portions

222e, 222a and 222a. These flared end portions project downwardly beyond the top of the movable contact 220, so that the movable contact is nested within the three fixed contacts. These fixed contacts serve to prevent the armature 224 or the movable contacts 220 from touching the casing of the switch.

A connection to the movable contact 220 is made by means of a wire 249 which extend downwardly through the center of the pilot tube and into the mouth of the cupshaped movable contact 220 in a pushfit with the movable contact. A saw-cut is 'formed at the end of the cylindrical portion 236 of the movable contact to receive the end of the wire 249 so as to provide a rigid connection between the wire and the movable contact. The wire 249 is relatively thin and liexible so that it can adjust its position in accordance with the pivotal movements of the armature 224. The pilot tube 248 may be composed of a goldsilver alloy or other non-magnetic material.

The fixed contact 222 is connected to a connecting wire 246, the movable contact is connected to a connecting wire 242 which is soldered to the pilot tube 248, and 4the fixed contact 222 is connected to a connecting wire 246. The fixed contact 222 is not used. As explained in the copending application 753,041, the axial position of the movable contact 220 can be adjusted by moving the wire 249 up or down in the pilot tube 248. This, in turn, serves to adjust the spacing between the movable contact and the flared portions at the lower ends of the fixed contacts. When the desired spacing has been achieved, the upper end of the pilot tube 248 may be crimped into engagement with the wire 249.

As noted above, when the magnetically-operated switches, such as the illustrated switch 142 in FIGURE 6, are inserted into the annular air gaps, the armature 224 is controlled normally to hold the movable contact 220 in engagement with the flared portion 222a of the fixed contact 222. However, each time a variation in flux is en` countered, the movable contact moves away from the fixed contact 222 into engagement with the flared portion 222a of the xed contact 222. Therefore, the desired single-pole doublethrow action for each magnetically operated switch is achieved.

One application for the switching assembly described above is illustrated in FIGURE 7. In this application, successive pairs of the magnetically-operated switches in the air gaps are used in corresponding floating capacitor measuring circuits. It is usual in each circuit of this type for a capacitor 360 to have its terminals connected to the respective armatures of a pair of single-pole double-throw switches, and this may be achieved by bringing the leads from the capacitor into connection with appropriate ones of the terminals 22 associated with a first pair of switches in the switching assembly. A unit providing a voltage to be measured, such as a strain gauge 306 has its terminals connected to the normally closed fixed contact of the respective switches of the first pair, and this is achieved by connecting the strain gauge to other appropriate ones of the terminals 22. The normally closed contacts for the first pair of switches, and of the other switches, are connected respectively to the bus leads 24 and 26. These leads are connected to an appropriate amplifier 310 which, in turn, connects with an output terminal 312.

The object of the system of FIGURE 7 is to measure the voltage developed across the strain gauge 306. When it is attempted to measure this voltage directly, noise voltages picked up by the leads from the strain gauge cause errors in the measurement. For that reason, the capacitor 380 is first connected across the gauge so that it assumes a charge equivalent to the voltage across the gauge. Then, the condenser is switched to the input of the amplifier 310 so that the output of the amplifier provides an accurate measurement of the voltage across the strain gauge, without the introduction of error-producing noise voltages- Therefore, the first pair of switches are controlled so that normally the capacitor 300 is connected across the strain gauge 306 to assume its voltage. However, each time the flux distortions sweep the first pair of switches, the condenser 300 is disconnected from the strain gauge and connected to the input of the amplifier 310. The amplifier then develops an output at the output terminal 312 which is proportional to the voltage across the capacitor 300.

Similar independent circuits may be connected to the successive pairs of switches, so that the switching assembly may successively sample a plurality of strain gauges, or similar elements, with the amplifier 310 providing a succession of outputs individually related to corresponding ones of the elements. A re-examination of the structure illustrated in FIGURES 1 and 2 will reveal that each group of three leads from each of the individual magnetically operated switches are brought in closely adjacent relationship from the switch to the terminals 22 and to the bus -leads 24 or 26. With this arrangement, any lead carrying a current is adjacent a lead carrying the same current in the opposite direction, this being illustrated by the arrows in FIGURE 7. Then, any noise currents induced into the leads are induced in the same direction, and effectively cancel one another.

As illustrated in FIGURE 8, the shaft '106 of the switching assembly extends outwardly from the end portion 14 of the switch housing and into the housing 5). A plurality of

discs

350, 352, 354 and 356 of magnetizable material are removably supported on the shaft 106 in the housing 50 by means, for example, of a nut 358 which is threaded on the shaft and which is tightened against the magnetizable disc-like members. A ring-shaped annular permanent magnet 360 is supported on the shaft 106 adjacent the

magnetizable members

350, 352, 354 and 356. The ring-shaped magnet 360 is axially magnetized to pro duce flux through the magnetizable members and through different ones of the electro-magnetic transducer heads 52 which, as mentioned above, are mounted on the housing 50 and which are magnetically coupled to respective ones of the magnetizable members. A disc 362 of non- -magnetic material may serve as a support for the magnet 360, and the nut 358 serves to tighten the magnetizable members, the magnet and the disc against a bushing 364 which is supported on the shaft 106 in a manner to be described.

Each of the

discs

350, 352, 354 and 356 may have inscriptions formed on its peripheral surface, with lthe number and angular positions of the inscriptions on each disc being in accordance with any predetermined pattern. For example, the inscriptions on the various discs may be arranged in accordance with a binary code. 'Ihis code is related by the positioning of the discs to the actuation of the individual switches of the switching assembly. Alternately, the inscriptions on the different discs may be made to correspond with the actuation of different selected switches of the switching assembly. These inscriptions produce variations in the flux through the magnetic transducer head, so that corresponding pulses are produced. These resulting pulses may be used in conjunction with and gates, to produce output pulses through the and gates from respective ones of the transducer heads, after the and gates have been conditioned for conduction by the switching action. This, as explained in the copending application 753,041, provides clean output pulses that are not disturbed by switching transients.

It is evident, however, that the

discs

350, 352, 354 Iand 356 may be used to provide any desired pattern of output pulses which are synchronized with switching actions of the switching assembly. As noted above, the discs are removable, so that they may be displaced by either the same or a different number of discs with different inscriptions on their peripheral surfaces.

The transducer heads S2 may be of extremely simple construction. Each of these may include a threaded probe 366 composed, for example, of soft low-carbon steel. The inner end of the probe 366 is tapered to `a point, and then blunted to a diameter of 2%000 of an inch. The probe 366 is threaded into a suitable casing 36S which is mounted on the housing 50 by means of appropriate mounting screws, as illustrated in FIGURES 1 and 2. The magnetizable discs, 350, 352, 354 and 356 may, for example, be .l inch thick and have a diameter of 3.5 inches. 'It should be noticed that the

discs

350, 352, 354 and 356 may be moved angularly with respect to one another for any desired phasing adjustment.

A suitable winding 370 is mounted on the probe 366. The flux from the corresponding disc 356 passes through the probe 370 and across an air gap formed between the probe and the casing 368. The iiux then returns through the housing t? to the permanent magnet 360. A variation in the flux is produced by each inscription in the member 356 so that a corresponding output pulse is produced across the winding 37d. The other transducer heads 52 respectively associated with the other discs may have a similar construction.

A second ring-shaped Iaxially magnetized permanent magnet 380 is positioned on the shaft 106 at the other end of the bushing 364. A disc-like member 382 of magnetizable material is positioned adjacent the magnet 380, yand the disc 382 is held in position by a nut 384 which is threaded onto the shaft 106. It will be apparent that the nut 358 and the nut 384 hold the various elements in an assembled rigid condition between them, with the held elements being fixedly mounted on the shaft 106.

As described above, the knurled end knob 56 supports a transducer head 50, and this transducer head extends into magnetically coupled relationship with the periphery of the disc 382. The magnetic flux from the magnet 380 passes through the disc 382 and through the transducer head 58 to be returned through the housing 50 back to the magnet 380. The disc 382 may carry a single inscription on its peripheral surface, for example, and this inscription produces a variation in the flux through the transducer head 58, each time the inscription is swept past the transducer head. As noted above, the member 56 may be manually rotated so that the transducer head 58 may be given any desired angular position with respect to the member 382. In this manner, the transducer head 58 may be caused to generate an output pulse corresponding to the actuation of any selected pair of the magnetically operated switches of the assembly.

One of the output leads from the transducer head 58 is grounded, and the other is connected to an and gate 336. The output terminal 312 of the system of FIGURE 7 may also be connected to the and gate 386, and the output terminal of the and gate may be connected to `an output terminal 390. And gates, such as the and gate 386, are extremely well known to the electronic art. These gates lare formed by diodes, transistors or the llike, and they serve to pass a signal to the output terminal 390 in the presence of a signal from the transducer head 58 and a signal `from the amplifier 310.

The system of FIGURE 7, as described above, produces successive pulses 'at the output terminal 312 with the amplitudes of the successive pulses corresponding to the measurements taken by the successively actuated pairs of switches. The and gate 386 of FIGURE 8, however, may be conditioned for conduction by the output pulse from the transducer head 58 only in correspondence with the 'actuation of a selected pair of switches. Therefore, only the pulses representing the voltage across a selected one of the elements 306 of FIGURE 7 appears at the output terminal 390. By rotating the knob 56, any desired switch pair can be selected and the corresponding reading can be displayed at the output terminal 390. As noted above, the knob 56 may be calibrated to identify it with corresponding ones of the switch pairs of the switching assembly.

The invention provides, therefore, an improved and simplified construction for a rapid acting magneticallyoperated switching assembly; the assembly being capable of high speed operation at a relatively low noise level. The improved construction of the present invention also incorporates electro-magnetic transducer means synchronized with the magnetically-operated switches to provide required controls for the switching circuits.

As noted above, the switching assembly of the present invention is particularly suited yfor displaying a succession of individual output signals corresponding respectively to la plurality of successively sampled sources whose respective voltages are to be measured. The invention also includes convenient mechanism whereby any selected one of the output voltages can be individually displayed.

I claim:

l. A magnetically controlled switching assembly including: first means including first and second magnetic pole members spaced to ydefine a first annular air gap therebetween and provided with `at least one contour in at least one of the members to define :at least one displ-acement in the first air gap, second means mechanically coupled to the first means in coaxial relationship therewith including third and fourth magnetic pole members spaced to define a second annular air gap therebetween `and provided with at least one contour in at least one of the members to define at least one displacement in the second air gap, magnetic means coupled to the pole members for providing in the first `and second annular -air gap a magnetic flux having uniform characteristics at successive positions in the lair gaps and exhibiting variations in characteristics at the positions of the displacements in the `air gaps, a housing for the switching `assembly having at one end a first support portion disposed in facing spaced relationship with the first annular air gap and having at its other end la second support portion disposed in facing spaced relationship with the second `annular air gap, a first magnetically operated switch mounted on the first support portion of the housing and extending into the first annular air gap, la second magnetically operated switch mounted on the second support portion of the housing tand extending into the second air gap, and means for irnparting relative motion between the switches and the first and second means to produce periodic actuation of the switches.

2. The combination defined in claim l in which the first and second switches are connected in a circuit at cpposite ends of the circuit to introduce the same extranei3 ous signals to the opposite ends of the circuit for minimizing such extraneous effects.

3. A magnetically controlled switching assembly including: a rota-taible drive shaft, first means mounted on the shaft and including first and second magnetic pole ymembers spaced to define a first annular air gap therebetween and provided with at least one contour in at least one of the members to define at least one displacement in the first air gap, first magnetic means positioned between the first and second pole members for providing in the first annular air gap magnetic fiux having uniform characteristics at successive positions in the first air gap and exhibiting variations in characteristics at the position of the displacement in the air gap, second means mounted on the drive shaft and affixed to the first means in coaxial relationship therewith and including third and fourth magnetic pole members spaced to define a second annular air gap therebetween and provided with at least one contour in at least one of the members to define at least one displacement in the second air gap, second magnetic means positioned between the third and fourth pole members for providing in the second annular air gap a magnetic fiux having uniform characteristics at successive positions in the second air gap and exhibiting variations in characteristics at the position of displacement in the second air gap, a housing for the switching assembly and having a first support portion at one end disposed in facing spaced relationship with the vfirst annular air gap and having a second support portion at its other end disposed in facing spaced relationship with the second annular air gap, first magnetically operated switching means mounted on the first support of the housing and extending into the first annular air gap, second magnetically operated switching means mounted on the second supporting portion of the housing and extending into the second annular air gap, and a motor mechanically coupled to the drive shaft for producing rotation thereof soas to impart relative motion between the switches and the first and second means so -as to produce successive and periodic actuations of the first and second switching means.

4. The combination defined in claim 3 in which the first switching means include a first plurality of switches and in which the second switching means include a second plurality of switches and in which the housing has `a cylindrical outer surface disposed in concentric relationship with said first means and said second means, a first plurality of terminals and a second plurality of terminals supported on said outer cylindrical surface of the housing, a firs-t group of leads extending from the switches of said first plurality through said one end of the housing to respective ones of the terminals of the first plurality, and a second group of leads extending from the switches of said second plurality through said other end of the housing to respective ones of the terminals of the second plurality and in which corresponding terminals in the first and second pluralities are connected in common circuits to minimize the effects of extraneous signals in the circuits.

5. The combination defined in claim 3 in which the housing has a cylindrical outer surface disposed in concentric relationship with said first means and said second means, a first plurality of terminals and a second plurality of terminals supported on said outer cylindrical surface of the housing, a lfirst ring-shaped bus lead and a second ring-shaped bus 'lead supported in spaced mutually insulated relationship on said outer cylindrical shaped surface of the housing in concentric relationship therewith, a lfirst group of leads extending from the switches of the first plurality through said one end of the housing to respective ones of the terminals of the first plurality, a second group of leads respectively extending from the switches of the first plurality to the first bus lead, a third group of leads extending from the switches of the second plurality through said other end of the housing to respective ones of the terminals of the second plurality, and a further group of leads respectively extending from the lil i4 switches of the second plurality to the second bus lead, and circuit means connected to said first and second bus leads and to terminals of corresponding terminals in the first and second pluralities to test the potentionals produced across the switches connected from the first and second pluralities to these terminals.

6. The combination defined in claim 3 in which each of the switches are of the single-pole double-throw type having `th-ree leads extending therefrom, in which the housing has a cylindrical Shaped outer surface having a plurality of terminal means supported thereon, and in which the three leads from each of the switches are mounted to extend in side-by-side relationship to corresponding ones of the terminal means, and in which the leads from corresponding switches in the first and second pluralities are connected in common circuit arrangements to minimize the effects of noise.

7. The combination defined in claim 4 in which at least one of the magnetic pole members has at least one shoulder formed thereon, and in which at least one transducer means is mounted on at least one of said support portions of the housing in magnetically coupled relationship with the shoulder.

`8. A magnetically cont-rolled switching assembly including: a rotatable drive shaft, means mounted on the drive shaft and including first and second magnetic pole members spaced to define an annular air gap therebetween and provided with at least one contour in at least one of the members to define at least one displacement in the air gap, a magnetic member positioned between the first and second pole members for providing in the annular air gap a magnetic flux having uniform characteristics at successive positions in the air gap and exhibiting variations in characteristics at the position of the displacement in the air gap, a housing for the switch-ing .assembly and having Ia support portion at one end disposed in facing spaced relationship with the annular air gap, magnetically operated switching means mounted on the support portion of the hou-sing and extending into the annular air gap, at least one member of magnetizable material mounted on the drive shaft and spaced along the shaft from said first and second pole members, at least one stationary electro-magnetic transducer positioned in magnetic coupled relationship with the magnetizable member, and magnetic means for producing a magnetic flux through the magnetizable member having a configuration to produce a variation in the flux through the transducer means for at least one angular position of the shaft upon rotation thereof.

9. The combination set forth in claim 8 in which the switching means include a plurality of switches.

l0. A magnetically controlled switching assembly including: a rotatable drive shaft, means mounted on the drive shaft and including first and second magnetic pole members spaced to define an annular air gap therebetween and provided with at least one displacement in the air gap, a magnetic member positioned between the first and second pole members for providing in the annular air gap a magnetic flux having uniform characteristics at successive positions in the air gap and exhibit Variations in characteristics at the position of the displacement in the air gap, a housing for the switching assembly having a support portion at one end disposed in facing spaced relationship with the annular air gap, a plurality of magnetically operated switches mounted on the support portion of the housing and extending into the annular air gap, a plurality of disc-like members of magnetizable material mounted in side-by-side relationship on the drive shaft and spaced thereon from said first and second pole members, each of said disc-like members lia-"ving inscriptions formed at predetermined angular positions about its peripheral surface, a cor-responding plurality of stationary electro-magnetic tr-ansducer lmeans positioned in magnetically coupled relationship with the peripheries of respective ones of the disc-like members, magnetic means positioned on the shaft adjacent the disc-like members for producing a magnetic 1 5 ux through the disc-like members and through the transducer means, said inscriptions on the peripheral surfaces of the disc-like members producing variations in the flux through the corresponding transducer means as the shaft is rotated, and a motor mechanically coupled to the shaft for producing rotation of the shaft.

11. A magnetically controlled switching assembly including: `a rotatable drive shaft, means mounted on the drive shaft and including lirst and second magnetic pole members spaced to define an annular air gap therebetween and provided with at least one contour in at least one of the members to define at least one displacement in the air gap, a magnetic member positioned between the first and second pole members for providing in the annular air gap a magnetic flux having uniform characteristics at successive positions in the air gap and exhibi-ting variations in characteristics at the position of lthe displacement in the air gap, a 4housing for the switching assembly and having at one end a support portion disposed in facing spaced relationship with the annular air gap, magnetically operated switching means mounted on the support portion of the housing and extending into the annular `air gap, at least one member of magnetizable material mounted on the drive shaft and spaced thereon from said irst and second pole members, at least one electro-magnetic transducer means positioned in magnetically coupled relationship with the magnetizable member, magnetic means positioned for producing a magnetic llux through the magnetizable member and through the transducer means, said magnetizable member having a configuration for producing a variation in the flux through the transducer means for at least one angular position of the drive shaft upon rotation thereof, and means for supporting the transducer means in angularly adjustable relationship with respect to the magnetizable member.

12. A magnetically controlled switching assembly including: a rotatable drive shaft, means mounted on the drive shaft and including rst and second magnetic pole members spaced to define an annular air gap therebetween and provided with at least one contour in at least one of the members to deline at least 1one displacement in the air gap, a magnetic merriber positioned between the first and second pole members for providing in the annular air gap a magnetic flux having uniform characteristics at successive positions in 4the air gap and exhibiting variations in characteristics at the position of 4the displacement in the air gap, a housing for the switching assembly and having at one end a support portion disposed in facing spaced relationship with the annular air gap, a plurality of magnetically operated switches mounted on the support portion of the housing and extending into the annular air gap, a disc-like member of magnetizable material mounted on the drive shaft and spaced thereon from the first and second pole members, said disc-like member having a variation in contour formed thereon, a stationary casing surrounding the disc-like member, an annular bracket mounted on the casing for angular adjustment with respect thereto, an electromagnetic transducer means mounted in the annular bracket in magnetically coupled relationship with the magnetiz'able member and with the variation `on `contour thereon, and magnetic means positioned adjacent the magnetizable member to produce a magnetic ux through the magnetizable member and through the transducer means with a variation occurring in the llux each time the variation in contour of the magnetizable means passes the transducer means.

13. The combination defined in claim 12 and which includes a gate network coupled to the transducer means and to said switches to pass an output signal upon the actuation of a selected one of the switches dependent upon the angular position of the annular bracket.

14. A switching assembly including: switching means, actuating means for actuating said switching means upon relative movement `between the actuating means and the switching means, drive means for producing relative move- CTI ment between the actuating means and the switchingmeans, at least one electro-magnetic transducer means, magnetic means positioned to produce a magnetic flux through the transducer means, said magnetic means having a configuration for producing a variation in the llux ythrough the transducer means upon relative motion therebetween -and at a particular point of such relative movement, means coupled to the d-rive means for producing relative movement between the magnetic means and the transducer means, and means for adjusting the location of said position at which the variation occurs in the flux through the transducer means.

15. The combination set forth in claim 14 in which the switching means includes a plurality of switches and in which the individual switches are sequentially actuated upon relative movement between the actuating means and the switching means and in which means are responsive to the actuation of the switches and the variation in the lluX through the transducer means for producing an output signal upon the variation in the flux through the transducer means concurrently with the actuation of one of the switches in the plurality.

16. A switching assembly including: switching means, rotatable actuating means for repetitively actuating said switching means upon rotation thereof, drive means for producing rotational motion of the actuating means, a rotatable member of magnetizable material mechanically coupled to the drive means to be rotated thereby, an electro-magnetic transducer means positioned in magnetically coupled relationship with the magnetizable member, magnetic means positioned to produce a magnetic flux through the magnetizable member and through the transducer means, said magnetizable member having a configuration for producing a variation in the llux through the transducer means at an angular point in each revolution of the magnetizable member, and angularly adjustable means for supporting the transducer means to permit adjustment of the angular point at which said variation in the lluX through the transducer means occurs.

17. The combination dened in claim 16 wherein the switching means includes a plurality of switches sequentially actuated by the actuating means and wherein a gate is coupled to the transducer means and to said switches, said gate producing an output signal upon the actuation of a selected one of the switches, as determined by the angular position of said angularly adjustable means.

18. A switching assembly including: switching means, actuating means for repetitively actuating said switching means upon relative motion between said actuating means and the switches, drive means for producing relative motion ybetween the actuating means and the switching means, adjustable means, transducer means mounted on the adjustable means and controlled by said actuating means to develop an output signal, and control means mechanically coupled to said drive means and coupled to the transducer means for causing the transducer means to develop the output signal upon the actuation of the switching means concurrently with the development of the output signal by the transducer means.

19. The combination set forth in claim 18 in which means are coupled to the switching means and the transducer means for producing an output signal upon the actuation of the switching means concurrently with the de- Yvelopment of the output signal by the transducer means.

20. The combination set forth in claim 19 in which the switching means include a plurality of switches and in which the adjustable means are adjustable to obtain the production of an output signal upon the actuation of any selected one of the switches.

21. A switching assembly including: a plurality of individual switches, actuating means disposed relative to the switches and movable relative tol the switches for successively actuating the switches upon relative motion between the actuating means and the switches, adjustable means, at least one transducer disposed relative to the actuating means and variable in positioning in accordance with the adjustments of the adjustable means, and constructed to develop a control signal upon movement `of the actuating means relative to the transducer, and means responsive to the concurrent development of the control signal vand the actuation of one of the switching means for developing an output signal.

22. The switching assembly set forth in claim 21 in which controfl means are mechanically coupled to the actuating means and are disposed relative to the transducer for causing the transducer to develop the control signal upon a relative motion between the control means and the transducer.

23. A switching assembly, including: a rotatable drive shaft, means mounted on the drive shaft and including lirst and second walls spaced to dene an annular air gap and provided with at least one contour in at least one of the walls to define at least one displacement in the air gap, means disposed relative to the iirstand second walls for providing in the annular air gap a eld having uniform characteristics at successive positions in the air gap and exhibiting variations in characteristics at the position of the displacement lin the `air gap, switching means extending into the annular air gap and actuatable between first and second states of operation in accordance with the disposition of the 4switching means relative to the variations in the characteristics of the field in the air gap, means coupled to the shaft for producing a rotary movement of the rst and second walls relative to the switching means, transducer means for developing a control signal, means operatively coupled to the motor for movement with the motor and constructed to develop a signal in the transducer upon the movement of such means past the transducer, and means responsive to the production of a signal by the transducer means and responsive to the concurrent actuation of the switching means to a particular one of the rst and second states for producing an output signal.

24. The switching assembly set forth in claim 22 in which means are provided for supporting the transducer means and in which such support means are adjustable to control the time of production of a control signal by the transducer means relative to the times of actuation of the switching means.

25. The combination set forth in claim 22 in which the switching means includes a plurality of switches and in which the transducer means are adjustable' in an annular direction to control the particular one of the switches producing the output signal.

References Cited in the le of this patent UNITED STATES PATENTS 2,112,214 Tognola Mar. 22, 1938 2,547,003 Hastings Apr. 3, 1951 2,872,597 Ormond Feb. 3, 1959 2,912,678 Robinson et al. Nov. 10, 1959 2,922,994 Kennedy Jan. 26, 1960 2,932,703 Haberland Apr. 12, 1960 FOREIGN PATENTS 1,105,896 lFrance Dec. 8, 1955 628,014 Germany Mar. 27, 1936