US2963699A

US2963699A - Analog-digital converters

Info

Publication number: US2963699A
Application number: US598661A
Authority: US
Inventors: Jr Thaddeus C Burnette
Original assignee: AMCEL PROPULSION Inc
Current assignee: AMCEL PROPULSION Inc
Priority date: 1956-07-18
Filing date: 1956-07-18
Publication date: 1960-12-06
Anticipated expiration: 1977-12-06

Description

Dec. 6, 1960 T. c. BURNETTE,. JR 2,963,699

ANALOG-DIGITAL CONVERTERS 8 Sheets-Sheet 1 Filed July 18, 1956 m T N I a w w /a An/ w a a M I- I m y W BY @WW ATTORNEYS Dec. 6, 1960 17. c. BURNETTE, JR 2,963,699

ANALOG-DIGITAL CONVERTERS Filed July 18, 1956 8'Sheets-Sheet 2 1N VENTOR 77/400506 a earn/77.15 JA.

Dec. 6, 1960 1-. c. BURNETTE, JR 2,963,699

ANALOG-DIGITAL CONVERTERS Filed July 18, 1956 8 Sheets-Sheet 3 IN VEN TOR 77/60566 c. wkA/amdle Dec. 6, 1960 "r. c. BURNETTE, JR

ANALOG-DIGITAL CONVERTERS 8 Sheets-Sheet 4 Filed July 18, 1956 1N VEN TOR 77/086645 c. awe/V4712; we

. ATTORNEYS Dec. 6, 1960 T. c. BURNETTE, JR 2,963,699

ANALOG-DIGITAL CONVERTERS Filed July 18, 1956 8 Sheets-Sheet 5 Dec. 6, 1960 T. c. BURNETTE, JR

ANALOG-DIGITAL CONVERTERS 8 Sheets-Sheet 6 Filed July 18, 1956 ATTORNEYa Dec. 6, 1960 T. c. BURNETTE, JR

ANALOG-DIGITAL CONVERTERS 8 Sheets-Sheet 7 Filed July 18, 1956 IN VENTOR Dec. 6, 1960 T. c. BURNETTE, JR 2,963,699

ANALOG-DIGITAL CONVERTERS Filed July 1a, 1956 s sheets-sheets BY m M ATTORNEYS United States Patent ANALOG-DIGITAL CONVERTERS Thaddeus C. Burnette, Jr., Swannanoa, N.C., assignor to Amcel Propulsion Inc., a corporation of Delaware Filed July 18, 1956, Ser. No. 598,661

13 Claims. (Cl. 340-347) This invention relates to analog-digital converters, and, more particularly, to apparatus for converting shaft position to a digital output at high shaft speed with minimal operating wear and minimal ambiguity of digital output.

Many designs of analog-digital converters have previously been made and used, but all have been subject to objection of one type or other. Many of the previous designs have been subject to early wearout, others have been incapable of operating at high speeds, others have required too high torque, and others have been susceptible to increased ambiguity as more digitizing stages were added.

The apparatus of the present invention is designed to substantially avoid all the objections above noted, as well as others. In particular, the apparatus is designed to permit addition of digital stages without increasing ambiguity, to provide much greater sensitivity than previously obtained, to avoid contact making and breaking at all the digital contacts and at all but one set of switching contacts to decrease wear, and to decrease further the mechanical wear on digitizing segments by provision of roller contacts therefor. For this last purpose particularly, a special arrangement of digitizing segments and roller contacts is provided.

Generally speaking, the apparatus of the invention includes a plurality of shafts with the usual step-down drive between them, a plurality of digital commutators and a pair of contact members associated with each commutator, one commutator for each shaft, a relay for each shaft for selecting which of the pair of associated contact members is connected to the voltage source, and switch means for selecting which of the relays is operated, the switch means including operating members mounted at least on the input shaft. The input shaft has both a digital commutator and a switch associated therewith to increase the sensitivity of the apparatus over those of the prior art. Moreover, the relays are operated under control of a common switch, rather than in sequence by preceding relays, to increase the permissible operating speed of the convertor.

Preferred embodiments of the invention will now be described in conjunction with the accompanying drawings.

In the drawings:

Fig. l is a simplified schematic drawing of the embodiments of the invention;

Fig. 2 is a longitudinal sectional view, with parts shown in elevation, of a first embodiment of the invention;

Fig. 3 is a sectional view taken along line 3-3 of Fig. 2 and of Fig. 8;

Fig. 4 is a sectional view taken along line 4-4 of Fig. 2;

Fig. 5 is a sectional view taken along line 5-5 of Fig. 2;

Fig. 6 is a sectional view taken along line 66 of Fig. 2;

Fig. 7 is a sectional view taken along line 7--7 of Fig. 2;

Fig. 8 is a longitudinal sectional view, with parts shown in elevation, of a second embodiment of the invention;

Fig. 9 is a sectional view taken along line 99 of Fig. 8;

Fig. 8;

ice

Fig. 11 is a sectional view taken along line 11-11 of Fig. 8;

Fig. 12 is a sectional view taken along line 12-12 of Fig. 8; and,

Fig. 13 is a sectional view taken along line 13-13 of Fig. 8.

The schematic showing of Fig. l is specifically applicable to the first form of the invention shown in Figs. 2 through 7, but, as will be explained later, it can also be used to describe the second form or embodiment. The figure shows the various cams and digitizing commutators in developed form. Three digitizing commutators are shown in Fig. 1, namely, the units, tens, and hundreds commutators, 10, 11, and 12, respectively. As indicated by the dashed lines, the units commutator is driven by the input shaft 13, while rotation of that shaft is stepped down by 10 to l to intermediate shaft 14, which drives tens commutator 11, and a 10 to l stepdown is also provided between shaft 14 and final shaft 15, which drives the hundreds commutator. Three digitizing sections are shown, but, as will be more fully explained later, more or less could be used, if desired.

Each of the digitizing commutators comprises a plurality of insulated segments or blocks of electrically conducting material, as shown at 16 in Fig. 1. Each commutator has ten segments, since conversion from shaft position to decimal notation is provided for by the forms of the invention shown in the drawings. However, it will be obvious that the apparatus of the invention could be designed for any other system than decimal, if desired, in which case a number of segments appropriate to the system and a stepdown between the shafts appropriate to the system would be used.

The various shafts may rotate the commutators or the associated contact elements, but the operation of the apparatus of Fig. 1 will be described as if the contact elements moved, for lucidity.

The contact elements associated with the commutators are shown as brushes in Fig. 1, again for convenience in explanation, though it is preferred that rollers be used, for reasons to be explained. The contact elements are preferably arranged in twos to avoid the necessity of circuit-breaking at the commutators when digits are changed, and the brushes 20 and 20' cooperate with the units segments 16, while brushes 21 and 21', and brushes 22 and 22' cooperate with the tens and hundreds segments, respectively. Each of the brushes is positioned so as to contact each of the associated segments in turn as the input shaft rotates through a complete revolution. The brushes for each commutator are preferably spaced one-half the distance between the centers of adjacent,

contacts 16.

' As shown in Fig. l, the trailing brushes are those iden-,

tified with the primed numerals.

The various brushes are connected to a source of voltage appropriate to the function of the digitizing system through digitizing relays. If the digital representation is to be furnished to a readout system, such as an appropriate typewriter or punch card system, a source of readout voltage, such as shown at 25, of appropriate characteristics, is provided. Brushes 20 and 20' are connected to the source by conductors 26 and 26 through contacts 27 and 27' of relay 28, while brushes 21 and 21' are connected to the source by conductors 29 and 29' through

contacts

30 and 30 of relay 31, and brushes 22 and 22' are connected to the source by

conductors

32 and 32 through contacts 33 and 33 of relay 34, respectively. The relays are connected to an appropriate source of voltage 35 through cams and switches, to be described.

As shown in Fig. 1, none of the relays is energized, so the trailing brushes are all connected to the readout source 25, and voltage is applied to segments 9 of the units and tens digitizers and segment 1 of the hundreds digitizer. As indicated for the units commutator, the segments 16 of each commutator are each connected by a conductor 36 of a cable 37 to the readout device (not shown). With the relays in the condition shown, the readout device would receive voltage appropriate to the decimal notation 199.

The input shaft 13 carries three earns 40, 41 and 42, which control the positions of cooperating rollers 43, 44, and 45, respectively. The rollers carry movable contacts 43, 44', and 45, respectively, which move into and out of contact with fixed contacts 43", 44", and 45", respectively. The alignment of the cam surfaces is as shown in Fig. 1, with cam 40 having ten V-shaped notches, equally spaced along the extent of the cam, cam 41 having two V-shaped notches spaced as shown, and cam 42 having a single long notch positioned as shown. Each time that the cams rotate to such positions that the notches thereof are opposite the associated rollers, the rollers move to move the associated movable contacts into engagement with their fixed contacts. 7

The intermediate shaft 14 carries two cams 46 and 47 which control the positions of cooperating rollers 48 and 49, respectively. The rollers carry movable contacts 48 and 49 which move into and out of contact with fixed contacts 48" and 4?", respectively. Cams 46 and 47 are identical in form and alignment with cams 41 and 42, respectively.

Relay 28 has its operating coil connected to movable contact 43' of cam 415 by conductor 50, while the cooperating fixed contact 43" is connected to the relay voltage source 35 by conductor 51. The movable contact 44' of cam 41 is connected to movable contact 43 by conductor 52, while movable contact 45 is connected to source 35 by conductor 53. Relay 31 has its operating coil connected to movable contact 48 of cam 46 by conductor 54, and that contact is connected in multiple to fixed contacts 44" and 45" of earns 41 and 4-2 by conductor 55. Relay 34 has its operating coil connected to fixed contacts 43 and 49 of earns 46 and 47 by conductor 56, while movable contact 49 of cam 47 is connected to the relay voltage source by conductor 57.

As indicated above, the digitizing segments 16 and the cooperating brushes never make or break circuits, the contacts of relays 28, 31 and 34 performing this function under the control of the cams and cam-operated switches. Ambiguity of the digital output is eliminated by controlling the switching relays by a common digitizing switch formed by contacts 43' and 43" operated by cam 40.

In the operation of the apparatus of Fig. 1, the relays are shown in their de-energized conditions, but with the switches just closed to change the digital output from 199 to 200. To effect this change, cam 46 has closed its switch to connect relay 34 to relay 31. Cam 41 has also closed its switch to connect relay 31 to the switch of cam 411 and cam 40 has closed its switch to connect relays 28, 31 and 34 across the source of relay voltage 35. All three relays then operate simultaneously to connect the leading brushes 2t), 21 and 22 to the readout voltage source 25. The digital output is thus changed to 200.

Next, cam 42 closes its switch to connect relay 31 directly across the relay voltage source. However, reiay 31 is already energized through the contacts of

cams

41 and 40, so the contacts of cam 42 act only to establish a holding circuit for the relay. Cam 41 then opens its contacts to disconnect relay 31 from the contacts of cam 41), but the holding circuit including the contacts of cam 42 keeps the relay energized. Cam 40 opens its switch to disconnect relay 28 from the voltage source but, by this time, brush 21) is in contact with segment 1 of commutator 10, so the reading does not change.

Next, relative movement between the brushes 20 and 20' and commutator carries the leading brush into position shown, when the tens digit and the units digitchange again simultaneously.

In the meantime, when shaft 13 has moved to a position such that brushes Z1 and 21 are both in contact with the first segment of commutator 11, cam 40 again closes its contacts and cam 41 closes its contacts to con nect relay 31 across the relay voltage source. Then, cam 42 opens its contacts, cam 43 opens its contacts to disconnect relays 31 and 28 simultaneously from the relay source and connect trailing brush 21 to the readout source, and finally cam 41 opens its contacts. It will be noted that neither the contacts of cam 41 nor the contacts of cam 42 open or close any circuit including a source of voltage, the contacts of cam 49 being the only ones to perform that function. Further, no circuit including a source of voltage is opened or closed by the commutator segments and brushes, the contacts of cam 40 again performing that function. Also, when relay 31 is operated or opened, it is operated and opened simultaneously with relay 23, so that there is no delay between the switching functions for the brushes of different commutators.

In the third stage, including commutator 12 and relay 34, operated under control of cams 411, 46, and 47, the switching sequence is similar to that taking place in the second stage, as described above, but at a ten-to-one reduction in speed. Shortly after switching from 199 to 200 output, described above, takes place, and before cam 46 opens its contacts, cam 47 closes its contacts to provide a holding circuit for relay 34 around the contacts of cam 46 and earns 41) and 41. Then, cam 46 opens its contacts before cam 42 closes its contacts to prevent a circuit from relay 31 to the relay source through the contacts of cam 46 being set up. Relay 34 remains energized through the contacts of 47 until both brushes 22 and 22' are in contact with the second segment of commutator 12. Then, when the digital reading in the second stage is going from 4 to 5, cam 49 closes its contacts,

cams

41 and 46 close their contacts to establish a holding circuit around the contacts of cam 47 for re" lay 34, and cam 47 opens its contacts. Then cam 40 opens its contacts to open the holding circuit and open relay 34 to change the relay connections to the relay source back to the trailing brush 22 of commutator 12. It will be noted that all three relays 28, 31, and 34 were connected across the source 35 when cam 40 opened its contacts, so that all three relays open simultaneously.

The sequence of operation of the apparatus of Fig. is then repetitive to furnish a continuously increasing three digit number at the commutator output contacts as the shaft 13 rotates continuously in the same direction. The system is also bidirectional, so that the output will decrease as the rotational direction of the shaft changes. Again, it is noted that only the contacts of cam 41 make and break any closed circuit including a source of voltage and that no relay operates another, so that relay operation may be simultaneous. Also, the relay contacts may be of the single pole-double throw type, for greatest simplicity.

If it is desired that the switching current of the contacts of cam 49 he of low level, a relay 69 may be provided, the relay contacts being operable when closed to connect conductor St to relay voltage source 35, and the contacts of cam 40 being used only to connect the relay 60 across the source of relay voltage. Then, the digitizing relays would operate when relay 60 was operated and open when the relay was opened, and the contacts of cam 40 would only have to control the operating current for relay 60.

Additional stages may be added to the apparatus of Fig. 1 through the addition of the combination including a shaft, a digital commutator and associated brushes and relay, and cams identical with cams 46 and 47 and their associated contacts, the shaft being geared in a stepdown manner between shaft 14 and shaft 15. It will be understood that the last stage does not require the control cams and their switches.

The apparatus of Fig. 1 has been designed for a decimal system of digital notation, but it will be evident that a similar apparatus for use with a different system of notation could be designed.

Practical embodiments of the apparatus shown schematically in Fig. 1 will now be described in conjunction with the remaining figures. In the apparatus of Figs. 2 through 7, referring first to Fig. 2, the input shaft 13 is formed by shaft sections 61, 62 and 63 journalled in bearings 64 and 65 in a casing 66 formed by a front cover 67, and other covers 68, 69 and 70. The three shaft sections are fixed together by roll pins 71 and 71'.

Referring now to Figs. 2 and 7, the second shaft 14 is sleeve-like, surrounds portions of shaft sections 61 and 62, and is freely rotatable with respect thereto by virtue of a bushing 73 spacing shaft 14 and shaft section 62 apart. A gear sleeve 74 carrying gear 75 is fixed to shaft section 61 by a collar 76 and the gear meshes with a gear 77 freely rotatable about a jack shaft 78 fixed in covers 70 and 69. Gear 77 also carries another gear 80 which meshes with gear 81 carried by gear sleeve 82. Gear sleeve 02 is fixed to shaft 14 by screw 83.

Gears 75, 77, 80 and 31 comprise a gear train providing a ten-to-one stepdown in speed between shaft 13 and shaft 14. Shaft 15 is coaxial with shaft 14 and spaced therefrom by bushing 85, so that shaft 15 is freely rotatable with respect to shaft 14.

Referring to Figs. 2 and 6, shaft 15 carries a gear 86 which meshes with a gear 87 held fast to a gear 88 by a collar 89. Gear 88 is freely rotatable about jack shaft 78 and engages a gear 90 carried by gear sleeve 82. Gears 86, 87, 88 and 90 comprise a gear train providing a tento-one stepdown in speed between shaft 14 and shaft 15.

Referring now to Fig. 3, along with Fig. 2, front cover 67 carries a digital commutator formed by a plurality of electrically-insulated segments 16 separated by insulating material 91.. Segments 16, twenty in number, are of conducting material and their inner surfaces form a complete circle coaxial with shaft section 63 of input shaft 13. A plurality of electrical contact terminals 92, one for each segment 16, extend into threaded bores in the associated segments and through slots 93 in the front cover which are larger than the diameters of the terminals. Insulating washers 94 separate the terminals from the outer surface of the front cover. The terminals 92 may be connected to the readout device by appropriate conductors, such as shown at 36 in Fig. l. A further layer of insulating material 95 separates the outer surfaces of the segments 16 from the front cover.

The function of brushes 20 and 20' of the commutator 10 of Fig. l is fulfilled by a roller contact assembly 98, which includes a pair of rollers 99 and 100 which act as contact members for the commutator 10. Rollers are used, rather than brushes, because a higher speed of rotation of the input shaft is thereby permitted, yet the wear on the commutator caused by friction between the commutator segments and the contact members is substantially reduced. The rollers must be so spaced with relation to the size and spacing of segments that they can contact the same segment simultaneously or contact adjacent segments, but the segments and roller spacings must not be such that a roller can bridge adjacent seg ments. However, it will be evident that the rollers are of such size that they cannot be physically spaced the distance between the centers of adjacent commutator seg ments that they should be forproper operation of the apparatus. The electrical equivalent, with a larger physical spacing, is provided by using twenty segments to form two series of segments, with ten segments in each series, and spacing the rollers phys'cally apart the distance between the centers of corresponding segments of adjacent series plus the appropriate electrical spacing which may be one-half the distance between the centers of adjacent commutator segments. The corresponding segments of different series are then connected together and the electrical circuit is the same as if the rollers were physically spaced by only one-half the distance between the centers of adjacent segments. In Fig. 3 the topmost and hottommost segments are corresponding segments of adjacent series and are connected together (not shown), and, proceeding counter-clockwise around the circle of the segments, the rollers 99 and are spaced apart the distance between the centers of these segments plus onehalf the distance between the center of the bottommost segment and the center of the adjacent segment to the right thereof.

Of course, it is not necessary that twice n segments be used, where n is the number of admissible digits in any digit position of the desired arithmetical system, for any multiple of n segments may be used. It is preferred, however, that the multiplier m be an integer greater than one to provide for the physical spacing shown in the drawings, that is, for a physical spacing a multiple of the electrical spacing of the contact members.

The roller contact assembly 98 further includes a sleeve 101 fixed to shaft section 63 of input shaft 13 by key 102. Sleeve 101 carries a cylindrical rocker arm support 103 spaced from the sleeve by a layer of insulation 104, and the rocker arm support carries a pair of rocker arms 105 on pivot shaft 106. Rocker arms 105 carry shafts 107 at their ends remote from their pivot shafts, on which rollers 99 and 100 rotate.

Springs 108 between the rocker arms and their supports urge the arms outwardly to force the rollers into contact with the commutator segments. In order that the rollers 99 and 100 will not be electrically connected together, the rocker arm support 103 is separated into two insulated sections by insulating material filling slots 109 through the support.

The rocker arms rotate with section 63 of input shaft 13 to sweep rollers 99 and 100 around the circle of segments, so that the rollers contact 20 segments per revolution of the input shaft.

In order to provide for connections to rollers 99 and 100, a pair of conducting rings 110 and 111 are mounted on the casing parallel to and on opposite axial sides of the commutator 10. The conducting rings are continuous cylinders of conducting material and are provided with electrical terminals 112 and 113 similar to terminals 92 of the commutator. Roller contacts 114 carried by shafts 107 and electrically connected to their respective rollers 99 and 100 through the shafts are held against the conducting rings by the rocker arms. The roller contact associated with roller 99 engages conducting ring 111, while the roller contact associated with roller 100 cugages conducting ring 110. Terminal 112 thereby providesfor connection to roller 100, While terminal 113 provides for connection to roller 99.

Referring next to Figs. 2 and 4, the cam 40 of Fig. l. and associated contacts, as they appear in the first embodiment of the invention, will now be described. The cam 40 actually includes two cam surfaces and 121 carried by a sleeve 122 fixed to shaft section 63 of input shaft 13 by key 102. Insulating material 123 separates the cam surfaces from sleeve 122. It will be noted that the cam surfaces are shown in elevation in Fig. 4, this for clarity. Each cam surface includes ten notches equally spaced around the input shaft, the notches of one cam surface coinciding with the risers of the other cam surface. Thereby it is possible to obtain twenty switching actions per rotation of the input shaft, to agree with the twenty digital segments of commutator 10 per rotation.

The function of roller 43 of Fig. 1 is performed by a pair of wheels 125 and 126 at opposite ends of a diameter of the cam surfaces and in contact, respectively, with cam surfaces 121 and 1213. The wheels form part of a cam follower assembly which includes a cylindrical rocker arm support 127 having slots through which the Wheels project, so they can contact the cam surfaces. The rocker arm support mounts a pair of rocker arm blies 128 and 129. Each assembly includes a rocker arm 130 pivoted to the support by a shaft 131 passing through a location between the ends of the rocker arm. A spring 132 for each rocker arm between a shoulder of the support and the adjacent end of the rocker arm urges that end of the rocker arm outwardly, so as to urge the other end of the rocker arm inwardly. Each rocker arm also carries a shaft 135 about which the corresponding wheel 125 or 126 is rotatable. Thus, the entire rocker arm assembly has its portion on the wheel side of pivot shaft 131 moved outwardly whenever a riser part of the corresponding cam surface engages the Wheel, while spring 132 moves the same portion inwardly whenever a notch portion of the cam surface engages the wheel.

The end of each rocker arm 13% remote from spring 132 carries a movable contact 136, and the movable contact is positioned radially outwardly of a fixed insulated contact 138 carried by the rocker arm support. Whenever the rocker arm assemblies are moved inwardly by spring 132, the movable contacts 136 engage the fixed contacts 138 while, when the assemblies are moved outwardly by the corresponding cam surface, the movable contacts move away from the fixed contacts. The movable contacts then correspond with the movable contac 43' of Fig. 1, while the fixed contacts 138 correspond with the fixed contact 43''.

Referring to Fig. 5, along with Fig. 2, the functions of cams 41 and 42 are fulfilled by cam surfaces 140 and 141, respectively, mounted on the same sleeve 122 with cam surfaces 121) and 121. These cam surfaces are like wise separated from the sleeve by insulating material 123. It will be noted that cam surface 141 includes four notches and cam surface 141 includes two broad notches, to provide four switching actions per revoltion by cam 140 and two switching actions per revolution by cam 141, in consonance with the twenty segments of commutator 10 per revolution of the input shaft.

The function of the roller 44 of Fig. l is taken care of by wheel 142, while the function of roller 45 is performed by wheel 143, in engsgernent with cam surfaces 140 and 141, respectively. The wheels are identical with the wheels 125 and 126 of Fi 4 and form parts of rocker arm assemblies 128 and 129' which are identical with the corresponding parts of Fig. 4. Wheels 142 and 143 control, through the cam action of cam surfaces 140 and 141, the positions or" movable contacts 136 which move into and out of engagement with fixed contacts 138, which also are identical with the corresponding parts of Fig. 4. Unlike the corresponding elements of Fig. 4, the fixed and movable contacts of the Fig. assembly are not connected together. The movable contacts 136 therefore fill the function of contacts 44' and 45 of Fig. 1, while the fixed contacts 138' fill the function of fixed contacts 44" and 45".

So far, all the elements directly cooperating with the input shaft 13 have been described. The shaft carries contact members formed by rollers 99 and 1th and which cooperate with the segments of stationary commutator 1n, and the shaft also carries cam surfaces 120 and 121, and 14d and 141, which control the positions of corresponding switch contact pairs.

Shaft 14 carries a roller contact assembly 98' identical with the corresponding assembly shown in Fig. 3, and which cooperates with a commutator 11 identical with commutator 10, and with corresponding conducting rings for the contact members of the roller contact assembly. To the left of the commutator 11 is shown a cam follower assembly identical with the assembly includng wheels 142 and 143, the corresponding wheels being labelled 142' and 143'. This cam follower assembly cooperates with cam surfaces 146' and 141', also identical with the corresponding parts of Fig. 5. The rocker arm assemblies carrying wheels 142' and 143 are shown 180 degrees from the corresponding parts of Fig. 5 to make it evident how the wheels for each cam surface cooperate therewith.

The intermediate shaft 14, then, carries a pair of roller contact members which cooperate with the segments of a stationary commutator, and the shaft also carries cam surfaces 14a and 141' which control the positions of corresponding switch contact pairs.

The final or hundreds shaft 15 carries a roller contact assembly 93" identical with the corresponding assembly shown in Fig. 3, and which cooperates with a commutator 12 identical with commutator 1t), and with corresponding conducting rings for the contact members of the roller contact assembly. It will be seen that the final shaft carries only the contact members to cooperate with the commutator, and has no switch means associated therewith.

Additional digitizing stages may he added to the apparatus of Figs. 2 through 7 by adding elements identical to those associated with the tens stage, including cams corresponding to 41 and 42 of Fig. 1 and the associated contact pairs, and by providing the appropriate gearing to supply a ten-to-one stepdown (for a decimal representation) for all shafts. The last stage will have no cams associated therewith and the first stage will be the only one to have the common control cam corresponding to cam 49 associated therewith.

It will be noted that the embodiment so far described has both digitizing commutator and switch means associated with the input shaft, thus providing a much greater sensitivity than if these elements were not so arranged. It will also be noted that the mechanical arrangment is relatively simple and capable of high speed operation, and that it can be added to without sacrifice of reading accuracy if additional digitizing stages are desired.

The second embodiment of the invention shown in Figs 8 through 13 is even more readily modified for additional digitizing stages and substitutes for the cam switching of the first embodiment binary commutator type switching.

Referring fiirst to Fig. 8, the input shaft 13 is not directly driven by the analog source, but rather is driven by a shaft 151': journalled in a bearing 151 carried by the input shaft. Referring to Fig. 13, as well as Fig 8, shaft carries a gear 152 which meshes with a gear 153 rotatable on bearings 154 about a jack shaft 155. The jack shaft is mounted in a bearing book 156 fixed to the front section 157 of the casing. Mounted on a sleeve portion of gear 153 is another gear 153 which meshes with a gear 159 which drives shaft 13. The gear train described provides a two-to-one stepdown between drive shaft 151) and input shaft 13. This gearing is usable to provide ten output digits per rotation of the input shaft, rather than the twenty provided with the apparatus of the first embodiment, as well as to reduce the torque and rotational speed of the commutator rollers by a factor of two from those found in conventional digitizers.

Input shaft 13 is journalled in bearing 160 supported by bearing block 156 and bearing 161 supported by a portion of casing front section 157. As shown in Fig. 12, as well as Fig. 8, the shaft carries a gear 162 at its rear end which meshes with a gear 163 rotatable about a jack shaft 164 supported by the rear end of front casing section 157. Also mounted on the gear sleeve which carries gear 163 is a gear 166 which meshes with a gear 167 carried by shaft 14. The gearing train composed of gears open when the relay was opened, and the contacts of cam 40 would only have to control the operating current for relay 60.

' Practical embodiments of the apparatus shown schematically in Fig. 1 will now be described in conjunction with the remaining figures. In the apparatus of Figs. 2 through 7, referring first to Fig. 2, the input shaft 13 is formed by shaft sections 61, 62 and 63 journalled in bearings 64 and 65 in a casing 66 formed by a front cover 67, and other covers 68, 69 and 70. The three shaft sections are fixed together by roll pins 71 and 71.

Referring now to Figs. 2 and 7, the second shaft 14 is sleeve-like, surrounds portions of shaft sections 61 and 62, and is freely rotatable with respect thereto by virtue of a bushing 73 spacing shaft 14 and shaft section 62 apart. A gear sleeve 74 carrying gear 75 is fixed to shaft section 61 by a collar 76 and the gear meshes with a gear 77 freely rotatable about a jack shaft 78 fixed in covers 70 and 69. Gear 77 also carries another gear 80 which meshes with gear 81 carried by gear sleeve 82. Gear sleeve 82 is fixed to shaft 14 by screw 83.

Gears

75, 77, 30 and 81 comprise a gear train providing a ten-to-one stepdown in speed between shaft 13 and shaft 14. Shaft 15 is coaxial with shaft 14 and spaced therefrom by bushing 85, so that shaft 15 is freely rotatable with respect to shaft 14.

Referring now to Fig. 3, along with Fig. 2, front cover 67 carries a digital commutator formed by a plurality of electrically-insulated segments 16 separated by insulating material 91. Segments 16, twenty in number, are of conducting material and their inner surfaces form a complete circle coaxial with shaft section 63 of input shaft 13. A plurality of electrical contact terminals 92, one for each segment 16, extend into threaded bores in the associated segments and through slots 93 in the front cover which are larger than the diameters of the terminals. Insulating washers 94 separate the terminals from the outer surface of the front cover. The terminals 92 may be connected to the readout device by appropriate conductors, such as shown at 36 in Fig. 1. A further layer of insulating material 95 separates the outer surfaces of the segments 16 from the front cover.

The function of brushes 20 and 20' of the commutator 10 of Fig. 1 is fulfilled by a roller contact assembly 98, which includes a pair of rollers 99 and 100 which act as contact members for the commutator 10. Rollers are used, rather than brushes, because a higher speed of rotation of the input shaft is thereby permitted, yet the wear on the commutator caused by friction between the commutator segments and the contact members is substantially reduced. The rollers must be so spaced with relation to the size and spacing of segments that they can contact the same segment simultaneously or contact adjacent segments, but the segments and roller spacings must not be such that a roller can bridge adjacent segments. However, it will be evident that the rollers are of such size that they cannot be physically spaced the distance between the centers of adjacent commutator seg'-- ments that they should be for proper operation of the apparatus. cal spacing, is provided by using twenty segments to form two series of segments, with ten segments in each series, and spacing the rollers physcally apart the distance between the centers of corresponding segments of adjacent series plus the appropriate electrical spacing which may be one-half the distance between the centers of adjacent commutator segments. The corresponding segments of different series are then connected together and the electrical circuit is the same as if the rollers were physically spaced by only one-half the distance between the centers of adjacent segments. In Fig. 3 the topmost and bottommost segments are corresponding segments of adjacent series and are connected together (not shown), and, proceeding counter-clockwise around the circle of the seg ments, the rollers 99 and are spaced apart the distance between the centers of these segments plus onehalf the distance between the center of the bottommost segment and the center of the adjacent segment to the right thereof.

In order to provide for connections to rollers 99 and 100, a pair of conducting rings 110 and 111 are mounted on the casing parallel to and on opposite axial sides of the commutator 10. The conducting rings are continuous cylinders of conducting material and are provided with electrical terminals 112 and 113 similar to terminals 92 of the commutator. Roller contacts 114 carried by shafts 107 and electrically connected to their respective rollers 99 and 100 through the shafts are held against the conducting rings by the rocker arms. The roller contact associated with roller 99 engages conducting ring 111, while the roller contact associated with roller 100 engages conducting ring 110. Terminal 112 thereby provides for connection to roller 100, while terminal 113 provides for connection to roller 99.

Referring next to Figs. 2 and 4, the cam 40 of Fig. l and associated contacts, as they appear in the first embodiment of the invention, will now be described. The cam 40 actually includes two cam surfaces and 121 carried by a sleeve 122 fixed to shaft section 63 of input shaft 13 by key 102. Insulating material 123 separates the cam surfaces from sleeve 122. It will be noted that the cam surfaces are shown in elevation in Fig. 4, this for clarity. Each cam surface includes ten notches equally spaced around the input shaft, the notches of one cam surface coinciding with the risers of the other cam The electrical equivalent, with a larger physisurface. Thereby it is possible to obtain twenty switching actions per rotation of the input shaft, to agree with the twenty digital segments of commutator 10 per rotation.

The function of roller 43 of Fig. l is performed by a pair of wheels 125 and 126 at opposite ends of a diameter of the cam surfaces and in contact, respectively, with cam surfaces 121 and 12 9. The wheels form part of a cam follower assembly which includes a cylindrical rocker arm support 127 having slots through which the Wheels project, so they can contact the cam surfaces. The rocker arm support mounts a pair of rocker arm assemblies 128 and 129. Each assembly includes a rocker arm 130 pivoted to the support by a shaft 131 passing through a location between the ends of the rocker arm. A spring 132 for each rocker arm between a shoulder of the support and the adjacent end of the rocker arm urges that end of the rocker arm outwardly, so as to urge the other end of the rocker arm inwardly. Each rocker arm also carries a shaft 135 about which the corresponding wheel 125 or 126 is rotatable. Thus, the entire rocker arm assembly has its portion on the wheel side of pivot shaft 131 moved outwardly whenever a riser part of the corresponding cam surface engages the Wheel, while spring 132 moves the same portion inwardly whenever a notch portion of the cam surface engages the wheel.

The end of each rocker arm 131) remote from spring 132 carries a movable contact 136, and the movable contact is positioned radially outwardly of a fixed insulated contact 138 carried by the rocker arm support. Whenever the rocker arm assemblies are moved inwardly by spring 132, the movable contacts 113s engage the fixed contacts 138 while, when the assemblies are moved out wardly by the corresponding cam surface, the movable contacts move away from the fixed contacts. The movable contacts then correspond with the movable contact 43' of Fig. 1, While the fixed contacts 138 correspond with the fixed contact 43".

Referring to Fig. 5, along with Fig. 2, the functions of cams 41 and 4-2 are fulfilled by cam surfaces 140 and 141, respectively, mounted on the same sleeve 122 with cam surfaces 1211 and 121. These cam surfaces are likewise separated from the sleeve by insulating material 123. It will be noted that cam surface 140 includes four notches and cam surface 141 includes two broad notches, to provide four switching actions per revoltion by cam 14-0 and two switching actions per revolution by cam 141, in consonance with the twenty segments of commutator 10 per revolution of the input shaft.

The function of the roller 44 of Fig. 1 is taken care of by wheel 142, while the function of roller 45 is performed by wheel 143, in engsgement with cam surfaces 141} and 141, respectively. The wheels are identical with the wheels 125 and 126 of Fig. 4 and form parts of rocker arm assemblies 125 and 129 which are identical with the corresponding parts of Fig. 4. Wheels 142 and 143 control, through the cam action of cam surfaces 140 and 141, the positions of movable contacts 136 which move into and out of engagement with fixed contacts 138', which also are identical with the corresponding parts of Fig. 4. Unlike the corresponding elements of Fig. 4, the fixed and movable contacts of the Fig. assembly are not connected together. The movable contacts 136' therefore fill the function of contacts 44 and 45 of Fig. 1, while the fixed contacts 138 fill the function of fixed contacts 24- and 45".

So far, all the elements directly cooperating with the input shaft 13 have been described. The shaft carries contact members formed by rollers 99 and 190 and which cooperate with the segments of stationary commutator 1i), and the shaft also carries cam surfaces 120 and 121, and 1&9 and 14-1, which control the positions of corresponding switch contact pairs.

Shaft 14 carries a roller contact assembly 98' identical with the corresponding assembly shown in Fig. 3, and which cooperates with a commutator 11 identical with commutator 10, and with corresponding conducting rings for the contact members of the roller contact assembly. To the left of the commutator 11 is shown a cam follower assembly identical with the assembly includng wheels 142 and 143, the corresponding wheels being labelled 142' and 143'. This cam follower assembly cooperates with cam surfaces 141) and 141', also identical with the corresponding parts of Fig. 5. The rocker arm assemblies carrying wheels 142 and 143' are shown 180 degrees from the corresponding parts of Fig. 5 to make it evident how the Wheels for each cam surface cooperate therewith.

The intermediate shaft 14, then, carries a pair of roller contact members which cooperate with the segments of a stationary commutator, and the shaft also carries cam. surfaces 1% and 141' which control the positions of corresponding switch contact pairs.

The final or hundreds shaft 15 carries a roller contact assembly 98" identical with the corresponding assembly shown in Fig. 3, and which cooperates with a commutator 12 identical with commutator 10, and with corresponding conducting rings for the contact members of the roller contact assembly. it will be seen that the final shaft carries only the contact members to cooperate with the commutator, and has no switch means associated therewith.

Additional digitizing stages may be added to the apparatus of Figs. 2 through 7 by adding elements identical to those associated with the tens stage, including cams corresponding to 41 and 42 of Fig. 1 and the associated contact pairs, and by providing the appropriate gearing to supply a ten-to-one stepdown (for a decimal representation) for all shafts. The last stage will have no cams associated therewith and the first stage will be the only one to have the common control cam corresponding to cam 40 associated therewith.

Referring fiirst to Fig. 8, the input shaft 13 is not directly driven by the analog source, but rather is driven by a shaft journalled in a bearing 151 carried by the input shaft. Referring to Fig. 13, as well as Fig 8, shaft 150 carries a gear 152. which meshes with a gear 153 rotatable on bearings 154 about a jack shaft 155. The jack shaft is mounted in a bearing back 156 fixed to the front section 157 of the casing. Mounted on a sleeve portion of gear 153 is another gear 158 which meshes with a gear 159 which drives shaft 13. The gear train described provides a two-to-one stepdown between drive shaft 151) and input shaft 13. This gearing is usable to provide ten output digits per rotation of the input shaft, rather than the twenty provided with the apparatus of the first embodiment, as well as to reduce the torque and rotational speed of the commutator rollers by a factor of two from those found in conventional digitizers.

Input shaft 13 is journalled in bearing 160 supported by bearing block 156 and bearing 161 supported by a portion of easing front section 157. As shown in Fig. 12, as well as Fig. 8, the shaft carries a gear 162 at its rear end which meshes with a gear 163 rotatable about a jack shaft 164- supported by the rear end of front casing section 157. Also mounted on the gear sleeve which carries gear 163 is a gear 166 which meshes with a gear 167 carried by shaft. 14. The gearing train composed of gears 9 162, 163, 166 and 167 provides a ten-to-one stepdown in speed between input shaft 13 and shaft 14. Shaft 14 rotates in bearings 168 and 169 mounted in center casing section 165.

A similar ten-to-one speed stepdown is provided between shaft 14 and shaft 15 by gearing identical to that just described and identified by the same reference numerals primed. Shaft 15 rotates in bearings 170 and 171 mounted in rear casing section 172.

Three separate axially-spaced digitizing shafts, the input orunits shaft 13, the intermediate or tens shaft 14, and the final or hundreds shaft 15, together with appropriate ten-to-one stepdown gearing for the shafts, have been described. Each shaft drives a roller contact as sembly 175, 176, and 177, all identical with that described in conjunction with Figs. 2 and 3, and each roller contact assembly cooperates with conducting rings and commutator segments 10, 11 and 12 identical with the same elements described in those figures. These elements therefore need not be described again. The digitizing commutators are mounted in separable cover or

casing sections

157, 165 and 172, respectively, along with the corresponding conducting rings.

As indicated above, however, the cam-operated switches of the first embodiment of the invention are replaced in this second embodiment by binary commutator type switches. Referring to Fig. 9, along with Fig. 8, input shaft 13 carries a distributing ring 180 through a key 181 which also fixes roller contact assembly 175 to shaft 13. The distributing ring comprises a sleeve 183 on which a plurality of arcuately-spaced blocks 184 of conducting material are mounted in insulating material 185. Certain of said conducting blocks identified by numeral l84a are isolated by insulating material, but others, labelled 184b, are connected at their inner ends to a continuous ring 186 of conducting material. This conducting ring is insulated from sleeve 183 by a layer of insulating material 187. Only the blocks 184b perform any electrical function, the blocks 184a being provided only to make the outer surface of the distributing ring as uniform and continuous as possible.

Cooperating with distributing ring 180 is a distributor roller assembly 190 which includes a roller brush support 191 fixed to a casing section 157. The roller brushsupport is a cylindrical sleeve separated electrically into two separate portions by insulation in slots 192 through the support. Each portion carries a rocker arm 193 in a slot in the support, the rocker arms carrying wheels 195 and 196 on shafts 197. The rockerarms are pivoted on shafts 198 carried by the support and have springs 199 between the support and the ends of the rocker arms remote from the wheels to urge the wheels into engagement with the outer surface of the distributing ring 180.

Electrical terminals

200 and 201 are threaded into the separate portions of the rocker arm support and extend outwardly of the casing, being insulated from the casing by Washers 202 of insulating material.

It will be seen that the distributing ring carries twenty conducting blocks 18% which connect to the central conducting ring 186, and the conducting wheels, which form a switch contact pair for the distributing ring, are positioned at the opposite ends of a diameter of the distributing ring. Therefore, the switch means formed by the wheels closes a circuit between

terminals

201 and 200 ten times during each rotation of the input shaft, to perform the function of the switch associated with cam 40 of Fig. 1.

As shown in Figs. 8, and 11, key 181 on shaft 13 also drives a distributor ring 205 mounted adjacent distributor ring 180. The distributor ring 205 includes a sleeve,206 carrying two

separate switching members

207 and 208 insulated from each other and both insulated from the sleeve by insulation 209. Switching member 207 includes a plurality of blocks of conducting material exposed to the outer surface thereof, there being four small blocks 210 equally spaced around the circle of the switching member and four larger blocks 211. The smaller blocks are in electrical contact with a ring 212 of conducting material, but the larger blocks are separated from the ring and from the adjacent smaller blocks by insulating material 213. The larger blocks 211 serve only to provide as uniform a surface as possible for the switching member, only the smaller blocks 210 performing any electrical function.

Switching member 208 includes two large blocks 215 of conducting material, spaced apart by other blocks 216 of conducting material, with insulation 217 separating the blocks from each other. Blocks 215 are in electrical contact with an inner ring 218 of conducting material which is insulated from the other blocks by insulating material. A layer 219 of insulating material separates the conducting ring from the mounting sleeve 206. Only blocks 215 perform any electrical function, the other blocks providing a uniform surface for the switching member.

Cooperating with switching

members

207 and 208 is a distributor roller assembly 220 generally similar to distributor roller assembly 190, but having a roller brush support 221 which carries four contact wheels 222-225 on corresponding rocker arms. Distributor roller assembly 220 is split into three separate portions by slots 226 through the roller brush support filled with insulating material.

Electrical terminals

227, 228 and 229 pro vide electrical contact to these separate portions in similar manner to

terminals

200 and 201 of assembly 190. The roller assembly 220 is otherwise identical with roller assembly 190 and so will not be further described, except to state that wheels 222 and 225 ride along switching member 208, while wheels 223 and 224 ride along switching member 207 as input shaft 13 rotates.

During rotation of the input shaft, switching member,

207 provides a connection between

terminals

227 and 228 through wheels 224 and 223 twice during each rotation, while switching member 208 provides a connection between terminals 229 and 228 through wheels 222 and 225 once during each rotation. Switching member 207 then fulfills the function of cam 41 of Fig. 1, while roller wheels 223 and 224 fill the function of switch pair 44' and 44". Switching member 208 fills the function of cam 42, while roller wheels 222 and 225 fill the function of switch pair 45' and 45".

Shaft 14 drives a distributor ring 205' identical with distributor ring 205, while a distributor roller assembly 220' identical with assembly 220 is supported by casing section and engages the distributor ring 205.

- The last shaft 15 has no distributor ring or distributor roller assembly associated therewith.

It will be evident that additional digitizing stages could readily be added to the embodiment of Figs. 8 through 13 merely by adding between the section contained within the middle casing section 165 and the section contained within the rear casing section 172 other sections identical with the middle section.

The electrical connections for the embodiments of both Figs. 2 through 7 and 8 through 13 are made identically with the connections shown in schematic form in Fig. 1, and the two embodiments perform in identical manner to that described in conjunction with Fig. 1.

It will be evident that an analog-digital converter of simple design, capable of high speed operation with slow wearout, and with minimal ambiguity of output representation has been described. It will also be evident that many minor changm could be made in the apparatus described as preferred embodiments of the invention without departing from the scope of the invention. The invention therefore is not to be considered limited to the embodiments described but only by the scope of the appended claims.

I claim:

1. Apparatus for converting shaft position into a decimal digital output comprising a plurality of rotatable shafts forming a train and including an input shaft, gearing driving each of the other shafts from the input shaft at a ten-to-one speed reduction from the preceding shaft in the train, a plurality of digitizing commutators, one for each of said shafts, each including m electricallyinsulated segments of conducting material arcuately spaced around its associated shaft to form a complete circle and forming output contacts, where m is an integer greater than one sothat m series of segments are provided on each commutator, the corresponding segments of each series being connected together electrically on each commutator, a plurality of pairs of electrical contact members, one for each shaft, spaced apart substantially the distance between the centers of corresponding segments of adjacent series plus a distance between the centers of adjacent segments appropriate with relation to segment spacing and size so that the contact members of each pair may simultaneously contact electrically corresponding segments and electrically adjacent segments but will not bridge physically adjacent segments, one of each commutator and the associated pair of contact members being connected to the associated shaft so that rotation of said shaft effects relative rotary movement between such commutator and its contact member pair to cause the contact members of such pair to engage the commutator segments successively, a source of voltage, a plurality of relays, one for each of said pairs of contact members, each of said pairs of contact members having one member connected through the contacts of the associated relay to the voltage source when the relay is energized and the other member connected through the contacts of the associated relay to the voltage source when the relay is de-energized, and circuit means operably connected to said relays to selectively energize the same, said circuit means including a plurality of switch means, said switch means including first, second, and third pairs of contacts, a plurality of switch operating members, one for each switch means, said switch operating members including a first, second, and third member all fixed to the input shaft and operable to close the first, second and third pairs of contacts, respectively, periodically during each rotation of the input shaft, the first operating member being operable to close the first pair of contacts 10m times, the second to close the second pair of contacts 2m times, and the third to close the third pair of contacts m times during each rotation of the input shaft, the first of said commutators being controlled by the input shaft and having its associated pair of contact members connected to the contacts of a first of said relays and a second of said commutators being controlled by a second of said shafts and having its associated pair of contact members connected to the contacts of a second of said relays, the actuating means of said first relay being connected by said circuit means directly to said first pair of contacts, said first and second pair of contacts being connected to the actuating means of sad second relay in series, said circuit means also including a portion connecting said third set of contacts in parallel with the series combination of said first and second pairs of contacts, said third operating member being operable to actuate said third pair of contacts only when both said first and second pairs of contacts are closed.

2. The apparatus of claim 1 in which said plurality of rotatable shafts includes a third shaft, said plurality of commutators includes a third commutator and said plurality of pairs of contact members includes a third pair, both of said third commutator and said third pair ofcontact members being associated with said third shaft, said plurality of relays includes a third relay having the third pair of contact members connected to its contacts, said plurality of switch means includes fourth and fifth pairs of contacts, and said plurality of switch operating members includes fourth and fifth operating members both fixed to the second shaft, the fourth and fifth operating members being identical to the second and third operating members, respectively, the fourth pair of contacts being operable to connect the third relay across the second relay when closed and the fifth pair of contacts being operable to complete a holding circuit connected in parallel with the series combination of said first, second and fourth pair of contacts when closed.

3. The apparatus of claim 1 comprising an output voltage source having a voltage level compatible with the function of the digital output and a relay voltage source having a voltage level compatible with the operating characteristics of the relays, said pairs of contact members all being connected to the output voltage source by the respective relay contacts and said relays all being connected across the relay voltage source by the respective pairs of contacts of said switch means.

4. The apparatus of claim 1 including a casing in which said shafts are journalled and in which each of said commutators is fixed to the casing and the associated pair of contact members is fixed to the associated shaft.

5. In an apparatus for translating rotational shaft position into digital electrical output, the combination of a plurality of commutators each comprising a plurality of electrically insulated, arcuately spaced, conductive segments; a plurality of pairs of contacts, each such pair being disposed to sweep the conductive segments of a different one of said commutators in sequence upon relative rotary movement between such commutator and contact pair, the dimension of the contact face of the individual contacts of said pairs in the direction of such relative movement being less than such dimension of the segments of the commutator associated therewith, such commutator segments being spaced by a distance in said direction greater than such dimension of said individual contacts, said individual contacts being so disposed that one thereof is always in engagement with one of said segments during such relative movement; a plurality of shafts including an input shaft, each of said shafts being operatively associated with a different one of said commutators and its related contact pair to effect relative rotary movement therebetween; a readout voltage source; a plurality of relays equal in number to said pairs of contacts, each of said relays comprising electrical actuating means and first and second contacts; means connecting one contact of each of said contact pairs to said readout voltage source through the first contact of a different one of said relays when the relay is energized and the second contact of such pair to said source through the second contact of the relay when the relay is deenergized; circuit means for selectively energizing said relays comprising circuit portions each operatively connected to the actuating means of a different one of said relays, said circuit means including digitizing switch means operated by rotation of said input shaft, each of said circuit portions being connected to be supplied with current via said digitizing switch means; and speed reduction drive means connecting said shafts together.

6. The apparatus of claim 5 wherein one of said circuit portions is connected directly to said digitizing switch means, a second one of said circuit portions is connected to said digitizing switch means via a second switch which is periodically operated in response to rotation of said input shaft, said circuit means including a holding circuit connected in parallel with the series combination of said second switch and said digitizing switch means, said holding circuit including a switch actuated by rotation of said input shaft.

7. An apparatus constructed in accordance with claim 5 for translating rotational shaft position into digital electrical output in an arithmetical system having it possible digits, where n is an integer greater than one, and wherein each of said commutators is connected to a different one of said shafts for rotation therewith, the conductive segments of each of said commutators being equal to m times n, m being an integer greater than one, so that each commutator includes m series of such segments, the corresponding segments of all of said series being electrically inter-connected, each contact of said pairs of contacts being a roller having a conductive peripheral portion disposed to roll sequentially over the segments of the associated commutator, said apparatus further including mechanical means mounting each such pair of contacts with the individual contacts thereof spaced chordwise of the commutator by a fixed distance such that when the lead contact of such pair engages a given segment in one series the trailing contact can engage only the corresponding segment of another series or the segment next preceding such corresponding segment.

8. An apparatus constructed in accordance with claim for translating rotational shaft position into digital electrical output in an arithmetical system having n possible digits, where n is an integer greater than one, and wherein each of said commutators is connected to a different one of said shafts for rotation therewith, the conductive segments of each of said commutators being equal to m times n, m being an integer greater than one, so that each commutator includes m series of such segments, the corresponding segments of all of said series being electrically inter-connected, said apparatus further including stationary mechanical means mounting each of said pairs of contacts with the individual contacts of each pair spaced, chordwise of the commutator associated therewith, by a fixed distance such that as the lead contact of such pair sweeps a given segment in one series the trailing contact will first traverse a portion of the segment of another series next preceding the segment of such other series which corresponds to said given negment, then move to such corresponding segment, and then traverse a portion thereof.

9. The apparatus of claim 8 wherein one of said circuit portions is connected directly to said digitizing switch means, and a second one of said circuit portions is connected to said digitizing switch means via a second switch which is periodically operated in response to rotation of said input shaft.

10. The apparatus of claim 8 wherein said digitizing switch means is cam operated and comprises annular cam means extending about said input shaft and connected to rotate therewith, said cam means having a number of switch actuating cam portions equal to n times m.

11. The apparatus of claim 8 wherein one of said circuit portions is connected directly to said digitizing switch means, a second one of said circuit portions is connected to said digitizing switch means via a second periodic switch, said circuit means including a holding circuit connected in parallel with the series combination of said second switch and said digitizing switch means, said holding circuit including a third switch, said digitizing switch means, said second switch and said third switch each including an annular operating means extending about said input shaft and rotatable therewith, the one of said operating means for said third switch being so constructed and arranged that said third switch closes and opens only when both said digitizing switch means and said second switch pass current.

12. In an apparatus for translating shaft rotation to digital electrical output in an arithmetical system having n possible digits, where n is an integer greater than one, the combination of a commutator having a plurality of electrically insulated conductive segments arranged to form a complete circle, said segments being equal in number to m times n, where m is an integer greater than one, so that the commutator includes m series of contacts, the corresponding segments of each such series being electrically inter-connected, all of said segments having the same dimension in the direction of the circle which they form and being equally spaced in said direction by a distance shorter than said dimension; a pair of roller contacts; means mounting said roller contacts for successive rolling engagement with the conductive segments of said commutator, said roller contacts being spaced chordwise of the circle formed by said segments, by a distance such that when the leading roller contact engages the area between a given segment and the next succeeding segment of one series the trailing roller contact is in engagement with the segment of another series corresponding to said given segment but the trailing contact cannot still engage said corresponding segment when the leading contact has disengaged from said next succeeding segment, said roller contacts being of such relatively large size that they could not be properly spaced to cooperate with only a single one of said series of segments; a rotatable shaft, one of said commutator and said contact pair being connected to rotate with said shaft so that rotation of the shaft causes said roller contacts to engage said commutator segments successively, a readout voltage source; a relay having electrical actuating means and first and second contacts; means connecting one of said roller contacts to said source through said first contact when said relay actuating means is energized and the other of said roller contacts to said source through said second contact when the actuating means is de-energized; digitizing switch means operated cyclically in response to rotation of said shaft, and circuit means controlled directly by said digitizing switch means and connected to said relay actuating means to energize the same cyclically in timed relation to engagement of said roller contacts with said commutator segments.

13. The apparatus of claim 12 comprising a casing through which said shaft extends, said commutator being mounted on said casing concentrically about said shaft, two contact carrier members mounted on said shaft, said roller contacts each being rotatably mounted on a difierent one of said carrier members, two conductive rings each fixed to said casing and arranged one on each side of said commutator with the inner surface of each ring coaxial with said shaft, and a pair of additional roller contacts each disposed to ride on the inner surface of a different one of said rings, each of said additional roller contacts being rotatively mounted on a different one of said carrier members and connected electrically to a differcut one of the roller contacts associated with said commutator.

References Cited in the file of this patent UNITED STATES PATENTS 290,350 Paine Dec. 18, 1883 608,721 Skeen Aug. 9, 1898 1,224,570 Sandreuter May 1, 1917 1,995,671 Dashner Mar. 26, 1935 2,496,585 Harper Feb. 7, 1950 2,666,912 Gow Jan. 19, 1954 2,809,369 Fecncy et a1. Oct. 8, 1957