US 3500389 A
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Description (OCR text may contain errors)
March 10, 1970 6.1'. ROBINSON 3,500,389
ELECTRIC CODING SWITCHES Filed April 28. 1966 .'5 Sheets-Sheet l /N VEN TO/Z Genres Eef/VCE Fa//vso/v f4 T TOENEYS March 10, 1970 G. 1'. RoBlNsoN 3,500,389
ELECTRIC CODING SWITCHES Filed April 28, 1966 I5 Sheets-Sheet 2 @.5 ,f5-lq. 2
.D7 /9 L Z /N VEN roe Geo/ees @PEA/c5 Poe//vsa/v By 2M H TTORNE YS March 10, 1970 c. 1'. RoBxNsoN ELECTRIC CODING SWITCHES 3 Sheets-Sheet 3 Filed April 28, 1966 /A/vfsA/To/ev G50/ws ERE/wf Pa/Nso/v 5y HTTORNEYS United States Patent O 3,500,389 ELECTRIC CODING SWITCHES George T. Robinson, Barnet, England, assignor to Phoenix Telephones Limited, London, England, a British company Filed Apr. 28, 1966, Ser. No. 546,092 Int. Cl. G08c 1/00 U.S. Cl. 340-364 4 Claims ABSTRACT F THE DISCLOSURE A hollow cylinder is rotatable on a support and one end face of the cylinder dene concentric cam tracks. Cam followers on the support actuate switches to provide a digital output upon rotational positioning of the cylinder. A series chain of resistors is mounted in the cylinder with tapping points on the other cylinder end face and wipers on the support engage the tapping points to provide an analog output upon rotational positioning of the cylinder.
This invention relates to electric coding switches.
It has already been proposed to provide electric coding switches which can be set to any one of a number of positions and which provide a coded output related to the set position of the switch.
Such switches serve to translate input information into a coded form which can then be fed into apparatus responsive to the coded information. Thus for example such a switch can be used for feeding numerical or similar information in a coded form into a digital computer or similar device, the particular coded information fed depending on the set position of the switch.
A number of such switches are sometimes used in con junction with a pulse counter for example for setting timed operational sequences in automatic machines, and it is often desirable in this case to provide safety-check timing means arranged to operate if any one of the coding switches fail to function correctly, thereby preventing damage in use of the automatic machines.
Hitherto the safety-check timing means has often comprised a duplicate set of coding switches, this resulting of course in disadvantageous increases in the cost of switching apparatus, and causing inconvenience in operation due to the duplication of the task of setting the switches.
It is an object of the present invention to provide an improved coding switch which will overcome these disadvantages.
According to the invention there is provided an electric coding switch including a rotatable member having a plurality of cam tracks thereon, cam followers associated with said cam tracks and arranged to operate a set of switch contacts so that a coded output is obtainable from the set of contacts in dependence on the rotational setting of the switch, impedance means, and a tapping contact engageable with said impedance means, the arrangement being such that relative movement of said tapping contact and said impedance means occurs with rotation of said rotatable member thereby providing a tapped impedance circuit the value of which is variable in dependence on the rotational setting of the switch.
It is to be understood that the term impedance means when used herein means resistance, capacitance, or inductance devices, and includes such devices both when used singly and in combination.
Thus it will be seen that the invention provides a coding switch which provides, in addition to the coded output, a separate analogue output also dependent on the rotational setting of the rotatable member. The second output can easily be arranged to control a device acting Patented Mar. 10, 1970 as a safety check on the device operated by the first coded output.
The impedance means may comprise a single device such as a continuous tappable inductance coil or a graphite resistance strip.
Alternatively and preferably the impedance means comprises a set of separate interconnected impedance elements, having tapping points therebetween engageable with said tapping contact. The impedance elements may comprise any suitable elements such as capacitors, resistors or inductances depending on the particular nature of the operation of the switch and the form of analogue output required.
In some cases, such as when the coded output of the switch is used for operation timing purposes, the set of interconnected elements may comprise a series chain of resistors so that by suitably connecting the tapping contact to a capacitor it is possible to obtain a time dependent resistor/capacitor charge circuit which can be used as a safety-check on the timing circuit fed by the coded output.
In a preferred embodiment of the invention the im pedance means is carried by said rotatable member and the tapping contact is mounted xed with respect to said rotatable member.
In this case the rotatable member may be of cylindrical shape mounted for rotation about its longitudinal axis, the cam tracks being provided on one end wall of the cylinder and the impedance means being carried by the other end wall. The cylinder may for convenience be hollow, and where the impedance means comprises a set,
of interconnected elements, these may be carried within the cylinder.
Again where a set of interconnected impedance elements is provided the tapping points may comprise foil coatings on an insulated disc and may be formed by any suitable printed circuit forming technique.
The cam track may be provided by a plurality of sets of protuberances on a surface of the rotatable mem-ber, thereby forming a cam disc.
In order that the invention may be more readily understood one embodiment thereof will now be described by way of example only with reference to the accompanying drawings in which:
FIG. 1 is a part-sectional plan view of a coding switch according to the invention;
FIG. 2 is an elevational view of the switch shown in FIG. 1;
FIG. 3 is a section on the line III-III of FIG. 1;
FIG. 4 is a section on the line IV-IV of FIG. 3; and
FIG. 5 is a fragmentary section on the line V-V of FIG. l.
Referring now to the drawings it will be seen that the switch includes a casing comprising a hollow container 1 and a at cover 2 secured together by means of four screws 3. Mounted within holes 4 and 5 in the container and cover respectively are reduced diameter portions 6 and 7 of a steel spindle 8. The spindle carries a rotatable member in the form of a hollow cylindrical drum 9 closed at one end.
The outer face of the closed end of the drum comprises a cam disc 10. As shown most clearly in FIG. 4 the cam protuberances 11 are arranged in seven Iconcentric tracks around the spindle 8, and are engageable as shown in FIGS. 3 and'S with follower pins 12 passing through holes 13 in the container and engaging the inner spring contacts 14 of seven contact pairs 15.
The coding switch illustrated is intended as a position switch, and the protuberances on the cam disc are so arranged as to provide at the contact pairs 15 a binary code output as hereinafter described corresponding to each of the 100 positions.
In order to locate the rotatable drum 9 in each of its 100 settings, two diametrically opposed spring urged locating pins 16 are provided in the drum which engage in the grooves of a circular progression of 100 ridges 17 formed on the inside of the cover 2 radially about the bearing hole 5.
The drum 9 is rotated by means of an outwardly protruding annular shoulder 18 having a knurled outer face 19 which partly protrudes through the side of the container 1 as shown at 20. The numerical setting of the switch at each position is indicated by an adhesive strip 21 carrying numbers from 1 to 100 `which is stuck around the periphery of the side wall 22 of the drum 9. The strip 21 is angularly aligned upon the drum in such a manner that the number marked thereon which is visible at any one setting of the switch through a transparent magnifying window 23 in the container wall corresponds to the binary code output obtainable from the set of contact pairs 15 at that setting.
Mounted within the drum on a central boss 24 through which the spindle 8 passes is an insulating epoxy resin circuit board 25. The circuit :board 25 is rotatable with the drum 9 and is secured thereto in abutment against an annular shoulder 26 on the inside of the side wall 22 of the drum 9. The outer face 27 of the insulating board 25, constituting one end face of the rotatable member, is provided with a printed circuit comprising separate contact strips 28 radially aligned about the spindle 8, and a continuous inner annular strip 29 connected to one of the separate strips 28 as shown at 30.
In the embodiment of the invention illustrated 100 resistors 31 are disposed within the drum 9, although for the sake of simplicity only a few of the resistors are shown in the drawings. The two connection wires 32 of each resistor 31 pass through connection lholes 33 in the circuit board 25 and are soldered to adjacent contact strips 28 as shown in FIG. 1 so that the resistors are connected in a series chain having a tapping point between each pair of adjacent resistors.
Secured to the cover 2 of the switch by means of nuts and bolts, one set of which is shown at 34 and 35, are tapping contacts 36 and 37 spring urged into contact with the circuit iboard 25 and engageable respectively with the annular strip 29 and with one of the radial strips 28 at each setting of the switch. It will be clearly seen that a series chain of resistors is electrically connected between the contacts 36 and 37, the number of the resistors and hence the magnitude of the resistance being variable in dependence on the rotational setting of the drum.
This embodiment of the invention is illustrated and described with a resistor connected between each pair of adjacent radial contact strips 28 so that the resistance connected between the tapping contacts 36 and 37 is different for each of the 100 set positions of the switch. However in some uses of the switch it is not necessary for the resistance to lchange for each change in the set position. Frequently a sufficiently accurate safety check is provided if the resistance changes for every two or three changes in the set position of switch for example. In this case, the resistors may interconnect every second or every third radial contact 28, the intermediate contacts 28 being suitably short-circuited.
Conveniently the circuit Iboard 25 is arranged to be easily removable so that it is a simple procedure to remove one circuit board and replace it with another board more suitably wired with resistors for the particular use in hand.
The seven contact pairs are carried within a block of synthetic resin insulating material 40 screwed to the container 1. The inner spring contacts 14 are normally disposed out of engagement with outer spring contacts 41 unless pressed into engagement therewith by the -cam protuberances 11 via the follower pins 12.
The connection tab end 42 of each of the outer contacts 41 is soldered to the output of one of seven diodes 43. The inputs of the diodes'43 are soldered to a common connection wire 44 which in turn is soldered to an input tab 45 secured within the insulating block 40. A cover 46 for the contact pairs 15 is mounted upon the container 1.
In one typical use of the switch illustrated, given by way of example only, the input tab 45 of the contact pairs 15 is connected to a triggering voltage pulse source (not shown), and the connection tab ends 47 of the inner spring contacts are soldered to separate leads which are connected to a binary pulse counter (not shown). A pulse generator (not shown) is connected to the input of the binary counter, the output of the counter being connected to an automatic machine (not shown), such as an automatic lwelding machine, so as to time and control the various operational sequences of the machine.
The switch is set to the required numerical value for the time of the operational sequence required, so that some of the seven conta-ct pairs 15 are engaged by the cam protuberances 11. A triggering pulse is then fed to the tab 45 through the diodes 43, through the engaged contact pairs 15 and the respective connection tab ends 47 of the inner spring contacts, to the binary counter. Hence a binary coded pulse is fed to the binary counter which sets it to count a predetermined number of pulses from the pulse generator in dependence on the setting of the coding switch, thereby enabling the counter to control the duration of each operation of the automatic machine.
In this use of the switch illustrated, the tapping contacts 36 and 37 are connected to a capacitor charge circuit (not shown), which together with the chain series of resistors 31 forms a timing circuit. This timing circuit is connected to the automatic machine as a safety check on the binary counter, the elements of this circuit being so chosen in value as to provide the same timing dura-v tion as the binary counter at each set position of the switch.
Usually a number of the switches illustrated will be connected to the binary pulse counter so as to provide a switch for each of the operational sequences to be timed. In this case the coded outputs from all of the switches will be connected in parallel to a commonset of seven input leads to the counter. Each of the switches is correctly set for the particular operation it controls, and triggering pulses are then fed from the triggering pulsesource as described above to each of the switches in turn as the operation of the automatic machine proceeds. A triggering pulse fed to any one switch is prevented from passing through the contact pairs 15 of the other switches connected in parallel thereto by means of the diodes 43.
In some uses of the coding switch, the full range of 1.00 positions is not required, and a range of 60 positions for example is suiicient. For this reason, stops (not shown) may be provided if desired to restrict the movement of drum 9 to the required range.
1. An electric coding switch including a support member, a rotatable member on said support member and having a plurality of cam tracks thereon, a cam follower on said support member associated with each of said cam tracks and arranged respectively to operate an associated one of a plurality of switch contacts on said support member so that a digital coded output is obtainable from the set of contacts in dependence on the rotational setting of the switch, impedance means on one of said members, and a tapping contact on the other rnem- -ber engageable with said impedance means, the arrangement being such that relative movement of said tapping contact and said impedance means occurs with rotation of said rotatable member thereby providing an analog output from said tapped impedance circuit the value of which is variable in dependence on the rotational setting of the switch, said impedance means being carried by said rotatable member and said tapping contact being mounted xed on said support member, said rotatable member being of cylindrical shape mounted `for rotation about its longitudinal axis on said support member, the cam tracks being provided on one end wall of the cylinder and the impedance means being carried by the other end wall.
2. An electric coding switch according to claim 1 including a pair of said tapping contacts, one of said tapping contacts engaging in all settings of the switch a conductor connected to one end of the resistor chain, and the other of said tapping contacts being arranged to engage at separate tapping points of the set of resistors for each setting of the switch.
3. An electric coding switch according to claim 1 wherein the cylinder is hollow and the impedance means is carried within the cylinder.
4. An electric coding switch according to claim 1 wherein the cam tracks are provided by a plurality of sets of protuberances on said end wall of the rotatable member, thereby forming a cam disc.
References Cited UNITED STATES PATENTS THOMAS A. ROBINSON, Primary Examiner U.s. C1. X.R. 20o- 6; 340-282