US3092752A

US3092752A - Drive circuit for electronic counters with means to prevent spurious switching

Info

Publication number: US3092752A
Application number: US30966A
Authority: US
Inventors: Roger W Wolfe
Original assignee: Burroughs Corp
Current assignee: Unisys Corp
Priority date: 1960-05-23
Filing date: 1960-05-23
Publication date: 1963-06-04
Anticipated expiration: 1980-06-04

Description

June 4, 1963 R W. WO

LFE DRIVE CIRCUIT FOR ELECTRONIC COUNTERS WITH MEANS TO PREVENT SPURIOUS SWITCHING Filed May 23, 1960 SET 42 5 J H I 56 32 /6 E- w M F V /6 -20 53 /52 CATHODE FOLLOWER CATHODE FOLLOWER 54 SWITCHING SIGNAL I soupcs 4 5 INVENTOR;

ROGER W WOLFE ATTORNEY 21511 MEANS TO PREVENT SPURIOUS SWITCH- Roger W. Wolfe, South Plainfield, NJ., assignor to Burroughs Corporation, Detroit, Mich., a corporation of Michigan Filed May 23, 1960, Ser. No. 30,966 4 Claims. (Cl. 3158.5)

This invention relates to drive circuits for electronic counting circuits and particularly to counting circuits using multi-position electron beam tubes as the basic counting unit.

One type of electronic counter utilizes a multi-position magnetron beam switching tube which includes an electrode assembly comprising a central cathode and a plurality of groups of electrodes surrounding the cathode. Each of the groups of electrodes comprises a position to which an electron beam may flow and from which an output signal may be derived. Suitable magnet means provides a longitudinal magnetic field which combines with electronic fields within the tube to provide the desired switching action. According to one method of operation, a flip-flop is employed to drive an electron beam from position to position in the tube. However, it has been found that, under some circumstances, for example where the flip-flop is plate-triggered, or when the flip-flop is changing state, undesired or spurious switching of the tube occurs.

Accordingly, the principles and objects of the present invention are directed toward the provision of an improved driving circuit for a multi-position beam switching tube wherein spurious switching of the tube is prevented.

Briefly, the circuit of the invention includes a mgnetron beam switching tube of the type described above in which each group of electrodes includes a target electrode to which an electron beam flows and from which an output signal is derived, a spade electrode which holds an electron beam on its associated target electrode, and a switching electrode which is used to switch a beam from one position to the next. The switching electrodes are connected in two sets, with alternate electrodes being connected together, and a driving circuit is coupled to the sets of switching electrodes. The driving circuit is of a type which may generate transient pulses which may cause spurious switching of the tube. According to the invention, means are provided for rendering the tube more difiicult to switch during the period when the driving eans might generate transient pulses and before the desired stable switching state has been reached. After this time has passed, the stable, steady-state pulses generated by the driving circuit cause the desired and normal switching operation.

The invention is described in greater detail by reference to the drawing wherein the single FIGURE is a schematic representation of a counting tube and a circuit in which it may be operated according to the invention.

The circuit described below is particularly suitable for use with a multi-position type 6700 magnetron beam switching tube. In actual construction, this type of tube is cylindrical in form but is shown schematically in linear form as tube It) in the drawing. The tube includes an envelope 12 which contains a central longitudinally elongated cathode 14- and ten groups of electrodes spaced radially equidistantly from the cathode and surrounding the cathode. For simplicity, only four groups of electrodes are shown numbered 0, 1, 8, and 9. Each group of electrodes includes a generally U-shaped elongated spade electrode 16 and a generally L-shaped target electrode 18 positioned so that each target occupies the space 3,092,752 Patented June 4, 1963 between adjacent spade electrodes. Each spade electrode serves to form and hold an electron beam on its correponding target electrode. A generally rod-like switching electrode 20 is also included in each group of electrodes and is positioned between one edge of each target electrode and the adjacent spade electrode. The switching electrodes are known as switching grids. An open-ended cylindrical permanent magnet represented schematically at 22 is provided surrounding the tube envelope and coaxial therewith. The magnet 22 provides an axial magnetic field which is utilized in conjunction with electric fields within the tube to form and switch an electron beam from the cathode to each of the groups of electrodes. The direction in which the beam switches, that is clockwise or counterclockwise, is always the same and is determined by the orientation of the electric and magnetic fields.

Briefly, in operation of tube 10, electrons emitted by the cathode are retained at the cathode if each of the spades, targets and switching grids carries its normal operating electrical potential. When a spade or swiching grid experiences a suitable lowering of its potential, an electron beam is formed and directed to the corresponding target electrode. The electron beam may be switched from one target electrode to the next by thus suitably altering the electrical potentials of a spade or switching grid. Under normal operating conditions, whenever electrode voltages are such that a beam might be supported at several positions, the beam will switch to themost leading position and lock in at this position.

In the circuit shown, the cathode 14 is connected through a suitable bias resistor 24 to ground. Each of the spade electrodes 16 is coupled through a spade load resistor 26 to a spade buss 28. The spade buss 28 is coupled through a common spade resistor 30- to a suitable positive DC. power supply V of about 200 volts. -A suitable zero-set circuit 32 for clearing an electron beam in the tube and resetting it at the 0 position is coupled to the spade buss 28 and the spade electrode 16 at the 0 position. A typical zero-set circuit operates by first reducing the potential of the spade buss to a level at which a beam cannot be maintained at any position and then holding the 0 spade at a lower voltage level than the other spades until a beam forms at the 0 position. Of course, any desired and suitable zero-set arrangement may be used.

The target electrodes 18 are connected through suitable load resistors 38 to a common target buss 49 which is coupled to a positive DC. power supply V of about 300 volts. In addition, an auxiliary output tap 42 is provided at each target for connection to a suitable utilization device such as an indicator tube, a printing mechanism 'or the like, if desired.

The switching grid electrodes 28 are connected in two sets, with the grids at the even-numbered positions connected together in one set and the grids at the odd-numbered positions connected together in another set.

Apparatus for driving the beam switching tube and switching an electron beam from position to position includes a source 44 of switching signals (negative pulses) which is coupled through a capacitor 45 to the plate electrodes of a conventional flip-cfiop circuit 46. The signal source is thus adapted to plate-trigger the flip-flop circuit. This method of driving a flip-flop is well known, and the elements of a typical flip-flop are shown without being described in detail. The flip-flop includes two output leads 4S and 50, one of which is connected to the input of a cathode follower circuit 52, the output of which is coupled by lead 53 to one of the sets of switching electrodes and the other of which is connected to the input of a cathode follower 54, the output of which is connected by lead 55 to the other set of switching electrodes. The

cathodefollower circuits are conventional and are not shown in detail. According to the invention, the signal source, in addition to being coupled to the plates of the flip-flop circuit 46, is also coupled through a capacitor 56 to the spade buss 28. The capacitor thus is adapted ,to couple a portion of the input switching signal to the spade buss.

In operation of the invention, when a switching pulse is applied from the signal source 44 to the plate circuit of the flip-flop 46, the same negative pulse is transmitted in part to the spade buss 28. Thus, the spade buss is lowered in potential by about 25 volts. This reduction in potential of the spade buss makes it more difficult to switch an electron beam during the short time in which the fiip-flop andthe cathode followers are changing state. Thus, spurious switching during this time due to transient pulses or the like is prevented and desired switching occurs when these components have completed their change in state and the proper stable, steady-state switching pulse is 7 applied to the appropriate switching electrode. 7

In operation of the invention, the magnitude of the switching pulses applied to the flip-fiop from the source 44 is deter-mined by the requirements of the flip-flop. In addition, the magnitude of the pulse coupled to the spade buss should be large enough only to resist spurious switching and should not be so large that the tube is cleared.

It is clear that the principles of the invention, whereby spurious switching of an electron beam is prevented, may be practiced where appropriate with other types of driving circuits and the invention is not limited to plate-driver flip-flops or flip-flops operated with cathode follower circuits. 7

What is claimed is:

1. A counter circuit including a magnetron type electron beam switching tube having a cathode and a plurality of' groups of electrodes; each group including a target electrode which receives an electron beam and produces an output signal therefrom, a spade electrode which holds an electron beam on its associated target electrode, and a switching electrode which serves to switch an electron beam from one group of electrodes to the next; means providing a longitudinal magnetic field in said tube; said switching electrodes being connected in two sets with alternate electrodes being connected together; flip-flop driving means coupled to said sets of switching electrodes; and switching signal input means coupled both to said flip-flop and to the spade electrodes of said beam switching tube whereby a switching signal is applied to said flip-flop and to said beam tube at the same time; said signal rendering said beam'tube temporarily difiicult to switch during the time when said flip-flop is changing states to provide desired steady-state switching of the tube.

2. A counter circuit including an electron beam switching tube having a cathode and a plurality of groups of electrodes; each group of electrodes including a target electrode which receives an electron beam and produces an output signal therefrom, a spade electrode which holds an electron beam on its associated target electrode, and a switching electrode which serves to switch an electron beam from one group of electrodes to the next; drive circuit means coupledto said tube for applying steady-state stable switching pulses't-hereto and thus causing an electron beam to switch from position to position;

and auxiliary circuit means coupled from said drive circuit means to said spade electrodes and applying a small negative potential thereto for rendering said tube. temporarily diificult to switch whereby transient pulses from said drive circuit do not cause spurious switching. 3. A circuit defined in claim 2 wherein said drive circuit means is coupled to the switching electrodes of said tube.

4. A counter circuit including an electron beam switching tube having a cathode and a plurality of groups of electrodes; each group including a target electrode which receives an electron beam and produces an output signal therefrom, a spade electrode which holds an electron beam on its associated target electrode, and a switching electrode which serves to switch an electron beam from one group of electrodes to the next; said switching electrodes being connected in two sets with alternate electrodes being connected together; circuit driving means coupled to said sets of switching electrodes; and driving signal input means coupled both to said circuit driving means and to the spade electrodes of said beam switching tube whereby a portion of the driving signal is coupled to the spade electrodes of said tube and renders the tube diflicult to switch during a portion of the time when said circuit driving means is energized by said driving signal.

References Cited in the file 'of this patent UNITED STATES PATENTS

Claims

1. A COUNTER CIRCUIT INCLUDING A MAGNETRON-TYPE ELECTRON BEAM SWITCHING TUBE HAVING A CATHODE AND A PLURALITY OF GROUPS OF ELECTRODES; EACH GROUP INCLUDING A TARGET ELECTRODE WHICH RECEIVES AN ELECTRON BEAM AND PRODUCES AN OUTPUT SIGNAL THEREFROM, A SPADE ELECTRODE WHICH HOLDS AN ELECTRON BEAM ON ITS ASSOCIATED TARGET ELECTRODE, AND A SWITCHING ELECTRODE WHICH SERVES TO SWITCH AN ELECTRON BEAM FROM ONE GROUP OF ELECTRODES TO THE NEXT; MEANS PROVIDING A LONGITUDINAL MAGNETIC FIELD IN SAID TUBE; SAID SWITCHING ELECTRODES BEING CONNECTED IN TWO SETS WITH ALTERNATE ELECTRODES BEING CONNECTED TOGETHER; FLIP-FLOP DRIVING MEANS COUPLED TO SAID SETS OF SWITCHING ELECTRODES; AND SWITCHING SIGNAL INPUT MEANS COUPLED BOTH TO SAID FLIP-FLOP AND TO THE SPADE ELECTRODES OF SAID BEAM SWITCHING TUBE WHEREBY A SWITCHING SIGNAL IS APPLIED TO SAID FLIP-FLOP AND TO SAID BEAM TUBE AT THE SAME TIME; SAID SIGNAL RENDERING SAID BEAM TUBE TEMPORARILY DIFFICULT TO SWITCH DURING THE TIME WHEN SAID FLIP-FLOP IS CHANGING STATES TO PROVIDE DESIRED STEADY-STATE SWITCHING OF THE TUBE.