WO1996025728A1

WO1996025728A1 - Method and apparatus for sensor logic control

Info

Publication number: WO1996025728A1
Application number: PCT/US1996/001849
Authority: WO
Inventors: E. Svacina Robert
Original assignee: Turck, Inc.
Priority date: 1995-02-14
Filing date: 1996-02-12
Publication date: 1996-08-22

Abstract

An apparatus and method for combining sensor input signals using solid state logic devices, and without signal degradation. Sensor input signals (22 and 23) are isolated and conditioned (34 and 36) before combination. A new output signal (24) is generated, allowing use of multiple solid state logic devices in series without signal degradation. Light emitting diodes (28, 29, 30) show input and output signal status. Quick disconnects allow easy changeover to a new device.

Description

METHOD AND APPARATUS FOR SENSOR OGIC CONTROL

BACKGROUND OF THE INVENTION

The present invention relates to the field of sensor logic control. Specifically it relates to

interconnection of electrical input components using solid state logic without voltage degradation problems.

On-the-machine logic has in the past been accomplished by wiring on-the-machine

components such as limit switches in such a manner that basic Boolean logic was

performed. Such mechanical limit switches are slow and have a tendency to wear out over time, due to mechanical wear from cycling on and off.

Solid state technology using semiconductors caused a major change in the art starting the

first half of the 1970s. Many on-the-machine limit switches were replaced with solid state inductive sensors, photoelectric sensors, or ultrasonic sensors. Also, instead of the large

and expensive control relays previously used, an industrial computer was substituted. In

the centrally located industrial computer, hundreds and even thousands of functionally

equivalent devices are available in the central processing unit. In contrast to the limit switch, on-the-machine solid state devices operate at high speeds and do not wear out as the device is switched on and off. However, solid state devices have a

voltage drop across their solid state switches. It is not advisable to wire more than two or

three of these solid state devices in series or the cumulative voltage drop becomes too great

and the final signal is below the threshold of the control relay or an input to the industrial computer. The input to the centrally located industrial computer is what changes the

external operating signals of typically 24 volts or greater to the internal operating voltage of

5 volts or less, and requires a minimum threshold value to be actuated. Many industrial

applications require the use of multiple logic devices in series. Degradation of voltage across each logic device rapidly and cumulatively builds up, resulting in erratic

performance, or total failure.

Currently, common practice wires all on-the-machine sensors back to the industrial computer, and the interconnection between the various sensors is accomplished by a

computer program. In modern production plants this means miles of wire. Each on-the-

machine sensor must be individually connected to the computer. To facilitate fast change to the next generation of product and to minimize labor disruptions, manufacturers have machines built off site where special bundles of wires configured for the specific system are premade. When the next generation of product comes out, the old machines are scrapped.

The wire, which is still good, is most often not the right length, right size, or in the right bundles to be useful in the new system. There is some value in scrapped wire, but very little, compared to the cost of new wire, because of the high cost of removing and recycling the plastic insulation of the wires.

Recently, the first bus system started to be used in manufacturing. The early bus systems

multiplexed signals from many on-the-machine sensors and actuators back to the input or

output points on the industrial computer. Anywhere from two to ten wires were used compared to the thousands required by traditional wiring. The early buses had only enough

intelligence to synchronize the nodes (input and output points where the sensors and other

devices were attached) but not enough to perform any logic on the data input signals.

These buses have made very minor inroads against traditional wiring.

Therefore, there are only two main systems presently in use for the transfer of sensor input

signals to a programmable logic controller or computer unit. The first option is a

programmable logic device, or "smart box" which is placed on the machine itself. These

smart boxes contain logic chips which must be programmed to perform the logic functions needed by the machines and the sensor configuration. Further, replacement of smart

boxes requires reprogramming of the boxes. The second major option used today is hard wiring of all the sensor input signals to an industrial controller or computer located away

from the machine. This option necessitates the use of a large amount of wire and a large

number of input points and contact points. Both options have roughly the same cost. The

first option, the smart box, has the advantage in performance over hard wiring because there are fewer contacts that can fail in some way. Still, the disadvantages set forth above

remain.

Quick disconnect smart connectors with logic capability are known in the art. U.S. Patent

No. 4,845,701 issued to Hayes et al. discloses such a device. However, specific logic

modules are not disclosed in Hayes et al. Further, the Hayes et al. connectors are open and

not suitable for on-the-machine wiring and are designed for use on the inside of a machine. Hayes et al. makes no disclosure or suggestion of isolating or conditioning input signals.

U.S. Patent No. 4,206,262 issued to Shue, Jr. et al. discloses an electrical connector with a logic interconnect function. No disclosure or suggestion is made in Shue, Jr. et al. of isolating and conditioning input signals or of a need to do so in order to avoid signal

degradation. The electrical connector of Shue, Jr. et al. requires manual setting of switches

in order to allow it to perform functions.

RRIEF SUMMARY OF THE, INVENTION

The present invention comprises a series of tap and junction connecting devices used to

combine sensor input signals with solid state logic, using signal isolating and conditioning

to inhibit signal degradation. It is an objective of the present invention to provide a device for interconnecting sensor

input signals of a machine to simulate limit switches using solid state components.

It is another objective of the present invention to provide logic functions on-the-machine

without the need for programming or reprogramming.

It is yet another objective of the present invention to provide a sensor signal receiving and

conditioning device capable of withstanding harsh conditions on-the-machine or away from

the machine.

It is still another objective of the present invention to provide status signals for quick and

easy detection of system problems.

It is yet another objective of the present invention to allow the connection in series of multiple solid state logic components at or near the machine.

The present invention accomplishes these objectives by providing a sensor logic control having solid state logic components for combining input signals. Circuit method and components beneficially isolate and condition the input signals so that each and every

signal passed to the solid state logic component has the same strength, within tolerance

limits. This isolation and conditioning of signals allows the logic component to be a solid state component. Since the logic is solid state it does not require programming on the

machine. The output signal from the logic component is a new signal. This new signal does not suffer from cumulative build-up of signal degradation due to the voltage drop over

a solid state component. This is because of the isolation and conditioning of the input signals, and the creation of a fresh output signal. The logic components used in the

invention may be of whatever type is necessary for the task at hand. Any number of sensor

logic controls of the type disclosed herein may therefore be connected in series without loss of signal strength.

LED status indicators may be provided with the present invention to indicate the status of

input signals, output signals, and whether the apparatus has power. These status indicators allow quick and easy determination of the location of any problems with the sensors or with the logic control device.

The single channel sensor logic control device comprises a housing fully enclosing a discrete signal conditioning and optical isolation unit and a solid state logic component.

The logic control device further includes signal input connections connectable to a

transmission line carrying sensor input signals, and input, output, and power status light

emitting diodes. Quick disconnect wiring to the tap and junction control devices allows placement of the logic control device close to or on-the-machine, for easy access by maintenance technicians

or operators. The quick disconnect also allows efficient replacement of logic control devices. The logic of each logic control device need not be reprogrammed every time a

new device is installed because the isolation and conditioning of the input signals allows the

logic component to be solid state.

These and other objects and benefits of the present invention will become apparent from the following detailed description thereof taken in conjunction with the accompanying

drawings, wherein like reference numerals designate like elements throughout the several views.

DESCRIPTION QF THE DRA INGS

Fig. 1 is a perspective view of a two channel embodiment of a control device of the invention in place on a typical application;

Fig. 2 is a front elevational view of a single channel embodiment of a control device of the

invention; Fig. 3 is an end view of the device of Fig. 2 taken along lines 3-3 thereof and showing the input pin configuration;

Fig. 4 is a circuit diagram of the wiring of the single channel control device of Fig.2;

Fig. 5 is a front elevational view of a two channel embodiment of a control device of the invention; and

Fig. 6 is a circuit diagram of the wiring of the two channel control device of Fig. 5.

DETAILED DESCRIPTION

Referring now to Figs. 2-4, the single channel sensor logic control device 10 will be

described in detail. Fig. 2 shows the sensor logic control 10 in its single channel embodiment. Sensor logic control 10 comprises T-shaped housing 20, two signal input connections 22 and 23, output connection 24, and a plurality of light emitting diodes

(LED) 28, 29, 30 and 31. Housing 20 is preferably molded in one piece of polypropylene.

For convenience in mounting, housing 20 may include a projecting boss 25 having a through hole 26 to receive a fastener. LED 28 indicates signal status from a sensor signal

at input connection 22. LED 29 indicates signal status from a sensor signal at input

connection 23. LED 30 indicates signal status for the signal at output connection 24. LED

31 indicates whether sensor logic control device 10 has power. Fig. 3 shows the preferred 4-pin configuration of input connection 22. Input connection 23

and output connection 24 also have 4-pin configurations. The wiring configuration of

single channel sensor logic control 10 may be seen in Fig. 4. Reference numerals 1-4 in

Fig. 4 refer to corresponding input pins 1-4 of Fig. 3. Single channel sensor logic control

10 is wired with one logic gate 32. In the configuration shown, logic gate 32 is an "AND" logic gate. Other logic functions including "OR," "NOR," and "NAND" could be used as

the situation dictates. Sensor logic controls 10 could be stocked with different logic gates

32 for different functions, allowing easy and quick changeover from one logic gate 32 to

another simply by replacing the entire sensor logic control 10. Inputs at input connection

22 on lines 1 and 3 of single channel sensor logic control 10 are used to power the logic

control 10 and connected sensors. LED 31 will light to indicate when power is present in

sensor logic control 10. Line 4 is used to carry the first of the two signals to be combined by logic gate 32. For purposes of clarity, like components at different positions or on

different items are indicated by the use of the original reference numeral followed by a prime or double prime designation. Line 4' at input connection 23 carries the second signal. LEDs 28 and 29 indicate the presence of signals on lines 4 and 4' respectively. The signals on lines 4 and 4' are isolated and conditioned before combination in gate 32 by

signal isolating and conditioning units 34 and 36 respectively. The presence of resulting

output from logic gate 32 is indicated by LED 30. All LEDs are yellow with the exception

of power TF-π 31 , which is green. LED color can be varied depending upon industry convention for different industries. The isolating and conditioning of signals carried by lines 4 and 4' results in a new output signal at output connection 24 that is free from

cumulative voltage drop across multiple solid state logic gates 32 and logic control devices

10, and allows numerous sensor logic controls 10 to be used in series as shown in Fig. 1 without the worry that the final signal strength will fall below the threshold value of an

industrial computer or other signal receiver.

The isolation of the discrete input signals at units 34 and 36 is accomplished using optical

isolation and a bipolar operational amplifier. The conditioning of the discrete input signals

is accomplished using a resistor network and a transistor to turn on one side of the operational amplifier. The logic gate 32 drives the new output signal to the next logic control device or the final output to a controller, relay, or industrial computer. The

isolating and conditioning components and circuitry may be collectively referred to as

isolating and conditioning units. The isolating and conditioning of signals is known and

will not be discussed further herein.

The components of sensor logic control 10 are fully contained within housing 20. Housing

20 seals and keeps from outside influence the electrical and electronic components used to

isolate, condition, and combine signals in sensor logic control 10, including LEDs 28-31. Sensor logic control 10 may be mounted using apertured mounting boss 25 and its through

hole 26. Connection of input and output lines or cables is made to input connections 22, 23 and output connection 24 using quick disconnects. Connectors 22 and 23 have knurled rings 27 for ease of use.

The control devices may be used with one channel input, or with a plurality of channel

inputs. For example, Figs. 5 and 6 show a two channel sensor logic control 40 and its circuit diagram. Two channel sensor logic control 40 may be seen to be similar to single

channel sensor logic control 10. It has a housing 42 constructed to provide an on-line input cable connection 44 and an output connection 46. Sensor signal input connections are

provided at 48 and 50. These are also quick disconnect connectors of the industrial plug

and receptacle type, as described above with respect to the single channel input control device 10 of Fig.2. Knurled rings 51 may also be used to facilitate connecting and disconnecting cables. Two channel sensor logic control 40 is wired with two logic gates

52 and 54. In the configuration shown, logic gates 52 and 54 are "AND" gates. Other

logic functions, including "OR," "NOR," and "NAND" could be used as the situation dictates. Sensor logic control 40 could have gates of different types within one unit if so

desired or required. Input fittings 47 and 49 carry input pin connections 48 and 50. The

input pin configuration of input connections 44, 48, and 50 of the two channel sensor logic control of Fig. 5 is the same 4-pin arrangement as that shown in Fig. 3.

Referring now to Fig. 6, the circuit diagram for two channel sensor logic control 40 may

be seen. As in single channel sensor control logic control 10, lines 1 and 3 are used to power the unit 40 and connected sensors such as sensors 86, 86' , 88, and 88' as shown in Fig. 1. At input connection 44, line 2 is used for the first signal on channel 1 , and line 4

for the first signal on channel 2. Line 4' at input connection 48 provides the second signal

on channel 1. Line 4" at input connection 50 provides the second signal on channel 2. The

channel 1 signals on lines 2 and 4' are isolated and conditioned by signal isolating and

conditioning units 56 and 58 respectively. Those units provide the same functions as

described above for isolating and conditioning units 34 and 36 on the single channel

embodiment of Fig's. 2-4. Following that, the signals are combined at logic gate 52 to form a new output signal. The channel 2 signals on lines 4 and 4" are isolated and

conditioned by signal isolating and conditioning units 60 and 62 respectively. Following

that, the signals are combined at logic gate 54 to form a new output signal.

LEDs indicate signal and power status as follows. LED 64 indicates signal status for the

signal on line 2. I FT) 65 indicates signal status for the signal on line 4' . LED 66 indicates

signal status for the signal on line 4. LED 67 indicates signal status for the signal on line

4". LED 68 indicates the output signal status from channel 1 logic gate 52. LED 69 indicates the output signal status from channel 2 logic gate 54. LED 70 indicates the

presence of power to two channel sensor logic control 40. All LEDs are yellow with the exception of power LED 70, which is green. LED color can be varied depending upon

industry convention for different industries. Channel 1 output signal is located on pin 2 at output connection 46. Channel 2 output signal is located on pin 4 at output connection 46. Housing 42 encloses, seals and keeps from outside influence the electrical and electronic

components of two channel sensor logic control 40, including those components used to

isolate, condition, and combine signals, as well as LEDs 64-70. Referring also to Fig. 1,

the connection of input lines or cables 13-18 is made using quick disconnects. Input connectors 44, 48, and 50 have knurled rings 51 for ease of use. A mounting boss 72

having a through hole 74 may be used with a fastener, such as socket head cap screws 74a, to mount control device 40 at a desired location as shown in Fig. 1.

Referring now to Fig. 1, two of the sensor logic control devices 40, 40' may be seen in

perspective in a typical on-the-machine application. The application illustrated is a

clamping operation wherein a work piece is clamped in place for welding, cutting, drilling or other operation on a stand 78. A pair of air cylinders 80, 80' are mounted on steel

beams 82. A pivotal clamping arm 84, 84' is connected to the top of each cylinder 80,

80' . Each cylinder 80, 80' has a first sensor 86, 86' for detecting the movement of a

piston inside the cylinder to an upper, clamping position, and a second sensor 88, 88' for detecting the movement of the cylinder piston to a lowermost, undamped position. The

upward movement of each cylinder piston pivots clamp arms 84, 84' downwardly to clamp

a work piece in place, and the downward piston movement pivots the clamp arms 84, 84'

to their open positions as shown in Fig. 1. As shown in Fig.l , two of the controllers as herein described are connected in series with each other. For purposes of the disclosed application the dual channel control device 40 of

Fig. 5 is utilized. Thus a first controller 40 has its input connection 44 connected to a

cable 13, with its sensor input signal connection fittings 47 and 49 connected to cable leads

14 and 15 from upper and lower sensors 86 and 88 respectively. Cable 13 carries a signal or signals from another sensor logic control, relay, or other device. The output connection

46 (Fig.5) of controller 40 is connected by multiple wire cable 16 to the on-line input connection 44 (Fig. 5) of second controller 40' . Similarly, controller 40' has its sensor

input signal fittings 47 and 49 connected to cable leads 17 and 18 from upper and lower sensors 86' and 88' respectively. The output connection 46 (Fig. 5) of controller 40' is

connected to a cable 19 leading to another sensor logic device, or a controller, e.g. an actuating controller for the automatic welding machine, drill or other device utilized to perform work on a piece of metal to be held on the clamping stand.

In a typical application cycle, cylinders 80, 80', and clamping arms 84, 84' are initially in

undamped position as shown in Fig. 1. A robot or transfer conveyer (not shown) moves one or more work pieces 92 into place under clamp 90 of clamping stand 78. A sensor or sensors (not shown) detect whether the pieces are in proper position, and activate

compressed air cylinders 80, 80' if so. A piston inside each cylinder 80, 80' moves up

under air pressure, thereby pivoting clamping arms 84, 84' down to clamp the piece(s) to clamping stand 78. Sensors 86, 86' monitor piston position inside cylinders 80, 80' . When each sensor 86, 86' detects its corresponding piston in a fully up position it sends an

"on" signal to respective sensor logic control 40, 40^* through cables 14 and 17. The signal from sensor 86 is combined in sensor logic control 40 with a similar signal from another

sensor logic control or from another sensor received through cable 13, as indicated

generally by reference numeral 11. Similarly, sensor 86' sends its corresponding signal to

sensor logic control 40', where that signal and corresponding output signals indicated as 12 from sensor logic control 40 are combined with the signal from sensor 86' into a new

output signal 12'. In a typical clamping operation as is shown in Fig. 1, the logic function

in sensor logic controls 40, 40' will be "AND" logic in order to combine sensor signals in

proper format for the application. The final output from the last sensor logic control in the circuit must be "on" in order to initiate further operation. For example, the output signal

12' from second sensor logic control 40' may be utilized to actuate a welder, drill or other

machine through a further control device to initiate work on a piece of metal clamped on stand 78.

Sensors 88, 88' monitor piston position as well. When the welding, drilling, or cutting

operation is finished, clamping arms 84, 84' are raised to their shown, open positions. Sensors 88, 88' detect an undamped piston position and so indicate by "on" signal outputs. These outputs are combined as explained above on the second channel of sensor logic

controls 40, 40' to provide a modified output signal through output cable 19 to a controller

used to actuate a device to automatically remove the work piece form clamping stand 78. It will thus be seen that in operation, appropriate input cables are secured to sensor logic

controls 10 and 40 at their inputs. LEDs indicate signal status for the presence of input and

output signals, as well as power. Inputs are isolated and conditioned by isolating and

conditioning units fully enclosed within the housings of the devices, and then are combined

by logic gates also fully enclosed within the housings of the devices. The output signal or

signals is/are sent to another sensor logic control 10 or 40 or to an industrial computer,

smart box, controller, or relay for operation of machine or material handling mechanisms without signal degradation due to voltage drops across multiple solid state components.

The type of solid state components in logic control device 10 and 40 described above will

change due to the type of current used. AC alternating current and DC direct current use similar but different types of components to perform the logic. Both AC and DC are

common choices in today's manufacturing. These solid state logic components are

integrated components or individual components that must be connected to perform the

stated logic. Modification of the embodiments of the invention to accommodate either AC or DC operation is within the knowledge of one skilled in the art, and within the scope of

the invention.

The detailed description outlined above is considered to be illustrative only of the principles of the invention. Numerous changes and modifications will occur to those skilled in the

ait, and there is no intention to restrict the scope of the invention to the detailed description. The preferred embodiments of the invention having been described in detail, the scope of the invention should be defined by the following claims.

Claims

WHAT IS CLAIMED

1. A method for combining sensor input signals without signal degradation, using solid state logic components, said method comprising the steps of: isolating and conditioning each of the sensor input signals;

combining the isolated and conditioned sensor inputs in the solid state logic

component to form a new output; and

transmitting said new output from the solid state logic component.

2. The method according to claim 1 and including the step of:

displaying a status light for each sensor input.

3. The method according to claim 2 and including the step of :

displaying a power status light.

4. The method according to claim 3 and including the step of:

displaying an output status light.

5. A sensor logic control device for combining sensor input signals, said control device comprising: a housing;

at least one signal input connection for receiving electrical input signals from a sensor;

means within said housing for isolating and conditioning each input signal; a solid state logic component within said housing for performing a logic function on

the input signals to form a new signal; and means for outputting said new signal without degradation.

6. The sensor logic control device of claim 5, wherein said solid state logic component is an "AND" gate.

7. The sensor logic control device of claim 5, wherein said solid state logic component

is an "OR" gate.

8. The sensor logic control device of claim 5, wherein said means for isolating and

conditioning each input signal comprises: a bipolar operational amplifier connected between each said input connection and said logic component;

said bipolar operational amplifier optically isolating each input signal; a transistor and a plurality of resistors connected between said input connection and said bipolar operational amplifies;

said transistor and resistors conditioning each input signal.

9. The sensor logic device of claim 3, and further comprising:

a plurality of light emitting diodes, each light emitting diode connected to a sensor

input connection; each light emitting diode providing a status signal for a sensor input signal; and

an output light emitting diode connected to said output signal, and providing a status signal therefore.

10. The sensor logic control device of claim 5 wherein said housing fully encloses said

means for isolating and conditioning and said solid state logic component and insulates

them from external forces.

11. The sensor logic control device of claim 5 wherein said means for receiving sensor

inputs signals is two separate input connections, each said input connection having a

multiple pin configuration.

12. The sensor logic control device of claim 5 wherein: said means for receiving sensor inputs comprises a first input connection, a second

input connection and a third input connection;

said first input connection capable of receiving a first input signal and a

second input signal;

said second input connection capable of receiving at least one input signal;

said third input connection capable of receiving at least one input signal; said logic component electrically connected to said first and said second input connections for combing the first signal and the signal from said second

input connection;

a second solid state logic component electrically connected to said first and said

third input connections for combining the second signal and the signal from said third input connection.

13. The sensor logic control device of claim 5, and further comprising industrial plugs

and receptacles for quick connection to and disconnection from the sensor input connection.

14. A sensor logic control device for action on sensor input signals, said control device

comprising:

a housing;

means on the housing for receiving sensor input signals; means in the housing for isolating and conditioning the sensor input signals; means for constructing a new output signal from said input signals; and means for transmitting said new output signal.

15. The sensor logic device of claim 14, and further comprising:

a plurality of light emitting diodes, each light emitting diode connected to one of the

sensor input signals, and each light emitting diode providing a status signal for its sensor input; and

an output light emitting diode connected to said output signal, and providing a status

signal therefore.

16. A sensor logic control device for combination of two sensor signals without degradation of the signals, said device comprising:

a housing having two input connections connectable to transmission lines

carrying sensor signals; means for isolating and conditioning each sensor signal; a solid state logic component electrically connected to receive one sensor

signal from each said input connection and to combine the signals to

form a new output signal; means for transmitting said new output signal.

17. A sensor logic control device for combination of two sets of two sensor signals

without degradation of the signals, said device comprising: a housing having a first, a second, and a third input connection connectable to a

transmission line carrying sensor signals;

means for isolating and conditioning each sensor signal;

a first and a second solid state logic component;

said first logic component electrically connected to receive one sensor signal from

said first input connection and one sensor signal from said second input connection and to combine the signals to form a first new output signal;

said second logic component electrically connected to receive one sensor signal

from said first input connection and one sensor signal from said third input connection and to combine the signals to form a second new output signal; means for transmitting said new output signals.