GB1576894A - Monitoring system for machine tools - Google Patents

Abstract

The machining apparatus has movable members (20, 120), the movement of which is monitored by limit switches (24, 25, 124, 125). Control devices (17, 117) control these movable members. To monitor the function of individual operations and movements, first monitoring units (34 to 37), e.g. signal lamps, are connected to a control means (11, 12, 26) for the automatic machining operations. The first monitoring units (34 to 37) are thus actuated by the individual machining operations or are illuminated. Second monitoring units (38, 39), which, for example, can likewise be designed as signal lamps, are connected to the control devices (17, 117) and are actuated by them. By a spatial allocation in accordance with the functional relationship between first and second monitoring units, it can thus immediately be established, when monitoring units respond, which control device is working or is not yet working during which machining operation. <IMAGE>

Description

(54) MONITORING SYSTEM FOR MACHINE TOOLS (71) We, ROBERT BOSCH GmbH., a German Company, of Postfach 50, 7 Stuttgart 1, Federal Republic of Germany, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: The invention relates to a system for the monitoring of machine tools in which automatically controlled operations take place entailing a movement of a member of the machine sensed by limit sensors, and to a machine tool embodying the monitoring 'system.

In machine tods, especially those of a complex kind, in which several movements and switching operations are frequently effected simultaneously, it is very difficult whne a fault develops, which usually will stop the machine abruptly, to ascertain where the fault lies. The fault may lie in the electronic control or, alternatively, may be caused.by the jamming of a mechanical part, or by a broken lead or a switching operation .which has not been effected.

In order to facilitate the detection of faults, it is known to.associate pilot lamps with individual switching operations in order to be able to determine whether the relevant switching operation has, or has .not, been carried out. The disadvantage -of these known monitoring systems resides in the fact that the operations and the sources of faults are frequently too complex to be detected by a simple pilot lamp. A solenoid valve is frequently triggered by a control signal of the electronic machine control and controls the pressure supplied to a cylinder which in turn effects a movement. If a fault should occur at this point in the .machining programme, the fault may reside in the control signal, the solenoid valve or the movement of the piston in the cylinder.

An electronics engineer is then generally called in to check the electronic control and, after a long period of time spent in tracing the error, might 'discover 'that only the piston has jammed in --the cylinder.

Therefore, -the object of the invention is to provide a system for the monitoring of machining devices, which is so simple and .easy to understand that -even the machinist himself can immediately detect the source of the fault, and even rectify the fault him self provided that it is a simple mechanical fault. By means of this monitoring system, it should be possible immediately to detect the point in the machining programme and precisely in which component the fault has occurred.

Hereinafter, the terms ('machining step" and "programme step" will be used. By the former is meant any one movement of a movable member of the machine tool effected in a machining operation, and by the latter is meant the setting up of a control signal condition which must exist as a precondition to permit a machining step to be carried out.

There is provided by the present invention a system which monitors a machine tool, in which automatically controlled operations take place in programmed steps and entail a movement of a member of the machine tool sensed by limit sensors : this system comprising a control device which controls the movable member and monitoring units for monitoring the function of individual operations, and movements: wherein a first.set of monitoring units in the form.of visual indicators is connected --to the .control device for monitoring the programme steps as hereinbefore defined, a second set of monitoring units in the form of visual indicators is connected to the control device for monitoring initiation of a machining operation effected by the movable mebmer, and the first and second sets of monitoring units are associated so that they are actuated in a particular combination when each machining step (as hereinbefore defined) is performed as required by the machine programme, but not otherwise the units of each combination being chosen so that the performance of a given machining step is indicated by the positional relationship of the units in the combination.

In an embodiment of the invention the association of the first set of monitoring units and the sceong set therof cntails a row and/or column arrangement of the monitoring units.

A third set of monitoring units in the form of visual indicators may be employed, which are connected to the limit sensors of the movable member, and the second and third sets of monitoring units are associated so that they are actuated in a particular spatial combination when a movable member assumes a predetermined position as required by the machine control, but not otherwise, again the units of a combination being chosen so that the assumption of the predetermined limit position by the movable members is indicated by the positional relationship of the units of the combination.

The advantages of the invention reside particularly in the fact that faults occuring in machining devices, particularly machine tools, can be readily recognized and traced -even by unskilled operators. In the case of faults which are simple to rectify, such as the jamming of a mechanical part, there is no need to call in an expert to remedy the fault even in very complex plant, thus reducing the period of time during which the machines are out of operation.

An embodiment of the present invention is illustrated by way of example, in the accompanying drawing, the sole figure of which is a schematic diagram of a monitoring system according to the invention.

Referring to the drawing a terminal 9 is connected to the position pole of a voltage source and, by way of a starting switch 10 and an AND gate 11, to the set input S of a flip-flop 12. Three further inputs of the AND gate 11 are connected to three further input terminals 13, 14, 15. The output Q1 of the flip-flop 12 is connected to the solenoid 17 of a three port, two position valve 18 by way of an amplifier 16 for amplifying the output signal of the flip-flop 12, and also to the set input of a second flip-flop 19.

The two position valve 18 is connected, on the one hand, to the forward-flow line P and the return-flow line R of a pressure medium system and. on the other hand. by way of a pressure line, to a cylinder 20 in which is arranged a movable, spnng-returned piston 21. A rod 22 is connected to the piston 21 and its end carries a marker 23 by means of which two limit switches 24, 25 are operable. Two contactless, magnetic limit switches 24, 25 are shown in the drawing, although, alternatively, mechanical limit switches or other types of limit switches may be provided. When the marker 23 reaches one of the limit switches 24, 25, the limit switch produces a signal.The piston 21 is in its start or rest position when the marker 23 is located opposite the limit switch 24, and in its fully extended working position when the marker 23 is located opposite the limit switch 25. The limit switch 25 is connected to the reset input R of the first flipflop 12.

The output Q1 of a third flip-flop 26 is connected to a system which corresponds to the described system 16 to 18, 20 to 25.

This second, identical, system is provided with reference numerals each increased by the number 100. Differences only result from the fact that the output Q 1 of the third flip-flop 26 is connected exclusively to the amplifier 116. The limit switch 24 is connected to the set input of a flip-flop 44 by way of an AND gate 27, and to the set input of the flip-flop 26 by way of a further AND gate 45. The limit switch 25 is connected by way of an AND gate 28 to the set input of a fifth. flip-flop 29. Analogously, the limit switch 125 is connected by way of an AND gate 30 to the set input of a sixth flip-flop 31. The output of sixth flip-flop 31 is connected by way of an AND gate 32 to the reset inputs R of the flip-flops 19, 29, 31, 44, and the complementary output of the flip-flop 31 is connected to a second input of the AND gate 45.

Furthermore, the output of the flip-flop 19 is connected by way of the AND gate 28 to the set input of, the flip-flop 29, the output of the flip-flop 29 is connected by way of the AND gate 27 to the set input of the flip-flop 44, and the output of the flip-flop 44 is connected by way of the AND gate 30 to the set input of the flip-flop 31. A second input of the AND gate 32 is connected to the limit switch 124.

Monitoring units in the form of pilot lamps are arranged on a control panel 33.

The pilot lamps 34 to 37 arranged in a row to form a first group of monitoring units which are connected between earth and the set outputs of the flip-flops 19, 29, 44, 31 respectively. A second group of monitoring units is formed by the two pilot lamps 38 and 39 connected between earth and the solenoids 17, 117 respectively. The pilot lamps 34 and 38 are arranged in a vertical row, as also are the pilot lamps 36 and 39.

The pilot lamps 40, 41 are connected between earth and the limit switches 24, 25 respectively; and the pilot lamps 42, 43 are connected between earth and the limit switches 124, 125 respectively. The pilot lamps 40, 41 form a horizontal row together with the pilot lamp 38, and the pilot lamps 42, 43 form a horizontal row together with the pilot lamp 39.

The mode of operation of the machine tool comprising the integers 18, 20, 118, 120 will be described in the first instance for the purpose of explaining the mode of operation of the monitoring system. This machine tool is controlled by an automatic control device comprising units 11, 12, 26.

The terms "one signal" and "zero signal" used hereinafter are terms customarily used in digital technology. A "one" signal signifies a potential which is of the order of magnitude of the supply voltage, and a "zero" signal signifies a potential which corresponds approximately to earth potential.

"One" signals must be present at the terminals 13 to 15 as initial conditions for the start of the programme. These "one" signals may be produced by switches which may be actuated by, for example, the lowering of a protective hood, the existance of an oil pressure, or further initial conditions for the operation of the machine. "One" signals are applied to all the inputs of the AND gate 11 by actuating the starting switch 10, whereby the output Q1 is set to a "one" signal by way of the set input of the flip-flop 12. Thus, the first programme step is attained, and the pilot lamp 34 is lit up by way of the flip-flop 19. The solenoid valve 17 is simultaneously actuated by way of the amplifier 16. The pilot lamp 38 lights up and the piston 21 of the cylinder 20 is set in motion.The pilot lamp 40, switched on by the limit switch 24 at the commencement of the machining operation, is extinguished, and the pilot lamp 41 lights up only when the marker 23 on the piston rod 22 has reached the second limit switch 25. However, the signal produced by the second limit switch 25 simultaneously resets the first flip-flop 12, and sets the flip-flop 29, whereby the pilot lamp 35 lights up. The solenoid 17 is switched off by the resetting of the first flip-flop 12, and the pilot lamp 38 is extinguished. The piston 21 returns to its start position, so that the pilot lamp 41 is extinguished in the first instance and the pilot lamp 40 lights up when the piston 21 reaches its end position.The flip-flop 44 is simultaneously set by way of the AND gate 27, whereby the pilot lamp 36 lights up. The two flip-flops 19, 29 remain in their set states. since a reset command has not been produced.

Since a "one" signal is present at the complementary output of the flip-flop 31, the flip-flop 26 is set by way of the AND gate 45 simultaneously with the setting of the flip-flop 44. The solenoid 117 is thereby energized by way of the amplifier 116, whereby the pilot lamp 39 also lights up.

Actuation of the solenoid valve 117 sets the piston 121 in motion in the cylinder 120.

whereby the pilot lamp 42 is extinguished and the pilot lamp 43 lights up when the marker 123 reaches the limit switch 125.

The latter operation in turn leads to the resetting of the third flip-flop 26 and the simultaneous setting of the sixth flip-flop 31, whereby the pilot lamp 37 lights up.

Analogously to what has been described above, the return movement of the piston 121 into its normal position in the first instance leads to the extinguishing of the pilot lamp 43, and to the lighting-up of the pilot lamp 42 when the marker 123 reaches the limit switch 124. This signal of the limit switch 124 is the last programme step and leads to the resetting of the flipflops 19, 29, 44, 31 by way of the AND gate 32, whereby the pilot lamps 34 to 37 are extinguished. The initial state which existed at the commencement of the programme now exists again, and a fresh programme can be started by means of the switch 10.

The arrangement described constitutes a very simple embodiment and is thus capable of optional modification. Thus, in automatic controls for complex machine tools, further fluid pressure control devices may be provided for actuating pistons in cylinders. When a plurality of hydraulic control devices are actuated simultaneously by one programme step, a plurality of pilot lamps, associated with the individual control devices, are correspondingly arranged in a vertical row below the particular pilot lamp for the programme. The associated movable members, particularly pistons and cylinders, then again have associated pilot lamps for the limit switches. Pilot lamps can also be provided for other switching operations during the course of the programme, for example, after introducing a pressure or when a workpiece passes a sensing device.

The invention is not confined to the use of pilot lamps, and other types of indicators can be used in an analogous manner. If monitoring devices are used which have a greater power requirement, amplifiers might have to be connected to the inputs of the monitoring units.

The monitoring units 34 to 37, in which, in the described arrangement, a further unit is actuated whenever the next programme step is reached, can also be provided without flip-flops 19, 29, 44, 31. In this case, a monitoring unit is actuated at each programme step and is extinguished at the next step.

WHAT WE CLAIM IS:- 1. A system which monitors a machine tool, in which automatically controlled operations take place in programmed steps and entail a movement of a member of the machine tool sensed by limit sensors: this system comprising a control device which controls the movable member and monitoring units for monitoring the function of individual operations and movements: wherein a first set of monitoring units in the form of visual indicators is connected to the control device for monitoring the programme steps, as hereinbefore defined, a second set of monitoring units in the form of visual indicators is connected to the

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (8)

**WARNING** start of CLMS field may overlap end of DESC **. used hereinafter are terms customarily used in digital technology. A "one" signal signifies a potential which is of the order of magnitude of the supply voltage, and a "zero" signal signifies a potential which corresponds approximately to earth potential. "One" signals must be present at the terminals 13 to 15 as initial conditions for the start of the programme. These "one" signals may be produced by switches which may be actuated by, for example, the lowering of a protective hood, the existance of an oil pressure, or further initial conditions for the operation of the machine. "One" signals are applied to all the inputs of the AND gate 11 by actuating the starting switch 10, whereby the output Q1 is set to a "one" signal by way of the set input of the flip-flop 12. Thus, the first programme step is attained, and the pilot lamp 34 is lit up by way of the flip-flop 19. The solenoid valve 17 is simultaneously actuated by way of the amplifier 16. The pilot lamp 38 lights up and the piston 21 of the cylinder 20 is set in motion.The pilot lamp 40, switched on by the limit switch 24 at the commencement of the machining operation, is extinguished, and the pilot lamp 41 lights up only when the marker 23 on the piston rod 22 has reached the second limit switch 25. However, the signal produced by the second limit switch 25 simultaneously resets the first flip-flop 12, and sets the flip-flop 29, whereby the pilot lamp 35 lights up. The solenoid 17 is switched off by the resetting of the first flip-flop 12, and the pilot lamp 38 is extinguished. The piston 21 returns to its start position, so that the pilot lamp 41 is extinguished in the first instance and the pilot lamp 40 lights up when the piston 21 reaches its end position.The flip-flop 44 is simultaneously set by way of the AND gate 27, whereby the pilot lamp 36 lights up. The two flip-flops 19, 29 remain in their set states. since a reset command has not been produced. Since a "one" signal is present at the complementary output of the flip-flop 31, the flip-flop 26 is set by way of the AND gate 45 simultaneously with the setting of the flip-flop 44. The solenoid 117 is thereby energized by way of the amplifier 116, whereby the pilot lamp 39 also lights up. Actuation of the solenoid valve 117 sets the piston 121 in motion in the cylinder 120. whereby the pilot lamp 42 is extinguished and the pilot lamp 43 lights up when the marker 123 reaches the limit switch 125. The latter operation in turn leads to the resetting of the third flip-flop 26 and the simultaneous setting of the sixth flip-flop 31, whereby the pilot lamp 37 lights up. Analogously to what has been described above, the return movement of the piston 121 into its normal position in the first instance leads to the extinguishing of the pilot lamp 43, and to the lighting-up of the pilot lamp 42 when the marker 123 reaches the limit switch 124. This signal of the limit switch 124 is the last programme step and leads to the resetting of the flipflops 19, 29, 44, 31 by way of the AND gate 32, whereby the pilot lamps 34 to 37 are extinguished. The initial state which existed at the commencement of the programme now exists again, and a fresh programme can be started by means of the switch 10. The arrangement described constitutes a very simple embodiment and is thus capable of optional modification. Thus, in automatic controls for complex machine tools, further fluid pressure control devices may be provided for actuating pistons in cylinders. When a plurality of hydraulic control devices are actuated simultaneously by one programme step, a plurality of pilot lamps, associated with the individual control devices, are correspondingly arranged in a vertical row below the particular pilot lamp for the programme. The associated movable members, particularly pistons and cylinders, then again have associated pilot lamps for the limit switches. Pilot lamps can also be provided for other switching operations during the course of the programme, for example, after introducing a pressure or when a workpiece passes a sensing device. The invention is not confined to the use of pilot lamps, and other types of indicators can be used in an analogous manner. If monitoring devices are used which have a greater power requirement, amplifiers might have to be connected to the inputs of the monitoring units. The monitoring units 34 to 37, in which, in the described arrangement, a further unit is actuated whenever the next programme step is reached, can also be provided without flip-flops 19, 29, 44, 31. In this case, a monitoring unit is actuated at each programme step and is extinguished at the next step. WHAT WE CLAIM IS:-

1. A system which monitors a machine tool, in which automatically controlled operations take place in programmed steps and entail a movement of a member of the machine tool sensed by limit sensors: this system comprising a control device which controls the movable member and monitoring units for monitoring the function of individual operations and movements: wherein a first set of monitoring units in the form of visual indicators is connected to the control device for monitoring the programme steps, as hereinbefore defined, a second set of monitoring units in the form of visual indicators is connected to the

control device for monitoring initiation of a machining operation effected by the movable member, and the first and second sets of monitoring units are associated so that they are actuated in a particular combina -tion when each machining step "(as hereinbefore defined) .is performed as required iby the machine programme, but not other, ;wise the units of each combination being chosen so that the performance of a given machining step is indicated by the positional relationship of the units in the combination.

2. A system as claimed in claim 1, wherein the association of the first set of monitoring units 'and 'the second monitoring sets of units entail a 'row 'and/or column like arrangement of the monitoring unites.

3. A system as claimed in claim 1 or 2, wherein a third set of monitoring units in 'the form of visual indicators is connected to the limit sensors of theimovable member and the second and third sets of monitoring units are associated so that they are actuated in a particular combination when the movable member assumes a predetermined limit position as required by the machine control, but not otherwise, the -units of each combination of the second and third sets of monitoring units being chosen so that the assumption of the predetermined limit position by the movable member is indicated by the positional relationship of the units in the combination.

4. A system as claimed in claim 3, wherein the associating of the third moni toring units and the second monitoring units entails a row- and / or column-like arrangement of the third and second monitoring units.

5. A system as claimed in any of the preceding claims, wherein electrical stores are connected in electrical series with the first monitoring units respectively.

6. A system as claimed in any of the preceding claims, wherein the monitoring units are in the form of pilot lamps.

7. A system for monitoring a machine tool, substantially as hereinbefore described with reference to the accompanying drawing.

8. A machine tool embodying a monitoring system according to any of the preceding claims.