GB2046371A - Lubricating system - Google Patents

Abstract

A method of and system for controlling the lubrication of a power press or like machine tool in which shots of lubricant are delivered to a plurality of lubrication stations at intervals determined by a timer (16) operating through a single shot circuit (20), lubrication solenoid (14) and oil pump (12) when the press or machine tool is running light and the frequency of the shots is increased by a load signal generating circuit having an input derived from a switch (17) operated by a cam on the crankshaft of the press or machine tool, and feeding input pulses to the single shot circuit through a counter (27) operating as a divider. A fault detector (31) is activated to stop the press or machine tool if a predetermined cycle count occurs without a load signal generated from switch (17) having been delivered to the single shot circuit (20) after the predetermined number of cycles selected by selector unit (28). At the start of operation motor start switch (18) feeds a signal to the single shot circuit (20) at or before the press or machine tool starts. <IMAGE>

Description

SPECIFICATION Improvements relating to methods of and systems for lubrication This invention relates to a method of lubrication and to a lubrication system. The method and the system are intended for use in association with apparatus which requires to be lubricated (hereinafter called the main apparatus) and which has a plurality of lubrication stations and delivery means for delivering lubricant thereto in response to a drive signal.

Each of the lubrication stations may be defined by a pair of associated surfaces which, during running of the apparatus, move relatively to each other and would be in contact were it not for the presence of an intervening film of lubricant required to be maintained between the surfaces. One of the members may rotate relatively to the other or may be moved in a translatory manner relative to the other. The delivery means for delivering lubricant to such a lubricating station may commonly comprise a bore, pipe, channel or other duct having a delivery end situated at or near an interfacial space defined between the surfaces and to which lubricant is required to be delivered, and connected or communicating at its other end with a source of lubricant.Such source may be a pump providing force feed of lubricant along the duct, or alternatively it may be a reservoir for lubricant, delivery of which is controlled by valve means for gravitational flow along the duct. It would be within the scope of the invention, however, were the delivery means to comprise a reservoir for lubricant situated locally, i.e. adjacent to the lubricating station concerned, and for there to be associated with such reservoir either a pump or a valve in the case where gravitational delivery of the lubricant is adequate.

The invention has been developed primarily in relation to the lubrication requirements of a power press or like machine tool, such as a press brake or guillotine. Such power press or like machine tool normally includes a flywheel acting as a power storage means and when a drive motorforthe press or like machine tool is switched on the flywheel is driven continuously. This represents a running condition for the press or like machine tool but one in which it is not under load. Such a press or like machine tool normally includes tool carrying members which may respectively comprise a bed or work table and a slide or ram movable relatively towards and away from each other under power derived from the flywheel and applied through the intermediary of mechanism for converting rotary to reciprocating motion.In most cases one of the tool carrying members, for example the work table or bed, is stationary, and the other tool carrying member, namely the slide or ram, is movable in a translatory manner in guideways secured to or forming part of the body or supporting structure of the press or like machine tool. Transmission of such motion from the flywheel is ordinarily effected through a clutch which is disengaged when the power press or like machine tool is running but is not under load.When the clutch is engaged and relative movement of the tool carrying members takes place with consequent engagement of a workpiece between the tools at the inner end of the stroke of the slide or ram in the guideways, the mechanism for converting rotary to reciprocating motion which formerly was stationary is then placed in motion and under load and the lubrication stations provided at appropriate places for lubrication of these parts of the press or like machine tool require to have lubricant delivered thereto.Under the loaded condition of operation the clutch, flywheel, and transmission means connecting the drive motor to the flywheel (which may comprise gear elements in mesh with each other) are also placed under greater load, and especially in the case of continuous operation under load, would require more lubricant to be supplied than formerly, it being understood that some lubricant would require to be supplied to lubrication stations of these parts of the press or like machine tool when running in the unloaded condition.

Various lubrication methods and systems have been adopted up to the present time. Thus, lubricant may be supplied to a lubricating station by means of an oil reservoir and a wick. One disadvantage of this arrangement is that it requires periodic attendance by personnel to ensure that the oil reservoir is filled to the correct level. Another system employed where lubrication is by way of grease is the provision of a grease nipple or a cup including a piston or screw-down cap, grease being caused to flow along a duct through the lubrication station whenever a grease gun is applied to force grease into the nipple or when the piston is operated or the cap screwed down. Again, a disadvantage of this system is that is requires periodic attention by personnel.Moreover, if it is inexpertly operated, an excess of lubricant delivered to the lubricating station is expelled from between the surfaces so as possibly to contaminate parts of the press or like machine tool which are required to be maintained free from lubricant. In yet another system a lubricant pump is driven continuously so long as the press or like machine tool is running. Such a system delivers insufficient lubricant when the press or like machine tool is operating under load, but delivers excess lubricant to certain of the lubrication stations when the press or like machine tool is running but is not under load.After a period of idleness, for example when a press or machine tool is standing over night, it is also highly desirable that lubricant be delivered to the lubrication stations, or such of them as may have become drained of lubricant during the period of idleness, before the relatively movable surfaces at these lubrication stations are actually set in motion.

The primary object of the present invention is to provide a new or improved method of lubrication and lubrication system by means of which one or more of these disadvantages occurring in the lubrication of power presses or like machine tools may be overcome or reduced. However, it will be understood that similar or analogous problems may arise in other forms of main apparatus, especially those which are operated sometimes in an unloaded running condition and sometimes in a loaded running condition, in the latter of which parts which were not formerly movable relatively to each other are set in relative motion and hence require lubrication at lubrication stations applicable to these parts.

According to one aspect the invention resides in a method of controlling lubrication of a main apparatus having a plurality of lubricating stations and delivery means for delivering lubricant thereto, said method comprising : a. feeding lubricant to said lubricating stations at a first rate when the main apparatus is running but is not under load, b. generating a signal (herein called the load input signal) in response to operation of the main apparatus under load, c. increasing the feed rate of the lubricant to a second rate higher than the first rate in response to incidence of said load input signal.

It will be understood that the increase in the feed rate of lubricant may arise from the fact that all the lubricating stations are fed with lubricant when the main apparatus is running but is not under load and an increase in the rate of feed of lubricant takes place in respect of all of the lubricating stations. Alternatively, the increased rate of feed may be confined to certain of the lubricating stations only, for example those at which there is no relative motion between the surfaces defining the lubricating station until the main apparatus is placed under load.

Alternatively, lubricant may not be fed to the last mentioned lubricating stations at all when the main apparatus is running but is not under load, and may be fed to these stations (thereby increasing the overall feed rate of lubricant) in response to generation of the load input signal.

Preferably the feeding of the lubricant to said lubricating stations when the main apparatus is running, but is not under load, is controlled by generating a signal (herein called the time signal) repeated at intervals of time, and feeding a shot of lubricant to each of said stations in response to each time signal.

Preferably also the method involves the generation of a start-up signal generated by an operation carried out to start the main apparatus running, and a shot of lubricant is delivered to some or all of said lubricating stations in response to said start-up signal.

From a further aspect the invention resides in the provision of a lubrication control system for, or in association with, a main apparatus having a plurality of lubrication stations and having delivery means for delivering lubricant to said stations in response to a drive signal, said control system comprising means responsive for putting the main apparatus into a running condition irrespective of load, for generating a succession of drive signals for application to said delivery means, and means responsive to the running of the main apparatus under load for increasing the number of drive signals occurring in a given time interval.

In a preferred arrangement according to the invention the control system comprises: a. time signal generating means for generating an input signal (herein called the time input signal) repeated as a function of the elapse of time while the main apparatus is running irrespective of load, b. load signal generating means for generating a further input signal (herein called the load input signal) which is repeated in dependence upon the main apparatus running under load, c. electrical conduit means connected to said time signal and load signal generating means to receive said time and load signals therefrom, and including means responsive to said signals to provide a drive signal for said delivery means and which is repeated more or less frequently as the frequency of the load signal rises or falls respectively, but which continues to be repeated at a frequency determined by the time signal while the main apparatus is running not under load.

Preferably also the lubrication control system includes start-up signal generating means for generating a start-up signal in response to performance of an operation for starting the main apparatus running, and said electrical circuit means is connected to said start-up signal generating means and includes means responsive to said start-up signal to generate a drive signal for said delivery means at a time before, or just as, the relatively moving surfaces at the lubrication station started relative movement.

It will be appreciated that if the start-up signal is generated concurrently with switching on of an electrical drive motorforthe main apparatus, the mechanical inertia of the moving parts may be such that there is no relative movement, or relatively movement at only a very slow speed, at the time at which a shot of lubricant will be delivered to the lubricating stations in response to the drive signal produced in consequence of the start-up signal.

The invention will now be described, by way of example, with reference to the accompanying drawings wherein: Figure lisa block schematic circuit diagram illustrating an embodiment of the lubrication system in accordance with the invention for carrying out the method thereof; Figure 2 is a circuit diagram of the system illustrated in Figure 1; Figure 3 is a view in front elevation of one embodiment of power press incorporating the lubrication control system of Figures 1 and 2.

The lubrication control system illustrated is intended to be applied to a power press or like machine tool which, as shown generally in Figure 3, comprises a body or supporting structure 1 having a bed or table 2 forming one of the tool carrying members and having a slide or ram 3 mounted in guideways 4 for reciprocatory movement towards and away from the bed or table. A flywheel 5 forming a power storage member is driven from an electrical motor through the intermediary of any suitable transmission means.

Such transmission means may comprise a belt drive direct from a motor pulley to the flywheel itself which is grooved peripherally to receive the belts, or alternatively such transmission means may include toothed gearing forming step-down gearbox having an input shaft driven from the motor and an output shaft coupled by a belt drive to the flywheel. The slide or ram 3 is reciprocated by means of a mechanism comprising a connecting rod 6 connected at its lower end to the slide or ram and at its upper end to a crank or eccentric 7 provided on the crankshaft 8 driven through the intermediary of a clutch, the driving member of which forms or is connected to the flywheel.

Lubrication stations would ordinarily be provided for all the shaft bearings, the meshing gearing, and the joints afforded in and by the connecting rod between the slide or ram and the crank pin or eccentric, and the surfaces of the slide or ram which cooperate with guide surfaces of the guideways. Typically such lubrication stations may be provided as follows: Crankshaft bearings 8a-8d (four stations) Slides 4a-4d (four stations) Connecting rod 6a (cap) Connecting rod 6b (body) Connecting rod 6c (ball pin) Flywheel bearing 5a In Figure 1 full lines represent electrical connections, chain lines mechanical connections, and dashed lines hydraulic connections.In this Figure, for the purposes of simplification only, it is assumed that the lubrication stations would be served by delivery means comprising a distributor chamber 10 connected by five ducts liato Ile to the respective lubrication stations 4a-4d; 5a; 6a; 6b; 6c; and 8a-8d. Further, the delivery means comprises an oil pump 12 connected by a duct 13 to the distributor chamber and itself operated by a solenoid 14, the armature of which is connected by a mechanical link or connection 15 to the operating member of the pump.Movement of the armature of the solenoid from an unoperated position to an operated position in response to receipt of a driving signal at the winding of the solenoid effects one stroke of the pump and produces feed of one shot of lubricant along each of the ducts 11 a to lie.

Controlling input signals which produce driving signals for the solenoid are derived from three sources, namely a timer 16 which generates time signals at predetermined intervals of time, a cam switch 17 operated in timed relation with operation of the press, for example by a cam on the crankshaft of the press.This generates load signals at a repetition frequency determined by the speed of rotation of the crankshaft typically providing 12 to 250 strokes per minute of the slide or ram, and a motor switch 18 which, in combination with a main isolator switch (not shown), operates to generate a start-up signal when the drive motor of the press is first switched on for each operational period of the press. "Operational period" means a period beginning with switch-on of electrical power by means of the main isolator switch controlling current supply to the motor supply circuit and ending with switch-off of electrical power to the motor supply circuit which itself includes switch means for switching the motor on and off during such period.It will thus be understood that during an operational period the motor itself may be switched on and off any number of times but it is only the first switch on involving closure of the main isolator switch followed by closure of the switch means of the motor supply circuit at the beginning of the operational period which produces a start-up signal. Another start-up signal is not generated until afterthe main isolator switch has been returned to its off position and again closed.

The timer 16 has associated therewith a time selector 19 to enable the repetition frequency of the time signals to be manually preset. These signals are fed to a single shot circuit 20 which produces a driving signal in the form of a square pulse to the lubrication solenoid 14, thereby producing one shot of lubricant in each of the ducts 1 la to 1 ideas aforesaid.

A duct 21 connected between the distributor chamber and a pressure switch 22 operates the latter in consequence of the increased pressure generated in the distributor chamber by operation of the oil pump 12 and feeds a reset signal via line 23 and filter 24 to a reset circuit 25 which resets the timer 16.

Load signals generated by the cam switch 17 are passed through a filter 26 and initiate operation of a counter 27 (acting as a divider so far as the load signals are concerned). A counter selector 28 includes selector means to enable the division ratio to be adjusted to any of a plurality of settings and the resultant output signal is fed via lines 29 and 30 to the single shot circuit 20 producing a further shot of lubricant to each of the lubrication stations. The counter 27 is reset by the pressure switch and reset circuit 25 in response to the establishment of pressure in the distributor 10 to deliver each shot of lubricant.

Associated with the counter 27 and counter selecter 28 is a fault detector 31 developing a stop signal to bring the press to a stop (at its top dead centre position) in the event of an output signal not having been delivered along the line 30 to the single shot circuit 20 after a predetermined number of revolutions of the crankshaft (this number being the quotient produced by operation of the counter (divider) 27). A fault signal is delivered along line 33 to the appropriate element of a control system for disengaging the clutch and applying the brake of the press.

The start-up signal generated in the motor start switch 18 is fed through a filter 34to a single shot circuit 35 which includes an input latch (not separately shown) and this circuit 35 delivers an output to the single shot circuit 20 for energising solenoid 14 and operating oil pump 12 for the first switch-on of power to the drive motor in a period of operation as above referred to.

Referring now to Figure 2, power supply is derived from a circuit providing a 24 volt d.c. output and a 12 volt regulated output. In Figure 2 terminals marked T1 are supplied from the 24 volt d.c. output and terminals marked TR from the 12 volt regulated output and terminal TO is connected to a common negative for the supply circuit.

The components of Figure 2 which perform the functions shown in the numbered blocks or boxes are enclosed in Figure 2 by correspondingly numbered broken lines boxes.

Referring to the timer circuit 16, this comprises an integrated circuit unit IC2 having four inputs a, b, c, d connected by respective lines to the time selector 19. The time selector comprises normally open manually closeable switches Sla to Sld connected in series with lines applying the stabilised 12 volt supply to each of these terminals from the upper ends of respective resistors Rla to Rid.

The integrated circuit unit lC2 and the components R2, C1, R3 connected to terminals e, f, g thereof provide a predetermined high frequency, typically 900 Hz which is divided according to the setting of the switches Sla to So do provide a time signal at the "decode" terminal which is a predetermined division ofthe fundamental frequency.

The switches could be set to provide time signals at a very wide range of time intervals of from 2.5 seconds up to approximately 3 hours but a typical selection of time intervals would be: Hours Minutes Seconds 0 10 40 0 21 20 0 42 40 1 25 20 The time signal is fed from terminal h via lines 40 and 41 to input c of an OR gate IC5a then by line 42 and inverter IC6d, to the trigger terminal a of integrated circuit unit IC8 incorported in the single shot circuit 20.

The output from IC8 at terminal c is fed via line 44to a driver 45 and from there on line 46 to solenoid 14, the other terminal of which is connected to TO. The output signal is a pulse the length of which is determined by the values of capacitor C4 and resistor R8. The latter may be variable, preferably being in the form of a pre-set rather than operator's control.

A test circuit comprising switch S2 and resistor R4 is connected to input terminal kofthe unit IC2 to provide for generation of a time pulse in response to manual closure ofthe switch S2.

Referring now to the load signal, this is generated by the cam switch 17, as previously mentioned, and fed along line 47 to filter unit 26 comprising resistors R5a, R6a, R7a and capacitor C2a, the filter having the function of suppressing unwanted signals arising from electrical "noise".

Output line 48 from the filter is connected to the "clock" input a of an integrated circuit counter unit IC1 used as a time divider.

This unit provides outputs as follows, namely at terminal b a square wave having a positive-going wave front at a count of 256 load input pulses and a negative-going wave front at a count of 512 pulses and so, the terminal b thus alternating between a low (0) and a high (1) every 256 pulses.

The output signals developed at terminals c, d, and e are of the same form alternating between 0 and 1 levels respectively after 512, 1024 and 2048 load input pulses.

AND gates IC3a and IC3b are connected to the output terminals b. c and d of unit IC1 in a configuration such as to provide change from a '0' state to a '1' state in terminals tl,t2, t3, t4 and t5 of the counter selector 28 after 512, 1024, 1538, 2048 and 2560 load input pulses respectively. The counter selector includes a manually settable switch S3 which enables a signal from any one of terminals tl to t5 to be fed onto lines 49 and 50.

The line 49 is connected to input terminal a of OR gate unit IC5a, and consequently as soon as terminal tl (or any other selected terminal t2 to t5) presents a '1' state, the trigger terminal a of IC8 is enabled via lines 42, inverter IC6d and line 43 to produce a driver pulse.

The driver pulse will give rise to operation of the solenoid 14 and the oil pressure pulse resulting will give rise to generation of a reset pulse at oil pressure switch 22.

This reset pulse is fed to filter circuit 34 having resistors and a capacitor R5c, R6c, R7c and C2c corresponding to those of filter unit 26, and thence via line 52 to terminal b of OR gate unit IC5b in reset circuit 25. Line 53 connected to the output terminal ddelivers a reset pulse to the reset terminal fof integrated circuit unit IC1 so that this starts counting again from the reset condition.

If, however, a '1' state is not achieved at terminal t1 after incidence of load pulse No.512, fault detector circuit 31 operates to provide a fault signal to clutch top stop terminal T2. The fault detector circuit comprises an AND gate unit IC3c which at its two input terminals a, b connected respectively to lines 50 and 51 receives signals from the slider of switch S3 (for example resting on terminal t1) and terminal b of IC1.

If the '1' state has not been developed at tl after incidence of pulse No.512, then at pulse No.768 both terminals or IC3e will be at '0' and the output of IC3 will be '0'. Amplifier IC9a will be changed from a high (1) output to a low (0) output and the incidence of a '0' state at terminal T2 will bring the top stop system into operation.

If any one of terminals t2, t3, t4 or t5 were selected, the same state would be achieved after load input pulse counts of 1280, 1794, 2304 and 2816, thereby giving rise to generation of a fault signal terminal T2. If, however, output pulses had been developed at terminals t2, t3, t4, t5 respectively at load input pulse counts of 1024, 1538,2048,2560, then a reset signal would have been generated at oil pressure switch 22 before a corresponding fault signal could be developed, and counter IC1 would have been reset (this being the normal manner of operation).

Generation of a driving pulse at the output terminal c of integrated circuit unit IC8 of the single shot circuit 20 produces an output on line 54 connected to an inhibit terminal ion the integrated circuit unit IC2 of the timer 16. This prevents the delivery of a time pulse from unit IC2 immediately following on a load pulse derived from IC1 before IC2 has become reset by that lubricant pressure pulse developed in consequence of the load pulse of IC1 and transmitted from the oil pressure switch 22 as an electrical pulse to terminal b of OR unit It56.

Referring now to the reset circuit 25, this includes a pulse generating circuit comprising diode D1, resistor R8, zener diode ZD1, capacitor C3 energised as shown from the regulated 12 volt supply and providing a pulse fed from ZD1 through inverter IC6e to terminal a of OR gate unit IC5b, the output of which resets both IC2 in the timer circuit 16 and IC1 in the counter circuit 27. Timer unit IC8 in the one shot circuit 20 is also reset by the same pulse fed through inverters IC6a and IC6b to terminal a of unit IC8. Two inverters are used in series because unit IC8 is of a type which requires a negative-going edge to reset it, and this together with additional squaring of the edge, is achieved by the series inverter arrangement.

Closure of the motor start switch 18 which is in the drive motor supply circuit (not shown) provides at the beginning of each period of operation of the press a start-up signal producing a feed of one shot of lubricant concurrently with the start of the power press or, having regard to the mechanical inertia of the latter, just before the power press starts. This start-up signal caused by the closure of switch 18 is fed through a filter circuit 34 similar to circuits 24 and 26 and comprising resistors R5b, R6b, R7b and capacitor C2b.Closure produces a high (1) output which is fed to a NAND latch comprising NAND units IC4a, IC4b,1C4c. The output from the NAND latch appears as a 1 at terminal a of an integrated circuit unit IC7 which is a monostable unit generating a positive-going squared output pulse at terminal b. This output pulse is fed to input terminal b of OR unit IC5a and then through inverter IC6b to the trigger terminal a, the timer IC8 producing the shot of lubricant already mentioned.

The NAND latch is so arranged as to prevent any further positive-going pulses, changing terminal a of IC7 from a '0' state to a '1' state, occurring during the ensuing operation or period, even though the motor start switch 18 may be opened and closed. The conditions of operation are illustrated in the Table below.

Input conditions NAND IC4a NAND IC4b NAND lC4c IC7 a b c a b c a b c a Isolator off 0 0 0 0 0 0 0 0 0 0 Isolator on 0 0 1 1 1 0 0 0 1 0 C3 discharged Isolator on 0 0 1 1 1 0 0 1 1 0 (NAND C3 charged (LATCH (SET FOR (CHANGE 18 closed 1 1 0 0 0 1 1 1 0 1 (NAND (LATCH 18 opened 0 0 1 1 0 1 1 1 0 1 (STABLE 18 re-closed 1 1 0 0 0 1 1 1 0 1 (AFTER (CHANGE Isolator off 0 0 0 0 0 0 0 0 0 0 C3 discharged The NAND latch units each require two '0' states at their inputs a and b before a '1' state will appear at the output c. If this condition is achieved the '1' state at c will revert to '0' only if both input terminals become '1'.

Thus, when input terminal b of IC4b becomes '0' whilst input a of IC4b is also '0' as a result of closure of motor switch 18, then a permanent '1' is held at output c of IC4b despite possible opening and closing of switch 18 during the continuance of the operational period, and the NAND latch thus provides a stable condition which can be changed only by opening of the isolator.

When the isolator is turned on at the beginning of the next operational period input b of IC4e temporarily has a '0' (until capacitor C3 charges), thereby establishing a '1' state at input b of IC4b until the first closure of switch 18.

According to the working conditions of the press, the time selector circuit 19, that is switches Sla to S1 d, would be set to provide an output pulse at the "decode" terminal g of the timer IC2 at intervals which typically range from about ten minutes to about ninety minutes. When the press is in operation the pulses generated on line 49 connected to the slider of the count selector will of course depend upon the number of working strokes per minute but typically would provide shots-of lubrication at a rather higher frequency typically at intervals of 2 to 10 minutes.

The oil pump may comprise a piston operating -in a cylinder and movable in one direction under pneumatic pressure to stress a spring. When the pneumatic pressure is released the spring may operate to move the piston in the opposite direction and at the same time expel a shot of lubricating fluid from the cylinder. Solenoid 14 may have its armature connected to a valve in a pneumatic circuit and controlling the admission of airto move the piston against the spring loading.

If it were desired to provide for delivery of lubricant selectively to the lubrication stations, those which serve parts of the press which are continuously in motion when the motor is switched on may be connected by ducts to one distributor while those which serve lubrication stations of parts of the press which are in operation only when the press is under load, i.e. the clutch engaged may be connected by ducts to a second distributor. The two distributors would be connected to respective oil pumps, and these in turn would be connected to respective solenoids such as 14. The channel for handling load pulses and the channel for handling time pulses would then terminate in respective single shot circuits and output drivers such as 20 connected to respective solenoids but both of these single shot circuits receive the start-up pulse.

Claims (13)

1. A method of controlling lubrication of a main apparatus having a plurality of lubricating stations and delivery means for delivering lubricant thereto, said method comprising: a. feeding lubricant to said lubricating stations at a first rate when the main apparatus is running but is not under load, b. generating a signal (herein called the load input signal) in response to operation of the main apparatus under load, c. increasing the feed rate of the lubricant to a second rate higher than the first rate in response to incidence of said load input signal.

2. A method according to claim 1 wherein the feeding of the lubricant to said lubricating stations when the main apparatus is running, but is not under load, is controlled by generating a signal (herein called the time signal) repeated at intervals of time, and feeding a shot of lubricant to each of said stations in response to each time signal.

3. A method according to either of claims 1 and 2 wherein a start-up signal is generated by an operation carried out to start the main apparatus running, and a shot of lubricant is delivered to some or all of said lubricating stations in response to said start-up signal.

4. A method according to any one of the preceding claims including the step of generating a stop signal for bringing the main apparatus out of operation if operation of the main apparatus under load has not resulted in an increase in the feed rate of lubricant after a predetermined stage from start of operation under load.

5. A method according to claim 4 including the step of counting or determining the number of cycles of operation of the main apparatus occurring without increase in the feed rate of lubricant and generating the stop signal when a predetermined value of such number is reached.

6. A lubrication control system for, or in association with, a main apparatus having a plurality of lubrication stations and having delivery means for delivering lubricant to said stations in response to a drive signal, said control system comprising means responsive for putting the main apparatus into a running condition irrespective of load, for generating a succession of drive signals for application to said delivery means, and means responsive to the running of the main apparatus under load for increasing the number of drive signals occurring in a given time interval.

7. A control system according to claim 6 wherein the control system comprises: a. time signal generating means for generating an input signal (herein called the time input signal) repeated as a function of the elapse of time while the main apparatus is running irrespective of load, b. load signal generating means for generating a further input signal (herein called tbe load input signal) which is repeated in dependence upon the main apparatus running under load, c. electrical circuit means connected to said time signal and load signal generating means to receive said time and load signals therefrom, and including means responsive to said signals to provide a drive signal for said delivery means and which is repeated more or less frequently as the frequency of the load signal rises or falls respectively, but which continues to be repeated at a frequency determined by the time signal while the main apparatus is running not under load.

8. A control system according to either of claims 6 and 7 wherein the system includes start-up signal generating means for generating a start-up signal in response to performance of an operation for starting the main apparatus running, and said electrical circuit means is connected to said start-up signal generating means and includes means responsive to said start-up signal to generate a drive signal for said delivery means at a time before, or just as, the relatively moving surfaces at the lubrication station started relative movement.

9. A control system according to any one of claims 6 to 8 wherein there is further included means for generating a stop signal for bringing the main apparatus out of operation in response to failure to increase the number of drive signals occurring in a given period at a predetermined state after the main apparatus has started to operate under load.

10. A control system according to claim 9 as appendant to claim 7 wherein the electrical circuit means includes counting means for counting the number of cycles of operation of the main apparatus occurring under load, means for sensing when a predetermined number of such cycles has been reached without operation of the delivery means by a drive signal generated in response to incidence of a load signal.

11. A method of controlling lubrication of a main apparatus substantially as herein described with reference to and as illustrated by Figures 1 and 2.

12. A lubrication control system substantially as herein described with reference to and as shown in Figures 1 and 2 of the accompanying drawings.

13. A power press or like machine.tool having a lubrication control system as claimed in any one of the preceding claims.