GB2091819A - Lubrication monitoring system - Google Patents

Abstract

A monitoring system is described for a lubricating system which includes reciprocating valve spools or pistons. A switching means is arranged to open and close as the piston reciprocates and is connected to a timing circuit (52-58) which produces an alarm indication if the cycle of operation of the piston exceeds a predetermined duration. The monitoring system also includes an oil temperature alarm circuit (30-38). <IMAGE>

Description

SPECIFICATION Lubrication monitoring system The present invention relates to a lubrication monitoring system and is particularly applicable to a system of oil circulation designed for metering small quantities of oil to a large number of lubrication points from one central pumping station.

Such systems of oil circulation are used for example on paper mills where several lubrication points are grouped together and several such groups are supplied from one pumping unit. The metering is effected by means of a flow divider which consists of a block containing several valve spools which reciprocate automatically within respective cylinders by virtue internally provided interconnecting ports and in so doing meter discrete predetermined charges to the output ports. Such flow dividers are for example sold by the present Applicants and termed 'Polyshot' flow dividers.

Although the invention was particularly designed to operate with the polyshot flow dividers it will operate equally satisfactorily in any system where metering of discrete charges is effected by a piston or valve spool.

Hitherto in order to monitor failure of the metering unit is has been common to monitor the pressure in the supply line measured between two flow restrictors. In the event of a blockage a pressure rise would occur whilst in the event of a failure in the supply or pressure loss in the lubrication system the pressure would drop. A pressure gauge fitted with maximum and minimum adjustable contacts thus provided an alarm indication but this system did suffer from some limitations. When a polyshot block containing several blocks was monitored by a single pressure gauge, sticking of one of the pistons would produce only a small pressure change at the gauge which could not readily be detected bearing in mind that the maximum and minimum permissible pressures had to be determined in such a manner as to allow a margin for changes caused by variation in the viscosity of the oil.

The present invention seeks to provide a simple and reliable monitoring of the operation of an oil metering unit or flow divider of a lubrication system.

In accordance with the present invention a monitoring system for a lubrication system which includes continuously recipricating spools or pistons comprises switching means arranged to open and close in each cycle of a piston or valve spool and a timing circuit for determining when the duration of any cycle exceeds a preset limit.

In a particularly simple embodiment of the invention the switching means comprises a plug carrying a contact which closes a return path on making physical contact with the valve spool or piston.

Alternatively, however, any other method may be used to detect when the piston is at the end of its stroke. Thus depending on the nature of the material used for the cylinder block, magnetic sensing of the proximity of the end of the piston or spool can be effected without physical contact.

The timing circuit may conveniently be a retriggerable monostable multivibratorwhich relaxes into its stable state if not retriggered within a predetermined time.

Conveniently, the monitoring system additionally comprises temperature sensing means to provide an indication of the oil temperature exceeding a predetermined value.

The invention will now be described further, by way of example with reference to the accompanying drawings, in which: Figure 1 shows a section through a plug to be screwed into a polyshot block, Figure 2 is a view showing a connector fitted to the plug and incorporating a light emitting diode, Figure 3 is a detailed circuit diagram of the system for monitoring lubrication.

In Figure la a plug is shown in section to be screwed into a polyshot block. The plug consists of a brass threaded exterior portion 10 a central rod 12 made of stainless steel and provided at its outer end with a nipple 14, the rod being retained within the body 10 of the plug by means of an epoxy resin 16.

In Figure 2 there is shown a right angle push-on connector 20 with incorporates a light emitting diode 22 and is fitted to the end of a cable 24. The connector internally resembles connectors conventionally used on motor vehicle spark plugs.

When screwed into the polyshot block, a return path is established to earth each time the rod 12 contacts the end of the reciprocating piston. Referring now to the circuit of Figure 3, the block generally designated 30 constitutes a DC power supply having a transformer which reduces the AC supply to 12 volts, a fullwave rectifier bridge and a smoothing capacitor. It will be appreciated that the DC power supply circuit is of conventional design and it will not therefore be described in detail.

The DC voltage supply serves to power two circuits the first monitoring the temperatures of the lubricating fluid and the other monitoring the timing of the operation of the polyshot. The temperature monitoring circuit consists of a bead thermistor 32 connected as part of a wheat stone bridge the out of balance voltage of which is connected to the two inputs of an operational amplifier 34 which may for example be an integrated circuit such as an IC 741.

The output of the amplifier 34 drives a power transistor 36 which powers an alarm device 38 when the temperature of the thermistor 32 exceeds a predetermined value.

The timing circuit shown in Figure 3 includes a voltage regulator generally designated 40 which provides a stabilized power supply and includes as its active component a voltage regulating integrated circuit such as an IC 7812. The diode 22 mounted on the connector shown in Figure 2 is connected by way of the cable to the input of a pulse shaper 44 formed by four NOR circuits which together constitute an IC 4001. Two of the Nor gates are connected with a capacitor 46 and a resistor 48 to form a monostable multivibrator while the remaining two NOR gates constitute inverters. The function of the pulse shaper 44 is to produce a pulse of given duration regardless of the time during which the piston makes contact with the rod 12.In the preferred embodiment this duration is selected as 500 milii-seconds and a green light emitting diode 50 is energised for this duration in each cycle, its glimmer indicating proper operation of the flow divider block. An output from the first inverter is applied to a retriggerable monostable multivibrator formed by a 555 timer 52 the timing capacitor 54 of which is connected in parallel with a discharge transistor 56. Provided that negative going pulses from the pulse shaper 44 follow from one another within the time period of the mono stable multivibrator, the latter remains energised and a red light emitting diode 58 connected to one of the pins of the timer remains off.If on the other hand due to sticking or breakdown, no pulses are received from the timer then the monostable multivibrator 52 relaxes into its stable state simultaneously energising the red light emitting diode 58 to indicate the presence of a fault. In an installation monitoring a plurality of blocks, a single alarm and DC power supply is provided but a timer is required for each individual block of the polyshot. Thus in Figure 3 there are shown in dotted lines connections for further pulse shapers and mono-stable multivibrators to monitor the operation of the respective blocks.

As compared with the prior art monitoring system involving the monitoring of supply pressure, the present system provides several advantages some of which are listed below. The reliability of the system is improved owing to the absence of moving parts, the use of solid state electronics and the absence of delicate settings.

The system is inherently fail safe in that at the absence of a repetitive signal from the polyshot a fault warning is automatically provided. Visual indication is provided both on the central console of the monitoring system, and at the manifold of the flow distributor to provide immediate warning and identification of a slow cycling block.

Claims (6)

1. A monitoring system for a lubrication system which includes continuously reciprocating spools or pistons comprising switching means arranged to open and close in each cycle of the piston or valve spool and a timing circuit for determining when the duration of any cycle exceeds a preset limit.

2. A monitoring system as claimed in claim 1, wherein the switching means comprises a plug carrying a contact operative to close a return path on making physical contact with the valve spool or piston.

3. A monitoring system as claimed in claim 1,for use with a piston arranged within a non-magnetic valve block wherein the switching means comprises means for magnetically sensing the proximity of the end of the piston or spool.

4. A monitoring system as claimed in any preceding claim, wherein the timing circuit comprises a retriggerable monostable multivibrator operative to relax into its stable state if not retriggered within a predetermined time.

5. A monitoring system as claimed in any preceding claim further comprising temperature sensing means to provide an indication ofthetempera- ture of the lubricant exceeding a predetermined value.

6. A monitoring system constructed, arranged and adapted to operate substantially as hereinbefore described with reference to and as iliustrated in the accompanying drawings.