GB2032012A - Lubrication systems - Google Patents

Abstract

A lubrication system is arranged to lubricate a fast-running chain mounted on a chain dredger drum. The system includes a pump (2), and a feed duct (3) coupled to the pump (2). Two lubricant dispensers (4 and 5) receive lubricant from the duct (3). Each dispenser (4, 5) is operable in response to the pressure of the lubricant reaching a predetermined value to discharge a discrete volume of lubricant to the chain. An electromagnetically operable valve (6) is located in the feed duct downstream of the coupling point for the lubricant dispensers (4 and 5). A switch when periodically tripped by a member moving with the chain energises the electromagnetic valve (6) to block the feed duct (3) to enable the pressure in said duct (3) to exceed said predetermined value and so cause the dispensers (4 and 5) to discharge lubricant onto the chain, The quantity of lubricant dispensed is thus related to the movement of the chain. <IMAGE>

Description

SPECIFICATION Lubrication systems The present invention relates to lubrication systems.

According to the invention, there is provided a lubrication system for lubricating a fast-running chain mounted on a chain dredger drum, the system comprising a pump, a feed duct coupled to the pump, at least one lubricant dispenser coupled to the feed duct to receive lubricant from the duct and operable in response to the pressure of the lubricant reaching a predetermined value to discharge a discrete volume of lubricant to the chain, an electromagnetically operable valve located in the feed duct downstream of the coupling point for the lubricant dispenser, a switch closable to energize the electromagnetic valve, and at least one vane mountable on the dredger drum to trip the switch to close periodically and thereby cause the valve to block the feed duct to enable the pressure in said duct to exceed said predetermined value.

According to the invention, there is further provided a lubricant system including a pump, duct means for feeding lubricant from the pump around a loop back to the pump, at least one lubricant dispenser coupled to the duct means, the lubricant dispenser being operable to dispense a discrete quantity of lubricant each time the pressure of the lubricant applied to the dispenser exceeds a predetermined value, and a valve located in the duct means downstream of the point at which the dispenser is coupled to the duct means, the valve being operable periodically to block the duct means for a period sufficient to allow the pressure of lubricant upstream of the duct to build up to a level exceeding that of said predetermined value.

Lubrication systems embodying the invention will now be described, by way of example, with reference to the accompanying diagrammatic drawings in which: Figure 1 is a block diagram of one of the lubrication systems; Figure 2 is a side elevation of the pump unit of the system of Figure 1; Figure 3 is a plan view of the lubricant dispenser of the system of Figure 1 partly in section; Figure 4 is a side elevation of chain dredger drum for the chain to be lubricated; and Figure 5 is a block diagram of another of the lubrication systems.

Figure 1 shows a lubrication system for lubricating a fast-running chain 1. The system includes a pump 2 which is driven by a motor M, and a feed duct 3 feeding two lubricant dispensers 4 and 5 through a branch duct 7. The feed duct 3 also supplies a 2-way magnetic valve 6, having an outflow duct 8 which opens out into the oil supply tank 9. A suction pipe 10 supplies oil to the pump 2 from the tank 9.

The two-way magnetic valve 6 is switched ON by means of a no-contact limit switch 11, which is triggered by at least one metal vane 12 mounted on the chain dredger drum 13 (see Fig. 4).

The motor M, the pump 2 and the two-way magnetic valve 6 are assembled to form a composite unit (see Fig. 2). The pump 2 is a geared pump rated to produce a volume flow of 1,000 c.c. per minute at a discharge pressure of 35 bar and has a rated power of 180 W. The lubrication device is particularly suitable for the lubrication of escalator chains.

Each lubricant dispenser 4 and 5 (see Fig. 3) has a housing 14 accommodating at its upstream end a spring-loaded ball valve 1 5 and centrally a sealing valve 16 which is spring-biassed into sealing engagement with a valve seat 1 7. In operation oil in the duct 7 while only under slight pressure will seep around the ball 15 to fill the chamber between the ball 1 5 and the valve seat 17. When the oil in the duct is pressurised the ball 1 5 is displaced in a downstream direction driving the oil in the chamber to open the valve 16 and discharge itself from the dispenser. When the movement of the ball 1 5 is halted by a step in the chamber, the valve 1 6 is returned into sealing engagement with the seat 17 by its biasing spring.

When the pressure in the duct 7 drops the ball 1 5 will be displaced in the upstream direction by its spring and the chamber will refil with oil through seepage around the ball.

Lubrication of the chain 1 is effected by means of an oil that has an oil viscosity of 50 to 250 centi strokes at an operational temperature range of from Ooh and +500C.Theoil has good creep characteristics when sprayed onto the link pins of the chain. As long as the two-way magnetic valve 6 remains in the position represented on the drawing, the pump unit pumps oil freely around a loop including the oil supply tank 9. When the limit switch 11 is triggered by the metal vane 12, the two-way magnetic valve 6 is closed for a short period. During this short period pressure builds up to put into operation the lubrication process.

During successive revolutions of the chain 1 different link pins are lubricated, so that after a few revolutions all the links are attended to. To ensure that this occurs the number of metal vanes 12 and the number of lubricant dispensers are selected in accordance with the number of the links in the chain 1 and the number of the teeth on the chain dredger drum 13.

In the lubrication system shown in Figure 5 parts similar to those in Figure 2 are similarly referenced. As shown the lubricating system includes two non-retum valves 18, 1 9 and a manually-actuable two-way valve 20.

The pump used in preferably a geared pump. As these pumps are never completely sealed, there is a danger that air will be introduced into the ducting system or into the dispensers. To prevent the introduction of air, the non-return valve 1 8 is provided in the feed duct 3, between the pump and the duct 7. The second non-return valve 1 9 is incorporated into the feed duct 3 between the duct 7 and the two-way magnetic valve 6. The non-return valve 1 8 prevents the oil column falling on relaxation over the pump, while the second non-return valve 1 9 maintains the pressure at a value of about 0.5 bar when the valve 6 is open.

The manually-actuated two-way valve 20, can be operated to restrict the flow of oil through the duct 8. The pressure in the duct 7 is built up until it just unseats the spring-loaded ball 15 in each lubricant dispenser without driving it towards the valve seat 17. Each dispenser thus remains in this hovering phase. The 2-way magnetic valve in this case is fully open. After this pressure-release phase the manually-operated two-way valve is no longer required.

The lubrication systems described can be switched ON and OFF manually, for which purpose a switch box S is provided. In addition, provision can be made for automatic switching after a predetermined period to make servicing easier.

Fully automatic operation is also possible by means of a time relay on the pump. Thus a switching-off provision can be made based on a predetermined lubricating time, and also, if required, switching ON again after a selected interval.

Claims (11)

1. A lubrication system for lubricating a fastrunning chain mounted on a chain dredger drum, the system comprising a pump, a feed duct coupled to the pump, at least one lubricant dispenser coupled to the feed duct to receive lubricant from the duct and operable in response to the pressure of the lubricant reaching a predetermined value to discharge a discrete volume of lubricant to the chain, an electromagnetically operable valve located in the feed duct downstream of the coupling point for the lubricant dispenser, a switch closable to energise the electromagnetic valve, and at least one vane mountable on the dredger drum to trip the switch to close periodically and thereby cause the valve to block the feed duct to enable the pressure in said duct to exceed said predetermined value.

2. A lubrication system according to claim 1, and a drive system including an endless chain mounted on a chain dredger drum, wherein the lubrication system includes a plurality of lubricant dispensers and vanes, the number of dispensers and vanes being selected in accordance with the number of links in the chain and the number of teeth of the chain dredger drum, such that lubricant is dispensed to different sections of the chain during successive revolutions of the chain.

3. A lubrication system according to claim 1 or to claim 2, including a time relay for switching OFF the pump after a predetermined period of operation.

4. A lubrication system according to any one of claims 1 to 3, wherein the or each lubricant dispenser includes an elongate chamber housing a ball valve, the ball being movable between the opposite ends of a section of the chamber having a cross-section substantially equal to that of the ball, biasing means for biasing the ball towards one end of the chamber, and a one way valve located at the other end of the chamber to allow the passage of lubricant from the chamber, the said one end of the chamber being arranged to receive lubricant from the feed duct whereby when the pressure reaches said predetermined value it exceeds the bias of the spring and forces the ball valve to said other end of the chamber.

5. A lubrication system according to any one of claims 1 to 4, wherein the pump is a geared pump and including a non-retum valve located in the feed duct between the pump and the point in the duct at which the lubricant dispenser is coupled.

6. A lubrication system according to claim 5, including a second non-retum valve located in the feed duct between the said point and the electromagnetically operable valve.

7. A lubrication system according to claim 6, including a manually operable valve located in the duct downstream of the electromagnetically operable valve.

8. A lubrication system including a pump, duct means for feeding lubricant from the pump around a loop back to the pump, at least one lubricant dispenser coupled to the duct means, the lubricant dispenser being operable to dispense a discrete quantity of lubricant each time the pressure of the lubricant applied to the dispenser exceeds a predetermined value, and a valve located in the duct means downstream of the point at which the dispenser is coupled to the duct means, the valve being operable periodically to block the duct means for a period sufficient to allow the pressure of lubricant upstream of the duct to build up to a level exceeding that of said predetermined value.

9. A system according to claim 8, wherein the valve comprises an electromagnetically operable valve arranged to be energised at intervals having a duration related to the speed of the subject to be lubricated.

10. A lubrication system substantially as hereinbefore described with reference to Figures 1 to 4 of the accompanying drawings.

11. A lubrication system substantially as hereinbefore described with reference to Figure 5 of the accompanying drawings.