GB2086545A

GB2086545A - A metering valve for a lubricant or a similar medium

Info

Publication number: GB2086545A
Application number: GB8133070A
Authority: GB
Original assignee: Safematic Ltd Oy
Current assignee: John Crane Safematic Oy
Priority date: 1980-11-03
Filing date: 1981-11-03
Publication date: 1982-05-12
Also published as: ES8207316A1; NO152666B; SE8106261L; GB2086545B; DE3141965A1; NO152666C; ES506787A0; FI60433C; FI60433B; DE3141965C2; SE448776B; NO813699L

Abstract

The metering valve prevents impurities contained in the medium to be supplied from clogging a throttling point (17) provided in the valve and from distorting the desired volumetric flow set in the valve. Two pistons (3,8) are mounted axially displaceably in a frame (1) of the metering valve to form a throttling point together with an adjustable throttling element (14) fastened in the frame. As the pressure in the supply pipe rises, causing the pistons to be displaced towards the throttling element, there is an open flow connection from an inlet (4) of the valve to an outlet (5) through the throttling point, but as the pistons are displaced away from the throttling element, when the supply pipe pressure falls, one (8) of the pistons closes the inlet and the other piston (3) presses a medium dose (12) from chamber 2A through the throttling point. As said other piston (3) is displaced away from the throttling means, the throttling point is widened so that said medium dose rinses off the impurities accumulated in the throttling point. In this way a self-cleaning, continuously feeding metering valve provided with an adjustable throttling point is provided. <IMAGE>

Description

SPECIFICATION A metering valve for a lubricant or a similar medium The present invention relates to a metering valve for a lubricant or a similar medium comprising - a frame, - a cylinder formed in said frame and communicating with an inlet and an outlet for said medium provided in said frame, - a metering piston axially displaceable in said cylinder, said piston separating said inlet and said outlet from each other and being provided with a connecting channel interconnecting the cylinder spaces separated by said piston1 - a charging piston axially displaceable in said frame and permitting flow of medium from said inlet to said cylinder when said inlet is pressurized, said charging piston opening said connecting channel in the metering piston when the metering piston has been displaced due to the action of the medium to the cylinder space facing said outlet and maintaining said connecting channel open as long as said inlet is pressurized and, in addition, while said charging piston is carrying out a movement in the opposite direction to the cylinder space facing said inlet as the pressure in said inlet is decreasing, and - a flow throttling point provided in said frame in the flow path of said medium for controlling the volumetric flow of said medium.

Metering valves of this type are previously known which are used for feeding a single dose of lubricant from a supply conduit to the object to be lubricated.

The operating principle of the metering valve involves an automatic displacement of both pistons in the metering direction as the pressure in the supply conduit increases and in the opposite charging direction as the pressure in the supply conduit decreases. As the pistons are displaced in the metering direction, the metering piston presses a dose of lubricant in front thereof through the outlet connection of the valve to the object to be lubricated while the charging piston allows a new dose of lubricant to enter behind the metering piston through the inlet connection.As the pistons are displaced in the charging direction, the charging piston closes the inlet connection while the metering valve presses a new dose of lubricant from behind the metering piston in front thereof ready for being pressed into the outlet connection of the valve when the supply conduit next time is pressurized.

When the object to be lubricated requires a relatively large lubrication dose, the metering valve will in a corresponding manner be rather large-sized.

Therefore it is previously known to arrange the pistons to cooperate so that after the pistons have been displaced in the metering direction, there will be an open connection from the inlet connection of the valve to the outlet connection of the valve through the connecting channel in the metering piston so that the valve will continuously feed lubricant from the inlet connection to the outlet connection as long as the feed conduit is pressurized.

In order to be able to control the volumetric flow of lubricant flowing continuously through the metering valve, it is previously known to provide in the metering valve an adjustable throttling point in the flow path of lubricant. However, such adjustable metering valves suffer from the disadvantage that impurities contained in the flowing medium cause malfunctions. It has namely proved that the impurities tend to accumulate at the throttling point and in this way continuously reduce the volumetric flow quantity and, in the end, clog the entire valve. The known metering valves provided with a possibility to adjust the volumetric flow have therefore required special external cleaning steps to be carried out periodically, which has required partial dismounting of the metering valve.Such a risk of clogging and the need for cleaning is particularly great when waste oil containing plenty of impurities is used as the medium to be metered.

The object of the present invention is to provide a metering valve which eliminates the abovementioned disadvantages and permits a continuous flow of the medium to be metered through the metering valve without any risk of clogging and without any need for external cleaning. This object is achieved by means of a metering valve according to the invention which is characterized - in that said frame is provided with a throttling element which together with said metering piston forms said flow throttling point when said metering piston is located in the cylinder space facing said outlet.

The invention is based on the idea that the throttling point required for the adjustment of the volumetric flow of the medium to be metered is arranged at such a point of the metering valve where the throttling entirely ceases or is considerably reduced at the final stage of metering and through which the medium dose retained by the charging piston is transferred from a position behind the metering piston to a position in front thereof. Due to such an arrangement, said medium dose is caused to rinse along with it impurities accumulated at the throttling point away from said throttling point which, during the rinsing step, is widened or enlarged at least to such an extent that there is enough space for the discharge of the impurities from the throttling point.For this purpose, the displaceable metering piston is arranged to form the throttling point in cooperation with an adjustable, stationary throttling element supported by the frame. The expansion of the throttling point to such an extent that there is enough space available for the discharge of the impurities is obtained automatically by such an arrangement at the end of the return travel of the metering piston. The medium dose rinsing off the impurities is obtained because the metering valve operates as a continuous metering device as long as the feed conduitforthe medium is pressurized and as single-dose metering device when the pressure in said feed conduit is decreasing.According to the invention there is thus provided a self-cleaning, continuously feeding metering valve which is provided with an adjustable throttling point and in which impurities contained in the medium to be fed are not able to clog the valve or to cause malfunctions.

The invention will now be described in more detail with reference to the accompanying drawing in which Figures 1 to 4 illustrate schematically different operating steps of one preferred embodiment of a metering valve according to the invention.

The metering valve shown in the drawing comprises a frame 1 provided with a cylinder 2 in which is mounted a metering piston 3. An inlet 4 and an outlet 5 are formed in the frame for a medium, for example, lubricating oil, to be metered. Between the cylinder 2 of the metering piston and the inlet 4 is formed an additional cylinder 6 which at its lower end communicates with the inlet and at its upper end through a slot 7 with a cylinder space 2A on the inlet side of the cylinder 2. In the additional cylinder is mounted a charging piston 8 on which is fastened a V-profile sealing 9. The charging piston is provided with an upwards directed valve spindle 10 provided with a head forming a closure element for an axial bore 11 provided in the metering piston. This bore is connecting with an axial throttling chamber 12.

In the upper part of the frame is mounted a vertically displaceable adjusting spindle 13 provided at its lower end with a throttling pin 14 coaxial with the throttling chamber. The spindle is provided with an axial channel which forms the above-mentioned outlet 5 and which, through a hole in the spindle wall, communicates with a cylinder space 2B on the outlet side of the cylinder 2. Between the frame and the piston is arranged a spring 15 which presses the piston downwards.

The metering valve operates in the following manner: Figure 1 shows the valve in the basic position in which a pressure lower than the closing force of the spring 15 prevails in a supply conduit 16 for lubricating oil to which the metering valve is fastened. The sealing 9 of the charging piston 8 is pressed against the inlet 4 and the bore 11 of the metering piston 3 is pressed againstthevalve spindle 10 of the charging piston. The throttling pin 14 of the adjusting spindle is located in the basic position entirely withdrawn from the throttling chamber 12 of the metering piston.

As the pressure in the supply conduit 16 increases, lubricating oil is allowed to flow past the V-sealing 9 and, at the same time, the pressure lifts the charging piston and along with it the metering piston upwards. Lubricating oil which has remained in the cylinder space 2B above the metering piston will be forced forwards through the outlet 5 of the adjusting spindle. Simultaneously, the metering piston 3 starts to move towards the throttling pin 14 so that a throttling slot 17 is formed between the throttling pin and the wall of the throttling chamber in the piston.

Figure 2 illustrates this situation.

As the pressure in the supply conduit increases and the pistons are displaced upwards, the movement of the charging piston 8 first stops against a shoulder 18 in the additional cylinder. The metering piston still continues to move upwards forced by the lubricating oil until its movement is stopped by a shoulder 19 in the cylinder 2. At this moment, the bore 11 in the metering piston opens whereby lubricating oil is allowed to flow from the inlet 4 past the charging piston through the bore 11 in the metering piston into the throttling chamber 12 and further through the throttling slot 17 to the outlet 5 of the adjusting spindle and from there forwards to the object to be lubricated. Figure 3 illustrates this situation.By means of the throttling slot 17 a volumetric flow control for the lubricating oil is obtained which is steplessly variable by turning the adjusting spindle upwards and downwards so as to varythethrottling distance L.

Impurities in the lubricating oil which are bigger than the slot remaining between the throttling pin 14 of the adjusting spindle and the throttling chamber 12 of the metering piston are gradually collected in the throttling point and thereby reduce the volumetric flow quantity.

As the pressure in the supply conduit 16 decreases, the sealing 9 of the charging piston prevents the lubricating oil dose in the cylinder space 2A from flowing back to the inlet 4. Simultaneously, the spring 15 presses the metering piston downwards while disengaging the piston from the throttling pin 14 and forcing the lubricating oil dose in the cylinder space 2A through the bore 11 and the throttling chamber 12 into the cylinder space 2B at the outlet side. The lubricating oil flow rinses the impurities accumulated in the throttling point 17 out from the throttling chamber 12 into the cylinder space 2B and in this way cleans the throttling point of impurities. Figure 4 illustrates this situation.

As the pressure continues to decrease in the supply conduit, the metering piston and the charging piston are returned to the basic position shown in Figure 1 under the influence of the force of the spring. Now the piston and the throttling pin are fully disengaged from each other and are ready for the next operation.

It will be noted that in the valve according to the invention the throttling slot 17 will be widened during the cleaning operation and that the cleaning is effected by means of the pumping operation of the valve itself.

The drawing and the description related thereto are only intended to illustrate the idea of the invention. In its details the metering valve according to the invention may vary considerably within the scope of the claims. Instead of the throttling element being pin-shaped and projecting into the piston, it can be sleeve-shaped and project upon the throttling chamber of the piston. It is also possible to substitute the connecting channel in the metering piston and the valve spindle of the charging piston with a sleeve-shaped slide known per se which in a corresponding manner opens and closes connecting grooves in the cylinder mantle of the metering piston and/or in the mantle of the metering piston depending on the relative positions of the pistons.

Claims

1. A metering valve for a lubricant or a similar medium comprising a frame, a cylinderformed in said frame and communicating with an inlet and an outlet for said medium provided in said frame, a metering piston axially displaceable in said cylinder, said piston separating said inlet and said outlet from each other and being provided with a connecting channel interconnecting the cylinder spaces separated by said piston, a charging piston axially displaceable in said frame and permitting flow of medium from said inlet to said cylinder when said inlet is pressurized, said charging piston opening said connecting channel in the metering piston when the metering piston has been displaced due to the action of the medium to the cylinder space facing said outlet and maintaining said connecting channel open as long as said inlet is pressurized and, in addition, while said charging piston is carrying out a movement in the opposite direction to the cylinder space facing said inlet as the pressure in said inlet is decreasing, and a flow throttling point provided in said frame in the flow path of said medium for controlling the volumetric flow of said medium, the valve futher comprising a throttling element in said frame which together with said metering piston forms said flow throttling point when said metering piston is located in the cylinder space facing said outlet.

2. A metering valve as claimed in claim 1, wherein said throttling element is fastened in said frame and extends into said connecting channel in said metering piston so that said element constricts the outflow area of said channel when the metering piston is located in the cylinder space facing said outlet and is disengaged from said connecting channel when the metering piston is located in the cylinder space facing said inlet.

3. A metering valve as claimed in claim 2, wherein said connecting channel in said matering piston extends axially through said metering piston and consists of a central, cylindrical bore, and in that said throttling element consists of an axially extending spindle concentric with said connecting channel.

4. A metering valve as claimed in claim 3, wherein said spindle is axially adjustably mounted in said frame.

5. A metering valve for a lubricant or a similar medium substantially as hereinbefore described with reference to and as illustrated in the accompanying drawing.