GB2186951A

GB2186951A - Rotary valve

Info

Publication number: GB2186951A
Application number: GB08702945A
Authority: GB
Inventors: Giancarlo Bonissone; Piero Mulas
Original assignee: FIP Formatura Iniezione Polimeri SpA
Current assignee: FIP Formatura Iniezione Polimeri SpA
Priority date: 1986-02-21
Filing date: 1987-02-10
Publication date: 1987-08-26
Also published as: GB8702945D0; NL8700383A; DE3705162A1; JPS62196473A; BE1001484A4; ES2004100A6; FR2594931A1; IT1191446B; IT8612432A0

Abstract

In a rotary plug valve, a frusto-conical plug 20 biassed away from its seat carries a seal 30 which surrounds the inlet 11 when the valve is closed; a cam 33 permits movement of the plug away from the seat when the plug moves out of its closed position. As shown the cam 33 coacts with projections 61 on the plug to hold it against the seat in the closed position, and stops (39, 40 Figs 4,6) define the valve open and closed positions. <IMAGE>

Description

SPECIFICATION Rotary valve BACKGROUND OF THE INVENTION It is well-known that most gas-tightvalves have a valve body with a truncated cone shaped seat in which a plug, also truncated cone shaped and having a passage perpendicularto its axis of rotation, may be made to turn.

Sealing between the lateral conical working edge of the plug and the complementary surface of the seat of thevalve body is obtained by means of film of grease in addition to a high degree of machining precision.

The degree of precision required in machining the seat ofthe valve body and the lateral surface ofthe plug entails high production costs.

Attempts have been madetoreducethecostof these valves by using sealing gaskets ofthe type used in valves for liquids, with the adoption of gaskets the cost of manufacturing were indeed reduced.

The running costs for these valves, however, were increased this is because it is necessary to inspect these valves very frequently, in order to check their state of wear.

In actual fact in valves for liquids, wear ofthe gaskets causes initially very minor leakages which, in the case of non hazardous liquids, mayeven be exploited to detect the state of wear of the gaskets, thus indicating when they have to be replaced.

lnthecaseofvalvesforgas,ontheotherhand,such leakages may be detected only by means of sophisti cated equipment, and itistherefore necessaryto check periodically the state of wear ofthe gaskets.

Since, however, during the valve opening and closing stages, the gaskets in question rub either against the seat ofthe valve body or against the external surface of the plug, they are subjectto considerable wear. The intervals between checks must therefore be extremely limited, with consequent high maintenance costs.

BRIEF SUMMARY OF THE INVENTION The scope of this invention is that of overcoming these problems.

To this end, according to the invention, the plug is given a mixed rotating and vertical movement, by means of suitable cams, so thatthe sealing gaskets are not subjected to wear by rubbing, or at least only to an extremely limited extent.

These sealing gaskets, according to the invention, are merely squeezed and released each time the valve is opened orclosed, sothatthey last a very longtime.

BRIEF DESCRIPTION OF THE DRAWINGS -Figure 1 shows a longitudinal section of a valve according to the invention, in a closed position; -figure 2 is a side view of the valve plug, in the same position as illustrated in figure 1; figure3 is aviewfrom above ofthesame plug; -figure 4 is a section on plane IV-IV offigure 1; --figure 5 is a outlineviewofthe cam which controisthevertical position ofthe plug, in this figure the cam is shown as having rotated by 90" from the position occupied in figure 1; -figure 6 is a view from above of the valve body, shown without the plug;; -figure 7 is a vertical section of the lower end of the valve body, shown withoutthe plug.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT With particular reference to the above figures, 10 indicates the valve body, which has an input fitting 11, an outputfitting 12, and a truncated cone shaped seat l3fora plug 12, also having atruncated cone shape, and therefore suitable for mating with the shape ofthe seat 13.

The plug 20 has a transverse passage 21 and an upper prismatic cavity 22, axial, in which the lower end of a control stem 23 is housed.

The plug 20 is maintained in position by a cylindrical stopper 14, which may be fixed to the body ofthe valve 10 by means of a spring stop ring 15, as illustrated in the figure, or by some other means, such as threading.

Suitablegasketsl6and 17 are placed between the external wall of the stopper 1 4 and the internal wall of the valve body 10, between the control stem 23 and the wall ofthe hole ofthe stopper 14, through which the control stem 23 passes. In known gas-tightvalves ofthis type, sealing of the valve is entrusted solely to a layer of grease inserted between the outer surface of the plug and the inner complementary surface ofthe seal of the valve body 10.

It follows that both the outer surface of the plug 20 and the inner surface ofthe seat of the valve body 10 must be machined with great accuracy, and this increases the manufacturing costs.

According to the invention, sealing ofthe valve in a closed position is entrusted to a ring-shaped gasket 30 positioned in a closed groove 31 made in the side surface ofthe plug 20.

This groove is made in one of the two parts ofthe side surface ofthe plug 20 situated between the end openings ofthe passage 21; its shape is such that it surrounds the terminal opening ofthe input fitting of the valve body.

The rotation ofthe plug 20, to move from a closed position to open or vice versa, would soon cause wear of the gasket 30. In order to avoid this, according to the invention, the gasket 30 comes into contact with the surface ofthe seat ofthe valve body only when the valve is in a closed position.

Intheopen position ofthevalve, and above all while the plug is passing from the open to the closed position or vice versa, according to the invention the gasket 30 is lifted away from the surface of the seat of the valve body.

To this end, on the bottom ofthe valve body 10 there is a spring 32 which tends to push the plug constantly upwards.

The axial position of the plug 20 is then defined by an annular cam 33 located underthe stopper 14, and which interacts with a pair of projections 61 located on the upperface of the plug 20, and which act as tappets.

In the position ofthe plug 20 corresponding to closure of the valve, the annular cam 33 has a stretch of cam surface protruding downwards, while in the position of the plug corresponding to opening of the valve, the annular cam has a stretch of cam surface receding upwards.

In the solution illustrated in the figure, the projections 61 which serve as tappets are two, so asto ensure forthe plug 20 a downwards thrust having a resultantcentredontheaxisoftheplug.

In orderto ensure a correct circumferential position ofthe annular cam 33, same is fitted with diametrically opposedteeth 35, which are housed in corresponding cavities 36, made on the internal surface ofthevalve body 10.

The seat ofthe spring 32 is obtained partly by means of a cavity 37 made in the bottom ofthe plug 20 and partly by means of a cavity 38 made in the bottom of the valve body 10.

In orderto allowthe plug 20 only a quarter of a turn to pass from the open to the closed position or vice versa, on the bottom ofthe valve body there are two stops 39 and 40. These stops interact with the end surfaces oftwo cavities 41 and 42 made in the lower area ofthe side surface of the plug 20.

These means of limitation ofthe rotation of the plug of a valve are well-known as such, and require no further explanations.

Theworking is as follows : the valve closed position, in spite ofthe upwardsthrust exerted by the spring 32on the plug 20, this is maintained in its lowered position againstthe bottom of the seat ofthe valve body 10 by the cam 33.

In this position the gasket 30 is pressed against the conical surface ofthe seat of the valve body 10 around the opening 11' (see figures 1 and 6) by means of which the inputfitting 11 ofthe valve body leads into the internal cavity of same.

The transverse passage 21 ofthe plug 20 is perpendicularto the axis ofthe two fittings 11 and 12, which therefore do not communicate with one another.

As soon as the plug 20startsto rotate in orderto move itfrom the closed to the open position,the projections 61 acting as tappets meetthe receding concave part of the cam profile of the annular cam and therefore allow the spring 32to push the plug 20 upwards: because the truncated cone shape both of the surfaces ofthe plug 20 and of the seat ofthe valve body 10, the gasket 30 loses contact with the surface of the seat of the valve body 10.

Therefore the gasket 30 does not rub against the seal ofthe valve body 10, as the plug passes from the closed to the open position orviceversa; this almost completely eliminates wear due to rubbing.

In addition the gasket 30 is squashed against the seal of the valve body onlywhen the valve is closed.

When the valve is open, and when the valve is in an intermediate position between the open and the closed positions, the gasket is slackened: this allows the gasketto retain its elastic characteristicsfor a longertime.

According to the invention, therefore, the double advantage is achieved of reducing abrasion of the gasketonthe one hand, and on the other hand of limiting the duration of the state of compression of same only to those periods of time during which the valve is closed.

Claims

1. Gas-tightvalve ofthetype having a truncated cone shaped seat into which two fittings, one input and one output, lead, and in which a plug rotates, a plug having a truncated cone shaped surface complementary to that of said seat, and crossed through by a transverse passage and fitted with means of operation, in which there is also an upper axial containment stopper ofthe above mentioned plug, characterized in which: a) said plug has an annular gasketwhich, in the valve closed position surrounds as a seal the opening ofthe input fitting in the truncated cone shaped seat of the valve body; b) elastic means which push the plug constantly upwards; c) cam means which allow upward movement of the plug when its angular position moves out ofthe position corresponding to the closed position of the valve.

2. Gas-tightvalve, according to claim 1 above, characterized by the fact that said annular gasket is housed in a groove prepared in the truncated cone shaped surface ofthe plug.

3. Gas-tight valve, according to claim 1, characterized in that on the bottqm ofthe seat ofthe valve body and on the bottom ofthe plug there are opposing cavities suitable for housing said elastic means, consisting preferably of a helical spring.

4. Gas-tightvalve, according to claim 1, characterized in that an annular cam is inserted between said stopper and the plug, and the cam surface of which, facing downwards, interacts with at least one projection acting as a tappet, made in the upper face of the plug.

5. Gas-tightvalve according to claim 4, characterized in thatthere are at least two projections acting as tappets, diametrically opposed, with the purpose of creating a force directed downwards, the resultant of which coincides with the axis of the plug.

6. Gas-tight valve, according to claim 4, characterized in thatthere are means of angular positioning for the above mentioned annular cam.

7. Gas-tight valve, according to claim 4, characterized in that there are stops between the plug and the valve seat, to define exactly the position of the plug, in the valve closed and valve open positions respectively.

8. Gas-tight valve, according to claim 1, characterized in that a film of grease is applied between the plug and the seal of the valve body.

9. A rotaryfluid-tightvalve having a rotary, truncated conical plug which seats in a com plementary valve seat having an inlet and an outlet four fluid, the plug defining a passagewayforfluid which interconnects the valve seat inlet and the valve seat outlet when the valve is open, the plug having a seal which surrounds the valve seat inlet when the plug is closed, and the valve having elastic means which push the plug axially away from the valve seat, and cam means which retain the plug againstthe valve seat when the valve is in its closed position and permit movement of the plug axially away from the valve seat when the valve is not in its closed position.

10. A rotaryfluid-tightva[ve, substantially as herein described with reference to, and as shown in, the accompanying drawings.