GB2263533A - Metering valve - Google Patents

Abstract

A metering valve particularly for metering particulate abrasive material in abrasive blast-cleaning equipment has a construction comprising an inlet 10 and an outlet 11, and an orifice plate 15 located therebetween, said orifice plate having an elongate slot 16 and being slidably mounted in the valve, there being actuating means attached to the plate and located externally of the valve. The actuating means may comprise a manually operated extension of the orifice plate or a screw and nut mechanism 17, 18. <IMAGE>

Description

METERING VALVES This invention relates to metering valves.

There are many applications where a controlled volume of material needs to be dispensed from a storage means. This applies particularly to abrasive-blast cleaning equipment, where particulate abrasive material is held in a pressurised hopper and needs to be dispensed at a required rate into a blast line through which pressure air is passing.The dispensing of fine particulate material can be particularly troublesome and to facilitate this, it has already been proposed to provide a valve having an inlet communicating with the hopper and an outlet communicating with the blast line, and having an orifice plate with an orifice opening located between the inlet and the outlet having an orifice of a size to suit the mean particle size of the particulate material and the rate at which the particulate material is required to be dispensed into the blast line, to suit the particular surface preparation to be performed.

The difficulty here is that if a different particulate material is to be dispensed, or if a different rate of dispensing particulate material is needed, it is necessary to remove the orifice plate and replace it with a further orifice plate with an orifice to suit the different mean particle size and/or different dispensing rate. This is time consuming and involves the safekeeping of a collection of orifice plates, and given the harsh working environment where blast cleaning ordinarily takes place, replacement orifice plates can easily become lost, and considerable care and attention has to be exercised by the operative to ensure that a correct orifice plate has been selected for location in the valve.

The objective of the invention is to avoid those disadvantages mentioned above.

According to the present invention, a metering valve comprises an inlet and an outlet, and an orifice plate located therebetween, said orifice plate having an elongate slot and being slidably mounted on the valve, there being actuating means attached to the plate and located externally of the valve.

Preferably, the actuating means comprises a captive screw mounted on the valve, rotatively attached by one end to the orifice plate, and whereby rotation of the screw causes a linear movement of the orifice plate. Thus, the orifice plate may have a nut secured to one side for engagement by the threaded stem of the screw, the screw being captive to and rotatable on a mounting plate secured to the valve. Further preferably, the linear movement of the orifice plate is a predetermined function related to the pitch of the threads of the screw, and whereby one full turn of the screw causes the plate to move linearly by said predetermined amount.

Thus, the valve may have a body with a throughpassage, and slotted partway along the passage at 900 thereto with the slot emerging at one side of the body. The orifice plate can then be slid into the slot and the operating screw mounting plate attached to the body adjacent the slot.

The orifice plate can then be positioned in the slot with its elongate slot overlapping the through-passage to any required degree by simple rotation of the screw.

To prevent leakage/discharge of fine particulate material through the slot containing the orifice plate, sealing means may be provided to engage the surfaces of the orifice plate. Thus, the inlet and the outlet of the metering valve may be formed by a threaded bore to receive a threaded tube, the ends of the threaded tubes having annular sealing means attached thereto to contact the orifice plate.

Another disadvantage of known constructions is the ease with which they can be blocked by rogue oversize particles in the particulate material or by foreign bodies inadvertently contained therein. With known constructions, the orifice plate must be removed to clear such blockages. It is a further feature of the invention to overcome this problem by so mounting the slotted orifice plate that it can be moved to expose a greater length of its slot, and to allow the blockage to clear. Thus, the slotted orifice plate can be held in its required position in relation to the screw by a spring, and once moved and released, returned by the spring to its previously set operating position.

To provide further assistance against clogging of fine particulate material, a vibrator means may be attached to the valve body, vibration of the body assisting the flow of fine particulate material.

The invention will now be further described, by way of example only, with reference to the accompanying drawings, in which:- Figure 1 is a side elevation of a metering valve in accordance with the invention; Figure 2 is a section on the line A- of Figure 1; and Figure 3 is a section on the line B-B of Figure 2.

In the drawings, a metering valve has a valve block formed by upper and lower valve block members 1, 2 suitably secured together by bolts 3 extending through cooperating holes 4, 5 in the upper and lower block members. Between the upper and lower block members a gasket 6 is provided.

In its front face, the valve block has a rebate 7 formed by cooperating rebate halves formed in the upper and lower block members, the rebate extending to a slot 8 formed by cooperating recesses in the adjacent faces of the upper and lower block members. Extending through the valve block is a passageway 9 formed by cooperating through-bores 10, 11 in the upper and lower block members 1, 2. Each through-bore 10, 11 is threaded to receive a correspondingly threaded tube 12, 13, at the end of each of which an annular seal 14 is provided.

Located in the slot 8 and emerging in the rebate 7 is an orifice plate 15 having an elongate through-hole 16, which in the operative position of the orifice plate extends across the passageway 9, with the orifice plate in contact with each annular seal 14. In one form of construction the orifice plate 15 can be a friction sliding fit in the slot 8 with its end emerging in the rebate such that the orifice plate can be manually slid to position the elongate through-hole to a required overlapping degree with respect to the passageway, and moved/removed from the slot 8 to clear blockages as required and as discussed in greater detail below. However, and preferably, a means is provided for the controlled movement of the orifice plate.Thus, the end of the orifice plate emerging in the rebate may have a captive nut 17 for engagement with the threaded stem of an adjusting screw 18, the adjusting screw 18 being captive with freedom for rotation on a mounting plate 19 attached to the front face of the valve block. Here, and for simplicity, the pitch of the threads on the screwed stem is arranged to be a predetermined function of a required linear movement of the orifice plate, the arrangement being such that a full turn of the screw causes plate movement to a predetermined linear degree.

Thus, and for example, with a metering valve as above defined located in the outlet from a hopper, with the outlet from the hopper connected to the inlet to the valve block and the outlet from the valve block connected to a blast line, and with the hopper containing a fine particulate material, the invention satisfied the two-fold need of enabling the metering of the fine particulate material into the blast line to a required degree with a minimum risk of fine particulate material clogging the metering valve, and in the relatively infrequent instances of valve blockage, enabling the movement of the orifice plate to expose a greater proportion of its hole 16 to enable the blockage to be cleared. If required, the plate can readily be removed simply by disconnecting the mounting plate for the adjusting screw and when the plate can be pulled clear of the slot 8.

Thus, and prior to the onset of operations, the orifice plate can be adjusted, and in the preferred form where an adjusting screw is provided, by simple rotation of the screw to move the orifice plate along the slot 8 to a degree to put the through-hole in the required overlapping relationship with the passageway 9. Following the application of pressure air to the blast line of the equipment, valve means between the metering valve and a hopper is opened and particulate material is dispensed into the blast line to the required degree. Should surface preparation requirements change an adjustment of the plate to increase or to decrease the dispensing of particulate material can be effected in exceedingly simple and expeditious manner without the need to remove the orifice plate and replace it by a plate having a different orifice.

Claims (10)

1. A metering valve comprising an inlet and an outlet, and an orifice plate located therebetween said orifice plate having an elongate slot and being slidably mounted on the valve, there being actuating means attached to the plate and located externally of the valve.

2. A metering valve as in Claim 1, wherein the actuating means is an extension to the orifice plate for the manual adjustment of the plate with respect to the valve.

3. A metering valve as in Claim 1, wherein the actuating means comprises a captive screw mounted on the valve rotatably attached by one end to the orifice plate and whereby rotation of the screw causes a linear movement of the orifice plate.

4. A metering valve as in Claim 3, wherein a nut is secured to the orifice plate to be engaged by the captive screw, the captive screw being located on a mounting plate for attachment to the valve.

5. A metering valve as in Claim 3 or Claim 4, wherein the pitch of the threads of the screw are predetermined and a function of a required movement of the orifice plate and whereby a predetermined degree of rotation of the screw causes a required movement of the orifice plate.

6. A metering valve as in any of Claims 1 to 5, wherein the valve has a body with a through-passage, a slot in the body perpendicular to the through-passage and extending from one side of the body to a point beyond the throughpassage, the orifice plate being located in the slot to extend across the through-passage, with the through-bore of the orifice plate extending across the through-passage to a required degree.

7. A metering valve as in Claim 3 to 6, wherein the orifice plate is held in its required position in relation to the screw by a spring to enable manual movement of the orifice plate with respect to the screw and the return of the orifice plate to its operative position on the screw.

8 A metering valve as in any of Claims 5 to 7, wherein the through-passage to each side of the slot is threaded to receive a correspondingly threaded tube, there being an annular sealing means at the end of each tube for engagement with the orifice plate.

9. A metering valve as in any of Claims 1 to 8,wherein a vibrator means is attached to the valve body.

10. A metering valve substantially as hereinbefore described with reference to the accompanying drawings.