GB2112124A - Gas cylinder fitting - Google Patents

Abstract

A fitting for use in making a gas- tight connection to a gas cylinder, which has an externally screw- threaded neck 14 with a sealing disc 15, has a tubular housing 1 into which the neck 14 is screwed. To form a seal, a member 5 is slidable and rotatable in the housing and carries an O-ring 20. As the neck 14 is screwed into the housing 1, the member 5 is pressed back against the action of a spring 7 and a fixed tubular piercer 16 pierces the disc 15. Gas under pressure from the cylinder then flows through the piercer 16 and thence through a valve 30 in an adapter 2 which is fixed to the housing 1. Further gas flows around the outside of the piercer 16 into a space 21 and its pressure assists the spring 7 in pressing the O-ring 20 against the end face of the neck 14. The member 5 with the O-ring 20 rotate in the housing 1 as the neck 14 is screwed in and in this way wear of the O-ring 20 by rubbing against the end face of the neck is prevented. <IMAGE>

Description

SPECIFICATION Gas cylinder fitting Carbonators for injecting carbon dioxide gas into water or other beverages in the production of fizzy drinks, commonly known as fizzy-drinks makers, have in the past always drawn the carbon dioxide from a refillable metal cylinder. Such cylinders have had a capacity of approximately 225 gms of gas and since they have been made of metal and have needed to include a valve for refilling purposes, have been comparatively heavy, e.g. of the order of 1.20 kg. When such a cylinder is empty it is normally returned to a dealer and exchanged for a full cylinder. Recently, disposable cylinders have become available and have certain advantages, the most important of which is that several can be bought at a time and when one cylinder is empty, it is merely removed from the carbonator and thrown away, a fresh cylinder then being fitted in its place.Since these cylinders are not refillable, they do not need to include a valve and instead are fitted with a sealing disc. The absence of the valve and the much lighter construction makes such disposable cylinders very much easier to handle.

The absence of any valve means that the cylinder merely needs to be provided with a screw threaded portion surrounding the sealing disc so that it can be screwed into a socket either in the carbonator itself or in a separate adapter, so as to bring the sealing disc into contact with a piercer and thus to release the gas from the cylinder. The piercing action occurs while the cylinder is being screwed into the socket and the screwing action is then continued until the cylinder has been screwed firmly home and a seal has been made with the socket. For this purpose, the end of the cylinder surrounding the disc needs to be made relatively smooth and flat so as to make a seal with a washer located on a seating within the socket.Generally speaking, this washer needs to be flat like a tap washer and since the end of the cylinder comes into engagement with the washer with increasing pressure during the last part of the screwing action, the washer is subjected to considerabíe wear. If the washer is made hard in order to withstand this wear, it is difficult to make a good seal whereas a softer washer which would make a better seal suffers more wear.

Accordingly, it is necessary to replace this washer at relatively frequent intervals.

According to the present invention, a fitting for use in making a gas-tight connection to a gas cylinder having a cylindrical screw-threaded end portion fitted with a sealing disc comprises a sealing ring for making a seal against the end face of the gas cylinder mounted on the end of a sliding member capable of turning and of sliding against the action of a spring within a cylindrical housing with which it forms a sealed fit and which is open at one end and is formed with an internal screw thread for co-operation with the thread on a gas cylinder and a piercer for the sealing disc of the gas cylinder which extends from a fixed mounting on the housing along an axial passage through the sliding member, the fitting being formed at the end remote from the internal screw thread with a cylindrical portion having an external screw thread and formed with an integral gas passage.

Accordingly, when the end of the cylinder comes into engagement with the sealing ring as the cylinder is being screwed into the socket, the frictional engagement causes the sealing ring together with the sliding member as a whole to rotate so that no rubbing contact occurs between the end of the cylinder and the sealing ring and wear to the latter is virtually eliminated. As the screwing action continues, the sliding member yields against the effect of its spring, and the sealing disc moves into engagement with the piercer until the disc is pierced and gas flows from the cylinder. The piercer is preferably tubular and the gas flows through the piercer and into the space at the other end of the housing where it acts on the end of the cylindrical member remote from the sealing ring and forces the latter into effective sealing contact with the end of the cylinder.As a result of this, the initial pressure between the sealing ring and the end of the cylinder produced by the spring is greatly increased and an effective seal is thus formed. This enables the sealing ring, which is conveniently in the form of an O-ring seated in the end of the sliding member, to be made of a relatively soft material capable of forming a good seal without the risk of this material being subjected to wear, since as soon as engagement occurs between the cylinder and the sealing ring, the two rotate together.

The fitting preferably includes means for positively retaining the sliding member within the housing. This is most desirable because if the cylinder were to become unscrewed while there was any residual gas pressure, this would force the member out of the housing.

As stated above, the sliding member forms a sealed fit with the housing and for this purpose an O-ring may be located in an external groove towards the end of the sliding member remote from the gas cylinder so as to seal against the inner surface of the housing.

As mentioned previously, the cylinder may be screwed directly into the carbonator itself, in which case the cylindrical housing forms part of the structure of the carbonator. Preferably, however, the cylindrical housing forms part of an adapter which is separate from the carbonator and which includes a control valve which may be similar to those normally fitted to refillable cylinders and which preferably includes a bursting disc to safeguard against excess pressure.

Accordingly, once the cylinder has been screwed into the adapter, the combination of the two is the equivalent of a refillable cylinder and the adapter may then be screwed into the carbonator in the same way as a refillable cylinder. The valve in the adapter may, for example, be of the kind described and claimed in our co-pending application no: 2,036,905, particularly the form illustrated in Figure 2 of that specification.

An example of a fitting in accordance with the invention will now be described in more detail, with reference to the accompanying drawing, which is an axial section of the fitting showing the end portion of a cylinder being screwed into position.

The drawing illustrates the combination of a fixing in accordance with the invention shown as 1 and an adapter 2 formed with a screw thread 3 identical with that on a refillable cylinder, so as to be capable of screwing directly into a carbonator.

The fitting 1 is in the form of a housing formed with a cylindrical recess receiving a circular sliding member 5 capable of both rotary and sliding movement. The member 5 is provided with an Oring seal 6 and is biased to the right as seen in the drawing by a compression spring 7. Movement of the member 5 to the right is restricted by pins 8 which extend across the recess in the housing 1 and are fixed in holes in the wall of the recess. The pins engage in a recess 9 formed in the outer surface of the member 5. As shown, the pins 8 are in engagement with the left hand end of the recess 9, thus preventing further movement of the member 5 to the right and, in particular, preventing it being ejected from the cylindrical recess in the housing 1. As the member 5 is forced to the left against the action of the spring 7, the pins 8 move along the recess 9.

At its mouth the cylindrical recess in the housing 1 is formed with a screw thread 12 forming a screwed socket for the reception of the complementary thread 13 formed on the end portion of a disposable cylinder for carbon dioxide, part of which is seen at 14. The end of the cylinder 14 is formed with a sealing disc 1 5 which can be pierced by a piercer 1 6 which is tubular and is fixed to the housing 1 at its left hand end 1 7 by being force fitted into an internal rebate in the housing. The piercer 1 6 extends through an axial passage 18 in the sliding member 5.

At its right hand end the member 5 is formed with a seating holding an O-ring 20 for forming a seal against the flat end of the cylinder 14. In the position illustrated, the cylinder 14 is partially screwed into position and is just touching the 0ring 20. Although, in this position, the pressure exerted on the O-ring 20 is extremely light, it is sufficient to cause the ring and hence the member 5 to turn with the cylinder, thus avoiding wear to the O-ring 20.As the cylinder is screwed further in, the member 5 is forced to the left against the action of the spring and as a result of continued movement in this direction, the sealing disc 1 5 moves into contact with the pointed right hand end of the piercer 1 6 and further rotation of the cylinder 1 4 causes the disc to be pierced to allow carbon dioxide to flow from the cylinder 1 4. The gas thus flows through the tubular piercer 1 6 and also along the passage 1 8 into a space at the left hand end of the member 5 shown as 21 where it acts against the left hand end 22 of the member 5.

This greatly augments the pressure exerted by the spring 7 and forces the O-ring 20 into effective sealing contact with the end of the cylinder 1 4. At this point the end 22 of the member 5 is close to an annular shoulder 24 at the left hand end of the space 2 1 and further slight rotation of the cylinder 14 brings the end 22 into sealing contact with the shoulder 24, thus augmenting the seal provided by the O-ring 6.

Gas which is released from the cylinder 1 4 and which flows through the bore of the tubular piercer 16, passes into the interior of the adapter 2 where it is controlled by a valve indicated generally as 30, the details of which are in accordance with Figure 2 of the co-pending application referred to above. For present purposes it is sufficient to say that the valve 30 comprises a member 31 which includes a bursting disc 32 to safeguard against excess pressure if, for example, the cylinder 1 4 were to be subjected to an unduly high temperature. The member 31 is biased to the left by a compression spring 33 so that a valve seat 34 is pressed against a fixed part 35 of the valve structure.When the adapter 2 is screwed into the carbonator and the carbonator is operated, the member 31 is forced to the right against the bias of the spring 33 and allows gas to flow from the cylinder 14 into the interior of the carbonator.

The housing 1 is provided with a safety vent hole 36 leading from the cylindrical recess in the housing 1 at the inner end of the screw thread 1 2.

If the cylinder 14 is inadvertently unscrewed from the cylindrical recess in the housing 1 while the cylinder 14 still contains carbon dioxide under pressure, this gas will be vented through the hole 36 as soon as the end face of the cylinder 14 moves out of contact with the O-ring 20. This happens before the screw thread 13 is fully unscrewed from the thread 12 and accordingly the gas pressure is prevented from forcing the cylinder violently out of the recess in the housing 1, which, if it happened, might be dangerous.

Claims (4)

1. A fitting for use in making a gas-tight connection to a gas cylinder having a cylindrical screw-threaded end portion fitted with a sealing disc, the fitting comprising a sealing ring for making a seal against the end face of the gas cylinder mounted on the end of a sliding member capable of turning and of sliding against the action of a spring within a cylindrical housing with which it forms a sealed fit and which is open at one end and is formed with an internal screw thread for cooperation with the thread on a gas cylinder and a piercer for the sealing disc of the gas cylinder which extends from a fixed mounting on the housing along an axial passage through the sliding member, the fitting being formed at the end remote from the internal screw thread with a cylindrical portion having an external screw thread and formed with an internal gas passage.

2. A fitting according to claim 1 including means for positively retaining the sliding member within the housing.

3. A combination of a fitting according to claim 1 or claim 2, and an adapter having a hollow body portion screwed on to the external thread of the fitting and itself formed with an external screw thread for screwing into a carbonator, the adapter including a control valve having an externally accessible portion whereby the valve can be opened to permit gas flow through the combination.

4. A combination according to claim 3 including, in association with the valve, a bursting disc to safeguard against excess gas pressure.