GB2180610A - Medical gas terminal unit - Google Patents

Abstract

A medical gas terminal unit comprises a body (24) having a central passageway (1) for receipt of a probe. The probe is retained in the passageway by a detent mechanism comprising a pair of pins (30) extending into the passageway through lateral bores (29) in the body, the pins being urged onto the passageway by a split spring (27). The pins also pass through channels (31) in an outer collar member (26), the channels permitting limited axial movement of the collar with respect to the pins and body. Part of the collar adjacent the outer openings of the channel provides an inclined planar cam surface (28) on which the heads of the pins ride. Axial movement of the collar in the direction further over the body causes the pins to be cammed out of the passageway to release the probe.

Description

SPECIFICATION Medical gas terminal unit This invention relates to medical gas terminal units.

It is usual for hospitals to have a central source of medical gases and for the gases to be supplied along pipelines to the location of use, such as an operating theatre. At the point of use the pipelines each terminate in a terminal socket into which a probe attached to the equipment for delivering gas to the patient is inserted. For each gas the probe and socket are different, or 'gas specific', so that misconnection is avoided. The probes each comprise a tapering nozzle that upon insertion into the correct terminal engines and opens a valve to permit gas to enter the probe and flow to the connected equipment. A circumferential recess is provided around each probe and the terminal has spring biased retaining bars that engage with the recess to prevent inadvertent withdrawal of the probe. A schematic drawing of a probe, terminal and locking mechanism is shown in Fig. 1.This terminal comprises a body with a central passageway 1 into which a probe 8 is inserted. The body has a pair of inclined slots 2 in which bars 3 are located, the bars being supported on a platform 4 that is urged upwards (as viewed) by a helical spring 5. When the probe 8 is inserted into the passageway 1 the nozzle eventually abuts the bars 3, depresses them against the bias of the spring 5 and they move downwards and outwards along the ramped edges of the slots 2 allowing the probe to move further into the passageway. The probe is pushed into the passageway until the bars 3 reach a circumferential recess 6 on the probe at which point the spring urges them into the recess to clamp the probe in position.Removal of the probe is achieved by depressing an outer collar 7 which depresses the platform 4 and permits the bars to move outwardly from the recess 6 so that the probe can be withdrawn from the passageway.

The disadvantage of an arrangement such as that shown is that the bars require movement in the axial direction of the terminal in order to effect the clamping and release. Thus in order to remove the probe the depression of the collar and downward (as viewed) movement of the bars is accompanied by a downward (again as viewed) movement of the probe until the bars have opened sufficiently to permit the probe to be removed. This axially inward movement of the probe is against the gas pressure and also requires the valve to be constructed to cope with this additional inward thrust. Furthermore the bars do not always properly release from the recess and jamming can be caused.

The present invention is directed towards providing a terminal unit that alleviates the above problems by removing the necessity for axial movement of the probe during the clamping and unclamping operation.

Accordingly the present invention provides a medical gas terminal unit for use with a detent retained probe, the unit comprising a body having a passageway for receiving the probe, at least one detent member moveable transversely inwardly and outwardly of the passageway to enable engagement with and disengagement from the probe, means for urging the detent member in the direction inwardly of the passageway and a collar moveable with respect to the body and having a cam surface for engagement with a cam follower associated with the detent member to enable outward movement of the detent member.

In a preferred embodiment the invention provides a medical gas terminal unit comprising a body having a central passageway for receiving a probe, a detent mechanism including a pair of pins positioned for extending into the passageway through lateral apertures in the body, a split ring urging the pins into the passageway, a collar member extending around the body and having channels for the pins, the channels allowing limited axial movement of the collar with respect to the pins, and an inclined cam surface adjacent each channel, the pins engaging the respective cam surface so that axial movement of the collar causes the pins to be withdrawn from the passageway.

The invention is now described by way of example with reference to the accompanying drawings in which: Figure 1 illustrates the prior art; Figure 2 is an exploded view of a preferred embodiment of the invention, and Figure 3 shows the embodiment of Fig. 2 when assembled.

The terminal unit shown in Fig. 2 can generally be divided into two parts. A first part, known as the 'first fix' is shown generally by reference 10 and consists of of a connection body 11 for connection to the gas pipeline, a valve seal 12, an '0' ring 13, a location pin 14 and an adaptor 15. This first fix is generally insalled in operating theatres and other appropriate installations during building. The rest of the terminal unit, shown generally by reference 16, is known as the second fix and is installed subsequently and (for a given gas) is interchangeable. The second fix includes a valve assembly comprising a spring 17 that engages with the first fix adaptor 15, a rear cover moulding 18, valve seal 19, seal washer 20 and '0' ring housing 21 with '0' ring 22, this valve assembly being held together by screws 23.The valve assembly is connected to a main body moulding 24 which has an axial central passageway 1 to receive the end of the probe and is apertured to provide a pair of lateral bores 29 for location of the shanks 30 of a pair of stainless steel locking pins. A gas specific collar moulding 26 fits over the main body moulding 24 and the locking pins pass through channels 31 in the collar moulding 26 and then into the bores 29 in the main body moulding to hold the two parts together. The locking pins have heads 25 with angled slots 32 into which a circular stainless steel split spring 27 engages. The pins are arranged so that the slots are directed in opposite directions thus capturing the spring 27 in position. A cover 33 to protect the spring and pin heads may also be provided.

The channels 31 in the collar moulding 26 are wider in the longitudinal direction of the terminal unit than the locking pin shank diameter and thereby enable the collar to have axial movement with respct to the body moulding 24. The heads 25 of the locking pins are wider in the circumferential direction of the terminal unit than the channels and have a shape that cooperates with an inclined plane part 28 of the collar adjacent the outer openings of the channels. Thus as the collar moulding is moved axially the pin heads ride up and down the inclined plane parts 28 and the pins are moved respectively outwardly and inwardly of the passageway 1.

Under the influence of the split spring 27 the pins are urged inwardly (with respect to the collar circumference) and the collar moulding is displaced axially outwardly (upwardly as viewed in the Figures) with respect to the body moulding so that the position shown in Fig. 3 is adopted, with the ends of the pins extending through the bores 29 into the passageway.

If a probe is now inserted into the terminal unit the tapered end of the probe contacts the ends of the pins extending into the passageway 1 and pushes the pins outwardly as the probe is pushed inwardly into the terminal.

The terminal is dimensioned so that when the probe end operably engages with the valve assembly the recess 6 of the probe is aligned with the pins which will be urged inwardly by the spring to clamp the probe. During this insertion procedure the collar 26 can remain stationary as the outer ends of the pins are restrained only by the spring 27 and the heads of the pins, when urged outwardly by the probe, can lift away from contact with the inclined plane surface 28. This contrasts with the prior art in which the bars are captured on each side and thus outward movement must be accompanied by movement of the platform 4 (Fig. 1).

Removal of the probe from the apparatus according to the invention is effected by pressing the collar moulding axially inwardly.

This causes the pin heads to ride up the ramps and move outwardly (with respect to the collar circumference) thus disengaging the ends of the pins from the probe recess to enable its withdrawal. During the axial movement of the collar and withdrawal of the locking pins the probe and main body moulding remain static and the pins are moved positively by the cammrng action of the pin heads on the inclined plane parts.

Thus insertion and withdrawal of the probe is achieved without additional inward movement of the probe. The use of a relatively light split spring makes positive location of the locking pins in the recess easier to determine: with a strong clamping spring and lateral gripping bars it is possible to mistake the grip on the tapered probe end for complete insertion, especially when the probe end meets with strong resistance at the same time. The positive movement of the pins by the inclined plane parts 28 during the removal of the probe eliminates sticking problems arising in other apparatus that rely on gravity-aided or probe-sided retraction during removal.

The invention may be modified to provide for example a circumferential inclined cam surface co-operating with the pins with an outer part of the collar being rotatable to cause the pins to ride up the cam surface. The valve assembly and first fix may take other forms than that shown. Other parts of the assembly may also be modified, for example the spring configuration may be changed or replaced by other inward biasing means and the pins may be replaced by wedges or other detent members.

Claims (9)

1. A medical gas terminal unit for use with a detent retained probe, the unit comprising a body having a passageway for receiving the probe, at least one detent member moveable transversely inwardly and outwardly of the pressure to enable engagement with and disengagement from the probe, means for urging the detent member in the direction inwardly of the passageway and a collar moveable with respect to the body and having a cam surface for engagement with a cam follower associated with the detent member to enable outward movement of the detent member.

2. A medical gas terminal unit according to claim 1 in which the detent member comprises a pin moveable in its longitudinal direction and the body has a lateral bore for the pin communicating with the passageway.

3. A medical gas terminal unit according to claim 1 or claim 2 in which the collar has a channel for the detent member which permits relative axial movement of the collar with respect to the body and the detent member.

4. A medical gas terminal unit according to any preceding claim in which the means for urging comprises a spring.

5. A medical gas terminal unit according to claim 4 in which the spring comprises a captive annular spring encircling the collar.

6. A medical gas terminal unit according to claim 5 and comprising two detent members having slots for retaining the spring.

7. A medical gas terminal unit comprising a body having a central passageway for receiving a probe, a detent mechanism including a pair of pins positioned for extending into the passageway through lateral apertures in the body, a split ring urging the pins into the passageway, a collar member extending around the body and having channels for the pins, the channels allowing limited axial movement of the collar with respect to the pins, and an inclined cam surface adjacent each channel, the pins engaging the respective cam surface so that axial movement of the collar causes the pins to be withdrawn from the passageway.

8. A medical gas terminal unit according to claim 7, in which each pin has a head portion which engages the respective cam surface.

9. A medical gas terminal unit according to claim 7 or claim 8 in which each pin includes a slot for retaining the ring.