GB2293285A - Electrical connectors - Google Patents

Abstract

An electrical plug and socket connector, for coupling a pair of power supply conductors to a pair of current feeder lead conductors for a cryogenic electromagnet winding, comprises two mutually engageable parts 1, 2, one part 2 having two terminals 9, 10 for receiving the current feeder lead conductors and the other part 1 having two terminals 7, 8 for receiving the power supply conductors and a shorting link 15 which is constrained to move so that is short circuits the terminals 9, 10 as the parts 1, 2 are mutually disengaged but is separated from the terminals 9, 10 upon engagement of the parts. The link 15 may be mounted on a tubular slider 18 having dog-legged slots in which pins 25 of an actuator sleeve 21 engage, the sleeve being rotatable to interlock movement of the link with engagement/disengagement of the parts 1, 2. <IMAGE>

Description

IMPROVEMENTS IN OR RELATING TO ELECTRICAL CONNECTORS This invention relates to electrical connectors and more especially it relates to electrical connectors for use with cryogenic electromagnets of the kind used in magnetic resonance imaging (MRI) apparatus.

Cryogenic electromagnets, as is well known to the cognoscenti, comprise magnet windings which are positioned within a cryostat containing liquid helium, whereby the windings are cooled during operation of the magnet to a temperature of about 40 K. In order initially to produce a magnetic field, current is injected into the windings from a power supply via a demountable current lead (DCL) and cables, which current is thereafter self sustaining since at 40 K the windings have substantially zero resistance.

With known apparatus, a very strict operating procedure must be followed when the magnet is energised or de-energised.

This is because incorrect procedures may cause the magnet to quench, whereby dangerous voltages could be present externally of the cryostat on the DCL or on associated current leads, and moreover the energy dissipated during the quench may cause damage to parts operatively associated with the magnet winding.

Although there are no problems when the prescribed operating procedure is followed, it is possible with presently known systems if the procedure is not followed, for accidents to occur due to human error.

It is therefore an important object of the present invention to provide a connector, by means of which a power supply may be coupled to a magnet and de-coupled from the magnet without any attendant risk to personnel or equipment.

According to the present invention, an electrical plug and socket connector for coupling a pair of power supply conductors to a pair of current feeder lead conductors for a cryogenic electromagnet winding comprises two mutually engageable connector parts, one part having two terminals for receiving the current feeder lead conductors one for each lead conductor, and the other part having two terminals for receiving the power supply conductors one for each supply conductor, and a shorting link which is constrained to move consequent upon mutual engagement of the connector parts from a first position whereat it serves electrically to short circuit the terminals of the said one part, to a second position whereat tlle short circuit is broken and which consequent upon disengagement of the connector parts is constrained to move from the said second position to the said first position.

Thus, exposed live connector parts are normally shorted together until safely enshrouded 'vitlin the connector, the short circuit being re-made before di.sentnaement of the two connector parts has been fully effected.

This has the two fold ad\ al e that potentially dangerous voltages are never present on pax \\liich might be touched by operating personnel and additiollalbs the event of a quench current is directed through the shorting link which serves to protect circuit parts operatively associated with the winding.

The said connector parts may each have generally cylindrical body portions which are adapted and arranged to fit one within the other. the terminals in each connector part being mutually insulated and arranged to extend within the body portions to define plug or socket contacts, the contacts in said one part being complementary to and engageable with the contacts in the said other part when the two connector parts are mutually engaged.

The terminals in the said one part may be coupled by the said shorting link in a region of each terminal which extends between an end thereof adapted to receive the said lead conductors and an end thereof defining the said contacts, the shorting link being contiguously slideable over the said regions of each terminal between the said first position whereat it makes electrical contact with conductive portions of the regions coextensive with the terminals and the second position whereat it makes contact with insulated portions of the regions which serves to break the short circuit.

The shorting link may be supported within a tubular slider which is slideably mounted within the cylindrical body portion of the said one connector part, the slider being operated consequent upon mutual engagement of the connector parts so that the shorting link is constrained to move from the said first position to the said second position, and so that consequent upon disengagement of the connector parts, the shorting link is constrained to move from the said second position to the said first position.

The slider in the said one part of the connector may be slideably engageable with a sleeve in the said other part of the connector, the sleeve being arranged to be rotatable with respect to its connector part through a limited rotational arc so that indexing parts mutually co-operate thereby to facilitate operation of the slider between the said first and second positions, consequent upon engagement or disengagement of the said connector parts.

The indexing parts may comprise arcuate slots in the sleeve which engage first pins in the body portion of the said other connector part so as to permit limited rotational movement therebetween, second pins which project from the sleeve to engage complementary dog-legged slots in the slider so as to permit bayonet like engagement there between, and elongate slots in the sleeve which engage pins supported in the body portion of the said one connector part so as to permit longitudinal movement only therebetween.

One embodiment of the invention will now be described by way of example only, with reference to the accompanying drawings, in which, FIGURE 1 is a sectional view of an electrical connector comprising two parts which are axiil', aligned but not fully engaged; FIGURE 2 is a plan view of the electrical connector shown in Figure 1, partly in section as viewed from the direction of arrow X as shown in Figure 1, and wherein, FIGURE 3 is a somewhat schematic circuit diagram showing a connector of the kind shown in Figures 1 and 2 used to couple a power supply to an MRI magnet.

Referring now to the drawings, the electrical connector comprises two parts 1 and 2, which house electrical connector contacts 3, 4 and 5, 6 respectively. The contacts 4 and 5 are pins which are arranged to be a push fit into the contacts 3 and 6 which are sockets. The contacts 3, 4, 5, and 6 are arranged to extend longitudinally within their associated connector part to define terminals 7, 8, 9, and 10 respectively. The terminals 7 and 8 are provided to receive a pair of power supply conductors (not shown) and the terminals 9 and 10 are provided to receive a pair of current feeder lead conductors (not shown) for a cryogenic electromagnet winding. Conveniently the power supply conductors may be soldered to the terminals 7 and 8, whereas the current feeder lead conductors are connected by means of nuts 11 and 12 which are received by threaded portions 13 and 14 respectively of the terminals 9 and 10 respectively.

Within the connector part 2, a shorting link 15 is provided, which in the position shown in the drawing, serves electrically to couple the contacts 5 and 6. The shorting link 15 is slideable from the position shown towards the terminals 9 and 10 so that it rests on insulating sleeves 16 and 17, the shorting link being secured within a tubular slider ls, made of insulating material such as nylon, by means of locking screws 19 which serve to hold the shorting link 15 in position within the tubular slider 18.The tubular slider 18 is arranged to be slideable within a cylindrical body portion 20 of ths connector part 2 from a first position whereat the shorting link serves electrically to short circuit the contacts 5 and 6 to a second position whereat the shorting link rests on the insulating sleeves 16 and 17 so that the short circuit is thereby broken.

The tubular slider 18 is moved only during connection or disconnection of the two parts 1 and 2 of the connector and in order to facilitate operation of the slider 18, the part 1 of the connector comprises an actuator sleeve 21 which is provided with radial slots 22. Set screws 23 supported in an insulating body portion 24, (which may be nylon) of the connector part 1, are arranged to engage the slots 22 so that the sleeve 21 is secured to the body portion 24 with limited rotatary movement as determined by the length of the slots 22. The actuator sleeve 21 is provided with interlock pins 25 which engage dog-legged slots in the slider 18.Additionally, the sleeve 21 is provided with slots 27 which extend longitudinally of the connector part 1, and engage interlock pins 28. which are fixed within the connector part 2.

The terminals 9 and 10. together with the contacts 5 and 6 respectively to which they are electrically connected, are mounted in insulating material 29 within the colinector part 2 and similarly the terminals 7 and 8 and their associated contacts 3 and 4 respectively are mounted in insulating material 30 within the connector part 1.

In operation, when the two connector parts 1 and 2 initially are engaged, the interlock pins 25 engage the dog-legged slots 26, further forward axial movement thereafter being prevented until the sleeve 21 has been rotated so that the slots 27 align with the interlock pins 28. The connector parts 1 and 2 can now be pushed further together so that electrical connection is made between the contacts 3 and 4 and the contacts 5 and 6. When the pins 25 reach the bottom of the dog-legged slots 26, the sleeve 21 has moved to a position where it abuts an internal shoulder 30 of the slider 18, whereby the slider 18 together with the shorting link 15 is constrained to move from the position shown in the drawing to a position whereat the shorting link 15 rests on the sleeves 16 and 17 so that the short circuit between the contacts 5 and 6 is broken.

In order to de-couple the connector parts 1 and 2, the parts 1 and 2 are pulled apart until the interlock pins 25 reach an elbow 31 of the dog-legged slots 26. When this point is reached the sleeve 10 cannot be rotated so as to disengage the interlock pin 25 from the dog-legged slot 26 because the interlock pin 28 is still engaged with the slot 27. However, further axial movement between the connector parts 1 or 2 so that they move apart constrains the slider 18 and therefore the shorting link 15 to move so that the short circuit is re-established between the contacts 5 and 6. When the slider 18 reaches the end of its travel, the short circuit is fully established and the interlock pins 28 move free from engagement with the slots 27 so that the sleeve 21 can be rotated about the body portion 24 until the interlock pins 25 are disengaged from the dog-legged slots 26.Further axial movement can then be effected so that the two parts 1, 2, of the connector are fully parted.

It is important to realise that with a connector according to the present invention, the contacts 5 and 6 are always shorted together by means of the shorting link 15 until they are safely enshrouded within the connector during an engagement operation.

Conversely, when the parts 1, 2, of the connector are disengaged, the short circuit is re-established before the parts 1, 2, of the connector are fully disengaged.

As will be appreciated by those skilled in the art, various modifications may be made to the arrangement shown without departing from the scope of the invention. For example, although it is arranged in the present embodiment that electrical connection is maintained between the contacts 5 and 6 and the contacts 3 and 4 until the short circuit is established when the connector is parted, in an alternative embodiment, the short circuit may be established after electrical connection between the contacts has been broken but before the connector parts are fully disengaged.

Additionally, although soldeied connections are provided for the power supply leads and nut and bolt connections are provided for the leads from the magnet any other suitable means of connection may be provided.

Furthermore, although the shorting link 15 in the present embodiment is positioned between the terminals 9, 10 and the contacts 5, 6, in an alternative embodiment the terminals may be arranged to lie between the shorting link and the contacts.

In use, connectors according to the present invention may be used to couple a power supply 32 and an MRI magnet 33 as shown schematically in Figure 3.

Referring now to Figure 3, the magnet 33 comprises a winding 34 which is supplied with current initially via a DCL 35.

In operation, when the current has been injected, a persistent mode switch 36 is closed, thereafter to provide a substantially zero impedance return path for the magnetising current. The magnet power supply 32 is arranged to be coupled to the removable current leads 35 by means of an electrical connector 37 which corresponds to the connector just before described with reference to Figure 1 and 2.

It will be appreciated that by using a connector of the kind described dangerous voltages which may otherwise obtain on the removable current leads are short circuited, and in an event of a quench, current which might otherwise damage the persistent mode switch, or parts associated therewith, is diverted by means of the shorting link 15 in the connector 37, whereby the magnet is protected.

Claims (10)

1. An electrical plug and socket connector for coupling a pair of power supply conductors to a pair of current feeder lead conductors for a cryogenic electromagnet winding comprising two mutually engageable connector parts one part having two terminals for receiving the current feeder lead conductors one for each lead conductor, and the other part having two terminals for receiving the power supply conductors one for each supply conductor, and a shorting link which is constrained to move consequent upon mutual engagement of the connector parts from a first position whereat it serves electrically to short circuit the terminals of the said one part, to a second position whereat the short circuit is broken and which consequent upon disengagement of the connector parts is constrained to move from the said second position to the said first position.

2. An electrical connector as claimed in Claim 1, wherein the said connector parts each have genes ally cylindrical body portions which are adapted and arranged to fit one within the other, the terminals in each connector part being mutually insulated and arranged to extend within the body portions to define plug or socket contacts, the contacts in said one part being complementary to and engageable with tlle contacts In the said other part when the two connector parts are mlltllallx engaged.

3. An electrical connector as claimed in Claim 1 or Claim 2, wherein the terminals in the said one part are coupled by the said shorting link in a region of each terminal which extends between an end thereof adapted to receive the said lead conductors and an end thereof defining the said contacts, the shorting link being contiguously slideable over the said region of each terminal between the said first position whereat it makes electrical contact with conductive portions of the regions co-extensive with the terminals and the second position whereat it makes contact with insulated portions of the region which serves to break the short circuit.

4. An electrical connector as claimed in Claim 2 or Claim 3, wherein the shorting link is supported within a tubular slider which is slideably mounted within the cylindrical body portion of the said one connector part, the slider being operated consequent upon mutual engagement of the connector parts so that the shorting link is constrained to move from the said first position to the said second position, and so that consequent upon disengagement of the connector parts, the shorting link is constrained to move from the said second position to the said first position.

5. An electrical connector as claimed in any preceding claim, wherein the slider in the said one part of the connector is slideably engageable with a sleeve in the said other part of the connector, the sleeve being arranged to be rotatable with respect to its connector part through a limited rotational arc so that indexing parts mutually co-operate thereby to facilitate operation of the slider between the said first and second positions, consequent upon engagement or disengagement of the said connector parts.

6. An electrical connector as claimed in Claim 5, wherein, the indexing parts comprise arcuate slots in the sleeve which engage first pins in the body portion of the said other connector part so as to permit limited rotational movement therebetween, second pins which project from the sleeve to engage complementary doglegged slots in the slider so as to permit bayonet like engagement therebetween, and elongate slots in the sleeve which engage pins supported in the body portion of the said one connector part so as to permit longitudinal movement only therebetween.

7. An electrical connector substantially as hereinbefore described with reference to Figure 1 and Figure 2 of the accompanying drawings.

8. A cryogenic electromagnet operatively associated with an electrical connector as claimed in any preceding claim.

9. An MRI system including an electromagnet as claimed in Claim 8.

10. A system including an MRI magnet substantially as hereinbefore described with reference to Figure 3 of the accompanying drawings.