GB2238182A

GB2238182A - Isolatable contact

Info

Publication number: GB2238182A
Application number: GB8922973A
Authority: GB
Inventors: Aubyn Nicholas Francis St
Original assignee: Gemini Clothescare Ltd
Current assignee: Gemini Clothescare Ltd
Priority date: 1989-10-12
Filing date: 1989-10-12
Publication date: 1991-05-22
Anticipated expiration: 2009-10-12
Also published as: GB2238182B; GB8922973D0

Abstract

An isolatable contact for a removable electrical appliance comprises a contact pin (15) carried on a mounting plate (14) constructed and arranged to be moved against a biassing pressure (15) from a rearward position in which the pin is retracted in a housing to a forward position in which the pin protrudes from the housing eg into a slot (11) to engage a corresponding contact on the appliance, in which the pin is displaceably mounted on the mounting plate for movement between a position in which it is isolated from an electrically live connection (13) and a position in which it is in contact with said connection, the pin being biassed (17) towards the isolated position and the arrangement being such that in use the presence of the appliance displaces the mounting plate to the forward position and substantially simultaneously displaces the contact pin to the contact position. The plate (14) may be moved by an earth pin of a cordless iron camming against a bar (18). Plural contacts (16) engage contacts on the iron before the iron contacts push the biassed contacts (16) onto the live connections (13). The latter may alternatively brush over an associated pin contact having an insulated and a conductive position. <IMAGE>

Description

ISOLATABLE CONTACT This invention relates to electrically isolatable contacts for use with removable electrical appliances, especially but not exclusively for domestic electric irons.

It is known to provide a so-called cordless electric iron which is electrically connected to a power source for raising the temperature of the sole plate when the iron is placed in position on a parking dock or stand.

One such arrangement is described in International Patent Application No. PCT/GB89/00765, in which electrical contact pins are carried on a T-shaped plate within the parking dock and the tips of the pins are arranged to protrude through apertures in the wall of a slot formed in the upper surface of the parking dock, when the iron is located thereon, to make electrical connection with contact pads on the tail of the iron.

The plate is slidably mounted and biassed so that the pins are retracted when the iron is removed, whereby they are located entirely within the body of the parking dock except when the iron is correctly located thereon.

Despite this arrangement, it is possible that a mechanical fault would develop which would result in live pins protruding or continuing to protrude from the apertures when the iron was removed, thereby creating a hazard.

It is an object of the present invention to mitigate this eventuality.

According to the invention, an isolatable contact for a removable electrical appliance comprises a contact pin carried on a mounting plate constructed and arranged to be moved against a biassing pressure from a rearward position in which the pin is retracted in a housing to a forward position in which the pin protrudes from the housing to engage a corresponding contact on the appliance, in which the pin is displaceably mounted on the mounting plate for movement between a position in which it is isolated from an electrically live connection and a position in which it is in contact with said connection, the pin being biassed towards the isolated position and the arrangement being such that in use the presence of the appliance displaces the mounting plate to the forward position and simultaneously displaces the contact pin to the contact position.

The contact position is attained, according to the invention, only when the conditions of displacement of the mounting plate and contact pin are satisfied, such that relative movement of the pin and plate, or the summation of their respective movements, as occasioned by the presence of the appliance, has resulted in the contact pin being connected to a live source. The arrangement results in enhanced safety since, even if the mounting plate were to be maintained in the forward position in the absence of the appliance, the contact pin would be urged by its bias to be isolated from the live connection.

Preferably contact with both live and neutral connections is made via isolatable contacts according to the invention, and in addition any other connections required by the appliance may desirably also be so made.

Various ways may be envisaged of providing an isolatable contact according to the invention. One way is to provide the contact pin with an insulating sleeving or an insulated portion at its foot end and a brush or rubbing contact connected to a live supply and making permanent physical contact with the pin, whereby the brush contact is normally in physical contact with the insulated part but, when the pin is fully displaced, the brush contact is in physical contact with the conductive part of the pin. Another way is to mount the pin so that it is physically spaced from a live contact pad except when the pin is displaced.

Preferably the displaceable extent of the contact pin is at least 3 mm and the summation of the pin displacement and the distance of the head of the pin in the isolated position with the mounting plate in the retracted position and the contact pad on the appliance is at least 6 mm. This therefore requires that the displacable travel of the mounting plate should also be at least 6 mm, the front 3 mm (at least) serving to bring the contact pin into engagement with the appliance and the second 3 mm (at least) of travel serving to cause relative displacement of the pin and mounting plate whereby the pin assumes the contact position.

Preferably the pin is physically prevented from protruding more than a predetermined distance from the housing.

Embodiments of the invention will now be described by way of example with reference to the accompanying drawings, which illustrate in diagrammatic form an arrangement suitable for a cordless iron parking dock as more generally described in co-pending application No.

PCT/GB89/00765.

In the drawings: Figure 1 is a fragmentary plan view of an iron parking dock in the absence of an iron, and Figure 2 is a sectional fragmentary side view of the parking dock of Figure 1, with an iron in position and connected to electrical power.

Referring to Figure 1, an iron parking dock housing has a slot 11 for receiving the tail end of a cordless iron, the slot having a central open-topped transverse housing 12. Electrical contacts 11 are provided (for power and temperature sensor), connected direct to the mains supply. A T-shaped mounting plate 14 is slidably mounted and biassed by spring 15 to the left as illustrated; the plate carries contact pins 16 each slidably mounted and biassed to the right as illustrated by springs 17. The feet of the pins are spaced from the contacts 13. Movement of the mounting plate is controlled by a bar 18 (see also Figure 2) carried thereon, the sloping end 19 of which is exposed through the open top of the housing 12. The pins are in alignment with apertures 20 in the rear wall of the slot 11.

Referring to Figure 2, the tail end 21 of the iron is offered to the slot 11 such that a central arm 22, conveniently the earth pin, enters the open top of the housing and displaces the bar 18 and hence the plate 14 to the right, against the pressure of spring 15. The heads of the pins 16 are thereby brought to a position at which they protrude from the apretures 20 and are approaching engagement with contact pads 23 on the iron.

However, the pins are not at this stage connected to power. Continued movement of the plate 14 to the right causes actual engagement of pins 16 with pads 23 and thereby displacement of the pins relative to the mounting plate, against the pressure of springs 17, such that the pins remain stationary while the plate continues to move to the right, thereby bringing the feet of the pins 16 into contact with the electrical contacts 13. The iron is in this condition connected to power. Removal of the iron from the dock will cause the mounting plate 14 to move to the left and contact pins relative to the plate to the right, thereby disconnecting them from the power as they retract into the housing. However, on failure of the slidability of the plate 14 or the spring 15, removal of the iron would result in disconnection or isolation of the pins from the power, even though they may be protruding into the slot 11.

As shown in Figure 2, the head of the pins may be shaped to prevent excess movement into the slot beyond that necessary to cause disconnection or isolation.

Claims

CLAMS

1. An isolatable contact for a removable electrical appliance, the contact comprising a contact pin carried on a mounting plate constructed and arranged to be moved against a biassing pressure from a rearward position in which the pin is retracted in a housing to a forward position in which the pin protrudes from the housing to engage a corresponding contact on the appliance, in which the pin is displaceably mounted on the mounting plate for movement between a position in which it is isolated from an electrically live connection and a position in which it is in contact with said connection, the pin being biassed towards the isolated position and the arrangement being such that in use the presence of the appliance displaces the mounting plate to the forward position and substantially simultaneously displaces the contact pin to the contact position.

2. An isolatable contact according to Claim 1, in which the contact pin is provided with an insulated portion and a rubbing contact connected to a live supply makes permanent electrical contact with the pin.

3. An isolatable contact according to Claim 1, in which the pin is physically spaced from a live contact except when the pin is displaced.

4. An isolatable contact according to any preceding claim, in which the displaceable extent of the contact pin is at least 3 mm.

5. An isolatable contact according to any preceding claim, in which the sum of the pin displacement and the distance between the head of the pin in the isolated position with the mounting plate in the retracted position and the contact pad on the appliance is at least 6 mm.

6. An isolatable contact according to any preceding claim, in which the pin is physically prevented from protruding from the housing by more than a predetermined distance.

7. . An isolatable contact according to any preceding claim, in which the mounting plate is T-shaped the limb of which carries a bar which engages in use with an arm of the appliance and the cross-piece of which carries electrical contacts and displaceable contact pins.

8. An isolatable contact substantially as herein described with reference to and as illustrated in the accompanying drawings.