GB2190243A - Waterproof switch - Google Patents

Abstract

A double pole, double throw waterproof switch 1 comprises a pair of power input terminals 24 and power supply terminals 10. Power supply terminals 10 have arms 18 biassed towards the input terminals 24. A cam member 35 is rotatable to urge the arms 18 away from the terminals 24. Can member 35 is sealed to a housing wall 3 by a labrynth seal 37. Power input leads connected to terminals 24 may be embedded in an epoxy resin in a space 31 and a sealant may be applied to tags, 10 where they penetrate the housing wall. The cam 35 is rotated by a rotary operating member 42 (Fig. 1) or by a pushbutton 56 and twisted transmission member 55 (Fig. 7). By providing a double pole double throw switch an electrical appliance may be isolated completely when the switch is off. <IMAGE>

Description

SPECIFICATION Switch The present invention relates to switches, and in particular to waterproof switches.

The use of electrical appliances in a wet environment can be dangerous because of the leakage of electricity. This problem is particularly acute when using an appliance such as a hair dryer in a bathroom, where the switch may be activated by a person with wet hands.

The risk of electrocution may be lessened by using a wall mounted switch so that the user cannot grip the switch but this is not particularly convenient.

The present invention aims to reduce or eliminate this risk by providing a waterproof switch which may be mounted on the appliance or, preferably, in a lead supplying power to the appliance.

The invention provides an electrical switch comprising a housing, a first terminal for electrical connection to a power supply lead, a second terminal for electrical connection to an electrical appliance, and switching means for making and breaking an electrical connection between the first and second terminals, wherein said switching means comprises a rotatable actuation member, said rotatable actuation member being sealed to a wall of the housing by a labrynth seal.

Preferably the first and second terminals each comprise a contact portion said contact portions being relatively movable, and said rotatable actuation member comprising a cam which bears on at least one of said contacts for movement into and out of engagement with the other contact.

Very preferably the switch is a single throw, double pole switch, having a pair of first terminals and a pair of second terminals, each terminal having a respective contact. With this arrangement the switch, in its off position, electrically isolates completely the appliance.

Preferably a terminal extends through the housing wall and is sealed to the wall by a sealant, such as an epoxy resin.

The cam member may be rotated directly, but preferably a push button is provided for rotating the cam member, the cam member being positioned in an aperture in the housing wall.

The invention will be further described by way of example, with reference to the accompanying drawings, in which: Figure 1 is a cross-section along the line I-I of Figure 2, showing a first embodiment of the invention; Figure 2 is a cross-section along the line ll-ll of Figure 1; Figure 3 is a cross-section along the line Ill- Ill of Figure 1; Figure 4 is a cross-section along the line IV IV of Figure 1; Figure 5 is an enlarged perspective view of a first terminal; Figure 6 is an enlarged perspective view of a second terminal; and Figure 7 is a cross-sectional part view showing a modification of the embodiment of Figure 1.

Referring to the drawings, Figure 1 shows a switch 1 comprising a housing 2 formed of plastics material, such as polycarbonate, by injecting moulding. The housing comprises upper and lower halves 3, 4 which are ultrasonically welded together during assembly, along the join line defined by the outer wall 5 of the lower housing half 4.

The lower housing half 4 comprises the peripheral outer wall 5 and a bottom wall 6.

Bottom wall 6 has an integrally formed upstanding block portion 7 which locates a pair of power output tags 8, 9 which have downwardly projecting terminals 10, 11 which are received in apertures 12, 13 in block 7. A downwardly projecting iug 14 formed integrally with the housing half 4 separates the terminals 10, 11.

Tags 8, 9 have shoulders 15 which bear on the bottom wall 6 and are splayed 16 where they penetrate the wall to lock them in position.

A sealant such as epoxy resin may be applied in the vicinity of tags 10, 11 to ensure a watertight seal in the apertures 12, 13.

The tags 8, 9 are of resilient, electrically conducting metal such as brass strip or Beryllium Copper. Arms 18, 19 extend along the inside of the housing wall. A bend 44, 45 in each tag 8, 9 joins the arms 18, 19 and terminals 10, 11 to provide a spring action urging the arms 18, 19 towards the centre line of the housing (to positions 18", 19" shown in Figure 2).

A pair of power supply tags 20, 21 each comprise a flat plate 22 which is received in a recess in the upper surface of bottom wall 6, a downwardly projecting tang 24 which passes through an aperture 32 the bottom wall 6, and upwardly projecting contact 25.

Supply tags 20, 21 are of copper alloy, such as berrylium copper or brass.

Each contact 25 bears a silver coated copper alloy button 26 which s positioned opposite a like button 27 on the respective arm 18, 19, the buttons 26, 27 being positioned to make electrical contact with each other on actuation of the switch.

The power supply terminals each have an aperture 28 which cooperates with an aperture 29 in the housing bottom wall 6. A power supply wire (not shown) is inserted through the aperture 28, 29, bent into an L shape to rest on the plate 21 and then forged or soldered to the plate. The wire enters via a space 31 enclosed by a wall 30 which projects down from the bottom housing wall 6.

After attaching the wires to the plates 21, the space 31 is filled with epoxy resin or some other water resistant and waterproof sealant to prevent water entering via the apertures 32 and to hold the wires firmly in position.

Figure 4 is a cross-section along the line IV IV of Figure 1 and shows the switch in its on position. A switch actuating member 33 of poiycarbonate is rotatable about an axis C.

The member 33 bears on the lower wall 6 via a button 34 formed integrally at the base of the member and received in a recess 47 in the bottom wall. A cam portion 35 is positioned at the height of the arms 18, 19.

Above the cam portion a sealing portion forms a labrynth seal 37 with an upper wall 38 of the top housing half 3.

The cooperating formations 38, 39 of the labrynth seal 37 are circular in plan view to provide a rotatable connection between the switch member 33 and the upper housing wall 38.

The distance between the formations 38 and button 34 is arranged so that the formation 38 is snugly received in formation 39 when the housing halves 3, 4 are welded together. A hydrophobic lubricant, such as silicone grease, is smeared on the formations 38, 39 to enhance the waterproof seal.

The cooperating formations 38, 39 comprise two annular wall portions 48, 49 and 50, 51 formed respectively on the actuating member 33 and the housing 3.

A collar 40 is formed on top of the housing wall 38 and surrounds an upper stem 41 of the member 33. The upper end 42 of stem 41 is of square cross-section and a bar 43 is a press fit on the stem for turning the actuating member 33.

Figures 5 and 6 are perspective views of an input tag 21 and an output tag 8.

To assemble the switch, the tags 8, 9, 20, 21 are fabricated, tags 8, 9 being of resilient material, with the contact buttons 26, 27 being welded to the respective arms of the terminals.

The tags are installed in the base of the switch. Wires from a supply lead are then fed through the holes 28, 29 and soldered to the plates 22 of tags 20, 22. The upper housing half 3 with the actuation member 33 is then positioned on the lower housing half and the two halves welded together, by ultrasonic welding. Cavity 31 is then filled with epoxy resin.

In another preferred form, tangs 24 24 extend into the cavity 31 and electrical connection is made between the supply leads and the tangs 24 in the cavity 31. In this way the switch can be assembled as a unit before connecting the supply lead.

To operate the switch, the actuating member 33 is rotated. In the on position, the cam member 35 is aligned with its long axis extending between the arms 18, 19. Arms 18, 19 are urged against the contacts 25, 26 by the spring action of the bends 44, 45, the arms being in the position 18", 19" shown in Figure 2.

As the actuating member 33 is rotated through 90" by the bar 43, cam surfaces 46 bear against the arms 18, 19 and urge them outwardly against the spring face of bends 44, 45, to positions 18', 19' breaking the contact between the input terminals and the output terminals. The flat surfaces 4, 6 rest against the arms 18, 19, which thus bear on the flat surfaces 46 to hold the cam in position until the handle 43 is rotated further, or rotated back, to turn the switch off.

Figure 7 shows a modification of the embodiment of Figure 1, in which the actuating member 3 is replaced by a lower rotatable cam portion 35' which is rotated by a push button assembly 52. Like parts to the switch of Figure 1 are given like reference numerals.

The cam portion 35' corresponds to the cam portion 35 of Figure 1 in its shape and function, including sealing portions 37, but instead of being intergrally formed with an upper stem it is provided with a recess 53 in its upper surface.

Recess 53 receives a member 54 attached to a vertical bar 55. Bar 55 is flat but has a 90 degree twist between its ends, as seen in Figure 7. The upper end of the bar is received in a push button 56 having a lower plate 57 with a slot 58 which snugly receives the bar 55. The push button has projections 59 which are received in slots 60 in the inside wall of column 40 to prevent rotation of the button 56 relative to the column 40.

A lower flange 60 on button 56 is urged against a flange 61 on stem 40.

As button 56 is depressed the bar 55 will be rotated through 90 degrees by the slot 58, thus rotating member member 54 through 90 degrees. Member 54 cooperates with cam 35' via cam surfaces forming a pawl and ratchet mechanism (not shown). Cam 35' is thus rotated through 90 degrees by member 54. On releasing the button 56, the bar 55 will rotate back through 90 degrees, bringing member 54 with it, but cam 35' remains in position. On further depression of the button the cam 35' is rotated again by 90 degrees, and so on.

The switch opens and closes as for the embodiment of Figure 1, the arms 18, 19 cooperating with cam 35 to cause it to rest at the position seen in Figure 2, or when rotated through 90 degrees.

Various modifications will be apparent to those skilled in the art and it is desired to include all such modifications as fall within the scope of the invention as defined in the accompanying claims.

Claims (11)

1. An electrical switch comprising a housing, a first terminal for electrical connection to a power supply lead, a second terminal for electrical connection to an electrical appliance, and switching means for making and breaking an electrical connection between the first and second terminals, wherein said switching means comprises a rotatable actuation member, said rotatable actuation member being sealed to a wall of the housing by a labrynth seal to form a substantially watertight connection therebetween.

2. A switch as claimed in claim 1, wherein a hydrophobic lubricant or grease is smeared on cooperating surfaces of said labrynth seal.

3. A switch as claimed in claim 1 or 2, wherein a said terminal projects through a wall of the housing and a sealant is applied thereto to form a watertight seal with the housing wall.

4. A switch as claimed in any one of claims 1 to 4, wherein each said terminal comprises a contact portion for contact with the other respective terminal, and said contact portions of said first and second terminals are relatively movable by said cam member.

5. A switch as claimed in clam 4, wherein a said first or second terminal comprises a connecting portion for connection to a power input or supply lead and said contact portion comprises an arm extending from said connection portion, said arm being resiliently connected to said connection portion.

6. A switch as claimed in claim 5, wherein said arm is biassed towards the other connection portion.

7. A switch as claimed in claim 6, wherein said arm is integrally connected to said connection portion by a resilient bend.

8. A switch as claimed in any one of claims 5 to 7, wherein said actuation member comprises a substantially planar cam surface portion which engages with said arm to hold the cam in position relative to the cam.

9. A switch as claimed in any one of claims 1 to 8, comprising a pair of first terminals and a pair of second terminals to form a double pole, single throw switch.

10. A switch as claimed in any one of claims 1 to 9, wherein said labrynth seal comprises a first annular wall provided on said housing wall and/or said actuation member and received in an annular groove portion in said actuation member and/or said housing wall.

11. A waterproof electrical switch, substantially as hereinbefore described with reference to Figures 1 to 6 of the accompanying drawings, or Figures 1 to 6 as modified by Figure 7.