GB2121605A - Improvements in or relating to electric relays - Google Patents

Abstract

A relay includes a housing 1 containing an electromagnetic assembly, including a bobbin on which a coil is wound and within which a magnetic core and yoke, an armature and contact actuator are accommodated. Opposing side walls of the housing 1 have recesses, in which a plurality of contact mounting and terminal members are accommodated, and provide contacts 14 and 15 at one end thereof and terminal pins, such as 18b, extending below a base wall of the housing 1 at the other end thereof. Protruding studs 13 on the side walls of the housing 1 are arranged to coincide with holes 23 in side plates 22, so that when the side plates 22 are correctly located, the contact members are "sandwiched" between the side walls and the side plates. The side plates 22 are then ultrasonically welded in position. <IMAGE>

Description

SPECIFICATION Improvements in or relating to relays This invention relates to improvements in relays and it relates especially, although not exclusively to miniature relays of the kind used in printed circuit board lay-outs.

In known relays of this kind, a two-part plastics housing is provided with means within each half of the housing for receiving an electromagnetic assembly comprising a yoke, coil and insulated core arrangement.

Contact plates are moulded within the wall of each half of the housing and the halves are typically joined together by ultrasonic welding.

This method of production of such relays can create a number of problems. Firstly, vapour given off during the moulding process is liable to contaminate the contacts of the contact plates and thus increase the resistance thereof. Secondly there is a substantial amount of difficulty in producing a welded join which is impervious to moisture.

An additional problem can also be encountered in the electromagnetic assembly, wherein, in known relays, the coil is wound directly onto the insulated core. Under these circumstances if the relay should overheat, there is the danger of the insulation melting and thus a short circuit occurring. Additionally in life, turns at the unsupported ends of the winding layers can become loose and fall into the armature gap causing malfunction.

It is therefore an object of the present invention to provide an improved type of relay and a method of assembling the same to substantially overcome the aforementioned problems.

According to the invention there is provided a relay including a housing containing an electromagnetic assembly and an armature and trip plate assembly, and a plurality of electrically-conductive contact members, some for supply of electrical current to said electromagnetic assembly and some constituting switch components, said contact members including portions extending beyond a base wall of said housing to form terminal pins for the relay, each of said contact members being disposed between a side member and an outer surface of said housing, said side member being secured to said outer surface by ultrasonic welding.

Further according to the invention there is provided a relay as set forth in the immediately preceding paragraph wherein the electromagnetic assembly includes a bobbin on which a coil is wound and within which a magnetic core is accommodated.

Still further according to the invention, there is provided a relay as set forth in either of the two immediately preceding paragraphs wherein the trip plate is formed of electrically insulating material and is secured to the armature by mechanical pressure or heat sealing fixings.

Still further according to the invention, there is provided a method of assembling a relay wherein an electromagnetic assembly is disposed within a housing consisting of a base, opposing side walls and opposing end walls, the electromagnetic assembly comprising a bobbin, on which a coil is wound and within which a core is situated, and a yoke secured to one end of the core, a pivotablymounted armature and trip plate assembly is positioned above said electromagnetic assembly and a contacted spring member is rested upon said trip plate, and a plurality of electrically conductive contact members are disposed between a side member and an outer surface of a side wall of the housing, said side member being secured to said outer surface by ultrasonic welding.

The invention will be further described by way of example only with reference to the accompanying drawings where: Figure 1 shows a sectional side view of a partially constructed embodiment of the invention, Figure 2 shows a side view of the construction shown in Fig. 1, and further including electrically conductive contact members in accordance with the invention, Figure 3 shows a side member in accordance with the invention, Figure 4 shows end views of the features shown in Figs. 2 and 3, looking in the direction of "A" onto each one, and Figure 5 shows a sectional side view of a final complete construction of an embodiment of the invention.

Referring now to Fig. 1, an electromagnetic assembly comprising a magnetic core 2, a yoke 3 and a coil 6 is placed in a rectanguiar plastics housing 1. The yoke 3 is secured onto the end of the core 2 by swaging over a reduced end section 4 and the coil 6 is wound around a plastics bobbin 5, within which the core 2 is situated. The end of the bobbin 5 has two protrusions, one of which can be seen at 7, each protrusion having an end of the wire forming the coil wound around it. This securing of the wire ends increases reliability, insulation resistance and dielectric withstanding voltage. An armature 8 is pivotably-mounted on the upper surface of the yoke 3 and there is an electrically-insu- lated trip plate 9 attached around one end thereof.The trip plate 9 is provided with studs 9a, which are pressed into holes in the armature and heat sealed instead of the trip plate being moulded around the end of the armature, which could cause misalignment thereof.

A return spring 10 is provided to ensure that the armature 8 is returned to the position shown after being pivoted during operation of th relay, which will be explained in detail below.

Fig. 2, in which like reference numerals refer to like parts with respect to Fig. 1, shows a later stage of construction of the relay, incorporating electrically conductive contact members 12, which are fitted into recesses provided in the wall of the housing 1, instead of being moulded into the side members, which could cause contamination of the contacts thereon. The contact members 12 are also fitted over protruding plastics studs 13, which are integrally formed with the wall of the plastics housing 1. Ends 1 8a to 1 8d of the contact members 12, which extend beyond the base of housing 1, are terminal pins which are intended to slot into holes in a printed circuit board, which is not shown in the diagrams.

Contacts 14 and 1 5 of contact members 1 2 provide electrical connections between pins 1 8c and either 1 8b or 1 boa, respectively.

Contacted spring 20 is supported on pole 16 of contact members 12, which provides an electrical connection through pin 1 by, and end 21 of contacted spring 20 rests on contact 1 5. Contact 1 7 of contact members 1 2 is electrically connected to the end of the wire of the coil to supply electrical current to the coil via pin 1 bud. Part 19, which joins the terminal pins 1 boa to 1 bud, is provided during construction of the relay to prevent the terminal pins from being damaged.

In the present embodiment, an identical arrangement to that shown in Fig. 2 is provided on the opposing side of the relay, including an electrical connection to the other end of the wire of the coil. Thus the relay includes two sets of switch contacts, each including a pole 16, a normally closed contact 1 5 and a normally open contact 14. On actuation of the relay, the normally closed contact is opened and the normally open contact is closed.

Fig. 3 shows a side plate 22, which is also formed from a plastics material and which has holes 23 formed thereon and a lug 24 integrally formed therewith.

Fig. 4, which shows end views from the direction of "A" in Figs. 2 and 3 indicates that the protruding studs 1 3 are arranged so as to coincide with holes 23 to provide positive location of the side plate 22 to the plastics housing 2. The contact members, which cannot be seen in Fig. 4 and which join contacts 14, 1 5 and terminal pins, the end pin 1 8b of which can be seen, are thus "sandwiched" between the wall of the housing 1 and the side plate 22. When the side plate is pressed onto the wall of the housing, lug 24 fits over the top of the wall. This side plate is finally ultrasonically welded in position.

Fig. 4 shows an end view of ends 21 of the contacted springs, which are supported above the trip member 9, thus showing that, in this embodiment, a contacted spring, contact members terminal pins and a side plate are provided identically on both sides of the relay.

Referring now to Fig. 5, in which any parts shown in the preceding diagrams are numbered the same, a complete construction of the embodiment is shown. The part 19 attached to the ends of the terminal pins 1 boa to 1 8d as shown in Fig. 2, has now been removed and a transparent plastics cover 25 has been fitted onto the top of the housing 1 to protect the exposed components of the relay. Cover 25 is provided with a pin identification pip, shown at 26, which indicates the position of pin 1 8d. Protrusions 11 on the base of the housing are provided as stop members for use when the terminal pins are pushed into holes in a printed circuit board.

During operation of the relay, electrical current is supplied to the coil 6 on the bobbin 5, through pin 1 8d and contact 1 7 and an identical pin and contact 9 provided on the other side of the relay, to energise the coil.

When the coil is energised, end 8a of the armature 8 is magnetically attracted to end 2a of the core 2. Due to the pivotal arrangement of the armature, the trip plate 9, which is attached to the opposite end of the armature to end 8a, is raised when end 8a is attracted to core end 2a.This action consequently raises the contacted spring 20, so that the end 21 loses contact with contact 1 5 and gains contact with contact 14, so that an electrical connection is made between pins 1 8c and 1 8b rather than between pins 1 8c and 1 boa. When the coil is de-energised, return spring 10 lowers the armature (and thus the trip plate and contacted spring) to its original position, lying flat along the top surface of the yoke 3, so that end 21 of the contacted spring is again in contact with contact 1 5 and electrical connection is again made between pins 1 8c and 1 boa.

It will be appreciated that, although in this embodiment two identical sets of electrical contacts are provided (one on either side of the relay housing), one set may be provided on only one side of the housing or alternatively more than one relay may be provided, thus supplying any number of electrical contacts. In the case of only one set being used, an additional contact, identical to the one shown at 17, and a terminal pin are required to provide an electrical connection for the other end of the wire of the coil.

Claims (11)

1. A relay including a housing containing an electromagnetic assembly having an armature and trip plate assembly associated therewith, and a plurality of electrically-conductive contact members, some for supply of electrical current to said electromagnetic assembly and some constituting switch components, said contact members including portions ex tending beyond a base wall of said housing to form terminal pins for the relay, each of said contact members being disposed between a side member and an outer surface of said housing, said side member being secured to said outer surface by ultrasonic welding.

2. A relay as claimed in Claim 1 wherein the electromagnetic assembly includes a bobbin on which a coil is wound and within which a magnetic core is accommodated.

3. A relay as claimed in Claim 2 wherein an end of the bobbin is provided with a first and a second protrusion, each protrusion having an end of a wire forming the coil secured thereto.

4. A relay as claimed in any one of Claims 1, 2 or 3 wherein the trip plate is formed of electrically insulating material and is secured to the armature by mechanical pressure or heat sealing fixings.

5. A relay as claimed in any preceding claim wherein said contact members are accommodated in recesses provided in the outer surface of a side wall of said housing.

6. A relay as claimed in any preceding claim wherein said outer surface of said housing is provided with protruding studs arranged so as to coincide with holes provided in said side member, so as to provide positive location of said side member to said outer surface.

7. A relay as claimed in any preceding claim wherein said housing and said side member are formed from a plastics material.

8. A relay as claimed in any preceding claim wherein said housing is provided with a cover formed from a plastics material to provide protection for exposed components therein.

9. A relay as claimed in any preceding claim wherein a first and a second plurality of contact members is disposed respectively between an opposing side wall of said housing and a side member.

10. A relay substantially as herein described with reference to the accompanying drawings.

11. A method of assembling a relay wherein an electromagnetic assembly is disposed within a housing consisting of a base, opposing side walls and opposing end walls, the electromagnetic assembly comprising a bobbin, on which a coil is wound and within which a core is situated, and a yoke secured to one end of the core, a pivotably-mounted armature and trip plate assembly is positioned above said electromagnetic assembly and a contacted spring member is rested upon said trip plate, and a plurality of electrically-conductive contact members are disposed between a side member and an outer surface of a side wall of the housing, said side member being secured to said outer surface by ultrasonic welding.