US3022388A

US3022388A - Automatic selecting switches as used in automatic telephone systems

Info

Publication number: US3022388A
Application number: US832927A
Authority: US
Inventors: Leslie John Douglas
Original assignee: Siemens Edison Swan Ltd
Current assignee: Siemens Edison Swan Ltd
Priority date: 1958-08-19
Filing date: 1959-08-11
Publication date: 1962-02-20
Anticipated expiration: 1979-02-20

Description

Feb. 20, 1962 J. D. LESLIE 3,022,388

AUTOMATIC SELECTING SWITCHES AS USED IN AUTOMATIC TELEPHONE SYSTEMS Filed Aug. 11, 1959 INV'ENTOR JOHN DOUGLAS LESLIE 3,022,388 AUTGMATIC SELECTING SWITiII-IES AS USED IN AUTOMATIC TELEPHONE SYSTEMS John Douglas Leslie, London, England, assignor to themens Edison Swan Limited, London, England, a British company Filed Aug. 11, 1959, Ser. No. 832,927 Claims priority, application Great Britain Aug. 19, 1958 1 Claim. (Cl. 200-11) This invention relates to automatic selecting switches of the type used in automatic telephone systems and in which wipers wipe over fixed contacts, termed bank con tacts, mounted to constitute a so-called contact bank.

It is well known to employ, in an automatic selecting switch of the type referred to, a form of contact bank which comprises a plurality of moulded bank units clamped together, each moulded bank unit comprising one or two rows of bank contacts moulded into insulating material. In general, known moulded bank units are such that the track wiped by a Wiper traversing a row of bank contacts is of a mechanically broken nature, the mechanically broken nature of the track being due to the fact that the wiped portions of the bank contacts are tip portions that protrude in cantilever fashion from, and quite clear of, the insulating material in which the bank contacts are moulded, so that the track is interrupted mechanically, as well as electrically, in the gaps between bank contacts of the row, Disadvantages of such a track are that its mechanically broken nature tends to increase the incidence of troubles due to wiper vibration or bounce and to increase the mechanical loadon the driving means of the switch.

With bank contacts and contact banks of the forms and sizes usually employed, a difficulty is encountered if it is attempted to avoid the disadvantage just mentioned by arranging that the insulating material of a moulded bank unit extends, in the form of small portions or tongues protruding from the main body of this material, into the gaps between bank contacts of a row so that these gaps are filled with insulating material flush with the contact ing surfaces of these bank contacts. This difficulty is the practical one that the small protruding portions or tongues of insulating material are too fragile or too readily displaced to be satisfactory. Y

The present invention provides an improved moulded bank unit which is such that the track wiped by a wiper traversing a rowof bank contacts is a smooth and me,- chanically unbroken one, and in which the difficulty referred to is fully overcome.

According to the main feature of the invention there is provided a moulded bank unit, comprising bank con tacts moulded into insulating material, wherein each of a plurality of bank contacts forming a row has a tag por tion which protrudes clear of the moulded insulating material from a face of a main body of this material, an embedded portion which is embedded in the main body of the moulded insulating material so that none of its surface is exposed, and a wiped portion Which protrudes from a further face of the main body of the moulded insulating material and which has its surface partly exposed to permit of requisite wiper engagement with it, and wherein the moulded insulating material so extends, in the form of strips protruding from the main body of this material, into the gaps between said wiped portions of the bank contacts, of the'row that these gaps are filled with insulating material flush with the contacting surfaces of said wiped portions to provide at least one smooth and mechanically unbroken wiper track, and wherein said strips are supported, at their ends remote from the main body of the moulded insulating material, by a sup porting portion of the moulded insulating material, this nite States atent supporting portion taking-the form of a continuous length of the moulded insulating material integral with said main body and with said strips and interconnecting said ends of said strips. It is contemplated that hard nylon may be employed as the insulating material.

According to a subordinate feature of the invention, in a moulded bank unit as just set forth each of the bank contacts forming the row has, in addition to the tag and embedded and wiped portions referred to, a further portion which is embedded in said supporting portion of the moulded insulating material, it being thereby arranged that this supporting portion is itself supported mainly by said bank contacts.

In order that the invention may be more readily and fully understood, a specific embodiment of it will now be described by way of example with reference to the accompanying drawing. This embodiment takes the form of a moulded bank unit for use in building up the contact bank of a selecting switch of the rotary uniselector type. Fig. 1 of the drawing shows a plan view of the bank unit, FIG. 2 shows (on a larger scale than FIG. 1) a view in isometric projection of a portion of the bank unit, and FIG. 3 shows a somewhat diagrammatic view illustrating how a composite. wiper cooperates with such a bank unit in a contact bank comprising a plurality of such bank units. FIGS. 4, 5, and 6 illustrate the preferred form of the contacting tip of a constituent wiper used in forming a composite wiper as just referred to, FIG. 4 being a plan view of the tip portion of the constituent wiper and FIGS. 5 and 6 being side and end views respectively.

Referring firstly to FIGS. 1 and 2, the moulded bank unit concerned comprises a single row of bank contacts 1 moulded into a unitary mass of insulating material 2. Each bank contact has the general form of a thin conducting metal strip, and the bank contacts as a whole are arranged in the well-known manner so that they lie in the same plane and are radial with respect to an axis. The main body 3 of the moulded insulating material has two major plane faces, such as the face 4, each having two edges which are radial with respect to said axis and two edges which are arcuate with respect to said axis, and has two minor plane faces, such as the face 5, which are end faces and are rectangular, and has a curved outer face (not seen in the figures) and a curved inner face 6. Each bank contact 1 has a tag portion 7 which protrudes from said curved outer face, an embedded portion 8 (see FIG. 1) which is embedded in the main body 3 of the moulded insulating material so that none of its surface is exposed, a wiped portion 9 which protrudes from said curved inner face and has its two major surfaces (i.e. the surfaces other than its two thin edges) exposed to permit of wiper engagement with them, a further portion it? (see FIG. 1) which is embedded in a supporting portion it of the moulded insulating material, and a still further portion 12 which protrudes from said supporting portion of the moulded insulating material. Strips 13 of the moulded insulating material protrude from the main body 3 of this material to fill the gaps between said wiped portions 9 of the bank contacts to provide two smooth and mechanically unbroken wiper tracks, one facing in the same direction as one of the two major plane faces of the main body of the moulded insulating material and the other facing in the opposite direction. Each of these two tracks is arcuate with respect to said axis and includes one of the exposed (contacting) major surfaces of said wiped portion 9 of each bank contact. Said supporting portion 11 of the moulded insulating material takes the form of a continuous arcuate length of insulating material which is of rounded cross-section, and which is integral with the main body 3 of the moulded insulating material and the protruding strips 13 of this material and interconnects the ends of these strips remote from said main body, and which serves to support the protruding strips at said ends. The supporting portion 11 of the moulded insulating material is itself supported mainly by the bank contacts. The cross-sectional dimesnion of said supporting portion 11 parallel to said axis is considerably less than the distance 'between the major faces of the main body 3 of the moulded insulating material. The holes 29 in the main body 3 of the moulded insulating material serve to accommodate the clamping bolts employed in clamping a plurality of such moulded bank units together to form a contact bank. The unit is intended for use with a composite wiper of the kind cornprising in effect two constituent Wipers which are electrically connected together and which are arranged so that one engages one contacting surface of said wiped portion 9 of a bank contact whilst the other engages the other contacting surface of this wiped portion, that, one wipes over one of the two tracks referred to whilst the other wipes over the other of these two tracks.

As has already been stated, FIG. 3 shows a somewhat diagrammatic view illustrating how a composite wiper cooperates with a moulded bank unit such as that illustrated in FIGS. 1 and 2. The parts represented in FIG. 3, which is largely in cross-section, comprise end portions 14 and 15 of the two constituent Wipers of a composite Wiper, a particular bank contact 1A engaged by these two constituent wipers and included in a moulded bank unit .16, a further moulded bank unit 17 similar to the bank unit 16 and included in the same contact bank as the bank unit 16, a metal spacer 18 situated between the two bank units 16 and 17, and a clamping plate 19 and resilient pad 20 used in forming the contact bank concerned (which will of course include other elements such as further bank units, further metal spacers, a further clamping plate, and clamping bolts). As will be clear from FIG. 3, when the two constituent Wipers of a composite Wiper are wiping the two wiper tracks on a bank unit, the tensioned blade of one constituent wiper lies on one side of the supporting portion 11 of the moulded insulating material of the unit and the tensioned blade of the other constituent wiper lies on the other side of this supporting portion. It will also be clear that, with a composite wiper of the kind referred to, effective electrical briding action can be obtained when required by arranging that the contacting tip of one of the two constituent wipers wipes slightly in advance of the contacting tip of the other of the two constituent wipers.

It is preferred to arrange that the contacting tip of each constituent wiper of a composite wiper has the form illustrated in FIGS. 4, 5, and 6. As has already been stated, FIG. 4 is a plan view of the tip portion of a constituent wiper of a composite wiper, and FIGS. 5 and 6 are repsectively side and end views of this tip portion.

4. The advantages of the form of contacting tip illustrated in FIGS. 4, 5, and 6 are that it offers an easy slope to the bank member it engages when entering the bank, and that it avoids engagement, and consequent wear, of the Wiper track by any sharp cutting edge.

Referring again to FiGS. 1 and 2, it should be noted that a strip 21 of the moulded insulating material, corresponding to, and supported in the same way as, the strips 13 that fill the gaps between said wiped portions of the bank contacts, precedes the first bank contact in the row so as to cause the two unbroken wiper tracks to commence in advance of this bank contact. This arrangement has the advantage that vibration of each constituent wiper caused by the initial engagement of a composite wiper with the bank unit has wholly or effectively died away before the constituent wipers reach the first bank contact.

What I claim is:

A moulded bank unit comprising a plurality of bank contacts moulded into insulating material to form a row of bank contacts spaced apart from one another, each of said bank contacts having a tag portion protruding clear of the moulded insulating material from a face of a main body of this material, a main embedded portion embedded in the main body of the moulded insulating material and having none of its surface exposed, a wiped portion protruding from a further face of said main body of the moulded insulating material and having its surface partly exposed to form at least one contacting surface to permit of wiper engagement with it, and a further portion extending from said wiped portion in the direction away from said main embedded portion, the moulded insulating material extending, in the form of strips protruding from said main body of this material, into the gaps between said wiped portions of said bank contacts to fill these gaps with insulating material flush with the contacting surfaces of said wiped portions to provide at least one smooth and mechanically unbroken wiper track, and said strips being supported, at their ends remote from said main body of the moulded insulating material, by a supporting portion of the moulded insulating material, this supporting portion taking the form of a continuous length of the moulded insulating material integral with said main body and with said strips and interconnecting said ends of said strips and having said further portions of said bank contacts embedded in it to cause it to be supported by said bank contacts.

References Cited in the tile of this patent