A snap-in adaptor plate for a circuit breaker

Abstract

 A snap-in adaptor plate is provided for a circuit breaker. The circuit breaker is of the type comprising a pair of shell halves which in combination define a front wall and a pair of opposed end walls. The front wall is formed with a pair of mounting recesses for accommodating a pair of corresponding internally threaded front mounting screw inserts for allowing the circuit breaker to be screw mounted against an interior face of a panel defining a relatively small conventional circular panel aperture. The adaptor plate comprises an elongate front plate having a central aperture through which a turret of the conventional circuit breaker is arranged to pass and a pair of mounting lugs extending from an inner surface of the front plate and adapted to be held captive within the mounting recesses when the front plate is fitted over the front wall. A pair of spaced apart retaining clips extend rearwardly from opposite ends of the front plate adjacent the end walls of the circuit breaker for allowing the assembled snap-in adaptor plate and circuit breaker to engage the opposed edges of an oversize panel aperture in a snap fit. The invention extends to a modified circuit breaker assembly comprising a snap-in adaptor plate of the type described and a conventional circuit breaker.

Description

BACKGROUND TO THE INVENTION

[0001] THIS invention relates to a snap-in adaptor plate for a circuit breaker.

[0002] Conventional circuit breakers, such as the C-frame 8340 range manufactured by Circuit Breaker Industries Limited of Tripswitch Drive, Elandsfontein, Gauteng, South Africa, are formed with a pair of case halves which in combination define a front wall having a central lever opening and a pair of mounting recesses on opposite sides of the lever opening. The mounting recesses formed in the shell or case halves are arranged to accommodate internally threaded brass front mounting inserts which are held captive when the shell halves are rivetted together.

[0003] The panel to which a breaker of this type is mounted is typically provided with a circular cut-out for the breaker handle lever, and two adjacent screw holes which are aligned with corresponding threaded openings in the aforementioned brass inserts. Each breaker is thus individually screwed into a panel. This is a relatively time consuming and labour intensive operation which is not particularly well suited to maintaining cost effective installation and maintenance programmes.

[0004] With a view to speeding up the installation procedure, snap-in circuit breakers have been designed with a dedicated housing which is arranged to form a removable snap fit within a standard panel aperture, which in the case of the C-frame range, has a width of 55.6mm.

[0005] It is an object of the invention to provide snap-in versions of circuit breakers of the type described above without having to redesign the entire circuit breaker housing.

SUMMARY OF THE INVENTION

[0006] According to a first aspect of the invention there is provided a snap-in adaptor plate for a conventional circuit breaker of the type comprising a pair of shell halves which in combination define a front wall and a pair of opposed end walls, a mounting recess being defined in the front wall for accommodating at least one corresponding internally threaded front mounting insert for allowing the circuit breaker to be screw mounted against an interior face of a panel defining a relatively small conventional panel aperture, the adaptor plate comprising an elongate front plate, at least one mounting lug extending from an operatively inner surface of the front plate and adapted to be held captive within the mounting recess when the front plate is fitted over the front wall, and a pair of spaced apart retaining clips formed integrally with the front plate and extending rearwardly from opposite ends thereof adjacent the end walls of the circuit breaker for allowing the assembled snap-in adaptor plate and circuit breaker to engage the opposed edges of an oversize panel aperture in a snap fit.

[0007] In a preferred form of the invention, the front wall of the conventional circuit breaker is formed with a pair of mounting recesses for accommodating a pair of corresponding internally threaded front mounting inserts, the pair of mounting recesses being located on opposite sides of a central turret from which a breaker lever extends, with the turret being arranged to pass through the relatively small panel aperture, the adaptor plate further comprising a central aperture through which the turret is arranged to pass and a pair of mounting lugs located on opposite sides of the central aperture, with the mounting lugs being arranged to locate within the corresponding pair of mounting recesses, and being spaced apart from one another by the same centre-to-centre distance z as the mounting recesses are spaced apart.

[0008] The mounting lugs are typically of top hat section terminating in expanded heads, and having essentially the same external profile as the internally threaded front mounting inserts.

[0009] Typically, the retaining clips comprise non-deflectable L-shaped brackets, and re-entrant inwardly deflectable clip portions extending from the base limbs of the brackets.

[0010] Advantageously, the clip portions comprise first and second resiliently deformable limbs joined in a shallow V-configuration, with the first limb extending from the base limb of the L, and the free operatively outermost surface of the second limb being formed with serrations for releasably engaging the opposed edges of the oversize panel aperture.

[0011] Conveniently, with the end walls of the conventional circuit breaker being spaced a distance y apart, the distance between the innermost surfaces of each retaining clip and the central axis defined by each mounting lug is (y-z)/2.

[0012] Preferably, with the opposed minor edges of the standard oversize panel aperture being spaced a distance y+Δy apart, the distance between deflectable portions of the retaining clips is equal to y+Δy when inwardly deflected and is greater than y+Δy when the deflectable portions of the retaining clips are holding the adaptor plate and circuit breaker captive within the oversize panel aperture.

[0013] The invention extends to a modified circuit breaker assembly comprising a conventional circuit breaker of the type comprising a pair of case halves which in combination define a front wall and a pair of opposed end walls, a mounting recess being defined in the front wall for accommodating at least one corresponding internally threaded front mounting insert for allowing the circuit breaker to be screw mounted against an interior face of a panel defining a relatively small conventional panel aperture, and a snap-in adaptor plate, the adaptor plate comprising an elongate front plate, at least one mounting lug extending from an operatively inner surface of the front plate and adapted to be held captive within the mounting recess when the front plate is fitted over the front wall, and a pair of spaced apart retaining clips formed integrally with the front plate and extending rearwardly from opposite ends thereof adjacent the end walls for allowing the snap-in adaptor plate and circuit breaker to engage the opposed minor edges of an oversize panel aperture in a snap fit.

[0014] In a preferred form of the invention, the front wall of the standard circuit breaker is formed with a pair of mounting recesses for accommodating a pair of corresponding front mounting inserts, the pair of mounting recesses being located on opposite sides of a central turret from which a breaker lever extends, with the turret being arranged to pass through the relatively small conventional panel aperture, the adaptor plate further comprising a central aperture through which the turret is arranged to pass and a pair of mounting lugs located on opposite sides of the central aperture, with the mounting lugs being arranged to locate within the corresponding pair of mounting recesses, and being spaced apart from one another by the same centre-to-centre distance z as the mounting recesses are spaced apart.

BRIEF DESCRIPTION OF THE DRAWINGS

[0015] 

Figure 1

shows a front view of a snap-in adaptor plate of the invention;

Figure 2

shows a side view of the adaptor plate of Figure 1;

Figure 3

shows an underplan view of the adaptor plate of Figure 1;

Figure 4

shows a partly cross-sectional side view of the adaptor plate;

Figures 5A & 5B

show respective end- and side-on details of the adaptor plate;

Figure 6

shows a front view of a typical C-frame circuit breaker;

Figure 6A

shows a cross-sectional detail on the line 6A-6A of Figure 6;

Figure 7

shows a partly cross-sectional side view of the snap-in adaptor plate fitted to one shell half of the housing of the C-frame circuit breaker; and

Figure 8

shows a side view of the snap-in adaptor plate fitted to the circuit breaker of Figure 6.

DESCRIPTION OF EMBODIMENTS

[0016] Referring first to Figures 1 to 4, a snap-in adaptor plate 10 is formed with a front face 12, a rear face 14 and a circular aperture 16 through which a conventional circuit breaker lever 18 and turret 52 (see Figures 7 and 8) is arranged to pass. Extending inwardly from the rear face 14 are a pair of mounting lugs 20 and 22 terminating in hex-shaped heads 24. Also extending inwardly and at right angles from the rear face 14 of the front plate are a pair of retaining clips 26 and 28. Both the lugs and the retaining clips are formed integrally with the front plate, with the entire snap-in adaptor being unitary and being injection moulded from a suitable rugged thermoplastic material.

[0017] As is clear from Figures 5A and 5B, each of the retaining clips includes a non-deflectable L-shaped bracket portion 29, with a resilient inwardly deflectable clip-portion 30 extending upwardly from the base leg of the L. The clip portion 30 includes first and second limbs 32 and 34 having a shallow V-configuration, with the limb 32 having a smooth outer surface 36 and the limb 34 having a serrated outer surface defined by a series of saw teeth 38 serving as a ratchet. The entire clip portion 30 is arranged to deform inwardly to a maximum deflection position indicated in broken outline at 40, in which it lies within a plane defined by the outer face 28A of the bracket portion. The V-shaped clip portion 30 is formed with an elbow 39, the inner portion of which defines an included angle x of 145° when in the unstressed position.

[0018] Referring now to Figure 6, a front view of a conventional 8340 C-frame circuit breaker 44 is shown formed from two shell halves 46 and 48 which are fixed together by means of rivets 50. A central circular raised boss 52 is formed with a diametrical rectangular aperture 54 through which the switch lever 18 projects. A pair of mounting recesses 58 and 59 are formed by the shell halves, and are arranged to hold captive internally threaded brass inserts 60 having hex heads 60A for allowing the circuit breaker 44 to be mounted up against a mounting plate by means of screws. A typical mounting arrangement is shown in Figure 6, in which the circuit breaker 44 and an adjacent circuit breaker 44A are shown mounted to a conventional distribution panel 60C via screws 60D, with the turrets 52 projecting through standard circular apertures 60E in the panel.

[0019] Referring now to Figure 7, the shell half 46 is shown with the snap-in adaptor plate 10 mounted in position. It can clearly be seen how the circular turret 52 extends through the aperture 16 when the inner face 14 of the snap-in adaptor is flush against the front wall 61 of the shell half 46. The recesses 58 and 59 include an inner hex cavity 62 defined by cavity halves in the shell halves 46 and 48 within which the hex head 24 of the lugs 20 and 22 locate in a snug fit. When the second shell half 48 is positioned over the first shell half 46, the hex cavity 62 defined by shell halves in combination effectively hold the lugs 20 and 22 captive, as was the case with the inserts. In this position, the retaining clips 26 and 28 are located with their inner surfaces 68 flush against the end walls 70 and 72 of the circuit breaker, which are spaced a distance y apart.

[0020] The centre-to-centre distance z between the lugs 20 and 22 corresponds to the centre-to-centre distance between the recesses 58 and 59. With the adaptor plate fitted in position, the entire circuit breaker can now easily be snap-fitted within a standard oversize snap-in panel aperture having, in this case, a width of 55.6mm, which is represented by the distance y+Δy. The panel edges defining the aperture are illustrated at 74 and 76. It is clearly apparent from the circled detail at 78 how the circuit breaker is held in position by virtue of the saw teeth 38 of the outwardly biased clip portion 30 engaging with the innermost corner 80 of the panel edge. As the circuit breaker is slid into position, the opposed edges 74 and 76 of the panel cause the clip to deflect inwardly to the position illustrated at 40 in Figure 5B as the edges ride over the smooth elbow 39 of the clip, after which the clip springs back to the engaged position illustrated in the circled detail at 78 of Figure 8. In this position, the elbow 39 extends beyond the plane defined by the outer face 28A of the bracket 29 of the retaining clip 26. The effective thickness of the brackets 29 of the clips 26 and 28 is equal to just less than Δy/2, with a small clearance allowing the circuit breaker assembly to be fitted between the standard slot width of y+Δy. In order to disengage the circuit breaker from the panel aperture, the limbs 32 and 34 of the retaining clips 26 and 28 are pushed towards one another so as to disengage the teeth 38 from the edges 74 and 76 defining the aperture.

[0021] The snap-in adaptor plate is fitted during the assembly of the circuit breaker, at the same time as the inner componentry of the circuit breaker is mounted within one of the shell halves. Thereafter, the two shell halves are brought together and rivetted in position so as to hold the adaptor plate captive. As the adaptor plate makes use of the existing insert mounting recesses, no modifications need to be made to the tooling of the existing circuit breaker. A snap-in version of the circuit breaker is thus easily provided by replacing the prior assembly step of fitting the brass inserts by the step of fitting the snap-in adaptor using the very same recesses.

Claims

1. A snap-in adaptor plate (10) for a conventional circuit breaker (44) of the type comprising a pair of shell halves (46,48) which in combination define a front wall (61) and a pair of opposed end walls (70,72), a mounting recess (58,59) being defined in the front wall for accommodating at least one corresponding internally threaded front mounting insert (60) for allowing the circuit breaker (44) to be screw mounted against an interior face of a panel (60C) defining a relatively small conventional panel aperture (60E), characterized in that the adaptor plate (10) comprises an elongate front plate, at least one mounting lug (20,22) extending from an operatively inner surface of the front plate and adapted to be held captive within the mounting recess (58,59) when the front plate is fitted over the front wall, and a pair of spaced apart retaining clips (26,28) formed integrally with the front plate and extending rearwardly from opposite ends thereof adjacent the end walls of the circuit breaker (44) for allowing the assembled snap-in adaptor plate and circuit breaker to engage the opposed edges (74,76) of an oversize panel aperture in a snap fit.

2. A snap-in adaptor plate (10) according to claim 1 characterized in that the front wall (61) of the conventional circuit breaker (44) is formed with a pair of mounting recesses (58,59) for accommodating a pair of corresponding internally threaded front mounting inserts (60), the pair of mounting recesses (58,59) being located on opposite sides of a central turret (52) from which a breaker lever (18) extends, with the turret (52) being arranged to pass through the relatively small panel aperture (60E), the adaptor plate (10) further comprising a central aperture (16) through which the turret (52) is arranged to pass and a pair of mounting lugs (20,22) located on opposite sides of the central aperture (16), with the mounting lugs (20,22) being arranged to locate within the corresponding pair of mounting recesses (58,59), and being spaced apart from one another by the same centre-to-centre distance z as the mounting recesses (58,59) are spaced apart.

3. A snap-in adaptor plate (10) according to claim 2 characterized in that the mounting lugs (20,22) are of top hat section terminating in expanded heads (24), and having essentially the same external profile as the internally threaded front mounting inserts (60).

4. A snap-in adaptor plate (10) according to any one of the preceding claims characterized in that the retaining clips (26,28) comprise non-deflectable L-shaped bracket portions (29), and re-entrant inwardly deflectable clip portions (30) extending from the base limbs of the bracket portions (29).

5. A snap-in adaptor plate (10) according to claim 4 characterized in that the clip portions (30) comprise first and second resiliently deformable limbs (32,34) joined in a shallow V-configuration, with the first limb (32) extending from the base limb of the L, and the free operatively outermost surface of the second limb (34) being formed with serrations (38) for releasably engaging the opposed edges (74,76) of the oversize panel aperture.

6. A snap-in adaptor plate (10) according to claim 2 characterized in that, with the end walls of the conventional circuit breaker (44) being spaced a distance y apart, the distance between the innermost surfaces (68) of each retaining clip (26) and the central axis defined by each mounting lug (20,22) is (y-z)/2.

7. A snap-in adaptor plate (10) according to claim 6 characterized in that, with the opposed minor edges of the standard oversize panel aperture being spaced a distance y+Δy apart, the distance between deflectable portions of the retaining clips (26) is equal to y+Δy when inwardly deflected and is greater than y+Δy when the deflectable portions of the retaining clips (26) are holding the adaptor plate (10) and circuit breaker (44) captive within the oversize panel aperture.

8. A modified circuit breaker assembly characterized in that it comprises a conventional circuit breaker (44) of the type comprising a pair of case halves (46,48) which in combination define a front wall (61) and a pair of opposed end walls (70,72), a mounting recess (58,59) being defined in the front wall for accommodating at least one corresponding internally threaded front mounting insert (60) for allowing the circuit breaker (44) to be screw mounted against an interior face of a panel (60C) defining a relatively small conventional panel aperture (60E), and a snap-in adaptor plate (10), the adaptor plate (10) comprising an elongate front plate (12), at least one mounting lug (20,22) extending from an operatively inner surface (14) of the front plate and adapted to be held captive within the mounting recess (58,59) when the front plate is fitted over the front wall, and a pair of spaced apart retaining clips (26,28) formed integrally with the front plate and extending rearwardly from opposite ends thereof adjacent the end walls for allowing the snap-in adaptor plate (10) and circuit breaker (44) to engage the opposed minor edges (74,76) of an oversize panel aperture in a snap fit.

9. A modified circuit breaker assembly according to claim 8 characterized in that the front wall of the standard circuit breaker (44) is formed with a pair of mounting recesses (58,59) for accommodating a pair of corresponding front mounting inserts (60), the pair of mounting recesses (58,59) being located on opposite sides of a central turret (52) from which a breaker lever (18) extends, with the turret (52) being arranged to pass through the relatively small conventional panel aperture (60E), the adaptor plate (10) further comprising a central aperture (16) through which the turret (52) is arranged to pass and a pair of mounting lugs (20,22) located on opposite sides of the central aperture (16), with the mounting lugs (20,22) being arranged to locate within the corresponding pair of mounting recesses (58,59), and being spaced apart from one another by the same centre-to-centre distance z as the mounting recesses (58,59) are spaced apart.

10. A modified circuit breaker assembly according to claim 9 characterized in that, with the end faces (70,72) of the conventional circuit breaker (44) being spaced a distance y apart, the distance between the innermost surfaces (68) of each retaining clip (26) and the central axis defined by each mounting lug (20,22) is (y-z)/2.

11. A modified circuit breaker assembly according to claim 10 characterized in that, with the opposed minor edges (74,76) of the standard oversize panel aperture being spaced a distance y+Δy apart, the distance between deflectable portions of the retaining clips (26,28) is equal to y+Δy when inwardly deflected and is greater than y+Δy when the deflectable portions of the retaining clips (26,28) are holding the adaptor plate (10) and circuit breaker (44) captive within the oversize panel aperture.

Drawing