BLADE ASSEMBLY

Abstract: A blade assembly (12) for a switch such as a circuit breaker comprises a blade member (2A), a trip lever (2B), a contact holder (2C) and preferably also a pawl (2D). The blade member (2A), trip lever (2B) and pawl (2D) are of an insulating plastics material. The blade member (2A) has a rear contact end (5) to which the contact holder (2C) is mounted and a front end (6) including an extension (12) which defines in use an indicator flag. A pawl mounting pivot pin (14) extends between side walls (3, 4) of the blade member to mount the pawl (2D). A trip lever mounting pin (20) integral with the blade member (2A) is used to mount the trip lever (2B). The trip lever (2B) has a front nose (24) for engaging with a corresponding recess (25) of the pawl (2D), and an integral flexible arm (27) which acts as a biassing spring to urge the nose (24) into engagement with the recess (25) of the pawl (2D).

Description: "Blade Assembly" The invention relates to a blade assembly, particularly for use in circuit breakers. Circuit breakers generally include a breaker mechanism mounted in a housing. Such breaker mechanisms generally comprise a large number of separate pieces which are assembled in the housing. Because of the number of pieces involved and the complexity of such mechanisms it is extremely difficult to automate the assembly operation. According to the invention there is provided a blade assembly for a switch such as a circuit breaker, the blade assembly including a blade member, a trip lever and a contact holder, the blade member being of insulating material, and having a trip lever mounting means and a contact holder mounting means . In a preferred embodiment of the invention the blade member includes a pawl mounting means . Preferably the blade member includes an integral indicator flag. In one embodiment of the invention the blade member comprises a pair of opposed side walls and connecting wall means extending between the side walls. Preferably the connecting wall means comprises a connecting web adjacent a contact end of the blade member and an end connecting wall adjacent an opposite end. Typically the end connecting wall includes an extension defining an integral indicator flag. Preferably the trip lever mounting means comprises means for snap fittingly engaging with the trip lever. Typically the trip lever mounting means comprises an integral pivot pin and the trip lever includes a recess corresponding to the integral pivot pin for snap fitting engagement. Preferably the trip lever includes a nose portion for engaging with a corresponding recess in the pawl. Advantageously the trip lever includes a spring means to urge the nose portion of the trip lever into engagement with the pawl . Preferably the integral spring means comprises a flexible arm which extends from the trip lever to engage with the blade member. Ideally the flexible arm is integral with the trip lever. In a preferred arrangement the trip lever is of insulating material. In one embodiment of the invention the contact holder is of electrically conductive material and the contact holder mounting means and contact holder have interengaging formations for engaging the contact holder with the blade member. Preferably the contact mounting means includes opposed recesses in side walls of the blade member adjacent a contact end of the blade member. Typically the assembly includes ramp means for guiding the contact holder into the recesses on fitting. In a preferred embodiment of the invention the pawl mounting means comprises opposed pivot holes in the blade member to receive a pawl mounting pivot pin, the pawl being mounted to the pivot pin. The invention also provides a switch incorporating a blade assembly according to the invention. The invention further provides a circuit breaker incorporating a blade assembly according to the invention. The invention will be more clearly understood from the following description thereof, given by way of example only with reference to the accompanying drawings in which:- Fig. 1 is an exploded perspective view of a blade assembly according to the invention; Fig. 2 is an elevational view of the assembly; Fig. 3 is a cross sectional view of the assembly; Fig. 4 is a plan view of a circuit breaker incorporating the assembly in an on position of use with the contacts closed; Fig. 5 is a plan view of the circuit breaker of Fig. 4 in a tripped position with a handle held in the on position; and Fig. 6 is a plan view of the circuit breaker of Fig. 4 in an off position with a handle switched off. Referring to the drawings and initially to Figs . 1 to 3 thereof there is illustrated a blade assembly according to the invention and indicated by the reference numeral 1. The blade assembly 1 comprises a blade member 2A, a trip lever 2B, a contact holder 2C and, in this case, also a pawl 2D. At least the blade member 2A, and preferably also the trip lever 2B and the pawl 2D are of insulating, typically plastics material and are typically injection moulded. The blade member 2A has a rear contact end 5 and a front flag end 6 and comprises a pair of opposed side walls 3, 4 which are joined by a flag end connecting wall 8, an intermediate wall 10 and a connecting web 11 adjacent the contact end 5. The flag end connecting wall 8 has an extension 12 which defines, in use, an indicator flag as will be described in more detail below. The extension 12 may extend upwardly as illustrated or downwardly. Opposed holes 13 are provided in each side wall 3, 4 adjacent the flag end 6 to receive a pawl mounting pivot pin 14 which passes through a first pivot hole 15 in the pawl 2D for pivotally mounting the pawl 2D to the blade member. The pawl 2D in this case also includes a second pivot hole 19 for receiving a link as will be described below. A trip lever mounting pivot pin 20 is integrally moulded with the blade member 2A and extends between and projects from the blade side walls 3, 4 to define stub projections 20a. The pin 20 is sized to snap-fittingly engage with a correspondingly shaped recess 21 in the trip lever 2B. The trip lever 2B has a rear leg 26 and a forward leg 23 with a front nose portion 24 which engages with a corresponding recess 25 in the pawl 2D as will be particularly apparent from Fig. 3. An integral flexible arm 27 extends rearwardly from the trip lever 2B to engage underneath the web 11 of the blade member 2A. The arm 27 acts as a biassing spring to urge the nose 24 of the trip lever 2B into engagement with the recess 25 in the pawl 2D. The contact holder 2C is of electrically conductive material and snap-fittingly engages with the blade member 2A at the contact end 5. A moving contact 34 (Figs. 4 to 6) is fitted to the contact holder 2C, for example by riveting, welding or forming in situ. The contact holder 2C is of generally L-shape having an upright portion 32 and a horizontal portion 31 which are cut-away on both sides at 33 to engage with the blade member 2A. At the contact end 5, the blade side walls 3, 4 each have an inwardly extending ramp formation 35 and an inwardly extending stop rib 36 which are spaced- apart to define therebetween recesses 37 for engaging with the contact holder 2C. On assembly, the upright portion 32 of the contact holder 2C is pressed forwardly to ride over the ramp formations 35 and snap into the recesses 37. Referring to Figs . 4 to 6 the blade assembly 1 described above is shown mounted in one particular circuit breaker 50. The circuit breaker 50 has a housing 56 and includes a line terminal 51 for coupling to a source of electricity and a load terminal 52 for coupling to a load. A braided pigtail 53 is connected for example by crimping, welding or fixing, between the line terminal 51 and the contact holder 2C of the blade assembly 1. The stub projections 20a of the trip lever mounting pivot pin 20 of the assembly 1 engage with corresponding pivot recesses (not shown) in the housing 56. In a normal contacts closed position illustrated in Fig. 4 the moving contact 34 carried by the contact holder 2C is engaged with a fixed contact 58. The current path from the fixed contact 58 includes a coil 60 and a load conductor 61 to which the load terminal 52 is connected. The circuit breaker in this case also includes an arc runner 63 and an arc stack 64 which cooperate to break any arc formed when the circuit breaker opens and the contacts 34, 58 are separated under load. The contacts 34, 58 may be separated in response to operation of a bimetal (not shown) or by a rod 65 which is normally biased downwardly by a solenoid spring 62. The rod 65 is disposed within the coil 60 and is engagable against the rear leg 26 of the trip lever 2B of the blade assembly 1. A cam 68 has an operating handle 69. A link 70 connects the cam 68 and pawl 2D through the hole 19 in the pawl 2D. The housing 56 includes a viewing window 71 through which the flag 12 of the blade member 2A may be viewed when the contacts 34, 58 are in the off and tripped positions illustrated in Figs. 5 and 6. In the tripped or off positions a spring 55 urges the blade assembly about the pivot defined by the stub projections 20a so that the moving contact 34 carried by the contact holder 2C is disengaged from the fixed contact 58. In use, the circuit breaker is tripped either by a thermal overload as detected by a bimetal (not shown) or by a current surge actuator defined by the coil 60. In the normal closed position the rod 65 is downwardly biased by the solenoid spring 62 and current passing through the coil 60 sets up an electromagnetic field acting on the rod 65. When the electromagnetic force set up in the coil 60 is disturbed by a current surge the rod 65 moves up to engage the rear leg 26 of the trip lever 2B of the blade assembly. This action pushes the forward leg 23 of the trip lever 2B downwardly so that the nose 24 of the trip lever 2B disengages from the recess in the pawl 2D. The spring 55 causes the contacts 34, 58 to separate. Referring to Fig. 6, when the handle 69 is moved to the off position movement of the link 70 causes the pawl 2D to move about from the nose 24 of the trip lever 2B. The spring 55 urges the blade assembly 1 about the pivot defined by the stub projections 20a and the moving contact 34 is disengaged from the fixed contact 58. It will be appreciated that the blade assembly of the invention is of low mass and is without expensive conducting materials such as copper components . There are substantially less parts than in conventional blade assemblies so that material and assembly costs are substantially reduced. Thus, a much more economical and efficient method of manufacture may be achieved. It will also be appreciated that the spring 55 may be of any suitable type such as a helical, coil or leaf spring. It will further be appreciated that while the invention has been described with particular reference to one type of circuit breaker it has wide applications not only to many different types of circuit breaker but also to switches in general. The invention is not limited to the embodiments hereinbefore described, but may be varied in construction and detail.

Claims: CLAIMS 1. A blade assembly for a switch such as a circuit breaker, the blade assembly including a blade member, a trip lever and a contact holder, the blade member being of insulating material and having a trip lever mounting means and a contact holder mounting means . 2. A blade assembly as claimed in claim 1 wherein the assembly includes a pawl and the blade member includes a pawl mounting means . 3. A blade assembly as claimed in claim 1 or 2 wherein the blade member includes an integral indicator flag. 4. A blade assembly as claimed in any preceding claim wherein the blade member comprises a pair of opposed side walls and connecting wall means extending between the side walls. 5. A blade assembly as claimed in claim 4 wherein the connecting wall means comprises a connecting web adjacent a contact end of the blade member and an end connecting wall adjacent an opposite end. 6. A blade assembly as claimed in claim 5 wherein the end connecting wall includes an extension defining an integral indicator flag. 7. A blade assembly as claimed in any preceding claim wherein the trip lever mounting means comprises means for snap fittingly engaging with the trip lever. 8. A blade assembly as claimed in claim 7 wherein the trip lever mounting means comprises an integral pivot pin and the trip lever includes a recess corresponding to the integral pivot pin for snap fitting engagement. 9. A blade assembly as claimed in any of claims 2 to 8 wherein the trip lever includes a nose portion for engaging with a corresponding recess in the pawl . 10. A blade assembly as claimed in claim 9 wherein the trip lever includes a spring means to urge the nose portion of the trip lever into engagement with the pawl. 11. A blade assembly as claimed in claim 10 wherein the spring means comprises a flexible arm which extends from the trip lever to engage with the blade member. 12. A blade assembly as claimed in claim 11 wherein the flexible arm is integral with the trip lever. 13. A blade assembly as claimed in any preceding claim wherein the trip lever is of insulating material. 14. A blade assembly as claimed in any preceding claim wherein the contact holder is of electrically conductive material and the contact holder mounting means and contact holder have interengaging formations for engaging the contact holder with the blade member. 15. A blade assembly as claimed in claim 14 wherein the contact mounting means includes opposed recesses in the side walls of blade member adjacent a contact end of the blade member. 16. A blade assembly as claimed in claim 15 including ramp means for guiding the contact holder into the recesses on fitting. 17. A blade assembly as claimed in any of claims 2 to 16 wherein the pawl mounting means comprises opposed pivot holes in the blade member to receive a pawl mounting pivot pin, the pawl being mounted to the pivot pin. 18. A blade assembly substantially as hereinbefore described with reference to the accompanying drawings. 19. A switch incorporating a blade assembly as claimed in any preceding claim. 20. A circuit breaker incorporating a blade assembly as claimed in any of claims 1 to 18. 21. A circuit breaker substantially as hereinbefore described with reference to the accompanying drawings.

Inventors: HURST DERMOT, SHORTT JAMES, HURST, DERMOT, SHORTT, JAMES
Applicants: HURST DERMOT, SHORTT JAMES, SQUARE D CO, HURST, DERMOT, SHORTT, JAMES, SQUARE D COMPANY
Application year: 1995
Main classification: H01H71
IPC codes: H01H71