GB2189352A

GB2189352A - Commutator segment terminal arrangement

Info

Publication number: GB2189352A
Application number: GB08608047A
Authority: GB
Inventors: David Yee Wai Lam
Original assignee: Johnson Electric Industrial Manufactory Ltd
Current assignee: Johnson Electric Industrial Manufactory Ltd
Priority date: 1986-04-02
Filing date: 1986-04-02
Publication date: 1987-10-21
Also published as: GB8608047D0

Abstract

Terminals 17 of the commutator segments 15 are bent into a U shape 18 and provided with an elongate slot 19 extending around the base 20 of the U.A wire is forged to the terminal 18 by bending the U-shaped portion under pressure to clamp the wire and passing an electric current through the terminal to forge the wire to the terminal. The slot 19 reduces the amount of pressure and heat which needs to be applied to achieve a low-resistance electrical connection, thus reducing distortion of the thermoplastics commutator support (11, Fig. 1). <IMAGE>

Description

SPECIFICATION Assembled commutator This invention relates to assembled commutators and more particularlytothe provision of an assembled commutator having an improved terminal forconnection tothewindings of an armature.

Assembled commutators for small electric motors comprise a plurality of commutator pieces mounted on a thermoplastics insulating cylindrical support, typically of nylon, and held in position by an insulating washer. The support is mounted on a motor shaft with portions of the commutator pieces extending axiallyandterminalsofthecommutator pieces extending generally radially.Wires from armaturewindings mounted on theshaftare connected to the respective terminals by bending the terminalsto form a U shape, enclosing the wire in the'U' shape and applying heatand pressureto collapsethe U onto the wire and weld orforgethe wire and terminal to produce a firm electrical connection. It has been foundthatthe pressure and heat required for this operation results in distortion ofthe support, upsetting the geometry ofthe commutator.

The present invention provides an assembled commutatorcomprising an insulating support and a plurality of commutator pieces mounted on the support, each commutator piece having an outwardly extending terminal for connection to a wirebyforging,whereintheterminal is provided with an aperture or slot in a region which is arranged to bearagainstthewireduring heating to forgethe connection.

The terminal is bent over, pressed against the wire and heated during the operation offorging a wire to theterminal. By providing a slotoraperture in the region in which theterminal is bentand contactsthe wire it is thought that as well as reducing the bending resistance of the terminal the pressure and heat at the connection ofthewireandterminal is concentrated. It has been found that less pressure and heat need by applied to the assembled commutator, thus reducing or avoiding distortion.

The invention also comprehends a rotor assembly for an electric motor, comprising a commutator as hereinbeforedefined and a wound armature, the commutator and armature being mounted on a shaft and each coil ofthewinding being connected to a commutator piece by bending a terminal of the commutator piece to clamp a wire ofthe coil and applying heat to forge a connection between the terminal and wire.

The invention will be further described by way of example with reference to the accompanying drawings, in which Figure lisa cross-section taken along an axis of a commutator according to the invention; Figure2 is an end view in the direction of arrowA of Figure 1, with a fibre washer removed; Figure 3 is a schematic side view of a top half of a rotor assembly; and Figure 4 is a perspective view of a commutator piece.

In Figure 1, an assembled commutator 10 comprises a thermoplastics support 11,which may be of nylon, comprising a first cylindrical portion 12 for receiving a motor shaft, and a radially extending collar 13. The collar 13 has recesses 16 to receive tangs 14 of a coppercommutatorpiece 15 (Figure 3) which position the commutator piece on the support 11 in the circumferential direction.

The commutator pieces 15 have an upwardly turned terminal 17 which is bentto lie againstthe radial and circumferential faces of the collar, as seen in Figure 1, with the outer portion of the terminal being benttoform a Ushape 18. The Ushaped portion 18 has an aperture 19 extending around and beyond each side of the bent region 20, at the base of the U.

To assemble the commutator, the commutator pieces 15 are first stamped and benttotheshape illustrated in Figures 1 and 2 and then fitted on the support 11 by sliding them againstthe collar 13to insert the tangs 14 in the recesses. Afibre washer 21 is then slid over the commutator pieces to hold them againstthecylindrical portion 12.

Toforge a wireto the commutatorterminalsthe wire is placed in the U of the terminal 17, this may be done during a winding operation (see Figure 3) and pressure is then applied radially to the end ofthe terminal in the direction of arrow B so thatthe terminal is bent over to clamp the wire. Heat is applied by means of an electric current to burn off enamelfromthewiresurfaceandto heatthewire and terminal to forge a jointtherebetween.

It can be seen that a variety of configurations for the slot 19 are possible. The slot may extend upto the top edge 26 of the terminal to form a two pronged fork, although a closed slot is presently preferred to avoid splaying of the ends of the terminal .

Figure 3 shows schematically a rotor comprising the commutator of Figure 1 mounted on a motor shaft 22. A shoulder 23 on the inside wali of the commutator 10 abuts against a shoulder on the shaft 22 to position the commutator in the axial direction.

Awinding of the armature coil is shown schematically at 25 and has an end of its wire looped aroundtheterminal 17duringthewinding,priorto forging of the wire 24 and terminal 17 as described previously.

Various modifications may be suggested by those skilled in the art and it is desired to include all such modifications as fall within the scope of the invention as defined herein.

1. An assembled commutator comprising an insulating support and a plurality of commutator pieces having an outwardly extending terminal for connection to a wire by forging, wherein theterminal is provided with an aperture or slot in a region which is arranged to bear against the wire during heating to forge the connection.

2. An assembled commutator as claimed in claim 1, wherein the terminal has a U-shaped portion for receiving the wire in the base ofthe U, and an

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Assembled commutator This invention relates to assembled commutators and more particularlytothe provision of an assembled commutator having an improved terminal forconnection tothewindings of an armature. Assembled commutators for small electric motors comprise a plurality of commutator pieces mounted on a thermoplastics insulating cylindrical support, typically of nylon, and held in position by an insulating washer. The support is mounted on a motor shaft with portions of the commutator pieces extending axiallyandterminalsofthecommutator pieces extending generally radially.Wires from armaturewindings mounted on theshaftare connected to the respective terminals by bending the terminalsto form a U shape, enclosing the wire in the'U' shape and applying heatand pressureto collapsethe U onto the wire and weld orforgethe wire and terminal to produce a firm electrical connection. It has been foundthatthe pressure and heat required for this operation results in distortion ofthe support, upsetting the geometry ofthe commutator. The present invention provides an assembled commutatorcomprising an insulating support and a plurality of commutator pieces mounted on the support, each commutator piece having an outwardly extending terminal for connection to a wirebyforging,whereintheterminal is provided with an aperture or slot in a region which is arranged to bearagainstthewireduring heating to forgethe connection. The terminal is bent over, pressed against the wire and heated during the operation offorging a wire to theterminal. By providing a slotoraperture in the region in which theterminal is bentand contactsthe wire it is thought that as well as reducing the bending resistance of the terminal the pressure and heat at the connection ofthewireandterminal is concentrated. It has been found that less pressure and heat need by applied to the assembled commutator, thus reducing or avoiding distortion. The invention also comprehends a rotor assembly for an electric motor, comprising a commutator as hereinbeforedefined and a wound armature, the commutator and armature being mounted on a shaft and each coil ofthewinding being connected to a commutator piece by bending a terminal of the commutator piece to clamp a wire ofthe coil and applying heat to forge a connection between the terminal and wire. The invention will be further described by way of example with reference to the accompanying drawings, in which Figure lisa cross-section taken along an axis of a commutator according to the invention; Figure2 is an end view in the direction of arrowA of Figure 1, with a fibre washer removed; Figure 3 is a schematic side view of a top half of a rotor assembly; and Figure 4 is a perspective view of a commutator piece. In Figure 1, an assembled commutator 10 comprises a thermoplastics support 11,which may be of nylon, comprising a first cylindrical portion 12 for receiving a motor shaft, and a radially extending collar 13. The collar 13 has recesses 16 to receive tangs 14 of a coppercommutatorpiece 15 (Figure 3) which position the commutator piece on the support 11 in the circumferential direction. The commutator pieces 15 have an upwardly turned terminal 17 which is bentto lie againstthe radial and circumferential faces of the collar, as seen in Figure 1, with the outer portion of the terminal being benttoform a Ushape 18. The Ushaped portion 18 has an aperture 19 extending around and beyond each side of the bent region 20, at the base of the U. To assemble the commutator, the commutator pieces 15 are first stamped and benttotheshape illustrated in Figures 1 and 2 and then fitted on the support 11 by sliding them againstthe collar 13to insert the tangs 14 in the recesses. Afibre washer 21 is then slid over the commutator pieces to hold them againstthecylindrical portion 12. Toforge a wireto the commutatorterminalsthe wire is placed in the U of the terminal 17, this may be done during a winding operation (see Figure 3) and pressure is then applied radially to the end ofthe terminal in the direction of arrow B so thatthe terminal is bent over to clamp the wire. Heat is applied by means of an electric current to burn off enamelfromthewiresurfaceandto heatthewire and terminal to forge a jointtherebetween. It can be seen that a variety of configurations for the slot 19 are possible. The slot may extend upto the top edge 26 of the terminal to form a two pronged fork, although a closed slot is presently preferred to avoid splaying of the ends of the terminal . Figure 3 shows schematically a rotor comprising the commutator of Figure 1 mounted on a motor shaft 22. A shoulder 23 on the inside wali of the commutator 10 abuts against a shoulder on the shaft 22 to position the commutator in the axial direction. Awinding of the armature coil is shown schematically at 25 and has an end of its wire looped aroundtheterminal 17duringthewinding,priorto forging of the wire 24 and terminal 17 as described previously. Various modifications may be suggested by those skilled in the art and it is desired to include all such modifications as fall within the scope of the invention as defined herein. CLAIMS

2. An assembled commutator as claimed in claim 1, wherein the terminal has a U-shaped portion for receiving the wire in the base ofthe U, and an elongate slot is provided,the slot extending around the base ofthe U.

3. A rotorfor an electric motor, comprising a shaft, a wound armature and a commutator as defined in claim 1 or2,thearmatureandcommutator being mounted on the shaft, wherein the armature windings are connected to the commutator by looping wire ofthe windings around the commutator terminals and pressing the terminals to clamp the wire, a current being passed through the terminal when under pressure, to forge thewireto the terminal.