Claims:We claim:
1. A segmental brush holder with separate earth termination for DC motors, comprises of:
a) a metal steel insert (104) for a first fixing onto the mounting bracket assembly;
b) an anti-rotation slot (117) at one end of the segmental brush holder to locate the segmental brush holder onto the mounting bracket assembly, wherein the slot arrests the rotational movement;
c) a platform (121) in a mounting bracket to fix an earth plate (106), wherein the earth plate (106) provides earth termination and provides a second fixing when the axial force is exerted on the brush holder, wherein the earth brush is welded to the earth plate (106);
d) a semi-circular extended portion (119) at an another end of the segmental brush holder to restrict the rotation of the brush holder while fastening onto the mounting bracket assembly; and
e) a plurality of the air vents (120a and 120b) at the bottom to reduce the temperature of the brushes. .
2. The assembly as claimed in claim 1, wherein said segmental brush holder is made up of any moldable material but not limited to phenolic injection moldable material used in DC motors.
3. The assembly as claimed in claim 1, wherein said first fixing is accomplished through a screw (105).
4. The assembly as claimed in claim 1, wherein said assembly is integrated to DC motor with four magnets and wave wound armature.
, Description:
[001] PREAMBLE TO THE DESCRIPTION:
[002] The following specification particularly describes the invention and the manner in which it is to be performed:
[003] DESCRIPTION OF THE INVENTION:
[004] Technical field of the invention
[005] The present invention relates to segmental brush holder. More particularly, the invention relates to a segmental brush holder with separate earth termination for direct current (DC) motors.
[006] Background of the invention
[007] Lap Winding is used in DC machines designed for high-current applications/automotive starter applications. The windings are connected to provide several parallel paths for current in the armature. For this reason, lap-wound armatures used in DC motors require several pairs of poles and brushes. In lap winding the number of parallel path is equal to the number of poles. The number of brush required by lap winding is always equal to the number of poles. Lap windings are used for low voltage and high current machines.
[008] Wave Winding is used in DC machines employed in high-voltage low current applications. In wave winding, the two ends of each coil are connected to commutator segments separated by the distance between poles. This configuration allows the series addition of the voltages in all the windings between brushes. This type of winding only requires one pair of brushes. In wave winding the number of parallel paths is always equal to 2. The number of brushes required by this winding is always equal to 2. More number of brushes can be used if the current density is more and to increase brush life. When two brush constructions are used always the brushes would be 90 degree apart.
[009] In existing systems the earth brush is fixed along with the brush holder, and due to the insulation property of the phenolic material, the return path will have high resistance. The return path is closed only through the brush holder fixing screw. Due to high current and high resistance, there is a chance of arcing and that may result in loose connection. Therefore, the system tends to fail.
[0010] Currently, the brush holders which are mounted in the mounting bracket assembly develop unnecessary rotational movement while tightening a slot in the brush holder. This is due to the inappropriate design of the brush holders.
[0011] Also, in the existing brush holders available in the market have no provision to maintain the brush temperature, which leads to decrease in shelf life of the brushes.
[0012] Hence, looking at the problems in the prior art, there is a need for a segmental brush holder, which must eliminate the problem of arcing and loose connection by providing a firm separate connection. The unnecessary rotational movement while tightening of the brush holder is avoided by a slot in the brush holder and a projection in the bracket. Moreover, the design of the brush holder assembly must maintain the brush temperature.
[0013] Summary of the invention:
[0014] The present invention overcomes the drawbacks in the prior art and provides a segmental brush holder with separate earth termination for DC motors. The present invention comprises a metal steel insert in the brush holder for a first fixing onto the mounting bracket assembly. An anti-rotation slot is designed at one end of the segmental brush holder to locate the segmental brush holder onto the mounting bracket assembly, wherein the slot arrests the rotational movement. A platform is constructed at a mounting bracket to fix an earth plate, wherein the earth plate provides earth termination and provides a second fixing when the axial force is exerted on the brush holder. The earth brush is welded to the earth plate. A semi-circular extended portion is designed at an another end of the segmental brush holder to restrict the rotation of the brush holder while fastening onto the mounting bracket assembly and a plurality of the air vents are provided at the bottom of the brush holder to reduce the temperature of the brushes.
[0015] In a preferred embodiment of the invention, the segmental brush holder is made up of any moldable material but not limited to phenolic injection moldable material used in DC motors.
[0016] In a preferred embodiment of the invention, the first fixing is accomplished through a screw.
[0017] In a preferred embodiment of the invention, the assembly is integrated to DC motor with four magnets and wave wound armature.
[0018] Brief description of the drawings:
[0019] The foregoing and other features of embodiments will become more apparent from the following detailed description of embodiments when read in conjunction with the accompanying drawings. In the drawings, like reference numerals refer to like elements.
[0020] Figure 1 illustrates an exploded view of the segmental brush holder with the bracket assembly, in accordance with an embodiment of the invention.
[0021] Figure 2 (a) and Figure 2 (b) illustrate an exploded view of the segmental brush holder, in accordance with an embodiment of the invention.
[0022] Figure 3 (a) and Figure 3 (b) illustrate a sectional view of the segmental brush holder, in accordance with an embodiment of the invention.
[0023] Figure 4 illustrates the sectional view of fixing the segmental brush holder with the bracket assembly, in accordance with an embodiment of the invention.
[0024] Detailed description of the invention:
[0025] Reference will now be made in detail to the description of the present subject matter, one or more examples of which are shown in figures. Each embodiment is provided to explain the subject matter and not a limitation. These embodiments are described in sufficient detail to enable a person skilled in the art to practice the invention, and it is to be understood that other embodiments may be utilized and that logical, physical, and other changes may be made within the scope of the embodiments. The following detailed description is, therefore, not be taken as limiting the scope of the invention, but instead the invention is to be defined by the appended claims.
[0026] The present invention provides a segmental brush holder with separate earth termination for DC motors. The present invention comprises a metal steel insert in the brush holder for a first fixing onto the mounting bracket assembly. An anti-rotation slot is designed at one end of the segmental brush holder to locate the segmental brush holder onto the mounting bracket assembly, wherein the slot arrests the rotational movement. A platform is constructed at a mounting bracket to fix an earth plate, wherein the earth plate provides earth termination and provides a second fixing when the axial force is exerted on the brush holder. The earth brush is welded to the earth plate. A semi-circular extended portion is designed at an another end of the segmental brush holder to restrict the rotation of the brush holder while fastening onto the mounting bracket assembly and a plurality of the air vents are provided at the bottom of the brush holder to reduce the temperature of the brushes.
[0027] Figure 1 illustrates an exploded view of the segmental brush holder with the bracket assembly, in accordance with an embodiment of the invention. The present invention comprises a metal steel insert (104) in the brush holder for a first fixing onto the mounting bracket assembly. An anti-rotation slot (117) is designed at one end of the segmental brush holder (103) to locate the segmental brush holder onto the mounting bracket assembly, wherein the slot (117) arrests the rotational movement. A platform (121) is constructed in a mounting bracket (101) to fix an earth plate (106), wherein the earth plate (106) provides earth termination and provides a second fixing when the axial force is exerted on the brush holder. The earth brush (108) is welded to the earth plate (106). A semi-circular extended portion (119) is designed at an another end of the segmental brush holder (103) to restrict the rotation of the brush holder while fastening onto the mounting bracket assembly and a plurality of the air vents (120a and 120b) are provided at the bottom of the brush holder to reduce the temperature of the brushes.
[0028] The first fixing is accomplished through a brush holder fixing screw (105). The earth plate and earth brush assembly (106) is fixed onto the mounting bracket assembly through an earth plate fixing screw (107).
[0029] Figure 2 (a) and Figure 2 (b) illustrates an exploded view of the segmental brush holder, in accordance with an embodiment of the invention. The segmental brush holder (103) comprises of an anti-rotation slot (117) in the brush holder to stop the rotational movement while tightening the segmental brush holder onto the bracket assembly. A platform (118) is provided for secondary fixing and ensures additional support while tightening the earth plate (106). The semicircular extended portion (119) of the brush holder is provided at another end of the segmental brush holder (103) to restrict the rotation and provide a second fixing when the axial force is exerted on the brush holder. The earth brush (108) is welded to the earth plate (106). The pluralities of air vents (120a and 120b) are provided at the bottom of the brush holder at both positive and negative brush locations. These air vents reduces the brush temperature and increases the brush life.
[0030] Figure 3 (a) and Figure 3 (b) illustrates a sectional view of the segmental brush holder, in accordance with an embodiment of the invention. In the preferred embodiment of the present invention, the segmental brush holder is made with phenolic injection moldable material with steel insert at the brush holder fixing locations to avoid breakage due to brittle nature of the phenolic material. In existing prior arts, the assemblies due to high current and high resistance develop electrical breakdown which is known as arcing and, further leads to loose connection. The present invention provides the assembly to terminate the earth brush. The earth brush is welded to an earth plate and the earth plate is fixed directly to the bracket in a separate platform as shown in Figure 3. A direct earth termination is accomplished to reduce voltage drop and increase reliability.
[0031] The fixed earth plate will exert an axial load to the brush holder and provides a second fixing. To avoid rotation of the brush holder while tightening, the anti-rotation slot (117) in the brush holder and the platform (121) in the bracket is provided at one side. At the other side the semicircular extended portion (119) of the brush holder restricts the rotation through the earth plate fixed on the platform of the bracket as shown in the Figure 3.
[0032] Figure 4 illustrates the sectional view of fixing the segmental brush holder with the bracket assembly, in accordance with an embodiment of the invention.
[0033] The present invention provides an assembly, which is simple in design, eliminates arcing and thus eliminating the loose connection occurring due to arcing. The present invention also reduces the brush temperature, thereby increasing the brush life.
[0034] It is to be understood, however, that even though several characteristics and advantages of the present invention have been set forth in the foregoing description, together with details of the structure and function of the invention, the disclosure is illustrative only. Changes may be made in the details, especially in matters of shape, size, and arrangement of parts within the principles of the invention to the full extent indicated by the broad general meaning of the terms in which the appended claims are expressed.