DESC:COMMUTATION SYSTEM

FIELD OF THE INVENTION
The present invention relates in general to electric motors and, more particularly, to an improved spring based commutation system.

BACKGROUND OF THE INVENTION
DC motor converts electrical energy into mechanical energy and runs on a DC (direct current) power source. DC motor works on the principle that when current is passed through a coil placed in a magnetic field a torque is produced. A typical DC motor consists of an armature around which a magnetic field is generated.

When a current passes through the coil, the side of the positive pole is acted upon by an upwards force. At the same time, the other side is acted upon by a downward force. These forces cause a turning effect on the coil, making it rotate. To make the motor rotate in a constant direction, DC commutators are used.

Commutators include a set of contact bars fixed to the rotating shaft of a machine and are connected to the armature windings. The brushes slide on the rotating commutator of the armature. Connection between brushes and commutator allows the flow of current to the coil . As the shaft rotates, the commutator reverses the flow of current in a winding. The armature current causes the fixed magnetic field to exert torque on the winding to make it turn. The commutator periodically reverses the direction of current flow through the winding so that current flow in the circuit external to the machine continues in only one direction.

However, existing systems have various shortcomings. The commutator and brush assemblies of existing motor assemblies are sometimes unable to create optimal pressure and contact, particularly as the system ages. This may be a result of brush wear, non uniform spring pressure, chipping or other physical change in the components of the system. Consequently, there is a need to find systems and methods for efficiently maintaining optimal contact between the commutator and brush assemblies.

OBJECTS OF THE INVENTION
It is an object of the invention to provide a commutation system that provides an improved contact between the brushes and the commutator.
It is another object of the invention to provide a commutation system that increases the life of the motor.
It is yet another object of the invention to provide a commutation system that is simple in design and economical to produce.
It is still another object of the invention to provide a commutation system that operates the motor at optimum efficiency.
It is also object of the invention to provide a commutation system which is consistent in performance for birectional rotation and entire life of motor
SUMMARY OF THE INVENTION
The present invention provides a new and novel spring based commutation system. A particular advantage of this new commutation system is improved contact between the brushes and the commutator. The commutation system comprises a housing, a commutator, brushes and constant force springs wherein constant force springs apply a constant and even pressure on the brushes such that an optimum contact is maintained between commutator and brushes even when brushes are wearing out.

BRIEF DESCRIPTION OF THE DRAWINGS
Fig. 1 illustrates structure of the commutation system according to an embodiment of the present invention.

Fig. 2 illustrates direction of spring force on the brushes according to an embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION
The detailed description set forth below in connection with the appended drawings is intended as a description of various embodiments of the present invention and is not intended to represent the only embodiments in which the present invention may be practiced. Each embodiment described in this disclosure is provided merely as an example or illustration of the present invention, and should not necessarily be construed as preferred or advantageous over other embodiments. The detailed description includes specific details for the purpose of providing a thorough understanding of the present invention. However, it will be apparent to those skilled in the art that the present invention may be practiced without these specific details. The embodiment provided herein is for the purpose of filing the present complete specification; however, further embodiments within this disclosure are possible.

Figure 1 illustrates a commutator system according to an embodiment of the present invention. The commutator system 100 includes a housing 110, constant force springs 120, terminals 130 extending through the housing 110, a commutator 140 and copper graphite brushes 150. Ideally the constant force springs 120 are of a circular shape and are located on opposite sides of each other. Each of the spring 120 is configured with an extended wire for engaging a slot in the housing 110 to anchor the spring into place. The spring preferably used is a single coil constant force spring wherein one end of the said spring is attached to the housing 110 by means of an locking arrangement 160.

The brushes 150 may be made of copper-graphite or carbon and are configured with an elbow. The elbow directs the force exerted by the spring towards the center of the commutator. To attach the brush to the housing 110, circular portion of the spring i.e. drum is pulled back and held in that position. Then, one end of the brush is attached to a pivot pin 170 in the endcap housing 110 and the drum of the spring 120 is released. As a result of this arrangenment, the spring 120 makes contact with elbow of the brush and starts exerting pressure on the commutator. The brushes 150 are positioned such that they are anchored on the housing 100 at a first end and are in physical contact with the commutator 140 at the other end. The elbow of the brushes are in constant contact with the outer diameter of the springs 120. The springs 120 cause pressure to be applied to the second ends of the brushes 150 such that physical contact is more readily accomplished and maintained with the commutator 140.

The present invention ensures that even as the brushes 150 and the commutator 140 wear out due to constant use, the springs 120 will exert a constant pressure on the brushes to ensure that contact is maintained. Further, the orientation and positioning of the springs 120 cause a more even pressure to be applied to the brushes 150. However, it is to be noted that the orientation and positioning of the springs may be altered as necessary to fit the housing 110 without departing from the scope of the invention.

Referring now to FIG. 2, the direction of spring force and spring action on the brushes 150 is illustrated. The initial position 1 is shown with continuous line and the position 2 when the graphite brush 150 is at the end of its life is shown by dashed lines. The spring 120 is in a stretched condition in the beginning or at the start of the brushes 150 life so that as the brushes 150 wear out, the spring 120 continues to apply a constant and even pressure to the brushes 150. The arrow shows the spring force that is directed towards the center of the commutator 140.

An advantage of the new and novel system is that it has two pairs of brushes and springs and as the forces from each brush have same line of action and are equal, they form a perfectly balanced holding on the commutator 140. The springs ensure constant and equal force is applied through the center of commutator 140 even when brushes start to wear out. The direction of rotation does not affect the system’s effectiveness. This helps in keeping a good contact between the brushes 150 and the commutator 140 and prevents loss of contact. In addition, because of the compensating effect of the forces, the system is able to work with larger deviations in commutator geometry.

Since other modifications and changes to fit particular requirements and environments will be apparent to those skilled in the art, the invention is not considered limited as described by the present preferred embodiments which have been chosen for purposes of disclosure, and covers all changes and modifications which do not constitute departure from the spirit and scope of this invention.
,CLAIMS:We claim:
1. A commutation system for a DC motor comprising:
a housing;
a plurality of constant force springs located opposite each other in the housing;
a commutator disposed in the housing; and
a plurality of brushes connected to the housing at one end and the commutator at other end,
characterized in that
the constant force springs are in constant contact with the brushes exerting a even pressure on the commutator.

2. The commutation system as claimed in claim 1, wherein the constant force spring is circular in shape.

3. The commutation system as claimed in claim 1, wherein the constant force spring is configured with an extended wire to engage a slot in the housing.

4. The commutation system as claimed in claim 1, wherein one end of the constant force spring is connected to the housing through a locking arrangement.

5. The commutation system as claimed in claim 1, wherein the constant force spring is a single coil constant force spring.

6. The commutation system as claimed in claim 1, wherein the brush is configured with an elbow to direct the force exerted by the constant force spring towards center of the commutator.
7. The commutation system as claimed in claim 1, wherein the brush at one end is connected to a pivot pin in an endcap of the housing.

8. The commutation system as claimed in claim 1, wherein the elbow of the brush is in continuous contact with the circular portion of the spring and the commutator.

9. The commutation system as claimed in claim 1, wherein the brush is made of copper-graphite or carbon.

Dated this 12th day of June 2015.

[JAYANTA PAL]
IN/PA No. 172
OF REMFRY & SAGAR
ATTORNEY FOR THE APPLICANT[S]