Motor assembly with a sealed commutator/brush interface

#The present invention is generally directed to motor assemblies. In particular, the present invention is directed to a sealed commutator/brush interface area of a motor assembly so as to restrict entry of volatile material into the interface area and contain carbon dust. Specifically, the present invention is related to a motor assembly which employs a seal around the commutator/brush interface so as to contain carbon dust generated from the brush in a confined area so as to eliminate the possibility of arcing between the brushes and a shaft bearing or a motor housing.

#It is well known that carbon brushes utilized in motor assemblies wear and generate carbon dust after prolonged motor use. Indeed, carbon dust is generated and thereafter migrates to various areas around the motor assembly. This is problematic in that some motor assemblies are used to pump or move highly volatile organic compounds such as paint and the like. The commutator brush interface causes sparking which in turn generates carbon dust. An accumulation of carbon dust may result in arcing between the interface area and the motor shaft or motor housing. The potential arcing in an environment of volatile organic compounds presents a significant safety hazard for those in proximity to the motor assembly. Yet another drawback of the carbon dust generation is that the dust migrates toward the bearings supporting the motor shaft. This dust may create an electrical shorting path and if this occurs the motor may be damaged or rendered inoperative.

#One attempt at solving the problem of sparking highly combustible materials is presented in U.S. Pat. No. 6,417,595. This patent discloses a seal that partially isolates the commutator assembly from the internal ambient atmosphere of the electric motor. However, the disclosed seal still provides gaps to allow migration of the carbon dust and as such sparking may still occur. Yet another problem with the assembly disclosed in the '595 patent and other similar assemblies, is that the carbon brush dust tends to collect in unwanted areas. Therefore, there is a need for an improved system to seal carbon dust within a confined area and prevent its migration to other areas of the motor assembly.

#For a complete understanding of the objects, techniques and structure of the invention, reference should be made to the following detailed description and accompanying drawings, wherein:

#FIG. 1 is an exploded perspective view of a motor assembly made in accordance with the concepts of the present invention;

#FIG. 2 is a cross-sectional view of an end bracket assembly provided in the motor assembly and made in accordance with the concepts of the present invention;

#Referring now to the drawings and in particular to FIG. 1 it can be seen that a motor assembly with a sealed commutator/brush interface is designated generally by the numeral 10. Although the motor assembly described herein is used primarily for paint sprayers and the like, it will be appreciated that the concepts disclosed herein are equally applicable to other types of motor assemblies. And the motor described herein is a 2-pole motor. Of course, the aspects described herein are equally applicable to 4-pole or other multiple pole motor assemblies. The motor assembly 10 includes a housing 12 which encloses an armature assembly 14. Axially extending from the armature assembly is a rotatable shaft 16 that carries a commutator 18. A distal bearing 20 is carried by one end of the shaft 16 for rotatable support of the armature assembly within the housing 12. A commutator end bracket assembly 24 rotatably receives an end of the shaft 16 opposite the distal bearing 20. The commutator end bracket assembly 24 includes a bearing side 26 which is opposite a housing side 28. The housing side 28 is received by and mates with the housing 12 and is supported thereby.

#As best seen in FIG. 2, the end bracket assembly 24 includes an outer ring 30 which has an outer ring surface 32. Concentrically disposed within the outer ring 30 is an inner ring 34. The inner ring 34 may be axially displaced with respect to the outer ring 30 away from the housing so as to accommodate components of the commutator 18. The inner ring 34 provides an axial opening 36 therethrough so as to rotatably receive the commutator 18. A plurality of radial ribs 40 may angularly and axially extend between the outer ring 30 and the inner ring 34.

#A pair of diametrically opposed brush tubes 42 also connect the outer ring 30 to the inner ring 34. Each brush tube 42 has a brush opening 44 to receive a brush 46. A pair of brushes are used in this embodiment and as such the motor assembly 10 is known in the art as a two-pole motor. It will be appreciated that the brushes 46 may be made of carbon, a carbon composite material or other like material that is used for brushes in electric motor assemblies. The brushes allow for electrical connection to the rotatable commutator 18 so as to generate rotation of shaft 16 when electricity is applied to the brushes 46. Also contained within the brush tubes 42 are springs 48 that bias the brush against the commutator 18. Each brush tube is enclosed at the end opposite the commutator by a brush cap 50 which also provides for connection of a power lead 52 to the spring which is mechanically and electrically connected to the brushes 46. It will be appreciated that as the commutator is rotated and bears against the ends of the brushes 46 that the frictional interaction between the two surfaces causes sparking and brush dust to be generated from the brushes. In order to minimize migration of the dust, which causes the problems previously discussed, it is desirable to confine that dust within the area defined by the inner ring 34.