Patent Publication Number: US-5256925-A

Title: Brush holder with improved spring clip arrangement

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates generally to a brush holder for an electrical brush and more particularly to a brush holder with an improved spring clip arrangement. 
     Electrical brushes are used with various types and sizes of machinery, e.g., generators and electric motors, for collecting current from moving components. In some instances electrical brushes are employed to simply act as a pick up for the removal of static electricity which has a tendency to accumulate in moving components supported by bushings and bearings. In order to avoid integrating a brush holder into the design of an unrelated component in a piece of machinery, separate brush holders have been developed and are generally known. The primary purpose of a brush holder is to maintain contact between an electrical brush held thereby and a moving component. Replacement of brushes becomes necessary due to wear and damage, and experience has shown that a substantial amount of time can be lost because of the manner in which brushes are secured in a brush holder. As brush holder design evolved the holders changed to accommodate rapid changing of the brushes. Accordingly, the concept of designing a brush holder to accommodate changing of the brushes is also known. 
     Most electrical brushes are made of a carbon and graphite composition and the amount of force holding the brush against the surface of a moving component will determine the rate of brush wear as well as the rate of wear caused in the surface of the moving component. Accordingly, brush holders must accommodate replacement of the brushes in addition to providing for the application of an appropriate amount of force for biasing the electrical brush into contact with the moving component. 
     One commercially available approach to the above noted compound problem includes a recoil constant force spring for biasing an electrical brush toward a moving component mounted on a spring clip having multiple bends for latching the spring clip assembly in an in use position in a brush holder body. This brush holder has sufficient material to accommodate a strong spring clip assembly for biasing as well as for facilitating the changing of the brushes when the brushes and holders are of a relatively large size. However, this approach has problems with the strength and durability of spring clips which are proportionately smaller in size when brush holders of this type are relatively small. Generally stated, these spring clips have a lack of consistency in latching and remaining latched relative to the brush holder body in the in use position. This inconsistency can result in the spring clip assembly sliding or being pushed to far into the brush holder pocket to a point where it can engage and damage the moving component. 
     It has been found that the failure of the prior art spring clip arrangement to be positively positioned is not only related to the spring clip being weakened by being diminutive in size or because the spring clip may have become worn or damaged, but is also due to the overall faulty configuration of the spring clip arrangement. Accordingly, the most significant problem in the prior art devices was recognized as being a faulty design which resulted in the failure of the devices to positively position a spring clip in a spring clip pocket and thereby prevent the spring clip from engaging a moving component while maintaining a constant force on a brush carried in a brush holder pocket. Searching for answers to these problems resulted in the instant invention, which not only answered the above noted problems but which also provided additional improvements not previously realized. 
     There is a market, then, for a brush holder design, which is effective for large and small brush holders utilizing a constant force spring on a spring clip to apply constant pressure to an electrical brush guided in a brush holder pocket in the brush holder body, and which is capable of permitting the rapid interchanging of electrical brushes, especially if such a device is simple in construction and easy to use. 
     SUMMARY OF THE INVENTION 
     It is a primary purpose and principle object of the present invention to provide a brush holder with an improved spring clip arrangement for supporting an electrical brush which is effective, simple to use, and economical to manufacture. 
     The present invention involves a brush holder with a spring clip arrangement which is effective for large and small brush holders. The spring clip arrangement includes a generally V-shaped spring clip carrying a constant force spring for biasing an electrical brush which is positioned and guided in a brush holder pocket in a brush holder body. One significant improvement is that the generally V-shaped spring clip includes a shoulder stop which stops the spring clip in a seated position in a spring clip pocket in the brush holder body to when the shoulder stop engages a stop formed in the holder body. Another improvement is that the generally V-shaped spring clip is held in the seated position by a latch pin engaging a latch aperture in one leg of the spring clip. A significant improvement is that the generally V-shaped spring clip is prevented from being separated from the brush holder body by an easily removable cross pin which, when the spring clip needs to be changed can be removed from the top of the holder body in the same general direction in which the spring clip is retracted from the holder body. It is the simplicity of the design, including the fact that the generally V-shaped spring clip has greater strength, which is the principal advantage of the instant invention. This advantage is particularly apparent when a relatively small brush holder is constructed in accordance with the principles of the instant invention. 
     Accordingly, it is also an object of the instant invention to provide a brush holder arrangement which includes a spring clip assembly that is positively stopped in a seated position in a brush holder body. 
     Another object of this invention to provide a brush holder with a durable generally V-shaped spring clip permitting the rapid changing of worn and defective electrical brushes in all sizes of brush holders. 
     It is a further object of this invention to provide a brush holder utilizing a generally V-shaped spring clip with a removable cross pin facilitating replacement of the spring clip and controlling retraction and pivoting of the spring clip relative to the brush holder body. 
     These and other objects and advantages of the present invention will be apparent and understood from the following detailed description when taken in conjunction with the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective view of a brush holder according to the present invention; 
     FIG. 2 is a perspective view of a spring clip assembly used with the brush holder seen in FIG. 1; 
     FIG. 3 is a perspective view of the spring clip assembly of FIG. 2 seen from another angle; 
     FIG. 4 is a top plan view of the brush holder, including the spring clip, as seen in FIG. 1; 
     FIG. 5 is a cross sectional view of the brush holder body, without the spring clip, taken along line V--V of FIG. 4; and 
     FIG. 6 is a cross sectional view of the brush holder, including the brush holder body, spring clip assembly, and an electrical brush disposed in the brush pocket, taken along line VI--VI in FIG. 4. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     A brush holder for an electrical brush, constructed in accordance with the principles of this invention, is described hereinbelow, with reference to the accompanying drawing, wherein like reference numerals are used throughout the various views to designate similar elements or components. 
     Referring now to FIG. 1, there is shown a brush holder 10 constructed according to the instant invention. Brush holder 10 includes a brush holder body 12 which in turn includes a brush pocket 14 and a spring clip pocket 16. Brush pocket 14 is sized to slidably receive an electrical brush 18 therein and an improved spring clip assembly 20 is sized to be seated in spring clip pocket 16. The brush holder 10 can be secured to supporting structure by any suitable means and bores 21 for receiving attaching bolts (not shown) are for this purpose. 
     Spring clip assembly 20 includes a generally V-shaped spring clip 22 having a recoil constant force spring 24, i.e., a negator spring, attached thereto for engaging and biasing electrical brush 18 relative to brush holder body 12 when the spring clip assembly is seated in spring clip pocket 16. Spring clip 22 includes a first leg 26 and a second leg 28 joined to one another at an apex 30. Constant force spring 24 is attached to first leg 26 by a rivet 32 generally in the vicinity of the apex and is arranged to uncoil in the direction of a free end of first leg 26. Second leg 28 includes a shoulder 34 generally midway along the length thereof and a latch aperture 36 disposed proximate the shoulder 34 between the shoulder 34 and the apex 30. As best seen in FIG. 6, shoulder 34 forms an offset in the second leg 28 and extends generally perpendicular to an offset portion of the leg. The length of the shoulder, when added to the thickness of the material of which the spring clip 22 is made, is sufficient to exceed the width of spring clip pocket 16 for reasons which will be discussed later. Free ends 38,40, respectively, of the first and second legs 26,28 include bends which facilitate gripping by a workman&#39;s fingers such that the generally V-shaped spring clip 22 can be squeezed together until the first and second legs, in the vicinity of the apex, are juxtaposed for reasons which will also become apparent from the discussion which follows. 
     Brush holder body 12 includes a stop 42 against which shoulder 34 engages when the spring clip assembly 20 is seated in spring clip pocket 16. A bore 44 is positioned just below stop 42 and a rolled expansion pin 46, operable as a latch pin, is inserted therein and protrudes into the spring clip pocket 16 a distance sufficient to engage latch aperture 36 when the spring clip assembly 20 is seated and released in the spring clip pocket. The outward bias away from one another of the first and second legs 26, 28 of the generally V-shaped spring clip 22 causes a positive engagement of the latch pin 46 with latch aperture 36 when the spring clip is seated in the brush pocket. 
     A cross pin 48, secured in the holder body 12, controls separation of the spring clip assembly 20 from the brush holder body 12 and is positioned to permit pivoting of the spring clip relative to the brush holder body when the spring clip assembly 20 is retracted from the spring clip pocket 16. Cross pin 48 can be fixed relative to the brush holder body by various means and preferably is removably secured in notches 50 by threaded fasteners 52. As best seen in FIG. 5, cross pin 48 can be a rolled expansion pin which rests in notches 50 and is held in place by the heads 56 of the threaded fasteners 52. 
     Referring again to FIG. 5, spring clip pocket 16 communicates with brush holder pocket 14 by way of a slot 54 which is wide enough to permit the constant force spring 24 to move relative thereto without binding. As best understood by referring to FIG. 6, as electrical brush 18 wears and becomes shorter the constant force spring 24 recoils while maintaining a constant force on the back end of the electrical brush. As the constant force spring recoils it passes into slot 54 without binding and, accordingly, without changing the amount of force applied to the electrical brush. In order to ensure a positive electrical connection between holder body 12 and electrical brush 18, a threaded fastener 55 is provided for the attachment of a connector cable extending from the electrical brush to the holder body. 
     In use, spring clip assembly 20 is retracted from spring clip pocket 16 and pivoted about cross pin 48 to a position wherein the constant force spring 24 is out of alignment with brush pocket 14. An electrical brush 18 can then be inserted in brush pocket 14 and spring clip assembly 20 is pivoted about cross pin 48 and seated in the spring clip pocket 16 with shoulder 34 engaging stop 42 and latch pin 46 engaging latch aperture 36 to fix the spring clip assembly 20 relative to the brush holder body 12. Constant force spring 24 engages the back end of the electrical brush and uncoils as spring clip 22 is seated thereby biasing the electrical brush 18 relative to the brush holder body 12 such that the electrical brush 18 engages a rotating component 58, e.g., a commutator, with a constant amount of force. As the electrical brush 18 wears and becomes shorter the constant force spring 24 shortens by recoiling. The coiled remainder of the constant force spring engages the back end of the remaining portion of the electrical brush without binding in slot 54. It should be readily apparent that an electrical brush supported by the brush holder can be quickly and easily changed by simply gripping the distal ends 38, 40 of the legs 26, 28 of the generally V-shaped spring clip 22 and squeezing the legs together to release the latch pin 46 from the latch aperture 36. The spring clip assembly 20 can then be retracted from the spring clip pocket 16, pivoted relative to the brush holder body 12 such that the constant force spring is out of engagement with the electrical brush and out of alignment with the brush pocket thereby permitting the replacement of an electrical brush disposed therein. It should also be apparent that the spring clip assembly 20 can not be inserted farther into the spring clip pocket than the seated position because of shoulder 34 engaging stop 42. The offset created by shoulder 34 has sufficient length to cause the spring clip 22 to have a dimension greater than the width of spring clip pocket 16, when squeezed together, thereby positively seating said spring clip assembly and preventing insertion or slippage of the spring clip 22 into the spring clip pocket 16 beyond the seated position. It should also be apparent that the spring clip assembly 20 can be easily changed by the removal of threaded fasteners 52 and cross pin 48. The fact that the cross pin 48 can be removed from the top of the brush holder body 12, in the same general direction that the spring clip assembly is retracted, simplifies the procedure and obviates the need to remove the entire brush holder 10 for repair. 
     The device disclosed herein can be formed from any of a number of different suitable materials and by any of a number of different processes and, in its preferred form, the brush holder body is made of brass and the generally V-shaped spring clip is made of stainless steel. 
     While this invention has been described with a certain degree if particularity, it should be understood that other forms of brush holders with improved spring clip arrangements are contemplated by the present invention and it is manifest that many changes may be made in the details of construction and in the arrangement of components without departing from the spirit and scope of the disclosure. It is understood that the invention is not limited to the embodiments set forth herein for purposes of exemplification, but is limited only by the scope of the attached claims, including the full range of equivalency to which each element is entitled.