Measuring and testing – By abrasion – milling – rubbing – or scuffing
Reexamination Certificate
2001-02-16
2001-11-13
Raevis, Robert (Department: 2856)
Measuring and testing
By abrasion, milling, rubbing, or scuffing
Reexamination Certificate
active
06314788
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATIONS
None.
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
Not Applicable.
BACKGROUND OF THE INVENTION
The present invention is directed generally to apparatus for grinding material for use in many different commercial activities where the material has a desired size or fineness grade and, more particularly, an improved drive shaft and method that allows for early detection of drive shaft bearing failure and that provides secondary support for the shaft and associated grinding apparatus in the event of bearing failure.
Various prior designs of grinding apparatus or roller grinding mills are known to the art. In general, the grinding apparatus of prior designs include a frame or housing and motor driven roller grinding assembly within the housing to grind material against a surface, sometimes referred to as a bullring. The grinding assembly, often a plurality of grinding rollers, is supported by a central shaft. The shaft usually has at least one supportive bearing assembly adjacent the bottom of the housing. The central shaft, which functions as a drive shaft, is operatively connected to thrust bearing in a gearbox and the gearbox is operatively associated with an electric motor, often via a clutch. The basic grinding apparatus may be associated with other peripheral apparatus such as separators, dryers and so forth. Examples of the inventor's prior grinding apparatus include U.S. Pat. Nos. 5,839,673; 5,611,494; 5,383,612; 4,830,290; 4,640,204; 4,522,343; 4,478,371; 4,184,640; 4,022,387; and 3,337,142.
In prior art grinding apparatus having drive shafts, failure of the support bearing could result in the shaft and, consequently the grinding assembly, slipping downward resulting in grinding mill failure. In most cases, there is no forewarning of bearing failure, which may result in the operator waiting to replace the bearings until after failure or to prematurely replace the bearings as a preventative measure. In the event the user wants to replace the bearings before complete bearing failure, the gearbox must be removed, the grinding assembly suspended within the housing, and the shaft lowered to allow access to the bearing. In some prior art roller grinding mills, which are not constructed to permit the removal of the shaft and bearing directly out of the bottom of the mill after removal of the gearbox, the entire mill must be disassembled to remove the shaft and bearing.
SUMMARY OF THE INVENTION
In accordance with the invention, briefly stated, a method is provided that allows the operator to determine roller grinding mill drive shaft support bearing failure before there is complete failure, and that allows for support of a grinding assembly in the presence of support bearing failure to allow the roller grinding mill to continue to function. The shaft includes a removable shaft section between an upper shaft section and the upwardly extending gearbox drive shaft, The removable shaft section is attached to the upper shaft section and to the gearbox drive shaft by removable couplings. A shaft driven roller grinding assembly is attached to the upper shaft section. The upper shaft section is supported by a thrust bearing. The upwardly extending gearbox drive shaft is operatively connected to a thrust bearing in the gearbox. A gap of a predetermined tolerance or dimension is left between the lower end of the upper shaft section and the upper end of the removable shaft section within the coupling. The coupling can be partially opened or removed and the gap between the shaft sections measured. A decrease in the gap size indicates that the upper shaft section is sliding down, thereby indicating support bearing wear or failure prior to total failure of the support bearing.
In the event the support bearing does fail, the upper shaft section, with the grinding assembly attached thereto, will slide downward until the gap between the upper and removable shaft sections is closed and the upper shaft section comes to rest on the removable shaft section. The couplings between the upper shaft section and the removable shaft section, and between the removable shaft section and the gearbox drive shaft, hold the drive shaft together. The weight of the grinding assembly is distributed to, and thus supported by, the couplings and the gearbox drive shaft. Due to the predetermined gap between the upper and removable shaft sections, the distance that the upper shaft section can slide down is limited. Consequently, the distance the grinding assembly can drop within the housing is limited so as to allow bottom clearance for the grinding assembly to operate, even in the presence of support bearing failure. To replace worn support bearings, the couplings are released and the removable shaft section is removed creating clearance between the upper shaft and the gearbox. This aspect of the invention allows access to the bearings without the necessity of moving the gearbox.
The foregoing and other objects, features, and advantages of the invention as well as presently preferred embodiments thereof will become more apparent from the reading of the following description in connection with the accompanying drawings.
REFERENCES:
patent: 4022387 (1977-05-01), Williams
patent: 4184640 (1980-01-01), Williams
patent: 4478371 (1984-10-01), Williams
patent: 4524917 (1985-06-01), Williams
patent: 4640204 (1987-02-01), Williams
patent: 4830290 (1989-05-01), Williams
patent: 5330110 (1994-07-01), Williams
patent: 6119504 (2000-09-01), Claus
patent: 1328594 (1987-08-01), None
Williams Direct Fired Systems; Bulletin 970; Index KK; 6 pages; no date.
Williams Direct Fired Systems; Bulletin 930; Index KK; 8 pages; no date.
Williams Direct Fired Systems; Bulletin 930R; Index KK; 8 pages; no date.
Williams Fluid Bed Roller Mill Systems; Bulletin 856R; 12 pages; no date.
Polster Lieder Woodruff & Lucchesi L.C.
Raevis Robert
LandOfFree
Grinding apparatus shaft with bearing failure detection and... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Grinding apparatus shaft with bearing failure detection and..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Grinding apparatus shaft with bearing failure detection and... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2618244