You are an expert at summarizing long articles. Proceed to summarize the following text:

You are an expert at summarizing long articles. Proceed to summarize the following text: 
FIELD OF THE INVENTION 
     This invention relates to discs and associated components intended principally, although not necessarily exclusively, for cleaners of liquid-containing vessels and more particularly to automatic pool cleaners having discs with rigidized fins or other protrusions. 
     BACKGROUND OF THE INVENTION 
     U.S. Pat. No. 5,421,054 to Dawson, et al., commonly-owned with this application, illustrates examples of discs having flexible fins. The fins extend upward beyond the peripheries of the (generally planar portions of the) discs. As noted in the Dawson patent, these fins “assist [the disc] in maneuvering over many objects (such as drains, lights, valves, and nozzles) projecting from internal surfaces of pools.” See Dawson, col. 2, 11. 59-61. Because located at the peripheries of discs, the fins also “contact most protrusions before the remainder[s] of” the discs. See id., 1. 63. 
     Commonly-owned U.S. Pat. No. 5,465,443 to Rice, et al. discloses additional examples of discs having flexible fins. Pending U.S. patent application Ser. No. 11/708,925 of Moore, et al. describes yet additional sample discs with flexible fins. The finned portions of these discs typically form the forwardmost structure of their associated pool cleaners, so that they usually contact protrusions and other obstacles in advance of the remainders of the cleaners. Stated in the Moore application is that the fins “provid[e] sufficient rigidity to [the] disc to enable it to ride over various objects, including many drains, lights, valves, and other nozzles, projecting from internal surfaces of pools.” See Moore, p. 8, 11. 20-22. 
     In these and other discs having fins (or similar outwardly-extending protrusions), the fins and generally planar portions of the discs are usually integrally formed. The fins of the Dawson and Rice patents, for example, may be molded together with generally planar portions of the corresponding discs. Fins of the Moore application, likewise, may be molded together with the forward section of the disc. 
     Lacking, therefore, from these patents and application is any discussion of outwardly-extending protrusions that comprise multiple pieces. Similarly lacking is any discussion of adaptors for the fins to accommodate circumstances in which the coefficient of friction of, e.g., the leading edge of the disc needs to be decreased or when lateral bending of the fins needs to be discouraged. Also not specifically addressed is any mechanism for enhancing integrated movement of the fins and planar disc sections when desired. 
     SUMMARY OF THE INVENTION 
     The present invention includes components configured to resolve the foregoing issues. Among these components are separate members, or covers, for the fins or other protrusions. Facially resembling false fingernails in some embodiments, the covers may be placed onto fins and removed therefrom as needed. Presently-preferred versions of the covers are made from material (a) more rigid and (b) having lower coefficient of friction than the fins, hence both discouraging lateral bending of the fins and decreasing frictional contact with surfaces when certain obstacles or walls are encountered by a corresponding disc operating within a pool. Versions of the covers also may contact planar portions of the disc adjacent the fins, resulting in more coordinated upward movement of the fins and planar portions in selected circumstances. 
     A cover of the invention may, if desired, be molded or otherwise formed in a single piece, with a generally horizontal portion and an upwardly-curved, generally vertically-oriented portion. The interior of the cover is hollow, allowing it to slide onto (over) and receive a fin. Frictional contact between the fin and interior of the cover may retain the cover in place, especially (although not exclusively) when the fin has non-uniform width. 
     Included as part of the generally horizontal portion of the cover may be a lower cut-out into which the generally planar portion of a disc is fitted. So fitting the planar portion permits the cover to contact both a fin and the planar portion, allowing the cover to influence motion of both portions of the disc jointly. The lower cut-out also arguably helps guide the fin for receipt by the hollow receiving portion of the cover. 
     It thus is an optional, non-exclusive object of the present invention to provide covers for protruding portions of discs. 
     It also is an optional, non-exclusive object of the present invention to provide covers that are separable from the discs, which covers may be added or removed as necessary or desired. 
     It is a further optional, non-exclusive object of the present invention to provide covers made from material of greater rigidity than the protruding portions of discs with which they are associated. 
     It is, moreover, an optional, non-exclusive object of the present invention to provide covers made from material having lower coefficient of friction than the protruding portions of discs with which they are associated. 
     It is another optional, non-exclusive object of the present invention to provide covers which, when in use, retain associated protruding portions of a disc via frictional fit. 
     It is an additional object of the present invention to provide automatic swimming pool cleaners including discs with which the covers may be used. 
     Other features, advantages, and objects of the present invention will be apparent to those of requisite skill in appropriate fields with reference to the remaining text and drawings of this application. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an isometric view of a cover of the present invention. 
         FIG. 2  is a worm&#39;s-eye view of the cover of  FIG. 1 . 
         FIGS. 3-4  illustrate placement of covers such as that of  FIG. 1  onto discs. 
         FIG. 5  shows portions of an automatic pool cleaner having a disc onto which covers such as that of  FIG. 1  may be seated. 
     
    
    
     DETAILED DESCRIPTION 
     Depicted in  FIGS. 1-4  is exemplary member or cover  10  of the present invention. Presently preferred versions of cover  10  are one-piece structures molded into a rigid shape. In particular, cover  10  typically is designed to be substantially harder (i.e. more rigid) than 80 A Shore, the typical hardness of its associated disc  14 . Alternatively, cover  10  may comprise more than one piece. 
     Whether a one- or multi-piece structure, cover  10  may include generally vertically-oriented portion  18  and generally horizontal portion  22 . As shown in  FIGS. 1-4 , portion  18  may extend upward from portion  22 . Portion  18  also may be curved, generally matching the shape of leading edges  26  of fins  30  spaced radially about disc  14  (see  FIGS. 3-5 ). If protrusions shaped other than fins  30  extend outward beyond periphery  34  of disc  14 , portion  18  may, of course, be shaped differently than as shown. 
     Generally vertically-oriented portion  18  may comprise wall  38  and, at upper end  42 , cap  46 . Wall  38  has generally U-shaped cross-section, thus forming hollow area  50  into which fin  30  may be frictionally fitted. Cap  46  functions as a stop, contacting uppermost part  54  of fin  30  when cover  10  is properly positioned. 
     Generally horizontal portion  22  may include spaced walls  58  and  62 , with walls  58  and  62  being connected at end  66  by bridge  70 . Walls  58  and  62  also are integrally formed with (or connected to) wall  38 . Additionally incorporated into portion  22  may be cut-outs  74  and  78 , in which parts of walls  58  and  62 , respectively, are not present. Cut-outs  74  and  78 , hence, may serve to receive generally planar portion  82  of disc  14 . In such event respective edges  86  and  90  of cut-outs  74  and  78  may act as stops by contacting periphery  34  when cover  10  is properly seated on fin  30 . 
     Although bridge  70  is among various optional features of cover  10 , if present it may be useful in guiding fin  30  into hollow area  50 . In particular, bridge  70  may contact and slide along trailing edge  94  of fin  30  as cover  10  is being positioned onto the fin  30 . Thereafter, bridge  70  may at times function too as a stop, preventing unwanted downward movement of cover  10  relative to generally planar portion  82  of disc  14 . 
       FIGS. 3-4  illustrate multiple covers  10  seated on fins  30  of disc  14 . Not every fin  30  (or other protrusion) of disc  14  need be covered, however. Likewise, preferred covers  10  are removable under manual or other force from fins  10  and, therefore, need not necessarily be used with any disc  14 . Nevertheless, deploying one or more covers  10  may be useful in certain situations, particularly in pools in which fins  30  tend to grip vertical pool walls and thereby slow climbing of the associated automatic pool cleaner (such as cleaner  98  of  FIG. 5 ). Alternatively, covers  10  may be overmolded onto or permanently connected to fins  10  (via water-insoluble adhesive or otherwise) if appropriate or desired. 
     Enhancing rigidity of fins  30  utilizing covers  10  also may inhibit undesired lateral bending of the fins  30 . Such lateral bending otherwise may occur when fins  30  contact obstacles or walls within pools. When fins  30  bend laterally upon contacting a vertical pool wall, the bending sometimes inhibits the associated cleaner from climbing the wall. Thus, preventing lateral bending of fins  30  may, at times, improve at least climbing performance of the cleaner. 
     The configuration and rigid nature of cover  10  also tend to integrate upward movement of fins  30  and disc  14 . As a fin  30  commences upward flexing, end  66  of cover  10  begins depressing planar portion  82 . This action in turn causes the portion of disc  14  between end  66  and periphery  34  to flex upward too. The overall effect of this activity is to decrease suction force applied to disc  14  near periphery  34 , facilitating continued lifting of disc  14  when prompted to do so by the upward motion of fins  30 . 
     The foregoing is provided for purposes of illustrating, explaining, and describing embodiments of the present invention. Modifications and adaptations to these embodiments will be apparent to those skilled in the art and may be made without departing from the scope or spirit of the invention. The disclosures of the Dawson and Rice patents and of the Moore application are hereby incorporated herein in their entireties by this reference.

Summary:
Separate covers for protruding portions of discs of automatic swimming pool cleaners are addressed. The covers may be placed onto protrusions, such as fins, and removed from the fins as needed. Version of the covers are made of material more rigid and having lower coefficient of friction than the fins to discourage lateral bending of the fins and decrease frictional contact of the fins with pool surfaces.