US3817590A - Means for supporting roller assemblies in a dishwasher tub - Google Patents

Abstract

A unit-handled roller assembly for front loading dishwashers employing a unipartite plastic tub includes a plastic roller mounting stud having an integral annular array of spaced resilient fingers at the tub wall engaging end thereof for maintaining a roller in assembled relationship with the stud prior to installation and serving as an integral washer between the roller and tub wall upon installation. The roller mounting stud also includes an integral, annular sealing ridge upstanding from the tub wall engaging end of the stud in surrounding relation to a central mounting bore for deforming and/or abrading the softer tub wall into fluid tight sealing engagement with the annular ridge. A plurality of the roller mounting assemblies are anchored in a common reinforcing channel member backing a metal collar adjacent the front open end of the dishwasher.

Description

United States Patent [191 Brezosky June 18, 1974 MEANS FOR SUPPORTING ROLLER ASSEMBLIES IN A DISHWASHER TUB [75] Inventor: Bernard J. Brezosky, Louisville, Ky.

[73] Assignee: General Electric Company,

Louisville, Ky.

22 Filed: Dec.29, 1972 21 Appl.No.:319,347

[52] US. Cl 312/341 R [51] Int. Cl A47b 88/00 [58] Field of Search 312/341 R, 344; 308/38; 248/43 D; 134/57 D, 58 D [56] References Cited UNITED STATES PATENTS 2,573,272 10/1951 Petkwitz 312/342 3,096,125 7/1963 Kendt 308/3.8

3,190,709 6/1965 Dutcher et al 312/228 Primary Examiner-James C. Mitchell Attorney, Agent, or Firm-Francis H. Boos, Jr.

[5 7] ABSTRACT A unit-handled roller assembly for front loading dishwashers employing a unipartite plastic tub includes a plastic roller mounting stud having an integral annular array of spaced resilient fingers at the tub wall engaging end thereof for maintaining a roller in assembled relationship with the stud prior to installation and serving as an integral washer between the roller and tub wall upon installation.

The roller mounting stud also includes an integral, annular sealing ridge upstanding from the tub wall engaging end of the stud in surrounding relation to a central mounting bore for deforming and/or abrading the softer tub wall into fluid tight sealing engagement with the annular ridge.

A plurality of the roller mounting assemblies are anchored in a common reinforcing channel member backing a metal collar adjacent the front open end of the dishwasher.

5 Claims, 3 Drawing Figures BACKGROUND OF THE INVENTION I The invention is directed to large capacity front loading dishwashers of the type normally comprising a permanent installation and employing upper and lower dish supporting racks as opposed to the smaller, low capacity, portable and/or top loading dishwashers. The reason for the distinction is that the ultimate objective of the invention is the employment of a unipartite plastic tub in large capacity, front loading dishwashers and while some of the problems presented by a proposed use of such a tub would be common to dishwashers of either type; the majority are distinct. Typical distinctions relate to increasing wall flexibility with increasing area, the absence of encompassing metal housings, greater tub shape complexity and additional interior tub mountings such as dual rack support structures. Accordingly, the ensuing background discussion relates primarily to front loading dishwashers of the type normally adapted for a permanent, under cabinet, installation.

The high temperature, corrosive environment to which automatic dishwasher chambers are subjected dictates that thesurfaces of those internal components in contact with such environment be either highly resistant, or immune, to corrosion. Corrosion resistant metals such as stainless steel represent a substantial cost factor in this highly competitive appliance field and the long term industry trend has been toward the use of inert materials to resist the corrosive effects of the chamber environment which are magnified adjacent the usual metal tub seam welds. Insofar as the tub itself, representing the far greater internal surface area exposure, is concerned; the general trend in the United States has been toward the application of an adherent plastic coating to the tub interior while European manufacturers have gone more to the use of plastic tub liners. In either event, the basic structural and design parameters that have prevailed since the advent of the modern front loading automatic dishwasher remained valid. This for the reason that overall dishwasher design parameters, both as regards utility and structural integrity, are virtually unaffected by whether the conventional metal tubis coated, lined or exposed.

Conceptually, the use of a unipartite plastic dishwasher tub, i.e., one not requiring a more rigid backing or outer support structure, represents a substantial advance in the art. Exemplary are the greatly decreased cost factors of a molded plastic tub vis-a-vis that of a metal tub requiring a further coating or lining operation; reduction in finishing labor requirements and particularly tub welding operations; longer tub life due to corrosion resistance which is independent of faulty coating procedures or chipping; decreased thermal and acoustical transmission thus minimizing the need for separate insulation; and a lesser inventory requirement for separable components susceptible of integral molding with the tub.

The reduction to practice of such a concept, as applied to front loading dishwashers on an assembly line basis, however, presents a myriad of problems which arise as a requirement for different approaches to those engineering considerations which had previously been predicated upon the use of a metal tub. The distinctions are primarily those associated with material strength, the unusually high temperature environment to which the tub is subjected and considerations relating to plastic molding procedures. Thus, while the structural in- 5 tegrity of a metallic box beam shape defined by the conventional front loading tub is more than sufiicient to resist excessive wall deformation as a function of normal loading forces as during installation, adjustment or use and temperature variations from room ambient to approximately 255F; such normally applied loading forces would, in the absence of appropriate compensating structure, produce unacceptable wall deformation in a like configured plastic tub. Similarly, impact strength is normally of little moment in the design and installation of metallic tubs but is a matter of major concern in plastic tub design. Furthermore, various structural features appearing in a formed plastic tub as an incident of the forming operation create problems not previously associated with metal tub fabrication. Exemplary of the latter distinction are the presence, on the finished product, of mold lines and/or mold retention ribs creating localized areas of decreased impact resistance as well as the usual wall draft to permit removal of the product, or tub, from the forming mold. One primary disadvantage arising from this necessary wall draft concerns the mounting of the dishwasher rack supporting racks in parallel.

In addition to the foregoing considerations which relate primarily to mounting and/or assembly procedures for larger capacity front loading machines, the desirability of precluding tub discoloration and the desirability for firewall separation of the tub and those electrical components constituting a fire hazard are common to all automatic dishwashing machines. As regards plastic tub discoloration, it is preferred to avoid the use of certain conventional reinforcing strand type fillers, such as chopped strand fiber glass, for the reason that their intersection with the interior plastic surface may provide a bleed path for food stains to permeate the tub structure.

The necessity for firewall separation is a safety requirement but one which may be used to dual advantage in connection with the construction herein disclosed, which is basically nothing more than a plastic tub equipped with a door and tub support frame, by utilizing the necessary firewall construction as a power equipment support.

The prior art suggestions relating to the use of small capacity plastic tubs of the top loading type, as in U.S.

Pat. No. 2,691,986 and the use of separate plastic tub components, as in U.S. Pat. Nos. 2,877,778; 3,385,306 and 3,460,878 offer little in the way of guide lines as regards a practical reduction to practice of a large capacity front loading tub for the reason that most of the problems requiring solution are not present in smaller and/or top loadingunits and particularly those which employ an enveloping metal housing.

The present invention relates to the construction of those roller assemblies used to support the upper dishwasher rack and their mounting to the inner sidewalls of the plastic tub while other of the aforementioned matters are more fully described and claimed in the following, commonly owned, copending applications:

Ser. No. 319,556, filed Dec. 29, 1972, for Double, Reversed Mounting Boss for Plastic Tub;

Ser. No. 319,201, filed Dec. 29, 1972, for Fill Funnel Construction for Plastic Tubs;

Ser. No. 319,555, filed Dec. 29, 1972, for Thermal Growth Compensation and Mounting for Plastic Dishwasher Tubs;

Ser. No. 319,203, filed Dec. 29, 1972, for Front Loading Dishwasher Employing Plastic Tub Construction;

Ser. No. 319,202, filed Dec. 29, 1972, for Radiused Mold Walls for Plastic Tubs;

Ser. No. 317,368, filed Dec. 22, 1972, for Angled Levelling Foot for Domestic Appliance;

Ser. No. 319,200, filed Dec. 29, 1972, for Torsionally Reinforced, Skeletal Support Frame for Plastic Tubs;

Ser. No. 319,557, filed Dec. 29, 1972, for Impact Protection for Plastic Tub Employing Mold Retention Ribs;

Ser. No. 319,199, filed Dec. 29, 1972, for Plastic Tub Wall Alignment for Dishwasher Rack Mounting.

Insofar as the mounting of the upper dish rack roller supporting assemblies are concerned; the elimination of the conventional front loading metal tub and the substitution therefor of a plastic tub necessitates the presence of mounting and/or support structure to compensate for those inherent characteristics previously available in the use of a metal tub which include relatively high abrasion resistance, a modulus of rigidity sufficient to preclude wall deformation and provide secure anchor points for roller assembly mounting, and a "box beam tub shape insuring adequate resistance to upper rack loading forces. It is apparent that if the advantages of the invention, as regards decreased cost and weight, are to be retained the necessary mounting and support structure must not, in effect, comprise a confining tub support housing. Rather, a purpose of the invention is to provide an operative, front loading dishwasher unit having a plastic tub whose outer walls comprise the great majority of the outer dishwasher unit construction and would actually be exposed to view prior to installation of the dishwasher unit within an outer decorative housing, which decorative housing may comprise a free standing, portable unit or a permanent undercabinet installation.

Although the tub sidewalls inherently present a relatively soft surface which is subject to abrasion by relatively movable component parts, such as the upper rack supporting rollers; this very characteristic can be used to advantage in sealing the tub interior with respect to the necessary through mounting bores in the tub walls.

SUMMARY OF THE INVENTION It has been found that the requisite structural integrity can be imparted to the overall dishwasher and tub construction through the use of a metal base assembly and a relatively narrow (as compared to the tub depth) metal collar upstanding from the base assembly and extending across the top and sidewalls of the tub immediately adjacent the open end thereof. The front, open end of the tub is then secured to the surrounding, composite box beam collar and base assembly thus anchoring the open end of the tub to a relatively rigid metal shape. The savings in fabrication cost and weight involved in bending a narrow metal strap into an approximate U-shape to form a collar and then joining the same to a base assembly as compared with the utilization of a complex metal shape to either form the tub or envelope a tub liner are obvious. The tub itself is comprised of an injection molded, homogeneous, unipartite polypropylene based plastic.

In front loading dishwashers of the type herein disclosed, upper rack loads of 40 pounds are common as is multiple daily usage over an expected dishwasher and tub lifetime in excess of 10 years. It is thus apparent that the tub walls, per se, having an exemplary wall thickness of less than 0.2 cannot be expected to support the upper rack mounting tracks both by reason of wall defonnation under such loads and inherent cold flow characteristics. As regards the latter, reference is had to the presence of track and/or roller mounting bores which, if supported solely by the plastic sidewalls, would fish tail or enlarge under repeated loading and impact. The problems of mounting bore enlargement and wall deformation are accommodated by positioning the anchored supports for the upper rack structure immediately adjacent the open end of the tub so that the supporting fasteners pass through the encompassing metal collar to find rigid anchorage relative thereto rather than in the tub sidewalls. In line with the obvious desideratum of mounting collar fonnation from as light gauge metal as is consistent with the performance of those supporting roles discussed, supra; separable reinforcing elements are provided to back the roller assembly mountings to the encompassing collar. More specifically, the roller assemblies are mounted, in pairs, to a common channel member backing the mounting collar to spread torque loads and transfer the primary loading forces from the mounting fastener bore walls in the metal collar to corresponding bore walls in the heavier gauge, backing channels.

The mounting of the relatively movable rollers in immediate proximity to the inner tub sidewalls requires the presence of an intermediate bearing structure to avoid abrasion of the relatively soft" plastic walls. Such a function would normally be served by a separable washer which, however, is undesirable from an assembly standpoint as is the usual multistep installation of a roller assembly. The utilization of a roller mounting stud having integrally formed, resilient fingers effectively defining a washer obviates the necessity for separate washer installation and permits the preassembly of a roller with the mounting stud which is retained thereon, to form a unit handled assembly, by the particular washer disposition, acting as a retainer, prior to installation.

The tub engaging end wall of the roller mounting stud is formed with an integral ridge surrounding a central mounting bore which, upon assembly and tightening engagement with a plastic tub wall, abrades and/or deforms the softer tub wall to effect a fluid tight seal around the tub wall mounting bore.

DESCRIPTION OF THE DRAWINGS FIG. 1 is a broken, front perspective of a front loading dishwasher employing a plastic tub and illustrating the mounting and placement of supporting roller assemblies for an upper dish rack, with the upper rack being omitted for clarity of illustration;

FIG. 2 is a section through one roller assembly taken along line 22 of FIG. 1; and

FIG. 3 is an exploded perspective of a roller assembly.

DESCRIPTION OF THE PREFERRED EMBODIMENTS In FIG. 1 is illustrated a front loading dishwasher having a unipartite, plastic tub 12 mounted to metal tub support frame 14 comprising base assembly 16 and mounting collar 18 which mounting collar encompasses, in backing relation, and is secured to the top and sidewalls 20, 22 of tub 12 immediately adjacent the forward open end thereof as by fasteners 24. It will be noted that in line with a primary purpose of the invention to eliminate any semblance of a metal tub or corresponding housing, the width of the mounting collar is kept as small as is consistent with its required role of imparting to the open tub front the necessary rigidity. Accordingly, all of the upper rack supporting rollers are grouped immediately adjacent the front end of the tub to permit this anchorage in mounting collar 18.

The roller assemblies 26 are grouped in spaced, paired relation on opposed tub sidewalls 22 with each vertically related pair being anchored to a common reinforcing channel element 28 backing mounting collar 18. As will be apparent from the foregoing discussion, the torque loads imparted to the roller assemblies upon maximum extension of the upper rack (not shown) viav the rack supporting track 30 are substantial. The transfer of these loads via the relatively heavy bore walls 32 of reinforcing element 28 to an extended surface area of the mounting collar permits the utilization of lighter gauge sheet metal for the mounting collar than would be required for rigid support of the roller assemblies through the mounting collar bore walls 34 and immediately surrounding surface area.

The tub wall mounting bores 36 for the various roller assemblies are sealed with respect to the tub interior by the embedment, in tub wall 22, of annular sealing ridges 38 integral with the tub wall engaging ends 40 of the various mounting studs 42 on which track supporting rollers 44 are journalled. In actuality, the seal surrounding tub wall mounting bore 36 is achieved by a combination of tub wall abrasion and wall deformation since the usual assembly procedure involves running the mounting stud 42 down on its supporting fastener 46 as by rotation of the stud via hex faces 48. Continued rotation of the stud after initial contact between annular ridge 38 and tub sidewall 22 results in abrasion and deformation of the sidewall until the sealing ridge is fully embedded as illustrated in FIG. 2. If the mounting stud is drawn up by rotation of fastener 46 then the sealing effect and at least partial embedment of the sealing ridge would be as a result of cold flow or wall surface deformation.

An annular array of spaced, resilient fingers 50, having outer surfaces continuous with the cylindrical bearing surface 52, are formed integral with mounting stud 42 and extend beyond the tub wall engaging end thereof. These fingers 50 are readily flexible between the initially formed, dotted line positions of FIG. 3 wherein the outer surfaces thereof define a straight angle with bearing surface 52 and a position displaced 90 therefrom as indicated in the roller assembly installation of FIG. 2, to collectively define a washer or wear surface intermediate roller 44 and tub wall 22. Additionally, these fingers define an integral retainer for roller 44 prior to tub wall installation of the assembly as the fingers assume an outwardly flared bias, indicated in solid lines in FIG. 3, which is mechanically im parted thereto following their emergence through the stud mounting bore 54 in roller 44. The fingers may, for example, be deformed to the solid line position of FIG. 3 by jamming the tub wall engaging ends 40 of the studs against a flat surface following assembly of the roller. The roller is thus maintained in unithandled relation on the mounting stud by opposed retainers at opposite ends of bearing surface 52 comprised of the relatively rigid stop shoulder 56 and the deformed, resilient fingers 50. A partial insertion of threaded fastener 46 into stud mounting bore 58 results in a three-part unit handled assembly which requires removal of the fastener prior to assembly with the dishwasher. Preferably, the fasteners 46 are permanently secured to their respective channels 28, such as by welding or the like, so that tub installation only requires manipulation of a channel 28 to insert its two attachedfasteners 46 through the mounting bores and then running down the roller assemblies on the fasteners. As the tub engaging end 40 of mounting stud 42 approaches the tub wall, the bevelled ends 60 of fingers 50 cam the fingers outwardly and further tightening of the roller mounting stud results in the movement of fingers 50 to the position of FIG. 2 whereupon the same are perpendicular to the axis of roller 44 and define a washer bearing surface separating the roller and tub wall.

Desirably, the plastic roller assembly components have a higher hardness rating than the plastic tub.

The concept discussed heretofore in regard to providing spaced apart component support fasteners having a backing plate or rigid portion from which the fasteners are extended is believed a unique concept not only in combination with the plastic tub and mounting collar herein disclosed but also in more conventional dishwasher tub constructions. It is common in conventional tub structures to rely on the compressive force of the fastening means pressing the roller stud, or other component support means, tightly against the tub wall to maintain the stud in the desired position under load. The arrangement disclosed herein, where a pair of component fasteners 46 are based to a reinforcing element 28, provides acomparatively enlarged base for receiving the load forces translated through the fasteners whereby undesirable effects such as bending of the substantially thin conventional tub wall in the area of each fastener and spreading of the bore in the tub wall in response to the load are avoided. The conventional practice has generally been to depend upon the compressive force of the connection against the tub wall to avoid the aforementioned efi'ects; however, the present invention curtails such effects without requiring relative high compressive force of the support means against the tub wall such that less expensive components made of plastic may be substituted for metal elements used heretofore and significant cost savings may be obtained. In accordance with the concept of providing a means of spreading loadforces over a wider area of the tub wall, it should be noted that the fastener means extending through the tub wall bores and interconnected by the reinforcing element common thereto may further be provided with means such as welds 62 to establish an integral means of spreading load forces over a substantially wide side wall area between separate component support fasteners.

While the background discussion of this specification is related primarily to front-loading dishwashers of the type normally adapted for a permanent undercounter installation as opposed to the type of dishwasher having a hinged top closure for top-loading, it should be emphasized that many such machines are commercially produced and purchased for indefinite use as a freestanding model adaptable at a later time by the owner to a built-in unit beneath a kitchen countertop to blend with the matching cabinet structure of the kitchen. Generally, the difference between the unit designed as a convertible" and the unit to be immediately permanently installed is the inclusion of side, rear and top cabinet appearance panels to the basic unit structure as designed for permanent installation. Therefore, it should be understood that the present invention is specifically directed to the front-loading type of dishwasher structure whether of the generally lower-cost unit having no appearance cabinet enclosure or the more elaborate, temporarily portable unit designed for later modification for use in a fixed location.

I claim:

1. In combination with a front loading dishwasher having a plastic tub of generally rectangular crosssection; a metal tub support frame including a base assembly underlying the lower tub wall and a tub mounting collar upstanding from the front end thereof and encompassing the top and sidewalls of the tub at the front open end thereof, the improvement comprising: a pair of track supporting roller assemblies; means mounting said roller assemblies in spaced relation on an interior sidewall of said plastic tub adjacent the front open end thereof for transmitting loading forces from said roller assemblies to said metal tub support; and said means including a reinforcing element engaging the exterior surface of said mounting collar and spaced fastener means extending through said reinforcing element, mounting collar and tub sidewall into supporting engagement with said roller assemblies.

2. The combination of claim 1 wherein said reinforcing element comprises a metal channel.

3. The combination of claim 1 including two pair of track supporting roller assemblies on each of two opposed tub sidewalls; and said mounting means including one of said reinforcing elements for each said roller assembly pair.

4. In combination with a washing appliance having an interior tub with at least two spaced-apart bores through the sidewall thereof for insertably receiving component fasteners therethrough, the improvement comprising said fasteners being integral with one another by means of a rigid interconnecting portion therebetween whereby load forces on said fasteners are translated to a substantially large area of said tub.

5. The combination of claim 4 wherein said rigid portion is a channel member.

4' k I! I I

Claims (5)

1. In combination with a front loading dishwasher having a plastic tub of generally rectangular cross-section; a metal tub support frame including a base assembly underlying the lower tub wall and a tub mounting collar upstanding from the front end thereof and encompassing the top and sidewalls of the tub at the front open end thereof, the improvement comprising: a pair of track supporting roller assemblies; means mounting said roller assemblies in spaced relation on an interior sidewall of said plastic tub adjacent the front open end thereof for transmitting loading forces from said roller assemblies to said metal tub support; and said means including a reinforcing element engaging the exterior surface of said mounting collar and spaced fastener means extending through said reinforcing element, mounting collar and tub sidewall into supporting engagement with said roller assemblies.

2. The combination of claim 1 wherein said reinforcing element comprises a metal channel.

3. The combination of claim 1 incluDing two pair of track supporting roller assemblies on each of two opposed tub sidewalls; and said mounting means including one of said reinforcing elements for each said roller assembly pair.

4. In combination with a washing appliance having an interior tub with at least two spaced-apart bores through the sidewall thereof for insertably receiving component fasteners therethrough, the improvement comprising said fasteners being integral with one another by means of a rigid interconnecting portion therebetween whereby load forces on said fasteners are translated to a substantially large area of said tub.

5. The combination of claim 4 wherein said rigid portion is a channel member.

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