Patent Document

RELATED APPLICATION 
     This application claims the benefit of co-pending U.S. Provisional Application Ser. No. 60/200,452 entitled “ROTOMOLDED HYDRAULIC RESERVOIR WITH INTEGRAL FILTER BOWL” filed on Apr. 28, 2000, which is incorporated herein in its entirety. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a hydraulic reservoir and, more particularly, to a hydraulic fluid reservoir formed by rotational molding with an inserted baffle. 
     2. Brief Description of the Prior Art 
     Rotational molding, or rotomolding, is a well-known method of forming objects from a plastic resin. It is often used for complex shapes including tanks and reservoirs. Various types of plastic resin can be used, such as polyethylenes, plastisols, nylons, fluoropolymers, polypropylenes, polyurethanes, and other suitable materials. 
     In general, a mold is loaded with a plastic resin and heated in an oven. As the mold is heated, the mold is rotated about two or three axes at a low speed. The heat melts the plastic resin inside the mold and melted resin coats the interior surface of the mold. The mold is then gradually cooled using air or water and the re-solidified plastic resin, which has assumed the shape of the interior walls of the mold, is removed from the mold. This process differs from injection molding in that the plastic resin is not pressurized (other than atmospheric pressure). 
     U.S. Pat. No. 5,285,923 illustrates the insertion of objects made of a material other than plastic resin into the object to be formed, such as brass inserts molded into a polyethylene material. In general, the insert is placed in a designated spot in the mold and the rotomolding process is initiated as described above. The melted plastic resin encapsulates the insert and the insert becomes part of the finished product. A problem is that the expansion and contraction properties of the resin and the inserted objects are not necessarily equal. Leaks or gaps can develop between the inserted object and the cooled plastic resin. This problem is amplified by the fact that plastic resin is known to shrink an appreciable amount as it cools. U.S. Pat. Nos. 3,364,292; 4,023,257; and 4,847,028; also discuss rotomolding with inserts added to the molded product. All of the above-cited references are incorporated herein by reference. 
     As noted in the above-cited prior art, rotomolding is well-suited for forming a plastic tank or reservoir structure. Such tanks are often used as hydraulic reservoirs for hydraulic systems, such as used in heavy machinery, including cranes, backhoes, demolition shears, bulldozers, and the like. In hydraulic systems, it is important to keep the hydraulic fluid free of debris. Consequently, filtering elements have been incorporated in the hydraulic systems to filter debris from the hydraulic fluid. Further, as set forth in U.S. Pat. Nos. 4,143,193 and 5,911,938 baffles are often incorporated into hydraulic reservoir tanks, as well as fuel tanks, to dampen the forces of moving liquid within the tank. The baffle designs suggested in these patents are integral with the finished tank. Further these designs increase the complexity of the mold, an increase in manufacturing time and expense. 
     It is an object of the present invention to provide a rotomolded hydraulic reservoir with an inserted baffle. It is a further object of the present invention to provide a rotomolded hydraulic reservoir with integral filter bowl having an extended integral filter enclosure with a coupling insert. It is another object of the present invention to provide a rotomolded hydraulic reservoir with a second fluid return. It is another object of the present invention to provide a hydraulic reservoir that is economically manufactured. It is a further object of the present invention to provide an effective, easily replaceable filter element for a hydraulic reservoir. 
     SUMMARY OF THE INVENTION 
     The above objects are achieved with a rotomolded hydraulic reservoir having an inserted baffle according to the present invention. The hydraulic reservoir is a one-piece tank structure. Specifically, the hydraulic reservoir includes a plastic container body defining a container cavity for receiving the hydraulic fluid. The insertable baffle is positioned in the container cavity through an access manway formed in the container body and is removable therefrom. The container body includes holding members for positioning and holding the baffle in place. A flange around the manway access may further include a baffle positioning mechanism, such as a pair of baffle receiving slots. 
     The removable baffle may be made of metal such as steel plate. The baffle may be held in place, in part, by opposed notches molded in the lower portion of the container body opposed from the manway access. The opposed notches may be formed as inwardly extending projections of the outer wall of the reservoir that are spaced to receive the baffle therebetween. 
     Several alternative modifications are possible with the inserted baffle design for the reservoir of the present invention. The holding members of the container body could be placed in a position extending from the sides of the reservoir, or may be offset from each other. The inserted baffle design of the present invention allows for a simple efficient mold construction while still allowing an efficient baffle to be easily positioned in and removed from the hydraulic reservoir. 
     The container body may form a filter cavity in fluid communication with the container cavity. A filter element coupling insert, such as a machined metallic bushing, may be molded in the container body adjacent the filter cavity. The insert defines an opening, specifically an internal bore, providing the communication between the container cavity and the filter cavity. A removable filter element is positioned within the filter cavity and coupled to the insert. The removable filter element seals to the exterior of the insert. 
     In order to help ensure a positive seal between the resin and the part to be included, the present invention generally provides a container body forming a filter cavity with an end having, in cross-section, a bowl-shape. The insert is positioned adjacent to the cross-sectional bowl-shape of the filter cavity. The bowl-shape offers controlled shrinkage tolerances in the general vicinity of the insert. 
     These and other advantages of the present invention will be clarified in the description of the preferred embodiments taken together with the attached drawings in which like reference numerals represent like elements throughout. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a front side view of a rotomolded hydraulic reservoir according to the present invention; 
     FIG. 2 is an enlarged view of an integral molded rib of the reservoir shown in FIG. 
     FIG. 3 is an rear side view of the present invention shown in FIG. 1; 
     FIG. 4 is a top view of the container shown in FIGS. 1 and 3; 
     FIG. 5 is a side view of a baffle insertable in the hydraulic reservoir of FIGS. 1-3; 
     FIG. 6 is a sectional view taken along line B—B of FIG. 4; 
     FIG. 7 is an end view of the hydraulic reservoir shown in FIGS. 1-3; 
     FIG. 8 is an enlarged top view of a manway access of the hydraulic reservoir shown in FIG. 4; 
     FIG. 9 is an enlarged bottom view of a baffle holding slot of the manway access of FIG. 8; 
     FIG. 10 is a top view of a filter cavity flange of the hydraulic reservoir shown in FIG. 4; 
     FIG. 11 is an enlarged plan view of outlet ports of the hydraulic reservoir shown in FIG. 1; and 
     FIG. 12 is a further enlarged side view of the bead of an outlet port shown in FIG.  11 . 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     One embodiment of the present invention is shown in FIGS. 1-12. As shown in FIGS. 1-4, the present invention is a one-piece integral container or hydraulic reservoir  10 , which may be formed as a generally cylindrically-shaped hydraulic reservoir  10 . Rotomolding allows for a variety of complex shapes to be easily molded such that the hydraulic reservoir  10  may be rectangular or other shapes dictated mainly by the intended use or environment of the hydraulic reservoir  10 . The hydraulic reservoir  10  has a container body  12  having a first upper portion  14 , a second lower portion  16 , a plurality of annular depressions or circumferential ribs  18  extending around the hydraulic reservoir  10 , an exterior surface  20 , a first body side  22 , and a second body side  24 . The first portion  14  and the second portion  16  are delineated by an imaginary plane passing through a midpoint, or centerline, of the container body  12 . The annular depressions or ribs  18  form reinforcing ridges for the hydraulic reservoir  10  and are shown in detail in FIG.  2 . The ribs,  18  are particularly useful for the hydraulic reservoir  10 , which may have an expected operating temperature range of −20° F. to 180° F. The first portion  14 , second portion  16 , and sides  22 ,  24  of the hydraulic reservoir  10  form a container cavity  26 . The term “hydraulic reservoir” within the meaning of this application refers to a container for holding working fluid that is conveyed and returned to the reservoir in a circulating system or a holding container for a fuel. Generally, the working fluid is for hydraulic power or for lubrication such as petroleum and water-based fluids. 
     The hydraulic reservoir  10  is preferably formed by rotomolding of a plastic resin resistant to chemical reactions with battery acid, hydraulic fluid, oil, transmission fluid, or UV light. Such plastic resins include but are not limited to treated polyethylenes, plastisols, nylon, fluoropolymers, polypropylene, polycarbonate, cellulose acetate, butyrate, elastomers, ionomer, polyurethane, EVA and other specially formulated compounds. The first and second portions  14 ,  16  and sides  22 ,  24  are approximately 0.25 inches thick, depending on the material selected and the ability to withstand operating temperature ranges of generally −20° F. to 150° F. and up to 180° F. intermittent. The tensile strength is preferably per ASTMD638 of 2600 PSI and the impact strength should be good to about −20° F./−40° F. The fluid capacity of the hydraulic reservoir  10  is in excess of 150 gallons, however the hydraulic reservoir  10  may be sized to the desired operating conditions. These criteria result in the hydraulic reservoir  10  being well-suited for use as a hydraulic reservoir in the hydraulic system of heavy equipment, such as a mobile crane. Although, the present invention is particularly designed for rotomolding, other molding techniques such as possibly blow molding may be used to form the present invention. 
     A removable baffle  28  (shown in detail in FIG. 5) may be inserted into the container cavity  26  through a manway access  52 . The baffle  28  may be made of metal such as 0.19″ thick mild steel plate, or other appropriate material. The baffle  28  may be held in place, at least in part, by opposed notches  29  molded in the lower portion  16  as shown in FIGS. 1,  3 ,  4  and  7 . The baffle  28  controls (e.g. dampens) the movement of fluid and gases in the container cavity  26  and assures the mixing of oil within the container cavity  26  to assure temperature equalization of the fluid in operation. The opposed notches  29  are preferably formed as inwardly extending projections of the outer wall of the hydraulic reservoir  10  such that they can be easily formed by rotomolding. The notches  29  are spaced to receive the baffle  28  therebetween as shown in FIG.  5 . The notches  29 , or projections, thereby form baffle holding members for the hydraulic reservoir  10 . The upper end of the baffle  28  may be secured to the manway access cover plate or lid (not shown). Alternatively, or in addition, the upper end of the baffle  28  is received in a pair of opposed slots  53  formed in the flange  54  formed around the manway access  52 . The slots  53  also form a baffle holding mechanism for the hydraulic reservoir  10 . A baffle is a term referring to a structure within the container body  12 , which is designed to effect the fluid flow within the container body  12 . The ribs  18 , for example, would not be considered as a baffle since the ribs  18  have no appreciable effect on flow within the container body  12 . 
     Several alternative modifications are possible with the inserted baffle  28  design for the hydraulic reservoir  10  of the present invention. For example, the notches  29  could be placed in a position extending from the sides of the hydraulic reservoir  10 , or may be offset in a different pattern rather than opposed in pairs as shown. The inserted baffle design of the present invention allows for a simple efficient mold construction while still allowing an efficient baffle to be easily incorporated into the hydraulic reservoir  10 . Additionally, the present design allows the design of the baffle  28  to be changed to accommodate a different use of the hydraulic reservoir  10 . For example, the use of the hydraulic reservoir  10  at a different operating temperature may lead to a design to change the internal flow pattern. The internal flow pattern can be easily changed by modifying the baffle to accommodate specific use of the hydraulic tank  16 . 
     The first portion  14  of the container body  12  forms, in cross-section, a generally U-shaped filter cavity  30  which extends toward the second portion  16  of the container body  12 . Returning again to FIGS. 1-6, the filter cavity  30  has a first end  34  and a second end  36 , with the second end  36  forming, in cross-section, a bowl shape which offers controlled shrinkage tolerances in the general vicinity of a metallic fluid element coupling insert  44  (discussed below). The first end  34  shown in FIG. 10 forms a connecting flange for a filter inlet coupling (not shown) to which one or more return lines may be coupled. The filter cavity  30  receives a conventional removable, replaceable filter element  33  connected to the insert  44  positioned adjacent the second end  36  of the filter cavity  30 . The insert  44  is preferably a machined aluminum or brass bushing forming an insert cavity or bore  46 , a first bushing end  48 , and a second bushing end  50 . The first bore  46  is preferably threaded for fastening to the inside of the mold during the rotomolding process. A conventional filter element  38  includes a connecting bore coupled to the outside diameter of the insert  44  through a sealing O-ring. The O-ring may be integral with the filter element  38  or provided as a separate element. If the O-ring is integral to the filter element  38 , then the filter element  38  with the integral O-ring is pressed onto the insert  44 . If the O-ring is a separate element, the O-ring is first positioned around the insert  44  or within the connecting bore of the filter around the insert  44  or within the connecting bore of the filter element  38  and then the filter element  38  is pressed into position. Any type of fluid tight connection between a conventional filter element  38  and the insert  44  is contemplated. 
     The metal insert  44  provides a more secure seal with the replaceable filter element  38  than having the seal be formed between the filter element  38  and the plastic forming the remainder of the container  10 . The smooth outside of the insert  44  allows the use of a conventional replaceable filter element  38 . The second end  36  of the filter cavity  30  is below the normal fluid level for the hydraulic reservoir  10 . A normal fluid level for a hydraulic reservoir varies between rest and operating conditions. Although, dynamic, the term normal fluid level is a specific defined range unique to a given hydraulic reservoir and a given application. 
     The first portion  14  of the container body  12  also forms the manway access  52  for inserting the baffle  28  or easily filling hydraulic reservoir  10  with hydraulic fluid, or other desired fluid. The access  52 , shown in FIG. 7, is preferably covered with the lid (not shown), preferably a fourteen gauge powder coated metal lid with provisions for an air breather (not shown) and shield (not shown). The lid attaches to the container body  12  via the band or flange  54 , which is also incorporated into the upper portion  14  of the container body  12 . 
     Ports  56 , such as 1.00 or 1.25 N.P.T. nozzles, are positioned adjacent the second portion  16  of the container body  12 , as shown in FIGS. 1-7. An inside surface  60  of each port  56  is free from plastic resin material. As shown in FIG. 12, the ports  56  can have a barb or bead  62  for helping to secure a hose with room for a hose clamp. In operation, the ports  56  would supply one or more hydraulic users in the hydraulic system with the hydraulic fluid return being through the filter element  38  which removes debris, such as grit, metal filings, and the like from the hydraulic fluid. The formation of the hydraulic reservoir  10  with integral filter bowl effectively combines the reservoir and the filtering unit while allowing the use of standard replaceable filters. Further, the incorporation of the insert  44  provides an effective seal between the filter element  38  and the hydraulic reservoir  10 . 
     The invention has been described with reference to the preferred embodiment. Obvious modifications and alterations will occur to others upon reading and understanding the preceding detailed description. It is intended that the invention be construed as including all such modifications and alterations insofar as they come within the scope of the appended claims or the equivalents thereof.

Technology Category: 4