Metal deforming – With cleaning – descaling – or lubrication of work or product – Lubricating
Reexamination Certificate
2001-04-02
2003-03-18
Jones, David (Department: 3725)
Metal deforming
With cleaning, descaling, or lubrication of work or product
Lubricating
C072S058000, C072S061000
Reexamination Certificate
active
06532784
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to a process known as “hydroforming”, which is a relatively new process for cold shaping of ductile objects, usually metals. In this process, a hollow ductile object, which has a closed cross section and ends that are capable of being temporarily sealed so as to withstand internal pressure, such a hollow object being hereinafter denoted for brevity as a “tube”
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, is filled with a fluid and then shaped by hydraulic pressure applied to the fluid. In all instances of relevance to this invention, the object being hydroformed is surrounded by an openable die with an internal surface that has the same shape as is desired for the external surface of the hydroformed part of the hydroformed object upon completion of the hydroforming.
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Without thereby implying any additional limitation on the shape of the object.
In what is usually the first if not the sole stage of a hydroforming process, internal hydraulic pressure pushes the tube evenly into the die cavity, from an initial position in which the tube does not directly contact the inner surface of the die. As the tube expands, its ends are drawn inwardly along the longitudinal axis of the tube. The area of the tube that contacts the inner die surface first keys the tube at the point of contact. Because this prevents any further longitudinal movement, part of the remainder of the tube expands, with corresponding reduction of wall thickness, as the material elongates. An axial force is usually applied to the tube ends to control wall thinning during expansion, and by this means the end regions of the tube being hydroformed may be kept from undergoing any substantial wall thinning, as is usually preferred. Surface friction between the tube blank and the die has a significant influence on the axial force required for the process, because high surface friction can counteract the axial force. In other types or stages of hydroforming, contact between the tube being hydroformed and most or all of the inner die surface already exists at the beginning of the hydroforming. In such alternative types or stages of hydroforming, the degree of surface friction between the tube being hydroformed and the die strongly influences the quality of the results achieved from the beginning of the hydroforming.
Surface friction in hydroforming has conventionally been reduced by the use of highly compounded, very high viscosity liquid lubricants or by dry film lubricants primarily consisting of soaps and/or polymers. However, the lubricants previously known in the art for this process have substantial disadvantages: The liquid ones tend to become non-uniformly distributed in the die cavity, generating a likelihood, and often an actuality, of inadequate lubrication on some part of the surface where the lubricant layer is thinned too much. The dry film lubricants are readily degraded by contact with water, which usually constitutes a large major fraction of the preferred hydraulic fluid for use in hydroforming, so that contact between the dry lubricant and the water can not be easily avoided. Also, the prior art dry film lubricants are expensive and difficult to reuse, require a considerable input of heat energy to convert them within a practical time from the aqueous dispersion and/or solution from which they are normally applied to the solid form in which they are used, and are difficult to clean from the dies and/or the hydroformed tubes.
A major object of the invention is to overcome one or more of the difficulties described above with hydroforming lubricants taught in other art. Other alternative or concurrent objects are to provide less costly hydroforming operations and lubricants therefor and to provide superior quality hdyroformed tubes. Other objects will be apparent from the description below.
Except in the claims and the specific examples, or where otherwise expressly indicated, all numbers in this description indicating amounts of material or conditions of reaction and/or use are to be understood as modified by the word “about” in describing the broadest scope of the invention. Practice within the numerical limits stated is generally preferred, however. Also, throughout this specification, unless expressly stated to the contrary: percent, “parts of”, and ratio values are by weight; the term “polymer” includes “oligomer”, “copolymer”, “terpolymer”, and the like; the description of a group or class of materials as suitable or preferred for a given purpose in connection with the invention implies that mixtures of any two or more of the members of the group or class are equally suitable or preferred; description of constituents in chemical terms refers to the constituents at the time of addition to any combination specified in the description, or as reduced or increased in amount in situ by chemical reactions explicitly stated in the description, and does not necessarily preclude unstated chemical interactions among the constituents of a mixture once mixed; specification of materials in ionic form additionally implies the presence of sufficient counterions to produce electrical neutrality for the composition as a whole (any counterions thus implicitly specified should preferably be selected from among other constituents explicitly specified in ionic form, to the extent possible; otherwise such counterions may be freely selected, except for avoiding counterions that act adversely to any of the objects of the invention); and the term “mole” means “gram mole” and the term itself and its grammatical variations may be applied to elemental, ionic, unstable, hypothetical, and any other chemical species defined by number and type of atoms present, as well as to compounds with well defined molecules.
BRIEF SUMMARY OF THE INVENTION
It has been found that waxes provide a lubricating performance in hydroforming that is superior to that of any previously used lubricants for this purpose, particularly when applied in a preferred manner described in detail below.
DETAILED DESCRIPTION OF THE INVENTION
A process according to the invention for hydroforming a tube of a ductile solid material, said tube having an outer surface, an interior, and an interior surface, comprises, preferably consists essentially of, or more preferably consists of at least the following operations:
(I) providing an openable die having an interior surface of a shape to which it is desired to have the hydroformed part of the outer surface of the tube of ductile solid material conform after said tube has been hydroformed;
(II) forming, over at least such portion of the outer surface of the tube of ductile solid material as is intended to contact the interior surface of the openable die during hydroforming, a coating of a solid wax, so as to form a coated ductile tube;
(III) emplacing the coated ductile tube within at least a part of said openable die and closing the die, so that a portion of the outer surface of the ductile tube that is desired to be hydroformed is within the closed openable die;
(IV) providing within the interior of the tube of ductile solid a hydraulic fluid that exerts equal pressure on all parts of the internal surface of the tube of ductile solid with which the hydraulic fluid is in physical contact; and
(V) applying to the hydraulic fluid provided in operation (IV) as described immediately above, while the ductile tube remains emplaced within the closed openable die as recited in operation (III) above, a sufficient pressure to cause at least a portion of the outer surface of the coated ductile tube to conform to the inner surface of the closed openable die.
For the purposes of this description, “wax” is defined as a substance that: (i) is a plastic solid at 25° C. under normal atmospheric pressure and (ii) can be maintained completely melted and in contact with the natural ambient atmosphere without visually evident decomposition at a temperature that is at least 75° C.
A wax often does not have a sharp melting point, probably because it is a mixture of chemically analogous materials of varying molecular weight. Accordingly,
Dunn Joseph A.
Elizondo Edward
Warkentin William P.
Brooks & Kushman P.C.
Henkel Corporation
Jones David
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