CA2528639A1 - Process for reclaiming rubber-to-metal bonded material - Google Patents

Abstract

For a work piece having a metal part bonded to a rubber part, a method is devised to separate the metal and rubber parts. A flame is used to heat a portion of an exposed surface of the metal part, while moving the metal part relative to the flame until substantially all the exposed metal surface is heated. The process is repeated until the metal and rubber parts separate.

Description

'CA 02528639 2005-12-09 Process For Reclaiming Rubber-To -Metal Bonded Material Background of Invention [0001 ] This invention relates in general to the processes for reclaiming rubber-to-metal bonded material. In particular, the invention relates to a process for using flame heat to remove rubber from parts where the rubber is bonded to a metal component while leaving the metal component in a reusable state, and preferably with the rubber component substantially unaltered.

[0002] When rubber is bonded to metal through any of the various conventional methods, the resulting bond often will not release, even when the rubber goes through tearing or splitting.
Thus, if a part is rejected after the bonding process, the whole part is often discarded. This is undesirable since the metal components are more costly to prepare than the rubber parts. Also, the rubber portion of the part often wears out while the metal portion is still perfectly usable. In either case, the expensive metal part is simply discarded along with the rubber.

[0003] There are numerous methods known for recycling structures having bonded rubber and metal parts that separate the rubber from the metal. The methods vary widely in principle, from grinding and destructive heating, to cryogenic freezing and chemical disintegration. In every case, either the metal or rubber components (or both) are dramatically affected.

[0004] U.S. Patent No. 3,670,969, issued to Terada on June 20, 1972, discloses a method of removing insulation from electrical wire by chopping the wire into short sections, then dumping the pieces into a liquid filled tank. The liquid with the cut up pieces is stirred by a special agitator designed to knock or chop the softer insulation off the wire. The specific gravity of the liquid is chosen so that the insulation knocked off the wire will float to the top of the liquid, while the wire will sink.

[0005] U.S. Patent No. 4,342,647, issued to McMillan et al. on August 3, 1982, teaches the removal of rubber from metal parts by bathing the parts in cryogenic liquid, during which the rubber becomes sufficiently embrittled that it can be removed by hammer milling. The rubber's properties undergo dramatic change as a result of cryogenic freezing. Also, the equipment required for handling the cryogenic liquid is relatively expensive and complex.

[0006] U.S. Patent No. 5,234,171 issued to Fantacci on August 10, 1993, discloses a method of grinding up vehicle tires and the like, whereupon the metal and the rubber are separated by conventional magnetic separation and air classification. Obviously, the metal pieces are no longer in their original form and must be smelted down and recast or forged before being used again.

[0007] Finally, U.S. Patent No. 5,505,008, issued to Hugo et al. on April 9'~, 1996, discloses removal of organic materials from metal by subjecting the organic material to heat in a no reactive atmosphere (to avoid combustion) for long enough that the organic material becomes brittle and either falls off or can easily be physically removed. While the metal work piece is not significantly affected, the rubber piece will be destroyed.

[0008] None of the previous stated methods can satisfactorily reclaim work pieces made when, rubber is bonded to metal, because they require physical or chemical destruction of either the metal of rubber portions, or in some cases both. A need remains for a method of separating bonded metal-rubber parts such as a metal insert with a rubber O-ring bonded to it, so that the metal is unaltered and the rubber is still in its whole state.

[0009] In general, the desired features and advantages of the invention are achieved on a work piece made of metal and rubber parts that are bonded together. The advantages are achieved by heating a portion of the metal part with a flame, while rotating the part relative to the flame, cyclically across the entire exposed metal part, so that a particular location on the metal is alternately heated by the flame for a short period of time, followed by a cooling period. The metal part with rubber bonded to it, is rotated on a turntable so that the metal component is evenly heated, while allowing the heat to absorb through the metal component until it reaches the bond (rubber to metal area) and dissolves or breaks the bond. This rotating heating / cooling process is repeated for a predetermined period of time , or until the heat from the flame has traveled to the metal surface that has the bonded rubber attached, when that metal surface reaches a temperature between 400°F and 700°F. The rubber releases from the metal at this point. The component is rotated at a rate of between 6 rpm and 60 rpm depending on the metal thickness and type of metal.

[0010] The method has an advantage that the component is not affected by the heating of the metal insert. Because the metal part of the component is evenly heated, the metal part does not change size of shape in any form, likewise the attached rubber has not ideally been exposed to a flame and simply releases from the metal component once the desired temperature is reached.
This means the rubber, which is unaltered can be ground up and recycled for road construction or other uses.
[0011 ] Additional features and advantages of the invention will become appartent in the following detailed description and in the drawings.

~CA 02528639 2005-12-09 Brief Description of Drawings [0012] FIG 1 is a cross section view of a typical work piece, having a metal retaining ring bonded to a surrounding O-ring.
[0013] FIG 2 is a front plan view of the method of the invention being carried out on the work piece.
[0014] In the following discussion, elements having the same function that are depicted in more than one drawing are given the same reference number. Also, the drawings a re not necessarily drawn to scale, and in some figures proportions may be exaggerated for clarity.
[0015] FIG. 1 shows a typical work piece (11) on which the method of the invention is carried out. The work piece (11) comprises a rubber O-ring about 6.3 centimeters (2.5 inches) in diameter having a channel (15) designed to receive a mating metal insert (17) about 3 millimeters high by one half millimeter wide. The metal insert ( 17) has an exposed surface ( 19) in order to carry out the method of the invention.
[0016] As shown in FIG.2 , the work piece is placed on a turntable (21), which turns the work piece (11) at a predetermined rate. A controlled flame (23) is brought within the proximity of the work piece ( 11 ) so that the flame comes in contact with the metals exposed surface (19). While a hand -held torch is shown for providing the flame, much more elaborate equipment can be utilized for providing the stationary flame. Direct contact between the rubber component and the flame is not desired. The work piece is turned at a rate dependant on the size, thickness and type of metal. Metal such as aluminum may require faster turning rates than metals such as steel.. For the work piece shown in the figures a turning rate of about 10 rpm has shown to be most effective.
[0017] As previously discussed, each spot on the exposed surface (19) is repeatedly subjected to a short period of heating, followed by a cooling period. This effect allows the heat to travel through the metal insert until the desired temperature has been obtained at the surface where the metal is bonded to the rubber. This eventually break the bond between the metal insert (17) and the rubber O-ring (13). The time required to separate the metal from the rubber part will vary with the size of the work piece and the composition , or type of the metal, in a manner similar to that just described for the turning rate. For the depicted work piece, a typical separation time is between 30 seconds and 1 minute and 30 seconds. Larger parts can take significantly longer but the same process applies.

[0018] Although each particular location on the exposed surface (19) I heated only a fraction of the total time, the bulk temperature of the metal insert (15) will rise over time. The bulk temperature is typically between about 200°F to 900°F
(93.3°C to 482.2°C) The temperature can be used as one parameter for setting up automate control for the process.
[0019] For work pieces where the metal part is completely encased inside the rubber. the method just described cannot be used directly. However, if the thickness of the rubber covering the metal is less than about six millimeters (1/4 inches), an additional step can be used to "blow ofF' the rubber to create an exposed metal surface for processing using the method of the invention. To remove the rubber, a super-oxygenated flame under high pressure using a mixture of oxygen at about 120 psig (827kpa) and propane at about 10 psig (69kpa) in a conventional burner jet to "blast" the rubber off the metal part, leaving a work piece with an exposed metal surface that can be treated as previously described.
[0020] This invention has several advantages over the prior art. The method can separate bonded rubber and metal components without significant damage to either the metal or rubber parts. The method is relatively fast and can be easily automated. It requires very little expenses per part to reclaim, uses no corrosive chemicals or cryogenic liquids and produces minimal pollutants. It consumes far less energy per piece reclaimed than other conventional methods.
[0021 ] The invention has been shown in one embodiment. It should be apparent to these skilled in the art that the invention is not limited to the embodiment, but is capable of being varied and modified without departing from the scope of the invention as set out in the attached claims.

Claims

Claims [c1]
A process for recycling a work piece having a rubber part and a metal part bonded together with the metal part having a surface exposed to the environment, comprising the steps of: A) heating a portion of the exposed metal surface using a flame; and B) while heating the metal in step (A), moving, the exposed metal relative to the flame.
[c2]
A process as recited in claim 1, wherein the post-combustion product of the flame contacts the metal piece.
[c3]
A process as recited in claim 1, wherein the flame is in contact with a component that is rotated at a rate relative to the exposed metal surface at a rate of between about 6 and 60 cycles per minute.
[c4]
A process as recited in claim 1, wherein the metal piece is heated to a bulk temperature ranging from about 200°F to about 900°F (93.3°C to 482.2°C) [c5]
A process as recited in claim 1, wherein the flame is stationary and the work piece is moved.