US3030225A

US3030225A - Gas plating bumpers

Info

Publication number: US3030225A
Application number: US812873A
Authority: US
Inventors: Jr Harry A Toulmin
Original assignee: Union Carbide Corp
Current assignee: Union Carbide Corp
Priority date: 1959-05-13
Filing date: 1959-05-13
Publication date: 1962-04-17
Anticipated expiration: 1979-04-17

Description

April 17, 1962 H. A TOULMIN, JR

GAS PLATING BUMPERS 2 Sheets-Sheet 1 Filed May 13, 1959 1 INVENTOR HARRY A. TOULM/N, JR.

Bympm ATTORNEYS April 17, 1962 H. A. TOULMlN, JR 3,030,225

GAS PLATING BUMPERS Filed May 13, 1959 2 Sheets-Sheet 2 INVENTOR HARRY A. TOULM/M R- ATTORNEY-5 States This invention relates to the art of deposition of metals. More particularly, the invention is concerned with the gas plating of metals on irregularly shaped objects, and especially bumpers, such as are used on automobiles, trucks, and the like transportation equipment.

Heretofore, the plating of irregularly shaped articles such as bumpers has been carried out utilizing wet electroplating methods. Such electroplating methods have been useful in the deposition of metals such as copper, chromium, nickel and the like on steel surfaces, but it has been difiicult to produce a firm adherent coating using wet electroplating methods.

It has furthermore been a difficult problem to selectively control the thickness of the metal deposited on articles having irregularly shaped surfaces. The present invention overcomes these difiiculties, for all practical purposes, and provides a commercially operable method of metal plating irregularly shaped objects particularly bumpers and the like, by gas plating the metal directly from a gaseous phase on the surface of the articles. In accordance with the invention, the metal gas plated on the bumpers is interlocked into the pores of the substrate metal surface and diffuses therein, providing a corrosionresistant outer shell portion.

A principal object of the present invention is to pro vide a method of gas plating metal onto irregularly shaped articles, particularly bumpers and the like, and wherein Unite the metal is deposited onto the outer or outside surface areas of the substrate so as to provide a deposit of uniform thickness throughout, or Where desired, areas of ditferent metal plate thickness.

A further object of the invention is to provide a method of plating onto bumpers as a continuous or semicon tinuous process. The bumpers are cleaned to remove foreign matter and then moved into and out of a gas plating chamber while simultaneously heated to gas plating temperature; the process being controlled whereby plating of metal onto areas such as the underside of the bumper, where it is not desired, is prevented or at least reduced to a minimum amount. In this manner, a more economical process is provided and a saving of metal used in plating is achieved.

A further object of the invention is to provide an apparatus and method for continuously gas plating irregularly shaped objects of the character referred to, and in which the plating of the metal on the objects is restricted substantially to the outer surface, and the thickness of the plating over the surface areas controlled.

These and other objects and advantages of the invention will become apparent from the following description, taken in conjunction with the drawings.

In the drawings FIGURE 1 illustrates a view in elevation of an automobile bumper which is supported for conveyance through a gas plating chamber, and wherein means is illustrated for heating said bumper, the conveyor mechanism being shown broken away and partly in section;

FIGURE 2 is a sectional view taken substantially on the line 2-2 of FIGURE 1, and looking in the direction of the arrows;

FIGURE 3 is a sectional view drawn on a large scale and taken substantially on the line 3-3 of FIGURE 1, looking in the direction of the arrows;

FIGURE 4 is a sectional view in enlarged scale and similar to FIGURE 3, and taken on the line 4-4 of FIGURE 1 and looking in the direction of the arrows;

atent FIGURE 5 is a view in elevation of a bumper and showing a resistance heater element in place for heating the bumper and bumper guards, parts of the bumper being broken away to better illustrate the structure of the heating element;

FIGURE 6 is a sectional view drawn on a large scale and taken substantially on the line 6-6 of FIGURE 5 and looking in the direction of the arrows;

FIGURE 7 is a view in elevation and illustrates a section taken through the gas plating chamber and showing the mechanism for supporting the bumper and conveying the same therealong through the gas plating chamber, as shown by the arrows;

FIGURE 8 is a sectional View taken substantially on the line 8-8 of FIGURE 7, and looking in the direction of the arrows;

FIGURE 9 is a detailed view illustrating a modification of a bumper electrical heating element which is molded to conform with the cross-sectional shape of the bumper and is adapted to be positioned thereagainst for heating the same;

FIGURE 10 is a sectional view drawn on an enlarged scale; the same being taken substantially on the line 10-10 of FIGURE 9 and looking in the direction of the arrows; and

FIGURE 11 is a detailed view of a modified heating element which is adapted to be disposed in the bumper for electrically heating the bumper to gas plate the same.

Referring to the drawings in more detail, and particularly FIGURES 1 through 8, there is illustrated in FIG- URE 1 a bumper 10, such as is conventionally constructed and installed on automobiles. The bumper, as shown, is suspended lengthwise by a combination hanger and heater element, and generally indicated at 1-2. The hanger 13 upon which hte bumper 10 is supported comprises an elongated channel 14 of U-shaped cross-section, and which extends substantially the length of the bumper. For removably securing the bumper on the hanger, adjustable bolts 16 are provided which bolts are spaced longitudinally of the U-shaped channel member and threadedly attached thereto, as illustrated in FIGURE 3. An S-shaped bracket 17, which forms an integral lowermost section of member 18, supports the hanger for movement on the overhead conveyor mechanism generally designated 19.

The conveyor mechanism 19 is of conventional construction and operation. Essentially, as illustrated, it includes a carriage 20 to which the hanger supporting member 18 is fastened. The carriage 20 is equipped with wheels 22 which are arranged to travel on a rail or track 24' extending above and longitudinally of the gas plating chamber generally designated 28.

Electrical connection is made from a source of electricity through the sliding

contact members

30 and 31 to the bumper hanger 13 and to the electrical resistance heating wires 33 of the heating element 34, as shown in FIGURE 2. The heating element 34 is placed in the hollow portion of the bumper and arranged so that the heating element is disposed closely adjacent the rear side of the bumper, as illustrated at 36, in FIGURE 3. Utilizing such an arrangement, heat as supplied by the heating element or heater 34, is confined to the outermost wall or shell portion of the bumpers, and which outer surfaces are to be gas plated with a corrosion-resistant element.

The heating element shown in the embodiment illustrated in the drawings of FIGURES 1 through 4 com- 7 prises a blanket or flexible heating member 38. This electric heating blanket comprises electrical resistance wires or hands 39 such as Nichrome wire or the like, which are disposed in the blanket in spaced electrically insulated relationship. Resistance heating of the blanket is thus provided when the resistance wires are connected to a source of electricity.

To insulate the back or rear portion of the bumper and prevent free access of the plating gas in contact therewith, the rear portion of the bumper is closed by a panel 41 which is made of asbestos or the like heat-insulating material, the closure panel being snugly fitted against the rear wall portion of the bumper as illustrated in FIG-

URES

3, 4 and 6. This arrangement conserves the heat and keeps the temperature inside the gas plating chamber 28 below that which would bring about thermal decomposition of the gaseous metal compound and deposition of metal on the walls of the plating chamber. The heating blanket 39 concentrates the heat along the rear wall surfaces of the bumper so that the outer or front wall surface 43 becomes locally heated to the desired temperature, and such as to bring about thermal decomposition of the gaseous metal compound brought in contact therewith in the gas plating chamber 28. This results in the deposition of the metal constituent of the metal bearing compound onto the outer heated surface of the bump- In FIGURE 4 the bumper 44 is shown with an integral bumper guard 45 which comprises a hollow shell-like structure. The bumper guard protrudesforward from the body of the bumper, as illustrated. To heat the bumper and guard portion an electrically heated blanket 46 is utilized of similar construction as heater 38. This heating blanket is in the form of an elongated strip and comprises resistance heater elements 47. The heating blanket, which may be in the form of an elongated strip of flexible material carrying resistance wires, is inserted in the hollow part of the bumper and pressed against the rear side wall of the bumper and guard portion, as shown at 48 in FIGURE 4. When the blanket is connected to a source of electric current the bumper and guard section are heated to the temperature requisite for gas plating the same. If desired, the bumper guards 45 may comprise additional electric heating elements to raise the temperature of the bumper guards to a higher temperature than the body of the bumper. In this way the deposition of metal on the surface of the bumper guards is increased over that plated on the body portion of the bumper.

In FIGURE 5 the bumper is arranged to be supported and heated by a heating element 49, the bumper and heating element being supported on the hanger 50 by bolts 51, similarly as the, arrangement illustrated in FIGURE 1. The heating element 49 is disposed closely adjacent the rear side wall 53 of the bumper, the outer surface of which is to be plated. Electrical contact is made at the upper and lower ends of the heating element 49 as shown at 55. To provide for heating the bumper guard 56, a spiral resistance heater element 58 is employed, as shown in FIGURE 6. the bumper guard 56, as shown on the enlarged scale, is heated by the spirally arranged heater coil 58 which is supported and electrically insulated from the elongated U-shaped hanger member 50, as shown at 60. Fastening bolts 51 which are threaded, as at 62, provide for adjustably securing the heater coil to the hanger member 50. Electrical connection is suitably made from a source of electricity to the heating element 58, as indicated at 63, whereby the bumper surface to be gas plated is heated to the proper temperature to effect gas plating of metal thereon.

In FIGURE 7 the bumper to be gas plated with metal, and generally indicated at 10, is supported for movement by the conveyor mechanism 18 through a gas plating chamber 28 similarly as illustrated and described with reference to FIGURE 1. Inlet and

outlet conduits

65 and 66, respectively, as shown in FIGURE 7, are provided for the introduction and circulation of the thermally decomposable metal bearing gas in the plating chamber 28. The plating chamber is closed at the top by cooperating flexible flap members 68 which are momentarily forced In this modification,

4 open by the thin shank hanger portion 74 as the bumper is conveyed along on the hanger through the gas plating chamber. Similarly, a folding door entrance means 70, and like folding exit door member 71, are provided which are suitably actuated to admit bumpers and to close the chamber while the bumpers are moved along through the plating chamber, the same being heated and brought in contact with a thermally decomposable metal bearing compound, for example, chromium carbonyl.

In gas plating bumpers in accordance with this invention, the same may be moved continuously along through the gas plating chamber while the plating is being effected, or the same may be intermittently moved into and out of the gas plating chamber. In either procedure, a plurality of the bumpers may be gas plated simultaneously, and while the same are moving along through the gas plating chamber or enclosed in the chamber momentarily while the gas plating of the metal onto the surface of the bumpers takes place.

In FIGURE 9 there is illustrated a modification of the resistance heating element for heating the bumpers during gas plating of the same. In this modification, a bumper 75, shown partly in section, is heated in the gas plating chamber by a heating element generally indicated at 76. The heater 76 is shaped from moldable material such as plaster of Paris, gypsum, or heat resistant plastic, and comprises a body portion 78 which is molded and shaped to fit snugly into the back of the bumper 75, as illustrated in FIGURE 9. The molded heat insulator shape 76 comprises electrical resistance heater elements 80 which are disposed along the inner surface of the insulating form. As shown in the molded member illustrated at the right in FIGURE 9, the electrical resistance element is adapted to be connected to a source of electricity at its upper and lower portion by wires 81 and 82, respectively.

The heat insulator shape 76 is fitted into the rear open portion of the bumper with the heating element 80 posi tioned closely adjacent or contiguous with the back of the outer wall of the bumper, as shown at 86. Heating of the bumper is thus restricted to the outer wall surface, and the flow of heat from the inner or back wall of the molded shape 76 is inhibited due to the fact that shape is made of material of low heat conductivity. The electrical heat resistance elements 80 are preferably embedded in the molded shape as indicated in FIGURE 9.

In the modification shown in FIGURE 11, the heating element is composed of laminated mica sheets 86 which are shaped to conform with the cross-sectional shape of the bumper, the mica sheet material being composed of an outer sheet 87 and an inner sheet 88, the latter containing the electrical resistance heater elements 90. A backing or heat insulating closure member 92 is provided, which is made of asbestos or the like similarly as the closure 41, to prevent the heat from being dissipated into the gas plating chamber, which would tend to raise the temperature of the gas plating oven and cause premature plating of metal onto substrate surfaces other than the bumper which, of course, is undesirable. Where the speed of the movement of the bumpers through the gas plating chamber is relatively high and such as to avoid heating of the gas plating chamber above the temperature at which the gas will decompose upon its entry into the gas plating chamber, then the use of the insulating

closure members

41 and 92 may be dispensed with, and the heating element fitted into the bumper and the same conveyed along through the gas plating chamber without the use of additional heat insulating means.

In FIGURE 10 a further modification of the heater element is shown, and wherein a bumper 94 having a bumper guard 95 is illustrated, being gas plated. In this modification the bumper 94 is fitted with a molded heat insulator member 96 which is provided with heater coils 97, the latter being disposed at the surface of the heat insulating element 96. The heater is shaped to fit snugly into the back of the bumper to position the heating element closely adjacent or contiguous with the bumper surfaces to be metal plated. Heating of the bumper and bumper guard may thus be controlled to effect gas plating of metal thereon while the bumper is moved or conveyed along through the gas plating chamber.

In operation of the equipment, the speed at which the bumpers are moved through the gas plating chamber determines the thickness of metal gas plated on the bumper. The apparatus and process of the invention makes it possible to gas plate corrosion resistant'metals on bumpers at a high rate of speed and under conditions to control the thickness of the plate. In the apparatus as shown, bumpers may be plated, for example, by moving the same from 1 to 30 feet per minute and generally at a rate of approximately 5 to feet per minute.

Bumpers may be gas plated with nickel, chromium, titanium, zirconium, molybdenum, and the like. The metals deposited are in substantially a pure nascent state by employing one or more of their thermally decomposable gaseous compounds. Metal compounds which are heat decomposable, for example the metal carbonyls, hydrides, metal alkyls, or metal bearing and organic esters, e.g., titanates, chromates, etc., are useful to effect a gas plating of the metals.

The various metals which it is desired to be deposited on bumpers and the like irregularly shaped articles, may be introduced into the gas plating chamber in the form of their heat-decomposable gaseous metal compounds. For this purpose, there may be used, as pointed out above, their metal carbonyls, which are preferably introduced in concentrations up to 75% by volume of inert carrier gas such as nitrogen, helium, argon or carbon dioxide. The metal carbonyls also may be introduced in the form of a spray in petroleum ether, or use may be made of nitroxyl compounds of the metals, nitrosyl carbonyls, metal hydrides, metal alkyls, metal halides, and the like.

Illustrative compounds of the carbonyl type are nickel, titanium, zirconium, aluminum iron, chromium, molybdenum, cobalt, and mixed carbonyls. Other metal bearing compounds useful are the nitroxyls, such as copper nitroxyl, nitrosyl carbonyls, cobalt nitrosyl carbonyl, hydrides, such as antimony hydride, tin hydride, metal alkyls, such as chrornyl chloride, and carbonyl halogens, for example, osmium carbonyl, bromide, ruthenium carbonyl, chloride, and the like.

Each material from which a metal may be plated has a temperature at which decomposition is complete. However, decomposition may take place slowly at a lower temperature or while the vapors are being raised in temperature through some particular range. For example, nickel carbonyl completely decomposes at a temperature in the range of 375 F. to 400 F. However, nickel carbonyl starts to decompose slowly at about 175 F. and, therefore, decomposition continues during the time of heating from 200 F. to 380 F.

A large number of the metal carbonyls and hydrides may be effectively and efliciently decomposed at a temperature in the range of 350 F. to 450 F. When working with most metal carbonyls we prefer to operate in a temperature range of 375 F. to 425 F.

Maintenance of the object at temperatures generally in the decomposition range is readily accomplished by causing the object to be heated by infra-red rays or by induction heating. The advantage of this type of heating is its ready control within the temperature ranges utilized in the process. These temperatures generally range from 350 F. to 450 F. in the plating zones and from 800 F. to 1200 F. in the annealing zones.

Preparatory to coating the bumpers or the like irregularly shaped objects, they may be cleaned by employing conventional methods of the art. Electrochemical cleaning methods may be employed, for example, the bumpers moving the object through aqueous baths of alkali or acid electrolyte. The bumpers may be picked with hydrochloric, sulfuric or nitric acid, or a combination of these acids, and then thoroughly rinsed and dried prior to gas plating. In carrying out the gas plating of metal onto bumpers, as described, the same will of course be initially cleaned as described before being subjected to gas plating. Where the bumpers are substantially free of foreign mat ter, the same may be merely heated to a temperature of about 500 F. and sufficient to drive off moisture, oils, and the like impurities, without heating the metal to a temperature high enough to melt or change the physical characteristics of the metal.

It is to be understood that while the apparatus and method aredisclosed and described more particularly with respect to the gas plating of bumpers and the like irregular shapes, the invention and modifications thereof can be made applicable to other irregular shapes and carried out without departing from the spirit and scope of this invention, and such modifications and variations that fall within the scope of the appended claims are intended to be included herein.

What is claimed is:

1. In apparatus for gas plating metal on selected areas of the outer surface of bumpers, a conveyor and a gas plating chamber operatively associated therewith, a hanger for supporting said bumper to be gas plated, and means comprising an electrical resistance heating means carried by said hanger and extending contiguous with the bumper for heating said bumper surface to be gas plated with metal as the bumper is moved through the gas plating chamber, said conveyor means comprising electrical contact means carried by the conveyor for conducting electricity to said heating means while the bumper is moving through said gas plating chamber, said gas plating chamber comprising entrance and exit openings, and means comprising flexible flap members at said entrance and exit for maintaining the gas plating chamber substantially closed during the gas plating operation.

2. In apparatus for gas plating metal on selected areas of the irregularly shaped articles, a conveyor and a gas plating chamber operatively connected together, with means for supporting a hanger on said conveyor, means for removably supporting an irregularly shaped article on said hanger, means comprising an electrical resistance heating means carried by said hanger and shaped to fit snugly against the back of said article for heating the surface of said irregularly shaped article as the irregularly shaped article is conveyed through said gas plating chamber, said heating means comprising a moldable heat insulating material shaped to conform with the inner shape of said bumper, electrical resistance wires embedded in said moldable material and connected to a source of electricity for heating the surface of the article to be gas plated.

3. In apparatus for gas plating metal on selected areas of the surface of bumpers, a conveyor and a gas plating chamber with means for supporting a bumper to be gas plated, and electrical resistance elements heating means carried by said hanger and shaped to conform with the bumper surface to be plated for heating said bumper, said heating element comprising a molded shape of heat insulating material which is adapted to fit snugly into the hollow rear side portion of the bumper, said heat insulating material comprising said electrical resistance elements embedded therein for heating the outer surface of said bumper While in contact with a gaseous heat-decomposable metal bearing compound whereby the surface of said bumper is gas plated With metal.

4. In apparatus for gas plating metal on selected areas of the surface of bumpers, a conveyor and gas plating chamber, hanger means for supporting said bumper to be gas plated, and means comprising electrical heating means carried by said hanger and adapted for heating said bumper, said heating element comprising laminated mica sheets shaped to conform with the cross-sectional shape of said bumper and wherein said mica sheet comprising said electrical resistance elements disposed therein and arranged contiguous therewith for-heating said bumper surfaces to be gas plated, and means for heating certain limited areas of said bumper to a different temperature than at other areas.

5. A method of gas plating metal on bumpers in a continuous operation comprising the steps of supporting a plurality of bumpers in a spaced relationship, heating the same and moving the bumpers while heated through an enclosure, subjecting the heated bumpers to a thermally'decornposable gaseous metal bearing compound While said bumpers are heated to a temperature whereby the surfaces to be gas plated are heated high enough to thermally decompose said gaseous metal bearing compound brought in contact therewith and cause the metal constituent to be deposited on said heated surfaces, of the bumper, said heating being controlled to selectively heat the surfaces of the bumper to be plated with metal, said bumper being movedthrough said enclosure to be gas plated at a speed of approximately 1 to 30 feet per minute.

bumpers which comprises the steps of supporting a bumper to be gas plated, heating the same at selected areas over the surface and moving the bumper while heated through an enclosure, and subjecting the heated,

bumper to a thermally'decomposable gaseous metal hear-- ing compound while the surface of said bumper is heated differentially to a temperature to thermally decompose said metal bearing compound and cause the metal constituent to be deposited to different thicknesses on the heated surfaces of the bumper, said bumper being cleaned temperature to cause thermal decomposition of the metal bearing compound brought in contact therewith and decomposition of metal on the heated surfaces of the bumper, and thereafter removing the bumper from said enclosure.

8. A method ofgas plating metal on the surface of bumpers comprising the steps of supporting a bumper to be gas plated, heating the same at different areas to different temperatures and moving the bumper While thus heated through a gas plating enclosure, subjecting the thus heated bumper to a thermally decomposable gaseous metal bearing compound while said bumper is thus heated to a temperature high enough to bring about thermal decomposition of the metal bearing compound and cause metal to be deposited to different thicknesses on the heated surfaces of the bumper, said heating being controlled to selectively heat predetermined surface areas of the bumper to control the deposition of metal thereon.

9. A method of gas plating metal on the surface of metal on the surface of irregular shaped bumpers comprising the steps of supporting said irregular shaped bumper, conveying the same to a heating chamber, heating said bumper while thus conveyed, and subjecting the heated andv moving irregular shaped bumper to an atmosphere comprising thermally decomposable gaseous metal bearing compound while said bumperis heated to a temperature high enough to bring about thermal decomposition of'said metal bearing'compound and cause metal to be deposited. onto the heated surface of the irregular shaped bumper, and controlling said heating whereby to selectively heat predetermined surface areasof said irregular shapedtbjumpers to cause the deposition of metal onto said selectively heated surface areas.

References Cited in the file of this patent 25:; v

[UNITED STATES PATENTS 2,614,059. Cooper Oct. 14, 1952 2,638,423 Davis et al.. May 12, 1953 2,698,812 Schladitz Jan. 4, 1955 2,785,997. Marvin Mar. 19, 1957 2,847,330 Toulmin Aug. 12, 1958 OTHER REFERENCES Phillips: The Iron Age, March 17, 1927, page 773.

Claims

6. IN A METHOD OF GAS PLATING METAL ON THE SURFACE FO BUMPERS WHICH COMPRISES THE STEPS OF SUPPORTING A BUMPER TO BE GAS PLATED, HEATING THE SAME AT SELECTED HEATED THROUGH AN ENCLOSURE, AND SUBJECTING THE HEATED HEATED THROUGH AN ENCLOSURE, AND SUBJECTING THE HEATED BUMPER TO A THERMALLY DECOMPOSABLE GASEOUS METAL BEARING COMPOUND WHILE THE SURFACE OF SAID BUMPER IS HEATED DIFFERENTIALLY TO A TEMPERATURE TO THERMALLY DECOMPOSE SAID METAL BEARING COMPOUND AND CAUSE THE METAL CONSTITUENT TO BE DEPOSITED TO DIFFERENT THICKNESS ON THE HEATED SURFACE OF THE BUMPER, SAID BUMPER BEING CLEANED ELECTROCHEMICALLY AND RINSED AND DRIED PRIOR TO GAS PLATING.