US3466157A

US3466157A - Composite metal containing copper for coinage purposes

Info

Publication number: US3466157A
Application number: US502738A
Authority: US
Inventors: Philip B Neisser; Morris V Boley
Original assignee: TREASURY USA
Current assignee: TREASURY USA
Priority date: 1965-10-22
Filing date: 1965-10-22
Publication date: 1969-09-09
Anticipated expiration: 1986-09-09

Description

Sept. 9, 1969 p, s5 ET AL 3,466,157

COMPOSITE METAL CONTAINING COPPER FOR COINAGE PURPOSES Filed Oct. 22, 1965 1N VENTORS PHIL/P B. NE/SSER MORRIS V. 80L E Y ATTORNEY United States Patent 3,466,157 COMPOSITE METAL CONTAINING COPPER FOR COINAGE PURPOSES Philip B. Neisser, Alexandria, Va., and Morris V. Boley, Bethesda, Md., assignors to the United States of America as represented by the Department of the Treasury Filed Oct. 22, 1965, Ser. No. 502,738 Int. Cl. B23p 3/20 US. Cl. 29-499 13 Claims ABSTRACT OF THE DISCLOSURE The present invention relates to a new composite metal strip having outer layers of either copper-nickel or silvercopper alloys bonded directly to either a pure copper or silver-copper base, the layers having appropriate alloy compositions and thicknesses to provide the composite strip with the necessary qualities of color, weight, brittleness, bounce, ring, electrical conductivity, magnetic attraction, and density to permit coinage which is compatible with present US. currency.

The invention described herein may be manufactured and used by or for the Government of the United States of America for governmental purposes withont the payment of any royalties thereon or therefor.

This invention relates to composite or clad metals and, more particularly, to clad metals for use in the minting of coins.

In recent years the increasing rate of consumption of silver has become a problem of major proportion. The amount of silver used for minting coins is increasing so rapidly that, along with the increasing demand for industrial and space purposes, the supply of silver will soon not be adequate. As with the governments of many foreign countries, the Government of the United States has found it necessary to produce a substitute for the silver coinage which has long been the traditional form of currency.

The substitution of a silver-free alloy, or even an alloy containing a smaller percentage of silver, presents many complex problems. Any metal or alloy which is to be used for coinage must possess certain mechanical, chemical and physical properties as Well as meet the stringent test of public acceptability. In a mechanical sense the metal should be sufficiently soft and ductile to be readily rolled, blanked and coined while, at the same time, be of adequate hardness to possess enough wear resistance after coining to permit a useful life in normal circulation of 25 to 30 years.

Since coins which are in circulation over a period of years are exposed to many corrosive elements, the more obvious being, perspiration, soft drinks, salt spray and the like, and inasmuch as each of these elements produces a luster-dulling effect, it is important that any metal used for coinage possess high corrosion resistance. Additionally, to accommodate for the possibility of a coin being swallowed or accidentally coming in contact with food, the metal should be essentially nonreactive and nontoxic.

Of the necessary physical properties, electrical conductivity, magnetic attraction and density are of prime importance, in that they directly effect the ability of coins to be accepted by coin-operated devices. That this requisite is of major importance is readily apparent When it is realized that the successful operation of nearly every coinop erated device, including vending machines, service-dispensing machines, toll-road collection boxes, pay telephones and amusement devices, depends upon these characteristics to operate the so-called coin selector mechaa ice nism. Although these mechanisms vary in degree of sophistication, their purpose is to accept genuine United States coins and reject all foreign coins, counterfeit coins, tokens and slugs. These coin selectors or reject mechanisms not only examine the coins for size, weight, magnetic attraction and absence of a center hole, but also test the resistivity-density product of the coin. This test, which is the most critical examination for genuine United States coinage, is based on the well-known eddy-current principle and is feasible due to the fact that United States coins are nonmagnetic and have certain definite known values of electrical resistivity and density.

Public acceptability, although of an indefinite and abstract nature, is related to a number of easily recognized factors. Experience with genuine coins has enabled the public to distinguish genuine from counterfeit coins on the basis of such factors as color, weight, brittleness, bounce and ring. If any of these features are radically changed, it is quite likely that the coin would not be trusted and, accordingly, not accepted.

Accordingly, an object of the present invention is to provide a composite or clad metal which fulfills all requirements necessary for United States coinage.

A further object of the invention is to provide a clad metal coin which is substatnially equivalent to the customary United States silver coinage in size, weight, color, bounce and ring.

Another object of the invention is to provide a clad metal coin having a resistivity-density product substantially equal to that of customary United States silver coinage.

A still further object of the invention is to provide a method of producing a clad metal coin suitable for use as United States coinage.

A still further object of the invention is to provide a method of producing a coin which is substantially equivalent to the customary United States silver coinage in size, weight, color, bounce, ring and resistivity-density product.

The exact nature of this invention, as well as other objects and advantages thereof, will be readily apparent from consideration of the following specification relating to the annexed drawing, in which:

FIG. 1 illustrates in a plan view a coin made in accordance with the present invention.

FIG. 2 shows a cross section taken along the line 2, 2 of FIG. 1 and illustrates one embodiment of the invention.

FIG. 3 illustrates another embodiment of FIG. 2.

FIG. 4 is a diagrammatic view of the eddy-current portion of the coin selector mechanism used in many coin-operated devices.

Referring now to the drawings, there follows a detailed description of the present invention. It has been discovered that a composite metal strip can be produced which possesses substantially all the characteristics of customary United States silver coinage, including the stringent requirement of resistivity-density product. Two embodiments of the invention are shown by way of ex ample in FIGS. 2 and 3, wherein, in FIG. 2, a layer of copper 20 is clad on its upper and lower surfaces with layers of cupronickel 22, and in FIG. 3 a silver-copper alloy 26 in Which copper predominates is clad on its upper and lower surfaces by layers of a silver-copper alloy 28 in which silver predominates.

The various embodiments of composite metals which may fall within the teachings of the present invention, including the embodiments illustrated in FIGS. 2 and 3, may be clad by any of the many well-known industrial methods such as cold bonding, hot bonding, brazing or explosive bonding.

The composite metal may be either originally clad to the desired thickness or may be clad and subsequently rolled. After rolling, or if originally clad to the necessary thickness, the composite strip is processed through the blanking mechanism which punches the coin blanks or planchets. These planchets may then be annealed, if desired, or forwarded directly to the riddle for cleaning. The clean coin blanks or planchets are then passed between rollers to raise or upset the rim of the blank. This operation is necessary in order to provide a rim thickness greater than that of any other portion of the coin to not only facilitate stacking but also to provide better wear protection to the central portions of the coin. The upset blanks then proceed to the coining operation wherein they are pressed simultaneously between obverse and reverse dies to form the complete coin design, including the milled edge or reeding.

Referring now to FIG. 4, a brief description of the eddycurrent coin selector mechanism will be set forth in order that the stringent requirement of a specific resistivity-density product may be better appreciated.

In the eddy-current mechanism illustrated in FIG. 4 an inclined track 30 supported at its upper and lower ends by support members 32 has a magnet 33 so arranged near is lower end to concentrate the magnetic lines of flux 36 perpendicular to the path of travel of coin 38 down the track 30. In accordance with the well-known law of physics, as coin 38 travels down inclined track 30 cutting lines of flux 36 eddy currents are generated in coin 38 creating a magnetic field which impedes the motion of coin 38 through the primary magnetic field 36. As is well known, the degree of retardation in the magnetic field is proportional to the product of the density and the electrical resistivity of the coin. The coin selector mechanisms presently in use throughout the United States accept customary United States silver coinage (resistivitydensity product of 21.6 micro-ohm-grams per square centimeter) and reject pure copper (resistivity-density product 15.4) on the low side and 95 copper-5 Zinc (resistivitydensity product of 27.0) on the high side. The various embodiments of the present invention including the specific examples hereinafter set forth have been found to have resistivity-density products which lie within this acceptable range.

As specific examples of composite metals encompassed by the teachings of the present invention, the following exampes are given. They are illustrative only.

EXAMPLE 1 A clad strip suitable for minting coins in dime denominations may consist of a base or inner layer of pure copper having a thickness of 021.001 inch and two outer layers composed of 7512.5% copper and 2512.5% nickel, each having a thickness of 0071001 inch, the total thickness of the strip being 0411.001 inch.

EXAMPLE 2 A clad strip suitable for minting coins in quarter dollar denominations may consist of a base or inner layer of pure copper having a thickness of 0361001 inch and two outer layers composed of 7512.5% copper and 2512.5% nickel, each having a thickness of 0091001, the total thickness of the strip being 0541.001 inch.

EXAMPLE 3 A clad strip suitable for minting coins in half dollar denominations may consist of a base or inner layer composed of 21.51.6% silver and 78.51.6% copper having a thickness of 0461002 inch and two outer layers composed of 801.6% silver and 201.6% copper having a thickness of 0101001 inch, the total thickness of the strip being 0661.001 inch.

It is to be noted that the amount of silver could vary from between 75% to 85% in the outer layers and from between 20% to 25% in the inner layer.

In addition to the many advantages already set forth there exist numerous other advantages inherent in the composite metals of the type encompassed in the present invention, some of which will now be described. Trial blanking operations on the illustrated embodiments of the invention have shown that as with the present United States coinage the strip may be blanked in a cold-rolled condition resulting in planchets having clean and sharp sheared edges. If annealing before blanking was required, as is the case with many other suggested substitutes, the punch drags the metal leaving unsatisfactory burred edges.

The inevitable result of punching circular blanks from strip stock is the relatively large percentage of scrap remaining as a skeleton after the coin blanks have been punched. In actual practice the remaining scrap amounts to approximately 30% of the original strip. With the composites of the present invention this scrap can readily be reverted directly into the melting cycle. Scrap from the cupronickel-copper combination, since it consists only of copper and nickel, can be utilized in the production of additional cupronickel simply by adding proportionately more nickel to the charge in the melting furnace. A similar result is possible with the silver-copper scrap by adding correct amounts of silver or copper.

Other unique features of the present invention are difficulty of counterfeiting, wear resistance superior to that of present silver coinage, and low cost.

As many changes could be made in the above composites without departing from the scope of the invention, it is intended that all matter contained in the above description shall be interpreted as illustrative and not in a limiting sense.

We claim:

1. In a coin a clad metal comprising a base layer of pure copper having a thickness of 0271001 inch and two outer layers composed of 7512.5 copper and 2512.5 nickel, each having a thickness of 0071.001 inch, the total thickness of the strip being 0411.001 inch.

2. In a coin a clad metal comprising a base layer of pure copper having a thickness of 0361.001 inch and two outer layers composed of 7512.5% copper and 2512.5 nickel, each having a thickness of 0091001, the total thickness of the strip being .0541001 inch.

3. In a coin a clad metal comprising a base layer composed of 21.51.6% silver and 78.51.6% copper having a thickness of 0461002 inch and two outer layers composed of 801.6% silver and 201.6% copper, having a thickness of 0101001 inch, the total thickness of the strip being 0661.001 inch.

4. A composite metal comprising two cupronickel layers, an intermediate layer of copper, said layers being bonded together, the cupronickel layers consisting of about 25% nickel, the relative thicknesses of the layers being such that the resistivity-density product of the composite metal lies in the range of 15.4 to 27.0 micro-ohmgrams per square centimeter.

5. In a coin a composite planchet comprising two cupronickel layers, an intermediate layer of copper, said layers being bonded together, the cupronickel layers consisting of about 25 nickel, the relative thicknesses of the layers being such that the resistivity-density product of the planchet lies in the range of 15.4 to 27.0 microohm-grams per square centimeter.

6. A composite metal having a sandwich structure, the outer layers being of substantially equal thickness and being made of a cupronickel alloy consisting essentially of about 25 nickel, an inner layer of high conductivity copper comprising about 50% to of the resulting metal thickness, said metal being characterized by a resistivity-density product which lies in the range of 15.4 to 27.0 micro-ohm-grams per square centimeter.

7. In a coin a composite planchet comprising a sandwich structure, having outer layers being of substantially equal thickness and made of a cupronickel alloy consisting essentially of about 25 nickel, and an inner layer of high conductivity copper comprising about 50% to 90% of the total metal thickness, said planchet being characterized by a resistivity-density product which lies in the range of 15.4 to 27.0 micro-ohm-grams per square centimeter.

8. A clad metal comprising two silver-copper outer layers consisting essentially of about 75 to 85% silver, an intermediate silver-copper layer consisting essentially of about 20% to 25% silver, said layers being bonded together, the relative thickness of the layers being such that the resistivity-density product lies in the range of 15.4 to 27.0 1nicro-ohm-grams per square centimeter.

9. A clad metal comprising two silver-copper layers consisting essentially of about 80% silver, an intermediate silver-copper layer consisting essentially of about 20% silver, said layers being bonded together, the relative thickness of the layers being such that the resistivity-density product lies in the range of 15.4 to 27.0 micro-ohmgrams per square centimeter.

10. In a coin a composite planchet comprising two silver-copper outer layers consisting essentially of about 75% to 85% silver, an intermediate silver-copper layer consisting essentially of about 20% to 25% silver, said layers being bonded together, the relative thickness of the layers being such that the resistivity-density product lies in the range of 15.4 to 27.0 micro-ohm-grarns per square centimeter.

11. In a coin a composite planchet comprising two silver-copper layers consisting essentially of about 80% silver, an intermediate silver-copper layer consisting essentially of about 20% silver, said layers being bonded together, the relative thickness of the layers being such that the resistivity-density product lies in the range of 15.4 to 27.0 micro-ohm-grams per square centimeter.

12. A clad metal having a sandwich structure, the two outer layers being of substantially equal thickness and being made of a silver-copper alloy consisting essentially of about 75% to 85% silver, an intermediate silver-copper alloy layer consisting essentially of about 20% to 25% silver, the intermediate layer comprising about to 90% of the metal thickness, the relative thickness of the layers being such that the resistivity-density product lies in the range of 15.4 to 27.0 micro-ohm-grams per square centimeter.

13. In a coin a composite planchet having a sandwich structure, two outer layers being of substantially equal thickness and made of a silver-copper alloy consisting essentially of about to silver, an intermediate silver-copper alloy layer consisting essentially of about 20% to 25 silver, the intermediate layer comprising about 50% to %of the planchet thickness, the relative thickness of the layers being such that the resistivitydensity product lies in the range of 15.4 to 27.0 microohm-grams per square centimeter.

References Cited UNITED STATES PATENTS 2,094,482 9/1937 Weder 29-199 3,407,050 10/1968 Trapp 29-199 1,077,977 11/1913 Fuller 29196.3

2,445,858 7/1948 Mitchell 29199 2,646,616 7/1953 Davignon 29-199 2,772,963 12/1956 Pease 29199 XR HYLAND BIZOT, Primary Examiner