US3469784A - Apparatus for reducing shells in outer-curve rails - Google Patents

Description

p 30, 1969 J. E. CAMPBELL ETAL 3,469,784

APPARATUS FOR REDUCING SHELLS IN OUTER-CURVE RAILS Filed June 6, 1967 2 Sheets-Sheet 1 INVENTORS JACKSON E. CAMPBELL ER ICH THOMSEN M, p a/ TANGENT SECTION '4 ATTORNEYS P 30, 1969 J. E. CAMPBELL ETAL 3,469,784

APPARATUS FOR REDUCING SHELLS IN OUTER-CURVE RAILS Filed June 6, 1967 2 Sheets-Sheet 2 INVENTORS JACKSON E. CAMPBELL BY ERICH THOMSEN ATTORNEYS United States Patent U.S. Cl. 238-287 19 Claims ABSTRACT OF THE DISCLOSURE Apparatus for use in reducing shells in outer-curve rails of a railroad track system in which the tangent and curve rails are laid with a standard 1 in 40 cant, by increasing the cant of the outer-curve rails by 245.

Background of the invention This invention relates to the improvement of railroad track performance by the increase in cant of the high rail of a section of curved track.

The main object of the invention is to provide a way in which failure of rails due to internal rail defects, primarily shelling, may be reduced or eliminated, and secondarily to improve wear characteristics of rails.

The development of track-laying over the years has concerned itself primarily with the Wear of rails. Before 1900, rails were generally spiked to wooden ties, without benefit of tie plates, with the rails being vertically disposed. At such time, wheel loads were light, labor and material were cheap, and the frequent replacement of rails and ties was accepted as necessary.

With increasing Wheel loads, the use of tie plates became common in the early 1900s. These plates general 1y had fiat rail seats that supported the rail in an upright, vertical position, as before. A raised shoulder on the plate, to engage the edge of the rail base and resist side thrust, soon became common.

Railroad wheels were then, and still are made with a conical tread, having a slope of 1 in 20. It was observed that the surface of the head of vertical rails wore to a sloping contour, and it was suggested that the rails should be canted relative to the ties so that the top surface of the rails would be sloped at a 1 in 20 slope downwardly towards the center of the track, so that the top surface of the rail heads would be normal to the wheel tread. The idea of canting the rails was strongly resisted by many at first, but gradually such canting was accepted and by the mid-1920s was commonly adopted. Experience showed that since the average worn wheel slope Was somewhere between the original 1 in 20 slope of a new wheel and a flat contour, rails canted at a l in 40 slope showed a better wear contour than those canted at a 1 in 20 slope, and the 1 in 40 cant became generally accepted, and has been used to the present time. The desired 1 in 40 cant is normally obtained by the use of tie plates having a 1 in 40 sloping rail seat to support the rail on the ties.

The very great majority of railroad trackage is located on tangent alignment, i.e., straight track, and the 1 in 40 cant that was found to give the, best wear results on tangent track was adopted as standard throughout the tangent and curved sections of trackage. The same tie plates were, and are, being used almost universally on curves. Since the life of curve rails was governed by the amount of metal worn from the side of the rail head, the wear condition at the top surface of the rail, although not ideal, was not a governing factor.

Since the 1950s, several factors have changed in the area of wheel-to-rail contact on curves. Wheel loads have ice increased greatly. The cast iron wheel has practically been replaced by the steel wheel. Diesel locomotives have increased train length, and regenerative braking has been introduced whereby the entire train is retarded by the locomotive instead of each car being retarded by its own brakes. Concurrently with these changes, a rail defect known as shelling has become prevalent on the outer, or high, rails of curves.

A shell is a horizontal separation of the metal of the rail head, in a plane usually between one-eighth and one-half of an inch below the top surface of the rail head, forming generally on the gauge corner of outer rails of curves. The separation generally begins at a length of less than an inch, then grows longitudinally along the rail, and at a length of four to six inches, the metal above the separation occasionally spalls off, creating a hazardous condition.

Although it has not become a significant problem until recent years, shelling has been recognized since the 1900s and much research has been undertaken in an effort to overcome it. At present little is known about its causes, other than a suspicion that non-homogeneity of the metal in the form of free carbon may be involved, and that highly concentrated loads on these rail defects lead to shelling. The shell problem was practically nonexistent on Western Pacific Railroad Company trackage in 1955, but has since reached epidemic proportions, an experience that is shared by all railroads having curvetrack territories and heavy trafiic.

Whereas formerly side-Wear of the head of a curve rail determined its life, under present conditions most outer rails of curves are failing from shelling long before the accepted sidewear limit is reached.

In an attempt to overcome the shelling problem, recent years have seen much activity in the area of flamehardening of curve rails on the assumption that hardening of the top and side surfaces of the rail head would resist abrasive wear and would minimize plastic flow of the metal to eliminate shelling. Many variations of hardness patterns, hardness depths, degrees of hardness, and hardness transitions have been and are presently being tried.

The results of these efforts, however, have been largely disappointing in that laboratory rolling load tests and field installations have shown no lessening and, indeed, have often shown an increase in the incidence of shelling. A possible explanation of the failure of rail hardening to eliminate shelling is that more time is involved in wearing the rail head to a full bearing contour. As a consequence, the rail head is subjected to the concentrated loads that create shelling for a longer time.

In addition, changes in rail lubrication have been and are being tried. The Association of American Railroads Test Laboratory has been and is studying the shelling problem from a metallurgical approach.

To date, however, the shell problem has not been solved.

Summary of the invention In 1955, the present inventors devised and caused to be adopted by Western Pacific Railroad Company a system of control by which the renewal of curve rails is regulated, to supplant the prior method whereby curve rails were renewed on the personal whim of the roadmaster in charge of the curve in question. As a part of that system, rail contours were and are taken by means of a small machine which is clamped to the worn rail head and which has a scriber that traces around the rail head and simultaneously draws an accurate cross section of the rail head on a card inserted in the machine. The rail contour could then be compared to the original contour of the rail when new so that the amount and manner of wear of the rail could be ascertained.

It was early noticed that the wear patterns in tangent track were not the same as those of curved track, in that in tangent track the top wear was such that the slope of the top surface remained essentially the same as th rails wore away, Whereas outer-curve rails always wore in a way that caused the slope of the top of the rail to slope towards the center of the track to increase, and that this increased slope was practically constant regardless of the degree of curvature of the track. Since at that time side wear of the rail head governed curve rail life, no remedial measures were considered in the matter of top wear, as such top Wear Was inconsequential as compared to side wear.

However, as mentioned above, under present conditions most outer rails of curves are failing from shelling long before the accepted side-wear limit is reached.

Upon further analysis of the rail contour cards which have been accumulated through the years, the present inventors have discovered that the top surface of new outer-curve rails of Western Pacific trackage, canted at the standard 1 in 40 cant, wears in such manner that the slope of the top surface increases an additional 245, and that such increased slope remains constant as the rail is subjected to further wear. Furthermore, it has been found that the additional 245 slope, created by rail wear, is substantially independent of the degree of curvature of the track.

Furthermore, the wear conditions on W stern Pacific curved trackage can be considered to be the same as that throughout the country, since the cars being run over Western Pacific trackage are a cross section of all of the cars in service in the country, and the average wheel condition of these cars is also an average of the wheel condition of the cars in service throughout the country.

The inventors have further realized that shelling is caused primarily by concentrated wheel loads on outercurve rails, and that such shelling can be greatly alleviated by the reduction in load concentration on the rails.

The present inventors have discovered that the load concentration on outer-curve rails results from an improper canting of such rails, and that rail performance can be improved by canting the outer-curve rail an additional 245 from the normal 1 in 40 cant, and that this additional cant will be the same for curved trackage throughout the country. With this increased cant, the wheel load will be distributed over a much greater top area of the rail, thereby reducing the load concentration on the gauge corner where shelling now occurs.

It is to be understood, however, that the increased canting of rail is to be applied only to outer-curve rails. The remainder of the track system, i.e., the rails of tangent track and the inner-curve rail, is to be left at the standard 1 in 40 cant, which cant for such rails is as correct today as when first adopted.

Brief description of the drawings Referring now to the drawings, wherein preferred emhodiments of the invention are shown and wherein like reference numerals are used throughout the same,

FIG. 1 is a generally diagrammatic illustration of a typical section of a railroad track system.

FIG. 2 is an elevational view, partly in section, of a way in which the cant of the high rail on a curved section of track is increased in accordance with the invention.

FIG. 3 is a plan view of a standard tie plate shown in FIG. 2.

FIG. 4 is a plan view of the tapered shim shown in FIG. 2.

FIG. 5 is an elevational view, partly in section, of a modification of the invention, wherein the cant of the high rail on a curved section of track is increased in accordance with the invention.

FIG. 6 is a diagrammatic illustration of a new railroad wheel riding on a new section of tangent rail which is canted at the standard 1:40 cant.

FIG. 7 is a diagrammatic illustration of an averagely worn railroad wheel riding on a new section of tangent track which is canted at the standard 1:40 cant.

FIG. 8 is a diagrammatic illustration of an averagely worn railroad wheel riding on the high rail of a new section of curved track which is canted at the standard 1:40 cant.

FIG. 9 is a typical contour of a section of the high rail of a curved track section which is canted at the standard 1:40 cant, with the upper dotted line illustrating the contour of the rail when new, the full line illustrating the contour of the rail after it has been subjected to normal wear, and the lower dotted line illustrating the rail contour after it has been subjected to further wear.

FIG. 10 is a diagrammatic illustration of an averagely worn railroad wheel riding on an averagely worn high rail of a curved track section which is canted at the standard 1:40 cant.

FIG. 11 is a diagrammatic illustration of an averagely worn railroad wheel riding on a new high rail of a curved track section wherein the cant of the high rail is increased in accordance with the invention.

Description of the preferred embodiment Referring now to the drawings, FIG. 1 illustrates in general a typical track system having rails 11 and 12 secured to ties 13. As illustrated, the track has a tangent section 14, a spiral, or run-01f, section 15 of decreasing radius, a curve section 16 of constant curvature, a spiral or run-01f section 17 of increasing radius and a tangent section 18. In the illustrated system, the rail 11 is the inner-curve rail and the rail 12 is the outer-curve rail.

FIGS. 6-11 illustrate the manner in which the present invention has been discovered and by which the proper cant of the outer-curve rail has been determined.

FIG. 6 illustrates a new wheel 20 running on a new rail 12 of tangent track. The wheel 20 has a standard 1 in 20 slope of the coned tread 21 thereof. A standard tie plate 22 is spiked to tie 13 and has a rail seat 23 which is canted at a standard 1 in 40 cant to seat the rail 12 thereon. The top surface 24 of rail 12 will accordingly be sloped at a l in 40 slope downwardly towards the center of the track.

The flange 26 of wheel 20 is away from the gauge corner 27 of the rail and the center of bearing of the Wheel, indicated by the arrow, is near the center line of the canted rail.

FIG. 7 shows a worn wheel 20' running on a new rail of tangent track at a l in 40 cant. The contour of the wheel 20 is a composite average of the contours of all wheels running on track, from new wheels to those worn to a degree at which they are to be replaced. Again, the flange 26 of the wheel is away from the rail and the center of bearing, indicated by the arrow, coincides with the center of the rail, showing the correctness of canting the rail to a slope of l in 40 on tangent track.

The wear of the top surface of rail 12 will be produced by the contacting portion of the worn tread 24' and the top rail surface 12 will be worn so that the contour remains the same, namely, so that the top surface will remain at a 1 in 40 cant.

FIG. 8 illustrates a worn wheel 20' running on a new outer-curve rail 12, at a standard 1 in 40 cant. Centrifugal force causes the flange 26' of the wheel to press against the side 25 of the rail head. Under such condition, the center of bearing, indicated by the arrow, is near the gauge corner 27. As will be noted, this hearing condition, typical of outer-curve rails, shows the standard cant of such rails to be incorrect, in that wheel loading is concentrated at the gauge corner of the rail.

FIG. 9 illustrates the typical rail contour of a worn outer-curve rail 12', at a standard 1 in 40 cant, as determined from the previously-mentioned rail contour cards. The original contour of the top surface of the rail is indicated by the dotted line 24. As will be noted, the top surface 24' of the rail has been unsymmetrically worn, and such wear increases the slope of the worn top surface 24 by approximately 245 from the original slope thereof. As wear continues, the top surface of the rail will wear to a contour as indicated by the dotted line 24". Significantly, the slope of the top surface 24" remains the same as that of the partially worn top surface 24, namely, at an angle of 245 relative to the original contour of the top surface. It has been found that the 245 wear of the top surface is measurable at about one-quarter of the wear life of the rail and that the slope remains constant for the remaining life of the rail.

The area between lines 24 and 24 represent the amount of metal worn from the outercurve rail and shows that the wear has been produced by a concentration of the wheel load in the vicinity of the gauge corner, where shelling primarily occurs. Such load concentration on the gauge corner causes fatigue in the rail head that leads to early failure.

FIG. illustrates a worn wheel running on a worn outer-curve rail 12, showing the manner in which the wheel has worn the rail to a contour as shown in FIG. 9, due to the fact that the wheel load has been concentrated in the vicinity of the gauge corner.

FIG. 11 illustrates the use of the invention and shows a worn wheel 20 running on a new outer-curve rail 12. In this particular embodiment, the standard tie plate 22 has been replaced by a tie plate 22 having a rail seat 23 having an additional 245 slope to the normal 1 in 40 slope. In this manner the slope of the top surface 24 of the rail is increased 245 over the standard cant thereof.

As will be seen from FIG. 11, wheel flange 26 still presses against the side surface of the rail head, but the top surface 24 of the rail conforms much more close- 1y than before to the shape of the worn wheel tread 21, and the center of bearing of the wheel has moved from the vicinity of the gauge corner towards the center line of the rail.

With the outer-curve rail so canted, wear of the rail will not be concentrated at the gauge corner, but instead will be spread out over the top surface of the rail, thereby reducing the shelling problem.

The increase of cant of outer-curve rails can also be accomplished by the use of tapered inserts 30, as illustrated in FIGS. 2 and 4. In such case, the insert 30, which could be of rubber, plastic, steel or wood, would be tapered to the proper degree, namely, about 245. The insert 30 would preferably be shaped to the size of the standard tie plate 22, and would be perforated, as at 31, in the same locations as the tie plate holes 32, for the standard spikes 33. To increase the cant of installed rails, the spikes are pulled, the insert 30 is put under the tie plate 22 and the tie plate and insert are respiked.

It is common practice at present to use resilient tie pads under tie plates on curves and frequently on tangent track. These are fiat pads of some resilient material, usually coated with an adhesive material that bonds to the tie. The purpose of such tie pads is to exclude abrasive matter from the contact area between the tie plate and tie, and to prevent wear and crushing of the wood fibers.

A tapered insert 30, as described, if made of plastic or rubber, could be used to obtain the benefits of the increased cant of the present invention as well as the benefits of standard resilient tie pads.

Yet another manner in which the desired canting can be achieved is illustrated in FIG. 5, wherein the tie 13' is adzed to provide a sloping seat 36 for a standard tie plate 22 at one end, the seat being sloped at the desired 245 angle. With such a tie, the inner-curve rail 11 would be positioned at the normal 1 in 40 cant, while the cant of the outer-curve rail 12 would be increased 245 over the standard cant. The adzing of the sloping tie plate seat 36 could be done in the field, but preferably should be done at the mill for closer control of the slope of the seat.

It will be realized that concrete ties can be made as in FIG. 5, with a normal tie plate seat at one end and a sloping tie plate seat for the desired increase in cant.

Also, if desired, a special contour rail could be rolled so that when seated in a standard tie plate the head of the rail would have the desired additional slope.

It is to be realized that the increase of cant is to be applied to the outer-curve rail only. Thus, in the track system of FIG. 1, the rail 11 would have a normal 1 in 40 cant throughout the system, including the curved portion thereof. The rail 12 would also be at a standard 1 in 40 cant in the tangent sections 14 and 18, but would have an increased cant in the spiral and constant curvature sections 15, 16 and 17.

To avoid an abrupt change in cant of the rail 12 from the tangent portions to the curved portion thereof, it is contemplated that inserts 30 of lesser degree can be used at the run-oft of each end of the curved section of the rail. For example, tapered inserts of 45 could be used for about one rail length, and then tapered inserts of 145 could be used for another rail length in order to provide a transition from the standard 1 in 40 cant to the additional 245 cant. The breakover between types of inserts should occur at mid-rail.

The invention described above has been discussed in particular connection with track systems wherein such systems are used by cars of all lines. However, there are also instances in which a different amount of cant may be optimal. For example, there are many private lines wherein a railroad may haul coal in its own heavy-weight cars, on which the wheels are permitted to wear more than is permitted by ICC regulations, and in which speeds of trains are very low. However, in such specialized situations, the present invention is just as applicable. The proper cant would be determined by obtaining rail contours of outer-curve rails so that the slope of the worn rail (produced by the average worn wheel of the cars using the system) can be compared with the original slope of such outer-curve rail. The increase in slope of the worn rail would then indicate the amount to which the outercurve rail should be additionally canted.

The present invention was primarily evolved in connection with the elimination of shelling in hardened rail, but this is not the limit of the benefits that can be realized therefrom. It is expected that the resistance to wear in hardened rail will be much improved, and the resistance to shelling and wear in unhardened rail will also be improved. Where relayer rail released from tangents is laid in curves, either flame-hardened or merely as work-hardened, the benefits to be derived will be comparable.

The additional canting of the outer-curve rail will also reduce the normal plastic flow deformation of the rail because of the de-concentration of wheel loading thereon. This will then enable the outer-curve rail, when worn to its permissible extent, to be relaid as the inner-curve rail.

It will be appreciated that although the 1 in 40 cant has been standard for many years, when such cant was adopted by the Association of American Railroads, tie plates having a rail seat at a 1 in 20 cant and a 1 in 29 cant were in common use prior to that time. Tie plates have 'a relatively long life, and there is at present a considerable amount of curve track in the United States which was laid prior to the adoption of the present 1 in 40 cant, using tie plates having a 1 in 20 or a 1 in 29 canted rail seat, and in which such tie plates are still in service. In such instances, to achieve the objects of the present invention, the increase in cant will be less than that required of a now standard 1 in 40 canted rail, but the total amount of cant will be the same, i.e., a cant of 1 in 40 plus the 2% In the claims, it will be understood that the 7 term standard cant is intended to include the present standard cant of l in 40 as well as the cants in common usage, unless the term is specified as being a standard 1 in 40 cant.

It is also to be realized that the various modifications of the invention herein shown and described are to be taken as preferred embodiments of the same, and that various changes may be made in the methods and in the shape, size and arrangement of parts without departing from the spirit of the invention.

Having thus described our invention, we claim:

1. An article of manufacture comprising a railroad tie having seats on the upper surface thereof for the reception of tie plates and in which one of said seats has an inclination downwardly from the upper surface of said tie towards the center of said tie by an angle approximately 245 greater than the inclination from said upper surface of the other of said seats.

2. A railroad track system having a tangent section and a curved section extending therefrom and comprising:

(a) a plurality of ties along said system,

(b) a pair of rails extending throughout the tangent and curved sections of said system,

() means securing the rails of said tangent section and the inner rail of said curved section to said ties with the crowns of said rails being canted downwardly to the center of said track,

((1) means securing the outer rail of the curved section to said ties with the crown of said outer-curve rail being canted downwardly towards the center of said track at an angle greater than that at which said rails of said tangent section and said inner rail of said curved section are canted.

3. A railroad track system having a tangent section and a curved section extending therefrom and compris- (a) a plurality of ties along said system,

('b) a pair of rails extending throughout the tangent and curved sections of said system,

(c) means securing the rails of said tangent section and the inner rail of said curved section to said ties with the crowns of said rails being canted downwardly towards the center of said track,

(d) means securing the outer curve rail of the curved section to said ties with the crown of said outer curve rail being canted downwardly towards the center of said track at an angle approximately equal to a 1:40 cant plus 245.

4. A railroad track system as set forth in claim 3 wherein said means (d) comprises tie plates having a rail seat inclined at an angle approximately equal to a 1:40 cant plus 245.

S. A railroad track system as set forth in claim 3 wherein said means (d) comprises tie plates having a canted rail seat and tapered wedges disposed between the tie plates and the ties, and wherein the cant of a rail seat and the taper of a wedge together total approximately a 1:40 cant plus 245.

6. A railroad track system as set forth in claim 3 wherein said means (d) comprises tie plates having a canted rail seat, said ties having inclined tie plate seats formed thereon to receive said tie plates, and wherein the cant of a rail seat and the angle of inclination of a tie plate seat together total approximately a 1:40 cant plus 245.

7. A railroad track system having a tangent section and a curved section extending therefrom and comprismg:

(a) a plurality of ties along said system,

(b) a pair of rails extending throughout the tangent and curved section of said system,

(0) means securing the rails of said tangent section and the inner rail of said curved section to said ties with the crowns of said rails being canted downwardly towards the center of said track at a 1:40 cant,

(d) means securing the outer curve rail of the curved section to said ties with the crown of said outer curve rail being canted downwardly towards the center of said track at an angle approximately equal to a 1:40 cant plus 245.

S. A railroad track system as set forth in claim 7 wherein said means (d) comprises tie plates having a rail seat inclined at an angle approximately equal to a 1:40 cant plus 245.

9. A railroad track system as set forth in claim 7 wherein said means (d) comprises tie plates having a 1:40 canted rail seat and wedges tapered at an angle of approximately 245 disposed between the tie plates and the ties.

10. A railroad track system as set forth in claim 7 wherein said means (d) comprises tie plates having a 1:40 canted rail seat, said ties having tie plate seats formed thereon at approximately a 245 inclination to receive said tie plates.

11. In a railroad track system having a railroad tie on which first and second tie plates are secured and in which inner and outer curve rails are seated on said first and second tie plates respectively, the inner curve rail being canted toward the center of the tie, the improvement comprising that the outer curve rail is canted towards the center of the tie at an angle greater than that at which the inner curve rail is canted.

12. In a railroad track system having a railroad tie on which first and second tie plates are secured and in which inner and outer curve rails are seated on said first and second tie plates respectively, the inner curve rail being canted towards the center of the tie, the improvement comprising that the outer curve rail is canted towards the center of the tie at an angle approximately equal to a 1:40 cant plus 245.

13. In a railroad track system as set forth in claim 12 and wherein the improvement comprises that said second tie plate has a rail seat thereon canted at an angle of 1:40 plus approximately 245.

14. In a railroad track system as set forth in claim 12 wherein the second tie plate has a canted rail seat and wherein the improvement comprises a tapered wedge disposed between said second tie plate and said tie, the cant of said second tie plate seat plus the taper angle of said wedge together totaling to approximately a 1:40 cant plus 245.

15. In a railroad track system as set forth in claim 12 wherein the second tie plate has a canted rail seat and wherein the improvement comprises an inclined tie plate seat formed on said tie to receive said second tie plate, and wherein the cant of said rail seat of said second tie plate plus the angle of inclination of said tie plate seat together total to approximately a 1:40 cant plus 245.

16. In a railroad track system having a railroad tie on which first and second tie plates are secured and in which inner and outer-curve rails are seated on said first and second tie plates respectively, the inner-curve rail being canted towards the center of the tie at a 1:40 cant, the improvement comprising that the outer-curve rail is canted towards the center of the tie at an angle approximately equal to a 1:40 cant plus 245.

17. In a railroad track system as set forth in claim 16 and wherein the improvement comprises that said second tie plate has a rail seat thereon canted at an angle of ap proximately a 1:40 cant plus 245.

18. In railroad track system as set forth in claim 16 wherein the second tie plate has a rail seat with a 1:40 cant and wherein the improvement comprises a tapered wedge disposed between said second tie plate and said tie said wedge having a taper angle of approximately 245.

19. In a railroad track system as set forth in claim 16 wherein the second tie plate has a rail seat with a 1:40 cant and wherein the improvement comprises a tie plate seat formed on said tie to receive said second tie plate, said tie plate seat having an inclination of approximately References Cited UNITED STATES PATENTS Rambacher 238281 Chance 238281 Morris 238269 8/1914 Berg 238288 2/1939 Kahn 238283 10/1952 Boyce 238--306 12/1965 Moses et a1. 238265 FOREIGN PATENTS 3/ 1954 Australia.

ARTHUR L. LA POINT, Primary Examiner Lunjie 23 g 3 5 10 RICHARD A. BERTSCH, Assistant Examiner mg UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,469,784 Dated September 30, 1969 Inventofls) Jacksonlnigmpbell and Erich Thomsen It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

In column 9, line 4 insert the following claim:

20 An article of manufacture comprising a tie plate for securing a rail to a tie, said tie plate having a rail seat thereon canted at 1 in 40 plus approximately 2 45' to the base of said plate In the heading to the printed specification, line 9, "19 Claims" should read 20 Claims Signed and sealed this 28th day of July 1970 (SEAL) Attest:

EDWARD M.FLETCHER,JR. WILLIAM E. SCHUYLER, JR. Attesting Officer Commissioner of Patents

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