US2256065A

US2256065A - Tubular car axle and method for making it

Info

Publication number: US2256065A
Application number: US300601A
Authority: US
Inventors: Bertis H Urschel; Harold C Urschel
Original assignee: Pittsburgh Steel Co
Current assignee: Pittsburgh Steel Co
Priority date: 1939-10-21
Filing date: 1939-10-21
Publication date: 1941-09-16
Anticipated expiration: 1958-09-16

Description

Sept. 16, 1941. B. H. URSCHEL ETAL TUBULAR GAR AXLE AND METHOD FOR MAKING IT Filed Oct. 21, 1939 3 Shee ts-Sheet 1 a ATTQRNEYS.

B. H. URSCHEL ETAL Sept. 16, 1941.

TUBULAR cm AXLE AND METHOD FOR MAKING IT 3 Sheets-Sheet 2 Filed Oct. 21, 1939 Ill Sept. 16, 1941. B. H. URSCHEL ETAL TUBULAR CAR AXLE AND METHOD FOR MAKING IT Filed 001:. 21, 1939 5 Sheets-Sheet Z5 I INVENTORS QM /v- M #wwMW M ATTORNEYS."

Patented Sept. 16, 1941 TUBULAR CAR AXLE AND METHOD FOR MAKING IT Bertis H.

Urschel and Harold C. Urschel,

Bowling Green, Ohio, assignors, by mesne assignments, to Pittsburgh Steel Company, Pittsburgh, Pa., a corporation of Pennsylvania Application October 21, 1939, Serial No. 300,601

8 Claims. (Cl. 29-165) lying between each outer heated portion and the This invention relates to hollow axles made from steel tubing for use with railroad cars, and the like, and is concerned also with improved methods for making axles of this type.

It has been proposed heretofore to make hollow axles for railroad cars by forging the axle in longitudinally split halves which are subsequently welded together. Further, it has been proposed to cast a hollow axle in a single piece either with or without associated integral wheels. Likewise, it has been proposed to forge a steel tube to shape its ends to provide wheel seats and bearing portions of increased wall thickness. One knownvmanner of forging a steel tube includes providing a short heavy walled tube of greater diameter than the finished axle which is forged to reduce the tube diameter and increase its length during the shaping operation.

We have found that the foregoing and other known methods of producing hollow steel axles are costly to practice and do not result in finished axles which possess a maximum of strength and a minimum of weight, and the known methods particularly fail to produce an axle having a wall section with a thickness atany given point which is in direct relation to the stress at that point.

Accordingly, it is the general object of our inventionto overcome the foregoing and other difficulties and objections to known hollow axles and methods of producing them by the provision of an improved light weight but strong and durable axle which can be inexpensively made directly. from steel tubing.

Another object of our inventionis to provide a hollow axlefor railroad cars and the like,

which axle has a wall thickness at any given" point in direct relation to the stress at that point. namely, the greater the stress the greater the center of the axle is very hot adjacent the outer end portion but tapers off in temperature so as to be relatively cool nearer the center portion of the axle, upsetting the outer end portions of; the tube to thicken the walls while maintaining the intemal surfaces of the tube to the desired configuration, said upsetting-action serving to thicken the walls of'the secondary' portions so that their walls are thickened adjacent the heated end portions and gradually wall thickness, but which while strong and durable is of a minimum weight.

Another object of our invention is to provide a method for rapidly and inexpensively forming ahollow axle directly from steel tubing by successive upsetting and forging operations.

The foregoing and other objects of our invention are achieved by the method of making a hollow axle, which includes the steps of upsetting the ends of a steel tube to thicken the wall I and subsequently reducing portions of the ends by forging to. further thicken the wall to .form journal bearings and wheel seats.

More particularly, we contemplate heating each outer .end portion of a tube to a uniform heat and so that a secondary portion of the tube 55 axle. Specifically, the tube l is heated to an taper off in thickness toward the center portion of the axle, and subsequently forging the outer end portions to form journal bearings and wheel seats of the desired shape.

We provide a hollow axle comprising a tube having upset ends, a bearing and wheel seat formed on each upset end. and with the center sections of the tube having substantially the same outside diameter and same wall thickness as the original tube. Again, we provide an axle comprising a tube having journal bearings formed on each end of increased wall thickness and uniform bore which are contiguous to the wheel seats of increased wall thickness but tapered bore. Stated in still another manner, we provide an axle comprising a tube having bearing surfaces with thickened walls, wheel seats contiguous with the thickened walls, a center portion of the tube being formed with a continuous bore and relatively thin walls, and the thickened walls of the bearing surfaces and wheel seats merging in a section of gradually reduced thickness into the relatively thin walls in the center portion of the tube.

For a better understanding .of our invention reference should be had to the accompanying drawings, wherein Fig. 1 is a side elevation partly brokenaway of an axle of our invention being formed by the method of our invention-this figure particularly illustrates the upsetting of one end of a tube; Fig. 2 is a side elevation partly in section of the tube of Fig. 1 after it has been forged to axle shape; Figs. 3 and 5 are views similar to Fig. 1 but illustrating modifications of our invention; and Figs. 4 and 6 are views similar to Fig. 2 and illustrating the fully formed axles of Figs. 3 and 5, respectively.

In the form of our invention illustrated in Figs. 1 and 2 of the drawings, the numeral I indicates a metal tube, usually of steeliwhich has a substantially uniform wall thickness throughout and which is subjected to successive upsetting and forging operations in forming the upsetting temperature on each end, either concurrently or separately, for a distance equal to the finished upset length plus the amount or metal to be gathered in one operation. This distance has been indicated in Fig. 1 of the drawings as terminating at the point II. The temperature of the tube from this point I l toward the center of the tube decreases gradually for a controlled distance until closer to its center the'tube is relatively cool. This graduation in temperature results ina tapered run out l of the upset formed in the end of the tube by the upsetting tool I. It will be recognized that the length of the taper 4 can be increased or decreased by controlling the temperature and the length of the temperature gradient from the point ll inwardly toward the center of. the axle. This controlled taper 4, adapted to have the proper length for any given axle, has a very beneficial effect as no sharp changes in the contour of the wall are permitted, thereby prevent ing any localization of strains which wou d cause fatigue break, or would result in failure of the axle In the upsetting of the ends of the tube walls the outside contour or diameter of the tube is not changed materially. Usually and preferably the ends of the tube areheld to the same diameter as the rest of thetube by suitable upsetter dies thickness nearest the run-out taper 4. The maximum stress occurs at this point in the use of the axle. The taper of the'mandrel 9 permits easy withdrawal of the upsettingtool. The wall thickness of the tube adjacent the mandrel I of the upsetting tool is increased, as at 2, to form the journal bearing. However, this portion of the axle does not have to have as great a wall thickness as at 3 because the journal bearing stress is not as great. It will be understood that all of the above changes in wall thickness are done in a single upsetting operation.

Fig. 2 of the drawings shows the axle after the upset ends have been forged to the proper contour. In the forging operation the wall thicknesses at 2 and 3 are again increased due to the reduction of the outside diameters and because the tube is held against elongation by an arresting block or'other suitable means placed at the end of the axle. This increased wall thickness results due to the fact that no attempt is made to maintain the inside diameter of the axle which. is substantially cylindrical adjacent the journal bearing 2 and substantially tapered adjjacent the wheel seat 3. The point 8, which is the junction betweenthe wall 2 and wall 3, tapers oil to a position within the length of the journal bearing, which is advisable, as this prevents any possible fracture-adjacent to the journal bearing and between the journal bearing and the wheel seat. A flanged edge III is vvformed in the forging operation at the end of the axle by the impres+ sion of the dies. The flange 10 when properly machined keeps the journal bearing liner (not shown) in place. Forging dies have not been what is to be the wheel seat with a maximum wall 40 illustrated in the-drawings inasmuch as any suitable type of dies may be employed in the usual forging operation to provide anaxle having the In the modification of our invention illustrated in Figs. 3 and 5 the tube la is first upset at both ends in the manner shown in Fig. 3. The tapered run-out section at 4a is controlled as to length, as already explained above in conjunction with the upsetting of the tube shown in Fig. 1. The upsetting tool 5a is formed with a shoulder 6a and a tapered mandrel Ia having a substantially uniform taper throughout its entire length. This type of upsetting tool results in an easy upsetting oi the metal of the heated tube ends inasmuch as the metal can flow along the tapered surfacetof the mandrel 1a. Further, the mandrel can easily be withdrawn due to the taper throughout its length. In the upsetting operation illustrated in Fig. 3, the outer diameter 01' the tube is usually maintained constant by upsetter dies I511. The maximum wall thickness at point II a is positioned during upsetting so that in the forging operation the point is on the inside of the wheel seat which is a maximum stress point in the axle when in use.

Fig. 4 shows the axle la after the forging operation with any suitable dies, not shown. Slightly more metal is required to form this type of axle than that shown in Fig. 2, as the wall at ill for the journal bearings'must be held somewhat thicker due to the taper being maintained on the inside of the diameter of the tube for the full length of the upsetting operation. The

forging operation further increases the wall thicknesses at 3a and 2a, as best shown in Fig. 4. The inner' surface of the bearing portion 2 and the inner surface of the wheel seat 3 are both tapered as evident from Fig. 4. I

The form of our invention illustrated in Figs. 5 and 6, similar to the modifications of our invention shown in Figs. 1 to 4, includes a tube lb having a wall thickness and an outside diameter that gives the required sectional modulus to carry thestress in the central section of the axle between the two wheel seats with a given factor of safety. The first step in the method of making the axle shown in Fig. 6 is somewhat different than in the modifications of our invention heretofore described, and comprises heating the tube to upsetting temperature only adjacent the area l8 so that when the tube is upset the wall thereof is thickened solely along the area I8.

This first upsetting operation is illustrated in dotted lines at the right-hand end of the tube shown in Fig. 5 of the drawings, and includes tapered run-outs 4b whose length is controlled in the manner heretofore described. In the upsetting of area l8 the outside diameter of thetube is maintained by suitable upsetter dies lib' at 3b is not heated. The end of the tube is then again upset in the manner shown at the lefthand side of Fig. 5. This results in the formae tion ,of the illustrated upset in the region l1 and outwardly to the end of the tube but does not affect any upsetting of the area 3b of the tube. The inside diameter of the. upset in the region I1. is controlled by the mandrel IS on the upsetting tool b.

In the upsetting operation the tube wall is thickened somewhat at the section 2b and the inside diameter of this portion of the tube is controlled by the enlargedinandrel portion 20 of the upsetting tool Ib. Shoulder b on the upsetting tool is the contacting area on the tool which pushes the tube longitudinally to shorten its length. The tapered intersection ll between the mandrel portions l6 and 20 controls the degree of taper between upset sections and section 2b of the tube. I

The finished upset end as shown on the left- "hand side of the tube illustrated in Fig. 5 can be made in one upsetting operation instead of two as Just described. Specifically, the section 3b of the tube is kept cold in a specially designed furnace while the sections on both sides for a predetermined length are heated. In the upsetting operation the outer diameter is maintained by the gripper dies lib of the upsetting apparatus. As the tool of the upsetter moves axially forward against the end of the tube lb the walls of the tube are thickened at area "and outwardly to the tube end and at area It until they engage mandrel l8.

Fig. 6 illustrates the finished axle of Fig. 5 after the forging operation is completed. The forging operation increases the wall thickness very slightly at point lb as the outside diameter is not decreased materially. The wall thickness at the point 22) is increased more as the diameter is decreased more at this point. In the axle shown in Fig. 6 the greatest reduction of weight is made of any of the axle modifications shown for the reason that the wall thickness at 3b is also kept at a minimum. This may be done because the center oi. the portion 3b is at the center of the wheel itself, so that the wheel hub extends across and strengthens and bridges the reduced center of the portion 3b. The thickened wall portions i1 and it are so located and are of such length that ample thickness of wall is provided at the outer edge of both sides of the wheel seats. It will be seen that the thickened wall I! extends not only from the inside of the wheel seat but also to and beyond the innermost edge of the journal bearing.

In the foregoing descriptions of our improved axles and methods of making them it has been implied that one end of the axle was heated and upset at a time. It should be recognized that it is possible with a special furnace to heat both ends to upsetting temperature and to leave the center portion relatively cold. Further, with a special upsetter including a ram at both ends of the machine it is possible to upset both ends of the axle at once. In such an upsetter no back stop is required as the pressures exerted by the rams counteract each other. In this case the gripper die of the upsetter would probably extend from one end of the axle to the other. Apparatus of this type materially cuts down the handling and other operations and effects further production savings.

After the forging operation the axles are in all cases heat treated. The tubular section is 7 ideal for heat treatment as the quenching medium can be circulated through the hollow tube, as well as on the outside of the tube. This gives a maximum depth of penetration of hardness,

5 resulting in maximum strength. The axle is then drawn back to a hardness that is Just machinable so that the machining operations can be performed on the wheel seats and journal bearings.

10 From the foregoing it will be recognized that the objects of our invention have been achieved by the provision of an exceptionally strong but exceedingly light weight hollow axle and by the provision of an inexpensive, rapid, and practical method, for making an axle of the statedtype.

, The formation of our improved axle is greatly expedited by leaving a considerable portion of the center of the tube from which the axle is made in an unworked state. The external and internal diameters of the central portion of the finished axle are substantially identical to those of the original tube. Further, the wall thickness of the center portion of the tube is the same as that of the finished axle. The upsetting and forging operations are confined to the ends of the axle and are so controlled as heretofore described that the maximum wall thickness in the hllow axle occurs in regions of maximum strain, and the wall thickness of the axle is at a minimum in such portions of the axle wherein the strain is at a minimum.

It should be understood that various modifications of our advance in the art can be practiced without depart ng from the spirit or scope of our invention. Specifically, we may slightly reduce or otherwise change the center section of a tube when forming it into an axle. Further, we may allow the outside diameter of the tube ends to increase during the upsetting operation which will reduce the frictional resistance of the gripper dies to upsetting. Also, in the final forging operation we may use either a hammering or a slow squeezing action.

Accordingly, while we have particularly illus- 0 trated and described several embodiments of our invention and particular methods of practicing it, it should be clearly understood that we are not to be limited thereto or thereby but that the scope of our invention is defined in the appended claims.

We claim:

1. As an article of manufacture, an axle for railroad cars comprising a relatively thin wall tube of substantially uniform external and intemal diameter along a long center section, the

ends of the tube being reduced in diameter and increased in wall thickness to form journal bearlngs and wheel seats, the junction point of the center section of the tube with each wheel seat having the maximum wall thickness and graduall' tapering in thickness from each wheel seat to the thin wall center section, the junction of each wheel seat and journal bearing having the next greatest wall thickness, and a central portion of each wheel seat being of substantially the same wall thickness as the center section of the tube.

2. The method of making a railway car axle, comprising upsetting axially the end portions only of-a thin walled cylindrical tube to increase their wall thickness by permitting their inner surfaces to contract, the connecting central portion of said tube remaining substantially undisturbed, and then reducing the diameter of at least a portion of said end portions to further 3. The method of making a railway car axle,-

comprising upsetting axially the end portions only of a thin walled cylindrical tube whose out.-

side diameter issubstantially the same as that of the central portion of the axle formed therefrom, maintaining said original tube diameter during said upsetting whereby the inside diameter of said upset end portions is, decreased and their wall thickness is increased, and then reducing the diameter of said end portions to further thicken their walls and provide bearings and wheel seats.

4. The method of making a railway car axle, comprising upsetting axially the end portions only of a thin walled tube to increase their wall thickness while holding their outside diameter substantially constant whereby their inner surfaces are contracted, controlling the contour of said inner surfaces by an interior support during said upsetting, and then forging said end por-ltions while free of interior sup 't to further thicken their walls and form bearings and wheel seats. 1

5. The method of making a railway car axle, comprising upsetting axially the end portions only of a thin walled tube to increase their wall thickness while holding their outside diameter substantially constant whereby their inner surfaces are contracted, controlling the contour of said inner surfaces by an interior support during said upsetting to provide the maximum wall thickness at the inner end of each end portion with a gradual reduction in thickness outwardly away from that point, and then forging said end portions while free of interior support to further thicken their walls and form bearings and wheel seats.

6. The method of making a railway car axle, comprising heating two spaced portions of each end portion ofa thin walled tube, said; spaced portions and end portions being connected by cooler portions, upsetting said spaced heated portions axially of the tube to increasetheir wall thickness while holding their outside diameter substantially constant whereby their inner surfaces are contracted, then heating all of each of said end portions, and thereafter reducing the diameter of said heated end portions to thicken their walls and form bearings and wheel seats. 7 r

7. The method of making a railway car axle. comprising heating substantially uniformly the bearing and wheel seat formingportions only of a thin walled tube. the central portion of the tube remaining cool and being connected to the heated wheel seat forming portions by short portions increasing in temperature outwardly, up-

setting axially the heated portions to increase their wall thickness while holding their outside diameter substantially constant whereby their inner surfaces are contracted, and controlling the contour of said inner surfaces during said upsetting whereby to connect said wheel seat portions to said central portion. by a wall section tapering in thickness toward the central portion. I 8. The method of making a tubular railway car axle, comprising heating the wheel seat forming portions of a tube, maintaining the central portion of the tube cool, heating short portions of the tube connecting the central portion to said wheel seats to temperatures increasing outwardly toward the tube ends, and upsetting axially the heated portions to increase their wall thickness and contract their inner surfaces and to connect said inner surfaces to said central portion by surfaces diverging toward said central portion.

I BERTIS H. URSCI-IEZL.

HAROLD C. URSCHEL.