Axle Spindle Forming Method

1. Field of the Invention

The present invention relates to an improved apparatus and method for forming an axle spindle on a hollow axle blank.

2. Description of the Prior Art

Spindles are formed on the ends of axle blanks in order to mount associated wheels, usually by anti-friction bearings that minimize friction during wheel rotation. Axle blanks on which the spindles are formed usually have a hollow configuration of a round tubular shape whose diameter must be decreased at its end or ends in order to provide various reduced diameter portions, axial ridges, and tapered frustoconical surfaces that define the axle spindle. A conventional method for forming such axle spindles is by hot forging at three work stations. Each work station incorporates a pair of split dies used in the forging. At the first station, the split dies grip the blank about its heated end and an axial upsetter is utilized to form the blank material to conform with the interior of the split dies. A hanner operation is performed at the second station by the split dies thereof, one die being mounted stationary with the heated blank supported thereby, and the other die being movably supported to pound the blank between the dies. Another axial upsetter is utilized at the third station to shape and size the blank between the split dies of this station.

Rough axle forgings made by the split die process described above must be machined in order to complete the spindle forming process. This machining usually requires a first semirough cut prior to a semi-finish cut that preceeds a finishing step during which the spindle is polished. Prior to the material removal during these machining steps, a parting flash that is caused by the split die construction must first be removed from the forged spindle as well as scale builds up during the forging process. Care must be taken during this forging process to prevent internal voids from occurring in the forged axle spindle and to make sure that the inner and outer axle spindle surfaces are concentric with each other. Rotation of the axle blank between each pound at the second work station must be limited in order to prevent the internal voids from forming.

Axle spindle forming, forging and other forming, etc. are shown by U.S. Pat. Nos. 2,053,975, 2,165,472, 3,165,199, 3,327,513, 3,465,418, 3,580,038, 3,668,918 and 3,673,888.

An object of the present invention is to provide an improved apparatus and method for forming an axle spindle from a hollow axle blank. Advantages resulting from the axle spindle forming apparatus and method are tighter tolerance of the forged spindle so that subsequent machining requirements are reduced, elimination of parting flash present with the split die type of forging, concentricity of the inner and outer axle spindle surfaces formed on the axle blank, reduction of the tendency to form internal voids, and easy removal of scale that is formed on the axle spindle by heating during forging of the spindle as it is formed.

In carrying out the above object and other objects of the invention in order to obtain the advantages resulting therefrom, the axle spindle forming apparatus and method incorporate a hollow punch including a metallic body with an inner work surface and a mandrel fixed within a work opening of the punch body defined by its work opening. The mandrel projects from a closed end of the punch body toward an open end defined by the work surface in a spaced relationship to this surface. During forming of an axle spindle on a hollow axle blank, the punch is moved relative to the axle blank along the direction the mandrel projects so that the mandrel is received within the axle blank as the punch work surface forms a spindle about the mandrel. Since the hollow punch body completely surrounds the axle blank as the spindle is formed thereon, no parting flash is present on the formed spindle unlike axle spindles which are formed by split die type of forging operations. Likewise, the construction of the punch with its mandrel fixed within the hollow body provides concentricity of the inner and outer axle spindle surfaces formed by the punch.

Several of the hollow punches are preferably utilized to form the axle spindle in progressive steps. The metallic body of each punch has an elongated annular shape whose inner extremity provides the work surface that defines the work opening for receiving the axle blank during forming of the spindle. The mandrel of each punch also has an elongated shape with one end fixedly mounted at the closed end of the punch body and another tapered end located adjacent the open end of the body. Between its two ends, the elongated mandrel has a round outer surface about which the spindle is formed. Certain of the punches have annular work surface portions that are oriented in an axial direction with respect to the direction the mandrel projects so as to engage the axle blank in an endwise manner during the forming. All of the punches but the first one to initially form the axle blank have a smaller diameter work surface portion adjacent the closed end of the punch body than adjacent the open end.

Formation of the axle spindle preferably begins by heating the axle blank end to a hot forging temperature and then positioning the blank in a stationary manner so that the punch can be moved relative thereto to forge the axle spindle as the mandrel is received within the end of the axle blank with the punch body work surface forging the axle blank about the mandrel. A pair of cooperable gripper dies including gripping portions are preferably utilized to position the axle blank and define an elongated opening with a round cross section for slidably receiving and guiding the punch body during the punch movement that forges the axle spindle. The punch body has a sufficient length so its work surface extends past the heated portion of the axle blank end to the unheated portion before deformation occurs. A lubrication passage in the punch may be provided for introducing lubricant into the punch body work opening between its work surface and the outer surface of the mandrel. An undercut on the mandrel at a work station where considerable outward movement of the blank material takes place facilitates punch withdrawal.

In addition to eliminating parting flash present with the split die type of axle spindle forging and maintaining the concentricity of the inner and outer axle spindle surface, the apparatus and forging method of the invention have been found to provide tighter tolerance to the forged spindle so that subsequent machining requirements are reduced. Likewise, it has been found that there is a decreased tendency to form voids in the axle material during forming the spindle and that any scale which may be formed on the spindle can be removed much easier than with previous forging processes.

The objects, features and advantages of the present invention are readily apparent from the following detailed description of the preferred embodiment taken in connection with the accompanying drawings.

FIG. 1 is a sectional view through axle spindle forming apparatus constructed according to the invention and utilized according to the method thereof to form axle spindles on hollow axle blanks;

FIG. 2 is an enlarged view of a portion of FIG. 1;

FIG. 3 is a sectional view taken along line 3-3 of FIG. 2;

FIG. 4 is a perspective view of the type of axle blank that can be formed by the apparatus and method of the invention to include an axle spindle;

FIG. 5 is an enlarged view of another portion of FIG. 1;

FIG. 6 is a sectional view taken along line 6-6 of FIG. 5;

FIG. 7 is a perspective view of a completed axis spindle that is formed by the apparatus of the invention from the type of axle blank shown in FIG. 4; and

FIG. 8 is a partial perspective view of a hollow punch of the apparatus shown in FIGS. 4 and 6.

Referring to FIG. 1, apparatus that embodies the present invention and is used in accordance with the method thereof is collectively indicated by reference numeral 10 and includes four work stations 12a, 12b, 12c, and 12d. Hollow axle blanks 14, FIG. 4, are indexed through the work stations 12a, 12b, 12c, and 12d shown in FIG. 1 either manually or by a suitable conveyor mechanism so as to be formed thereby to include an axle spindle 16, FIG. 7, that is ready for a light finishing machining cut or polishing operation. Each work station includes a hollow punch 18a, 18b, 18c and 18d and cooperable axle blank grippers 20a, 20b, 20c and 20d used to form the axle spindles by a hot forging process. The punches 18a, 18b, 18c and 18d are mounted on a ram 22 that is power actuated to move to the left and to the right as shown by arrow A while the grippers 20a, 20b, 20c and 20d are mounted on a stationary support 24 so as to hold the axle blanks 14 against movement.

The punch 18b and its cooperable gripper 20b of work station 12b are further illustrated in FIGS. 2 and 3 while the punched 18d and its cooperable gripper 20d of work station 12d are further illustrated in FIGS. 5, 6 and 8. It is understood that the description and drawings regarding these further illustrated work stations 12b and 12d are also applicable to the work stations 12a and 12c, like reference numerals with the appropriate letter subscripts being used to identify like components and portions thereof of each work station.

With reference to FIGS. 2 and 3, the hollow punch 18b of work station 12b includes a metallic body 26b which has an elongated annular shape. A round outer surface 28b of the punch body 26b and a round inner work surface 30b cooperate to provide the annular punch body shape. Inner work surface 30b defines a work opening generally indicated by numeral 32b and having a first open end 34b as well as a closed second end 36b. A mandrel 38b of punch 18b is received within the punch body work opening 32b projecting from its closed end 36b toward its open end 34b. A first enlarged mandrel end 40b is fixed within a socket 42b of a threaded punch body end portion 44b. A threaded insert 46b press fitted into an opening 48b of the reciprocating ram 22 threadedly receives the punch body end portion 44b so that both the body end portion and the enlarged mandrel end 40b engage a wall 50b of the insert so as to fix both the punch and the mandrel to the ram. From its enlarged end 40b, mandrel 38b projects through a round hole 52b in the closed end of the punch body and has a round outer surface 54b extending to a second tapered mandrel end 56b. The mandrel surface 54b is located in a spaced relationship to the punch body work surface 30b so that the work opening 32b has an annular shape.

With particular reference to FIG. 3, the axle blank gripper 20b includes a pair of cooperable upper and lower gripper dies 58b and 60b that define an annular shape in the clamping position shown in FIG. 3. An overcenter toggle 62b mounts the upper die 58b for vertical movement between an upper nonclamping position and the lower clamping position where semi-circular die gripping portions 64, FIG. 2, cooperate to clamp the axle blank 14. To the right of its gripping portion 64 as viewed in FIG. 2, the upper and lower gripping dies 58b and 60b include semi-circular guide surfaces 66b that define an elongated guide opening of a round cross section for slidably receiving and guiding the metallic punch body 26b as the punch 18b is moved to the left by ram 22.

During the forging process, an axle blank 14 is heated to a hot forging temperature of about 2100.degree. F or so and after first being forged at the work station 12a in a manner subsequently described, the axle blank is positioned and clamped by the gripper 20b shown in FIGS. 2 and 3 ready for forging by the hollow punch 18b. Ram 22 is then actuated to move from the right toward the left to the position shown. During this movement toward the left, the outer end of punch body 26b is first received within the guide opening defined by the guide surfaces 66b of the upper and lower gripper dies 58b and 60b. The larger diameter open end 34b of punch body 26b slidably receives the end of axle blank 14 as the punch movement to the left proceeds at a conventional fast rate used in forging, the end of the axle blank then initially having the same diameter as the rest of the blank as shown at work station 12a in FIG. 1. As punch 18b proceeds moving toward the left, the work surface 30b impacts with the axle blank 14 and begins to form it about the outer surface 54b of mandrel 38b to the shape shown in FIG. 2. The length of punch body 26b is sufficiently long so that it extends past the red hot heated portion of the axle blank to its unheated portion before the impact and consequent material movement takes place. One impact with punch 18b completes the forging at work station 12b and the axle blank is then ready for indexing to the next work station.

As the forging proceeds in the manner described above, the hollow punch body 26b completely surrounds the axle blank 14 in a continuous manner so that its end being forged does not have any parting flash like that present during forging with conventional split dies. Likewise, the concentricity of the inner and outer axle spindle surfaces being formed can be maintained due to the fixed relationship of the mandrel 38b within the punch body 26b. It has also been found that there is a lessened tendency of the forging material to form internal voids than is the case with the more conventional split die type of forging and that any scale which is formed on the axle blank can much more easily be removed. With regard to the scale formed during the forging, it should be noted that the metallic body 26b of punch 18b includes a lubrication passage 68 cooperatively defined by a pair of perpendicular bores 70 so that a lubricant can be introduced into the punch between its work surface 30b and mandrel 38b prior to the forging. The lubricant may be an oil that is atomized and blown in with air so that the air removes any scale that may be present on the work surface or the mandrel while the oil adheres thereto ready to provide lubrication during the subsequent forging. It is also possible to flood the punch with a liquid oil lubricant that provides cooling as well as lubrication. Lubrication in either manner is particularly helpful at the work station 12b because there is a considerable amount of inward material movement as the axle blank 14 is forged at this work station. In this regard, it should also be noted that the closed end 36b of the punch body work opening 32b is axially spaced from the end of the axle blank 14 in the fully inserted punch position so that the material can flow axially without restraint and thereby accommodate for variances in the blank wall thickness. Also, the other punches likewise include similar lubrication passages although this is not shown in the drawings.

With reference to FIGS. 5 through 8, the axle blank 14 is forged to a semi-finished condition shown in FIG. 7 by the hollow punch 18d of work station 12d and its cooperable gripper 20d. Except for the configuration of its punch body work surface 30d and a few other modifications, the construction of hollow punch 18d is the same as the punch 18b previously described in connection with FIGS. 2 and 3 and the description thereof is thus applicable to the structure of work station 12d so as not to necessitate repetition of this description. The work opening 32d defined by the work surface 30d has a shape that is conjugate to the shape of the final axle spindle 16 being forged. This axle spindle after forging at work station 12d is in a semi-finished condition ready for a light machining cut or other finishing operation prior to use. It is possible to achieve the tolerances necessary to decrease the material removal due to the hollow punch construction with the internal mandrel about which the spindle is formed by the cooperable work surface. Likewise, as previously noted, the concentricity of the inner and outer spindle surfaces are maintained accurately, parting flash present with split die type of forging is eliminated, the tendency to have internal voids formed during the forging is reduced, and any scale that may be formed on the spindle is much more easily removed.

As seen by particular reference to FIG. 5, the mandrel 38d has a somewhat different configuration than the mandrel 38b shown in FIG. 2. This mandrel 38d is inserted through the round punch body hole 52d at work opening closed end 36d from the left toward the right rather than from the right toward the left as with the mandrel 38b shown in FIG. 2. End portion 40d of mandrel 38d is threaded into a nut 72 that axially seats against the punch body end portion 44d as well as with the insert wall 50d. At its left-hand tapered end 56d, mandrel 38d has a squared portion 74d that can be held by a wrench during tightening of nut 72. As the nut 72 is tightened, an enlarged diameter intermediate mandrel portion 76d is pulled into engagement with the punch body about the left-hand end of hole 52d so as to secure the mandrel in place. Tightening of the threaded punch body end portion 44d within the threaded insert 46d is also achieved by applying a wrench to the squared mandrel end portion 74d. An annular work surface portion 78d of mandrel portion 76d is oriented in an axial direction and engages the end of axle blank 14 during forging of the spindle 16 to ensure precise formation of the spindle end.

Intermediate its ends, the mandrel 38d shown in FIG. 5 includes an undercut 86d that facilitates withdrawal of the punch 18d after its impact with the heated axle blank. This undercut construction is particularly helpful at work stations where there is outward material movement, i.e. work station 12c as well as work station 12d.

With reference to FIG. 1, forging of the axle spindle begins at work station 12a as a heated tubular axle blank 14 is clamped by the gripper 20a. Work surface 30a of hollow punch 18a at this station has a uniform diameter and its axially oriented annular work surface portion 78a of mandrel 38a impacts the mandrel endwise to forge a thickened wall portion 80a that extends inwardly about a blunt end nose 82 of the tapered mandrel end portion 56a. The mandrel surface 54a may also have a slight inward taper toward the left depending on the particular configuration of the axle to be formed. As previously described, the hollow punch 18b at work station 12b forms the mandrel end portion to the right of thickened wall portion 80b inwardly about the mandrel 38b so as to have a reduced diameter shape that tapers outwardly toward the left. Subsequently, at work station 12c, the axially oriented annular work surface portion 78c impacts the mandrel end so that the work surface 30c can forge an annular ridge 84 that begins outward material movement for forming the final axle spindle shape to be forged. At the final work station 12d, the semi-finished axle spindle is forged in the manner previously described to complete the forging process.

In summary, many advantages are achieved by the spindle forming apparatus and method of the invention, namely; the tighter tolerance so that subsequent machining requirements are reduced, elimination of parting flash present with conventional split die forged spindles, concentricity of the inner and outer axle spindle surfaces formed, reduction of the tendency to form internal voids in the axle spindle material, and easy removal of scale caused by heating of the axle as it is formed by hot forging.

Of course, the relative movement between the axle blanks 14 and the punches 18a, 18b, 18c and 18d can be achieved by mounting the axle blanks on a movable ram and holding the punches stationary. However, moving the punches and holding the axle blanks stationary, as disclosed, is a more preferred way of forging the spindles. Likewise, although the advantages achieved are best obtained by use of the preferred apparatus and method disclosed, other apparatus and methods of using the same are possible for practicing the present invention as defined by the following claims: