US3424893A - Method and apparatus for forming a flange on thin shell bearings - Google Patents

Description

Jan. 28, 1969 H. W ANDERSON ND APPARATUS FOR FORMING A FLANGE HELL BE Sept. 2, 1965 H0 ward arczndey am 3 I m xii? 19 United States Patent 9 Claims ABSTRACT OF THE DISCLOSURE Flanges are formed on the shells or cups for thin shell bearings by a method generally comprising the steps of: placing each bearing shell or cup within a die set, partially closing the die set so that the bearing shell or cup is engaged therebetween, applying current through the die set to the shell until the edge at one end is heated to a plastic state and simultaneously withdrawing heat from the main portion of the bearing shell or cup to prevent overheating of such main portion, closing the die set further to deform the same edge into a radially inwardly directed flange, and permitting the heated flange to air harden. Preferably the bearing shell or cup has initially outwardly tapering side walls which are drawn into a cylinder upon cooling and shrinking of the heated flange.

My present invention relates to a bearing cup or shell which is adapted to enclose bearings, a cage and/ or seal, and to a method and apparatus for forming a flange on such a bearing cup or shell which has been hardened prior to formation of the flange.

In the manufacture of a hearing, such as a thin shell needle bearing, it is necessary to assemble the cage, rollers and/or seal within the open end of the cup or shell, which may be predrawn, prior to forming the closing flange which keeps the bearing elements in assembled relation. The forming of this flange, however, poses a diflicult manufacturing problem since the open end drawn cup must be heat treated (carbonitrided and hardened) prior to forming the flange, thus making it brittle and impossible to form cold without attendant cracking of the case hardened surface layer.

The conventional method of solving this problem is to copper plate the shell in the area where the forming is to be done in order to prevent the penetration of carbon during carbonitriding. As a consequence, the plated area remains in a soft or annealed condition so that the flange can be formed cold after the shell has been hardened. This solution, however, is costly both in time and equipment required. Furthermore, the flange of the assembled bearing unit does not have the same degree of hardness as the remainder of the shell.

Is an object of my present invention to provide a method and apparatus whereby a bearing cup or shell may be formed with a closing flange while in a hardened state without cracking.

It is a feature of my present invention that the formed flange is essentially as hard as it was before forming.

It is another feature of my present invention that the forming can be accomplished at a single station on an automatic assembly line, thus obviating secondary operations such as plating.

It is a further feature of my present invention that the closing operation requires a minimum of time; the total cycle time for positioning, forming and removing the bearing assembly is on the order of three seconds.

Now, in order to acquaint those skilled in the art with the manner of practicing my present invention, I shall describe in connection with the accompanying drawing a preferred embodiment of my invention.

In the drawing:

FIGURE 1 is a view, partly in setcion and partly in elevation, of a die set, in open position, used in practicing my present invention;

FIGURE 2 is an enlarged fragmentary sectional view of the upper die of the die set of FIGURE 1;

FIGURE 3 is an enlarged fragmentary sectional view of a bearing cup prior to formation of the closing flange;

FIGURE 4 is an enlarged fragmentary sectional View of the die set of FIGURE 1 in an initial or partially closed position; and

FIGURE 5 is a further enlarged fragmentary view of the die set of FIGURES 1 and 4 in a final or fully closed position.

Referring now to FIGURE 1, there is indicated generally by the reference numeral 10 a die set comprising an upper die assembly 12 and a lower die assembly 14.

The upper die assembly 12 may include, for example, a die 16 suitably secured to a die backup member 18, in turn, secured by flanges 20 and bolts 22 to a mounting plate 24. The upper die 16, which is preferably fabricated of tungsten carbide, is provided with a cavity 26 (FIG- URE 2) having a tapered side wall 28 and a bevelled corner wall 30. The various geometric parameters of the cavity 26 may be varied in accordance with the size of the bearing cup or shell on which a closing flange is to be formed and with the shape of flange desired.

The lower die assembly 14 may include, by way of illustration, a die 32 which incorporates a heat sink ring 34 and which is supported on a mounting plate 36. The lower die 32 and heat sink ring 34, which are provided with a cavity 38 for receiving a bearing cup or shell 40 to be formed, may each be of one-piece construction as shown or split diametrically whereby a clamping action may be imposed on the cup 40. The cup 40 is an open end, preferably drawn, steel cup which has been heat treated, i.e., carbonitrided and hardened. The side walls of the bearing cup 40 preferably taper outwardly in the direction of the open end as shown in FIGURE 3 for a purpose that will be described hereinafter, and the side walls of the cavity 38 are formed with a taper to accommodate the tapered cup.

The die set 10 is adapted to be mounted in a resistance welding machine, with the upper and lower die assemblies 12 and 14 serving as the electrodes of the machine. One welding machine that I have found satisfactory for my purposes is manufactured by National Electric Welding Machines Co., of Bay City, Mich, and is identified as NEMA #2-l2" projection welder. In mounting the die set 10 in a welding machine, the upper and lower mounting plates 24 and 36 are respectively secured in a conventional manner to the upper and lower platens of the machine. Because the welding machine itself forms no part of my present invention, I have deemed it unnecessary illustrate and describe the same.

In using the foregoing apparatus, and practicing the method of my present invention, the bearing cup 40, containing a cage 42, roller or needle bearings 44 and a seal 46, is first placed with the open end facing upwardly into the cavity 38 of the open die set as shown in FIGURE 1. Then, the upper die assembly 12 is moved downwardly to the position shown in FIGURE 4 until the walls of the cavity 26 engage the upper edge of the hearing cup 40 with sufficient pressure to maintain a satisfactory electrical contact. The required pressure is known as the counter balance pressure.

Next, current from a welding transformer is applied through the upper and lower die assemblies 12 and 14 to the cup 40 until the upper edge of the latter is heated to a plastic state. The metal within the current path is heated because of its resistance to the flow of current. The heat affected zone is minimized by permitting the bearing cup 40 to protrude from the cavity 38 only to the extent necessary to allow forming of the closing flange. Also, the heat sink ring 34 serves to draw heat away so the main portion of the cup 40 does not become overheated.

After the upper edge of the cup 40 has been heated to the plastic stage, the counter balance pressure is released, and the die set is fully closed. In this step, the upper die assembly 12 is moved downwardly with sufficient force pressure to cause the walls of the cavity 26 to deform the upper edge of the cup 40 into a radially inwardly directed closing flange 48 as shown in FIGURE 5. Because the flange 48 is heated and then formed in an enclosed die set, the flange shrinks upon cooling. This shrinkage draws the tapered side walls of the cup 40 into a cylinder. Thus,

'pre-tapering of the cup 40 serves to compensate for shrinkage of the flange 48.

Finally, the die set is opened and the bearing assembly is removed. The reheated area of the cup 40 tends to air harden so that the formed flange 48 is essentially as hard after forming as it was before forming. This is especially advantageous where a steel cage or rollers rub against this flange, because the hardened surface has greater wear resistance than a soft or annealed surface. It will be appreciated that the principles of my present invention may be used in connection with a bearing shell having an open bottom and a lower retaining flange, as well as with a bearing cup having a closed bottom as shown. Also, the interior bearing elements 42, 44 and 46 may the rearranged within the cup 40, or certain of these interior elements may even be eliminated, Without affecting the application of my invention.

While I have shown and described what I believe to be a preferred embodiment of my present invention, it will be understood by those skilled in the art that various rearrangements and modifications may be made therein without departing from the spirit and scope of my invention.

I claim:

1. A method of forming a flange at one end of a thin hardened steel bearing shell, comprising the steps of: placing the bearing shell within a die set, partially closing said die set so that said bearing shell is engaged therebetween, applying current through said die set to said shell until the edge at said one end is heated to a plastic state and simultaneously withdrawing heat from the main portion of said shell to prevent overheating of the latter, closing said die set further to deform said edge of said shell into a radially inwardly directed flange, and per mitting said heated flange to air harden.

2. A method of forming a flange at one end of a thin hardened steel bearing shell having side walls tapering outwardly in the direction of said one end, comprising the steps of: placing the bearing shell within a die set, partially closing said die set so that said bearing shell is engaged therebetween, applying current through said die set to said shell until the edge at said one end is heated to a plastic state and simultaneously withdrawing heat from the main portion of said shell to prevent overheating of the latter, closing said die set further to deform said edge of said shell into a radially inwardly directed flange, and permitting said heated flange to cool whereupon shrinkage thereof draws said side walls of said shell into a cylinder.

3. A method of forming a flange at the open end of a thin hardened steel bearing shell having side walls, comprising the steps of: placing the bearing shell in engagement with a lower die, moving an upper die downwardly to engage the upper edge of said bearing shell to maintain an electrical contact, applying current through said upper and lower dies which serve as electrodes to said shell until said upper edge is heated to a plastic state and simultaneously withdrawing heat from said side walls to prevent overheating of said side walls, moving said upper die downwardly with sufficient pressure to deform said upper edge of said shell into a radially inwardly directed flange, and permitting said heated flange to cool.

4. A method of forming a flange at the open end of a thin hardened steel ibearing shell having side walls, comprising the steps of: placing the bearing shell with the open end facing upwardly into the cavity of a lower die, moving an upper die having a cavity therein downwardly to engage the upper edge of said bearing shell to maintain an electrical contact, applying current through said upper and lower dies which serve as electrodes to said shell until said upper edge is heated to a plastic state and simultaneously withdrawing heat from said side walls to prevent overheating of said side walls, moving said upper die downwardly with suflicient pressure to cause the walls of the cavity therein to deform said upper edge of said shell into a radially inwardly directed flange, and permitting said heated flange to cool.

5. A method of forming a flange at the open end of a thin hardened steel bearing cup having side walls tapering outwardly in the direction of the open end, comprising the steps of: placing the bearing cup with the open end facing upwardly into the cavity of a lower die, moving an upper die having a cavity therein downwardly to engage the upper edge of said bearing cup to maintain an electrical contact, applying current through said upper and lower dies which serve as electrodes to said cup until said upper edge is heated to a plastic state, and simultaneously withdrawing heat from the main portion of said cup to prevent overheating of the latter, moving said upper die downwardly with sufficient pressure to cause the walls of the cavity therein to deform said upper edge of said cup into a radially inwardly directed flange, and permitting said heated flange to cool whereupon shrinkage thereof draws said side walls of said bearing cup into a cylinder.

6. A method of forming a closing flange at the open end of a thin hardened steel bearing cup having side walls tapering outwardly in the direction of the open end, comprising the steps of: placing the main portion of said bearing cup with the open end facing upwardly into the cavity of a lower die, moving an upper die having a cavity therein downwardly to engage the upper edge of said bearing cup with suflicient pressure to maintain a satisfactory electrical contact, applying current through said upper and lower dies which serve as electrodes to said cup until said upper edge is heated to a plastic state, simultaneously withdrawing heat through said lower die from said main portion of said cup to prevent overheating of the latter, releasing said pressure, moving said upper die downwardly with suflicient pressure to cause the Walls of the cavity therein to deform said upper edge of said cup into a radially inwardly directed closing flange, and permitting said heated flange to cool whereupon shrinkage thereof dr aws said side walls of said bearing cup into a cylinder.

7. Apparatus for forming a flange at the one end of a thin hardened steel bearing shell, comprising a die set for receiving a bearing shell, said die set serving as electrodes whereby current may be passed therethrough to the shell to heat the one end of the shell, said die set incorporating means for simultaneously withdrawing heat from the main portion of said shell to prevent overheating of the later, and said die set being closable to deform the heated end of the shell into a radially inwardly directed flange.

8. Apparatus for forming a flange at the open end of a thin hardened steel bearing cup, comprising a lower die receiving a bearing cup, an upper die being initially movable downwardly to engage the upper edge of the bearing cup, said upper and lower dies serving as electrodes whereby current may be passed therethrough to the cup to heat the upper edge of the cup, said lower die incorporating means for simultaneously withdrawing heat from the main portion of the cup to prevent overheating of the latter, and said upper die being subsequently movable downwardly to deform the upper edge of the cup into a radially inwardly directed flange.

9. Apparatus for forming a flange at the open end of a thin hardened steel bearing cup, comprising a lower die having a cavity therein with side walls tapering outwardly for receiving a bearing cup, an upper die having a cavity therein and being initially movable downwardly to engage the upper edge of the bearing cup, said upper and lower dies serving as electrodes whereby current may be passed therethrough to the cup to heat the upper edge of the latter, said lower die incorporating means for simultaneously withdrawing heat from the main portion of the cup to prevent overheating of the latter, and said upper die being subsequently movable downwardly to cause the 6/1932 Ra-bezzana 219149 X 3/1938 Middleton 219149 X RICHARD M. WOOD, Primary Examiner.

B. A. STEIN, Assistant Examiner.

US. Cl. X.R. 2195O

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