Longitudinal component with mass accumulations

Abstract

A method for forming a longitudinal component (1) with mass accumulation at each end thereof from an elongate blank. The method comprising, placing the blank in a cavity of a die means (20) having a longitudinal axis about which is disposed a plurality of movable forming elements (6, 7, 8, 9, 10, 11 etc), and at least first and second movable abutment elements spaced apart and disposed on the longitudinal axis at opposite ends of the cavity. Moving the forming elements into engagement with a central portion (2) of the blank thereby squeezing and narrowing the blank in the central portion, and urging resultant mass accumulations towards each end of the blank. Also relatively moving the first and second abutment elements (16, 17) towards each other along the longitudinal axis to engage with mass-accumulations at respective opposite ends of the cavity. This in combination with the forming elements determines the final form of the component.

Description

TECHNICAL FIELD

[0001] This invention relates to an apparatus and method for manufacture of a longitudinal component with mass accumulations at each end. The longitudinal component may be used as a preform for the manufacture of parts with mass accumulations at each end, such as automotive steering rods and connecting rods. The invention is described with an embodiment suited to the manufacture of a component that can be used as preform for the manufacture of a flashless metal automotive connecting rod.

BACKGROUND

[0002] Connecting rods for internal combustion engines typically include a crank end and a pin end interconnected by a body portion. Such connecting rods are typically made by one of three primary metal forming processes, which are “conventional hot forging”, “casting” and “powder metal forming and machining”. A more recent forging process is a flashless forging process in which a preform is induction heated prior to undergoing a sequence of forging steps. U.S. Pat. No. 5,544,413(Stevens et al.) describes such a flashless forging process for manufacturing a connecting rod, as well as providing details on the earlier mentioned three primary metal forming processes typically used to manufacture connecting rods.

[0003] An advantage of flashless forging a connecting rod is that only a precise quantity of raw material is used for the preform, virtually eliminating flash that would otherwise result on the finished forging and the need for a secondary trim operation. Another advantage, is that the weight is precisely controlled, thereby allowing shaping substantially close to the final component stage.

[0004] The preform shown in FIG. 2 of U.S. Pat. No. 5,544,413 is of a generally cylindrical cross-section and is constructed from a high carbon steel or other suitable material. It can be manufactured by a number of known techniques such as extruding, cross-rolling, machining or a combination of techniques. A problem associated with such a preform, is that whilst it has a body having first and second ends, it requires a heating operation to achieve a forging temperature in the range of 1700° F.-2250° F., prior to forging in at least three steps to achieve a finished form. This makes it a four step shaping operation if the step to make the preform is counted.

[0005] It would be more desirable to start with a preform for use in flashless forging process, where the preform is a longitudinal component with mass accumulations at each end that more closely approximates the desired shape of the connecting rod to be forged. This would allow for at least one forging step and heating operation to be eliminated.

[0006] The present invention is directed to an apparatus and method for manufacture of a longitudinal component with mass accumulations from bar stock of constant cross section.

SUMMARY OF INVENTION

[0007] In a first aspect the present invention consists in a method for forming a longitudinal component with mass accumulations at each end thereof from an elongate blank, said method comprising

[0008] (i) placing said blank in a cavity of a die means having a longitudinal axis about which is disposed a plurality of movable forming elements, said die means also having at least first and second movable abutment elements spaced apart and disposed on said longitudinal axis at opposite ends of said cavity;

[0009] (ii) moving said forming elements into engagement with a central portion of said blank, thereby squeezing and narrowing said blank in said central portion, and urging resultant mass accumulations towards each end of said blank; and

[0010] (iii) relatively moving said first and second abutment elements towards each other along said longitudinal axis to engage with mass-accumulations at respective opposite ends of said cavity, which in combination with said forming elements determine the final form of said component.

[0011] Preferably at least four of said forming elements are primary forming elements pivotally movable inwardly about respective axes which are at right angles to said longitudinal axis during step (ii) of the method.

[0012] Preferably at least four of said forming elements are secondary forming elements each of which engage said blank in a region adjacent to the central portion of said blank between two primary forming elements.

[0013] Preferably at least four of said forming elements are tertiary forming elements each of which are movable to a respective primary forming element and engage with the blank at or near said first abutment element.

[0014] Preferably said elongate blank is of substantially constant cross section.

BRIEF DESCRIPTION OF DRAWINGS

[0015] FIG. 1 is a perspective view of a first embodiment of the shape of a preform to be manufactured according to the present invention;

[0016] FIG. 2 is a perspective view of die assembly for forming the preform shown in FIG. 1.

[0017] FIGS. 3(a)-(e) are schematic views of a portion of die assembly viewed in direction A of FIG. 2.

[0018] FIGS. 4(a)-(c) are schematic plan views of two adjacent primary forming elements and a secondary forming element of the die assembly as they engage the blank.

MODE OF CARRYING OUT THE INVENTION

[0019] FIG. 1 depicts an embodiment of a longitudinal component 1, which has a narrow central portion 2, with mass accumulations at each end 3,4 thereof. Component 1 is suitable for use as a preform for flashless forging a connecting rod for an internal combustion engine.

[0020] FIGS. 2-4 depicts a die assembly 20 used to manufacture component 1, from a blank 5, of steel round bar.

[0021] FIG. 2 depicts a die assembly 20 used to manufacture component 1, from a blank 5 of round bar. Die assembly 20 has a cavity 18 with a longitudinal axis Z, which is surrounded by four primary forming elements 6,7,8,9 and four secondary forming elements. For ease of clarity, only two of the secondary forming elements 10, 11 are shown. Die assembly 20 also has four tertiary forming elements, only two of which are shown as tertiary forming elements 13, 15. Die assembly 20 also has two abutment forming elements 16, 17.

[0022] Primary forming elements 6, 7 are a first pair of dies, whose forming faces are opposed to each other about longitudinal axis Z in cavity 18. Primary forming elements 8,9 are a second pair of dies, whose forming faces are also opposed to each other about longitudinal axis Z in cavity 18. The first pair of primary forming elements 6,7 are disposed at right angles to the second pair of primary forming elements 8,9, thereby spacing each of the four primary forming elements 6,7,8 and 9 equally at 90° about axis Z.

[0023] The operation of die assembly 20 will now be described with reference to FIGS. 3(a)-3(f) which only show the first pair of primary forming elements 6,7, respective tertiary forming elements 12,13 and abutment forming elements16, 17 about cavity 18, in which blank 5 is formed into component 1. FIG. 3(a) shows the closed position of the various die elements about cavity 18, which has a profile similar to the finished profile of component 1. The dotted outline 5a represents the original position of bar 5. Primary forming elements 6,7 are rotatably movable about their respective pivotal axes 6′ and 7′, which are parallel and disposed at right angles to axis Z. Tertiary forming elements 12, 13 are linearly movable to the respective primary forming elements 6,7, and abutment forming elements 16, 17 are linearly movable along axis Z.

[0024] FIG. 3(b) shows the various positions of the forming elements immediately after die assembly 20 has been opened and a blank bar 5 has been placed within cavity 18. FIGS. 3(c)-3(e) show the closure of the various forming elements in a step by step basis. As primary forming elements 6,7 gradually close inwardly, their respective convexly contoured forming faces 21,22 engage and squeeze central region 19 of blank 5, thereby urging some of the centrally located mass of blank 5 downwardly towards abutment element 16 and upwardly towards abutment element 17. As primary forming elements 6,7 squeeze blank 5, tertiary forming elements 12, 13 slide inwardly and in combination with the inward movement of abutment forming elements 16, 17 along axis Z, create the final shape of cavity 18, which results in blank 5 being formed into component 1 with mass accumulated ends 3,4.

[0025] Whilst the operation of die assembly 20 shown in FIGS. 3(a)-(f) has been, described with reference to the first pair of primary forming elements 6,7, and their associated tertiary forming elements 12, 13, it should be understood that the second pair of primary forming elements 8,9 and their associated tertiary forming elements also close inwardly on blank 5, simultaneously with the first pair of primary forming elements 6,7, and their associated tertiary forming elements 12, 13.

[0026] Also, for ease of clarity and reference, FIGS. 3(a)-(f) do not show the operation of secondary forming elements 10, 11 shown in FIG.2. During closure of die assembly 20, as the primary forming elements move pivotally inwardly to engage with blank 5, so do the secondary forming elements. Their operation will now be described with reference to FIGS. 4a-4(c), in which secondary forming element 11 is disposed between primary forming elements 7 and 8. As shown in FIG. 4(a), secondary forming element 11 moves linearly inwardly along with primary forming elements 7 and 8 towards blank 5. It engages with blank 5 along a longitudinal front between primary forming elements 7 and 8, thus preventing flash occurring therebetween as shown in FIG. 4(b) and in enlarged detail in FIG. 4(c). It should be understood that each two adjacent primary forming elements has a secondary forming element, operationally arranged in a similar manner to that shown in FIGS. 4a-4(c).

[0027] It should be understood that the forming of component 1 with mass-accumulated ends 3,4 is achieved without any substantial loss of material. In this preferred embodiment, component 1 can be readily used as a preform for flashless forging a connecting rod for an internal combustion engine, in which at least one forging step and the heating operation of the preform is eliminated when compared to the prior art U.S. Pat. No. 5,544,413.

[0028] Whilst in the above mentioned embodiment, tertiary forming elements 12, 13 which act in combination with abutment element 16 as shown in FIG. 3(a), are only shown on the lower portions of the respective primary forming elements 6,7. It should be understood that in another not shown embodiment, the primary forming elements may have similar tertiary forming elements associated therewith acting in combination with abutment element 17.

[0029] Also, whilst in the above mentioned embodiment the secondary forming elements 10, 11 move linearly inwardly on blank 5, it should be understood that in other not shown embodiments the movement could be pivotal movement, or a combination of linear and pivotal movement.

[0030] It should also be understood that whilst the present embodiment of die assembly 20 utilises four primary forming elements and four secondary forming elements, in another not shown embodiment the die assembly may have only three primary forming elements disposed at 120° intervals about axis Z, thereby only requiring three secondary forming elements.

[0031] It should also be understood that whist the above mentioned embodiment has been described with blank 5 being round bar, in other embodiments blank 5 may have any suitable substantially constant cross section.

[0032] A “longitudinal component” as referred to herein is a component having a longitudinal axis.

Claims

1. A method for forming a longitudinal component with mass accumulations at each end thereof from an elongate blank, said method comprising

(i) placing said blank in a cavity of a die means having a longitudinal axis about which is disposed a plurality of movable forming elements, said die means also having at least first and second movable abutment elements spaced apart and disposed on said longitudinal axis at opposite ends of said cavity;

(ii) moving said forming elements into engagement with a central portion of said blank thereby squeezing and narrowing said blank in said central portion, and urging resultant mass accumulations towards each end of said blank; and

(iii) relatively moving said first and second abutment elements towards each other along said longitudinal axis to engage with mass-accumulations at respective opposite ends of said cavity, which in combination with said forming elements determine the final form of said component.

2. A method as claimed in claim 1, wherein at least four of said forming elements are primary forming elements pivotally movable inwardly about respective axes which are at right angles to said longitudinal axis during step (ii) of the method.

3. A method as claimed in claim 1, wherein at least four of said forming elements are secondary forming elements each of which engage said blank in a region adjacent to the central portion of said blank between two primary forming elements.

4. A method as claimed in claim 1, wherein at least four of said forming elements are tertiary forming elements each of which are movable to a respective primary forming element and engage with the blank at or near said first abutment element.

5. A method as claimed in claim 1, wherein said elongate blank is of substantially constant cross section.