Patent Publication Number: US-6905054-B2

Title: Method and apparatus for fracturing connecting rods and the like

Description:
This application is a continuation of Ser. No. 08/750,909 filed on Jan. 10, 1997 which is a national phase filing from a PCT international patent application no. PCT/US95/03620 filed on Mar. 22, 1995, which claimed priority to Ser. No. 08/220,490, filed Mar. 31, 1994, granted as U.S. Pat. No. 5,503,317. 

   This invention relates to the fracture separation, into a bearing cap and a connecting rod, of an integral preform, while ensuring that the separated pieces will be capable of re-unification, in a high production environment. 
   BACKGROUND OF THIS INVENTION 
   Numerous methods have been employed to separate connecting rod preforms by fracturing, both in laboratory and production environments. These include cryogenic cooling or electron beam exposure to embrittle the fracture area, fracturing by wedge actuation of an expanding mandrel, and linear opposing pulling forces to separate the bearing cap from the connecting rod preform. The following patents are representative of the prior art:
         U.S. Pat. No. 4,569,109, issued Feb. 11, 1986;   U.S. Pat. No. 4,768,694, issued Sep. 6, 1988;   U.S. Pat. No. 4,993,134, issued Feb. 19, 1991.       

   Despite these prior developments, certain elements vital to fracture separation continue to have the greatest influence on the quality of the finished connecting rod. Two of these elements are:
         (1) achieving simultaneous fracture along the cracking plane of both legs of the connecting rod. Failure to achieve simultaneous fracture is likely to result in plastic deformation of the crank bore and inhibit re-mating of the two parts;   (b) maintaining positive control over the position of the separated bearing cap and connecting rod body, to ensure accurate micro-alignment during re-mating. Failure to do this may negate the inherent advantages of fracture separation.       

   GENERAL DESCRIPTION OF THIS INVENTION 
   The present invention provides an apparatus and a process for accomplishing the fracture separation, into a bearing cap and a connecting rod, of an integral preform, the latter being composed of powdered metal, cast iron, forged steel, aluminum or any other material suitable for use as a connecting rod. The process of this invention is conducted under ambient conditions and requires no prior embrittlement of the preform, as called for by earlier developments utilizing cryogenic chilling or electron beam hardening. 
   However, a stress-riser is required to control the location of fracture initiation (i.e. the location of the joint line). The stress-riser may be provided in a prior process by way of (a) V-notch broaching or other equivalent machining means, (b) laser etching, or (c) preforming a stress-riser in the “green” preform prior to firing (baking) and forging. 
   The present process utilizes a work-holding fixture which retains and locates the connecting rod preform with respect to its manufacturing datum features. The mechanism includes a dual slide ram coupled to a unilateral wedge interposed between a two-piece mandrel which, when activated, effects the fracture separation of the preform into a bearing cap and the connecting rod. 
   A further aspect of this process is the ability of the work-holding fixture to locate the pre-separated connecting rod preform on the manufacturing datum features, and to maintain this location throughout separation and re-mating. This goal is achieved by constructing the work-holding feature on a precision slide. A lower portion of the work-holding fixture, which rigidly secures the connecting rod body, is affixed to the slide and restrains the connecting rod against any movement. The upper portion of the work-holding fixture, which locates and retains the bearing cap of the ultimate connecting rod, is affixed to a slide saddle movable on the precision slide. 
   This arrangement allows the bearing cap to move independently of the connecting rod body during separation, while continuing to maintain its precision location with respect to the connecting rod body. The arrangement of the present invention further eliminates any tendency for the bearing cap to rotate during separation, thus promoting simultaneous fracture of both of the connecting rod legs. The re-mating of the separated bearing cap to the connecting rod body is passively accomplished by spring loading the upper portion of the work-holding fixture to return it to its pre-fracture position. Subsequent to the fracture separation and re-mating of the bipartite connecting rod, the work-holding fixture, with is re-mated connecting rod still retained and located, can index out of the separation area for fastener insertion and further processing as required. 
   More particularly, this invention provides an apparatus for the fracture separation, into a bearing cap and a connecting rod, of an integral preform which is configured to define a cylindrical aperture and two spaced-apart bolt seat shoulders, the apparatus comprising: 
   a base member; 
   a guide member fixed with respect to said base member, the guide member defining a first guideway extending in a first direction, 
   a first slide member mounted to said guide member for sliding movement along said first guideway in said first direction, the first slide member defining a second guideway also extending in said first direction, 
   a second slide member mounted to said first slide member for sliding movement with respect to said first slide member along said second guideway in said first direction, 
   a mandrel which is split to define an upper part fixed with respect to the first slide member and a lower part fixed with respect to said base member, said upper part being movable between a first position in which it is spaced away from the lower part and a second position in which it is juxtaposed against the lower part to define a substantially cylindrical body having its axis lying substantially in a second direction perpendicular to said first direction, movement of said upper part being simultaneous with movement of the first slide member along the first guideway with respect to said guide member, the upper and lower parts of said mandrel defining an internal tapered passageway, 
   a wedge member adapted, when the upper part is in its second position, to enter said tapered passageway and force said mandrel parts apart, 
   power means for moving said wedge member, 
   projections defined by said second slide member and adapted to contact the bolt seat shoulders of an integral preform while the cylindrical aperture thereof receives the split mandrel, and 
   means for selectively urging the second slide member toward the mandrel, thereby securely holding the integral preform in place, 
   whereby the wedge member can enter the tapered passageway, forcing the mandrel parts apart and fracturing the preform into a bearing cap and a connecting rod. 
   Further, this invention provides a process for the fracture separation, into a bearing cap and a connecting rod, of an integral preform which is configured to define a cylindrical aperture and two spaced-apart bolt seat shoulders, the process comprising: 
   a) fitting they cylindrical aperture of the preform over a substantially cylindrical mandrel which includes separate upper and lower parts, 
   b) holding the preform in place over the mandrel by pressing against the bolt seat shoulders in the direction toward the mandrel, and 
   c) forcing the mandrel parts apart while holding the preform in place, thereby to fracture the preform into a bearing cap and a connecting rod. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     One embodiment of this invention is illustrated in the accompanying drawings, in which like numerals denote like parts throughout the several views, and in which: 
       FIG. 1  is an elevational view looking at the front of the separation station in a direction perpendicular to the direction of transfer; 
       FIG. 2  is a side elevational view, looking at the separation station from a direction at right angles to the direction of  FIG. 1 , and is partly broken away to show a section along the line  2 — 2  in  FIG. 3 ; 
       FIG. 3  is a horizontal sectional view taken at the line  3 — 3  in  FIG. 2 , and the line  3 — 3  in  FIG. 1 ; and 
       FIG. 4  is a view similar to that of  FIG. 2 , showing a variant of the element causing the fracture separation. 
   

   DETAILED DESCRIPTION OF THE DRAWINGS 
     FIG. 1  illustrates, in broken lines, a pre-separated preform  1 A integrally incorporating a connecting rod  1  and a bearing cap  2 , located and secured in a separation station work-holding fixture  3 . It is to be noted that the preform  1 A is configured to define a cylindrical aperture  6  and two spaced-apart bolt seat shoulders  8  and  9 , this being the typical construction. 
   One of the key features of the fixture  3  is the attainment of a three-point, wedge-locked retention for the bearing cap  2 , both before and after fracturing. This is accomplished through the use of a small slide assembly  4 , which is best understood by comparing  FIGS. 2 and 3 . 
   A slide unit  21  is mounted for horizontal movement along the direction of the arrow  21 A. Secured to the slide unit is a base member  30  which is integral with the lower part  19  of a split mandrel (the remainder of which will be described subsequently), and a guide member  18 . Defined by the guide member  18  is a first guideway  18 B which has two oppositely extending rectangular recesses  18 A (See FIG.  3 ). The guideway  18 B extends in a direction perpendicular to the arrow  21 A. 
   A first slide member  5  is mounted to the guide member  18  for sliding movement along the first guideway  18 B in the vertical direction (arrow  5 A in the drawings), and itself contributes to defining a second guideway  5 B, parallel with the direction of the first guideway. The second guideway  5 B extends in the vertical direction intermediate lateral edges  5 C of the first slide member  5 . In  FIG. 3 , which is a horizontal section through the upper part of the assembly shown in  FIG. 2 , a second slide member  10  of rectangular section in its upper portion is trapped between the first slide member  5  and a slide assembly cover  12 . In  FIG. 3 , the cover  12  defines a rectangular recess  12 A and has lateral projections  12 B for securely location the cover  12  on the first slide member  5 . As can also be seen in  FIGS. 1 and 3 , threaded fasteners  13 A are utilized to secure the cover  12  against the first slide member  5 . 
   As illustrated in  FIG. 2 , the first slide member  5  integrally supports an upper part  7 A of a split mandrel  7 , from which it will be understood that, when the first slide member  5  moves upwardly with respect to the guide member  18 , the upper part  7 A of the split mandrel  7  moves upwardly away from the lower part  19 . It will further be noted that the axis of the split mandrel  7  lies in a direction substantially parallel to the arrow  21 A, and is thus substantially perpendicular to the first guideway  18 B. 
   As further illustrated in  FIG. 2 , the upper and lower parts  7 A and  19  of the mandrel  7  together define an internal tapered passageway shown in broken lines at  19 A, the passageway  19 A being such as to accept a wedge member  20  which, when driven to the left in  FIG. 2 , forces the mandrel parts  7 A and  19  apart. It is to be noted that the passageway  19 A has a substantially horizontal lower portion  19 B and a sloping upper portion  19 C, and that the leftward end of the wedge member  20  is correspondingly configured. The purpose for this configuration is to avoid downward force against the lower part  19 , and to maximize upward force against the upper part  7 A. 
   Power means for moving the wedge member  20  in  FIG. 2  is illustrated schematically as a hydraulic or pneumatic cylinder  32 . As an alternative, the wedge member  20  may be actuated by a slaved spring motion of known construction (not illustrated). 
   In an alternative construction, illustrated in broken lines in  FIG. 4 , a wedge  20 A can first come into direct contact with the tapered passageway at a low force level, creating a pre-load upon the contact surfaces of the internal tapered passageway, whereupon a separate high-velocity ram  33  could impact upon the wedge  20 A, thus causing separation of the preform into a cap and a rod. The pre-load by the wedge has the effect of taking up all slack, and leaving no free travel or lost motion in the upper and lower parts  7  and  19  defining the internal tapered passageway  19 A. In  FIG. 4 , the ram  33  is the end of a piston  33 A moving in a cylinder  33 B. The position of the wedge  20 A is controlled by an auxiliary cylinder  23  acting on a schematically illustrated flange  24  secured to the wedge  20 A. 
   Referring now to  FIGS. 1 and 2 , the second slide member  10  has a widened portion  34  at the bottom, the portion  34  supporting projections  36  and  38  which are adapted to contact the bolt seat shoulders  8  and  9  while the cylindrical aperture  6  in a preform  1 A receives the split mandrel  7 . 
   Means are provided, utilizing a camming member  11 , for selectively urging the second slide member  10  toward the mandrel  7 , thereby securely holding the integral preform  1 A in place. In  FIG. 1 , short hatch lines on portions  7 A,  36  and  38  show the three-point “capture” of the upper part of the preform  1 A. 
   It will now be understood that, when the wedge member  20  enters the tapered passageway  19 A, it forces the mandrel part  7 A upwardly away from the part  19 , thereby fracturing the preform  1 A into a bearing cap and a connecting rod. 
   The camming member  11  will now be described in greater detail. The cover  12  defines a horizontal, rectangular passage  11 A to either side of the recess  12 A. The camming member  11  is a Z-shaped cam adapted to be moved by a force along the arrow  13 . The upper part of the second slide member  10  is machined to define a sloping passageway  40  for receiving a central part  42  of the cam, having the same slope as the passageway  40 . It will be understood that, as the camming member  11  moves leftwardly (as seen in FIG.  1 ), the second slide member  10  will move downwardly. 
   Illustrated schematically in  FIG. 1  are locate and retention locators  14 - 17 . The locators  14  and  15  are fixed or static, whereas the retainers  16  and  17  are dynamic clamps that apply a constant force leftwardly on the preform, seating it firmly against the locators  14  and  15 . 
   More particularly, the locators  14 - 17  include a first static locator  14  adapted to contact one side of the portion of the preform  1 A which is intended to become the bearing cap, and a second static locator adapted to contact one side of the portion of the preform  1 A intended to become the connecting rod. On the right in  FIG. 1 , the dynamic locator  16  is adapted to contact the other side of the portion of the preform  1 A which is intended to become the bearing cap, while the second dynamic locator  17  is adapted to contact the other side of the portion of the preform  1 A which is intended to become the connecting rod. The dynamic locators  16  and  17  can be urged leftwardly by the use of resilient means, such as springs. The locators  14  and  16  are mounted on the base member  30 . It will thus be seen that the locators remain engaged with the preform (the connecting rod components) throughout the fracture and separation cycle. 
   Utilization of the illustrated apparatus may be defined as a process for the fracture separation, into a bearing cap and the connecting rod, of an integral preform configured to define a cylindrical aperture and two spaced-apart bolt seat shoulders. The process involves first fitting the cylindrical aperture of the preform  1 A over the substantially cylindrical mandrel  7  that includes separate upper and lower parts  7 A and  19  respectively, then holding the preform  1 A in place on the mandrel  7  by causing the projections  36  and  38  to press downwardly against the bolt seat shoulders  8  and  9  respectively in the direction toward the mandrel than forcing the parts  7 A and  19  apart (while holding the preform  1 A in place) thereby fracturing the preform  1 A into a bearing cap  2  and a connecting rod  1 . Upon fracture, caused by the high-velocity of the wedge member  20  entering between the mandrel halves  7 A and  19 , the following portions move vertically upward: the first slide member  5  with its integral part  7 A of the split mandrel  7 ; the cover  12 , the second slide member  10 , the can member  42 , the locators  14  and  16 , and the bearing cap  2  (which has been split from the connecting rod  1 ). The following parts remain stationary: the lower part  19  of the expanding mandrel  7 , the guide member  18 , the base member  30  and the slide unit  21 . 
   Immediately upon completion of fracture separation, the wedge member  20  is withdrawn from between the mandrel halves  7 A and  19 , allowing the first slide member  5  to return to its pre-separation position. Actuation to return the first slide member  5  downwardly utilizes a linear force device shown schematically at  44 . The linear force device  44  may he any known device, such as springs, cylinders, etc., or gravitation. 
   It will no be understood that the apparatus and process described above allow the bearing cap  2  to be fracture-separated from the connecting rod body  1 , while all throughout the separation and re-mating process the location uniqueness of the bearing cap  2  with respect to the connecting rod body  1  is maintained. 
   With respect to the slide unit  21  seen in  FIG. 2 , its purpose is 1) to bring the equipment required to separate and re-mate the connecting rod bipartite while it is located and retained in the part carrier, and 2) to perform separation and re-mating, and then withdraw from the connecting rod bipartite, leaving it located and retained as it was prior to separation. 
   While this invention has been described and illustrated with the connecting rod preform  1 A in a vertical attitude, the particular part attitude is not a limitation of this invention. The process outlined above can be carried out with the connecting rod in any desired attitude. Of course, the various slides, actuators, clamps, locators and directions of motion, as previously described, would change their attitudes in a similar way, in order to keep the relative motions and directions consistent. 
   A detailed description of the process follows: 
   Firstly, the locators  14 - 17  are activated to grip the preform. 
   Secondly, with the second slide member  10  withdrawn upwardly such that the projections  36  and  38  do not interfere, the preform aperture  6  is engaged with the split mandrel  7  and the ram slide assembly by a linear motion, with the split mandrel parts  7 A and  19  being juxtaposed against each other. 
   Next, the three-point retention of the connecting rod bearing cap is activated, this talking place between the cap half  7 A of the split mandrel  7  and the projections  36  and  38 , which contact the bolt seat shoulders. 
   Then, the wedge member  20  or the wedge  20 A is activated to split the mandrel  7 , following which the wedge member  20  or wedge  20 A is withdrawn. 
   Then, the bearing cap retention constituted by the projections  36  and  38  is disengaged. 
   Then, the split mandrel and the ram slide assembly is disengaged from the connecting rod by moving the slide unit  21  (illustrated in FIG.  2 ). 
   Finally, the locators  14 - 17  are disengaged at the point of removal of the 2-piece preform which has been reassembled using two bolts. 
   While one embodiment of this invention has been illustrated in the accompanying drawings and described hereinabove, it will be evident to those skilled in the art that chances and modifications may be made therein without departing from the essence of this invention, as set forth in the appended claims.