Abstract:
The apparatus comprises a frame supporting two fixtures, of which at least one is movable, and which have respective crescents adapted to be brought together to form a circular profile engageable with the big end of a connecting rod and separable by an opening device for fracturing the big end of the connecting rod. The opening device comprises a pusher device which has a sloping surface and is slidably supported with respect to one of the crescents to abut against the other crescent, and a driving member, which is slidable transversely to the pusher device under control of driving elements, and has a sloping surface that is adapted to cooperate with a camming action with the sloping surface of the pusher device.

Description:
[0001]     This invention relates to an apparatus for separating the bearing cap of a connecting rod by fracture.  
       BACKGROUND OF THE INVENTION  
       [0002]     Separation of the bearing cap from the body of the rod by fracture has been known for several years. More particularly, prior patent IT-A-01.310.716 of Applicant describes an automated apparatus for implementing the separation of the bearing cap from the body of a connecting rod, with subsequent remating and screwing of the union bolts. Such apparatus is suitable both for rods having an orthogonal cracking plane and for rods having a cracking plane that is askew to the body of the rod. With reference to the apparatus described in the above patent, the big end of the connecting rod, which is to be cracked, is engaged by two crescents that are operable to radially move away from each other by a piston, which is sealingly slidable within a radial chamber made in one of the crescents, and is driven by a hydraulic cylinder via a hydraulic pressure multiplier.  
         [0003]     The above device, having a hydraulically operated piston, allows the connecting rods to be cracked with satisfactory accuracy and repeatability, in a way that minimizes deformation of the workpiece caused by yield stress. However, the biasing action of the piston in said prior document is applied to the connecting rod in a way that is partially asymmetrical so that, also in consideration of the unavoidable wear over time, the above, known apparatus is frequently subjected to malfunctions and requires replacements.  
       SUMMARY OF THE INVENTION  
       [0004]     It is a main object of the present invention to improve the apparatus described in the above prior patent, so that cleaner and sharper fractures are obtained, with higher reliability and lower maintenance costs.  
         [0005]     The above and other objects and advantages, such as will better appear from the following disclosure, are achieved by an apparatus having the features set out in claim  1 , while the other claims state other advantageous features of the invention. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0006]     The invention will be now described in more detail with reference to a preferred, non-exclusive embodiment shown by way of non-limiting example in the attached drawings, wherein:  
         [0007]      FIG. 1  is a plan, broken-away view of the apparatus for separating the bearing cap of a connecting rod by fracture according to the invention;  
         [0008]      FIG. 2  is a cross-section view along line II-II of the apparatus of  FIG. 1 ;  
         [0009]      FIG. 3  is a cross-section view along line III-III of a detail of the apparatus of  FIG. 2 , in which the connecting rod has been removed for better clarity of illustration. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0010]     With reference to the above Figures, the apparatus of the invention comprises a frame  10  on which is integrally supported a stationary fixture  12  comprising a massive body extending upwardly to form a stationary, semicircular crescent  14 , and a movable fixture  16 , also comprising a massive body extending upwardly to form a movable, semicircular crescent  18 . The two crescents are arranged in mirror positions with respect to their flat sides, and at right angles to the direction of motion of the movable fixture, so that a circular profile is generated, which is engaged by the big end of the piston rod. Movable fixture  16  is slidable along horizontal guides  20  which are integral with frame  10 , and is driven by a hydraulic actuator  22  mounted on frame  10 , through a rod  24 . Hydraulic actuator  22  has the main task of bringing back together the movable crescent to the stationary crescent after fracturing the cap, as well as other accessory tasks as explained below.  
         [0011]     Having now more particular reference to  FIGS. 2 and 3 , stationary crescent  14  has a longitudinal hole  26  in which is slidingly received the end portion of a bar  28  that is operatively connected to a piston  29  of a hydraulic cylinder  30  that is incorporated in frame  10 . A sloping surface  28   a  is defined on the outer skirt of the bar, which has positive slope in the direction of the free end of the bar, with respect to the longitudinal axis of the bar. The flat side of stationary crescent  14  has a port  32  open to longitudinal hole  26 . A sleeve  34  projects from port  32  in cantilever fashion and has a cylindrical chamber defined therein, in which is slidably received a pusher device in form of a piston  36 . The outer end of piston  36  is adapted to abut against movable crescent  18 , while a sloping surface  38  on the opposite, inner end of piston  36  is adapted to cooperate with a camming action with sloping surface  28   a  of bar  28 , which acts as driving member, thereby forming a mechanical device for expanding or prying open the crescents.  
         [0012]     Sleeve  34  is slidably received in a corresponding cylindrical cavity  40  bored in movable fixture  16  and having a bottom  40   a  that forms the abutment area for piston  36 . An annular gasket  42  is received in cylindrical cavity  40  and sealingly engages the outer skirt of sleeve  34 . A lubricating channel  43 , open to cylindrical cavity  40 , is provided in movable fixture  16  and is connected to means for feeding lubricating fluid (not shown).  
         [0013]     Frame  10  also supports a first locking device comprising a hydraulic actuator  44  which controls a V-shaped block  46  slidable along guides  48 , and is arranged for pressing on the little end of connecting rod  19  and therefore to lock the rod body against the stationary crescent.  
         [0014]     Movable fixture  16  carries a second locking device, also comprising a hydraulic actuator  52  arranged for pressing both ends of a pivoting rocker  54  against the bolt seats on the bearing cap of the connecting rod, so that this is locked against the movable crescent.  
         [0015]     In operation, while crescents  14  and  28  are close to each other and bar  28  is positioned in its outer position, connecting rod  19  is pushed around the crescents by positioning means (not shown) which are known from the above prior patent IT-A-01.310.716. Actuator  52  is then operated to press rocker  54  against the bearing cap, and a moderate pressure is applied to hydraulic actuator  22 , in order to lock the big end of the connecting rod. Actuator  44  is also driven to engage V-shaped block  46  on the little end. Both the body and the bearing cap of the connecting rod are therefore locked independently from each other, respectively between block  46  and stationary crescent  12 , and between movable crescent  16  and rocker  54 .  
         [0016]     The pressure in cylinder  22  is now increased, so that the resisting sections between the cap and the body of the connecting rod are pre-tensioned up to a load slightly lower than the yield stress. Hydraulic cylinder  30  is now operated to withdraw bar  28 , thereby causing piston  36  to move outwardly by mutual engagement between the sloping surfaces of the piston and the bar respectively. Therefore, the movable crescent is quickly moved away from the stationary crescent and the cap&#39;s breaking stress is rapidly exceeded, so that the bearing cap is separated from the body of the connecting rod. This causes an instantaneous, fragile fracture, simultaneous on both surfaces. The two portions of the connecting rods each remain firmly held in the respective clamps, as explained above. During this step, actuator  22  is pressurized in its backward chamber, while the forward chamber is depressurized. The clamps formed by V-shaped block  46  and by rocker  54  are then released, so that connecting rod  19  is freed.  
         [0017]     As will be understood by a person skilled in the art, the downwardly directed, radial component of the force applied to piston  36  by bar  28 , due to the friction between their respective, mutually sliding, sloping surfaces, is reacted by sleeve  34  via the piston. Due to this advantageous feature, the force applied to movable fixture  16  by piston  36  has no radial components. In contrast, if such radial components were not neutralized as described above, they would be applied by friction to movable fixture  16 , thereby causing the crescents to misalign from each other while prying open and therefore affecting the accuracy and regularity of the fracture.  
         [0018]     In order to have a braking action to the travel of the movable fixture when the peak of fracturing pressure is applied, a moderate pressure is applied to the back chamber of actuator  22 , such that it will not affect the quickness of the fracture, but such that it will present a braking resistance to the travel of the movable crescent after it has been freed by the fracture. Alternatively, in order to improve the durability of the device, actuator  22  may also be used to contribute to the fracturing force, by pressurizing its forward chamber with a higher pressure than its backward chamber.  
         [0019]     Of course, may changes can be made to the preferred embodiment as described above, within the teachings of the invention. Particularly, in case of connecting rods where the fracturing plane is required to be oblique rather than at right angles to the rod body, the apparatus can be modified similarly to what has been described in the above prior patent No. IT-A-01.310.716, by replacing V-shaped block  46  with a profiled block gauged for pressing with a balanced pressure on the side of the connecting rod. Similarly, V-shaped block  46  can also be replaced by an U-shaped block having two elongated arms straddling the rod body and abutting against opposite sides of the big end, as described in the above prior patent, in order to unload the rod body so that the elastic behavior of the body does not affect the dynamic system, avoiding possible undesirable effects. Moreover, as a way of braking the movable member, conventional stopper devices might be used, as known in the art, instead of a counter-pressure in actuator  22 . Further, although the arrangement where the connecting rod is horizontal and is loaded from above, according to the embodiments disclosed above, is preferable for ease of loading and unloading of the workpiece and also for ease of disposal of the chips and dust, nevertheless the apparatus might be designed so that the connecting rod is vertical or inclined, or horizontal but loaded from below, with suitable changes in the devices, such as will be obvious for the person skilled in the art. Finally, other driving means rather than hydraulic cylinder  30  might be implemented for driving bar  28 , such as, e.g., mechanical actuators.  
         [0020]     The disclosures in European Patent Application No. 05425058.4 from which this application claims priority are incorporated herein by reference.