Abstract:
Linkage pins are commonly used to join two members to provide a rigid connection or to function as a pivot point. They are often manufactured from piece parts that ideally are provided with a protective coatings before assembly. The joint needs to be able to withstand the harsh environments linkage pins may be used in and the joining process must cause minimal disturbance to the coating to prevent it from having to be reapplied after manufacturing. The present invention discloses a method and linkage pin including a mechanical deformation to form a joint. The components are arranged in a particular orientation to provide optimum durability by aligning them in a direction dependent on the direction of the flexing caused by the forces acting upon the pin.

Description:
TECHNICAL FIELD  
       [0001]     The present invention relates to a linkage pin and a manufacturing method for the same. More specifically it relates to a linkage pin for connecting two or more members of a work machine.  
       BACKGROUND  
       [0002]     Work machines such as tracked loaders, excavators and the like commonly use metal pins to connect two sections of the machine together. This may be done for several reasons, such as to create a pivot arrangement or to allow simplified removal and fitting of components like hydraulic rams which often are specifically provided with eye ends to receive such pins. Pins like this are often exposed to severe and a wide range of differing loads such as torsional, longitudinal and lateral loading. To maintain the pin in the desired position a common form of retention is to provide a lever arm which is typically a metal plate fixed perpendicularly to the pin. One end of the lever arm is fixed to the pin whilst another end forms a portion that may be bolted or clamped to prevent displacement of the lever arm and hence the pin. The lever arm may be fixed so as to substantially prevent any movement, but if preferred some degree of movement may be allowed. Pins having a construction as described often fail prematurely, especially the connection between the lever arm and the pin being prone to fatigue.  
         [0003]     It is often preferred to provide the components with a surface treatment such as an anti-corrosion protective coating. The manufacturing process of such pins would be greatly improved if the individual components receive such treatment before they are joined together, but commonly used processes such as welding damage the coating and require the assembly to be recoated after the operation.  
         [0004]     The present invention aims to overcome one or more of the above disadvantages.  
       SUMMARY OF THE INVENTION  
       [0005]     According to a first aspect of the present disclosure there is provided a linkage pin having a pin with an elongated boss at a first end whereby the elongated boss defines a first longitudinal axis. The linkage pin further has a lever arm which is provided with an aperture corresponding to the elongated boss whereby the lever arm defines a second longitudinal axis. The pin is fixedly connected to the lever arm such that the elongated boss is located in the corresponding aperture and that the first and second longitudinal axes are substantially parallel to each other.  
         [0006]     Another aspect of the present disclosure is a method for manufacturing a linkage pin wherein the following steps are present: 
    a) forming a pin having an elongated boss at a first end whereby the elongated boss defines a first longitudinal axis,     b) forming a lever arm and providing the lever arm with an aperture that corresponds to the elongated boss whereby the lever arm defines a second longitudinal axis,     c) positioning the elongated boss in the corresponding aperture,     d) fixing the pin to the lever arm such that the first and second longitudinal axes are substantially parallel to each other.    
 
         [0011]     A third aspect of the disclosure provides a linkage pin having a pin with a first longitudinal axis and an elongated boss at a first end whereby the elongated boss defines a second longitudinal axis. The linkage pin further has a lever arm provided with an aperture corresponding to the elongated boss whereby the lever arm defines a third longitudinal axis. The pin and second lever arm are fixedly connected whereby the elongated boss is positioned within the aperture and the first and third longitudinal axes form a virtual angle α. The pin is adapted to be subjected to forces in a direction that primarily influence angle α by having the second and third longitudinal axes substantially parallel to each other.  
         [0012]     Other features of the present disclosure will be apparent from the following description and the accompanying drawings. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0013]      FIG. 1  is a schematic isometric view of a linkage pin according to the current invention.  
         [0014]      FIG. 2  is an exploded view of the linkage pin shown in  FIG. 1 .  
         [0015]      FIG. 3  shows a schematic cross-sectional view of the pin from  FIGS. 1 and 2  applied to a typical linkage arrangement.  
         [0016]      FIG. 4  shows an exploded partial end representation of interfaces of a lever arm and a pin according to the present invention.  
         [0017]      FIG. 5  is a part representation of an assembled pin and lever arm from  FIG. 4 . 
     
    
     DETAILED DESCRIPTION  
       [0018]     With reference to  FIGS. 1, 2  and  3 , a linkage pin  10  has a pin  12  and a lever arm  14 . Pin  12  is shown as a substantially cylindrical body but may also have a non-cylindrical body and may be shaped irregular such as stepped or tapered if preferred. Pin  12  defines a longitudinal axis  13 .  FIG. 3  shows a typical application of linkage pin  10 , wherein it forms a link between a first member  16  and a second member  18 . The first and second members  16  and  18  may be for example loader arm segments of a work machine such as an excavator or the like. Where the linkage pin  10  is designed to function as a pivot point for the two members  16  and  18  the pin  12  will be at least partially cylindrical to accommodate the rotational movement of the first member relative to the second member. The pin  10  may however still be stepped or vary in diameter along its length if that is suitable for the application. Either or both of the members  16  and  18  may be provided with some kind of load bearing and wear part arrangement such as a bushing  20 .  
         [0019]     With reference to  FIG. 2 , the pin  12  is at one end provided with a projection such as boss  22  with a longitudinal axis  24 . This boss may be formed by milling two radially opposite sides of one end of the pin  12  such that an elongated projection remains. The end portions  26  and  28  of the boss which intersect the longitudinal axis  24  may be left intact so the length of the boss  22  is substantially identical to the diameter of the pin  12 , but alternatively the ends may be machined to form for example a straight edge. Providing the pin  12  with the boss  22  also leads to the formation of a shoulder  30  on the pin  12 . The end of the pin  12  opposite to the end provided with boss  22  may be tapered to facilitate installation.  
         [0020]     The lever arm  14  may be a flat steel plate in a multitude of possible shapes and defines a longitudinal axis  32 . Lever arm  14  is furthermore provided with an aperture such as slot  34 . Slot  34  defines a longitudinal axis  35  which is substantially parallel to and may even coincide with the axis  32  of the lever arm  14 . Of course it is to be understood that due to manufacturing tolerances a perfect parallelism may not be achieved. In one embodiment, the lever arm  14  may be provided with a second aperture  36  for receiving a fastener such as bolt  38 .  
         [0021]     The longitudinal axis  32  of lever arm  14  and the longitudinal axis  13  of pin  12  may lie in the same plane or in different planes but appear to intersect at a virtual angle α when seen from the side as shown in  FIG. 3 . In one embodiment α is substantially 90°, but other angular relationships may be adopted if preferred. The lever arm  14  and the pin  12  are connected by locating the boss  22  in the slot  34 . The dimensions of both the boss  22  and the slot  34  are matched so as to provide a good fit. The lever arm  14  and the pin  12  are then engaged in a permanent or semi-permanent fixation by an operation such as glueing, welding, swaging or by using a fastener such as a setscrew.  
         [0022]      FIGS. 4 and 5  show one embodiment for achieving a fixation of the lever arm  14  and the pin  12 . The lever arm  14  has a first surface  39  and a second surface  40 . The height of the boss  22  as measured from the shoulder  30  is greater than the distance between the surfaces  39  and  40 . With the lever arm  14  placed around the boss  22  such that the surface  40  abuts the shoulder  30 , the boss  22  then extends into and beyond the surface  39 . The part of the boss  22  that extends beyond the surface is then mechanically deformed by a process such as swaging with a swaging tool  44  to create a retaining portion.  
         [0023]     As can be seen from  FIGS. 4 and 5  the contact area between the pin  12  and the lever arm  14  may be increased by providing at least part of the circumference of the slot  34  with a chamfered edge  42 . This will allow a greater portion of the pin  12  to be deformed whilst attaining a more elaborate shape so as to form a stronger joint.  
       INDUSTRIAL APPLICABILITY  
       [0024]     The pin  12  and the lever arm  14  may be manufactured separately. Once all the preferred features have been provided to both the pin  12  and the lever arm  14 , both may undergo a protective treatment to shield them from corrosion or other types of damage being either functional or aesthetic. The treatment may include a process such as for example zinc-plating or phosphate coating. Once treated, the pin  12  and the lever arm  14  are assembled and a swaging process may be applied to form a permanent fixation. The elongated shapes of both the slot  34  and the boss  22  combined with the swaged end portion of the pin  12  prevent the two parts from moving relatively to one another. Swaging the components results in no or minimal disturbance of the protective coating and does therefore not require a coating to be reapplied after the joining operation.  
         [0025]     The pin may thereafter be assembled into a work machine such as described earlier. The aperture  36  may be aligned with a threaded portion in the first member  16  and an at least partially threaded fastener  38  may be positioned in the aperture  36  and threadingly engaged with the first member  16 . This will retain the pin in its desired position and thus prevents lateral movement or rotation of the pin relative to the member  16 . Alternative retention means may of course be applied. It is for example known in the art to apply a semi-fixed retention method wherein the pin  10  may be allowed a certain degree of rotational movement. This could for example be achieved by providing the lever arm with an oversize aperture and providing a spacer and washer arrangement whereby the pin  10  can rotate for a limited amount. Another alternative retention means known in the art is to provide the surface  16  with one or more projections to which a retainer plate can be fixed so as to form a ‘cage’ in which the lever arm can be locked or semi-locked.  
         [0026]     Once assembled into a work machine, the pin  10  is exposed to a wide range of forces. For example, the pin  10  may be used in applications where the pin  10  provides a hinge function, i.e. it is fixed in a position relative to member  16  whilst member  18  can pivot around the pin  10 . If lubrication between the surfaces of the pin  10  and the member  18  or its bushing  20  is insufficient, the friction may increase even to the point where the pin  10  and the bushing  20  are cold-welded together. When the two members are operated to pivot relative to one another and friction is high a torsional force is generated in the pin  10  as one end is restraint by the lever arm  14 . This torsional force is counteracted by the non-cylindrical or elongated shape of both the slot  34  and the boss  22 .  
         [0027]     In one embodiment a plurality of external forces acting in the same or different directions act upon the pin  10 . One force or a particular set of forces are identified as being the so-called primary forces because they are the main contributor to causing flexing of the lever arm  14  relative to the pin  12 , or vice versa. Angel α may be described as the angle between the pin  10  and the lever arm  14  that lies substantially in or parallel to the plane of the primary forces acting on the pin. For example, the primary forces may act on the pin  10  or the lever arm  14  in a manner to increase or decrease the angle a α. By using a pin  10  as described, and aligning the longitudinal axes of boss  22 , and slot  34  with the direction of the flexing, the robustness of the joint between the pin  12  and lever arm  14  is significantly increased.  
         [0028]     Although embodiments of this invention have been described herein, improvements and modifications may be incorporated without departing from the scope of the following claims.