Abstract:
A pin comprises an inner element and an outer sleeve. The inner element is insertable into and removable from the outer sleeve, and the outer surface of the inner element and the inner surface of the outer sleeve are tapered along at least a part of their lengths.

Description:
FIELD OF THE INVENTION  
       [0001]     The present invention relates to pins and in particular to pins that mount equipment that must be removed from time to time.  
       BACKGROUND OF THE INVENTION  
       [0002]     Pins are often used to mount elements of equipment which must be removed from time to time. For example there are many applications in the oil and gas industry where pins are used to mount hydraulic cylinders. Hydraulic cylinders must be serviced regularly in order for them to perform reliably.  
         [0003]     Where machines are used in harsh conditions they suffer from corrosion. It is often the case that due to corrosion pins are difficult to remove when they have been in service for only a modest period. In the off-shore oil and gas industry it is common practice for hydraulic cylinders to be removed from service and taken away for repair. Typically, hydraulic cylinders are removed every six years. Off-shore oil rigs are exposed to the most extreme environments, and it is common for pins to be so corroded that a machine such as an oxy-acetylene torch, spark eroder, hydraulic press or in line borer is required to remove the pin. In most areas of off-shore oil/gas rigs health and safety regulations forbid the use of equipment generating in excess of 240 C. As such, normal practice is for pins to be pressed or bored out. The equipment required for either pressing or boring out a pin is substantial, requiring transport to and from the rig by vessel and a team of four men for its operation who would be transported by helicopter.  
         [0004]     The requirement to bring in specialist equipment to remove a pin is not desirable. It is expensive in terms of manpower, equipment requirements and plant downtime (for example when a pin must be removed at a non-scheduled time).  
         [0005]     An example of a device for removing pins that have been working in harsh environments can be found in U.S. Pat. No. 4,870,739 which describes a device for forcing the pins out of links in chains that have been used to secure anchors or buoys.  
         [0006]     As well as being a problem in the oil and gas and marine industries, corrosion of pins is a problem in other areas. For example in the construction and agricultural industries machines work outside and are subjected to dust, debris, extremes of temperature, rain, etc, all resulting in corrosion. In the chemical industries elements of machines may be located in environments which cause corrosion.  
         [0007]     It would therefore be desirable to provide an improved pin.  
       SUMMARY OF THE INVENTION  
       [0008]     According to one aspect of the invention there is provided a pin as specified in Claim  1 .  
         [0009]     According to another aspect of the invention there is provided mounting arrangement as specified in Claim  14 .  
         [0010]     According to another aspect of the invention there is provided a method of mounting an object as specified in Claim  15 .  
         [0011]     The pin of the invention provides for much easier removal of parts of machines secured in position by pins. Using the pin of the invention the job of removing a hydraulic cylinder (or other part) becomes a one man job requiring only a spanner and a grease gun or a hammer and chisel, instead of being a four man job requiring specialist equipment that must be transported to the site.  
         [0012]     Releasing the pin of the invention does not require heat making the pin particularly suitable for use on oil and gas installations. In fact, the pin of the invention will find application in any scenario involving uncoated pins used in harsh environments.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0013]     In the drawings, which illustrate a preferred embodiment of the invention, and are by way of example:  
         [0014]      FIG. 1  is a schematic representation of a pin according to the invention;  
         [0015]      FIG. 2  is a cross-sectional elevation of the pin illustrated in  FIG. 1 ;  
         [0016]      FIG. 3   a  is a side view of a mounting arrangement according to the invention; and  
         [0017]      FIG. 3   b  is a plan view of the mounting arrangement illustrated in  FIG. 3   a.   
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0018]     Referring now to  FIGS. 1 and 2 , there is shown a pin  1  comprising an inner element  2  having a first end  4  and a second end  4   a  and an elongate portion  2   a  extending between the said first and second ends. The elongate portion  2   a  is tapered between the first and second ends  4 ,  4   a , the cross-section of the portion  2   a  being greater at the first end  4  than at the second  4   a . A seal  5  adjacent the first end  4  sits in a seal housing  5   a . The taper terminates at a seal  6  located in a seal housing  6   a , the second end  4   a  including portion  7  having parallel sides. The second end  4   a  further includes a stub  8  including a threaded portion  10 . A seal  9  is mounted on the stub  8 .  
         [0019]     The inner element  2  is housed in a sleeve  3 , the inner element  2  and the sleeve  3  forming a substantially cylindrical pin, the external diameter of the sleeve  3  being substantially the same as the external diameter of the first end  4  of the inner element  2 .  
         [0020]     The sleeve  3  includes an opening  12  through which the stub  8  passes, the threaded portion  10  extending beyond the outer end of the sleeve  3 . A seal  9  sits in a seal housing  9   a  in the form of a groove in the sleeve  3 . An internally threaded nut  11  is fastened onto the threaded portion  10  of the stub  8  to secure together the inner element  2  and the sleeve  3  to form the pin  1 .  
         [0021]     The stub  8  may be unthreaded and lockable cap screws used to hold the inner element  2  in place.  
         [0022]     The end wall of the sleeve  3  includes a bore  13  of a first diameter and extending therefrom a second bore that communicates with the chamber formed between the inner surface of the sleeve  3  and the outer surface of the parallel sided portion of the elongate element  2 . The second bore is threaded, in use receiving either grub screw  15  which covers the grease nipple  14 , the function of which is described in greater detail below.  
         [0023]     To remove the pin  1 , first the lock nut  11  is slackened and removed, then the grub screw  15  is removed allowing access to the grease nipple  14 . A grease gun is attached to the grease nipple and is operated to force grease into the cavity  16 . The cavity  16  is bounded by a face of the ‘O’ ring  9 , the internal surface  17  of the sleeve  3 , the outer surface  7  of the inner element  2  and one face of the seal  6 . The build up of pressurised grease in the cavity  16  causes the inner element to move in the direction X. Due to the taper of the elongate section  2   a  and the inner surface of the sleeve  3 , a relatively small amount of movement of the inner element  2  in the direction X results in the two parts of the pin being free of each other.  
         [0024]     Referring now to  FIGS. 3   a  and  3   b , a mounting arrangement comprises a levis  50  including bores  51  in each of the bifurcations  52  of levis  50 . A piston rod  53  of a hydraulic cylinder terminates in a bracket  54  including a bore  55 . The pin  1  passes through aligned bores  51  and  55  and the lock nut  11  is fastened onto the threaded portion  10  of the stub  8 . A lip  17  of the end  4  engages with the outer surface of one of the bifurcations  52  and the lock nut  11  engages with a washer  18 , which may be a spring washer or an unsprung washer, to secure the pin  1  in a working position.  
         [0025]     The method of assembling the arrangement illustrated in  FIG. 3  comprises the steps of: 
        i) aligning the bores  51 ,  55 ;     ii) removing the lock nut  11  from a pin  1  as illustrated in  FIG. 1 ;     iii) passing the pin  1  through the bores  51 ,  55 ;     iv) presenting a washer  18  up to an outer face of one of the bifurcations  52  over the stub  8 ; and     v) fastening lock nut  11  onto the stub  8  and tightening the same.        
 
         [0031]     The method of disassembling the arrangement illustrated in  FIG. 3  comprises the steps of: 
        i) slackening off the lock nut  11 ;     ii) removing the washer  18 ;     iii) removing the grub screw  15 ;     iv) attaching a grease gun to the grease nipple  14 ;     v) filling the cavity  16  with grease until the inner element  18  is force sufficiently far in the X direction to release the inner element  2  from the sleeve  3 ;     vi) removing the inner element  2  from the sleeve  3 ;     vii) removing the sleeve  3  or the remains thereof from the aligned bores  51 ,  55 .        
 
         [0039]     Where the mounting arrangement illustrated in  FIGS. 3   a  and  3   b  has been located in a very harsh environment, such as an off-shore oil rig, the corrosion of the sleeve is usually such that when the inner element  2  is released the sleeve collapses, allowing the bracket  54  of piston rod  53  to be removed.  
         [0040]     In a simplified embodiment of the invention instead of using a hydraulic system to separate the inner element from the sleeve a hammer, or hammer and chisel are employed. A fitter removes the lock nut  11  and taps on the end of the stub  8  with a hammer, or hammer and chisel. In such an embodiment there is no need for the seals  5 ,  6  and  9 .