Abstract:
A bearing extractor including a probe having an inlet bore at one end for pressurised hydraulic fluid, an outlet for the pressurised hydraulic fluid in an outer circumference of the probe, and a seal on each side of the outlet for forming a seal between the probe outer circumference and a surrounding bearing surface. Pressurised hydraulic fluid is fed through bore to outlet. The fluid fills the gap between the bearing ends and forces the bearings apart, to urge at least one of them from the housing. Greater radial force is applied to one bearing by positioning the respective seal further from the gap, and that bearing is preferentially held in the housing, the other bearing being urged from the housing and carrying the extractor with it.

Description:
INTRODUCTION AND BACKGROUND  
       [0001]     The present invention relates to a bearing extractor. The invention is particularly concerned with an extractor for extracting bearings from aircraft undercarriage and flying control assemblies, but it has wider applicability.  
         [0002]     With aircraft assemblies it is a particular challenge to minimise damage to the bearing housing when extracting the bearing. Also, when extracting a bearing for inspection purposes it is desirable to avoid damage to the bearing so that the bearing can be re-used.  
         [0003]     My applications GB-A-2370527 and GB-A-2401572 show examples of bearing extractors. A difficulty with these and other prior art extractors is that it is difficult to deal with bearings of small size because of the need to couple the extractor head, which bears on an end of the bearing, to the puller device which pulls the extractor head and bearing from the bearing housing.  
       SUMMARY OF THE INVENTION  
       [0004]     A first aspect of my invention provides an extractor in which hydraulic pressure is brought to bear directly on an end of a bearing to urge the bearing from its housing. The invention is particularly suitable for use when a bearing is fitted in a blind bore or two bearings are mounted end to end in a housing, the hydraulic fluid being fed between the bearing ends to urge the bearings apart.  
         [0005]     Another aspect of my invention provides a bearing extractor comprising a probe having an inlet at one end for pressurised hydraulic fluid, an outlet for the pressurised hydraulic fluid in an outer circumference of the probe, and a seal on each side of the outlet for forming a seal between the probe outer circumference and a surrounding surface. The seal prevents substantial leakage of hydraulic fluid past the seals so that the intervening space can be pressurised with the hydraulic fluid. The probe is positioned with the seals sealing against respective surfaces, at least one being a surface of a removable bearing. Hydraulic fluid is pumped into the region between the seals and so will cause the bearing to move. The seals are preferably arranged to increase their sealing efficiency under the pressure from the hydraulic fluid. The invention is particularly useful when bearings are mounted end to end with a space between them. The hydraulic fluid is pumped into the space between the bearing ends and so pushes the bearings apart, forcing at least one of them out of the housing.  
         [0006]     The invention also provides a bearing extractor for extracting a bearing form a blind bore, in which a probe has an inlet for pressurised hydraulic fluid, an outlet distal of the inlet and a seal around the circumference of the probe for sealing against the bearing inner surface.  
         [0007]     Other aspects and preferred features of the invention will be apparent from the following description and the accompanying claims. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0008]     The invention will be further described with reference to the accompanying drawings, in which  
         [0009]      FIG. 1  is an axial cross-section thorough an extractor forming an embodiment of the invention, positioned in two bearings prior to extraction of a bearing;  
         [0010]      FIG. 2  is a perspective view of a probe of the extractor of  FIG. 1 ;  
         [0011]      FIG. 3  is an axial cross-section corresponding to  FIG. 1 , with a bearing partially extracted;  
         [0012]      FIG. 4  illustrates a further embodiment of the invention, and  
         [0013]      FIG. 5  illustrates schematically the extraction of a bearing from a blind bore. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0014]     Referring to  FIG. 1 , an extractor  10  of the present invention comprises a probe  12  having an elongate body  14  and collar  16  at one end  14   a  of the body  14  for coupling the probe  12  to a pressurised hydraulic fluid supply (not shown).  
         [0015]     The probe  12  has an axial bore  18  extending from an inlet end  18   a  to mid way along the length of the probe body  14  where it fluidly connects with a radial bore  20  forming a hydraulic fluid outlet.  
         [0016]     The collar  16  has a threaded recess  22  for receiving an end of a pressurised hydraulic fluid supply line (not shown). The base  24  of the recess  22  has a conical face  26  to form a seal with the fluid supply line and defines an entrance to the axial bore  18 .  
         [0017]     A radial passageway  28  extends from the recess  22  to the collar  16  and provides a means for pressure relief during the coupling of the collar  16  to the hydraulic fluid supply line.  
         [0018]     The collar  16  is preferably integrally formed with the elongate probe body  14 . The collar  16  may be provided with a partially threaded through bore for receiving a threaded end portion of the probe  14 .  
         [0019]     The elongate probe body  14  is of circular cross-section. Seals are formed by circumferential sealing rings  34   a ,  34   b ,  34   c  positioned in respective circumferential grooves  30   a ,  30   b ,  30   c  in the outer peripheral surface  32  of the body  14 .  
         [0020]     The grooves  30   a ,  30   b ,  30   c  are generally U-shaped in cross section. The cross-section tailored to the particular sealing elements  34   a ,  34   b ,  34   c  to form a seal between the probe body  14  and the surrounding bearing surfaces  36 ,  38  when pressure is applied in the axial direction by urging hydraulic fluid through radial bore  20 , as will be described hereinafter. The grooves  30   a ,  30   b  have a sloping surface  31   a ,  31   b , on the unpressurised side of the sealing element  34   a ,  34   b  to form a tapered housing, encouraging the seal to migrate outwards under pressure and increasing the sealing efficiency under the high pressures which are to be applied. Preferably, the sealing elements may be of the elastomeric O-ring type with a well-defined hardness/extensibility, though they are not limited thereto. One such type of sealing element is marketed as an O-ring by James Walker Group.  
         [0021]     The diameter of bore  18  is stepped along its length, reducing in diameter as it reaches the radial bore  20 . If the diameter of bore  18  is too large compared to the overall diameter of probe body  14 , the body  14  may be weakened and liable to fracture in use.  
         [0022]     As seen in  FIG. 1 , the probe  12  is dimensioned to allow a snug fit within bearings  40 ,  42  which are held in a bearing housing  46  which may be, for example, part of an aircraft undercarriage assembly. Preferably the clearance between the outer circumferential surface  44  of the probe body  14  and the inner surfaces  36 ,  38  is about 0.002 to 0.005 inches and preferably about 0.004 inches. The clearance should be small enough to prevent creep of the sealing element  34  under the pressure of the hydraulic fluid but large enough to allow the hydraulic fluid to penetrate between the probe surface  44  and the bearings  40 ,  42  in the region between the sealing elements  34   a ,  34   b.  Bearings  40 ,  42  are positioned in housing  46  with a gap  50  between their end surfaces  52 ,  54 , as is typical in the art.  
         [0023]     In use, the probe body  14  is fed into bearings  40 , 42  so that a respective sealing element  34   a ,  34   b  mates against a respective bearing inner surface  36 ,  38 . Hydraulic fluid is fed under pressure though bore  18  and radial bore  20  into the region of the gap  50 . The pressurised fluid acts on the end surfaces  52 ,  54  of the bearings  40 , 42  and when a sufficiently high pressure is reached the bearings are urged apart, thus forcing one of the bearings from the housing  46 . A pressure up to 40,000 p.s.i. has been found sufficient to achieve movement of most bearings from their housing.  
         [0024]     Because there is clearance between the probe outer surface and the bearing, the radial bore  20  need not align with the gap  50  when the probe is inserted into the bearings  40 ,  42 —hydraulic fluid will pass between the probe and bearing to reach and fill the gap  50 . However, it is preferable that the bore  20  align with or be close to the gap  50 .  
         [0025]     We have found that it is particularly advantageous to position the sealing elements  34   a ,  34   b  asymmetrically with respect to the gap  50  between the bearings  40 ,  42 . As seen in  FIG. 1 , sealing element  34   a  is closer to the gap  50  than sealing element  34   b.  The effect of this is that a higher total force is applied in the radial direction to bearing  42 . This appears to expand the bearing sufficiently to increase the grip of the bearing  42  on the housing wall  56 , and so the other bearing  40  will tend to be moved preferentially out of the housing  46 . Referring to  FIG. 3 , as bearing  42  moves out of the housing  46 , i.e. to the left in  FIG. 1 , it will abut collar  16  and so carry the probe  12  with it. In turn, sealing element  34   b  will move along the bearing  42 . The sealing element  34   b  will leave the bearing  42  before bearing  40  has been completely removed from the housing  46 . Thus, we provide a third sealing element  34   c , at the outer end  14   b  of the probe body  14  to seal against the bearing  42 .  
         [0026]     The outer end  14   b  of the probe  14  is tapered to facilitate mounting of the sealing elements.  
         [0027]     Where there is a large clearance between the probe body  14  and the surrounding bearings  40 ,  42 , for example due to high wear or oval or damaged bores, it may be helpful to provide a backing ring in the O-ring grooves  34   a ,  34   b.  The backing rings expand radially outwards under the pressure of the hydraulic fluid to provide support in the axial direction for the sealing elements.  
         [0028]     The extractor of this invention is particularly useful with bearings of internal diameter up to about 1.75 inches.  
         [0029]     Once one bearing of a pair has been extracted with the extractor of this invention, the other bearing can be readily removed by applying a mechanical force to the exposed bearing end surface.  
         [0030]     Referring to  FIG. 4 , this shows a rotatable coupling for a hydraulic fluid supply. The probe body  14  has an integral end collar  16 ′ and is similar to the probe of FIGS.  1  to  3 . The probe  12  is coupled to a spigot  58  on a handle by a cap  62  which is threadedly attached to the spigot  58  and bears on a shoulder  64  of the collar  16 ′. A bullet  66  fluidly connects the hydraulic fluid passage  18  of the probe with a hydraulic fluid path  68  though the handle  60 . A T-piece  70  is rotatably mounted in the handle  60  to rotate about an axis A-A and is held in place by a circlip  72 . O-rings  74  form a seal with the handle  60 . A stem  76  is in turn rotatably mounted in the T-piece  70  to rotate about axis B-B and be coupled to a hydraulic fluid supply as at inlet  76   a.  Stem  76  is held in place by a circlip  78  and O-rings  80  form a seal with the T-piece  70 . Bores  82 ,  84  in the stem and the T piece provide a fluid connection with fluid path  68  thorough to the probe  12 .  
         [0031]     Referring to  FIG. 5 , the method and apparatus of this invention may also be used to extract a bearing  86  from a blind bore  88  in a housing  46 ′. A probe body  14 ′ is inserted in the bore  88  with an outlet  20 ′ for hydraulic fluid inward of a sealing element  90  which forms a seal with between the probe body  14 ′ and the bearing  86 . The probe  12 ′ is clamped to the housing  46 ′ by a strap  92  and screw  94  with enough clearance between the collar  16  and the housing  46 ′ for the bearing  86  to leave the housing  46 ′, and hydraulic fluid is pumped through the probe hydraulic passage, bore  18 . The O-ring sealing element  90  prevents escape of the hydraulic fluid and so the interior of the bore  88  is pressurised and the fluid acts on the distal end  86   a  of the bearing to urge it out of the housing, past the sealing element  90 .  
         [0032]     Various modifications will be apparent to those in the art and the scope of the invention described and claimed herein is not be limited to the details of the specific embodiments which have been described by way of example only.