Abstract:
Disclosed is a taper bolt connection including a taper bolt received in a taper bush, a fastening nut and a washer, the taper bush having a continuous longitudinal slot, and the taper bush being capable of being spread open uniformly in the radial direction by means of a fastening nut screwable onto the taper bolt. Since the taper bolt and/or the taper bush have/has, at least in regions, an at least Teflon-containing coating, tribochemical processes between the taper bush wedge surface and the taper bolt wedge surface are largely avoided, so that the taper bolt connection can be released again without great effort even after a long period of connection. Furthermore disclosed is the use of the taper bolt connection for connecting a rudder unit to a carrying structure of a fuselage cell of an aircraft.

Description:
FIELD OF THE INVENTION 
     The invention relates to a taper bolt connection with a taper bolt received in a taper bush, with a fastening nut and with a washer, the taper bush having a continuous longitudinal slot, and the taper bush being capable of being spread open uniformly in the radial direction by means of a fastening nut screwable onto the taper bolt. 
     The invention relates, furthermore, to the use of a taper bolt connection for fastening a rudder unit to a carrying structure of a fuselage cell of an aircraft. 
     BACKGROUND OF THE INVENTION 
     Known embodiments of taper bolt connections partially have, in the wedge surface region, bronze coatings which, if necessary, are additionally greased. 
     As a result of the relatively soft and thick bronze layer and of the grease layer, however, tribochemical reactions between the contact surfaces are caused under alternating loads. On account of this, often very high forces, which may reach the 400 kN range, are required for demounting connections of this type. 
     SUMMARY OF THE INVENTION 
     It is one of the objects of the invention to provide a taper bolt connection which can easily be released again without the need to apply high tensile forces, so that the maintenance or mounting of taper bolt connections of this type is simplified. 
     This object is achieved by means of a taper bolt connection comprising a taper bolt received in a taper bush, a fastening nut and a washer. The taper bush has a continuous longitudinal slot, and the taper bush is capable of being spread open uniformly in the radial direction by means of a fastening nut screwable onto the taper bolt. The taper bolt has a coating. A taper bush wedge surface of the taper bush has a longitudinal extent which corresponds approximately to a longitudinal extent of a taper bolt wedge surface of the taper bolt. The coating of the taper bolt has at least three polytetrafluoroethylene strips which are arranged, uniformly spaced apart from one another, around the circumference of the taper bolt and each extending essentially over the entire longitudinal extent of the taper bolt wedge surface. 
     The taper bolt and/or the taper bush have/has, at least in regions, an at least Teflon-containing coating, a taper bush wedge surface having approximately a longitudinal extent which corresponds approximately to a longitudinal extent of a taper bolt wedge surface of the taper bolt. This results, even after a lengthy period of connection between the taper bolt and the taper bush, in a surprisingly easy releasability of the taper bolt connection according to the invention, since tribochemical reactions between the contact surfaces are largely avoided. Furthermore, the Teflon-containing coating has, in comparison with the greased bronze coating of the taper bolt, a significantly reduced coefficient of friction, so that mounting is also made easier and quicker. 
     In one embodiment of the taper bolt connection according to the invention, the taper bolt wedge surface and the taper bush wedge surface each have an inclination of 0.01 to 0.1. As a result, during the axial bracing of the taper bolt connection by means of the fastening nut, very high radial tension forces for fastening can be generated. 
     According to one particular embodiment, the Teflon-containing coating has a thickness of 0.01 mm to 0.5 mm, preferably a thickness of 0.15 mm. These ranges of coating thicknesses ensure an effective prevention of tribochemical reactions and consequently an easier demounting of the connection, but nevertheless make it possible to join the taper bolt and taper bush together with an exact fit. 
     Moreover, the object according to the invention is achieved by a taper bolt connection as described above that is used for fastening a rudder unit to a carrying structure of a fuselage cell of an aircraft, so that, because tribochemical reactions between the taper bolt and the taper bush are avoided, the rudder unit, if required, can easily be demounted from the carrying structure of a fuselage cell of an aircraft. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention is explained in more detail below using preferred exemplary embodiments and with reference to the attached figures of the drawings, in which: 
         FIG. 1   a  shows a side view of the taper bush of the taper bolt connection, 
         FIG. 1   b  shows a top view of the taper bush of the taper bolt connection, 
         FIG. 2   a  shows a side view of the taper bolt of the taper bolt connection, 
         FIG. 2   b  shows a top view of the taper bolt of the taper bolt connection, 
         FIG. 3  shows a side view of the fastening nut, 
         FIG. 4  shows a top view of the washer, and 
         FIG. 5  shows a cross-sectional illustration through the mounted taper bolt connection. 
     
    
    
     In the figures, the same reference numbers refer to identical or functionally identical components unless otherwise stated. 
     DETAILED DESCRIPTION OF THE INVENTION 
       FIGS. 1   a  and  1   b  show a side view and a top view of a taper bush  1  of the taper bolt connection according to the invention. The taper bush  1  has a continuous taper bore  2  with a taper bush wedge (or keying) surface  3  for receiving a taper bolt. The taper bush wedge surface  3  with a longitudinal extent  4  has, in the exemplary embodiment shown, an only slight inclination with respect to the horizontal, which corresponds approximately to a ratio of 1:20. Furthermore, a continuous longitudinal slot  5  extends in the axial direction over the entire length of the taper bush  1 , so that the taper bush  1  can be spread open uniformly in the radial direction over its entire length as a result of the introduction of a correspondingly designed taper or taper bolt. Furthermore, the taper bush  1  has at one end a flange  6  and at an end directed away from this an outer edge  7 . 
       FIGS. 2   a  and  2   b  show a side view and a top view of a taper bolt  8  of the taper bolt connection. Similarly to the above-described inclination of the taper bush wedge surface  3 , a taper bolt wedge (or keying) surface  9  likewise has an inclination with respect to the horizontal, which corresponds approximately to a ratio of 1:20. A longitudinal extent  10  of the taper bolt wedge surface  9  corresponds approximately to the longitudinal extent  4  of the taper bush wedge surface  3 . Both the taper bush wedge surface  3  and the taper bolt wedge surface  9  may in each case have inclination ratios of 1:100 to 1:10 with respect to the horizontal, depending on the respective structural requirements. What is critical is that the inclination of the taper bush wedge surface  3  and the inclination of the taper bolt wedge surface  9  are selected so as to be approximately identical, with the exception of possible manufacturing tolerances, so that, during the bracing of the taper bolt connection, the taper bolt  8  is not drawn too far through the taper bolt connection. The said inclination range ensures the possibility of generating very high radial bracing forces by the taper bush  1  being spread open by means of the taper bolt  8 , and, consequently, an extremely firm fit of the connection in a fastening bore or the like. The longitudinal extents  4 ,  10  are preferably dimensioned approximately identically, but, if necessary, may also have values deviating from one another. 
     At one end of the taper bolt  8 , a threaded portion  11  is arranged, which is preferably provided with a fine-pitched thread. Furthermore, in the region of the threaded portion  11 , a bore  12  is arranged, into which a suitable securing means, for example a securing cotter pin, not illustrated in any more detail, can be introduced, in order to avoid an unwanted twisting of the taper bolt  8  about its longitudinal axis. 
     According to one aspect of the invention, the taper bolt wedge surface  9  is provided, at least in regions, with an at least Teflon-containing coating  13 . The Teflon-containing coating  13  is applied to the taper bolt wedge surface  9  preferably over the entire area and, in a particularly preferred embodiment, has a thickness of about 0.15 mm. However, the material thickness of the Teflon-containing coating may have any amount between 0.01 mm and 0.5 mm. The Teflon-containing coating contains, in addition to pure Teflon or polytetrafluoroethylene (PTFE), further auxiliary components which serve, for example, for adhesion improvement or the like. The coating  13  may also be formed solely from Teflon, that is to say pure polytetrafluoroethylene. 
     In an exemplary embodiment, as illustrated in  FIG. 2 , it is likewise possible to apply the Teflon-containing coating to the taper bolt wedge surface  9  in regions only. For example, the Teflon-containing coating may be formed by three, four or more strips  13   a , each including a Teflon-containing material and arranged, spaced uniformly apart from one another, around the circumference of the taper bolt  8 . Surfaces not provided with a Teflon-containing coating are located between the strips. The length of the strips preferably extends over the entire longitudinal extent  10  of the taper bolt wedge surface  9 . 
     Furthermore, in an alternative design variant of the invention, it is possible also to provide the taper bush wedge surface  3  additionally with an at least Teflon-containing coating. In a further alternative, even only the taper bush wedge surface  3  may be provided with a Teflon-containing coating, whereas the taper bolt wedge surface  9  has no Teflon-containing coating. 
     Both the taper bush  1  and the taper bolt  8  are formed by the same high-strength material, for example titanium, high-grade steel or the like, in order to avoid mechanical stresses as a result of temperature fluctuations. Alternatively, both the taper bush  1  and the taper bolt  8  may be formed from titanium alloys or high-grade steel alloys. 
       FIG. 3  shows a side view of a castle nut  14  which is screwed onto the threaded portion  11  of the taper bolt  8  in order to brace the taper bolt  8  with the taper bush  1 . The castle nut  14  has at least two recesses  15 , in which a securing cotter pin, not illustrated in any more detail, is received, in order to prevent an inadvertent release of the castle nut  14  from the threaded portion  11 . 
       FIG. 4  shows a top view of a washer  16  which is preferably arranged between the castle nut  14  and the outer edge  7  of the taper bush  1 , in order, inter alia, to ensure a uniform tightening of the castle nut  14 . 
     In the exemplary embodiment shown in  FIG. 5 , the taper bolt connection connects a rudder unit  17  to a fork  18  which is firmly connected to a carrying structure of a fuselage cell, not illustrated in any more detail, of an aircraft. A sleeve  19  is arranged in the rudder unit  17 , which is preferably formed by a fibre-reinforced plastic material, such as, for example, CFRP. The fork  18  has two bores  20 ,  21 . 
     The taper bush  1  is received in the sleeve  19  and the two bores  20 ,  21 . The taper bolt  8  is introduced into the taper bush  1  and is braced with the latter by means of the castle nut  14 . The washer  16  is located between the castle nut  14  and the taper bush  1 . By the taper bolt  8  being braced with the taper bush  1 , the latter spreads uniformly outwards in the radial direction, so that the rudder unit  17  is braced firmly with the fork  18  after the tightening of the castle nut  14 . In this operation, the taper bolt  8  is drawn into the taper bush  1  by an amount of at most 10 mm. As a result of the operation of spreading open the taper bush  1 , the outside diameter of the latter increases, so that this results in a press fit of the taper bore connection in the bores  20 ,  21  and in the sleeve  19  of the rudder unit  17 . The consequence of this being that a connection durable even with respect to highly alternating mechanical stresses (in particular, high shear forces) is obtained between the rudder unit  17  and the fork  18  connected to the carrying structure of the fuselage cell of an aircraft. 
     The embodiment according to the invention of the taper bolt connection also makes it possible, during the mounting operation, to have tolerance compensation between the rudder unit  17  and the fork  18  firmly connected to the carrying structure of the fuselage cell. 
     During operation, the taper bolt connection formed essentially by the taper bush  1 , the taper bolt  8 , the washer  16 , the castle nut  14  and the securing cotter pin, not illustrated in any more detail, is subjected essentially to high mechanical shear forces. 
     The invention thus affords a taper bolt connection with a taper bolt  8  received in a taper bush  1 , a fastening nut and a washer  16 , the taper bush  1  having a continuous longitudinal slot  5 , and the taper bush  1  being capable of being spread open uniformly in the radial direction by means of a fastening nut screwable onto the taper bolt  8 , the taper bolt  8  and/or the taper bush  1  having, at least in regions, an at least Teflon-containing coating  13 , a taper bush wedge surface  3  having approximately a longitudinal extent  4  which corresponds approximately to a longitudinal extant  10  of a taper bolt wedge surface  9  of the taper bolt  8 . 
     For example, the taper bolt wedge surface  9  and the taper bush wedge surface  3  have in each case an inclination in a ratio of 0.01 to 0.1. 
     The Teflon-containing coating  13  has, for example, a thickness of 0.01 mm to 0.5 mm, preferably a thickness of 0.15 mm. 
     Preferably, the taper bolt  8  has, to form the Teflon-containing coating  13 , at least three strips  13   a  which are arranged, preferably uniformly spaced apart from one another, around the circumference of the taper bolt  8  and extend in each case essentially over the entire longitudinal extent  10  of the taper bolt wedge surface  9  and which are formed by a Teflon-containing material or from Teflon. 
     The taper bush  1  and the taper bolt  8  are formed, for example, by titanium or high-grade steel. 
     A washer  16  is preferably arranged between the fastening nut and the taper bolt  8 . 
     The fastening nut is designed, for example, as a castle nut  14  which is secured against inadvertent release by means of a securing element, in particular a securing cotter pin. 
     The above-described taper bolt connection may be used, for example, for fastening a rudder unit  17  to a carrying structure of a fuselage cell of an aircraft.