FR2557936A1 - BORGNE ATTACHE - Google Patents

Abstract

TUBULAR BODY FASTENER PRESENTING A HEAD PREFORMED SO AS TO START ON A FACE OF A PERFORATED PART, WITH EXTENDED ROD JOINED TO THE PREFORMED HEAD AND CAPABLE OF PASSING THROUGH THE PART SO AS TO EXCEED BEYOND THE OPPOSITE OF THE FACE THE PIECE, AND A NOSE AT THE END OF THE ROD OPPOSED TO THE PREFORMED HEAD. THE OUTER SURFACE OF THE NOSE 22, WHICH ACTS TO CAUSE THE EXPANSION OF THE SLEEVE 16, IS SHRINKED TO A GREATER ANGLE, RELATIVE TO THE LONGITUDINAL AXIS OF THE BODY, IN REGION 46 ADJACENT TO STEM 18 THAN IN REGION 44 CLOSER TO THE SMALLER DIAMETER END OF THE NOSE 22, THIS LARGER ANGLE BEING ENOUGH LARGE SO THAT WHEN THE SLEEVE 18 IS PUSHED OVER THE NOSE 22 SO THAT ITS FRONT END 48 EXCEEDS THE NOSE, THE END ANTERIOR 48 OF SLEEVE 16 CONTINUES TO EXPAND RADIALLY TO A DIAMETER SIGNIFICANTLY GREATER THAN THE OUTER DIAMETER OF ROD 18, AND THUS DEFORMS TO AN EXTENT SUCH THAT ITS INSIDE DIAMETER REMAINS SIGNIFICANTLY GREATER THAN THE OUTER DIAMETER OF ROD 18.

Description

The invention relates to a blind and

  particularly a blind fastener of the species comprising a body provided with a head and having a narrowed nose and a tubular sleeve and which is placed by pushing the sleeve over the nose of the body so as to expand the sleeve radially, the expanded sleeve attaching to the body and forming a blind head which can cooperate with the body provided with a head to fix together elements

perforated of a room.

  The invention particularly, but not exclusively, relates to an attachment of the indicated species which

  has a threaded bolt with a screwed head in a perfora-

  threaded body and that can be brought to move

  along its axis by rotation relative to the body, so that the head of the bolt can be moved towards the body and push the tubular sleeve over the narrowed nose so as to

to form a blind head.

  Fasteners of this last species are well

  known and commercially accessible under the brand name

  asked "Jo-Bolt" and are widely used in the in-

  aerospace industry, particularly to fix

  metals such as aluminum alloy sheets

  nium, to each other or to other elements such as structural support elements, but they are less satisfactory when the room to which

the one-eyed head is fragile.

  In particular, some composite materials such as plastics reinforced with carbon fiber and glass are now often used in the form of plates where previously used

  metals, have desirable characteristics of

  density and high resistance to trac-

  but are fragile in that they have low compressive and shear strengths and are

  sometimes unable to withstand the constraints to which

  they are subject when fixed with

classics of the type mentioned.

  The main reason for the unsatisfactory result

  given by the classical attachments of

  in fragile materials is that the head

  blind formed by the expanded sleeve applies only

  a small surface of the part, at the periphery of the opening through which the fastener passes and in the immediate vicinity of the edge of the material which borders the opening. This has the effect that the fragile material is subjected to localized stresses to which it

is unable to resist.

  This disadvantage of the conventional fasteners can be attributed at least in part to the fact that while the outer diameter of both the sleeve and the body part which passes through the opening of the

  piece is necessarily limited by the diameter of the

  verture, the nose of the body is of simple frustoconical

  and the body is shaped such that, during the installation of the fastener, the sleeve which expands tends to follow

  near the contour of the body parts over which

  he is pushed. Therefore, the inside diameter

  maximum of the dilated sleeve is not appreciably

  less than the diameter of the part of the body that we have

  passes through the opening of the room and the di-

  maximum outside diameter of the expanded sleeve exceeds

  than twice the wall thickness of the di-

  laté. It is therefore almost inevitable that the blind head thus presented by conventional fasteners of the species referred to applies to the piece in the marginal region closely bordering the opening and leads

  the application of constraints to the material in this re-

region.

  We have now imagined a link of the species

  this mentioned general in which the body has a

  such as it expands a portion of the sleeve to form a blind head having a substantially larger inner diameter than the outer diameter of the portion of the sleeve.

  body passing through the room.

  According to the invention, there is provided a

  member comprising a tubular body having a head preformed so as to abut on a face of a perforated piece, an elongated shank joined to the preformed head

  and able to pass through the room in order to de-

  beyond the opposite face (hereinafter referred to as the blind face) of the part, and a nose at the end of the rod opposite to the preformed head, this nose narrowing externally of a diameter equal to that of the rod at a smaller diameter at the end opposite the rod, a ductile tubular sleeve and means for

  push the sleeve over the narrowed nose and

  the preformed head so as to cause a di-

  progressive radial lining of the sleeve to form a blind head, characterized by the fact that the outer surface of the nose, which acts to cause the expansion of the sleeve, is narrowed at a greater angle relative to the longitudinal axis of the body in a region adjacent to the stem than in a region closer to the smaller diameter end of the nose, this larger angle being large enough that when the sleeve is pushed over the nose so that

  its anterior end protrudes from the nose, the extremity

  anterior tee of the sleeve continues to expand radially

  to a diameter significantly larger than the diameter

  outside the stem, and thus deforms in a

  measure such that its inside diameter remains

  higher than the outer diameter of the stem.

  The nose can be narrowed by several frustoconical parts.

  The nose may have two truncated parts

  which the nearest part of the stem has a plus

  wide angle at the top than the distant part of the stem.

  The nose may have a frustoconical portion immediately adjacent to the stem and two or more other portions, one of which may have an apex angle as large as that of the portion adjacent to the stem, provided that the nose has another portion having a smaller angle at the top, between the first another

  mentioned part and the part adjacent to the stem.

  The nose can be narrowed to a smaller dia-

  meter by several parts one of which, closer to the stem, is narrowed more sharply to a larger

  angle at the top than the previous one, closer to the former

  the tremite of the nose which is distant from the stem.

  The nose may have an outer surface that forms, in the longitudinal direction of the body, a concave curve forming narrowed portions of

  more abruptly closer to the stem.

The curve can be continuous.

  The curve can be an arc of a circle.

  The curve can be an elliptical arc.

  Concrete embodiments of the invention will now be described by way of example and with reference to the appended drawings in which:

  FIG. 1 is an axial section of a first

  attached, inserted through a room, before the installation

  lation in this one; Figure 2 is similar to Figure 1, but shows the installed fastener;

  Figure 3 illustrates the shape of the nose of the

  age of the fastener and Figure 4 is similar to Figure 3, but

  illustrates the shape of the nose of a second fastener.

  As shown in Figure 1, a terminal tie

  10 comprises three pieces, namely a tubular nut.

  re 12 which constitutes the body of the fastener, a bolt 14

and an expandable sleeve 16.

  The nut 12 comprises a cylindrical rod allon-

  18, an enlarged hexagonal head 20 at one end of the rod and a nose 22 at the end of the rod which is opposed to the head 20. The nose 22 narrows to a smaller diameter away from the head 20 The nut has a threaded perforation 24 which extends axially

  through the head, stem and nose.

  The bolt 14 includes an elongate shaft 30 and an enlarged head 32 at one end of the shaft. The rod is threaded so as to cooperate with the thread

  the hole in the nut and it has a length of

  less than the total length of the nut 12 and the

  16. Tgte 52 is almost the same diameter as

  the stem of the nut. The bolt shank has a

  tail tie 40 opposed to the head 32 and provided with two diametrically opposed flats 42 to facilitate gripping

  and the rotation of the bolt. The tail portion 40 is

  connected to the rest of the rod by a break neck 34 at which the rod breaks when subjected to a predetermined torque, thereby detaching the tail portion 40 from the remainder of the remaining bolt.

  as an essential part of the installed fastener.

  The sleeve 16 of this embodiment is a

  tubular cylinder having an outside diameter

  equal to that of the rod 18 of the nut and presents

  a smooth axial perforation which is chamfered internally

  the anterior end to allow the smaller diameter end of the nose 22 to enter easily. The diameter of the perforation of the sleeve 16 is sufficiently large to allow the rod 30 of the bolt to pass through the perforation with a slight clearance. Before use, the nut 12, the bolt 14 and the sleeve are assembled together. 26, inserting the bolt rod through the sleeve and then screwing it into the end of the nut that is opposite the head

  hexagonal until the tail portion 40 de-

  goes from the head end of the nut. We can then

  insert the assembled fastener into

  FIGS. 35, 36 of elements of a part 37 which are to be fixed together, so that the rod 18 passes through the elements, the hexagonal head 20 abutting against the close 38 of the workpiece and the head of the bolt, the sleeve, the nose and a part of the rod exceed the

  opposite or blind side 39 of the piece.

  You can put the fastener by grabbing the tail

  protruding from the bolt and turning it relative-

  nut so that the head of the bolt moves axially towards the nut and pushes the sleeve over the nose of the nut until the front end of the sleeve tightens the elements of the nut.

  the head against the head 20. At this stage, the couple needs

  to rotate the bolt increases sharply and continued rotation causes the bolt to break at the break

throw the tail part.

  According to the invention, the nose 22 of the nut of this

  execution mode is such that when the man-

  chon is pushed to the head so that the end

  front of the sleeve goes over the nose and the

  As a result, the anterior end of the sleeve expands to a diameter substantially greater than that of the shaft of the nut.

  Thus, as is shown particularly by the

  1, the nose 22 has a truncated end portion

  44 at the end of the nut which is opposite

  at the head 20 and a second frustoconical portion 46

  between the end portion 44 and the cylindrical rod 18.

  The end portion 44 extends about two-thirds of the axial length of the nose and the second part

46 extends over the remaining third.

  As shown in Figure 3, in this mode of

  the outer surface of the truncated part

  that terminal 44 shrinks to an apex angle of 40, while the outer surface of the second frusto-conical portion 46 narrows more sharply, to an apex angle of 70. Thus, the angle at the top of Part 44 is significantly lower than that at Part 46 and

  the angle at the top of Part 46 is significantly higher than

  at the corners at the top of the nose at a single taper

  conventional fasteners of this general type, which are generally

  from 30 to 42. The angle between the surfaces of the two parts must be greater than 90 and in this mode

execution is 165.

  So we can understand that when the sleeve

  is pushed over the nose during the pose of the

  the anterior end 48 of the sleeve first encounters the end portion 44 with soft conicity and with relative ease, it expands progressively radially, the dilation progressing on the

  length of the sleeve, starting from its anterior end

  higher, so that the sleeve flares out. Then, the former

  already flared end of the sleeve meets the second part 46 with a more abrupt taper by which it is

  dilated to a higher degree per unit of movement

  longitudinally that it performs under the action of the bolt head. Finally, the anterior end of the sleeve reaches and exceeds the point of intersection between the second portion 46 of the nose and the cylindrical stem.

  Since the rod 18 is cylindrical and has a diameter

  constant meter, equal to the maximum diameter of the nose, the

  ge does not ensure the inner support of the sleeve. As a result of the taper of the second part 46 of the nose and

  despite the growing circumferential constraint

  drde by the expanding sleeve, the anterior extremity

  the sleeve continues to move practically

  the alignment of the surface of the part 46 on a court

  The distance and thus the diameter will then expand radially until the circumferential stress in the sleeve overcomes the tendency of the anterior end to continue to expand. The anterior end ceases

then to expand further.

  It is preferable that the anterior portion of the sleeve protruding from the nose takes a substantially cylindrical shape in the region adjacent to the end.

  previous while also having an inner diameter no-

  larger than the stem, instead of flaring toward the anterior end. So we do

  so that the second part 46 meets the cylindrical rod

  drique 18 from an angle such as finally, and before

  the anterior end 48 does not meet the room, the

  the sleeve to continue to expand at the same time

  than by passing over the surface of the second

  part 46 is practically balanced by the

  circumferential drag of the sleeve, which tends simultaneously

  to ensure that the front end of the sleeve rotates inward and

  outer surface of the nut shaft. The pre-existing angle

  cis under which the second part of the nose must meet

  trimming the nut stem to balance the forces

  acting on the front part so that it

  comes cylindrical must be determined given the

  length of the second part and the physical properties

  particularly the ductility, elasticity and hardness of the anterior end of the sleeve. In

  In practice, the angle is determined empirically.

  The continuation of the bolt rotation relatively

  to the nut, the effect is that the anterior part

  cylindrical sleeve 16 advance, under the stress

  bolt head at the other end of the man-

  chon, until it stops against the blind side 39 of the room and applies a force to it. This is done on an annular zone which is spaced radially from the edge of the opening 36 so that no stress is applied to the part immediately near this edge. The dilated sleeve forms a one-eyed head which, together with the head

  preformed 20 of the nut, tightly grips both

  parts of the room against each other. The rotation resistance of the bolt increases and the tail portion 40 breaks, leaving the fastener installed in the workpiece, as shown in Figure 2. The nut, bolt and the expanded sleeve are effectively secured to each other by

  friction. The inner chamfer is distinct from the

  anterior mound of the sleeve no longer appears, having been

  smoothed by the passage of the sleeve along the nose of the nut.

  The angles chosen for this mode of execution and

  mentioned above were found suitable for a lack of

  chon formed of stainless steel called A.I.S.I. 304 (that is

  to say no. 304 designation of the American Iron and Steel

  Institute). Generally, it has been found that the angle at

  Part 46 must be larger than usual for the unique conicity used in conventional fasteners of this species and preferably

  not be less than about 60.

  However, it should be noted that if the angle at

  part 46 is too big, not only will excessive force be needed to push the sleeve

  over this part of the nose, with the risk of

  seal the sleeve or cause premature failure of the

  neck of rupture, but in addition the circumferences

  in the anterior end of the sleeve does not se-

  will not be sufficient to pocket the front end

  The sleeve should continue to expand at a reasonable distance of longitudinal displacement, which would give the anterior portion of the sleeve a flared shape.

  instead of a cylindrical form. This is not desirable.

  Instead of two different narrowed parts

  only the nose can have several parts, each

  that part closer to the rod of the nut being re-

  trecie more abruptly than the previous part, more

  near the end opposite the head 20.

  Thus, in another embodiment, as an extreme but practical example of such a structure, a fastener generally similar to that of FIG.

  1 and shown fragmentarily in FIG.

  a nose 22 whose outer surface forms, in

  the longitudinal direction of the nut, a concen-

  ve continues that one can consider as constituting

  killed by an infinite number of those parts that shrink

feel more and more suddenly.

  In this embodiment, the curve has the shape

  an arc of circle of radius r whose center C is spa-

  a short distance dl in front of the end of

  nose which is opposite to the head of the nut and spaced out

  dialement of the axis A of the nut, a distance d2 which is greater than the sum of the spokes of the perforation

of the nut and the circle itself.

  The distance d1 is preferably chosen such

  that at the point where the curved outer surface of the nose

  against the terminal face of the nose, a tangent to the curve meets the end face at an angle larger than, so that there is an immediate increase in

  diameter of the nose away from the end face.

  The distance d2 is preferably chosen such

  that there is a finite radial distance, on the

  the inner surface of the nut perforation and the outer surface of the nose, so that the

  terminal face is not a sharp edge.

  The length of the radius of curvature r of the sur-

  the outer face of the nose is chosen such that the speed of variation of the diameter of the surface

  outside the nose is acceptable in relation to

  diameter variation that the sleeve may be forced to undergo, given the size of the fastener, the ductility of the sleeve and the available force

to deform the sleeve.

  In a concrete example of this embodiment the rod of the nut has an outer diameter of 7.9 mm, the largest diameter of the threaded perforation is 6 mm and the minimum diameter of the nose is 5. 9 mm. The radial width of the end face of the nose is therefore (5.9 - 5.6): 2 mm = 0.15 mm. The curvature of the outer surface of the nose, in the longitudinal direction, is such that it forms part of a circle having a radius of 7 mm and the distance d1, which is determined by the angle

  under which the outer surface of the nose meets the

  this terminal is 1.0 mm and the distance d2, which is determined by the radial width of the end face

  and the dl value is slightly less than 0.15 mm.

  The effect exerted on the sleeve by the nose with

  Curved narrowing, when the sleeve is pushed on the nose and beyond it, is practically the same as

  in the previous embodiment, in that the former

  The anterior end of the sleeve expands progressively and at a rate which increases as the anterior end progresses from the nose boix to the shaft of the nut. As in the previous execution mode, the angle

  under which the anterior end of the sleeve leaves

  nally, at the intersection of the nose and stem

  of the nut, is sufficient to ensure that the

  Anterior tremity continues to expand radially before the increasing stress in the anterior end of the sleeve restricts

  appreciably radial expansion. As in the

  nrevious execution, circumferential contra-

  it is minimally dilated enough to dilate

  make sure that the part of the sleeve that follows the ex-

  anterior tremity takes a practically cylindrical

  drique, around the% but acyec radial spacing, the over-

  outer face of the stem of the nut The previous part

  upper cylindrical. sleeve continues to advance, under

* -selling of the head of the bolt to the other end

  Tee the sleeve, until it abuts against the piece and thus constitutes a blind head that, in cooperation e7936 with the head of the nut, serves to fix the elements of the piece.

  Unlike the nose of the first mode of execution

  tion, in which the conicity is ensured by two

  distinct frustoconical elements, the second of which has a substantially larger angle at the top than the first or terminal part, the speed of variation, of the small

  diameter at the maximum diameter of the nose of this mode of

  tion, is regular throughout the nose and, therefore,

  the magnitude of the force needed to push the man-

  chon over the nose does not increase suddenly. Thus, with this embodiment, there is less chance of a shock reaction causing the premature rupture of the

rupture collar.

  In this embodiment, the concave curvature corresponds by its function and effect to the internal angle relationship of the two frustoconical portions of the first

execution mode.

  Instead of the concave curvature of the nose being in the form of a circular arc, it could be in the form of an elliptical arc without significantly modifying the result,

  provided that the criterion concerning the angle

  what a line or tangent to the narrowing curve

  meets the outer surface of the stem and,

  the end face or the tip of the nose, be satis-

  made. While in the execution modes above

  the structure of the fastener is such that it can be

  by turning the bolt to push the sleeve over and over the nose, due to the effect of

  screw mother made by screwing between the nut and the bonu-

  lon, other constructions, to push the

  sleeve over the nose and, once it has been dilated

  ted and pushed together to secure the elements of

  a piece, to attach to the body of the clip, are possible

ble.

255? 936

  Thus, it is not necessary that the stem of

  bolt and the perforation of the nut

  However, the nut could instead be a body with a head and a stem, a narrowed nose, and a smooth perforation instead of a threaded perforation, and the bolt shank could then be

  be drawn axially along the perforation of

  to ensure that the bolt head pushes the sleeve over the nose and against the workpiece, the bolt shaft then being secured to the body so as to retain the sleeve in position in any suitable manner, for example by deforming it to form a stop capable of

  cooperate with the body in order to prevent retraction

  bolt and the loss of the expanded sleeve.

  In embodiments of the invention o

  the narrowed nose is formed of several truncated portions

  As in the embodiment of FIG. 1, for example, it should be noted that the length of the frustoconical portion closest to the rod has an influence on the extent to which the anterior end of the sleeve continues to expand. radially after leaving the support surface of the nose. Thus, we found

  that between certain limits, the longer the length of the

  truncated cone closest to the shank is large, the greater is the measure of which the diameter of the sleeve

  dilated will exceed the diameter of the stem.

  Similarly, in modes of execution

  where the nose has a concave curved surface that meets the outer surface of the stem, the radius of curvature of the curved surface will influence the

  extent to which the sleeve continues to expand.

  In yet another embodiment, the body of the fastener has a nose provided with a frustoconical part near the stem and, closer to the end of the

  nose, another frustoconical part whose angle at the

  puts may be equal to or even possibly greater than

255? 936

  that of the part adjacent to the stem, the two parts

  frustoconical parts being separated from one another

  axially by an intermediate corner

puts smaller or no.

  With regard to the size of the angle formed in any embodiment between the longitudinal axis

  bolt and the surface of the end part or the tan-

  the curve as it approaches the face

  terminal at the end of the nose, any angle formed by any

  bucket or any rounded tip of the nose to prevent it from

  be acute or to facilitate its implementation in

  sleeve drilling may be neglected.

  Certain modes of execution have been described

  crets and certain dimensions, it will be understood that the invention

  This is not restricted to these as it is possible to make changes to the shape and size details. For example, when the narrowed nose is formed

  several frustoconical parts, a truncated part

  that can join the next by a party to profile

concave appropriate.

Claims (13)

  1. A blind fastener comprising a tubular body   re having a head preformed so as to abut on one side of a perforated piece, an elongate rod joined to the preformed head and able to pass through the piece so as to protrude beyond the opposite face (hereinafter referred to as the blind side) of the piece, and a nose at the end of the stem opposite to the preformed head, this   nose narrowing externally with a diameter equal to   it of the rod to a smaller diameter at the end opposite the rod, a ductile tubular sleeve and means for pushing the sleeve over the narrowed nose and towards the preformed head so as to cause radial expansion of the sleeve to form a blind head, characterized in that the outer surface of the nose (22), which acts   in order to cause the expansion of the sleeve (16), is   trecie at a larger angle relative to the longitudinal axis   tudinal body, in a region (46) adjacent to the   ge (18) than in a region (44) closer to the extreme   a smaller diameter of the nose (22), this larger angle being so large that when the sleeve (18) is pushed over the nose (22) so that its anterior end (48) extends beyond the nose, the anterior end (48) of the sleeve (16) continues to expand radially to a substantially larger diameter than the outer diameter of the shank (18) and thus deforms to such an extent that its inside diameter remains substantially greater than the diameter outside the stem (18).   2. A fastener according to claim 1, characterized   brought about by the fact that the nose (22) is narrowed by   some frustoconical partiess (44,46).   5. A binding according to claim 1 or 2,   characterized by the fact that the nose (22) has two parts   frustoconical portions (44,46) having a portion (46) closest to the shank (18) at a greater angle at the top   the portion (44) remote from the rod (18).   4. Fastener according to claim 1 or 2,   characterized by the fact that the nose (22) has a   frustoconical tie (46) immediately adjacent to the stem   and two or more other parties, one of which (not   presented) may have a vertex angle as large as   that of the portion (46) adjacent to the rod (18), to   that the nose (22) has another portion (44) having a smaller apex angle between the first other portion and the portion (46) adjacent to the stem (18).   The fastener according to claim 1, characterized   due to the fact that the nose (22) is narrowed to a smaller diameter by a plurality of portions (44, 46) which can form a curve and each of which portions closer to the shank (18) is narrowed more sharply to a larger   angle at the top than the previous one, closer to the former   tremité du nez (22) which is remote from the stem (18).   A fastener according to any of the claims   cations, characterized in that the nose (22) has an outer surface which forms, in the   longitudinal direction of the body (12), a concave curve   ve continues forming narrowed parts of more and   more abruptly closer to the stem (18).   The fastener according to claim 6, characterized   laughed at the fact that the curve is an arc of a circle.   Fastener according to claim 6, characterized   laughed at the fact that the curve is an elliptical arc.   Fastener according to any of the claims   cations, characterized by the fact that the nose   (22) is narrowed, in the region (46) immediately ad-   underlying the stem (18), towards an apex angle not passing 60.   10. Fastener according to any one of the   preceding statements, characterized in that the region (46) of the nose (22) which is immediately adjacent   at the shank (18) narrows to an apex angle of 70.   11. Fastener according to any one of the   preceding statements, characterized in that the sleeve (16) is a tubular cylinder having a   smooth parallel axial perforation.   12. A fastener according to claim 11, characterized   characterized by the fact that the perforation of the sleeve (16) is slightly flared at each end to allow   at the smaller diameter end of the nose (22) of easily.   13. Fastener according to any one of the   wherein the angle at which the more abruptly narrowed region (46) of the nose (22) meets the shank (18) and the length of the narrowed region (46) are provided such that once that the front end (48) of the sleeve (16) has been forced past the nose (22) 9 a portion of the sleeve (16), in a region adjacent the forward end (48), has a substantially cylindrical shape having an inside diameter significantly greater than   outer diameter of the rod (18).