Classifications

• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
  • F16B—DEVICES FOR FASTENING OR SECURING CONSTRUCTIONAL ELEMENTS OR MACHINE PARTS TOGETHER, e.g. NAILS, BOLTS, CIRCLIPS, CLAMPS, CLIPS OR WEDGES; JOINTS OR JOINTING
  • F16B41/00—Measures against loss of bolts, nuts, or pins; Measures against unauthorised operation of bolts, nuts or pins
  • F16B41/002—Measures against loss of bolts, nuts or pins

Definitions

• the invention relates to a method for making a screw and a sleeve captive for implementing this method.
• two mechanical parts for example a cover to a casing using one or more screws
• Devices achieving this goal are known as captive screws. These devices are produced by machining, for example, a standard screw.
• the screw thus turned is mounted in a hole in the cover, a tapped hole with the same diameter as the nominal diameter of the screw.
• the thickness of the cover at this hole being less than the length of the low-cut part of the body of the screw.
• the screw remains attached to the cover.
• This screw thus modified is specific to the two elements which are fixed to one another. This specificity is a drawback, especially when the production is unitary or in small series. Indeed, the screw, most often from a standardized screw, is also modified in small series, which considerably increases its cost price. Thereafter, we will call standard element, an element which is not designed for a particular use. A standard item is a standard item.
• the method according to the invention eliminates this drawback by using only standard elements, screw used without specific modification to which a sleeve is also added.
• a method for making a screw captive passing through a hole in a mechanical part, the screw comprising a head and a threaded body, characterized in that it consists of screwing onto the end of the body of the screw opposite the head of the screw a cylindrical sleeve tapped in a way complementary to the thread of the body of the screw, sleeve externally threaded, and to immobilize the sleeve relative to the screw and in that the screw provided with its sleeve turns freely in the hole without intermediary.
• process for making captive a screw comprising a head and a threaded body, characterized in that it consists in screwing at the end of the body of the screw opposite to the head of the screw, a cylindrical sleeve tapped in a manner complementary to the threading of the body of the screw, sleeve externally threaded, and to immobilize the sleeve relative to the screw.
• the invention also provides externally threaded and internally threaded sleeves specially adapted by the addition of immobilization means on the screws.
• the main advantage linked to the invention lies in the fact that the sleeve is standard.
• the same sleeve can be used in multiple applications regardless of the length and head of the screw on which it is mounted. Thus, it can be mass produced and used in any type of industry. Its cost will be low.
• FIG. 1a and 1b show a screw and a sleeve
• FIG. 2 shows a sleeve immobilized on a screw by means of a film of glue
• FIG. 3 shows a sleeve immobilized on a screw by means of a solder joint
• FIG. 4 shows a sleeve, one end of which is extended by a cylinder portion for immobilization by crimping
• Figure 5 shows the sleeve shown in Figure 4 screwed and crimped on a hexagonal head assembly screw
• FIG. 6 shows a front view and left view of a sleeve immobilized on a screw by means of two pins
• - Figure 7 shows an example of a sleeve having two pin guide grooves
• FIG. 8 represents an example of a pin with an extended rectangular section of a part with a circular section
• FIG. 9 shows an example of a rectangular section spindle extended by a section with sharp edges section
• - Figure 10 shows an example of a sleeve as shown in Figure 7 having a pin
• FIG. 11 shows an example of a sleeve as shown in Figure 10, sleeve screwed onto the end of a screw;
• - Figure 12 shows the assembly shown in Figure 11 after pressing the pins.
• FIG. 1a represents a standard assembly screw 1 with a hexagonal head of axis 3.
• FIG. 1a also represents a sleeve 2 of cylindrical shape with the same axis 3 as screw 1, the internal surface 4 of which is tapped in a manner complementary to the thread. of the screw 1.
• the screw 1 with a hexagonal head is taken only by way of example, the invention can be applied to any form of thread and screw head.
• a feature of the invention is that the thread of the screw 1 is complementary to the thread of the sleeve 2 so that the sleeve can be screwed onto the screw.
• the outer surface 5 of the sleeve 2, meanwhile, is threaded. This thread is determined according to the use of the device.
• the sleeve 2 thus produced is screwed onto the end of the screw 1 opposite the screw head as shown in FIG. 1 b.
• the length of the sleeve measured along axis 3 may for example be 1.5 times the nominal diameter of the sleeve thread, which ensures good mechanical strength of the screw made captive in a housing into which it is screwed.
• Figure 1b also shows, at reference 6, a partial section of a mechanical part such as for example, a cover whose screw 1 is made integral.
• the thickness of the cover 6 measured along the axis 3 is less than the length of the screw 1 between the sleeve 2 and the head of the screw 1.
• the screw 1 provided with its sleeve 2 thus rotates freely in the hole 7 of the cover 6 without intermediary.
• this cover 6 may include a hole 7 tapped in a manner complementary to the thread of the sleeve 2. This hole 7 tapped allows the screw 1 fitted with its sleeve 2 to be screwed into the cover 6.
• An advantageous variant for the realization of the hole 7 consists in making in the cover 6 a smooth hole 7 whose diameter is between the nominal diameter of the screw 1 and the nominal diameter of the thread of the sleeve.
• the advantage of this variant is that the screw 1 fitted with its sleeve 2 is completely secured to the cover 6.
• Another characteristic of the invention is that the sleeve 2, once screwed on the screw 1, is immobilized relative to the screw.
• a first embodiment consists in gluing the sleeve onto the screw as shown in FIG. 2.
• a film of adhesive 10 could for example be placed in the contact zone between the threads of the screw 1 and those of the sleeve 2.
• This embodiment does not require a particular shape for the sleeve 2.
• bonding requires great rigor in the operating mode in order to ensure good reproducibility.
• a second embodiment consists in welding the sleeve and the screw between them.
• An example of a welding process known to have little deformation of the elements welded together is electron beam welding.
• FIG. 3 represents an example of a sleeve 2 immobilized on a screw 1 by means of a weld joint 20.
• This weld joint 20 is located in the zone of contact between the threads of the screw 1 and of the sleeve 2. It forms a cone whose base is located at the end of the screw 1, opposite end to the head of the screw 1, the tip of the cone is located substantially in the middle of the sleeve 2.
• a single gasket welding is shown, it is understood that as many joints can be made as the tightening torque that one wishes to apply to the screw made captive can be required.
• This embodiment does not require any particular shape for the sleeve 2. On the other hand, it requires substantial tools.
• a third embodiment consists in crimping the sleeve on the screw.
• An example of a sleeve 30 suitable for crimping is presented in FIG. 4.
• the sleeve presented in FIG. 1 forms a first part 31 cylindrical.
• This part 31 is extended at one of its ends by a second coaxial cylindrical part 32 of the first part 31.
• the internal surface of the second part 32 is the extension of the internal surface of the first part 31.
• the thread of the sleeve 30 is also extended.
• the outer surface of this second part 32 is smooth, its diameter is less than the diameter of the bottom of the threads of the thread of the sleeve 30.
• the sleeve 30 is oriented as so that the second part 32 is on the side of the screw head 1. It is understood that the reverse orientation is possible.
• the sleeve 30 is immobilized relative to the screw 1 by means of several crimping imprints 33. Two indentations 33 of oblong shape are shown in FIG. 5. The longest length of the oblong forms has the same orientation as the axis 3 of the screw 1. It is understood that the number of indentations 33 can vary according to the torque tightening that you want to apply to the captive screw. This embodiment requires much less tool than for welding, the implementation time is also shorter. On the other hand, the sleeve requires a particular shape suitable for crimping.
• a fourth embodiment consists in placing one or more pins which shear the threads of the screw.
• the principle is described in Figure 6.
• Figure 6 shows, as in Figure 1b, a sleeve 2 screwed on a connecting screw 1.
• the immobilization is achieved by two cylindrical pins 40 put in place, parallel to the axis 3 of screw 1 between the bottom diameter of threads of screw 1 and the bottom diameter of threads of tapping of the sleeve 2. It is understood that the immobilization of the sleeve 2 relative to the screw 1 operates with a single pin 40.
• Any number of pins 40 can be chosen greater than or equal to one.
• the number of pins 40 is determined according to the criteria for choosing the embodiment, criteria defined above.
• two pins 40 are used for nominal screw diameters 1 less than or equal to four millimeters and four pins 40 beyond.
• An exemplary embodiment of this broaching principle consists in providing a groove in the sleeve to guide each spindle.
• An example of a sleeve 2 having two symmetrical grooves 50 is shown in FIG. 7. Only the view representing the section of the sleeve is shown here.
• the sleeve 2 has externally an ISO standard thread of nominal diameter M5, it internally has an ISO standard thread of nominal diameter M3.
• the groove 50 is a recess whose section is T-shaped. The groove 50 thus extends over the entire length of the sleeve 2 parallel to the axis 3 of the sleeve.
• the section of the groove 50 has an opening 52 which opens on the inner surface 4 of the sleeve 2 symmetrically with respect to an axis 51 of symmetry of the section of the sleeve 2.
• the width of the opening 52 is 0 , 8 millimeters, it forms the vertical bar of the T.
• the opening 52 is extended by a rectangular part 53 wider than the opening 52 forming the horizontal bar of the T.
• the width of this rectangular part is 1.1 mm, its depth 0.27 mm.
• the total depth of the groove 50 is 1.87 millimeters. It is understood that the dimensions mentioned above are only given by way of example constituting a preferred embodiment of a sleeve comprising two grooves 50.
• Pin 40 has two parts.
• a first part 60 used for guiding the spindle in a groove 50 of FIG. 7 has a rectangular section whose dimensions are close to the dimensions of the rectangular part 53 of the section of the groove 50 in FIG. 7.
• the part 60 must be able to be fitted into the rectangular part 53 of the groove 50 with a slight tightening.
• the first part 60 is extended by a second part 61 of circular section.
• the second part 61 is used to shear the thread of the screw.
• the diameter of this circular section is close to the width of the opening 52 of the groove 50.
• the part 61 is tangent to the plane 62 containing the width of the rectangular part 60.
• the plane 63, perpendicular to the plane 62, is a plane of symmetry for the two parts 60 and 61. The intersection of this plane 63 with the pin 40 is hatched in FIG. 8.
• the variant of spindle 40 previously described is advantageously used with sleeves whose nominal diameter of the internal surface tapping does not exceed four millimeters, beyond, we will prefer a form of spindle 40 having sharp angles for the part which will shear the screw threads.
• An exemplary embodiment of such a pin 70 is shown in Figure 9.
• This pin 70 has two parts.
• a first part 71 is similar in shape to the first part 60 of the pin 40 shown in FIG. 8.
• the first part is extended by a second part 72 of section with sharp angles.
• This second part 72 is used to shear the thread of the screw.
• the section of this second part 72 has a rectangular shape, a large side of which is replaced by a V, the point of which makes the section concave.
• the length of the long side is close to the width of the opening 52 of the groove 50 of the sleeve 2.
• the edges 73 forming an acute angle will be used to shear the threads of the screw.
• the plane 62 contains the width of the rectangular part 71 and the planar surface of the part 72 opposite the V.
• the plane 63, perpendicular to the plane 62, is a plane of symmetry for the two parts 71 and 72.
• the intersection of the plane 63 with the spindle 70 is hatched in FIG. 9. It is optionally possible to produce on the spindle 70 a chamfer 74 on the second part 72 near the first part 71, which will allow better start of shearing of the threads of the screw.
• the rectangular section of a pin 40 or 70 is inserted into a groove 50 of the sleeve 2, the plane 60 being in contact with the bottom of the groove 50.
• the sleeve thus equipped with one or more pins, a pin by groove 50, can be referenced as a spare part.
• the pin for example 70 thus inserted into the sleeve is shown in FIG. 10.
• the sleeve represented in FIG. 10, is screwed onto the end of a screw 1, the pins for example 70 being located for example on the side of the sleeve 2 opposite the head of the screw 1
• the pins for example 70 being located for example on the side of the sleeve 2 opposite the head of the screw 1
• the chamfer 74 shown in FIG. 9 which, for the spindle 70 abuts on the end of the screw 1.
• the screw 1 abuts on the second part 61. Then, the pins are pressed along the axis 3 of the screw 1 in the direction of the head of the screw 1 in order to shear the threads of the screw 1.
• This fourth embodiment has the advantage of a simple installation of the sleeve 2 on the screw 1. It suffices to bring the screw 1 into abutment on the pins of the sleeve 2.
• Another advantage hey to this embodiment is that it requires only a very simple tool for immobilizing the sleeve. Only a pressure on the pins is sufficient.
• the sleeve requires a particular shape adapted to the broaching.

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• Engineering & Computer Science (AREA)
• General Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Connection Of Plates (AREA)

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• 1996
  • 1996-10-08 FR FR9612235A patent/FR2754320B1/fr not_active Expired - Fee Related
• 1997
  • 1997-10-03 WO PCT/FR1997/001758 patent/WO1998015744A1/fr not_active Application Discontinuation
  • 1997-10-03 AU AU45599/97A patent/AU4559997A/en not_active Abandoned
  • 1997-10-03 JP JP10517241A patent/JP2001501717A/ja active Pending
  • 1997-10-03 EP EP97943939A patent/EP0929747A1/fr not_active Withdrawn
  • 1997-10-03 CA CA002268348A patent/CA2268348A1/fr not_active Abandoned

Non-Patent Citations (1)

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