RU2534896C1 - Screw with captive parts - Google Patents

Abstract

FIELD: construction.

SUBSTANCE: screw with captive parts is made in the form of a body with a threaded part on one end, with a head on the other end and with a plain part on the body between the threaded part and the head of the screw; it includes a packing and spring washer and a sleeve, and the plain part of the screw has a diameter equal to an arithmetic mean value of average and inner diameters of the thread. The sleeve is provided on one of its edges with an annular flange, the diameter of which is larger than that of a hole made in the part or an assembly unit, which is intended for installation of the screw. Outer diameter of the sleeve without any annular flange corresponds to inner diameters of packing and spring washers. Inner diameter of the sleeve is made so that free passage of the threaded part of the screw is provided through it. A slot is made on the sleeve in a longitudinal direction along the symmetry axis. On the sleeve symmetrically to the slot on the side opposite to the annular flange there are two mouldings of a spherical shape, which face with their projecting parts inside the sleeve so that distance between them is equal to the average diameter of the screw thread. Length of the sleeve to the annular flange is equal to total thickness of the part through which the screw passes, thickness of the packing washer and half thickness of the spring washer. Length of the threaded part of the screw is equal to distance from the annular flange of the sleeve to the mouldings of spherical shape.

EFFECT: simpler installation method of screws with captive parts.

3 dwg

Description

The invention relates to the field of general engineering, namely to fasteners for detachable screw connection of parts and assembly units, and serves to protect the joints from loss of screws and washers when removing removable parts and assembly units during operation.

A threaded connection [1] is known, which contains a captive bolt, a washer and a fixing element in the form of a stepped sleeve with a threaded hole and a blind groove, the fixing element of which is installed in a smooth stepped hole of the joining part. The disadvantages of this connection are: the implementation in the joined part of a more complex, compared with a smooth hole, holes of strictly specified geometry; low ability to compensate for errors in the implementation of the center-to-center distances coordinating the axis of the screw holes and, as a result, the designation of increased accuracy of the maximum deviations of the center-to-center distances for these holes.

Closest to the proposed invention in technical essence is a screw securing the cover to the equipment case [2], containing a sleeve, a washer and a spring washer, in which the rod passes through a threaded hole in the washer, with the possibility of radial movement in the sleeve. This fastening allows, especially for large covers with a large number of fastening points and distances between them, to assign tolerance fields for making the center-to-center distances coordinating the axis of the screw holes more than with conventional captive screws passing through the threaded hole in the fastened part. The disadvantage of this mount is the complexity of the installation method: it is necessary to roll the washer in the extension of the sleeve to keep it from axial movement; to fix the sleeve in a metal cover, it is necessary to press fit, for which it is necessary to perform high precision machining of mating parts to obtain an interference fit or use a solder joint, or in the case of a plastic cover, use an adhesive joint, which requires the use of special technological equipment (press, soldering iron) and additional consumables (solder, glue).

The objective of the invention is to simplify the method of mounting screws with captive parts, providing improved conditions for the collection of parts and assembly units by compensating for errors in the execution of center-to-center distances coordinating the axis of the screw holes.

The task is achieved in that the screw is equipped with a sleeve having a floating installation in the hole of the fixed part, the sleeve has an annular bead, a slot and spherical moldings holding the screw, consisting of a head, smooth and threaded parts, in the sleeve, thereby ensuring in the mating mutual protection against the loss of the screw and the sleeve, as well as the washers worn on the screw, from the hole of the fixed part or assembly unit, while the pairing of the screw with the sleeve is due to the elastic deformation of the sleeve It does not require any tooling or equipment.

The invention is illustrated by drawings, where

figure 1 shows a screw with captive details in a perspective view;

figure 2 - screw with captive details in the context of a perspective view;

figure 3 - sleeve in a section in a perspective view.

The screw 1 with captive parts contains a washer 2 and a spring 3 washer and a sleeve 4. The screw 1 is made in the form of a rod with a threaded part 5 at one end, with a head 6 at the other, and a smooth part 7 is made between the threaded part and the screw head on the rod diameter equal to the arithmetic mean of the average and internal diameters of the thread. The sleeve 4 has at one edge an annular bead 8, the diameter of which is larger than the diameter of the hole in the part or assembly unit designed to install the screw. The diameter of the outer surface 9 of the sleeve 4 without an annular collar 8 corresponds to the inner diameters of the washer 2 and the spring 3 washers, ensuring their free landing on the outer surface 9 of the sleeve 4, the diameter of the inner surface 10 of the sleeve 4 is made so that a threaded portion of the screw part 5 is provided through it 1. On the sleeve 4 in the longitudinal direction along the axis of symmetry, a slot 11 is made, and from the side opposite to the annular collar 8 symmetrically of the slot 11, two spherical moldings 12 are made, facing the protruding parts inside the sleeve, so that the distance D between them is equal to the average diameter of the thread of the screw (see figure 3). The length of the sleeve 4 to the annular shoulder 8 is made equal to the total thickness of the part through which the screw 1 passes, the thickness of the washer 2 and half the thickness of the spring washer 3. The length of the threaded portion of the screw 1 is equal to the distance from the annular shoulder 8 of the sleeve 4 to the spherical molds 12.

The installation of the screw with washers and sleeve is as follows. The spring 3 and washer 2 are put on the smooth part 7 of screw 1 so that the spring washer 3 is between the head 6 of screw 1 and the washer 2. Then screw 1 is inserted by the threaded part 5 into the hole of the fixed part or assembly unit, and then the sleeve 4 side with molds 12 is put on the threaded part 5 of the screw 1 with a force directed along the axis of the screw 1, while the screw 1 with the threaded part 5 presses on the spherical molds 12 and the axial force, transmitted normally from the screw 1 through the molds 12, unloads the sleeve 4, what contribute the slot 11. Once the threaded portion 5 of the screw 1 will pass the molding 12 of the sleeve 4, under the action of the elastic properties of the sleeve material compressed and the distance between the molding 12 again becomes equal to the average diameter of the thread. In this state, the sleeve 4 and the screw 1 with the washers put on it mutually hold each other from falling out of the hole of the fixed part or assembly unit, because when the screw 1 moves in the direction of the head 6, it expands on the moldings 12 of the sleeve 4 with an expanding threaded part 5 and pulls it along with it, while the sleeve 4 with an annular collar 8 rests against the part or assembly unit and thereby prevents the loss of screw 1. Similarly, when moving of the sleeve 4 in the direction of the annular collar 8 with its molds 12 abuts against the expanding threaded part 5 of the screw 1 and pulls it along with the washers, as a result of which the screw 1 rests itself through the washers with the head 6 on the part or assembly unit and thereby prevents you the sleeve 4 is dropped. The disassembly of screw 1 is performed as follows: when an axial force is applied to the sleeve 4, it presses with spherical molds 12 onto the expanding threaded part 5 of screw 1 and the axial force, transmitted along the normal from the screw through the moldings 12, unloads the sleeve, which is facilitated by the slot 11. After the moldings 12 of the sleeve 4 pass the threaded part 5 of the screw 1, the sleeve is compressed under the action of the elastic properties of the material and the distance between the moldings 12 again becomes equal to the average diameter of the thread, while the screw 1 and sleeve 4 come out of the bushing After this, the washers can be removed from screw 1.

Thus, the screw is interfaced with the washer, spring washers and the sleeve due to the elastic deformation of the sleeve and does not require the use of any tooling or equipment during installation and dismantling.

Due to the wide supporting surface of the washer 2 on one side of the hole of the fastened part or assembly unit and the annular collar 8 on the sleeve 4 on the other side of the hole, the screw with captive parts is securely held in the hole with an increased clearance between the sleeve 4 and the walls of the hole, which allows to compensate errors in the implementation of the center-to-center distances coordinating the axis of the screw holes.

Information sources

1. USSR Copyright Certificate No. 1681076 A1, cl. F16B 41/00, 09/30/1991.

2. Patent DE 4131779 A1, cl. F16B 41/00, 03/25/1993.

Claims (1)

A captive screw made in the form of a rod with a threaded part at one end, with a head on the other and a smooth part on the rod between the threaded part and the screw head, containing a washer and spring washers and a sleeve, characterized in that the smooth part of the screw is made with a diameter equal to the arithmetic mean of the average and internal diameters of the thread, the sleeve has an annular flange on one edge, the diameter of which is larger than the diameter of the hole in the part or assembly unit designed to install the screw, the bushing diameter without an annular collar corresponds to the inner diameters of the washer and spring washers, ensuring their free fit on the bushing, the bushing’s inner diameter is made so that a threaded portion of the screw passes through it, a slot is made in the longitudinal direction along the axis of symmetry on the bushing, on the bushing symmetrically cuts from the side opposite the annular flange, two spherical moldings are made, facing the protruding parts inside the sleeve, so that the distance between them is equal to the average the diameter of the screw thread, the length of the sleeve to the annular collar is equal to the total thickness of the part through which the screw passes, the thickness of the washer and half the thickness of the spring washer, the length of the threaded part of the screw is equal to the distance from the annular collar of the sleeve to spherical formations, while the sleeve is installed with a gap into the smooth through hole of the removable part or assembly unit from the side opposite to the installation of the screw, so that the annular collar is pressed against the surface of the part or assembly unit from the side against lower from the screw head, and the edge of the sleeve on which the moldings are located, enters the holes of the washer and spring washers.

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