RU2450175C1 - Thread joint unit - Google Patents

Abstract

FIELD: machine building.

SUBSTANCE: threaded joint unit of machines, preferably hydraulic machines comprises studs and nuts mounted in the holes of the parts to be connected, cylindrical sleeves made with an internal tapered hole and a radial unilateral slit along the axis through which the studs pass. The cylindrical sleeves are mounted within the cylindrical grooves of the parts to be connected and are made with an internal tapered hole mating without a clearance from the outer conical part of the studs whose smaller base is directed towards the side of a threaded part of rods and studs.

EFFECT: increased stiffness of the structure and fatigue strength of the connection by reducing bending stress under the threaded part of a stud.

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Description

The invention relates to mechanical engineering, in particular to hydraulic engineering, and can be used to connect the shafts of hydraulic turbines with the shafts of hydrogenerators, shafts with impellers of hydraulic turbines and working bodies of agricultural machines.

Known designs of threaded joints in which bolts are installed in the holes of the parts to be connected with and without a gap [1].

In the case of installing bolts with a gap, they must create a friction force on the joint surface that exceeds the external load by the amount of safety margin, and ensure that the joint is fixed. The design disadvantages are low bearing capacity and durability, especially under the action of vibrational loads, at which the friction force is practically not realized.

In the case of installing bolts without a gap, they are counted on shear and crushing under the assumption of their uniform loading. To ensure a tight fit, a joint bore of the holes in the parts to be connected and a high accuracy in the manufacture of bolt rods are necessary. These technological operations are very laborious, which leads to significant costs in the manufacture and installation of connection nodes. The second disadvantage of this design is the uneven distribution of shear forces in the group flange connection in the manufacture of parts for the transitional fit of the slide [2]. The implementation of a denser fit is virtually eliminated due to a significant increase in the complexity of this operation for a group threaded connection of a large machine assembly.

There is also known a node for connecting machine parts (prototype), containing cylindrical bushings and studs with nuts installed in the holes of the parts to be connected [3]. Cylindrical bushings made with an internal conical hole and a radial one-sided slot along the axis are mounted within the cylindrical grooves of one connected part at the landing with a gap. The stud rods from the threaded part to the end of the interface with the bushings are made conical.

However, in this design, the bending stiffness of the studs installed in the holes with a gap throughout the thickness of one connected part from the bearing surface of the nut to the joint plane is negligible. In addition, the maximum bending stresses fall on the cross section of the threaded part of the studs, which coincides with the first turn of the nut, where significant stress concentrations occur, and which, first of all, breaks down in the joints. As a result, the fatigue strength of the entire joint assembly is reduced.

The purpose of the invention is to increase the rigidity of the structure and the fatigue strength of the joint by reducing the bending stress under the threaded part of the studs.

This goal is achieved in that the cylindrical bushings are installed within the cylindrical grooves of the parts to be joined and are made with an internal conical hole that mates without a gap with the outer conical part of the studs, the smaller base of which is directed towards the threaded part of the stud rods.

Figure 1 shows a longitudinal section of a threaded connection unit, and figure 2 shows a cylindrical sleeve.

The threaded connection assembly (Fig. 1) comprises studs 4 installed in the holes of the parts 1 and 2 to be joined with nuts 5 and 6. Cylindrical bushings 3 made with an internal conical hole 9 and a radial one-sided slot 10 along the axis (Fig. 2) are installed in within the cylindrical grooves 11 and 12 of the connected parts 1 and 2 in the area l ₁ previously with a minimum gap (within 10-50 microns). The outer conical part 7 of the rods of the studs 4 from the threaded part to the cylindrical section 8 is mated without a gap with the inner conical hole 9 of the cylindrical bushings 3. The rods of the studs 4 within the cylindrical section 8 are installed in the holes of the connected parts 1 and 2 with a gap Δ in the range 1 ... 2 mm

When tightening the nuts 5 and 6 of the threaded joint assembly, the cylindrical bushings 3 under the influence of internal pressures from the outer conical part 7 of the stud rods 4 are easily expanded in the radial direction and pinched in the cylindrical grooves 11 and 12 of the connected parts 1 and 2 in the area l ₁ . In this case, the minimum clearance between the outer diameter d of the cylindrical bushings 3 and the cylindrical recesses 11 and 12 of the connected parts 1 and 2 is selected, forming an interference fit. Thus, this design provides for pinching the outer conical part 7 of the rods of the studs 4 and cylindrical bushings 3 in the cylindrical grooves 11 and 12, as well as pinching the supporting surfaces of the nuts 5 and 6 in the connected parts 1 and 2. As a result, the most dangerous section of the threaded part of the studs 4, coinciding with the first turn of nuts 5 and 6, does not bend. Bending stresses are transmitted only to the cylindrical section 8 along the length l ₂ , where the cross-sectional area of the rods of the studs 4 is maximum and, as a result, the structural rigidity increases.

During the operation of the threaded connection unit, the external load will be transmitted evenly to all cylindrical bushings 3, clamped by interference fit in the cylindrical grooves 11 and 12, as well as to the studs 4 due to their rigid jamming on the mating conical surfaces and jamming of the supporting surfaces of the nuts 5 and 6 in the connected parts 1 and 2. The uniform distribution of the external load is also facilitated by the symmetry of the structure relative to the joint plane of the connected parts.

Thus, in the proposed site increases the rigidity and fatigue strength of the entire connection.

Information sources

1. Ivanov M.N. Machine parts. - M .: Higher school. 1991 - 383 p.

2. Bugov A.U. Flange connections. Calculation and design. - L .: Mechanical engineering. L.O. 1975 - 191 p.

3. Patent for invention No. 2319868 "The unit for connecting machine parts", Bugov H.U., Apazhev A.K., Demyanov V.A. et al. March 20, 2008 (prototype).

Claims (1)

A threaded assembly of machines, mainly hydraulic machines, comprising studs with nuts installed in the openings of the parts to be joined, cylindrical bushings made with an internal conical hole and a radial one-sided slot along the axis through which the studs pass, characterized in that the cylindrical bushings are installed within cylindrical grooves connected parts and are made with an inner conical hole that mates without a gap with the outer conical part of the studs, the smaller is based e which is directed towards the threaded portion of rod pins.

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