CS233115B1 - A device for tightening and prestressing or loosening screws and nuts - Google Patents

Abstract

The device is designed for tightening and pre-tensioning or loosening screws and nuts and solves the required pre-tensioning of the screw without damaging the thread. The clamping sleeve with a thread for the shaft of the screw being tightened is equipped with a support that rests against the face of the hollow screw, which is placed in the moving nut, which rests on the body of the device. Using a nut or torque wrench, the moving nut is rotated, while the hollow screw is moved, which carries the pre-tensioned screw with it. The nut can then be tightened with a slight torque in a relaxed state.

Description

Devices for tightening and preloading or loosening screws and nuts

The device is designed to tighten and preload or loosen screws and nuts and solve the required preload of the screw without damaging the thread. The threaded collet for the screw to be tightened is provided with a support which is supported on the face of the hollow screw, which is housed in a movement nut resting on the body of the device. Using a nut or torque wrench, it rotates the motion nut while sliding the hollow screw that carries the pre-tensioned screw with it. The nut can then be tightened with a slight torque in the unloaded state.

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FIG

233 115

The invention provides a device for tightening and preloading or loosening screws and nuts.

The devices used to tighten and preload bolts and nuts can be divided into two types. The first type is the normal tightening of the nut using a normal or torque wrench. This type is the simplest and most commonly used, but it is also the least accurate and only applicable to smaller size screws. Due to the friction between the threads and the bearing surface of the nut, only a small part of the applied torque is used to exert an axial force on the bolt. In addition, the bolt is subjected to severe torque when tightening, and larger bolts often become seized and damaged. In some cases, the screw may be completely destroyed. The second type is that the bolt is pre-tensioned by means of a special, mostly hydraulic device. In this case, the required axial force is generated by a linear hydraulic motor specially designed for this purpose. The device is a screw _t elastically prestressed with a predetermined force. This creates a play between the nut and the bearing surface. This clearance is limited by the rotation of the nut and the bolt remains preloaded after the hydraulic biasing force is removed. The nut rotates in the unloaded state with a slight torque so that the thread is not damaged. The biasing force can be adjusted precisely so that the screws can be tightened evenly. When using this type, however, in addition to the pre-pumping device itself, a relatively high pressure source, a hydraulic fluid reservoir and a device for regulating and measuring this pressure must be provided. Often there are problems with sealing and leakage of oil and maintenance requirements are not negligible.

The aim of the device for tightening and biasing or loosening the screws and nuts according to the invention is to substantially reduce these disadvantages and by providing a mechanical simple device to ensure the desired biasing of the screw without damaging the thread. The principle of the present invention is that the tensioning unit is formed

233 115 with a hollow screw with a motion nut and it is mounted on a bearing that is provided in the body of the device. The body of the device is supported on the base.

The advantage of the device according to the invention lies in the fact that in its use it is possible to derive the required bias in the screw in a purely mechanical manner relatively precisely, without damaging the thread and with a relatively small torque mement.

An example of a practical embodiment of the device according to the invention is shown in the accompanying drawing, in which Fig. 1 shows a cross-section of the device using a motion screw and motion nut with a threaded ball; In the right-hand part of both FIG. 1 and FIG. 2 there is shown a device mounted on a screw and ready for prestressing. In the left-hand part of FIGS. 1 and 2, there is shown a device with a pre-tensioned screw.

As can be seen from FIG. 1, the device for tightening and biasing or loosening screws and nuts consists of a body 5 of the device in which a bearing nut 3 with a hollow screw 2 having a ball thread is mounted on the bearing 4. In the center of the hollow screw 2, the clamping sleeve 1 extends, in the cavity of which the thread is provided to be screwed onto the tightened or tightened screw. preloaded screw 7 · When preloading the screw 7, the device according to the invention is fastened to the protruding shaft 9 of the screw

As the friction between the face of the hollow screw 2 and the support 10 of the chuck 1 is greater than the friction in the threads of the movement nut 3, the hollow screw 2 is only axially rotated. This creates a play X between the nut 8 and the base 6. By rotating the nut 8, e.g. through the cut-out 11 provided in the body 5 of the device, the clearance X defines and after the force biasing is canceled, it remains in the movement nut 3 and in the hollow screw 2 the efficiency of the device is constant, and thus the dependence of the biasing force on the torque is constant.

FIG. 2 shows an alternative solution of the device, wherein instead of a ball thread, a movement nut 25 and a hollow screw 2 with a normal metric or other thread are used.

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OBJECT OF THE INVENTION2U

Claims (1)

233 115 A device for tightening and preloading or screwing nuts and bolts consisting of a threaded clamping sleeve and supported by a stepped face on a tensioning unit provided in a device body, characterized in that the tensioning unit consists of a hollow screw (2) with a movement nut (3) ) _t which is mounted on a bearing (4) disposed in the body (5), September to