GB2120346A - Screw threaded fasteners - Google Patents

Abstract

To prevent loosening under vibration, the bearing surface of a screw 1 and/or a nut 2 has radial anti- slip corrugations or undulations 3. <IMAGE>

Description

SPECIFICATION Screw fasteners This invention relates to screw fasteners and in particular to machine screws, bolts and the like.

Machine screws, bolts, nuts and the like usually have smooth contact surfaces. When they are used in conditions in which they are subjected to vibration, they may be loosened by the vibration. To overcome this, it is usual to use locking washers, split pins or lock nuts. Selflocking nuts are also available, for example with nylon locking inserts, to prevent loosening under vibration, but these are relatively complicated and expensive.

The object of the present invention is to provide screw fasteners capable of resisting vibration without the use of additional elements such as spring washers, and of simple and cheap design.

According to the present invention a screw fastener has anti-slip corrugations on its contact surface, that is to say on the underside of the head of a screw, or on at least one side, preferably both sides of a nut.

In the accompanying drawings:- Figure 1 shows a screw and nut embodying the invention, and Figure 2 shows a screw embodying the invention.

Figure 1 shows a hexagon-head machine screw 1 and a hexagon nut 2. The contact surface of the screw head, that is to say the underside of the screw head, has radially extending corrugations or undulations 3 forming an anti-slip surface. The nut has corresonding corrugations or undulations on both sides. These anti-slip surfaces lock the screw and nut to the elements fastened by them, in a manner which prevents loosening under vibration. It is not necessary to use an additinoal locking washer, split pin or lock nut.

Such a screw can be used without a nut, in a threaded hole of a machine element, and accordingly Figure 2 shows a corresponding machine screw alone. In this case it is preferred that the machine element being secured by the screw is provided with a corresponding anti-slip surface around the screw hole.

It is to bye observed that the anti-slip contact surface should be substantially perpendicular to the screw or nut axis. The invention can however be applied to screws and nuts of substantially any basic form for example square nuts, square-head screws, and screws with slotted or socket heads.

Screw fasteners according to the invention are simpler to use and cheaper than known screw fasteners incorporating or provided with antivibration means.

Claims

1. A screw fastener characterised by anti-slip corrugations on the contact surface thereof.

2. A screw fastener as claimed in claim 1 comprising in combination a nut having anti-slip corrutations on at least one side and a screw having anti-slip corrugations on its head.

3. A new set screw is characterised by furnished with wave-shaped anti-slide jaw on the contact surface of screw and the fixed element.

4. A new set screw as claimed in claim 1 wherein the contact surface of head of screw and fixed element are vertical to body of screw and have wave-shaped anti-slide jaw on it.

5. A new set screw as claimed in claim 1 wherein two sides of nut are designed waveshaped anti-slide jaw.

6. Screw fasteners substantially as herein described with reference to Fig. 1 or Fig. 2 of the accompanying drawing.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (6)

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Screw fasteners This invention relates to screw fasteners and in particular to machine screws, bolts and the like. Machine screws, bolts, nuts and the like usually have smooth contact surfaces. When they are used in conditions in which they are subjected to vibration, they may be loosened by the vibration. To overcome this, it is usual to use locking washers, split pins or lock nuts. Selflocking nuts are also available, for example with nylon locking inserts, to prevent loosening under vibration, but these are relatively complicated and expensive. The object of the present invention is to provide screw fasteners capable of resisting vibration without the use of additional elements such as spring washers, and of simple and cheap design. According to the present invention a screw fastener has anti-slip corrugations on its contact surface, that is to say on the underside of the head of a screw, or on at least one side, preferably both sides of a nut. In the accompanying drawings:- Figure 1 shows a screw and nut embodying the invention, and Figure 2 shows a screw embodying the invention. Figure 1 shows a hexagon-head machine screw 1 and a hexagon nut 2. The contact surface of the screw head, that is to say the underside of the screw head, has radially extending corrugations or undulations 3 forming an anti-slip surface. The nut has corresonding corrugations or undulations on both sides. These anti-slip surfaces lock the screw and nut to the elements fastened by them, in a manner which prevents loosening under vibration. It is not necessary to use an additinoal locking washer, split pin or lock nut. Such a screw can be used without a nut, in a threaded hole of a machine element, and accordingly Figure 2 shows a corresponding machine screw alone. In this case it is preferred that the machine element being secured by the screw is provided with a corresponding anti-slip surface around the screw hole. It is to bye observed that the anti-slip contact surface should be substantially perpendicular to the screw or nut axis. The invention can however be applied to screws and nuts of substantially any basic form for example square nuts, square-head screws, and screws with slotted or socket heads. Screw fasteners according to the invention are simpler to use and cheaper than known screw fasteners incorporating or provided with antivibration means. Claims

1. A screw fastener characterised by anti-slip corrugations on the contact surface thereof.

2. A screw fastener as claimed in claim 1 comprising in combination a nut having anti-slip corrutations on at least one side and a screw having anti-slip corrugations on its head.

3. A new set screw is characterised by furnished with wave-shaped anti-slide jaw on the contact surface of screw and the fixed element.

4. A new set screw as claimed in claim 1 wherein the contact surface of head of screw and fixed element are vertical to body of screw and have wave-shaped anti-slide jaw on it.

5. A new set screw as claimed in claim 1 wherein two sides of nut are designed waveshaped anti-slide jaw.

6. Screw fasteners substantially as herein described with reference to Fig. 1 or Fig. 2 of the accompanying drawing.