The present invention relates to a washer.

Most washers have an inner hole which is larger than the diameter of the thread of a corresponding screw, or bolt, but smaller than the size of the head of the screw or bolt. Thus, such washers can be easily inserted over the thread but not the head of a corresponding screw, or bolt.

Automatic screw insertion machines generally comprise a screw supply bin, a screw gun and a flexible feed line which connects the supply bin to the screw gun. Screws are placed in the supply bin and rotated about the bin before being consecutively fed down the feed line to the screw gun. The screw gun receives the fed screw and is constructed so as to sequentially eject a screw from an opening therein and screw the screw into an object disposed adjacent the opening whenever the gun is activated. The gun may be activated automatically.

A significant problem associated with screw insertion machines is that it is extremely difficult to insert a washer on screwing a screw into the object during an assembly process. As the gun is placed against the object when inserting a screw it is very difficult to hold and align a washer with the screw, prior to insertion, and it cannot, for safety reasons, be done manually. One possible solution is to place washers on respective screws and then place the screws and washers in the supply bin. The screws and respective washers are fed down the feed line consecutively and inserted together by the screw gun into the object. This, however, suffers the disadvantage that the washers cannot be maintained on the screws until they

reach the opening of the gun as the washers are "shaken off", or removed by vibration of the screws as they are rotated by the supply bin and fed down the feed line.

Furthermore, there are a number of situations where a screw and a washer must be inserted in a position which is not readily accessible. The washer is invariably placed on the screw first and the screw carefully moved to the position, using a magnetic head screw driver, whilst trying to ensure the washer does not become dislodged from the screw, which is almost impossible to achieve if the screw must be inserted with its head upstanding.

There are screws available which capture washers during manufacture of the screws. Such captive screws are first made without a thread and a respective washer is inserted thereon. A thread is then added to the screw during this process the thread raises and increases the diameter of the screw at the thread so that the inserted washer is captured between the head and thread of the screw. The screws are also manufactured by providing a blank portion in the thread of the screws over which a split washer is inserted and then captured by the screw by compressing the washer onto the screw. Captive screws of this type, however, are expensive (compared to commonly available sets of screws and washers) primarly due to the difficult manufacturing process involved.

Thus, it is desirable to provide a washer which can simply engage a threaded member, such as a bolt or screw, to overcome, at least in part, the problems discussed above.

In accordance with the present, invention there is provided a washer having an inner edge adapted to engage a thread of a threaded member so as to prevent said washer being dislodged from said threaded member after insertion thereon.

Preferably said threaded member includes a head portion which may assist in preventing said washer being dislodged. Preferably said washer comprises at least one projection disposed on said inner edge and is adapted to be threadably received by said threaded member such that said washer can be threaded onto said threaded member.

Preferably said projection comprised one or more teeth or one or more elastomeric inserts formed as one or more teeth or formed as a membrane.

Alternatively, said inner edge may be eliptical or triangular or any asymetrical shape and adapted to be threadably received by said threaded member.

The washer may also be made of changeable material such that the threaded member may be easily inserted through the washer and the dimensions of the washer then altered to engage the threaded member.

Preferably said threaded member is a screw of a bolt.

The present invention also provides a washer having at least one or more teeth' (preferably three equally spaced) disposed on an inner edge thereof.

Preferably said washer is annular and said teeth are disposed on said inner edge at equiangular distances with respect to one another.

Preferably said washer includes three teeth.

Preferred embodiments of the present invention will now be described, by way of example only, with reference to the accompanying drawings, wherein:

Figure 1 is a plan view of a first preferred embodiment of a washer;

Figure 2 is a plan view of a second preferred embodiment of a washer;

Figure 3 is a side view of the washer attached to a screw;

Figure 4 is a plan view of a third preferred embodiment of a washer;

Figure 5 is a side view of a washer attached to another screw; and

Figure 6 shows the simple flat washer as a combination of metal and non-metal material.

A washer 2, as shown in Figure 1, comprises an annular piece of metal 4 having three teeth 6 disposed on the inner circular edge 8 of the washer 2. The teeth 6 project from the edge 8 towards the centre 10 of the washer 2. The teeth 6 are positioned so as to be displaced an equiangular distance with respect to one another. For the washer 2, the teeth 6 are substantially 120 degrees apart, whereas if the washer included four teeth they would be substantially 90 degrees apart. The minimum number of teeth is one but optimum number is three equally spaced apart.

The washer 2 is illustrated as including a plurality of slits 12 along the inner edge 8 so as to define a plurality of gripping portions 14. The gripping portions 14 have edges 16 which are not coplanar with the outer circular edge 18 of the washer 2. The gripping portions 14 are deformed when a screw, or bolt, is inserted through the washer 2 and inserted into an object. The portions 14 press into the object and the head of the screw, or bolt, so as to enhance attachment of the screw, or bolt, to the object. Washers with gripping portions of the type described above are known as shake-proof washers.

The teeth 6 are configured, as shown in Figure 2, to be receivable by the thread 20 of a screw 22. The provision of the teeth 6 thereby enables the washer 2 to be threaded onto a screw 22 ready for insertion of the screw 22. The thickness or any geometrical characteristic (various shapes) can be different and modified according to the type of screws, material or assembly technology in order to make the assembly process more efficient. For example, if the screw 22 and the washer 2 are to be placed in a screw insertion machine, the washer 2 need only be secured to the screw 22 sufficiently to prevent the washer 2 being dislodged, or shaken off, from the screw 22 as it is rotated by the supply bin and passed down the feed line of the machine. The screw 22 and washer 2 can thereby be dispensed and inserted in an object by the screw gun. Theinsertion of the washer and the locking property is based on temporary _^ deformation of the locking parts.

A second shake-proof washer 30, as shown in Figure 3, is the same as the first washer 2 except the gripping portions 14 are more numerous and are disposed along the outer edge 18 of the washer 30. Also the teeth 6 are smaller in size and resemble nodules disposed on the inner edge 8.

A washer 50, as shown in Figure 4, has an inner peripheral edge 52 which, for example, is eliptical and an outer edge 54 which is circular (but can be designed in any shape which internally will provide the minimum two contact points between the washer and the screw) . In the eliptical example shown, inner edge 52 is demensioned so that, like the teeth 6, it enables the washer 50 to be suitably received by the thread of a screw or bolt. The eliptical shape of the edge 52 can be varied, as desired, to vary the manner in which the washer 50 engages a thread. One possible type of engagement is illustrated in Figure 5

where the washer 50 is configured so it can be loosely threaded past the thread 56 of a captive screw 58. The washer 50 is disposed on the neck 60 of the captive screw 58 and is prevented from being dislodged from the screw 58 by the head 62 of the screw 58 and the thread 56, which have larger outer diameters than the neck 60.

Figure 6 shows the simple flat washer 40 as a combination of metal 42 and non-metal material 44. As an example, a flat metal washer is shown and is covered by a non-metal elastomer layer bonded to the top washer surface. The elastomer layer 44 can be bonded on either one side or both sides or inside the hole to the internal surface of the metal part 42 depending upon the specific application and use. Washer 40 can be covered uniformly or elastomer can be formed as a section (portion) symetrically or randomly located.

The washers 2, 30 and 50 discussed above are preferably made of metal, such as steel, but they may be made of resilient deformable material. This would enable the inner edges of the washers to be deformed so as to enable insertion of the washers on to the corresponding screws or bolts without having to screw, or thread, the washers on to the screws, or bolts. In particular, pressure may be applied to the outer edge 54 of the third washer 50 so as to deform the elpitical inner edge 52 into another shape thereby enabling a screw or bolt to be easily inserted through the temporary larger hole of the washer 50. After insertion, the pressure applied to the outer edge 54 would be removed and the washer 50 would return to its original shape so as engage the corresponding screw or bolt.

Temporary deformable material may also be used in the design and production of this new type of washer. To make more flexible locking parts, and in an application which

requires special care in relation to fine or precisely formed thread, it is recommended that a combination of elastomeric materials as a neopren, various kinds of rubber composition, plastics which are bonded to the metal surface carried out by vulcanizing, gluing, molding, spraying, fluiding or another technology to achieve the proper structure, property and quality be used.

It should be understood that the engaging inner edge and the rest of the washer 2, 30 or 50 may be made of the same or different materials (eg. metal, plastic, rubber resin, etc) and using the same or different technologies.

The washers 2, 30 and 50 may also be made of material which during or after a formation process undergoes a latent change of shape. For example, the washers could be made of material which contracts when subject to a particular heat process or chemical treatment or time memory properties of materials (the choice depends upon the particular application) . Alternatively the material would contract ofits own accord after a predetermined period of time. This would enable the washers to be configured initially so they can be easily inserted onto screws, or bolts, without engaging the threads thereof and then the washers would contract so that the respective inner edges engage the respective screws or bolts so they cannot be dislodged therefrom.

The inner edge of the washers may also be triangular and any other shape provided the inner edge is configured so it is adapted to engage thread of a threaded member, such as a screw, or bolt, so as to prevent the washer being dislodged therefrom.

Many modifications will be apparent to those skilled in the art without departing from the scope of the present invention as hereinbefore described with reference to the accompanying drawings.