GB2123718A - Screw-washer assemblies and machine for the assembly thereof - Google Patents

Abstract

An automatic machine for assembling washers (12) to screws (9), comprising a section (10) for feed of the screws and a section (11) for feed of the associated washers, by way of synchronised forward-feed and orientation means (14, 16), to an assembly section (13) provided with control means (18) for fitting each washer on to the shank of a respective screw. A punch (30) (Fig. 5) cuts an axuiliary washer (31) from a strip (26) of plastics material and fits it with a force fit on the shank of the screw. The punch (30) and means (28) for driving the strip are actuated synchronously with said control means. The washer (12) is axially locked on the shank of the screw (9) between the head and the auxiliary washer (31). <IMAGE>

Description

SPECIFICATION Screw-washer assemblies and machine for the assembly thereof The present invention relates to a machine for automatically assembling washers to screws, and to the screw-washer assembly produced by such a machine.

Automatic machines for assembling washers to screws are well known and are normally associated with lines for assembling pieces of equipment which require a large number of screwtype fixing points. In substance, such machines comprise a vibratory bowl for orienting the screws and a timing device for the forward feed of the screws towards the assembly region where the respective washers also arrive in a synchronised mode, along a suitable conveyor channel or passage. The screws are joined to the washers by means of clamping devices or the like and the assemblies comprising a washer and a screw which are formed in that way are passed to at least one screw tightening head, for example by way of a pneumatic feed system.

The entire system continuously supplies a screw tightening area provided on an assembly line but obviously it is not capable of simultaneously supplying a plurality of screw tightening areas requiring screw-washer assemblies with different dimensional characteristics.

In that case, which arises frequently, practically each different screw tightening area has to be supplied continuously from a respective automatic machine of the above-described type.

The need to use the screw-washer assemblies immediately after the two components have been joined together is due in particular to the impossibility of temporarily storing, in batches, the screw-washer assemblies which could easily become disconnected from each other.

In order to overcome that disadvantage, automatic machines have already been proposed which, during the phase of manufacture of the screw, fit thereto a respective washer which is trapped on the shank of the screw by means of deformation thereof, in particular deformation of the thread.

The screw-washer assemblies which are produced in that way can then easily be stored in batches which, depending on the various dimensional characteristics for which a single machine can be adapted from time to time, are used in a second phase for simultaneously feeding different screw tightening areas.

The machines of the last-mentioned type are complicated but however suffer from severe limitations: in particular, they produce screwwasher assemblies of predetermined shapes and characteristics and they do not take account of the many requirements and possibilities in regard to combination between various types of screws and washers, which may vary according to circumstances. In addition, they normally use components which, for the particular processing operation to which they are to be subjected (thermal stresses and/or surface treatments), have to be preselected for the specific use concerned, which is undesirable.

According to the present invention, there is provided an automatic machine for the assembly of washers to screws, comprising: a section for feeding the screws; a section for feeding the associated washers, through respective synchronised forward-feed and orientation means, to at least one assembly section provided with control means for fitting each washer to the shank of a respective screw; and a fixing device for fitting to the shank of said screw axial abutment means capable of preventing the washer and the screw from coming apart.

The invention further provides a screw-washer assembly wherein the washer is fitted on to the shank of the screw between the head of the screw and axial abutment means which are fitted on said shank.

As will become apparent from the following description the present invention can provide a simple and reliable machine which can be easily automated and which is suitable for assembling standard screws and washers, of normal commercial type, in a substantially nondisconnectible fashion, as well as a simple and economical screw-washer assembly which readily lends itself to being stored without the danger of the components coming apart.

Preferably, said axial abutment means comprise an auxiliary washer of plastics material, which is a press fit or a force fit on the shank of the screw.

The features and advantages of the invention will be clearly apparent from the following description given solely by way of non-limiting example with reference to the accompanying drawings in which: Figure 1 is a diagrammatic plan view of a preferred embodiment of the automatic machine according to the invention, Figure 2 is a diagrammatic side view in crosssection of a detail of the machine shown in Figure 1, Figures 3 to 6 are diagrammatic side views of the detail shown in Figure 2, in respective operating positions, Figure 7 is a diagrammatic side view in crosssection of another detail of the machine shown in Figure 1, and Figure 8 is a side view of a preferred embodiment of the screw-washer assembly according to the invention.

Referring in particular to Figure 1, the illustrated machine embodying the present invention is of a type substantially comprising a section 10 for the feed of screws 9 and a section 11 for the feed of washers 12. In known manner, the screw feed section 10 comprises a vibratory bowl for orienting the screws in a suitable position and is connected to at least one assembly section 13 by means of a timed or cyclically operated forward-feed device 1 4 and a flexible conduit 1 5 for conveying the screws.

Also in known manner, the feed section 11 comprises a vibratory bowl for orientation and successive forward feed of the washers 1 2 (for example by way of a slide conduit or chute 1 6), to the vicinity of the assembly section 1 3. Disposed at a position adjoining the end of the conduit 1 6 is a pusher means (shown for the sake of simplicity merely by the arrow 17) for feeding the washers 12 to the assembly section 13, one by one, by way of a double self-centering gripper member 18. The gripper member 18 is also of per se known type and is arranged to rotate through 1 80O alternately in the two directions indicated by the respective arrows 1 9 and 20, with intermediate pause positions in which the opposite ends of the double gripper member 18 are disposed in association with respective hoppers or feeders 21.

As will be clearly apparent hereinafter, the hoppers 21 are used for storing the screw-washer assemblies which are produced and the double gripper member 1 8 also performs an alternating movement in a vertical direction.

With reference also to Figure 2, when the double gripper member 1 8 is in the angular position shown in Figure 1, one of the ends thereof (which is holding a respective washer 12) is disposed in association with the assembly section 1 3.

Also disposed in vertical alignment with the assembly section 13, preferably above the double gripper member 18, is a fitting head 23 (see Figure 2), at which the conduit 1 5 for transporting the screws 9 terminates. The fitting head 23 is of per se known type and is vertically movable and comprises clamping or claw members 24 which are actuable in a controlled manner, in association with a pusher member 25, for manipulating the screws 9.

According to this embodiment of the invention, the automatic machine for assembling washers to screws is provided with a device for axially fixing each washer 12 on the respective screw 9.

Preferably, that device comprises a thin strip 26 of deformable plastics material which is supplied from a roll 27 and advanced with a stepwise motion by means of a drive device 28, at the assembly section 1 3. In particular, with respect to the double gripper member 18, the strip 26 is disposed on the opposite side to the fitting head 23. Upstream of the assembly section 13, the strip 26 passes through the position of a punch 22 operable to produce in the strip a succession of holes 29 whose diameter is slightly less than that of the shank of the screws 9.

Also disposed at the assembly section 13, on the side of the strip 26 remote from the double gripper member 18, is a main punch member 30 which has an annular head and which is capable of cutting out of the strip 26 a succession of auxiliary washers 31 which are concentric with the holes 29 (Figures 5 to 8).

Preferably, the outside diameter of the auxiliary washers 31 is less than that of the washers 12 which are normally made of metal.

The machine is completed by actuating and control means (which are not part of the present invention and which will not be described herein) of per se known type, which can be easily provided by the man skilled in the art, for synchronised actuation of the various arrangements described above.

In operation, the screws 9, which are already in an oriented condition, are passed by way of the conduit 15, one by one, to the fitting head 23 while the punch member 22 produces a corresponding hole 29 in the strip 26 which advances with a stepwise motion (see Figure 2).

Each screw remains projecting from the clamping members 24 of the fitting head 23 while the double gripper member 18 transfers a corresponding washer 12 from the chute 1 6 of the feed section 11 to the assembly section 1 3 (see Figures 1 and 3) in a position concentric with an associated hole 29 in the strip 26.

The fitting head 23 is lowered and the clamping members 24 release the screw 9 which is pressed by the pusher member 25 so as to be fitted in the washer 12 and (by a force or push fit) in the subjacent hole 29 in the strip 26 (see Figure 4).

While the pusher member 25 remains in its downwardly displaced position, the annular-head punch member 30 is raised (see Figure 5), thereby cutting from the strip 26 an auxiliary washer 31 which remains locked, in a press fit, on the shank of the screw 9, preferably in association with the thread. That therefore resuits in a screw-washer assembly (see Figure 8) in which the washer 1 2 is axially locked on the shank of the screw 9 between the head of the screw and the auxiliary washer 31 of thin, flexible plastics material.The screw-washer assembly is thus ready for any type of use (during the screwing operation, the auxiliary washer 31 easily deforms or fractures), it can be easily produced by the use, from time to time, of standard washers and screws of different types (by means of easy dimensional adaptive modifications in the components of the machine) and it can be easily stored in batches, without particular precautions.

For that purpose, after the screw-washer assembly has been formed, the assembly is removed from the assembly section 13 by means of the double gripper member 18 which is raised, together with the fitting head 23, while the punch member 30 moves downwardly into its rest position (see Figure 6).

The double gripper member 1 8 then rotates through 90 , whereby the opposite ends thereof are in positions associated with the hopper members 21; the jaws at one end of the double gripper member open (see Figure 7), allowing the screw-washer assembly to drop into the respective hopper member 21. The double gripper member 1 8 then rotates through a further angle of 90 and is moved downwardly again in order on the one hand to pick up a fresh washer from the conduit 16 and at the same time, on the other hand, to position another washer 1 2 at the assembly section 13. Operation of the machine then continues in a similar fashion.

The foregoing description clearly shows the design simplicity and the operational reliability of the machine according to the invention which is particularly suitable to being actuated automatically.

It will be appreciated that the machine and/or the screw-washer assembly produced therewith may be the subject of many modifications without departing from the scope of the invention. For example, the axial fixing device may be of the type which is suitable for depositing on the shank of the screw 9 adhesive material (or the like) which, once it has set, performs the same function as the auxiliary washer 31. Alternatively, the auxiliary washer may be made of a different material, for example, metal or paper or card.

In addition, with suitable modifications in the dimensions of the machine, the washers 1 2 may be of plastics material, being produced directly by being cut out of the strip 26 and fitted with a press fit on the shank of the screws 9; it will be appreciated that in that case the auxiliary washer 31 is redundant and the section 11 for the feed of metal washers 12 is not used.

Claims (7)

1. An automatic machine for the assembly of washers to screws, comprising: a section for feeding the screws; a section for feeding the associated washers, through respective synchronised forward-feed and orientation means, to at least one assembly section provided with control means for fitting each washer to the shank of a respective screw; and a fixing device for fitting to the shank of said screw axial abutment means capable of preventing the washer and the screw from coming apart.

2. An automatic machine according to claim 1 wherein-said fixing device comprises a main punch member for cutting an auxiliary washer constituting said axial abutment means from a strip and force-fitting it on to the shank of said screw, the main punch member and means for driving the strip being arranged to be actuated synchronously with said control means.

3. An automatic machine according to claim 2 wherein disposed upstream of the assembly section is a further punch member operable to produce in said strip holes, the main punch member being operable to cut said auxiliary washers concentrically with respect to said holes.

4. A screw-washer assembly wherein the washer is fitted on to the shank of the screw between the head of the screw and axial abutment means which are fitted on said shank.

5. A screw-washer assembly according to claim 4, wherein said axial abutment means comprise an auxiliary washer which is a force fit on the shank of the screw.

6. An automatic machine for assembling washers to screws, constructed and arranged to operate substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.

7. A screw-washer assembly substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.