GB2145022A - A riveter - Google Patents

Abstract

Relative movement together of upper and lower tool holders 11 and 8 respectively of a riveter is carried out in two stages. The first stage of movement, in the illustrated embodiment, is performed by actuating a pneumatic cylinder 9 which allows the upper tool holder to drop under the action of gravity. The force applied is thus very small enabling the operator with safety to manipulate various parts of a work-piece 6 so that the rivet R passes through holes 6e. Only when the upper tool holder is in its lowermost position, when there is insufficient space above the work piece for the operator to insert his fingers, is the upper tool holder 11 locked by pneumatically driving a bolt 16 so that it engages the upper surface 18A of the tool holder 11. The lower tool holder 8 is then driven rapidly up and down a short distance 11 to deform the rivet. This distance 11 is insufficient for insertion of the operator's fingers and in any case the lower tool holder is guarded by suitable means against access by the operator. <IMAGE>

Description

SPECIFICATION A riveter This invention relates to a riveter. It arose in the design of a special purpose riveter for securing electrical contact strips and their as sociated spring clips to a backing board. This operation is typical of many riveting opera tions in that it is necessary to separate the opposing tools of the riveter by a substantially greater distance than the length of the rivet in order to allow manipulation of the work-piece (which may have projecting parts such as the aforementioned spring clip) between the rivet ing tools. This separation of the tools by a greater distance than the length of the rivet is also necessary when, as is normal, it is de sired to fit a rivet into engagement with one of the tools before inserting the rivet into the work-piece during movement of the tools to gether.

The need to separate the tools by a substantial distance as mentioned above can create a safety problem in that the separation is sufficient to allow an operator to insert his fingersbetween the work-piece and one of the tools. This problem is particularly acute when the operator needs to use his fingers to align prefformed holes for the rivet in different components of the work-piece. In these circumstances it is not practicable to eliminate danger by providing a safety guard.

This invention provides a riveter comprising means for relatively moving two tools together to deform the rivet characterised in that the means for relatively moving the tools together is designed to cause that relative movement to take place in two stages namely: by a first amount during which a force bringing the tools together is limited to a safe value; and by a second amount during which the rivet is deformed to secure it in a work-piece. By employing the invention it is possible to ensure that the first amount of movement brings the tools together sufficiently to prevent the operator from subsequently inserting his fingers between them. The second amount of movement, during which considerable force needs to applied to the rivet, can therefore be performed without significant danger.

In one preferred form of the invention the riveter comprises first and second tool holders, each mounted on a supporting structure, means for moving the first tool holder relative to the supporting structure thereby effecting the said first amount of movement, means for locking the first tool holder against reverse movement and means for moving the second tool holder relative to the supporting structure thereby effecting the said second amount of movement to deform the rivet secure it in the work-piece. If the design is such that the locking means can operate only after the first amount of movement has been completed, the possibility of undue force being applied during the first stage of movement can be eliminated.

The riveter preferably includes means for supporting the work-piece between the tools and guard means for obstructing access of the operator's fingers between the work-piece and the second tool holder, the configuration of the rivet allowing access of the operator's fingers between the first tool and the workpiece to manipulate the rivet into the workpiece. In this way it is possible for the second amount of movement (i.e. the movement of the second tool holder) to take place through a substantial distance if this is necessary to provide clearance of obstructions on the same side of the work-piece as the second tool holder.

One way in which the invention may be performed will now be described by way of example with reference to the accompanying schematic drawing, showing, partly in elevation and partly in cross-section, a riveting machine constructed in accordance with the invention.

The illustrated machine is designed to apply two rivets simultaneously, the parts for applying each rivet being identical and being arranged symmetrically about a central plane indicated by the lines x-x of the drawing. The drawing shows only those parts to one side of this line x-x.

The machine comprises a main frame indicated very schematically by the outline 1. On this main frame 1 are mounted: a work-piece supporting assembly; the work piece itself; the lower tool operating assembly; an upper tool operating assembly; an upper tool locking device; a rivet raceway; a pneumatic controller; and three pneumatic sensors. These parts will now all be described in detail.

The work-piece supporting assembly comprises a pair of rails 2 which are spaced in a direction perpendicular to the plane of the drawings. Each of these rails 2 carries a runner 3 and the runners 3 carry further rails 4 which extend in a direction perpendicular to rails 2. The rails 4 carry a jig 5 which forms a support for a work-piece indicated generally at 6. The two perpendicular sets of rails 2 and 4 enable the jig 5 to be moved in any horizontal direction so as to position the work-piece in the desired position.

The work-piece 6 is formed from a number of separate components parts to be riveted together and comprises a flange, 6A a baseboard 6B, spring clip 6C, and an edge connector strip 6D. The illustration shows only one of these edge connector strips 6D but in fact there are many of them to be fixed to the same baseboard 6B. These are adapted to receive the edges of respective circuit boards in the completed product and have pins (not shown) extending from their undersides and passing through the baseboard 6B. The pins are eventually interconnected by a wire wrapping technique. The wiring wrapping operation is performed by a machine which requires the pins to be very accurately located and this in turn means that the edge connector strips 6D must be riveted very accurately in position.For this purpose the various components of the work-piece are preformed with holes to receive the rivets. These holes are accurately aligned as indicated by the broken lines 6E.

The lower tool operating assembly comprises a pneumatically operated piston and cylinder arrangement 7 having a piston 7A and spring 7B. On application of pneumatic pressure the piston 7A moves a lower tool holder 8 up through a short distance 11. The tool holder 8 carries a tool 8A at its upper end as illustrated. The upper tool operating assembly comprises a second piston and cylinder arrangement 9 comprising a piston 9A and a return spring 9B. The piston 9A drives a cross-member 10 which engages an abutment 1 1A on an upper tool holder 18 so that, on its upperward stroke, under the action of the return spring 9B, the crossmember 10 lifts tool holder 11 to the illustrated position.On the lower stroke of the piston 9A the upper tool holder is allowed to fall under gravity through a distance 12, the maximum pressure exerted during this action being that due to the effect of gravity on the upper tool holder.

The upper tool holder slides in ball bearings 12 supported in a sleeve 13 mounted on the frame.

The upper tool locking device comprises a third piston and cylinder arrangement 14, also mounted on the frame 1 and comprising a piston 1 4A and return spring 1 4B. The piston 1 4A drives a shaft 15 and thence a bolt 16 which slides horizontally in a guide 17, the guide 17 being fixed to the frame 1. The bolt 16 can be driven by means of the piston 1 4A from its illustrated withdrawn position towards the left hand side of the drawing so as to engage top surface 18 of the upper tool holder when the latter is in its lowermost position. An important feature of this machine is that the bolt 16 cannot be moved into its engaged position where it contacts the face 1 8A of the upper tool holder until the latter has moved through the distance 12 thereby completing the first stage of movement.

The raceway is of conventional design and is thereffore not shown in detail in the drawing. it is driven by a fourth piston and cylinder arrangement 19 comprising a piston 1 9A and return spring 1 9B. A bifurcated piston rod 1 9C is pivoted to the raceway indicated generally at 21 so as to swivel the latter about a pivot pin 21A from the illustrated position to a withdrawn position when its lower end is held clear from the area between the two tool holders. The raceway 21 contains a channel for feeding the rivet to its lower end, this channel not being shown on the drawing.

Also fixed to the main frame 1 is a pneuma- tic controller 20 which is conventional in design and can be set so that the occlusion of each vent a b c d causes the application of pneumatic pressure to or the release of pneumatic pressure from any of a number of output ports shown at A B C D E; either immediately; or after a delay. The delay can be set as desired. For the purpose of this particular machine the controller 20 is set to perform the following operations 1. Occlusion of control port d causes pneumatic pressure to be applied immediately to main port D and, after a delay, to main port B.

2. Occlusion of control port a causes pneumatic pressure to be applied immediately to main port E.

3. Occlusion of control port b causes pneumatic pressure to be applied immediately to main port C; after a short delay causes main port C to be vented; after a longer delay causes main port E to be vented and; after a still further delay causes the main port B to be vented.

4. Occlusion of control port c causes pneumatic pressure to be vented from main port D immediately; and causes pneumatic pressure to be applied to main port A after a delay; and causes pneumatic pressure to be released from main port A after a further delay.

Also fixed to the main frame 1 is a fifth piston and cylinder arrangement 22 having a piston 22A and a return spring 22B. This drives a shaft 22C which passes down a central bore of the upper tool holder 18. The lower end of the shaft 22C bears on the upper end of a rivet pick-up pin 23, the latter being urged upwardly by a return spring 23A.

Finally, the sensors, which are illustrated schematically, from the open ends of corresponding pipes connected to respective control ports a, b and c. The sensors S, and S3 are closed by the cross-member 10 when the latter reaches its lowermost and upermost positions respectively; and the sensor S2 is closed when the shaft 15 reaches the left hand position, i.e. when the bolt 16 is acting to lock the upper tool holder in position.

Operation of the illustrated machine commences with the parts in the illustrated position, the work-piece 6 having been manipulated into the illustrated position as shown with the holes shown at 6e at least roughly aligned with the opposing tools. The operator then presses a start button (not shown) which occludes the control port d of the controller 20. The controller then applies pressure to the piston and cylinder arrangement 19 and the raceway 21 is consequently moved to its withdrawn position. The controller 20 then causes the piston and cylinder arrangement 9 to drive the cross-member 10 downwardly thereby allowing the upper tool holder 18 to fall under the action of gravity through the distance 12.During this movement, which is the first stage of movement previously referred to, the rivet,indicated at R on the drawing is held by the pick-up pin 23 against the upper tool and must enter the hole 6e in the work piece. This is a delicate operation since it requires exact positioning and alignment of the holes in the work piece parts 6A, 6B, 6C and 6D. The operator frequently finds it necessary to manipulate these parts to allow the rivet to pass through the holes 6E but this can be done without any danger since the maximum force applied to the rivet is due to its own weight plus that of the upper tool holder and pick-up pin. Even operation of the lower tool holder e.g. due to a fault in the machine, cannot cause trapping of the operator's fingers since the upper tool is free to move upwardly.Only when the rivet is fully home in the holes 6E of the work piece, as detected. by occlusion of the sensor S, by the cross-member 10, does this situation change.

The controller 20 then operates piston and cylinder arrangement 14 causing the bolt 16 to move to the left thereby locking the upper tool holder in its lowermost position. At this stage it is impossible for the operator to put his fingers between the opposing toolssince there is no space to do so above the workpiece and because the various components 3, 4, and 5 act as a guard preventing the operator from putting his fingers below the work-piece. In any event, in the illustrated apparatus the distance 11 through which the lower tool holder moves is too small to allow access to an operator's finger.The locked position of the bolt 16 is detected by the sensor S, whereupon the controller 20 causes the piston and cylinder arrangement 7 to operate causing the lower tool member 8 to move rapidly up under considerable pressure to deform the rivet and secure it in position.

The return spring 7B then returns the lower tool holder to its illustrated position. The controller then releases the pressure from the piston and cylinder arrangement 14 allowing the return spring 1 4B to withdraw the bolt. It then removes the pressure from piston and cylinder arrangements 9 allowing the return spring 9B to lift the upper tool holder to its illustrated position. This is sensed by the sensor S3 whereupon the controller releases the pressure from piston and cylinder arrangement 19 causing the return spring 1 9B to pivot the rivet raceway 21 back to its illustrated position, bringing a fresh rivet into position immediately under the upper tool holder. Finally, the controller applies pressure from the piston and cylinder arrangement 22 so as to drive the pick-up pin 23 into the top of the rivet to hold it in position beneath upper riveting tool.The pressure in the piston and cylinder arrangement 22 is then released and the pick-up pin return spring 23a moves the rivet into abutment with the upper tool holder.

The cycle of operations is then repeated.

Whilst the illustrated machine is designed for use with tubular rivets, the invention is equally applicable to the application of solid rivets. The term "rivet" is defined for the purpose of this specification as any fastening member designed to be passed through a work-piece and to be fixed in position in the work-piece by deforming it.

An embodiment of the invention built along the principles of the illustrated machine has been found to be particularly effective. Many modifications are however possible. For example the spring return piston and cylinder arrangements could be replaced by pneumatic return springs. Another possibility would be to use a fixed lower tool and to arrange for the upper tool to move downwardly through an initial stage of movement before being locked by the bolt 16, and then to drive the bolt 16, its guide 17 and the upper tool holder under increased pressure downwardly through the final stage of movement, to head the rivet.

Finally, of course, a hydraulic, mechanical or electrical control system could be used in place of the pneumatic system illustrated.

Claims (4)

1. A riveter comprising means for relatively moving two tools together to deform the rivet characterised in that the means for relatively moving the tools together is designed to cause that relative movement to take place in two stages namely: by a first amount during which a force bringing the tools together is limited to a safe value; and by a second amount during which the rivet is deformed to secure it in a work-piece.

2. A riveter accordingly to Claim 1 comprising first and second tool holders, each mounted on a supporting structure, means for moving the first tool holder relative to the supporting structure thereby effecting the first amount of movement, means for loading the first tool holder against reverse movement and means for moving the second tool holder relatively to the supporting structure thereby effecting the said second amount of movement to deform a rivet and secure it in the work-piece.

3. A riveter according to Claim 2 including means for supporting the work-piece between the tools and guard means for obstructing access of an operator's fingers between the work-piece and the second tool holder, the configuration of the riveter allowing access of the operator's fingers between the first tool and the work-piece to manipulate the rivet into the work-piece.

4. A riveter substantially as described with reference to the accompanying drawing and as substantially as illustrated therein.