GB2246732A

GB2246732A - Structural assembly method

Info

Publication number: GB2246732A
Application number: GB9115802A
Authority: GB
Inventors: Armando Corsi
Original assignee: Jobs SpA
Current assignee: Jobs SpA
Priority date: 1990-08-09
Filing date: 1991-07-22
Publication date: 1992-02-12
Anticipated expiration: 2011-07-22
Also published as: GB2246732B; IT9044817A0; DE4125946A1; IT1247590B; ES2044759A2; FR2665656B1; ES2044759R; FR2665656A1; IT9044817A1; JPH04231135A; ES2044759B1; GB9115802D0

Abstract

In a method for assembling structures by automatic rivetting, a pair of machine tools position themselves on opposite sides of a workpiece; pressure devices P, P' mounted on said machines are moved forward to clamp the piece; the different tools 6-10 for carrying out the various operations including rivetting are aligned without releasing the grip on the piece; on termination of the work cycle the piece is released and the machines are moved to the next point. <IMAGE>

Description

"A STRUCTURAL ASSEMBLY METHOD, IN PARTICULAR FOR AERONAUTICAL STRUCTURES-

The present invention proposes a method for the assembly of structures, in particular aeronautical structures, by automatic rivetting or other types of fasteners, using two coupled machines which work at the same time on opposite sides of the piece.

In accordance with the method in the invention, the machines are lined up at the point to be worked on, the parts are clamped and' all the necessary work carried out without ever having to move the main axes of the machine.

The method in the invention has a specific though not exclusive application in the aeronautical construction sector for the.assembly of aeroplane structures, for example during the assembly of panels, where considerable difficulties are encountered. These difficulties are due to the fact that various different operations have to be carried out within a minimal range of tolerance, and on pieces which are difficult to position and to manouevre, such as fuselage panels.

These are in fact structures of a considerable size - their length and width may measure a number of metres - whilst being very thin and curved. As well as this they must be attached to the curved structure of the aeroplane by rivets.

For this to be done, the pieces to be worked upon have first to be positioned and clamped next to each other and a series of operations carried out, including drilling, possible deburring and countersinking of the hole, the application of glue, the insertion of rivets and their clinching.

Until a few years ago these operations were done manually with the aid of drilling masks and tools capable of working at a controlled 2 depth.

Only in more recent years have machine tools been developed which are capable of carrying out a series of operations automatically and with the necessary precision.

Machines of this kind consist of a mobile structure along a triad of Cartesian axes on which a tool-carrying head is mounted with freedom of movement in two or more directions, and to which tools or the required end effectors are attached each time.

Each time the end effectors are substituted electronic and mechanical variables (zeroes) of the machine must be reset. Since this is a procedure which takes considerable time, with currentlyknown automatic procedures all the operations of a certain kind are carried out on the panel first, the panel then being removed from the support, stored, and the same operations carried out on the -next panel.

On termination, the machine is stopped, the end effector substituted and the panels repositioned one at a time on the support so as to proceed with the next operation.

Thus, for example, first all the holes of a certain diameter are made, the end effector is substituted, the rivets are put in place etc.

Clearly, this solution creates a number of difficulties because the pieces a number of large pieces have to be moved and stored which are difficult to manouevre and on which not all the operations have been carried out.

In other cases, first all the holes are drilled, then the glue is applied in each hole and lastly the rivets are put in. However, this system also leads to time lost in the substitution of the end effectors and the possibility of an error in repositioning the machines.

Furthermore, there are also machines which carry out all the operations on each hole before passing on to the next one. These 1 i j 1 1 1 1 i i 1 1 k 3 are, however, fixed machines which means that the pieces must be moved, being inserted in the machine to carry out the operations. This has obvious limitations in that the size of the piece is limited by the size of the machine.

For this reason, the need is felt for a means which allows all the necessary operations for the placing of the fastener to be carried out consecutively without having to stop or move the machine.

For this purpose the present invention proposes a method for the assembly of structures, particularly in the aeronautical sector, using a machine pair working simultaneously but on opposite sides of the panel or the piece to be assembled.

In the method in the invention, the machines transport themselves to the work point in line with the hole, clamp the parts and then carry out all the necessary operations, substituting the tool automatically.

Machines which substitute the end effector automatically are -described in the Italian patent application N. 44815 A/89, of the same applicant.

The present invention will now be described in detail for purely illustrative purposes, with reference to the drawings enclosed in which:

- fig. 1 shows the whole of one of the machines used with the method in the invention; - fig.2 shows a cross-section of a support plate for the end effectors to be applied to the tool-carrying head of the machine; fig.3 is the view of a unit for employing the method invented, comprising two paired machines which work simultaneously on the same piece.

- fig. 4 illustrates schematically the series of operations for placing rivets according to the method in the invention; - fig. 5 is a block diagram illustrating the equipment and its controls; 4 - fig. 6 is a block diagram illustrating the successive phases of the method in the invention; The invented method uses a pair of machine tools, as shown for example in fig.l. These comprise a support 1 which moves along a base 2 in the direction of the X-axis. On this support a metal tube 3 is mounted which is movable along the Y and Z axes, which together with the X-axis make up a Cartesian triad.

At the end of the metal tube or arm 3 is a tool-carrying head 4 with freedom of movement in two directions, defined by the rotation axes A and C.

The head 4 has attachments for the rapid application of a plate carrying end effectors, such as that shown in cross-section in fig.5.

The plate, attached to the tool-carrying head 4 has freedom of movement in two directions, along right-angled axes V and W, the latter being perpendicular to the plane of the drawing in fig.5.

These machines are already known of and have been described, for example in the Italian patent application 44804 A/88 published on 09/09/89 and to which teference should be made for any other details. For a better understanding of the idea presented here, it is enough to know that a series of end effectors are mounted on the plate, each provided with a tool whose axis is parallel with the W axis.

The end effectors are each transported to the work point by running the plates along the V-axis, after which the individual end effectors are moved forward along the W-axis, with movements controlled by the MC of the machine, for carrying out the tasks.

The method in the invention uses a pair of these machines which work simultaneously on opposite sides of the piece.

Each of the machines is equipped with a plate on which a number of end effectors are fitted. These can be the same for both machines or different according to the type of operation.

i 1 1 i i 1 j i i i i In the particular case of rivetting, end effectors will be mounted on one of the machines with tools capable of pressing against the piece being worked upon to hold it in position, tools capable of carrying out drilling and countersinking, tools for applying glue and for the placing and clinching of the rivet.

On the second machine, as well as a presser capable of cooperating with that of the first machine, devices will be present for cleaning the hole, deburring and for possible checks for the presence of a rivet and an anvil.

In fig. 4 is a diagram of the series of operations in a rivetting cycle using the method in the invention.

In this drawing the piece to be worked on is indicated by the number 5. Numbers 6 to 10 indicate the different end effectors mounted on the machines whilst P and P' are the pressers.

The first phase of the method of the invention is to transport both the machines in line with the work point (phase A).

Both machines are equipped with pressers P and P' which are moved forward until they clamp the parts to be worked on (b), such as a panel and the relative support to which it must be attached.

The pressers currently known about and applied to this type of machine have known devices which allow the pressure exerted to be regulated, to avoid damaging the piece.

once the sides have been clamped, and with the machines keeping the same positions, the first of the machines (which we shall define as the main or master machine) brings the drilling tool (c) into position on the axis and then controls its progress along the W-axis to carry out the drilling and countersinking (d).

The tool is then retracted while the piece is kept blocked and the second machine (a slave to the first machine) moves an end effector forward to blow away the dust or for deburring (e).

The main machine then brings the second end effector (f) into position and controls its progress for possible application of 6 glue (g).

On termination this end effector is also withdrawn (h) and the main machine brings the third tool (i) into position for the placing of the rivet.

The rivet is then fed in, its presence being checked for by an end effector mounted on the second machine, after which the rivet is clinched (1).

Lastly, the tool which carried out the clinching of the rivet (m) is withdrawn and the piece is left, the fastener cycle being complete. The machines can now align themselves with the second work point and start the cycle again.

A characteristic advantage of the method in the invention is that all the operations necessary for completing a work cycle are carried out while keeping the piece clamped and without moving the axes of the machine.

This leads to obvious advantages both in time-saving and in the greater precision obtained.

A diagram of the control system of the machine is illustrated in fig.5. The activity of both the machines is controlled by a main computer 10 to which an operator terminal 11, a printer 12 a disk system for memorizing programs and a back-up tape system are connected.

This main computer is connected by an Ethernet network using ISO/OSI communications protocol to the two machines or robots 15 and 16 and to a controller in charge of the running of equipment and pieces to be worked on and the relative automatic and semi automatic mechanisms for positioning and maintaining the work point. A The numeric control of each robot manages the controller of the end effectors and the controller 20 of the rivet supply equipment, which in turn receives the rivets from a feed station 21.

Each robot is interfaced with a sensor 18.

i 1 j 1 i i i i 1 1 j i 1 7 Before the operative cycle is set in motion and as soon as the controller 17 confirms the positioning of the piece to be worked on, the robot moves the feeler 18 forward and the machine resets itself according to the position of the piece revealed by the feeler.

The network which connects th rob ts to the controllers 19 and 20 is of the BITBUS type (an INTE 11 brand name).

In fig.6 a block diagram illustrates the coordination and the order of the different operative phases of the method in the invention. The meaning of this block diagram is extremely clear to experts in the sector.

From the description given, the advantages of the method in the invention are clear. Once the parts to be assembled have been fixed in position all the operations for placing the fastener without releasing the parts and without moving the machine axes may be carried out with greater rapidity and precision.

An expert in the field may foresee a number of variations and modifications, all of which must be held to be included within the bounds of the present invention.

A 8

Claims

1) Method for assembling structures by automatic rivetting, characterized by the following:

- a pair of machine tools position themselves on opposite sides of a piece; - Pressure devices mounted on said machines are moved forward to clamp the piece; the different tools for carrying out the various operations are aligned without releasing the grip on the piece; on termination of the work cycle the piece is released and the machines are moved to the next point.

2). Method as claimed in claim 1, with the particular feature that all the operations in the work cycle are carried out without moving the machine axis.

3). Method for the assembly of structures by automatic rivetting with the following features:

- a pair of machine tools under numeric control are positioned at the work point in opposing positions and on opposite sides of the piece to be worked on; - pressure is applied to the piece from both sides by pressers mounted on said machines, in order to squeeze the sheets with a controlled degree of clamping; - the end effectors of the first machine are moved so as to bring a drilling tool in line with the hole; - said tool is moved forward to obtain the hole and the countersinking; - said tool is retracted and an end effector brought into position mounted on the second machine, to carry out the deburring; - a second end effector mounted on the first machine is brought into line with the hole for the glue to be applied; - a third end effector is mounted on the first machine to supply the rivet; 1 1 %k 1 i i i i 1 1 1 i i 9 said rivet is clinched; the piece is released are the machines are moved to the next 4). Method for the assembly of structures by the automatic placing of fasteners as described and illustrated, CIM- 5). Two machine tools for assembling structures by automatic rivetting whenever programmed or otherwise controlled or used to carry out the method substantially as herein described with reference to the accompanying drawings.

4 Published 1992 at 7be Patent Office. Concept House. Cardiff Road, Newport. Gwent NP9 lRH. Further copies may be obtained from Sales Branch. Unit 6, Nine Mile Point. Cwnifelinfach. Cross Keys. Newport, NP1 7HZ. Printed by Multiplex techniques jtd, St Mary Crkv. Kent.