WO2019097372A1

WO2019097372A1 - An operating unit for applying adhesive or sealant, a method for its use, and production plant

Info

Publication number: WO2019097372A1
Application number: PCT/IB2018/058807
Authority: WO
Inventors: Giovanni Di Stefano; Marco SPAGNOLI; Apostolos FYSIKOPOULOS; Mauro Maestri
Original assignee: Comau S.P.A.
Priority date: 2017-11-14
Filing date: 2018-11-09
Publication date: 2019-05-23

Abstract

An operating unit for dispensing an adhesive fluid or sealant, comprises a fluid dispensing nozzle (7), one or more fluid accumulator cylinders (5) and one or more pumping cylinders (6), each having a piston (61 ) operable in a first direction for drawing a fluid charge from a respective fluid accumulator cylinder (5) and in a second direction for supplying said fluid charge to the dispensing nozzle (7). The fluid accumulator cylinders (5) can be replaced when they are empty with full accumulator cylinders (5) and/or can be refilled without having to remove them from the operating unit.

Description

“An operating unit for applying adhesive or sealant, a method for its use, and production plant”

Field of the invention

The present invention relates to an operating unit for dispensing a relatively viscous fluid, such as an adhesive or a sealant, said operating unit being of the type comprising:

- a support structure, provided with a coupling device for removable connection to a robot or other base structure,

- a fluid dispensing nozzle, carried by said support structure, and

- at least one pumping cylinder, also carried by said support structure and with a chamber configured to receive a fluid charge, and a piston inside the pumping cylinder, wherein said piston can be driven in a first direction for drawing a fluid charge into said chamber of the pumping cylinder, and in a second direction, for supplying said fluid charge from said chamber of the pumping cylinder to said dispensing nozzle,

The invention is, in particular, directed at devices for applying adhesive or sealant to parts of motor-vehicle structures, in motor-vehicle production plants. However, this application is mentioned here only as an example, being understood that the invention is of general application.

In a preferred application, the operating unit according to the invention is carried by a robot, for example, a multi-axis manipulator robot, or by any other automated device, which is controlled to move the operating unit with respect to the part on which the adhesive or sealant fluid is to be applied. In an alternative application, the operating unit is mounted on a stationary base structure, and is the part to be assembled is moved with respect to the operating unit, for example, with the aid of a robot.

Prior art

An operating unit of the type indicated above is, for example, described in the document WO 9851405 A1.

Operating units of this type are used by robots in industrial assembly cells to apply adhesive or sealant on parts to be assembled in the assembly cell.

The main drawback of known devices consists in the fact that the operating unit carried by the robot is connected by means of a fluid supply tube to a fluid accumulator located in a stationary position adjacent to the robot. This involves occupation of space in the assembly cell, acting as an obstacle to the freedom of movement of the robot, and is a limitation of the working area of the robot. Moreover, during each halt of the plant, particularly in the case of plants equipped with a system for keeping the fluid at a required temperature (and consequently at a required viscosity), the fluid remaining in the supply tube progressively degrades, so that it must then be replaced with fresh fluid, thus involving a waste of time and material.

Object of the invention

The object of the present invention is to resolve the drawbacks of the known solutions, by producing an operating unit of the type indicated above, which is not necessarily linked to a stationary fluid accumulator and which, nevertheless, has an extensive operational autonomy.

An additional object of the invention is to provide an operating unit of the type indicated above which is characterized by a high operational flexibility, in the sense of being configured to operate according to different operating modes, according to the requirements of the specific application, in order to ensure that, in any case, the unit always has the amount of fluid needed to perform and complete a given work cycle.

An additional object of the invention is to provide an operating unit of the type indicated above that is able to operate with a precise and accurate control of the temperature, and consequently of the viscosity, of the fluid dispensed.

Still another object of the invention is to provide an operating unit of the type indicated above, which has a relatively simple and relatively low- cost structure.

Still another object of the invention is to provide an operating unit of the type indicated above which can operate by ensuring, on one hand, the availability of the required amount of fluid for the duration of a given operating cycle and allowing, on the other hand, substantial reduction of the amount of unused fluid that must be eliminated following each halt of the plant.

Summary of the invention In view of achieving one or more of the aforesaid objects, the invention relates to an operating unit comprising:

- a fluid dispensing nozzle, carried by said support structure, and

- at least one pumping cylinder, also carried by said support structure and with a chamber configured to receive a fluid charge, and a piston inside the pumping cylinder, wherein said piston can be driven in a first direction for drawing a fluid charge into said chamber of the pumping cylinder, and in a second direction, for supplying said fluid charge from said chamber of the pumping cylinder to said dispensing nozzle, said operative unit being further characterized in that:

- the operating unit comprises at least one fluid accumulator cylinder, also carried by said support structure,

- said at least one fluid accumulator cylinder is replaceable and/or refillable, in the latter case with no need for removing it from the operating unit,

- said at least one accumulator cylinder has a fluid-accumulating chamber and a piston within the accumulator cylinder movable in a first direction for accumulating fluid within the chamber of the accumulator cylinder, and in a second direction, for ejecting the fluid out of the accumulator cylinder,

- the chamber of said at least one pumping cylinder communicates with the chamber of said at least one fluid accumulator cylinder by means of a first duct wherein a first shut-off valve is interposed, said chamber of said at least one pumping cylinder communicating also with said dispensing nozzle of the operating unit by means of a second duct in which a second shut-off valve is interposed,

in such a way that the chamber of said at least one pumping cylinder can receive a fluid charge from said at least one fluid accumulator cylinder, by means of said first duct when the respective first shut-off valve is opened, and the respective second shut-off valve is closed,

whereas said at least one pumping cylinder can supply a fluid charge from the respective chamber of the pumping cylinder to said dispensing nozzle through said second duct, when the respective second shut-off valve is opened and the respective first shut-off valve is closed.

Thanks to the aforesaid characteristics, the operating unit according to the invention is characterized by a plurality of advantages.

Firstly, the operating unit is able to operate using the fluid charge contained in one or more fluid accumulators arranged on the operating unit. Therefore, the operating unit according to the invention is not obliged to be connected to a stationary fluid accumulator adjacent to the robot, which avoids hindering the operating freedom of the robot and avoids limiting its working area, as well as avoiding the expenditure of time and material deriving from the need to replace the fluid left in the supply tubes, which occurs in the known solutions after each halt of the plant.

A further important advantage of the operating unit according to the invention lies in the fact that it is arranged with one or more accumulator cylinders which are configured to be replaceable and/or to be refillable, which opens a series of options that can be used in succession, when necessary, to guarantee the supply to the operative unit of the quantity of fluid necessary for its normal operation.

In the preferred embodiment, one or more fluid accumulators are in the form of replaceable cartridges, each having a body removably connected to the support structure of the operating unit, and an outlet that can be connected to the respective first duct of said operating unit by means of said first shut-off valve.

According to a further optional characteristic, the first duct that connects the chamber of a respective pumping cylinder to a respective fluid accumulator is associated with an inlet fitting provided with an additional shut-off valve for connection to a source of fluid external to the operating unit, usable to refill fluid into the respective accumulator cylinder.

Thanks to this characteristic, the operating unit according to the invention has an additional operating mode in which one or more fluid accumulator cylinders arranged on the operating unit are not replaced with new full accumulators, when they are empty, but are refilled by the aforesaid connection to an external fluid source.

In one embodiment, said second shut-off valve, which controls the connection to the dispensing nozzle, and said shut-off valve for connection to the external fluid source, are integrated into a single 4-way valve, having a first operating position, in which the pumping cylinder communicates with the external source, and the fluid accumulator cylinder communicates with the dispensing nozzle, and a second operating position, in which the pumping cylinder communicates with the fluid accumulator cylinder, and the external source communicates with the dispensing nozzle.

This solution allows a reduction of weight and an increase in the efficiency of the unit according to the invention, for reasons which will be illustrated in detail below.

According to an additional characteristic, the pistons of one or more pumping cylinders and the aforesaid shut-off valves are controlled by respective actuators. The operating unit comprises at least one electronic control unit programmed to control said actuators to implement one or more predetermined operating cycles.

An additional characteristic of the invention resides in that one or more fluid temperature control devices, and one or more fluid temperature sensors are associated with the chambers of one or more pumping cylinders, and/or with the first duct which connects the chamber of each pumping cylinder with the dispensing nozzle, and/or with the second duct which connects the chamber of each pumping cylinder with a respective fluid accumulator. The electronic control unit is configured and programmed to receive signals from said temperature sensors and to control said temperature controlling devices on the basis of said signals. The temperature control devices comprise one or more electrically- operated heating modules and, in addition, preferably one or more cooling modules, also electrically-operated.

In the preferred embodiment, each pumping cylinder is associated with a Peltier module configured to be controlled by said electronic control unit so as to act as a cooling device or a heating device.

In the solution which envisages refilling of a fluid accumulator by connecting the first duct with an external source, a docking station may be provided in the assembly cell, having a connecting member communicating with the external fluid source. When refilling is required, a connection is established between the first duct of the empty fluid accumulator cylinder and the aforesaid connecting member of the docking station.

In the solution in which replacement of an empty accumulator with a new full accumulator is envisaged, the use of one or more vehicles of the AGV (Automated Guided Vehicle) type may be envisaged for transporting full fluid accumulator cylinders and empty fluid accumulator cylinders between the assembly cell and a remote storage station of the fluid accumulator cylinders, located inside the factory.

In a preferred embodiment, said operating unit comprises two pumping cylinders in total, both cylinders being carried by said support structure, each pumping cylinder having a respective chamber configured to receive a fluid charge, and a piston inside the pumping cylinder which can be driven in a first direction for drawing a fluid charge into the respective chamber of the pumping cylinder, and in a second direction for supplying said fluid charge from the respective chamber of the pumping cylinder to said dispensing nozzle. In this embodiment, the operating unit also comprises two fluid accumulator cylinders in total, said accumulator cylinders also being carried by said support structure of the operating unit, both said fluid accumulator cylinders being replaceable and/or refillable, without removing them from the operating unit, and each having a fluid- accumulating chamber, and a piston within the accumulator cylinder, movable in a first direction for accumulating fluid within the chamber of the accumulator cylinder, and in a second direction, for ejecting the fluid out of the accumulator cylinder. In the case of this embodiment, the chamber of each pumping cylinder communicates with the chamber of a respective fluid accumulator cylinder by means of a respective first duct in which a respective first shut-off valve is interposed; it also communicates with said dispensing nozzle of the operating unit by means of a respective second duct, in which a respective second shut-off valve is interposed, in such a way that the chamber of each pumping cylinder can receive a fluid charge from the respective fluid accumulator cylinder, through the respective first duct, when the respective first shut-off valve is open and the respective second shut-off valve is closed, while each pumping cylinder can supply a fluid charge from the respective chamber of the pumping cylinder to said dispensing nozzle, through the respective second duct, when the respective second shut-off valve is open and the respective first shut-off valve is closed. In this preferred embodiment, said pumping cylinders and said shut-off valves can be controlled to operate:

- either with operating cycles which are in phase with each other, so that the two pumping cylinders simultaneously draw fluid charges from respective fluid accumulator cylinders and simultaneously supply fluid charges to the dispensing nozzle,

- or with operating cycles which are in opposite phases to each other, so that while one pumping cylinder supplies a fluid charge to the dispensing nozzle, the other pumping cylinder draws a fluid charge from the respective fluid accumulator cylinder.

The arrangement of two separate pumping cylinders connected to two separate fluid accumulators creates a high operative flexibility, as the pumping cylinders can operate both in phase and in counter-phase. In the case, for example, of applying a two-component adhesive, the two fluid accumulators are filled with two different components of the adhesive, and the two pumping cylinders operate in phase to simultaneously supply the two components to the dispensing nozzle. However, in the case of a single-component adhesive or sealant, the two pumping cylinders can operate in counter-phase, so that the operating unit firstly dispenses the fluid charge contained in a first fluid accumulator and successively dispenses the fluid charge contained in the second fluid accumulator. This allows a relatively high operating autonomy to be achieved, while providing fluid accumulators on-board the operating unit, each having a relatively reduced volume.

In the case of the preferred embodiment, each of the two first ducts that connect the chambers of the two pumping cylinders to the respective accumulator cylinders is associated with an inlet fitting, provided with an additional shut-off valve, for connection to a source of fluid external to the operating unit, usable to refill fluid into the respective accumulator cylinder. In this operating mode, it is possible to refill one or both of the fluid accumulators, while one or both of the pumping cylinders are operating to dispense fluid, in such a way that exhaustion of the charge of the fluid accumulators involves reduced or even zero dead times in the production cycle, since the refill can take place in substantially“hidden” time, that is, without extending the duration of the normal production cycle.

The invention also relates to a production plant, comprising a plurality of stations or assembly cells, at least some of which include one or more operating units according to the invention.

In one embodiment, the plant according to the invention is further characterized in that:

- each station or assembly cell comprises at least one docking station, having an outlet connected or connectable to said at least one accumulator cylinder of the operating unit, and an inlet connectable to an external fluid source, for filling said at least one cylinder accumulator,

- said external fluid source comprises a fluid tank and a pump for supplying fluid from the tank towards a dispensing outlet of the external fluid source,

- said external fluid source is carried by a vehicle movable between the stations or assembly cells of the plant, so as to be able to serve the various assembly cells, each time connecting the dispensing outlet of the external fluid source with the inlet of the docking station of a specific assembly cell.

Preferably, said vehicle is an automated guided vehicle, or AGV, configured to move between stations or assembly cells and provided with an electronic control unit that communicates with a stationary electronic controller, which is arranged to send control signals to the electronic control unit of the AGV in order to take the external fluid source - each time - to a predetermined docking station.

In this way, it is possible to guarantee the required quantity of fluid at each operating unit during the entire execution of a given cycle of operations, without however the risk of having large quantities of unused fluid that must be eliminated after each halt of the plant.

Detailed description of preferred embodiments

Further characteristics and advantages of the invention will become apparent from the description that follows with reference to the attached drawings, provided purely by way of non-limiting example, wherein:

- Figure 1 is a perspective view showing an embodiment of the operating unit according to the invention, arranged on a multi-axis manipulator robot, - Figures 2 and 3 are perspective views from opposite sides of the operating unit of Figure 1 ,

- Figures 4, 4A and 5 are diagrams illustrating the operating principle of the operating unit according to the invention, in two different operating modes,

- Figure 6 is a front, partially cross-sectioned elevational view of the operating unit of Figure 1 ,

- Figures 6A, 6B illustrate two alternative embodiments of the fluid dispensing device, which must be associated with the lower end of the operating unit of Figure 6,

- Figures 6C, 6D illustrate a variant of a detail of Figure 6, in two different operating positions,

- Figures 7 and 8 are additional diagrams illustrating the operating principle of the operating unit according to the invention, in two additional operating modes,

- Figure 9 is a perspective view showing an operator during an installation operation of two new full cartridges onto the operating unit according to the invention, in which the cartridges have been transported so that they are adjacent to the operating unit with the aid of an AGV-type vehicle (Automated Guided Vehicle), and

- Figure 10 is an additional perspective view showing the location of the fluid temperature control devices,

- Figures 1 1 and 12 are perspective views of an additional embodiment of the operating unit according to the invention,

- Figure 13 is a schematic plan view of an assembly plant including a plurality of assembly cells or stations, at least some of which are equipped with one or more manipulator robots carrying an operating unit according to the invention,

- Figure 13A is a schematic enlarged scale view of one of the docking stations provided in the plant of Figure 13,

Figure 14 is a schematic perspective view of a vehicle of the AGV type used in the plant of Figure 13, and

- Figure 15 schematically illustrates the use of the vehicle of Figure 14 in association with an operating unit according to a further embodiment of the present invention. In Figure 1 , the number 1 indicates - in its entirety - an operating unit, carried by a multi-axis manipulator robot 2 and used to apply an adhesive fluid or sealant on parts to be assembled in an assembly cell, for example, parts of a motor-vehicle body, in an industrial plant for producing motor-vehicles. As indicated above, this solution is only a preferred embodiment example. As an alternative to the use of a robot, the operating unit could be carried by any other automated device, controlled to move the operating unit with respect to the part on which the adhesive or sealant fluid is to be applied. In another embodiment that also falls within the scope of the present invention, the operating unit is mounted on a stationary base structure, and it is the part to be assembled that is moved with respect to the operating unit, for example, with the aid of a robot.

The robot 2 is illustrated purely by way of example, being evident that it can be of any known configuration. In the illustrated example, the robot is of the type comprising a base 200 resting on the floor of the assembly cell, a structure 201 mounted on the base 200 rotatably about a first vertical axis I, an arm 202 having a first end carried by the structure 201 in an articulated manner about a horizontal axis II, and another arm

203 connected to the second end of the arm 202 in an articulated manner about a horizontal axis III parallel to the axis II. On the arm 203, a body

204 is rotatably mounted about the longitudinal axis IV of the arm 203, carrying an articulated wrist of the robot 205, including two additional rotation axes and terminating with a flange 206 for coupling the robot tool, in the case specific for the coupling of the operating unit 1.

As already indicated, the robot used to carry the operating unit 1 can be of any other type or configuration.

Referring now in particular to Figures 2 and 3, in the preferred embodiment illustrated, the operating unit 1 includes a metal support structure 3 including a coupling flange 4, for coupling with the flange 206 of the robot wrist. The flange 4 of the robot and the flange 206 of the operating unit 1 include connections for electrical conductors and any service fluid tubes, through which the electrically-operated devices that are located on the operating unit 1 are supplied, along with any pneumatic or auxiliary hydraulic devices, which can be provided on-board the operating unit 1.

With reference, in particular, to Figure 2, the support structure 3 includes a bottom plate 300 having a central portion on which two supporting cylindrical modules 301 are rigidly connected.

On the modules 301 , two cartridges 5, consisting of two accumulating cylinders of the adhesive fluid or sealant, are removably supported, which will be illustrated in detail below.

The end portions of the plate 300 rigidly support two pumping cylinders 6 above them, which will also be described in detail below, each configured to draw a fluid charge from a respective fluid accumulator cylinder and to supply said fluid charge to a dispensing nozzle 7, forming part of a dispensing device 70.

In the embodiment that is illustrated here purely by way of non limiting example, the dispensing device 70 is rigidly connected to the lower end of a lower portion 8 of the structure of the operating unit, which is - in turn - rigidly connected to the lower surface of the plate 300 of the support structure 3. In the case of this specific example, the lower portion 8 consists of a plurality of metal modules screwed together, which will be described in detail below, and which define within them passages for connecting the pumping cylinders 6 with the dispensing nozzle 7 and with the fluid accumulator cylinders 5.

As already indicated, the embodiment of Figures 2, 3 is provided here purely by way of example. The support structure of the operating unit, the structure and conformation of the fluid accumulator cylinders 5 and the pumping cylinders 6, and the structure 8 defining the communication passages between the pumping cylinders, the dispensing nozzle and the fluid accumulators, can be completely different, as will be apparent to those skilled in the art. More generally, the layout of the structure and arrangement of the main components of the operating unit 1 is shown in Figure 4.

With reference to Figure 4, each fluid accumulator cylinder 5 comprises a fluid-accumulating chamber 50 and a piston 51 within the accumulator cylinder 5, movable in a first direction (upwards with reference to Figure 4) for accumulating fluid within the chamber 50 and in a second direction (downwards), for ejecting fluid from the accumulator cylinder 5.

Still with reference to Figure 4, each pumping cylinder 6 has a chamber 60 configured to receive a fluid charge, and a piston 61 inside the pumping cylinder which can be actuated in a first direction (upwards, with reference to Figure 4) for drawing a fluid charge within the chamber 60 and in a second direction (downwards) to supply said fluid charge from the chamber 60 to the dispensing nozzle 7.

Still with reference to Figure 4, the chamber 60 of each pumping cylinder 6 communicates with the chamber 50 of a respective fluid accumulator cylinder 5 by means of a first duct 9 in which a first shut-off valve 91 is interposed, said chamber communicating with said dispensing nozzle 7 by means of a second duct 10 in which a second shut-off valve 100 is interposed. In the embodiment of Figures 2, 3 and 10, and in the diagrams of Figures 4, 5, 7 and 8, a further shut-off valve 90 is also provided in each of the ducts 9, in addition to the aforesaid first shut-off valve 91 , In these examples, the first shut-off valve 91 is interposed between a first end of the respective first duct 9 and the chamber of the respective accumulator 5, while the additional shut-off valve 90 is interposed between a second end of the first duct 9 and the chamber 60 of the respective pumping cylinder 6.

The additional shut-off valves 90, however, are not essential and may also be eliminated, as in the embodiment illustrated in Figure 4A, which is identical to Figure 4 except for removal of the valves 90.

Thanks to the arrangements described above, the chamber 60 of each pumping cylinder 6 can receive a fluid charge from the respective fluid accumulator cylinder 5, by means of said first duct 9, when the respective first shut-off valve 91 is open (and when the additional valve 90, if provided, is also open) and when the respective second shut-off valve 100 is closed.

Similarly, each pumping cylinder 6 can supply a fluid charge from the respective chamber 60 to said dispensing nozzle, by means of said second duct 10, when the respective second shut-off valve 100 is open, and when the respective first shut-off valve 91 and the additional valve 90, if provided, are closed.

Each shut-off valve 91 at the end of each duct 9 connected to the respective fluid accumulator cylinder 5 also allows isolation of the duct 9 with respect to the external environment when a fluid accumulator 5 is removed from the operating unit 1.

Referring again to Figures 2 and 6, in the specific embodiment illustrated therein purely by way of non-limiting example, the two fluid accumulator cylinders 5 are in the form of cartridges with cylindrical bodies rigidly connected at their upper ends by a plate 52, in order to be mounted above the two modules 301 , or removed therefrom, as a single unit, with a single operation. However, an alternative embodiment is also provided, in which the two cartridges 5 are not connected, so that they can be removed and replaced separately from one another.

In the operating condition, the two cartridges 5 are maintained in a coupling condition with the two lower modules 301 by a locking device 1 1 of any known type. The illustrated example refers to a device 1 1 comprising a lever 1 10 operable by a pneumatic actuator 1 1 1 (visible in Figure 3) so as to be able to rotate between a lowered locked condition (shown in Figure 2) and a raised position, in which the two cartridges 5 can be removed.

As shown, in particular, in the cross-sectional view of Figure 6, each cartridge 5 has its piston 51 provided on its outer surface with a sealing ring that engages with the inner surface of the cylinder body. Each piston 51 is lowered within the respective cylindrical body when the fluid in the cartridge 5 is drawn by the respective pumping cylinder 6, while it is raised when the cartridge 5 is filled with a new fluid charge.

Still with reference to the embodiment illustrated in Figure 6 purely by way of non-limiting example, at its lower end, each fluid accumulator cylinder 5 has an outlet connector 53 configured to couple within an upper port of an axial duct 302 which crosses the respective module 301 and the plate 300 for connecting to one end of the respective duct 9, which connects the chamber 50 of the respective fluid accumulator cylinder 5 with the chamber 60 of the respective pumping cylinder 6 (see Figure 4).

In the illustrated example, the first shut-off valve 91 mentioned above is interposed within the axial duct 302 of each module 301. In the illustrated example, the valve 91 is a ball valve. The two shut-off valves 91 are controlled by electric actuators 910, visible in Figure 3. As shown in Figures 2, 3 and 6, in this embodiment each pumping cylinder 6 has a plunging piston 61 operatively connected to an actuator rod 62. In the illustrated example, the two pumping cylinders 6 and the two actuating rods 62 are arranged according to two axes 63 parallel to the axes of the fluid accumulator cylinders 5. Each actuator rod 62 is controlled in any manner known per se by a respective electric motor 64 (see Figure 3), by means of a mechanical transmission of any known type (not illustrated).

Still with reference to the specific example illustrated by way of non limiting example, each pumping cylinder 6 has a lower outlet port 65 (see Figure 6), which communicates, by means of a hole formed through the plate 300, with passages defined in the metal modules forming the lower part 8 of the structure of the unit 1.

Again with reference to the example of Figure 6, the valves 90 and 100 described above with reference to the diagram of Figure 4 in this embodiment are ball valves arranged within respective modules 90A and 100A forming part of the structure 8. Each module has end flanges for connecting (for example, by screws) to the adjacent modules and is crossed by an axial passage in which the respective valve is interposed. The valves 90 and 100 are controlled by electric actuators 900 and 1000 (Figure 3), for example, in the form of electric motors. The passages formed through the modules 90A communicate with the chambers of the two fluid accumulator cylinders 5 by means of the passages of the base blocks 301 (in which the shut-off valves 91 are interposed), and by means of passages formed in additional modules 90B, each of which is screwed on one side to the lower surface of the plate 300, and on the opposite side to the respective module 90A. The passages formed through the modules 90A also communicate with the chambers of the two pumping cylinders 6 by means of passages formed in modules 100B, each one fixed below the plate 300 and each connected to both the respective module 90A and to the respective module 100A. Each module 100A is connected on one side to the respective module 100B, and on the other side to a module 100C terminating with a flange connecting to the dispensing device 70.

Figure 6 shows the dispensing device 70 which is intended to be coupled with the flanges of the two modules 100c. This dispensing device 70, including the dispensing nozzle 7, can be of any known type, and in particular of the known type illustrated in Figure 6A or of the known type illustrated in Figure 6B. In both cases, the dispensing device 70 comprises two inlet ports 70A, which communicate with the chambers 60 of the two pumping cylinders 6 by means of the passages of the modules 100C, 100A and 100B. In the case of Figure 6A, the device 70 has two ducts that, from the ports 70A converge towards the dispensing nozzle 7, passing through a flowmeter 701. In the case of Figure 6B, the device 70 has two ducts that, from the ports 70A continue separately through respective flowmeters 701 and then converge towards the dispensing nozzle 7. The device 70 of Figure 6A is suitable for applying a single component adhesive, while the device of Figure 6B is suitable for applying a two-component adhesive.

As can be seen, in the example of Figure 6, the passages formed through the modules 90B, 90A, 100B, 100A and 100C define the ducts 9 and 10 of the general scheme of Figure 4, which connect the chamber 60 of each pumping cylinder 6 with the chamber 50 of the respective fluid accumulator cylinder and with the dispensing nozzle. In particular, each duct 9 is defined by the inner passage to one of the two modules 100B, and by the inner passages to the modules 90A, 90B and to the respective base block 301. The duct 10 is defined by the inner passage to a respective module 100B, and by the passages of the modules 100A and 100C, and by the inner passages to the dispensing device 70.

In the specific embodiment illustrated, each module 100B is provided with another connecting module 12A in which a shut-off valve 12 is arranged for controlling the communication with a tube 13 connected to an external fluid source 17 (see also Figure 7) in the form of a stationary fluid accumulator with which a fluid supply pump (not shown) is associated, in a conventional manner. The valve 12 is, for example, of a ball valve and is controlled by an electric actuator 120 (Figure 3) including, for example, an electric motor.

Still with specific reference to the illustrated example, by way of non-limiting example, in Figures 2, 3 and 6, an electronic control unit E is carried on the support structure 3, which controls the actuators 64, 120, 900, 1000 and 910. During operation, the operating unit 1 is provided with the fluid accumulator cylinders 5, each filled with its fluid charge. Each pumping cylinder 6 is capable of drawing its own fluid charge from the respective fluid accumulator cylinder 5 and then supplying it to the dispensing nozzle 7. In a typical application example, the robot moves the operating unit 1 along a part to be assembled to apply a bead of adhesive or sealant by means of the dispensing nozzle 7.

Each pumping cylinder 6 is capable of receiving a fluid charge from the respective fluid accumulator cylinder 5 by means of the respective duct 9 when the respective shut-off valve 91 is open, the respective shut off valve 90 (if provided) is open and the respective shut-off valve 100 is closed. In this condition, an upwards movement (with reference to the drawings) of the piston of the pumping cylinder 6 causes a transfer of fluid from the respective fluid accumulator cylinder 5 to the pumping cylinder 6, through the respective duct 9. This fluid transfer is accompanied by a lowering of the piston 51 within the fluid accumulator cylinder 5.

After a pumping cylinder 6 has been filled with a fluid dose, the same pumping cylinder 6 is able to supply the fluid charge to the dispensing nozzle 7 by means of the duct 10, after closing the respective shut-off valve 91 (and closing the valve 90, if provided) and opening the respective shut-off valve 100.

The operating unit can operate according to different operating modes.

Figures 4 and 4A show a first operation mode in which the two pumping cylinders 6 are controlled with counter-phase operating cycles, so that while a pumping cylinder 6 supplies a fluid charge to the dispensing nozzle 7 (in the specific case, the pumping cylinder illustrated on the right in Figure 4), the other pumping cylinder draws a fluid charge from the respective fluid accumulator (see the dashed lines). Once this phase has been completed, the two functions are reversed, so that the pumping cylinder, which is illustrated on the left in Figure 4, starts to supply fluid to the dispensing nozzle, while the other pumping cylinder starts to draw a new fluid charge within the chamber 76.

Figure 5, which is identical to Figure 4 (except for the different conformation of the dispensing device 70, which in Figure 4 has a single passage with a single flowmeter 701 , and in Figure 5 has two separate passages, each with a respective flowmeter 701 ), shows an operation mode in which two pumping cylinders 6 operate in phase, so that they automatically load a fluid charge, taking it from the respective fluid accumulator cylinders 5, and then simultaneously supply their own fluid charge to the dispensing nozzle 7. This operating mode is selected, for example, in the case of applying a two-component adhesive, in which case the two fluid accumulator cylinders 5 are arranged with charges of the two components, and the pumping cylinders are then able to supply the two different components simultaneously to the dispensing device 70.

According to a preferred characteristic of the invention, an electrically-operated Peltier device, controllable to act as a heater or a cooler, is associated with the body of each pumping cylinder 6, in order to control the temperature of the fluid within the pumping cylinder 6. A temperature sensor device is also associated with the same pumping cylinder 6. The respective electronic control unit E is arranged to receive the temperature signal of the aforesaid sensor and to control the Peltier device according to a predetermined logic, in order to maintain the temperature of the fluid, and consequently the viscosity of the fluid, within a predetermined range.

Similarly, additional heating or cooling devices can be provided both along the connecting duct 9 between each pumping cylinder 6 and the respective fluid accumulator cylinder 5, and along the connecting duct 10 between each pumping cylinder 6 and the dispensing nozzle 7, with associated temperature sensors, also connected to the respective electronic control unit for controlling and regulating the temperature, and consequently the viscosity, of the fluid along the entire path followed by the fluid to reach the dispensing nozzle, as well as at the dispensing nozzle.

With reference to the embodiment illustrated in Figures 2, 3 and 10 by way of non-limiting example, and with reference in particular to Figure 10, in this Figure, P1 -P10 indicate the points where the aforesaid heating and/or cooling devices are arranged with the associated temperature sensors. In the case of this example, the aforesaid Peltier devices with associated temperature sensors are provided at the points P1 and P2 (pumping cylinders 6). At the remaining points, electrical heating devices are provided, for example, in the form of electrical resistances with relative temperature sensors. In the illustrated example, these devices are arranged in the modules 90B (see Figure 2), that is, with reference to Figure 10, at P3 and P4, in the modules 100B (P5 and P6), in the modules 100C (P7 and P8), and at points P9, P10 and P1 1 of the dispensing device 70.

Of course, if for any reason, during operation the fluid accumulator cylinders are completely emptied before the operating unit has completed its operating cycle of applying the adhesive fluid or sealant, an external fluid source 17 can also be used, in a conventional manner, (see Figures 7 and 8), by opening one or both of the shut-off valves 12 to allow direct supply to the respective accumulator 5 of the adhesive fluid or sealant, by means of the tube 13. This arrangement is, of course, entirely optional and is used only when circumstances make it indispensable.

More generally, when the two fluid accumulator cylinders 5 are empty, it is envisaged, according to the invention, that said accumulator cylinders are replaced with two new full accumulator cylinders or, in an alternative embodiment, that they are refilled without being removed from the operating unit.

According to a further embodiment, the operating unit is arranged to operate both in the first mode (replacement of the accumulator cylinders 5) and in the second mode (refilling of the accumulator cylinders 5).

In the case of replacement of the accumulator cylinders 5, the unit comprising the two cartridges 5 can be removed and replaced with a unit comprising two full cartridges, for example manually, as exemplified in Figure 9. Figure 9 refers to an example in which the production plant uses vehicles of the AGV (Automated Guided Vehicle) type 14 to transport full cartridges 5 and empty cartridges 5 between an assembly cell, in which a robot operates that is equipped with an operating unit according to the invention, and a remote site within the production plant, used as a cartridge storehouse. As can be seen in Figure 9, an operator can manually replace two empty cartridges mounted on the operating unit with two full cartridges transported adjacent to the operating unit by the AGV 14.

Figure 7 instead shows an embodiment in which filling of the empty cartridges 5 is provided, without removing the cartridges 5 from the operating unit 1. In this case, each duct 9 can be connected by means of the shut-off valve 12 to the duct 13 for supplying fluid under pressure from a fluid source in the form of a stationary fluid accumulator 17, with which a fluid supply pump (not illustrated) is associated, in a conventional manner.

As illustrated in Figure 7 (see dashed lines), the refilling operation of one of the two cartridges 5 can take place while the pumping cylinder 6, which is associated with the other cartridge 5, is in its active operating phase, in which it supplies adhesive or sealant to the dispensing nozzle 7. Therefore, as can be seen, in this embodiment, the cartridges 5 can be refilled in a“hidden” time, without introducing dead times, or with very short dead times, in the normal production cycle.

Figure 8 shows an alternative embodiment to Figure 7, in which refilling of the cartridges 5 is arranged in a completely analogous manner to that described in Figure 7, with the difference, however, that the duct 13 is not placed in direct communication with the fluid source 17, but with a coupling element of a docking station 18 arranged in the assembly cell, which - in turn - communicates with the source 17 by means of a duct 19.

- Figures 1 1 and 12 are perspective views of an additional embodiment of the operating unit according to the invention. In these figures, the parts corresponding to those illustrated in Figures 1 -10 are indicated by the same reference numbers. A first difference with respect to the example of Figures 2, 3, 6, 10 consists in the fact that the unit of Figures 1 1 and 12 corresponds to the diagram of Figure 4A, in which the valves 90 have been eliminated. A second difference lies in the fact that, in this case, the downward movement of the pistons of the accumulator cylinders 5 is accompanied by two rods 54 driven by two actuators 55, for example, in the form of electric motors that actuate the rods 54 by means of transmissions of any known type. Elimination of the valves 90 consequently results in elimination of the actuators 900 provided in the first embodiment described above.

As an alternative, or in addition to the solution described above, for actuating the pistons of the accumulator cylinders 5, a fluid actuation can be provided, by means of pressurized air, for example, taken from a distribution plant available within the factory, or by using a pressurized air amplifier (air booster), which can be included in the unit of the invention. The pneumatic actuation simplifies the controls and reduces the volume and weight of the unit and, more importantly, reduces the volume of the electrical cabinet, since electrical power is not required for operating the pressure amplifier.

Another difference with respect to the first embodiment consists of a different conformation of the support structure 3, which - in this case - has a cage configuration. In the embodiment of Figures 2, 3, 6 and 10, the axes of the two accumulator cylinders 5 and the axes of the two pumping cylinders 6 are substantially contained in the same plane. In the case of the embodiment of Figures 1 1 , 12, the axes of the two accumulator cylinders 5 are contained in a first plane, and the axes of the two pumping cylinders 6 are contained in a second plane, parallel to the aforesaid first plane. Instead of the structure 8 of the embodiment of Figures 2, 3, 6, 10, including a plurality of connected modules, the solution of Figures 1 1 , 12 provides a single metal body 8 in which the ducts 9, 10 are formed for machine processing. In the case of Figures 1 1 and 12, the electronic unit is contained in a single casing, and the two Peltier devices P1 and P2 are contained in respective casings connected to the structure 3.

As is evident from the above description, the embodiment described here achieves a series of important advantages.

Firstly, the operating unit is able to operate using the fluid charges contained in the two fluid accumulators arranged on the operating unit. Therefore, the operating unit according to the invention is not obliged to be connected to a stationary fluid accumulator adjacent to the robot, which avoids obstructing the operating freedom of the robot and limiting its working area.

Secondly, the arrangement of two separate pumping cylinders connected to two separate fluid accumulators creates a high operative flexibility, as the pumping cylinders can operate both in phase and in counter-phase. In the case, for example, of applying a two-component adhesive, the two fluid accumulators are filled with the two different components of the adhesive, and the two pumping cylinders operate in phase to simultaneously supply the two components to the dispensing nozzle. However, in the case of a single-component adhesive or sealant, the two pumping cylinders can operate in counter-phase, so that the operating unit firstly dispenses the fluid charge contained in a first fluid accumulator and successively dispenses the fluid charge contained in the second fluid accumulator. This allows a relatively high operating autonomy to be achieved, while providing fluid accumulators on-board the operating unit, each having a relatively reduced volume.

A further important advantage of the operating unit according to the invention lies in the fact that the two fluid accumulator cylinders arranged on-board the operating unit are configured to be replaceable and/or refillable, which opens a series of options that can be used in succession when necessary, to guarantee the supply to the operative unit of the quantity of fluid necessary for its normal operation.

However, it should be noted that the invention also comprises a simplified embodiment, substantially corresponding to one half of the preferred embodiment, and therefore including a single pumping cylinder, a single accumulator cylinder and only the ducts and shut-off valves associated with them. Even in this simplified embodiment, the invention retains many of the advantages indicated above and results, at the same time, in reduced dimensions and weight.

Figures 6C, 6D refer to a variant of Figure 6, in which the shut-off valve 100 for connecting to the dispensing nozzle, and the shut-off valve 12 for connecting to the fluid source 17 external to the operating unit are integrated in a single 4-way valve 4WV, having a first operating position (Figure 6C), in which the pumping cylinder 6 communicates with the external source 17 (to enable external refilling), and the fluid accumulator cylinder 5 communicates with the dispensing nozzle 7 (to enable the dispensing/application of the sealant through the nozzle), and a second operating position, in which the pumping cylinder 6 communicates with the fluid accumulator cylinder 5 (to enable internal refilling) and the external source 17 communicates with the dispensing nozzle 7.

Above all, this solution reduces the weight and volume of the unit. It also results in less heat loss, which reduces the size of the electrical cabinet, improving energy efficiency and further reducing the weight and volume of the unit. Finally, more importantly, this solution limits the protection required against high pressure. During standard sealant applications, high pressure is required during dispensing/application of the sealant. By limiting the high pressure to just the passage through the 4- way valve, the remaining part of the equipment is directly protected against high pressure by the 4-way valve, which gives the advantage of having cheaper and lighter equipment, suitable for relatively lower pressures.

Of course, without prejudice to the principle of the invention, the details of construction and the embodiments may vary widely with respect to those described and illustrated, without departing from the scope of the present invention.

For example, the operating unit may also have more than two pumping cylinders and more than two fluid accumulator cylinders, each pumping cylinder being able to be selectively connected to one or more fluid accumulator cylinders, to draw the fluid charge to be successively supplied to the dispensing nozzle.

Although in the present description reference is made to an adhesive fluid or sealant, the invention can be used to apply any type of fluid. Figure 13 shows a schematic plan view of an example of a production plant comprising a plurality of assembly cells or stations 1.1 , 1.2, ..., 1.n, 2.1 , 2.2, ..., 2.n, ..., n.1 , n.2, ..., n.n (for simplicity, the drawing only illustrates three stations of a first array of stations and three stations of a last array of stations). In Figure 13, reference R1 is used to schematically illustrate the manipulator robots each equipped with the operating unit according to the invention as described above, while reference R2 is used to indicate manipulator robots intended to perform other types of operations. Each assembly station or cell equipped with a robot R1 is also provided with at least one docking station DO having an output DO_u (Figure 13A) connectable with the accumulator cylinder, or accumulator cylinders of the operating unit carried by the robot R1 , and an inlet DO, connectable to an external fluid source S (described in detail below), for refilling the accumulator cylinder or accumulator cylinders of the operating unit carried by the robot R1.

Referring to Figure 14, the external fluid source can be in the form of a fluid tank S including a pump P for supplying the fluid contained in the tank S to a dispensing outlet E. In the illustrated example, the dispensing outlet E is carried by a manipulator arm 500, preferably a robotized arm, which allows the position of the dispensing outlet E with respect to the tank S to be varied.

As also shown in Figure 14, the external fluid source S is carried on-board a vehicle V, which is guided along paths S1 , S2, S3, S4, S5, S6 between the assembly stations to connect the dispensing outlet E of the external fluid source with the inlet of the docking station of a specific assembly station each time, according to the requirements of the different stations.

Preferably the vehicle V is an automated guided vehicle (AGV), having an electronic unit W on board for controlling one or more electric motors located on-board the vehicle V, for actuating one or more driving wheels of the vehicle, and for controlling the steering of at least two of the wheels of the vehicle V. The electronic unit W is in wireless communication with a stationary electronic controller W1 (Figure 13), which is arranged to send control signals to the unit W to drive the vehicle to the docking station DO, where its intervention is required. Of course, the plant can be provided with more than one vehicle V with respective fluid sources S. Once a specific docking station has been reached, the electronic control unit W also controls the robotized arm 500, with the aid of an optoelectronic system 01 associated with the dispensing outlet E, in order to take the outlet E to the correct coupling position with an inlet DO, of a given docking station DO.

Of course, the possibility of providing manually-towable vehicles V, with manually operated 500 arms, is also not excluded.

The solution illustrated by way of example in Figure 13 provides just one example of a possible use of the operating unit according to the invention. This specific method of use achieves the advantage of using operating units with relatively small-dimensioned accumulator cylinders, given the refilling possibility offered by the system illustrated above. In this way, on one hand, the continuity of the sealant supply is ensured during a given work cycle. On the other hand, it can be avoided, once a cycle of operations has been completed, that a considerable quantity of adhesive remains in the accumulator cylinders, which would tend to deteriorate during the machining breaks, and would make it necessary to perform operations to restore the cylinders before starting a new cycle of operations, with a consequent waste of time and resources. With this procedure, the amount of fluid that must be discarded at the end of a production cycle is extremely reduced compared to that which occurs with the systems currently in use.

Figure 15 is a schematic view similar to that of Figure 14, in which the vehicle V carrying the fluid source S is used in association with an operating unit 1 according to another variant of the present invention. In this case, between the support structure of the operating unit 1 , which can be produced in the manner described above, and the device TC (which can be of any known type) for coupling to the robot wrist, an auxiliary tank S1 , with a buffering function is interposed. The tank S1 has an inlet S1 , that can be coupled with the dispensing outlet E of the source S, and an outlet S1 _u that can be connected with the accumulator cylinder, or with the accumulator cylinders of the operating unit 1. Using the buffer S1 is also possible in association with a single operating unit 1 , regardless of the use of a vehicle V.

With reference to Figure 15, the device 1 can be any end-effector of a known type (for example, one of the devices commonly referred to as “Spray”,“Bead”,“Swirl”,“Jet-Stream”, etc.) and can be changed through the quick-coupler S1 M.

Of course, without prejudice to the principle of the invention, the details of construction and the embodiments may vary widely with respect to those described and illustrated purely by way of example, without departing from the scope of the present invention.

Claims

1. An operating unit for dispensing an adhesive fluid or sealant, said operating unit comprising

- a support structure (3), provided with a coupling device (4) for connecting to a robot (2) or other base structure,

- a fluid dispensing nozzle (7), carried by said support structure (3),

- at least one pumping cylinder (6), also carried by said support structure (3) and with a chamber (60) configured to receive a fluid charge, and a piston (61 ) inside the pumping cylinder (6), wherein said piston can be driven in a first direction for drawing a fluid charge into said chamber (60) of the pumping cylinder (6), and in a second direction, for supplying said fluid charge from said chamber (60) of the pumping cylinder (6) to said dispensing nozzle (7),

said unit (1 ) being characterized in that:

- the operating unit (1 ) comprises at least one fluid accumulator cylinder (5), also carried by said support structure (3),

- said at least one fluid accumulator cylinder (5) is replaceable and/or refillable, in the latter case with no need for removing it from the operating unit,

- said at least one accumulator cylinder has a fluid-accumulating chamber (50) and a piston (51 ) within the accumulator cylinder (5) movable in a first direction for accumulating fluid within the chamber (50) of the accumulator cylinder, and in a second direction, for ejecting the fluid out of the accumulator cylinder (50),

- the chamber (60) of said at least one pumping cylinder (6) communicates with the accumulating chamber (50) of said at least one fluid accumulator cylinder (5) by means of a first duct (9) wherein a first shut-off valve (91 ) is interposed, said chamber of said at least one pumping cylinder (6) communicating also with said dispensing nozzle (7) of the operating unit (1 ) by means of a second duct (10) in which a second shut-off valve (100) is interposed,

in such a way that the chamber (60) of said at least one pumping cylinder (6) can receive a fluid charge from said at least one fluid accumulator cylinder (5), by means of said first duct (9), when the respective first shut-off valve (91 ) is opened and the respective second shut-off valve (100) is closed,

whereas said at least one pumping cylinder (6) can supply a fluid charge from the respective chamber (60) of the pumping cylinder to said dispensing nozzle (7) through said second duct (10), when the respective second shut-off valve (100) is opened and the respective first shut-off valve (91 ) is closed.

2. An operating unit according to claim 1 , characterized in that said at least one fluid accumulator cylinder (5) is in the form of a replaceable cartridge, having a body removably connected to the support structure (3) of the operating unit, and an outlet (53) which can be connected to the first duct (9) of said operating unit (1 ) by means of said first shut-off valve (91 ).

3. An operating unit according to claim 1 , characterized in that an inlet connecting member (12A) is associated with said second duct (10) which connects the chamber (60) of said at least one pumping cylinder (6) to the dispensing nozzle (7), said connecting member being provided with a shut-off valve (12) for connecting to a fluid source (17) located outside the operating unit, which can be used for filling fluid into the respective accumulator cylinder (5) without removing the fluid accumulator cylinder (5) from the operating unit.

4. An operating unit according to claim 3, characterized in that said second shut-off valve (100) for connection to the dispensing nozzle and said shut-off valve (12) for connection to the fluid source (17) - outside the operating unit - are integrated into a single 4-way valve (4WV) having a first operating position, wherein the pumping cylinder (6) communicates with the external source (17) and the fluid accumulator cylinder (5) communicates with the dispensing nozzle (7) and a second operating position, in which the pumping cylinder (6) communicates with the fluid accumulator cylinder (5) and the external source (17) communicates with the dispensing nozzle (7).

5. An operating unit according to claim 1 , characterized in that the piston (61 ) of said at least one pumping cylinder (6) and the aforesaid shut-off valves (91 , 100, 90, 12) are controlled by respective actuators (64, 900, 1000, 910, 120), and in that the operating unit comprises an electronic control unit (E) programmed for controlling said actuators (64, 900, 1000, 910, 120) for implementing one or more predetermined operating cycles.

6. An operating unit according to claim 5, characterized in that one or more temperature controlling devices (P1 -P1 1 ), for controlling the temperature of the fluid, and one or more temperature sensors are associated with the chamber (60) of said at least one pumping cylinder (6), with the first duct (9) connecting the chamber (60) of said at least one pumping cylinder (6) with said at least one fluid accumulator cylinder (5) and/or with the second duct (10) connecting the chamber (60) of said at least one pumping cylinder (6) with the dispensing nozzle (7),

said electronic control unit (E) being configured and programmed for receiving signals from said temperature sensors and for controlling said temperature controlling devices on the basis of said signals.

7. An operating unit according to claim 6, characterized in that said temperature controlling devices comprise one or more electrically- operated heating modules.

8. An operating unit according to claim 7, characterized in that said temperature controlling devices also comprise one or more electrically- operated cooling modules.

9. An operating unit according to claim 8, characterized in that a Peltier module (P1 , P2) is associated with said at least one pumping cylinder (6), configured for being controlled by said electronic control unit (E) so as to act either as a cooling device or as a heating device, depending upon the temperature detected by a temperature sensor associated with the Peltier device.

10. An operating unit according to any of the previous claims, characterized in that:

- the operating unit (1 ) has two pumping cylinders (6) in total, both cylinders being carried by said support structure (3), each pumping cylinder (6) having a respective chamber (60) configured to receive a fluid charge, and a piston (61 ) inside the pumping cylinder (6) which can be driven in a first direction for drawing a fluid charge into the respective chamber (60) of the pumping cylinder, and in a second direction for supplying said fluid charge from the respective chamber (60) of the pumping cylinder (6) to said dispensing nozzle (7),

- the operating unit (1 ) also comprises two fluid accumulator cylinders (5) in total, said accumulator cylinders also being carried by said support structure (3), said fluid accumulator cylinders (5) being replaceable and/or refillable, with no need for removing them from the operating unit, and each having a fluid-accumulating chamber (50) and a piston (51 ) within the accumulator cylinder (5) movable in a first direction for accumulating fluid within the chamber (50) of the accumulator cylinder, and in a second direction, for ejecting the fluid out of the accumulator cylinder (50),

- the chamber (60) of each pumping cylinder (6) communicates with the accumulating chamber (50) of a respective fluid accumulator cylinder (5) by means of a respective first duct (9) in which a respective first shut off valve (91 ) is interposed, and said chamber communicates with said dispensing nozzle (7) of the operating unit (1 ) by means of a respective second duct (10) in which a respective second shut-off valve (100) is interposed,

in such a way that the chamber (60) of each pumping cylinder (6) can receive a fluid charge from a respective fluid accumulator cylinder (5), by means of said first duct (9), when the respective first shut-off valve (91 ) is opened and the respective second shut-off valve (100) is closed,

while each pumping cylinder (6) can supply a fluid charge from the respective chamber (60) of the pumping cylinder to said dispensing nozzle (7) through said second duct (10), when the respective second shut-off valve (100) is opened and the respective first shut-off valve (91 ) is closed, said pumping cylinders (6) and said shut-off valves (90, 91 , 100) can be controlled to operate:

either with operating cycles which are in phase with each other, so that the two pumping cylinders (6) simultaneously draw fluid charges from the respective fluid accumulator cylinders (5) and simultaneously supply fluid charges to the dispensing nozzle (7),

or with operating cycles which are in opposite phases to each other, so that while one pumping cylinder (6) supplies a fluid charge to the dispensing nozzle (7), the other pumping cylinder (6) draws a fluid charge from the respective fluid accumulator cylinder (5).

11. An operating unit according to claim 1 , characterized in that an auxiliary tank with a buffering function is interposed between said support structure (3) of the operating unit and said coupling device for connection to a robot (2) or another structure.

12. An operating unit according to claim 1 , characterized in that the pistons of the accumulator cylinders (5) are driven by pressurized air, for example, taken from a distribution system available within the factory and/or by using a pressure amplifier forming part of said unit.

13. A method for applying an adhesive fluid or sealant onto a part to be assembled in an industrial assembling cell, in particular onto a motor-vehicle component, said method comprising the steps of:

- providing an operating unit (1 ) according to claim 9,

- moving the operating unit (1 ) relative to the part to be assembled, or moving the part to be assembled relative to the operating unit (1 ), according to a predetermined operating cycle, with the aid of an automated device, for example, a multi-axis manipulator robot (2),

- activating said operating unit (1 ) during said operating cycle, for supplying fluid contained within the fluid accumulator cylinders (5) of said operating unit to the dispensing nozzle (7) of the operating unit (1 ),

- controlling the pumping cylinders (6) and the shut-off valves (90, 100, 91 , 12) of the operating unit (1 ) for operating:

or with operating cycles which are in opposite phases to each other, so that while one pumping cylinder (6) supplies a fluid charge to the dispensing nozzle (7), the other pumping cylinder draws a fluid charge from the respective fluid accumulator cylinder (5).

14. A method according to claim 13, characterized in that it comprises the step of replacing each of said fluid accumulator cylinders (5) when it is empty, with a full fluid accumulator cylinder (5).

15. A method according to claim 13, characterized in that it comprises the step of refilling a fluid accumulator cylinder (5) without removing said fluid accumulator cylinder (5) from the operating unit, by establishing a connection between said first duct (9) of the fluid accumulator cylinder (5) to be refilled with a fluid source (17) located outside the operating unit (1 ).

16. A method according to claim 15, characterized in that it comprises the steps of:

- providing a docking station (18) having a connecting member communicating with said external fluid source (17),

- refilling a fluid accumulator cylinder (5) with fluid coming from said external fluid source (17), by establishing a connection between the first duct (9) of the fluid accumulator cylinder (5) to be refilled, with said connecting member of said docking station (18).

17. A method according to claim 14, characterized in that it comprises the step of providing at least one AGV (Automated Guided Vehicle) for conveying full fluid accumulator cylinders (5) and/or empty fluid accumulator cylinders (5) within a production plant, between said assembling cell in which the operating unit (1 ) is used and a remote station for storing and/or refilling fluid accumulator cylinders (5).

18. A production plant, comprising a plurality of assembly stations or cells (1.1 , 1.2, ... n.n), at least some of which include one or more operating units (1 ) according to claim 1.

19. A production plant according to claim 18, characterized in that:

- each station or assembly cell (1.1 , .., n.n) comprises at least one docking station (DO), having an outlet (DO_u) connected or connectable to said at least one accumulator cylinder (5) of the operating unit (1 ) and an inlet (DO,) connectable with an external fluid source (S), for refilling said at least one accumulator cylinder (5), without having to remove the accumulator cylinder from the operating unit,

- said external fluid source (S) comprises a fluid tank (T) and a pump (P) for supplying fluid from the tank (T) towards a dispensing outlet (E) of the external fluid source (S),

- said external fluid source (S) is carried by a vehicle (V) movable between the stations or assembly cells (1.1 , n.n) of the plant, so as to be able to serve the various assembly cells, connecting - each time - the dispensing outlet (E) of the external fluid source (S) with the inlet (DO,) of the docking station (DO) of a specific station or assembly cell.

20. A production plant according to claim 19, characterized in that said vehicle (V) is an automated guided vehicle, or AGV, able to move between stations or assembly cells (1 .1 , ..., n.n) and provided with an electronic control unit (W) that communicates with a stationary electronic controller (W1 ), which is arranged to send control signals to the electronic control unit of the AGV (V) in order to take the external fluid source (S) - each time - to a predetermined docking station (DO).

21. A production plant according to claim 19, characterized in that the dispensing outlet (E) of the external fluid source (S) is carried by a robotized manipulator arm (500), provided with an optoelectronic guide system (01 ) for automatically controlling the movement of the dispensing outlet (E) towards a position of coupling with the inlet (DO,) of a predetermined docking station (DO).

22. A production plant according to claim 20, characterized in that said vehicle is a manually-towable vehicle.