Suction Cup Gripping System

The invention relates to gripping systems and devices for handling and moving objects and in particular relates to a suction cup gripping system suitable for gripping and moving objects.

Gripping and moving systems are known and widely used that use suction cups to grasp objects by adhering firmly to their external, substantially flat and non-porous surface. These suction cup gripping systems are, for example, widely used in automatic machines for sheet metal cutting and/or punching, in particular to load the metal sheets onto a work table of the machine and to remove from this table the final pieces thus obtained after the cutting and/or punching.

As is known, creating a negative pressure inside a suction cup placed in contact with the external surface of an object generates a gripping force which, if it is greater than the weight of the object itself, allows it to be held firmly and then lifted and moved with relative safety. The negative pressure or partial vacuum is realized inside the cavity formed by the suction cup and the external surface of the object by connecting with a vacuum source, typically a vacuum pump.

For this purpose, it is very common to use vacuum pumps or Venturi vacuum generators or ejectors that use compressed air and the Venturi principle to generate the vacuum. More precisely, such pumps comprise a Venturi nozzle or tube (converging/diverging duct) supplied by, and crossed by, compressed air and connected at a narrowing or constriction section thereof, in which a negative pressure or partial vacuum is generated, to the inside of the suction cup.

A valve is generally provided on the compressed air supply line, configured and selectively operable to supply the compressed air to the Venturi ejector and generate the vacuum needed for the suction cup to grasp and move the piece or to stop this supply of compressed air and to vent the suction cup, that is, to connect it to the external environment so as to allow the suction cup to release the piece.

Venturi vacuum generators are economical and reliable, since they have no moving parts and are not subject to wear and also have reduced dimensions and weight. Furthermore, unlike rotary vacuum pumps, Venturi vacuum generators can operate in a discontinuous manner, i.e. only when the suction cups need the negative pressure, which they can achieve, given the reduced volume of the internal cavities of the suction cups, in a very short time. A disadvantage of gripping systems with suction cup and Venturi vacuum generator is that the negative pressure, or partial vacuum, must be maintained inside the suction cup by supplying the Venturi ejector with compressed air throughout the duration of the gripping and moving of the object. In the case of gripping and moving systems in which the gripping of the pieces must be maintained for a relatively long period of time (for example 20-30 s), the consumption of compressed air, and therefore of electrical energy, necessary to produce said compressed air through suitable compressors, is very high and therefore the operation of such systems is quite expensive.

An object of the present invention is to improve suction cup gripping systems, in particular associated with a Venturi vacuum generator and therefore supplied and operated by compressed air.

Another object is to realize a device and a suction cup gripping system that allows significant reduction in the consumption of compressed air during operation, in particular during the gripping and moving of an object.

A further object is to provide a suction cup gripping system that allows objects of various sizes and weight to be gripped and held firmly, reliably and safely.

Another object is to make a gripping system having a simple, robust and economical construction.

In a first aspect of the invention a suction cup gripping system according to claimis provided.

In a second aspect of the invention a suction cup gripping system according to claimis provided.

The gripping devicealso comprises a Venturi vacuum generator, or Venturi ejector, connectable to a line or source of compressed airand in flow connection with the internal cavityof the suction cup. The Venturi vacuum generator, of known type and not described in further detail, is configured to generate a negative pressure or partial vacuum in the internal cavitywhen it is supplied with compressed air and when the suction cupengages the external surfaceof the object. More precisely, a narrowing section of a converging/diverging duct of the Venturi vacuum generator, in which a negative pressure or partial vacuum is generated as the compressed air passes through, is in flow connection with the internal cavityof the suction cup.

The Venturi vacuum generatoris for example of the multi-stage type, in particular it comprises two or three stages for realizing a higher value of partial vacuum or negative pressure inside the internal cavity, for example comprised between −0.85 kPa and −0.65 kPa i.e. between 0.15 and 0.35 kPa (bar) in absolute value.

The gripping devicefurther comprises a release valveand a check valve. The release valveis in flow connection with the internal cavityand is operable to connect the latter to an external environment or to the source of compressed airin order to eliminate the partial vacuum inside the internal cavity, and thus allow releasing the object. The check valve, or one-way valve, is in flow connection with and interposed between the Venturi vacuum generatorand the internal cavityand is configured to prevent air from entering the internal cavitywhen the Venturi vacuum generatoris not supplied with compressed air, as better explained below.

The gripping devicecomprises a casing, for example fixed to a connecting elementof the suction cup, suitable to house and contain the Venturi vacuum generator, the release valveand the check valve.

The casing, having for example a prismatic shape, comprises a first connection, in flow connection with a supply inlet of the Venturi vacuum generator, a second connection, in flow connection with the release valve, a third connectionfor the flow connection of the internal cavityof the suction cupwith the Venturi vacuum generatorand the release valve.

The casingis further provided with a fourth connectionin flow connection with the Venturi vacuum generatorand the internal cavity.

The casingalso comprises a fifth connectionin flow connection with a discharge outlet of the Venturi vacuum generator.

The first connectionis connectable to the compressed air line, in particular via a first supply duct, for supplying compressed air to the Venturi vacuum generatorso as to generate a partial vacuum inside the internal cavityof the suction cup.

The second connectionin the illustrated embodiment is also connectable to the compressed air line, in particular by means of a second supply duct, to send compressed air to the release valvewhich, when activated, sends the air into the internal cavityin order to eliminate the partial vacuum in the internal cavityand thus allow the release of the object.

The third connectionis connected to the Venturi vacuum generator, in particular to its narrowing section, by a first ductand to the release valveby a second ductwhich is connected to the first ductat a branch point.

The fourth connectionconnects the Venturi vacuum generatorand the internal cavityto a manifoldprovided with a vacuum sensoror directly to the vacuum sensor, as better explained in the description below.

The fifth connection, in flow connection with the discharge outlet of the Venturi vacuum generator, can be connected, for example, to a silencerin such a way as to reduce the noise generated by the compressed air leaving the Venturi vacuum generatorand dispersed into the environment.

The check valveis inserted in the first ductin the portion thereof that is between the Venturi vacuum generatorand the branch point.

A filteris inserted in the first ductin the section between the branch pointand the third connection.

The release valveis for example a pneumatic valve, in particular a two-way, two-position pneumatically operated valve. In particular, the release valveis normally closed i.e. it closes the flow connection between the second connectionand the internal cavitywhen it is not pneumatically supplied and controlled. Conversely, when the release valveis supplied with compressed air coming from the pneumatic supply line, it is switched to the open operating position so as to open the flow connection between the second connectionand the internal cavityfor the entry of compressed air into the internal cavity.

The casingalso comprises a fastening elementfor connecting the gripping deviceto the suction cup gripping system. The fastening elementis in particular aligned and opposite the connecting elementof the suction cup.

With particular reference to, the suction cupcomprises a bodyprovided with an upper portionand a deformable central portion, in particular compressible and/or crushable along a direction parallel to a longitudinal axis X of the suction cup, and defining the internal cavity. The connecting elementis connected to the upper portionand is provided with an internal ductfor the passage of air.

The central portionincludes a peripheral edgethat surrounds a lower access opening to the internal cavityand is configured to abut the external surfaceof the objectto be picked up.

The suction cupfurther comprises a stop elementpositioned in the internal cavity, fixed to the upper portionand suitable to abut the external surfaceof the objectwhen the suction cupengages said external surfaceand the internal cavityis placed in negative pressure, so as to limit a deformation or crushing of the central portion. The stop elementcomprises a respective central ductprovided with axial openingsand lateral openingsfor the passage of air.

With reference to, the suction cup gripping system, or gripping system, of the invention comprises a plurality of gripping devices, for example seven, as described above and illustrated in, valve means.in flow connection with the Venturi vacuum generatorsand the release valvesof the gripping devicesfor supplying compressed air selectively to said Venturi vacuum generatorsor said release valves.

In particular, each gripping deviceincludes at least one gripping suction cupadapted to abut the external surfaceof an objectto be gripped and provided with an internal cavity, a Venturi vacuum generatorconnectable to the compressed air lineand in flow connection with the internal cavityto generate a negative pressure or partial vacuum in the internal cavitywhen supplied with compressed air and when the gripping suction cupis engaged to the external surfaceof the object, a release valvein flow connection with the internal cavityand operable to connect the internal cavity to an external environment or to the compressed air linein order to eliminate the partial vacuum in the internal cavityand a check valvein flow connection and interposed between the Venturi vacuum generatorand the internal cavityand configured to prevent the air from entering the internal cavitywhen the Venturi vacuum generatoris not supplied with compressed air.

The gripping systemfurther comprises a manifoldin flow connection with the internal cavitiesof the suction cupsof the plurality of gripping devices, in particular via respective measuring ducts, and a vacuum sensor, in flow connection with the manifoldand suitable to measure a value of partial vacuum inside the manifoldand therefore inside the internal cavitiesof suction cups.

The gripping systemalso includes a control unitconnected to valve means,and vacuum sensorand configured to control the valve means,so as not to supply compressed air to the Venturi vacuum generatorsof the gripping deviceswhen the pressure sensordetects a value of partial vacuum in the manifoldand therefore in the internal cavitiesof the suction cupthat is greater than or equal to a defined first threshold value P, i.e. an absolute pressure inside the internal cavitiesof the suction cupslower than said defined first threshold value P. The first threshold value Pis for example −0.80 kPa and −0.65 kPa in relative value or 0.20 kPa in absolute value.

The control unitcan be the control unit of an operating machine, for example a machine for cutting and/or punching metal sheets, on which the gripping systemof the invention is installed and operated.

It should be noted that the plurality of gripping devicesof the gripping systemof the invention, which are supplied with compressed air by the same valve means,and share a single vacuum sensormounted on the manifoldto which the Venturi vacuum generatorsof gripping devicesare connected, define a gripping zone or area. In particular, the gripping systemallows one or more objectscontained within said gripping zone to be picked up or moved at the same time.

Valve means,comprise, in particular, a pair of valves activated and operated by the control unit, in particular a pair of electrically operated valves of the known two-way and two-position type, connected to the compressed air supply lineand to an air exhaust line. For example, the valve means comprise a pair of pneumatic valves having solenoids with indirect operation, i.e. pneumatically switched into the two operating positions on the basis of electrical signals sent by the control unit. In particular, the valves are connected to a pneumatic switching lineand to a switching exhaust line.

In the illustrated embodiment, the valve means comprise a first valveassociated with the Venturi vacuum generatorand a second valveassociated with the release valve. The first valveis for example of the normally open type, i.e. when it is not electrically activated it keeps the flow connection between the pneumatic supply lineand the Venturi vacuum generatoropen, while it connects the Venturi vacuum generator to the exhaust linewhen it is activated.

Conversely, the second valveis of the normally closed type, i.e. when it is not activated it keeps the release valvein flow connection with the exhaust line, while when it is electrically activated connects the release valveto the pneumatic supply line.

Each gripping devicefurther includes a respective adjustment nozzlewith calibrated hole, in particular with a size between 0,2 and 0,4 mm, in particular equal to 0,3 mm, said adjustment nozzlebeing in flow connection with and interposed between the internal cavityof suction cupand the manifoldand suitable to limit an air flow entering the manifold, in particular when the corresponding suction cupis not engaged with the external surfaceof the object. More precisely, the adjustment nozzlewith a calibrated hole for the passage of the air flow makes it possible to limit the loss of vacuum in the manifoldin the event that the associated gripping deviceis not gripping the object, since it reduces the suction of air by the other gripping devicesthrough said suction cupnot gripping.

In particular, each adjustment nozzleis connected to the fourth connectionof the casingof the respective gripping deviceand is in flow connection with the Venturi vacuum generatorand the internal cavity. Therefore, the adjustment nozzleis inserted in the respective measurement duct, interposed between the fourth connectionand the manifold.

The vacuum sensorcomprises, for example, a vacuum switch of known type suitable to detect the first threshold value Pand a further first threshold value P′ and to send related signals to the control unitto control the valve means,so as to maintain in the manifoldand therefore in the internal cavitiesof suction cupsa value of partial vacuum substantially equal to the first threshold value Pl or the further first threshold value P′ in particular according to the characteristics of the objectto be picked up and moved. The vacuum switchis therefore able to automatically detect two different vacuum values to allow the gripping force of suction cupsto be managed, for example as a function of a thickness of the object or objects (sheets, plates, slabs . . . ) to be moved. For example the first threshold value Pmay be a lower vacuum value suitable for picking up and moving thin sheets (up to 0,8 mm), in particular without deforming them, and the further threshold value P′ may be a higher vacuum value suitable for picking up and moving sheets of thickness greater than 0,8-1 mm.

As illustrated in, the suction cup gripping systemof the invention comprises a supporting frameconfigured to support the plurality of gripping devices, in particular arranged spaced apart according to a plurality of parallel rows.

The operation of the gripping systemof the invention, in a procedure of gripping and moving for example a single objectprovided with an external surface, suitable to interact with the gripping suction cups, i.e. for example a flat and non-porous surface, provides an initial step of approach and positioning of the gripping devices, in which the suction cupsare positioned on the external surface. More precisely, the peripheral edgeof the central portionof each suction cupabuts the external surfaceof the object.

It should be noted that since the plurality of gripping devicesof the gripping systemdefines a gripping area, the gripping systemof the invention allows a plurality of distinct objects present inside the gripping area to be gripped and therefore moved.

In order to grip the objectthe first valveis arranged in the open position so as to supply compressed air coming from the supply lineto the Venturi vacuum generatorsthat suck air from the internal cavitiesof suction cupsof gripping devicesso creating a negative pressure, which allows the suction cupsto adhere strongly to the external surfaceof the object. In this way, each gripping devicegenerates a gripping force that is directly proportional to the pressure difference between ambient pressure and pressure inside the suction cup.

The overall gripping force exerted by all the gripping devicesacting simultaneously on the object, if greater than the weight force of the object, allows the gripping system. fixed to a suitable handling apparatus, to lift and move the object.

When the value of the negative pressure or partial vacuum inside the internal cavityof the suction cup, measured by the vacuum sensorconnected to the control unit, reaches and exceeds the first threshold value Pl (for example equal to −80 kPa) or the further first threshold value P′, such as to generate the required gripping force, the first valvecan be switched to the closed position by the control unit. In this way, the valvedoes not further supply the Venturi vacuum generatorswith unused compressed air that will be dispersed into the environment. The compressed air, after passing through the converging/diverging duct of each Venturi vacuum generator, in fact escapes into the external environment through the fifth connectionof the casing.

The internal cavitiesof the suction cupsof the gripping devicesare however kept in negative pressure thanks to the respective check valvesthat close the first ductsand prevent air from entering said internal cavities.