Device for gripping a container comprising a nose wherein expansion jaws are held circumferentially in position

A device (20) for gripping a container (16) made of a thermoplastic material, includes: a nose (30) having a main shaft (B) which is suitable for axially inserting into the neck (24) of the container (16); a plurality of jaws (46) which are mounted in the nose (30) in a radially mobile manner between a retracted position allowing the free axial sliding of the nose (30) in the neck (24) and an expanded position allowing the immobilization of the neck (24) in relation to the nose (30) by pressing against the inner part of the neck (24); and elements (54) for elastically returning the jaws to their expanded position, wherein the jaw assembly (46) is maintained circumferentially in a determined circumferential position in relation to the nose (30).

TECHNICAL FIELD OF THE INVENTION

The invention relates to a device for gripping a container made of thermoplastic material.

The invention relates more particularly to a device for gripping a container made of thermoplastic material, in particular a preform that is intended to be shaped into a final container, with the gripping device comprising:A head that has a main axis and that is suitable for being inserted axially into the neck of the container;At least three jaws (in the shape of an angular sector) that are distributed uniformly around the axis of the nose and that are mounted to move radially in the nose between a retracted position that makes possible the axial sliding of the nose in the neck and an expanded position that makes possible the gripping of the neck in relation to the nose by pressing against the inside wall of the neck;Elastic return means of the jaws toward their expanded position.

TECHNICAL BACKGROUND OF THE INVENTION

It is known to manufacture containers of thermoplastic material by forming preforms, for example by blow molding or by stretch blow molding.

The preforms are in general manufactured by injection molding. A preform has a body that is intended to be stretched to be shaped into the final container during the forming operation. The preform also has a neck that is injected into its final shape. It is therefore important to protect the neck throughout the process for transforming the preform into the final container.

To carry out the forming operation, it is necessary to heat in advance the bodies of the cold preforms at a glass transition temperature so as to make them malleable. The facilities for mass-producing containers for this purpose comprise furnaces for heating preforms.

A heating furnace in general has the shape of a tunnel in which at least one of the walls comprises heating means. The preforms move along the tunnel in front of the heating means while turning round and round so that their bodies are heated in a uniform manner to a temperature that is suitable for the forming operation.

For this purpose, the furnace comprises a device for transporting preforms that in general comes in the form of a closed chain, each link of which forms a movable support that is provided with an associated device for gripping a preform.

Each transporting device comprises an end mandrel that is formed by a head in which the jaws are mounted to slide radially, with the jaws being returned to an expanded position by an elastic ring that is inserted between the jaws and the nose. The nose that is equipped with jaws thus forms a radial expansion mandrel that is forced inside the neck of the preform.

The nose is engaged with the neck of the preform during an insertion operation that is sometimes called “covering.”

At the outlet of the furnace, the preforms are transferred to a forming station, by blow molding or by liquid injection, by means of a transfer wheel. During the passage of preforms from the furnace to the transfer wheel, the mandrels are extracted from the neck of the preforms so that the preforms are ejected from the transporting device during an ejection operation, sometimes called “uncovering.” The thus ejected preforms are received in suitable slots of the transfer wheel.

The machines for mass-producing containers should allow preforms to move at high speed into the furnace. This involves being able to carry out the operations for inserting preforms and the operations for ejecting preforms at a fast enough rate not to slow down the movement of the preforms into the furnace.

In the known gripping devices, the jaws are free to move circumferentially in relation to the nose. The jaw assembly is thus free to rotate around the main axis of the nose.

Circumferential operational play is in general provided between two adjacent jaws for making possible a free individual movement of each jaw. This makes it possible in particular to ensure that the insertion operation takes place under the best conditions.

Nevertheless, it happens that all of the jaws wind up crammed together circumferentially on one side of the nose. Thus, a single circumferential operational play is expanded while the other circumferential operational plays are reduced to zero. The result is that the jaws lose certain degrees of freedom of movement, thus creating the danger that the nose will be prevented from being correctly inserted into the neck of the preform.

In addition, the single existing circumferential play accumulates the operational plays that are normally provided. The ring made of elastomer material then runs the risk of forming a hernia in the single circumferential play, locking the jaws in their crammed-together position. In addition, in this configuration, the elastic ring is no longer able to become deformed enough to allow a return of the jaws toward a retracted position. This therefore runs the risk of compromising the ejection operation.

BRIEF SUMMARY OF THE INVENTION

The invention proposes an improved gripping device of the type described above, characterized in that the jaw assembly is held circumferentially in a circumferential position that is determined in relation to the nose by individual circumferential immobilization means of at least one jaw.

According to other characteristics of the invention:Keeping the jaw assembly in the circumferential position is done by individually immobilizing each jaw circumferentially in relation to the nose by means of a guide pin that is stationary in relation to one of the elements between said jaw and the nose, with the guide pin being accommodated by sliding into a groove that is stationary in relation to the other one of the elements between said jaw and the nose;The groove and the guide pin are positioned in an axial plane oriented along the radial axis of displacement of said jaw;The guide pin is stationary in relation to the nose, while the groove is stationary in relation to said jaw;The guide pin has a main axis that is parallel to the axis of the nose;The guide pin has a shape that is suitable for allowing angular travel of the jaw in relation to the nose around an axis that is parallel to the axis of the nose;The elastic return means are formed by a ring made of elastomer material that is inserted radially between the nose and the jaws;The gripping device comprises at least one axial pin for ejecting the container that is mounted to slide axially in relation to the nose between an upper rest position in which a free end of the pin is arranged axially above the jaws, and a lower ejection position in which the free end of the ejection pin is arranged axially below the jaws;During its sliding, each ejection pin is able to come into contact with an imaginary cylinder circumscribing the jaws in the expanded position, one passage being provided in the jaws at the intersection between the circumscribed imaginary cylinder and each ejection pin for making it possible for each pin to slide toward its ejection position without colliding with the jaws;The jaws comprise at least one flat surface forming the passage of the associated pin;The gripping device comprises a shoulder face in relation to the nose that is intended to abut against a rim of the neck when the nose is inserted into the neck, with the ejection pin passing through the shoulder face for the benefit of an opening that segments the annular stop surface intended to be effectively in contact with the rim;The gripping device comprises a radiator that is arranged above the nose and that extends in radial projection in relation to the nose;The radiator is immobilized in rotation by a head that forms the upper end of at least one of the guide pins.

The invention also relates to a device for transporting a preform into a furnace for heating a facility for forming containers of thermoplastic material, with the preform being obtained by injection molding and comprising, at an upper axial end of its body, a tubular neck that is injected directly into its final shape, characterized in that the preform is held on the transporting device by a gripping device produced according to the teachings of the invention.

DETAILED DESCRIPTION OF THE FIGURES

In the description below, elements having an identical structure or analogous functions will be designated by the same references.

In the description below and in the claims, the following will be adopted in a nonlimiting manner:An axial orientation that is parallel to the main axis “B” of the nose30of the gripping device20, which is directed from bottom to top and which is indicated by the arrow “A” of the figures;Radial orientations that are orthogonal to the main axis “B” of the gripping device20and directed from the inside to the outside by moving away from said main axis “B.”

Shown diagrammatically inFIG. 1is a facility10for forming final containers such as bottles made of thermoplastic material. Such a facility10comprises a furnace12for heating and a station14for forming, for example by blow molding or stretch blow molding.

Initial containers, which are preforms16here, are intended to move into the furnace12for conditioning before being transferred one after the other to the forming station14. The movement of the preforms16into the furnace12is carried out by means of a transporting device18comprising a conveying chain forming a closed loop.

The conveying chain is formed by the articulation of links (not shown). Each link comprises at least one device20for gripping a preform16. The transporting device18comprises numerous gripping devices20. With all of the gripping devices20being essentially identical, a single one of these gripping devices20will be described below.

As shown in part inFIG. 2, a preform16is made of a thermoplastic material, such as PET, by injection molding. The preform16comprises a tubular body22that is open upward by means of a neck24. The neck24has a tubular shape with axially oriented axis “B.” The neck24is delimited downward by a collar26and upward by an upper end edge called “rim28.” The neck24is injected into its final shape, while the body22is intended to be deformed by stretch blow molding during a subsequent forming stage.

The gripping device20makes it possible to pick up a preform16by its neck24.

The gripping device20shown inFIGS. 2 and 3comprises a lower end nose30that has an overall cylindrical shape with axially oriented main axis “B.” As shown inFIG. 3, the nose30is suitable for being inserted axially into the neck24of the container16. The nose30thus has a diameter that is slightly smaller than the inside diameter of the neck24of the preform16so as to make possible the axial sliding with radial play of the nose30in relation to the neck24.

As shown inFIG. 4, the nose30is made of a lower element32and an upper element34that are attached to one another.

The two elements32,34of the nose30axially delimit a peripheral annular housing36radially emptying toward the outside.

The upper element34is extended axially upward by a shaft38of axis “B” that is intended to be connected to an element (not shown) that controls the axial sliding of the gripping device20in relation to the conveying chain. The shaft38has a diameter that is smaller than that of the nose30.

The upper element34also comprises a cylindrical intermediate segment40with a diameter that is larger than that of the nose30that is inserted between the nose30and the shaft38. The intermediate segment40acts as a delimiter downward by a shoulder face42in relation to the nose30. The intermediate segment40also comprises an upper face44.

The shoulder face42is intended to abut against the rim28of the neck24when the nose30is inserted into the neck24. The shoulder face42thus comprises an annular support surface that is formed only by the surface that is intended to come effectively into contact with the rim28.

The gripping device20also comprises a number of jaws46that are enclosed in the housing36of the nose30. The jaws46are uniformly distributed around the axis “B” of the nose30. The jaws46are three in number here.

The jaws46are all identical. Each jaw46has the shape of a ring segment with a diameter that is slightly larger than that of the inside wall of the neck24. Each jaw46extends over an angular sector that is slightly smaller than 120° so that there is a circumferential operational play “j” between two adjacent jaws46when they are all housed in the nose30, as shown inFIG. 5.

Thus, only the circumferential operational play “j” that is left free separates the circumferential end of each jaw46circumferentially from the end that is circumferentially opposite each adjacent jaw46. “Left free” means that no obstacle is inserted circumferentially between two adjacent jaws46.

Each jaw46has an outside support face48that is overall in the shape of a cylindrical sector that is intended to be arranged radially opposite the inside wall of the neck24. In top view, as shown inFIG. 5, the outside faces48of the jaws46are circumscribed by a common imaginary cylinder49that is centered on the axis “B” and that is indicated in dotted lines inFIG. 5.

Each jaw46is mounted to move radially in the nose30between:A retracted position in which the support face48of the jaw46is retracted radially toward the inside for making possible the free axial sliding of the nose30in the neck24; andAn expanded position in which the support face48is moved radially toward the outside in radial projection in relation to the nose30for making possible the gripping of the neck24in relation to the nose30by pressing the support face48against the inside cylindrical wall of the neck24.

Each jaw46is held prisoner in the nose30by means of lower or upper axial flanges50, which are intended to abut radially against an axial skirt52associated with the lower element32, or the upper element34. This makes it possible to keep the jaws46prisoner in the nose30. Each axial skirt52delimits here toward the outside an annular groove that is formed respectively in the upper face of the lower element32and in the lower face of the upper element34.

The nose30also comprises elastic return means of the jaws46toward their expanded position. In the example shown in the figures, the elastic return means are formed by a ring54made of elastomer material that is inserted radially between the bottom of the housing36of the nose30and the jaws46.

The nose30is thus intended to be “forced” into the neck24. For this purpose, each jaw46has a draft angle that makes it possible to control automatically the sliding of the jaws46toward their retracted position during the axial insertion into the neck24by contact of the jaws46with the rim28.

The housing36of the nose30has a shape that allows each jaw46limited travel by pivoting around an axial axis and around a circumferential axis. These degrees of freedom make it possible to keep the jaws46from jamming into the nose30during the forcible insertion of the nose30into the neck24of the preform16.

The jaw assembly46is held circumferentially in a circumferential position that is determined in relation to the nose30. Thus, the jaws46cannot rotate around the axis “B” of the nose30. The jaws46are held in their circumferential position that is determined regardless of their radial position between the retracted position and the expanded position.

For this purpose, each jaw46is immobilized individually in a circumferential direction in relation to the nose30. Each jaw46is immobilized here by means of a single associated guide pin56that is stationary in relation to one of the elements between said jaw46and the nose30, with the guide pin56being accommodated by radial sliding into a groove58that is stationary in relation to the other one of the elements between said jaw46and the nose30.

As is shown inFIGS. 4 and 5, in this example, the guide pin56is stationary in relation to the nose30, while the groove58is stationary in relation to said jaw46.

Each guide pin56has an axially oriented main axis here. Each pin is accommodated in an opening59that passes through the intermediate segment40of the upper element34of the nose30, on a level with the upper flange50of the associated jaw46.

The groove58is formed by a slot that is made in the upper flange50of the associated jaw46. Thus, when the guide pin56is inserted into its opening59, its end is engaged in the groove58of the associated jaw46.

As shown inFIG. 5, for each jaw46, the groove58and the guide pin56are positioned in an axial plane “P,” i.e., a plane that contains the main axis “B” of the nose30, with the plane “P” being oriented along the radial axis of displacement of said jaw46. In the configuration shown in the figures, the groove58is thus arranged in the center of the jaw46in the circumferential direction, and it is oriented radially. This makes it possible to preserve the angular travel of the associated jaw46in relation to the nose30around an axis that is parallel to the axis “B” of the nose30.

In addition, the guide pin56has a suitable shape for making possible said angular travel. The guide pin56has, for example, a circular cross-section. Thus, the mechanical link created between the jaw46and the nose30is not, strictly speaking, a slide link because of this possibility of angular travel.

As shown inFIGS. 2 to 4, the gripping device20comprises a ribbed radiator60that has an overall cylindrical shape of main axis “B.” The radiator60is pierced axially by a central opening62.

The shaft38is shrunk-on in the central opening62of the radiator60so that a lower face of the radiator60is resting flat against the upper face44of the upper element34of the nose30. The radiator60is thus arranged above the nose30.

The radiator60has an outside diameter that is larger than that of the intermediate segment40so as to extend in radial projection in relation to the nose30.

The radiator60is immobilized in rotation around the axis “B” by an upper end head64of at least one guide pin56, as is illustrated inFIG. 3. For this purpose, the radiator60has a suitable counterbore66for housing the head64.

The head64has a diameter that is larger than that of the passage opening59of the guide pin56. Thus, the head64is able to abut against the upper face44of the upper element34for positioning axially the guide pin56in relation to the nose30. In particular, this keeps the pin from entering into contact with the associated jaw46.

Only one guide pin56comprises a projecting head64, with the other pins56being fixed axially in their respective opening59either by forcible insertion or by a non-projecting head (not shown) in relation to the upper face44of the intermediate segment40.

As a variant of the invention, not shown, the three guide pins comprise a projecting head.

The gripping device20comprises means for ejecting the preform16when the nose30is held in the neck24by the jaws46.

The ejection means comprise at least one axial ejection pin68. Here, the ejection means comprise three identical ejection pins68that are distributed angularly around the main axis “B” of the nose30. One free lower end70of each pin68is arranged axially on a level with the rim28of the neck24.

As shown inFIG. 5, each pin68is arranged radially here opposite an associated circumferential play reserved between two adjacent jaws46.

The pins68are mounted integrally to slide axially in relation to the nose30between:An upper rest position, as illustrated inFIG. 2, in which the free lower end70of each pin68is arranged axially above the nose30; andA lower ejection position, as illustrated inFIG. 6, in which the free end70of the ejection pin is arranged axially below the nose30.

Each ejection pin68impinges upon, or at the very least is tangent to, the straight cylinder49of imaginary revolution circumscribing the jaws46in the expanded position, with the imaginary cylinder49being centered on the axis “B.” To keep the free end70of the pins68from abutting against a jaw46in the expanded position, a passage72is provided in the jaws46at the intersection between the circumscribed cylinder49and each ejection pin68for making it possible for each pin68to slide toward its ejection position. The passage72is carried out in such a way as to reserve an adequate radial play between the pins68and the jaws46to ensure that no collision will have taken place between these two elements even in the expanded position of the jaws46.

In the example shown in the figures, the jaws46comprise at least one flat surface that forms the passage72of the associated pin68. In the configuration that is shown in the figures, the passage72that is associated with a pin68is formed by a flat surface that is provided astride two adjacent jaws46.

As shown inFIG. 7, the intermediate segment40and the radiator60also comprise axial passages each making it possible to house one of the pins68.

Each passage empties downward in the shoulder face42in relation to the nose30, for the benefit of an associated opening74.

The free end70of each pin68is intended to stress the rim28of the neck24to eject the preform in relation to the jaws46. To ensure a good support of pins68on the rim28, each pin rests on the total thickness of an angular sector of the rim28. Thus, the annular support surface of the shoulder face42is segmented by the passage openings74of the pins68. The result is that when the pins68come into contact with the rim28during an ejection operation, certain so-called angular support sectors of the rim28rest only on the shoulder face42, while the other so-called angular ejection sectors of the rim28are in contact only with an associated pin68, with the support sectors being arranged to alternate circumferentially with the ejection sectors.

During the mounting of the gripping device20, with reference toFIG. 4, the jaws46and the ring54that are elastic are first enclosed between the two lower and upper elements32,34for forming the nose30. The passages72of the jaws are axially arranged lined up with the passage openings74of the shoulder face42.

Then, the guide pins56are inserted axially downward into their associated openings59in such a way as to immobilize the jaws46in their circumferential position that is determined in relation to the nose30. The passages72of the jaws46thus remain constantly lined up with the passage openings74of the upper element34of the nose30.

Next, the radiator60is threaded onto the shaft38in such a way that the heads64of the projecting guide pins56are accommodated in the counterbores66of the radiator. This makes it possible to immobilize the radiator60angularly in relation to the nose30so that the passages of pins68of the radiator60remain lined up with the passage openings74of the shoulder face42of the intermediate segment40.

The guide pins56thus simultaneously make it possible to index the radiator60and the jaws46angularly in relation to the nose30.

Finally, each ejection pin68is arranged in its respective passage. It will be possible to plan to insert a pad circumferentially from each side between the radiator60and the pin68to prevent the pins68from being offset in relation to their passage. The pads are advantageously produced from a material making it possible to promote the sliding of ejection pins68.

During an operation for ejecting the preform46, the pins68initially occupy their upper rest position as shown inFIGS. 2 and 3. The nose30is already inserted into the neck24of the preform16in such a way that the rim28is resting against the shoulder face42, and the jaws46are forced radially against the inside cylindrical wall of the neck24to hold the preform16.

Then, the pins68are slid axially toward their lower ejection position until they rest against the rim28of the preform16. The pins28continue their sliding downward, stressing the rim28thus to bring about the sliding of the preform16in relation to the nose30, until the pins68reach their lower ejection position, as indicated inFIG. 6. The nose30has then totally left the neck24, and the preform30is ejected from the gripping device20.

The gripping device20that is produced according to the teachings of the invention makes it possible to prevent the jaws46from clustering on just one side of the nose30. This makes it possible in particular to keep the jaws46from jamming during the insertion into a neck24.

In addition, the circumferential immobilization of the jaws46in a determined circumferential position makes it possible to create passages72for the ejection pins68in the jaws46without these passages72being offset circumferentially in relation to the pins68. Thus, the pins68can be arranged radially close to the nose30in such a way as to rest on the entire radial thickness of the rim28. This is in particular very advantageous when the thickness of the rim28is very small.