Conveyors: power-driven – Conveyor for changing attitude of item relative to conveyed... – By actuating item-holder relative to holder-carrying conveyor
Reexamination Certificate
2000-04-28
2001-11-06
Valenza, Joseph E. (Department: 3651)
Conveyors: power-driven
Conveyor for changing attitude of item relative to conveyed...
By actuating item-holder relative to holder-carrying conveyor
C198S374000, C198S370120
Reexamination Certificate
active
06311824
ABSTRACT:
The invention relates to a rotatable gripper device for picking up and rotating a product which is supplied on a conveyor belt, comprising a gripper head with a gripping member which can rotate about a vertical central shaft and about an axis of the gripper head, and a cam wheel which is connected to the gripping member and runs over a running surface of a cam disc which is located transversely on the central shaft, when the gripper head rotates about the central shaft, the position of which running surface varies along the central shaft in a circumferential direction around the central shaft, for the purpose of displacing the gripper head between a lowered gripping position and a retracted conveying position.
Rotatable gripper devices for picking up a series of products supplied by means of vacuum, in order to change the direction in which these products are conveyed before they are fed to a packaging device, such as a flow wrap packer, are known per se. EP-A-0,895,951 has disclosed a station for turning absorbent products, in which the gripper heads are rotated along an epicyclic path about a central shaft. The products which are oriented in the longitudinal direction of the product on a conveyor belt are lifted up by a gripper head, rotated and released in the transverse direction of the product to a downstream conveyor belt. Rotation of the gripper head about the central shaft and about its axis is effected by means of a relatively complex planetary gear system, while the lifting movement of the gripper head is driven by two levers which are under spring stress and engage on a sliding bush of the gripper head. The top lever of the known gripper device is provided, at a first end, with a cam roller which rolls along a cam track, the running surface of which, as seen in the circumferential direction, varies in height along the central shaft. Via a vertical transmission arm and a connected second lever, the sliding bush of the gripper head is displaced upwards, counter to the stress of a coil spring which is positioned around the sliding bush, into a conveying position. When the cam roller rolls further along the cam track, the gripper head returns to its lowered gripping position under the influence of the spring pressure.
The known turning station has the drawback that the drive mechanism for rotating the gripper head about the central shaft and for the upward and downward displacement of the gripper head is relatively complex. Furthermore, the large number of components employed means that the mass of the known device is relatively great, with the result that at high speeds problems associated with the inertia forces generated may arise. Also, the rotation of the gripper head about its axis is linked to and dependent on the movement of the gripper head around the central shaft, so that the movement of the gripper head in the area where a product is picked up and put down is difficult to adjust. Therefore, one object of the invention is to provide a gripper device which is of relatively simple design. Another object of the invention is to provide a gripper device in which the rotating mass is minimized and which can be used to produce a large number of product orientations. Another object of the invention is to provide a gripper device which can be used to rotate products with a small displacement of the gripper. A further object of the present invention is to provide a gripper device which can be deployed at a large number of positions and in which at-rest positions for picking up and putting down products can be set.
To this end, a gripper device according to the invention is characterized in that the gripper head comprises a support bush in which a sliding bush, to which the cam wheel is attached, is slidably mounted, the support bush being provided with an opening through which the cam wheel projects in the radial direction to outside the support bush, a suspension member being accommodated rotatably inside the sliding bush, with the gripping member at a bottom end, to which suspension member a second cam wheel is connected, and the gripper device being provided with a second cam disc, which lies transversely with respect to the central shaft and has a running surface, against which the second cam wheel is supported, and the distance of which from the central shaft varies in a circumferential direction about the central shaft, for rotation of the gripping member about the axis in the event of rotation of the gripping member about the central shaft.
Since the vertical displacement of the ripper head and its rotation about the axis are controlled by separate cam discs, a simple and lightweight structure is obtained. Since movements of the gripper head about the central shaft are to a large extent independent of rotation of the gripper head about the axis, the upward and downward and the rotational movements of the gripper head can be adjusted separately by adapting the shape of the cam discs. By adjusting the shape of the second cam disc, it is possible to slow down the rotational speed of the gripper head when it picks up and puts down the product, so that gradual transfers without jolting and risks of the product shifting or becoming detached are obtained. Orientation of the gripping member by means of the second cam disc allows a product to be turned within a relatively small displacement path of the gripper head. Furthermore, the gripper heads can easily be removed for maintenance and/or replacement, and the second cam discs for rotating the gripping, member are easy to exchange in order to obtain different product orientations.
In one embodiment of a gripper device according to the invention, the suspension member is connected to a spring element for exerting a rotational restoring force around the axis. As a result of the second cam wheel rolling along the running surface of the second cam disc, the gripping member can be rotated 90° about its axis counter to the force of the torsion spring. As a result of the spring force, the second cam wheel bears closely against the running surface of the second cam disc, and the gripper head is quickly and accurately restored to its starting position. The torsion spring provides a simple and compact drive for the gripping member about the axis of the gripper head.
In a further embodiment of a gripper device according to the present invention, the first cam disc comprises two separate running surfaces, between which the cam rollers for a downward and upward displacement, respectively, of the gripper head are accommodated. By allowing the vertical displacement of the gripper head to take place via the running surfaces of the first cam disc, it is possible for the cam rollers to be accommodated in a tight-fitting manner without the load which they exert increasing excessively, as is the case if the cam roller for the vertical displacement is pressed against the cam disc under spring load.
In a further embodiment of a gripper device according to the invention, a plurality of gripper heads are attached to a support which can rotate about the central shaft, which support is suspended from a vertical arm which is supported on a base. The gripper device can be placed above any desired conveyor belt. Also, the gripper device can easily be displaced with respect to the conveyor belt, for example in order to replace the cam disc.
The gripper heads can be activated in succession by means of a vacuum port, so that different turning patterns are obtained.
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patent: 5921375 (1999-07-01), van Laar
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patent: 2551538A1 (1977-05-01), None
patent: 19605265A1 (1996-08-01), None
Klockner Hansel Tevopharm B.V.
Valenza Joseph E.
Young & Thompson
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