Patent Application
20060033350
The invention relates to a load-lifting device for handling items, in particular cartons and loads with irregular contours or nonplanar gripping faces, comprising two spaced-apart, mutually opposite gripper arms which are equipped on the mutually facing sides with flexibly inflatable gas chambers which can be filled and emptied and between which the item is held when the gas chambers are in the inflated state.
The handling of cartons, in particular cartons of poor quality, and loads which are unsuitably shaped for handling purposes, for example cylindrical loads, and also of cartons and loads of significantly different sizes is problematic using known load-lifting devices. The various load-lifting devices currently used are saddled with disadvantages, as illustrated below.
Jaw grippers grip cartons in a force-fitting manner; this means that reliable handling is not always guaranteed in the event of poor carton quality. The handling of cartons with significantly different dimensions (for example Δ 200 mm) is not generally possible with jaw grippers, and if it is possible for the gripper jaws to be moved far enough apart, the gripping times are increased considerably by the time required to adjust the gripper jaws. The handling of noncuboidal shapes (for example cylindrical loads) is only possible by placing them on shelves which are suitable for handling. These shelves are employed as loading aids if it is not possible for cartons of different base areas to be stored on angle rests.
Suction jaw grippers do, however, reliably grip even cartons of poor quality although, here again, the handling of cartons with significantly different dimensions (Δ 200 mm) is not possible or is only possible when the gripping times are considerably increased. The rotary movement to be performed by the suction jaw gripper at the storage/retrieval point for load delivery and load pick-up as well as rearrangement within the rack reduce the storage capacity. It is not intended for objects other than cartons to be handled when using suction grippers.
Telescopic grippers, by virtue of gripping in a form-fitting manner, also reliably grip cartons of poor quality although, given that the gripper is required to move over the entire length of the carton, very high cycle times occur here. For this reason, telescopic grippers are used only rarely.
Load-lifting devices for gripping and displacing cartons have also been disclosed which, operating on the principle of a pneumatic vise, clamp and hold the particular item on both sides between flexible clamping membranes arranged on two gripper arms. The clamping membranes are each part of a gas chamber which can be filled with and emptied of compressed air via control lines, with the two gas chambers expanding during filling and pressing against the lateral faces of the item and thereby clamping the load to be held (DE 36 24 000 A1). Although the device described is suitable for clamping, and thus also for handling, certain articles, it presupposes that the item has substantially planar lateral walls with only very slightly differing spacings between the items, since the membrane is designed in such a way as to permit only very small clamping travels.
An object of the present invention is, starting from the prior art described, to improve the known load-lifting device, which is equipped with two spaced-apart, mutually opposite gripper arms which are provided on the mutually facing sides with flexibly inflatable gas chambers which can be filled and emptied, in such a way that it is also possible to rapidly, reliably and securely grip items, in particular cartons and loads with irregular contours or nonplanar gripping faces, including those with significantly different dimensions.
The object is achieved by proposing a load-lifting device which is characterized in that the gas chambers are designed as collapsible cushions or bellows whose inflated thickness, measured in the direction of action, corresponds in each case to a multiple of the thickness of the bellows or cushions in the deflated state.
The use of cushions or bellows, which produce the force-fitting connection with respect to the item, ensures a secure grip even when the items have irregular contours or nonplanar gripping faces. This is possible on account of the thickness of the bellows or cushions, which have the ability to “follow” the surface of the object to be gripped. This is advantageous in the case of poor carton qualities and noncuboidal shapes.
It is advantageous according to the invention if the thickness of the bellows or cushions in the inflated state corresponds to at least twice to three times the thickness of the bellows or cushions in the deflated state. The invention also makes it possible, by suitable selection of the pneumatic cushions or bellows, to handle objects with significantly different dimensions.
In a preferred embodiment of the invention, it is provided that, in order to grip the item, the deflated bellows or cushions can be moved substantially horizontally on both sides of and alongside the item and can be filled in the gripping position. However, that does not rule out using the invention in handling equipment which grips from above.
If, according to another embodiment of the invention, the gripper arms can be adjusted with respect to the item in a position in which mutually opposite bellows or cushions engage at least partially around the edges of the item, it is possible using this measure to reliably prevent possible rotary movements of the load caused by slippage between the cushion or bellows and the lateral face of the load. The same result can be achieved if, according to yet another embodiment of the invention, each gripper arm is equipped with more than one bellows or cushion.
In order to be able to manage the weight of the item to be handled without problems and to minimize deformations of the cushions or bellows transversely with respect to the gripping direction, provision is additionally made to provide the bellows or cushions with transversely stabilizing reinforcements and/or stiffeners.
The pressure medium provided for filling the bellows or cushions may be compressed air, although other suitable gases are also conceivable.
Varying the amount of gas blown into the cushions/bellows allows the “approach” of the gripping device to be controlled. Since the filling time is not critically influenced thereby, it is possible to handle objects with significantly different dimensions while maintaining short gripping times.
The pressure for filling the bellows or cushions with compressed air and/or gas can be adjusted. As a result, the retaining forces can be variably adapted to the item to be handled.
In one embodiment of the invention the load-lifting device is designed for picking up items from and delivering them to a rack, where the load-lifting device may be arranged on a storage/retrieval machine.
A number of advantages result from using the load-lifting device according to the invention. For instance, the cushions or bellows produce a force-fitting connection with respect to the load and this ensures a secure grip because the gripping surface is capable of “following” the surface of the object to be gripped. This is beneficial in the case of poor carton qualities and noncuboidal shapes. The handling of objects with significantly different dimensions also becomes possible by suitable selection of the pneumatic cushions or bellows, since, by varying the amount of gas filled into the cushions or bellows, the “approach” of the gripping device can be controlled without moving the gripper arms together. Since the filling time is not critically influenced thereby, it is possible to handle objects with significantly different dimensions while maintaining short gripping times. In many cases it is possible to dispense with symmetrical positioning of the loads at the storage point, since the gripper according to the invention compensates for any central deviation through a “reliable” grip. Since unfavorably shaped items can also be stored on shelves, the invention allows better volume filling of the warehouse and makes handling easier.
Exemplary embodiments of the invention are represented in the drawings and are described below.
now expanded, specifically from a collapsed thickness a (
Another advantage of the load-lifting device according to the invention is illustrated in
As illustrated in
The bellows may consist of a material which is dimensionally rigid in the transverse direction, i.e. transversely with respect to the retaining force, which material can additionally be provided with stiffeners or reinforcements 8.
Changes and modifications in the specially described embodiments can be carried out without departing from the principles of the present invention, which is intended to be limited only by the scope of the appended claims, as interpreted according to the principles of patent law including the doctrine of equivalents.
| Number | Date | Country | Kind |
|---|---|---|---|
| 102004039661.2 | Aug 2004 | DE | national |
