GB1568433A

GB1568433A - Gripper device

Info

Publication number: GB1568433A
Application number: GB5019177A
Authority: GB
Original assignee: Maschinen und Stahlbau Julius Lippert GmbH and Co KG
Current assignee: Maschinen und Stahlbau Julius Lippert GmbH and Co KG
Priority date: 1976-12-01
Filing date: 1977-12-01
Publication date: 1980-05-29
Also published as: DE2654445B1; IT1114169B; DE2654445C2

Description

(54) GRIPPER DEVICE (71) We, MASCHINEN-UND STAHLBAU JULIUS LIPPERT GMBH & CO. a Germany Body Corporate of Bottgerstrasse 46, D-8481 Pressath, West Germany do hereby declare the invention for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: The invention relates to a gripper device for gripping the top one of a number of stacked saggers for ceramic products.

In a known gripper device described in East German Patent Specification 113,730, a stop member is provided essentially for the purpose of converting the movement of placing the gripper device onto the top sagger of a stack into the actual gripping movement, the gripper members being laid against the outside of the saggers as the result of further vertical displacement by deflection over rollers and corresponding levers. That known device takes no account of the fact that saggers very frequently are stuck to the adjacent sagger when they emerge from the baking oven. Consequently, when the known gripper device which merely ensures a secure gripping of the top sagger, is used, there is a considerable risk of the next sagger or even several saggers also being taken along when lifting or gripping the particular top sagger.Difficulties then arise on emptying the particular saggers since, if appropriate, the adhering saggers must first be released manually. Moreover, the adhering of the saggers also involves the risk that the sticking sagger which is not held by the gripper device, will suddenly become detached, after a certain lifting distance, and drop down so that, on the one hand, the course of operation can be disturbed and, on the other hand, there is of course the danger that the sagger which drops down, or its contents, will be broken. Thus, using the above known gripper device, work which is free from disturbance can hardly be expected and, in particular, no rapid satisfactory work can be expected.

Furthermore, it is already known from German Patent Specification 2,039,640 to lift saggers off a stack by means of a suction device, after the particular top sagger of a stack has been detached beforehand by lateral displacement relative to the sagger below by means of a special device. Understandably, the problems discussed above no longer arise in this case.

However, on the one hand, this known device is relatively expensive due to the constructional components required due to the use of a suction device, and particularly due to the presence of a special installation, comprising several levers and an actuating cylinder, for detaching the particular top sagger. Moreover, a relatively large force is required for the lateral displacement of the top sagger, which displacement is effected in the known device by means of rolls which press against the sagger from the outside. In the case of unfavourable conditions and a strongly adhering sagger, it is also possible that the top sagger or even the sagger below will be destroyed by this action of force.

According to the present invention there is provided a gripper device for gripping the top one of a stack of saggers for ceramic products, the device comprising at least three gripper members which are distributed around a central axis and are movable radially of said axis so as to engage a sagger with a gripper surface thereof and a stop member having a seating surface to engage an upper surface of a sagger to be gripped, wherein the gripper members are provided with separator elements each having a sharp edge protruding beyond the gripping surface of the associated gripper member for reaching, during gripping, under the bottom surface of a sagger to be gripped and the stop member is so arranged that axial distance between the sharp edges of the separator elements and the seating surface of the stop member is invariant when gripping a sagger and is at other times adjustable so as to be set to be equal to the height of a sagger to be gripped.

Thus, the separator elements can engage in the gap between adjacent saggers and in this way reliably ensure that, during the gripping process, the sagger to be held is detached from the particular sagger below. In order to accommodate saggers of different heights, the stop member should be adjustable relative to the separator elements but arranged so as not to move during a gripping cycle. Embodiments of device according to the invention can have an extremely simple construction while working very reliably since the separator elements can always engage at the correct point and in conjunction with the gripping members. A further advantage is that the separation process can take place virtually simultaneously with the gripping process.

In an embodiment of the gripper device, which has proved particularly advantageous, the gripper members are formed by gripper rolls which are provided with elastic casings and carry, on their lower portions, sharp-edged rolls as the separator elements, it being advantageous if the sharp-edged rolls can rotate independently of the gripper rolls. In this case, the sharp-edged rolls appropriately have cylindrical cores with diameters smaller than the gripper rolls, the sharp-edges of the separators having diameters larger than the gripper rolls and protruding radially from the circumferential surface of the core. The roll-like design of gripper members and separator elements has a large number of advantages. On the one hand, these elements have only a relatively small surface area of contact with the saggers.On the other hand, a circular sharp edge penetrates more easily into the gap between adjacent saggers, even if the latter were adhering to one another, without there being an excessive risk of damage.

When gripper rolls and sharp-edged rolls are used, it can be very advantageous if the gripper rolls carrying the sharp-edged rolls are each mounted on the free end of a pivoted lever which is pivotable in a plane parallel to the upper surfaces of the saggers because, in this case, the sharp-edged elements are not merely pressed in radially between adjacent saggers during the separation process. but are inserted gradually rolling thereon, so that a particularly gentle treatment of the saggers is attainable.

Advantageously, the actuation of the pivoted levers is effected in such a way that these are mounted on the free ends of stationary radial arms and are conjointly pivotable via a lever system by means of a single servo-motor, the lever system advantageously possessing a lever star which is rotatable about the axis, bearing the radial arms, of the gripper device and has a number, corresponding to the number of pivoted levers, of lever arms, the free ends of which are each connected by means of a connecting lever to the corresponding pivoted lever, and that at least one of the pivoted levers is movable by the servo-motor so as to lay the gripper rolls against the circumferential surface of the sagger.

The length of the connecting levers can be variable in order to make extensive adjustment to differing sagger diameters possible and, in addition, to keep the required paths of movement as small as possible, if necessary. The servo-motor used is appropriately a hydraulic or pneumatic cylinder which acts on two adjacent pivoted levers between their bearing axis and the free end carrying the gripper rolls.

The stop member suitably is formed by three radially extending support arms which are mounted to be centrally and vertically displaceable in common relative to the gripper members and which have horizontally extending outer end parts which extend outwards over the largest diameter of saggers to be gripped and extend inwards over the smallest diameter of saggers to be gripped. Such a stop member is very simple constructionally and, equally, can remain in the device for all the saggers normally to be gripped.

For the purpose of reliably eliminating damage to the saggers when the stop member seat thereon and, at the same time, also enabling slight tolerances (if the height of the saggers differs somewhat) to be compensated it is provided that the horizontally extending end parts of the stop member can carry a padding on the underside.

To eliminate unnecessary stresses on the saggers when they are gripped, the stop member can be mounted in such a way that it cannot rotate relative to a common carrier for the stop member and the gripper members with the separator elements, in which case additionally the saggers are also secured in this way against rotation on gripping. Securing against rotation is achieved in a simple manner if at least one of the support arms of the stop member carries on its top a bolt which is guided so that it can move vertically in a guide bore of one of the radial arms.

The vertical adjustability of the stop member to adapt it to differing sagger heights. rapid and simple operations being desired, can be achieved in a simple manner if, for vertically adjustable mounting of the stop member, a central bearing bush is used which is provided with an internal thread, can rotate relative to the stop member, can be screwed onto a vertical threaded journal of the carrier and the lower end of which carries an external thread onto which a nut can be screwed which lays the stop member against a collar on top of the bearing bush.

To simplify the adjustment of the device during gripping, the carrier for the gripper members with the separator elements and for the stop member can be mounted so that it can be adjusted vertically but cannot rotate.

Finally, embodiments of the invention can also have three gripper members with separator elements, which gripper members are evenly distributed over the sagger periphery, since in this case the sagger is reliably held evenly by its circumferential surface even if it slightly deviates from the circular shape.

The invention will be further described with reference to the accompanying drawings, in which: Figure 1 shows a vertical axial section through one embodiment of gripper device according to this invention, Figure 2 shows a plan view onto the gripper device in section along line II-II in Figure 1, and Figure 3 shows, in an enlarged representation, a gripper member with the associated separator element.

As can be clearly seen from the axial section of Figure 1, the gripper device is fixed to a carrier arm 2 in a vertically adjustable manner. The carrier arm 2 can, for example, be part of a device for the automatic charging and discharging of saggers. To mount the gripper device 1 on the carrier arm 2, a ballbearing 3 is used which permits relative axial displacement but prevents relative rotation of the mounted parts. For this purpose, grooves 4 which contain the balls 5 are provided on the central bolt 6 and in the sleeve 7. The downward movement of the central bolt 6 is limited by a cap 9 which is fixed thereto by means of the nut 8 and which rests on the top of the carrier arm 2. as can be seen from Figure 1. Bellows 10 are provided to protect the bearing 3 against contamination.

The central bolt 6 serves as the carrier for the entire gripper device. For this purpose, an end part 11 (Figure 1) is provided to which radial arms 12, each offset by 1200, are rigidly joined, for example welded. Each of the radial arms 12 is provided with a bearing bush 13 at its end. To fix the end part 11 in its position, a holder part 14 is used, the upper end of which is screwed onto a threaded extension 15 of the central bolt 6 and which carries an external thread 16 at its lower end.

A bearing bush 17 for the stop member 18 is screwed onto the external thread 16 of the holder part 14. Unscrewing of the bearing bush 17 is prevented by the locking plate 19 which protrudes beyond the diameter of the external thread 16.

In the illustrative embodiment shown, the stop member 18 consists of three support arms 20 which are each located below the radial arms 12, that is to say they are likewise offset by an angle of about 1200, and which are fixed, for example, welded, to a common carrier ring 21. This carrier ring 21 is seated on the bearing bush 17, as can be seen from Figure 1, and its upper rim is pressed by the nut 23 against a shoulder 22. The nut 23 is fixed in position on an external thread of the bearing bush 17 by means of the grub screw 54 so that the unit consisting of the bearing bush 17 and the nut 23 can still be rotated relative to the external thread 16.It will be readily seen that the bearing bush 17 can be adjusted along the external thread 16, that is to say with respect to its position on the holder part 14, so that the position of the support arms 20 of the stop member 18 relative to the holder part 14, and hence relative to the end part 11 and the radial arms 12, is also changed. Locking the particular position is then effected by the spring-loaded plug 55 which is screwed into the nut 23 and which engages in recesses provided in the periphery of the carrier ring 21.

As can also be clearly seen from Figure 1, the support arms 20 are double-bent and have an approximately horizontal end part 24. This end part 24 extends horizontally over a zone which reaches so far outwards that the horizontal end part 24 still is in contact even with the largest saggers 25, indicated in Figure 1 by dots and dashes, in the region of their outer peripheries but that, on the other hand, seating on the saggers of smallest diameter is still ensured, as was indicated in Figure 1 by the line 26. Furthermore, the undersides of the end parts 24, which come into contact with the particular top sagger 25, to be gripped, of a stack are provided with a padding 27 which consists, for example, of an appropriate rubber material and is intended reliably to prevent damage to the sagger.

Furthermore, at least one of the support arms 20 of the stop member 18 is provided on its top with a bolt 28 which engages in a guide bore 29 of the hollow radial arm 12 located above so that relative rotation of the stop member 18 and the radial arms 12 is prevented.

Nevertheless, the support arms 20 can of course be vertically adjusted relative to the radial arms 12 by a corresponding adjustment of the bearing bush 17.

To grip and lift the particular top sagger 25, gripper rolls 30 - three in the present case are used which are provided with a casing 31 of an elastic material. These gripper rolls 30 are each mounted on the free end of a pivoted lever 32, 33. 34 so that they can freely rotate.

At their lower end, they have a bearing bolt 35 for a roll 36 having a sharp-edged peripheral flange which is used as the separator element and the design of which can be seen m particular from Figures 1 and 3. The sharp-edge roll 36 has a core 37, the diameter of which is smaller than the external diameter of the casing 31, as can be clearly seen from the Figures 1 and 3. The actual sharp edge 38, the diameter of which is somewhat greater than the external diameter of the casing 31, protrudes radially from this core 37 so that the sharp edge 38 is capable of engaging in the gap 39 between adjacent saggers, before the sagger 25 is gripped by the casing 31 of the gripper roll 30, and in this way reliably detaches the saggers from one another along the gap 39.

The pivoted levers 32, 33, 34 are each guided in the bearing bush 13 by means of a pivot bolt 40. A further lever arm 41, the free end of which is provided with a bore 42, is fixed to the upper end of the pivot bolt 40, so that it cannot rotate relative thereto.

The bores 42 each serve as a pivot bearing for connecting levers 43, of which only one is shown complete in Figure 2 and the others are merely indicated by dot-and-dash lines. As Figure 2 shows, the connecting levers 43 are designed to be of adjustable length. The end 44, facing away from the lever arm 41, of each of the three lever arms 43 is mounted, so that it can move by pivoting, on a lever arm 45 of a lever star 46. The lever 46 is mounted, so that it can freely rotate, by means of the ballbearing 47 on the end part 11 which is fixed to the central bolt 6 serving as the carrier.The construction explained above thus ensures that a pivoting motion of one of the pivoted levers 32, 33, 34, for the purpose of laying the gripper roll 30 against the circumferential surface 48 of the sagger 25, results in a corresponding pivoting motion of the other pivoted levers carrying the further gripper rolls 30.

In the illustrative embodiment shown, a hydraulic or pneumatic cylinder 49, the case 50 of which is pivotably mounted on the pivoted lever 34 by means of a bolt 51, is used for moving the pivoted levers 32, 33, 34. The piston rod 52 is pivotably mounted correspondingly on the pivoted lever 33 by means of a bolt 53. When the piston rod 52 is now axially displaced relative to the case 50 of the servo-motor 49, the pivoted levers 32, 33, 34, which form the actual gripper device are moved radially in common in a pivoting motion relative to the circumferential surface 48 of the sagger 25.

The device according to the illustrative embodiment explained operates in the following way: Before the gripper device 1 is employed for gripping the particular top sagger of a stack of saggers, it is necessary to adjust the position of the stop member 18 relative to the sharp edge 38 of the separator element 36, to correspond to the height of the particular saggers 25 to be gripped. For this purpose, the bearing bush 17 is correspondingly screwed by means of the nut 23 along the external thread 16 until the required position has been reached. The locking of the nut 23 relative to the bearing bush 17 is then effected, as explained, by means of the spring-loaded plug 55.

After the stop member 18 has been appropriately set, the operation can start.

The gripper device 1 is here brought above the appropriate stack of saggers by a corresponding movement of the carrier arm 2, and the carrier arm 2, and together with it the gripper device 1, is then lowered until the stop member 18 seats on the top of the upper rim of the particular top sagger 25 in a manner which can be seen from Figure 1. As soon as this position has been reached, the further lowering process for the carrier arm 2 is ended by means of a limit switch (not shown) of any desired design and the servo-motor 49 is actuated whereby the piston and, conjointly, the piston rod 52 are retracted. During this movement of the servo-motor 49 or the piston rod 52, the pivoted levers 32, 33, 34 with the sharp-edged rolls 36 and the gripper rolls 30 pivot inwards in the direction of the circumferential surface of the particular top sagger 25.During this inward movement, the sharp edge 38 of the sharp-edged roll 36 then first enters into the gap 39 between the top sagger and the next sagger 25, an accurate engagement of course depending on the correspondingly accurate setting of the position of the stop member 18, with respect to which the gripper rolls 30 and sharp-edged rolls 36 are indeed not movable vertically. The pivoting motion of the sharp-edged rolls 36 here ensures that the sharp edge 38 enters only gradually into the gap 39 so that excessive local stresses cannot occur.

The top sagger 25, if it were adhering is reliably detached from the next lower sagger of the stack by the entry of the sharp edge 38 into the gap 39. Due to continued pivoting motion, the elastic casing 31 of the gripper rolls 30 then comes to lay against the circumferential surface 48 of the top sagger 25. In this position, the servo-motor 49 is then blocked as soon as an adequate force has built up. Subsequently thereto the top sagger 25 of the stack can then be lifted off by moving the carrier arm 2 with the gripper device 1 upwards and can then be transported by a corresponding movement of the carrier arm 2 to any desired place where the servo-motor 49, if appropriate after lowering, is then again actuated in such a way that the pivoted arms 32. 33, 34 with the gripper rolls 30, 31 pivot outwards and release the sagger 25.

Subsequently the cycle explained above can restart, the stack of saggers, from which the particular top sagger is to be taken off, being lifted on a lifting table or the like by a height corresponding to a sagger. Slight differences in height (say of the order of the length of the bellows 10) can here by readily compensated so that a very accurate setting of the carrier arm 2 before the gripping process is thus not necessary.

WHAT WE CLAIM IS: 1. A gripper device for gripping the top one of a stack of saggers for ceramic products, the device comprising at least three gripper members which are distributed around a central axis and are movable radially of said axis so as to engage a sagger with a gripper surface thereof and a stop member having a seating surface to engage an upper surface of a sagger to be gripped, wherein the gripper members are provided with separator elements each having a sharp edge protruding beyond the gripping surface of the associated gripper member for reaching, during gripping, under the bottom surface of a sagger to be gripped and the stop member is so arranged that axial distance between the sharp edges of the separator elements and the seating surface of the stop member is invariant when gripping a sagger and is at other times adjustable so as to be set to be equal to the height of a sagger to be gripped.

2. A device according to Claim 1, wherein the gripper members are formed by gripper rolls provided with elastic casings providing said gripper surfaces and carry, on their lower portions, separator elements in the form of sharp-edged rolls.

3. A device according to Claims 1 and 2, wherein the sharp-edged rolls can rotate independently of the gripper rolls.

4. A device according to Claims 1, 2 and 3, wherein the sharp-edged rolls have cylindrical cores having diameters smaller than the gripper rolls, sharp edges having diameters larger than that of the gripper rolls protruding radially from the circumferential surface of the cores.

5. A device according to any one of Claims 2 to 4, wherein the gripper rolls carrying the sharp-edged rolls are each mounted on the free end of a pivoted lever which is pivotable in a plane transverse to said axis.

6. A device according to Claim 5, wherein the pivoted levers are mounted on the free ends of stationary radial arms and are conjointly pivotable via a lever system by means of a single drive device.

7. A device according to Claim 6, wherein the lever system comprises a lever star which is rotatable about said axis, which star carries the radial arms and has a number, corresponding to the number of pivoted levers, of lever arms, the free ends of which are connected by means of a connecting lever to the corresponding pivoted lever, at least one of the pivoted levers being movable by the drive device so as to lay the gripper roll against the surface of a sagger to be gripped.

8. A device according to Claim 7, wherein that the lengths of the connecting levers are variable.

9. A device according to any one of Claims 6 to 8, wherein the drive device is a hydraulic or pneumatic cylinder which acts on two adjacent pivoted levers at a location between their bearing axis and their free ends carrying the gripper rolls.

10. A device according to any one of the preceding claims, wherein the stop member is formed by three support arms extending radially of said axis, which are mounted to be centrally and vertically displaceable in common relative to the gripper rolls and which have horizontally extending outer end parts.

11. A device according to Claim 10, wherein the horizontally extending end parts carry padding on the underside.

12. A device according to any one of the preceding claims, wherein the stop member is mounted in such a way that it cannot rotate relative to a common carrier for the stop member and the gripper members with the separator elements.

13. A device according to Claims 6 and 12 wherein at least one of the support arms of the stop member carries on its top a bolt which is guided so that it can move vertically in a

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. particular top sagger is to be taken off, being lifted on a lifting table or the like by a height corresponding to a sagger. Slight differences in height (say of the order of the length of the bellows 10) can here by readily compensated so that a very accurate setting of the carrier arm 2 before the gripping process is thus not necessary. WHAT WE CLAIM IS:

1. A gripper device for gripping the top one of a stack of saggers for ceramic products, the device comprising at least three gripper members which are distributed around a central axis and are movable radially of said axis so as to engage a sagger with a gripper surface thereof and a stop member having a seating surface to engage an upper surface of a sagger to be gripped, wherein the gripper members are provided with separator elements each having a sharp edge protruding beyond the gripping surface of the associated gripper member for reaching, during gripping, under the bottom surface of a sagger to be gripped and the stop member is so arranged that axial distance between the sharp edges of the separator elements and the seating surface of the stop member is invariant when gripping a sagger and is at other times adjustable so as to be set to be equal to the height of a sagger to be gripped.

guide bore of one of the radial arms.

14. A device according to any one of the preceding claims, wherein a central bearing bush is provided for vertically adjustable mounting of the stop member, the bearing bush being provided with an internal thread, and being rotatable relative to the stop member can be screwed onto a vertical threaded journal of the carrier and having a lower end which carries an external thread onto which a nut can be screwed to hold the stop member against a collar on top of the bearing bush.

15. A device according to any one of the preceding claims, wherein the or a carrier for the gripper members with the separator elements and for the stop member is mounted so that it can be adjusted vertically but cannot rotate.

16. A gripper device constructed and arranged to operate substantially as hereinbefore described with reference to the accompanying drawings.