TRANSFERRING A PALLET OR A WORK PIECE

Field of the invention

The invention relates to a transfer table for transferring a pallet or a work piece. The invention also relates to a system. Furthermore, the invention relates to a method for transferring a pallet or a work piece.

Background of the invention

It is known to use various automatic pallet exchangers in connection with machine tools. In these configurations of prior art, a new pallet introduced by a lift and transfer apparatus, such as, for example, a stacker crane, is delivered via a transfer table or an intermediate table to a pallet exchanger, from which the pallet is transferred, for example, to a work table of a machine tool for machining. In this chain of operations, the transfer table is normally used for help for the reason, among other things, that at the machine tool there is not enough space for forks to deliver or receive a pallet or a work piece, or there is otherwise a risk that the forks hit the structures of the machine tool.

A stacker crane normally manipulates pallets by means of a fork, wherein the fork generally comprises two parallel arms which are usually spaced from each other but which may also be attached to each other. In many cases, said arms also have a telescopic movement for delivering and receiving a pallet and/or a work piece. The arms are normally placed below the horizontal supporting surfaces of the pallet, to support the pallet. These horizontal supporting surfaces are often some kind of projections extending from opposite sides of the pallet. It is also feasible that the fork or the arms support the pallet from the bottom of the pallet. The fork is normally connected to the lifting carriage of the stacker crane, used for performing the lifting and lowering movements. The horizontal movement is achieved by means of said telescopic movement or by transferring the fork in the lifting carriage. These constructions of prior art relating to transfer tables are normally relatively complex and expensive to implement, because they usually require various actuators and their control devices for implementing the movements of the transfer table.

Brief summary of the invention

The aim is to solve the above-mentioned problems in such a way that the pallet or work piece can be moved in a simple way with low costs, for example, between a stacker crane and a machine tool so that the automatic stacker crane or a corresponding machine can be programmed to be compatible with the transfer table. The transfer table according to the invention for transferring a pallet or a work piece is presented in claim 1. The system according to the invention is presented in claim 8. The method according to the invention for transferring a pallet or a work piece is presented in claim 11. In an exemplary embodiment of the transfer table, the transfer table is provided with a mechanical transfer mechanism, by means of which the pallet can be transferred from a stacker crane to a machine tool, and typically also back. The transfer table is placed between two machines, such as, for example, the stacker crane and the machine tool. The machine tool typically also comprises a pallet exchanger or another device for manipulating pallets, whereby the pallet can be received from the transfer table or delivered to the transfer table. In connection with the reception and/or delivery, a lifting movement and/or a lowering movement of the pallet exchanger is normally applied. The work piece is normally connected to a pallet, but on the work table, work pieces can often be manipulated without a pallet as well, if the shape and structure of the work pieces are such that the stacker crane and the machine tool can manipulate them like a pallet. The transfer mechanism of the transfer table according to the above example can be implemented even completely mechanically, without electronically, hydraulically or pneumatically controlled actuators and automation. If necessary, sensors are included in the system.

According to an embodiment, the transfer table is implemented in such a way that the machine, particularly its load manipulating device, engages in a temporary or momentary and detachable manner the transfer mechanism of the transfer table and moves, with its movement, the pallet table or a corresponding support, on which the pallet or work piece is transferred, on the transfer table. Thus, for example a forward directed movement of the fork will push the pallet forward, and a retraction of the fork, that is, the movement of the fork backwards, will pull the pallet backwards.

In an embodiment, the transfer mechanism of the transfer table is implemented in such a way that the load manipulating device does not need to perform any extra movements for moving the pallet. For example, after bringing the pallet, the fork must always retract, which movement can also be utilized in the transfer of the pallet table. This means that the engagement of the fork to the transfer mechanism and its retraction backwards will cause a movement of the pallet forward, for example to the machine tool. The transmission of the transfer mechanism is constructed so that said movement is possible.

In an embodiment, the load manipulating device also engages the transfer mechanism without any extra movements. In practice, this is preferably implemented so that, for example, the fork grips the transfer mechanism simultaneously when it delivers the pallet to the transfer table, which typically takes place in such a way that the fork moves downwards in connection with placing the pallet onto the transfer table.

Preferably, the transfer of the pallet to the load manipulating device and picking up the pallet from the transfer table can also be performed by said transfer mechanism, but for example the motion path of the fork has an opposite direction to that described above. When the fork moves up, it simultaneously disengages the transfer mechanism and receives the pallet. In an embodiment, the transmission of the transfer mechanism is configured so that the movement of the fork in relation to the movement of the pallet is, for example, 1 :2, wherein the distance between the machines can be selected more freely.

Description of the drawings

In the following, the invention will be described in more detail by means of some examples and with reference to the appended drawings, in which

Fig. 1 shows a transfer table according to an example in a side view;

Figs 2 and 3 show the function of the transfer members of the transfer table in a side view;

Fig. 4 shows the function of the transfer table and the machine according to Fig. 1 seen in a slanted side view; and

Fig. 5 shows the function of the transfer table and the machine according to Fig. 1 seen in a slanted side view. Detailed description of different embodiments of the invention

In the present application, the term machine refers to any suitable machine comprising a load manipulating device that is compatible with a pallet or a work piece to be transferred. It may be, for example, a forklift, but typically it is a stacker crane that functions automatically and whose high capacity is maintained by avoiding unnecessary paths of movement, for example, during the delivery and reception of a pallet. The function of a stacker crane is often to transfer pallets and work pieces from and to a storage, in cooperation with other machines. A transfer table refers to some kind of an intermediate station located between a first machine and a second machine. The first machine is, for example, said stacker crane, and the second machine is, for example, a machine tool, often provided with a pallet manipulating device, such as a pallet exchanger that receives and delivers pallets or work pieces. Naturally, it is also possible that both of the machines are equal, comprising for example forks, and they both engage a transfer table, for example in an alternating manner. A transfer table 1 shown in the example of Fig. 1 comprises a frame structure, comprising, in this example, two legs 10. The function of the legs 10 is to take care that the support 4 carried by the legs is placed at a suitable working level. The support 4 is substantially horizontal, and in some cases it may also be inclined at a suitable angle, wherein the pallet either rises or descends during the transfers. The legs 10 and the frame structure can be implemented in any suitable way, and they will not be described in more detail in the present application. The actual functional mechanisms of the transfer table 1 will be explained in more detail in the following description.

Figure 1 shows, among other things, the transfer table 1 , a separate pallet 2 to be transferred, a pallet table 11 , a support 4 for the transfer table, legs 10 of the transfer table, bending members 5a-5c and elongated transfer members 12a-12b belonging to the transfer mechanism, as well as a range of movement for the movable bending member 5c, including end points 7a-7b. The term pallet table also refers to other corresponding supports, by which a pallet or a work piece can be moved in a way presented in this description. The embodiment shown in Fig. 1 is one in which the movement of the load manipulating device produces a movement of the pallet table 11 in the opposite direction, and the transmission of the transfer mechanism is fitted to the ratio 1 :2. Figure 1 shows one exemplary way of providing a functional mechanical system in such a way that the pallet 2 and the work piece 13 mov- ing with it can be transferred in a simple and reliable manner from the transfer table 1 , for example, to a pallet exchanger 6 of a machine tool, or from the pallet exchanger 6 back to the transfer table 1. Supported by the frame structure, the substantially horizontal pallet table 11 moves back and forth and is intended, among other things, for supporting the pallet 2. Carried by the support 4, the pallet table 11 is moved, for example, by the transfer members 12a-12b shown in Fig. 1 in such a way that the pallet table 11 either glides or rolls in a desired direction, for example by means of a guide, or on wheels or rolls. In this respect, it is possible to apply mechanisms known as such. The transfer members 12a-12b are provided with bending members 5a-5c, preferably at least three bending members for each transfer member. At least one bending member is movable, see the bending member 5c of Fig. 1. The transfer arm 3 moves with the movable bending member 5c. The transfer arm 3 is connected to the transfer mechanism in such a way that when the transfer arm 3 is moved, the bending member 5c is also moved substantially in the same direction substantially at the same speed. In this example, the transfer arm 3 is connected to the bending member 5c.

The transfer arm refers to various members, which the machines can engage and which transmit movement. With respect to the transfer table, the machines are external and separate devices which often function independently, such as stacker cranes, or as part of the rest of the apparatus, such as a machine tool.

The movable bending member 5c is, for example, a return wheel, such as a chain wheel. When a chain wheel is used, the elongated transfer members 12a-12b are preferably chains intended, for example, for power transmission and engaging to the return wheel. The transfer member may comprise several parallel chains. The transfer mechanism may also be implemented by using, for example, a belt, a wire cable or rope instead of chains, and by using some kind of a peg, shaft or return roller instead of a return wheel. With reference to Figs. 1 , 2 and 4, the movement of the pallet 2 from the right to the left, to the position shown in Fig. 1 , is achieved with the transfer member 12a. One end of the transfer member 12a is connected to the transfer table 1 in a stationary manner. The transfer member 12a is connected to the first end point 7a of the range of movement of the bending member 5c. The fixing point is stationary and is located at that end point of the range of movement which is farther away from the pallet exchanger 6 than the end point 7b. The range of movement represents the travel length of the bending member 5c. The other end of the transfer member 12a is movable and is, in turn, fixed to the pallet table 11. The transfer member 12a is bent between these two fixing points so that it first goes around the movable bending member 5c and then around the stationary bending member 5b. By means of the transfer member 12a, one bend, the movable bending member 5c, and two parallel chain portions, a transmission ratio 1 :2 is achieved.

With reference to the Figs. 3 and 5, the movement of the pallet 2 from the left to the right is achieved with the transfer member 12b. The transfer member 12b, in turn, is bent so that its one end is fixed to the transfer table 1 in a stationary manner. The transfer member 12b is connected to the second end point 7b of the range of movement of the bending member 5c. The fixing point is stationary and is located at that end of the range of movement which is closest to the pallet exchanger 6. The other end of the transfer member 12b is movable and is, in turn, fixed to the pallet table 11. The transfer member 12b is bent between these two fixing points so that it first goes around the movable bending member 5c and then around the stationary bending member 5a. Also in this case, by means of the transfer member 12b, one bend, the movable bending member 5c, and two parallel chain portions, a transmis- sion ratio 1 :2 is achieved.

The transfer members 12a and 12b are bent in opposite directions. The transfer mechanism of the transfer table 1 implements at least one of said movements, that is, the movement to the left and/or to the right. In one of said directions, the movement can also be implemented, for example, by stored potential energy, for example by a spring or by gravity, connected between the pallet table 11 and the stationary frame structure of the transfer table, for example the support 4.

In practice, the movement of the pallet table 11 functions by the princi- pie that when the bending member 5c moves from the end point 7b towards the end point 7a, the transfer member 12a is loosened. At the same time, however, the movement of the bending member 5c tightens the transfer member 12b. The conveying of the elongated transfer members via the bending members 5a, 5b and 5c thus produces a situation, in which the otherwise loosening part of the transfer member 12 is transferred in favour of the transfer member 12b so that, in practice, both the transfer members remain substantially equally tight all the time. In other words, because both the transfer members 12a and 12b are connected to the pallet table 11 and engaged to the bending mem- ber 5c, and because they both remain constantly substantially equally long, in practice, in the above-described case, the tensioning transfer member 12b pulls the pallet table 11 towards the pallet exchanger 6 at the same time when the loosening transfer member 12b enables the pallet table 11 to move with the transfer member 12b. Thus, by the effect of the transfer members 12a, 12b, the pallet table 11 is subjected to a force that makes the pallet table move closer to the pallet exchanger 6.

In a corresponding manner, the pallet table 11 is subjected to a corre- sponding but opposite force when the movable bending member 5c moves from the direction of the end point 7a towards the end point 7b. Thus, the pallet table 11 naturally moves in the opposite direction, that is, away from the pallet exchanger 6 towards the fork 8. Due to the placement of the elongated transfer members 12a, 12b and the bending members 5a, 5b and 5c, the transfer mechanism of Fig. 1 moves the pallet table 11 a distance twice the travel length of the bending member 5c. However, this ratio can be altered by increasing the number of bending members and bends, for example so that said ratio is 1 :3 or 1 :4. The movement of the bending member 5c takes place by the effect of the load manipulating device. In practice, this can be implemented, for example, by providing the load manipulating device with a required shape or a member, to which the transfer arm 3 or the contact member 9 engages. Such a member can be, for example, a protrusion, a slot, or an opening.

In the example shown in Figs. 4 and 5, the load manipulating device is a fork 8. At least one of the arms of the fork 8 engages at least one transfer arm 3. There are preferably two transfer arms placed on two opposite sides of the pallet table 11. The engagement takes place preferably when the fork 8 puts the pallet 2 in place on the transfer table 1. Thus, the pallet table 11 remains between the arms of the fork 8 and receives the pallet 2 being lowered down. The fork 8 lowering down engages simultaneously the transfer arm 3, as shown in Fig. 4. After this, the pallet 2 moves onto or above the pallet exchanger 6 simultaneously when the fork 8 pulls back from the transfer table 1 , as shown in Fig. 5. Disengagement of the transfer arm 3 takes place, for example, by a short vertical movement of the fork. Thus, the fork 8 does not need to make any unnecessary extra movements to move the pallet table 11. The fork 8 moves the bending member 5c by means of the transfer arm 3.

To move the pallet 2 away from the pallet exchanger 6, the fork 8 is first lowered, wherein it engages the transfer arm 3 as shown in Fig. 5. The arms of the fork 8 are placed on opposite sides of the pallet table 11 at the latest when the fork has pushed the transfer arm 3 towards the pallet exchanger 6, wherein the pallet table 11 moves above the fork, as shown in Fig. 4. The pallet 2 on the pallet table 11 moves onto the fork 8 simultaneously when the fork is lifted up and the fork 8 disengages the transfer arm 3.

Preferably, the load manipulating device is lowered onto the transfer arm 3. Alternatively, the load manipulating device can be connected, for example, below or to the side of the transfer arm 3, particularly when the load manipulating device also applies extra movements for engaging and moving the pallet table. After the engaging, the transfer arm 3 and the bending member 5c moving with it can be transferred mechanically with the movement of the load manipulating device in a desired direction, that is, normally from the end point 7a to the end point 7b or from the end point 7b to the end point 7a.

In the example shown in Figs. 1 to 5, the transfer mechanism and its transmission are utilized. A corresponding transfer mechanism with opposite movements can also be implemented in other ways which are obvious for a person skilled in the art on the basis of the above description. It is thus possible to apply various mechanical transmissions with varying transmission ratios. One mechanical transmission comprises, among other things, toothed bars and toothed wheels connected to them, wherein the load manipulating device engages a mov- able toothed bar, for example by means of the transfer arm 3 or a corresponding means. Said toothed bar, in turn, rotates a toothed wheel which moves another toothed bar that moves with the pallet table 11. Said transfer table can be provided with a suitable transmission ratio by increasing the number of toothed wheels and varying their dimensions. One way of implementing the transfer mechanism is to apply various lever mechanisms coupled between the transfer arm 3 and the pallet table 1 1.

In one embodiment, the transfer arm 3 and/or the contact member 9 is coupled directly to the pallet table 11 , wherein the transmission ratio 1 :1 is achieved. In that case, the transfer mechanism consists merely of, for example, the transfer arm 3 and/or the contact member 9. Thus, the load manipulating device always moves in the same direction as the pallet table 1 1 , unlike in the above-presented example. Thus, a very simple configuration is achieved, but extra movements of the load manipulating device are required, and the travel length of the pallet table is longer than in the above-presented example.

In yet another embodiment, the transfer arm is constructed so that the load manipulating device engages it and disengages it merely by a horizontal movement, wherein a configuration is achieved, in which the number of extra movements can be minimized. Thus, the load manipulating device, such as a fork, comprises a member, for example a horizontal peg that is transverse to the longitudinal direction of the fork. During the movement, the peg is pushed into a member, such as a slot, in the transfer arm, in which the peg is locked and engages the transfer arm. At the end of the movement of the transfer arm, the peg disengages the transfer arm by the same horizontal movement, and the fork can be lifted off, either without or with a pallet, depending on the location of the pallet table.

The transfer arm is thus constructed, for example, in such a way that it comprises movable elements and it rotates at its end positions around a horizontal axis line which is transverse to the movement of the fork. Furthermore, the transfer arm also comprises, for example, a system of slots and pegs, which allows said rotation at the end positions but locks the position of the transfer arm in other situations so that by means of the system, the fork can carry the transfer arm with it, for example, by means of the peg of the fork. In one alternative embodiment, the machine comprises a member separate from the load manipulating device, such as a fork, which member engages the transfer arm. The invention is not limited solely to the examples presented in the above figures and in the above description, but the configurations are characterized in what will be presented in the following claims.