Telescopic platform for receipt of loads

A telescoping table with a base and at least two slides and a support table, which can be displaced linearly on it in a telescoping manner, and with drive devices assigned to these components, is to be operated in such a way that, even at small degrees of extension, at least the support table is fully or almost fully extended on the slide which guides it, and, to the extent possible, the second slide is also extended relatively far forward on the first slide, the required drive devices being installed in readily accessible and easy-to-maintain locations. For this purpose, it is proposed that the base be equipped with two drive devices, the first of which is connected only to the first slide, whereas the second operates tension cables, tension belts, tension bands, tension chains, and/or lengths of chain which operate a second slide or a second slide plus additional slides as well as the support table.

BACKGROUND OF THE INVENTION
 1. Field of the Invention
 The invention pertains to a telescoping table with a base and at least two
 slides and a support table, which are guided in linear fashion on the base
 in a telescoping manner, and with at least two drive devices mounted on
 the base, one of which is connected by drive means to the first slide
 only, whereas the second operates cables or lengths of chain, which move
 the second slide or the second slide plus additional slides as well as the
 support table.
 2. Description of the Related Art
 Telescoping tables of this type are used, for example, in high-shelf
 warehouses to load the shelving compartments with goods an d to remove the
 s tacked goods again later. The distance by which the telescoping table
 can extend inward is limited by the width of the aisle between the
 shelving units; often, however, not only normal but also oversized
 extensions are required, when, for example, two pallets are to be stored
 one behind the other in a deep shelf compartment, or when special
 conditions must be dealt with such as the presence of a fire wall.
 Although it is possible not only to extend the individual slides and the
 support table fully to achieve the optimum telescopic extension but also,
 in principle, to extend them only partially to achieve smaller telescopic
 extensions, the conventional drive devices of the slides and of the
 support table are designed in such a way that the end surfaces of the
 support table and of, for example, the two slides following along after it
 are so close together when only partially extended that the two slides
 which support the support table must also enter the shelf compartment.
 Therefore, with respect to the maximum height of the load which can be
 accepted, it is necessary to take into account the height not only of the
 support table itself but also of the slides which guide it.
 As a way of eliminating this disadvantage, EP 0,410,286 A2 proposes that
 the support table and the slides connected to it not be extended in the
 conventional manner, that is, in a chronologically parallel or synchronous
 manner; instead, they are to be extended one after the other under the
 control of locking devices, so that, for example, when the support table
 is to telescope out only a short distance, the support table moves out
 first and then the slides which carry it move out, until the desired
 degree of extension is achieved. The extra complexity associated with the
 locking devices, however, is unfavorable. The jerky operation of the
 support table, caused by the acceleration and deceleration of the
 telescoping components in question, and the limitation on the speed at
 which the table can be extended under operating conditions of this type
 are also disadvantageous.
 PCT WO 94/04,447 pertains to support forks which are designed to accept
 containers and discloses another possibility of keeping a large distance
 between the pick-up fork, which is provided in place of a support table,
 and the following slide even in cases where the fork is extended only a
 short distance. Namely, two drive devices, which are guided on the base,
 are assigned to the slides; one of these drives determines the
 displacement of the slides, while the other determines the displacement of
 the support table or support fork with respect to the preceding slide. One
 of the drive devices acts by way of shiftable gears or a gear boxes with
 different ratios. Thus, although the support table or support fork can
 always be extended fully with respect to the slides supporting and guiding
 it, the mounting of the drive devices, their energy supply lines, and the
 gear boxes subordinate to them on a slide present considerable
 difficulties. The transmission of the movement to the support table or
 support fork by way of any additional slides which might be provided also
 proves to be highly complicated and susceptible to breakdown.
 FR-A-2,709,745 discloses a telescoping tab le, which is equipped with two
 drive devices, installed on the base, which move the slides and the
 support table; each of the drive devices drives an endless chain. One of
 these chains is attached to the first slide, the other to another endless
 belt, which for its part is attached to an endless belt in the following
 slide. Thus, although it is possible for the slides to be extended to
 different degrees in a controlled manner, the use of anchors extending
 crosswise to the chains to attach them impairs the precision of the
 control and the drive moments which can be generated to move the slides.
 SUMMARY OF THE INVENTION
 The invention is therefore based on the task of creating a telescoping
 table of the general type described above in which, even when the table is
 extended only a short distance, at least the support table is completely
 or almost completely extended on the slide which guides it, and in which
 the degrees of extension are determinable and can be executed at high
 accelerations. The drive devices are also to be located in such a way that
 they can be easily installed and supplied with electric power or hydraulic
 medium and also so that they can be easily and reliably maintained, with
 the result that they can be operated for long periods of time without the
 need for service.
 This task is accomplished by the following features. The telescoping table
 has a base and at least two slides and a support table, which are guided
 in linear fashion on the base in a telescoping manner. At least two drive
 devices are mounted on the base, one of which is connected by drive means
 to the first slide only, whereas the second device operates cables and/or
 lengths of chain, which move the second slide or the second and additional
 slides as well as the support table. The first drive device operates a
 chain, which passes over guide pinions, the two ends of the chain crossing
 each other as they proceed to opposite ends of the first slide, to which
 they are attached. These features ensure a relatively simple design, and
 the forces of acceleration in question are transmitted purely by lengths
 of chain, so that even relatively large forces can be transmitted with
 almost no elastic stretching or yielding. Thus, by the use of separate
 drive devices, it is possible either to extend the second slide and any
 following slides and the support table or, to achieve greater extension,
 to extend additionally the first slide on the base as well. This means
 that, for the extensions required in practice, the support table is always
 fully extended, advisably by means of the second slide, whereas the first
 slide is also extended only when the degree of extension to be achieved
 requires it. Thus, in accordance with the task, the height of the
 telescoping components which must be moved into a shelving compartment at
 small extensions is advantageously limited, and the need for complicated
 arrangements to prop up the deposited loads can be dispensed with. Because
 the drive devices are installed on the base, there is sufficient room to
 install them, and no complications are to be expected from the supply
 lines for power and/or pressurized media, which can be laid permanently in
 the base. Permanent installation on the roomy base not only allows the
 device to be assembled quickly, easily, and reliably but also simplifies
 subsequent maintenance, so that desirably long service times and reliable
 operation without frequent breakdowns are to be expected.
 Additional effective, advantageous, and inventive elaborations of the
 invention will be explained in the following.

DESCRIPTION OF THE PREFERRED EMBODIMENTS
 FIG. 1 shows a schematic diagram of a telescoping table 1 in its starting
 position, in which a first slide 3, a second slide 4, and a support table
 5 are almost perfectly aligned with each other above base 2 of the table.
 FIG. 2 shows telescoping table 1 of FIG. 1 after it has been moved out to a
 certain fraction of its maximum extension; in this situation, first slide
 3, operated by a first drive device, is still lined up with base 2,
 whereas second slide 4 and support table 5 have been fully extended by a
 second drive device. Thus, however, support table 5 and slide 4 now jut
 out over slide 3 to the maximum extent, and the end surface of slide 3 is
 as far away as possible from the extended telescoping components.
 FIG. 3 shows that, as a result of the action of the first drive device,
 slide 3 is now also extended versus base 2, and thus support table 5 has
 reached its maximum possible extension.
 FIG. 4, again in the form of a schematic diagram, shows telescoping table 1
 with slide 3, slide 4, and support table 5, after they have been extended
 out from base 2. To move slide 3, a pinion 6 is provided, which is turned
 by a drive motor (not shown); the pinion engages with a chain 7. This
 chain, shown in broken line, passes around guide pinions 8 and 9, and its
 free ends then cross each other as they proceed to slide 3, to which they
 are attached at two points. When pinion 6 is now driven, the chain is
 moved in one of the two possible directions, one free end of chain 7
 pulling while the other yields. Slide 3, which is connected to both ends
 of the chain, is thus pushed out of its position in a linear manner along
 its guide in base 2, which, for the sake of simplicity, is not shown in
 FIG. 4.
 Base 2, however, is equipped with yet another drive device, which is not
 shown either, and which is able to displace a carriage 10 along a
 horizontal guide within base 2, as indicated by horizontal dashes.
 Carriage 10 carries a double pinion 11, which is supported on an axle so
 that it is free to rotate. One end of a tension chain 12, shown in
 dash-dot line with three dots, is attached to a chain take-up 13, from
 which it then proceeds toward double pinion 11, around which it makes a
 180.degree. turn. From double pinion 11, tension chain 12 now passes
 around another guide pinion 14, supported at the end of base 2, and
 proceeds from there to the facing side of slide 3, where it wraps around a
 guide pinion 15 supported at the opposite end. From here, the chain now
 proceeds back again to the opposite end of slide 4, to which it is
 attached. In an approximately symmetrical manner, one end of a tension
 chain 16 shown in dash-dot line, is attached to a chain take-up 17, wraps
 around the second pinion of double pinion 11, passes from there to guide
 pinion 18, which is supported at the end of base 2 opposite guide pinion
 14. From here, tension chain 16 crosses tension chain 12 on its way to a
 guide pinion 19 supported at the opposite end of slide 3, and, crossing
 tension chain 12 again, is attached to slide 4 near the end. What this now
 means is as follows: When, for example, the second drive device (not
 shown) pushes carriage 10 to the right, the loop of tension chain 12
 passing around double pinion 11 is shortened, and the end of this tension
 chain passing around guide pinions 14, 15 is lengthened. At the same time,
 however, the loop formed by tension chain 16 passing around double pinion
 11 becomes larger, so that a corresponding length of tension chain is
 pulled out over guide pinions 18, 19, and slide 4 is thus shifted to the
 right in its linear guide by the free end of the chain.
 This motion is also transmitted to support t able 5: Slide 3 is connected
 to support table 5 by two tension chains 20, 21, each shown by finely
 dashed lines. After first crossing each other, these chains pass around
 guide pinions 22, 23, which are supported at the two ends of slide 4.
 Guided by these guide pinions 22, 23, the free end sections of tension
 chains 21, 21 cross again, and their ends are then attached to support
 table 5. As a result, movements between slides 4 and 3 are also
 transmitted to support table 5, which moves with respect to slide 4.
 Thus, by shifting carriage 10 by means of the second drive device (not
 shown) and by the use of tension chains 12, 16, 20, 21 provided as drive
 means, slide 4 can be extended on slide 3, and support table 5 can be
 extended on slide 4, as shown in FIG. 2, without the position of slide 3
 on base 2 being changed. On the other hand, by actuation of the first of
 the drive devices (not shown), which acts by way of pinion 6 and chain 7
 serving as drive means, the position of slide 3 on base 2 can be changed,
 in which case tension chains 12, 16, 20, 21, as a result of the
 displacement of guide pinions 15, 19, are able to push slide 4 and support
 table 5 out. This also means that, as an option, by actuating only the
 second drive device, slide 4 and support table 5 alone can be extended,
 which is usually sufficient for a small extension requirements such as
 those present when loads lying at the front of the shelving compartment
 are to be transferred. If a load situated farther toward the rear is to be
 picked up or deposited, then, instead of this, the first drive device is
 actuated, and slide 3 is extended with respect to base 2 along with slide
 4 and the support table 5. The extension maneuvers of the telescoping
 components, furthermore, are not limited to either the complete extension
 of slide 4 and support table 5 alone or to the extension of all the
 telescoping elements; instead, any desired intermediate degrees can be
 selected, where advantageously slide 4 and support table 5 are extended
 completely first, and if any further extension is required, this is
 provided by the actuation of slide 3.
 So as not to overload either the description or the figures, many details
 have not been either illustrated or described specifically. For example,
 support table 5 can slide in a linear manner in guideways on slide 4,
 which in turn can slide in guideways on slide 3, and this in turn slides
 in guideways on base 2. In addition, control means attached to the drive
 and/or stops can be used to limit the degrees to which the individual
 telescoping elements can extend. It is advantageous, furthermore, for the
 drive means to consist of two sets of components and for these two sets to
 be arranged symmetrically so as to avoid the torques which would impair
 the linear advance.
 For the rest, the drive devices are not limited to electric motors, nor are
 the drive means limited to tension chains. Thus, electric motors,
 especially geared motors, can be provided as drive devices, but hydraulic
 motors, pneumatic cylinders, etc., are also possible. In particular with
 respect to the drive of slide 3, endless chains in conjunction with
 pushers which engage with the chains can be used as drive means. In
 addition, a drive based on the use of a toothed rack has also proven to be
 advantageous; racks can also be in the form of flat-link articulated
 chains, which are stretched out tightly in a straight line. A drive based
 on tension cables, tension bands, and/or tension belts is also possible. A
 minor variant can also be obtained by not guiding tension chains 12, 16
 around double pinions supported on carriage 12 but rather by connecting
 them directly to the carriage. This can be driven by a pneumatic cylinder,
 but pinions engaging in racks or spindle nuts mounted on driven, threaded
 spindles can also be used. Thus the invention can be varied in many
 different ways without departing from the basic inventive idea.