A telescopic fork

Abstract

 The telescopic fork comprises a fixed lower base (10) and two or more movable slides or telescopically extensible members, wherein each slide is slidable by means of a respective set of rollers which are arranged symmetrically with respect to a vertical plane of symmetry (P). The rollers (13) slidably supporting a given movable slide (20) are located transversely farther from the central vertical plane (P) than the rollers (14) that are interposed between that given slide (20) and the slide (30) immediately above it. The top slide (30) and the base (10) each comprise optical devices (C,F) which align with an opening (28) in the intermediate slide when the fork is in its working position.

Description

[0001] The present invention relates to an improved telescopic fork. Telescopic forks are used in the automatic handling and industrial automation fields and are widely used, for example, in automatic warehouses, typically in association with pallet-moving translators/elevators. The pallets may be stored on single-depth or double-depth shelving.

[0002] As is known, a telescopic fork is a machine that is composed of a lower fixed base and one or more superimposed, extensible elements which move in a bilateral, telescopic manner for the translation of loads. The number of movable telescopic elements (two, three or four) is selected according to the overall travel to be achieved and the magnitude of the loads to be supported.

[0003] For a better understanding of the prior art and of the problems inherent therein, a conventional telescopic fork, which is illustrated in Figures 4-6 of the appended drawings, will be described first of all. The fork comprises a lower fixed base 10 which has central vertical walls 11, 12 with two opposed surfaces from which a first set of rollers 13 with horizontal axes projects. These rollers engage an intermediate slide or extending member 20 in positions that are defined herein as transversely inner positions. A second, transversely outer set of rollers 14, coplanar with those of the first set, serves to support, in a telescopically slidable manner, a top slide 30 suitable for directly supporting the loads that are to be transferred, in operating conditions. The top slide 30 has a substantially inverted-U-shaped cross-section with a pair of outer vertical flanges 36, 37 which are fixed to the sides of a horizontal plate 32. The object of the present invention is to provide a telescopic fork which is constructed in such a manner as to facilitate the insertion and the picking-up of the pallets. Another object of the invention is to improve the stability of the telescopic forks. A further object is to reduce and optimize overall dimensions.

[0004] These and other objects and advantages which will be explained further below are achieved, according to the present invention, by a telescopic fork having the features defined in the appended claims.

[0005] A preferred but non-limiting embodiment of the telescopic fork according to the invention will now be described; reference is made to the appended drawings, in which:

Figure 1 is a cross-section through a telescopic fork according to the invention;

Figure 2 is a schematic, perspective view of the fork of Figure 1;

Figure 3 is a schematic, longitudinal section through the fork of Figure 1;

Figure 4 is a cross-section through a conventional telescopic fork;

Figure 5 is a schematic, perspective view of the fork of Figure 4; and

Figure 6 is a schematic, longitudinal section through the fork of Figure 4.

[0006] With reference now to Figure 1, a preferred embodiment of the telescopic fork according to the invention comprises a lower base 10, an intermediate slide 20 which is movable telescopically relative to the base 10, and a top platform or slide 30 which in turn is movable telescopically relative to the intermediate slide 20. The general telescopic constructional layout of the fork shown in Figures 1-3 can be considered generally known. Only the elements that are of specific importance and interest for the purposes of the implementation of the present invention will therefore be described in detail in the following description. For the implementation of the parts and elements that are not described in detail, reference may therefore be made to any known solution of a telescopic fork, for example, with regard to the actuations which bring about the sliding of the slides.

[0007] The selection to provide a fork with only two movable slides may of course be preferable for some conditions of use but it is certainly not essential for the purpose of implementing the invention. In particular, the fork may be constructed in the form of a fork comprising three or more movable slides.

[0008] The lower base 10 has a pair of vertical lateral flanges 11, 12 which are spaced uniformly transversely with respect to a central or median vertical plane P. Throughout the description and in the appended claims, terms and expressions indicating orientations and relative positions, such as "longitudinal", "transverse", "outer", and "inner", are intended to relate to the central vertical plane P and to the "longitudinal" direction of movement of the fork perpendicular to the plane of the drawing of Figure 1.

[0009] The flanges 11, 12 extend from the opposite longitudinal sides of the base 10 and support a first set of rollers 13 with horizontal axes, which rollers project in a cantilever-like manner towards the central plane P from respective facing surfaces of the flanges 11, 12. The rollers 13 engage for rolling in two guides in the form of lateral longitudinal cavities 21 of the intermediate slide 20. The cavities 21 face in opposite, transversely outward directions and are formed by respective opposed C-shaped portions 22, 23. The two lateral C-shaped portions are formed integrally with and are connected by a flattened central portion 24 which defines an upwardly open, U-shaped channel 25 which is delimited laterally by the C-shaped portions 22, 23 and at the bottom by the flattened portion 24.

[0010] Each of the two C-shaped portions 22, 23 has an upper series of aligned holes 27 which house the axles of a second set of rollers 14 with horizontal axes, which rollers project in a cantilever-like manner towards the central plane P from the respective facing surfaces of the C-shaped portions 22, 23. The rollers 14 engage for rolling in respective guides in the form of lateral longitudinal cavities 31 of the top slide 30. The cavities 31 face in transversely outward directions and are defined by the upper horizontal plate 32 and by two opposed L-shaped rails 33, 34 which project downwards from the plate 32. The rails 33, 34 of the top slide 30 are housed in the U-shaped channel 25 of the intermediate slide 20.

[0011] The structure of the fork as a whole is symmetrical with respect to the vertical central plane P, in particular as far as the arrangement of the rollers is concerned. A pyramidal configuration of the first and second sets of rollers 13 and 14, in which the rollers 14 which support the top slide 30 are arranged in more central positions than the rollers 13 of the first set which support the intermediate slide 20, can be seen from Figure 1. In other words, the rollers 13 which support the intermediate slide 20 are transversely farther from the central plane P than the rollers 14 that are interposed between the intermediate slide 20 and the top slide 30. More generally, with reference also to telescopic forks with three or more movable members, the rollers which support a given slide are transversely farther from the central vertical plane than the rollers that are interposed between that given slide and the slide above it.

[0012] In comparison with the conventional configuration shown in Figure 4, the "pyramidal" arrangement of the rollers according to Figure 1 ensures greater stability of the slides and consequently of the load to be moved, since the transverse distance between the rollers of the first set is considerably increased. In a conventional configuration, on the other hand, the pyramidal arrangement is inverted: the lower rollers which support the intermediate slide are laterally farther in than those which support the top slide.

[0013] By virtue of the above-described configuration, the fork of the present invention exhibits less lateral play, above all when the fork is in the extended or open condition. By way of indication, for a given overall length in the extended condition, a fork according to the invention has lateral play of about 2 mm in comparison with the conventional 4-5 mm.

[0014] The geometrical arrangement of the top platform or slide 30 advantageously allows converging bevels 35 to be formed on the corners of the upper plate 32; the bevels facilitate the insertion of the slide in the pallet to be picked up without weakening the structure of the slide. In fact, as can be seen in Figure 2, the lower rails 33, 34 which constitute the stiffening elements of the slide 30, are not affected by the bevels 35. In contrast, it is not possible to bevel the edges of a top slide in a conventional fork (Figure 5) since that would involve cutting off the end portions of the lateral flanges 36, 37 on which the rollers 14 are mounted.

[0015] It will also be appreciated that, in the fork of the present invention, the top slide has a reduced height h in comparison with that of a conventional fork. This reduction in the vertical dimension, which is shown by a comparison of Figure 3 and 6, reduces the chances of collisions with the shelving and with the pallets. The reduction in collisions lengthens the useful life of the equipment and consequently reduces maintenance costs.

[0016] The configuration of the intermediate slide permits the use of an optical monitoring unit for directly monitoring the position of the top slide. By virtue of the formation of openings 28 in the relatively thin, central portion 24 of the intermediate slide 20, a reflector C fitted on the lower face of the top slide can be read directly by a photocell F which is mounted in a protected position on the lower base 10. This constitutes an advance over the monitoring systems that have been used up to now on conventional forks which provide for mechanical or inductive travel-limit devices D (Figure 4) which are mounted outside the fork body and have a size (a further 5-10 cm) which is added to that of the slides at the sides or underneath.

[0017] The invention is not intended to be limited to the embodiment described and illustrated herein which should be considered as an example; rather, the invention may undergo modifications in relation to the shape, size, and arrangements of parts and constructional and operational details.

Claims

1. A telescopic fork comprising a fixed lower base (10) and a plurality of movable slides or telescopically extensible members, wherein each slide is slidable by means of a respective set of rollers which are arranged symmetrically with respect to a vertical plane of symmetry (P), characterized in that the rollers (13) slidably supporting a given movable slide (20) are located transversely farther from the central vertical plane (P) than the rollers (14) that are interposed between that given slide (20) and the slide (30) immediately above it.

2. A telescopic fork according to claim 1, characterised in that it comprises a top movable slide (30) including an upper horizontal plate (32) from which two parallel rail portions (33, 34) project downwards, the rail portions extending longitudinally and being arranged symmetrically with respect to the plane (P) in respective transversely intermediate positions between the central plane (P) and the opposite longitudinal edges of the upper plate (32).

3. A telescopic fork according to claim 2, characterised in that the rail portions (33, 34) combine to define two longitudinally extending cavities (31) facing in transversely outward and opposite directions and constituting respective guides for rollers (14) which are mounted rotatably on a movable slide (20) that is located immediately beneath the top slide (30).

4. A telescopic fork according to claim 3, characterised in that the rail portions (33, 34) have opposed L-shaped cross-sections.

5. A telescopic fork according to claim 3 or claim 4, characterised in that the cavities (31) are defined at the top by the upper plate (32) and laterally and at the bottom by the rail portions (33, 34).

6. A telescopic fork according to claim 2, characterised in that the rail portions (33, 34) of the top slide (30) are accommodated in an upwardly open, U-shaped channel (25) of the movable slide (20) that is located immediately beneath the top slide (30).

7. A telescopic fork according to any one of the preceding claims, characterised in that the corners of the upper plate (32) of the top slide (30) have converging bevels (35).

8. A telescopic fork according to any one of the preceding claims, characterised in that the base (10) has a pair of vertical flanges (11, 12) extending from opposite longitudinal sides of the base and supporting a set of rollers (13) with horizontal axes, which rollers (13) project in a cantilever-like manner towards the central plane (P).

9. A telescopic fork according to any one of the preceding claims, characterised in that it comprises an intermediate movable slide (20) which is located between the top movable slide (30) and the fixed base (10) and which has:

- two parallel, longitudinally extending portions (22, 23) with opposed C-shaped cross-sections defining respective longitudinally extending cavities (21) facing in transversely outward and opposite directions, the cavities (21) constituting respective guides for rollers (13) mounted rotatably on the lower fixed base (10) or on a movable slide located beneath the movable slide (20);

- a central, flattened or vertically thinner portion (24) which connects the two parallel portions (22, 23); and

- an upwardly, open U-shaped channel (25) which is delimited laterally by the C-shaped portions (22, 23) and at the bottom by the flattened central portion (24).

10. A telescopic fork according to any one of the preceding claims, characterised in that:

- a first optical device (C) is fitted on a lower surface of the top movable slide (30);

- a second optical device (F) is secured to the lower fixed base (10); and

- at least one opening (28) is formed through the intermediate slide or slides (20) which is/are located between the top movable slide (30) and the fixed lower base (10), so that the opening is aligned with the first and second optical devices (C, F) in at least one working position of the fork.

11. A telescopic fork according to claims 8, 9 and 10, characterised in that the opening (28) is formed through the thinner portion (24) of the intermediate slide (20), and in that the second optical device (F) is mounted in a transversely intermediate position between the two side flanges (11, 12) of the lower base (10).

Drawing