Expandable shaft

Abstract

The present invention relates to an expandable shaft (10) comprising: - a substantially cylindrical central body (20) having at least one groove (21 ) formed on its outer surface; - at least one substantially rod-shaped slat (30) arranged within the groove (21 ) and configured to translate from a retracted position to an expanded position and vice versa; - at least one inner tube (40) interposed between the bottom (21c) of the groove (21 ) and the slat (30), whereby this inner tube (40) is configured to translate the slat (30) from the retracted position to the expanded position. The peculiarity of this expandable shaft (10) is that the central body (20) has at least one first recess (22a) and at least one opposite second recess (22b) formed at the side edges (21a, 21 b) of the groove (21 ) and that the slat (30) has at least one trough (30b) obtained on its upper surface (30a) configured to be aligned with the first recess (22a) and the second recess (22b). Furthermore, said expandable shaft (10) comprises holding means (50) arranged within the trough (30b) and with their ends (50a, 50b) inserted within the first recess (22a) and the second recess (22b) so as to block the translation of the slat (30) from the retracted position to the expanded position.

Description

[0001] EXPANDABLE SHAFT.

[0002] DESCRIPTION

[0003] The invention relates to an expandable shaft.

[0004] Expandable shafts able to support, unwind and rewind rolls and reels of any material are currently known.

[0005] Such a known-type of expandable shaft comprises:

[0006] - a substantially cylindrical central body having grooves on its outer surface; these grooves have two undercuts along the entire length of the grooves themselves adapted to block the expansion of rod-shaped slats arranged within these grooves;

[0007] - inner tubes, interposed between the bottom of the grooves and the respective slats, connected to inflation means and configured to allow the slats to translate.

[0008] Such an expandable shaft, although well known and appreciated, has some important limitations related to the torsion and bending strength of the central body.

[0009] In particular, the presence of undercuts hinders the torsion and bending strength of the central body.

[0010] This geometry in fact favours the concentration of stresses near the edges between the side walls of the grooves and the protuberances forming the undercuts.

[0011] Moreover, this geometry is even more detrimental in terms of torsion and bending strength when this central body is made of carbon fibre due to the interruption of the fibre path along the extension of the aforementioned grooves.

[0012] The task of the present invention is to develop an expandable shaft capable of obviating the aforementioned drawbacks and limitations of the prior art.

[0013] In particular, the object of the present invention is to manufacture an expandable shaft whose central body geometry leads to a greater strength of this central body in terms of torsion and bending strength if compared to similar expandable shafts of the known type.

[0014] It is also the object of the present invention to manufacture an expandable shaft whose production time is shorter than similar expandable shafts of the known type.

[0015] The above-mentioned task and objects are achieved by an expandable shaft according to claim 1 .

[0016] Further characteristics of the expandable shaft according to claim 1 are described in the dependent claims.

[0017] The task and the aforesaid object, together with the advantages that will be mentioned hereinafter, are indicated by the description of an embodiment of the invention, which is given by way of non-limiting example with reference to the attached drawings, where:

[0018] - Figure 1 represents a perspective view of an expandable shaft according to the invention;

[0019] - Figure 2a represents a perspective view of a first detail of the central body of the expandable shaft of Figure 1 ;

[0020] - Figure 2b represents a perspective view of a second detail of the central body of the expandable shaft of Figure 1 ;

[0021] - Figure 3 represents a side view of a slat of the expandable shaft of Figure 1 ;

[0022] - Figure 4 represents a front view of an element of the expandable shaft of Figure 1 ;

[0023] - Figure 5a represents a front section view of the expandable shaft of Figure 1 in a first operating position;

[0024] - Figure 5b represents a front section view of the expandable shaft of Figure 1 in a second operating position;

[0025] - Figure 6a represents a detail of Figure 5a;

[0026] - Figure 6b represents a detail of Figure 5b.

[0027] With reference to the above-mentioned figures, an expandable shaft according to the invention is indicated as a whole with the number 10 and is clearly visible in Figures 1 , 5a and 5b.

[0028] This expandable shaft 10 comprises:

[0029] - a substantially cylindrical central body 20, clearly visible in Figures 1 , 2a, 2b, 5a, 5b, 6a and 6b, and having six grooves 21 arranged in diametrically opposite pairs, visible in Figures 2a, 2b, 5a, 5b, 6a and 6b, formed on its outer surface in a direction substantially parallel to its longitudinal extension axis X; however, it cannot be excluded that said central body 20 has a different number of grooves 21 than those shown in the present embodiment of the invention;

[0030] - a plurality of slats 30, in a number equal to said grooves 21 and well visible in Figures 1 , 3, 5a, 5b, 6a and 6b, substantially rod-shaped and each of which is arranged within one of said grooves 21; said slats are configured to translate in a direction substantially radial to the axis X from a retracted position, visible in Figures 1 , 5a and 6a, to an expanded position, visible in Figures 5b and 6b, and vice versa; furthermore, these slats 30 are configured to have in this expanded position their upper surface 30a, clearly indicated in Figures 1 , 3, 6a and 6b, projecting with respect to the cylindrical surface of the central body 20;

[0031] - a plurality of inner tubes 40, in a number equal to the aforesaid grooves 21 and clearly visible in Figures 5a, 5b, 6a and 6b, interposed between the bottom 21c of the grooves 21 and the corresponding slat 30, where these inner tubes 40 are configured to be operatively connected to known-type inflation means adapted to control the expansion step and the contraction step of the inner tubes 40, wherein said inner tubes 40 are configured to translate the slats 30 from the retracted position to the expanded position.

[0032] The peculiarity of the present expandable shaft 10 lies in the fact that the central body 20 has, for each groove 21, nine recesses 22a, visible in Figures 2b, 6a and 6b, and nine opposite recesses 22b, visible in Figures 2a, 6a and 6b, formed at the side edges 21a and 21b of this groove 21.

[0033] Moreover, said slats 30 each have nine troughs 30b, visible in Figures 1 and 3, formed on the upper surface 30a over the entire width of these slats 30 and configured to be aligned with the recesses 22a and 22b when each of these slats 30 is arranged within the corresponding groove 21.

[0034] It is also important to note that this expandable shaft 10 comprises fifty-four holding means 50, represented in Figures 1 , 4, 5, 5a, 5b, 6a and 6b, arranged within said troughs 30b with the ends 50a, 50b of each holding means 50 inserted respectively within the recesses 22a and the opposite recesses 22b so as to block the translation of the slats 30 from the retracted position to the expanded position; in particular, in the present embodiment the holding means 50 are rod-shaped elements.

[0035] It is not excluded, however, that the holding means have a different shape from what herein described.

[0036] Furthermore, it cannot be excluded that the opposite pairs of recesses 22a and 22b are in a number different from the one previously described.

[0037] Therefore, the number of troughs 30b and the number of holding means 50 may also differ from what is shown in the present embodiment of the invention, still falling within the scope of protection of the invention itself.

[0038] Such an expandable shaft 10 advantageously allows to obtain greater torsion and bending strength of the central body 20, due to the fact that it no longer has undercuts along the entire length of the grooves 21 adapted to block the translation of the slats 30 during the expansion step, but rather as it has punctual recesses 22a, 22b along the length of the grooves 30 adapted to contain the ends 50a, 50b of the holding means 50.

[0039] This configuration makes it possible to obtain a lower concentration of torsion and bending stresses to which the expandable shaft is subjected during operation, and consequently it is possible to reduce the mass of the central body, thus advantageously increasing the expandable shaft rotational speed and thus the speed of unwinding and rewinding the reels.

[0040] In the present embodiment of the invention, the central body 20 is configured to be operatively connected to rotation means adapted to rotate the central body 20 about the axis X.

[0041] In particular, in the present embodiment, the central body 20 is connected by one of two side pins 23, clearly visible in Figure 1 , to an electric motor located at the side, not visible in the figure but known in itself.

[0042] In addition, such an expandable shaft 10 comprises return elastic means 60, clearly visible in Figures 4, 6a and 6b, interposed between the holding means 50 and the trough 30b and configured to translate the slats 30 from the expanded position to the retracted position.

[0043] In particular, in the present embodiment, the elastic means 60 are elastic slots projecting from the holding means 50.

[0044] It is not excluded, however, that such elastic means 60 are different, for example have the form of linear springs, or are completely absent in other embodiments of the present invention.

[0045] These elastic means 60 make it easier for the slats 30 to return to a retracted position during the contraction step of the respective inner tubes 40.

[0046] The first end 50a and the second end 50b of the holding means 50 have a thickness lower than the respective thickness of the first recess 22a and the second recess 22b.

[0047] This configuration allows for the translation of the holding means 50 within these recesses 22a and 22b in such a way as to allow for a greater excursion of the slats 30 between the retracted position and the expanded position. The elastic means 60 comprise a flexible foil projecting from one of the end 50a, 50b of the holding means 50 towards the trough 30b.

[0048] It is not excluded, however, that such elastic means 60 comprise two or more flexible foils projecting from one or both of the aforementioned ends 50a and 50b of the holding means 50 towards the trough 30b.

[0049] In the proposed version of the invention, the holding means 50 and the elastic means 60 are formed from a single piece body.

[0050] This configuration allows to make the assembly as well as the maintenance of the expandable shaft 10 easier.

[0051] It is not excluded, however, that the holding means 50 and the elastic means 60 are distinct elements.

[0052] In the present embodiment of the invention, the bottom of the trough 30b is in contact with the elastic means 60 when the slat 30 is in the retracted position, as is clearly shown in Figure 6a.

[0053] This advantageously allows to eliminate the clearance of the slats 30 between the retracted position and the expanded position.

[0054] It is not excluded, however, that the bottom of the trough 30b is spaced by the elastic means 60 or the holding means 50 when the slat 30 is in the retracted position.

[0055] In a possible version of the expandable shaft 10, the central body 20 is made of a material comprising carbon fibre.

[0056] In such a version, the described configuration is even more advantageous since carbon fibre is an anisotropic material.

[0057] This anisotropy, i.e. the property whereby the value of a physical quantity such as the breaking strength in a material such as carbon fibre is not equal in all directions, is critical for torsion and bending strength in the known configuration.

[0058] Instead, the configuration described by the invention succeeds in making the anisotropy condition of the carbon fibre less critical for torsion and bending strength.

[0059] Referring to the present embodiment, the recesses 22a, 22b are aligned with each other orthogonally to the longitudinal extension of the grooves 21.

[0060] A further aspect of the invention is that, preferably, the aforementioned first and second recesses 22a, 22b have an upper closure section 23a, 23b adapted to prevent the ends 50a, 50b of the holding means 50 from disengaging in a radial direction.

[0061] Advantageously, such a configuration makes it possible to avoid the use of additional fasteners, e.g. screws, to retain the holding means 50, in particular the ends 50a, 50b, within their respective recesses.

[0062] Furthermore, the first recess 22a has an inlet portion 24a configured to allow for the insertion in a radial direction of the end 50a of the holding means 50 within said first recess 22a.

[0063] Preferably, said insertion portion 24a is adjacent to the upper portion 23a of the first recess 22a.

[0064] This configuration facilitates the insertion of the ends 50a, 50b within the first and the second recess 22a, 22b.

[0065] In particular this configuration facilitates the insertion in a radial direction of the end 50a of the holding means 50 within said first recess 22a.

[0066] It is therefore possible to easily insert the ends 50a, 50b of the holding means 50 into the first and the second recess 22a, 22b by first inserting the end 50b directly into the second recess 22b and, subsequently, inserting the end 50a into the first recess 22a via the inlet portion 24a.

[0067] In practice, it has been established that the invention achieves the intended task and objects.

[0068] In particular, with the invention, an expandable shaft has been developed whose central body geometry leads to a greater strength of said central body in terms of torsion and bending strength if compared to similar expandable shafts of the known type.

[0069] In addition, an expandable shaft was developed whose production time is shorter than similar expandable shafts of the known type.

[0070] The invention thus conceived is susceptible to numerous modifications and variations, all of which are within the scope of the inventive concept; moreover, all the details may be replaced by other technically equivalent elements.

[0071] In practice, the components and materials used, as well as the dimensions and the contingent shapes can be any according to the requirements and the state of the art, as long as they are compatible with the specific use.

[0072] If the characteristics and techniques mentioned in any claim are followed by reference signs, these reference signs are to be intended for the sole purpose of increasing the intelligibility of the claims and, consequently, such reference signs have no limiting effect on the interpretation of each element identified by way of example by these reference signs.

Claims

CLAIMS1 ) Expandable shaft (10), comprising:- a substantially cylindrical central body (20) having at least one groove (21 ) formed on its outer surface in a direction substantially parallel to its longitudinal extension axis (X);- at least one substantially rod-shaped slat (30) arranged within said groove (21 ) and configured to translate in a direction substantially radial to said axis (X) from a retracted position to an expanded position and vice versa, said slat (30) being configured to have in said expanded position its upper surface (30a) projecting with respect to the cylindrical surface of said central body (20);- at least one inner tube (40) interposed between the bottom (21c) of said groove (21 ) and said slat (30), said inner tube (40) being configured to translate said slat (30) from said retracted position to said expanded position; characterised by the fact that said central body (20) has at least one first recess (22a) and at least one opposite second recess (22b) formed at the side edges (21a, 21 b) of said groove (21 ), said slat (30) having at least one trough (30b) formed on said upper surface (30a) over the entire width of said slat (30) and configured to be aligned with said first recess (22a) and said second recess (22b), said expandable shaft (10) comprising holding means (50) arranged within said trough (30b) and with their ends (50a, 50b) inserted within said first recess (22a) and said second recess (22b) so as to block the translation of said slat (30) from said retracted position to said expanded position.2) Shaft (10) according to claim 1 , characterised by the fact that said ends (50a, 50b) of said holding means (50) have a thickness lower than the respective thickness of said first recess (22a) and of said second recess (22b).3) Shaft (10) according to claim 1 or 2, characterised by the fact that it comprises return elastic means (60) interposed between said holding means (50) and said trough (30b) and configured to translate said slat (30) from said expanded position to said retracted position.4) Shaft (10) according to claim 3, characterised by the fact that said elastic means (60) comprise at least one flexible foil projecting from one of said ends (50a, 50b) of said holding means (50) towards the bottom of said trough(30b).5) Shaft (10) according to claim 3 or 4, characterised by the fact that the bottom of said trough (30b) is in contact with said elastic means (60) when said slat (30) is in said retracted position.6) Shaft (10) according to any one of claims 3 to 5, characterised by the fact that said holding means (50) and said elastic means (60) are formed from a single piece body.7) Shaft (10) according to any one of the preceding claims, characterised by the fact that said central body (20) is made of a material comprising carbon fibre.8) Shaft (10) according to any one of the preceding claims, characterised by the fact that said first recess (22a) and said second recess (22b) are aligned with each other orthogonally to the longitudinal extension of said groove (21 ).9) Shaft (10) according to any one of the preceding claims, characterised by the fact that said central body (20) has a plurality of said grooves (21 ).10) Shaft (10) according to claim 9, characterised by the fact that said central body (20) has at least one diametrically opposite pair of said plurality of grooves (21 ).11 ) Shaft (10) according to any one of the preceding claims, characterised by the fact that said first and said second recess (22a, 22b) have an upper closure section (23a, 23b) adapted to prevent said ends (50a, 50b) of said holding means (50) from disengaging in a radial direction.12) Shaft (10) according to claim 11 , characterised by the fact that said first recess (22a) has an inlet portion (24a) adjacent to said upper section (23a) and configured to allow the insertion in a radial direction of said end (50a) of said holding means (50) within said first recess (22a).

Images