EP0527110A1 - Strut - Google Patents

Abstract

The strut comprises a central screw (3) which can move axially in an external tube (1) forming a support and two jaws (6, 6%) which can pivot against a compression spring (14, 14%). Each of the jaws comprises a rim (9, 9%) intended to bear on the internal surface of a widened part (10) located at the upper end of the external tube. Each of the jaws furthermore comprises a front part in the shape of an angular nut portion (8, 8%) intended to be engaged with the thread (5) of the screw. The result of this is that the angular nut portions are engaged/disengaged with the thread of the screw by the sole rotation (18, 18%) of the jaws. <IMAGE>

Description

The present invention relates to a forestay comprising a central screw movable axially in an external tube forming a support and a nut comprising at least two angular portions of nut arranged so as to be displaceable radially with respect to the screw between a position of cooperation with the thread of the screw and a clear position of this thread.

Shores of this type are described in Swiss patent no. 321018 and in European patent no. 0349485. They allow the screw to be brought quickly to the approximate working position, fine adjustment being effected by rotation of the nut in the cooperation with the screw.

One of the drawbacks of the props mentioned above is that, when it is desired to remove the prop, to release the two nut portions from the thread of the screw, in order to allow the screw to fall back by gravity into its position lower, it is necessary to push up the arms for actuating the movement of the nut portions, then to pull laterally on these arms. Such manipulation is not always easy, especially when it is large props. This manipulation is made necessary by the fact that the release of the nut portions of the thread of the screw is carried out firstly by lifting up said nut portions, then by pivoting thereof. This operating mode also involves a risk that at least one or the other of the nut portions will remain blocked in the thread of the screw, when for example mortar is introduced there. On the other hand, when disassembling the stays mentioned above by removing the central screw from the outer tube, the number of spare parts is important, and the reassembly of the stay is rather complicated.

The realization of the forestay described in the Swiss patent mentioned above is also quite rudimentary. In particular the presence of a single portion of fillet on the portions of nut makes it a forestay difficult to use in practice.

As for the forestay described in European patent 0349485, the shape of the thread of the central screw implies on the one hand significant manufacturing costs and on the other hand a significant risk of detachment when lifting large loads, such as for example when it comes to readjusting a formwork that has collapsed after the pouring of a slab. In addition, experience has shown that the split circular spring of this forestay gets stuck or breaks easily, and therefore no longer performs the safety function assigned to it.

The object of the present invention is to provide a prop of the movable central screw type, making it possible in particular to remedy the drawbacks mentioned above, simple to carry out, inexpensive and easy to set up.

To this end, the invention relates to a forestay comprising a central screw movable axially in an outer tube forming a support and a nut comprising at least two angular portions of nut arranged so as to be displaceable radially with respect to the screw between a position of cooperation with the thread of the screw and a position released from this thread, as defined in claim 1.

• la figure 1 est une vue schématique en perspective d'un étai selon l'invention;
• la figure 2 est une vue en coupe verticale schématique d'un mode d'exécution de l'étai selon l'invention, sans sa cape de protection;
• la figure 3 est une vue partielle en perspective de l'ouverture des mâchoires libérant la vis centrale;
• la figure 4 est une vue en élévation d'une demi-bague de fixation de l'étai de la figure 2;
• la figure 5 est une vue depuis dessus de la demi-bague de fixation de la figure 4;
• la figure 6 est une vue en élévation d'une des mâchoires de l'étai de la figure 2;
• la figure 7 est une vue latérale depuis l'extérieur de la mâchoire de la figure 6;
• la figure 8 est une vue latérale depuis l'intérieur de la mâchoire de la figure 6;
• la figure 9 est une vue en coupe verticale schématique d'une première variante d'exécution de l'étai selon l'invention;
• la figure 10 est une vue depuis dessus d'un exemple de cape ou cloche de protection;
• la figure 11 est une vue en coupe verticale longitudinale de la cape de protection de la figure 10;
• la figure 12 est une vue schématique en élévation, partiellement en coupe, d'une seconde variante d'exécution de l'étai selon l'invention;
• la figure 13 est une vue de profil de l'étai de la figure 12;
• la figure 14 est une vue en élévation d'une des mâchoires de l'étai de la figure 12;
• la figure 15 est une vue de profil depuis la gauche de la mâchoire de la figure 14;
• la figure 16 est une vue depuis dessus de la mâchoire de la figure 14;
• la figure 17 est une vue en élévation d'un exemple de bride de l'étai de la figure 12;
• la figure 18 est une vue en plan de la bride de la figure 17;
• la figure 19 est une vue en perspective d'un second exemple de cape ou cloche de protection;
• la figure 20 est une vue en coupe verticale selon un plan médian de la cape de la figure 19;
• la figure 21 est une vue en coupe verticale de la cape de la figure 19 selon la ligne A-A de la figure 20;
• la figure 22 est une vue en coupe horizontale selon la ligne C-C de la cape de la figure 20;
• la figure 23 illustre le détail A de la figure 21;
• la figure 24 illustre un exemple de dispositif anti-déboîtement de l'étai;
• la figure 25 est une vue en coupe verticale d'une variante de la mâchoire représentée aux figures 14 à 16; et
• la figure 26 est une vue depuis dessus de la mâchoire de la figure 25, sans le ressort.

The following description is given by way of example. It refers to the attached drawing in which:

• Figure 1 is a schematic perspective view of a forestay according to the invention;
• Figure 2 is a schematic vertical sectional view of an embodiment of the forestay according to the invention, without its protective cap;
• Figure 3 is a partial perspective view of the opening of the jaws releasing the central screw;
• Figure 4 is an elevational view of a half-ring for fixing the forestay of Figure 2;
• Figure 5 is a view from above of the fixing half-ring of Figure 4;
• Figure 6 is an elevational view of one of the jaws of the forestay of Figure 2;
• Figure 7 is a side view from the outside of the jaw of Figure 6;
• Figure 8 is a side view from inside the jaw of Figure 6;
• Figure 9 is a schematic vertical sectional view of a first alternative embodiment of the forestay according to the invention;
• FIG. 10 is a view from above of an example of a protective cap or bell;
• Figure 11 is a longitudinal vertical sectional view of the protective cap of Figure 10;
• Figure 12 is a schematic elevational view, partially in section, of a second alternative embodiment of the forestay according to the invention;
• Figure 13 is a side view of the forestay of Figure 12;
• Figure 14 is an elevational view of one of the jaws of the forestay of Figure 12;
• Figure 15 is a side view from the left of the jaw of Figure 14;
• FIG. 16 is a view from above of the jaw of the Figure 14;
• Figure 17 is an elevational view of an exemplary brace of the forestay of Figure 12;
• Figure 18 is a plan view of the flange of Figure 17;
• FIG. 19 is a perspective view of a second example of a protective cap or bell;
• Figure 20 is a vertical sectional view along a median plane of the cap of Figure 19;
• Figure 21 is a vertical sectional view of the cape of Figure 19 along the line AA of Figure 20;
• Figure 22 is a horizontal sectional view along line CC of the cape of Figure 20;
• Figure 23 illustrates detail A of Figure 21;
• FIG. 24 illustrates an example of an anti-disengagement device of the forestay;
• Figure 25 is a vertical sectional view of a variant of the jaw shown in Figures 14 to 16; and
• Figure 26 is a view from above of the jaw of Figure 25, without the spring.

As shown in Figures 1 and 2, the forestay comprises an outer tube 1, forming a support, provided at one of its ends with a foot 2, intended to rest on the ground, for example in the form of a plate welded to the tube. An inner tube 3 is placed in the tube 1 so that it can slide axially inside the tube 1. The inner tube is provided at its upper end with a support element 4, for example in the form of a plate welded on the tube 3. As can be seen in FIG. 2, the tubes are fitted inside their corresponding end plate. The tube 3 is provided with an external thread 5, intended for adjusting its position inside the tube 1 by cooperation with respective threaded parts of the ends of two jaws 6, 6 ′, said ends each forming an angular portion d 'nut and each comprising a limited number of thread portions 7 (Figures 3 and 8), for example six in number in the example shown in the drawing, the lowest thread portion of each nut portion being made with a reduced depth, so as to facilitate the release of the jaws.

Each of the jaws (Figures 6 to 8) has a protruding part 8 constituting the half-portion of nut provided with threads 7. This protruding part has a lower flange 9 intended to come to bear on the inner part of an annular flare 10 in the form of a conical seat located at the upper part of the outer tube 1. The two jaws 6, 6 ′ are made integral with one another by means of two half-rings 11 secured by means of two pins 12 , 12 ′. Each of the half-rings 11 is provided on its sides with two fixing bars 20, 20 ′ in which are provided holes 21, 21 ′ intended for the passage of the pins 12, 12 ′. The ring-jaw assembly is arranged so as to be able to rotate freely around the outer tube 1, by simply pressing the flanges 9, 9 ′ of the jaws on the upper part 10 in the form of a conical seat of the outer tube (Figures 2 and 3) . The pins 12, 12 ′ are arranged horizontally. They cross the jaws right through, so as to allow the jaws to pivot around the pins. The amplitude of this rotational movement is limited by the space formed between the base parts 13, 13 ′ of the jaws and the outer surface of the ring, the width of said space being chosen so that in any case the flanges 9 , 9 ′ of the jaws cannot come out of the conical seat 10 at the upper end of the outer tube 1. Maintaining the jaws in the cooperation with the thread of the threaded inner tube is obtained by means of two compression springs 14, 14 ′ arranged horizontally at a level substantially lower than that of the pins 12, 12 ′, one of the ends of each of said springs pressing against the outer surface of the ring (or according to a variant inside a housing provided on the surface of the ring) and at its other end against the bottom of a housing 39 produced inside the base part 13 of the jaw. Each of the ends of the spring can be fixed to the elements against which it is supported. Arms, or handles, 15, 15 ′, are mounted in rotation on the rear parts 16, 16 ′ of the jaws. According to the embodiment shown in Figure 2, the arms are mounted on the jaws using pins 17, 17 ′, distinct from the pins 12, 12 ′. According to a first, simplified alternative embodiment, represented in FIG. 9, the forestay has only one pair of pins 19, 19 ′ serving both as the axis of rotation of the jaws and as the axis of rotation of the arms.

In order to quickly bring the screw to a position close to the working position, it suffices to lift the inner tube, which automatically releases the nut parts 8, 8 ′ of the thread 5 of the inner tube. When the inner tube has been thus displaced, the portions 8, 8 ′ of nut re-engage in the thread 5 of the inner tube under the effect of compression of the springs 14, 14 ′, and if necessary by light manual pressure down on the screw. It then suffices to make the fine adjustment by rotating the jaws around the inner tube 1 using the arms 15, 15 ′. The dismantling of the forestay is carried out in reverse, by first loosening the forestay by rotating the jaws around the inner tube 1, then by quickly dropping the inner tube by gravity, a simple lateral support on the arms 15, 15 ′ in the direction of the arrows 18, 18 ′ sufficient for the release of the nut parts 8, 8 ′ of the thread 5 of the inner tube 3.

A second alternative embodiment of a forestay comprising only a single pair of pins 19, 19 ′, serving both as the axis of rotation of the jaws and the axis of rotation of the arms, is shown in FIGS. 12 and 13. The jaws 36, 36 ′ (shown in detail in FIGS. 14 to 16) of this second prop of the forestay have a general external shape more rounded than that of the jaws of the forestay of FIG. 9, this gives them a more aesthetic appearance. On the other hand, the configuration of the jaws 36, 36 ′ has been studied so as to facilitate their operation, in particular thanks to the greater spacing between the base parts 37, 37 ′ of the jaws and the outer tube 1.

According to this second alternative embodiment, the jaws 36, 36 ′ are pivotally mounted at the end of fixing bars 43, 43 ′ of two fixing flanges 42, each of the flanges 42 being fixed, for example by welding, on a unitary ring 41 placed around the outside tube 1. The inside diameter of the ring 41 is substantially greater than the outside diameter of the outside tube 1, so that the ring can rotate freely around the tube 1. As can be seen in the figures 17 and 18, the flange 42 and its two bars 43, 43 ′ are in one piece. According to another variant, the two flanges 42 could be replaced by four bars, directly fixed in pairs on the ring 41. According to yet another variant, the ring 41 can be replaced by two half-rings of the type of those of FIGS. 4 and 5, but provided with oblique bars, each of the half-rings and its bars being made up of a single piece.

There is shown in Figures 25 and 26 an alternative embodiment of the jaw 36 shown in Figures 14 to 16. According to this variant, the compression springs 14, 14 ′ are replaced by flat springs 45. For this purpose, the housing 39 formed in the base part 37 of the jaw can be replaced by a recess 46 of lesser importance.

In order to prevent possible accidents during the fall of the inner tube by gravity, the length of the inner tube is greater than that of the outer tube, for example 10 cm, so as to constitute a hand guard during the sudden fall of said inner tube by gravity. On the other hand, for reasons of stability, the inner tube has at its lower part a non-threaded part, for example 30 cm in length, as well as a stop device.

A blocking or anti-disengagement device may be provided so as to prevent the removal of the central screw from the outer tube. An example of an anti-dislodging device is shown in FIG. 24. This device comprises two rivets 55, arranged near the upper end of the outer tube 1, on the same axis on either side of the tube. These rivets are intended to cooperate with the flared part 56 of the lower end of the inner tube 3. They can be replaced by screws or any other members projecting inside the tube. The number of two is not imperative, there can be one or more. The flared part 56 at the base of the inner tube can also be replaced by an outer rib disposed around the inner tube, in its lower part.

According to one embodiment, the outer tube and the inner tube, as well as the two half-rings (or the ring and the flanges of the variant) and the handles are made of steel, the two jaws can be made of special cast iron , for example in spheroidal graphite cast iron or malleable cast iron. The shape of the thread of the inner tube, as well as that of the thread portions of the jaws can be trapezoidal, the thread of the inner tube can be obtained by cold rolling, which in particular has the advantage of not weakening the mechanical strength of the tube. The angle of inclination (relative to the axis of the tube) of the annular flare 10 at the upper end of the outer tube can be chosen very freely depending on the embodiment of said flare.

The forestay may be provided with a protective cap or bell 24, such as for example that shown in FIGS. 10 and 11. This cap covers the jaws as shown in FIG. 1. Its sole function is to avoid infiltration of dirt in the forestay, such as cement milk, in particular between the thread of the inner tube and the conical seat of the outer tube. It comprises two ribs 25, 25 ′ intended for its stiffening and a flange 26 intended to be clipped around the flared part of the end of the outer tube 1.

A 24 ′ variant of this type of cape is shown mounted on the forestay of FIG. 12.

Another embodiment of the protective cap or bell is shown in FIGS. 19 to 22. This cap 50, preferably made of plastic material, in particular of thermoplastic material (for example of the PE-ND Carlona Shell type), is shaped so as to be able to thread around the inner tube 3 and come to cover the threaded part of the two jaws, as well as the upper part 10 in the form of a conical seat of the outer tube, closing, thanks to its elasticity, below the rounding 38, 38 ′ of the jaws, the edges 51, 51 ′ of the legs 52, 52 ′ of the cap coming to bear under said rounded parts 38, 38 ′. The configuration of this cap 50 makes it possible to be able to raise it along the inner tube 3, after having spread the tabs 52, 52 ′, thanks to the elasticity of the material of the bell, so as to allow for example the cleaning of the prop.

As can be seen in the detail in FIG. 23, the upper end of the bell 50 has an internal chamfer so as to prevent the bell from catching on the thread of the tube.

Besides the advantage of overcoming the drawbacks mentioned above, the forestay according to the invention still has many advantages over the forestays that are known. In particular, the design of the jaws and their actuating arms, which need only be actuated downward to release the nut portions from the thread of the screw, makes it possible to obtain the release of the nut portions by a single pivoting movement of the jaws and not by a combined movement as is the case with known props. The solution adopted greatly simplifies and facilitates this release. On the other hand, when the central screw is removed from the outer tube, the number of spare parts of the forestay described here is limited to two (cape not included), since the ring-jaw assembly remains integral with the outer tube . There is therefore no risk of losing parts. The reassembly of the forestay is very simple, since it suffices to press laterally on the arms to rotate the jaws and introduce the screw. It can also be noted that, the cape having the sole function of preventing dirt from entering the forestay, but having no function for the actuation of the device (such as the head support function known props described above), this cape can be made of a particularly light material, for example light sheet or plastic.

It can also be added that the forestay described here can be used without any risk of detachment in a standing position with the head up or head down, as well as in the lateral position.

Claims (12)

Forestay comprising a central screw (3) movable axially in an outer tube (1) forming a support and a nut comprising at least two angular portions of nut (8, 8 ′) arranged so as to be displaceable radially with respect to the screw between a position of cooperation with the thread (5) of the screw and a position released from this thread, characterized in that each of the angular portions of nut is secured to a jaw element (6, 6 ′) which can pivot around d '' an axis substantially perpendicular to the longitudinal axis of the screw against an elastic means (14, 14 ′), the engagement / disengagement of the angular portions of the nut with the thread of the screw being effected by the only rotation of the jaws. Forestay according to claim 1, characterized in that each of the jaw elements comprises a flange (9, 9 ′) intended to come to bear on the internal surface of a flared part (10) situated at the upper end of the tube outside. Forestay according to claim 2, characterized in that the jaw elements are mounted in rotation at the ends of members shaped so as to constitute a ring around the outer tube. Stay according to claim 2, characterized in that each of the jaw elements is mounted in rotation (19, 19 ′) at the ends (43, 43 ′) of two flanges (42) mounted on a ring (41) arranged around the tube outside. Stay according to claim 2, characterized in that the two jaw elements are made integral by means of two half-rings (11) secured by two axis elements (12, 12 ′) serving as an axis of rotation to said said jaws. Forestay according to one of claims 3 to 5, characterized in that the elastic means each comprise at least one compression spring (14, 14 ′) disposed horizontally and pressing at one of its ends against the outer surface of the ring, or inside a housing provided on the surface of the ring, and at its other end against the jaw, or inside a housing provided in the lower part of the jaw. Stay according to one of claims 3 to 5, characterized in that the elastic means each comprise at least one flat spring (45) fixed against the wall of the jaw and coming to bear against the external surface of the ring or the tube outside. Forestay according to one of the preceding claims, characterized in that the thread of the central screw and the thread portions of the nut portions are of trapezoidal shape. Stay according to one of the preceding claims, characterized in that each of the jaws comprises an arm (15, 15 ′) mounted in articulation on the jaw, said arms being intended to be used on the one hand to rotate the jaws around the screw for fine adjustment of the screw and on the other hand to activate the rotary movement of the jaws for the release of the nut parts of the screw thread. Forestay according to claim 9, characterized in that the actuation of the rotation movement of the jaws is effected by lateral support (18, 18 ′) on the arms, so as to bring them closer to the outer tube. Forestay according to the preceding claim, characterized in that the arms are mounted so as to pivot around the axes of rotation of the jaws. Forestay according to one of the preceding claims, characterized in that it comprises an anti-dislodging device comprising at least one member (55) projecting inside the outer tube and disposed near the upper end of said outer tube, said member being intended to cooperate with a inner tube member projecting outwardly from said inner tube and disposed near the lower end of said inner tube.

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