Auxiliary safety sistem for tower rotating crane

Abstract

 An auxiliary safety system for crane and particularly for tower crane with horizontal slewing jib. In order to give the greatest safety either to such slewing jib against yieldings of those mechanical members or elements which are provided to maintain them in their horizontal slewing state, and to the upper slewing section of the crane tower the axis of which is to be maintained in its vertical position within the forecast limits of tolerance, such auxiliary safety system comprises a first auxiliary safety means formed by tension ropes (20, 21) operating elastically through the co-operation of spiral springs (28) to maintain the jib/jibs (11,12) in their horizontal slewing plane, and a second auxiliary safety means formed by a cage (16) extended upwards from the area of thrust bearing (15) between stationary and slewing sections (13, 14), respectively of crane tower and provided with a top collar (30) on the inner perimetrical surface of which rollers (31) mounted on said slewing section (14) are pushed elastically and rolling, in order to maintain the axis of this latter in its vertical, central position.

Description

[0001] The invention relates to an auxiliary safety system for crane and particularly for tower crane with horizontal slewing jib, with or without an opposite jib for counter-weight, that is to say a system the auxiliary function of which is to give the greatest safety either to both slewing jibs against yieldings of those mechanical members or elements which are provided to maintain them in their horizontal slewing state, and the upper section of the crane tower in its satisfactory slewing motion about its own vertical axis, also when the component members and elements are subjected to sudden, unexpected stresses which exceed the limits usually forecast. This upper slewing section of the crane tower is generally mounted on a thrust bearing and provided with gear pairs to carry out an efficient slewing motion about its vertical axis, such members as well as other component elements (e.g. lock-bolts ) being however subjected to serious drawbacks when the crane structure cannot be maintained in its designed condition.

[0002] It is certainly well known to the skilled in the art that, for example, in the building field wherein the use. of these cranes is very enlarged, great or even fatal accidents are possible because of the limited safety actually reached by machines up to date suggested or applied in accordance with the prior art. Original defects may concern the casting, working, material of the components used to install a crane, e.g. thrust bearing, lock-bolts, gear pairs for the slewing motion of the upper section of the crane tower, and may give rise to accidents. To these original defects it is important to add, among other things, the possibility of unexpected, sudden stresses which exceed the limits usually forecast for a normal running of all the components, cither stationary or movable.

[0003] In accordance with some statistical data, a more or less considerable number of accidents are possible which are due to different causes. For example:

[0004] On the ground of remarks of this kind, the safety rules relating to the cranes have really been improved, and consequent improvements concerns the materials, technological processes to produce suitable components, as well as the assembly, maintenance and operative features.

[0005] In spite of these improvements, drawbacks and accidents, which are also very great and fatal, are still possible with cranes manufactured, assembled and operating in accordance with the prior art, particularly when the variations of load and stresses of the crane components are so remarkable and sudden, that wear and strains are possible also within a time course, and give rise to negative or even disastrous results.

[0006] Those skilled in the art may thus understand that a mention of possible sources of accidents and drawbacks is very important, because of their connection with the constructive and operative features of the crane components .

[0007] One source concerns mechanical failures and particularly the yielding of the orientation mechanism of the slewing jib. Such mechanism is generally forced by a horizontally operating crown gear and one or two pinions driven by a geared motor whose axis is vertical. The coupled members of the mechanism are solid for the stationary and slewing section of the tower, respectively and a person skilled in the art knows that the one and/or the other of these members are often so stressed by moments of different kind, that some deformations are provid-ed which relate, for example, to the teeth and/or lock-bolts.

[0008] Referring to the lock-bolts used to fasten component elements of the stationary and slewing tower sections, it is to recall here that they remain in a stressed state after the locking, because of the bending and twisting moments. The bolt shank is moreover biased by variations either of the load and direction of this latter with a slow but continuous deformation, particularly when remarkable, sudden variations take place, so that the connecting efficiency of the bolts is actually reduced. It will be understood that in such a condition the verticality of the slewing section cannot be maintained, and the safety of the crane is consequently reduced. Sources of drawbacks and accidents are also the repeated vibrations and stresses during the operative phases of the crane.

[0009] The invention as claimed is intended to remedy the drawbacks and disadvantages of cranes still now proposed and applied in accordance with the prior art. It solves the problem of how to provide an auxiliary safety system for tower crane with slewing jib/jibs, which may also be applied on cranes of the type usually used, not expensive modifications of its structure being only necessary which are neverthless suitable to give the maximal operative safety also for a long time.

[0010] In substance, the claimed auxiliary safety system comprises:

- an auxiliary means mounted and operating to better protect the horizontal slewing jib of a tower crane, the aim of which is to make void or reduce to not-dangereous levels the negative inflence of stresses on the projecting jib, e.g. because of sudden, remarkable variations of load, such auxiliary means providing for the use of ropes suitable to elastically oppose these negative influences;

- an auxiliary means to maintain the slewing section of the crane tower in its central position to slew about its vertical axis, that is to say an auxiliary means capable to allow angular deviations of the slewing axis only within the tolerance limits provided by the designer and in accordance with the laws; such auxiliary means being formed by a protecting cage solid for the stationary section of the crane around the area of a conventional thrust bearing, outwordly the slewing upper section of the tower and extended up to a desired height, a collar being provided at the top end of the cage and solid for same, against the inner perimetrical surface of which and rolling thereon being elastically pushed some rollers mounted on the slewing section of the tower. Dangereous stresses usually supported by the component members which carry out the angular motion of the slewing section of the crane tower are in this manner transferred to the stationary section of this latter.

[0011] One way of carrying out the invention is described in detail below with reference to the accompanying drawings which illustrate only one sipecific embodiment. That is to say, description and illustrations do not constitute a limitation for some other embodiments, and modifications and/or changes are then possible within the ground principles of the present invention as pointed out in the claims.

[0012] In the drawings:

Flg.1 is a. schematic elevation view of a tower crane with horizontal slewing jib having an opposite jib to support a conter- weight, wherein auxiliary safety means with tension ropes for said jibs and a cage for maintaining the central position of the slewing axis are provided in accordance with the invention;

Fig.2 is a schematic detail of the auxiliary safety means for the slewing jibs of the crane, according to Fig.l;

Fig.3 is a schematic, partially removed elevation view of the auxiliary safety means relating to the centrality of the slewing auxiliary safety means relating the centrality of the slewing section axis, wherein the cage and its top collar are shown with rollers of said tower section in their leaning position on the inner perimetrical surface of that collar;

Fig.4 is a top view of the protective cage and its top collar, the slewing section of the crane tower being illustrated enclosed therein in a cross section with respective rollers.

[0013] Turning now to the drawings and first of all to Figs.l and 2, it is possible to see that crane 10 selected as an example of embodiment to describe the invention is provided with an operative jib 11 and an opposite jib 12 to support a counter-weight, substantially as in a conventional tower crane of this type. Stationary section 13 and slewing section 14 of a trestle tower crane 10 are also of a conventional type, and this latter section 14 has solid for operative jib 11 and opposite counter-weight jib 12.

[0014] In Fig.1 the skilled in the art may also see a schematic show of a cage 16 as auxiliary safety eans in accordance with the invention, the features and function of which will be explained below. Such cage 16 is placed around stationary section 13 of crane tower 10, solid for this latter or forming a single piece with same, and is in any case extended from the area of the thrust bearing 15 of slewing section 14 up to a height considered sufficient to carry out its function in accordance with the invention. The thrust bearing is not a part of the invention and is then not described here, but indicated only by that numeral reference 15 between stationary section and slewing section 13 and 14, respectively of the crane tower.

[0015] The structure of operative jib 11 and jib 12 to support a counter-weight has been schematically shown in Fig.l to evidence the solid connection of same with slewing section 14 of the crane tower. Conventional tension rods 17 and 18 are also shown to support the crane jibs, the features of which must obviously be suitable to ensure the strength against unexpected, sudden stresses for variations of load at the free end 19 of protruding jib 11. Such variations give rise to corresponding variations of moments and are obviously dependent on the distance from the central vertical axis of the slewing upper section 14. Tension rods 17, 18 may be replaced by tension ropes, if desired, and that which relates to operative jib 11 is evidently much more subjected to additional stresses because of variations of load, the effects of which may be actually dangerous when sudden and remarkable, as said above.

[0016] The auxiliary safety means for jibs 11 and 12 comprises ropes 20, 21, the function of which is that of elastic tension ropes as they are connected to and operating through spiral springs to improve the strength condition of the jibs and particularly of the operative jib 11 during any sudden and remarkable variation at its free end 19.

[0017] Tension ropes 20, 21 have like arrangement, so that it is suffi- ci-ent to make reference to tension rope 20 only which concerns jib 11, to explain the application and function.

[0018] Referring to Figs.l and 2, at the top of slewing tower section 14 of crane 10 a plate 22 is provided to which one end of both ropes 20, 21 is fastened. On the trestle structure of jib 11, towards the free end of same, and idle rope pulley 23 is mounted, while a second like pulley 24 is mounted on the upper central part of slewing section 14. A support 25 solid for the jib structure is provided with a horizontal threaded through-hole wherein a screw 26 is inserted and movable to allow the regulation of elastic tension rope 20 through a tension spiral spring 28. To one end of this latter is hooked the free end of rope 20, while the other end of spiral spring 28 is connected to the corresponding end of screw 26. A nut 27 is provided to define the right elastic tension of rope 20.

[0019] A person skilled in the art may easily understand that in this manner such auxiliary safety means for jibs 11 and 12 of a tower crane 10 may carry out an efficient function either through the own features of tension ropes 20, 21 and the selected features of springs 28, as each spring acts as an intermediate elastic means between top plate 22 and the structure of corresponding jib 11 or 12.

[0020] The other auxiliary safety means of the system according to the present invention is to be considered as very important regarding the maintenance of the axis of slewing section 14 in its vertical central position. In accordance with the illustration of Fig.l, such slewing section 14 is still provided with a trestle structure. A more satisfactory application of this auxiliary safety means was found by providing for a slight lowering of the bottom end of the slewing section 14 in respect to conventional cranes of this type, wherein the connection with stationary section 13 is provided through a thrust bearing 15. In this case such auxiliary safety means is formed by a cage 16 of a quadrangular shape like slewing section 14 and stationary section 13, if desired, which in any case must allow the free rotation of slewing section 14 inside same.

[0021] As stated above, the aim of this auxiliary safety means is to discharge on the stationary vertical structure of crane 10 those eventual stresses which could damage the component members and elements carrying out the angular motion of the slewing section about its central vertical axis, and particularly the gear toothings in thrust bearing area as well as the lock-bolts ^pro- vided in the slewing and stationary sections of the crane.

[0022] By looking through Figs.l, 3 and 4 it is possible to see that cage 16 of this embodiment has a quadrangular shape like slewing section 14 and extends vertically at least from an upper stretch of stationary section 13 up to a height of slewing section 14 which is considered sufficient to reach the desired finality. A top collar 30 is solid for cage 16 and within the inner perimetrical surface of same the slewing section 14 of crane 10 may freely rotate.

[0023] As stated above, collar 30 is solid for cage 16 and then for the stationary structure of crane 10, so that it constitutes a very suitable component to discharge thereon those eventual, unexpected stresses which have a negative effect as regards the safety features of crane 10, either for the operation and stability during a satisfactory period of time.

[0024] To this end, slewing section 14 of crane 10 is provided with rollers 31 outside the trestle structure, which are rotatirg freely about vertical axses, for example as shown in Fig.4. To improve the meeting collar 30-rollers 31, each one of these rollers may, in its turn, be mounted on support which allows that radial shift which pushes the roller elastically against the inner perimetrical surface of collar 30 by rolling thereon, in order to continuously maintain ths axis of slewing section 14 and solidly connected jibs 11, 12 in its vertical position, any eventual angular motion in respect to the vertical, referred to the supporting base,being only within the tolerance limits.

Claims

1. Auxiliary safety system for a tower crane (10) having a horizontal slewing jib (11) and eventually an opposite jib (12) to support a counter-weight, which is formed by a first auxiliary safety means provided with ropes (20, 21) and springs (28) co-operating therewith in order to function as elastic tension ropes to maintain said crane jibs in their horizontal slewing plane, and by a second auxiliary safety means formed by a stationary cage (16) solid for the lower stationary section of crane (10) and having a collar (30) at its top end, the function of which is to maintain in its vertical position the axis of the slewing tower section (14) of the crane through the continuous elastic pushing of rollers (31) of such slewing section on the inner perimetrical surface of said collar (30), characterized in that each rope (20, 21) of said first auxiliary safety means has one end fastened to a plate (22) at the top end of said slewing tower section (14) and acts as an elastic tension rope on a corresponding jib (11, 12) to which is fastened after its winding on rollers (23, 24) of upper slewing tower section (14) and its hooking to said intermediate spiral spring (28), the position of this latter and consequently the tension of each rope (20, 21) being controlled through a fit (25, 26) and screw nut (27); that said stationary trestle cage (16) is provided around the area of said thrust bearing (15) of the tower crane between said stationary and slewing sections (13, 14), respectively, and extends upwards sufficiently to reach the desired finality, with a collar (30) at its top end and solid for same as a stationary part of the tower crane structure; that a set of suitable idle rollers (31) are mounted on said slewing section (14) and push elastically and continuously n the inner perimetrical surface of said collar (30) to maintain the axis of said slewing . section (14) in its vertical, central position; that said cage (16) is so positioned and dimensioned that said slewing section (14) of the crane may rotate freely inside same, with said rollers (31) rolling on said inner perimetrical surface of said collar (30).

2. An auxiliary safety system for crane as claimed in claim 1, characterized in that two coaxial idlers may be mounted on the upper central area of said slewing section (14) to take the place of said distinct idlers (24, 24') and support said ropes (20, 21) provided as auxiliary safety means for said jibs (11, 12).

3. An auxiliary safety system for crane as claimed in claim 1, characterized in that said idle rollers (31) are each one supported by a telescopic pair of pipes having therein a compression spiral spring so that they are pushed elastically and continuously in a radial direction on the inner perimetrical surface of said collar (30) of said protective cage (16).

Drawing