Abstract:
A method of installing and removing concrete blocks involves using handling device that is equipped with means for attaching and suspending a concrete block and which itself comprises a protective barrier placed temporarily on the concrete block to safeguard the operations of detaching or attaching this block. The barrier advantageously has safeguarded lateral access of the safety bow type that comes into register or alignment with rungs with which the concrete blocks are equipped. The method keeps an operator safe while installing and removing stackable concrete blocks, particularly an operation in which the concrete blocks are stacked on a base chassis of a tower crane.

Description:
BACKGROUND 
       [0001]    The subject-matter of the present invention is, in general, a method for installing and removing stackable concrete blocks, this method being more particularly applicable to concrete ballast blocks that can be stacked on a base chassis of a crane in order to ballast the crane. Another subject of the invention is a handling device intended for implementing this method that handles the concrete blocks and affords protection. 
         [0002]    In a way that is generally known, a crane, and particularly a tower crane, is weighted down by placing and stacking varying numbers of concrete ballast blocks on the base chassis of such a crane. 
         [0003]    A handling device suitable for handling stackable concrete ballast blocks that allows the ballast blocks to be brought in succession one on top of the others is already known, for example, from French Patent FR 2 854 393 B1. When using such handling device, an operator must, after placing each concrete block, climb up onto the top of the stack already produced, which may be at a height of several metres, in order to detach the slings of the handling device. During these operations, the operator does not currently enjoy any measure of safety against the risks of falling, unless he uses a safety harness, which appears challenging. 
         [0004]    To make it easier for the operator to gain access to the top of a stack of concrete ballast blocks when installing or removing crane ballast, it has already been proposed for each concrete ballast block to be equipped with at least one stirrup or rung, situated on its edge. Thus, the superposed corresponding rungs of the stacked ballast blocks form a kind of ladder making it easier for the operator to gain access to the top of the stack of ballast blocks, as seen in European Patent EP 1 205 422 B1. 
         [0005]    This arrangement may well make the operations of installing crane ballast blocks easier, but it affords no measure of safety to an operator who has arrived at the top of the stack of ballast blocks. 
         [0006]    Various protective barrier systems for operators working at a height or in other hazardous situations are known from elsewhere. 
         [0007]    For example, Japanese Patent JP 11-152944 and U.S. Pat. No. 7,213,715 B2 disclose protective barriers designed to avoid accidental falls through a “manhole”. 
         [0008]    Other documents, such as French Patent FR 2 894 232 B1 or European Patent Application EP 2 253 580 A1, disclose platforms for working at height with guard rails and lateral access. These platforms have a solid floor which prevents certain types of intervention. In addition, their lateral access usually consists of a simple gate, which does not afford safety. 
         [0009]    These known protective barrier systems are not suitable for the operations of placing and stacking concrete ballast blocks, particularly for ballasting a crane. 
       BRIEF SUMMARY 
       [0010]    The present invention seeks to overcome the aforementioned disadvantages and its object is therefore to provide a method and a handling device which are suitable for affording the operator optimum safety when installing and removing stackable concrete blocks, particularly during operations of ballasting a crane using such blocks. 
         [0011]    To this end, the method of the invention consists essentially, for installing and removing stackable concrete blocks, particularly concrete blocks provided with at least one rung on their edge. A handling device or equipment for use with these concrete blocks is equipped with means for attaching and suspending a concrete block. The handling device itself comprises a protective barrier closed up on itself and provides lateral access. The protective barrier is placed temporarily on a concrete block in order to safeguard the operations of detaching or attaching the concrete block to the handling device. 
         [0012]    In one preferred embodiment of the method of the invention, the handling device comprises a protective barrier. The lateral access to the protective barrier includes a safety bow that comes into register or alignment with rungs of the stacked concrete blocks when the protective barrier is placed on a concrete block situated at the top of the stacked concrete blocks. 
         [0013]    Thus, the idea underlying of embodiments of the invention is to use a special-purpose handling device or equipment which is used both as a lifting beam for picking up and handling the concrete ballast blocks and as a protective barrier for the operator stationed at the top of the stack of concrete blocks during operations of detaching or attaching these blocks. In addition, in so far as the protective barrier is provided with a safeguarded lateral access of the safety bow type that aligns or registers with a ladder made up of the vertical alignment of the rungs of the stacked concrete blocks, the method thus affords greater safety at the moment the operator gains access via this ladder to the top of the stack of concrete blocks. 
         [0014]    The special-purpose handling device used in the method of the invention is itself handled using an auxiliary lifting appliance such as a truck-mounted lifting apparatus, which may in particular be the truck used to bring the ballast blocks onto the site concerned or another mobile crane. 
         [0015]    The handling device intended for implementing the method, defined hereinabove, comprises a protective barrier closed up on itself and provided with a lateral access but no floor. The protective barrier further comprises means for suspending it from a hook of a lifting appliance, notably by slings, and means for attaching and suspending under said the protective barrier a concrete block that is to be installed or removed. 
         [0016]    In an embodiment of this handling device, the lateral access of the protective barrier includes a safety bow extending at least to a height of the protective barrier in a region thereof. By climbing up the ladder formed by the superposed rungs of the stacked concrete ballast blocks, the operator comes up inside the safety bow and from there gains direct access to the space delimited by the protective barrier that surrounds him on all sides. The absence of any floor under the protective barrier may give the operator direct access to the attachment and suspension means, notably for detaching a concrete block which has just been placed at the top of the stack. 
         [0017]    Overall, embodiments of the invention thus provide a solution which, while remaining constructionally simple and economical, affords optimum safety during operations of installing concrete ballast blocks and, naturally too, during the reverse operations of removing these concrete ballast blocks, by virtue of a protective barrier that forms a handrail, preferably supplemented by a safety bow. In so doing, the operator finding himself relieved of the need for equipment of the harness type which is difficult to work with for this kind of operation. In addition, the fact that there is no floor at the base of the protective barrier prevents the handling device from being misused as a gondola for transporting or lifting people, which current regulations prohibit. 
         [0018]    In any event, the invention will be better understood from the description which follows, with reference to the attached schematic drawing which, by way of example, depicts an embodiment of this handling device and illustrates the use thereof in accordance with the method of the invention. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0019]      FIG. 1  is a perspective view of a handling device on its own; 
           [0020]      FIG. 2  shows the handling device of  FIG. 1  suspended from a crane (not depicted); 
           [0021]      FIG. 3  illustrates the placing of the handling device of  FIG. 1  on a ballast block; 
           [0022]      FIG. 4  illustrates the attaching of the ballast block to the handling device of  FIG. 1 ; 
           [0023]      FIG. 5  illustrates the picking up and lifting of the ballast block using the handling device; 
           [0024]      FIG. 6  illustrates the placing of the ballast block at the top of a stack of such blocks; 
           [0025]      FIG. 7  illustrates the placing of the handling device of  FIG. 1  itself on the ballast block that has just been placed; 
           [0026]      FIG. 8  illustrates an operator accessing the placed handling device; 
           [0027]      FIG. 9  finally illustrates the detaching of the ballast block that has just been placed. 
       
    
    
     DETAILED DESCRIPTION 
       [0028]    With reference to  FIG. 1 , the handling device or handling equipment denoted overall by the reference  1  takes the form of a protective barrier  22  closed up on itself and produced in the manner of a handrail. Thus, the protective barrier  22  comprises at least one upright  2 —and in some embodiments a plurality of uprights  2 —which connects at least one lower profile section  3 —and in some embodiments a plurality of lower profile sections  3 —to at least one intermediate rail  4  and to at least one top rail  5 . Optionally, another lower profile section  3 ′ is situated on the same side as a safety bow  8 . The another lower profile section  3 ′ is advantageously bent downwards. There is no floor at the base of the protective barrier  22  in the region of the lower profile sections  3  and the another lower profile section  3 ′ which form a simple rectangular surround  24 . In other words, the protective barrier  22  remains completely open at its base. 
         [0029]    Viewed from above, the handling device  1  has a rectangular overall shape with at least one and, in some embodiments, at least one longitudinal side  6 —an in some embodiments a plurality of two or more longitudinal sides  6 —connected by at least one transverse side  7 . The transverse side  7  in some embodiments, including the one pictured, is straight. On the opposite side to this straight transverse side  7 , the handling device  1  comprises a lateral access  26 , including a safety bow  8  which extends at least to a height  28  of the protective barrier  22 . 
         [0030]    On the two longitudinal sides  6 , the uprights  2  of the protective barrier  22  are equipped with means for attaching and suspending a concrete block  14 . These means include means for attaching and suspending the concrete block  14  that is to be installed or removed from under the protective barrier  22 . These means include, for example, a respective horizontal crossmember  9  that connect the uprights  2 ; rings  10 ; cables  11 ; and hooks  12 . On each side, two rings  10  are passed around or coupled to the crossmember  9 . The rings  10 , in turn, are connected by respective cables  11  to two hooks  12 . A length  32  of the cables  11  is such that in the free state the hooks  12  are located a little lower down than the profile sections  3  of the protective barrier  22 . In other words, the hooks  12  hang below the lower profile section  3  when the hooks  12  are not connected to anything. Overall then, the handling device  1  has four hooks  12  arranged at the four corners of a rectangle, in one and the same horizontal plane. 
         [0031]    As illustrated in  FIG. 2 , the handling device  1  described hereinabove includes means for attaching and suspending the protective barrier  22  from a hook of a lifting appliance, such as a mobile crane. For example, the protective barrier  22  can be suspended from a mobile crane (not depicted) using means for attaching and suspending the protective barrier  22  that include four slings  13  connected to a hook of the mobile crane. The means for attaching and suspending the protective barrier  22  further include the rings  10  that are passed around or coupled to the crossmembers  9 . The slings  13  are themselves, in turn, attached to the rings  10 . 
         [0032]    When the handling device  1  is in use, this use being illustrated in  FIG. 3  and the following figures, the hooks  12  are designed for attaching and suspending a concrete ballast block  14  intended for ballasting a tower crane. In a known way, such ballast blocks  14  are stacked, in varying numbers, on the base chassis  15  (seen in  FIGS. 6-9 ) of the tower crane. Each ballast block  14  here comprises, on its top face  16 , four cavities  17  each one fitted with a lifting ring. Each ballast block  14  is also provided, on its edge  18 , with a rung  19  (seen in  FIGS. 5-9 ). Thus, the vertically aligned rungs  19  belonging to a number of superposed ballast blocks  14  form a ladder making it easier to gain access to the top of the stack of these ballast blocks  14 . In so far as the rung  19  of the bottom ballast block  14  is already situated a certain height above the ground, a short ladder  20  (seen in  FIGS. 6-9 ) may be installed at the base chassis  15  in order to make access to this first rung  19  easier. 
         [0033]    The use of the handling device  1  itself will now be described, considering the operation of installing an additional ballast block  14  at the top of a stack already made up of several similar ballast blocks  14 . 
         [0034]    With the additional ballast block  14  ready and waiting, in a horizontal position, the handling device  1  handled by the mobile crane through the slings  13  is first of all brought towards this block and placed on the top face  16  thereof, as shown by  FIG. 3 . It will be noted that another lower profile section  3 ′ situated on the same side as the safety bow  8  is advantageously bent downwards so as to form an end stop  30  which, in collaboration with the edge  18  of the ballast block  14 , serves to position the handling device  1 . The four cables  11  and their respective hooks  12  then come into register with the four cavities  17  of the ballast block  14 . 
         [0035]    As illustrated in  FIG. 4 , an operator can then attach the four hooks  12  to the corresponding lifting rings of the cavities  17 , the length of the cables  11  giving them enough “slack” that this attachment operation can be performed. The ballast block  14  is thus attached under the handling device  1 . 
         [0036]    Next, the mobile crane is used to lift the device  1  via the slings  13  and the handling device  1  in turn lifts the ballast block  14  that has just been attached via the cables  11 . The cables  11  become tensioned, and the ballast block  14  finds itself suspended beneath the handling device  1  as shown by  FIG. 5 . 
         [0037]    The handling device  1 , carrying with it the ballast block  14 , is moved into position by means of the mobile crane and brought towards the top of the stack already formed of several identical ballast blocks  14 , as shown by  FIG. 6 . Thus an additional ballast block  14  is placed at the top of the stack while the handling device  1  itself remains suspended “in mid-air”. 
         [0038]    As the handling device  1  continues to be lowered, this handling device  1  is itself placed on the upper top face  16  of the last ballast block  14  that has just been placed, as shown by  FIG. 7 . The safety bow  8  of the handling device  1  then comes into register or aligns with the ladder made up of the vertical alignment of rungs  19  belonging to the stacked ballast blocks  14 . 
         [0039]    As  FIG. 8  illustrates, the operator can then, using this ladder, gain access to the top of the stack of ballast blocks  14  and, more specifically, to the space situated inside the protective barrier  22  formed by the handling device  1 . On arriving at the top of the ladder, the operator is kept safe by the safety bow  8 . 
         [0040]    By remaining inside the space delimited by the protective barrier  22 , as  FIG. 9  finally shows, the operator will be able to detach the last ballast block  14  placed atop the stack of ballast blocks  14  by releasing the hooks  12  from the cavities  17 . 
         [0041]    Once the detachment operation has been performed, the operator leaves the top of the stack of ballast blocks  14  by coming back down the ladder formed by the aligned rungs  19  of these ballast blocks  14 . The freed handling device  1  can then be lifted up and taken away using the mobile crane so that it can be brought towards the next ballast block  14  that is to be placed, the same process being repeated as many times as necessary while keeping the handling device  1  suspended from the mobile crane. 
         [0042]    As will be appreciated, the same handling device  1  with protective barrier could also be used for removing the ballast blocks  14 ; it then protects the operator while the latter is attaching a ballast block  14  that is to be removed from the top of the stack. 
         [0043]    The fact that the handling device  1  is open at its bottom and therefore does not constitute a platform or a gondola prevents this handling device  1  from being hijacked or misused for any other purpose, such as a means for transporting or lifting people. 
         [0044]    As goes without saying, the invention is not restricted to the one single form of embodiment of this handling device that has been described hereinabove by way of example; on the contrary, it encompasses all alternative forms of embodiment and alternative applications that follow the same principle. Thus, in particular, structural modifications or modifications to the shape of the protective barrier or adaptation of the handling device to suit concrete blocks of a different shape or for a different purpose would not constitute departures from the scope of the invention.