PATENT ABSTRACT
Escape device that comprises a sliding box worn by each escaping person, such that the escape device is combined with an escape cable. The sliding box comprises a supporting structure; a driven wheel supported in the structure for rotation, and adapted to be in engagement with the escape cable and to be driven thereby into rotation. The rotary speed correspond to the speed of the motion of the sliding box relative to the escape cable, and therefore, corresponds to the speed of descent of the escaping person; means for measuring the rotary speed of the driven wheel and therefore, the speed of descent of the escaping person; and braking means, for slowing the rotation of the driven wheel, and therefore the speed of descent of the escaping person, whenever it is required to maintain the speed of descent within predetermined limits.

PATENT DESCRIPTION
FIELD OF THE INVENTION 
   The present invention relates to personal escaping equipment. More particularly, the invention relates to a personal escaping device for allowing persons to escape skyscrapers in emergency cases. 
   BACKGROUND OF THE INVENTION 
   As population grows all over the world, land has become more and more expensive, especially when it comes to a land under the jurisdiction of major cities. In order to allow relatively large population to occupy a given area, while maintaining reasonable costs, building tall buildings in general and sky scrappers in particular has become a necessity, and therefore, a common practice. Accordingly, tall buildings, including sky scrapers, are most typical to modern cities all over the world. However, tall buildings pose a special problem, which is related to their being high; i.e., escaping high buildings in; e.g., a case of fire, is problematic. The problem is related to several facts: (1) most aerial ladder trucks have standard collapsible fire ladders, or tower ladders, that are incapable of coping with the loftiness of high buildings. That is, a standard collapsible fire ladder may reach only limited number of floors of a tall building; (2) Even in cities where the fire brigade has very long ladders, it is most likely that the ladder truck would get stuck in a traffic jam, which is most common phenomena in modern cities. Any delay in reaching a building where a long ladder is required, might jeopardize the lives of the building residents; (3) Even if a sufficiently long ladder is brought to the site on time, the ladder could support, at a given time, only a few people because the longer the ladder, the more it tends to swing, thereby risking the lives of the people that it supports; (4) Due to the physical strength that is required when descending a long ladder, it is usually very difficult for fat or sick people to utilize such tall ladders, if at all; (5) The environmental circumstances may be so, that there might be a chance that even though long ladders are available, it would be very difficult, if at all, to handle the turntable mounting of the aerial ladder truck and put the ladder in the right place and/or on time. 
   Currently, there are several solutions for coping with the problem of people being required, or compelled, to timely evacuate tall buildings. 
   U.S. Pat. No. 6,550,576 discloses a rescue system for rescuing occupants from high floors in tall buildings. However, the rescue system of U.S. Pat. No. 6,550,576 has the drawback that each one of the rescued persons would have to use a personal cable cartridge. The problem is that the weight of a replaceable cable cartridge depends on the cable housing and also on the overall length of the cable, which, in some cases, must match the maximum height of the building. Therefore, a heavy replaceable cable cartridge would be rather difficult to handle by; e.g., old, sick and, in general, weak people. 
   U.S. Pat. No. 6,467,575 discloses a rescue system that is based on a spiral-tube. However, the spiral-tube has to be lowered from the roof of a building using crane equipment that is mounted on top of the roof of the building. 
   U.S. Pat. No. 6,467,575 discloses a controlled descent device that is based on rotatable drum that is coupled to a centrifugal brake mechanism. 
   All of the above-mentioned solutions have not provided a satisfactory solution to the problem of ensuring that residents of a tall building are able to timely and conveniently escape the tall building. 
   It is therefore an object of the present invention to provide an escape kit for ensuring that residents of a tall building would be able to escape the building timely and independently of external rescue services. 
   It is another object of the present invention to provide an inexpensive escape kit that is very easy to operate by unskilled, or inexperienced, persons. 
   Other objects and advantages of the invention will become apparent as the description proceeds. 
   SUMMARY OF THE INVENTION 
   The present invention provides a personal escaping device for allowing persons escaping high buildings in emergency cases. 
   The escape device of the present invention comprises a sliding box that is worn by the escaping person and which is combined with an escape cable. 
   The sliding box comprises:
     a) a supporting structure;   b) a driven wheel, supported in said structure, for rotation, the driven wheel being adapted to be in engagement with the escape cable and to be driven thereby into rotation with a rotary speed corresponding to the speed of the motion of the sliding box relative to the escape cable, and therefore corresponding to the speed of descent of the escaping person;   c) means for measuring said rotary speed of said driven wheel and, therefore, said speed of descent of the escaping person; and   d) Brake means for slowing the rotation of said driven wheel, and therefore the speed of descent of the escaping person, whenever required to maintain said speed of descent within predetermined limits.   

   The sliding box preferably comprises engaging means for maintaining the engagement of the driven wheel with the escape cable. The engaging means are preferably one or more wheels. 
   A harness permitting a person to carry said sliding box is also a part of the escape device of the invention. 
   At least one escape cable is attached to the building from which escape is provided, at or above the level from which the escape of persons may occur. Preferably, a number of escape cables are provided, to permit the concurrent escape of several persons, and each cable is kept in a wound-up condition, preferably in a container fixed to the building, from which condition it may be unwound when desired by an escaping person. For example, each cable may be wound on a wheel, from which it may be unwound by exerting a moderate pull on its free end. 
   The driven wheel is preferably a toothed wheel and the escape cable is preferably formed by elements shaped so as to engage the teeth of said wheel and pivoted to one another or strung on a central cable. 
   The sliding box is preferably provided with a control which receives the measurement of the speed of descent of the escaping person, compares it with a predetermined desired speed, and if it is greater than said desired speed, actuates the aforesaid brake means to reduce it to said desired speed. While said speed of descent is automatically controlled by said control device, emergency brake means are preferably provided, to be actuate by the escaping person, if required. 
   The engaging means are preferably one or more wheels. According to an aspect of the invention, the engaging means is an option. 
   Preferably, the elements of the escape cable are made of fire proof and heat-resisting materials, such as ceramic materials, or metal (e.g., light weight aluminum alloy), or a combination thereof, with or without plastic components. 
   According to an aspect of the invention, some of the elements of the escape cable are anchor elements, each of which is rigidly affixed to the escape cable for preventing excess load on the lower elements, and the spacing between each two anchor elements is predetermined according to preferred distance or preferred number of elements. 
   The most preferred structures of the escape device, and particularly of the sliding box, will now be described. 
   According to a first preferred embodiment of the present invention, the control is implemented by a hydraulic system. 
   According to a first aspect of the first preferred embodiment, the relative motion is controlled by utilizing a counteracting force that is generated for limiting the rotational speed of an oil pump that is mechanically coupled to the driven wheel. 
   Preferably, the hydraulic system comprises:
     1) Oil pump—the rotation axis of which is mechanically coupled to the rotation axis of the driven wheel, for transferring rotational motion, caused by the relative motion, from the driven wheel to the oil pump, and for providing a counteracting force, which is generated by the oil pump in response to the rotational motion, to the driven wheel, for regulating the relative motion. The oil pump includes oil inlet and oil outlet. If the oil outlet is blocked, for some reason, the axis of the oil pump immediately slows down to a speed that depends on the mechanical gap(s), which normally exists between the rotating elements inside the oil pump and the housing of these elements, through which there exists some minimum flow of oil; and   2) Hydraulic control unit—the control unit includes:
       oil inlet that is connected to the oil outlet of the oil pump and to an oil passage inside the control unit;   regulating valve, for closing/opening the oil inlet of the hydraulic control unit, for regulating the flow rate of the oil passing through the oil inlet of the control unit, and thereby, the pressure in the oil passage. The regulating valve comprises a piston that is connected to a rod movable through a sealed opening. The piston is movable inside a cylindrical housing, and its position inside the cylindrical housing is determined according to the pressure exerted by a spring on one of its sides, and a pressure exerted on its other side by oil that is contained within the cylinder, through which the piston is movable, and has a free access to the oil passage;   valve, for determining the amount and rate of oil that enters the cylindrical housing of the regulating valve;   accumulator, which comprises a piston that is connected to a rod movable through a sealed opening. The piston is movable inside a cylindrical oil reservoir, which is connected to the oil passage, and its position in the cylinder is determined according to the pressure exerted by a spring on one of its sides, and a pressure exerted on its other side by the oil contained within the oil reservoir. The rods of the accumulator and regulating valve are mechanically coupled to one another in a way that whenever the rod of the regulating valve moves to close the oil inlet of the control unit, the rod (and therefore the piston) of the accumulator is moved in a way that oil from the cylindrical oil reservoir is pushed, via the oil passage, to fill the additional volume that is created by the movement of the rod of the regulating valve. The oil reservoir allows changes in the oil passage while a relative motion is being regulated;   oil outlet that is connected to the oil inlet of the oil pump; and   adjustable valve, for allowing changing the flow rate threshold of oil that returns to the oil pump through the oil outlet of the control unit.   
       

   According to a second aspect of the first preferred embodiment, the relative motion is controlled by utilizing a brake force that is employed directly on the driven wheel by a hydraulic braking piston, and the oil pressure release (i.e., which causes the brake force to decrease) is implemented by utilization of hydraulic needle valve. 
   Preferably, the hydraulic system comprises, according to the second aspect:
     1) Oil pump—the rotation axis of which is mechanically coupled to the rotation axis of the driven wheel, for transferring rotational motion caused by the relative motion from the driven wheel to the oil pump. The oil pump includes oil inlet and oil outlet;   2) Hydraulic control unit—the control unit includes:
       oil inlet that is connected to the oil outlet of the oil pump and to an oil passage inside the hydraulic control unit; and   Oil outlet that is connected to the oil inlet of the oil pump and to an oil reservoir inside the hydraulic unit;   hydraulic needle valve, for closing/opening the oil passage inside the hydraulic control unit, for regulating the flow rate of the oil passing between the oil inlet and the oil outlet of the control unit, and thereby, the pressure in the oil passage. The hydraulic needle valve comprises a piston that is connected to a needle-like rod that is movable through a sealed opening. The piston is movable inside a cylindrical housing of the hydraulic needle valve, and its position inside the cylindrical housing is determined according to the pressure exerted by a spring on one of its sides, and a pressure exerted on its other side by oil that is contained within the cylinder, through which the piston is movable, and has a free access to the oil passage;   Braking cylinder, which comprises a piston that is connected to a rod movable through a sealed opening. The position of the piston is determined according to a first force exerted on one side of the piston by a spring, and a second force that counteracts the first force and is exerted on the other side of the piston by the oil pressure existing in the oil passage. One end of the movable rod is connected to the piston, and the other end of the rod is connected to a rubbing strip. The piston of the braking cylinder is pushed outwards (i.e., with respect to the hydraulic control unit) whenever the pressure in the oil passage increases as a result of an increase in the relative motion, thereby pushing said rubbing strip against the driven wheel, for providing counteracting, or braking, force that will limit the increase in the relative motion. The pressure increase in the oil passage pushes outwards also the piston of the hydraulic needle valve, thereby causing the oil passage between the oil inlet and oil outlet to open, for allowing reducing the relatively high pressure in the oil passage, after which the braking force, which is employed on the driven wheel by the rubbing strip, is reduced, or weakened; and   Accumulator, which comprises a piston that is connected to a rod movable through a sealed opening. The piston is movable inside a cylindrical oil reservoir, which is connected to the oil outlet end of the hydraulic control unit, and its position in the cylinder is determined according to the pressure exerted by a spring on one of its sides, and a pressure exerted on its other side by the oil contained within the oil reservoir.   
       

   According to a second preferred embodiment of the present invention, the control is implemented by an electrical system, in which the relative motion is regulated by a counteracting force that is generated by use of electrical motor. 
   Preferably, the electrical system comprises:
     1) Speed sensor, for monitoring the rotational speed of the driven wheel, and thereby, the descend speed. The speed sensor is capable of generating an electrical signal that represents the rotational speed (i.e., rpm) of the driven wheel;   2) Electric motor, on the rotation axis of which is coupled the driven wheel, and in which a first magnetic field is induced by the rotation of the driven wheel. The aforesaid rotation and induced current represent the descend speed;   3) Electronic control unit, for accepting the electrical signals and outputting a corresponding electrical signal to the electric motor in a way that the latter corresponding signal generates in the electric motor a second magnetic field that essentially counteracts the first magnetic field, thereby providing the required counteracting force; and   4) Battery pack, for powering the speed sensor, electric control unit, and for providing the electrical signal required for generation of the second magnetic field.   

   According to a third preferred embodiment of the present invention, the counteracting force generating system is an electromechanical system, in which the relative motion is controlled by utilizing a brake force that is employed directly on the driven wheel by a hydraulic braking piston, and the oil pressure release (i.e., which causes the brake force to decrease), is implemented by utilization of electro-mechanical needle valve. 
   Preferably, the electromechanical brake system comprises:
     1) Speed sensor, for monitoring the rotational speed of the driven wheel, and thereby, the descend speed. The speed sensor is capable of generating a electrical signal that represents the rotational speed (i.e., rpm) of the driven wheel;   2) Oil pump—the rotation axis of which is mechanically coupled to the rotation axis of the driven wheel, for transferring rotational motion caused by the relative motion from the driven wheel to the oil pump. The oil pump includes oil inlet and oil outlet;   3) Hydraulic control unit—the hydraulic control unit includes:
       oil inlet that is connected to the oil outlet of the oil pump and to an oil passage inside the hydraulic control unit;   Oil outlet that is connected to the oil inlet of the oil pump and to an oil reservoir inside the hydraulic unit;   Electro-mechanical needle valve, for closing/opening the oil passage inside the hydraulic control unit, for regulating the flow rate of the oil passing between the oil inlet and the oil outlet of the hydraulic control unit, and thereby, the pressure in the oil passage. The electromechanical needle valve comprises an electrical portion capable of translating electric signals into physical positioning of a needle-like rod that is movable through a sealed opening;   Braking cylinder, which comprises a piston that is connected to a rod movable through a sealed opening. The position of the piston is determined according to a first force exerted on one side of the piston by a spring, and a second force that (opposes the first force and) is exerted on the other side of the piston by the oil pressure existing in the oil passage. One end of the movable rod is connected to the piston, and the other end of the rod is connected to a rubbing strip. The piston of the braking cylinder is pushed outwards (i.e., with respect to the hydraulic control unit) whenever the pressure in the oil passage increases as a result of an increase in the relative motion, for providing counteracting force that will limit the increase in the relative motion. Whenever required, the passage between the oil inlet and oil outlet is opened, by retracting the electromechanical needle valve, for allowing reducing relatively high pressure in the oil passage, after which the braking force, which is employed on the driven wheel by the rubbing strip, will ease, or cease;   Accumulator, which comprises a piston that is connected to a rod movable through a sealed opening. The piston is movable inside a cylindrical oil reservoir, which is connected to the oil outlet end of the hydraulic control unit, and its position in the cylinder is determined according to the pressure exerted by a spring on one of its sides, and a pressure exerted on its other side by the oil contained within the oil reservoir. The oil reservoir allows changes in the oil passage while a relative motion is being regulated;   
       4) Electronic control unit, for accepting the electrical signals and outputting a corresponding signal to the electromechanical needle valve, for regulating the braking force employed on the driven wheel; and   5) Battery pack, for powering the speed sensor, electronic control unit and the electromechanical needle valve.   

   According to an aspect of the present invention, the rubbing strip is further connected to a mechanical emergency braking arrangement, which comprises a screw-like rod, handle, nut, bearing, lever, pivot and mechanical arrangement that keeps the screw-like rod in a fixed longitudinal position with respect to the sliding box. Screw-like rod is screwable through the nut, to which a bearing is mechanically affixed. The screw-like rod is intended to be rotated by a person utilizing the sliding box for descending, by operating the handle. When the screw-like rod is rotated in the corresponding direction, nut, and therefore bearing that is affixed thereto, advance, along the screw-like rod, such that the bearing slides on the lever. Since the right end of the lever (i.e., according to this example) is rotatable around the fixed pivot, the movement of the bearing to the left-hand side direction causes the rubbing strip, which is affixed to the distal end of the lever, to push one side of the driven wheel, and, thereby, to provide a brake force for slowing the driven wheel, or, if so required, for slowing the driven wheel until the driven wheel, and therefore, the sliding box, is completely stopped. 
   Optionally, moving bearing to the extreme left-hand side of lever results in sustaining some predetermined minimal down-motion of the sliding box with respect to the escape cable. 
   According to another preferred embodiment of the present invention, there is provided means for connecting a descending person to an escape cable, and the sliding boxes is rigidly affixed to strategic place, for example, to an outer side of a wall of a building, and the escape cable is allowed to slide down along the wall of the building. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The above and other characteristics and advantages of the invention will be better understood through the following illustrative and non-limitative detailed description of preferred embodiments thereof, with reference to the appended drawings, wherein: 
       FIG. 1  schematically illustrates a person wearing a flexible harness, according to a preferred embodiment of the present invention; 
       FIGS. 2   a  to  2   c  schematically illustrate the basic steps of escaping a building, according to a preferred embodiment of the present invention; 
       FIG. 3  shows the transmission section of the sliding box, according to a preferred embodiment of the present invention; 
       FIGS. 4   a  and  4   b  show sketches of the cable and its dimensions, according to an aspect of the present invention; 
       FIGS. 5   a  and  5   b  show the sliding box in its “open” and “close” state, respectively, according to a preferred embodiment of the present invention; 
       FIG. 5   c  shows an external view of the sliding box, according to a preferred embodiment of the present invention; 
       FIGS. 6   a  and  6   b  show in separate the control unit of the sliding box and a side view thereof, respectively, according to a preferred embodiment of the present invention; and 
       FIG. 6   c  schematically illustrates the inner components of the control unit, according to a preferred embodiment of the present invention; 
       FIGS. 7   a  and  7   b  show mechanical emergency brake system, according to an embodiment of the present invention; 
       FIGS. 8   a  and  8   b  show in more details the internal structure of the mechanical speed control unit  71  shown in  FIGS. 7   a  and  7   b;    
       FIGS. 9   a  and  9   b  show a manually-operable mechanical emergency braking arrangement, according to an embodiment of the present invention; 
       FIGS. 10   a  to  10   c  show a sliding box, according to another preferred embodiment of the present invention; 
       FIGS. 11   a  to  11   c  show an electromechanical sliding box, according to another preferred embodiment of the present invention; 
       FIGS. 12   a  and  12   b  show in more details the internal structure of the electromechanical speed control unit shown in  FIG. 11 ; and 
       FIG. 13  shows the proportion between a person&#39;s hand palm and an exemplary sliding box and escape cable, according to the present invention. 
   

   DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     FIG. 1  schematically illustrates a person wearing an escape kit that comprises a flexible harness and a sliding box, according to a preferred embodiment of the invention. The escape kit comprises harness  11 , which person  10  is wearing, and sliding box  12 , which is firmly affixed to harness  11 . Optionally, the escape kit may comprise helmet  13 , which may, or may not, carry a spotlight/flashlight. Harness  11 , which is constructed from several belts is capable of supporting at least 250 Kgs. Sliding box  12  includes, on its external face, several rounded wheels  12 / 1  to  12 / 4 , for allowing sliding box  12  to slide down along a wall (e.g., of a building). 
     FIGS. 2   a  to  2   c  schematically illustrate the basic steps of escaping a building, according to a preferred embodiment of the invention. Escape cable  21  is normally (i.e., when not in use) winded over winch drum ( 22 ), ready to be used in cases of emergencies. A first end of escape cable  21  is firmly affixed to winch  22 , and the second end of winch  22  is a throwing end that is intended to be thrown by a person outside an escaping window or hatch. Winch ( 22 ), together with the escape cable  21  winded there upon, could be hidden inside some sort of a closet (generally indicated by reference numeral  22 / 1 ), for aesthetic purpose, and its location could be predetermined according to preferred strategy. For example, the location of winch  22  could be chosen in a way that escape cable  21  would pass as close to as many windows of the building as possible (that is, on its way down). Of course, any aesthetic arrangement of winch  22  must allow easy access to, and convenient operation of, escape cable ( 21 ). Several winches, such as winch  22 , and several escape cables such as cable  21  might be located in several strategic locations with respect to a building, for ensuring, in cases of emergencies, safe and fast rescue of the building residents. 
   Referring to  FIG. 2   a , after the escaping person  10  wears its escape kit, which comprise at least harness  11  and sliding box  12 , escaping person  10  approaches closet  22 / 1 , opens the closet, grabs the throwing end of escape cable  21 , and starts unwinding escape cable  21  from winch  22 . Then, person  10  approaches the escape window, or hatch, and continues to unwind escape cable  21  through the escape window/hatch, until escape cable  21  is completely unwounded. Next (see  FIG. 2   b ), person  10  opens sliding box  12 , inserts escape cable  21  into sliding box  12 , locks and secures sliding box  12  with the escape cable inside, and moves his body beyond the threshold of the escape window/hatch. Then, person  10  turns around so that his face is against the escape window and starts sliding down (see  FIG. 2   c ). Of course, additional persons might utilize escape cable  21  for escaping. For example, woman  10 / 1  could fetch her escape kit from closet  14 , and perform the required escaping procedure, except that in the cases of other escaping persons, there would be no need to uncoil escape cable  21 , as this cable was previously uncoiled by the first escaping person. One or more closets, such as closet  14 , could be deployed in every floor of a building. Escape cable  21  could be coiled again, if desired, by operating winch  22 , provided, of course, that the emergency case no longer exists and the conditions (i.e., of the building, escape cable, winch, etc.) allow it. 
     FIG. 3  depicts one cross section of the sliding box, according to one preferred embodiment of the invention. Sliding box  12  comprises, in general, two sections. One section, which is shown in  FIG. 3 , includes engaging means for keeping escape cable  21  in a velocity-controlling route within sliding box  12 , for allowing sensing the relative velocity of sliding box  12  with respect to escape cable  21  (i.e., sensing the descending rate of sliding box  12 ). The function of guiding elements  34 / 1  and  34 / 2  is to allow safe/smooth entry and exit of cable  21  into/from sliding box  12 , respectively. The function of main pulley  31 , which is, according to this example, the driven wheel, is sensing the relative velocity between sliding box  12  and cable  21 , for allowing a second section of sliding box  12  (not shown) to generate a counter pressure, or momentum, in response to the sensed velocity difference, for controlling the velocity of sliding box  12  while descending along cable  21 . Pulley  31  is a toothed wheel that includes a plurality of ‘teeth’ that form a contour line that essentially counter matches the unique shape/design of the elements of escape cable  21  shown in  FIGS. 4   a  and  4   b . The dimensions of the teeth and the spacing therebetween provide adequate coupling between pulley  31  and escape cable  21  even in cases where the distance between adjacent connecting elements  40  might slightly change for any reason, for example when a heavy person slides down along escape cable  21  exerting considerable force on the connecting elements. The function of pulleys  32  and  33  is to assure engagement of escape cable  21  to main pulley  31 . Preferably, there are two secondary pulleys ( 32  and  33 ). However, any suitable number of secondary pulleys, or some other engaging arrangement (i.e., between escape cable  21  and the driven wheel, in this case main pulley  31 ), might be utilized instead. According to an aspect of the present invention, the secondary pulleys are optional. 
   Referring to  FIG. 4   a , cable  21  (only a portion of it is shown) comprises a plurality of elements, such as element  40 , and flexible cable  44 . Each one of the elements has a central cylindrical bore hole through which flexible cable  44  passes. Each one of the elements includes a first cylinder  42  and a second cylinder  41  which has essentially the shape of a disc. First and second cylinders  41  and  42  have a common longitudinal axis  44 / 1 . Cylinder  41  has a diameter larger than that of the cylinder  42 , and is located essentially in the central portion of the perimeter of cylinder  42 . One end of cylinder  42  has essentially the shape of a convex  45 , and the opposite end of cylinder  42  has essentially the shape of a concave  43 . The convex of each one of a elements is brought in contact with the concave of the next element, and so on, and the concave and convex portions of the elements allow utilizing the flexibility of escape cable  21 , which might be helpful also in cases where an escaping person whishes to bypass obstacles while descending from a high building The function of cylinders  41  is to prevent any sliding between the sliding box  12  and the escape cable  21 , and relay the descending velocity to toothed wheel  31  and wheels  32  and  33  (see  FIG. 3 ), thereby allowing sliding box  12  to control its descend rate along escape cable  21 . 
   Whenever escape cable  21  is essentially in vertical position (i.e., as it would be normally the case when utilized for escaping from tall places), each one of elements  40  exerts pressure on the elements below it. The resulting pressure on specific element  40  will be, therefore, a function of the accumulative mass of the elements  40  above that specific element, and of the weight of the sliding box and sliding person. Consequently, the lowermost elements of the escape cable will be under high pressure, which might result in rupturing the escape cable. 
   In order to avoid exerting too much pressure on the lowermost elements of escape cable  21 , an element  46  (herein “anchor element”) will be firmly affixed to the flexible cable  44  ( FIG. 4   a ) each predefined distance or number of elements. For example, one element could be firmly affixed to the cable each five meters, or each 30 elements. This way, the maximum pressure that would be exerted on an element just above an anchor element will be limited to the pressure exerted by the remaining elements existing between the corresponding anchor elements, plus the weight of the sliding box and person. Referring to the example shown in  FIG. 4   c , an anchor element  46  is affixed to flexible cable  44  each three ‘ordinary’ elements  40 . The elements  40  allow rolling the escape cable on a roller, or cylindrical drum, the diameter of which could be, e.g., 0.6 meter, for allowing convenient and aesthetic storage of the escape cable inside a closet whenever the escape cable is not in use, and fast deployment, or unwinding, of the escape cable in cases of emergencies. The closet could be conveniently installed at a desirable location on the preferred floor. 
   Referring to  FIGS. 4   b  and  13 , an exemplary dimensions of the connecting elements are 1=18 millimeters (‘l’—length of individual element), and d=15 millimeters (‘d’—the diameter of the larger cylinder  41 ). These dimensions can change from one type of a sliding box to another. 
     FIGS. 5   a  and  5   b  schematically illustrate sliding box  12  in “open” and “closed” positions, respectively. In  FIG. 5   a , sliding box  12  is opened in a way that main pulley  31  (i.e., the driven wheel) is separated from secondary pulleys  32  and  33  (pulley  33  not shown) for making room for cable  21 , which is arranged therebetween as shown in  FIG. 3 . After placing cable  21  between the pulleys  31  and  32 / 33 , sliding box  12  is then closed, thereby securing the passage of cable  21  therein; i.e., by pressing cable  21  against main pulley  31  by secondary pulleys  32  and  33  ( FIG. 5   b ). Reference numeral  56  denotes a pivot axis around which sliding box  12  is opened/closed. Reference numeral  57  denotes the supporting structure to which the driven wheel (i.e., according to this example main pulley  31 ), the engaging means (i.e., according to this example secondary pulleys  32  and  33 ), and the means for measuring the rotary speed of the driven wheel and providing the required brake force for slowing the rotation of the driven wheel (i.e., according to this example oil pump  52  and hydraulic control unit  54 ) are rigidly affixed. 
   Referring to  FIGS. 5   b  and  5   c , whenever sliding box  12  descends along cable  21 , pulleys  31  to  33  rotate at an angular velocity corresponding to the descending rate. Pulley  31  is mechanically coupled to oil pump  52  (i.e., by means of driveshaft  51 ) that is part of the hydraulic system that is contained within sliding box  12 . Therefore, the rotational movement of pulley  31  is transferred to the axis of a “toothed wheel” type oil pump  52 . The rate of the angular velocity of the oil pump, and therefore, the angular velocity of main pulley  31  (and also the descend rate), is controlled by (“weight/velocity”) hydraulic control unit  54 , which regulates the oil circulation in the hydraulic system. Hydraulic control unit  54  includes oil inlet  55 / 4 , which is connected by means of pipe  53 / 1  to the oil outlet of oil pump  52 , and oil outlet  55 / 5 , which is connected by means of pipe  53 / 2  to the oil inlet of oil pump  52 . 
   The rate of oil flow, which enters control unit  54  through oil inlet  55 / 4 , is adjusted by a regulating valve that is implemented by an oil piston arrangement, in a way that is described herein below in connection with  FIG. 6   c . Likewise, the oil flow rate that returns to oil pump  52  (i.e., from outlet  55 / 5 ) is controlled by an adjustable needle valve  55 / 2 . Reference numeral  55 / 1  denotes an oil accumulator, the task of which is to compensate for variations in the oil pressure within the (closed) hydraulic system; the pressure variations being caused by changes in the angular momentum that is exerted on the axis of oil pump  52  as a result of the descending sliding box  12 . Control unit  54  includes additional needle valve  55 / 3  for regulating the extent of the aforesaid compensation (i.e., of oil pressure). 
     FIG. 6   a  shows a general and isolated view of the control unit shown in  FIG. 5   b , and  FIG. 6   b  shows a side view of control unit  54 . 
     FIG. 6   c  is an A-A cross-section of  FIG. 6   b . Oil accumulator  55 / 1  comprises piston  66  to which piston rod  64  is connected, member  64 / 1 , through which piston rode  64  is freely slidable, spring  65  and oil reservoir  67 . The position of piston  66  (i.e., within the cylinder in which it is moveable), at any given time, depends on the mechanical characteristics of spring  65 , on the area of piston  66  and on the instantaneous oil pressure residing within the oil reservoir ( 67 ). Put otherwise, the final position of piston  66  will be such that equilibrium will exist between the force exerted by spring  65  on one side of piston  66  and the force exerted by the oil pressure on the other side of piston  66 . 
   Likewise, regulating valve  61  comprises piston  63  to which piston rod  68  is connected, member  68 / 1 , through which piston rod  68  is freely moveable, spring  65 / 2  and oil reservoir  67 / 2 . The position of piston  63  (i.e., within the cylinder in which it is moveable), at any given time, depends on the mechanical characteristics of spring  65 / 2 , on the area of piston  63  and on the instantaneous oil pressure residing within the oil reservoir ( 67 / 2 ). Put otherwise, the final position of piston  63  will be such that an equilibrium will exist between the force exerted by spring  65 / 2  on one side of piston  63  and the force exerted by the oil pressure on the other side of piston  63 . 
   The task of springs  65  and  65 / 2  is to keep pistons  66  and  63 , respectively, at some initial position whenever there is no pressure in oil passage  62  (i.e., oil pump  52  is inactive). 
   The way of controlling the descending rate will be described immediately below. While sliding box  12  is at rest (i.e., no rotational moment is applied to pulley  31 ), there is no oil circulation in the system (i.e., oil pump  52  is at rest) and no oil pressure is built in oil passage  62  inside control unit  54 . However, as a person wearing a sliding box such as sliding box  12  starts descending along cable  21 , pulley  31  starts rotating and the rotational moment is transferred to oil pump  52  ( FIG. 5   b  or  5   c ), which, in turn, starts pushing oil into control unit  54  through inlet  55 / 4  of control unit  54 . Needle valve  55 / 2  is adjusted such that a the oil flow rate through inlet valve  55 / 4  is higher than the oil flow rate through outlet valve  55 / 5 . Consequently, the pressure in oil passage  62  increases, causing piston  63  to move towards inlet  55 / 4 , for reducing the oil flow rate through inlet  55 / 4 . Since the hydraulic system is a closed system (i.e., there is a fixed amount of oil in the hydraulic system), enlarging volume  67 / 2  is allowed because the additional oil in volume  67 / 2  comes from volume  67 . The latter feature is possible, because rods  64  and  68  are mechanically coupled to one another in a way that each “up” movement of piston  63  is followed by a counter “down” movement of piston  66 , and vice versa. This way, every increase in volume  67 / 2  is followed by a corresponding decrease in the volume  67 , and vice versa, meaning that oil is exchanged between volume  67  to volume  67 / 2 . 
   At the same time the increased oil pressure in passage  62  causes piston  63  to move towards inlet  55 / 4  for reducing the flow rate of oil coming from oil pump  52 , oil pump  52  continues sucking oil through outlet  55 / 5 , and, therefore, the pressure in oil passage  62  decreases, thereby causing piston  63  to open inlet  55 / 4  (i.e., by use of spring  65 / 2 ) and oil pump  52  to inject oil there through at an increased flow rate, which results in an increase in the pressure in oil passage  62 . As long as force is exerted on oil pump  52  by pulley  31 , piston  63  will repetitively close and open inlet  55 / 4 , in a cyclic manner, wherein each cycle includes one “open” (or “closed”) state (i.e., of inlet  55 / 4 ) that is followed by one “close” (or “open”) state. 
   The heavier the descending person, the more frequent inlet  55 / 4  will open and close, because the force exerted on oil pump  52  will be greater, causing a rapid increase in the oil pressure in oil passage  62 , which will cause, in turn, inlet  55 / 4  to rapidly close. The moment inlet  55 / 4  closes, there will be a rapid decrease in the oil pressure in oil passage  62 , which will cause inlet  55 / 4  to rapidly open, and so on. The changes in the increase and decrease rates in the pressure in oil passage  62  (i.e., in response to changes in the descending person) allow, therefore, maintaining essentially the same descending velocity, regardless of the weight of the descending person. Put otherwise, load changes on pulley  31  will be translated into corresponding changes in the frequency of the “open” and “close” states of inlet  55 / 4 . 
   Of course, the descending velocity may be set as desired (e.g., 2 meter/second), by adjusting needle valves  55 / 2  and  55 / 3 , as well as by using springs  65  and  65 / 2  with different mechanical characteristics, and/or by changing the absolute diameter of pistons  63  and  66  or the ratio therebetween. Valves  55 / 2  and  55 / 3  are utilized only for testing and calibration purposes, after which they are permanently set. 
   Of course, for some cases sliding box  12  could be fixed to a point of a building, or elsewhere, and the cable sliding therein, though the above described embodiment would be preferable. 
     FIGS. 7   a  and  7   b  schematically illustrate a sliding box with automatic hydraulic brake system, according to one preferred embodiment of the present invention. Whenever pulley  31  rotates, oil pump  52  pushes oil to oil inlet  55 / 4  of speed control unit  71  (i.e., via pipe  71 / 1 ). Oil returns from outlet  55 / 5  of speed control unit  71  to oil pump  52  (i.e., via pipe  71 / 2 ). 
     FIGS. 8   a  and  8   b  show in more details the internal structure of the mechanical speed control unit  71  shown in  FIGS. 7   a  and  7   b . Oil is pushed by oil pump  52  ( FIG. 7   a , for example) through inlet  55 / 4 . Needle valve  81  closes oil outlet  55 / 5 , in which case a pressure is formed, by the oil that is pushed through inlet  55 / 4 , which causes piston  84  to move upwards, thereby moving also a rod, the end  83  of which exerts braking force on pulley  31  (i.e., by applying friction to pulley  31 ) for slowing down the rotational speed of pulley  31 . With the increasing pressure inside oil passage  82 , and after piston  85  applies friction to pulley  31 , there is a pressure threshold above which the oil pressure inside oil passage  82  overcomes the force exerted on piston  86 / 2  by spring  86 / 1 . Therefore, piston  86 / 2  starts moving downwards, thereby opening outlet  55 / 5  and releasing some of the oil pressure locked inside oil passage  82 . As a result of the decreasing pressure in oil passage  82 , friction end  83  retracts, and the braking friction applied on pulley  31  is removed. The oil pressure decreases in the oil passage  82  until it gets lower than the force exerted on piston  86 / 2  by spring  86 / 1 , in which case springs  86 / 1  overcomes the aforesaid oil pressure and moves, once again, piston  86 / 2  upwards, so that needle valve  81  closes again oil outlet  55 / 5 , after which the oil pressure in oil passage  82  increases again, thereby causing friction end  83  to apply, again, a friction against pulley  31 , and so on. In other words, pressure is built up in oil passage  82  as a result of an increase in the rotational speed (RPM) of the oil pump, caused by increased relative motion between the escape cable ( 21 ) and the sliding box ( 12 ), and the built up oil pressure generates a braking moment that is exerted on the main pulley ( 31 ) for reducing the aforesaid relative motion, after which the oil pressure in oil passage  82  decreases. The decrease in the oil pressure in oil passage  82  causes releasing of at least some of the aforesaid braking moment, causing, thereby, to the relative motion to increase again, and so on. Oil accumulator  87  provides oil for the oil passage  88  in order to prevent oil passage  88  from being in a state of vacuum. 
     FIGS. 9   a  and  9   b  schematically illustrate a sliding box with manually-operable mechanical emergency brakes, according to an aspect of the present invention. Under normal operating conditions (i.e., a person descends at a regulated velocity), the regulated velocity is automatically maintained by pushing friction strip  96  towards one face of pulley  31 , and causing friction strip  96  to retreat from pulley  31 , at intervals. Friction strip  96  is pushed and retreated by utilizing a mechanical arrangement such as the one shown in  FIG. 8   a  (i.e., rod  83 ). However, an external intervening means is provided in the sliding box, which allows to manually bypass the automatic mode of operation of the sliding box in emergency cases, or whenever a descending person wishes to slow down his descend. The intervening means operates in the following way: screw-like rod  92  is screwable through nut  93 , to which bearing  94  is mechanically affixed. Screw-like rod  92  is rotatable by a person wearing the harness and sliding box  12  for descending, by operating handle  91 . When screw-like rod  92  is rotated in one direction, screw  93  and bearing  94 , which is affixed thereto, advance along the screw-like rod  92 , in a way that bearing  94  slides on lever  95 . Since the right end of lever  95  (i.e., according to this example) is rotatable around fixed pivot  97 , the movement of bearing  94  to the left-hand side direction (as seen in the drawing) causes friction strip  96 , which is affixed to the distal end of lever  95 , to be pushed against one face of pulley  31 , and, thereby, providing braking moment for slowing down pulley  31 , and maintaining a preferred descending velocity of; e.g., 1 meter per second. 
     FIGS. 10   a  to  10   c  show a sliding box, according to another preferred embodiment of the present invention. Sliding box  12  includes velocity sensor  101 , the function of which is to measure the rotational speed of pulley  31 , by generating an electrical signal that represents the rotational speed. Velocity sensor  101  could be, for example, a magnetic pickup sensor, such as any of the magnetic pickup sensors from the NJ series manufactured by Pepperl &amp; Fuchs (P&amp;F), which generates a train of pulses having a frequency that linearly depends on the rotational speed of pulley  31 . The train of pulses can be forwarded to control unit  104 , which includes electronic circuitry for translating the train of pulses back into rotational speed. Another function of the electronic circuitry contained within electrical control unit  104  is to output electrical control signal to electric motor  102  for generating a magnetic moment that counteracts the mechanical moment exerted on pulley  31  by the descending sliding box  12 . The rotational speed, as measured by speed sensor  101 , is compared to a (“set-point”) rotational speed that corresponds to a wanted (i.e., preferred) descending rate of sliding box  12 . The higher the measured rotational speed, with respect to the preferred (i.e., set-point) rotational speed, the stronger is the generated moment, and therefore, the braking force. This way, it is possible to obtain essentially an accurate and uniform sliding rate irrespective of the weight of the descending person. 
   According to an aspect of the present invention, the control unit includes setting means for allowing a descending person to change the preferred descending rate, by changing the set-point rotational speed of pulley  31 . According to an aspect of the present invention, the setting means includes a scale that is calibrated to descending rate (e.g., 0.5, 1.0 and 3.0 meters/second). 
   Battery pack  103  provides the electric power required by the electronic circuitry inside control unit  104  and by electric motor  102 . Utilizing an electric motor for controlling the descend rate allows obtaining a more accurate and stable/fixed descending speed, comparing to the above-mentioned hydraulic solutions. 
     FIGS. 11   a  to  11   c  show an electromechanical sliding box, according to another preferred embodiment of the present invention. According to this embodiment, the mechanical portion of sliding box  12  resembles to the mechanical portion of sliding box  12  shown in  FIGS. 7   a  and  7   b , and  FIGS. 8   a  and  8   b , as it includes oil pump  52 , hydraulic control unit  115  and related oil pipes (i.e.,  71 / 1  and  71 / 2 ). In addition, according to this embodiment, the electrical portion of sliding box  12  resembles to the electrical portion of sliding box  12  shown in  FIG. 10 , as it also includes speed sensor  101  and electronic control unit  104 . However, unlike in the embodiment shown in  FIG. 10 , according to this embodiment the electronic control unit (i.e., electronic control unit  101 ) receives the picked-up train of pulses, which corresponds to the descend speed, and outputs a corresponding controlling electric signal that is forwarded to the hydraulic portion for regulating the descend speed. 
     FIGS. 12   a  and  12   b  show in more details the internal structure of the electromechanical speed control unit shown in  FIG. 11 . The functionality of speed control unit  115  is essentially the same as the functionality of speed control unit  71  (see, for example,  FIG. 8   a ), except that in speed control unit  115 , the needle valve  81  is operated electrically (i.e., by electromechanical means  121 ) rather than by hydraulic piston that is movable in accordance with an oil pressure. 
   The controlling electric signal, which is outputted by electronic control unit  114  ( FIG. 11 ), moves the hydraulic needle valve  81  so as to open/close the oil passage between inlet  55 / 4  and outlet  55 / 5 . When the descending speed is zero, oil pump  52  ( FIG. 11 ) does not circulate oil in the hydraulic system, needle valve  81  is in “retracted” position and a free passage of oil is allowed between oil inlet  55 / 4  and outlet  55 / 5 . As the descend speed starts to increase, oil pump  52  starts circulating oil; i.e., oil is pushed by the oil pump through inlet  55 / 4  and oil returns to the oil pump through outlet  55 / 5 . However, along side with the increase of the descend speed, electronic control unit  114  ( FIG. 11 ) outputs an electric signal to electromechanical means  121 , which moves needle valve  81  so as to partially close the oil passage between inlet  55 / 4  and outlet  55 / 5 . As a result of the partial closure of the aforesaid oil passage, the oil pressure in oil passage  82  increases, and piston  84  moves upwards, so as to cause friction end  83  to be pushed against pulley  31 , for employing a counteracting force there against, in order to prevent pulley  31  from further increasing its rotational speed. The more the descend speed tends to increase (i.e., due to gravitational force and a descending person having heavier weight), the more the needle valve ( 81 ) will close the oil passage between inlet  55 / 4  and outlet  55 / 5 , and the higher pressure will be built in oil passage  82 , which will result in a stronger counteracting (i.e., braking) force that is employed on pulley  31 . 
     FIG. 13  shows the proportion between an exemplary sliding box and cable and a person&#39;s hand, according to the present invention. Hand  131  is shown gripping escape cable  21  (i.e., only for illustrating purpose), which is shown after having been inserted into sliding box  12 . Sliding box  12  includes projecting “eyes”  133  (only three are shown), which are intended to be connected to a harness that the person has to wear (see harness  11  in, e.g.,  FIG. 11 ). In order to insert escape cable  21  into sliding box  12 , the person opened sliding box  12  around pivot axis  56  (see also, for example,  FIG. 5   a ). Reference numerals  134  and  135  denote securing elements, the function of which is securing sliding box  12  in its close position, for preventing unintentional escaping of escape cable  21  from sliding box  12 . When a person utilizes sliding box  12  to descend, securing elements  134  and  135  face the wall of the building (i.e., away from the descending person), in order to ensure that the descending person does not accidentally (e.g., out of panic) opens sliding box  12 . Wheels  136  prevent friction between the external side of the wall of the building and the sliding box. Wheels  136  can be of any suitable size. Wheels  136  can be replaced by any other friction-preventing, or friction-protecting, means. For example, a friction-protecting means can be an arcuated plate, which could be made of metal, plastics, etc. 
   The sliding box shown in  FIG. 13  is only a prototype, and the commercial sliding box is intended to be as small as half the size of the prototype sliding box. 
   While some embodiments of the invention have been described by way of illustration, it will be apparent that the invention can be carried into practice with many modifications, variations and adaptations, and with the use of numerous equivalents or alternative solutions that are within the scope of persons skilled in the art, without departing from the spirit of the invention or exceeding the scope of the claims.