Patent Publication Number: US-2016245349-A1

Title: Braking mechanism and load support mechanism

Description:
BACKGROUND OF THE INVENTION 
     1. Technical Field 
     The present invention relates to a braking mechanism for controlling movement of an object. In particular, the present invention relates to a braking mechanism that is suitably used in a load support mechanism that supports a target article at a desired position in such a way as to be able to move the target article, as well as to the load support mechanism. 
     2. Description of the Related Art 
     In general, a support mechanism that supports various articles, such as a computer, a television monitor device, a top plate of an OA desk or work table, and a heavy object, at a desired height position in such a way as to be able to move the articles up and down preferably includes a braking mechanism to carry out or cancel braking of movement of the articles, thereby ensuring safety at the time of use. For example, an elevator that lifts a car up and down by winching a rope using a winch sheave includes a brake device; the brake device presses a brake shoe against a braking surface of the winch sheave using a braking spring to stop the car, and separates the brake shoe from the braking surface using an electromagnetic coil to start lifting the car up or down (Such a device is disclosed in Patent Document 1, for example). 
     The brake device disclosed in Patent Document 1 is designed to mitigate, when the car is braked at the time of emergency or is suddenly stopped, the shock caused by stopping the car is weakened by controlling a braking torque applied to the winch sheave. It is considered that, to start lifting the car up or down, the elevator is designed to cancel the braking of the brake device by energizing the electromagnetic coil while activating the winch sheave. 
     PRIOR ART DOCUMENT 
     Patent Document 
     
         
         [Patent Document 1] Japanese Patent Application Publication No. 2010-105795 
       
    
     SUMMARY OF THE INVENTION 
     In conventional brake devices, such as the one disclosed in Patent Document 1, the repeated shift of a to-be-braked body between a moving state and a braked state causes a braking force to weaken, as a brake shoe, especially only a portion being pressed by the brake shoe, wears out earlier due to friction each time it is used. In particular, in the case of a device for moving up or down a heavy object, an article might not stop at a predetermined position even when a braking action is carried out. 
     The object of the present invention is to provide a braking mechanism that prevents a decrease in the braking force with a pressing position, which exerts the strongest braking force on the to-be-braked object, moving it to a side where the braking force is increased, even when a brake portion worn out after years of being used. 
     A brake mechanism of the present invention includes a brake portion and a to-be braked portion that relatively move in a first direction and a second direction, which is opposite to the first direction, wherein the brake portion includes a brake surface that is disposed in such a way as to face the to-be braked portion, and a brake arm having a fulcrum that can turn between a pressing position, where the brake surface brakes the to-be-braked portion, and a cancellation position, where the pressing is cancelled, and the brake surface is disposed in such a way as to be inclined so that, at a time of braking, a pressing force by the brake surface against the to-be-braked portion becomes stronger toward a side apart from the fulcrum while becoming weaker toward the fulcrum. 
     Accordingly, even after the brake surface worn out after years of being used, the pressing position, where the to-be-braked portion is pressed, moves toward the turning fulcrum side and to a new pressing position. The braking is therefore carried out by a portion that is relatively less worn out. Moreover, the brake surface is disposed in such a way as to be inclined, so that frictional resistance against the to-be-braked portion increases after being used. Therefore, it is possible to provide a brake device that can make up for a decrease in braking force caused by wearing-out, even after years of its use. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a front view showing the basic configuration of a load support mechanism according to the present invention; 
         FIG. 2  is a view as seen in the direction of arrow along line II-II of  FIG. 1 ; 
         FIG. 3  is a diagram illustrating the relationship between major sections when a second cam follower is in a first region S 1  of a fixed cam surface; 
         FIG. 4  is an explanatory diagram similar to  FIG. 3  when a second cam follower is in a second region S 2  of a fixed cam surface; 
         FIG. 5  is an explanatory diagram similar to  FIG. 3  when a second cam follower is in a third region S 3  of a fixed cam surface; 
         FIG. 6  is a perspective view of a first embodiment of an article support device to which the present invention is applied; 
         FIG. 7  is an exploded perspective view of the first embodiment of  FIG. 6 ; 
         FIG. 8  is a front view of an article support device whose support frame section is at an uppermost position; 
         FIG. 9A  is a partially enlarged vertical cross-sectional view of  FIG. 8 , with one cam follower being viewed from above; 
         FIG. 9B  is a view as seen in the direction of arrow along line IX-IX of  FIG. 9A , with a fixed cam member omitted; 
         FIG. 10  is an enlarged view showing a lower frame below a support frame section, and a second spring; 
         FIG. 11  is a partially enlarged view of a support frame section as viewed from above in a planar manner; 
         FIG. 12  is a partially enlarged view showing a fixed cam surface of  FIG. 8  and a cam follower member; 
         FIG. 13  is a front view similar to  FIG. 8  when a support frame section is at a middle position; 
         FIG. 14  is a partially enlarged view showing a fixed cam surface of  FIG. 12  and a cam follower member; 
         FIG. 15  is a front view similar to  FIG. 8  when a support frame section is at a lowermost position; 
         FIG. 16  is a partially enlarged view showing a fixed cam surface of  FIG. 15  and a cam follower member; 
         FIG. 17  is a partially enlarged view showing an area around an upper end of a fixed cam surface; 
         FIG. 18  is a partially enlarged view showing an area around a lower end of a fixed cam surface; 
         FIG. 19  is a partially enlarged perspective view showing a brake mechanism of a first embodiment; 
         FIG. 20  is a front view of a brake mechanism of  FIG. 19 ; 
         FIG. 21  is a front view showing a moving-up release operation of a brake mechanism of  FIG. 19 ; 
         FIG. 22  is a front view showing a moving-down release operation of a brake mechanism of  FIG. 19 ; 
         FIG. 23  is a front view showing a modified example of a brake mechanism of  FIG. 19 ; 
         FIG. 24  is a front view showing a moving-up release operation of a brake mechanism of  FIG. 23 ; 
         FIG. 25  is a front view showing a moving-down release operation of a brake mechanism of  FIG. 23 ; 
         FIGS. 26A and 26B  are schematic diagrams illustrating the concept of a braking action of a brake device of a present embodiment; 
         FIG. 27  is a partially crushed enlarged view of a speed limiter mechanism as seen from a back side of an article support device; 
         FIGS. 28A and 28B  are partially crushed enlarged front views of a centrifugal brake mechanism when the mechanism is not operated and is operated; 
         FIG. 29  is a perspective view of an upper half of a second embodiment of an article support device to which the present invention is applied; 
         FIG. 30  is a partially enlarged perspective view showing a brake mechanism of a second embodiment from a front side; 
         FIG. 31  is a partially enlarged perspective view showing a brake mechanism of  FIG. 30  from a back side; 
         FIG. 32  is a front view showing a braking state of a brake mechanism of  FIG. 30 ; 
         FIG. 33  is a front view showing a situation where only an upper side of a brake mechanism of  FIG. 30  is released; 
         FIG. 34  is a front view showing a full release state of a brake mechanism of  FIG. 30 ; 
         FIGS. 35A and 35B  are diagrams illustrating an operation of an operation handle section in an article support device of a second embodiment; and 
         FIGS. 36A and 36B  are diagrams illustrating an operation of an operation handle section of a conventional configuration, in comparison to  FIGS. 35A and 35B . 
         FIGS. 37A and 37B  are enlarged views of a mechanism of an upper-right brake device of  FIG. 32 :  FIG. 37A  is an explanatory diagram showing a state of the brake device at the start of use;  FIG. 37B  is an explanatory diagram showing a state of the brake device in which a brake pad worn out after being used many times. 
         FIGS. 38A and 38B  are diagrams showing an improved version of the brake device of  FIGS. 37A and 37B :  FIG. 38A  is an explanatory diagram showing a state of the brake device at the start of use;  FIG. 38B  is an explanatory diagram showing a state of the brake device in which a brake pad worn out after being used many times. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     With reference to the accompanying drawings, preferred embodiments of the present invention will be described in detail. Incidentally, in the accompanying drawings, similar components throughout this specification are represented by the same reference symbols. 
       FIGS. 1 and 2  conceptually show the basic configuration of a load support mechanism according to the present invention. As shown in the diagrams, a load support mechanism  1  includes a fixed support section  2 , which is for example installed on a floor or a table; a movable support section  3 , which receives a load of an article; and a first spring  4 , which is for example an extension coil spring. For example, a television monitor device, or article A, can be supported by a mounting stay  5 , which is provided on the movable support section  3 , as the article A is attached to a front side of the load support mechanism  1 . 
     According to the present embodiment, the fixed support section  2  has an outer frame structure, including left and right vertical frame members  6   a  and  6   b , which extend vertically, and a lateral frame member  7 , which is provided horizontally between upper ends of the two vertical frame members. On one vertical frame member  6   a , a fixed cam  8 , which extends from around an up-down-direction central position thereof to around a lower end, is provided integrally. 
     The fixed cam  8  includes a fixed cam surface  9 : The fixed cam surface  9  is convex toward the right side of  FIG. 1 , or toward the other vertical frame member  6   b , and the fixed cam surface  9  is curved in such a way that the slope of the tangent direction thereof is changed across the entire length from the upper end to the lower end or is changed partially. As shown in  FIG. 2 , one pair of fixed cams  8 ,  8  and fixed cam surfaces  9 ,  9  is preferably provided in a front side portion of the vertical frame member  6   a , and another pair in a rear side portion of the vertical frame member  6   a , in such a way as to be symmetric in the front-back direction. 
     According to the present embodiment, the movable support section  3  has a rectangular frame structure, including upper and lower lateral frame members  10   a  and  10   b , which horizontally extend between the vertical frame members  6   a  and  6   b  of the fixed support section  2 , and left and right vertical frame members  11   a  and  11   b , which extend vertically. The vertical frame members  11   a  and  11   b  are provided in such a way as to be able to move up and down along inner-side guides  12   a  and  12   b  of the vertical frame members  6   a  and  6   b  of the fixed support section  2 . After the article A is placed on the movable support section  3 , the movable support section  3  can move in the up-down direction relative to the fixed support section  2  as the movable support section  3  is guided by the guides. 
     An upper end  4   a  of the first spring  4  is fixed to the lateral frame member  7  of the fixed support section  2 . A lower end  4   b  of the first spring  4  is fixed to the upper lateral frame member  10   a  of the movable support section  3 . The first spring  4  expands or contracts in the vertical direction, thereby generating a biasing force FA in a vertically upward direction. The biasing force FA of the first spring  4  helps to support the movable support section  3  and the article A in such a way that the movable support section  3  and the article A can move in the vertical direction. 
     Furthermore, the movable support section  3  includes, as a movable cam that moves together with the movable support section, a cam groove  13 : The cam groove  13  passes through the lower lateral frame member  10   b  in the front-back direction, and extends in the horizontal direction or in a direction perpendicular to the direction in which the movable support section is moved. The cam groove  13  includes a first movable cam surface  14   a , which is on the upper side and faces downwards; and a second movable cam surface  14   b , which is on the lower side and faces upwards; the first movable cam surface  14   a  and the second movable cam surface  14   b  face each other and run parallel. 
     In the cam groove  13 , a cam follower member  15  is provided. The cam follower member  15  includes a first cam follower  16 , which has a straight rod shape or circular tube shape that is circular in cross section and passes through the cam groove  13  in the front-back direction; and second roller-shaped cam followers  17 ,  17 , which are provided on the front and rear ends of the first cam follower  16  that protrudes from the cam groove in the front-back direction. 
     The outer peripheral surfaces of the first cam follower  16  are in contact with first and/or second movable cam surfaces  14   a ,  14   b  when the first cam follower  16  moves in the left-right direction in the cam groove  13  along the cam groove. The second cam followers  17  are preferably rotatable with respect to the two ends of the first cam follower  16 ; the second cam followers  17  each are disposed in such a way as to be in contact with the fixed cam surface  9  of a corresponding fixed cam  8 . 
     Around the lower lateral frame member  10   b  of the movable support section  3 , a second spring  18 , which is a compression coil spring, is fitted. The fixed cam  8 &#39;s side end portion  18   a  of the second spring  18  is fixed to the first cam follower  16 . The other side end portion  18   b  is fixed to an appropriate area of the lateral frame member  10   b  that is on the opposite side from the fixed cam  8 . The second spring  18  is provided in such a way as to press the cam follower member  15 , so that the second cam followers  17  are constantly pressed against the fixed cam surfaces  9 . 
     At this time, as described later, the biasing force FB of the second spring  18  generates a force in a vertically upward direction or downward direction for the second cam followers  17 , depending on the slope of the fixed cam surface  9 . Due to the existence of the lateral frame member  10   b , the second spring  18  is always compressed and kept straight without buckling. 
     According to the present embodiment, the cam groove  13  extends from an area near the fixed cam  8 &#39;s side end portion of the lateral frame member  10   b  to the opposite side. Therefore, a range in which the cam follower member  15  can move in the horizontal direction in such a way that the second cam followers  17  remain in contact with the fixed cam surfaces  9 , or horizontal stroke, can be set as large as possible. Accordingly, a range in which the biasing force FB of the second spring  18  can be used to press the second cam followers  17  against the fixed cam surfaces  9  can be made even wider. 
     When the article A is supported by the load support mechanism  1 , the first spring  4  is stretched downward due to load W of the article A, and that force is conveyed via the movable support section  3 , and the force acts in such a way that the downward-facing first movable cam surface  14   a  of the cam groove  13  pushes down the cam follower member  15 . Meanwhile, the bias force FA of the first spring  4  is similarly conveyed via the movable support section  3 , and the force acts in such a way that the upward-facing second movable cam surface  14   b  of the cam groove  13  pushes up the cam follower member  15 . 
     According to the above configuration, as can be seen from  FIG. 2 , in a plane perpendicular to the movement direction of the movable support section  3  or in the horizontal plane, the first spring  4  and the second spring  18  can be disposed in such a way as to overlap at least partially in the up-down direction. This arrangement makes it possible to make the depth of the load support mechanism  1  smaller or design a thin load support mechanism  1 , when the load support mechanism  1  is turned into an actual device. This arrangement is also effective for the case where a large biasing force of the first spring  4  and/or the second spring  18  is required as the load to be supported becomes heavier, and the larger springs are therefore required. 
     According to another embodiment, as the first spring  4 , instead of an extension coil spring, a compression coil spring is used; the first spring  4  is disposed below the movable support section  3  in such a way as to push up the movable support section  3 . According to still another embodiment, instead of the first spring of  FIG. 1 , an additional compression coil spring is provided below the movable support section  3  in such a way as to pushup the movable support section  3 . In either case, the depth of the load support mechanism  1  can be made smaller, when the load support mechanism  1  is turned into an actual device. 
     According to the present embodiment, as shown in  FIG. 2 , two fixed cams  8  and two second cam followers  17  are provided along the axis direction of the first cam follower  16 ; the two fixed cams  8  and the two second cam followers  17  are provided on the opposite sides of the lower lateral frame member  10   b  in such a way as to be symmetric in the front-back direction and form a pair. Due to this arrangement, the force that the fixed cams  8  exert on the cam follower member  15  spread symmetrically in the front-back direction and in a well-balanced manner along the axis direction of the first cam follower  16 . Therefore, this configuration is suitable because the first cam follower is unlikely to be bent or deformed. The dispersion of the force reduces the load on each fixed cam  8 , and the fixed cams  8  can be made thinner. As a result, the entire device can be made thinner and lighter. 
     Furthermore, on the first cam follower  16 , the pressing force of each fixed cam  8  is concentrated on the contact position and acts in the same direction. If the axial-direction length thereof is too long, the first cam follower  16  could bend or deform excessively, or break. According to the present embodiment, any other component does not exist between the lateral frame member  10   b , on which the cam groove  13  is provided, and the fixed cams  8 . Therefore, the first cam follower  16  can be short in the axis-direction length and is advantageous. 
     An area of the fixed cam surface  9  that comes in contact with the second cam follower  17  is divided into the following three regions, depending the position thereof. A first region S 1  is a region where the normal direction at a contact point with the second cam follower is upward relative to the horizontal direction. A second region S 2  is a region where the normal direction at a contact point with the second cam follower is substantially horizontal. In other words, in the second region S 2 , the tangential direction at the contact point with the second cam follower is substantially vertical. Here, the term “substantially” means that the direction is slightly upward or downward compared to the exact horizontal direction, and the degree of deviation thereof is small enough to be negligible in terms of the operation and effects of the present invention, the operation of the present embodiment, or the function. Therefore, the direction can be considered to be horizontal. A third region S 3  is a region where the normal direction at a contact point with the second cam follower is downward relative to the horizontal direction. 
     In  FIGS. 1 and 2 , the second cam follower  17  of the movable support section  3  carrying the article A remains still at an upper position that is within the first region S 1  of the fixed cam surface  9 . At this position, the amount of displacement of the first spring  4  is small, and the force FA of the spring is smaller than the load W.  FIG. 3  schematically shows an equilibrium state of forces acting on a system made up of the cam follower member  15 , the movable support section  3 , and the fixed cam  8  at this stationary position. 
     Here, throughout this specification, the term “equilibrium” means that, when several external forces are applied to a certain object or member (e.g. second cam follower  17 ), the sum of those forces is zero, and that the object or the member therefore remains stationary. The external forces that are applied to that certain object or member include the load of that certain object or member itself, or its own weight; a frictional force that is generated between that certain object or member and another object or member; a frictional force or resistance that is generated on another object or member that exerts the external force on that certain object or member. In actual use, the frictional forces and the like can serve as forces to keep that certain object or member at the stationary position, when the weight of that certain object or member and the weight of another object or member are included among the above forces applied to the periphery of the cam follower and when the frictional forces and the like are equal to or larger than the sum of those forces. 
     For ease of explanation, the loads of the movable support section  3 , second spring  18 , and cam follower member  15 , and the frictional forces between the guides  12   a  and  12   b  of the fixed support section  2  and the vertical frame members  11   a  and  11   b  of the movable support section  3 , between the first cam follower  16  and the cam groove  13 , and between the second cam follower  17  and the fixed cam  8  are omitted. Needless to say, those factors need to be taken into consideration in designing the actual device. 
     In this case, if the load or weight of the movable support section, second spring, and cam follower member is included among the forces acting on the system made up of the cam follower member, the movable support section, and the fixed cam, the equilibrium state is maintained when the sum of those forces is equal to or smaller than the frictional forces generated between the guides and the vertical frame members, between the first cam follower and the cam groove, and between the second cam follower and the fixed cam spring. When the movable support section  3  is in the equilibrium state and remains stationary at a certain position, the frictional forces help to keep the movable support section  3  at that stationary position. 
     For example, if a torque limiter is provided between the first cam follower  16  and the second cam follower  17 , a force that keeps the movable support section at the stationary position may be a force that the torque limiter exerts between the two cam followers. If a contact surface of the second cam follower  17  with the fixed cam surface  9  is made of a material with a large friction coefficient such as rubber, the stationary-position holding force also can be obtained from a frictional force acting between the rubber surface and the fixed cam surface. 
     In general, the spring force F of a coil spring with a spring constant of k is represented by F=k·x, with respect to the amount x of axis-direction displacement of the coil spring (or the amount of displacement from the free length of the spring or the length of the spring in an unloaded state; the compression direction is regarded as positive in this case). In order to support the article A in a stationary manner at an uppermost position of the movable support section  3 , the first spring  4  already exerts an initial spring force (FA 0 =kA·xA 0 ) in the vertically upward direction as the first spring  4  is stretched in advance by a predetermined initial displacement amount xA 0  from the free length. At the same time, the second spring  18  already exerts an initial spring force (FB 0 =kB·xB 0 ) in the vertically upward direction as the second spring  18  is similarly compressed in advance by a predetermined initial displacement amount xB 0  from the free length. 
     In  FIG. 3 , between the first cam follower  16  and the cam groove  13 , at contact point Pa with the first movable cam surface  14   a , the load W of the article A acts on the first cam follower from the first movable cam surface in the vertically downward direction via the movable support section  3 . In this state, ideally, the first cam follower  16  is assumed to be in contact not only with the first movable cam surface but also with the second movable cam surface  14   b  in such a way as to make the transmission of force possible. In such a case, at contact point Pb of the first cam follower  16  with the second movable cam surface  14   b , the biasing force FA of the first spring  4  is considered to act on the first cam follower in the vertically upward direction. 
     Actually, it is difficult for the first cam follower  16  to come in contact with the second movable cam surface  14   b  in such a way as to make the transmission of force possible in such an ideal state. In this case, at the contact point Pb, the forces acting on each other do not exist. This situation is equivalent to the situation where, at the contact point Pa, from the first movable cam surface  14   a  to the first cam follower  16 , a force Fv whose magnitude is calculated by subtracting the biasing force FA of the first spring  4  from the load W of the article A is being applied in the vertical downward direction. In either case, from the cam groove  13  to the first cam follower  16 , the force Fv whose magnitude is calculated by subtracting the biasing force FA of the first spring  4  from the load W of the article A is substantially being applied in the vertical downward direction. 
     At contact point Pc between the second cam follower  17  and the fixed cam surface  9 , the pressing force applied from the second cam follower to the fixed cam surface is balanced against reaction force Rc that is applied from the fixed cam surface in the normal direction thereof. The pressing force applied from the second cam follower to the fixed cam surface is the sum of the biasing force FB of the second spring  18  and the force Fv applied to the first cam follower  16  in the vertically downward direction as described above. The reaction force Rc of the fixed cam surface includes an upward vertical component Rc 1  and a horizontal component Rc 2 . 
     When the second cam follower remains stationary at a certain position on the fixed cam surface, between the load W, the spring force FA of the first spring  4 , and the vertical component Rc 1  of the reaction force Rc, the following relation always holds theoretically, if the direction in which the force acts, or the vertically upward direction, is positive: 
         W+FA+Rc 1=0 
     Incidentally, in the actual design, as described above, frictional forces are generated between the members. Even if the combined forces represented by this relational expression is not zero and has a small value, the equilibrium state would be maintained if the combined forces are less than the frictional forces between the members. 
     Between the biasing force FB of the second spring  18  and the horizontal component Rc 2  of the reaction force Rc, the following relationship always holds theoretically, if the direction in which the force acts in the horizontal direction, or the direction toward the right side of the diagram, is positive: 
         FB+Rc 2=0 
     Accordingly, the magnitude of the horizontal component Rc 2  of the reaction force Rc is equal to that of the biasing force FB of the second spring  18 . Based on the magnitude of the biasing force FB, the magnitude of the reaction force Rc and the magnitude of the vertical component Rc 1  are determined. 
     In the case of  FIG. 3 , the spring force FA of the first spring  4  is smaller than the load W. Therefore, by applying the vertical component Rc 1  of the reaction force Rc, which is applied from the fixed cam surface in the upward direction, as an assist force, the equilibrium with the load W in the vertical direction is achieved. In this state, if the movable support section  3  is pushed down or up, that force is added to the load W or the spring force FA, leading to the collapse of the equilibrium. Therefore, the article A can be easily lifted up or down by a relatively small force. 
     When the movable support section  3  is moved up or down, the cam follower member  15  moves downward or upward as the first cam follower  16  is shifted in the left-right direction along the cam groove  13  and as the second cam follower  17  is shifted in the left-right direction along the fixed cam surface  9 . While the second cam follower is being located within the first region S 1  of the fixed cam surface, the spring force FA of the first spring  4  is assisted by the upward vertical component Rc 1  of the reaction force Rc in such a way as to achieve the equilibrium with the load W. 
     Inside the first region S 1 , as the movable support section  3  goes down and the amount of displacement of the first spring  4  increases, the spring force FA becomes larger accordingly. As a result, only a smaller assistance force is required from the vertical component Rc 1  of the reaction force Rc. Therefore, the slope of the tangential direction of the fixed cam surface  9  relative to the vertical direction becomes smaller toward the lower second region S 2 . 
     Meanwhile, as the movable support section  3  goes down and the second cam follower  17  moves downward along the fixed cam surface  9 , the amount of compression and displacement of the second spring  18  increases, leading to a rise in the spring force FB. As a result, the pressing force applied from the second cam follower to the fixed cam surface, i.e. the reaction force Rc, grows. The slope of the fixed cam surface  9  is preferably determined in such away to gain an optimal assist force from the vertical component Rc 1  of the reaction force Rc, by taking into consideration a change in the spring force FA of the first spring  4  as well as a change in the spring force FB of the second spring  18 . 
       FIG. 4  schematically shows an equilibrium state of forces applied to the system made up of the cam follower member  15 , the movable support section  3 , and the fixed cam  8 , when the movable support section  3  carrying the article A is pushed down from an upper position of  FIG. 1  until the second cam follower  17  is stopped at a middle position within the second region S 2  of the fixed cam surface  9  as indicated by imaginary line in  FIG. 1 . For ease of explanation, the loads of the movable support section  3 , second spring  18 , and cam follower member  15 , and the frictional forces between the guides  12   a  and  12   b  of the fixed support section  2  and the vertical frame members  11   a  and  11   b  of the movable support section  3 , between the first cam follower  16  and the cam groove  13 , and between the second cam follower  17  and the fixed cam  8  are similarly omitted in the description below. 
     In this case, between the first cam follower  16  and the cam groove  13 , in the vertical direction, the spring force FA of the first spring  4  is substantially balanced against the load W. Therefore, the spring force FA does not require an assist force from the reaction force Rc exerted by the fixed cam surface  9 . 
     At contact point Pc between the second cam follower  17  and the fixed cam surface  9 , the reaction force Rc from the fixed cam surface  9  is balanced against the biasing force FB that is applied to the second cam follower from the second spring  18 , and does not contain a vertical component. Even in this state, if the movable support section  3  is pushed down or up, that force is added to the load W or the spring force FA, leading to the collapse of the equilibrium. Therefore, the article A can be easily lifted up or down with a relatively small force. 
     The movable support section  3  carrying the article A is further pushed down and is then stopped at a lower position where the second cam follower  17  is located within the third region S 3  of the fixed cam surface  9  as indicated by imaginary line in  FIG. 1 . At this time, the amount of displacement of the first spring  4  further grows, and the spring force FA thereof becomes greater than the load W. 
       FIG. 5  schematically shows an equilibrium state of forces applied to the system made up of the cam follower member  15 , the movable support section  3 , and the fixed cam  8  at that stationary position. Similarly, for ease of explanation, the loads of the movable support section  3 , second spring  18 , and cam follower member  15 , and the frictional forces between the guides  12   a  and  12   b  of the fixed support section  2  and the vertical frame members  11   a  and  11   b  of the movable support section  3 , between the first cam follower  16  and the cam groove  13 , and between the second cam follower  17  and the fixed cam  8  are omitted in the description below. 
     In the diagram, between the first cam follower  16  and the cam groove  13 , at the contact point Pb with the second movable cam surface  14   b , the biasing force FA of the first spring  4  is applied to the first cam follower in the vertically upward direction. In this state, ideally, the first cam follower  16  is assumed to be in contact not only with the second movable cam surface but also with the first movable cam surface  14   a  in such a way as to make the transmission of force possible. In such a case, at the contact point Pa of the first cam follower  16  with the first movable cam surface  14   a , the load W of the article A is considered to act on the first movable cam surface in the vertically downward direction via the movable support section  3 . 
     Actually, it is difficult for the first cam follower  16  to come in contact with the first movable cam surface  14   a  in such a way as to make the transmission of force possible in such an ideal state. In this case, at the contact point Pa, the forces acting on each other do not exist. This situation is equivalent to the situation where, at the contact point Pb, from the second movable cam surface  14   b  to the first cam follower  16 , a force Fv whose magnitude is calculated by subtracting the load W of the article A from the biasing force FA of the first spring  4  is being applied in the vertical upward direction. In either case, to the first cam follower  16 , the force Fv whose magnitude is calculated by subtracting the load W of the article A from the biasing force FA of the first spring  4  is substantially being applied in the vertical upward direction from the cam groove  13 . 
     At contact point Pc between the second cam follower  17  and the fixed cam surface  9 , the pressing force applied from the second cam follower to the fixed cam surface is balanced against the reaction force Rc that is applied from the fixed cam surface in the normal direction thereof. The pressing force applied from the second cam follower to the fixed cam surface is the sum of the biasing force FB of the second spring  18  and the vertically upward force Fv that is applied to the first cam follower  16  as described above. The reaction force Rc of the fixed cam surface contains a downward vertical component Rc 1  and a horizontal component Rc 2 . 
     At the above lower position, the magnitude of the spring force FA of the first spring  4  is greater than the load W. Therefore, the vertical component Rc 1  of the reaction force Rc that is applied from the fixed cam surface  9  in the downward direction works in a direction in which the upward biasing force of the spring force FA, or push-up force, is reduced. Accordingly, the equilibrium with the load W is achieved in the vertical direction. Even in this state, if the movable support section  3  is pushed down or up, that force is added to the load W or the spring force FA, leading to the collapse of the equilibrium. Therefore, the article A can be easily lifted up and down with a relatively small force. 
     When the movable support section  3  moves up or down, the cam follower member  15  moves downward or upward as the cam follower  16  is shifted in the left-right direction along the cam groove  13  and the cam follower  17  is shifted in the left-right direction along the fixed cam surface  9 . When the second cam follower is being within the third region S 3  of the fixed cam surface, the downward vertical component Rc 1  of the reaction force Rc works in a direction in which the push-up force of the spring force FA of the first spring  4  is reduced, thereby achieving the equilibrium with the load W. 
     In the third region S 3 , when the amount of displacement of the first spring  4  becomes smaller as the movable support section  3  goes up, the spring force FA decreases accordingly. As a result, a smaller vertical component Rc 1  of the reaction force Rc is required to reduce the push-up force of the spring force FA. Therefore, the slope of the tangential direction of the fixed cam surface  9  relative to the vertical direction becomes smaller toward the upper second region S 2 . 
     Meanwhile, the amount of compression and displacement of the second spring  18  grows as the movable support section  3  goes up and the second cam follower  17  moves up along the fixed cam surface  9 , resulting in an increase in the spring force FB. As a result, the pressing force applied from the second cam follower to the fixed cam surface, or the reaction force Rc, becomes larger. The slope of the fixed cam surface  9  is preferably determined in such a way as to achieve an optimal reduction in the push-up force of the spring force FA, based not only on a change in the spring force FA of the first spring  4  but also on a change in the spring force FB of the second spring  18 . 
     In that manner, according to the present embodiment, in the entire region of the fixed cam surface  9 , an equilibrium between the load W of the article A acting on the system made up of the cam follower member  15 , the movable support section  3 , and the fixed cam  8 , the spring force FA of the first spring  4 , the spring force FB of the second spring  18 , and the reaction force applied from the fixed cam  8  is achieved around the cam follower member  15 . Therefore, in the up-down stroke range of the movable support section  3 , the movable support section  3  carrying the article A can be stopped at a desired height position and kept at that position, or can be easily lifted up or down with a relatively small force. 
     The above-described basic configuration of the present invention may be changed or modified in various ways and embodied. For example, the lateral frame member  10   b  may be a tubular member, and the second spring  18  may be fitted into the tubular member. The movable support section  3  can take various configurations other than the above-described rectangular frame. 
     Furthermore, another set of the fixed cam  8 , cam groove  13 , cam follower member  15 , and second spring  18  shown in  FIG. 1  may be added and be disposed in mirror symmetry with respect to a left-right-direction center line of the fixed support section  2  and movable support section  3 . In this case, it is preferred that the second springs be formed as one common compression spring, and that the cam follower members  15  be provided at both ends thereof. This left-right-direction symmetrical configuration reduces the load borne by the fixed cam, and can support a larger load in a well-balanced, stable manner in the left-right direction as a whole. 
       FIGS. 6 to 8  show a first embodiment of an article support device to which such a modified example of the present invention has been specifically applied. An article support device  20  of the present embodiment is designed to support a relatively heavy article B, such as a large-screen television monitor. The article support device  20  includes a base  21 , which is placed on a floor surface or the like in a movable manner; a fixed frame section  22 , which is fixed to the base; a support frame section  23 , which is mounted on the fixed frame section in such a way as to be able to move up and down; a first sprint  24 ; and an operation handle section  25 , which is used to move up or down the support frame section  23 . 
     As described later, the article B is integrally attached to the support frame section  23  in a detachable manner. A lower portion of the fixed frame section  22  is erected and firmly fixed by stays  21   b  to an upper surface of a base plate  21   a  of the base  21 . 
     The fixed frame section  22  is a roughly rectangular frame structure, including upper and lower frames  26  and  27 , which extend horizontally, and left and right side frames  28  and  29 , which extend vertically between the upper frame and the lower frame. Furthermore, at the center of the fixed frame section  22 , a first brake rail  31  is provided in such a way as to extend vertically between the upper frame and an intermediate frame  30 , which extends horizontally between the left and right side frames  28  and  29  and is substantially located at a mid-height position. 
       FIG. 9A  shows the cross-section of one side frame  28  of the fixed frame section  22 . The other side frame  29  is formed exactly symmetrically to the side frame  28 , and therefore is not shown in the diagram. As shown in  FIG. 9A , in the side frame  28  or  29 , a guide rail  32  or  33  is formed from an almost upper end of the side frame to a lower end: the guide rail  32  or  33  is U-shaped in cross-section and open to the inner side of the frame structure. 
     To the inner-side portion of the left or right side frame  28  or  29  of the fixed frame section  22  that is lower than the intermediate frame  30 , a fixed cam member  34  or  35  is attached symmetrically in the left-right direction. The fixed cam member  34  or  35  includes two cam plates, which are long in the up-down direction and fixed to the front and back surfaces of the side frame  28  or  29  and which run parallel to each other. The fixed cam member  34  or  35  includes a fixed cam surface  36  or  37 , which extends from around an upper end thereof to around a lower end. The fixed cam surface  36  or  37  forms a convex shape in a direction in which the fixed cam surfaces  36  and  37  face each other. The fixed cam surface  36  or  37  is provided in such a way that the slope of the tangential direction thereof is curved and is changed across the entire length from an upper end to a lower end or changed partially. 
     The support frame section  23  is a roughly rectangular frame structure, including left and right guide frames  38  and  39 , which extend vertically, an upper frame  40 , which extends horizontally between the two guide frames, and two lower frames  41  and  42 , which are slightly separated in the up-down direction. The support frame section  23  is mounted on the fixed frame section  22  in such a way as to be able to move up and down along the guide rails, as the left and right guide frames  38  and  39  are fitted into the guide rail  32  and  33  of the corresponding left and right side frames  28  and  29  of the fixed frame section in a slidable manner. 
     On the left and right guide frames  38  and  39 , a plurality of rollers  43  are mounted in such a way as to slide and roll on the inner surfaces of the guide rails; the rollers  43  are intended to reduce or eliminate a frictional force generated between the left and right guide frames  38  and  39  and the inner surfaces of the guide rails  32  and  33  when the left and right guide frames  38  and  39  slide inside the guide rails  32  and  33 , and other kinds of resistance. Therefore, the support frame section  23  can smoothly move in the up-down direction without rattling or being displaced in the left-right direction with respect to the fixed frame section  22 . 
     As described above, the support frame section  23  is mounted in such a way that the outer frame of the support frame section  23  is directly supported by the outer frame of the fixed frame section  22 . Therefore, the structural strength of the support frame section  23  itself and the entire device is improved. As a result, the article support device  20  that can bear a high load and has a high strength structure can be realized: the article support device  20  can handle a heavier article B. 
     On the support frame section  23 , a pair of left and right mounting stays  44  are provided in such a way as to extend vertically just ahead of the guide frames; the mounting stays  44  are used to fix the article B. Furthermore, in the support frame section  23 , at the center of the upper frame  40 , a brake device  45  is provided. As described later, as the operation handle section  25  is operated, the brake device causes a brake shoe (described later) to engage with a brake rail or cancels that engagement. 
     The first spring  24  includes two extension coil springs  46  just near the inner side of the left guide frame  38  of the support frame section  23 , and two extension coil springs  47  just near the inner side of the right guide frame  39 ; the extension coil springs  46  and  47  are disposed symmetrically in the left- and right direction and in parallel in the left-right direction. An upper end of each of the extension coil springs  46  and  47  is fixed to the upper frame  26  of the fixed frame section  22  in such a way that each of the extension coil springs  46  and  47  hangs vertically; a lower end of each of the extension coil springs  46  and  47  is fixed to the upper-side lower frame  41  of the support frame section  23 . 
     As shown in  FIG. 10 , on the lower-side lower frame  42  of the support frame section  23 , two cam grooves  48  and  49  are so provided as to be symmetrical in the left-right direction; the two cam grooves  48  and  49  pass through the lower frame in the front-back direction. As for the cam groove  48  which is shown in the left section of the diagram, as shown in  FIGS. 9A and 9B , each cam groove  48  or  49  includes a first movable cam surface  50   a  or  51   a , which extends horizontally a predetermined distance from around a left or right end of the lower frame  42  toward the opposite side and which is located on the upper side and faces downward; and a second movable cam surface  50   b  or  51   b , which is located on the lower side and faces upward. The first movable cam surface  50   a  or  51   a  and the second movable cam surface  50   b  or  51   b  face each other and run parallel to each other. 
     Onto the lower frame  42 , a second spring  52 , which is a compression coil spring, is fitted. In this manner, the second spring  52  is fitted onto the straight lower frame  42 , which is part of the support frame section  23 . This configuration can reliably prevent buckling, which could occur due to the compression of the second spring  52 . According to another example, the second spring  52  may be fitted into a tubular lower frame  42 . 
     On the left and right sides of the second spring  52 , via cam follower holders  53  and  54 , into which the lower frame  42  is inserted in such a way as to allow the cam follower holders  53  and  54  to freely slide, cam follower members  55  and  56  are provided. As for the cam follower member  55  shown in the left section of the diagram, as shown in  FIG. 9A , the cam follower member  55  or  56  includes a straight, rod-shaped first cam follower  57  or  58 , which is circular in cross-section and passes through the cam groove  48  or  49  in the front-back direction. Furthermore, the cam follower member  55  or  56  includes roller-shaped second cam followers  59  or  60 , which are provided on the front and rear ends of the first cam follower  57  or  58  that protrudes from the cam groove in the front-back direction. 
     The first cam follower  57  or  58  can move in the left-right direction in the cam groove  48  or  49  along the cam groove, as the outer peripheral surface of the first cam follower  57  or  58  is being in contact with the first movable cam surface  50   a  or  51   a  and the second movable cam surface  50   b  or  51   b . The second cam followers  59  or  60  may be mounted in a rotatable manner with respect to the two ends of the first cam follower  57  or  58 , for example, via a rolling bearing. 
     The second cam followers  59  or  60  are disposed in such a way as to be in contact with the fixed cam surface  36  or  37  of the corresponding fixed cam member  34  or  35 . The second cam followers  59  or  60  are pressed by the second spring  52  in a horizontally outward direction, against the fixed cam surface  36  or  37  of the corresponding fixed cam member  34  or  35 . 
     As for the cam follower holder  53  shown in the left section of the diagram, as shown in  FIG. 9B , the cam follower holder  53  or  54  includes an outer-side first holder member  61  or  62 , which extends along the axis direction of the second spring  52 ; and an inner-side second holder member  63  or  64 . For example, the first holder member holds the first cam follower  57  or  58  in a rotatable manner via a bearing. The second holder member is a spring receiver, an end surface of which receives an end portion of the second spring  52 . 
     The first holder member  61  or  62  and the second holder member  63  or  64  each includes an abutting surface on which a plurality of steps are provided in a terraced manner in the circumferential direction in such a way as to be complementarily engageable; the first holder member  61  or  62  and the second holder member  63  or  64  form a meshing joint when being joined together. The first holder member  61  or  62  and the second holder member  63  or  64  are rotated in the circumferential direction relative to each other, so that the abutting position of the members is changed. In this manner, the axis-direction length of the cam follower holder  53  or  54  can be changed. 
     As shown in  FIG. 9A , the two cam plates of the fixed cam member  34  are disposed along the axis direction of the cam follower member  55  in such a way as to be symmetric in the front-back direction. Therefore, the each cam plate&#39;s force to press the cam follower member  55  is dispersed along the axis direction, and acts symmetrically in the front-back direction. Although not shown in the diagrams, in the other cam follower member  56 , the pressing force that each cam plate of the fixed cam member  35  exerts is similarly dispersed along the axis direction, and acts symmetrically in the front-back direction. Accordingly, the cam follower members  55  and  56  are kept in the cam grooves  48  and  49  stably and horizontally. The dispersion of the force reduces the burden on each cam plate of the fixed cam member  35 . Therefore, the cam plates can be made thinner. As a result, the entire device can be made thinner and lighter. 
     Moreover, between each cam plate of the fixed cam member  34  or  35  and the lower frame  42  of the support frame section  23  on which the cam groove  48  or  49  is provided, another component does not exist, allowing those parts to be placed at smaller intervals in the front-back direction. As a result, the axis-direction length of the first cam followers  57  and  58  of the cam follower members  55  and  56  can be made shorter, eliminating in advance the risk of being excessively bent, deformed, or broken, which the device could have faced if the first cam followers were too long. 
       FIG. 11  is a partially enlarged view of the left portion in the diagram of the support frame section  23  as seen from above in planar view. As shown in the diagram, in the article support device  20  of the present embodiment, the almost entire extension coil springs  46  of the first spring  24  are disposed on a plane in such away as to overlap with the second spring  52  in the up-down direction. Although not shown in the diagram, the almost entire extension coil springs  47  on the other side are similarly disposed on a plane in such away as to overlap with the second spring  52  in the up-down direction. This arrangement helps to minimize the depth of the article support device  20  and thereby make the article support device  20  thinner even if the outer diameters of the first spring  24  and/or the second spring  52  become larger. 
     As shown in  FIG. 8 , as described above in relation to  FIG. 1 , the fixed cam surface  36  or  37  is divided into the following three regions, depending on the contact position with the second cam follower  59  or  60 . A first region S 1  is a region where the normal direction at a contact point with the second cam follower is upward relative to the horizontal direction. A second region S 2  is a region where the normal direction at a contact point with the second cam follower is substantially horizontal; that is, the second region S 2  is a region in which the tangential direction is substantially vertical. As described above, the term “substantially” means that the direction is slightly upward or downward compared to the exact horizontal direction, and the degree of deviation thereof is small enough to be negligible in terms of the operation and effects of the article support device  20 , or the operation of the article support device  20 , or the function. Therefore, the direction can be considered to be horizontal. A third region S 3  is a region where the normal direction at a contact point with the second cam follower is downward relative to the horizontal direction. 
     The operation handle section  25  includes left and right vertical transmission rods  65 , which are mounted on front portions of the left and right guide frames  38  and  39  of the support frame section  23  in such a way as to be able to move and slide within a predetermined small range in the up-down direction relative to the front portions. To a lower portion of each transmission rod  65 , an almost L-shaped connection stay  66  is joined. Tip end portions of the two connection stays  66  that protrude forward hold a handle lever  67 , which is long and extends in the left-right direction. The handle lever  67  is grabbed by hands to operate the operation handle section  25  and thereby lift up or down the support frame section  23  and the article B. 
       FIGS. 8 and 12  show the case where the support frame section  23  on which the article B is mounted is located at an uppermost position of a movement range thereof. The second cam followers  59  and  60  remain stationary at the upper ends of the first regions S 1  of the fixed cam surfaces  36  and  37 . At this position, the load W of the article B acting on the system made up of the cam follower members  55  and  56 , the fixed frame section  22 , and the support frame section  23 , the spring force FA of the first spring  24 , the spring force FB of the second spring  52 , and the reaction force applied from the fixed cam surfaces are balanced against each other around the cam follower members. 
     In the first region S 1 , the amounts of displacement of the extension coil springs  46  and  47  of the first spring  24  are small, and that spring force FA is smaller than the load W of the article B. The reaction force Rc that is applied to the second cam follower  59  from the fixed cam surface  36  contains an upward vertical component. Therefore, this component is used as an assist force and is added to the spring force FA of the first spring  24 . As a result, an equilibrium with the load W is achieved in the vertical direction. 
       FIGS. 13 and 14  show the case where the support frame section  23  on which the article B is mounted is located at a middle position of the movement range thereof. The second cam followers  59  and  60  remain stationary at a position inside the second region S 2  of the fixed cam surfaces  36  and  37 . Even at this middle position, the load W of the article B acting on the system made up of the cam follower members, the fixed frame section, and the support frame section, the spring force FA of the first spring, the spring force FB of the second spring, and the reaction force applied from the fixed cam surfaces are balanced against each other around the cam follower members. 
     In the second region S 2 , the spring force FA of the first spring  24  is substantially balanced against the load W. In effect, the reaction force Rc applied from the fixed cam surfaces  36  and  37  only contains a horizontal component, and is balanced against the spring force FB of the second spring  52 , and does not include a vertical component. 
       FIGS. 15 and 16  show the case where the support frame section  23  on which the article B is mounted is located at a lowermost position of the movement range thereof. The second cam followers  59  and  60  remain stationary at the lower end of the third region S 3  of the fixed cam surfaces  36  and  37 . Even at this lower-end position, the load W of the article B acting on the system made up of the cam follower members, the fixed frame section, and the support frame section, the spring force FA of the first spring, the spring force FB of the second spring, and the reaction force applied from the fixed cam surfaces are balanced against each other around the cam follower members. 
     In the third region S 3 , the amounts of displacement of the extension coil springs  46  and  47  of the first spring  24  are large, and the spring force FA thereof is larger than the load W of the article B. The reaction force Rc that is applied to the second cam follower  59  from the fixed cam surface  36  contains a downward vertical component, which acts in a direction in which the push-up force of the spring force FA of the first spring  24  is reduced. As a result, the force is balanced against the load W in the vertical direction. 
     If the load W of the article B becomes smaller, the spring force FA of the first spring  24  becomes relatively larger because the first spring  24  remains the same. Therefore, in the first region S 1 , the assist force added to the spring force FA from the fixed cam surface needs to be smaller; in the third region S 3 , the force that is applied downward to reduce the push-up force of the spring force FA needs to be larger. 
     If the load W of the article B becomes larger, the spring force FA of the first spring  24  becomes relatively smaller. Therefore, in the first region S 1 , the assist force added to the spring force FA from the fixed cam surface needs to be larger; in the third region S 3 , the force that is applied downward to reduce the push-up force of the spring force FA needs to be smaller. 
     In the article support device  20 , the axis-direction length of the cam follower holders  53  and  54  are changed to adjust the amount of compression and displacement of the second spring  52 . In this manner, the adjustment is made in such a way as to increase or decrease the biasing force FB of the second spring  52  that is at the same height position of the support frame section  23 , or the reaction force Rc applied from the fixed cam surface. If the load W is small, the axis-direction length of the cam follower holders is shortened to reduce the biasing force FB of the second spring  52 , thereby decreasing the reaction force Rc applied from the fixed cam surface and the vertical component thereof. If the load W is large, the axis-direction length of the cam follower holders is increased to boost the biasing force FB of the second spring  52 , thereby increasing the reaction force Rc applied from the fixed cam surface and the vertical component thereof. 
     In the article support device  20 , since the forces are balanced in the vertical direction at the stationary position, the article B can easily be moved with a relatively small force from any height position to another height position. However, if the mass of the article is increased, an inertial force acting on the moving article increases accordingly, and it might be difficult to stop at a desired position. In the worst case scenario, the support frame section  23  carrying the article B could violently hit the fixed frame section  22  at the upper or lower end of the movement range or of the up-down stroke. 
     As a means to solve the above problem, in general, what is known is an elastic body, such as a damper, shock absorber or rubber, which works to attenuate or absorb kinetic energy. For example, if a gas spring or an oil damper, which makes use of fluid resistance, is used, it becomes difficult to handle the device and the device becomes expensive, as the device as a whole becomes complicated, larger, and heavier. The elastic body such as rubber may not always be sufficiently effective. 
     The article support device  20  of the present embodiment includes a cushioning mechanism of an effective, simple configuration to slow down the movement of the support frame section  23  at the upper and lower ends of the up-down stroke of the support frame section  23  and thereby stop the support frame section  23  without a large shock. The cushioning mechanism is realized in an effective manner based on the basic technical concept of the present invention by applying a new, novel idea to the cam plates of the fixed cam members  34  and  35  that drive the second cam followers  59  and  60 , as described below. 
       FIG. 17  is an enlarged view of an area around the upper end of the fixed cam surface  36  of the fixed cam member  34  shown in the left section of the diagram. In the diagram, a contact point of the second cam follower  59  with the fixed cam surface  36 , indicated by solid line, is an upper-limit position C 1  of an effective region S of the fixed cam surface where the function of causing the support frame section  23  on which the article B is mounted to stop at a desired height position is demonstrated. The fixed cam surface  36  further extends upward from the upper-limit position C 1 , and an upper cushioning area L 1  and an upper stopper area M 1  are successively provided. 
     The upper cushioning area L 1  is significantly curved in a direction opposite to a virtual fixed cam surface extension section  36 ′ indicated by imaginary line in the diagram. The upper cushioning area L 1  is curved in such a way as to pass through a point D 1 , where the tangential direction thereof is vertical, on the way to the upper stopper area M 1 . The upper stopper area M 1  is a horizontal surface that faces downward to completely stop the upward movement of the second cam follower  59 . 
     In the upper cushioning area L 1 , from the upper-limit position C 1  to the point D 1 , the slope of the tangential direction relative to the vertical direction becomes rapidly smaller. Accordingly, an upward vertical component of the reaction force applied from the fixed cam surface  36  to the second cam follower  59  rapidly decreases, and drops to zero at point D 1 . As a result, the assist force added from the fixed cam surface  36  to the biasing force FA of the first spring  24  is rapidly lost, significantly slowing the upward movement of the article B and the support frame section  23 . 
     In the range extending from the point D 1  to the upper stopper area M 1 , the reaction force applied from the fixed cam surface  36  to the second cam follower  59  generates a downward vertical component, thereby pushing down the second cam follower  59 . As a result, the upward movement of the article B and the support frame section  23  is further slowed down. 
     Due to such a downward deceleration action, the guide frames  38  and  39  of the support frame section  23  do not collide with the upper end of the guide rail  31  of the fixed frame section  22 , and the second cam follower  59  is stopped in the upper cushioning area L 1 . Even if the second cam follower  59  is not stopped, the second cam follower  59  enters the upper stopper area M 1  at a relatively low speed before being stopped there. At this stop position, the weight of the article B and the support frame section  23  combined is greater than the push-up force of the first spring  24 . Therefore, after being stopped very temporarily, the article B and the support frame section  23  start gradually and slightly going down due to their own weight, and the second cam follower  59  is stopped after returning to an area near the upper-limit position C 1 . 
       FIG. 18  is an enlarged view of an area around the lower end of the fixed cam surface  36 . In the diagram, a contact point of the second cam follower  59  with the fixed cam surface  36 , indicated by solid line, is a lower-limit position C 2  of the effective region S of the fixed cam surface. The fixed cam surface  36  further extends downward from the lower-limit position C 2 , and a lower cushioning area L 2  is provided. 
     The lower cushioning area L 2  is significantly curved in a direction opposite to a virtual fixed cam surface extension section  36 ″ indicated by imaginary line in the diagram. The middle of the lower cushioning area L 2  is further curved after passing through a point D 2 , where the tangential direction thereof is vertical. From the lower-limit position C 2  to D 2 , the slope of the tangential direction relative to the vertical direction becomes rapidly smaller. 
     Accordingly, a downward vertical component of the reaction force applied from the fixed cam surface  36  to the second cam follower  59  rapidly decreases, and drops to zero at point D 2 . As a result, the force of pushing down the support frame section  23  against the biasing force of the first spring  24  is rapidly lost, significantly slowing the downward movement of the article B and the support frame section. 
     In the range beyond the point D 2 , the reaction force applied from the fixed cam surface  36  to the second cam follower  59  generates an upward vertical component, thereby pushing up the second cam follower  59 . As a result, the downward movement of the article B and the support frame section  23  is further slowed down. 
     Due to such an upward deceleration action, the guide frames  38  and  39  of the support frame section  23  do not collide with the lower end of the guide rail  31  of the fixed frame section  22 , and the second cam follower  59  is stopped in the lower cushioning area L 2 . At this stop position, the push-up force of the first spring  24  is greater than the weight of the article B and the support frame section  23  combined. Therefore, after being stopped very temporarily, the article B and the support frame section  23  go up slightly due to the biasing force of the first spring, and the second cam follower  59  is stopped after returning to an area near the lower-limit position C 2  of the fixed cam surface  36 . 
       FIGS. 17 and 18  only show the fixed cam member  34 , which is shown in the left sections of the diagrams. In the right fixed cam member  35 , the upper cushioning area L 1 , the upper stopper area M 1 , and the lower cushioning area L 2  may be similarly provided. Needless to say, those areas may be provided in either the fixed cam member  34  or  35 . Moreover, either a set of the upper cushioning area L 1  and upper stopper area M 1  or the lower cushioning area L 2  may be provided. 
     According to the present embodiment, in order to slow and/or stop the support frame section  23  at the upper and lower ends of the up-down stroke, the fixed cam surface  36  is extended above and below the effective region S, and the cushioning areas in which the forces acting around the cam follower member  55  will not be balanced are provided. According to another embodiment, a region in which the forces acting around the cam follower member  55  will not be balanced may be provided between regions where the forces acting around the cam follower member will be balanced, or may be provided within the effective region S of the fixed cam surface  36 . 
     For example, in the first region S 1  of the fixed cam surface  36 , a non-equilibrium region with a slope that reduces the upward assist force more than an equilibrium state, and a non-equilibrium region with a slope that brings the assist force back to the original level, may be successively provided between an equilibrium region and an equilibrium region. In the third region S 3  of the fixed cam surface  36 , a non-equilibrium region with a slope that reduces a downward force of reducing the biasing force of the spring more than an equilibrium state, and a non-equilibrium region with a slope that brings that force back to the original level, may be successively provided between an equilibrium region and an equilibrium region. 
     In such a case, the moving support frame section  23  would cause a temporary change in the traveling speed and suffer a mild shock associated with the change, as the support frame section  23  gets into a non-equilibrium region from an equilibrium region and goes back to the equilibrium region. Therefore, a user who is manually operating the handle lever  67  of the operation handle section  25  can recognize the height position of the moving support frame section  23 . 
     In a non-equilibrium region, the forces acting around the cam follower member  55  are balanced against each other at a position where the direction of the slope is changed. Therefore, if this position is preset, the support frame section  23  can be easily stopped at a desired height position. Such a height position may be a middle position of the up-down stroke of the support frame section  23 , for example. 
     According to the above-described embodiment of  FIGS. 1 to 6 , the cam grooves  13 ,  48 , and  49  are provided in such a way as to horizontally extend on the lateral frame member  10   b  or the lower frame  42 . According to another embodiment, depending on the structure and purpose of the support mechanism, design conditions, and the like, the cam grooves  13 ,  48 , and  49  may be provided diagonally, or may be provided in a cross direction that is not perpendicular to the movement direction of the movable support section or support frame section. 
     The first movable cam surface and the second movable cam surface in the cam groove  13 ,  48 , or  49  may not be provided in parallel. All that is required is for the first movable cam surface and the second movable cam surface to be disposed in such a way as to face each other, with one of the movable cam surfaces coming in contact with the cam follower member to make it possible to transmit the load and the spring force of the first spring therebetween. 
     Furthermore, the article support device  20  of the present embodiment includes the brake mechanism that can keep the support frame section  23  at a desired height position even when an external force, such as vibration or shock, is applied, and can easily move or stop the support frame section  23  through a simple operation. The brake mechanism includes the brake device  45  of the support frame section  23  and the first brake rail  31  of the fixed frame section  22 . As the handle lever  67  of the operation handle section  25  is operated, the brake device  45  is activated via the transmission rods  65  or is released. 
     As shown in  FIG. 19 , the brake device  45  is disposed just ahead of the upper frame  40  of the support frame section  23  in such a way as to be slightly separated therefrom and run parallel to the upper frame  40 ; and is disposed right behind the first brake rail  31  of the fixed support frame section  22 . The brake device  45  includes a transmission plate  71  that extends in the left-right direction. The left and right end portions of the transmission plate  71  is mounted integrally and fixed to the upper end portions of the left and right transmission rods  65  via appropriate stays  72 , for example. 
     The transmission rods  65  are mounted in such a way as to be able to move up and down relative to the left and right guide frames  38  and  39  of the adjacent support frame section  23  within a predetermined small range. More specifically, the transmission rods  65  and the transmission plate  71  can move up and down between a home position shown in  FIG. 20 , an upward release position shown in  FIG. 21 , and a downward release position shown in  FIG. 22 . 
     On at least one transmission rod  65 , a rack  73  is provided integrally; a pinion  74 , which meshes with the rack, is mounted integrally and coaxially with a spring shaft  75 , which is horizontally stretched between the two guide frames and is provided in the axis direction and in a rotatable manner. Around the spring shaft  75 , a return spring  76 , which is a coil spring for example, is gently wound, and is used to push up the transmission rod  65  via the pinion  74  and the rack  73 . One end  76   a  of the return spring  76  is fastened to a claw  75   a  on the spring shaft  75  in a direction in which the transmission rod  65  is pressed upward. The other end  76   b  is provided in such a way as to be freely engaged with or detached from an engagement portion (not shown) of the guide frame depending on a rotation position of the spring shaft  75 . 
     At the home position shown in  FIG. 20 , the other end  76   b  of the return spring  76  engages with the engagement portion and presses the transmission rod  65  and the transmission plate  71  upward. When the operation handle section  25  is manually pushed down to move the transmission rod and the transmission plate from the home position to the downward release position of  FIG. 22 , the other end  76   b  of the return spring  76  still remains engaged with the engagement portion. After that, once a user gets his/her hands off the operation handle section, the transmission rod and the transmission plate start to move upward due to the biasing force of the return spring  76  and return to the home position. 
     When the operation handle section  25  is manually pushed up to move the transmission rod and the transmission plate from the home position to the upward release position of  FIG. 21 , the other end  76   b  of the return spring  76  is released from the engagement portion, and the biasing force of the return spring is lost. After that, once a user gets his/her hands off the operation handle, the transmission rod and the transmission plate go down due to their own weight and return to and stop at the home position where the biasing force of the return spring is restored. 
     On the transmission plate  71 , on the left and right sides of the first brake rail  31 , pairs of transmission pins  77   a ,  77   b ,  78   a , and  78   b  are provided integrally and symmetrically in the left-right direction in such away as to protrude forward. The transmission pins  77   a ,  77   b ,  78   a , and  78   b  are disposed just outside of the first brake rail  31  in such a way that the pairs are separated from each other in the up-down direction with a certain distance therebetween. 
     On the upper frame  40  of the support frame section  23 , pairs of support shafts  79   a ,  79   b ,  80   a , and  80   b  are provided on both sides of the first brake rail  31  in such a way as to be closer to the outer sides than the transmission pins; the support shafts  79   a ,  79   b ,  80   a , and  80   b  are provided integrally and symmetrically in the left-right direction in such a way as to protrude forward. The upper support shafts  79   a  and  80   a  are disposed below the upper transmission pins  77   a  and  78   a . The lower support shafts  79   b  and  80   b  are disposed above the lower transmission pins  77   b  and  78   b . The tip of each support shaft is inserted into a release hole (not shown) that is made in the transmission plate  71 , and extends from the front side of the transmission plate. The release holes of the transmission plate  71  are large enough not to obstruct the up-down movement of the transmission plate when the operation handle section  25  is operated as described above. 
     On the tips of the support shafts  79   a ,  79   b ,  80   a , and  80   b  that protrude from the front side of the transmission plate  71 , brake arms  81   a ,  81   b ,  82   a , and  82   b  are pivotally mounted in a rotatable manner along a plane of the transmission plate  71 , respectively. The upper brake arms  81   a  and  82   a  are disposed above the upper transmission pins  77   a  and  78   a , which are adjacent to the tip portions of the upper brake arms  81   a  and  82   a . The lower brake arms  81   a  and  82   b  are disposed below the lower transmission pins  77   b  and  78   b , which are adjacent to the tip portions of the lower brake arms  81   a  and  82   b.    
     On base end portions of the brake arms, gear sections  83   a ,  83   b ,  84   a , and  84   b  are formed on the outer peripheries of the brake arms. The gear sections of the brake arms  81   a  and  81   b  that are paired in the up-down direction mesh with one another, and the gear sections of the brake arms  82   a  and  82   b  that are paired in the up-down direction mesh with one another. Therefore, in each pair of brake arms, as one is rotated, the other starts to rotate in the opposite direction. 
     Between the gear sections  83   a  and  83   b  and  84   a  and  84   b  that mesh with one another, there is backlash. Accordingly, as for the brake arms  81   a  and  81   b  and  82   a  and  82   b  that are paired in the up-down direction, as one starts to rotate, the other starts to rotate with a short delay. Therefore, the brake arm on the side to which the support frame section  23  is to be moved is released from the engagement with the side surface of the first brake rail  31 , before the other-side brake arm is released from the engagement with the side surface of the first brake rail. During the period in which the release is delayed, the support frame section  23  is held in such a way as not to move to the side opposite to the direction in which the section is supposed to move. 
     On the tips of the brake arms, brake shoes  85   a ,  85   b ,  86   a , and  86   b  are provided. Between the tip portions of the brake arms  81   a  and  81   b  and  82   a  and  82   b  that are paired in the up-down direction, extension springs  87   a  and  87   b  are placed to press the brake arms toward each other. Due to the biasing force of the extension springs  87   a  and  87   b , each of the brake shoes is pressed against the side surface of the first brake rail  31  at the home position of  FIG. 22 . The spring strength of each extension spring is set in such a way as to exert frictional resistance or braking force strong enough to make it difficult for the support frame section  23  on which the article B is mounted to move from the stationary position, between the brake shoes and the side surfaces of the first brake rail  31 . 
     The upper brake arms  81   a  and  82   a  are designed to exert a larger braking force for the upward movement of the support frame section  23  than for the downward movement, or to exert a larger braking force in the downward direction than in the upward direction. The lower brake arms  81   b  and  82   b  are designed to exert a larger braking force for the downward movement of the support frame section  23  than for the upward movement, or to exert a larger braking force in the upward direction than in the downward direction. The reason, as described later, is that the upper brake arms  81   a  and  82   a  are disposed obliquely in such a way that the fulcrums or support shafts  79   a  and  80   a  are positioned below the contact points of the brake shoes  85   a  and  86   a  with the side surfaces of the first brake rail  31 , and that the lower brake arms  81   b  and  82   b  are disposed obliquely in such a way that the fulcrums or support shafts  79   b  and  80   b  are positioned above the contact points of the brake shoes  85   b  and  86   b  with the side surfaces of the first brake rail  31 . 
     When the operation handle section  25  is lifted up to move the transmission plate  71  to the upward release position shown in  FIG. 21 , the upper transmission pins  77   a  and  78   a  come in contact with side edges of the upper brake arms  81   a  and  82   a , thereby turning the upper brake arms  81   a  and  82   a  in an upward outward direction against the biasing forces of the extension springs  87   a  and  87   b . In response, the lower brake arms  81   b  and  82   b  are turned in the downward outward direction. As a result, the brake shoes are released from the engagement with the side surfaces of the first brake rail  31 , allowing a user to keep pushing up the operation handle section  25  and freely move the support frame section  23  upward. 
     When the operation handle section  25  is pulled down to move the transmission plate  71  to the lower release position shown in  FIG. 22 , the lower transmission pins  77   b  and  78   b  come in contact with side edges of the lower brake arms  81   b  and  82   b , thereby turning the lower brake arms  81   b  and  82   b  in a downward outward direction against the biasing forces of the extension springs  87   a  and  87   b . In response, the upper brake arms  81   a  and  82   a  are turned in an upward outward direction. As a result, the brake shoes are released from the engagement with the side surfaces of the first brake rail  31 , allowing a user to continue pushing down the operation handle section  25  and freely move the support frame section  23  downward. 
       FIG. 23  shows a brake device  110  as a modified example of the brake device  45  of the first embodiment of  FIG. 19 . Incidentally, in the description below and accompanying drawings pertaining to the brake device  110 , the same components as those of the brake device  45  of  FIG. 19  are represented by the same reference symbols. 
     The brake device  110  is different from the brake device  45  of  FIG. 19  in that, on the outer peripheries of the base end portions of brake arms  111   a ,  111   b ,  112   a , and  112   b , gear sections are not provided. The brake arms  111   a  and  111   b  and  112   a  and  112   b  that are paired in the up-down direction are able to rotate independently. 
     In  FIG. 23 , brake shoes  85   a ,  85   b ,  86   a , and  86   b  of the tips of the brake arms  111   a ,  111   b ,  112   a , and  112   b  are pressed against the side surfaces of the first brake rail  31  by the biasing forces of the extension springs  87   a  and  87   b . As a result, the support frame section  23  remains in a braking state and stationary at a desired height position. 
       FIG. 24  shows the situation where the transmission plate  71  is moved to the upward release position shown in the diagram as the operation handle section  25  is lifted up. As in the case of the brake device  45  of  FIG. 19 , the upper transmission pins  77   a  and  78   a  come in contact with side edges of the upper brake arms  111   a  and  112   a , thereby turning the upper brake arms  111   a  and  112   a  in an upward outward direction against the biasing forces of the extension springs  87   a  and  87   b . At this time, due to the biasing forces of the extension springs  87   a  and  87   b , the brake shoes  85   b  and  86   b  of the lower brake arms  111   b  and  112   b  remain pressed against the side surfaces of the first brake rail  31 . 
     As a result, in the brake device  110 , only the braking forces of the upper brake arms  111   a  and  112   a  are released, while there still remain the braking forces of the lower brake arms  111   b  and  112   b . As described above in relation to the brake device  45  of  FIG. 19 , the lower brake arms are disposed obliquely in such away that the support shafts  79   b  and  80   b  are positioned above the contact points of the brake shoes  85   b  and  86   b  with the side surfaces of the first brake rail  31 . That is, the lower brake arms are provided in such a way as to extend downward and obliquely from the support shafts  79   b  and  80   b  toward the side surfaces of the first brake rail  31 . Therefore, the lower brake arms exert a larger braking force in the upward direction than in the downward direction, or exert a larger braking force for the downward movement than for the upward movement. 
     Therefore, when the operation handle section  25  is lifted up, the frictional resistance applied from the lower brake shoes  85   b  and  86   b  is relatively small, thereby requiring a larger operation force than in the brake device  45  of  FIG. 19 . However, the support frame section  23  can be similarly moved upward. On the other hand, a relatively large braking force occurs in the downward direction. Therefore, this configuration effectively prevents the support frame section  23  from unexpectedly going down due to an external force or the like, contributing to improving the safety. 
       FIG. 25  shows the situation where the transmission plate  71  is moved to the downward release position shown in the diagram as the operation handle section  25  is pulled down. As in the case of the brake device  45  of  FIG. 19 , the lower transmission pins  77   b  and  78   b  come in contact with side edges of the lower brake arms  111   b  and  112   b , thereby turning the lower brake arms  111   b  and  112   b  in a downward outward direction against the biasing forces of the extension springs  87   a  and  87   b . At this time, due to the biasing forces of the extension springs  87   a  and  87   b , the brake shoes  85   a  and  86   a  of the upper brake arms  111   a  and  112   a  remain pressed against the side surfaces of the first brake rail  31 . 
     As a result, in the brake device  110 , only the braking forces of the lower brake arms  111   b  and  112   b  are released, while there still remain the braking forces of the upper brake arms  111   a  and  112   a . The upper brake arms are disposed obliquely in such a way that the support shafts  79   a  and  80   a  are positioned below the contact points of the brake shoes  85   a  and  86   a  with the side surfaces of the first brake rail  31 . That is, the upper brake arms are provided in such a way as to extend upward and obliquely from the support shafts  79   a  and  80   a  toward the side surfaces of the first brake rail  31 . Therefore, the upper brake arms exert a larger braking force in the downward direction than in the upward direction, or exert a larger braking force for the upward movement than for the downward movement. 
     Therefore, when the operation handle section  25  is pulled down, the frictional resistance applied from the upper brake shoes  85   a  and  86   a  is relatively small, thereby requiring a larger operation force than in the brake device  45  of  FIG. 19 . However, the support frame section  23  can be similarly moved downward. On the other hand, a relatively large braking force occurs in the upward direction. Therefore, this configuration effectively prevents the support frame section  23  from unexpectedly going up due to an external force or the like, contributing to improving the safety. 
     The description of the brake arms of the present embodiment that have directional properties in the braking forces will be supplemented with  FIGS. 26A and 26B .  FIGS. 26A and 26B  show the braking action of a pair of one-side brake arms  81   a  and  81   b  of the brake device  45  of  FIG. 19 , using an example in which the support frame section  23  is moved upward. For ease of explanation, each of the brake arms  81   a  and  81   b  will be schematically described as one straight line, and suppose that the end portions Ta and Tb of the extension spring  87   a  are attached to points on straight lines extending from contact points Qa and Qb of the brake shoes  85   a  and  85   b  with the side surface of the first brake rail  31  to the support shafts  79   a  and  79   b  of the brake arms. 
     As shown in  FIG. 26A , the upper brake arm  81   a  is disposed and tilted at angle θ to the side surface of the first brake rail in such a way that the fulcrum or support shaft  79   a  is positioned below the contact point Qa with the side surface of the first brake rail  31 , or is positioned on the side opposite to the movement direction U of the support frame section  23 . To the brake arm  81   a , the biasing force Fs of the extension spring  87   a  is constantly applied in the vertically downward direction. 
     When the support frame section  23  is being moved upward, an upward external force F acts on the support shaft  79   a  of the brake arm  81   a . Right before the brake shoe  85   a  starts to slide on the side surface of the first brake rail  31  due to the external force F, a maximum static frictional force Fsa is acting in the downward direction between the brake shoe and the side surface of the first brake rail  31  against the external force F. The reaction force that is applied to the brake shoe from the side surface of the first brake rail  31  in the normal direction is represented by Na. 
     At this time, moments around the support shaft  79   a  are being balanced as follows: 
         Mfa+Msa−Mna= 0 
     Here, if the distance from the support shaft  79   a  to the contact point Qa is represented by d 1 , and the distance to the end portion Ta of the extension spring is represented by d 2 , the following equations are obtained: 
         Msa=Fs ·sin θ× d 2
 
         Mfa=Fsa ·sin θ× d 1
 
         Mna=Na ·cos θ× d 1
 
     As shown in  FIG. 26B , the lower brake arm  81   b  is disposed and tilted at angle θ to the side surface of the first brake rail in such a way that the fulcrum or support shaft  79   b  is positioned above the contact point Qb with the side surface of the first brake rail  31 , or is positioned on the same side as the movement direction U of the support frame section  23 . To the brake arm  81   b , the biasing force Fs of the extension spring  87   a  is constantly applied in the vertically upward direction. 
     When the support frame section  23  is being moved upward, an upward external force F acts on the support shaft  79   b  of the brake arm  81   b . Right before the brake shoe  85   b  starts to slide on the side surface of the first brake rail  31  due to the external force F, a maximum static frictional force Fsb is acting in the downward direction between the brake shoe and the side surface of the first brake rail  31  against the external force F. The reaction force that is applied to the brake shoe from the side surface of the first brake rail  31  in the normal direction is represented by Nb. 
     At this time, moments around the support shaft  79   b  are being balanced as follows: 
         Mfb−Msb+Mnb= 0 
     Here, similarly, if the distance from the support shaft  79   b  to the contact point Qb is represented by d 1 , and the distance to the end portion Tb of the extension spring is represented by d 2 , the following equations are obtained: 
         Msb=Fs ·sin θ× d 2
 
         Mfb=Fsb ·sin θ× d 1
 
         Mnb=Nb ·cos θ· d 1
 
     The magnitude of the moments Mna and Mnb associated with the reaction forces Na and Nb that are applied to the brake shoes  85   a  and  85   b  from the side surface of the first brake rail  31  are: Mna=Msa+Mfa and Mnb=Msb−Mfb. Since Msa=Msb, Mna&gt;Mnb. If the static friction coefficient between the brake shoes and the side surface of the first brake rail is represented by μ, Na=μ·Fsa and Nb=μ·Fsb. Accordingly, Fsa&gt;Fsb. In this manner, if the support shafts  79   a  and  79   b  of the brake arms  81   a  and  81   b  are disposed in such a way as to be tilted to one side with respect to the contact points of the brake arms with the side surface of the first brake rail  31 , a larger braking force is generated toward the tilted side than the opposite side. 
     The support frame section  23  can be lifted up or down with a relatively small force. If a user operates the operation handle section  25  with a strong force by accident, the operation handle section  25  might move so fast that the operation handle section  25  cannot be stopped at a desired position, or that a sufficient deceleration cushioning effect cannot be achieved even by the cushioning mechanism. To solve this problem, the article support device  20  of the present embodiment further includes a speed limiter mechanism to curb or limit the movement speed of the support frame section  23 . 
     As shown in  FIG. 27 , a speed limiter mechanism  90  of the present embodiment includes a centrifugal brake device  100 , which is provided in the support frame section  23 ; and a second brake rail  92 , which is provided in the fixed frame section  22 . The second brake rail  92  is disposed on the rear side of the first brake rail  31  of the fixed frame section, and extends vertically downward from the center of the upper frame  26 , and is long enough to sufficiently cover the up-down stroke of the support frame section. The second brake rail  92  is U-shaped in cross-section in such a way as to be open to the front side. On one internal surface thereof, a rack  92   a , which extends in the vertical direction, is formed integrally. 
     The centrifugal brake device  100  is disposed between a center plate  91 , which is fixed to the center of the back surface of the upper frame  40  of the support frame section  23 , and the second brake rail  92 . The centrifugal brake device  100  includes a circular frame  101 , which is fixed to the back surface of the center plate  91 ; and a rotation plate  102 , which is supported within the circular frame in such a way as to freely rotate around a center shaft  103   a  thereof. The rotation plate  102  includes a pair of parallel long sides and a pair of arc-shaped short sides. At the center thereof, a small gear  103  is provided integrally and concentrically with the center shaft  103   a  of the circular frame. 
     As shown in  FIG. 28A , on one of the short sides of the rotation plate  102 , a pair of brake arms  104   a  and  104   b  is attached; at base end portions of the brake arms  104   a  and  104   b , the brake arms  104   a  and  104   b  can swing around support shafts  105   a  and  105   b , and are mounted symmetrically in the left-right direction with respect to the longitudinal direction of the rotation plate. The brake arms  104   a  and  104   b  each have a semicircular arc shape, and are bent in such a way as to extend along the inner peripheral surface of the circular frame  101 . An extension spring  107 , which is provided between the brake arms  104   a  and  104   b , presses the brake arms  104   a  and  104   b  toward each other. Pins  109   a  and  109   b  are provided at free ends of the brake arms  104   a  and  104   b  in such a way as to protrude; the pins  109   a  and  109   b  are inserted into long holes  108   a  and  108   b , which are formed in the rotation plate  102 . The long holes  108   a  and  108   b  limit the swingable range. 
     On the brake arms  104   a  and  104   b , brake shoes  106   a  and  106   b  are mounted in such a way that at least portions of the brake shoes  106   a  and  106   b  protrude from the outer peripheral edges of the brake arms toward the inner peripheral surface of the circular frame  101 . The brake shoes  106   a  and  106   b  are disposed in such a way as to be not in contact with the inner peripheral surface of the circular frame  101  as shown in  FIG. 28A  at a time when the centrifugal brake device  100  is not working, or to be engaged with the inner peripheral surface of the circular frame as shown in  FIG. 28B  at a time when the centrifugal brake device is working. 
     As shown in  FIG. 27 , between the centrifugal brake device  100  and the second brake rail  92 , a gear member  93  is provided in such a way as to freely rotate around a central shaft  93   b , which is fixed to the center plate  91 . The gear member  93  includes a pinion  94 , which is a small gear provided concentrically with the central shaft  93   b , and a large gear  95 , which is provided along the outer periphery. The gear member  93  is mounted in such a way that the pinion  94  meshes with the rack  92   a  of the second brake rail  92 , and that the large gear  95  meshes with the small gear  103  of the rotation plate  102 . 
     As the support frame section  23  is moved up or down, the gear member  93  is rotated by the rack  92   a  and the pinion  94 . As a result, the rotation plate  102  starts to rotate at high speeds depending on the gear ratio of the large gear  95  and the small gear  103 . The rotation speed of the rotation plate  102  increases or decreases depending on the speed at which the support frame section  23  is moved up or down. 
     When the support frame section  23  is stationary or is moving at a very slow speed, the brake arms  104   a  and  104   b  of the centrifugal brake device  100  do not swing at all from the position shown in  FIG. 28A  due to the biasing force of the extension spring  107 . Therefore, the brake shoes do not come in contact with the inner peripheral surface of the circular frame  101 . As a result, the support frame section  23  can continue to move at slow speed. 
     As the movement speed of the support frame section  23  becomes faster, the brake arms  104   a  and  104   b  start to move away against the biasing force of the extension spring  107 . When the movement speed of the support frame section is relatively low, and when the swinging of the brake arms is small, the brake shoes similarly do not come in contact with the inner peripheral surface of the circular frame  101 . Therefore, the support frame section  23  can continue to move. 
     After the movement speed of the support frame section  23  exceeds a certain level, the brake arms are significantly separated against the biasing force of the extension spring  107 , and the brake shoes are coming in contact with the inner peripheral surface of the circular frame as shown in  FIG. 28B . Therefore, the movement of the support frame section  23  is slowed down depending on the magnitude of friction between the brake shoes and the inner peripheral surface of the circular frame. After the movement of the support frame section  23  is decelerated to a certain degree, the brake arms start to come close to each other due to the extension spring  107 , and the brake shoes are released from their contact with the inner peripheral surface of the circular frame. Therefore, the support frame section  23  can smoothly move at the decelerated speed. 
     As the movement speed of the support frame section  23  becomes even faster, the brake arms are separated to a maximum extent against the biasing force of the extension spring  107 , and the brake shoes are therefore strongly pressed against the inner peripheral surface of the circular frame. As a result, the support frame section  23  is significantly decelerated and can be stopped in some cases. After the movement of the support frame section  23  is decelerated to a certain degree or stopped, the brake arms similarly start to come close to each other due to the extension spring  107 , and the brake shoes are released from their contact with the inner peripheral surface of the circular frame. As a result, the support frame section  23  can smoothly move at the decelerated speed, or can move again. 
     In that manner, according to the present embodiment, the above speed limiter mechanism  90  curbs or limits the movement speed of the support frame section  23 , thereby eliminating in advance the risk of being unable to control the moving or stopping of the support frame section through a user&#39;s careless or accidental operation. Therefore, especially in the case where a heavy object such as a large television monitor is supported, this configuration further improves safety. 
       FIG. 29  shows a second embodiment of an article support device to which the present invention has been applied. In the article support device  120  of the present embodiment, a brake mechanism and an operation handle section are different from those of the article support device  20  of the first embodiment. The rest of the configuration is substantially identical to that of the article support device  20  of the first embodiment, and therefore will not be detailed. Incidentally, in the description below and accompanying drawings pertaining to the article support device  120 , the same components as those of the brake device  45  of  FIG. 19  are represented by the same reference symbols. 
     As in the case of the article support device  20  of the first embodiment, in order to support an article such as a large-screen television monitor, the article support device  120  includes a base, which is placed on a floor surface or the like; a fixed frame section  22 , which is fixed to the base; a support frame section  23 , which is mounted on the fixed frame section in such a way as to be able to move up and down; a first sprint  24 ; and an operation handle section  121 , which is used to move up or down the support frame section  23 . 
     The fixed frame section  22  is a roughly rectangular frame structure, including upper and lower frames  26  and  27 , which extend horizontally, and left and right side frames  28  and  29 , which extend vertically between the upper frame and the lower frame. Furthermore, at the center of the fixed frame section  22 , a first brake rail  31  is provided in such a way as to extend vertically between the upper frame and an intermediate frame  30 , which extends horizontally between the left and right side frames  28  and  29  and is substantially located at a mid-height position. 
     The support frame section  23  is a roughly rectangular frame structure, including left and right guide frames  38  and  39 , which extend vertically, an upper frame  40 , which extends horizontally between the two guide frames, and two lower frames  41  and  42 , which are slightly separated in the up-down direction. The support frame section  23  is mounted on the fixed frame section  22  in such a way as to be able to move up and down along the guide rails, as the left and right guide frames  38  and  39  are fitted into the guide rails of the corresponding left and right side frames  28  and  29  of the fixed frame section in a slidable manner. 
     On the support frame section  23 , a pair of left and right mounting stays  44   a  and  44   b  are provided in such a way as to extend vertically just ahead of the guide frames; the mounting stays  44   a  and  44   b  are used to fix the article. Furthermore, in the support frame section  23 , at the center of the upper frame  40 , a brake device  122  is provided. 
     A brake mechanism of the present embodiment includes the brake device  122  and the first brake rail  31  of the fixed frame section  22 . In the brake device  122 , the operation handle section  121  causes brake pads  145  and  146  to engage with the first brake rail  31  or be released from the engagement. 
     The operation handle section  121  includes left and right vertical transmission rods  123   a  and  123   b , which are mounted on the front sides of the left and right guide frames  38  and  39  of the support frame section  23  and on the outer sides of the mounting stays  44   a  and  44   b  in such a way as to be adjacent to those components. To a lower portion of each transmission rod, an almost L-shaped connection stay  66   a  or  66   b  is joined. Tip end portions of the two connection stays that protrude forward hold a handle lever  67 , which is long and extends in the left-right direction. The handle lever  67  is grabbed by hands to operate the operation handle section  122  and thereby lift up or down the support frame section  23  and the article. 
     As shown in  FIG. 30 , to the upper inner portions of the transmission rods  123   a  and  123   b , connection members  124   a  and  124   b  are fixed. The connection members  124   a  and  124   b  are L-shaped in the up-down-direction cross-section and have a certain length in the up-down direction. The mounting stays  44   a  and  44   b  are U-shaped, and guide holes  125   a  and  125   b  are defined inside in such away as to extend in the up-down direction. 
     The transmission rods  123   a  and  123   b  are provided in such a way as to be able to move up and down relatively along the front surfaces of the left and right guide frames  38  and  39  and the outer surfaces of the mounting stays  44   a  and  44   b , as the connection members  124   a  and  124   b  are inserted into the guide holes  125   a  and  125   b  from outside the mounting stays  44   a  and  44   b . At the upper and lower ends of the connection members  124   a  and  124   b , stopper pieces  126   a  and  126   b  are provided. At the upper and lower ends of the guide holes, engagement portions  127   a  and  127   b  are provided. 
     The connection members  124   a  and  124   b  can move up and down in a range in which the stopper pieces  126   a  and  126   b  can be stopped by engaging with the engagement portions  127   a  and  127   b , as guided by the guide holes  125   a  and  125   b . The range in which the connection members can move up and down inside the guide holes determines a vertical-distance range in which the transmission rods  123   a  and  123   b  can move relative to the support frame section  23 . 
     As shown in  FIG. 31 , behind the connection member  124   b  ( 124   a ), a hook piece  128  is provided in such a way as to extend backward. On the upper frame  40  of the support frame section  23 , an opening section  129  is provided right behind the connection member  124   b  ( 124   a ) in such a way as to pass through and extend in the up-down direction. Right above the opening section  129  and in the end portion of the upper frame  40 , a hook piece  130  is similarly provided in such a way as to extend backward. Between the hook piece  128  of the connection member  124   b  ( 124   a ) and the hook piece  130  of the upper frame  40 , an extension coil spring  131  is hooked up. The extension coil spring  131  is constantly lifting up the transmission rods  123   a  and  123   b  via the connection members. 
     As shown in  FIG. 32 , between the left and right connection members  124   a  and  124   b , a pair of left and right connection plates  132   a  and  132   b  is provided. The connection plates  132   a  and  132   b  each has a long plate-like shape in the left-right direction as a whole. The centers of the connection plates  132   a  and  132   b  are attached through pivot shafts  133   a  and  133   b , which are provided on the front surface of the upper frame  40  of the support frame section  23  in such a way as to protrude; the connection plates  132   a  and  132   b  therefore can freely rotate along the plane of the upper frame  40 . 
     The left and right end portions of the connection plates  132   a  and  132   b  are bent backward in such a way as to have a crank shape. At the edges of the connection plates  132   a  and  132   b , gear sections  134   a ,  134   b ,  135   a , and  135   b  are formed. In the left and right end portions of the connection plates  132   a  and  132   b , arc-shaped guide grooves  136   a ,  136   b ,  137   a , and  137   b  are provided close to the inner sides of the gear sections in such a way as to pass therethrough. Into the guide grooves  136   a ,  136   b ,  137   a , and  137   b , guide pins  138   a ,  138   b ,  139   a , and  139   b , which are provided on the front surface of the upper frame  40  of the support frame section  23  in such a way as to protrude, are inserted. Accordingly, the connection plates  132   a  and  132   b  can rotate around the pivot shafts  133   a  and  133   b  in both directions within a range in which the guide pins remain engaged between the two ends of the guide grooves. 
     On the up-down direction inner edges of the connection members  124   a  and  124   b , rack sections  140   a  and  140   b  are formed. The connection plates are disposed in such a way that the inner-side gear sections  134   b  and  135   b  mesh with one another, and that the outer-side gear sections  134   a  and  135   a  mesh with the rack sections  140   a  and  140   b  of the corresponding connection members  124   a  and  124   b . In this manner, the left and right transmission rods  123   a  and  123   b  of the operation handle section  121  are connected to each other through a gear train made up of the rack sections  140   a  and  140   b  and the gear sections  134   a ,  134   b ,  135   a , and  135   b.    
     For example, when one transmission rode  123   a  is moved upward relative to the guide frame  38  of the support frame section  23 , as shown in  FIG. 33 , the upward movement of the connection member  124   a  causes the connection plate  132   a  to turn clockwise through the rack section  140   a  and the gear section  134   a . In response, the other connection plate  132   b  turns counterclockwise, causing the other transmission rod  123   b  to move upward in synchronization with the one transmission rod  123   a  through the gear section  135   a  and the rack section  140   b.    
     As shown in  FIG. 30 , the brake device  122  includes brake arms  141   a ,  141   b ,  142   a , and  142   b  that are paired in the up-down direction between the upper frame  40  of the support frame section  23  and the connection plates  132   a  and  132   b ; the brake arms  141   a ,  141   b ,  142   a , and  142   b  are disposed on both sides of the first brake rail  31  in such a way as to be symmetrical in the left-right direction. At the base end portions of the brake arms  141   a ,  141   b ,  142   a , and  142   b , the brake arms  141   a ,  141   b ,  142   a , and  142   b  are pivotally attached via support shafts  143   a ,  143   b ,  144   a , and  144   b , which protrude from the front surface of the upper frame  40 , in such a way as to freely rotate along the plane of the upper frame  40 . 
     To the tips of the brake arms, brake pads  145   a ,  145   b ,  146   a , and  146   b  are attached. In the braking state of  FIG. 32 , the entire pressing surfaces of the upper brake pads  145   a  and  146   a  are engaged with the side surfaces of the first brake rail  31 . The upper brake pads  145   a  and  146   a  are mounted obliquely, so that, as the braking action is gradually released, the gaps between the upper brake pads  145   a  and  146   a  and the side surfaces of the first brake rail gradually grow from the upper side. Similarly, in the braking state of  FIG. 32 , the entire pressing surfaces of the lower brake pads  145   b  and  146   b  are engaged with the side surfaces of the first brake rail  31 . The lower brake pads  145   b  and  146   b  are mounted obliquely, so that, as the braking action is gradually released, the gaps between the lower brake pads  145   b  and  146   b  and the side surfaces of the first brake rail gradually grow from the lower side. 
     In general, the brake pad exerts a larger braking force by pressing at a pressing position that is a concentrated point than by starting to press with a plane that goes along a displacement direction thereof. Accordingly, as described above, the brake pad is disposed in such a way as to be inclined in a direction moving away from the fulcrum. As a result, against the engagement surface of the first brake rail  31 , the upper brake pads  145   a  and  146   a  generate a large upward braking force, while the lower brake pads  145   b  and  146   b  generate a large downward braking force. 
     On the inner peripheral portions of the brake arms  141   a ,  141   b ,  142   a , and  142   b  that are paired in the up-down direction, hook pieces  147   a ,  147   b ,  148   a , and  148   b  are formed; between the hook pieces  147   a  and  147   b  and  148   a  and  148   b , extension springs  149   a  and  149   b  are hooked up. Therefore, the brake arms that are paired in the up-down direction are pressed toward each other. That is, the brake pads are pressed against the side surfaces of the first brake rail  31 . The spring strength of the extension springs  149   a  and  149   b  is set in such a way as to generate frictional resistance strong enough to make it difficult for the support frame section  23  on which the article is mounted to move from a stationary position, between the brake pads and the side surfaces of the first brake rail  31 . 
     On the back surfaces of the connection plates  132   a  and  132   b , first transmission pins  150   a ,  150   b ,  151   a , and  151   b  are provided above and below the pivot shafts  133   a  and  133   b  in such a way as to protrude backward; the first transmission pins  150   a ,  150   b ,  151   a , and  151   b , which are paired in the up-down direction, are an equal distance away from the pivot shafts  133   a  and  133   b . On the back surfaces of the connection plates, between the pivot shafts  133   a  and  133   b  and the first brake rail  31 , second transmission pins  152   a  and  152   b  are provided in such a way as to protrude backward and to be symmetrical in the left-right direction. 
     At the outer peripheries of the base end portions of the brake arms, first engagement projections  154   a  and  154   b  are formed in such a way as to extend toward the side opposite to the brake pads. Furthermore, at the base end portions of the brake arms, second engagement projections  156   a  and  156   b  are formed in a direction that is roughly perpendicular to the first engagement projections. Incidentally,  FIGS. 32 to 34  offer a partially crushed view of the connection plate  132   b  to only show the entire brake arms  142   a  and  142   b , which are shown in the right sections of the diagrams. 
     In the braking state of  FIG. 32 , the first engagement projections  154   a  and  154   b  are provided in such a way that the side edges of the first engagement projections  154   a  and  154   b  are in contact with the corresponding first transmission pins  151   a  and  151   b . After the braking state of  FIG. 32 , if the connection plate  132   a  shown in the left section of the diagram is rotated clockwise and if the right connection plate  132   b  is rotated counterclockwise, the upper first transmission pins  150   a  and  151   a  push the side edges of the first engagement projections  153   a  and  154   a  of the upper brake arms  141   a  and  142   a , and the brake arms  141   a  and  142   a  are therefore rotated in the direction that makes the brake pads  145   a  and  146   a  move away from the first brake rail  31 . After the braking state of  FIG. 32 , if the connection plate  132   a  shown in the left section of the diagram is rotated counterclockwise and if the right connection plate  132   b  is rotated clockwise, the lower first transmission pins  150   b  and  151   b  push the side edges of the first engagement projections  153   b  and  154   b  of the lower brake arms  141   b  and  142   b , and the brake arms  141   b  and  142   b  are therefore rotated in the direction that makes the brake pads  145   b  and  146   b  move away from the first brake rail  31 . 
     In the braking state of  FIG. 32 , the second engagement projections  155   a ,  155   b ,  156   a , and  156   b  are placed an equal distance away from the corresponding second transmission pins  152   a  and  152   b . When the left connection plate  132   a  is rotated clockwise by a certain angle or more and when the right connection plate  132   b  is rotated counterclockwise by a certain angle or more, the second transmission pins  152   a  and  152   b  come in contact with the side edges of the second engagement projections  155   b  and  156   b  of the lower brake arms and press the second engagement projections  155   b  and  156   b , and the brake arms  141   b  and  142   b  are therefore rotated in the direction that make the brake pads  145   b  and  146   b  move away from the first brake rail  31 . When the left connection plate  132   a  is rotated counterclockwise by a certain angle or more and when the right connection plate  132   b  is rotated clockwise by a certain angle or more, the second transmission pins  152   a  and  152   b  come in contact with the side edges of the second engagement projections  155   a  and  156   a  of the upper brake arms and press the second engagement projections  155   a  and  156   a , and the brake arms  141   a  and  142   a  are therefore rotated in the direction that make the brake pads  145   a  and  146   a  move away from the first brake rail  31 . 
     In the braking state shown in  FIG. 32 , the brake pads  145   a ,  145   b ,  146   a , and  146   b  of the brake arms  141   a ,  141   b ,  142   a , and  142   b  are engaged with the side surfaces of the first brake rail  31 , thereby braking in such a way as to keep the support frame section  23  from moving from the stationary position. From this state, the handle lever  67  is lifted up to move the transmission rods  123   a  and  123   b  upward. Accordingly, as shown in  FIG. 33 , the connection plate  132   a  starts to rotate clockwise and the connection plate  132   b  starts to rotate counterclockwise via the rack sections  140   a  and  140   b  and the gear sections  134   a  and  135   a.    
     Then, the upper first transmission pins  150   a  and  151   a  press the side edges of the first engagement projections  153   a  and  154   a  of the upper brake arms  141   a  and  142   a , thereby rotating the brake arm  141   a  counterclockwise and the brake arm  142   a  clockwise and causing the brake pads  145   a  and  146   a  to move away from the first brake rail  31 . In this manner, in the brake device  122 , the upward braking force is released. 
     At this time, the lower brake pads  145   b  and  146   b  remain engaged with the side surfaces of the first brake rail  31 . In this manner, the brake device  122  is keeping a fairly large downward braking force. Therefore, even if the force of lifting up the handle lever  67  is abruptly lost for some reason, the support frame section  23  does not immediately go down from the stationary position, thereby ensuring safety. 
     In this state, the stopper pieces  126   a  and  126   b  of the connection members  124   a  and  124   b  stay away from the upper engagement portions  127   b  of the guide holes  125   a  and  125   b , and therefore can move in the guide holes without being restricted by the guide frames  38  and  39  of the support frame section  23 . Therefore, since a load has yet to be applied to the handle lever  67  from the support frame section  23 , the handle lever  67  can be lifted up with a relatively small force. 
     From this state, the handle lever  67  is further moved up, so that the transmission rods  123   a  and  123   b  go upward relative to the guide frames  38  and  39  of the support frame section  23 . Then, as shown in  FIG. 34 , the stopper pieces  126   a  and  126   b  of the connection members  124   a  and  124   b  come in contact with the upper engagement portions  127   a  of the guide holes  125   a  and  125   b  and are stopped there in an engaged state. After that, the transmission rods  123   a  and  123   b , together with the guide frames  38  and  39 , can move the support frame section  23  upward. 
     At this time, the left connection plate  132   a  rotates clockwise and the right connection plate  132   b  rotates counterclockwise, and the second transmission pins  152   a  and  152   b  come in contact with the side edges of the second engagement projections  155   b  and  156   b  of the lower brake arms and press the side edges. As a result, the brake arm  141   b  rotates clockwise, and the brake arm  142   b  rotates counterclockwise, and the brake pads  145   b  and  146   b  move away from the first brake rail  31 . In this manner, the braking force of the brake device  122  is completely released, allowing a user to continue to lift up the handle lever  67  and freely move the support frame section  23  upward. 
     In this example, as shown in  FIG. 33 , slightly before the stopper pieces  126   a  and  126   b  of the connection members  124   a  and  124   b  come in contact with the upper engagement portions  127   a  of the guide holes  125   a  and  125   b , the second transmission pins  152   a  and  152   b  come in contact with the side edges of the second engagement projections  155   b  and  156   b . Since there is a brief space of time from this state until the braking forces of the lower brake pads  145   b  and  146   b  are released, the support frame section  23  can start to move smoothly at a time when the transmission rods  123   a  and  123   b  begin to move together with the guide frames  38  and  39 . 
     The operation of the article support device  120  of the present invention will be outlined with reference to  FIGS. 35A and 35B , at a time when the end portions of the long handle lever  67  are grabbed by hands and lifted up. Incidentally, in the diagram, for ease of explanation, the transmission rods  123   a  and  123   b  of the operation handle section  121 , and the guide frames  38  and  39  of the support frame section  23  are represented by single solid line. 
     As shown in  FIG. 35A , when the support frame section  23  remains stationary relative to the fixed frame section  22 , the left and right transmission rods  123   a  and  123   b  and the guide frames  38  and  39  stay at the same height, maintaining a predetermined rectangular frame structure. In this stationary state, an upward operation force F is applied to the left end portion of the handle lever  67  to move the support frame section  23  upward. 
     As shown in  FIG. 35B , as the handle lever  67  is moved up from the stationary position of  FIG. 35A  to a certain height H, the handle lever  67  is bent upward as a joint with the transmission rod  123   a  on the side close to the position where the operation force F has been applied serves as a fulcrum. This means that a larger percentage of the operation force F from the handle lever  67  is being transmitted to the nearby transmission rod  123   a  than to the far-side transmission rod  123   b.    
     In the article support device  120  of the present invention, as described above, when one transmission rod  123   a  is moved, part of the operation force is transmitted from the transmission rod  123   a  to the other transmission rod  123   b  via a gear train made up of the rack sections  140   a  and  140   b  of the connection members  124   a  and  124   b  and the gear sections  134   a ,  134   b ,  135   a , and  135   b  of the connection plates  132   a  and  132   b . Therefore, the other transmission rod  123   b  moves the same distance in the same direction in synchronization with the transmission rod  123   a . Accordingly, even if the handle lever  67  is bent, the support frame section  23  can smoothly and reliably move along the side frames  28  and  29  of the fixed frame section  22  in such a way as to keep a predetermined rectangular frame structure. 
       FIGS. 36A and 36B  show how an article support device moves; the article support device has left and right transmission rods  123   a  and  123   b  that are not connected via the above connection members and connection plates. Incidentally, the components that are the same as or similar to those in  FIG. 34  are represented by the same reference symbols. 
     As shown in  FIG. 36A , when the support frame section  23  remains stationary relative to the fixed frame section  22 , the left and right transmission rods  123   a  and  123   b  and the guide frames  38  and  39  stay at the same height, maintaining a predetermined rectangular frame structure. In this stationary state, an upward operation force F is similarly applied to the left end portion of the handle lever  67  to move the support frame section  23  upward. 
     As shown in  FIG. 36B , as the handle lever  67  is moved up from the stationary position of  FIG. 36A  to a certain height H, the handle lever  67  is significantly bent upward. In this case, not only does a joint with the transmission rod  123   a  on the side close to the position where the operation force F has been applied serve as a fulcrum, but a joint with the far-side transmission rod  123   b  does so. Therefore, even as the transmission rod  123   a  near the operation position is moved to a desired height H, the far-side transmission rode  123   b  is only moved up to a lower level. 
     As a result, the support frame section  23  could fail to maintain a predetermined rectangular frame structure and be warped or twisted. The warped or twisted support frame section  23  will likely lead to backlash between the support frame section  23  and the side frames  28  and  29  of the fixed frame section  22 , making it difficult for the support frame section  23  to move upward smoothly and reliably. 
     Such a warping or twisting can be avoided to a certain extent by making the rectangular frame structure of the support frame section sufficiently rigid. However, the rigid rectangular frame structure is not necessarily preferred because such a structure could lead to an increase in size and/or weight. Moreover, if the article to be supported is heavy or large, it may be difficult to make the rigid rectangular frame structure. 
     In the article support device  120  of the second embodiment, regardless of the rigidity of the support frame section  23 , the predetermined rectangular frame structure can be kept at any time when moving. Even when a heavy or large article is to be supported, the higher-than-required rigidity of the rectangular frame structure of the support frame section  23  is unnecessary. When a relatively light or small article is to be supported, the predetermined rectangular frame structure can be kept at any time and moved smoothly even if the rigidity of the support frame section  23  is decreased accordingly. 
     An improved type of the above-described brake device  122  (brake portion) of the second embodiment of  FIGS. 29 to 34  will be explained. The brake device repeats the operation of exerting and cancelling the braking on the first brake rail  31 . When the braking is to be exerted, the braking is being applied as the situation sequentially shifts from  FIG. 34  to  FIG. 33  and to  FIG. 32 . 
     For ease of explanation, among pairs of upper and lower brake pads  145   a ,  145   b ,  146   a , and  146   b  shown in  FIG. 32 , the mechanism of an upper-right portion in  FIG. 32  is enlarged, and an area (area HA surrounded by broken line in  FIG. 32 ) around the brake pad  146   a  of the brake device  122  (brake portion) will be described with reference to  FIGS. 37A and 37B . After that, an improved type thereof will be described with reference to  FIGS. 38A and 38B . 
     First,  FIG. 37A  is an explanatory diagram showing a state of the initial brake device  122 , showing the mechanism of  FIG. 32 . As described above, the brake pad  146   a  is supported in a rotatable manner by the brake arm  142   a , which turns around the fulcrum of the support shaft  144   a , with respect to the first brake rail  31 , which is a to-be-braked member. The brake arm  142   a  turns between a position where the brake pad  146   a  is in contact with and pressed against the first brake rail  31 , and a separated position that is separated from the first brake rail  31 . Moreover, at the tip of the brake arm  142   a , a pad mounting portion  205 , where the brake pad  146   a  is mounted, is provided. The brake pad  146   a  is fixed to the pad mounting portion  205  with a pad mounting screw  207  and a nut  208 , which are provided on the opposite side from the friction surface of the brake pad  146   a.    
     A brake surface  200 , which is the friction surface that comes in contact with the first brake rail  31  of the brake pad  146   a , includes a pressing position  203 , where a braking force is imposed as a result of the strongest pressing force being applied to the first brake rail  31  as the brake surface  200  is turned along with a tip portion  201  of a direction apart from the fulcrum of the rotation shaft  144   a  and a base end portion  202  of the side closer to the rotation shaft  144   a . The one shown in  FIG. 37A  is designed to get the base end portion  202 &#39;s side to exert the strongest pressing force on the first brake rail  31  in order to apply a higher braking force; from the base end portion  202  toward the tip portion  201 &#39;s side, the brake surface  200  is inclined (at an angle of θ 3 ) in such a way as to be gradually separated from the first brake rail  31 , when being mounted. 
     That is, the inclination (at an angle of θ 3 ) is created by inclining the pad mounting portion, so that, at the pad mounting portion  205  of the brake arm  142   a , the brake surface comes with a gap  204  from the side closer to the support shaft  144   a  toward the far side. In this case, an appropriate spacer may be inserted and mounted in such a way as to generate the inclination between the brake pad  146   a  and the pad mounting portion. In this manner, the pad mounting portion  205  of the brake arm  142   a  is mounted in such a way as to create the gap  204  from the side closer to the support shaft  144   a  toward the far side. As a result, the angle formed by a line (L 1   a ), which connects the pressing position  203  where the braking force is exerted to the support shaft  144  that constitutes the fulcrum, and by the first brake rail  31  is set at angle θ 1  (shown in the diagram; about 58 degrees in the embodiment shown in the diagram), which is smaller than 90 degrees. This setting offers a stronger braking force than when the brake surface  200  comes in contact with a flat plane. 
     In the case of the above-described configuration of  FIG. 37A , at the start of the use of the brake device  122 , the pressing position  203  is located close to the base end portion  202  as planed. Therefore, the braking force is being applied as anticipated between the brake pad  146   a  and the brake rail  31 . However, as the braking is repeatedly exerted and cancelled by the brake device  122 , the brake surface  200  of the brake pad  146   a , which is made of rubber or any other friction material, wears out. Moreover, after years of its use, chippings of the brake pad  146   a  and dust adhere to the brake surface  200 , resulting in a decrease in the frictional force and the braking force. 
     Furthermore, it came to light that, when the pad mounting portion  205  of the brake arm  142   a  is inclined and mounted in such a way as to create the gap  204  from the side close to the support shaft  144   a  toward the far side as shown in  FIG. 37A , a contact position  203 , where the brake pad  146  comes in contact with the first brake rail  31 , gradually shifts from the base end portion  202 &#39;s side to the tip portion  201 &#39;s side as shown in  FIG. 37B . As a result, as for angle θ 1  (shown in  FIG. 37A ) formed by a line (L 11   a ), which connects the pressing location  203  where the strongest braking force is exerted to the support shaft  144   a  that constitutes the fulcrum, and by the first brake rail  31 , as well as angle θ 2  (shown in  FIG. 37B ) formed by a line (L 2   a ), which connects the pressing location  203  moved by wearing-out to the support shaft  144  that constitutes the fulcrum, and by the first brake rail  31 , the angle θ 2  has become smaller than the angle θ 1  and changed to (about 52 degrees in the case of the example shown in  FIG. 37B ). The angle is changed from the initial angle θ 1  to the angle θ 2  after wearing-out. The smaller angle leads to a further decrease in the resistance by the brake pad  146   a  against the brake rail. As a result, it was found that the decrease in the braking force becomes larger as a result of wearing-out. It became clear from  FIG. 37A  of this example that, as a result of the movement of the pressing location of the brake pad  146   a  caused by wearing-out, the braking force falls about 25%. This is because: 90 degrees&gt;θ 1 &gt;θ 2 . 
     In order to deal with this, as an improved type of the brake device  122  of  FIGS. 37A and 37B  of the second embodiment, the configuration shown in  FIGS. 38A and 38B  is adopted: This configuration curbs the decrease in the braking force or increases the braking force.  FIGS. 38A and 38   b  are diagrams showing an improved version of the brake device of  FIGS. 37A and 37B :  FIG. 38A  is an explanatory diagram showing a state of the improved braking device  122  at the start of use;  FIG. 38B  is an explanatory diagram showing a state of the brake device  122  in which a brake pad  146   a  worn out after being used many times. They will be explained below. 
       FIG. 38A  is an explanatory diagram showing an initial state of the improved braking device  122  (brake portion) of  FIG. 32 . The one shown in this diagram is the same as the brake device shown in  FIGS. 37A and 37B  in that: the brake pad  146   a  is supported in a rotatable manner by the brake arm  142   a , which turns around the fulcrum of the support shaft  144   a , with respect to the first brake rail  31 , which is a to-be-braked member; and that, at the tip of the brake arm  142   a , the pad mounting portion  205  (mounting portion) where the brake pad  146   a  is mounted is provided, and the brake pad  146   a  is fixed to the pad mounting portion  205  with the pad mounting screw  207  and the nut  208 , which are provided on the opposite side from the friction surface of the brake pad  146   a . However, the one shown in this diagram is different from the brake device shown in  FIGS. 37A and 37B  as described below. 
     That is, the brake pad  146   a  shown in  FIG. 38A  is disposed and inclined (at an angle of θ 13 ) in such a way as to gradually generate a gap  304 , so that the brake surface  300  applies the strongest pressing force at the far-side tip portion  301 &#39;s side from the support shaft  144   a , with the pressing force gradually weakening toward the nearby base end portion  302 &#39;s side. As for how the inclination is created, in the case of  FIGS. 37A and 37B , the base end portion  202 &#39;s side is pressed much stronger against the first brake rail  31 . In the case of the improved type of  FIGS. 38A and 38B , the brake pad  146   a  is disposed and inclined in such a way that the tip portion  301 &#39;s side of the brake pad  146   a  presses the first brake rail  31  stronger than the base end portion  302 . In this manner, the one shown in  FIGS. 37A and 37B  and the improved version shown in  FIGS. 38A and 38B  are opposite in the inclination direction. 
     The brake surface  300  is inclined (at an angle of θ 13 ) in such a way as to realize the relation shown in  FIG. 38A . As a result, the angle formed by the line (L 11   a ), which connects the pressing location  303  where the strongest braking force is exerted to the support shaft  144   a  that constitutes the fulcrum, and by the first brake rail  31  is set at angle θ 11  (shown in the diagram; about 57 degrees in the case of the example in this diagram), which is smaller than 90 degrees. This setting offers a stronger braking force than when the brake surface is in contact with a flat plane. 
     According to the above-described arrangement relation, when the brake device  122  is used, the pressing location  303  of the brake pad  146   a  is located near the tip portion  301  as planned at the start of the use. Therefore, the braking force is applied to the brake rail  146   a . It became clear that, even after the brake surface  300  of the brake pad  146   a  has worn out as the brake device  122  repeated the braking and its cancellation, which leads to a decrease in the frictional force of the brake surface  300  after years of its use, the braking force do not decline as much as the one shown in  FIGS. 37A and 37B . 
     This is because, as shown in  FIG. 38A , the brake pad  146   a  of the brake arm  142   a  is mounted on the support shaft  144   a  in such a way as to be inclined (at an angle of θ 13 ) so that the gap  304  emerges from the far-side tip portion  301  toward the nearby base end portion  302 . In this case, as shown in  FIG. 38B , the contact position  303  where the brake pad  146   a  is in contact with the first brake rail  31  gradually moves from the tip portion  301  to the base end portion  302 &#39;s side as a result of wearing-out. Accordingly, the angle formed by line (L 12   a ), which connects the pressing position  303  where the strongest braking force is exerted and the support shaft  144   a  that constitutes the fulcrum, and by the first brake rail  31  is changed to angle θ 12  (from about 57 degrees to about 61 degrees in the example shown in the diagram), which is larger than angle θ 11  shown in  FIG. 38A ; angle θ 12  is larger than angle θ 11 . As a result, the frictional resistance force by the brake surface  300  of the brake pad  146   a  against the first brake rail  31  increases, resulting in an increase in the braking force and thereby making up for a decrease in the braking force caused by wearing-out. 
     That is, as shown in  FIG. 38A , the brake pad  146   a  is mounted on the support shaft  144   a  in such a way as to be inclined (at an angle of θ 13 ) so that the gap  304  emerges from the far-side tip portion  301  toward the nearby base end portion  302 . Accordingly, the pressing position  303  where the pressing force is the strongest moves toward the side of the support shaft  144   a  that constitutes the fulcrum as a result of wearing-out. Then, the post-use angle θ 12  becomes larger than angle θ 11  at the start of the use. This angular relation increases the resistance and thereby boosts the braking force. Actually, as the pressing position of the brake pad  146   a  moves on the first brake rail  31  toward the fulcrum due to wearing-out as shown in  FIG. 38B , the braking force is increased by about 38%. This is achieved by the relation: initial angle θ 11 &lt;post-use angle θ 12 &lt;90 degrees. 
     As described, the advantageous effects, described below, can be achieved by the embodiment for carrying out the invention. 
     1. A brake mechanism comprising a brake device  122  (brake portion) and a first brake rail  31  (to-be braked portion) that relatively move in an upward direction (first direction) and an downward direction (second direction), which is opposite to the upward direction, wherein the brake device  122  includes a brake surface  300  that is disposed in such a way as to face the first brake rail  31 , and a brake arm  142   a  having a fulcrum  114   a  that can turn between a pressing position, where the brake surface  300  brakes the to-be-braked portion, and a cancellation position, where the pressing is cancelled, and the brake surface  300  is disposed in such a way as to be inclined (at an angle of θ 13 ) so that, at a time of braking, a pressing force by the brake surface  300  against the brake rail  31  becomes stronger toward a side apart from the fulcrum  114   a  while becoming weaker toward the fulcrum  114   a.    
     Even as the brake surface  300  of the brake pad  146   a  wears out, the pressing position  302 , where the pressing force is strong, moves toward the turning fulcrum side. Accordingly, the angle θ 12  formed by line L 12   a  connecting the fulcrum  144   a , on which the brake arm  146   a  turns, to the pressing position  303  becomes larger, resulting in an increase in the frictional resistance. In this manner, it is possible to make up for a decrease in the braking force caused by wearing-out, even after years of its use. 
     2. The brake mechanism according to 1, wherein the brake surface  300  is inclined in such a way that a gap  304  gradually emerges toward the fulcrum  144   a &#39;s side between the brake surface  300  and the first brake rail  31  (brake rail). 
     According to this configuration, the angle θ 12  formed by line L 12   a  connecting the fulcrum  144   a , on which the brake arm  146   a  turns, to the pressing position  303  becomes larger, resulting in an increase in the frictional resistance. In this manner, it is possible to make up for a decrease in the braking force caused by wearing-out, even after years of its use. 
     3. The brake mechanism according to 1, wherein the first and second directions are in an up-down direction. 
     According to this configuration, the mechanism is suitable as a brake device for an apparatus in which a load is constantly applied downwards. 
     4. The brake mechanism according to 3, wherein: 
     the brake device  122  includes a brake pad  146   a ; the to-be-braked portion includes the brake rail  31  (brake rail); and the inclination of the brake pad  146   a  with respect to the brake rail  31  is achieved by a mounting portion  305  of the brake arm. 
     According to this configuration, the inclination of the brake pad  146   a  is set by the mounting portion  305  of the brake arm  142   a . Therefore, it is easy to set the inclination direction and its angle setting. 
     5. The brake mechanism according to 4, wherein a pair of the brake portions  122  are provided in such away as to face front and back sides of the brake rail  31 , and two such pairs are disposed as a pair in an up-down direction. 
     According to this configuration, the inclined brake portions  122  can be set in four locations, or on the upper, lower, left, and right sides. This configuration prevents a significant decrease in the braking force regardless of wearing-out after years of its use. 
     6. A brake mechanism comprising: a brake device  122  (brake portion) and a first brake rail  31  (to-be braked portion) that relatively move in an up-down direction, wherein the brake device  122  includes a brake surface  300  that faces the brake rail  31 , and a brake arm.  142   a  that has a turning shaft  144   a  (fulcrum) around which the brake arm  142   a  can turn between the pressing position  303 , where the brake surface  300  is pressed against the brake rail  31  in order to generate a braking force, and a separated position, which is separated from the pressing position, and the pressing position of the brake surface  300  by the brake arm  142   a  satisfies the following condition as for angle θ 11 , which is formed by line (L 11   a ) connecting the pressing position at the start of use to the fulcrum and by the to-be-braked portion, and angle θ 12 , which is formed by line (L 12   a ) connecting the pressing position of the brake surface that has worn out after years of use to the fulcrum and by the to-be-braked portion: θ 11 &lt;θ 12 &lt;90 degrees. 
     According to this configuration, the brake pad  146   a  wears out as the brake pad  146   a  is used, and angle θ 12  is set larger than the beginning. In this manner, it is possible to curb a decrease in the braking force despite wearing-out, and to use the brake device for a long time. 
     7. A load support mechanism comprising: a fixed support section  2 ; a movable support section  3  that can move within a predetermined range along a predetermined direction relative to the fixed support section  2  and receives a load; and the brake mechanism claimed in one of claims 1 to 6 in order to keep the movable support section  3  at a predetermined position along the predetermined direction with respect to the fixed support section  2 , wherein the brake portion  122  of the brake mechanism is provided on either the movable support section  3  or the fixed support section  2 , while the brake rail  31  of the brake mechanism is provided on the other. 
     According to this configuration, the use of the above-described brake mechanism makes it possible to provide a load support mechanism that can prevent a decrease in the braking force even after being used many times over years. 
     Incidentally, in the explanation of the advantageous effects of the above-described embodiment, as for each part of the present embodiment, each component in claims is expressed by brackets, or reference numbers are displayed, in order to make clear the relation between the two. 
     Furthermore, the present invention is not limited to the above-described embodiments. Various modifications may be made without departing from the scope of the present invention. All technical matters included in the technical ideas described in the appended claims fall within the scope of the present invention. The above-described embodiments have shown preferred examples. A person with ordinary skill in the art can realize various examples of alternatives, modifications, variations, or improvements, based on what has been disclosed in this specification. These examples fall within a technical scope described in the appended claims.