Mast securing mechanism of lift device

Description: TECHNICAL FIELD [Detailed description of the invention]

[Industrial application field] The present invention relates to a lift device capable of moving a work table up and down to lift personnel and materials to a high position, and in particular, a mast of a lift device capable of operating a plurality of masts by sliding them one step at a time. Regarding the fixing mechanism. [Conventional technology] Lifting devices that lift personnel and materials to high positions were often used for assembly, painting, repair, indoor ceiling repair, inspection, or maintenance of lighting equipment in high places such as building construction. .. It has become customary to place workers and materials on the workbench of this lift device and lift or lower it to perform various work, maintenance, and inspection work. Nowadays, lift devices that lift personnel and materials together with the work table are used for work on ceilings, two-story buildings, tall walls, etc. that are out of reach. In the past, ladders and stepladders were used for work that was out of reach, or scaffolding was assembled for work. However, there is a limit to the height that can be lifted by ladders and stepladders, and even if workers can get on and off, it is troublesome to lift materials. Further, when assembling the scaffolding at the site, it takes time to assemble and remove the scaffolding, and the work at one place takes a relatively long time, resulting in extremely poor work efficiency. In response to such demands, various lift devices have come to be used in which wheels are attached to lift devices that expand and contract up and down so that they can move on the floor surface. In many of these lift devices, multiple mast rails are combined so that they can be expanded and contracted up and down, and these mast rails are expanded and contracted by a hydraulic device or winch, and the workbench fixed to the top of the mast rail is moved up and down. It was. However, in order to lift the workbench of such a lift device to a high position, it is necessary to increase the number of stages of the mast rail that expands and contracts, and if the number of stages of expansion and contraction is increased, the mast in a state of being extended due to a failure or the like. The rail suddenly fell and was dangerous. Further, when assembled with a plurality of mast rails, it is uncertain which mast will be raised, and it is difficult to sequentially lift the mast rails one by one. For this reason, it is desirable to first lift only a specific mast rail among the multi-stage mast rails, and then sequentially connect and fix the raised guide rails to other guide rails by a fixing mechanism. [Problems to be solved by the invention] In this way, the lift device that raises the work table by combining multiple mast rails is often used because its mechanism is relatively simple and the worker is lifted to a position higher than the ladder and stepladder. However, there were various problems in order to raise it safely. Therefore, a lift device that can identify the mast rails that rise sequentially from the mast rails having a plurality of stages and raise the mast rails one step at a time is preferable. It has also been desired to develop a mechanism that ensures that the mast rails are connected to each other when the mast rails are raised and prevents the workbench from falling. [Means to solve problems] The first invention of the present application is a first mast that is raised slightly vertically, a second mast that slides in the length direction of the first mast, and a slide in the length direction of the second mast. A moving third mast, a winding means that is wound around the first, second, and third masts and lifts the second and third masts with respect to the first mast, and a part of the first mast. The locking means fixed to the second mast, the selective engaging means fixed to the second mast and selectively engaging with the locking means, and the selective engaging means attached to the third mast and the selective engaging means engaging the locking means. It consists of a rotating locking means that controls engagement with, and by activating the winding means, the third mast moves with respect to the second mast and the rotating locking means comes into contact with the selective engaging means. After that, the engagement with the locking means is released to allow the first mast to move the second mast, and the locking means and the turning unlocking means are each at the bottom. A block-like object having a locking surface and an inclined surface at the top, and the selective engaging means is a pinion, a rack that meshes with the pinion from a direction opposite to the pinion and moves in opposite directions, and these. It is configured to have a roller provided at the tip of the rack and in contact with the locking surface and the inclined surface of the block-shaped locking means and the turning and unlocking means, and a spring for urging the rack in the direction of the roller. The rollers are pushed by the inclined surfaces of the locking means and the turning and unlocking means against the urging force of the spring, and the racks move in opposite directions to lock and release the masts. It provides a mast fixing mechanism for a lift device, which is characterized in that it is performed. The second invention of the present application is a first mast that is raised slightly vertically, a second mast that slides in the length direction of the first mast, and a slide in the length direction of the second mast. A moving third mast, a winding means that is wound around the first, second, and third masts and lifts the second and third masts with respect to the first mast, and a part of the first mast. The locking means fixed to the second mast, the selective engaging means fixed to the second mast and selectively engaging with the locking means, and the selective engaging means attached to the third mast and the selective engaging means engaging the locking means. It consists of a rotating locking means that controls engagement with, and by activating the winding means, the third mast moves with respect to the second mast and the rotating locking means comes into contact with the selective engaging means. After that, the engagement with the locking means is released to allow the first mast to move the second mast, and the locking means and the turning unlocking means are each at the bottom. It is a block-shaped object having a locking surface and an inclined surface at the upper part, and the selective engaging means engages with a blade that rotates with a central portion as a fulcrum from a direction opposite to each tip of the blade. In the direction of the sliding bodies that move in opposite directions, and the rollers that are provided at the tips of these sliding bodies and are in contact with the locking and inclined surfaces of the block-shaped locking means and the turning and unlocking means. It is configured to have a spring for urging the sliding body, and the roller is pushed by the inclined surface of the locking means and the turning and unlocking means against the urging force of the spring to push each of the sliding bodies. Provided is a mast fixing mechanism for a lift device, characterized in that the masts move in opposite directions to lock and release each mast. [Action] In the present invention, when the wire is wound by the winding means, the wire is wound in order above and below the mast of each stage to lift the third mast first. At this time, both the first mast and the second mast are locked by the locking means, and the second mast does not rise with respect to the first mast. When the lower part of the third mast reaches the top of the second mast, the rotating locking means comes into contact with the selective engaging means, and the locking means and the selective engaging means are disengaged. At the same time, the rotating locking means and the selective engaging means mesh with each other. Therefore, the second mast can freely slide with respect to the first mast, and the third mast is connected to and slides with the second mast. Therefore, the second mast and the third mast rise together, and the workbench is firmly held. In particular, in the present invention, the locking means and the turning unlocking means are block-shaped having a locking surface at the bottom and an inclined surface at the top, respectively, and the selective engaging means is a pinion or a blade and these pinions or blades. A rack or a sliding body that engages from a direction opposite to each other and moves in opposite directions, and a locking surface and an inclination of a block-shaped locking means and a turning locking means provided at the tip of the rack or the sliding body. It is configured to have a roller in contact with the surface and a spring that urges the sliding body in the direction of the roller, and the roller is placed on the inclined surface of the locking means and the turning / unlocking means against the urging force of the spring. Since each rack or sliding body is pushed to move in opposite directions to lock and release each mast, each mast can be moved and stopped more reliably. [Example] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a perspective view showing an embodiment of the lift device of the present invention, FIG. 2 is a side view showing a state in which the workbench is lowered to the lowest position, FIG. 3 is a front view of the same, and FIG. The figure is a side view showing the state where the work table is lifted to the maximum height, and FIG. 5 is a plan view thereof. First, wheels 2 are pivotally supported on the front, rear, left, and right sides of the vehicle body 1 assembled in a slightly ladder shape, and the vehicle body 1 can be freely moved on the floor surface by the wheels 2. Axle support plates 3 bent in a U shape are fixed to both sides of the center of the vehicle body 1, and leg columns 4 that can rotate in the horizontal direction are connected to each shaft support plate 3 with pins. A fixed leg 5 that can be moved up and down is attached to the tip of the leg support 4, and this fixed leg 5 acts as an outrigger. The center of the upper surface of the vehicle body 1 is bent slightly downward to be lowered, and a winch 6 driven by a motor or the like is placed in the center of the upper surface of the vehicle body 1. Next, on the upper surface of the vehicle body 1, at a position between the front and rear wheels 2 and 2, the fixed mast 10, which is the first mast, is erected so as to face each other at intervals. The upper ends of two columns 11 are connected to the back surface of these fixed masts 10, and the lower ends of both columns 11 are arranged so as to radiate to the left and right of the upper surface of the vehicle body 1 so as to form a C shape. It is connected. The fixed mast 10 is held vertically by these columns 11. Grooves are formed in these fixed masts 10 in the vertical direction, and an intermediate mast 12, which is a second mast, is slidably inserted into each of the fixed masts 10. Further, the intermediate mast 12 is vertically grooved, and the upper mast 13, which is a third mast, is slidably inserted into the intermediate mast 12. A groove is formed in the upper mast 13 in the vertical direction, and a moving mast 15 having a short length is slidably inserted vertically into the groove. The telescopic mast 14 is formed by the fixed mast 10, the intermediate mast 12, the upper mast 13, and the moving mast 15. The pair of telescopic masts 14 are arranged so as to face each other at a distance. A flat plate-shaped workbench 16 is arranged between these two telescopic masts 14. The workbench 16 has a rectangular shape, and the center of each short side is cut into a slightly U-shape so that it can be moved up and down by fitting the telescopic mast 14 into the cut portion. It is set to. The moving mast 15 is inserted into the notches on the left and right sides of the workbench 16, and the workbench 16 is fixed to the moving mast 15. Further, around the work table 16, a handrail 17 for preventing the worker from falling is erected and fixed. Next, FIG. 6 is a cross-sectional view showing a combination of each component member in the telescopic mast 14. The fixed mast 10, the intermediate mast 12, the upper mast 13, and the moving mast 15 have the same cross-sectional shape, and for example, an aluminum alloy or the like is processed by pultrusion. The cross-sectional shapes of the fixed mast 10, the intermediate mast 12, the upper mast 13, and the moving mast 15 are the same. Both ends of these one side surface (opposing inner surface) are guide parts 10-A, 12-A, 13-A, 15-A that are slightly bent inward in an L shape, and both guide parts 10-A. , 12-A, 13-A, and 15-A are each bent inward to form a U-shaped space. Then, on the opposite side surface (outer surface), flat plate-shaped slider portions 10-B, 12-B, 13-B, and 15-B are formed. The slider portion 12-B of the intermediate mast 12 is inserted into the space of the guide portion 10-A of the fixed mast 10, and the slider portion 13-B of the upper mast 13 is inserted into the space of the guide portion 12-A of the intermediate mast 12. It is inserted in. The slider portion 15-B of the sliding guide 15 is inserted into the space of the guide portion 13-A of the upper mast 13. In this way, the intermediate mast 12 can slide up and down with respect to the fixed mast 10, the upper mast 13 can slide up and down with respect to the intermediate mast 12, and the moving mast 15 can slide up and down with respect to the upper mast 13. On the other hand, it is combined so that it can slide up and down. The stopper mechanism 18 is fixed to the left and right upper ends of the side surface of the intermediate mast 12, and the stopper mechanism 19 is fixed to the left and right upper ends of the side surface of the upper mast 13. Next, FIGS. 7, 8, 9, and 10 show an enlarged view of the mast fixing mechanism 18 shown in FIG. Here, FIG. 7 shows the mounting state of the mast fixing mechanism 18, FIG. 8 shows a vertical sectional view thereof, FIG. 9 shows a side sectional view of the same as above, and FIG. 10 shows an exploded perspective of each component. The figure is shown. In these figures, only one mast fixing mechanism 18 is shown, but the configuration of the other mast fixing mechanism 19 is exactly the same. A locking block 20 as a locking means is fixed to the upper side surface of the fixed mast 10, and an engaging machine 21 as a selective engaging means is fixed to the upper side surface of the intermediate mast 12. A control block 22 as a turning unlocking means is fixed to the lower side surface of the upper mast 13. In FIG. 7, the locking block 20, the engaging machine 21, and the control block 22 are shown to be in the same horizontal position, but in actual operation, the engaging device 21 is thus the locking block 20. , It is not located above the control block 22, and is shown in this figure for illustration purposes. The locking block 20 has a rectangular parallelepiped shape as a whole, the lower surface thereof is a horizontal locking surface 24, and the upper portion is formed as an inclined surface 25 which is diagonally cut off. The inclined surface 25 is directed toward the engaging machine 21. The control block 22 also has the same shape, and a horizontal locking surface 25 is formed on the lower surface thereof, and the upper portion is obliquely cut off to form an inclined surface 27, which is an inclined surface 27. Is facing the engaging machine 21. Next, the engaging machine 21 will be described in detail together with FIGS. 8 to 10. The engaging machine 21 selectively engages with either one of the locking block 21 and the control block 22 to control the sliding of the intermediate mast 12 up and down. In this engaging machine 21, first, there is a thin plate-shaped substrate 30 that is in close contact with the side surface of the intermediate mast 12, and in the center of this substrate 30, a holding frame 31 obtained by bending a thin steel plate into a slightly U shape is closely fixed. The holding frame 31 is fixed so that its opening is directed toward the side surface. The shaft 32 is fixed to the center of the holding frame 31 so as to be perpendicular to the substrate 30, and the tip of the shaft 32 is positioned at the center of the U-shaped opening of the holding frame 31. There is. Two collars 33 and 34 are rotatably inserted into the shaft 32, a pinion 35 is formed on the outer circumference of the collar 33, and a pinion 36 is formed on the outer circumference of the collar 34. A block-shaped guide body 37 is in close contact with the upper space of the holding frame 31, and the guide body 37 is fixed to the upper part of the holding frame 31 by screws 38. Further, a block-shaped guide body 39 is inserted into the lower space of the holding frame 31, and the guide body 39 is fixed to the lower part of the holding frame 31 by screws 40. The lower surface of each guide body 37 and the upper surface of the guide body 39 are shaped so as not to come into contact with the pinions 35 and 36, respectively. Then, on the lower surface of the guide body 37, guide grooves 41 and 42 elongated in the direction perpendicular to the shaft 32 are cut and formed, and further on the upper part of the guide grooves 41 and 42, in parallel with the guide grooves 41 and 42. Spring holes 43 and 44 with a round cross section are cut and formed so as to be. Therefore, when viewed from the side (see Fig. 9), the guide grooves 41 and 42 and the spring holes 43 and 44 form a gourd-shaped space, and this space is one side surface of the guide body 37. It is formed so as to penetrate to other sides. Similarly, guide grooves 45 and 46 are cut and formed on the upper surface of the lower guide body 39 in a direction perpendicular to the shaft 32. An elongated rack body 47 having a tooth surface formed on the lower side is slidably inserted into the guide groove 41, and the rack teeth on the lower surface of the rack body 47 are engaged with the pinion 35. Further, a rack body 48 is slidably inserted into the guide groove 42, and the rack teeth on the lower surface of the rack body 48 are meshed with the pinion 36. Further, an elongated rack body 49 is slidably inserted into the guide groove 45, and the rack teeth on the upper surface of the rack body 49 are engaged with the pinion 35. An elongated rack body 50 is slidably inserted into the guide groove 46, and the rack teeth on the upper surface of the rack body 50 are engaged with the pinion 36. With this configuration, when the pinion 35 rotates, the rack bodies 47 and 49 move in opposite directions, respectively. Similarly, when the pinion 36 rotates, the rack bodies 48 and 50 move in opposite directions, respectively. In FIG. 10, a roller 51 is pivotally supported on the left side of the rack body 47, a roller 52 is pivotally supported on the right side of the rack body 48, and a roller 53 is pivotally supported on the right side of the rack body 49. It is supported, and a roller 54 is pivotally supported on the left side of the rack body 50. Each roller 51, 52, 53, 54 is housed in a groove 55, 56, 57, 58 formed so as to be cut open vertically at one end of the rack body 47, 48, 49, 50, respectively, and each roller 51. , 52, 53, 54 are rotatably supported by pins 59, 60, 61, 62. Next, pin-shaped actuating pins 63 and 64 are vertically erected in the center of the upper surface of the rack bodies 47 and 48, respectively, and the actuating pins 63 are housed so as to move inside the spring hole 43. Yes, the actuating pin 64 is housed so as to move within the spring hole 44. A coiled spring 65 is inserted into the spring hole 43 from the right side in FIG. 10, one end of the spring 65 is in contact with the operating pin 63, and the other end is perpendicular to the spring hole 43. It is in contact with the spring retainer 67 inserted into the pin hole 66 formed in the direction. The end of the spring 65 comes into contact with the spring retainer 67, and the actuating pin 63 and the rack body 47 are always urged to the left in FIG. Further, a coiled spring 68 is inserted into the spring hole 44 from the left side in FIG. One end of the spring 68 is in contact with the actuating pin 64, the other end is in contact with the spring retainer 70 inserted through the pin hole 69 formed on the side surface of the guide body 37, and the spring 68 is in contact with the actuating pin 64. Then, the actuating pin 64 and the rack body 48 are urged to the right in FIG. Then, when the structure of each part in FIG. 10 is assembled, a flat plate-shaped closing plate 72 is brought into close contact with the upper and lower end faces of the holding frame 31 as shown in FIG. 9, and the closing plate 72 is brought into close contact with the upper and lower end faces. The top and bottom of the holding frame 31 are fixed to the top and bottom end faces of the holding frame 31 by screws 73 and 74, respectively. Next, the winding state of the wire, which is the lifting means in this embodiment, will be described with reference to FIG. In this figure 11, the fixed mast 10, the intermediate mast 12, the upper mast 13, and the moving mast 15 are shown by moving them up and down little by little for the sake of explanation. Note that it differs from the behavior of. An operating shaft 80 projects from the side surface of the winch 6, and a winding drum 81 is fixed to the operating shaft 80. A pulley 82 is rotatably supported at the lower portion of the fixed mast 10, and a pulley 83 is pivotally supported at the upper end of the fixed mast 10. In addition, pulleys 84, 85, 86, and 87 are rotatably supported above and below the intermediate mast 12 and above and below the upper mast 13, respectively. A wire 88 is wound around the outer circumference of the drum 81, and the wire 88 is wound around pulleys 82, 83, 84, 85, 86, and 87, respectively, and is wound in sequence so as to form an S shape at the end thereof. Is connected to the moving mast 15. In this way, one wire 88 is wound around the fixed mast 10, the intermediate mast 12, and the upper mast 13. Next, the operation of this embodiment will be described. The case where this lift device is used and the case where the device is moved to a work place will be described first. First, as shown in FIGS. 2 and 3, the intermediate mast 12, the upper mast 13, and the moving mast 15 are moved downward, respectively, and the entire device is moved in a state where the vertical height is reduced. In this case, since the wheel 2 is pivotally supported on the lower surface of the vehicle body 1, it can be moved extremely lightly and freely by pushing the whole body. When the vehicle body 1 is moved to a place where the vehicle body 1 is to be worked, the leg support 4 is rotated from the side surface of the vehicle body 1 and the leg support 4 is positioned so as to be perpendicular to the side surface of the vehicle body 1 as shown in FIG. After that, the fixed leg 5 is lowered so that the lower surface of the fixed leg 5 is brought into contact with the floor. The fixed legs 5 prevent the vehicle body 1 from moving and fall in the lateral direction of the vehicle body 1 to be temporarily fixed. Next, the workbench 16 is lifted. In this lifting operation, the winch 6 is operated, and the workbench 16 can be lifted by winding the wire 88 around the drum 81 by the winch 6. When the winch 6 is operated, the drum 81 rotates, and the wound wires 88 are pulled, respectively, and acts to reduce the total length of the overhanging wires 88. Then, the intermediate mast 12 acts on the fixed mast 10, the upper mast 13 acts on the intermediate mast 12, and the moving mast 15 acts on the upper mast 13 so that the length of the wire 88 between them is shortened. .. However, since the mast fixing mechanism 19 is attached to the side surface of the upper mast 13 and the mast fixing mechanism 18 is attached to the side surface of the intermediate mast 12, the wire 88 first lifts only the moving mast 15 to lift the moving mast 15. Lift it until it touches the upper edge of the upper mast 13. Then, since the lower part of the moving mast 15 comes into contact with the mast fixing mechanism 19, the mast fixing mechanism 19 is released, and the upper mast 13 can slide with respect to the intermediate mast 12, and the moving mast 15 and the upper mast 13 and 13 move upward at the same time. Then, when the lower part of the upper mast 13 moves to the vicinity of the upper end of the intermediate mast 12, the lower part of the upper mast 13 releases the mast fixing mechanism 18, and the fixed mast 10 is released from the movement of the intermediate mast 12, and is intermediate. Mast 12 can now move freely with respect to fixed mast 10. Then, the intermediate mast 12 rises together with the moving mast 15 and the upper mast 13, and the workbench 16 is lifted further upward. These operations are sequentially performed by pulling the wire 88, and the sliding control of the masts 10, 12, 13 and 15 is sequentially switched by the mast fixing mechanisms 18 and 19, respectively. When observing this series of operations, each of the moving mast 15, the upper mast 13, and the intermediate mast 12 is sequentially fed out from the fixed mast 10, and the movement of the respective masts 12, 13, and 15 is controlled. can do. Therefore, the workbench 16 is always lifted in a parallel state, and the operation is not unbalanced. The operation of the mast fixing mechanisms 18 and 19 that control the intermediate mast 12, the upper mast 13, and the moving mast 15 so that they can move in order will be described with reference to FIG. In FIG. 12, the upper part shows the mast fixing mechanism 18 connected by the surfaces of the pinion 36 and the rack bodies 48 and 50, and the lower part of FIG. 12 shows the mast fixing mechanism 18 connected to the pinion 35 and the rack body 47. , 49 shows the state of disconnection. The reason why the mechanism is divided into upper and lower parts in Fig. 12 is to explain the operation of pinion 35, 36 and rack body 47, 48, 49, 50 respectively, and the upper and lower mechanisms operate at the same time. is there. Then, in FIG. 12, the process in which the mast fixing mechanism 18 is unlocked and the intermediate mast 12 and the upper mast 13 are combined in the order of A, B, and C is described. In FIG. 12A, the wire 88 is pulled and only the upper mast 13 is moving in the X direction in the figure. In the state of FIG. 12A, the actuating pin 64 is pushed to the right by the spring 68, and the rack body 48 is also pushed out. Therefore, at the same time, the rack body 50 also protrudes in the fixed mast 10 direction. Rollers 52 and 54 project to the sides of the intermediate mast 12, respectively. Therefore, the roller 54 is in contact with the locking surface 24 of the locking block 20, and the rack body 50 is blocked by the locking block 20, so that the intermediate mast 12 moves upward with respect to the fixed mast 10. You can't. Further, when the intermediate mast 12 is engaged with the fixed mast 10, the spring 65 pushes the operating pin 63, and the rack body 47 is urged to the left in the drawing. However, the roller 51 is in contact with the side surface of the locking block 20, and the rack body 47 does not protrude from the side surface of the intermediate mast 12. Therefore, the side end of the rack body 49 on the opposite side also does not protrude from the side surface of the intermediate mast 12, and the roller 53 is located inside the side surface of the upper mast 13. Next, when the upper mast 13 gradually rises and slides in the X-shape in FIG. 12, the state in which the control block 22 finally contacts the roller 52 is shown in the state shown in FIG. 12B. is there. When the inclined surface 27 of the control block 22 comes into contact with the roller 52, the roller 52 and the rack body 48 are pushed to the left in the figure, and the control pin 64 rotates the pinion 36 counterclockwise while compressing the spring 68, and the rack Move body 50 to the right in the figure. Then, the roller 54 is pulled in from the locking surface 24 of the locking block 20, and the engaging of the locking block 20 and the roller 64 is released. Therefore, the intermediate boom 12 is released from the fixed mast 10. Is allowed to move freely upwards. When the rack body 48 is pushed to the right in the figure by the control block 22 in this way, as shown in the lower part of FIG. 12B, the locking surface 26 on the lower surface of the control block 22 is the rack body. It means that it is located above the position of the roller 53 at 49 and is moving. Next, as described above, the engaging surface 24 of the locking block 20 and the roller 54 are disengaged, so that the upper mast 13 and the intermediate mast 12 are of Y as shown in C in FIG. It will move in the direction at the same time. This is because the intermediate mast 12 moves at the same time as the upper mast 13 because it is pulled by the wire 88. Then, since the roller 52 is already pushed by the inclined surface 27, the rack bodies 48 and 50 do not move any more, and the pinion 36 does not rotate. However, when the intermediate mast 12 moves upward, the position where the roller 51 of the rack body 47 contacts moves upward and comes into contact with the inclined surface 25 above the locking block 20, the spring 65 operates. The pin 63 is pushed out to move the rack body 47 along the slope of the inclined surface 25 in the direction indicated by the arrow C in FIG. This movement is transmitted to the pinion 35, and at the same time acts to push the rack body 49 to the right in the figure, and the roller 53 protrudes more than the side surface of the intermediate mast 12 and is located below the locking surface 26 of the control block 22. It will be. Therefore, if the intermediate mast 12 tries to move further upward, the roller 53 comes into contact with the locking surface 26, and the intermediate mast 12 and the upper mast 13 rise at the same time. In this way, the control block 22 hits the roller 52 in the order of FIGS. A, B, and C, and the rack body 48 is moved to disengage the intermediate mast 12 with the fixed mast 10, and the intermediate mast 12 is released. Can rise freely. Since the rack body 48 protrudes at the same time, the roller 53 comes into contact with the engaging surface 26 and controls the intermediate mast 12 and the upper mast 13 to be engaged and moved, and these series of operations are performed. Will do. Contrary to the above, when the drum 81 is reversed and the wire 88 is loosened, the upper mast 13 and the intermediate mast 12 are lowered at the same time, but in this case, only the upper mast 13 is lowered. Instead, the upper mast 13 and the intermediate mast 12 are lowered at the same time because the roller 53 is in contact with the engaging surface 26. Contrary to the above, in FIG. 12, the upper mast 13 and the intermediate mast 12 are disengaged in the order of C, B, and A, and at the same time, the intermediate mast 12 and the fixed mast 10 are engaged. The reverse operation will be performed. In this way, only the upper mast 13 can move freely with respect to the intermediate mast 12, and only the upper mast 13 is lowered. Next, FIGS. 13 and 14 show other examples of the mast fixing mechanism 18 in the present invention. In this embodiment, the same members as those in the first embodiment are designated by the same reference numerals, and the description thereof is omitted. Two collars 100 and 101 are inserted through the shaft 2, and blades 102 and 103 are vertically projected on the collar 100 in opposite directions. The collar 101 also has blades 104 and 105 protruding in opposite directions. These blades 102, 103, 104, 105 have a shape with a tapered tip, and have a butterfly-like shape. Block-shaped sliding bodies 106 and 107 are inserted through the guide grooves 41 and 42 formed in the guide body 37, and similarly block-shaped sliding bodies 45 and 46 are inserted through the guide grooves 45 and 46 of the guide body 39. 108 and 109 are inserted. Then, engaging grooves 110 and 111 recessed upward are formed in the center of the lower surface of each of the sliding bodies 106 and 107, and blades 102 are meshed with the engaging groove 110 to form the engaging groove 111. The blades 104 are engaged with each other. Engagement grooves 112 and 113 are formed in the center of the upper surfaces of the sliding bodies 108 and 109, the blades 103 are meshed with the engaging grooves 112, and the blades 105 are meshed with the engaging grooves 113. There is. With this configuration, when the collar 110 rotates, the blades 102 and 103 slide the sliding bodies 106 and 108 in opposite directions. Similarly, when the collar 101 rotates, the blades 104 and 105 cause the sliding bodies 107 and 109 to move in opposite directions. Roller grooves 114 and 117 are formed vertically on the left side of the sliding bodies 106 and 106 in FIG. 14, and roller grooves 115 vertically on the right side of the sliding bodies 107 and 108 in FIG. , 116 are formed by cutting. Rollers 118, 119, 120 and 121 are housed in the roller grooves 114, 115, 116 and 117, respectively, and the rollers 118, 119, 120 and 121 are rotated by pins 122, 123, 124 and 125, respectively. It is freely shaft-supported. Further, an actuating pin 126 is projected and fixed at the center of the upper surface of the sliding body 106, and an actuating pin 127 is projected and fixed at the center of the upper surface of the sliding body 107. In this embodiment, as described above, when the upper mast 13 rises, the control block 22 rises, and the inclined surface 27 of the control block 22 comes into contact with the roller 119. Then, the roller 119 and the sliding body 107 are pushed to the left in FIG. Then, the blade 104 meshing with the engaging groove 111 rotates counterclockwise in FIG. 13 around the shaft 32, and the blade 105 on the opposite side pushes the engaging groove 113. Therefore, the sliding body 109 slides to the right in FIG. 13, and the roller 121 disengages from the engaging surface 24 on the lower surface of the locking block 20. Therefore, the intermediate mast 12 can move upward because the contact with the engaging block 20 is released. Further, FIG. 15 shows an example in which the mast fixing mechanism of the present invention is applied to another elevating device. In the embodiment shown in FIG. 1, the telescopic mast 14 for lifting the workbench 16 is composed of four members, a fixed mast 10, an intermediate mast 12, an upper mast 13, and a moving mast 15, and the telescopic mast 14 is used for work. It is provided on the left and right of the stand 16. However, in the embodiment of FIG. 15, the telescopic mast 130 is composed of a set of mechanisms, and is composed of a lower mast 131, an intermediate mast 132, and an upper mast 133. The lower mast 131 is vertically fixed to the vehicle body 135 with the wheels 134, and the upper portion thereof is held by a stay 136 that opens in a figure eight shape. The intermediate mast 132 can move up and down with respect to the fixed mast 131, and the upper mast 133 can slide up and down with respect to the intermediate mast 132. A work table 137 having a square shape is placed and fixed on the upper end of the mast 133. Further, a telescopic ladder 138 composed of a plurality of ladders that can be expanded and contracted up and down is connected between the vehicle body 135 and the workbench 137. A locking block 20 is fixed to the upper side surface of the lower mast 131, an engaging machine 21 is fixed to the upper side surface of the intermediate mast 132, and a control block is fixed to the lower side surface of the upper mast 133. 22 is fixed. A handle 139 is pivotally supported on the back surface of the lower mast 131, and the wire 140 can be wound up by the handle 139. At the rear of the vehicle body 135, a fan-shaped leg support 141 and a fixed leg 142 attached to the tip of the leg support 141 and rotating up and down are provided. In this embodiment, the wire 140 is wound by rotating the handle 139, and the upper mast 133 and the intermediate mast 132 are moved upward by the winding force of the wire 140 according to the same configuration as in FIG. The pedestal 137 can be raised. At this time, when the upper mast 133 rises first and the control block 22 of the upper mast 133 comes into contact with the engaging machine 21, the intermediate mast 132 is disengaged from the fixed mast 131, and the upper mast 133 and the intermediate mast are disengaged. 132 can rise upwards at the same time. [Effect of the invention] Since the present invention is configured as described above, in a configuration in which a workbench is lifted by a telescopic mast that is a combination of a plurality of masts, a plurality of combined masts can be sequentially raised, and only a specific mast is prioritized. Can be moved. The priority of the mast to be raised is automatically given, and it is possible to prevent each mast from being unspecifiedly raised by the pulling force of the wire. In particular, in the present invention, the locking means and the turning unlocking means are block-shaped having a locking surface at the bottom and an inclined surface at the top, respectively, and the selective engaging means is a pinion or a blade and these pinions or blades. A rack or a sliding body that engages from a direction opposite to each other and moves in opposite directions, and a locking surface and an inclination of a block-shaped locking means and a turning locking means provided at the tip of the rack or the sliding body. It is configured to have a roller in contact with the surface and a spring that urges the sliding body in the direction of the roller, and the roller is placed on the inclined surface of the locking means and the turning / unlocking means against the urging force of the spring. Since each rack or sliding body is pushed to move in opposite directions to lock and release each mast, each mast can be moved and stopped more reliably. In this way, since the mast is raised sequentially from a specific mast among the plurality of masts, the workbench can be lifted safely and firmly. Therefore, even if the mechanism is to lift the lift with a wire, its operation is reliable and the safety is high.

[Simple explanation of drawings]

FIG. 1 is a perspective view showing the appearance of the lift device according to an embodiment of the present invention in a state where the work table is lifted to the maximum height position, and FIG. 2 is a state in which the work table of the lift device is lowered to the lowest position. 3 is the same side view, 4 is the side view showing the work table lifted to the maximum height position, 5 is the same plan view, and 6 is the telescopic mast. FIG. 7 is a cross-sectional view showing the combined state of the above, FIG. 7 is an enlarged perspective view showing the configuration of the mast fixing mechanism, FIG. 8 is a side view showing a part of the same as above, and FIG. 9 is among the above-mentioned mast fixing mechanisms. A cross-sectional view showing an upper body obtained by cutting the engaging machine in the vertical direction, FIG. 10 is an exploded perspective view of the engaging machine as above, FIG. 11 is an explanatory view showing a wire surrounding state, and FIG. 12 is the present embodiment. Explanatory drawing which shows the operation of. FIG. 13 is a partially cutaway sectional view showing another embodiment of the mast fixing mechanism of the present invention, FIG. 14 is an exploded perspective view of the same engaging machine, and FIG. 15 shows the mast fixing mechanism of the present invention. It is a perspective view which shows the example applied to other kinds of lift devices. 1 ... body, 6 ... winch, 10 ... fixed mast, 12 ... middle mast, 13 ... upper mast, 14. ..... Telescopic mast, 15 ... Moving mast, 16 ... Work table, 20 ... Locking block, 21 ... Engagement machine, 22 ... Control block, 47, 48, 49, 50 ... Rack body, 35, 36 ... Pinion, 51, 52, 53, 54 ... Roller, 88 ...... Wire, 102, 103, 104, 105 ...... Blade, 106, 107, 108, 109 ...... Sliding body, 118, 119, 120, 121. ..... Roller, 130 ...... Telescopic mast, 131 ...... Fixed mast, 132 ...... Intermediate mast, 133 ...... Upper mast, 137 .. .... Winch.