Tunnel center lifting jack

Abstract

To provide a jack for lifting a tunnel center, which can surely prevent damage to a motor or a rotating mechanism. [Solution] This lifting jack is provided with a receiving part 31 that supports the form of a tunnel center, and is configured by connecting a motor to the rotation operating part 22 of the screw-type jack main body 2. The upper end of a cylinder 3 that rises and falls from a housing 21 of the jack main body 2 serves as the receiving part 31, and the housing 21 is provided with a position detection means for detecting when the cylinder 3 has reached its lowering end. The position detection means is composed of a limit switch 4A provided in the housing 21 and whose actuator 41 is biased forward, and a recess 32 formed at a predetermined longitudinal position on the outer periphery of the cylinder 3 with which the tip of the actuator 41 abuts.

Description

[Technical Field]

[0001] The present invention relates to a lifting jack for a tunnel center, and more particularly to a damage prevention structure for a lifting jack that uses an electric journal jack. [Background technology]

[0002] After the secondary lining concrete is poured into the pouring space formed between the inner periphery of the tunnel ground and the outer periphery of the formwork (form) of the tunnel center, the entire form is often lowered to separate the crown form from the formed concrete layer, and a lifting jack is used to raise and lower the entire form. An example of this is shown in Patent Document 1, for example. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication No. 2021-193267 Summary of the Invention [Problem to be solved by the invention]

[0004] Incidentally, hydraulic lifting jacks are often used for this type of lifting jack, but hydraulic lifting jacks require a separate hydraulic unit, which increases costs and makes them large in size.

[0005] Therefore, it is possible to automate the raising and lowering operation of the lifting jack by connecting a motor to the rotation operating part of the main body of a commercially available screw-type jack. However, if a lifting jack is installed at each of the four corners of a form that is square in plan view, the height of the installation surface of each lifting jack attached to a traveling cart or the like will vary depending on the height of the traveling rail, and even when the cylinder of one of the four lifting jacks reaches its lowering end, the form (and the frame supporting it) in this part may remain floating. If a position detector for the lowering end is installed on the form side, the motor will continue to rotate in the downward direction of the cylinder at the lowering end of the cylinder, which may cause damage to the motor or rotation mechanism.

[0006] SUMMARY OF THE INVENTION The present invention is intended to solve such problems and aims to provide a jack for lifting and lowering a tunnel center that can reliably prevent damage to the motor and rotating mechanism. [Means for solving the problem]

[0007] In order to achieve the above object, the first invention provides a lifting jack (1) provided with a receiving part (31) for supporting a form (M1) of a tunnel center (M), in which a motor (5) is connected to a rotation operating part (22) of a screw-type jack body (2), and the upper end of a cylinder (3) that moves up and down from a housing (21) of the jack body (2) is the receiving part (31), and the housing (21) is provided with position detection means (4A, 7A) for detecting that the cylinder (3) has reached its lowering end. The position detecting means is composed of a limit switch (4A) provided in the housing (21) and having an actuator (41) biased to move forward, and a recess (32) formed at a predetermined position in the longitudinal direction on the outer periphery of the cylinder (3) against which the tip of the actuator (41) abuts. .

[0008] According to the first invention, when the cylinder reaches its lowering end, even if the frame is floating at that time, the position detection means provided in the housing of the jack body will reliably detect that the cylinder has reached its lowering end, thereby stopping the motor rotation and avoiding damage to the motor or rotation mechanism.

[0010] In the second invention, a lifting jack (1) is provided with a receiving part (31) for supporting a form (M1) of a tunnel center (M), and a motor (5) is connected to a rotation operating part (22) of a screw type jack main body (2). The upper end of a cylinder (3) that moves up and down from a housing (21) of the jack main body (2) is the receiving part (31), and position detection means (4A, 7A) are provided in the housing (21) for detecting when the cylinder (3) has reached its lowering end.The position detection means is composed of proximity sensors (7A, 7B) provided in the housing (21) and a recess (34) formed at a predetermined longitudinal position on the outer periphery of the cylinder (3) facing the proximity sensor (7A).

[0011] The symbols in parentheses above indicate, for reference, the correspondence with specific means described in the embodiments to be described later. [Effects of the Invention]

[0012] As described above, the tunnel center lifting jack of the present invention can reliably avoid damage to the motor and rotation mechanism. [Brief explanation of the drawings]

[0013] [Figure 1] 1 is a schematic side view of a tunnel center equipped with a lifting jack of the present invention. [Figure 2] 1 is a schematic plan view of a tunnel center equipped with a lifting jack of the present invention. [Figure 3] 1 is a half-sectional side view of a jack body when a cylinder is lowered in a first embodiment of the present invention. FIG. [Figure 4] 1 is a half-sectional side view of a jack body when a cylinder is raised in a first embodiment of the present invention. FIG. [Figure 5] FIG. 2 is a partial cross-sectional overall side view of the lifting jack. [Figure 6] FIG. 10 is a half-sectional side view of a jack body when the cylinder is lowered in a second embodiment of the present invention. [Figure 7] FIG. 10 is a half-sectional side view of a jack body when the cylinder is raised in a second embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0014] The embodiments described below are merely examples, and various design improvements made by those skilled in the art without departing from the gist of the present invention are also included in the scope of the present invention.

[0015] (First embodiment) The lifting jacks 1 of the present invention are provided, for example, at four locations symmetrically across the width of the tunnel (Fig. 2) at the front and rear ends (Fig. 1) of the tunnel longitudinal direction of the tunnel center M. That is, each lifting jack 1 is erected on a traveling carriage V that can move on rails R (Fig. 1) laid in the longitudinal direction of the tunnel, and the lower ends of the pedestals F1 provided at the four corners of a frame F that supports the form M1 of the tunnel center M are placed on the upper ends of the lifting jacks 1.

[0016] 3 and 4 show a half-sectional side view of the jack body 2 constituting the lifting jack 1. The jack body 2 is a commercially available screw-type jack and includes a cylindrical housing 21 with a bottom and a diameter that gradually increases downward. A cylindrical cylinder 3 is disposed within the housing 21 and protrudes from the upper opening. The upper end of the cylinder 3 is closed to form a large-diameter receiving portion 31. The internal structure for raising and lowering the cylinder 3 is known and is therefore not shown. However, a threaded portion is formed on the inner periphery of the cylinder 3, and a threaded rod is threadedly engaged with this from below. The threaded rod is connected to an input shaft 22, which serves as a rotation operating portion and protrudes from the side surface of the lower end of the housing 21, via a bevel gear or the like provided within the housing 2. With this structure, when the input shaft 22 is rotated forward or backward, the threaded rod is rotated forward or backward via the bevel gear or the like, and the cylinder 3 housed within the housing 21 accordingly advances (rises) (as shown in FIG. 4) or retreats (descends) (as shown in FIG. 3).

[0017] In this embodiment, limit switches 4A and 4B for detecting the lowering end and the upper end are provided at upper and lower positions on the outer periphery of the side wall near the upper end opening of the housing 21, and the rod-shaped actuator 41 of each limit switch 4A, 4B that is biased to advance penetrates horizontally through the side wall of the housing 21 and advances into the cylinder, with its tip abutting against the outer periphery of the cylinder 3. Meanwhile, recesses 32 and 33 are formed at the upper and lower end positions, respectively, on the outer periphery of the cylinder 3 where the tips of the actuators 41 of the limit switches 4A and 4B abut.

[0018] With this structure, when the cylinder 3 is at the lowering end (Fig. 3), the recess 32 of the cylinder 3 reaches a position opposite the tip of the actuator 41 of the limit switch 4A, and the actuator 41 advances into the recess 32, activating the lowering end detection limit switch 4A. On the other hand, when the cylinder 3 is at the upper end (Fig. 4), the recess 33 of the cylinder 3 reaches a position opposite the tip of the actuator 41 of the limit switch 4B, and the actuator 41 advances into the recess 33, activating the upper end detection limit switch 4B. In this way, it is reliably detected that the cylinder 3 has reached the upper end or the lowering end.

[0019] As shown in Fig. 5, the input shaft 22 of the jack body 2 is connected to the output shaft 51 of the motor 5 provided on the traveling carriage V (see Fig. 1). As a result, when the motor 5 is rotated forward or backward, the cylinder 3 of the jack body 2 moves up and down, and by controlling the rotation of the motor 5, the lifting and lowering of the cylinder 3 can be remotely controlled.

[0020] The housing 21 of the jack main body 2 is covered by a cylindrical lower cover body 61 provided on the traveling carriage V, while the raised cylinder 3 (FIG. 5(1)) is covered by a cylindrical upper cover body 62, slightly larger in diameter than the lower cover body, which protrudes downward from the frame stud F1 (see FIG. 1) of the tunnel center M. These cover bodies 61, 62 slide relative to each other and move up and down, functioning as guide members. Even when the cylinder 3 moves up and down, the cylinder 3 and the housing 21 are always covered by both cover bodies 61, 62 (FIGS. 5(1) and (2)), preventing the intrusion of foreign matter and the like.

[0021] In the lifting jack 2 having such a structure, as described above, even when the cylinder 3 is at the lowermost position, the form M1 (and the frame F) in this portion may remain floating, in which case the frame F and the upper cover body 62 integrated with it also float upward (Fig. 5(3)), and the upper cover body 62 remains in an upward position even when the cylinder 3 is at the lowermost position. For this reason, if a position detector for the lowering end is provided on the upper cover body 62, which is easy to attach, the motor 5 may continue to rotate in the cylinder lowering direction even when the cylinder 3 is at the lowering end, which may cause damage to the motor 5 or the rotation mechanism inside the housing 21.

[0022] In this embodiment, as described above, a limit switch 4A for detecting the lowering end is provided in the housing 21, and when the cylinder 3 is at the lowering end, the actuator 41 of the limit switch 4A advances into the recess 32 formed in the cylinder 3 (see Figure 3), thereby reliably activating the limit switch 4A, thereby stopping the rotation of the motor 5 and preventing damage to the motor 5 and the rotation mechanism.

[0023] (Second embodiment) 6 and 7, in this embodiment, proximity switches 7A and 7B for detecting the lowering end and the rising end are embedded horizontally at upper and lower positions, respectively, in the side wall near the upper end opening of the housing 21. Meanwhile, recesses 34 and 35 are formed at the upper and lower ends of the outer peripheral surface of the cylinder 3 opposite the proximity switches 7A and 7B.

[0024] When the cylinder 3 is at the lowering end (Fig. 6), the recess 34 of the cylinder 3 reaches a position opposite the proximity switch 7A, changing the distance between the proximity switch 7A and the outer circumferential surface of the cylinder 3 and activating the proximity switch 7A. When the cylinder 3 is at the upper end (Fig. 7), the recess 35 of the cylinder 3 reaches a position opposite the proximity switch 7B, changing the distance between the proximity switch 7B and the outer circumferential surface of the cylinder 3 and activating the proximity switch 7B. In this way, it is possible to reliably detect whether the cylinder 3 is at the upper or lowering end.

[0025] In this way, even if the proximity switches 7A and 7B are used instead of the limit switches 4A and 4B of the first embodiment, the same effects as those of the first embodiment can be obtained.

[0026] In the above embodiments, the present invention has been described as being applied to a center with a structure in which almost the entire structure, including the frame, rises and falls (i.e., a structure in which the form is supported via the frame), but the present invention can also be applied to a center with a structure in which only the form rises and falls on the frame. [Explanation of symbols]

[0027] 1...lifting jack, 2...jack body, 21...housing, 3...cylinder, 31...receiving part, 32, 33, 34, 35...recess, 4A, 4B...limit switch (position detection means), 7A, 7B...proximity switch (position detection means), F...frame, F1...leg, M...tunnel center, M1...form.

Claims

1. A lifting jack provided with a receiving part for supporting the tunnel center form, in which a motor is connected to the rotating operating part of the screw-type jack body, the receiving part being the upper end of a cylinder that rises and falls from the housing of the jack body, and the housing is provided with a position detection means for detecting when the cylinder has reached the lower end, the position detection means being composed of a limit switch provided in the housing and whose actuator is biased forward, and a recess formed at a predetermined longitudinal position on the outer periphery of the cylinder against which the tip of the actuator abuts.

2. A lifting jack for a tunnel center having a receiving part that supports the form of the tunnel center, wherein a motor is connected to the rotation operating part of the screw-type jack body, the receiving part being the upper end of a cylinder that rises and falls from the housing of the jack body, and the housing is provided with a position detection means for detecting when the cylinder has reached its lowering end, the position detection means being composed of a proximity sensor provided in the housing and a recess formed at a predetermined longitudinal position on the outer periphery of the cylinder that faces the proximity sensor.

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