JPS6221697A - Hydraulic jack for monitoring load - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] [Industrial application field]

The present invention relates to a hydraulic jack having a main body forming a cylinder and a piston slidably engaged with the cylinder of the main body, and more particularly to a hydraulic jack for load monitoring suitable for temporary receiving work. [Conventional technology l] In conventional temporary support construction, that is, when temporary support piles are used to support structures until some of the existing piles of the structure are replaced with new piles, load fluctuations that act on temporary support piles The following methods can be used to monitor temporary piles while they are in service. All of these are used after replacing the hydraulic jack with a mechanical jack. The first method is a load cell method in which a load cell is inserted between the mechanical jack and the structure, the second method is to attach a strain gauge to the mechanical jack, and the third method is to install an earth pressure meter at the bottom of the mechanical jack. The fourth method is to install reinforcing rods in the newly constructed foundation concrete. The load cell method requires a large installation space and is expensive. The pressure gauge of the jack with an earth pressure gauge is a Bourdon tube type, which has problems with accuracy, is affected by temperature changes, and is expensive. The accuracy of the strain gauge attachment method decreases due to the stroke of the mechanical jack. The rebar needle installation method has poor accuracy because it is impossible to verify the meter while it is installed, and the rebar gauge may be damaged during foundation construction. [Problems to be Solved by the Invention] The purpose of the present invention is to provide a hydraulic jack for load monitoring that uses a hydraulic jack as is, has a simple structure, is highly accurate, is not affected by temperature, and is capable of stable measurement over a long period of time. do. [Means and Effects for Solving the Problems 1] As shown in FIG. 1, the hydraulic jack according to the present invention is provided with an external thread on a piston 10 that engages in a cylinder 4 formed in a main body 2, and engages a nut 16. Then, tighten the nut 16 at the required height to receive the load directly on the upper end surface of the main body, and remove the hydraulic pressure. 1. Attach a strain gauge such as a differential transformer type strain gauge 28 to the outer surface of the main body 2 to measure the strain acting on the main body 2. Measure directly. Therefore, there is no influence of temperature, there is no need to replace the hydraulic jack with a mechanical jack, and the structure is simple. Furthermore, the receiving member 20 is engaged via the spherical seat 18 to absorb eccentric loads. [Embodiment J] A hydraulic jack 1 for load monitoring according to the present invention is shown in Fig. 1.2.The main body 2 has a hydraulic cylinder 4 and a hydraulic pressure introduction hole 6 at the bottom.A flange 8 is integrally or fixedly attached to the bottom of the main body. A piston 10 is slidably engaged within a hydraulic cylinder 4 of the main body 2. The piston 10 is sealed with the cylinder 4 by a seal 12. An external thread 14 is provided on the outer surface of the upper part of the piston 10, and the nut 1
6 is engaged. The spherical portion 22 of the receiving member 20 is brought into contact with the spherical seat 18 formed at the upper end of the piston 10 to absorb angular errors. A plurality of sets of holders 24 and 26 are attached to the outer surface of the main body 2 at equal angular intervals, four sets in the illustrated example, and a differential transformer type strain meter 28 is attached.
Install them respectively. In place of or in combination with the differential transformer type strain gauge 28, a plurality of strain gauge type strain gauges (not shown) may be used.
For example, 12 pieces can be pasted. The operation will be explained. The hydraulic jack of the present invention is suitable for carrying work. For example, when excavating a part of the lower part of a structure and replacing the existing pile with another pile, the hydraulic jack l of the present invention can be installed on the upper end of the temporary pile.
Hydraulic pressure is applied from the introduction hole 6 to raise the piston 10, the supporting member 20 supports the structure, and the existing pile is cut, the structure is supported by the new foundation and the new pile, and the temporary supporting pile is installed. Remove. During this operation, the hydraulic jack is raised to a predetermined position, the piston 10 is fixed in this supporting position by turning the nut 16, and the hydraulic pressure is removed, thereby reducing the weight of the structure to the piston 10. Acting on the body 2 via the nut 16, the pressure within the cylinder 4 is irrelevant. That is, the strain gauge 28 attached to the outer surface of the main body 2
measures the strain of the main body 2 due to the weight of the structure. A need has arisen for continuous monitoring of the applied load by continuously recording and displaying the output of the strain gauge 28 by means of well-known circuitry, thereby providing automatic monitoring over the entire period of temporary acceptance. At this time, hydraulic pressure is applied to move the piston up and down, and the nut is tightened again.

【Effect of the invention】

In the hydraulic jack according to the invention, during load monitoring, the load acts on the main body from the piston via the nut, the hydraulic pressure is irrelevant, the operating system is extremely simple, and no separate strain receiver is required. Therefore, it does not require a separate space for installing the strain gauge, is not affected by temperature changes, and has high accuracy. Eccentric loads are absorbed by the use of spherical bearing members. The structure is simple and inexpensive.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a hydraulic jack for load monitoring according to the present invention, and FIG. 2 is a sectional view taken along line A-Al1 in FIG. l... Hydraulic jack 2... Main body 4... Cylinder 10... Piston 16... Nut 20... Receiving member 28... Differential transformer strain meter agent Patent attorney Nara Takeshi I figure

Claims (3)

[Claims] (1) In a hydraulic jack having a main body forming a cylinder and a piston that slidably engages with the cylinder of the main body, a nut (16) that is screwed into the piston (10) and capable of contacting the upper end surface of the main body (2) and a plurality of strain gauges (28) for measuring strain in the main body (2). (2) The hydraulic jack for load monitoring according to claim 1, wherein the piston (10) engages with a receiving member (20) via a spherical seat (18). (3) The load according to claim 1 or 2, wherein the strain gauge (28) is a plurality of differential transformer strain gauges (28) attached to the outer surface of the main body (2). Hydraulic jack for monitoring.