JPS5975124A - Method and device for measuring boom 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] Regarding the device.

As such a load measuring device, for example, United States Patent Application No. 2,319,299 discloses a device that uses deformation of a beam to measure the load of an object suspended from the tip of a boom.

The measured beam deformation is proportional to the load of the object suspended from the end of the main boom, and measurement of such deformation allows a load value to be obtained. As a mechanism having a boom, one that rotates the boom in the vertical direction by operating a hydraulic cylinder that supports the boom within its entire rotation range is generally known. Such a boom is part of a hydraulic crane or other similar device and has a pulley mechanism at its end for lifting the load. The deformation beam used for load measurement is attached to the base of the boom and is fixed so that it deforms in proportion to the degree of load applied to the tip of the main boom.

Furthermore, as a mechanism for measuring the degree of load inside a storage container, a mechanism consisting of a strain gauge that can be attached to a support leg of a large storage container is generally known. Such strain gauges are made of a special metal whose impedance changes in proportion to the strain forces exerted on the support legs of the container to which they are attached. This impedance is detected electrically and processed by a load measuring device. Such strain gauges are manufactured by Kistler ΦMors Corporation (Klsl
There is one made by Morse Corporation, which is commercially available.

Further, United States Patent Application No. 3,490,015 discloses a load measuring device that uses a dynamometer attached to the tip of a boom for suspending an object to measure the load applied to the tip. Also, United States Patent Application No. 2030
No. 529 discloses a load measuring device that utilizes a pulley mechanism that determines the path of a load supporting cable to measure the load of an object suspended by the cable. In addition, U.S. Pat. No. 3,756,423 discloses a load measuring device having a load cell installed at the load suspension end of a boom to directly measure the load applied to the hoisting cable. A more commonly known mechanism is one in which a pressure transducer is installed inside the hydraulic cylinder that supports the load-supporting boom. such electrical signals are then converted into loads.

SUMMARY OF THE INVENTION The object of the invention is to provide a load measuring device for a load-bearing boom that is economical, reliable and has little exposure to external environments such as work areas. Known mechanisms currently available are mounted on the exterior of the boom and are therefore susceptible to damage or deleterious effects if the work is not properly filled. This applies especially to devices of this type located at the end of the boom. A further object of the invention is to provide a load measuring device which is reliable and is not affected by variations in mechanical properties during operation of the boom device. Because fluid viscosity and boom deflection change with operating and ambient temperature, load measurement devices that rely on measuring fluid pressure or boom deflection may be affected by changes in viscosity, ambient temperature, and other variables. Inherently prone to fluctuations in readings. The prior art system also suffers from the problem that it cannot be economically retrofitted to existing lifting equipment in the field.

Therefore, the load measuring device of the present invention has a strain gauge mechanism attached to the outside of the piston 07 that supports the load supporting boom, and this strain gauge mechanism continuously detects the compression state of the piston rod and generates an electrical signal. The analog signal is sent to an external data processing mechanism to convert strain measurements into loads. In other words, the strain gauge provides the load applied to the end of the boom by measuring the strain that is proportional to the piston rod that supports the boom. The piston rod here plays a dual role as the main drive in the vertical plane of the load-bearing boom and as part of the load-measuring device.

The Piston Red can be fitted with numerous strain gauges, and by averaging the data obtained by these strain gauges, we account for the effects of load imbalance, wind, and other variables that affect these unique readings. can be compensated.

Yet another invention is a method of measuring the load of an object suspended from a load-supporting boom, the invention comprising: attaching at least one strain gauge to the outer surface of a piston red supporting the load-supporting boom; The steps include connecting an electrical 1iIA structure to the strain gauge to convert piston rod strain measurements into loads supported by the piston rod.

The above-mentioned drawbacks of the prior art are solved by the present invention, in which the strain gauge is mounted on the piston rod of the lift cylinder, and such an arrangement provides great protection from contact damage and the effects of the working environment. It becomes. Furthermore, the compression state of the piston red is relatively unaffected by changes in the ambient air temperature and changes in the operating characteristics of the boom mechanism. Additionally, practice of the invention does not require any modification to standard lifting equipment components, allowing for retrofit into existing lifting equipment in the field.

Next, one embodiment of the present invention will be described with reference to the drawings.

In FIG. 1, the load support mechanism 2 includes a load support end 6,
An extension boom member 4 is provided having an opposite end 8 pivotally connected to the crane chassis or a low rotation member thereof. The boom member 4 is provided at its load-bearing end 6 with a mechanism (not shown), such as a pulley mechanism, for supporting the applied load. This type of mechanism is commonly found in crane units, aerial platforms, and the like. The load support mechanism 2 also includes a fluid motor 10 having a piston thread 12 and a hydraulic cylinder 14 of the type commonly used in industry. One end 16 of the piston rod 12 is connected and fixed to the boom member 4 between its ends, and the other end projects into the interior of the hydraulic cylinder 14 . Piston rod 12 raises and raises boom member 4 under the control of an operator under the action of hydraulic fluid. A pair of strain gauges 18 are attached to the piston rod 12 adjacent to the connection portion of the piston rod to the boom member 4 . These strain gauges 18 are connected to conductive wires 20 for electrical input and output.

In FIG. 2, which shows an enlarged perspective view of one of the strain gauges 18, the strain gauge 18 has a generally rectangular body with longitudinal support legs 22 and a pair of mounting screws 24.
is used to attach the strain gauge 18 to the piston rod 12 and is screwed into the piston rod 12 through a hole 26, as explained below. The strain gauge 18 is of a commercially available type, and is used industrially to primarily monitor the capacity of containers such as tanks, barrels, and pipes.

In particular, such a common type of strain gauge is used to measure the volume inside a cylindrical container by detecting the amount of compression of the support member of the container. Normally, each support member has −
One or more strain gauges can be attached. The structure of each of these gauges consists of two semiconductor crystals bonded together, and when attached to an object, no matter how much the object is compressed, it will be compressed in the same way, and the degree of compression will be applied to the semiconductor crystal. produces an elastic deformation directly proportional to . An electrical package can be used to extract electrical output corresponding to elastic deformation from the strain gauge and convert such elastic deformation into load. The strain gauge is also made from a material that matches the coefficient of thermal expansion of the material to which it is attached. Such a monolithic strain gauge includes the Model 50 manufactured by Kistler-Morss Corporation of Bellevue, Washington.
6 microcell (Mo d e 1 503 Micr
oeell).

In FIG. 3, the strain gauge 18 is connected to the piston rod 12.
The piston rod 12 is placed in a predetermined position by a fixing receiving plate 28 having an arcuate inner surface 30 having a shape that matches the curved surface of the piston rod 12 . This provision of a pair of strain gauges 18 compensates for load imbalances, wind and thermal effects and increases the accuracy of the readings. After positioning the strain gauges 18 on both sides of the piston wand 120 via the receiving plate 28, a pair of screw holes are provided in the piston rod 12 by drilling and tapping. Next, the strain gauge 18 is fixed to the piston rod 12 by inserting the mounting screw 24, and as shown in FIG.
Remove 8.

It will be understood by those skilled in the art that the piston rod 12 is compressed by the loading of the boom member 4 against the hydraulic fluid pressure applied to the rad 12 by the fluid motor 10. The degree of compression of the piston rod 12 will be directly proportional to the load applied to the load bearing end 6 of the boom member 4. When piston rod 12 is compressed, strain gauge 18 detects the degree of compression and generates an analog voltage signal proportional to the degree of compression. An analog output can be taken from the strain gauge 18 using a general-purpose electrical package to continuously display the load of the object lifted by the boom member 4. The present invention has the advantage that since the strain gauge 18 is mounted on the outside of the piston 07 door 12, the strain gauge 18 can be zero-fitted into existing equipment. Furthermore, those skilled in the art will appreciate that the strain gauges are located remote from the load-bearing end of the boom and in a relatively protected location with less potential for damage. Additionally, it can be seen from FIG. 1 that the strain gauges 18 may function independently of changes in the viscosity of the fluid within the fluid motor 10, and substantially independently of changes in the ambient air temperature. Will. For these reasons, the present invention allows highly reliable reading. In addition, since the detection device is attached to the outside, the load support device to which such a detection device is attached is attached to the boom member 4.
It should be appreciated that this is considerably less expensive than similar prior art devices for measuring the load of an object supported on a body. In addition, the piston rod 12 will serve a dual role as the main drive of the boom and as part of the load measuring device.

The above description relates to one embodiment of the present invention, and it will be readily apparent to those skilled in the art that other embodiments may be devised using techniques and other techniques not disclosed above without departing from the scope and spirit of the present invention. I hope you understand that.

[Brief explanation of the drawing]

The figures show one embodiment of the present invention, in which Figure 1 is a side view of a load supporting device that includes a boom, a fluid motor that supports the boom, and a pair of strain gauges, and Figure 2 is a side view of a load supporting device that includes a mounting screw. Figure 3 is a perspective view of the strain gauge showing the state in which the strain gauge is removed, and Figure 3 shows the state in which the strain gauge is accurately positioned using the pedestal. FIG. 4 is a partial perspective view of the piston rod showing a state in which the strain gauge has been installed. 2...Load support mechanism 4...Boom member 6...
・Load supporting end 8...Opposite end 10...Fluid motor 12...Piston rod 14...Hydraulic cylinder 18...Strain gauge Applicant: JLG Industries, Inc.

Claims (6)

[Claims] (1) A boom load measurement method for measuring the load of an object suspended from one end of a boom member, in which nearly all of the load of the object is applied to the boom member as a compressive force. attaching a strain gauge to the outer surface of the rond in order to measure the compressive stress applied to the zero point by the object and generate an output accordingly; and connecting a circuit to the strain gauge. A boom load measuring method comprising the steps of: extracting the output as a load of the object suspended from the boom member. (2) A fluid motor comprising a boom member having a free end for suspending an object, a cylindrical main body, and a piston rod that projects inside the main body and has an end connected to the boom member. and a strain gauge attached to the outer surface of the piston rod to detect compressive stress inside the piston rod. (3) The boom member has a proximal end opposite the free end, and the proximal end is rotatably supported so that the boom member can rotate about the proximal end in a vertical plane. The boom load measuring device according to claim 2, characterized in that: (4) Claim 2, further comprising an electric circuit for extracting the compressive stress inside the piston rod as a proportional value of the load of the object suspended from the boom member. Boom load measuring device as described. (5) The piston rod has an intermediate portion located outside the main body, and the strain gauge is attached to the intermediate portion.
Boom load measuring device as described in section. (6) Claim 2, wherein the piston rod rotates the boom member around the base end by reciprocating with respect to the main body by pressurized fluid inside the main body. Boom load measuring device as described.