US3872458A

US3872458A - Crane boom-out transmitter

Info

Publication number: US3872458A
Application number: US320682A
Authority: US
Inventors: Savely Solomonov Schedrovitsky; Leonid Fomich Goncharevich; Karl Vladimirovich Pruss; Alexei Pavlovich Lebedev; Valentin Nikolaevich Gontar
Original assignee: Individual
Current assignee: Individual
Priority date: 1971-12-31
Filing date: 1973-01-02
Publication date: 1975-03-18
Anticipated expiration: 1992-03-18

Abstract

A crane boom radius transmitter employs a boom radius-toelectric signal converter comprising a movable member made in the form of a screen consisting of two sections, which movable member rotates as the boom angle changes. The screen moves between the coupling cores of an inductively coupled detector and sine-wave generator to produce a signal proportional to the boom inclination. Simultaneously, the cores are arranged to rotate relative to the screen as the boom length changes, thereby causing the output signal of the detector to be proportional to the boom radius.

Description

United States Patent [191 Schedrovitsky et al.

[4 1 Mar. 18, 1975 CRANE BOOM-OUT TRANSMITTER [22] Filed: Jan. 2, 1973 [21] Appl. No.: 320,682

[30] Foreign Application Priority Data Dec. 31, 1971 U.S.S.R 1,732,412

[52] US. Cl. 340/267 C, 212/39 A, 235/92 MP, 324/34 PS [51] Int. Cl. G08b 21/00 [58] Field of Search 340/267 C, 282; 212/39 A, 212/39 R; 324/34 PS, 34 L; 235/92 MP [56] References Cited UNITED STATES PATENTS 3,456,132 7/1969 Dechelotte 340/282 3,638,212 [/1972 Peter et al 340/267 C Primary Examiner-Glen R. Swann, ill

[57] ABSTRACT A crane boom radius transmitter employs a boom radius-to-electric signal converter comprising a movable member made in the form ofa screen consisting of two sections, which movable member rotates as the boom angle changes. The screen moves between the coupling cores of an inductively coupled detector andsine-wave generator to produce a signal proportional to the boom inclination. Simultaneously, the cores are arranged to rotate relative to the screen as the boom length changes, thereby causing the output signal of the detector to be proportional to the boom radius.

4 Claims, 5 Drawing Figures PATENIED MAR I 8 I975 SHEET 1 OF 3 PAIENTEDHARI8I975 3,872,458

SHEETZOFS i I I I I I I I I l I I I I I I I l I I I I I I I I I I I I I I I I I I L.

' PATENTED 1 819.?5

snmao a CRANE BOOM-OUT TRANSMITTER BACKGROUND OF THE INVENTION The present invention relates generally to instruments effecting position control of movable elements of various machines and mechanisms, and more particularly it relates to a crane boom radius transmitter.

Crane boom radius transmitters operating on the principle of mechanical-electrical conversion are known in the art.

In the prior art crane boom radius transmitters, the boom radius-to-electric signal converter comprises a movable member mechanically linked to the input shaft of the transmitter, which movable member rotates as the boom angle changes, and means for converting the angle of rotation of the movable member into an electric signal.

Used as the movable member in the known transmitters is a cam coupled through the medium of a leverage to the means for converting the angle of rotation of the movable member into an electric signal, which means is a potentiometer.

A disadvantage of the prior art crane boom radius transmitters resides in the fact that the accuracy of measurement of the boom radius depends on the condition of the cam, leverage and potentiometer proper which are susceptible to wear and are not reliable and durable enough.

Another disadvantage inherent in the abovementioned transmitters is that they have been designed without any allowance being made for a simultaneous measurement of the boom length and the boom angle, which substantially limits the scope of their application.

Still another disadvantage of the prior art transmitters resides in the fact that a too low level of the potentiometer output signal exists, which necessitates an additional amplification thereof and, consequently, involves superfluous consumption of energy.

A further disadvantage of the prior art transmitters is a limited range of measurement of the boom radius due to the imperfection of the leverage.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a crane boom radius transmitter that will ensure high accuracy of measurement within a wide range.

Another object of the invention is to provide such an embodiment of the transmitter that will permit of simultaneously measuring the boom angle and the boom radius of cargo cranes.

Still another object of the invention is to provide a crane boom radius transmitter with a low consumption of energy.

With this and other objects in view, the essence of the present invention resides in the fact that in a crane boom radius transmitter, the boom radius-to-electric signal converter comprises a movable member mechanically linked to an input shaft of the transmitter, which shaft rotates as the boom angle changes, and means for converting the angle of rotation of the movable member into an electric signal, and the movable member is, according to the invention, made in the form of a screen consisting of two sections each described by a similar compound curve, while the means for converting the angle of rotation of the movable member into an electric signal comprises a detector and a sinewave generator inductively coupled to the detector through the medium of two pairs of windings positioned in cores, the primary winding of each pair being incorporated in the generator circuit, the secondary winding of each pair being incorporated in the detector circuit, and the cores of each pair of windings are magnetically coupled and arranged relative to each other so that the screen section corresponding to each pair always remains, as the screen rotates, within the working gap between respective cores, thus reversing the inductive coupling of each pair of windings and altering the output signal.

It is expedient that in the transmitter both pairs of cores be secured coaxially to the screen so as to move when the crane boom is extended, thus ensuring measurement of the boom radius as the latter changes together with the boom angle and boom length.

It is advantageous that both screen sections be made in the form of disks.

Both screen sections should be preferably arranged in one plane opposite to each other in the form of a disk.

It is also preferable that both screen sections be arranged in parallel planes and oriented in opposite directions in the form of two disks.

Both screen sections may also be made in the form of a helix and symmetrically arranged on a common axis.

Such an embodiment of the crane boom radius transmitter allows for substantially simplifying its design and extending the measurement range.

Another advantage of the proposed crane boom radius transmitter resides in the possibility of measuring the overall boom radius depending on the boom angle and extension.

Still another advantage of the proposed crane boom radius transmitter is the low energy consumption at a high level of the output signal.

BRIEF DESCRIPTION OF THE DRAWINGS The invention will now be explained in greater detail with reference to embodiments thereof taken in conjunction with the accompanying drawings, wherein:

FIG. 1 is a general cut-away view of a crane boom radius transmitter, according to the invention;

FIG. 2 is a general view of the connection pattern of the crane boom radius transmitter, according to the invention;

FIG. 3 is a circuit diagram of the means for converting the angle of rotation of the movable member into an electric signal, according to the invention;

FIG. 4 is a general view of the mechanical part of another embodiment of the crane boom radius transmitter, according to the invention; and

FIG. 5 is a general view of the mechanical part of still another embodiment of the crane boom radius transmitter, according to the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT shaft 5 coaxial with the first input shaft 1 and coupled through a link 6 to a bracket 7 rotatable round the axis of the shaft 1. Two pairs of

cores

8, 9, 10 and 11 are secured to the bracket 7, the cores 8 and 9 forming one pair and being so arranged relative to each other and to the section 3 of the screen 2 so that the section 3 is always within the working gap between the cores 8 and 9. The

cores

10 and 11 are in turn arranged relative to their respective section 4 of the screen 2 so that the section 4 is always within the working gap between the

cores

10 and 11. Ferromagnetic shell cores are used as the

cores

8, 9, 1 and 11, the cores 8 and 11 incorporating

primary winding

12 and 13, and the cores 9 and incorporating

secondary windings

14 and 15, respectively. The cores 8 and 9 represent a magnetic circuit for the respective inductively coupled

windings

12 and 14, while the cores l0 and 11 perform the same function for the inductively coupled windings l3 and 15. The windings 12, l3, l4 and 15 together with the cores 8, 9, l0 and 11 constitute the circuit of means 16 for converting the angle of rotation of the movable member into an electric signal. The latter means 16 together with the screen 2 form the boom radius-to electric signal converter. The whole transmitter is contained in a housing 17 provided with packed supports for the input shafts 1 and 5, as well as with power supply leads.

The pattern of connection of the crane boom radius transmitter to a crane boom is shown in FIG. 2.

The first input shaft 1 of the transmitter is coupled to a crane boom 19 through the medium of a carrier 18. The second input shfat 5 of the transmitter is connected, through a transmission mechanism comprising a reduction gear 20 and a measuring drum 21 rotated by a wire rope 22, to an extending portion 23 of the boom 19.

The electric circuit of the means for converting the angle of rotation of the movable member into an electric signal is represented in FIG. 3.

The circuit comprises a sine-wave generator 24 using a transistor 25 in a known three-point capacitance circuit. The circuit of the generator 24 also includes the

primary windings

12 and 13 inductively coupled to the

secondary windings

14 and 15. The latter two form part of the circuit of a peak detector 26 which circuit also includes two diodes 27, capacitors 28 and resistors 29. The peak detector circuit is arranged on the lines of a known differential circuit. Two

stabilitrons

30 and 31 are provided at the input of the electric circuit to stabilize the supply voltage, while an emitter follower 32 using a conventional circuit and intended to match the electric circuit with the following stages, is connected to the output of the circuit of the peak detector 26. The terminals of a DC. source are marked in the diagram with and and the output signal is obtained at points A and B.

Another embodiment of the mechanical part of the crane boom radius transmitter of the prpesent invention is shown in FIG. 4. In this case, both

sections

3 and 4 of the screen 2 are also made in the form of disks, but they are arranged in two parallel planes and their profiles (also described by similar compound curves) are oriented in opposite directions. In this embodiment, the disks are arranged in an off-set manner each with an equal eccentricity with respect to the common axis of rotation (shaft 1). Both

sections

3 and 4 are secured on the first input shaft 1, while the

cores

8, 9, 10 and ll 4 are mounted on the bracket7' rotatably round the shaft 1.

FIG. 5 shows still another embodiment of the mechanical part of the crane boom radius transmitter of the present invention.

In this embodiment, both

sections

3 and 4 of the screen 2 are made in the form of conical helices mounted on a hollow shaft 33- moving along the first input shaft 1 and secured thereto by means of a sliding key 34 ensuring the movement of the hollow shaft 33 along the input shaft 1. The

sections

3 and 4 are described by helicoidal lines of the same sense of rotation with a constant lead but with the vertices of the cones oriented in opposite directions, i.e., the

sections

3 and 4 are arranged symmetrically on a common axis.

A threaded portion 35 with a pitch equal to the lead of the helicoidal line describing the

sections

3 and 4 is provided on the end of the hollow shaft 33. The threaded portion 35 is fitted in a fixed nut 36. The bracket 7" with the

cores

8, 9, 10 and 11 mounted thereon, is provided with a bushing 37 fitted on a threaded portion 38 with a pitch equal to that of the threaded portion 35.

In the latter two embodiments, the mechanical part of the crane boom radius transmitter is connected to the crane boom in a manner similar to that of the embodiment shown in FIG. 2, and the electric circuit of the means 16 for converting the angle of rotation of the movable member into an electric signal (FIG. 1) is the same for all the three embodiments, as shown in FIG. 3.

The crane boom radius transmitter operates as follows.

As the boom 19 (FIG. 2) is lowered or raised, the change of the boom angle is transmitted via the carrier 18 to the first input shaft 1. The latter turns, and, in so doing, makes the screen 2 (FIG. 1) turn through a pro- .portional angle. The displacement of the extending portion 23 (FIG. 2) of the boom (change of the boom length) is transmitted via the wire rope 22, the measuring drum 21 and the reduction gear 20 to the second input shaft 5, turning the latter and, consequently, the bracket 7 (FIG. 1), carrying the cores 8, 9, l0 and 11, through an angle proportional to the displacement of the boom. As a result, the screen 2 and the pair of the cores 8 and 9 rotate relative to each other through an angle proportional to the boom radius which depends on the boom angle and length.

According to the embodiment of the mechanical part of the transmitter as shown in FIG. 1, the rotation of the screen 2 and

cores

8, 9, 10 and 11 relative to each other is possible within as the screen 2 is made in the form of a disk.

As the

sections

3 and 4 of the screen 2 are arranged opposite to each other, the section 3 of the rotating screen 2 goes deeper into and the second section 4 comes out to the same extent from the working gap between the other two cores l0 and 11, thus reversing the inductive coupling of each pair of the

windings

12, 13, 14 and 15. The sinusoidal voltage induced in the secondary windings 14 and 15 (FIG. 3) has an amplitude which depends on the position of the screen 2 in the working gap between the

cores

8 and 9 and 10 and 11 respectively; the voltage is then rectified and smoothed by the detector 26. There appears across the output of the detector 26 a rectified and smoothed voltage equal to the difference of the signals obtained in the

secondary windings

14 and 15. The input signal of the crane boom radius transmitter is unidirectional (boom radius is always positive) and, consequently, the output voltages corresponding to this input signal are of an invariable polarity. To obtain a more powerful output signal, use is made of th emitter follower 32 obtained wherefrom is the useful signal proportional to the boomradius of the boom 19.

The second embodiment of the mechanical part of the transmitter, shown in FIG. 4, enables the operating angle of rotation of the screen 2 to be increased to 360 as the

sections

3 and 4 thereof are arranged in parallel planes. In other respects, the transmitter of this embodiment operates in a manner similar to the one described above.

The third embodiment of the mechanical part of the transmitter, shown in FIG. 5, enables the screen 2 to rotate through an angle exceeding 360. As the hollow shaft 33 rotates together with the first input shaft 1, the threaded portion 35 of the hollow shaft 33 cooperates with the fixed nut 36 to displace the hollow shaft 33 together with the

screen sections

3 and 4 along the first input shaft 1. Since the thread of the portion 35 has a pitch equal to the lead of the helices of the

sections

3 and 4, the rotation of the first input shaft 1 directly linked to the measuring drum 21 (FIG. 2) revolving as the boom 19 is extended, the sections 3 and 4 (FIG. 5) of the screen 2 travel in the working gap of both pairs of the

cores

8, 9, 10 and 11. While the section 3 gradually enters into the working gap between the cores 8 and 9, the other section 4 gradually comes out of the working gap between the cores l and 11. As the second input shaft rotates, the bracket 7" does so, together with the

cores

8, 9, 10 and 11 mounted thereon, across the portion 38 by means of the bush 37, at the same time advancing along the hollow shaft 33. As a result, the boom radius of the boom 19 (FIG. 2), varying due to a simultaneous change of the boom angle and length, can be measured. The means 16 (FIG. 1) for converting the angle of rotation of the movable member into an electric signal operates, in the third embodiment of the mechanical part of the transmitter, as it does in the first embodiment thereof.

The proposed crane boom radius transmitter can be used for measuring the boom radius range-of a crane, dependent upon the boom angle and change of boom length as well as in load-lifting capacity limiting devices and for determining the position of working members of various machines.

The use of the proposed crane boom radius transmitter allows for substantially increasing the accuracy of measurement by eliminating the effect of friction and plays due to the contactless arrangement of the means 16 for converting the angle of rotation of the movable member into an electric signal.

The proposed transmitter is advantageous in that its measurement range is substantially extended due the employment of the screen 2 consisting of two

sections

3 and 4 made in the form of two disks or two conical helices.

Another advantage of the proposed transmitter resides in increasing the level of the output signal from 0 to 12 V at a low energy consumption, which is due to the circuit of the detector 26 (FIG. 3) also permitting of substantially increasing the sensitivity of the whole means 16 (FIG. 1) for converting the angle of rotation of the movable member into an electric signal.

Still another advantage of the proposed transmitter is its simplified structure which makes the transmitter easy in manufacture.

What is claimed is:

1. A crane boom radius transmitter comprising: a first input shaft coupled to a crane boom and rotating the boom angle changes; a second input shaft coaxial with said first shaft and mechanically coupled with said crane boom and rotating as the boom length changes; a boom radius-to-electric signal converter having a movable member and means for converting the angle of rotation of said movable member into an electric signal, said converter being mechanically linked with said first and second input shafts; said movable member being mechanically coupled with said first input shaft and being made in the form of a screen comprising two sections; said means for converting the angle of rotation of said movable member into an electric signal coupled to said screen and including an inductively coupled detector and a sine-wave generator; two pairs of windings positioned in magnetically coupled cores and effecting the inductive coupling between said detector and said sine-wave generator; said pair of windings each having a primary winding incorporated in the circuit of said sine-wave generator and a secondary winding incorporated in the circuit of said detector; said cores being mechanically linked with said second shaft and moving relative to said screen when said second shaft is rotated; a first section of said screen having a profile defined by a variable radius curve and being arranged with regard to said cores of said first pair of windings so that said first section is constantly in the working gap of said magnetically coupled cores and, while moving, it alters the magnetic coupling therebetween; a second section of said screen having a profile defined by said curve of a variable radius and being arranged relative to said cores of said second pair of windings such that it constantly, while moving, is arranged in the working gap of said magnetically coupled cores, thereby altering the magnetic coupling therebetween in an inverse manner to the alteration of the magnetic coupling between said first pair of windings, thus altering said electric signal.

2. The transmitter as set forth in claim 1, wherein said sections of said screen are each arranged in one plane opposite each other in the form of disks.

3. The transmitter as set forth in claim 1, wherein both of said sections of said screen are made in the form of disks arranged in parallel planes with opposite orientations of the profiles thereof.

4. The transmitter as set forth in claim 1, wherein each of said sections of said screen are made in the form of a spatial helix and are arranged on a common axis symmetrical to one another.