[0001] The subject of the present invention is a unit for measurement of overturning moment
of a heavy working machine, especially a crane, mounted on a crane.
[0002] Known units for measurement of overturning moment are provided with several indicators
installed on a crane, which measure forces of the rope, oil pressure in the cylinder,
the inclination angle of the jib, the length of the jib arm, etc. The obtained parameters
are fed into the system of the lifting capacity limiter in which they are converted
into overturning moment.
[0003] Those skilled in the art know from the G.F.R. patent specification no. 155339 a device
for limiting the load torque of a crane or other crane units, which is characterized
by that the load toroue is measured by means of an elasticity meter or other instrument
situated in the screw fixing the bearing outer ring. The instrument measures the force
in the place of the measurement plane transferring the moments of structural elements
through lifting and lowering impulses of the jib, which cause switching off of the
alarm device. The instrument signals also parameters of an unloaded crane, and at
exceeding the permissible weight it switches off the lifting mechanism.
[0004] The known units have such a disadvantage that they determine overturning moment by
means of many indicators placed in several places of the crane and by means of other
additional devices. The production cost of said units is high, whereas measurements
obtained by them have little accuracy.
[0005] The essence of the solution is a unit which has a measurement indicator, preferably
touchless, which is situated perpendicularly to the rotation plane of the crane and
lies in the vertical plane of symmetry of the jib and is set at a constant distance
of about IL from the axis of rotation of the crane, that is, in the vicinity of rolling
elements of the bearing. In the unit the force R may be determined on the basis of
the ouantity of the dimension originated from elastic strain of fasteners connecting
the crane body with the bearing.
[0006] An advantage of the unit according to the invention is, first of all, the fact that
it is simple in design, whereas in operation it determines measurements of overturning
moment with high accuracy.
[0007] The solution is presented in more detail in an example of its embodiment in the attached
drawing, in which figs 1 and 2 present the side view of the place of location of indicators
in a crane with hydraulic and mechanical drive, fig.3 - the top view of the place
of location of an indicator in a crane, and fig.4 presents the axial section of a
detail of location of an indicator.
[0008] The unit has a touchless indicator 1 which is connected with a measuring instrument
converting impulses produced in the result of a change of a measuring port Δ, the
size of which depends on elastic strain of screws 3 fixing the body arm 5 to the inner
track of a bearing 6. Said indicator is situated perpendicularly to the rotation plane
of the crane and lies in the vertical plane of symmetry of the jib and is set at a
constant distance smaller from a 2 from the axis of rotation of the crane, that is,
in the vicinity of rolling elements of the bearing 2. The bearing is designed so that
it has the outer track composed of an upper ring 7 and a lower ring 8 which are connected
together and attached by means of screws 4 to the crane undercarriage 2.
[0009] In the solution according to the invention the measurement of overturning moment
consists in a measurement of the reaction force R whose value is equal to the sum
of the loading force, the force of the jib weight, the wind force, and other forces
where said force R is directed upwards and is perpendicular to the plane of rotation
and lies in the vertical plane of symmetry of the jib and is measured at the distance
smaller from a 2 from the axis of rotation of the crane, that is, in the vicinity
of rolling elements of the bearing. The reaction force is established from elastic
strain of screws 3 connecting the body arm with the crane base. The measurement is
made on the basis of a change of the distance Δ of the position of the indicator 1
fixed to the body arm 5 in relation to the inner track of the bearing 6, being the
crane base. Reduced overturning moment P · L has a constant value, thus, also the
total force R = P·L a has a constant value as well.
[0010] For the measurement of reaction a touchless room indicator built in point A has been
applied.
1. A unit for measurement of overturningmoment of a heavy working machine, especially
a crane, comprising an indicator connected with a measuring instrument serving for
determination of the total force R, said force R being the sum of the loading force,
the force of the jib weight, the wind force, and other forces, characterized in that
the indicator /1/ is situated perpendicularly to the rotation plane of the crane and
lies in the vertical plane of symmetry of the jib and is set at a constant distance
of about a 2 from the axis of rotation of the crane, that is, in the vicinity of rolling
elements of the bearing /2/.
2. A unit according to claim 1, characterized in that the force R is determined on
the basis of the dimension Δ resulting from elastic strain of fasteners /3/ connecting
the crane body /5/ with the bearing /6/.
3. A unit according to claim 1, characterized in that the reaction force P is detamined
by means of a touchless indicator /1/.
