Unbalance vibrator

An unbalance vibrator comprises a drive shaft mounting unbalance weights, one of which is fixed stationary while the other one is turnable with respect to the drive shaft, and a mechanism for adjusting their mutual position made in the form of a rod spring-loaded in an axial direction and fitted in the movable unbalance weight so as to be movable radially, and adapted to interact with the other unbalance weight. The fixed unbalance weight is made in the form of a cylindrical sleeve having radial holes provided on its inside cylindrical surface. The movable unbalance weight is made in the form of at least a part of a cylinder arranged inside the cylinder, the rod being mounted so as to be engageable in one of the radial holes provided on the inside cylindrical surface of the sleeve.

TECHNICAL FIELD 
The present invention relates generally to vibration engineering and, more 
specifically, to the unbalance vibrator for vibratory devices. 
The invention may be used to best advantage for a number of applications 
which include vibrostabilizing treatment of components machined by 
press-working or cutting as well as by welding or casting for the purpose 
of stabilizing their geometric dimensions and shape or reducing residual 
stresses; vibration loading for testing the effect of vibrational 
overloads on the operational reliability and vibration-resistance, for 
example, of aircraft. 
The present invention can also be employed in other fields such as 
vibroabrasive treatment of components, for example, in deburring or 
descaling machines, construction materials industry (e.g., concrete 
compaction machines or pile driving machines), highway engineering (e.g., 
asphalt or gravel compaction machines), as well as transportation devices, 
such as vibratory feeding or conveying appartus. 
BACKGROUND OF THE INVENTION 
At the present time, the problem of extending the processing capacities of 
vibratory equipment under development is very urgent since it allows 
reductions in the component machining time and, consequently, in power 
consumption, which leads to increased productivity per unit time and 
improved quality of vibration treatment. Unbalance vibrators used most 
commonly for the generation of disturbing forces are of the mechanical 
inertia unbalance type which offers simplicity in operation and fairly 
high disturbing forces. Under operating conditions, a necessity may often 
arise for the amount of disturbing force generated by the vibratory device 
to be adjusted over a wide range, for example, in order to adjust the 
oscillation amplitude in the vibratory device. 
The amount of vibrational force generated is directly proportional to the 
mass of unbalance weight, which is arranged eccentrically with respect to 
the axis of rotation of the drive shaft, the distance of the centre of 
this mass from the axis of rotation of the drive shaft, and to the squared 
frequency of rotation (angular velocity) of the drive shaft. 
By virtue of the fact that varying the frequency of rotation of the drive 
shaft over a wide range necessitates the use of a d.c. motor in 
conjunction with a supply voltage regulator, the simplest ways of varying 
the amount of the disturbing force would be either by changing the 
eccentric mass of the unbalance vibrator or by altering the distance from 
the centre of its masses to the axis of rotation of the drive shaft. 
Known in the present state if the art is an unbalance vibrator comprising a 
drive shaft which is rotatably mounted in the housing and carries a 
balanced disk fixed stationary on the shaft and having holes adapted to 
receive one or several rods to provide for adjustment of the eccentric 
mass (cf., e.g., a textbook "Mechanisms", in Russian, "Mashinostroyenie" 
Publishers, Moscow, 1976, p. 669, FIG. 11.4). Such an unbalance vibrator 
is too complicated in manufacture because of the need to provide reliable 
clamping of the movable rods in conjunction with their rapid replacement 
required for changing the amount of the eccentric mass. 
Another unbalance vibrator known presently comprises a drive shaft carrying 
an unbalance weight fixed stationary on the shaft and another unbalance 
weight which is movable in a circular direction and can be fixed in 
position on the shaft by means of a key joint and offers a plurality of 
key slots determining the number of its positions relative to the fixed 
unbalance weight (cf., e.g., a texbook "Mechanisms", in Russian, 
"Mashinostroyenie" Publishers, Moscow, 1976, p. 668, FIG. 11.3, b). 
Turning the movable unbalance weight with respect to the fixed unbalance 
weight causes displacement of their common mass centre relative to the 
axis of rotation of the drive shaft and, consequently, a change in the 
amount of vibrational force which the vibratory device will produce. 
A common disadvantage of both of the aforedescribed unbalance vibrators 
resides in the fact that the produced vibrational force can only be varied 
within a comparatively narrow range, which restricts the field of 
application of unbalance vibrators of these types. 
The closest to the herein proposed invention is a centrifugal unbalance 
vibrator (DE, C, 1,297,928) comprising a fixed shaft fitted in a rotary 
electric motor. Fixed stationary on the housing of the electric motor is 
an unbalance weight made in the form of an arc-shaped guide supporting 
another movable unbalance weight made in the form of an arc-shaped 
element. The unbalance weights are provided with a mechanism for adjusting 
their mutual position and fashioned as a pin retainer spring-loaded in a 
radial direction. One end of the retainer projects over the fixed 
unbalance weight while the other end engages in and is movable within a 
blind radial hole passing through the fixed unbalance weight and the motor 
housing. The projecting end of the pin retainer is engageable in one of 
the through radial holes provided in the movable unbalance weight 
dependent on the amount of static moment which can be varied by displacing 
the centre of masses of the movable and the fixed unbalance weights 
effected through circular movement of the movable unbalance weight. The 
amount of static moment of the unbalance weights is proportional to the 
amount of the disturbing force produced. For adjusting the disturbing 
force, a cylindrical pin or screwdriver is fitted in the hole interacting 
with the rod end by means of which the retainer end is held in the radial 
hole, while the unbalance weight is moved to another position 
corresponding to the angle between two adjacent holes, so that the 
retainer should engage in one of the adjacent holes in the movable 
unbalance weight, from which hole it can be disengaged using said pin or 
screwdriver. 
A substantial disadvantage of the prior-art unbalance vibrator mentioned 
above resides in the fact that the mechanism for adjusting the mutual 
position of the unbalance weights does not allow the disturbing force to 
be varied over a wide range, which prevents vibration treatment of a wide 
range of products. Another disadvantage of the prior-art unbalance 
vibrator lies with the sophisticated adjustment of the disturbing force, 
since the adjustment process involves the use of an additional tool such a 
cylindrical pin or rod, which has to be fitted, in succession, in each of 
the through holes passing underneath the movable retainer, thus increasing 
the total adjustment time. 
Furthermore, the unbalance vibrator discussed above features a 
comparatively high drag coefficient because of the clearance between the 
movable unbalance weight and the motor housing, which increases noise 
during operation of the unbalance vibrator. 
SUMMARY OF THE INVENTION 
It is therefore an object of the present invention to extend the processing 
capacities of the unbalance vibrator. 
It is also an object of this invention to simplify the adjustment of the 
amount of the disturbing force and to reduce the adjustment time. 
It is another object of this invention to reduce noise caused by the 
operation of the unbalance vibrator. 
With the foregoing and other objects in view the present invention thus 
resides in the fact that in an unbalance vibrator comprising a drive shaft 
mounting unbalance weights one of which is fixed stationary while the 
other one is turnable with respect to the shaft, and a mechanism for 
adjusting their mutual position made in the form of a rod spring-loaded in 
an axial direction and fitted in one of the unbalance weights so as to be 
movable radially and adapted to interact with the other unbalance weight, 
according to the invention, one of the unbalance weights is made in the 
form of a cylindrical sleeve having radial holes provided on its inside 
cylindrical surface, whereas the other unbalance weight is made in the 
form of at least a part of a cylinder which is arranged in the sleeve and 
adapted to mount a rod engageable in one of the radial holes provided in 
the sleeve. 
The herein proposed construction of the unbalance weights makes it possible 
to increase the number of holes adapted to receive the radially movable 
rod, thus extending the adjustment range of the static moment which can be 
varied from zero to its greatest. A streamline shape given to the 
unbalance weights abates noise produced by the unbalance vibrator during 
operation owing to reduced drag of each of the unbalance weights. 
According to the preferred embodiment of the present invention, the 
adjusting mechanism comprises an additional rod spring-loaded in a radial 
direction and mounted on the inner unbalance weight. 
Provision of an additional rod in the unbalance weight of the unbalance 
vibrator, in combination with the main rod, makes it possible to reduce 
diameter of the holes adapted to receive both of the rods, thus increasing 
the number of holes provided in the cylindrical sleeve of preset 
dimensions, which extends the adjustment range of the disturbing force 
and, consequently, the processing capacities of the unbalance vibrator. 
According to another embodiment of the invention, each of the rods is 
provided with a projection, while the outside end face of the inner 
unbalance weight is provided with radial slots adapted to receive the 
projections of the rods, the radial holes provided in the cylinder being, 
in fact, blind holes. 
Provision of a projection engageable in the radial slot provided on the 
outside surface of the unbalance of the unbalance weight makes it possible 
to simplify disengagement of the retainer from its mating hole in the 
cylinder, thus decreasing the time required for adjusting a desired amount 
of vibrational force of the unbalance vibrator and facilitating its 
attendance. 
Provision of blind holes in the unbalance weight made in the form of the 
cylindrical sleeve makes it possible to substantially reduce the level of 
noise produced by the unbalance vibrator in the course of its operation 
due to reduced drag of the cylindrical sleeve casing and, consequently, to 
improve the operating conditions for the attending personnel. 
According to still another embodiment of the invention, the rods are 
disposed diametrically opposite to each other so that the centre of mass 
of the inner unbalance weight is arranged on a line coinciding with the 
axes of the rods. 
Such an arrangement of the rods facilitates their being disengaged from the 
mating holes by means of bringing them closer to each other, which reduces 
the adjustment time and facilitates the attendance of the unbalance 
vibrator. 
Arrangement of the rods on a line coinciding with the centre of mass of the 
inner unbalance weight improves retention reliability since the direction 
of movement of the rods will coincide, in this case, with the action 
vector of the centrifugal force produced by the inner unbalance weight. 
According to yet another embodiment of the invention, the radial holes 
provided on the inside cylindrical surface of the cylindrical sleeve are 
made in the form of spline grooves. 
Provision of the radial holes made in the form of spline grooves enables 
them to be readily cut, for example, by a milling cutter, which 
facilitates the unbalance vibrator manufacturing process.

BRIEF DESCRIPTION OF PREFERRED EMBODIMENTS 
An unbalance vibrator comprises a rotatable drive shaft 1 (FIGS. 1, 2, 4) 
which carries a unbalance weight 2 which is turnable with respect to the 
shaft and is made in the form of at least a part of a cylinder 3 having an 
unbalance bob 4 secured on its inside face 5. The unbalance weight 2 is 
coaxially arranged within an unbalance weight 6 fixed stationary on the 
shaft 1 and made in the form of a cylindrical sleeve 7 having an unbalance 
bob 8 secured on an inside face 9. The unbalance weight 2 is secured on 
the drive shaft 1 by means of a flange 10. The unbalance vibrator is 
provided with a mechanism for adjusting the mutual position of the 
unbalance weights 2, 6 which mechanism is made in the form of two 
cylindrical rods, a main rod 11 and an additional rod 11' fitted in two 
diametrically opposite radial cylindrical holes 12, 12' of the unbalance 
weight 2. The centre of mass of the unbalance weight 2 is arranged on the 
line coinciding with the axes of the rods 11, 11'. The rods 11, 11' are 
loaded, in a radial direction, by means of elastic elements such as, for 
example, cylindrical spiral compression springs 13, 13', and provided with 
projections 14, 14'. The axis of symmetry of each of the projections 14, 
14' is square to the axis of symmetry of each of the rods 11, 11', and the 
projections 14, 14' pass through the radial slots 15 provided 
diametrically opposite, on the outside end face of the inner movable 
weight 2. Ends 16, 16' of the rods 11, 11' extending from the holes 12, 
12', engage in radial blind spline slots 17 provided on the inside 
cylindrical surface of the sleeve 7. 
The unbalance vibrator operates as follows. 
In the initial position, the ends 16, 16' of the rods 11, 11' extending 
from the holes 12, 12' of the inner unbalance weight 2, engage in the 
spline slots 17 of the sleeve 7 so as to form a detachable joint. The 
disturbing force generated with the operation of the electric motor (not 
shown) is transmitted, via the unbalance weights 2 and 6, to the drive 
shaft 1 and to the motor housing, the amount of the disturbing force being 
dependent on the angle of turn between the mutual positions of the 
unbalance weights 2, 6. For adjusting the amount of the disturbing force, 
the electric motor is to be turned off whereby the unbalance vibrator is 
stopped, and the cylindrical rods 11, 11' have to be moved, using the 
projections 14, 14', in a radial direction against tension of the springs 
13, 13', until the rods 11, 11' should disengage from the spline slots 17 
so that the inner unbalance weight 2 can be freely turned with respect to 
the drive shaft 1 and the outer unbalance weight 6. While holding the rod 
projections 14, 14' in a position when the springs 13, 13' are compressed 
the unbalance weight 2 is turned, relative to the unbalance weight 6, 
through an angle corresponding to a required amount of the static moment, 
whereupon the projections 14, 14' of the rods 11, 11' are gradually 
released so as to allow their free ends 16, 16', which are moved under 
tension of the springs 13, 13', to engage in two diametrically opposite 
spline slots 17 provided on the inside cylindrical surface of the sleeve 
7. Next, the drive motor is started to continue treatment. 
According to another embodiment of the invention, the inner unbalance 
weight 2 is made in the form of a cylindrical insert whose inside surface 
is provided with sector-shaped recesses 18 (FIG. 3). 
For increasing the distance from the axis of rotation of the drive shaft 1 
to the centre of mass of the outer unbalance weight 6, its end face wall 
19 (FIG. 1) may be provided with sector-shaped recesses 20 (FIG. 5). 
According to still another embodiment of the outer unbalance weight 6, its 
end face wall 19 (FIG. 1) is provided with cylindrical recesses 21 (FIG. 
6).