[0001] This patent application concerns a barycentric support for balancing the motor-rotor
unit on airtight combustion chamber boilers employed in heating systems.
[0002] These boilers generally have a centrifugal fan which on one hand ensures an intake
of comburent air and, on the other, permits the forced discharge of combustion smoke.
[0003] The screw housing of the rotor is generally fixed to the supporting framework of
the boiler, while the motor-rotor unit is screwed to the exterior of the rear wall
of the screw by means of a number of interposed shock absorbing rubber collars which
prevent the vibrations of the unit from being fully transmitted to the screw and by
this to the boiler body, thereby producing unwanted noisiness.
[0004] In particular, said rubber collars are fitted between the screw and the front support
U-bolt of the motor-rotor unit, namely the one facing the fan and immediately opposite
the rear wall of the screw.
[0005] Despite the dampening action of the shock absorbing collars, weak vibrations nonetheless
reach the boiler body; in fact boilers featuring a balancing device for the motor-rotor
unit have recently been introduced on the market in order to eliminate the cause of
these vibrations at the source.
[0006] This device consists of a supporting shelf screwed to the exterior of the rear wall
of the screw below the motor-rotor unit; it should be noted that once the motor-rotor
unit has been installed its shaft is positioned horizontally; this means that the
rear wall of the screw lies on a vertical plane, as does the front support plate-shaped
U-bolt of the motor-rotor unit, while the axes of the above shock-absorbing collars
are parallel to the horizontal axis of the rotor shaft.
[0007] Said shelf supports a rubber cylinder having a vertical axis which is wedged between
said shelf and the edge of the overlying plate-shaped U-bolt, thrusting the latter
upwards in order to balance, be it very approximately, the weight of the motor-rotor
unit consisting of the shaft, the fan, the motor and relevant rear and front support
U-bolts.
[0008] Said balancing device can not be considered as totally satisfactory in that even
though the system of forces consisting of the motor-rotor unit weight and the external
balancing thrust (provided by the rubber cylinder compressed between the U-bolt and
the shelf) allows a resulting force which is practically zero, the resulting moment
of this system of forces is not zero, in that the external balancing thrust is applied
along a vertical straight line which does not pass through the barycentre of the motor-rotor
unit.
[0009] This means that even when this balancing device is used, the motor-rotor unit continues
to vibrate and to transmit its vibrations to the boiler body, producing unwanted noisiness.
[0010] The purpose of this invention is to design a balancing device which provides complete
and precise static balancing of motor-rotor units installed on boilers with airtight
combustion chamber.
[0011] This has been attained by means of a device which makes it possible to apply on the
motor-rotor unit a vertical upward thrust, of adjustable intensity, passing through
the barycentre of the unit, in order to zero both the resultant of the forces and
the resultant of the moments of the forces.
[0012] The device in question consists of a rubber collar which, thanks to an adjusting
screw, can be thrust, with the required force, either against the bottom wall of the
stator unit at a point aligned vertically with the overlying barycentre of the motor-rotor
unit.
[0013] In a second preferred embodiment of the device according to the invention, the above
rubber collar, is thrust under a projecting tab, towards the back, from the bottom
edge of the above front support U-bolt of the motor-rotor unit, instead of directly
pinning down the stator unit; the use of said tab permits discharging the balancing
force on the U-bolt, while applying it at a point aligned vertically with respect
to the barycentre of the motor-rotor unit, notwithstanding the fact that the U-bolt
is positioned further forwards with respect to the barycentric vertical direction.
[0014] Using the same invention principle, a structural variation is possible by positioning
said collar above the motor-rotor unit so that the balancing force exerted by the
same is perfectly vertical and passes through the barycentre of the motor-rotor unit
below.
[0015] In the case of the latter, the collar, resting on a support shelf fixed to the screw,
abuts from under a bracket fitted on the top edge of the above front support U-bolt
of the motor-rotor unit which is consequently suspended from said collar at a point
aligned vertically to the barycentre of said unit.
[0016] For major clarity the description of the invention continues with reference to the
enclosed drawings which are intended for purposes of illustration and not in a limiting
sense, where:
- fig. 1 is a rear view of a motor-rotor unit installed on the rear wall of a screw,
balanced by means of the barycentric support according to the invention;
- fig. 2 is an orthogonal view of fig. 1 in direction II-II of fig. 1;
- fig. 3 is the same as fig. 1 but refers to an alternative structural embodiment of
the device;
- fig. 4 is the same as fig. 1 but refers to a third structural embodiment of the device.
[0017] With reference to the above figures, the device in question includes a rubber collar
(1) having a vertical axis, supported by an annular plate (2) fixed along the shank
of a screw (3) having a vertical axis, projecting from the end of a support shelf
(4) on which said screw (3) may be fixed in the positioned required by means of a
nut (5) and lock nut (6).
[0018] Said support shelf (4) is screwed on the rear wall (7) of the screw (7a), to which
the front support U-bolt (8) of the motor-rotor unit (9) is screwed.
[0019] As illustrated in the drawings, said U-bolt (8) is shaped like a three-lobe plate,
staggered by 120°, where the U-bolt is screwed to the screw (7a) with interposing
rubber collars (10) which act as shock absorbers.
[0020] As mentioned previously, the characteristic of the device according to the invention
is that the collar (1) no longer presses on the bottom edge of the U-bolt (8) as in
the past, but under the stator unit (11) at a point along the vertical straight line
passing through the barycentre of the motor-rotor unit.
[0021] It is important to note that adjustment of the screw (3) makes it possible to regulate
the pressure of the rubber collar (1) as required and consequently the lifting thrust
exerted on the stator unit (11), so as to balance the weight of the motor-rotor unit
very precisely.
[0022] In this regard it should be noted that the shelf (4) features a slot (4a) which permits
regulating the end position of the collar (1) with respect to the shelf (4) in order
to ensure a perfect alignment of the collar (1) with respect to the barycentre of
the motor-rotor unit, from time to time.
[0023] With reference to fig. 3, it can be noted that the collar (1), in a alternative structural
embodiment, presses under a bracket (8a) projecting from the U-bolt (8), by means
of which the balancing thrust of the collar (1) pushes against the U-bolt instead
of on the stator unit (11), as in the embodiment referred to in figs. 1 and 2.
[0024] Fig. 4 illustrates a third structural embodiment whereby the U-bolt (8) features
on its top edges a bracket (8b) on which the upward thrust of the collar (1) is exerted,
and whose support shelf (4) is in this case fixed at the top of the rear wall of the
screw (7a), above the motor-rotor unit.
[0025] The dislocation and shape of the brackets (8a and 8b) ensure that the balancing force
exerted by the collar (1) on the U-bolt (8) by means of the brackets (8a and 8b) lie
in a vertical direction passing through the barycentre of the motor-rotor unit.
1) A barycentric support for balancing the motor-rotor unit on airtight combustion chamber
boilers, featuring a rubber collar (1) positioned at the end of a rigid support shelf
(4) screwed to the exterior of the rear wall (7) of the screw (7a) under the motor-rotor
unit (9) characterized in that the collar (1) exerts an upward thrust under the stator
unit (11) at a point along the vertical straight line passing through the barycentre
of the motor-rotor unit.
2) A barycentric support for balancing the motor-rotor unit on airtight combustion chamber
boilers, featuring a rubber collar (1) positioned at the end of a rigid support shelf
(4) screwed to the exterior of the rear wall (7) of a screw (7a) under the motor-rotor
unit (9), characterized in that the collar (1) exerts an upward thrust under a bracket
(8a) projecting from the bottom edge of the front support U-bolt (8) of the motor-rotor
unit; said thrust being exerted at a point of the bracket (8a) along the vertical
straight line passing through the barycentre of the motor-rotor unit.
3) A barycentric support for balancing the motor-rotor unit on airtight combustion chamber
boilers, featuring a rubber collar (1) positioned at the end of a rigid support shelf
(4) screwed to the exterior of the rear wall (7) of a screw (7a) above the motor-rotor
unit (9), characterized in that the collar (1) exerts an upward thrust under a bracket
(8b) projecting from the top edge of the front support U-bolt (8) of the motor-rotor
unit; said thrust being exerted at a point of the bracket (8b) along the vertical
straight line passing through the barycentre of the motor-rotor unit.
4) A barycentric support for balancing the motor-rotor unit on airtight combustion chamber
boilers according to the previous claims, characterized in that said rubber collar
(1) is supported by an annular plate (2) fixed along the shank of a screw (3) having
a vertical axis, projecting from the ends of support shelf (4), on which said screw
(3) may be fixed at the height required from time to time by means of a nut (5) and
lock nut (6).
5) A barycentric support for balancing the motor-rotor unit on airtight combustion chamber
boilers according to the claim (4), characterized in that shelf (4) features a slot
(4a) for regulating the end opposition, of the screw (3) with respect to the shelf
(4).