EP0596837A2

EP0596837A2 - A barycentric support for balancing the motor-rotor unit on airtight combustion chamber boilers

Info

Publication number: EP0596837A2
Application number: EP93830416A
Authority: EP
Inventors: Alberto Bacchiocchi
Original assignee: Fime - Fabbrica Italiana Motori Elettrici - Srl
Current assignee: Fime - Fabbrica Italiana Motori Elettrici - Srl
Priority date: 1992-10-28
Filing date: 1993-10-14
Publication date: 1994-05-11
Also published as: EP0596837A3; ITAN920039A1; ITAN920039A0; IT1265782B1

Abstract

This invention concerns a barycentric support for balancing the motor-rotor unit on airtight combustion chamber boilers employed in heating systems.

The device in question consists of a rubber collar (1) which, thanks to an adjusting screw (3), can be pushed with the force required, either against the bottom wall of the stator unit (11) or against a special bracket (8a), projecting from the front support U-bolt (8) of the motor-rotor unit; the balancing thrust of the collar is applied in a vertical direction which passes through the barycentre of the motor-rotor unit.

Description

This patent application concerns a barycentric support for balancing the motor-rotor unit on airtight combustion chamber boilers employed in heating systems.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.

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).
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.
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.
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.
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.
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.
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.
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.
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.

Claims

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).