WO1997029855A1

WO1997029855A1 - Air-cooled electric motor installation

Info

Publication number: WO1997029855A1
Application number: PCT/EP1997/000754
Authority: WO
Inventors: Angelo Toschi
Original assignee: Iperfin S.P.A.
Priority date: 1996-02-19
Filing date: 1997-02-18
Publication date: 1997-08-21
Also published as: EP0883448A1; CA2247116A1

Abstract

An air-cooled electric motor installation comprising a least an electric motor (2) connected to a primary user (14), and means (7) for generating a cooling air stream for cooling said motor (2), wherein with said motor (2) is associated a pipe (15) which receives the cooling air leaving the motor (2) and conveys said cooling air to a secondary user (10) in which said cooling air is further exploited. Said secondary user (10) is formed, for example, by a falling path of a conveyor belt or separation screen (14) delivering a crushed rubble mixture stream (13) to be separated in light (11) and heavy (12) components.

Description

"Air-cooled electric motor installation"

BACKGROUND OF THE INVENTION

The present invention relates to an air-cooled electric motor installation according to the preamble of claim 1.

The invention also relates to plants containing said electric motor installation according to the preambles of claim 11 and 12, respectively.

For purposes of this application and the invention disclosed, with the term

"primary users" are intended users provided with an own electric motor and forming with said motor the installations referred to in the present invention.

It is customary to use electric motors for driving, for example, conveying belts, conveyor chains, pumps or other primary users, which are connected to the shaft of the respective motor, for instance, in plants and devices for handling or separating/grading crushed materials in conditioning plants and the like.

It is also known to cool said electric motors by creating an air stream which is directed onto the warm parts of the motor. When passing onto the warm parts of the motor the cooling air, having room temperature, becomes warm and lowers the motor temperature. After having cooled the motor the warm air stream is exhausted and diffused.

For providing and orienting the cooling air stream into a motor to be cooled are already known several solutions as a function of, among others, the motor power. Generally are provided blowers or fan wheels keyed by wedges on the motor shaft at one or both motor sides. Generally the motor frames have air intake apertures or slots for cooling air sucking. All the known installations having a combination of electric motor-primary user have the common feature that the cooling air after having cooled the motor is simply exhausted. Said cooling represents, therefore, an additional cost of the general operating expenses for running said air-cooled electric motors, that is the plant or equipment containing the latter.

The motors of said primary users often have a remarkable power and require, therefore, a large quantity of cooling air.

For instance in the field of rubble crushing the mill motors have a power of about 100 KW and the vibrating screen motors have a power of about 5 - 10

KW.

In said rubble crushing plants is also known a device for separating the light components from the heavy ones of a crushed rubble stream by means of a sucking belt. Said sacking belt is provided with sucking apertures, is placed at a small distance above a screen for the large-size separation and parallel to said separating screen. The motor needed for creating the necessary sucking action has a power of 55 KW. One can easily imagine the operation and purchasing costs of such a separating device or stage.

A pneumatic separation stage of components having different specific gravities by means of an air jet is also per se known. In order to create the necessary air stream is provided the use of a specific motor-fan ventilator group. Beside the above mentioned drawbacks, in said separation stage is further necessary the investment for the specific motor-fan ventilator group.

The provided air stream has a room temperature.

SUMMARY OF THE INVENTION

It is an object of the invention to provide, in an installation ofthe mentioned kind, or in a plant or device containing such an installation, a further utilization of the cooling air in a secondary user by exploiting the kinematic energy and/or the temperature of said exhausted cooling air.

It is another object of the invention to provide a particular utilization of the exhausted cooling air for carrying out a step of a material handling process, for instance an improved pneumatic separation step for separating the light components from the heavy ones of a crushed mixture of building demolition rubble in a treating process for obtaining re-usable aggregate, or for separating other kind of mixtures components having different specific gravities.

These objects are solved by the present invention by an improved installation set forth in claim 1, 11, 12 and 13, respectively.

Further advantageous embodiments of the present invention as well advantageous uses thereof are evident from the dependent claims.

It has been noted that when using very powerful motors there are reductions ofthe rate of flow delivered by the cooling air receiving and conveying pipe. said reductions of the conveyed cooling air mean a detriment of a reliable motor cooling as well as of an efficient utilization of said cooling air in said secondary user, so that the desired results thereof are compromised. These shortcomings can be overcome with the features set forth in claim 2.

Claim 3 suggests a connection union which is easy to manifacture and to secure to said motor housing jacket and said cooling air receiving and conveying pipe.

Claim 4 indicates a reliable means for adjusting the rate of flow to be blown, i. e. delivered, by said cooling air receiving and conveying pipe.

A good separation degree of the light components of a conveyed mixture stream is obtained with an installation and a secondary user as suggested in claim 5. A good separation degree of the light components of a conveyed mixture stream is also obtained with the teaching of claim 6.

An efficient separation degree by using a powerful motor can be achieved with the dimensional features set forth in claim 7.

It has been noted that in case of very light components like rather small pieces of paper, plastics sheet and the like the blowing action of an air blade results in a spin and a stall of said light pieces which have difficulties in reaching a light component receiving area provided downstream a separation area. This phenomenon can be avoided by adopting a nozzle as taught in claim 8.

The better lift feature of a warm air flow can be efficiently kept with the features of claim 9.

By using a diaphragm as set forth in claim 10 it is easily possible to adapt the delivered air jet to the specific requirements ofthe secondary user.

The claims 1 1, 12 and 13 refer to advantageous uses of the invention in specific plants or equipments as well as in a green-house.

A general advantage of the present invention is that it is possible to further exploiting an already existent compressed air source, which is gratuitously available. Due to the fact that in a final separation stage for rubble said rubble mixture is practically free of dust, the use of said exhausted cooling air does not result in any polluting dust formations.

Another advantage is to be seen in the fact that by using a separation by a sucking action with a kind of Venturi tube it is also possible to take up efficiently the light mixture components as well as possibly dust still trapped into the mixture stream. Still another advantage is that the solution according to the invention can be easily integrated in already existent plants or equipments without limiting the operation speed or efficiency thereof. Should the rated cooling air be insufficient for the secondary user requirements, so it is advantageously possible to increase said cooling air flow practical at at all negligible costs.

Other objects, features and advantages ofthe invention will be apparent from the following detailed description taken in connection with the accompanying drawings illustrating several preferred embodiments and in which like reference numerals identify like elements in the figures.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings, the following are shown diagrammatically or in principle:

Fig. 1 shows in principle a known installation of an air-cooled electric motor;

Fig. 2 shows a side elevation view of a combination according to the present invention ofthe installation of Fig. 1 with a secondary user;

Fig. 3 shows a front view on the user of Fig. 2 seen along the sectional plane

III - III of Fig. 2;

Fig. 4 shows a plant view of a second embodiment of the invention applied to a conveyor belt or separating screen illustrated in Fig. 2 and 3;

Fig. 5 shows a fragmentary view of the cooling air receiving and conveying pipe associated with an electric motor;

Fig. 6 shows a plant view on a third embodiment according to the present invention applied to a secondary user as shown in Fig. 2 and 3; and

Fig. 7 shows a cross-sectional view taken along the sectional plane VII -VII of Fig. 6.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

A known installation of the type referred to in the context of the present invention is indicated by 1 in Fig. 1 and it contains an electric motor 2 on whose motor shaft 3 is keyed a driving wheel 4, driving by means of a belt transmission 4', a not shown conveyor belt which conveys a mixture stream to be processed and forms a primary user. The motor frame 5 is provided with known air sucking apertures or slots schematically indicated by 6. A cooling air stream is created by a ventilator fan 7. Said cooling air is drawn from the environment and conveyed through the motor in order to lap the warm parts thereof.

During the contact with the motor warm parts said cooling air warms itself while cooling the motor and then it is exhausted from the motor (arrow F).

The temperature of said warmed cooling air is of course a function of motor and operation parameters as, for instance, the dissipated motor power, the motor speed and construction, the rate of flow of the sucked air, the temperature thereof and so on.

A device or plant comprising the installation 1 is indicated by 8.

The present invention is now depicted with more detail with reference to Fig.

2 and 3, in which as a primary user is provided, for example, a conveyor belt

14 which conveys a mixture of materials with different specific gravities to be separated, for example a mixture 13 of crushed rubble having a granulometry of, for instance, 10 - 35/40 mm, and as a secondary user 10 is provided a separation final stage for separating the light components (small pieces of paper, plastic sheets or films, and so on) from the heavy ones 12 ( cementish materials, tiles, metal or wooden pieces, paving tiles, and so on) of said mixture 13.

It is stressed that said mixture 13, whose components with a larger granulometry have already been previously separated in known and not shown separation stages, is conveyed by said conveyor belt or separating screen 14.

According to the present invention with the motor 2 on its exhaust side is associated a cooling air receiving and conveying pipe 15. At the delivering or blowing end of said pipe is provided, for example, a head 16 whose width is essentially equal to the width of said belt or screen 14 and is tapered towards a blowing nozzle 17. The latter is configured as a box-like blade nozzle 17 whose rectangular blowing aperture has a width which is preferable bigger than the width of said belt or screen 14, whereas the height of said blowing aperture is in the range of, for example, 5 and 15 cm, preferably 10 cm, and more preferably 7 - 8 cm.

Advantageously with said blowing aperture of said blade nozzle 17 may be associated a diaphragm, not shown, operating for instance like a vertical sluice gate, which can be operated manually or with a motor, for example a step motor.

Said diaphragm can be easily realized by a person skilled in the art and permits to adjust the delivered or blown rate of flow according to the features of the mixture to be respectively treated or processed, that is the nature, the granulometry, the specific gravity, and the quantities of the mixture components.

The mixture flow or stream 13 falls from the end 19 of said belt or screen 14 and forms a mixture curtain 20 which falls by gravity along the falling path

21.

The blade-like nozzle 17 faces said mixture curtain 20 and is mounted parallel and transversally with respect to said curtain 20, and at a distance therefrom of, for example, 5 to 15 cm, preferably of 10 cm.

The reference numerals 22 and 23 (Fig. 3) indicate sidewalls defining the width of the falling path 21. A partition wall 25, for instance made of metal sheet, rests on support feet 26 and 27 with which can be associated conveyor belts 26' and 27', respectively, for conveying away the separated light 11 and heavy 12 components according to arrows Fl and F2. With reference to Fig. 5, it is shown that into the pipe 15 is advantageously mounted an adjusting means for adjusting the delivered air flow, for example a throttle valve 29 and/or a gravity hinged cover 30 for exhausting the possibly exceeding air quantity. Said throttle valve 29 can be operated manually or automatically by means of a motor, for instance a step motor, controlled by the control unit or computer ofthe not shown separation plant. In Fig. 5 the cover 30 is illustrated with full line in its closed position and with dashed line in a partially open position during operation. In order to avoid or at least reduce a cooling of the warmed cooling air into the pipe 15, the latter can be coated outside and/or inside with an heat insulating material, for example plastics or rubber, or it consists of said material.

The operation of the combination formed by said installation 1 -secondary user 10 shown in Fig. 2 and 3 is as follow: the cooling air flow exhausted, that is blown, through the blade nozzle 17 crosses through ~ like an air blade according to arrow FL ~ said mixture curtain 20 along the falling path 21 of the latter and trails with it the light components 1 1 while drawing them off from said curtain 20 and blowing them beyond the partition wall 25 into an area downstream where, due to the depletion of the air flow kinematic energy, the light components fall onto said foot 27 or conveyor belt 27'. Said trailing action is facilitated by the warm or tepid temperature of the conveyed cooling air, which latter has so an improved static lift.

In contrast, the heavy components 12 are not essentially affected by the blowing action and may slightly vary their vertical falling trajectory but do not pass the partition wall 25 and fall onto the foot 26 or conveying belt 26', whose driving wheel is indicated by 26". The embodiment shown in Fig. 4 differs from that one shown in Fig. 2 and 3 by the fact that the separation ofthe light components 11 from the heavy ones

12 of the mixture stream 13 takes place by a sucking action. To this purpose the blade nozzle 17 is provided on a sucking leg 15' like a Venturi tube 32 provided at the exhausting end of said cooling air receiving and conveying pipe 15.

The exhausting direction of the cooling air is indicated by arrows f, whereas the direction ofthe sucked air, that is the air trailing the light components 11, is indicated by arrows fl . The sucking nozzle aperture faces the underlying belt or screen 14. In the embodiment of Fig. 4 said leg or nozzle 17 extends parallel and obliquely with respect to said belt or screen 14. Downstream the exhausting end 33 of said pipe 15 is provided a container 34 for collecting the removed light components 11. Also with said container 34 can be associated a not shown discharging belt for the separated light parts 11. The heavy parts or components 12 pass below said sucking nozzle 17 in the direction of arrow F3 and fall along the falling path 21 onto a discharging belt 26' as shown in Fig. 2.

Due to the effective sucking action are achievable good results even with sucking air having room temperature.

By providing the ventilator wheel or wheels 7 at the motor exhausting side as illustrated in Fig. 2 it is possible to obtain an optimum cooling as well as an advantageous pressurization ofthe cooling air inside the pipe 15.

Reference is now made to Fig. 6 and 7 showing an embodiment similar to that illustrated in Fig. 2 and 3, however adapted for the use of a powerful primary user motor 2.

As shown in Fig. 2, also in Fig. 6 the cooling air receiving and conveying pipe is indicated by 15, the exhausting or blowing nozzle by 17, the secondary user, i. e. the separation stage, by 10 and the conveyor belt or separating screen by 14. Said motor 2 drives, as the primary user, for example, said vibrating separating screen 14 or the underlying driving wheel 26" of the conveyor belt 26'. Said latter case has the advantage that the unit motor 2-driving wheel 26" is provided near the secondary user 10, that is said mixture falling path 21 , so that the length of said pipe 15 is rather short and the loss of pressure due to friction in pipe 15 is negligible. In the embodiment of Fig. 6 and 7 the motor 2 is ducted into a jacket 40. Advantageously said jacket 40 has a flat bottom 41 supporting a bracket 42 supporting the motor 2. The jacket 40 is connected to the pipe 15 by means of a correspondent interposed union 44 which engages the adjacent end of said jacket 40 and pipe 15, respectively. The connections can take place by means of a plurality of schematically shown screws 45 or a clip 47 or the like. The union 44 can advantageously be provided with a not shown flange or bracket for securing the unit jacket 40-motor 2 to the plant structure. According to the invention, between the ventilator fan 7 and the adjacent motor end 2' is provided a connecting chamber 48 having an axial length s. Said connecting chamber 48 is, therefore, provided between a cooling air path lapping the motor 2 inside the jacket and an air path downstream said ventilator fan 7. Fig. 6 shows that between the motor outside diameter d and the jacket inside diameter D is formed an air space 49. The cooling air sucked by the ventilator fan 7 flows through the motor and onto the motor frame in the air space 49 as shown by arrow F 4.

Fig. 6 shows further that the diameter of fan 7 is smaller than the inside diameter D of jacket 40. By Dl is indicated the inside diameter of pipe 15. By reducing said pipe diameter Dl increase of course the air speed and pressure in said pipe 15. By considering the above stated parameters a person skilled in the art can easily calculate the rate of flow of the cooling air as well as the ventilator fan and the connecting chamber length s for the specific secondary user.

Considering a secondary user 10 as shown in Fig. 2, a practical example is as follow: d = 23 cm

D = 60 cm s = 10 cm

Dl = 50 cm

Motor power = 7.5 KW

Motor speed = 1 ,450 φm

The ventilator fan 7 has an outside diameter of 50 cm and 7 blades.

In order to better exploiting the large quantity of available cooling air and for obtaining a very efficient taking up or trailing action on the mixture light components, the cooling air exhausting or blowing nozzle is configured as a box-like beam nozzle having a bigger height than the blade nozzle 17 of Fig.

2 and 3, that is a height of between 20 and 60 cm, preferably of 40 cm. With a width ofthe rubble mixture stream of 50 cm (dashed lines, Fig. 6) delivered by a 1.5 m wide conveyor belt and a nozzle width reduced by lateral symmetrical taperings (dashed lines, Fig. 6) to 60 cm it is possible to obtain a nearly total separation degree, i. e. a separation degree of 95 - 98 %, referred to the total light components contained in the rabble mixture 13.

In operation the connecting chamber 48 enables the cooling air flowing through the motor inside and said air space 49 to freely enter the pipe 15 without any formations of bottlenecks or cloggings in the air flowing path, so that the limitations ofthe rate of flow ofthe cooling air and the drawbacks thereof set forth in the introductory part are efficiently avoided. With the teaching of the invention it is easily possible to create an overdimensioned cooling air stream, that is an overdimensioned rate of flow with respect to that which is necessary for the motor cooling. This feature is important in particular when an effective utilization of said cooling air in said secondary user requires a larger rate of flow than that which is needed for the motor cooling.

In operation the beam-like air stream leaving the nozzle 17 will impinge a height of, for example, 40 cm of the mixture falling path 21, so that onto the light components 11 will be exerted a soft taking up or trailing action, thus avoiding a rotational movement on themselves of said light components or spin thereof as well as a stall action of said light components. The single light components are, therefore, pushed by the blowing air in a progressive way in said stream height of 40 cm. This results in a downwardly inclined trajectory of the light components as if the latter would slide on a sloping side of a virtual wedge.

Also said beam-like nozzle 17 can be provided with a control means for adjusting the rate of flow as set forth for the blade-like nozzle 17 of the embodiments shown in Fig.2, 3 and 4.

Separation devices or stages similar to those shown in Fig. 2, 3; 4 and 6, 7 can of course be also used for the separation of mixtures different from rubble and having light components separable by a blowing or sucking action.

From the above structural and functional description it is inferable that with the teachings of the invention it is possible to efficiently solve the above stated objects and achieve the above indicated advantages.

It lies within the scope of the present invention to provide secondary users of different kind. Exemplary, is mentioned the possibility of using the motors, provided in a green-house equipments, for climate conditioning purposes inside said green-house as well as the possibility of conveying cooling air in a cleaning net having blownozzles delivering blow jets for cleaning, for example, workpieces.

Within the scope ofthe invention lie further plants and devices or equipments comprising the improved installation according to the teaching of the present invention.

Claims

14C L A I M S

1. Air-cooled electric motor installation comprising:

- at least an electric motor (2) connected to a primary user (14), and

- means (7) for generating a cooling air stream for cooling said motor (2), characterized in that with said motor (2) is associated a pipe (15) which receives the cooling air leaving the motor (2) and conveys said cooling air to a secondary user (10) in which said cooling air is further exploited.

2. Installation according to claim 1, characterized in that said cooling air receiving pipe (15) is connected to a cooling air guiding jacket (40) housing said electric motor (2) as well as said cooling air generating means (7), and in that said cooling air generating means (7) consists of at least one ventilator fan (7) which is mounted onto the motor shaft (3) at the cooling air downflow side and is spaced from the adjacent motor end (2') by a connecting chamber (48) provided between said motor end (2') and the fan side facing said motor end (2'). (Fig. 6)

3. Installation according to claim 2, characterized in that is provided a tubular pipe union (44) for connecting together said cooling air guiding jacket (40) at one side and said cooling air receiving pipe (15) at the other side of said union (44). (Fig. 6)

4. Installation according to claims 1 and 2, characterized in that said cooling air receiving and conveying pipe (15) is provided with control means (29) for adjusting the rate of flow of said cooling air, and in that said control means (29) are formed by a throttle valve (29) hinged into said pipe (15) and/or by a hinged cover (30) hinged on said pipe and acting as an exhaust valve for exhausting the possibly exceeding air quantity. (Fig. 5)

5. Installation according to claims 1 to 4, wherein the primary user (14) is formed by a fine granulometry or gap-grading separation stage for separating the light components (1 1) from the heavy ones (12) of a crushed mixture (13) of building demolition rubble or the like, comprising a conveyor belt or a separation screen (14) delivering said crushed rubble mixture (13) to be separated, characterized in that:

- said conveyor belt or separation screen (14) has a falling end where the conveyed mixture (13) flow falls by gravity along a falling path (21) in said secondary user (20),

- in that the free end of said cooling air receiving and conveying pipe (15) is shaped as a blade-like nozzle (17) having a box like configuration with a rectangular aperture, wherein the aperture height is between 5 and 15 cm, preferably of 10 cm, and most preferably of 7 - 8 cm,

- in that said blade-like nozzle (17) is essentially horizontally supported facing a frontal side of said falling path (21) of said mixture flow (13), is adjacent to said falling path (21) and has a width which is essentially equal to or slightly bigger than the width of said mixture flow (21), in that the air exhausted by said blade-like nozzle (17) impinges and crosses through said falling mixture curtain (20) while trailing the light components (1 1) into a falling area downstream said mixture flow falling path (21), and

- in that it preferably comprises separated collecting means (22, 23,25) and/or conveyor means (26', 27') for conveying away said separated light (11) and heavy (12) components. (Fig. 2 and 3)

6. Installation according to the preamble of claim 5, characterized in that:

- said conveyor belt or separation screen (14) itself forms said secondary user, - in that from said cooling air receiving and conveying pipe (15) is branched a sucking leg (15') like a Venturi tube (32),

- in that said sucking leg (15') on its side facing said conveyor belt or separating screen (14) is provided with a longitudinal blade-like nozzle (17),

- in that said blade-like nozzle (17) is supported parallel to and transversally with respect to said conveyor belt or separating screen (14), has a length which is essentially equal to or slightly bigger than the width of said conveyor belt or separating screen (14), and is supported at a small distance above said conveyed mixture flow (13) in order to enable a reliable drawing ofthe mixture light components (11) by a sucking action, and

- in that said light components (1 1) drawn through said sucking leg (15') are exhausted through the exhausting end (33) of said cooling air receiving and conveying pipe (15). (Fig. 4)

7. Installation according to claim 2, characterized by the following features:

- the axial width (s) of said connecting chamber (48) is comprised between 2 and 20 cm, preferably between 5 and 15 cm, and most preferably amounts to 10 cm,

- using an electric motor (2) having an external diameter (d) of 23 cm and a power of 7.5 KW, the inside diameter (D) of said motor housing jacket (40) is between 80 and 40 cm, and preferably of 60 cm,

- the ventilator fan diameter is smaller than said inside diameter (D) and is of the magnitude order of the inside diameter (Dl) of said cooling air receiving and conveying pipe (15). (Fig. 6)

8. Installation according to claim 5, 6 and 7, characterized in that said blowing nozzle (17) associated to said cooling air receiving and conveying pipe (15) has a beam-like configuration, wherein the rectangular nozzle aperture has a height between 20 and 60 cm, and preferably of 40 cm, whereas the width is between 30 and 100 cm, and preferably of 60 cm, and wherein the chosen height is lower than said mixture falling path (21 ). (Fig.

6)

9. Installation according to claims 1 and 2, characterized in that said cooling air receiving and conveying pipe (15) and/or said motor housing jacket (40) are coated outside and/or inside with an heat insulating material or consist of said material.

10. Installation according to claims 5 and 8, characterized in that with said blade like or beam like blowing nozzle (17) is associated a diaphragm which is controllable manually or by a control motor and is able to vary the exhausting area of said blowing nozzle (17), that is the thickness of the delivered air blade or beam.

1 1. Plant for separating the light components (1 1) from the heavy ones ( 12) of a crushed rubble mixture (13) of building demolition or similar discard material, characterized in that it comprises at least an installation according to one ore more of claims 1 to 4, 9 and 10 co-operating with a secondary user (10, 14) formed by a separating device or stage according to claims 5 to 8.

12. Plant for treating a mixture (13) of components (1 1, 12) having different specific gravities comprising at least a light component separating stage, characterized in that it comprises at least an installation according to claims 1 to 4, 9 and 10 co-operating with at least a separation stage as secondary user.

13. Green-house for horticulture, characterized in that it comprises an installation according to one or more of claims 1 to 4, 9 and 10, wherein the motor cooling air is utilized for climate conditioning purposes inside said green-house.