WO2012056481A1

WO2012056481A1 - Roll-forming process and system, in particular for producing a high-precision housing for high- performance electric motors, and housing produced through such process

Info

Publication number: WO2012056481A1
Application number: PCT/IT2010/000436
Authority: WO
Inventors: Alberto 1/1)Dal Poz
Original assignee: Individual
Current assignee: Individual
Priority date: 2010-10-28
Filing date: 2010-10-28
Publication date: 2012-05-03
Anticipated expiration: 2013-04-28

Abstract

A roll-forming process is described, in particular for producing metal housings (1) for electric motors, comprising the steps of stamping a metal band to obtain at least one metal strip (2) to be worked and rolling such metal strip (2), such step of rolling comprising the steps of mechanically bending such metal strip (2) to make a cylindrical housing (1) and hydraulically calibrating such housing (1) around a cylindrical punch (3).

Description

ROLL-FORMING PROCESS AND SYSTEM, IN PARTICULAR FOR PRODUCING A HIGH-PRECISION HOUSING FOR HIGH- PERFORMANCE ELECTRIC MOTORS, AND HOUSING PRODUCED THROUGH SUCH PROCESS

The present invention refers to a roll-forming process and system, in particular for producing metal housings for electric motors, and to a housing produced through such process and system.

Processes and systems aimed to produce housings are known in the art.

In general, these processes sometimes are not satisfactory and have the following problems:

^■ The circularity of manufactured products in sections along its axis of symmetry is not satisfactory, namely it has high tolerances.

■ This sometimes creates operating noise problems in the electric motors that use such housings ("sirening" effect) and deterioration problems of some internal components of the housings.

^■ Too high tolerances in the housing circularity affect the rotation dynamics of the rotor of the electric motor, generating a potential reduction of its reliability.

■ The thermal welding processes used in many cases to put together and fasten the edges of the rolled sheet induce local distortions that increase roundness tolerances in some areas.

^■ The contact area of the sheet edges that have been put together and mutually fastened is often not well "clenched".

Examples of processes according to the prior art are disclosed in US-A-3131 62 , WO-A-20061920, US-A-4784312.

In particular, the disclosed processes use progressive and not rolling dies, with double sheet and double thickness (like in US-A-3131462) , housing with double thickness, outline shearing, coining to lower the outline, coining plus shearing and rolling (like in WO-A-20061920), motors for actuating numerically controlled machines, that require cooling devices, and that are focused on the application of cooling wings (like in US-A- 3131462), internal oval punch and non-uniform forces exerted by external punches (also disclosed in US-A-4784312), rolling with the application of particular hydraulic and mechanical forces. Object of the present invention is solving the above prior art problems, by providing a process that is able to produce a housing having much striate tolerances in the housing circularity.

Another object of the present invention is providing a process that produces a product with high "clench" in the contact area of the sheet edges that are put together and fastened.

A further object of the present invention is providing a process for producing housings with great thickness, aimed to manufacture big-sized and high-reliability electric motors.

Another object of the present invention is providing a process for producing products similar to housings for electric motors, but using aluminium as material. The use of such material, coupled with suitable shearing on the sheet development, allows obtaining very lightweight objects, always characterized by:

■ very strict tolerances in object circularity.

^■ high sealing ("clench") quality in the contact area of sheet edges that are put together and fastened.

^■ where required, lower magnetic permeability than the steel ones. A further object of the present invention is providing products similar to housings for electric motors made through the process according to the present invention.

A further object of the present invention is providing a system for producing objects similar to housings for electric motors, to make a process and products as mentioned above.

The above and other objects and advantages of the invention, as will appear from the following description, are obtained with a process, a product similar to a housing or other, and a system as claimed in the respective independent claims.

Preferred embodiments and non-trivial variations of the present invention are the subject matter of the dependent claims.

It will be immediately obvious that numerous variations and modifications (for example related to shape, sizes, arrangements and parts with equivalent functionality) could be made to what is described without departing from the scope of the invention as appears from the enclosed claims.

The present invention will be better described by some preferred embodiments thereof, provided as a non-limiting example, with reference to the enclosed drawings, in which:

Figure 1 shows a perspective view of a preferred embodiment of a housing with great thickness for electric motors, produced by the process according to the present invention;

Figure 2 shows a perspective view of a preferred embodiment of an aluminium housing, produced by the process according to the present invention;

- Figures 3a, 3b, 3c and 3d show some plan views of some types of closure used in the process according to the present invention;

Figure 4 shows a step of shearing in the process according to the present invention;

- Figure 5 shows a step of bending of the process according to the present invention; and

Figure 6 shows a step of calibrating of the inventive process.

In general, the process according to the present invention allows obtaining the product finished through rolling, performed and checked in a novel way, of a piece of plane steel sheet, suitably pre-sheared through a suitable stamping step, followed by a mechanical working step, adapted to bind and seal the sheet edges, that have been previously approached and put together with the rolling operation.

With reference to the Figures, the process according to the present invention for producing housings comprises the steps of:

stamping (FIG. 4), for example through shearing, from a metal band at least one metal strip 2 having the development of the housing 1; - rolling the metal strip 2 with a following step of putting together the edges of the metal strip 2, and following pressing and joining steps for the edges to obtain the sealing of the closure of such edges.

In particular, the step of rolling of the process according to the present invention comprises the steps of:

mechanically bending (Figure 5) the metal strip 2 to.make a cylindrical housing 1; and

- hydraulically calibrating (Figure 6) the housing 1 around at least one cylindrical punch 3.

The step of stamping can comprise the step of shearing a shaped outline form 4 on two opposite edges of the metal strip 2. In particular, such outline can be shaped as teeth 4. Alternatively, the step of stamping can comprise the step of shearing a double shaped outline form 5, 6 (Figures 3b and 3c) on two opposite edges of the metal strip 2 and the step of additionally coining for the closure.

In this case, the double shaped outline 5, 6 comprises a first outline 5 shaped as a parallelepiped recess with slanted sides, and a second outline 6 equipped with at least two protuberances 7, 8 adapted to be inserted into the recess 5 and to engage it when closing the metal strip 2 (Figure 3d) .

Finally, the inventive process also comprises the steps of :

- docking the rolled and calibrated strip 2 in order to approach and put together its edges; and jointing in the closure area of the metal strip 2.

The invention further deals with a system to perform the above-described process.

Such roll-forming system is used in particular to produce metal housings 1 for electric motors, and substantially comprises:

means for stamping a metal band to obtain the metal strip 2 to be worked; and means for rolling the metal strip 2, wherein the means for rolling comprise:

means for mechanically bending the metal strip 2 to make a cylindrical housing 1; and

- means for hydraulically calibrating the housing 1 around ad at least one cylindrical punch 3.

Moreover, the inventive roll-forming system comprises :

- means for docking the rolled and calibrated strip 2 in order to approach and put together its edges; and

means for jointing the closure area of the metal strip 2.

In particular, as input to the working line, the roll of metallic band 2 is placed on a winding coil, whose thickness and whose length depend on the sizes of the housing 1 that has to be produced.

In particular, the width of the metal strip must correspond to the desired height of the housing 1.

In the first working step, the metal strip 2 is sheared with one or more press strikes, in order to obtain the development of the housing 1. The length of the metal strip segment 2 depends on the diameter of the housing 1 that has to be obtained.

In the second working step, the piece rolling, the mechanical bending is performed on a cylindrical roll (not shown) , while the hydraulic calibration of the rolled piece is performed through suitable hydraulic rollers 11 around the cylindrical punch 3.

The hydraulic calibration is performed in particular through the action of a pair of hydraulic actuators that operate at an adequate pressure on the external surface of the housing and allows, due to an adequately distributed pressure preferably included between 15 and 30 tons, to keep the shape of the housing itself.

The present invention further refers to a housing 1, produced through the process according to the present invention. In particular, the housing 1 according to the present invention is composed of:

a cylindrical body 13 made through bending of the pre-sheared metal strip 2;

a buttoning line 15, suitable to join the longitudinal edges of such cylindrical body 13.

Advantageously, the body 13 of the housing 1 is made of aluminium.

Claims

RIVENDICAZIONI

1. Roll-forming process, in particular for producing metal housings (1) for electric motors, comprising the steps of:

- stamping a metal band to obtain at least one metal strip (2) to be worked; and

rolling said metal strip (2), characterised in that said step of rolling comprises the steps of: mechanically bending said metal strip (2) to make said cylindrical housing (1); and

hydraulically calibrating said housing (1) around at least one cylindrical punch (3) .

2. Process according to claim 1, characterised in that said step of stamping comprises the step of shearing a shaped outline form (4) on two opposite edges of said metal strip (2) .

3. Process according to claim 2, characterised in that said outline is shaped as teeth (4) .

4. Process according to claim 1, characterised in that said step of stamping comprises the step of shearing a double shaped outline form (5, 6) on two opposite edges of said metal strip (2) and the step of additionally coining for the closure.

5. Process according to claim 4, characterised in that said double shaped outline comprises a first outline (5) shaped as a parallelepiped recess with slanted sides, and a second outline (6) equipped with at least two protuberances (7, 8) suitable to be inserted into said recess (5) and to engage it when closing said metal strip (2) .

6. Process according to any one of the previous claims, characterised in that it further comprises the steps of:

locking the rolled and calibrated strip (2) in order to approach and put together its edges; and jointing the closure area of the metal strip

(2) .

7. Roll-forming system, in particular for producing metal housings (1) for electric motors, comprising:

means for stamping a metal band to obtain a metal strip (2) to be worked; and

means for rolling said metal strip (2), characterised in that said means for rolling comprise:

means for mechanically bending said metal strip (2) to make a cylindrical housing (1); and means for hydraulically calibrating said housing (1) around a cylindrical punch (3) .

8. Roll-forming system according to claim 7, characterised in that it further comprises:

means for docking the rolled and calibrated strip (2) in order to approach and put together its edges; and

means for jointing the closure area of the metal strip (2) .

9. Roll-forming system according to claim 7, characterised in that said means for mechanically bending are at least one cylindrical roll (10) .

10. Roll-forming system according to claim 7, characterised in that said means for hydraulically calibrating the rolled piece are hydraulic rolls (11) around the cylindrical punch (3) .

11. Housing (1) produced through the process according to any one of claims 1 to 6 using the system according to any one of claims 7 to 10.

12. Housing (1) according to claim 11, composed of:

- a cylindrical body (13) made by bending the pre-sheared metal strip (2) ;

a buttoning line (15) , adapted to join the longitudinal edges of said cylindrical body (13) .

13. Housing (1) according to claim 11, characterised in that said cylindrical body (13) is made of aluminium.