GB2167607A

GB2167607A - Ribbed sheet metal case

Info

Publication number: GB2167607A
Application number: GB08429236A
Authority: GB
Inventors: Frantisek Caslava; Jiri Hamrla; Josef Simek; Jan Novotny
Original assignee: VYZK USTAV SILNOPROUDE ELEKT
Current assignee: VYZK USTAV SILNOPROUDE ELEKT
Priority date: 1984-11-20
Filing date: 1984-11-20
Publication date: 1986-05-29
Also published as: GB8429236D0

Abstract

A ribbed sheet metal casing 6, in particular a frame for a rotating electrical machine, has longitudinal discontinuous welds 5 at the points of ribs 2 on the inner surface of the casing 3 6 to maintain the integrity of the ribs. This reduces energy consumption, labour requirement and speeds up manufacture and enables larger lots in series manufacture of such casing compared to prior art techniques. <IMAGE>

Description

SPECIFICATION Ribbed sheet metal case The invention relates to a ribbed metal-sheet case, particularly for a frame of a rotating electrical machine, having cooling ribs on its outer periphery formed by compressed folds in the metal sheet.

The walls of such ribs are usually joined together mechanically or more often by welds, particularly for reasons of mechanical strength, stiffness and heat transfer. Arc welding a continuous weld is relatively high in energy consumption, the energy consumption being equal to or exceeding that necessary for the manufacture of a cast frame. In view of this drawback the manufacture of metal-sheet frames is not a reasonable proposition. Among other drawbacks there are technological difficulties because the metal-sheet welded parts tend to deform, diverting in the form of a V from the weld point. To prevent this, it is necessary to weld the frame, which has a very intricate configuration. Therefore it is necessary to chuck it by means of a complicated fixture. This in itself makes the manufacture dearer and extends the time of manufacture.Nevertheless, a relatively high stress results in the welded frame. To reduce this stress, the welding is sometimes carried out in both directions. In this way the arising stresses are mutually released, but the energy consumption again rises. It is very difficult to execute spot or projection welding of the rib walls because of the small space between the ribs and the necessity of frequent replacement of the quickly wearing electrodes and the rib walls can be joined together in this way only above their footings.

Mechanical interconnection of the rib walls to remove the difficulties of electrical welding is relatively laborious and requires adaption of the rib walls owing to the necessity of stamping projections and holes for the projections. This results in elasticity in the whole frame and insufficient stiffness. This leads to an increase in vibration and noise and to the deterioration of heat transfer from the yoke of the stator laminated core into the curved part of the frame, in an electrical machine.

It is, therefore, an object of the present invention to overcome partially or wholly such drawbacks.

According to the invention the bends of the folds are joined together by a longitudinal discontinuous weld at the points of ribs on the inner surface of the case.

In comparison with cases provided with longitu dinal, uninterrupted welds and cast cases, a substantial reduction of power requirement in the manufacture of the cases of the present invention is achieved.

So by the present invention the manufacture of metal-sheet cases finds its raison d'etre. Also mechanical strength and stiffness are increased by performing the welds on the inner surface of the case, the individual weld sections being preferably arranged in planes perpendicular to the longitudinal axes of the ribs. Further a reduction in the labour needed is achieved, production is speeded up, it is possible to weld parallelly on both sides of the case.

Lots in series manufacture can be larger. The stress in the case is reduced and therefore it is not necessary to use complicated clamping fixtures. A good conducting contact between the frame and the stator laminated core is achieved.

The invention will be further described by way of example with reference to the accompanying drawings, in which: Figure 1 illustrates a rib of a frame of a rotating electrical machine in a radial, sectional view; and Figure 2 illustrates a portion of a ribbed frame of a rotating electrical machine in a developed state.

A rib 2 of a frame 6, seen in Figure 1 in a radial sectional view, is formed by compressed folds in a metal sheet 1, so that the inner surfaces 3 of the rib walls are in contact. The bends at the point of ribs 2 are joined together by a longitudinal discontinuous weld 5 which does not protrude in radial direction, beyond the level of the internal surface of the frame 6.

A portion of the developed metal-sheet frame 6 is illustrated in Figure 2 as seen from the interior of the frame 6. The folds of the metal sheet 1 are joined together by four separate longitudinal sections of a longitudinally discontinuous weld 5 on the inner surface 3 of the frame 6 below each rib 2, the individual sections of the longitudinal discontinuous weld 5 registering in the tangential direction.

The length and the number of individual sections of the longitudinal discontinuous weld 5 on the inner surface of the frame 6 below the rib 2 can differ from those shown in Figure 2. They are dependent, above all, on the size of the frame 6, its design and the required stiffness. The length of individual sections of the longitudinal discontinuous weld 5 preferably lies in the range from 1 mm to 50 mm, preferably from 5 mm to 10 mm. The distance of the edges of adjacent sections of one weld 5 preferably liesin the range from 1 mm to 200 mm, preferably from 50 mm to 70 mm.

The ribbed metal-sheet case according to the present invention can also be used other than in rotating electrical machines. It can be used there where a rigid stiffened part is necessary which has its surface enlarged by means of cooling ribs for the removal of heatflowfrom its surface. The inner surface of the ribbed case can be even or deformed, or curved into a cylindrical form respectively, for example for being pressed on a stator laminated core of a rotating electrical machine. The individual sections of the longitudinal discontinuous welds 5 registering in the tangential direction or in one or more planes arranged perpendicularly to the longitudinal axes of the ribs contributes to the stiffness of the ribbed metal-sheet case.

Required stiffness of the edge portions of the frame 6 can be attained by placing longitudinal sections of the discontinuous weld 5 in radial planes at the edges of the frame 6.

1. A ribbed sheet metal case, particularly a frame of a rotating electrical machine, having cooling ribs on its outer periphery formed by compressed folds in the metal sheet, wherein the bends of the folds are joined together by a longitudinal discontinuous weld

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Ribbed sheet metal case The invention relates to a ribbed metal-sheet case, particularly for a frame of a rotating electrical machine, having cooling ribs on its outer periphery formed by compressed folds in the metal sheet. The walls of such ribs are usually joined together mechanically or more often by welds, particularly for reasons of mechanical strength, stiffness and heat transfer. Arc welding a continuous weld is relatively high in energy consumption, the energy consumption being equal to or exceeding that necessary for the manufacture of a cast frame. In view of this drawback the manufacture of metal-sheet frames is not a reasonable proposition. Among other drawbacks there are technological difficulties because the metal-sheet welded parts tend to deform, diverting in the form of a V from the weld point. To prevent this, it is necessary to weld the frame, which has a very intricate configuration. Therefore it is necessary to chuck it by means of a complicated fixture. This in itself makes the manufacture dearer and extends the time of manufacture.Nevertheless, a relatively high stress results in the welded frame. To reduce this stress, the welding is sometimes carried out in both directions. In this way the arising stresses are mutually released, but the energy consumption again rises. It is very difficult to execute spot or projection welding of the rib walls because of the small space between the ribs and the necessity of frequent replacement of the quickly wearing electrodes and the rib walls can be joined together in this way only above their footings. Mechanical interconnection of the rib walls to remove the difficulties of electrical welding is relatively laborious and requires adaption of the rib walls owing to the necessity of stamping projections and holes for the projections. This results in elasticity in the whole frame and insufficient stiffness. This leads to an increase in vibration and noise and to the deterioration of heat transfer from the yoke of the stator laminated core into the curved part of the frame, in an electrical machine. It is, therefore, an object of the present invention to overcome partially or wholly such drawbacks. According to the invention the bends of the folds are joined together by a longitudinal discontinuous weld at the points of ribs on the inner surface of the case. In comparison with cases provided with longitu dinal, uninterrupted welds and cast cases, a substantial reduction of power requirement in the manufacture of the cases of the present invention is achieved. So by the present invention the manufacture of metal-sheet cases finds its raison d'etre. Also mechanical strength and stiffness are increased by performing the welds on the inner surface of the case, the individual weld sections being preferably arranged in planes perpendicular to the longitudinal axes of the ribs. Further a reduction in the labour needed is achieved, production is speeded up, it is possible to weld parallelly on both sides of the case. Lots in series manufacture can be larger. The stress in the case is reduced and therefore it is not necessary to use complicated clamping fixtures. A good conducting contact between the frame and the stator laminated core is achieved. The invention will be further described by way of example with reference to the accompanying drawings, in which: Figure 1 illustrates a rib of a frame of a rotating electrical machine in a radial, sectional view; and Figure 2 illustrates a portion of a ribbed frame of a rotating electrical machine in a developed state. A rib 2 of a frame 6, seen in Figure 1 in a radial sectional view, is formed by compressed folds in a metal sheet 1, so that the inner surfaces 3 of the rib walls are in contact. The bends at the point of ribs 2 are joined together by a longitudinal discontinuous weld 5 which does not protrude in radial direction, beyond the level of the internal surface of the frame 6. A portion of the developed metal-sheet frame 6 is illustrated in Figure 2 as seen from the interior of the frame 6. The folds of the metal sheet 1 are joined together by four separate longitudinal sections of a longitudinally discontinuous weld 5 on the inner surface 3 of the frame 6 below each rib 2, the individual sections of the longitudinal discontinuous weld 5 registering in the tangential direction. The length and the number of individual sections of the longitudinal discontinuous weld 5 on the inner surface of the frame 6 below the rib 2 can differ from those shown in Figure 2. They are dependent, above all, on the size of the frame 6, its design and the required stiffness. The length of individual sections of the longitudinal discontinuous weld 5 preferably lies in the range from 1 mm to 50 mm, preferably from 5 mm to 10 mm. The distance of the edges of adjacent sections of one weld 5 preferably liesin the range from 1 mm to 200 mm, preferably from 50 mm to 70 mm. The ribbed metal-sheet case according to the present invention can also be used other than in rotating electrical machines. It can be used there where a rigid stiffened part is necessary which has its surface enlarged by means of cooling ribs for the removal of heatflowfrom its surface. The inner surface of the ribbed case can be even or deformed, or curved into a cylindrical form respectively, for example for being pressed on a stator laminated core of a rotating electrical machine. The individual sections of the longitudinal discontinuous welds 5 registering in the tangential direction or in one or more planes arranged perpendicularly to the longitudinal axes of the ribs contributes to the stiffness of the ribbed metal-sheet case. Required stiffness of the edge portions of the frame 6 can be attained by placing longitudinal sections of the discontinuous weld 5 in radial planes at the edges of the frame 6. CLAIMS

1. A ribbed sheet metal case, particularly a frame of a rotating electrical machine, having cooling ribs on its outer periphery formed by compressed folds in the metal sheet, wherein the bends of the folds are joined together by a longitudinal discontinuous weld at the points of the ribs on the inner surface of the case.

2. A case according to claim 1, wherein the length of the individual weld sections lies in the range from 1 mm to 50 mm, preferably from 5 mm to 10 mm, and the distance of the ends of adjacent weld sections lies in the range from 1 mm to 200 mm, preferably from 50 mm to 70 mm.

3. A case according to claim 1 or 2, wherein the individual weld sections are arranged in planes perpendicular to the longitudinal direction of the ribs.

4. A case substantially as herein described with reference to the accompanying drawings.