GB1561098A - Method of connecting members together in a rotary electrical machine - Google Patents

Description

(54) METHOD OF CONNECTING MEMBERS TOGETHER IN A ROTARY ELECTRICAL MACHINE (71) We, ASEA AKTIEBOLAG, a Swedish Company of Vasteris, Sweden, do hereby declare the invention, for which we pray that a Patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following Statement: This invention relates to a method of connecting together a laminated member and a further member in a rotating electric machine. The invention has particular utility in fastening a laminated pole of a rotary electrical machine to a stator ring which is furnished with at least one axially directed slot arranged to receive an end portion of said pole. The method of the invention utilises a connecting device which is located in a slot formed between the members to be connected together, the wall of said of said slot being formed partly by each of said members.

It is known to attach a laminated pole to a laminated stator ring by forming the pole laminations and the stator laminations with semi-circular recesses in such a way that two substantially circular holes are formed at each pole attachment. The pole is retained in the stator ring by pressing a round bar into each of the holes, for example, as shown in U.S.

Patent 3,809,938. Normally, however, such a bar only makes contact with a few protruding edges of the laminations, which then become so heavily loaded that permanent deformations occur after some time in operation and give rise to play in the connection between the pole and the stator ring. Even at the stage of manufacturing it is difficult to avoid such play, unless the bar is specifically selected by trial and experiment in each case.

According to the invention there is provided a method of connecting together a laminated member and a further member in a rotating electrical machine which method comprises locating a connecting device in a slot formed between the members, said slot wall being formed partly by each of said members, wherein the connecting device is an elongate expansible device comprising a pressure tube of plastically deformable metal surrounding a filling body which, at both ends, is attached in a pressure-tight manner to the expansible tube around its circumference, there being a channel formed in said filling body providing communication between the internal surface of the expansible tube and a filling tube into which a hardenable pressurised liquid medium can be injected; and wherein after its insertion in the slot, said pressure tube is expanded into closer conformity with the slot walls by injecting said liquid medium into said filling tube at a pressure of at least 50 bar thereby to increase the pressure tube volume mainly by means of plastic deformation of the pressure tube material. Elastic deformation perferably constitutes at the most 20 per cent of the total deformation.

The invention will now be described, by way of example, with reference to the accompanying schematic drawings, in which Figures 1 and 2 are sectional views of two different expansible bars which can be used in a method according to the invention, taken along the line I-I of Figure 3 and the line II-II of Figure 4, respectively, Figure 3 is a sectional view taken along the line III-III of Figure 1, Figure 4 is a sectional view taken along the line IV-IV of Figure 2, Figure 5 is a sectional perpendicular to a machine shaft showing a stator pole fastened to a stator ring according to the invention, Figure 6 is a detail of Figure 5 in partial section along VI-VI of Figure 5, only part of the machine length being included. Also Figure 1 shows a section along VI-VI, but at a stage before complete fastening has taken place, Figure 7 is a radial section of a pole fastened according to invention while using a non-magnetic additional element.

In Figure 1, the numeral 1 designates a soft-annealed cylindrical tube of steel in which there is enclosed a filling body in the form of a steel cylinder 2 having a small radial clearance with respect to the inner surface of the tube 1. The narrow annular gap between the parts 1 and 2 is sealed by means of annular argon welding seams 3 and 4. A filling tube 5 is inserted through a hole 7 which is bored into one end of the cylinder 2 and attached to the latter by means of silver solder 6. The silver solder 6 covers the welding seam 4 and provided additional safety against leakage due to microcracks in said seam. The welding seam 3 may also be covered by silver solder in some cases soldering only may suffice. From the hole 7 there extends a channel 8 leading to the inner cylindrical surface of tube 1.

When expansion of the expandible bar shown in Figure 1, is to be achieved for example to conform the outer surface of the tube 1 to the shape of an irregular hole in a member 9, liquid, curable plastics material is pumped in through the filling tube 5 under high pressure, for example with the help of the equipment described in U.K. Patent Specification No.

1,454,120. The pressure should be at least 50 bar, preferably higher than 200 bar, and under certain circumstances it may be necessary to use a pressure of up to 5000 bar. When the desired expansion has been attained, the pressure is maintained until the plastics material in the filling tube cures.

The internal diameter of the tube 1 is designated d, and the external diameter of the cylinder 2 is designated df. If, instead of using the cylinder 2, the ends of the tube 1 had been sealed by means of end plates welded thereto, the force acting in the longitudinal direction of the tube 1 at the pressure p would have been pud,2. By employing the cylinder 2, as shown in Figure 1, the axial force on the expandible bar usually becomes less than 10% of the above-mentioned force, namely p .-(dr2 - df2) and this force is for the main part taken up by the cylinder 2.

As an example there can be mentioned a case in which the tube 1 has a length of 450 mm and where dr is 8.8 mm and df is 8.6 mm. Expressed in percentage of the above hypothetical force, the axial force, K,, in a bar according to the invention will then be as follows:

The embodiment of the invention shown in Figures 2 and 4 differs from that described above mainly by the fact that the filling body 11 is welded together from two parts and has an elongate central cavity 12, which at its upper end is hydraulically connected to the filling tube 5 and to a number of distribution channels 13 which form a hydraulic connection between the central cavity 12 and the inner surface of the expansion tube 1. When pumping in the viscous curable plastics material, the amount of air initially contained in the tube 5 will be collected and compressed in the cavity 12, a plug of liquid plastic being formed between the contained gas and the distribution channels 13. When the pressure becomes so high that the wall portions located at the distribution channels 13 are pressed radially outwardly at the channel openings, only plastic flows out through these openings and provides a plastic deformation of the tube 1. The space that is formed, after completed expansion, between the expandible tube 1 and the filling body 11 consequently contains no air inclusions but only homogeneous plastic.

The method according to the invention is particularly advantageous when the intention is to achieve an evenly distributed transmission of force between two very uneven surfaces which are facing each other. Figure 5 shows an example of such a use of an expandible bar according to the method of the invention for attaching a laminated pole 9 to a laminated stator ring 10. The pole laminations and the stator laminations are formed with semi-circular recesses 14' and 14" in such a way that two substantially circular holes 14 are formed at each pole attachment. The pole is retained in the stator ring by arranging an expansible tube in each of the holes 14. Normally, however, such a tube only makes contact with a few protruding edges of the laminations, which then become so heavily loaded that permanent deformations occur after some time in operation and give rise to play in the connection between pole and stator ring. Even at the stage of manufacture it is difficult to avoid such play, unless than tube diameter is specifically chosen to suit each case. An expanding device for this purpose is designated 15 in Figure 5. In Figure 6 a connection carried out by means of an expansible device is shown in greater detail, in axial section. The pumped-in, polymerisable plastics material, for example epoxy resin, is designated 16.

During the pumping in of the plastics material the space surrounded by the expansible tube 1 undergoes an increase in volume, of which at least 80% takes places due to plastic deformation of the expansible tube (i.e. elastic deformation constitutes at most 20% of the total deformation).

When using an expansible pressure tube according to the invention for retaining a laminated commutating pole 17 in a slot 23 of a stator ring 18, as shown in Figure 7, the tube 1 and the filling body 2 are made of steel in the usual manner. In order to avoid magnetic iron connection between the pole 17 and the stator ring 18, the expansible pressure tube is contacted by jaws 19 which are made of non-magnetic material. These jaws and a couple of non-magnetic rods 20 are arranged in auxiliary slots 19' formed in the walls of the slot 23.

WHAT WE CLAIM IS: 1. A method of connecting together a laminated member and a further member in a rotating electrical machine which method comprises locating a connecting device in a slot formed between the members, said slot wall being formed partly by each of said members, wherein the connecting device is an elongate expansible device comprising a pressure tube of plastically deformable method surrounding a filling body which, at both ends, is attached in a pressure-tight manner to the expansible tube around its circumference, there being a channel formed in said filling body providing communication between the internal surface of the expansible tube and a filling tube into which a hardenable pressurised liquid medium can be injected; and wherein after its insertion in the slot, said pressure tube is expanded into closer conformity with the slot walls by injecting said liquid medium into said filling tube at a pressure of at least 50 bar thereby to increase the pressure tube volume mainly by means of plastic deformation of the pressure tube material.

2. A method as claimed in claim 1, in which the liquid medium is injected at a pressure in the range 200-5000 bar.

3. A method as claimed in claim 1 or claim 2, in which the members are a laminated pole and a stator ring.

4. A method as claimed in any preceding claim, in which part of one of the members forming the slot wall is made of a non-magnetic material.

5. A method as claimed in any preceding claim, in which elastic deformation constitutes at the most 20 per cent of the total deformation.

6. A method as claimed in any preceding claim, in which said filling body has a longitudinal, central cavity into which said channel opens, said cavity commnicating with said filling tube.

7. A method as claimed in any preceding claim, in which said filing tube is connected to one end of said expansible pressure tube.

8. A method of connecting together two members in a rotating electrical machine substantially as herein described with reference to, and as illustrated in Figures 1-and 3, Figures 2 and 4 or Figures 5, 6 and 7 of the accompanying drawings.

9. A rotating electrical machine having members connected together by the method claimed in any preceding claim.

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

Claims (9)

**WARNING** start of CLMS field may overlap end of DESC **. During the pumping in of the plastics material the space surrounded by the expansible tube 1 undergoes an increase in volume, of which at least 80% takes places due to plastic deformation of the expansible tube (i.e. elastic deformation constitutes at most 20% of the total deformation). When using an expansible pressure tube according to the invention for retaining a laminated commutating pole 17 in a slot 23 of a stator ring 18, as shown in Figure 7, the tube 1 and the filling body 2 are made of steel in the usual manner. In order to avoid magnetic iron connection between the pole 17 and the stator ring 18, the expansible pressure tube is contacted by jaws 19 which are made of non-magnetic material. These jaws and a couple of non-magnetic rods 20 are arranged in auxiliary slots 19' formed in the walls of the slot 23. WHAT WE CLAIM IS:

1. A method of connecting together a laminated member and a further member in a rotating electrical machine which method comprises locating a connecting device in a slot formed between the members, said slot wall being formed partly by each of said members, wherein the connecting device is an elongate expansible device comprising a pressure tube of plastically deformable method surrounding a filling body which, at both ends, is attached in a pressure-tight manner to the expansible tube around its circumference, there being a channel formed in said filling body providing communication between the internal surface of the expansible tube and a filling tube into which a hardenable pressurised liquid medium can be injected; and wherein after its insertion in the slot, said pressure tube is expanded into closer conformity with the slot walls by injecting said liquid medium into said filling tube at a pressure of at least 50 bar thereby to increase the pressure tube volume mainly by means of plastic deformation of the pressure tube material.

2. A method as claimed in claim 1, in which the liquid medium is injected at a pressure in the range 200-5000 bar.

3. A method as claimed in claim 1 or claim 2, in which the members are a laminated pole and a stator ring.

4. A method as claimed in any preceding claim, in which part of one of the members forming the slot wall is made of a non-magnetic material.

5. A method as claimed in any preceding claim, in which elastic deformation constitutes at the most 20 per cent of the total deformation.

6. A method as claimed in any preceding claim, in which said filling body has a longitudinal, central cavity into which said channel opens, said cavity commnicating with said filling tube.

7. A method as claimed in any preceding claim, in which said filing tube is connected to one end of said expansible pressure tube.

8. A method of connecting together two members in a rotating electrical machine substantially as herein described with reference to, and as illustrated in Figures 1-and 3, Figures 2 and 4 or Figures 5, 6 and 7 of the accompanying drawings.

9. A rotating electrical machine having members connected together by the method claimed in any preceding claim.