GB1585721A

GB1585721A - Bearing seat and a method of making the bearing seat

Info

Publication number: GB1585721A
Application number: GB626/78A
Authority: GB
Original assignee: SKF Industrial Trading and Development Co BV
Current assignee: SKF Industrial Trading and Development Co BV
Priority date: 1978-01-09
Filing date: 1978-01-09
Publication date: 1981-03-11

Description

(54) A BEARING SEAT AND A METHOD OF MAKING THE BEARING SEAT (71) We, SKF INDUSTRIAL TRADING AND DEVELOPMENT COMPANY B.V., a Company organised and existing under the laws of the Kingdom of the Netherlands, of P.O.

Box 50, Jutphaas, the Netherlands, 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:- The present invention is an improvement in or modification of the invention of our Application No 18502/75, Serial No 1 502 996 and relates to a bearing seat for a rolling bearing and also to a method of making such a seat.

It is important for rotary machines, such as electric motors, that the rotor is accurately journalled in bearings with respect to the stator and that the bearings and the bearing seats are so constructed that the accuracy thereof does not materially deteriorate during the lifetime of the machine. One condition therefore is that the play between the outer race ring of the bearing and the housing varies only within certain limits, so that the outer race ring can move axially for avoiding unacceptable axial forces, but that the play is so small that creep of the outer race ring in the bearing seat is prevented.

The bearing housing or the bearing shield with the bearing seat is usually manufactured from a metal such as steel, cast iron or aluminium. From a technical and economical point of view it is sometimes advantageous to make the bearing shield from a plastics material. However, the great difference in the linear expansion coefficients of a plastics and steel is a serious drawback. On account of this difference the play between the steel outer race ring and the bearing seat will vary appreciably. At low temperatures there is a risk that the outer race ring will be locked in the housing, which may result in great axial forces on the hearing. At high temperatures the play may be so large that the outer race ring will rotate in the bearing seat, which will then quickly wear.

The invention provides a bearing seat for seating a rolling bearing which seat is made from a moulded material and includes a radially stressed helical member moulded into the material of the seat, the helical member having a different coefficient of linear expansion to that of the moulded material, the seating surface comprising at least in part a layer of moulded material covering the helical member.

The layer may have a thickness in the range of from 0.1 to 0.3 mm.

The helical member may be made from steel and the moulded material may be an epoxy plastics.

The invention also provides a method of making a bearing seat according to any one of the immediately preceding three paragraphs comprising locating a helical member around but radially spaced from, for at least a part of its circumferential extent, a cylindrical mandrel or in, but radially spaced from, for at least a part of its circumferential extent, a cylindrical cavity, moulding the seat from a material having a different coefficient of linear expansion to that of the helical member such that the member is embedded in the said material and the seating surface comprises, at least in part, a layer of the said material covering the member.

The helical member may be sand blasted before it is located around the cylindrical mandrel or in the cylindrical cavity.

An embodiment of the invention will now be described by way of example and with reference to the accompanying drawings of which: Figure 1 is a section on A-A of Figure 2 showing part of a helical member located around a cylindrical mandrel; and Figure 2 is a section on the line B-B of Figure 1.

The drawings show a mandrel 1 having a cylindrical portion around which is located a helical member 2. The mandrel 1 is positioned in a recess of another member 3 to define a mould cavity 4. The mandrel 1 has a number of axially extending pro tuberances 5 running along the cylindrical surface of the mandrel and at a radius R whereas the remainder of the surface is at a radius R2. The helical member 2, in its relaxed state, has a radius less than A1 and possibly less than R2 so that it has to be forced over the mandrel 1. The protuberances 5, radially space the helical member 2 for a part of its circumferential extent a distance x(=R1-R2) from the cylindrical surface of the mandrel 1.

With the helical member 2 in position on the mandrel 1 liquid epoxy plastics is introduced into the cavity 4, at high pressure and at a high speed. By spacing the helical member 2 from the mandrel 1 the introduction of the plastics is made easier. The bearing seat produced is for an outer race ring. A bearing seat for an inner race ring can be produced by providing axially extending protuberances on the inner cylindrical surface of the member 3 and by locating a helical member in the mould cavity having a radius larger than that of the cavity.

The bearing seat produced in this way will have a seating surface comprising at least in part a layer of moulded material covering the helical member and a coefficient of linear expansion which is the same as that of the helical member. The layer will have a thickness in the range of from 0.1 to 0.3 mm. The helical member usually is made from steel as is the race ring of the bearing which will be seated upon the seating surface of the member As the plastics has a greater coefficient of linear expansion than that of steel and the curing of the plastics is carried out at an elevated temperature, the steel helical member will be pre-stressed after the cooling. The bearing seat consisting of the steel helical member and the plastics will then have the same co-efficient of linear expansion as the race ring of the bearing.

Before the helical member is inserted into a mould cavity or mounted on a mandrel, it may be cleaned by sand blasting.

WHAT WE CLAIM IS: 1. A bearing seat for seating a rolling bearing which seat is made from a moulded material and includes a radially stressed helical member moulded into the material of the seat, the helical member having a different coefficient of linear expansion to that of the moulded material, the seating surface comprising at least in part a layer of moulded material covering the helical member.

2. A bearing seat as claimed in claim 1 wherein the layer has a thickness in the range of from 0.1 to 0.3 mm.

3. A bearing seat as claimed in claim 1 or 2 wherein the helical member is made from steel.

4. A bearing seat as claimed in claim 1, 2 or 3 wherein the moulded material is an epoxy plastics.

5. A bearing seat substantially as herein described with reference to the accompanying drawings.

6. A method of making a bearing seat as claimed in any one of claims 1 to 5 comprising locating a helical member around but radially spaced from, for at least a part of its circumferential extent, a cylindrical mandrel or in, but radially spaced from, for at least a part of its circumferential extent, a cylindrical cavity, moulding the seat from a material having a different coefficient of linear expansion to that of the helical member such that the member is embedded in the said material and the seating surface comprises at least in part a layer of the said material covering the member.

7. A method as claimed in claim 6 including sand blasting the helical member before it is loacted around the cylindrical mandrel or in the cylindrical cavity.

8. A method of making a bearing seat substantially as herein described with reference to the accompanying drawings.

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

Claims

**WARNING** start of CLMS field may overlap end of DESC **. tuberances 5 running along the cylindrical surface of the mandrel and at a radius R whereas the remainder of the surface is at a radius R2. The helical member 2, in its relaxed state, has a radius less than A1 and possibly less than R2 so that it has to be forced over the mandrel 1. The protuberances 5, radially space the helical member 2 for a part of its circumferential extent a distance x(=R1-R2) from the cylindrical surface of the mandrel 1. With the helical member 2 in position on the mandrel 1 liquid epoxy plastics is introduced into the cavity 4, at high pressure and at a high speed. By spacing the helical member 2 from the mandrel 1 the introduction of the plastics is made easier. The bearing seat produced is for an outer race ring. A bearing seat for an inner race ring can be produced by providing axially extending protuberances on the inner cylindrical surface of the member 3 and by locating a helical member in the mould cavity having a radius larger than that of the cavity. The bearing seat produced in this way will have a seating surface comprising at least in part a layer of moulded material covering the helical member and a coefficient of linear expansion which is the same as that of the helical member. The layer will have a thickness in the range of from 0.1 to 0.3 mm. The helical member usually is made from steel as is the race ring of the bearing which will be seated upon the seating surface of the member As the plastics has a greater coefficient of linear expansion than that of steel and the curing of the plastics is carried out at an elevated temperature, the steel helical member will be pre-stressed after the cooling. The bearing seat consisting of the steel helical member and the plastics will then have the same co-efficient of linear expansion as the race ring of the bearing. Before the helical member is inserted into a mould cavity or mounted on a mandrel, it may be cleaned by sand blasting. WHAT WE CLAIM IS:

1. A bearing seat for seating a rolling bearing which seat is made from a moulded material and includes a radially stressed helical member moulded into the material of the seat, the helical member having a different coefficient of linear expansion to that of the moulded material, the seating surface comprising at least in part a layer of moulded material covering the helical member.