GB2343555A

GB2343555A - Mounting fan cowl on an electric motor

Info

Publication number: GB2343555A
Application number: GB9922849A
Authority: GB
Inventors: Walter Ripplinger
Original assignee: Frankl and Kirchner GmbH and Co KG
Current assignee: Frankl and Kirchner GmbH and Co KG
Priority date: 1998-10-07
Filing date: 1999-09-27
Publication date: 2000-05-10
Anticipated expiration: 2019-09-27
Also published as: FR2784519A3; GB2343555B; IT1307360B1; ITTO990858A1; ITTO990858A0; DE29817873U1; FR2784519B3; GB9922849D0

Abstract

In order to prevent distortion when securing the cowl to the motor, end shield (6) is provided with at least one supporting annulus and mounting element 17 formed integrally with the end shield 6, the annulus having a threaded bore 20 for receiving a fastening bolt 21 and having an outwardly directed inner peripheral flange 18 which extends into or just through a U shaped slot 26 in the cowl 10 so that the bolt tightens onto the flange. The cowl 10 has a part annular ridge 31 having a sector angle a greater 180{ spaced from and surrounding the slot in the region receiving the bolt 21 such that the sides of the bolt head 22 engage within the ridge to prevent axial movement of the shroud. The bolt head 22 of the fastening bolt (21) at least partially overlapping the peripheral region in the screw-in direction 30.

Description

2343555 Title: Electric motor This invention relates to electric motors.

With an electric motor, it is known to use bolts to fasten a plastic fan cowl app lied to the end. These bolts are generally screwed radially into an end shield made of metal. The screw-on forces occurring have to be absorbed by the fan cowl, the end face of the bolt head pressing onto the plastics material. Depending on the plastics material selected, deformations of the plastic material occur immediately or 10 subsequently on the fan cowl so it loses its fixing. It is accordingly an aim of the present invention to provide an electric motor with a connection between the fan cowl and the rest of the electric motor which holds the fan cowl securely in its position for a long time. 15 According to the invention, there is provided an electric motor comprising a stator with a central longitudinal axis; a shaft arranged concentrically to the axis in the stator; a fan; at least one end shield which is fastened on the stator and in which the shaft is mounted, at least one supporting web being formed integrally with the 20 end shield with a threaded bore being provided in the supporting web for receiving a fastening bolt; and a fan cowl which externally covers the fan adjacent to the end shield and has at least one recess; wherein the peripheral region of the fan cowl surrounding the recess embraces the supporting web and wherein the bolt head of the fastening bolt at least partially overlaps the peripheral region in the 25 screw-in direction. The crux of the invention is to cause the fastening bolts to strike, with the full screw-on force, not against the fan cowl but against the supporting web connected to the end shield. The forces exerted on the fan cowl by the bolts are therefore 30 markedly reduced. Owing to the resultant more exact fastening of the fan cowl, air gaps which otherwise exist incorrectly between the fan cowl and the rest of the 2 electric motor can be avoided so that the ventilation of the motor by the fan is improved.

Preferably, the or each supporting web has a stop face against which the bolt head is arranged to strike.

The recess is desirably designed as a slot open on one side towards the periphery of the fan cowl.

According to a preferred embodiment of the invention, the bolt head is received in an external indentation of the fan cowl adapted to it so that it is impossible to remove the fan cowl in the direction of the longitudinal axis. The indentation may have a cross section which is substantially circular sector 15 shaped in the screw-in direction with a circular sector angle a greater than 180'. Preferably the diameter of the bolt head is greater than the width of the slot. It is also preferred that the external contour of the supporting web is partially 20 adapted to the internal contour of the slot perpendicularly to the screw-in direction in each case. The thickness of the fan cowl in the region of the indentation is desirably equal to or slightly greater than the height of the supporting web parallel to the screw-in 25 direction in each case.

Desirably, the end should comprise at least one fastening arm which extends substantially radially to the longitudinal axis and on which the supporting web is provided.

The threaded bore preferably extends substantially radially to the longitudinal axis.

3 The invention will now be described in detail, by way of example, with reference to the drawings, in which:

Fig. I is a side elevation of one embodiment of a n electric motor according to the invention, Fig. 2 is a cross-section through the electric motor taken along the section line II H in Fig. 1, in the direction of the arrows; and Fig. 3 is a partial view in the direction of the arrow III in Fig. 2.

The motor I shown in Fig. I comprises a stator 2 and a rotor shaft 4 which is rotatable therein round an axis 3 and is rotatably mounted in end shields 5, 6, namely an output-side end shield 5 and a fan-side end shield 6. The end shields 5, 6 are connected to the stator 2 by tie rod bolts 7. A drive shaft journal 8 formed integrally with the shaft 4 issues from the output-side end shield 5, concentrically to the axis 3.

A fan 9 which can be driven via the shaft 4 is provided adjacent to the fan-side end shield 6. This fan 9 is covered by a fan cowl 10 which comprises ventilating slots I I and is connected to the fan-side end shield 6. For the sake of completeness, it is mentioned that a cable cover 12 is fastened on the fan-side end shield 6 and stator 2 by bolts 13, by means of which an electric supply line 14 and an electric control line 15 for the motor 1 are covered and fixed.

The fastening of the fan cowl 10 on the end shield 6 will be described in more detail hereinafter with reference to Figs. 2 and 3. The end shield 6 comprises a wall 16 which extends concentrically to the axis 3 and to which four fastening arms 17 which project radially outwardly and are arranged at equal angular intervals of 90' are integrally connected. The number of fastening arms 17 can be selected according to the external contour of the fan cowl 10. Radially to the axis 3, each fastening arm 17 comprises a supporting web 18 which projects radially 4 from a supporting face 19 surrounding it. In the supporting web 18 and the fastening arm 17 there is provided a radially extending threaded bore 20 which receives a self-securing fastening bolt 21, in particular a ratchet bolt. The bolt head 22 of the fastening bolt 21 strikes against a stop face 23 of the supporting web 18. All or only a proportion of the fastening arms 17 can be provided with a corresponding threaded bore 20. For the sake of completeness, it is mentioned that a further bore 24which extends parallel to the axis 3 and through which an above mentioned tie rod bolt 7 is guided is provided in the fastening arm 17.

io. The fan cowl 10 has slots 26 which are open on one side toward its edge 25 and of which one is shown in Fig. 3. Each slot 26 is provided in the comer region between two lateral walls 27, 28 of the fan cowl 10 substantially perpendicular to one another. The slot 26 is designed in such a way that the fan cowl 10 can be slipped over the supporting web 18 substantially parallel to the axis 3. A slot is portion 29 located at the internal end of the slot 26 is semicircular in design and embraces the supporting web 18. The diameter D of the bolt head 22 is greater than the width B of the slot 26, so the fan cowl 10 is held in the screw- in direction of the bolt 21 between the supporting face 19 and the bolt head 22. The bolt head 22 is shown in dot-dash lines in Fig. 3.

The bolt head 22 is received in an external indentation 31 of the fan cowl 10 adapted to it so it is impossible to remove the fan cowl 10 along the axis 3. The indentation 31 has a cross-section which is substantially circular sector shaped in the screw-in direction 30, with a circular sector angle (x greater than 180'. The diameter V of the indentation 31 is as great as or slightly, in particular a few tenths of a millimetre, greater than the diameter D of the bolt head 22. An interlocking connection is therefore created between the bolt head 22 and the fan cowl 10 along the axis 3. Therefore, it is impossible to remove the fan cowl 10.

The thickness L of the fan cowl 10 in the region of the indentation 31 parallel to the screw-in direction 30 is as great as or slightly greater than the height H of the supporting web 18 relative to the supporting face 19 parallel to the screw-in direction 30. If L is slightly greater than H, the difference is only a few tenths of a millimetre.

For assembly purposes, the fan cowl is slipped onto the end plate.6 and the fan 9 parallel to the axis 3. The supporting webs 18 slide into the slots 26 until they strike the portion 29 therein. The fastening bolts 21 are then screwed into the corresponding threaded bores 20 from the exterior. The tightening moment of the fastening bolts 21 is absorbed completely by the stop faces 23 so the fastening bolts 21 do not exert a force on the fan cowl 10 in the screw-in direction 30. To allow particularly secure catching of the fan cowl 10, L can be selected slightly greater than H, so a small proportion of the tightening moment of the fastening bolt 21 acts on the fan cowl 10 and restrains it. Deformation and destruction of the fan cowl 10 which generally consists of plastics material are thus avoided. Removal of the fan cowl 10 in the direction of the axis 3 is prevented in that there is an interlocking fit between the inventive bolt head 22 in the indentation 31 and the fan cowl 10.

6

Claims

1. An electric motor comprising a stator with a central longitudinal axis; a shaft arranged concentrically to the axis in the stator; a fan; at least one end shield which is fastened on the stator, and in which the shaft is mounted, at least one supporting web being formed integrally with the end shield with a threaded bore being provided in the supporting web for receiving a fastening bolt; and a fan cowl which externally covers the fan adjacent to the end shield and has at least one recess; wherein the peripheral region of the fan cowl surrounding the recess embraces the supporting web and wherein the bolt head of the fastening bolt at least partially overlaps the peripheral region in the screw-in direction.

2. An electric motor according to claim 1, wherein the or each supporting web has a stop face against which the bolt head is arranged to strike.

3. An electric motor according to claim 1 or claim 2, wherein the recess is designed as a slot open on one side towards the periphery of the fan cowl.

4. An electric motor according to claim 3, wherein the bolt head is received in an extemal indentation of the fan cowl adapted to it so that it is impossible to remove the fan cowl in the direction of the longitudinal axis.

5. An electric motor according to claims 4, wherein the indentation has a cross-section which is substantially circular sector shaped in the screwin direction with a circular sector angle a greater than 180'.

6. An electric motor according to any one of claims 3 to 5, wherein the diameter of the bolt head is greater than the width of the slot.

7 7. An electric motor according to any one of claims 3 to 6, wherein the external contour of the supporting web is partially adapted to the internal contour of the slot perpendicularly to the screw-in direction in each case.

8. An electric motor according to any one of claims 4 to 7 wherein the thickness of the fan cowl in the region of the indentation is equal to or slightly greater than the height of the supporting web parallel to the screw in direction in each case.

9. An electric motor according to any one of the preceding claims, wherein the end shield comprises at least one fastening arm which extends substantially radially to the longitudinal axis and on which the supporting web is provided.

10. An electric motor according to any one of the preceding claims, wherein the threaded bore extends substantially radially relative to the longitudinal axis.

11. An electric motor substantially as described herein with reference to the drawings.