GB1593478A

GB1593478A - Electromagnetic drum brake

Info

Publication number: GB1593478A
Application number: GB2393178A
Authority: GB
Original assignee: HEEMOF BV
Current assignee: HEEMOF BV
Priority date: 1977-07-14
Filing date: 1978-05-30
Publication date: 1981-07-15
Also published as: NL163605B; DE2825026C2; DE2825026A1; NL7707880A; NL163605C

Description

(54) ELECTROMAGNETIC DRUM BRAKE (71) We, HEEMAF B.V. of no. 5, Bornv estraat, Hengelo, The Netherlands, a private limited liability company organized under the Laws of 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 par ticularly described in and by the following statement: An electromagnetic drum brake, the drum of which accommodates an annular, ferromagnetic magnet body ararnged concentrically with the axis of the drum and having an energizing winding concentric with said axis, brake linings engageable with the drum and being fastened, with ferro-magnetic armatures cooperating with the magnet body, to the free ends of leaf springs, the stroke of each free end being limited by a stop. Such a drum brake is known from German Patent Application DAS 1 227 287.

According to the above mentioned patent application the stop is formed by a pin. This pin, which has a flange-shaped head, serves to limit the stroke of the brake lining in order to prevent the armature from striking and damaging the drum in the event of wear of the brake lining. Under normal conditions the brake lining is in engagement with the drum when the motor is out of operation and, for example, in the event of disturbance of the current supply, so that the shaft of the motor is fixed.

This may be inconvenient under various conditions, for example, when the motor is employed for driving a crane, which must be cap able of turning freely with the wind, when out of operation. Moreover, with the known drum brake the stroke limitation is independent of the degree of wear of the brake lining.

The object of the invention is to obviate the aforesaid disadvantages. According to the present invention there is provided an electro magnetic drum brake, the drum of which accommodates an annular, ferro-magnetic mag net body arranged concentrically with the axis of the drum and having an energizing winding concentric with said axis, brake linings engage able with the drum and being fastened, with ferro-magnetic armatures co-operating with the magnet body, to the free ends of leaf springs, the stroke of each free end being limited by a stop which is adjustable for adjusting the said stroke.

It is thus possible, for example, when the electric motor is out of operation, to release oI to block the brake at will. In a preferred embodiment a stationary intermediate piece hav ing a stop for each leaf spring may be arranged between neighbouring free ends of the leaf spring. Each stop may be formed by a movable body displaceable in an intermediate piece radially with respect to the drum. Such a body has sufficient strength for absorbing the forces exerted thereon even during longer periods of use. The radial position of the body is deter mined by a sliding piece adapted to move parallel to the drum axis, a bevelled end of the sliding piece being in contact with the body.

As an alternative the radial position of the body in the bore may be defined by a sliding piece moving the body along a bevelled part of the intermediate piece. The movement of the sliding piece may be controlled by a rotatable ring concentric with the drum axis and having an inclined part on the lateral face acting on the end of each sliding piece.

The movement of the ring is limited by a pin extending in a slot in the ring. The ring may be turned with the aid of a lever arm which may be manually operable. In order to prevent the body from falling out of the intermediate piece, it is trapped therein by the leaf spring in respect of which it acts as the stop.

The invention will be described more fully with reference to the drawings, in which: FIGURE 1 is an axial sectional view of an electric motor comprising an electromagnetic brake in accordance with the invention, FIGURE 2 is an elevational view and partly a sectional view of the drum brake in accordance with the invention, FIGURE 3 is a sectional view partially taken on the line III--IIIa in Figure 2 and partly taken on the line III--IIIb in Figure 2, FIGURE 4 is a sectional view taken on the line IV-IV in Figure 2, and FIGURE 5 shows a variant of Figure 4.

The motor comprises a closed housing 1 having end shields 2, a stator with a winding 4 fixed in said housing and a motor shaft 5 having a rotor 6 and a winding 7 and being rotatably journalled in the end shields 2.

To the outer side of the right-hand end shield 2 is fastened an annular, ferro-magnetic circuit 8 of a brake concentrically with the motor shaft 5. The magnetic circuit 8 comprises an energizing winding 9. Around the periphery are arranged a plurality of brake shoes, each formed by an armature 10 and a brake lining 11 on the outer side thereof. A brake drum 12 is secured to the motor shaft.

The brake shoes 10, 11 are loaded by leaf springs 13, which urge the brake shoes 10, 11 against the inner wall of a brake drum 12.

When the motor is started, the energizing winding 9 is also fed so that the armatures are attracted and the brake is released.

Viewed in the circumferential direction an intermediate piece 14 is arranged between every two neighbouring leaf springs. This intermediate piece has two axial channels 15 and 16, each of which has a sliding piece 17 and 18 respectively (see also Figure 4). A bore 19 (see Figure 4) extends perpendicular to each of said channels. A ball 20 is displaceable in each of said bores. Referring now to Figure 4, the position of the ball 20 is determined by the sliding piece 17, a bevelled portion of which is in engagement with the ball. By the position of the ball 20 the stop position of the leaf spring 13 is also determined. The displacement of the sliding piece 17 is controlled by a ring 22 having, on the side directed towards the sliding piece, an inclined portion 23 (See Figure 2). The ring is concentrical with the motor shaft and is disposed between the annular magnet body 9 and the bearing shield 2. The ring 22 is displaceable with the aid of the manually operable lever arm 24. The displacement of the ring is limited by a slot-shaped recess holding a pin on the bcaring shield.

The brake torque is adjusted by a turn of the ring 22. Therefore, it is also possible, even when the motor is standing still, to discouple, at will, the brake 10, 11 completely from the drum 12. The drum brake described thus permits the brake torque to be varied from zero to a given maximum value.

As an alternative the position of the body 20 may be determined by a sliding piece 26 (see Figure 5) pushing the body along a bevelled surface 4 in the intermediate piece 14 rather than by a slanting portion 21 of the sliding piece.

As an alternative the slanting portions 21 of the sliding pieces 17 and 18 can be replaced by bevelled surfaces located in the channels 15 and 16.

WHAT WE CLAIM IS:- 1. An electromagnetic drum brake, the drum of which accommodates an annular ferro-magnetic magnet body arranged concentrically with the axis of the drum and having an energizing winding concentric with said axis, brake linings engageable with the drum and being fastened, with ferro-magnetic armatures co-operating with the magnet body, to the free ends of leaf springs, the stroke of each free end being limited by a stop which is adjustable for adjusting the said stroke.

2. An electromagnetic drum brake according to claim 1, wherein each adjustable stop comprises a movable body retained in a stationary intermediate piece, and comprising an adjusting mechanism with sliding pieces acting on the movable bodies, each sliding piece being movable parallel to the said axis and having a bevelled end acting on the movable body to effect movement thereof in the radial direction.

3. An electromagnetic drum brake according to claim 1, wherein each adjustable stop comprises a movable body retained in a stationary intermediate piece, and comprising an adjusting mechanism with sliding pieces acting on the movable bodies, each sliding piece being movable parallel to said axis to move the movable body along a bevelled surface of the intermediate piece so that the body moves in the radial direction.

4. An electromagnetic drum brake according to claim 2 or 3, wherein each stationary intermediate piece is disposed between adjacent free ends of two leaf springs.

5. An electromagnetic drum brake according to claim 2, 3 or 4, wherein the displacement of each sliding piece is controlled by a rotatable ring concentric with the said axis, the ring having an inclined portion in contact with each sliding piece.

6. An electromagnetic drum brake as claimed in claim 5, wherein the movement of the ring is limited by a pin extending in a slot in the ring.

7. An electromagnetic drum brake as claimed in claim 5 or 6, wherein the ring can be rotated with the aid of a lever.

8. An electromagnetic drum brake as claimed in the preceding claims substantially as des cribed with reference to the accompanying drawing.

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

Claims

**WARNING** start of CLMS field may overlap end of DESC **. having end shields 2, a stator with a winding 4 fixed in said housing and a motor shaft 5 having a rotor 6 and a winding 7 and being rotatably journalled in the end shields 2. To the outer side of the right-hand end shield 2 is fastened an annular, ferro-magnetic circuit 8 of a brake concentrically with the motor shaft 5. The magnetic circuit 8 comprises an energizing winding 9. Around the periphery are arranged a plurality of brake shoes, each formed by an armature 10 and a brake lining 11 on the outer side thereof. A brake drum 12 is secured to the motor shaft. The brake shoes 10, 11 are loaded by leaf springs 13, which urge the brake shoes 10, 11 against the inner wall of a brake drum 12. When the motor is started, the energizing winding 9 is also fed so that the armatures are attracted and the brake is released. Viewed in the circumferential direction an intermediate piece 14 is arranged between every two neighbouring leaf springs. This intermediate piece has two axial channels 15 and 16, each of which has a sliding piece 17 and 18 respectively (see also Figure 4). A bore 19 (see Figure 4) extends perpendicular to each of said channels. A ball 20 is displaceable in each of said bores. Referring now to Figure 4, the position of the ball 20 is determined by the sliding piece 17, a bevelled portion of which is in engagement with the ball. By the position of the ball 20 the stop position of the leaf spring 13 is also determined. The displacement of the sliding piece 17 is controlled by a ring 22 having, on the side directed towards the sliding piece, an inclined portion 23 (See Figure 2). The ring is concentrical with the motor shaft and is disposed between the annular magnet body 9 and the bearing shield 2. The ring 22 is displaceable with the aid of the manually operable lever arm 24. The displacement of the ring is limited by a slot-shaped recess holding a pin on the bcaring shield. The brake torque is adjusted by a turn of the ring 22. Therefore, it is also possible, even when the motor is standing still, to discouple, at will, the brake 10, 11 completely from the drum 12. The drum brake described thus permits the brake torque to be varied from zero to a given maximum value. As an alternative the position of the body 20 may be determined by a sliding piece 26 (see Figure 5) pushing the body along a bevelled surface 4 in the intermediate piece 14 rather than by a slanting portion 21 of the sliding piece. As an alternative the slanting portions 21 of the sliding pieces 17 and 18 can be replaced by bevelled surfaces located in the channels 15 and 16. WHAT WE CLAIM IS:-

1. An electromagnetic drum brake, the drum of which accommodates an annular ferro-magnetic magnet body arranged concentrically with the axis of the drum and having an energizing winding concentric with said axis, brake linings engageable with the drum and being fastened, with ferro-magnetic armatures co-operating with the magnet body, to the free ends of leaf springs, the stroke of each free end being limited by a stop which is adjustable for adjusting the said stroke.