US3680665A

US3680665A - Brakes

Info

Publication number: US3680665A
Application number: US65186A
Authority: US
Inventors: Richard William Harris
Original assignee: Individual
Current assignee: Individual
Priority date: 1969-08-25
Filing date: 1970-08-19
Publication date: 1972-08-01
Anticipated expiration: 1989-08-01
Also published as: FR2059022A5; JPS50230B1; DE2042157A1; GB1315816A

Abstract

A brake for slowing down a reel of wrapper web when the demand for the web by the wrapping machine diminishes. The shaft of the reel of the web carries around with it by means of a spring a mounting for a brake arm. A cam on the reel shaft bears against a cam follower caused by the brake arm to apply the brake. Due to the spring, deceleration of the reel shaft (caused by diminished tension in the wrapper web) allows the cam to rotate relative to the follower so that the brake is applied harder.

Description

United States Patent Harris [4 Aug. 1, 1972 [54] BRAKES 2,310,787 2/1943 Hoye ..192/8 R Inventor: W l am M 1 Lans- Faust et al. R X ton Way, London, S.E.3, England Primary Exananer Duane A Reset [22] Filed: Aug. 19, 1970 Attorney-Craig, Antonelli & Hill [21] Appl. No.: 65,186

[30] Foreign Application Priority Data Aug. 25, 1969 Great Britain ..42/ 190/69 [52] US. Cl ..188/134, 192/8 R, 242/99 [51] Int. Cl. ..B60t 7/12 [58] Field of Search ..188/134-136;

192/8 R, 8 A; 242/75.4, 75.47, 84.52 A, 84.52 C, 84.52 R, 99, 156, 156.2

[56] References Cited UNITED STATES PATENTS 1,170,216 2/1916 Blanch ..l92/8R [57] ABSTRACT A brake for slowing down a reel of wrapper web when the demand for the web by the wrapping machine diminishes. The shaft of the reel of the web carries around with it by means of a spring a mounting for a brake arm. A cam on the reel shaft bears against a cam follower caused by the brake arm to apply the brake. Due to the spring, deceleration of the reel shaft (caused by diminished tension in the wrapper web) al- I lows the cam to rotate relative to the follower so that the brake is applied harder.

6 Clairm, 2 Drawing Figures BRAKES The present invention relates to brakes and more particularly to brakes designed to inhibit overrunning of a rotating member.

In a wrapping machine, for example of the kind disclosed in US. Pat. No. 3,380,227 dated Apr. 30, 1968 a web of wrapping material is unwound from a reel for use in the wrapping machine. If for any reason the wrapping machine stops, for example due to jamming or to cure a fault, then the momentum already im- -parted to the reel by the web being drawn from it and into the wrapping machine would normally cause the reel to continue rotating after the wrapping machine had stopped and after the web had stopped being consumed by the wrapping machine, with the result that the web would unwind from the reel and form into folds or generally become snarled up between the reel and the wrapping machine.

The present invention provides a brake which can be used to prevent the reel overrunning when the web is no longer being drawn off the reel.

According to the present invention there is provided a brake comprising a stationary brake drum, a rotatable shaft to be braked and coaxial therewith, a brake mounting member rotatable about the axis of the shaft and driven therefrom by a first resilient connection, a brake arm pivoted on the rotatable brake mounting member and carrying a brake shoe to engage with the brake drum, a cam carried by the shaft, and a cam follower carried from the brake arm by a second resilient connection, the cam being shaped so that deceleration of the shaft with respect to the rotatable member causes the cam follower to-ride up the cam and increase the braking pressure, and vice versa.

The rotatable shaft may carry a flange with a circumferential groove, the first resilient connection being a coil spring connected at one end to the rotatable member and at its other end to the flange, and resting in the groove.

The second resilient connection may be a spring blade secured at one end to the rotatable member and carrying the cam follower.

How the invention may be carried out will now be described, .by way of example only, with reference to the accompanying drawings:

FIG. 1 is a side elevational view of a brake according to the invention; and

FIG. 2 is a section taken on the line A-A of FIG. I.

The brake comprises a brake drum 1 which is mounted on a fixed member 2 so that the drum is stationary. A brake shoe 3 is carried on a brake arm 4 which is pivotally mounted at 5 on a plate 6.

The plate 6 is carried by bearings 7 on a rotatable input shaft 8 which is itself supported in bearings 9 within a portion of the fixed member 2.

The rotary input member of shaft 8 carries a cam 10 which is engaged by a cam follower in the form of a roller 1 l. The roller 11 is carried on a resilient blade 12 which has one end 12a secured to the brake arm 4. An adjustable screw 27 carried by the brake arm 4 urges the resilient blade 12 towards the cam 10 in order to maintain the roller 11 in contact with the cam surface.

The left hand end, as viewed in FIG. 2, of the input shaft 8 is formed with a head 13. A tension coil spring 14 has one end secured at 15 to the plate 6 and the other end secured to a mounting 16 carried by the head 13 of the input shaft 8. The coil spring 14 locates'in a groove 26 formed in the periphery of the head 13.

A stop 17 is carried by the plate 6 and is adapted to be engaged by a stud 18 which is secured in an arcuate slot 19 in the head 13; the position of the stud 18 along the slot 19 is adjustable by means of a threaded head which is screwed into the stud. The purpose of the stud 18 and the stop 17 is to limit the amount that the plate 6 can rotate anti-clockwise relatively to the head 13, as viewed in FIG. 1.

In this embodiment the input shaft 8 carries a reel of wrapping material 20. The reel has a hub 21 with an integral end plate 21a, the hub 21 being keyed, splined or otherwise arranged to rotate with the shaft 8. The web of wrapping material 20 is wound on a tube 22 which is slid on to the hub 21 so that spikes 23 carried by the hub 21 are impaled in the end of the tube 22, which in this case is made of cardboard. The wrapping material is held in position on the hub 21 by a removable end plate 24 which is held in position by a nut 25 which is threaded on to the end of the shaft 8.

The manner in which the brake described above operates, will now be described.

In the position shown in FIG. 1, in which it is assumed that the shaft 8 is stationary, the tension coil spring 14 is tending to rotate the plate 6 in an anticlockwise direction and thus in turn rotate the brake arm 4 in an anti-clockwise direction about the pivot 5 and maintain the brake shoe 3 in contact withthe internal surface of the brake drum 1. If the shaft 8 is now rotated in an anti-clockwise direction, by the drawing off of the web of wrapping material from the reel, then the shaft 8 and thus the head 13 will rotate in an anticlockwise direction, as viewed in FIG. 1, and tend to carry the plate 6 and brake arm-4 with it. However, the tension applied by the coil spring 14 to the plate 6 will be opposed by the frictional force between the brake lining 3 and the brake drum 1 thus causing the plate 6 and brake arm 4 to lag behind the head 13. This lagging will of course result in an extension of the spring 14 and thus an increase in its tension. In the absence of any other forces, the plate 6 would then commence to rotate in unison with the head 13 when this tension exceeded the value of the frictional force between the lining 3 and the drum 1 opposing it. However, the cam member 10, although circular, has its center offset with respect to the axis of the shaft 8 so that any rotation of the shaft 8 with respect to the plate 6 will result in the cam surface of the cam 10 moving with respect to the cam follower 11 and in particular will result in radial movement of the cam follower 11 with respect to the axis of the shaft 8.

Thus, as the head 13 rotates in an anti-clockwise direction (FIG. 1) with respect to the plate 6 the cam follower 11 will move radially inwardly towards the axis of the shaft 8, under the influence of the resilient blade 12. This radially inward movement of the cam follower 11 will result in the brake lining 3 moving inwards to reduce the pressure of the lining on the brake drum 1.

Therefore, torque applied to the input shaft 8 results in relative movement between the head 13 and the plate 6 which in turn results in increased tension in the spring 14, and radially inward movement of the cam follower 11, the latter two factors combining to bring the brake shoe 3 out of contact with the brake drum 1. This condition will continue along as there is suflicient torque being applied to the input shaft 8 by the tension in the wrapper web being drawn 011 the reel, but as soon as this tension reduces belowapredetermined level, or ceases altogether due to stopping of the machine which is consuming the wrapper web, the coil spring .14 will contract and thus cause the plate 6 to rotate anti-clockwise with respect to the head 13 and thus in turn move the roller 11 anti-clockwise around the cam surface 10 to cause the roller 11 to move radially outwardly. The effect of the anti-clockwise movement of the plate 6 with respect to the head l3, and the radially outward movement of the roller 11 is to cause the brake-arm 4 to rotate anti-clockwise about its pivot 5 and bring the brake shoe 3 into contact with the brake drum 1 to brake the reel of wrapping material 20.

The purpose'of the stop 17 and associated stud 18 will now be described.

lf when the wrapper web commences to be drawn off the reel it is done with a sudden jerk then this will result in a relativelylarge extension of the coil spring 14 before the plate 6 commences to rotate. The stored energy in the extended coil spring 14 will then be converted into kinetic energy of the plate 6 as it moves to catch up the head 13. This will thenin turn result in the coil spring 14 being compressed and becoming loose around the peripheral groove 26. If there were no stop 17 and associated stud 18 this could result in the coil spring 14 falling completely away from the groove 26, as viewed in FIG. .1, and possibly becoming an entangled mass between the periphery of the head 13 and the inner surface of the brake drum 1. However, the presence of the stop 17 and associated stud 18 means that the plate 6 can then only rotate a limited amount in an anti-clockwise direction with respect to the head 13, thus preventing the aforementioned undesired compression of the coilspring l4.

Although the brake of the invention has been desire to secure by brake mounting member rotatable about the axis of the shaft and driven therefrom by a first resilient connection, a brake arm pivoted 'on the rotatable brake mounting member and carrying a brake shoe to engage with the brake drum, a cam carried by the shaft, and a cam follower carried from the brake arm by a second resilient connection, the cam being shaped so that deceleration of the shaft with respect to the rotatable member causes the cam follower to ride up the cam and increase the braking pressure, and vice versa.

2. A brake as claimed in claim 1 whereinthe rotatable shaft carries a flange with a circumferential groove,

the first resilient connection being a coil spring connected at one end to the rotatable member and at its other end to the flange, and resting in the groove.

3. A brake as claimed in claim 1 wherein the second resilient connection is a spring blade secured at one end to the rotatable member and carrying the cam fol- XF A brake as claimed in claim 3 and comprising an adjustable screw member bearing against the spring blade to adjust the braking force.

5. A brake as claimed in claim 1 wherein the rotatable member has a part which abuts a part carriedby the rotatable shaft when the load in the'first resilient connection reaches a predetermined minimum value.

6. A brake as claimed in claim 5 wherein the part carried by the rotatable shaft is a stud, the position of which is adjustable along a slot in the. flange.

a s a a s

Claims

1. A brake comprising a stationary brake drum, a rotatable shaft to be braked and coaxial therewith, a brake mounting member rotatable about the axis of the shaft and driven therefrom by a first resilient connection, a brake arm pivoted on the rotatable brake mounting member and carrying a brake shoe to engage with the brake drum, a cam carried by the shaft, and a cam follower carried from the brake arm by a second resilient connection, the cam being shaped so that deceleration of the shaft with respect to the rotatable member causes the cam follower to ride up the cam and increase the braking pressure, and vice versa.

2. A brake as claimed in claim 1 wherein the rotatable shaft carries a flange with a circumferential groove, the first resilient connection being a coil spring connected at one end to the rotatable member and at its other end to the flange, and resting in the groove.

3. A brake as claimed in claim 1 wherein the second resilient connection is a spring blade secured at one end to the rotatable member and carrying the cam follower.

4. A brake as claimed in claim 3 and comprising an adjustable screw member bearing against the spring blade to adjust the braking force.

5. A brake as claimed in claim 1 wherein the rotatable member has a part which abuts a part carried by the rotatable shaft when the load in the first resilient connection reaches a predetermined minimum value.

6. A brake as claimed in claim 5 wherein the part carried by the rotatable shaft is a stud, the position of which is adjustable along a slot in the flange.