BRAKE DEVICE ACTING ON A DRUM

Abstract: A brake device acting directly or indirectly on a drum (1) so as to automatically brake the drum in the event that a certain speed of the drum (1) is exceeded. The braking device comprises a gear (9, 10, 11, 12, 16) driven by and gearing up the speed of the drum (1), which gear in turn is arranged to rotate a brake body (4) rotatably suspended in its one end (6) with an inherent weight adapted to the said speed. The brake body (4) is pretensed by means of, for example, a spring (5) or the like adapted to the said inherent weight and said speed to be kept from braking via direct or indirect contact with the drum (1), at a speed that is lower than said speed and that is unable at a speed that is higher than the said speed to prevent the brake body (4) through the centrifugal force exercised on account of rotation from making direct or indirect contact with the drum (1) and thus braking the same. The drive force which is arranged by the gear (9, 10, 11, 12) to be applied to the brake body (4) is applied to the brake body (4) via an actuating member (13, 16 and 18, respectively) working between the gear (9-12) and the brake body (4) which is so elaborated that when the brake body (4) directly or indirectly contacts the drum (1) a servo effect is caused to begin to act, which is arranged to increase the braking action of the brake body (4).

Description: Brake device acting on a drum The present invention relates to a brake device acting directly or indirectly on a drum in order to automatically brake the drum in the event of the drum exceeding a specific speed, the said brake device consisting of a gear driven by the drum and gearing up its speed, which gear in its turn is arranged to rotate a pivotably suspended brake body in one end with an inherent weight adapted to the said speed, the said brake body being pretensed for instance by means of a spring or similar device adapted to the said inherent weight and " said speed so that at a speed that is lower than the said speed is prevented from braking via direct or indirect contact with the drum and at a speed that is higher than the said speed is unable to prevent the brake body from making direct or indirect contact with the drum and thus braking the drum through the centrifugal force exercised on account of rotation. It is prior art knowledge to bring rotatably suspended weights into rotation in order to be turned outwards around a point of articulation at a certain speed and thereby to brake the said weights through the friction contact against the drum. The masses of the said weights and the opposing force of a spring are so selected that the braking is adap¬ ted so that it takes place when the speed of the drum- exceeds a specific speed. This prior art type of brake device is used in roller conveyors, among other things, on which the speed of entering goods is to be re¬ tarded or braked. With the prior art braking device use is currently made in order to be able to obtain different requisite braking forces, which are re¬ lated to the different weights of the transported goods and different transport speeds, of different gears to gear up the speed of rotation of the brake weights. In other words, the greater the braking force required the greater the number of gears will be required. Such gears are relatively expensive to produce and also have the inherent disadvantage that the braking weight or weights are placed further from the ends of the drum and thus from the bearing points of the drum, whereby the drum shaft and more specifically its downhang can influence the braking action. In order to counteract this disadvan¬ tage it is necessary to eliminate the downhang, for example by also * introducing one or more support bearings for the shaft of the drum. Apart from this a higher torque is also obtained in idling on account of friction between the included parts of the gears, which circumstance negatively influences the ability of the roll to roll easily at low speed. One object of the present invention is to provide in a braking device of the type mentioned in the preamble a significantly improved braking action without it being necessary per se to use further, expensive gears and support bearings and without it being necessary to increase the masses or rotational speeds of the brake weights. This task is solved in the type of brake device mentioned in the preamble in that the braking action generated by the rotating weight directly or indirectly against the drum in accordance with the present invention is utilized in principle also to generate or trigger an addi¬ tional braking force as defined in closer detail in the accompanying main claim. This generation or triggering of an additional braking force can be carried out by various means, for example by generating in accor¬ dance with the accompanying claim 2 an additional braking force on the actual brake weight apart from the braking force that is due to the influence of centrifugal force on the brake weight or by using accord¬ ing to the accompanying claims 4 and 5 separate brake devices, the brak¬ ing action of which is triggered by the braking action of the brake weights. The invention is described in greater detail below and with reference to the accompanying drawing, v/herein Fig. 1 shows a cross-section through a brake device for a roller conveyor, Fig. 2 shows a cross-sec¬ tion through the brake device according to Fig. 1 but with only certain parts drawn for the sake of clarity and Fig. 3 shows a cross-section through a brake device with a different design. It should be noted that the same referens numerals are used throughout in the figures for equi¬ valent parts. The first embodiment of the invention, of which only the left-hand part of the braking device is shown, as illustrated by Fig. 1 comprises a drum 1, with the outer peripheral surface of which entering goods make contact and thus cause the drum 1 to rotate. If the speed of the arriving goods is higher than the specific speed, the drum 1 is to be braked. Via endplates 8, 8a (the latter not shown in the drawing) and bearings 21, 21a (the latter not shown in the drawing), the drum 1 is rotatably established relative to a stationary arranged shaft 2. An intermediate part 9 rigidly attached to the endplate 1 is provided with inner teeth 20 and is rotatably mounted on the stationary shaft 2. Ob¬ viously, the end plate 8 and the intermediate part 9 can be designed in one piece if so desired. A seat 22 is fixed in the stationary shaft and comprises a seat for, say, three shafts which rotatably support toothed rollers 9, 10, 11 mounted on the said shafts, the teeth of which rollers interact with the inner teeth of the intermediate part 19. The said three toothed rollers 9, 10, 11 are preferably symmetrically dis¬ posed around the stationary shaft 2. A second body 16 is rotatably mounted on the stationary shaft 2 and is driven via teeth 12 by the teeth rollers 9, 10, 11. In this context it should be noted that the second body 16 on account of the selected gear ratio rotates at a significantly higher speed than the drum 1 does in itself. The other body 2 is in the vicinity of its periphery fitted with a bearing trunnion en which a roller 13 is rotatably disposed. This roller 13 is in turn arranged to drive and thus to rotate a brake body 4 around the stationary shaft 2 through contact against the brake body 4, preferably close to its other end 14. The brake body 4 is also rotatably suspended in a bearing journal 15, which is fixed in a first body 3 which in turn is rotatably mounted on the stationary shaft 2. The brake body 4 is pretensed away from the inside of the drum 1 by means of, for example, a spring 5 and is provided on its outer side with a wear and brake lining 7. This wear lining 7 is preferably sited closer to one end of the brake body 4 than the ohter end 14 of the brake body 4 and has an extent in the direction of rotation of the drum that is significantly shorter than a αuarter of a revolution. The location of the wear lining 7 on the outer surface of the brake body 4 and the extent of the wear lining 7, and the choice of the material in the wear lining 7, must be made with great care. The inherent weight of the brake body 4 and the tensile force of the spring 5 must be selected so that braking occurs at the intended speed of the drum 1. As an alternative or complement obviously several brake bodies 4a, OMPI not shown in the drawing, can be driven by one or a plurality of drive members 13a, indicated in the drawing with broken lines. ' The brake device according to Fig. 1 and Fig. 2 works in the follow¬ ing manner. Goods with a higher speed than can be accepted by the brak- ^ ing device contact the peripheral surface of the drum 1 and the drum 1 rapidly gains the same speed as that of the goods: this speed is trans¬ ferred and geared up via gear 9, 10, 11, 20, 12 to the second body 16, whereby the drive member 13 drives the brake body 4 to rotate with a significantly higher speed than that of the drum 1. This high speed -^ causes the brake body on account of its inherent weight or mass and rotation through the influence of the centrifugal force and on account of the fact that the force exerted on the brake body 4 is greater that the counterforce accomplished by the spring 5 commences to rotate around the bearing journal 15, where lining 7 contacts the inner surface of ■ L5 the drum 1 and commences to brake the speed of the drum 1. In that the brake body 4 is forced to rotate with constant contact in its other . end 14 with the drive member 13 the latter, upon this initial braking contact with the inner surface of the drum 1, will act as a pushing lever for this initial, braking contact. Since the distance between 20 the point of contact of the drive member 13 with the brake body 4 and the wear lining 7 is selected relatively large, a large lever is attain¬ ed, whereby the initial braking action accomplished solely on account of the centrifugal force is amplified to a significant degree. By this means, a servo braking action is obtained which causes the drum 1 to 2 ^ be rapidly braked down to the intended speed and when this intended lower speed has been reached the braking action ceases automatically, because the centrifugal force in this position is lower than the force exercised by the spring 15 on the brake body 4 away from braking contact with the inner surface of the drum 1. 3 ^ in this context, the elaboration of the other end 14 of the brake body 4, i.e. the end Interacting with the drive member 13, should also be noted. Seen in the direction of rotation around the shaft 2 for the brake body 4 the other end 14 has a relatively weakly angled surface 14a. 35 This elaboration of the surfaces of the other end 14 imply that the total braking force exercised by the wear lining 7 against the drum "BURE T OMPI 1 will be very large at the moment when the drive member 13 interacts with the weakly angled surface 14a. . A second embodiment of the invention is shown in Fig. 3. The parts fulfilling the same function as in the embodiment according to Fig. 1 and 2 have been allocated the same reference numerals and are conse¬ quently not described further hereinafter. Disposed between the second body 16 and the first body 3, both of which said bodies are rotatably mounted on the stationary shaft 2, is a body 16, fixed stationally on the shaft 2. A drive and braking device 18 is wound around this stationa- ry body 7 and may, for example, comprise a relatively soft belt, the said belt 18 being fixed at one end to a pin 23 which in turn is fixed in the second body 16 and in its other end fixed at the pin 15. It should be observed that the brake body 4 and the first body 3 in this embodiment have changed places in comparison with the embodiment accord- ing to Fig. 1 and Fig. 2. This second embodiment works in the following manner: the drum 1 is caused to rotate by goods which at a certain motional speed contact the peripheral surface of the drum 1. Via gears 20, 10, 11, 12, 16 the pin 23 is caused to rotate at a higher speed and is accompanied by the belt 18 wound around the stationary body 17, the drive and braking de¬ vice, which belt 18 slides on the surface of the stationary body 17 and drive the bearing pin 15 which is thereby caused to rotate the first body 3 rotatably mounted on the shaft 2 and the brake body 4. When the wear lining 7 of the brake body 4 contacts the inner surface of the drum 1, i.e. when the rotation of the brake body 4 around the stationary shaft 2 and the force generated on account of the centrifugal force is thus greater than the counterforce exerted by the spring 5 and the wear lining 7 thus contacts the drum 1, the belt 18 tightens around the stationary body 17 and in this way increases the total braking force exerted on the drum 1 significantly. The number of turns the belt 18 is wound around the stationary body 17 and thus the total friction-gene¬ rating surface can naturally vary within wide limits in order thus to vary the total braking force exerted on the drum 1. It should be noted that the lengths of the opposingly directed bearing pin 15 and the pin 23, viewed in the direction of extension of the shaft 2, are so selected that the mutual displacement of these pins 15 and ■ BU EΛI O PI . IPO _ 23 is limited, they can for example strike against each other, and that the pin 23 and/or 15 also prevents the belt 18 from changing "tracks". There is therefore not risk that the belt 18 will occupy faulty posi¬ tions on the stationary body 17. In the same way as the embodiment according to Fig. 1 and Fig. 2, the embodiment according to Fig. 3 can be provided with several drive and braking devices 17, 18, if so desired or required and/or a plurality of brake bodies influenced by the centrifugal force. In addition, the embodiment according to Fig. 1 and Fig. 2 can obviously be combined in an optional manner with the embodiment according to Fig. 3. OMPI

Claims: CLAIMS 1. A brake device acting directly or indirectly on a drum (1) so as to automatically brake the drum (1) in the event that a certain speed of the drum (l) is exceeded, the said brake device comprising a gear (9, 10, 11, 12, 16) driven by and gearing up the speed of the drum (l), which gear in turn -is arranged to rotate a rotatably suspended brake body (4) in its one end (6) with an inherent weight adapted to the said speed, which brake body (4) is pretensed by means of, for example, a spring (5) or the like adapted to the said inherent weight and said speed, so that at a speed that is lower than the said speed is prevented from braking via direct or indirect contact with the .drum (1), and at a speed that is higher than the said speed is unable to prevent the brake body (4) from making direct or indirect contact with the drum (1) and thus braking the drum through the centrifugal force exercised on account of rotation, c h a r a c t e r i z e d in that the driving force which is arranged by the gear (9 10, 11, 12) to be applied to the brake body (_4) is ap¬ plied to the brake body (4) via an actuation member (13, 16 and 18, respectively) working between the gear (9-12) and the brake body (4) and further gearing up the drive force of the gear (9-12), which is so elaborated that when the brake body (4) directly or indirectly con¬ tacts the drum (1) a servo effect is caused to commence to act, which is arranged to increase the braking action of the brake body (4). 2. A brake device according to claim 1 with a gear lining (7) disposed on the surface of the brake body (4) which is arranged to directly or indirectly contact the drum (l) and is sited closer to one end of the brake body (l) than to its other end (14), c h a r a c t e r i z e d in that the said drive force is applied by means of the actuating member (13) to the brake body (4) near its other end (14). 3. A brake device according to claim 2, c h a r a c t e r i z e d in that the said actuating member comprises a roller (13) which is driven by the said gear (9-12, 16) to rotate with geared up speed in comparison with the speed of the drum (l) and is arranged to act against and drive the brake body (4) appropriately 'BUREΛ^ OMPI via its other end (14). 4. A brake device according to claim 1 with a drive and braking device (18) in the shape of, for example, a friction belt (17), c h a r a c t e r i z e d in that the said actuation member comprises a stationary body (17), appropriately working between said gear (9-12, 16) and the brake body (4), around which stationary body (17) is wound the said drive and braking device (18) which, when driven by the said gear (9-12), is arranged to drive in its turn the brake body (4) but tightens around the stationary body (17) when the brake body (4) direct- ly or indirectly brakes agains" the drum (l), whereby the drive and braking device (18) by this means in turn brake around the stationary body (17). 5. A brake device according to any of claims 1 to 4, c h a r a c t e r i z e d in that a plurality of actuating members (13, 13a and 17, 18, respectively) are arranged to actuate a plurality of brake bodies (4) and/or a plurality of drive and braking devices (17, 17a, 18, 18a). SURE C OMPI

Inventors: TOERNQVIST PETER TORSTEN JOHAN, TOERNQVIST, PETER, TORSTEN, JOHAN
Applicants: CAVOTEC AB
Application year: 1984
Main classification: B65G13
IPC codes: B65G13, F16D59