FIELD OF THE INVENTION

The present invention relates to friction brake units and in particular to unidirectional friction brake units.

BACKGROUND OF THE INVENTION

Such unidirectional friction brake units are well known and all involve a capacity to facilitate motion in one direction whilst restricting motion in an opposite direction by the generation of a frictional resistance to such motion. It is the object of the present invention to provide a new and improved unidirectional friction brake unit which has this capacity.

SUMMARY OF THE INVENTION

According to the present invention there is provided a uni¬ directional friction brake unit comprising: a unit support; a friction wheel rotatably mounted with respect to said unit support; a flexible, substantially inextendible band embracing said friction wheel over a major portion of its peripheral surface; one end of said band being fixedly coupled to said unit support; means for frictionally coupling said band to said friction wheel over said major portion; elastic biassing means coupling an opposite end of said band to said unit support for biassing said band into frictional engagement with said wheel; and means for rotating said friction wheel with respect to said unit support; the arrangement being such that rotation of said wheel in a first sense results in tightening said band around said friction wheel so as to resist said rotation , while rotation of said friction wheel in a second and opposite sense results in loosening said band with respect to said friction wheel. This effect is at times referred to as the "belt-like tension effect", wherein the friction force increases in one direction and decreases in the opposed direction.

The biasing means according to the present invention may be constituted by a tension spring, wherein the tension of said spring may be adjusted by a tension adjusting means for varying the tension of the spring. In accordance with a first embodiment of the present, said tension adjusting means comprises a bolt coupled to said unit support and having one end thereof coupled to said opposite end of said band, and a coil spring constituting said tension spring surrounding said bolt, whereby rotation of

- r. - said bolt with respect to said unit support in opposite senses results in tensioning or releasing said spring.

In accordance with a preferred embodiment of the present invention, said friction coupling means is a friction strap attached to an inner face of said inextendible band adapted for frictionally embracing said friction wheel. In still a further preferred embodiment, said friction strap is made of leather and said band is made of steel.

According to one embodiment of the present invention, the brake unit further comprising at least one spool attached to the friction wheel on which a flexible cable or wire can be wound and unwound and which may be integrally formed with said friction wheel.

In accordance with one aspect of the invention, at least two such spools of different diameters are attached to the friction wheel, allowing for flexible cables or wires to be wound or unwound at different rates. This arrangement is useful for tilting a suspended element as it is being elevated or lowered by the hoisting mechanism.

According to a second aspect of the present invention, the brake unit serves as a uni-directional rotary damper, useful in damping rotation of a hinged member in one direction and allowing essentially free rotation in an opposed direction.

In one application of the second aspect, the unit support is fixed to a wall member and said friction wheel is hinged to an axis of a door member swingable about said wall member.

BRIEF DESCRIPTION OF THE DRAWINGS

For better understanding, the invention will now be described by way of example only with reference to the accompanying drawings, in which:

Fig. 1 is a cross-sectional side view of one embodiment of a brake unit according to the present invention;

Fig. 2 is a front view of the brake unit seen in Fig. 1 with the cover removed, the unit being in a "braking" condition;

Fig. 3 is a front view of the brake unit seen in Fig. 1 with the cover removed, the unit being in the "releasing" condition;

Fig. 4 is a perspective and partially sectioned partial view of a piano, illustrating how the brake unit according to the present invention may serve as a rotary damper;

Fig. 5 is an enlargement of the brake unit shown in Fig. 4;

Fig. 6 shows how the brake unit according to the present invention is used as a hoisting device, illustrating a clothes rack in its elevated, horizontal position;

Fig. 7 shows how the brake unit according to the present invention is used as a hoisting device, illustrating the clothes rack in its lowered, inclined position;

Fig. 8 is a cross-sectional side view of another embodiment of the present invention, the brake unit comprising two spools;

Fig. 9 is a front view of the brake unit seen in Fig. 8 with the cover removed; and

Fig. 10 is a cross-section similar to Fig. 8, the brake unit further comprising a spool depth adjusting insert;

DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS

Attention is first directed to Figs. 1 to 3 of the drawings, in which a brake unit 2 comprises a unit support 4 consisting of a cover 6 and a base plate 8 provided with holes 9 for mounting the brake unit on a wall or the like.

A friction wheel 10, made for example of plastic material, in the form of a smooth cylinder having a peripheral cylindrical surface 10a bounded by a pair of peripheral ridges 11 is integral with a central hub 12 mounted on a sleeve 14. The sleeve 14 is supported at its ends by bushings 16 and 17 received in openings 18 and 19 of the cover 6 and of the base plate 8 respectively. A tube 20 is fixed within sleeve 14 by means of a bolt 22 and a tapering fastener 24 adapted for expanding the end of tube 20 and fixing it within sleeve 14 as known per se.

A substantially inextendible steel band 26 is fixed at one end 27 to the base plate 8 of the unit support by bolt 28 and its opposite end 29 is coupled to a tension adjusting device 30 (seen in more detail in Figs. 2 and 3), whereby the band 26 embraces the friction wheel 10 over a major portion of its peripheral surface. The tensioning device 30 comprises a coiled tension spring 32 mounted over a bolt 34 and having one end thereof bearing against a plate member 36 rigid with the base plate 8 of the unit support 4 and the second end thereof, bearing against a retainer ring 38 fixed to the bolt 34.

One end of bolt 34 is screwingly engaged with a nut 40 coupled to the opposite end 29 of the steel band 26. A setting knob 42 is mounted on the opposite end of the bolt 34.

The arrangement is such that upon screwing bolt 34 into nut 40, the spring 32 is expands between plate member 36 and retaining ring 38, the outcome of which is loosening the steel band 26 around the friction wheel 10.

A friction strap 46, made for example of leather, is attached ,e.g. by bonding, to the steel band 26, and extends at least along the arc of contact of the steel band 26 with the friction wheel 10.

A removable housing 48 (seen in Fig. 1) covers the brake unit 2, protecting it from dirt and unauthorized tampering, with only the setting knob 42 and an end of tube 20 protruding from the housing 48. In the embodiment of Fig. 1, tube 20 will be connected to an axle of a device (not shown) for damping its rotary motion as will hereinafter be explained in more detail with reference to Figs. 4 and 5.

Attention is now directed to Figs. 1-3 for describing the manner in which the brake unit according to the invention operates. As seen in Fig. 2, when the friction wheel 10 is rotated in a counter-clockwise direction as indicated by arrow 50, the friction coupling between the friction wheel surface 10a and the friction band causes the end 29 of the band together with the bolt 34 and the retainer ring 38 to be displaced outwardly thereby extending the spring 32 and increasing the tensioning of the band around the wheel.

The outcome of the above is that the friction force between the friction strap 46 and between the friction wheel 10 increases, whereby rotation of the friction wheel and the device attached to it (not shown) becomes significantly more difficult.

However, when the friction wheel 10 is rotated in a clockwise direction as indicated by arrow 52 in Fig. 3, the frictional coupling between the friction wheel surface 10a and between the friction band causes the end 29 of the band together with the bolt 34 and the retaining ring 38 to be displaced inwardly , thereby retracting the spring 32 and thus reducing the tensioning of the band around the wheel. In consequence the frictional coupling between the band and the friction wheel loosens, allowing relatively free rotation of the friction wheel and anything attached to it (not shown).

It should be realized that the tension adjusting means 30 may be pre-tensioned by means of setting knob 42 (seen in Fig. 1) for predetermin¬ ing the minimal force required for rotating the friction wheel 10.

The brake unit 2 described with reference to Figs. 1-3 may be used in a variety of mechanical applications in which is required to enable free rotary motion in one direction and dampen the rotary motion in an opposed direction, at an adjustable rate.

One example wherein such a brake unit may be used is illustrated in Figs. 4 and 5, showing a portion of a piano 50 with a lid 52 rotatable about axle 54 hingedly connected via brake units 56 to side brackets 58 of the piano.

The arrangement is such that opening the lid 52 rotates the friction wheels 10' of the brake unit 56 in the clockwise direction, i.e., in the direction in which the steel band 26' becomes loose over the friction wheel 10', as explained hereinbefore with reference to Fig. 3, according to which the person lifting the cover has to overcome practically only the weight of the lid 52.

However, in the event that lid 52 is open and it accidentally drops, it will not slam due to the damping effect of the brake unit 56 which will be activated by axle 54 rotating the friction wheel 10' in a counter¬ clockwise direction, tensioning the steel band 26' over the friction wheel 10', as explained with reference to Fig. 2, whereby the friction force is substantially increased. If necessary, the resistance may be regulated by changing the setting of the adjusting means 30'.

Although the embodiment of a brake unit useful as a rotary damper was illustrated with respect to only one application, it should be obvious to a person versed in the art that the brake unit according to the present invention may be applicable in a variety of devices with the necessary adjustments made.

According to a second embodiment of the present invention, the brake unit is useful as a hoisting device paying out or winding cables.

When it is merely required to elevate or lower a light load, the brake unit 2 may comprise only a single spool (not shown), or it may comprise two or more spools for heavy loads whereby, each spool winds a wire and tangling of wires is avoided. For this purpose, the spools have similar diameters and the load maintains its angular position as it is being elevated or lowered, as will hereinafter be explained. however, at times it may be required to change the angular position of a load as it is being elevated or lowered. Such an arrangement is useful, for example, for a clothes rack, which in its elevated position is substantially horizontally displaced adjacent the ceiling as seen in Fig. 6 and in its lowered position is inclined so as to facilitate hanging of laundry, as seen in Fig. 7.

For this purpose a brake unit is used having two spools of different diameters, as illustrated in Figs. 8 and 9 as will hereinafter be explained in more detail. Those elements which are similar to those of the previous embodiment are designated with the same reference numerals.

As seen in Figs 8 and 9, two spools 60 and 62 are integrally formed with the friction wheel 10, the first spool 60 having a bigger cylinder diameter than that of the second spool 62. The spools 60 and 62 and the friction wheel 10 have a common hub 12' to which is connected a tube 20 as explained with reference to Fig. 1, rotatable by a handle 66 connected to it.

Cover 6 and the housing 48, each comprise a pair of openings 80, 82 and 84, 86 respectively, each pair of holes being in register with the other pair.

Two cables (not shown) are wound around spools 60 and 62, having their beginnings extending- through holes 68 and 72 respectively and

secured by knots (not shown), preventing them from running free. The other end of the cables penetrates through openings 80, 82 and 84, 86 respectively and are in turn connected to the object (load-e.g, clothes rack) to be elevated or lowered by the brake unit 2.

The operation of the hoisting mechanism hereinabove described is similar to that described in connection with the previous embodiment of Figs. 1 to 3. Rotating handle 66 in the clockwise direction will in turn cause winding of the cables over spools 60 and 62, whereby the force required for elevating the load will essentially be that required for overcom¬ ing the weight of the load.

However, presetting knob 42 at a predetermined friction force even slightly bigger than the load, will ensure that after elevating the load, when the handle 66 is left, the load will not drop, owing to the friction force increasing when rotary motion in the counter-clockwise direction is imparted to the friction wheel 10 by the load. If, however, the friction force was preset at a value less than the load, then, when the handle 66 is left, the load will slowly descend.

In order to lower the load, the handle 66 is rotated counter¬ clockwise at a force substantially equal to the difference between the force generated by the load and between the preset friction force. For example, if the load weights 20 Kg. and the friction force is set to 22 Kg., thus the force required for lowering the load will be about 2 Kg. (the difference between forces), whereas the force required for elevating the load will be about 20 Kg. (not considering the moment of the handle 66 over its axis of rotation, which assists in elevating the load).

Referring back to Figs. 6 and 7, the clothes rack 100 consists of a frame 102 with a plurality of laundry lines 104 tensioned over the frame 102. The frame is suspended from a ceiling (not shown) by four pulleys, 106, 108, 110 and 112, each pulley being associated with a respective cable 114, 116, 118 and 120. Cables 114 and 120 meet and pass

ovcr pulley 122, whereas cables 116 and 118 meet and pass over a pulley 124 and 128. Each pair of cables is wound on a respective spool 60 and 62. Pulleys 126 and 128 are merely guidance pulleys.

The arrangement is such that when the cables are wound over the spools the clothes rack 100 is elevated and is substantially horizontal, as seen in Fig. 6. However, when the handle 66 of the brake unit 2 is rotated in the clockwise direction, while paying out the cables 114-120, the clothes rack 100 will descend while gradually inclining to the position seen in Fig. 7 owing to the unequal diameters of spools 60 and 62. In this position the lines 104 are best accessible which is helpful in particular for handicapped persons.

If it is required to cancel the feature of inclined hoisting, then it is possible to add an insert 120 as seen in Fig. 10, which may be a resilient open ring member or segments constructing a ring, which when mounted on the smaller spool 62 equal its diameter with that of the larger spool 60. Alternatively, instead of mounting an insert, it is possible to add ineffective coils over the smaller spool, so as to level the height of the spools 60 and 62. By adding only few ineffective coils onto the smaller spool 60, the inclination ratio of the clothes rack may be changed.

As already explained, the tensioning means 30 is preset by knob 42 to an estimated load according to the weight of the laundry hung on the rack, whereby elevating the rack 100 requires substantially only overcoming the weight of the laundry, which is facilitated by the lever of the handle generating a moment assisting in rotating the brake unit.

Presetting the adjusting means by knob 42 to slightly more than the weight of the clothes rack with the laundry hanging on it, will prevent rack 100 from falling without any necessary precautions. Lowering the rack 100 is carried out by simply rotating handle 66 in the clockwise direction at a force substantially equal to the difference between the loads i.e.,

between the weight of clothes rack 100 with the laundry hanging on it and between the load preset at the tension means 30 by knob 42.

If, however, the user finds it difficult to lower the clothes rack (e.g. due to difference in weight of the dried laundry compared with respect to the weight of the wet laundry, then, the tension means 30 may be readjusted by knob 42 so as to ease the rotation of handle 66.

It should be obvious to a person versed in the art that the brake unit may be employed in a variety of mechanisms with suitable arrange¬ ments being made mutatis mutandis. Furthermore, instead of a manual handle 66 an electric motor may be used (not shown).