US 3353792 A
Description (OCR text may contain errors)
Nov. 21, 1967 AlTKEN 3,353,792
CRANES, GRABS AND THE LIKE Filed June 28, 1966 6 Sheets-Sheet 1 FMXMWMQ W Nov. 21, 1967 R. L. AITKEN 3,353,792
CRANES, GRABS AND THE LIKE Filed June 28, 1966 6 Sheets-Sheet 2 Nov. 21, 1967 R. L. AITKEN CRANES, GRABS AND THE LIKE 6 Sheets-Sheet 5 I Filed June 28, 1966 A J R my M azr" all Nov. 21, 1967 R. 1.. AITKEN 3,353,792
CRANES, GRABS AND THE LIKE Filed June 28, 1966 '6 Sheets-Sheet 4 @M fi/ M Nov. 21 1967 R. AITKEN 3,353,792
. I CRANES, GRABS AND THE LIKE Filed June 28, 1966. I 6 Sh et -Sh e 5 Nov. 21, 1967 R. L. 'AITKEN 3,353,792
CRANES, GRABS AND THE LIKE Filed June 28, 1966 6 Sheets-Sheet 6 United States Patent 3,353,792 CRANES, GRABS AND THE LIKE Robert London Aitken, 117 Sedlescombe Road N., St. Leonards-on-Sea, Sussex, England Filed June 28, 1966, Ser. No. 562,067 Claims priority, application Great Britain, July 27, 1965, 32,148/65 2 Claims. (Cl. 254150) ABSTRACT OF THE DISCLOSURE A spring driven reel mechanism for a line for attachment to a suspended load to prevent twisting, comprising a stationary member, a rotatable reel arranged coaXially with said stationary member, at least one coiled spring connected between said reel and said stationary member, one end being drivingly connected to said rotatable reel and the other end being anchored to said stationary member, brake means comprising two relatively rotatable parts, one of said parts carrying friction elements pressed in slipping engagement against the other of said parts under constant load, and unidirectional clutch means coupled between one part of said brake means and one of said reel and said stationary member, the other part of said brake means being secured to the other of said reel and said stationary member, whereby said brake means applies a slipping and constant braking load to said reel upon rotation of said reel in the spring tensioning direction. I
This invention relates to cranes, grabs and the like and in particular it relates to a mechanism for preventing a grab bucket or like load suspended from a boom from turning or spinning during operation and thus preventing the twisting of the cables when the load is suspended on a multi-part cable, passing through a block, supporting the load.
It is known to achieve this aim by attaching a springloaded line to the rear of such load to counteract the couple causing spinning or twisting of the hoisting cables. It is known to utilise a spring-driven reel comprising a stationary tubular casing inside which is located a central rotatable shaft, which is in driving engagement with a cable drum or reel on which the line is wound. The stationary casing is attached to the boom or to some other under tension by the spring effecting reverse rotation of the drum when the load is hoisted. It is usual in this type of mechanism to provide a means for automatically disconnecting one end of the spring to protect it from damage by excessive unwinding if the line breaks when the spring is tightly wound. There are several known devices for exercising this protective function.
Instead of employing a helical coiled spring, a flat spiral clock-type spring is sometimes used for tensioning the line, the spiral spring most commonly being housed inside the cable reel.
It has now been appreciated that the tension applied by the spring to the tagline, as it is called, need not be so great when the line is being wound in, as it is when it is being drawn out from its drum. The function of the tagline is to prevent the load from twisting and it Patented Nov. 21, 1967 will readily be seen that any movement of the load in a twisting direction will be accompanied by a movement of the point of attachment of the tagline to the load in a direction away from the tagline drum.
It will therefore be sufficient for the proper functioning of the apparatus if the spring is suificiently strong to draw in the tagline and wind it on the drum without maintaining it under any very great tension, whilst adequate tension to prevent twisting may be applied as a subsidiary braking load to the tagline drum, when the drum is turning in the unwinding direction only.
According to the present invention there is provided a spring-driven reel mechanism having a rotatable reel, a stationary member for attachment to a crane and a coiled spring connecting the reel to the stationary member, characterised by a brake which is effective to apply a greater braking load to the reel when the reel is turning in the unwinding, spring-tensioning direction than when the reel is turning in the winding-in direction. Preferably the associated brake is entirely ineffective to apply a braking load when the reel is turning in the winding-in direction. The preferred method of achieving this result is to employ a permanently engaged brake, one element of which is connected for drive to the reel through a unidirectional clutch, so that the resistance of the brake to rotation is only effective when the uni-directional clutch clutches it to the reel. A pawl-and-ratchet is one well-known simple form of uni-directional clutch for fulfilling this function, but there are many other known forms of such device which can be employed and the device selected will depend upon the physical space available within which to fit it.
An alternative construction employs a brake of known type having the design of the braking parts such that (a) when the drum is rotated in one direction the frictional contact with the friction linings causes a servoaction giving increased braking torque and (b) when the drum is rotated in the opposite direction the servo-action is ineffective and little or no braking ocurs.
Since commercially available uni-directional clutches for transmission of large torques are at present rather expensive, it may be desirable to use an alternative arrangement in the case of large sizes of spring-driven reels. In almost all brakes the force applied to a brake control to hold the brake shoes or band in engagement with the brake drum is only a small proportion of the actual braking torque produced in the brake. Ina modified construction a uni-directional clutch is utilised to actuate a brake control lever or the like when the reel is driven in the unwinding direction so that the brake applies a braking force to the reel.
In a further modification a resilient ring or member grips the shaft of the spring drum so as to turn with it, but at the same time can turn relative to the shaft when 'sufiicient force is applied. The resilient ring has a projectionwhich is trapped between a pair of projections on a stationary member, one of which is a blank stop and the other of which is a limit switch, so that when the shaft is turned in the unwinding direction, the projection on the resilient member depresses the limit switch to initiate the energisation of an electromagnetic brake acting on the reel, the brake being automatically released when the drum shaft direction of rotation is reversed and the limit switch is allowed.
Referring to the accompanying drawings:
FIGURE 1 is a longitudinal section of one form of spring-driven reel constructed in accordance with the pres ent invention;
FIGURE 2 is a part-longitudinal section of an alternative form of construction;
FIGURE 3 is a detail showing a brake load adjuster for use in the construction of FIGURES 1 and 2;
FIGURES 4 and 5 are detail views showing a device for alternatively actuating or releasing an electro-magnetic brake depending upon the direction of rotation of the cable drum shaft;
FIGURE 6 illustrates a brake of a type in which the shoes remain permanently engaged with the brake drum and are adapted to apply a greatly increased braking torque when the cable drum shaft is turned in one direction; and FIG. 7 is a plan view of the brake shown in FIG. 6.
FIGURE 8 illustrates an arrangement for moving a brake control member when the cable drum shaft is turned in one direction; and FIG. 9 shows a plan view of a portion of FIG. 8.
FIGURE 10 is a longitudinal section of a further alternative construction employing a spiral spring for winding in the reel.
In the construction shown in FIGURE 1 the cable drum or reel 1 is carried on a hub 2, which is pinned by a bolt 3 to a shaft 4, which is in turned pinned by a pin 5 to the hollow spring shaft 6. The shaft 6 is rotatably mounted within a stationary casing 7, within which is mounted a large helical torsion spring 8, connected at one end to the shaft 6 and at the other end anchored to the casing 7. The connection between the spring 8 and the shaft 6 is by means of a pin 9, which engages in a ring 10, secured in the end of the shaft 6, the pin 9 being locked in position by a grub screw 11. The ring 10 forms a bearing for the hollow shaft 6 and is supported on a stub shaft 12 mounted in the end of the casing. At its opposite end the spring 8 is anchored to a ring 14, which has a snail cam formation thereon, providing an abutment, which presses against the side of a pin 15, frictionally engaged in the wall of the housing 7, so that the spring 8 automatically disengages from the housing in the event of excessively rapid rotation of the reel 1 if the tagline 1a breaks.
A bearing support member 16 is secured to one end of the casing 7 and hold plain bearing sleeves 17 for the shaft 4. A brake assembly 18 is arranged between the bearing member 16 and the reel 1. The brake assembly is a standard commercial unit and comprises a stationary member 19 and a brake drum 20. Components of the brake assembly are illustrated in FIGURE 3 only and comprise shoes 21 which are pressed outwardly against the drum under constant load, the value of which depends upon the longitudinal tension applied to a control rod 22. The adjustment of the braking load applied by the shoes 21 to the drum may be varied according to requirements by the means illustrated in FIGURE 3. The control rod 22 is pivotally connected to a lever 23, which has a shaped end 24 for engagement with an abutment 25 on the bearing member 16. The force applied to the control rod 22 is derived from a tension spring 26, housed in a housing 27 secured to the main spring housing 7. The spring 26 is connected through a rod 28 to the lever 23 and is anchored to an adjuster rod 29, provided with adjusting nuts 30 and, if desired, a concealed lock nut 31, hidden by the end member 32.
The brake drum 20 is secured to a hub 33, which is rotatably mounted on the shaft 4 and is provided with a bearing sleeve 34. The hub 33 is secured to an outer element 35 of a uni-directional clutch or freewheel, the inner element 36 of which is'secured to the shaft. The uni-directional clutch is only indicated diagrammatically, since its precise construction is not relevant to the invention. A seal 37 is provided to protect the uni-directional clutch.
The conventional uni-directional clutch composed of elements 35, 36 acts as a free-wheel device and is arranged to turn the brake drum 20 only when the cable reel 1 is turned in the direction for drawing cable off the reel, rotation in this direction being accompanied by an increase in tension in the helical torsion spring *8.
4 When the torsion spring 8 drives the reel for the purpose of drawing in tagline 1a and winding item the reel 1, the drum 20 is declutched from the shaft 4.
The alternative construction illustrated in FIGURE 2 also employs a uni-directional clutch between the cable reel 1 and the brake drum 20. Except for this the springdriven reel is essentially the same as in FIGURE 1.
In the construction of FIGURE 2 a ratchet plate 42 is secured to the brake drum 20 and/ or to a modified brake drum hub 43, which is provided with a bush 44. The ratchet plate 42 is engaged by a pawl 45, which is carried on the outer member of a standard rubber torsion bush 46, non-rotatably mounted on a pin 47, secured to the reel 1. The rubber torsion bush acts as a means for resiliently pressing the pawl 45 into engagement with the ratchet plate 42 and also as a means for cushioning shocks arising on the reversal of rotation of the reel from the winding-indirection to the drawing-out direction. The pawl can, of course, be held against the ratchet plate by a conventional spring.
As an alternative to this arrangement the ratchet plate could be secured to the reel 1 and the pawl be mounted on the brake assembly.
The particular advantage of the present invention is that it permits greater restraining force on the grab or like load to be exerted by the tagline for a specified spring size. Alternatively the diameter of the cable reel 1 may be greatly increased without increase of the size of the spring 8 as compared with prior art constructions which relied solely upon the spring tension to apply sufficient tension to the tagline to prevent a grab bucket or other load twisting around on the hoist rope of a crane or like machine.
Whilst in the above described apparatus the reel is wound in by a single spring, which is tensioned as line is drawn oif the reel, it is possible to employ two or more parallel helical springs, each mounted in an individual casing and each connected to an individual shaft. All the individual shafts may be coupled by drive chains or gearing to the reel shaft. In such case the brake may be on 'the reel shaft or brakes may be provided on each of the spring shafts. In either event one part, preferably the drum, is connected to the shaft on which it is mounted through a uni-directional clutch. It is preferred however for the brake to be on the reel shaft. There are a number of other possible variants, but in each case the essential feature is that the brake or brakes operate only when the line is being drawn off the feel and be inoperative when the line is being reeled in by the action of the tensioned spring or springs.
In the arrangement illustrated in FIGURE 4 and 5 the brake drum 20 is the drum of an electromagnetic brake, which is normally unapplied. In this instance the brake drum 20 is fast with the reel 1, being either secured directly to the reel or keyed to the shaft 4. The stationary end plate 19 of the brake carries a microswitch 50 of known construction, which controls the energisation of the electromagnetic brake, and a stop 51.
A spring steel band 52 is mounted in a groove 53 in the 'hub 33 and its ends are connected together, as by a small tension spring 54 or alternatively by a small bolt, so that band 52 clamps lightly on the hub 33, but can slip thereon when its upturned ends 55 are arrested by limit switch 50 or stop 51, depending on the sense of the rotation of the reel 1. p I
It will be understood that if the limit switch 50 is of the normally closed type, the position of the switch 50 and the stop 51 may be reversed so that the upturned end 55 comes into contact with the switch to de-activate the brake when the spring reel commences to wind in the tagline, but this is a relatively unsatisfactory arrangement. In the arrangement illustrated in FIGS. 6 and 7, like parts have applied to them the'same reference numerals as are employed in FIGURE 1. In this construction braking is effected by the interaction of a brake disc 60, bolted to the reel 1, with a plurality of friction elements 61, mounted on wedge-shaped slipper ('62) which are free to slide on inclined caged rollers 63, When the reel 1 rotates in the paying-out direction (shown by arrow A in FIGURE 7) the slipper 62 climb the inclined rollers 63 under the servo action of the friction elements 61 gripping the disc 60. Light pressure springs 64 maintain contact between friction elements 61 and the brake disc 60. When the disc 60 rotates in the opposite direction the frictional engagement between the disc 60 and friction elements 61 moves the slipper 62 down the inclination of the rollers 63 and no appreciable braking action results.
If the arrangement illustrated in FIG. 8, the brake 20 is rigidly attached to the boss 2 of the drum and to sprocket 68 which is connected by chain 69 to sprocket 70 mounted on a freewheel 71 on sleeve 72 which is free to rotate on shaft 73. Sleeve 72 carries a clutch face working in association with friction lining 72 and clutch plate 75 held in contact by spring 76. Clutch plate 75 is free to rotate on shaft 73 and has an extension as shown in FIG. 9, restricting the movement to between two abutments 80, 81 of support member 16.
When drum 1 rotates in the paying-out direction (arrow B in FIG. 9) freewheel 71 connects sprocket 70 rigidly t0 sleeve 72 and through lining 74 rotates plate 75 until it hits one of the abutments on support member 16. This abutment is positioned such that the brake cable 77 attached to plate 75 will have travelled the desired amount to move lever 23 sufiicient to apply the brake. Continued rotation of the reel causes clutch slip to take place between the clutch faces of members 72 and 75. Both ends of the outer casing 78 in which the brake cable 77 slides are anchored to support member 16. When reel 1 rotates in the opposite direction to arrow B the freewheel 71 disconnects the drive to sleeve 72 and the tension on cable 77 is relieved and the brake returns to the OE position.
A further construction of spring driven reel mecha nism in accordance with the present invention is illustrated in FIGURE 10. In this construction the brake and associated parts are constructed as shown in FIG- URE 3, like parts therefore being indicated by the same reference numerals in FIGURE as are utilised in FIG- URE 3.
In this construction the reel 1 is secured to a hub 90 whi h a a u h 1 to e a e t to t m abo t a s 6 tionary shaft 92 held in a flange 93, which may be secured to a suitable part of a crane.
The reel 1 is connected by a flat helical spring 94 to a ring 95 pinned by a pin 96 to the shaft. A uni-directional clutch or freewheel 97 is arranged between the hub 91 and a sleeve 98, to which the brake drum is secured. A hearing 99 is arranged between the sleeve 98 and the hub 92.
1. A spring driven reel mechanism for a line for attachment to a suspended load to prevent twisting, comprising a stationary member, a rotatable reel arranged coaxially with said stationary member, at least coiled spring connected between said reel and said stationary member, one end being drivingly connected to said rotatable reel and the other end being anchored to said stationary member, brake means comprising two relatively rotatable parts, one of said parts carrying friction elements pressed in slipping engagement against the other of said parts under constant load, and uni-directional clutch means coupled between one part of said brake means and one of said reel and said stationary member, the other part of said brake means being secured to the other of said reel and said stationary member, whereby said brake means applies a slipping and constant braking load to said reel upon rotation of said reel in the spring tensioning direction.
2. A spring driven reel mechanism according to claim 1, in which said uni-directional clutch means provides a driving connection between one part of said brake means and said reel when said reel is rotated in the spring tensioning direction.
References Cited UNITED STATES PATENTS 2,382,955 8/1945 Billings 242107.3 2,442,571 6/ 1948 Ruddock 242107.3
FOREIGN PATENTS 927,410 5/ 1955 Germany.
EVON C. BLUNK, Primary Examiner.
ORNSBY; si t xam n