Description:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to an escape device adapted to engage a rope frictionally, the device supporting a person descending the rope.
2. Prior Art
Escape devices adapted to engage a rope and to support a person escaping are known. Often these devices utilize friction braking means driven by rollers in engagement with the rope, braking being controlled by the person escaping. Sometimes in the confusion of escaping he lets go of the brake and is subsequently injured or killed due to a too rapid descent down the rope. Unconscious or otherwise incapacitated persons cannot use these devices as the brakes are operated by the person escaping.
SUMMARY OF THE INVENTION
The invention reduces difficulties above by providing an escape device that has an automatic brake that can be set at a particular rate of descent between a maximum and minimum speed. An additional manually operable brake can be included to stop the descent. The device can be set to lower an unconscious person, or a person otherwise incapacitated. Compensation is provided for weight differences of persons using the device.
One embodiment of the device includes a frame that journals a first series of rollers for rotation on a plane containing the rope, the rollers being aligned in spaced relationship on one side of the rope, each roller having a groove to accept the rope. A second roller or series of rollers, journalled for rotation in the plane containing the rope, are provided on a side of the rope remote from the first series of rollers and are staggered between the rollers so as to urge the rope into frictional engagement with the first rollers. The rollers are synchronized so as to have equal peripheral speeds, thus reducing a tendency of the rope to slip on the rollers. The rollers are coupled to a centrifugal brake having a braking disc, the disc being rotated by the rollers and being axially slidable to contact a brake block complementary to the disc. By selection of gearing between the rollers and the centrifugal brake, a relatively light braking force on the braking disc can support a relatively heavy person hanging from the device. A tensioning means maintains sufficient tension in the rope to remove kinks. Total arc of contact of the rope on the grooved rollers maintained by the complementary means produces negligible rope slippage in the rollers when the rollers are braked so that a controlled descent of the rope is attained.
A detailed description following, related to drawings, gives exemplification of apparatus according to the invention which apparatus, however, is capable of expression in structure other than that particularly described and illustrated.
DESCRIPTION OF THE DRAWINGS
FIG. 1 is a small scale diagram showing a person using an escape device according to the invention,
FIG. 2 is a front elevation of the device, showing a harness attached,
FIG. 3 is a front elevation, partially diagrammatic, similar to FIG. 2, the harness and some portions being removed to show interior construction,
FIG. 4 is a simplified section on 4--4 of FIG. 3, some portions being omitted, and some not being shown sectioned,
FIG. 5 is a simplified section on 5--5 of FIG. 3, some portions being omitted,
FIG. 6 is a simplified section on 6--6 of FIG. 3, some portions being omitted,
FIG. 7 is a simplified section on 7--7 of FIG. 3, some portions being omitted,
FIG. 8 is a simplified section on 8--8 of FIG. 3, some portions being omitted,
FIG. 9 is a simplified fragmented section of a portion of the device showing a centrifugal braking mechanism, some portions not shown in section,
FIG. 10 is a simplified section on 10--10 of FIG. 9, some parts omitted,
FIG. 11 is a simplified, fragmented section of a hand brake actuation mechanism,
FIG. 12 is a simplified section of rope tensioning rollers,
FIG. 13 is a simplified section of an alternative simplified escape device.
DETAILED DISCLOSURE
Figs. 1 and 2
A person 10 escaping from a building 11 is shown descending a rope 12, for example a braided steel rope. The rope passes through an escape device 13 according to the invention, the device having a harness to carry the person, FIG. 2. The rope extends to a low end, two or three feet above the ground 14, a weight 15 hanging from the end tensions the rope to remove kinks in the rope.
With reference to FIG. 2, the device 13 has a structural frame (not shown) within a housing 17, the housing having left hand and right hand side walls 18 and 19, a rear wall 20 (see FIGS. 3 and 4), a front wall 21, and top and bottom walls 22 and 23. A harness 24 adapted to carry the person in a slightly inclined upright position as seen in FIG. 1, has main straps 25.1, 25.2 secured to releasable fasteners 26.1, 26.2 on the bottom wall 23. The straps 25.1, 25.2 are secured to a circumferential strap 27, ends of which are joined by a buckle 28. Loops at lower ends of the straps 25.1, 25.2 accept thighs of the person escaping, the strap 27 passing around the chest. Other harnesses are known and can be substituted.
A central longitudinal plane 29, appearing as a central axis in FIG. 2, bisects front rear top and bottom walls producing two halves of the housing. Each housing half has a corresponding divided wall, for example, the rear wall 20 has right and left divided walls 20.1 and 20.2 (FIG. 3), the front wall 21 has divided walls 21.1 and 21.2, the top wall 22 has divided walls 22.1 and 22.2, and similarly the bottom wall 23 has divided walls 23.1 and 23.2.
The rear divided walls 20.1 and 20.2 are hinged at 30 to permit the two halves of the housing to open or close, to permit easy engagement of the rope for threading. A latch 32 on the front wall holds the two halves together when the rope has been threaded as will be described. A hand wheel 34 extending from the side wall 18 provides a means of adjusting rate of descent to a particular speed, as is later described with reference to FIG. 9. A hand-operated brake has a handle 36 used to stop descent.
Figs. 3 and 4
With reference to FIG. 3, the rope 12 passes through a slot 42 between the divided walls and the top wall 22, and through a slot 43 between the divided walls of the bottom wall 23. The rope passes freely through the slot 42, peripheral rollers 41 being provided for the rope to run on. The slot 43 has a tensioning roller assembly 44 straddling the rope, described with reference to FIG. 12.
Two series of grooved rollers engage the rope as shown, the rope passing between each series of rollers in a generally sinusoidal path. Hereinafter, and in the claims, vertical, left and right hand sides are as viewed in FIG. 3. Rollers on the left hand side of the rope are designated severally 45, and rollers on the right hand side are designated severally 46. The grooved rollers are journalled for rotation in a common plane, and are aligned in spaced vertical relationship on opposite sides of the rope, centre-to-centre distance measured normal to the plane 29 being designated 47 in FIG. 3, hereinafter roller row spacing. The grooved rollers are staggered as shown and are described in more detail with reference to FIGS. 6, 7, and 8.
The grooved rollers 45 and 46 have integral gear teeth which mesh with synchronizing gears 48 and 49 respectively, the gears meshing with and synchronizing adjacent grooved rollers so as to equalize surface speeds of grooves of adjacent rollers. The left hand side train of gears and rollers has a coupling roller 51 and the right hand side train has a coupling roller 52, peripheries of the rollers being engaged frictionally, so as to interconnect the left hand side train with the right hand side train, the coupling rollers serving as synchronizing means. Thus, peripheral groove speeds of the rollers 45 and 46 are equalized to reduce a tendency of the rope to slip on the rollers. The grooves are also surfaced with a material that has a high coefficient of friction when in contact with the rope 12, one example of such material being leather. Hereinafter, peripheral groove speed refers to mean tangential speed of the groove in contact with the rope. Gear ratios and relative diameters of grooves are selected as to maintain essentially equal peripheral groove speeds for all rollers in contact with the rope, thus tendency of the rope to slip on the rollers is reduced.
A plurality of brake shoes 54 of a hand brake 55 are adapted to engage braking surfaces of the gears 49, described with reference to FIGS. 7, 8, and 11. The brake shoes 54 are secured to and operated by a sliding brake rod 56 (FIG. 11), the rod being connected to the handle 36 which is used to operate the hand brake. Braking as above slows or stops rotation of the rollers 46, which, through the gears and coupling rollers, slows or stops the rotation of all the rollers, slowing or stopping motion of the device 13 relative to the rope.
A manually adjustable centrifugal brake 58 is provided at an upper end of the left hand side train of gears and rollers. The brake 58 is coupled to an adjacent grooved roller 45 by an idler gear 60 and a synchronizing gear 48. The brake is adjustable to a particular speed of descent by the hand wheel 34 and is later described with reference to FIG. 9.
A central concept of the invention is to maintain a relatively large arc of contact of the rope with the grooved roller, whilst providing a device that is relatively compact and easy to thread. The arc of contact of the rope with a particular roller 45 is designated 61, about ninety degrees. The total arc of contact for all the grooved rollers 45 is ninety degrees times the number of rollers. The total arc of contact of the grooved rollers 46 is similarily calculated. Thus, total arc of contact of the rope is proportional to the sum of the total arcs of contact. The relationship between the arc of contact and tensions on either side of a pulley is well known in the art of belt drives, and is expressed in the equation
log e (T 1 /T 2 ) = μ θ
where T 1 and T 2 are tensions in the belt on either side of a pulley, μ is the coefficient of friction and θ is the arc of contact expressed in radians.
Other factors being constant, the greater the total arc of contact, the greater the work that can be absorbed from the rope without slippage between the rope and rollers. Arc of contact can be increased by one or both of two approaches. A first approach is to decrease the roller row spacing by increasing centre-to-centre distance between the rollers measured parallel to the axis, i.e. vertical spacing of rollers, thus permitting the rows of rollers 45 and 46 to move closer towards the longitudinal axis. The second approach is to increase the number of rollers. The two series of rollers are thus complementary to each other, serving to increase arc of contact. When considering the series of rollers 46, the rollers 45 are complementary means journalled for rotation within a common plane containing the rope and the rollers 46.
Closeness of rollers and vertical spacing of roller row spacing determines ease of closing the housing after threading the rope between the grooved rollers. Clearly, a stiff steel rope resists bending and difficulty can be experienced in bending the rope to close conformity with grooved rollers, which rollers have a diameter of about two inches.
Flexible braided steel rope of about 2,000 pounds ultimate tensile strength is used for the rope 12 and is relatively easy to handle and has resistance to fire damage.
Figs. 5, 6, 7, and 8
Referring to FIG. 5, the centrifugal brake 58 rotates in a direction shown by an arrow 65. The brake can be adjusted, during descent if required, by the hand wheel 34 to attain a descent speed of between four and eight feet per second. The hand brake 55 (not shown in FIG. 5), controlled by the handle 36, is actuated to stop the escaper near the ground, and is not generally used during the descent.
Referring to FIG. 6, one grooved roller 46 of the right hand side train is journalled on a spindle 67, has an annular groove 68 in engagement with the rope 12, and has gear teeth 70 meshing with adjacent synchronizing gears 49 (not shown).
Referring to FIG. 7, the coupling roller 51 is journalled on a spindle 71, and has a groove 72 to accept the rope 12, and gear teeth 73 meshing with adjacent synchronizing gears 48 (not shown). The roller 51 has a tire 75 in frictional engagement with a corresponding tire of the roller 52, shown in FIG. 8. The gear teeth 73 mesh with the adjacent gears (not shown). The synchronizing gear 49, journalled for rotation on a spindle 77, is provided with a cylindrical braking surface 78 adapted to be engaged by the brake shoes 54, so as to slow rotation of the gear 49 so as to slow rotation of the grooved rollers 45 and 46. The braking surface can be provided on the grooved rollers instead of on the synchronzing gears. Position of the braking surface is immaterial provided that it is effectively coupled to the grooved rollers such that speed of rotation of braking surface is proportional to descent speed.
As seen in FIG. 8, the rope 12 is held in grooves 72 and 79 of the rollers 51 and 52. The tires 75 and 76 are in frictional engagement, synchronizing each train of rollers and gears.
Figs. 9 and 10
The centrifugal brake 58 is driven by gearing 81 (broken outline), which is driven by the idler 60 (broken outline). The gearing 81 drives a first shaft 83, a lower end 84 of which is journalled for rotation in a bearing 85, which bearing restricts the downward movement of the shaft 83. The gearing 81 is any suitable known gearing that provides a step-up velocity ratio from the idler 60 to the shaft 83. The gearing can be worm and worm wheel, bevel or any other type that has a sufficient velocity ratio to produce a rotational speed as later described.
The shaft 83 is aligned with a second shaft 88, which shaft has a bore 89 at a lower end to accept the shaft 83 in a sliding fit, forming a telescoping drive shaft 87. An upper end of the shaft 88 is journalled in a bearing 91, which bearing permits vertical sliding movement of the shaft 88. Radial pins 90 extend outwards from the shaft 83 and engage longitudinal slots 93 in the shaft 88, permitting longitudinal sliding motion of the shaft 88 relative to the shaft 83, whilst preventing relative rotation of the shafts.
Centrifugal fly weights 94 and 95 are secured to flexible spring strips 96 and 97, upper ends of which strips are secured to the shaft 88, and lower ends are secured to the shaft 83. Rotation of the shaft 83 causes the fly weights 94 and 95 to move outwards, the shaft 88 being pulled downwards relative to the shaft 83 due to outward movement of the strips 96 and 97. Pinned links or other members can be substituted for the flexible strips.
A braking disc 92 is secured to the shaft 88, a lower surface 98 of the disc serving as a braking surface. The hand wheel 34 is secured to a shaft 99 journalled in the side wall 18. An inner end of the shaft 99 has a cylindrical lobe 101 mounted eccentrically relative to the shaft, as a cam.
With reference to FIG. 10 a brake block 102 serving as a complementary braking member is provided at an outer end of an arm 103, an inner end 104 of the arm being hinged to a portion of the rear wall 20.1 permitting rotation of the arm. An upper surface 105 of the brake block 102 serves as a complementary brake surface and is adapted to contact the lower surface 98 of the disc. The block 102 has a bore which accepts the lob 101 in a sliding fit. Rotation of the shaft 99 by the wheel 34 moves the surface 105 upwards or downwards, which determines the position of the disc at which braking commences, which position limits downward movement of the disc.
When the upper surface 105 is separated from the surface 98, acceleration down the rope increases speed of rotation of the shaft 88, the centrifugal weights moving outwards and forcing the disc downward until the surface 98 contacts the upper surface 105. Braking of the disc occurs, which braking slows rotation of the grooved rollers 45 and 46, thus reducing speed of descent, which reduction in speed slows the shaft 88, permitting the fly weights to move inward, easing brake pressure between the brake and the surface 98, thus increasing speed of descent. Successive damped oscillations of speed of descent about an average speed of descent rapidly diminish, permitting attainment of a steady speed. Rotation of the hand wheel 34 such that the upper surface 105 attains a second position further remote from the surface 98, permits attainment of a higher rmp before contact of the disc with the brake surface.
Thus the centrifugal brake is a brake responsive to speed of descent down the rope, and can be set to operate between maximum and minimum descent speeds. Additional parameters which determine speed of descent include rope stiffness, rope hysteresis loss, rope tension, energy losses due to friction in the gear train, and weight of person descending. A scale (not shown) can be provided on the hand wheel 34 to be read in conjunction with a pointer (not shown), the scale being calibrated to a person's weight and desired speed of descent, so that, prior to starting the descent, compensation for weight can be made.
A further central concept of the invention is thus use of a relatively small braking force on the brake disc to control a relatively large force suspended from the device. Such control is attained by a mechanical advantage arising from the gearing between the grooved rollers 45 and 46 and the braking disc 92. For a descent speed of four to eight feet per second, the disc 92 is geared to rotate at a speed of between 1,500 and 3,000 rpm. The frictional losses in the gear train, particularly at the gearing 81 if a worm and worm wheel is used, account for a proportion of the energy to be absorbed, remainder being absorbed at the brake.
Fig. 11
a portion of the hand brake 55 is shown, in which the brake rod 56 is slidably mounted in a bracket 112, the bracket having an elongated slot 113 to accept the rod 56, and to permit limited lateral movement of the rod. The bracket 112 extends from the side wall 19 at a position adjacent each synchronizing gear 49 so as to provide support for the rod 56 against excessive movement. The brake shoe 54 engages the braking surface 78 of the gear 49 and is secured to the rod 56 by an arm 116. A cam 118, secured to the rod 56, is in engagement with a roller 119 journalled on a bracket 120, the bracket 120 being secured to the side wall 19. The cam 118 has a working surface 121 inclined to the rod at such an angle as to move the brake shoe 54 essentially radially against the braking surface of the gear 49 when the rod 56 is moved in a direction shown by an arrow 125. Thus the roller 119 serves as a cam follower secured relative to the frame, the cam working surface moving in response to movement of the rod 56. A tension spring 122 extends between the rod 56 and the side wall 19, providing a force generally in the direction of an arrow 123, tending to release the brake shoe 54 from engagement with the braking surface 78. Thus the spring 122 has an axis essentially parallel to the working surface of the cam 118.
Fig. 12
the rope 12 passes through the slot 43 between the divided walls 23.1 and 23.2 as previously described. The tensioning roller assembly 44 straddles the rope 12 as shown, and has rollers 130 and 131 made from a hard resilient substance. The rollers are journalled at upper ends of spring-urged arms 133 and 134, lower ends of the arms being secured to the divided walls 23.1 and 23.2. The rollers are urged inwards and downwards so as to squeeze the rope as it passes upwards in a direction shown by an arrow 136. The rollers are mounted so as to tend to swing away from the rope as the device descends, thus applying a limited tension. Thus the rollers are not adapted to grip the rope tighter as the rope runs in direction of the arrow 136 -- this is in contrast to a wedge-action device. The rollers serve as tensioning means, being sufficient to apply a relatively low tension on the rope so as to tend to straighten a portion of the rope prior to that portion passing through the device. Such tensioning reduces a tendency to slippage of the rope on the grooved rollers.
ALTERNATIVES AND EQUIVALENTS
Other means of rope tensioning are known, such as a second person pulling the rope at the lower end, or use of the relatively light weight 15 on the lower end of the rope, as shown in FIG. 1. If the tensioning rollers are provided and the rope extends freely downwards, its own weight can provide sufficient tension thus eliminating the weight 15. However, with such a rope as the low end of the rope is approached, tension is reduced and speed of descent tends to increase. If the tensioning rollers are not provided then, use of light ropes may not provide sufficient tension without the weight 15.
With reference to FIG. 3, the left hand and right hand trains of rollers and gears are synchronized by the coupling rollers 51 and 52. Other means of synchronization are known, such as a duplicate centrifugal brake for the right hand side similar to the brake 58. When two centrifugal brakes are used, both brakes are actuated together to ensure essentially equal braking on each side to reduce differences in peripheral speeds on either side of the rope. Hereinafter such means to ensure essentially equal braking on each side is referred to as means to attain synchronized braking of the rollers.
If one train of gears only is braked, e.g. by elimination of the coupling rollers 51 and 52, braking effectiveness is reduced. Also, the hand brake 55 can be eliminated if the rate of descent is sufficiently slow to ensure safe landing when the device is controlled only by the centrifugal brake. Elimination of the hand brake prevents a panic stricken person from locking the device on the rope, as the centrifugal brake cannot be set below a minimum rate of descent. Simple stop means (not shown) can be provided to make the hand brake inoperative.
Other types of descent speed responsive brakes can be used, such as a centrifugal brake in which weights on bellcranks move radially outwards as speed increases, extending a rotating braking disc against a stationary complementary braking component. Also the braking surface 78 for the brake shoes can be provided on the grooved roller, instead of on the synchronizing gears 49. In either case the braking surface rotates with or is coupled to the grooved rollers.
Fig. 13
an alternative simplified device 140 is provided with fewer grooved rollers to produce a more compact device, three rollers being a minimum.
The alternative device 140 has a housing 141, having a longitudinal central plane 142. The rope 12 passes through slots 144 and 145 and follows a curved path (as shown). The left hand side of the casing has a grooved roller 147, journalled for rotation and staggered between similar grooved rollers 148 and 149 on the right hand side of the case. The roller 147 has a tire 146 adapted to mesh with a tire 150 of the roller 149, thus synchronizing peripheral speeds of both rollers and serving as a complementary means journalled for rotation within a common plane containing the rope and the rollers 148 and 149. The rollers 148 and 149 have gear teeth meshing with a synchronizing gear 151. The gear 151 has a braking surface similar to the surface 78 of the gear 49, and is braked by a hand-operated brake 153 similar to the brake 55 (see FIG. 11). A centrifugal brake 154 is coupled to the gear of the grooved roller 148 through an idler gear 156, the centrifugal brake having a telescoping drive shaft 157 and a disc 158. A hand wheel 160 controls a lobe 161, similar to the brake 58 of FIG. 9. A similar disc 163 and a lobe 162 is preset before use and can be used to apply extra braking if required, setting a maximum speed of descent. Operation of the centrifugal brake 154 is similar to that of the brake 58, being a braking means responsive to speed of descent.
It should be noted that compared to the device 13, (FIG. 3 etc.) fewer grooved rollers are used in the device 140. This reduces total arc of contact of the rope on the rollers which, other factors being equal, increases tendency of the rope to slip on the grooved rollers. Thus, it may be preferable to use a stiffer rope with the alternative device, or to use a tensioning means which applies a greater tension. Alternatively, the device should be limited to use by relatively light persons only, thus requiring less braking effort.
The grooved roller 147 serves as a complementary means to urge the rope against the synchronized rollers 148 and 149, all three rollers being simultaneously braked because of coupling between, and synchronization of, the rollers. Other means complementary to the grooved rollers and adapted to urge the rope onto the grooved rollers can be substituted. As with the device 13, the hand brake 153 can be eliminated if, with the centrifugal brake alone, speed of descent is sufficiently slow.
OPERATION
To descend a rope hanging generally vertically under tension, the person opens the device by unhooking the latch 32 and engages between the rollers a portion of the rope approximately level with himself. He then closes the device with the latch, ensuring that the rope is guided cleanly through the slots and is aligned with the grooves of the roller. The rope is clamped between adjacent opposing pairs of grooved rollers, being in effect threaded in a sinusoidal passage existing between the rollers, thus locking the device onto the rope. The person then climbs into the harness, adjusting where necessary to obtain a good fit, as in a parachute harness. He takes the hand brake handle 36 in one hand, but does not actuate it unless he is required to stop. He steps off into space and is carried by the harness which hangs below the device as seen in FIG. 1. Speed of descent down the rope is increased or decreased between limits by adjusting the handwheel 34 of the centrifugal brake. Near the ground the hand brake 55 is applied to stop the descent.
When the person escaping reaches the ground, he unclips from the harness, disengages the device from the rope, and leaves the rope for others escaping using additional escape devices.