Safety device
United States Patent Kankkunen Apr. 22, 1975 1 1 SAFETY DEVICE [75] lnventor: Kauko Kankkunen, Lake Worth, Pmfmry Spar Fla. Assistant lzxummer-Kenneth Noland Allornqv. Agent. or Firm-John F. Ohlandt [73] Assignee: Sisarakenneteollisuus 0y Sirate AB, Helsinki. Finland Filedl P 1973 A safety device for lowering persons or loads from [211 App] 395,287 high elevations. such device featuring a revolving cylinder which is selectively coupled to a rope drum or wheel when the velocity of the drum is sufficiently [52] US. Cl. 254/158; 254/160; 188/295; great The cylinder is mounted on a Sing|e shaft and 188/305 encloses a centrally located or middle piston which is [51] Int. Cl A62b 1/12 pinned to e cylinder and Serves as a partition to Field of Search 254/l58. 160; 188/27 vide the inner chamber into two portions. The middle 188/305 295; 192/58 A piston is movable rotationally with the cylinder but is immovable axially. Two other pistons within the re- Reierences Cited spective chamber portions are fixed to the immovable UNITED STATES PATENTS shaft but they are movable axially. All of the pistons 1.247.094 11 1917 Petersen &amp; Eibyc 188/305 are Propeller Shaped; that y are contoured to 1,813,069 7 1931 Morgan 188/305 have high a low points; and the inn r end walls of 1.870.871 8/1932 Richard 188/305 the cylinder are correspondingly contoured or shaped. 2.688.385 9/1954 McLaughlin ct al 188/271 3.595.528 7/1971 Virkki 254/158 13 Clams sDl&#39;awlng Flgul&#39;es SAFETY DEVICE BACKGROUND, OBJECTS AND SUMMARY OF THE INVENTION This invention relates to safety devices and more particularly to a device for lowering persons. or loads of one kind of another, from high elevations.  
  The category of safety devices to which the present invention pertains generally includes a rope drum or wheel from which a safety rope. suitably attached to a person or load, is to be discharged. The drum is hydraulically braked so as to bring the load to an extremely small velocity at least by the time the rope has been significantly discharged.  
  As background for an appreciation of the novel principles of the present invention reference may be made to US. Pat. No. 3,595,528 in which a safety device is described. such device being characterized in that a rope drum is arranged to drive. by means of a screw transmission. a piston coacting with a brake cylinder. The drive mechanism of this drive causes the piston to move in the direction of the longitudinal axis of the cylinder. The safety device of this patent is further characterized in that the cylinder is closed and filled with a fluid and that the flow of the fluid from one side of the piston to the other side, when the safety device operates and the piston moves in its cylinder, is very strongly restricted or throttled.  
  Whatever the merits of the safety device described in the aforesaid patent, certain serious drawbacks are presented by designs of the type represented by this patent. in particular, because of the operational principle involved in the drum-cylinder-piston coaction, the length of the cylindrical chamber constitutes a severe limitation on load movement. This is for the reason that substantial braking or deceleration only takes effect when the piston has been moved a substantial axial distance within the cylinder. Accordingly, a high degree of throttling or restriction is only operative over a portion of the total piston displacement. However, even when it does occur, there is rapid movement of the piston within the cylinder. Consequently, there is little room for extension of the rope at the sufficiently low velocity ultimately acquired and the rope will necessarily be abruptly halted in its discharge when the end of the cylindrical chamber is reached by the piston. Therefore, despite the attainment of the desired low velocity. a dangerous state of affairs exists because the sudden jerking effect is likely to result in breaking of the rope.  
  Also accompanying the described deficiency in this particular safety device design is the fact that the rope drum is always being unwound against some resistance. Thus, under normal, or safe, conditions when, for example. a person is working some distance from the point of attachment of the safety device to a building or the like, he must fight some throttling effect because the piston is always working against the tension of the rope.  
  Accordingly, it is a fundamental object of the present invention to overcome the difficulties and drawbacks presented by prior art designs.  
  Another object of the present invention is to remove the limitation imposed by the length of the cylindrical chamber upon the permissible movement of the rope drum under decelerating conditions.  
  Another object is to eliminate the resistance to unwinding of the rope drum by selectively decoupling the rope drum from the brake cylinder.  
  A further object is to enable selective coupling of the drum and brake cylinder only when emergency conditions exist such that a high degree of braking is required.  
  Another major object is to eliminate the use of valves in the brake cylinder forming part of a safety device.  
  Another object is to utilize the maximum braking force that can be developed by the brake cylinder immediately upon coupling of the cylinder to the revolving rope drum.  
  The above and other related objects are fulfilled in accordance with the several features of the present invention.  
  Broadly considered, the primary feature of the invention resides in an arrangement for avoiding the limitation imposed on the permissible extension of the safety rope. This limitation arises from the nature of prior art constructions which involve unidirectional movement of a piston through the length ofa cylindrical chamber. instead, a piston means is moved axially in a reciprocating manner over a comparatively slight distance within a hollow braking cylinder containing hydraulic fluid. The axially movable piston means is provided with an undulating contour defined by a succession of alternating high and low points and is arranged to respond to alternate driving engagement with complementarily contoured surfaces at opposite ends of the chamber defined within the cylinder. The hydraulic fluid in the chamber offers great resistance to being shifted from one side of the piston means to the other side thereof. This high degree of resistance is achieved by reason of the fact that only slight clearances are defined at the peripheral surfaces of the piston means. As a result. the cylinder movement is effectively braked and the rope drum is brought to an acceptably low velocity.  
  A more specific feature of the invention resides in a particular construction of the hydraulic braking device which includes a plurality of reciprocating pistons usually a pair. The pistons are disposed within the aforenoted hollow cylinder, which is selectively connectable to the rope drum so as to revolve therewith. A disk is located midway longitudinally within the chamber defined by the hollow cylinder, and serves as a partition to divide the chamber into two portions. This disk is pinned to the cylinder for rotational movement therewith, being immovable axially; and the two pistons are disposed respectively in said two chamber portions in relationship to a shaft so as to be immovable rotationally but movable axially on said shaft.  
  A further more specific feature of the present invention resides in the particular configurations for the surfaces or faces of the disk and the several pistons, and also for the corresponding end walls of the cylinder. The disk and the pistons are each propeller-shaped. that is, they are provided with an undulating contour made up of alternating low and high points on each of their faces; similarly the inner end walls of the cylinder are correspondingly contoured or shaped.  
  Other objects, features. and advantages of the present invention will become apparent from the following detailed description in conjunction with the accompanying drawing.  
 BRIEF DESCRIPTION OF DRAWING FIG. 1 is a sectional view taken through the center of the safety device of the present invention.  
  FIG. 2 is a sectional view. particularly illustrating a ratchet-pawl locking mechanism. such viewing being taken on the line 22 of FIG. 1.  
  FIG. 3 is an exploded sectional view of the braking device in accordance with the present invention. particularly illustrating the three pistons involved. as well as the cylinder portions.  
  FIG. 4 is an elevation view taken from the plane 44 in FIG. 3.  
  FIG. 5 is an elevation view of the left piston taken from the plane 5-5.  
  FIG. 6 is an elevation view of the middle piston taken from the plane 66.  
  FIG. 7 is an elevation view of the right piston taken from the plane 77.  
  FIG. 8 is an elevation view of the right cylinder portion taken from the plane 88.  
 DESCRIPTION OF PREFERRED EMBODIMENT Referring now to FIGS. 1-8 of the drawing. there will be seen illustrated a safety device 10 which includes a housing I2 consisting of two parts in the form of covers 12A and 12B. The essential operating components or elements comprise a revolvable rope wheel or drum 14 which is adapted to revolve about a shaft 16 in either a counterclockwise direction. as seen in FIG. 2., so as to discharge a rope 17 or oppositely. that is. clockwise. in order to retract such rope.  
  The shaft 16 is divided into a number of sections for purposes to be explained hereinafter. such sections being of different radial dimensions and of different cross sectional shapes. The largest section is section 16A which is hexagonal in cross section. Sections 168. to the left and right of section 16A. are circular in cross section. while sections 16C are square in cross section. Sections 16D are circular in cross section and are suitably threaded for engagement by the nuts 18 provided at either end of the shaft.  
  A hydraulic braking device 20 seen in FIG. I. is adapted to be selectively connected or coupled to the drum I4 by a locking device 22 (FIG. 2). to be described later. The hydraulic braking device includes a cylinder 21 divided into two parts 21A and 21B, these two parts being coupled together by means of the coupling element 24 which is seen in threaded engagement with part 218. The brake cylinder 21 is enabled to rotate about the shaft I6 by reason of the bearings 26 disposed about the shaft sections l6B. these bearings including O-ring seals 28. A ball bearing device 30 is provided for the journaling of the drum 14.  
  Within cylinder 21, which is filled with oil or other suitable fluid. there are situated a disk 40 and a pair of pistons 42 and 44. These elements are variably spaced from each other. during the braking operation. within the chamber defined by the hollow cylinder. as will be explained hereinafter.  
  It will be noted that the axially movable piston 42 is enclosed within the chamber portion 46A. whereas the axially movable piston 44 is enclosed within the chamber portion 468. The disk 40 is pinned to the cylinder 21 by means of pins 50 which extend into. and are retained in. grooves 52A provided in the cylinder part 21A. grooves 528 provided in the cylinder part 21B.  
  and also in grooves 54 provided at the periphery of the piston 40. A flange 56 is also provided at the periphery of the piston 40 in order to prevent axial movement of the piston. such flange being adapted to fit into the ap- 5 propriately located channel 58 in the peripheral wall of the cylinder 21.  
  It will be understood that the rope drum 14 carries the locking mechanism 22. such mechanism comprising a pair of arcuate members 60 which are pivotable about suitable shafts and are secured by nuts 62. Each of the members 60 is provided at one end with a pawl 64 adapted to engage with a ratchet 66 forming an integral part of the cylinder 21. The other ends of the members 60 are spring-biased by means of the springs 66.  
  A more or less conventional spiral spring 70 is utilized to urge the drum 14 in the direction to keep the rope taut; also. to retract the rope after it has been discharged and the load has been removed. The spring is attached at the section 16B of the shaft 16 by the screw 48 which is received in a suitable bore in the shaft; the spring 70 is fastened at its other end to the outstanding fixer 71 on the drum.  
  The rope 17 is paid out or discharged as it is unwound from the drum 14 by way of the opening defined by the grommet or bushing 70. The other end of the rope is fixedly secured to the drum by a suitable shaft &#39;72 around which the rope is looped and then secured by connector 74.  
  For an appreciation of the primary aspects of the present invention as these are embodied in the hydraulic braking device. reference is now made to FIGS. 3-8 in which a variety of view of the braking device 20 are provided. It will be seen that the braking cylinder 21 includes a pair of covers or end plates 80 and 82 for the cylinder parts 21A and 218 respectively. These cover plates are adapted to fit around the bearings 26 for rotational movement or revolving of the cylinder 21 around the shaft i6. As has been previously noted, the peripheral wall of the cylinder part 218 includes an outwardly projecting ratchet 66. It will be especially noted that the internal surface of each of the cover plates 80 and 82 is provided with an undulating contour such that it has alternating high and low points and that the respective surfaces 80A and 80B of these cover plates are displaced in phase by 60. Thus the essential contouring is the same in both instances; however. the orientation is especially adapted to achieve certain effects to be described.  
  It will be understood that the alignment of all of the parts shown in FIG. 3 on the shaft 16 is such that the phase relationships. depicted by FIGS. 4-8 are estab-&#39; lished. However. it is to be observed that certain of the figures. for example FIGS. 5 and 6, depict opposed faces on the respective piston 42 and disk 40, whereas FIGS. 6 and 7 depict like faces on the respective disk 40 and piston 44. The opposed faces on a given disk or piston are of course complementary, that is to say. a low point depicted at a certain location on one face of a given piston corresponds with a high point at the same location on the other face of the same piston.  
  It will be apparent that. because of the hexagonal openings 42A and 44A in the respective pistons 42 and 44, these pistons are fitted exactly to the hexagonal portion 16A. of the shaft l6; consequently. they are incapable of rotating about the axis of the shaft. On the other hand. disk 40 is fitted to the shaft by means of a bushing 84 which is designed to have an inner hexagonal opening so that it will exactly fit the shaft portion 16A. but it has a circular outer periphery. whereby the disk 40, which has a circular opening is able to rotate about the shaft 16. The cusp-shaped recesses 86 immediately adjacent the openings 42A and 44A in the respective pistons 42 and 44 are spaced so as to correspond with the location of the high points on the surfaces of those pistons (which appear in FIGS. 5 and 7). These recesses permit clearance for the bushing 84 so that the complementarily contoured surfaces of the disk 40 and the respective pistons 42 and 44 can entirely abut so that the disk 40 becomes nested with each piston at different points in its rotational movement.  
 OPERATION The device of the present invention is intended to be used by persons operating at great heights. for example in working on tall buildings or the like. For such purposes. the device 10 is preferably attached by means of the ring 90, to a receptacle permanently fixed to the building. The end of the rope l7 emerging from the lower part of the device 10 is intended to be attached. for example by means of the hook 92. shown in phantom outline in FIG. 2, to the workers safety belt or other equipment.  
  In the normal operation of the safety device. which takes place in the course of the workers duties on a building or the like. he will be able to move freely since only slight tension will be produced by the spring 70 in urging retraction of the rope 17. At this time. obviously. there is no coupling or connection between the drum l4 and the braking device 70. However. should the worker slip and lose his footing such that the drum 14 moves at a sufficiently great velocity. such as. for example. greater than 1.5 meters per second. the result will be that the arcuate members 60 will be moved due to centrifugal force against the spring bias such that the pawls 64 will move inwardly and engage with the ratchet members 66. thereby causing the cylinder 21 to revolve about the stationary shaft 16. Since the disk or partition is pinned to the cylinder 21 it will likewise revolve about the shaft.  
  Rotational movement of the cylinder 21 and of the disk or partition 40 results in reciprocating movement along the axis of the shaft 16 for each of the pistons 42 and 44. Taking piston 42 as an example. it will be appreciated from FIGS. 3-8 that the arrangement and the spacing allowed between parts is such within the chamber of the cylinder 21 that the right face of piston 42 is l either completely abutting or contacting the adjacent. complementarily undulating surface of the disk 40 i.e. its left face. which is also complementary to the contour of the end wall 82A. or (2) the left face of piston 42 is completely contacting that end wall or (3) the piston 42 is at an intermediate point along the axis. This is for the reason that when disk 40 begins to rotate such that high points on its left side or face begin to move into driving engagement with corresponding high points on the right face of the rotationally immovable piston 42, the piston 42 will be forced to move to the left. Because of the complementary contour of the left face ofpiston 42, it will eventually nest with the interior surface 82A of the end wall 82. Once this nesting occurs with the surface 82A. it will be apparent that degrees later. the movement of high points on the surface 82A will cause movement of piston 42 in the opposite axial direction; that is. the left face of piston 42 will be drivingly engaged such that eventually the original condition will again obtain.  
  Essentially the same kind of reciprocating action occurs for the piston 44 except there is a 30 degree phase 5 difference between the forceful engagement of the left surface of disk 40 with the high points on piston 42 and the forceful engagement of the right surface of disk 40 with corresponding high points on the piston 44. This will be readily understood when it is taken into consideration that HO. 6 depicts the left face of disk 40 and that the opposite face of this disk possesses complementary symmetry.  
  It will be apparent from the preceding description that the basic objective of the present invention has been accomplished; that is. there has been removed the limitation formerly imposed by the length of the cylinder chamber upon the permissible movement of a safety device rope drum under decelerating conditions. The unique design of the piston means insures that there will be a high degree of resistance to the shifting of the hydraulic fluid from one side of the piston means to the other. whereby extremely effective braking action is realized. Moreover. a very smooth descent of the person or load under decelerating conditions is effectuated in the specific embodiment illustrated because the braking cylinder is divided into two separate portions and the braking action individually produced in each of the two chambers is separated by a predetermined phase angle so that any tendency towards jerking movement is avoided. As specifically mentioned previously. hydraulic oil is the preferred fluid; however a variety of fluids can quite clearly be utilized.  
  While there has been shown and described what is considered at present to be the preferred embodiment of the present invention. it will be appreciated by those skilled in the art that various modifications may be made. Accordingly. it is desired that the invention not be limited to this embodiment and it is intended to cover in the appended claims all such modifications as fall within the true spirit and scope of the invention.  
 What is claimed is:  
 1. The combination comprising:  
 1. a hollow cylinder containing fluid. said cylinder having end walls with undulating surfaces defined by alternating high and low points;  
 2. a disk located midway longitudinally within the chamber defined by said hollow cylinder. said disk serving as a partition to divide said chamber into two portions. a piston means comprising at least two axially movable pistons disposed respectively in said two chamber portions. each of said axially movable pistons having undulating end faces defined by alternating high and low points and each piston being reciprocally movable along the shaft axis responsive to alternate driving engagement with complementarily undulating surfaces at a respective disk face and at a respective opposing surface at one of the end walls of said cylinder.  
 3. means for producing relative rotational movement between said piston means and said cylinder such that alternate driving engagement is established between the end faces on said piston means and on said respective end walls;  
 4. a shaft;  
 5. a housing in which said shaft is held against rotation;  
 6. a drum revolvable about said shaft;  
 &#39; 7 7. a hydraulic braking device. formed by the aforesaid hollow cylinder. said device being selectively connectable to said drum so as to revolve therewith.  
  2. A safety device as defined in claim 1. in which said disk is secured to said cylinder for rotational movement therewith. said disk being immovable axially.  
  3. A safety device as defined in claim 1, in which said two pistons are fixed to said shaft against rotational movement.  
  4. A safety device as defined in claim 1. further including means for selectively connecting said drum and said cylinder so that the two revolve together.  
  5. A safety device as defined in claim 1. in which said previously recited disk and pistons are propellershaped.  
  6. A safety device as defined in claim 5. in which each of said disk and pistons is shaped so as to have high and low points on each of its end faces. said faces having complementary symmetry; and in which opposed faces of said disk and an adjacent piston have complementary symmetry.  
 7. A device as defined in claim 6. further including cover plates for the ends of said cylinder, said cover plates including surfaces with complementary high and low points with respect to the opposed faces of adjacent pistons.  
  8. A safety device as defined in claim 1, in which a fluid fills the entire chamber defined by said hollow eyl&#39; inder.  
  9. A safety device as defined in claim 8. in which said fluid is a liquid.  
  10. A safety device as defined in claim 9, in which said liquid is oil.  
  11. A safety device as defined in claim 1. in which each of said axially movable pistons is reciprocally moved in response to alternating driving engagement with a respective end wall of the cylinder and said disk when said cylinder is caused to revolve.  
  12. A safety device as defined in claim 11 in which said alternating engagement occurs at a 60 rotational phase difference.  
  13. A safety device as defined in claim 10 in which said disk drivingly engages the two axially movable pistons at a 30 rotational phase difference.