U.S. patent number 3,879,016 [Application Number 05/395,287] was granted by the patent office on 1975-04-22 for safety device.
This patent grant is currently assigned to Sisarakenneteollisuus Oy Sirate AB. Invention is credited to Kauko Kankkunen.
United States Patent |
3,879,016 |
Kankkunen |
April 22, 1975 |
Safety device
Abstract
A safety device for lowering persons or loads from 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 great. The cylinder is mounted on a single
shaft and encloses a centrally located or middle piston which is
pinned to the cylinder and serves as a partition to divide the
inner chamber into two portions. The middle piston is movable
rotationally with the cylinder but is immovable axially. Two other
pistons within the respective chamber portions are fixed to the
immovable shaft but they are movable axially. All of the pistons
are propeller shaped; that is, they are contoured to have high and
low points; and the inner end walls of the cylinder are
correspondingly contoured or shaped.
Inventors: |
Kankkunen; Kauko (Lake Worth,
FL) |
Assignee: |
Sisarakenneteollisuus Oy Sirate
AB (Helsinki, SF)
|
Family
ID: |
23562427 |
Appl.
No.: |
05/395,287 |
Filed: |
September 7, 1973 |
Current U.S.
Class: |
242/396; 188/295;
254/267; 182/238; 188/305; 254/377; 242/381.5 |
Current CPC
Class: |
A62B
1/10 (20130101); B65H 75/4442 (20130101) |
Current International
Class: |
B65H
75/38 (20060101); B65H 75/44 (20060101); A62B
1/10 (20060101); A62B 1/00 (20060101); A62b
001/12 () |
Field of
Search: |
;254/158,160
;188/271,305,295 ;192/58A |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Spar; Robert J.
Assistant Examiner: Noland; Kenneth
Attorney, Agent or Firm: Ohlandt; John F.
Claims
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;
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 propeller-shaped.
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 cylinder.
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.degree. 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.degree.
rotational phase difference.
Description
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 U.S. 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 of a
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 2--2 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 4--4 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 6--6.
FIG. 7 is an elevation view of the right piston taken from the
plane 7--7.
FIG. 8 is an elevation view of the right cylinder portion taken
from the plane 8--8.
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 12
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 16B, 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. 1, is adapted to be
selectively connected or coupled to the drum 14 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 21B. The brake
cylinder 21 is enabled to rotate about the shaft 16 by reason of
the bearings 26 disposed about the shaft sections 16B, 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 46B. 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 52B 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 appropriately 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 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 21B respectively. These cover plates are
adapted to fit around the bearings 26 for rotational movement or
revolving of the cylinder 21 around the shaft 16. As has been
previously noted, the peripheral wall of the cylinder part 21B
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.degree.. 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 established. 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 16; 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 17 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 worker's safety belt or other equipment.
In the normal operation of the safety device, which takes place in
the course of the worker's 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 14 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 40 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 (1) 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 of
piston 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 60 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 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 FIG. 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.
* * * * *