U.S. patent number 3,811,151 [Application Number 05/350,156] was granted by the patent office on 1974-05-21 for joint for collapsible ladders.
This patent grant is currently assigned to Firma Zarges Leichtbau GmbH. Invention is credited to Walter Kuemmerlin.
United States Patent |
3,811,151 |
Kuemmerlin |
May 21, 1974 |
JOINT FOR COLLAPSIBLE LADDERS
Abstract
A joint for collapsible ladders, wherein two members are
pivotally connected to each by means of a hinge pin. Each member
has a flange portion, through which the hinge pin extends, and a
shaft portion adapted to be connected to the ladder stringer. A
locking member comprising at least two parts adapted to be moved
from a first locking position onto a second locking position and
viceversa for locking the two members in at least two predetermined
angular positions relating to each other. Biasing means connected
to the two part of the locking member, which may be telescopically
extended, for urging the locking member into one of the locking
positions. The locking member being guidingly mounted on the hinge
pin and includes a projecting portion which extends through an
opening in the flange portion of each member when the locking
member is in a locking position. Each flange portion having at
least two openings each one of which is adapted to be aligned with
a mating opening of the other flange portion when the ladder
stringers are in a predetermined angular position to receive the
projecting portion of the locking member and thereby lock the two
ladder stringers in a predetermined angular position relative to
each other.
Inventors: |
Kuemmerlin; Walter (Bissingen,
DT) |
Assignee: |
Firma Zarges Leichtbau GmbH
(Bayern, DT)
|
Family
ID: |
25763036 |
Appl.
No.: |
05/350,156 |
Filed: |
April 11, 1973 |
Foreign Application Priority Data
|
|
|
|
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Apr 11, 1972 [DT] |
|
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2217258 |
Feb 19, 1973 [DT] |
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2308095 |
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Current U.S.
Class: |
16/329; 182/163;
403/92 |
Current CPC
Class: |
E06C
1/32 (20130101); Y10T 403/32327 (20150115); Y10T
16/540254 (20150115) |
Current International
Class: |
E06C
1/00 (20060101); E06C 1/32 (20060101); E05d
011/10 () |
Field of
Search: |
;16/144,145,146,141
;403/92,93,101,102,100 ;182/163,164 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Gay; Bobby R.
Assistant Examiner: Troutman; Doris L.
Attorney, Agent or Firm: Klein; Arthur O.
Claims
What is claimed is:
1. A joint for collapsible ladders, comprising in combination;
two members each of which has a flange portion and a shaft
portion;
a hinge pin extending at least partially through said flange
portion of each member for forming a pivotal connection between
said two members;
said shaft portion of each member being adapted to be connected to
a ladder stringer of the collapsible ladder;
a locking member comprising at least one locking rod portion and
one guide rod portion which are parallel and which are adapted to
be moved from a locking position to a non-locking position and
vice-versa; said ladder stringers and two members being swingable
about said hinge pin relative to each other when said locking
member is in a non-locking position;
said guide rod portion being guidingly axially movable in said
hinge pin from said locking to said non-locking position and
vice-versa;
biasing members operatively connected to said guide rod portion for
urging it into said locking position;
said flange portion of each member having at least two openings
each of which is adapted to be aligned with a mating opening in the
other flange portion and said locking rod portion being adapted to
pass through said openings to lock said two members in a
predetermined angular position relative to each other.
2. The joint for collapsible ladders as set forth in claim 1,
wherein said hinge pin is hollow and has a central bore in which
said guide rod portion is axially slidably movable.
3. The joint for collapsible ladders as set forth in claim 2,
wherein said locking member includes two locking rod portions which
are parallel to said guide rod portion and are connected to it by a
manually adjustable yoke member.
4. The joint for collapsible ladders as set forth in claim 3,
wherein both of said locking rod portions are equally radially
spaced from said hinge pin but have different cross-sectional areas
and said openings in said flange portions having corresponding
different cross-sectional areas so that an alignment of openings of
the same size in said flange portions permits the passage of a
mating guide rod portion therethrough.
5. The joint for collapsible ladders as set forth in claim 4,
wherein said locking rod portions are round and have different
diameters and the openings in the flange portions have a width in
the radial direction relative to said hinge pin which substantially
corresponds to the diameter of the coacting locking rod
portion.
6. The joint for collapsible ladders as set forth in claim 3,
wherein said two locking rod portions are differently radially
spaced relative to said hinge pin.
7. The joint for collapsible ladders as set forth in claim 6,
wherein both locking rod portions are formed as round-shaped rods
of equal diameter, and said openings in said flange portions have a
width in the radial direction which corresponds substantially to
the diameter of the coacting locking rod portion.
8. The joint for collapsible ladders as set forth in claim 2,
wherein said biasing means is formed as a coil spring, said guide
rod portion defining an annular space within said central bore of
said hinge pin, and said coil spring being axially disposed within
said annular space.
9. The joint for collapsible ladders as set forth in claim 8,
including at least one bushing slidably axially mounted within said
central bore in said annular space, and a second coil spring
coaxially mounted between said guide rod portion and said bushing,
said coil spring abutting with one end against said hinge pin and
with the other end against said bushing and said second coil spring
abutting with one end against said bushing and with the other end
against said guide rod portion.
10. The joint for collapsible ladders as set forth in claim 9,
wherein said hinge pin, said guide rod portion and said bushing
have substantially equal axial lengths.
11. The joint for collapsible ladders as set forth in claim 10,
wherein said rod portion has at its free end a radially outward
projecting first collar, said hinge pin has, at the end distance
from said first collar when the locking member is in the locking
position, a second radially inwardly projecting collar, and the
bushing has, at the end adjacent to the first collar of the guide
rod portion when the locking member is in the locking position, a
third radially outward projecting collar and at the other end a
fourth radially inward projecting collar, whereby the outer
diameter of the first collar is larger than the inner diameter of
the fourth collar and the outer diameter of the third collar is
larger than the inner diameter of the second collar.
12. The joint for collapsible ladders as set forth in claim 11,
wherein an opening is provided in each flange portion for each
angular position in which the ladder is to be locked in position by
the passage of a locking rod portion and the corresponding openings
in each flange portion only overlap when these angular positions
are assumed by the flange portions.
13. The joint for collapsible ladders as set forth in claim 12,
wherein one of said overlapping openings in one of the flange
portions when the two flange portions assume an acute angle
relative to each other, is formed as a concentric circular slot
with respect to the hinge pin which permits a swinging of both
shaft portions when the locking member is in the locking position.
Description
BACKGROUND OF THE INVENTION
The invention concerns a joint for collapsible ladders wherein two
members of the joint are pivotally connected to each other by means
of a hinge pin. The two members are each provided with a flange
portion and a shaft portion. The pivotal connection is mounted on
the flange portion of the two members. The joint forming part of
this invention also includes a locking member which is urged by a
suitable spring means from a non-locking position into a locking
position. The locking member can be manually moved from its locking
position against the force of the spring into a non-locking
position and can be returned into a locking position after the
ladder stringers have been angularly moved towards each other from
one predetermined angular position into a second predetermined
angular position. When such a movement has been completed suitable
mating openings in the flange portions are aligned with each other
and a projecting portion of the locking member extends through
these mating openings to lock the two members into the
predetermined angular position.
The collapsible ladder joints of the prior art have open grooves
located in the outer periphery of the flange member and the locking
member is formed as a slidable bolt which moves in a radial
direction against the outer periphery of the flange portion when
being moved into a locking position. Since the open grooves are
exposed, either completely or partially, debris might accidentally
enter into it such as plaster, chips of brick and the like. If this
occurs the locking bolt may enter into the groove only partially
thereby form an insecure joint. This is particularly dangerous
because the sliding bolt is covered in one of the shaft portions of
the ladder joint and therefor the fact that the ladder joint is not
securly bolted can easily be overlooked. Thus the ladder joint must
be strictly examined and controlled to ascertain whether the
sliding bolt has penetrated sufficiently deep into the groove or if
the groove has to be cleaned. A further drawback of the
aforementioned known type of collapsible ladder joint resides in
that dirt, cement, plaster, colors and the like may penetrate into
the shaft portion, which can lead to a partial blocking of the
sliding bolt and thereby could damage its correct operation in
particular its return movement by its return spring. This can also
lead to an insufficient locking of the two members forming the
ladder joint, and also the danger of a failure to recognize such an
insecure locking operation by the person using the ladder.
SUMMARY OF THE INVENTION
It is accordingly a primary object of the present invention to
provide a joint for collapsible ladders which is of a simpler
construction as the aforementioned joint construction of the prior
art while at the same time eliminating the danger of carrying out
an insufficient locking operation or to at least indicate that such
insufficient locking has occurred. This object is effected in
accordance with the invention by providing a locking member which
includes a projecting rod portion which is slidingly movably
mounted relative to the hinge pin of the joint and which extends in
an axial direction, when the locking member is in its locking
position, through both flange portions of the joints.
Such a rod portion will push out any dirt, cement or the like which
may have accumulated in the opening due to the fact that the rod
portion is axially guided as it moves through openings in the
flange portions. In the event the return spring has not sufficient
force to push the accumulated dirt out of the corresponding
opening, the position of the rod indicates clearly that the joint
is insufficiently locked. A blow by hand on the rod portion then
practically always suffices to place this rod portion into the
correct locking position. This represents another significant
advantage when compared to the joint construction of the prior art
because, in addition to clearly indicating the incorrect or correct
locking of the joint, the prior art constructions require normally
a special tool for cleaning the joint so that the locking bolt may
again penetrate into the complete locking position, whereas in
applicant's joint construction no such special tool is
necessary.
A further advantage resides in that the locking arrangement
requires no shaft portions, so that it can be connected with
aluminum stringers without difficulty, whereas normally connecting
elements with relatively large diameters are required. In the shaft
portion of the prior art which includes the locking bolt there is
no space for such connecting elements.
In a preferred embodiment of the invention the joint is provided
with a central longitudinal bore or bush in which a guide rod which
is connected to the rod portion is guidingly, axially, movably
mounted. This arrangement provides a substantial protection against
soiling of the guiding arrangement. In such general arrangement of
guiding the guide rod and the locking member or locking members,
the arrangement can be provided with a cross beam for manually
moving the locking member. It has been found to be of particular
advantage to mount the return spring in the longitudinal bore which
is defined by the hinge pin preferrably in the annular space
between the guide rod and the walls of the bore. In this manner
considerable space saving is effected and the return spring is
practically completely protected against any accumulation of
dirt.
A particular advantage of the joint for collapsible ladders in
accordance with this invention resides in the space saving that can
be effected with the construction. The dimension in the axial
direction can be kept at a minimum in that at least one bushing
with limited slidability in the longitudinal direction is mounted
on the guide rod as well as in the longitudinal channel of the
hinge pin in that in addition to the first return spring there are
mounted additional springs corresponding in number to the number of
bushings. One of the return springs bears at on of its end against
the guide rod and with its other end against the bushing and the
other return spring bears with one of its end against the bushing
and with its other end against the hinge pin in an axial direction.
In this constructional arrangement the length of the guide rod and
its guiding means can be limited to the axial length of the hinge
pin even when, for reasons of constructional reliability, the
locking member or the locking members have an axial length which
makes it possible that in the locking position both flange portions
are completely traversed.
A further advantageous feature of the joint for collapsible ladders
in accordance with this invention, resides in that a plurality
(preferrably two) locking members are diametrically arranged
relative to hinge pin and can be manually adjusted by means of a
yoke or cross beam which joins the locking members to each other.
For example if two locking members, diametrically arranged relative
to the hinge pin, are used the distance of their locking rod
portions relative to the hinge pin need only be about one half the
distance if one locking rod portion is used in order to provide the
same load resistance of the joint in its locked position. Thereby
the overall dimensions of the flange portion can also be
significantly smaller as compared to the size of the flange portion
of a joint having one single locking member.
A further particular advantage of the construction of the invention
resides in that that it permits, when an actual angular movement of
the ladder stringers relative to each other is effected, to
preselect the new angular position so that when it is reached the
joint is automatically locked. This advantageous feature can be
incorporated in the embodiments of the invention having only one
single locking member as well as in the embodiments having a
plurality of locking members. The feature requires that there are
openings in both flange portions which align when a predetermined
angular position is reached. It is possible in such an arrangement
to position the locking rod portion or portions into one opening or
openings of one flange portion before the ladder stringers are
moved into the new angular position without thereby locking the
joint. The locking is effected automatically by means of the force
of the return spring only when the new angular position is reached,
because only then when this position is reached are the openings of
the two flange portions aligned with each other and permit the
passage of the locking rod portion or portions.
Such a preselection of the new angular position and the automatic
locking in the new angular position is even possible when at least
two locking rod portions are used, as long as the openings in the
flange portions are arranged in such a way that the passage of the
locking rod portion is only possible when the correct angular
position of the ladder stringers is reached. In a particular simple
constructional arrangement the locking rod portions have different
cross sectional areas and the mating openings in the flange
portions have corresponding cross sectional areas thereby assuring
passage of the locking rod portions only when the correct angular
position is assumed. In this simplified arrangement the distances
of the locking rod portion from the hinge pin can be different
while the locking rod portion cross sections and corresponding
openings can be identical. In this way the same result is
achieved.
BRIEF DESCRIPTION OF THE DRAWING
The invention is illustrated by way of example in the accompanying
drawing which forms part of the application and in which various
embodiments of joints for collapsible ladders which embody the
invention are shown.
FIG. 1 is a partial side elevational view of a first embodiment in
which the ladder stringers and the joint are in an angular position
relative to each other adapted for transporting the ladder;
FIG. 2 is a partial elevational side view of the joint illustrated
in FIG. 1 wherein the ladder stringers are in an angular position
relative to each other which corresponds to a working position of
the ladder;
FIG. 3 is a partial side elevational view of the first embodiment
of the joint wherein the ladder stringers are in an angular
position relative to each other which corresponds to the second
working position of the ladder;
FIG. 4 is a cross sectional view along line IV--IV in FIG. 3 at a
larger scale than FIG. 3;
FIG. 5 is a partial side elevational view of a second embodiment of
a joint for collapsible ladders, in accordance with the invention,
wherein the ladder stringers are in a non-working position that is
adapted for transportation;
FIG. 6 is a partial side elevational view of the joint illustrated
in FIG. 5 wherein the ladder stringers are in an angular position
corresponding to a first working position of the ladder;
FIG. 7 is a partial elevational side view wherein the ladder
stringers are shown in a second angular position relative to each
other corresponding to a second working position of the ladder;
FIG. 8 is a cross sectional view along line IV--IV in FIG. 7
wherein the parts are shown in a larger scale;
FIG. 9 is a partial elevational side view of a third embodiment of
a joint in accordance with the invention, wherein the members of
the joint are shown in an angular position corresponding to a
second working position of the ladder stringers in which the ladder
is fully extended;
FIG. 10 is a cross sectional view along line X--X of FIG. 9 wherein
the parts are shown in a larger scale;
FIG. 11 is a cross sectional view similar to FIG. 10 illustrating a
fourth embodiment of the joint for collapsible ladders forming part
of this invention wherein the joint is shown in a locked position;
and
FIG. 12 is a cross sectional view corresponding to FIG. 11 of the
fourth embodiment of the invention wherein the joint is shown in an
unlocked position.
DESCRIPTION OF PREFERRED EMBODIMENTS
Referring now to the drawing and in particular to the embodiment
illustrated in FIGS. 1-4, there is shown a joint for collapsible
ladders with which the ladder may be used as a step ladder as well
as an extension ladder. The joint includes two members 2 and 3
which are pivotally connected to each other by means of a hinge pin
1. The members 2 and 3 may consist of aluminum sheet metal but can
also be made of any other suitable material. Each member 2 and 3
includes a flange portion 4, 5 and a shaft portion 6, 7, the latter
being adapted to be joined to the ladder stringers.
The two shaft portions 6 and 7 are preferably in the illustrated
embodiment formed in the shape of a square tube which for
facilitating the mass manufacture is formed of two U-portion 6'
respective 6" and 7' respectively 7". If the ladder stringers are
also formed by square shaped aluminum tubes, it is advantageous, to
provide the two shaft portions 6 and 7 with two bores 8 and 9 of
relatively large diameters. The aluminum tubing which forms the
stringers can then be joined by means of hollow rivets which extend
through the shaft portions, the diameter of which corresponds to
the diameter of the bores 8 and 9, thereby forming a strong
connection and eliminating for all practical purposes the danger of
failure of the joint.
As can be noted from FIG. 4, the total width in the longitudinal
direction of the shaft portions 6 and 7 is equal double the width
of the sheet metal which has been selected for making the members 2
and 3. Thereby there is formed a space between the substantially
round flange parts 4' and 4", which form the flange portion 4,
which is equal to double the wall thickness of the sheet metal of
which the members 2 and 3 are made. Again referring to FIG. 4 it
can be noted that the shaft portion 7 is made of the U-shaped
portions 7' respectively 7" which form a unit and which have the
bores 9. Because of the unitary construction of the flange
portions, formed by both a U-shaped portions 7' and 7", it is
necessary that in the corner zone of the shaft portion 7, a shank
portion is omitted which corresponds in length to the circular
segment of the round-shaped flange portion 4 along which the ladder
is joined to the shaft portion 7.
There are mounted two adjoining flange parts 5' and 5" between both
flange parts 4' and 4', which form jointly which the shaft portion
6, consisting of two U-shaped parts 6', 6", a unitary construction.
The diameter of the flange parts 5' and 5" is equal to the diameter
of the flange parts 4' and 4". Furthermore the position of the
flange parts 5', 5" relative to the shaft part 6 corresponds to the
position of the flange parts 4', 4" relative to the shaft part 7.
As can be noted from FIG. 1-3 the center of the flange portions 4
and 5 lies outside of the shaft portions 6 and 7. This construction
makes it possible to move the members 2 and 3 from a position in
which they are parallel to each other (FIG. 1) to a position in
which they are aligned with each other and their front faces
contact each other (FIG. 3).
A locking between the members 2 and 3 is carried out by means of a
locking arrangement, which includes a locking rod 10, having a
locking rod portion and a guide rod 11 which is axially slidably
guided in the central bore 12 of a hinge pin 1. The bore 12 has an
enlarged portion for accommodating three compressed coil springs 13
which bears with one of its end against the shoulder defining a
narrow portion of the bore 12 and at the other end against an
enlarged collar 14 of the guide rode 11. The length of the hinge
pin 1 is selected in such a way that the collar 14 is in all
positions of the locking rod portion 10 situated in the bore 12. By
correctly dimensioning the bore of the hinge pin so that little
clearance is provided between the guide rod 11 and the narrow
portion of the bore 12 as well as between the collar 14 and the
enlarged portion of the bore 12, an accumulation of dirt and debris
within the bore 12 is practically eliminated and thus the correct
functioning of the coil spring 13 is assured.
A shoulder 15 of the guide rod 11 prevents the return spring 13
from moving the guide rod 10 beyond a predetermined locking
position in which the yoke or cross beam 25 is still located at a
sufficient position from the flange part 4' to permit the manual
grasping of the yoke or cross beam 25. It is thus possible by a
simple manipulation of the yoke 25 to adjust the locking rod
10.
The hinge pin 1 of the first embodiment is secured against axial
displacement by means of two oppositely spaced rings 16 which are
mounted in mating grooves in the hinge pin 1. Furthermore the hinge
pin 1 is provided with a lateral flat cut portion which bears
against a mating flat surface in the flange parts 4 and 5, thus
securing the hinge pin 1 against rotation. The hinge pin 1 has just
enough axial length to accommodate the guide rod 11 and to securely
guide it as well as to accommodate the coil springs 13. Thus due to
the combination wherein the hinge pin extends axially bilaterally
beyond the width defined by the flange portions 4 a space saving
arrangement is provided.
At a distance corresponding to the distance between the
longitudinal axis of the locking rod portion 10' from the axis of
the joint, there are provided in each flange part 4', 4" a bore 17,
which are aligned relative to each other. In order to facilitate
the sliding in and sliding out of the locking rod portion 10' the
diameter of the bores 17 is slightly larger than the diameter of
the locking rod portion 10'. The flange part 5 is provided with a
longitudinal slot 18 extending in a circumferential direction, the
width of which corresponds to the diameter of the bores 17 and one
end of which overlaps completely with the bores 17 when the shaft
portion 6 and 7 assume an acute angle as illustrated in FIG. 2,
said acute angle corresponding to the angle which the ladder
stringer assume when thy are in a normal working position, that is
in a position where the ladder forms a step ladder. The other end
of the longitudinal circumferential slot 18 overlaps with the bore
17 when both shaft portions 6 and 7 are situated parallel to each
other. This position corresponds to the position wherein the ladder
is ready to be transported. By providing a longitudinal
circumferential slot 18 in lieu of two individual bores it is
possible to move the ladder without actuating the locking
arrangement from the angular position illustrated in FIG. 1 to the
angular position illustrated in FIG. 2 and vice versa.
There are provided in the flange parts 4' and 4" at a distance from
the bores 17 overlapping bores 19 respectively 20, which are
aligned towards a bore 21 in the flange portion 5 when both shaft
portions 6 and 7 are in the position illustrated in FIG. 3. The
locking rod 10 can, in this position, pass through the bores 19, 20
and 21, and thereby lock the joint in position. In view of the fact
that there are provided special bores for locking the joint in the
position illustrated in FIG. 3, it is possible, when the members 2
and 3 ought to be moved relative to each other from the position
illustrated in FIG. 2 to the position illustrated in FIG. 3, to
preset the locking rod 10 into the bore 19. The locking rod portion
10 then passes automatically into the bore 21 and the bore 20, as
soon as the position illustrated in FIG. 3 is reached by the
members 2 and 3. Similarly, before the moving of the ladder from
the position in FIG. 3 to the position illustrated in FIG. 2 the
locking rod 10 is first placed into one of the bores 17. Both hands
are then available for fringing the ladder stringers into the
desired position. Despite this release of the locking rod 10 the
arrangement nevertheless secures a locking operation when the
ladder stringers have reached the desired position. By narrowing
the free end 10" of the locking rod portion 10' the introduction of
the locking rod 10 into the various bores is facilitated.
FIGS. 5-8 illustrate a second embodiment of the joint of the
invention. Since the variation from the first embodiment resides
primarily in the provision of a second locking rod portion, the
reference numerals have not been changed for those parts and
portions of the arrangement which have not changed relative to the
embodiment of FIGS. 1 to 4 so that these parts and portions are
referred to with the same reference numerals as in the first
embodiment and are not described in detail herein-below.
Diametrically opposite to the locking rod portion 10 and parallel
to it as well as parallel to the guide rod 11 there is provided a
second locking rod portion 110. The distances between both locking
rod portions 10' and 110 relative to the guide rod 11 are equal.
The yoke 125 joins the locking rod portions 10' and 110 with the
guide rod 11 at one of its ends. The second locking rod portion 110
has a circumferential cross section as has the first locking rod
portion 10'. As can be noted clearly from FIG. 8, however, the
diameter of the locking rod portion 10' is substantially smaller
than the diameter of the locking rod portion 110.
There is provided in both flange parts 4' and 4" at a distance from
the joint axis, corresponding to the distance of the longitudinal
axis of the locking rod portion 110 from the joint axis,
diametrically opposite to the bores 17 in each flange part a bore
117 which overlap each other completely. The diameter of these
bores is slightly larger than the exterior diameter of the locking
rod portion 110 so that there exists a play between the latter and
the walls of the bores 117 thereby facilitating an easy
introduction and removal of the locking rod portion 110.
Diametrically opposite from the longitudinal circumferential slot
18 there is provided in the flange portion 5 a longitudinal
circumferential slot 118. The width of this circumferential slot in
the radial direction is equal to the diameter of the bore 117. One
end of the longitudinal slot 118 overlaps completely with the bore
117, when both of the shaft portions 6 and 7 assume the angular
position illustrated in FIG. 6. The other end of the longitudinal
circumferential slot 118 overlaps with the bore 117, and both of
the shaft parts 6 and 7 extend parallel and next to each other.
To the same extent and direction in which the bores 19 and 20 are
offset in the circumferential direction relative to the bores 17,
the bores 119 and 120 are offset relative to the bore 117. When the
shaft portions 6 and 7 assume the position illustrated in FIGS. 7
both of the bores 119 and 120 are overlapped with a bore 121 in the
flange portion 5, that is they have their wall surfaces aligned
with each other. In such a position the locking rod portion 10'
then passes through the bores 19, 20 and 21 whereas the locking rod
portion 110 can pass through the bores 119, 120 and 121 thereby
locking the joint. Since there are provided special bores and the
diameters of the locking rod portion 10' and 110 as well as the
diameters of the appurtenant bores and longitudinal circumferential
slots are different, it is possible, for locking the joint in the
position illustrated in FIG. 7, when swinging both shaft parts from
the position illustrated in FIG. 2 to the position illustrated in
FIG. 3, to place the locking rod portion 10' into the bore 119
prior to carrying out the aforementioned swinging movement. The
locking rod portions remain during this swinging process in their
position, since the diameter of the bore 21 which is smaller when
compared to the diameter of the locking rod portion 110 prevents a
sliding of the locking rod into the locking position even when the
locking rod portion 110 is aligned with the bore 21. Only when the
position illustrated in FIG. 3 is reached can the locking rod
portions 10' and 110 automatically penetrate the bores 20 and 21,
respectively 120 and 121. Similarly, the locking rod portions 10
10' and 110 can first of all be respectively inserted in to the
bore 17 respectively 117 before swinging the ladder from the
position illustrated in FIG. 7 into the position illustrated in
FIG. 6. Thus the person servicing the ladder has at all times both
hands free for manipulating the ladder before carrying out the
swinging operation. Thereafter an automatic locking of the ladder
is secured as soon as the desired angular position has been
reached.
In lieu of providing locking rod portions with different
cross-sectional areas it is also possible to provide locking rod
portions with equal cross-sectional areas if the locking rod
portions are differently radially spaced from the axis. This
variation of the invention is illustrated in a third embodiment (6,
9 and 10). In these figures there is illustrated a yoke 225 which
joins the guide rod 211 with the locking rod portions 210, 210'
having equal diameters. However, the distance of the locking rod
portion 110 from the guide rod 211 is smaller as the corresponding
distance of the locking rod portion 210.
As is shown in FIG. 9, these different distances are required so
that the corresponding locking rod portions between the bores and
longitudinal circumferential slots in both flange portions 203 and
205 are correspondingly located. Thus they are arranged in suitable
locations the bores 217, 219, 220 and 221 as well as the
longitudinal circumferential slot 18 for coaction with the locking
rod portion 210 and the bores 217', 219', 220', 221' as well as
longitudinal circumferential slot 218' which coact with the locking
rod portion 210'. The relative positions of these bores and
longitudinal circumferential slots is identical to the bores and
slots described in relation to the locking rod portion 10'
respectively 110 described in connection with the embodiment of
FIGS. 7 and 8. Therefore also in this embodiment the locking rod
portions 210 and 210' can with their free ends be placed into the
bores in the flange portion 204 by manually handling the yoke 225
before the axial swinging movement of the members is effected,
whereby an automatic locking of the joint in the newly selected
regular position is effected. Here again therefor the person using
the ladder has both hands free for carrying out the swinging
movement.
In any other respect the embodiment is in principle constructed
identically to embodiments described hereinabove. Although the two
members 202 and 203 are somewhat differently shaped in FIGS. 9 and
10 this in no way affects the basic inventive concept of the
locking arrangement and is therefore not described in detail, in
particular since the members forming the joint as well as the hinge
pin 201 and the guid rod 211 can be constructed identically to the
construction of the preceedingly described embodiments.
Independent of the feature of using only single locking rod
portions or a plurality of locking rod portions with different
cross-sectional areas or differently distanced from the joint axis;
there can still be obtained a substantial reduction in the overall
dimension of the joint in the axial direction by providing a
telescopic-like arrangement for the guide rod or hinge pin. Such a
variation is illustrated in the embodiment of FIGS. 11 and 12. In
this embodiment there are also provided two identical locking bolts
310 and 310'. The length of these locking bolts are, as compared to
the embodiment of FIG. 10, substantially shorter which is due to
the telescopic arrangement between the hinge pin and the guide
rod.
Both of the flange portions 304 and 305 are pivotally connected to
each other by means of a hinge pin 301. This hinge pin is
constructed in the form of a bushing and has on the side which
faces the two locking rod portions 310 and 310', which are joined
by a yoke 235, a collar portion 329 which extends into the central
bore 312. The radial height of this collar portion 329 is somewhat
larger than the wire thickness of the coils of a first return
spring 313, said return spring 313 being mounted within the bore
312 and has an interior diameter, which is somewhat larger than the
interior diameter of the collar portion 329.
A bushing 326 is mounted in the bore 312 and has an axial length
that is equal to the axial length of the hinge pin 301. The
exterior diameter of the bushing 326 is so demensioned that it can
easily but without large play be slidably moved into the axial
direction within the hinge pin. The end of the bushing 326, which
is situated within the collar portion 329, when the latter is
completely pushed inside of the hinge pin, has in turn an
interiorily projecting collar portion 327, whereas the opposite end
is provided with an exteriorly projecting collar portion 328. The
radial height of the collar portion 328 is approximately equal to
the radial height of the collar portion 329 due to this arrangement
the bushing 326 is guided when being actually moved by the collar
portion 329 as well as by the collar portion 328. Both of these
collars also serve for supporting surfaces for the precompressed
coil spring 313, which is mounted in the annular space between the
bushing 326 and the interior wall surfaces of the hinge pin
301.
The guide rod 311 extends within the bushing 326, the diameter of
the guide rod 311 being somewhat smaller than the interior diameter
of the collar portion 327 of the bushing 326, so that an axial
displacement relative to the bushing 326 can be easily effected
without large play. The guide rod 311 has at its free end a
radially outward projecting collar portion 314, the radial height
of which is equal to that of the collar portion 327. A second,
similarly precompressed coil spring 313 is mounted within the
annular space between the guide rod 311 and the bushing 326 and
abuts, on the one hand against the collar portion 327, and on the
other hand, against the collar portion 314.
Both of the coil return springs tend to maintain the bushing 326 as
well as the guide rod 311, and thereby also both locking rod
portions 310 and 310', in the position illustrated in FIG. 11,
which is the locking position. The yoke 325 prevents a further
displacement of the bushing and the guide rod towards the right as
viewed in FIG. 11. Since both of the return coils springs 313 and
313' can only be compressed to the extent when their individual
helical coils abut against each other, the bushing 326 can only be
partially pulled out from the hinge pin 301 and the guide rod 311
can only be partially pulled out from the bushing 326. However,
both of these axial displacements suffice to move the locking rod
portions 310 and 310' out of their locking position in which they
are situated in corresponding bores, as is shown in FIG. 12.
The bores and longitudinal circumferential slots for accommodating
the locking rod portions are arranged and constructed similarly to
the arrangement and construction of the embodiment illustrated in
FIGS. 9 and 10. The same applies to the other parts of the joint.
Therefor a detailed description of the other features of the joint
construction is not necessary.
Although the invention is illustrated and described with reference
to a plurality of preferred embodiments thereof, it is to be
expressly understood that it is in no way limited to the disclosure
of such a plurality of preferred embodiments, but is capable of
numerous modifications within the scope of the appended claims.
* * * * *