CA2157842C - Extension ladder with telescopic legs - Google Patents
Extension ladder with telescopic legs Download PDFInfo
- Publication number
- CA2157842C CA2157842C CA 2157842 CA2157842A CA2157842C CA 2157842 C CA2157842 C CA 2157842C CA 2157842 CA2157842 CA 2157842 CA 2157842 A CA2157842 A CA 2157842A CA 2157842 C CA2157842 C CA 2157842C
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- CA
- Canada
- Prior art keywords
- tube
- members
- extension ladder
- tube member
- ladder
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Fee Related
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Classifications
-
- E—FIXED CONSTRUCTIONS
- E06—DOORS, WINDOWS, SHUTTERS, OR ROLLER BLINDS IN GENERAL; LADDERS
- E06C—LADDERS
- E06C7/00—Component parts, supporting parts, or accessories
- E06C7/06—Securing devices or hooks for parts of extensible ladders
-
- E—FIXED CONSTRUCTIONS
- E06—DOORS, WINDOWS, SHUTTERS, OR ROLLER BLINDS IN GENERAL; LADDERS
- E06C—LADDERS
- E06C1/00—Ladders in general
- E06C1/02—Ladders in general with rigid longitudinal member or members
- E06C1/04—Ladders for resting against objects, e.g. walls poles, trees
- E06C1/08—Ladders for resting against objects, e.g. walls poles, trees multi-part
- E06C1/12—Ladders for resting against objects, e.g. walls poles, trees multi-part extensible, e.g. telescopic
- E06C1/125—Ladders for resting against objects, e.g. walls poles, trees multi-part extensible, e.g. telescopic with tubular longitudinal members nested within each other
Abstract
Disclosed is an extension ladder mainly including a pair of telescopic legs consisting of a plurality pairs of straight round tube members, a plurality of rungs in the same numbers as that of the tube member pairs and each having two lateral ends for the two legs to pass therethrough, a plurality sets of locking mechanisms and lock ensuring mechanisms, and a general switch assembly disposed beneath the lowest rung. The tube member each has a sleeve member and a plug assembly disposed around a top end and in a bottom end, respectively. Each plug assembly includes a set of cover members and a set of inserts having an upper and a lower movable hook members connected thereto. The upper hook member in a lower tube member separately links with the lower hook member in a higher tube member, limiting the tube members of the telescopic legs to be sequentially extended stair by stair. The upper hook member each has an air cock provided at a bottom end thereof to close or open an air port formed on a base of the inserts. The air cocks and the air ports, together with two one-way valves separately disposed at a lower portion of the lowest tube member pairs, enable the ladder to be quickly extended from a collapsed state and be collapsed from an extended state at moderate speed. The locking mechanisms and lock ensuring mechanisms are disposed beneath each rung to effectively prevent the ladder from unexpectedly collapsed due to any accidental touch of the locking mechanisms. The general switch assembly serves to actuate and control the sequential and moderate collapse of the rungs.
Description
Y
215"~8~2 _ 1 _ AN EXTENSION LADDER WITH TELESCOPIC LEGS
BACKGROUND OF THE INVENTION
1. Field of the Invention The present invention relates to an extension ladder with telescopic legs, and more particularly to an extension ladder which can be quickly extended for use or be , telescoped in a slow and sequential manner for safe storage when it is not in use. Moreover, the extension ladder of the present invention can be easily assembled and is provided with automatic locking and lock ensuring means to further ensure the safety in use.
215"~8~2 _ 1 _ AN EXTENSION LADDER WITH TELESCOPIC LEGS
BACKGROUND OF THE INVENTION
1. Field of the Invention The present invention relates to an extension ladder with telescopic legs, and more particularly to an extension ladder which can be quickly extended for use or be , telescoped in a slow and sequential manner for safe storage when it is not in use. Moreover, the extension ladder of the present invention can be easily assembled and is provided with automatic locking and lock ensuring means to further ensure the safety in use.
2. Description of the Prior Art Fig. 1 shows a conventional extension ladder with multiple rungs. The ladder includes a pair of legs 800, 900 each consisting of multiple tapered telescopic sections (in the drawing, four sections of each leg are shown, separately indicated by reference numerals 100A, 200A, 300A, 400A and 100B, 200B, 300B, 400B, from bottom to top. Please see Fig.
lA for the structure of these legs), multiple rungs (in the drawing, three rungs are shown, separately indicated by reference numerals 500, 600, 700, from bottom to top) each having a reverse U-shaped cross section, and multiple sets of locking mechanism for firmly locking the telescopic sections of the legs in place after they are fully extended.
The numbers of the rungs are equal to that of the telescopic sections of the legs.
The telescopic sections are provided at their upper and middle portions with locating holes (in the drawing, ,.
_ 2 _ locating hole 111 on the upper portion of the telescopic section 100A, locating holes 211, 221 respectively on the upper and the middle portions of the telescopic section 200A, and locating hole 321 on the.middle section of the telescopic section 300A are shown). The rungs 500, 600, 700 each has two ring-like ends 500A and 500B, 600A and 600B, 700A and 700B, respectively, for tightly engaging with a pair of reduced parts 112, 212, or 312 at the upper portions of their corresponding telescopic sections 100A, 100B; 200A, 200B; or 300A, 300B. In addition, the ring-like ends 500A, 500B; 600A, 600B; 700A, 700B of the rungs 500, 600, 700, resepctively, are provided with a hole 501A, 601A, 701A, respectively, correspoqding to the locating holes 111, 211, -etc. on the upper ,portion of the telescopic sections.
Retaining rods 512, 612, etc. respectively having a push arm 514, 614, etc, and a return spring 513, 613, etc. are disposed near the ring-like ends 500A, 500B; 600A, 600B;
700A, 700B of the rungs 500, 600, 700, respectively, to form the locking mechanisms. Moreover, wear-proof plug members 222, 322, 422 with vents 222A, 322A, 422A are separately plugged into a bottom end of the telescopic sections 100A, 200A, 300A, 400A, 100B, 200B, 300B, 400B.
Following disadvantages are found in the above-described conventional extension ladder:
1. To assemble the extension ladder, each tapered telescopic section thereof must be engaged into a lower section by inserting its top end into a lower end of the lower section one by one, and the rungs must be riveted to each top of the telescopic sections. Such assembling procedures can not be easily performed and the sections are not easily aligned with one another when they are assembled according to the above procedures.
~I5~842 _ g _ 2. When the ladder is extended for use, the higher rungs are always separated from each other and locked in place before the lower rungs are completely pulled out to their true-positions. Therefore, the telescopic sections of the conventional extension ladder can not be sequentially extended and located in place one by one from bottom to top.
Also, the ladder might unexpectedly and dangerously collapse due to operational mistake by an operator.
lA for the structure of these legs), multiple rungs (in the drawing, three rungs are shown, separately indicated by reference numerals 500, 600, 700, from bottom to top) each having a reverse U-shaped cross section, and multiple sets of locking mechanism for firmly locking the telescopic sections of the legs in place after they are fully extended.
The numbers of the rungs are equal to that of the telescopic sections of the legs.
The telescopic sections are provided at their upper and middle portions with locating holes (in the drawing, ,.
_ 2 _ locating hole 111 on the upper portion of the telescopic section 100A, locating holes 211, 221 respectively on the upper and the middle portions of the telescopic section 200A, and locating hole 321 on the.middle section of the telescopic section 300A are shown). The rungs 500, 600, 700 each has two ring-like ends 500A and 500B, 600A and 600B, 700A and 700B, respectively, for tightly engaging with a pair of reduced parts 112, 212, or 312 at the upper portions of their corresponding telescopic sections 100A, 100B; 200A, 200B; or 300A, 300B. In addition, the ring-like ends 500A, 500B; 600A, 600B; 700A, 700B of the rungs 500, 600, 700, resepctively, are provided with a hole 501A, 601A, 701A, respectively, correspoqding to the locating holes 111, 211, -etc. on the upper ,portion of the telescopic sections.
Retaining rods 512, 612, etc. respectively having a push arm 514, 614, etc, and a return spring 513, 613, etc. are disposed near the ring-like ends 500A, 500B; 600A, 600B;
700A, 700B of the rungs 500, 600, 700, respectively, to form the locking mechanisms. Moreover, wear-proof plug members 222, 322, 422 with vents 222A, 322A, 422A are separately plugged into a bottom end of the telescopic sections 100A, 200A, 300A, 400A, 100B, 200B, 300B, 400B.
Following disadvantages are found in the above-described conventional extension ladder:
1. To assemble the extension ladder, each tapered telescopic section thereof must be engaged into a lower section by inserting its top end into a lower end of the lower section one by one, and the rungs must be riveted to each top of the telescopic sections. Such assembling procedures can not be easily performed and the sections are not easily aligned with one another when they are assembled according to the above procedures.
~I5~842 _ g _ 2. When the ladder is extended for use, the higher rungs are always separated from each other and locked in place before the lower rungs are completely pulled out to their true-positions. Therefore, the telescopic sections of the conventional extension ladder can not be sequentially extended and located in place one by one from bottom to top.
Also, the ladder might unexpectedly and dangerously collapse due to operational mistake by an operator.
3. To collapse the extension ladder, the push arms of the locking mechanisms of the lowest rung is pulled to disengage the retaining rod thereof from the corresponding locating hole, allowing the next, higher telescopic section to descend until the locking mechanisms of the next higher rung touches the lower rung below it. The contact of the higher rung with the lower rung shall release the higher telescopic sections from the locking mechanisms of the higher rung.
With the same movement, the remaining telescopic sections and rungs collapse and descend one by one. However, there is not any buffer provided between every two of the telescopic sections, the rungs descend at a speed high enough to unexpectedly and dangerously injure a user's fingers. A buffer member disposed at the bottom end of each teL~scopic sections might effectively slow the descending of the rungs, the extension of the telescopic sections will, however, become slow, too.
With the same movement, the remaining telescopic sections and rungs collapse and descend one by one. However, there is not any buffer provided between every two of the telescopic sections, the rungs descend at a speed high enough to unexpectedly and dangerously injure a user's fingers. A buffer member disposed at the bottom end of each teL~scopic sections might effectively slow the descending of the rungs, the extension of the telescopic sections will, however, become slow, too.
4. The locking mechanisms can be easily unlocked by pulling the push arm. In the case the push arm is unexpectedly pulled by someone, especially a child, accident might very possibly occur.
5. The telescopic sections of the extension ladder frictionally contact with one another when they are ~
215'842 extended or collapsed and are therefore worn out and -become loosely connected after being used for a long period of time.
Therefore, it is necessary to provide an improved extension ladder to eliminate the above shortcomings.
SUMMARY OF THE INVENTION
It is a primary object of the present invention to provide an extension ladder having a safer and more effective structure. The extension Ladder of the present invention includes two legs which each consists of a plurality of sequentially telescoped sections. These telescopic sections each is a straight round tube having uniform diameter which .
facilitates the assembly of the telescopic sections and the rungs.
Another object of the present invention is to provide an extension ladder in which a plug assembly is mounted to a bottom end of each telescopic section thereof. The plug assembly each consists of an upper and a lower movable hook members. When the extension ladder is in a fully extended state, the upper hook members may separately extend their pointed end into retaining holes formed on the telescopic sections. The upper hook member each has a bevelled projection formed at an upper corner thereof on which a Lower hook member of the plug assembly in the next higher telescopic section hooks.when the extension ladder is in a fully collapsed state. When the ladder is extended and the upper hook members separately extends into the retaining holes on the telescopic sections, the lower hook members of the upper plug assemblies disengage from the bevelled -215°7842 _ 5 _ projection of the upper hook member, allowing the telescopic sections of the ladder to be pulled upward one by one from bottom to top.
It is a further object of the present invention to provide the above-mentioned extension ladder in which the plug assembly each is provided at a bottom portion of the upper hook member with an air cock, and at a base thereof with an air port corresponding to the air cock, and the lowest telescopic sections and the lowest rung are provided With one-way valves and cooperating air tube, respectively, whereby when the extension ladder is extended and the upper hook members pivot to .extend through the retaining holes on the telescopic sections with their bottom portions lifted, the air ports are opened to together with the one-way valves and the cooperating air tube allow the air in the telescopic sections to quickly flow through the legs and thereby permits the ladder to be quickly extended. Or, when the ladder is collapsed and the upper hook members pivot to disengage from the retaining holes on the telescopic sections with their bottom portions and accordingly the air cocks descended, the air ports are closed to slow the air flow in the telescopic sections and the collapse speed thereof.
It is still a further object of the present invention to provide an extension ladder in which locking mechanisms are separataely mounted below the rungs centered on each end thereof and a lock ensuring mechanism is disposed behind each locking mechanism, Whereby when the lock ensuring mechanisms are in a locked state, the corresponding locking mechanisms would not be unexpectedly and dangerously unlocked by pulling an pushing arm thereof. When the top ., surface of a lower rung touches the lock ensuring mechanisms of the next higher rung, the lock ensuring mechanisms of the next higher rung are unlocked to free their associated -locking mechanisms, permitting the rung and the telescopic sections of the next higher stair of the ladder to collapse.
Therefore, the rungs and the telescopic sections of other higher stairs of the ladder can be sequentially and safely collapsed from bottom to top in the same manner as described -above.
It is still a further object of the present invention to provide an extension ladder in Which a wear-proof ring member is fitted around a bottom outer periphery of each telescopic section to prevent the same from directly frictionally contacting with each other at their wall -surfaces lest the telescopic sections should become wearing and loosely contacting with each other which is dangerous to any user.
BRIEF DESCRIPTION OF THE DRAWINGS
The detailed structure and functions of the present invention can be best understood through the following detailed description of the preferred embodiments and the accompanying drawings, wherein:
Fig. 1 is a fragmentary perspective view of a conventional extension ladder, a part of which is cut away to show the manner in which the rungs are connected. to the legs of the ladder;
Fig. lA is a fragmentary, exgloded perspective view of Fig.
1 showing the structure of the leg of the ladder;
215?842 Fig. 2 is a fragmentary, exploded perspective view of an extension ladder according to the present invention, a part of which is cut away to show the assembling of a rung to two vertically telescoped sections of the legs;
Fig. 2A is a fragmentary, sectional view taken on line A-A
of Fig. 2;
Fig. 3 is an exploded perspective view of a plug assembly disposed at a bottom end of each telescopic section of the present invention;
Fig. 3A is a fragmentary, assembled, sectional view showing the positions of an upper and a lower hook members of the plug assembly in a telescopic section of the present invention;
Fig. 4A is a fragmentary, sectional view showing the manner in Which the telescopic sections of the legs of the present invention is sequentially extended from a collapsed state;
Fig. 4B is a fragmentary, sectional view showing the manner in which the telescopic sections of the legs of the present invention is gradually collapsed from an extended state;
2s Fig. 5A is a fragmentary, exploded perspective view of a locking mechanism and an associated Iock ensuring mechanism disposed in a rung other than the first or the lowest rung of the present invention;
Fig. 5B is a fragmentray, exploded perspective view of . a general switch assembly and the associated locking mechanism disposed in the first or the lowest rung of the present invention;
_$_ Figs. 6A to 6E are fragmentary, sectional views showing the operation of the mechanisms at different stairs ofthe ladder of the present invention to collapse the same; and Fig. 7 schematically shows another embodiment of the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Please refer to Fig. 2. The extension ladder of the present invention mainly includes a pair of legs lA, 1B each consisting of a plurality of telescopic section pairs, a plurality of rungs each having a peripheral wall which gives the rung a substantially reverse U-shaped cross section, a plurality of locking mechanisms 80 for locking the telescopic section pairs of the legs lA, 1B in place, and a plurality of lock ensuring mechanisms 82 cooperating with the locking mechanisms 80. The numbers of the rungs are equal to that of the telescopic section pairs. In the first embodiment of the present invention, reference numerals 50A
and 50 are designated to the first (the lowest) and the other higher rungs, respectively. The telescopic sections of the legs lA, 1B each is formed from a straight round tube member having uniform diameter through its length. A lower telescopic section or tube member always has an inner diameter larger than an outer diameter of a telescopic section or tube member immediately above it, such that every higher telescopic section can always be fitly received in a telescopic section immediately below it. In this embodiment, the telescopic sections of the legs lA, 1B are sequentially named the first tube member 10, the second tube member 20, the third tube member 30,..... from bottom to top.
21~78~~
_ g A sleeve member 60 and a plug assembly 30A are disposed on a top end and a bottom end of each telescopic section, respectively. Figs. 2 and 2A illustrate the manner in which the next lower or the second rung 50 (that is, the rung immediately above the first rung 50A) and the next lower telescopic section pairs (that is, the second tube members 20) are assembled and locked in place. Since every other stairs of the ladder of the present invention and either lateral side thereof are assembled in the same manner, they are not repeatedly explained herein. Of course, in the actual assembling, it must begin with the lowest (that is, the first) pair of telescopic sections and the lowest rung from either side thereof.
Please refer to Figs. 2 and 2A. To form the second stair of the extension ladder, first insert the third tube members 30 downward to pass through the sleeve members 60 fitted over the top end of the second tube members 20. The third tube members 30 each is premounted at its lower end with a plug assembly 30A. The manner in which the plug assembly 30A is assembled and functions will be described in more details later in this specification. Then, the second rung 50 is put over and engaged with a top end of the third tube members 30. Allow the third tube members 30 and the plug assemblies 30A at their bottom ends to extend into the second tube members 20. The sleeve member 60 each is formed at a top end with an outward extended upper flange on which an upper and a lower locating bosses 61A, 61B are provided to respectively engage with a first locating recess 55 -formed on the second rung 50 and a second locating recess 21 formed near an upper edge of the second tube member 20, causing a first locating hole 62 to aligne with a locating hole 54 formed at one end of the second rung 50. The second tube members 20 are firmly engaged into two ends of the 2I5'~842 second rung 50 with the sleeve members 60 between them without the risk of turning relative to the the second rung 50. An elongated slot 51 is formed at either end of the second rung 50 and a pair of threaded holes 52 are oppositely formed on the peripheral wall of the second rung 50 at two sides of each slot 51, whereby fastening screws 53 can be passed through the threaded holes 52 to narrow the slots 51 and thereby tightly bind the second rung 50 With the second tube members 20.
The locking mechanisms 80 are disposed near the ends of the second rung 50 on a central axis thereof and the lock ensuring mechanisms 82 are separately disposed just behind the locking mechanisms 80. For the first (lowest) stair of the ladder, a general switch assembly 90 can be additionally provided beneath the first rung 50A to cooperate with the lock ensuring mechanism to control the extension or collapse of the entire ladder.
Fig. 3 illustrates in details the manner in which the plug assembly 30A and the third tube member 30 are assembled.
The plug assembly 30A each consists of a front cover 33A, a rear cover 33B, a front insert 31A, and a rear insert 31B.
Both the front insert 31A and the rear insert 31B are formed at their lower outer wall with a lower flange. A first pin 32I is used to pass an inner side of the front insert 31A
while.threading through a first return spring 32H and pivotally connecting an upward extended and movable upper -hook member 32A to the front insert 31A. The upper hook member 32A is provided on its one side surface at an upper corner thereof with a bevelled projection 32G. A roller 32F is disposed in a hollow space formed at a front portion of the upper hook member 32A with a somewhat flexible cover plate 32J fitted in front of the roller 32F, such that when the upper hook member 32A extends into a locating hole 33C 'formed on the front cover 33A, the locating hole 33C is airtightly sealed. An air cock 32E is provided at a bottom end of the upper hook member 32A. An air port 31D is formed on a base of the front insert 31A
corresponding to the air cock 32E, whereby the air part 31D
is opened or closed when the upper hook member 32A is pivotally turned about the first pin 32I to lift or lower the bottom end, respectively.
A ring ear 31E is connected to. an underside of the front insert 31A. A downward extended and movable lower hook member 32B is pivotally connected to the ring ear 31E by means of a second pin 32D which is threaded through a scond reuturn spring 32C and an upper portion of the lower hook member 32B and the ring ear 31E. The lower hook member 32B
is eccentrically positioned below the front insert 31A and is vertically aligned with the bevelled projection 32G of the upper hook member 32A. A projected block 31C is formed near a front portion of the front insert 31A such that when the front insert 31A is placed into the third tube member 30 and fitted into a locating hole 30B thereof, the front cover 33A is engaged at its bottom flange 33H With the bottom end of the third tube member 30 with a locating projection 33E
thereof extendi:ag into the locating hole 30B of the third tube member 30 and vertically abutting against the projected block 31C of the front insert 31A just beneath it, permitting a front half of the plug assembly 30A to be firmly fixed to the third tube member 30.
Then, the rear insert 31B having an air outlet 31F is inserted into the third tube member 30, permitting an 2Z5'~842 opening 33F on the rear insert 31B to communicate with an opening 30C on the third tube member 30. Then, the rear cover 33B is fitted around the third tube member 30 with a bottom flange 33G of the rear cover 33B engaging into a- -clearance between the bottom end of the third tube member 30 and the rear insert 31B. At this point, a locating projection 33D on an inner wall of the rear cover 33B
extends through the opening 33F of the rear insert 31B and engages into the opening 30C,,permitting the rear half of the plug assembly 30A to be firmly fixed to the third tube member 30.
As shown in Fig. 4A, when the assembled ladder is to be extended from a collapsed state, the lower hook members 32B
of the plug assemblies 30A in the next higher tube members that are connecting with the upper hook members 32A of the plug assemblies 30A in the lowest tube members 10 by means of the bevelled projections 32G shall become disengaged from the upper hook members 32A after one-way 20 valves 70 disposed ne-ar bottom ends of the first tube members 10 are opened due to a pressure differential resulted from the extending operation. The open of the valves 70 permits air to be supplied to the first tube members 10. Due to the air flowing in the tube members forming the legs of the ladder, the telescopic sections of the legs can be quickly extended. When the upper hook members 32A of the plug assemblies 30A in the second tube members 20 are moved to a point in alignment with locating holes l0A formed on the first tube members 10, the upper hook members 32A are sprung toward the locating holes l0A
under the spring force of the first return springs 32H
and thereby open the air ports 31D. At this point, the air further flows upward. Meanwhile, the lower hook members 32B
s ~ 215'842 of the immediately higher telescopic sections 30 are released from the bevelled projections 32G of the upper hook members of the second tube members 20 because they move upward along with their upper hook members 32A. At this point, the next higher rung, that is, the second rung 50 can be pulled upward. After the upper hook members of the next higher tube members 30 are moved upward and engaged into the corresponding locating holes formed on the lower tube members 20, the next higher rung, that is, the third rung 50, can be further pulled upward. In the same manner, other higher telescopic sections and rungs can be sequentially extended.
Reversely, when the ladder is downward pushed to collapse it, the rollers 32F in front of the upper hook members 32A
in the second tube members 20 rotate when they are pressed against an inner wall of the tube members 20, allowing the upper hook members 32A to disengage from the locating holes l0A of the tube members 10. A compression effect similar to the function of a piston will be created on each of the plug assemblies at the bottom of the tube members, forcing the one-way valves 70 to close. Air in the tube members is compressed and can only escape from the relatively small air outlet 31F on the rear insert, permitting the ladder to be-collapsed slowly. When the tube members 20 are collapsed to such an extent that the lower hook members 32B thereof engage with the bevelled projections 32G of the upper hook members 32A of the plug assemblies 30A in the first tube members 10 due to the spring force of the return springs 32H
and the bevel surfaces of the bevelled projections 32G, the higher tube members 20 are therefore connected to the lower tube members 10. In the same manner, the other higher tube members are sequentially collapsed and connected to their 215'842 respective immediate lower tube members, permitting the completely collapsed ladder to be carried by just holding its highest rung without the risk of unexpectedly extending again. Moreover, with the locking mechanisms, the lock ensuring mechanisms, and the general switch assembly which will be described in more details later, the ladder can be automatically and sequentially collapsed stair by stair from bottom to top.
Fig. SA shows the locking mechanism and the lock ensuring mechanism of the present invention, Wherein the locking mechanism 80 each consists of a sleeve member 80A, a locking pin 81, a touch arm 81A, a push block 81B, a first pin member 81C, and a spring 81D. The sleeve member 80A is fitted into the locating hole 54 formed at each end of the _ second rung 50. One end of the locking pin 81 is inserted into the sleeve member 80A while the other end of the locking pin 81 is threaded through the spring 81D to extend into a substantially reverse U-shaped stopper 57 disposed in the second rung 50.' Below the locking pin 81, the first pin member S1C is used to connect the touch arm 81A to the push block 81B and fixedly locate them in the rung 50, such that when the touch arm 81A is touched, the locking pin 81 can be moved backward so as to unlock the locking mechanism 80.
The lock ensuring mechanism 82 each is composed of a locking block 83, an unlocking touch arm 83D, a first stop screw 56, and a third return spring 83E. The lock ensuring block 83 is formed at each side With a straight slide channel 83B to receive a slide block 58 in the second rung 50, whereby the Lock ensuring block 83 can be vertically slided relative to the second rung 50. The lock ensuring block 83 has an indicating block 83C projecting from a top thereof, whereby 215'7842 when the lock ensuring block 83 is moved upward to a top position of the second rung 50, the indicating block 83C
protrudes beyond a warning opening 59 formed on a top surface of the second rung 50 to indicate , the actual operating state of the lock ensuring mechanism 82.
The lock ensuring block 83 has a pin hole 83A
provided at a ,front end thereof to receive one end of the locking pin 81 extending through the reverse U-shaped stopper 57. The third return spring 83E and the unlocking touch arm 83D are disposed on a side of the locking block 83 near a rear end thereof. The unlocking touch arm 83D is formed at an outer side tacing the peripheral wall of the second rung 50 with a recess. A notch 83F is provided on a peripheral wall surrounding the recess of the unlocking touch arm 83D, such that when the lock ensuring block 83 is placed into the second rung 50 and the first stop screw 56 is screwed through the peripheral wall of the second rung 50, a lower side of the screw 56 abuts against the peripheral wall of. the recess of the unlocking touch arm 83D
to limit the lock ensuring block 83 to travel only within a distance defined by the unlocking touch arm 83D.
Fig. 5B shows the general switch assembly 90 and the locking mechanism 80 mounted in the first (the lowest) rung 50A of the present invention. Since these components are somewhat different from those mounted in other rungs 50, they are separately described herein. The general switch assembly 90 includes a shifting wheel 90K having a shifting arm 90B, two lock ensuring push plates 90J separately disposed at two ends of the first rung 50A, two 1 resilient engaging pieces 90C, and two pull rods 90A each being connected at one end to the shifting wheel 90K and at the other end to a locking pin 81 of the locking mechanism 80 by extending through a ~~J~~$~~
_ 16 _ central pin hole 90I formed on each lock ensuring push plate 90J.
To assemble the general switch assembly 90 and the locking S mechanisms 80 to the first rung 50A, the shifting wheel 90K
is fixed to a bottom central portion of the first rung SOA
by means of extending a second pin member 90M through the peripheral wall of the first rung 50A and through the shifting wheel 90K. The lock ensuring push plates 90J each is disposed in the first rung SOA With two lateral edges thereof separately received in slide channels 90N formed on the peripheral wall of the first rung 50A near each end thereof, allowing the lock ensuring push plates 90J to vertically move in the first rung 50A up and down. Second stop screws 900 are separately screwed into the peripheral wall of the first rung SOA to extend into dents 90P
separately formed on a side edge of the two ensuring push .
plates 90J, so as to limit the lock ensuring push plates 90J
to vertically move within a distance defined by the dents 90P. The lock ensuring push plates 90J each has a top indicating block 83C which protrudes beyond the warning opening 59 formed on the first rung 50A. The lock ensuring push plate 90J each is formed with a central pin hole 90I
and a projected block 90D. The central pin hole 90I each has a vertical length larger than a diameter of the locking pin 81, whereby the locking pin 81 can be moved into or out of the central pin hole 90I. The resilient engaging pieces 90C each is engaged with the projected block 90D while its two lower ends are received in slide channels 90Q formed in the first rung SOA.
With the above arrangements, the extension ladder of the present invention, can be automatically and sequentially collapsed in a manner as shown in Figs. 6A, 6B, 6C, 6D and 6E, wherein the plug assemblies 30A are only schematically illustrated.
Fig. 6A illustrates the extension ladder in an extended and locked state. At this point, the lock ensuring blocks 83 of the rungs 50 and the lock ensuring push plates 90J of the rung 50A serve to disengage the locking pins 81 from the pin holes 83A and the central pin holes 90I, respectively, c allowing the rungs 50 and 50A to be in a firmly locked position relative to the higher tube members and the first tube members, respectively. Meanwhile, the resilient engaging pieces 90C separately engage with the projected blocks 90D of the lock ensuring push plates 90J.
Fig. 6B illustrataes the first step to collaps the extension ladder. First, the lock ensuring push plates 90J are pushed upward to disengage the resilient engaging pieces 90C from the projected blocks 90D of the lock ensuring push plates 90J. At this point, the indicating blocks 83C on the top of the lock ensuring push plates 90J moves upward to protrude beyond the warning openings 59, indicating the rungs and the telescopic tube members of legs are released from the safely locked position. The indicating blocks 83C can be painted in red color or with any other warning mark. Before using the extension ladder, first check for any indicating blocks 83C protruded beyond the rungs. Any protruded -indicating block 83C means the ladder is not in a locked position for safe use. At this point, the locking pins 8I each abuts against a lower edge of the central pin holes 90I, leaving a gap between the locking pin 81 and an upper edge of the central pin hole 90I. The locking pins 81 at this position are allowed to extend into the central pin holes 90I to interact with the pull rods 90A and the shifting wheel 90K.
That is, as shown in Fig. 6C, when the shifting arm 90B of the shifting wheel 90K~is shifted to pull the pull rods 90A, causing the locking pins 81 to move toward the center of the rung 50A until the locking pins 81 abut against the resilient engaging pieces 90C. At this point, the resilient engaging pieces 90C are pushed by the locking pins 81 to disengage from t'he projected blocks 90D of the lock ensuring push plates 90J. Meanwhile, the gaps between the locking pins 81 and the upper edge of the central pin holes 901 cause the lock ensuring push plates 90J to move downward which further causes the resilient engaging pieces 90C to separate from the projected blocks 90D. Therefore, when the locking pins 81 are further inserted into the lock ensuring push plates 90J and be locked thereto, the lock ensuring push plates 90J will not be stopped by the resilient engaging pieces 90C and are therefore, permitted to slide downward to a firmly and safely locked position. When the shifting wheel 90K is shifted to an upper position, a retaining leaf spring 90H on the shifting wheel 90K is stopped by a retaining projection 90U formed on a bottom center of the first rung 50A and the shifting wheel 90K is prevented from further rotating and is restricted to a fully unlocked position. This avoids undesired partial collapse of the extension ladder due to instantaneous extension by manual operation.
When the immediate higher rung 50 descends and the unlocking touch arms 83D touch the first (lowest) rung 50A, as shown in Fig. 6D, the lock ensuring blocks 83 are forced to move upward. At the same time, the indicating blocks 83C
protrude beyond the warning openings 59. When the lock ensuring blocks 83 move to an upmost position, the pin holes ~
~ 2157842 83A are aligned with the locking pins 81, allowing the locking pins 81 to move into the pin holes 83A. Meanwhile, the notches 83F of the unlocking touch arms 83D are aligned with the first stop screws 56. At this point, a downward -projected pin 90F disposed on a central position of the upper rung 50 approaches to and is aligned with a hole 90E
formed on the first (lowest) rung 50A.
As shown in Fig. 6E, before the upper rung 50 is collapsed to its lowest position, the unlocking touch arms 83D and the touch arms 81A connected to the locking pins 81 are forced to pivotally turn sideward away from the lock ensuring blocks 83 and the locking pins 81 are further moved.into the pin holes 83A, leaving the telescopic tube.members in an unlocked state and permitting the upper rung 50 to descend.
At this point, the projected pin 90F fitly engages into the hole 90E to press the retaining leaf spring 90H of the shifting wheel 90K and disengage the same from the retaining projection 90U. The shifting wheel 90IC shall restore to its .
home position due to the springs 81D at two ends of the rung. At this point, the locking pins 81 are in a position with their outer ends closing to the tube members for readily springing into the tube members and lock the same and the rung together.
Fig. 7 illustrates another embodiment of the present invention, wherein a hollow fixing beam 95 is connected between the two one-way valves 70 appositely disposed near the bottom of the first tubes 10 below the first rung 50.
An air tube 95A is disposed in the fixing beam 95 to communicate with the two one-way valves 70. In addition, a quick breather adapter 95B is provided at a center of the fixing beam 95 to communicate the air tube 95A With the ~
atmosphere. As mentioned previously, the upper hook member 32A may extend into the locating hole 33C on the front cover 33A and airtightly seals the locating hole 33C, whereby a compressed air source can be connected to the quick breather adapter 95B for the air pressure in the ladder to automatically and quickly increase.
In conclusion, the extension Ladderof the present invention can be sequentially extended for safe use. In addition, the extension of the ladder can be performed quickly while the collapse thereof- can be achieved in a slower manner.
Moreover, the extension ladder of the present invention can be easily manufactured. Therefore, the shortcomings and possible dangers in using the conventional extension ladders as mentioned in the beginning of the specification can be effectively eliminated.
What to be noted is the above embodiments are only used for illustrating the present invention, not intended to limit the scope thereof. Many modifications of the embodiments can be made without departing from the spirit of the present invention.
215'842 extended or collapsed and are therefore worn out and -become loosely connected after being used for a long period of time.
Therefore, it is necessary to provide an improved extension ladder to eliminate the above shortcomings.
SUMMARY OF THE INVENTION
It is a primary object of the present invention to provide an extension ladder having a safer and more effective structure. The extension Ladder of the present invention includes two legs which each consists of a plurality of sequentially telescoped sections. These telescopic sections each is a straight round tube having uniform diameter which .
facilitates the assembly of the telescopic sections and the rungs.
Another object of the present invention is to provide an extension ladder in which a plug assembly is mounted to a bottom end of each telescopic section thereof. The plug assembly each consists of an upper and a lower movable hook members. When the extension ladder is in a fully extended state, the upper hook members may separately extend their pointed end into retaining holes formed on the telescopic sections. The upper hook member each has a bevelled projection formed at an upper corner thereof on which a Lower hook member of the plug assembly in the next higher telescopic section hooks.when the extension ladder is in a fully collapsed state. When the ladder is extended and the upper hook members separately extends into the retaining holes on the telescopic sections, the lower hook members of the upper plug assemblies disengage from the bevelled -215°7842 _ 5 _ projection of the upper hook member, allowing the telescopic sections of the ladder to be pulled upward one by one from bottom to top.
It is a further object of the present invention to provide the above-mentioned extension ladder in which the plug assembly each is provided at a bottom portion of the upper hook member with an air cock, and at a base thereof with an air port corresponding to the air cock, and the lowest telescopic sections and the lowest rung are provided With one-way valves and cooperating air tube, respectively, whereby when the extension ladder is extended and the upper hook members pivot to .extend through the retaining holes on the telescopic sections with their bottom portions lifted, the air ports are opened to together with the one-way valves and the cooperating air tube allow the air in the telescopic sections to quickly flow through the legs and thereby permits the ladder to be quickly extended. Or, when the ladder is collapsed and the upper hook members pivot to disengage from the retaining holes on the telescopic sections with their bottom portions and accordingly the air cocks descended, the air ports are closed to slow the air flow in the telescopic sections and the collapse speed thereof.
It is still a further object of the present invention to provide an extension ladder in which locking mechanisms are separataely mounted below the rungs centered on each end thereof and a lock ensuring mechanism is disposed behind each locking mechanism, Whereby when the lock ensuring mechanisms are in a locked state, the corresponding locking mechanisms would not be unexpectedly and dangerously unlocked by pulling an pushing arm thereof. When the top ., surface of a lower rung touches the lock ensuring mechanisms of the next higher rung, the lock ensuring mechanisms of the next higher rung are unlocked to free their associated -locking mechanisms, permitting the rung and the telescopic sections of the next higher stair of the ladder to collapse.
Therefore, the rungs and the telescopic sections of other higher stairs of the ladder can be sequentially and safely collapsed from bottom to top in the same manner as described -above.
It is still a further object of the present invention to provide an extension ladder in Which a wear-proof ring member is fitted around a bottom outer periphery of each telescopic section to prevent the same from directly frictionally contacting with each other at their wall -surfaces lest the telescopic sections should become wearing and loosely contacting with each other which is dangerous to any user.
BRIEF DESCRIPTION OF THE DRAWINGS
The detailed structure and functions of the present invention can be best understood through the following detailed description of the preferred embodiments and the accompanying drawings, wherein:
Fig. 1 is a fragmentary perspective view of a conventional extension ladder, a part of which is cut away to show the manner in which the rungs are connected. to the legs of the ladder;
Fig. lA is a fragmentary, exgloded perspective view of Fig.
1 showing the structure of the leg of the ladder;
215?842 Fig. 2 is a fragmentary, exploded perspective view of an extension ladder according to the present invention, a part of which is cut away to show the assembling of a rung to two vertically telescoped sections of the legs;
Fig. 2A is a fragmentary, sectional view taken on line A-A
of Fig. 2;
Fig. 3 is an exploded perspective view of a plug assembly disposed at a bottom end of each telescopic section of the present invention;
Fig. 3A is a fragmentary, assembled, sectional view showing the positions of an upper and a lower hook members of the plug assembly in a telescopic section of the present invention;
Fig. 4A is a fragmentary, sectional view showing the manner in Which the telescopic sections of the legs of the present invention is sequentially extended from a collapsed state;
Fig. 4B is a fragmentary, sectional view showing the manner in which the telescopic sections of the legs of the present invention is gradually collapsed from an extended state;
2s Fig. 5A is a fragmentary, exploded perspective view of a locking mechanism and an associated Iock ensuring mechanism disposed in a rung other than the first or the lowest rung of the present invention;
Fig. 5B is a fragmentray, exploded perspective view of . a general switch assembly and the associated locking mechanism disposed in the first or the lowest rung of the present invention;
_$_ Figs. 6A to 6E are fragmentary, sectional views showing the operation of the mechanisms at different stairs ofthe ladder of the present invention to collapse the same; and Fig. 7 schematically shows another embodiment of the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Please refer to Fig. 2. The extension ladder of the present invention mainly includes a pair of legs lA, 1B each consisting of a plurality of telescopic section pairs, a plurality of rungs each having a peripheral wall which gives the rung a substantially reverse U-shaped cross section, a plurality of locking mechanisms 80 for locking the telescopic section pairs of the legs lA, 1B in place, and a plurality of lock ensuring mechanisms 82 cooperating with the locking mechanisms 80. The numbers of the rungs are equal to that of the telescopic section pairs. In the first embodiment of the present invention, reference numerals 50A
and 50 are designated to the first (the lowest) and the other higher rungs, respectively. The telescopic sections of the legs lA, 1B each is formed from a straight round tube member having uniform diameter through its length. A lower telescopic section or tube member always has an inner diameter larger than an outer diameter of a telescopic section or tube member immediately above it, such that every higher telescopic section can always be fitly received in a telescopic section immediately below it. In this embodiment, the telescopic sections of the legs lA, 1B are sequentially named the first tube member 10, the second tube member 20, the third tube member 30,..... from bottom to top.
21~78~~
_ g A sleeve member 60 and a plug assembly 30A are disposed on a top end and a bottom end of each telescopic section, respectively. Figs. 2 and 2A illustrate the manner in which the next lower or the second rung 50 (that is, the rung immediately above the first rung 50A) and the next lower telescopic section pairs (that is, the second tube members 20) are assembled and locked in place. Since every other stairs of the ladder of the present invention and either lateral side thereof are assembled in the same manner, they are not repeatedly explained herein. Of course, in the actual assembling, it must begin with the lowest (that is, the first) pair of telescopic sections and the lowest rung from either side thereof.
Please refer to Figs. 2 and 2A. To form the second stair of the extension ladder, first insert the third tube members 30 downward to pass through the sleeve members 60 fitted over the top end of the second tube members 20. The third tube members 30 each is premounted at its lower end with a plug assembly 30A. The manner in which the plug assembly 30A is assembled and functions will be described in more details later in this specification. Then, the second rung 50 is put over and engaged with a top end of the third tube members 30. Allow the third tube members 30 and the plug assemblies 30A at their bottom ends to extend into the second tube members 20. The sleeve member 60 each is formed at a top end with an outward extended upper flange on which an upper and a lower locating bosses 61A, 61B are provided to respectively engage with a first locating recess 55 -formed on the second rung 50 and a second locating recess 21 formed near an upper edge of the second tube member 20, causing a first locating hole 62 to aligne with a locating hole 54 formed at one end of the second rung 50. The second tube members 20 are firmly engaged into two ends of the 2I5'~842 second rung 50 with the sleeve members 60 between them without the risk of turning relative to the the second rung 50. An elongated slot 51 is formed at either end of the second rung 50 and a pair of threaded holes 52 are oppositely formed on the peripheral wall of the second rung 50 at two sides of each slot 51, whereby fastening screws 53 can be passed through the threaded holes 52 to narrow the slots 51 and thereby tightly bind the second rung 50 With the second tube members 20.
The locking mechanisms 80 are disposed near the ends of the second rung 50 on a central axis thereof and the lock ensuring mechanisms 82 are separately disposed just behind the locking mechanisms 80. For the first (lowest) stair of the ladder, a general switch assembly 90 can be additionally provided beneath the first rung 50A to cooperate with the lock ensuring mechanism to control the extension or collapse of the entire ladder.
Fig. 3 illustrates in details the manner in which the plug assembly 30A and the third tube member 30 are assembled.
The plug assembly 30A each consists of a front cover 33A, a rear cover 33B, a front insert 31A, and a rear insert 31B.
Both the front insert 31A and the rear insert 31B are formed at their lower outer wall with a lower flange. A first pin 32I is used to pass an inner side of the front insert 31A
while.threading through a first return spring 32H and pivotally connecting an upward extended and movable upper -hook member 32A to the front insert 31A. The upper hook member 32A is provided on its one side surface at an upper corner thereof with a bevelled projection 32G. A roller 32F is disposed in a hollow space formed at a front portion of the upper hook member 32A with a somewhat flexible cover plate 32J fitted in front of the roller 32F, such that when the upper hook member 32A extends into a locating hole 33C 'formed on the front cover 33A, the locating hole 33C is airtightly sealed. An air cock 32E is provided at a bottom end of the upper hook member 32A. An air port 31D is formed on a base of the front insert 31A
corresponding to the air cock 32E, whereby the air part 31D
is opened or closed when the upper hook member 32A is pivotally turned about the first pin 32I to lift or lower the bottom end, respectively.
A ring ear 31E is connected to. an underside of the front insert 31A. A downward extended and movable lower hook member 32B is pivotally connected to the ring ear 31E by means of a second pin 32D which is threaded through a scond reuturn spring 32C and an upper portion of the lower hook member 32B and the ring ear 31E. The lower hook member 32B
is eccentrically positioned below the front insert 31A and is vertically aligned with the bevelled projection 32G of the upper hook member 32A. A projected block 31C is formed near a front portion of the front insert 31A such that when the front insert 31A is placed into the third tube member 30 and fitted into a locating hole 30B thereof, the front cover 33A is engaged at its bottom flange 33H With the bottom end of the third tube member 30 with a locating projection 33E
thereof extendi:ag into the locating hole 30B of the third tube member 30 and vertically abutting against the projected block 31C of the front insert 31A just beneath it, permitting a front half of the plug assembly 30A to be firmly fixed to the third tube member 30.
Then, the rear insert 31B having an air outlet 31F is inserted into the third tube member 30, permitting an 2Z5'~842 opening 33F on the rear insert 31B to communicate with an opening 30C on the third tube member 30. Then, the rear cover 33B is fitted around the third tube member 30 with a bottom flange 33G of the rear cover 33B engaging into a- -clearance between the bottom end of the third tube member 30 and the rear insert 31B. At this point, a locating projection 33D on an inner wall of the rear cover 33B
extends through the opening 33F of the rear insert 31B and engages into the opening 30C,,permitting the rear half of the plug assembly 30A to be firmly fixed to the third tube member 30.
As shown in Fig. 4A, when the assembled ladder is to be extended from a collapsed state, the lower hook members 32B
of the plug assemblies 30A in the next higher tube members that are connecting with the upper hook members 32A of the plug assemblies 30A in the lowest tube members 10 by means of the bevelled projections 32G shall become disengaged from the upper hook members 32A after one-way 20 valves 70 disposed ne-ar bottom ends of the first tube members 10 are opened due to a pressure differential resulted from the extending operation. The open of the valves 70 permits air to be supplied to the first tube members 10. Due to the air flowing in the tube members forming the legs of the ladder, the telescopic sections of the legs can be quickly extended. When the upper hook members 32A of the plug assemblies 30A in the second tube members 20 are moved to a point in alignment with locating holes l0A formed on the first tube members 10, the upper hook members 32A are sprung toward the locating holes l0A
under the spring force of the first return springs 32H
and thereby open the air ports 31D. At this point, the air further flows upward. Meanwhile, the lower hook members 32B
s ~ 215'842 of the immediately higher telescopic sections 30 are released from the bevelled projections 32G of the upper hook members of the second tube members 20 because they move upward along with their upper hook members 32A. At this point, the next higher rung, that is, the second rung 50 can be pulled upward. After the upper hook members of the next higher tube members 30 are moved upward and engaged into the corresponding locating holes formed on the lower tube members 20, the next higher rung, that is, the third rung 50, can be further pulled upward. In the same manner, other higher telescopic sections and rungs can be sequentially extended.
Reversely, when the ladder is downward pushed to collapse it, the rollers 32F in front of the upper hook members 32A
in the second tube members 20 rotate when they are pressed against an inner wall of the tube members 20, allowing the upper hook members 32A to disengage from the locating holes l0A of the tube members 10. A compression effect similar to the function of a piston will be created on each of the plug assemblies at the bottom of the tube members, forcing the one-way valves 70 to close. Air in the tube members is compressed and can only escape from the relatively small air outlet 31F on the rear insert, permitting the ladder to be-collapsed slowly. When the tube members 20 are collapsed to such an extent that the lower hook members 32B thereof engage with the bevelled projections 32G of the upper hook members 32A of the plug assemblies 30A in the first tube members 10 due to the spring force of the return springs 32H
and the bevel surfaces of the bevelled projections 32G, the higher tube members 20 are therefore connected to the lower tube members 10. In the same manner, the other higher tube members are sequentially collapsed and connected to their 215'842 respective immediate lower tube members, permitting the completely collapsed ladder to be carried by just holding its highest rung without the risk of unexpectedly extending again. Moreover, with the locking mechanisms, the lock ensuring mechanisms, and the general switch assembly which will be described in more details later, the ladder can be automatically and sequentially collapsed stair by stair from bottom to top.
Fig. SA shows the locking mechanism and the lock ensuring mechanism of the present invention, Wherein the locking mechanism 80 each consists of a sleeve member 80A, a locking pin 81, a touch arm 81A, a push block 81B, a first pin member 81C, and a spring 81D. The sleeve member 80A is fitted into the locating hole 54 formed at each end of the _ second rung 50. One end of the locking pin 81 is inserted into the sleeve member 80A while the other end of the locking pin 81 is threaded through the spring 81D to extend into a substantially reverse U-shaped stopper 57 disposed in the second rung 50.' Below the locking pin 81, the first pin member S1C is used to connect the touch arm 81A to the push block 81B and fixedly locate them in the rung 50, such that when the touch arm 81A is touched, the locking pin 81 can be moved backward so as to unlock the locking mechanism 80.
The lock ensuring mechanism 82 each is composed of a locking block 83, an unlocking touch arm 83D, a first stop screw 56, and a third return spring 83E. The lock ensuring block 83 is formed at each side With a straight slide channel 83B to receive a slide block 58 in the second rung 50, whereby the Lock ensuring block 83 can be vertically slided relative to the second rung 50. The lock ensuring block 83 has an indicating block 83C projecting from a top thereof, whereby 215'7842 when the lock ensuring block 83 is moved upward to a top position of the second rung 50, the indicating block 83C
protrudes beyond a warning opening 59 formed on a top surface of the second rung 50 to indicate , the actual operating state of the lock ensuring mechanism 82.
The lock ensuring block 83 has a pin hole 83A
provided at a ,front end thereof to receive one end of the locking pin 81 extending through the reverse U-shaped stopper 57. The third return spring 83E and the unlocking touch arm 83D are disposed on a side of the locking block 83 near a rear end thereof. The unlocking touch arm 83D is formed at an outer side tacing the peripheral wall of the second rung 50 with a recess. A notch 83F is provided on a peripheral wall surrounding the recess of the unlocking touch arm 83D, such that when the lock ensuring block 83 is placed into the second rung 50 and the first stop screw 56 is screwed through the peripheral wall of the second rung 50, a lower side of the screw 56 abuts against the peripheral wall of. the recess of the unlocking touch arm 83D
to limit the lock ensuring block 83 to travel only within a distance defined by the unlocking touch arm 83D.
Fig. 5B shows the general switch assembly 90 and the locking mechanism 80 mounted in the first (the lowest) rung 50A of the present invention. Since these components are somewhat different from those mounted in other rungs 50, they are separately described herein. The general switch assembly 90 includes a shifting wheel 90K having a shifting arm 90B, two lock ensuring push plates 90J separately disposed at two ends of the first rung 50A, two 1 resilient engaging pieces 90C, and two pull rods 90A each being connected at one end to the shifting wheel 90K and at the other end to a locking pin 81 of the locking mechanism 80 by extending through a ~~J~~$~~
_ 16 _ central pin hole 90I formed on each lock ensuring push plate 90J.
To assemble the general switch assembly 90 and the locking S mechanisms 80 to the first rung 50A, the shifting wheel 90K
is fixed to a bottom central portion of the first rung SOA
by means of extending a second pin member 90M through the peripheral wall of the first rung 50A and through the shifting wheel 90K. The lock ensuring push plates 90J each is disposed in the first rung SOA With two lateral edges thereof separately received in slide channels 90N formed on the peripheral wall of the first rung 50A near each end thereof, allowing the lock ensuring push plates 90J to vertically move in the first rung 50A up and down. Second stop screws 900 are separately screwed into the peripheral wall of the first rung SOA to extend into dents 90P
separately formed on a side edge of the two ensuring push .
plates 90J, so as to limit the lock ensuring push plates 90J
to vertically move within a distance defined by the dents 90P. The lock ensuring push plates 90J each has a top indicating block 83C which protrudes beyond the warning opening 59 formed on the first rung 50A. The lock ensuring push plate 90J each is formed with a central pin hole 90I
and a projected block 90D. The central pin hole 90I each has a vertical length larger than a diameter of the locking pin 81, whereby the locking pin 81 can be moved into or out of the central pin hole 90I. The resilient engaging pieces 90C each is engaged with the projected block 90D while its two lower ends are received in slide channels 90Q formed in the first rung SOA.
With the above arrangements, the extension ladder of the present invention, can be automatically and sequentially collapsed in a manner as shown in Figs. 6A, 6B, 6C, 6D and 6E, wherein the plug assemblies 30A are only schematically illustrated.
Fig. 6A illustrates the extension ladder in an extended and locked state. At this point, the lock ensuring blocks 83 of the rungs 50 and the lock ensuring push plates 90J of the rung 50A serve to disengage the locking pins 81 from the pin holes 83A and the central pin holes 90I, respectively, c allowing the rungs 50 and 50A to be in a firmly locked position relative to the higher tube members and the first tube members, respectively. Meanwhile, the resilient engaging pieces 90C separately engage with the projected blocks 90D of the lock ensuring push plates 90J.
Fig. 6B illustrataes the first step to collaps the extension ladder. First, the lock ensuring push plates 90J are pushed upward to disengage the resilient engaging pieces 90C from the projected blocks 90D of the lock ensuring push plates 90J. At this point, the indicating blocks 83C on the top of the lock ensuring push plates 90J moves upward to protrude beyond the warning openings 59, indicating the rungs and the telescopic tube members of legs are released from the safely locked position. The indicating blocks 83C can be painted in red color or with any other warning mark. Before using the extension ladder, first check for any indicating blocks 83C protruded beyond the rungs. Any protruded -indicating block 83C means the ladder is not in a locked position for safe use. At this point, the locking pins 8I each abuts against a lower edge of the central pin holes 90I, leaving a gap between the locking pin 81 and an upper edge of the central pin hole 90I. The locking pins 81 at this position are allowed to extend into the central pin holes 90I to interact with the pull rods 90A and the shifting wheel 90K.
That is, as shown in Fig. 6C, when the shifting arm 90B of the shifting wheel 90K~is shifted to pull the pull rods 90A, causing the locking pins 81 to move toward the center of the rung 50A until the locking pins 81 abut against the resilient engaging pieces 90C. At this point, the resilient engaging pieces 90C are pushed by the locking pins 81 to disengage from t'he projected blocks 90D of the lock ensuring push plates 90J. Meanwhile, the gaps between the locking pins 81 and the upper edge of the central pin holes 901 cause the lock ensuring push plates 90J to move downward which further causes the resilient engaging pieces 90C to separate from the projected blocks 90D. Therefore, when the locking pins 81 are further inserted into the lock ensuring push plates 90J and be locked thereto, the lock ensuring push plates 90J will not be stopped by the resilient engaging pieces 90C and are therefore, permitted to slide downward to a firmly and safely locked position. When the shifting wheel 90K is shifted to an upper position, a retaining leaf spring 90H on the shifting wheel 90K is stopped by a retaining projection 90U formed on a bottom center of the first rung 50A and the shifting wheel 90K is prevented from further rotating and is restricted to a fully unlocked position. This avoids undesired partial collapse of the extension ladder due to instantaneous extension by manual operation.
When the immediate higher rung 50 descends and the unlocking touch arms 83D touch the first (lowest) rung 50A, as shown in Fig. 6D, the lock ensuring blocks 83 are forced to move upward. At the same time, the indicating blocks 83C
protrude beyond the warning openings 59. When the lock ensuring blocks 83 move to an upmost position, the pin holes ~
~ 2157842 83A are aligned with the locking pins 81, allowing the locking pins 81 to move into the pin holes 83A. Meanwhile, the notches 83F of the unlocking touch arms 83D are aligned with the first stop screws 56. At this point, a downward -projected pin 90F disposed on a central position of the upper rung 50 approaches to and is aligned with a hole 90E
formed on the first (lowest) rung 50A.
As shown in Fig. 6E, before the upper rung 50 is collapsed to its lowest position, the unlocking touch arms 83D and the touch arms 81A connected to the locking pins 81 are forced to pivotally turn sideward away from the lock ensuring blocks 83 and the locking pins 81 are further moved.into the pin holes 83A, leaving the telescopic tube.members in an unlocked state and permitting the upper rung 50 to descend.
At this point, the projected pin 90F fitly engages into the hole 90E to press the retaining leaf spring 90H of the shifting wheel 90K and disengage the same from the retaining projection 90U. The shifting wheel 90IC shall restore to its .
home position due to the springs 81D at two ends of the rung. At this point, the locking pins 81 are in a position with their outer ends closing to the tube members for readily springing into the tube members and lock the same and the rung together.
Fig. 7 illustrates another embodiment of the present invention, wherein a hollow fixing beam 95 is connected between the two one-way valves 70 appositely disposed near the bottom of the first tubes 10 below the first rung 50.
An air tube 95A is disposed in the fixing beam 95 to communicate with the two one-way valves 70. In addition, a quick breather adapter 95B is provided at a center of the fixing beam 95 to communicate the air tube 95A With the ~
atmosphere. As mentioned previously, the upper hook member 32A may extend into the locating hole 33C on the front cover 33A and airtightly seals the locating hole 33C, whereby a compressed air source can be connected to the quick breather adapter 95B for the air pressure in the ladder to automatically and quickly increase.
In conclusion, the extension Ladderof the present invention can be sequentially extended for safe use. In addition, the extension of the ladder can be performed quickly while the collapse thereof- can be achieved in a slower manner.
Moreover, the extension ladder of the present invention can be easily manufactured. Therefore, the shortcomings and possible dangers in using the conventional extension ladders as mentioned in the beginning of the specification can be effectively eliminated.
What to be noted is the above embodiments are only used for illustrating the present invention, not intended to limit the scope thereof. Many modifications of the embodiments can be made without departing from the spirit of the present invention.
Claims (19)
1. An extension ladder comprising a pair of legs, a plurality of rungs each having two lateral ends for said legs to pass therethrough, and a plurality of locking mechanisms disposed at a bottom side of said rungs, being characterized in that each of said legs consists of a plurality of telescoped straight circular tube members and a sleeve member is disposed in an upper end of each said tube member near where said tube member connecting with one of said rungs, and that said sleeve member each has a top flange which just rests on said upper end of each said tube member when said sleeve member is mounted in said tube member to support and fitly engage with one of said rungs.
2. An extension ladder as claimed in claim 1, wherein said sleeve member each is formed at said top flange with an upper locating boss and said rungs each is formed at a position corresponding to said upper locating boss with a locating recess, permitting said sleeve member to fitly connect said rung by engagement of said locating boss with said locating recess.
3. An extension ladder as claimed in claim 1 or 2, wherein said sleeve member each is further formed with a lower locating boss and said tube member each is formed at a position corresponding to said lower locating boss with a locating recess, permitting said sleeve member to firmly attach to said tube member without turning relative to said tube member.
4. An extension ladder as claimed in claim 1, wherein said two lateral ends of each said rung are in the form of a ring and are respectively provided with an elongated slot at a predetermined position, and threaded holes are formed on a peripheral wall of each said rung at two opposite sides of each said elongated slot, permitting fastening screws to separately extend through said threaded holes to narrow the elongated slots, such that said tube member each is tightly received within said ring-shaped end of said rung.
5. An extension ladder as claimed in claim 1, wherein a plug member is mounted to a bottom end of each said tube member, said plug member each having a lower flange at a bottom end thereof, to extend beyond said bottom end of said tube member to serve as a buffer when said telescopic tube members are collapsed.
6. An extension ladder as claimed in claim 5, wherein said plug member each is formed with a locating projection at an outer portion thereof to correspond to a hole formed on each said tube member for said plug member to firmly locate in said tube member.
7. An extension ladder as claimed in claim 1, wherein cover members are fitted around each said tube member to prevent said telescopic tube members from directly frictionally contacting with each other.
8. An extension ladder as claimed in claim 7, wherein said cover members each is formed at an inner wall with a locating projection to correspond to a locating hole formed on each said tube member for said cover member to firmly attach to said tube member.
9. An extension ladder as claimed in claim 1, wherein a plug assembly is mounted to a bottom end of each said tube member, said plug assembly each consisting of an insert member and a cover member, said insert member being disposed in each said tube member while said cover member being disposed around each said tube member, said insert member each having a lower flange at a bottom end thereof to extend beyond said bottom end of said tube member and contact with a lower end of said cover member, serving as a buffer when said telescopic tube members are collapsed and preventing said telescopic tube members from directly fractionally contacting with each other.
10. An extension ladder as claimed in claim 9, wherein said cover member each is formed at a bottom portion with an inward flange and said insert member each is formed with a locating projection at an outer portion thereof to correspond to and extend into holes separately formed on each said tube member and on each said cover member for said insert member to firmly locate in said tube member with said inward flange of said cover member abutting against said lower end of said tube member and said lower flange of said insert member extending beyond said inward flange of said cover member, such that said plug assembly is firmly attached to said tube member.
11. An extension ladder as claimed in claim 9, wherein said insert member each consists of a front insert and a rear insert and said cover members consists of a front cover and a rear cover.
12. An extension ladder as claimed in claim 11, wherein said front and said rear covers are respectively formed at their bottom portion with an inward flange, said front insert is formed with a locating projection at an outer portion thereof to correspond to and extend into holes separately formed on each said tube member and on each said front cover, and said rear cover being formed at an inner wall with a locating projection to correspond to and to extend into holes separately formed on each said tube member and on each said rear insert, such that said inward flanges of each said front and said rear cover abut against said bottom end of each said tube member and said lower flanges of each said front and said rear insert extend beyond said inward flanges of said cover member, permitting said plug assembly to firmly attach to said tube member.
13. An extension ladder as claimed in claim 5 or 9, wherein said plug member or said plug assembly each is provided with a resilient movable upper hook member having a hook portion which extends into a corresponding locating hole formed on each said tube member to retain said tube member in a fixed position without the risk of unexpectedly sliding down again when said ladder is pulled to extend from a bottom end toward an upper end thereof.
14. An extension ladder as claimed in claim 13, wherein a roller is disposed in a front portion of each said upper hook member, whereby said upper hook member can move along an inner wall of each said tube member in a rolling manner without abrading said inner wall of said tube member.
15. An extension ladder as claimed in claim 13, wherein said upper hook member each has a bevelled projection disposed on one side at an upper rear corner thereof, and wherein said plug member or said plug assembly each is further eccentrically provided at a bottom side with a resilient movable lower hook member such that said lower hook member is vertically aligned with said bevelled projection of said upper hook member, whereby when said ladder is in a collapsed state, each said upper hook member, by means of its bevelled projection, links with a lower hook member in a next higher tube member of said ladder, and when said ladder is to be extended from the collapsed state and a first pair of said upper hook members are caused to extend into said corresponding locating holes formed on a first pair of said tube members, said lower hook members of said next higher tube members originally linking with said upper hook members disengage from said upper hook member now, permitting said first pair of telescopic tube members to be extended, and other higher pairs of telescopic tube members can extended sequentially from bottom to top in the same manner.
16. An extension ladder as claimed in claim 13, wherein said upper hook member each is provided at a lower bottom with an air cock and said plug member or said plug assembly each is provided at its base portion with an air port corresponding to said air cock on said upper hook member, such that when each said upper hook member extends into said corresponding locating hole formed on said tube member and causes its lower bottom and accordingly said air cock to lift, said air port is opened, and when each said upper hook member moves out of said corresponding locating hole formed on said tube member and causes its lower bottom and accordingly said air cock to lower, said air port is closed, thereby, air flow in and through said legs of said extension ladder can be controlled to facilitate the quick extension or the moderate collapse of said extension ladder.
17. An extension ladder as claimed in claim 16, wherein a one-way valve is provided near a bottom end of the first or the lowest pair of said tube members to supply additional air into said legs to facilitate a quick extension and a moderate collapse of said extension ladder.
18. An extension ladder as claimed in claim 17, wherein a cover plate having dimensions slightly larger than those of said locating hole formed on each tube member corresponding to each said upper hook member is provided in front of said upper hook member for the latter to extend through a middle opening on said cover plate before it extends into said locating hole, such that said locating hole is airtightly sealed when said upped hook member extends into it.
19. An extension ladder as claimed in claim 18, wherein an air tube is connected to each said one-way valve at said first pair of tube members for supplying pressurizing air into said first pair of tube members which have been airtightly sealed at said locating holes to speed the extension of said extension ladder.
Priority Applications (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA002291986A CA2291986A1 (en) | 1995-09-08 | 1995-09-08 | An extension ladder with telescopic legs |
| CA 2157842 CA2157842C (en) | 1995-09-08 | 1995-09-08 | Extension ladder with telescopic legs |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA 2157842 CA2157842C (en) | 1995-09-08 | 1995-09-08 | Extension ladder with telescopic legs |
Related Child Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002291986A Division CA2291986A1 (en) | 1995-09-08 | 1995-09-08 | An extension ladder with telescopic legs |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CA2157842A1 CA2157842A1 (en) | 1997-03-09 |
| CA2157842C true CA2157842C (en) | 2000-06-13 |
Family
ID=4156576
Family Applications (2)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA 2157842 Expired - Fee Related CA2157842C (en) | 1995-09-08 | 1995-09-08 | Extension ladder with telescopic legs |
| CA002291986A Abandoned CA2291986A1 (en) | 1995-09-08 | 1995-09-08 | An extension ladder with telescopic legs |
Family Applications After (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002291986A Abandoned CA2291986A1 (en) | 1995-09-08 | 1995-09-08 | An extension ladder with telescopic legs |
Country Status (1)
| Country | Link |
|---|---|
| CA (2) | CA2157842C (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN103291205A (en) * | 2013-05-03 | 2013-09-11 | 浙江迈尔工具有限公司 | Telescopic bamboo joint ladder locking mechanism |
Families Citing this family (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US8225906B2 (en) | 2008-08-22 | 2012-07-24 | Core Distribution, Inc. | Extendable/retractable ladder |
| US9416591B2 (en) * | 2014-12-02 | 2016-08-16 | Core Distribution, Inc. | Telescoping ladder with stabilizers |
| US10233692B2 (en) | 2014-12-02 | 2019-03-19 | Core Distribution, Inc. | Foldable ladder |
| NL2015340B1 (en) * | 2015-08-24 | 2017-03-16 | Lampe Holding Bv | Telescopic ladder assembly. |
| NL2018437B1 (en) * | 2017-02-28 | 2018-09-19 | Lampe Holding Bv | Telescopically extendable and collapsible ladder with air dampers |
| EP3707340B1 (en) | 2017-11-08 | 2021-06-23 | Core Distribution Inc. | Locking assembly for a telescoping ladder |
| US11795760B2 (en) | 2019-10-24 | 2023-10-24 | Core Distribution, Inc. | Ladder tripod assembly and system |
-
1995
- 1995-09-08 CA CA 2157842 patent/CA2157842C/en not_active Expired - Fee Related
- 1995-09-08 CA CA002291986A patent/CA2291986A1/en not_active Abandoned
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN103291205A (en) * | 2013-05-03 | 2013-09-11 | 浙江迈尔工具有限公司 | Telescopic bamboo joint ladder locking mechanism |
Also Published As
| Publication number | Publication date |
|---|---|
| CA2157842A1 (en) | 1997-03-09 |
| CA2291986A1 (en) | 1997-03-09 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| EEER | Examination request | ||
| MKLA | Lapsed |