EP1063387A2

EP1063387A2 - Ladder having locking device and method for manufacturing the same

Info

Publication number: EP1063387A2
Application number: EP99310087A
Authority: EP
Inventors: Ik Woo Lee
Original assignee: Individual
Current assignee: Individual
Priority date: 1999-06-22
Filing date: 1999-12-15
Publication date: 2000-12-27
Also published as: EP1063387A3; EP1063387A4

Abstract

A ladder with a locking device comprises a pair of inner rotating plates (102, 103) provided with a plurality of hinge holes spaced apart at predetermined angles; a rotating plate (106) with notch portions (105) corresponding to the hinge holes, said rotating plate rotating on an outer surface of the inner rotating plates (102, 103) to selectively open the hinge holes; a resilient member (107) biasing the rotating plate (106) to an initial state of closing the hinge holes, one end of said resilient member (107) being secured to the rotating plate (106) and the other end secured to one of the inner rotating plates (102); a pair of outer rotating plates (109, 110) with fixing holes formed on one side and supporting said inner rotating plates (102, 103) rotatably; and a locking key (114) including a guide pin (112) for securing the rotating plate (106), inner rotating plates (102, 103) and outer rotating plates (109, 110), and a fixing pin (113) for selective insertion into the hinge holes, said locking key (114) being adapted to lock after the ladder has been spread by rotating the inner rotating plates (102, 103) with respect to the outer rotating plates (109, 110), this being possible when the fixing pin (113) has been released from the hinge holes by the pressing of a push cover (115). The releasing of the hinge assembly due to an external force is prevented, thereby preventing accidents whilst facilitating the use of the ladder by enabling easy control of the locking and releasing of the assembly. Furthermore, the number of operations for assembling the ladder is reduced, thereby increasing the workability. Also, clearance between hollow beams of the ladder and the hinge assembly is obviated, thereby increasing the durability of the ladder. Furthermore, the number of parts for assembling the ladder is reduced, which in turn reduces the cost for manufacturing the ladder considerably.

Description

BACKGROUND OF THE INVENTION

The present invention relates to a ladder having a locking device and a method for manufacturing the same. Specifically, the present invention relates to a ladder obviating separate engaging members needed for connecting hollows beams to hinge assemblies of the ladder and further comprising a locking device preventing the hinge assemblies from being released due to external forces while the ladder is spread for a certain angle for use. The present invention also relates to a method of manufacturing the same ladder
Fig. 1 is a schematic perspective view of a prior art ladder. As can be seen, the ladder comprises a hinge assembly 6 composed of a pair of outer rotation plates 1 & 2, a pair of inner rotation plates 4 & 5 inserted rotatably between the outer rotation plates 1 & 2 and hinged by means of a fixing pin 3, and hollow beams 7 & 8 extending from the inner and outer rotation plates 1, 2, 4 & 5 to which foot plates (not shown) are attached. In order to connect beams 7 & 8 to the rotation plates 1, 2, 4 & 5, through holes 11 & 12 for receiving rivets (or other engaging members) 9 & 10 are formed on the rotation plates 1, 2, 4 & 5. Correspondingly, through holes 13 & 14 are formed on the hollow beams 7 & 8 to which rivets 9 & 10 are inserted.
However, clearance occurring between the beams 7 & 8 and the rotation plates 1, 2, 4 & 5 and clearance formed between the through holes 11 & 12 and the through holes 13, 14 receiving the rivets 9 & 10, deteriorates tight fits between the rotation plates 1, 2, 4 & 5 and the beams 7 & 8. Therefore, clattering may occur between these elements, which reduces endurance of the ladder. Furthermore, a plurality of rivets 9 & 10 are required to secure the rotating plates 1, 2, 4 & 5 and the beams 7 & 8, which increases the parts required for the assembly and raises the production cost. Also, this increases number of operations since it involves insertion of the rivets 9 & 10 into the through holes 11, 12, 13 & 14 after assembling the rotation plates 1, 2, 4 & 5, making the assembly procedure cumbersome.
Fig. 2 is a schematic exploded view of a hinge assembly of the ladder according to the prior art, and Fig. 3 is a schematic sectional view showing the locking state of the assembly.
As shown in Fig. 2 & 3, the ladder comprises a hinge assembly A rotating freely when released, a pressing member B and a stopper member C. The hinge assembly A comprises a pair of outer rotation plates 1 & 2, and a pair of inner rotation plates 4 & 5 inserted between the outer rotation plates 1 & 2 in a rotatable manner.
An elongated hole 19 connected to a hole 18 for receiving a stopper protrusion 16 of the stopper member C is formed on the outer rotation plates 1 & 2 of the hinge assembly A. A through hole 20 for receiving a bush 15 supported by the stopper member C is formed at a center portion of the outer rotation plates 1 & 2. A through hole 21, which receives the bush 15, is also formed at the center portion of the inner rotation plates 4 & 5. A plurality of shaft hole 22 & 23 are formed on the inner rotation plates 1 & 2 at locations radially outward with regard to the through hole 21.
The pressing member B comprises a pressing plate 24 and a pressing shaft 25 connected to the plate 24. A spring 26 is mounted on the pressing shaft 25.
Slider protrusions 30 & 31 with stopper shoulders 28 & 29 on the stopper protrusions 16 & 17 of right and left ends of the stopper handle 27 are protrudingly formed on the stopper member C which is secured to the pushing shaft 25 of the pressing portion B by means of a pin 32.
When using the above-described ladder, a user presses the pressing plate 24 of the pressing member B which causes the slider protrusions 30 of the stopper member C to reposition itself from the hole 18 to the elongated hole 19. This enables the inner rotating plates 4 & 5 to rotate with respect to the outer rotating plates 1 & 2. After the inner plates 4 & 5 are rotated so that the hole 18 of the outer rotating plates 1 & 2 moves into alignment with the corresponding holes of the inner plates 4 & 5, the stopper protrusions 16 & 17 repositions themselves into the holes of the plates. As can be seen in Fig. 3, the stopper protrusions 16 & 17 are of slanted form which enables a stable securing of the inner rotation plates 4 & 5 and the outer rotation plates 1 & 2.
However, since the pressing plate 24 of the pressing portion B protrudes from the outer rotation plate 1 and is thereby exposed, when the pressing plate 24 of the pressing portion B is pressed in axial direction of the pressing shaft 25 occurring in occasions such as when contacting with external structures, the stopper member C is released from the hole 18 of the outer rotating plates 1 & 2. Therefore, the locking of the ladder is released, rendering the inner rotation plates 4 & 5 to rotate freely with respect to the outer rotation plates 1 & 2. Hence, exposing the user to dangers of accidental falls from the ladder.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a ladder comprising a locking device preventing the hinge assembly from being released due to contact with external materials which can prevent accidental fall of a user, and a method for manufacturing the same.
It is another object of the present invention to provide a ladder comprising a locking device which can be easily released by the user to facilitated the use of the ladder, and a method for manufacturing the same.
It is still another object of the present invention to provide a ladder comprising a locking device with a simple structure reducing number of operations needed for assembling, and a method for manufacturing the same.
It is still another object of the present invention to provide a ladder, which does not result in clearance between hollow beams and the hinge assembly in order to maintain tight fits.
It is still another object of the present invention to provide a ladder with reduced number of parts in order to reduce the cost for manufacturing the ladder, and a method for manufacturing the same
In order to achieve the above objects, a ladder with a locking device according to the present invention comprises, a pair of inner rotating plates with a plurality of hinge holes spaced apart for predetermined angles; a rotating plate with notch portions corresponding to the hinge holes, said rotating plate rotating on an outer surface of the inner rotating plates to selectively open the hinge holes; a resilient member biasing the rotating plate to an initial state of closing the hinge holes, one end of said resilient member secured to the rotating plate and the other end secured to the inner rotational plate; a pair of outer rotating plate with fixing holes formed on a side and supporting said inner rotating plates rotatably; and a locking key including a guide pin securing the rotating plate, inner rotating plates and outer rotating plates, and a fixing pin selectively inserted into the hinge holes, said locking key locking after spreading the ladder by rotating the inner rotating plates with respect to the outer rotating plates when the fixing pin is released from the hinge holes by pressing of a push cover.
Above stated objects are accomplished by a method of manufacturing a ladder with a locking device according to the present invention comprising, a first step of securing a pair of inner rotating plates into a symmetrical outer rotating plates in a hinged manner; a second step of forming a securing groove at left and right corners of the elongated portion of the pair of inner rotating plates and the rotating plates forming a hinge assembly; and a third step of engaging a mold with shape identical to the sectional shape of the elongated portion having the securing groove to an outer side of the beam to engross the corners of the beams to the securing groove by press working after securing the hollow beams to elongated portions.
Preferably, the push cover is engrossed within a safety cover mounted on the outer rotating plate in order to prevent the locking key from being released and the ladder from spreading.
Preferably, a slanted surface is formed at one side of the notch portion, and further comprises another slanted surface guiding said fixing pin of the fixing key sliding along the slanted surface to the hinge holes when the fixing pin is released to spread the ladder.
Preferably, said hinge holes are formed at 40, 105 and 180 degrees and the inner rotating plates being rotated with respect to the outer rotating plates and locked thereto at said angles.
Preferably, a stopper is provided which configures the engaging location of the beam to the outer rotating plates and the inner rotating plates.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic perspective view showing a ladder according to the prior art.
FIG. 2 is a schematic drawing showing a hinge assembly of the ladder according to the prior art.
FIG. 3 is a schematic sectional view showing the use of the locking device of Fig. 2.
FIG. 4 is a schematic exploded view of the locking portions of the ladder comprising a locking device according to the present invention.
Fig. 5 shows a ladder according to the present invention assembled.
Fig. 6a & 6b is a schematic view showing the locking device according to the present invention locked and released.
Fig. 7 shows the ladder including a locking device being used.
Fig. 8 is a flow chart showing a method of manufacturing the ladder with the locking device according to the present invention.
Fig. 9 is a sectional view of the connecting portion of the hinge assembly and the hollow beams according to the present invention.

DETAILED DESCRIPTION OF THE INVENTION

A preferred embodiment of the present invention will be described hereafter in detail for illustrative sense only, and this embodiment should not be in any sense be interpreted as restricting the scope of the present invention.
In FIG. 4 to 7, an embodiment according to the present invention comprises a pair of symmetric inner rotation plates 102 & 103 where a plurality of hinge holes are formed at 40 degrees, 105 degrees and 180 degrees locations, and a pair of outer rotating plates 109 & 110 where a fixing hole is formed on a location corresponding to the hinge holes and a engaging hole 111 is formed at a center portion thereof. The outer rotating plates 109 & 110 support the inner rotating plates 102 & 103 in a rotatable manner.
The embodiment further comprises a rotating plate 106 and a resilient member 107. On the rotating plate 106, a fixing hole 104, notch portions 105 corresponding to the hinge holes 101 are formed. The rotating plate 106 selectively opens the hinge holes 101 and is rotatably mounted on the outer surface of the inner rotating plate 102. One end of the resilient member 107 is fixed onto the rotating plate 106 while the other end is fixed to the inner rotating plate 102, thereby resiliently biasing the rotating plate 106 to close the hinge holes 101 when external force is not exerted.
A guide pin 112 fixing the inner and outer rotating plates 109 & 110 and the rotating plate 106 and a fixing key 114 are provided. The guide pin 112 comprises a fixing pin 113. The fixing key 114 fixes the ladder after it rotates by moving the inner rotating plates 102 & 103 with respect to the outer rotating plates 109 & 110 when the fixing pin 113 is released from the hinge holes 101 by pressing a push cover 115 provided at one end of the guide pin 112.
In order to prevent the ladder from released from the locked state when the push cover 115 is pressed unintentionally which can release the fixing key 114, the push cover 115 is engrossed in a safety cover 116 mounted on the outer rotating plate 109.
When the fixing key 113 of the fixing key 114 is released from the hinge holes 101 by pressing the push cover 115, slanted surfaces 105a are formed on the notch portions 105 in order to guide the fixing pin 113 into the hinge holes 101 after rotating the inner rotating plate 102 & 103 with respect to the outer rotating plates 109 & 110. The reference numerals 117 & 118 denotes beams connected to lower portions of the inner and outer rotating plates 102, 103, 109 & 110 while the reference numeral 119 denotes a rivet securing the outer rotating plates 109 & 110. The reference numeral 120 denotes a locking knob which shows the user if the locking key 121 is in a locked or a released state. The reference numeral 114 denotes a resilient member securing the fixing key 114.
Hereinafter, a method of manufacturing the ladder will be described in detail.
As shown in the flow chart of Fig. 8, a pair of outer rotating plates 109 & 110 and inner rotating plates 102 & 103 which form the hinge assembly are bent in symmetrical manner(S10).
Within the spacing formed between the outer rotating plates 109 & 110, the inner rotating plates 102 & 103 are inserted and fixed so that they can make relative rotations(S20).
Fixing grooves 102b, 103b, 109b & 110b are formed on the left and right corners of the extending portions 102a & 103a of the inner rotating plates 102 & 103 and the extending portions 109a & 110a of the outer rotating plates 109 & 110(S20).
After securing the hollow beams 117 & 118 to the extended portions 102a, 103a, 109a & 110a, press molds(not shown) having identical shape as the sectional shape of the extended portions 102a, 103a, 109a & 110a with fixing grooves 102b, 103b, 109b & 110b are placed at sides of the beams 117 & 118(S40).
By pressing the press mold using a press machine, the corners of the beams 117 & 118 are engrossed within the fixing holes 102b, 103b, 109b & 110b(S50).
Therefore, as shown in Fig. 9, the method according to the present invention does not require any rivet or bolt to secure the hollow beams 117 & 118 to the inner rotating plates 102 & 103 and outer rotating plates 109 & 110.
Furthermore, since the extending portions 102a, 103a, 109a & 110a of the hinge assembly and the beam 117 & 119 are tightly connected, clearance between these parts does not occur, thereby enhancing the durability of the ladder.
Hereinafter, the method of using the ladder with the locking device according to the present invention will be described in detail.
As shown in Fig. 6a and Fig. 7, the ladder is initially collapsed for storing when not in use. Here, the fixing pin 113 of the fixing key 114 is inserted into the hinge hole 101 a on the inner rotating plates 102 & 103.
As shown in Fig. 6b, when expanding the ladder 40 degrees for use, the user presses the push cover 115 and engrosses it into the safety cover 116. This releases the fixing pin 113 of the fixing key 114 from the hinge hole 101. Simultaneously, by moving the locking knob 120 fixed on the rotating plate 106 mounted on outer side of the inner rotating plate 102, the hinge hole 101 is closed by the rotating pin 106, thereby releasing the fixing key 114 from the locking state.
At this time, the front end of the fixing pin 113 is located at upper surface of the rotating plate 106 which enables the inner rotating plates 102 & 103 to rotate with respect to the outer rotating plates 109 & 110. When spreading the ladder by rotating the inner rotating plates 102 & 103 with respect to the outer rotating plates 109 & 110, the locking pin 113 rotates along the upper surface of the rotating plate 106 and slides into the hinge holes 101b along the slanted surface 105a of the notch portion 105. Thereafter, releasing of the fixing pin 113 of the fixing key 114 from the hinge hole 101b is prevented by the resilient force of the resilient member 121 provided on the fixing pin 113. That is, the locking key 114 locks the inner rotating plates 102 & 103 and the outer rotating plates 109 & 110 at 40 degrees.
Since the push button 115 releasing the fixing key 114 from the locking state is engrossed within the safety cover 116 mounted on the outer rotating plate 109, the locking of the locking key 114 can be maintained. That is, when the user is operating on the ladder, the releasing of the fixing key 114 due to external force is prevented, thereby preventing accidents.
As can be seen in the preferred embodiment, the locking of the hinge assembly due to external force is prevented, thereby preventing the safety accidents. However, intentional control of the locking and releasing of the assembly is easy, facilitating the use of the ladder.
Furthermore, the number of operations for assembling the ladder is reduced, thereby increasing the workability.
Also, clearance between the hollow beams and the hinge assembly is prevented, thereby increasing the durability of the ladder. Furthermore, the number of parts for assembling the ladder is reduced, which in turn reduces the cost for manufacturing the ladder considerably.

Claims

A ladder with a locking device comprising:

a pair of inner rotating plates with a plurality of hinge holes spaced apart for predetermined angles;

a rotating plate with notch portions corresponding to the hinge holes, said rotating plate rotating on an outer surface of the inner rotating plates to selectively open the hinge holes;

a resilient member biasing the rotating plate to an initial state of closing the hinge holes, one end of said resilient member secured to the rotating plate and the other end secured to the inner rotational plate;

a pair of outer rotating plate with fixing holes formed on a side and supporting said inner rotating plates rotatably; and

a locking key including a guide pin securing the rotating plate, the inner rotating plates and the outer rotating plates, and a fixing pin selectively inserted into the hinge holes, said locking key locking the ladder after spreading the ladder by rotating the inner rotating plates with respect to the outer rotating plates when the fixing pin is released from the hinge holes by pressing of a push cover.
The apparatus of claim 1, wherein the push cover is engrossed within a safety cover mounted on the outer rotating plate in order to prevent the locking key from being released and the ladder spreading.
The apparatus of claim 2, a slanted surface is formed at one side of the notch portion, and further comprising another slanted surface guiding said fixing pin of the fixing key sliding along the slanted surface to the hinge holes when the fixing pin is released to spread the ladder.
The apparatus of claim 1, wherein said hinge holes are formed at 40, 105 and 180 degrees and the inner rotating plates being rotated with respect to the outer rotating plates and locked thereto at said angles.
A method of manufacturing a ladder with a locking device comprising:

a first step of hinge securing a pair of inner rotating plates into a symmetrical outer rotating plates in a hinged manner;

a second step of forming a securing groove at left and right corners of the elongated portion of the pair of inner rotating plates and the rotating plates forming a hinge assembly; and

a third step of engaging a press mold with shape identical to the sectional shape of the elongated portion having the securing groove to an outer side of the beam to engross the corners of the beams to the securing groove by press working after securing the hollow beams to elongated portions.
The method of claim 5, a stopper configuring the engaging location of the beam to the outer rotating plates and the inner rotating plates.