Patent Description:
The present invention is related to extension ladders where the movement of the fly section relative to the base section is assisted with a force applicator. (As used herein, references to the "present invention" or "invention" relate to exemplary embodiments and not necessarily to every embodiment encompassed by the appended claims. ) More specifically, the present invention is related to extension ladders with the movement of the fly section relative to the base section is assisted with a force applicator attached to the base rails of the base section and the fly rails of the fly section.

This section is intended to introduce the reader to various aspects of the art that may be related to various aspects of the present invention. The following discussion is intended to provide information to facilitate a better understanding of the present invention. Accordingly, it should be understood that statements in the following discussion are to be read in this light, and not as admissions of prior art.

Extension ladders have a fly section that slides relative to a base section to extend the length of the extension ladder. Moving the fly section upwards requires the user to be able to lift the fly section. Similarly, when moving the fly section downwards requires the user to be able to control the fly section so the fly section does not come crashing down, possibly damaging the extension ladder. What is needed is to provide an assistance force that is part of the extension ladder itself which reduces the weight of the fly section to make it easier to lift the fly section, and separately, make it easier and safer to control the fly section when the fly section downwards relative to the base section.

<CIT> discloses a two-stage ladder. The two-stage ladder comprises: a first ladder portion provided with a plurality of first horizontal rods; a second ladder portion slidably coupled to the first ladder portion, and provided with a plurality of second horizontal rods; and a clamping portion provided in a connection part between the first ladder portion and the second ladder portion such that a gap between the second ladder portion and the first ladder portion is fixed when the second ladder portion slides to a bottom end from the first ladder portion.

Some optional features are defined by the dependent claims.

Embodiments of the invention are shown by <FIG>. <FIG> are provided to assist in understanding the invention.

Referring now to the drawings wherein like reference numerals refer to similar or identical parts throughout the several views, and more specifically to <FIG>, <FIG> and <FIG> thereof, there is shown an extension ladder <NUM>. The extension ladder <NUM> comprises a base section <NUM> having a first base rail <NUM> and a second base rail <NUM> in parallel and spaced relationship with the first base rail <NUM> and rungs <NUM> attached to and between the first and second base rails <NUM>, <NUM>. The extension ladder <NUM> comprises a fly section <NUM> having a first fly rail <NUM> and a second fly rail <NUM> in parallel and spaced relationship with the first fly rail <NUM> and rungs <NUM> attached to and between the first and second fly rails <NUM>, <NUM>. The fly section <NUM> in sliding engagement with the base section <NUM>. The extension ladder <NUM> comprises a force applicator <NUM> attached to the base section <NUM> and the fly section <NUM> which offsets some or all weight of the fly section <NUM>.

The force applicator <NUM> may offset at least <NUM>% of the weight of the fly section <NUM>. The force applicator <NUM> includes a spring assembly <NUM> attached to the first base rail <NUM> and a cable <NUM> extending from the spring assembly <NUM> and attached to the first fly rail <NUM>. As the first fly rail <NUM> slides relative to the first base rail <NUM>, the cable <NUM> moves relative to the spring assembly <NUM> and the spring assembly <NUM> applies a spring force through the cable <NUM> to the first fly rail <NUM>. The spring force may counterbalance the weight of the fly section <NUM> through the cable <NUM> when the fly section <NUM> is slid upwards relative to the base section <NUM>, making it easier for a user to slide the fly section <NUM> upwards relative to the base section <NUM>.

The spring force may counterbalance the weight of the fly section <NUM> through the cable <NUM> when the fly section <NUM> is slid downwards, making it easier for the user to slide the fly section <NUM> downwards relative to the base section <NUM>. External guides <NUM> at the top of the base section <NUM> may securely interlock the first and second base rails <NUM>, <NUM> with the first and second fly rails <NUM>, <NUM>, respectively. There is a center pulley <NUM> attached to one of the rungs <NUM> of the base rail through which a rope <NUM> extends, and a rope clamp <NUM> attached to one of the rungs <NUM> of the fly rail to attach the rope <NUM> to the fly section <NUM> so when a free end of the rope <NUM> that has passed through the center pulley <NUM>, is pulled by the user, the fly section <NUM> slides upwards relative to the base section <NUM>, and when the fly section <NUM> is moved downwards relative to the base section <NUM>, the free end of the rope <NUM> can be held by the user to slow down and control the descent of the fly section <NUM>. The force applicator <NUM> further assists the movement of the fly section <NUM> relative to the base section <NUM> by counterbalancing the weight of the fly section <NUM> so less force is necessary to pull on the rope <NUM> to slide the fly section <NUM> upwards against the action of gravity relative to the base section <NUM> compared to when the force applicator <NUM> is not present. Similarly, the force applicator <NUM> further assists the movement of the fly section <NUM> relative to the base section <NUM> by counterbalancing the weight of the fly section <NUM> so less force is necessary to hold on to the rope <NUM> and let the rope <NUM> move through the hands of the user as the fly section <NUM> slides down under the action of gravity relative to the base section <NUM> compared to when the force applicator <NUM> is not present. Internal guides on the bottom of the fly section <NUM> securely interlock the first and second base rails <NUM>, <NUM> with the first and second fly rails <NUM>, <NUM>, respectively. Locks <NUM> on the fly section <NUM> securely hold the fly section <NUM> to the base section <NUM> at a desired position. In all the embodiments described herein of the force applicator <NUM> with the ladder <NUM>, preferably there is present on the ladder <NUM> a center pulley <NUM> and a rope <NUM> to assist the user in moving the fly section <NUM>, although the center pulley <NUM> and the rope <NUM> are not necessary. The center pulley <NUM> and the rope <NUM> are completely separate and apart from the force applicator <NUM>. They do not interfere with each other. The operation of the force applicator <NUM> to move the fly section <NUM> relative to the base section <NUM> assists with the operation of the rope <NUM> and center pulley <NUM> and vice versa, but the force applicator <NUM> does not need the presence of a rope <NUM> and pulley <NUM>, and the rope <NUM> and pulley <NUM> does not need the presence of the force applicator <NUM> to operate.

The spring assembly <NUM> includes an output spool <NUM> and a storage spool <NUM> disposed adjacent the output spool <NUM>, and a power spring <NUM> positioned about the output spool <NUM> and the storage spool <NUM> and extending therebetween. As the cable <NUM> is extended from the spring assembly <NUM>, the output spool <NUM> rotates causing the power spring <NUM> on the storage spool <NUM> to be pulled over to the output spool <NUM> and wrap around the output spool <NUM>, with the power spring <NUM> on the storage spool <NUM> producing a resistive force which serves to counterbalance the weight of the fly section <NUM> through the cable <NUM>. As the cable <NUM> is retracted to the spring assembly <NUM>, the power spring <NUM> on the output spool <NUM> is caused to be pulled over to the storage spool <NUM> with the power spring <NUM> on the storage spool <NUM> producing a retractive force which serves to counterbalance the weight of the fly section <NUM> through the cable <NUM> and retract the cable <NUM>.

The spring assembly <NUM> may include a drum portion <NUM> positioned below the output spool <NUM> and attached to the output spool <NUM> in between the output spool <NUM> and the first fly rail <NUM>. The cable <NUM> wraps about the drum portion <NUM>. As the cable <NUM> extends from the drum portion <NUM> when the first fly rail <NUM> slides downwards relative to the first base rail <NUM>, the cable <NUM> rotates the drum portion <NUM> which in turn rotates the output spool <NUM> causing the power spring <NUM> on the storage spool <NUM> to move to the output spool <NUM> and apply the resistive force to the cable <NUM>. As the cable <NUM> is retracted to the drum portion <NUM> when the first fly rail <NUM> slides upwards, the power spring <NUM> on the storage spool <NUM> pulls back the power spring <NUM> on the output spool <NUM>, applying the retractive force and causing the output spool <NUM> and thus the drum portion <NUM> to rotate and retract the cable <NUM> to the drum portion <NUM>. The spring assembly <NUM> may include a roller <NUM> adjacent the output spool <NUM> over which the cable <NUM> extends from the output spool <NUM>. The roller <NUM> serves to assist the proper movement of the cable <NUM> to and from the drum portion <NUM>, and avoid the cable <NUM> from tangling and guiding the cable <NUM> to the proper position. The drum portion <NUM> and the output spool <NUM>, and the storage spool <NUM> may extend from rods <NUM> that extend from a foundation <NUM> which attaches to the first base rail <NUM>, preferably on the inside of the web <NUM> of the first base rail <NUM>. The roller <NUM> may extend from a corner of the foundation <NUM> in parallel with the rods <NUM> that extend from the foundation <NUM>.

The spring assembly <NUM> may include a housing <NUM>, as shown in <FIG>, in which the drum portion <NUM>, the output spool <NUM>, the roller <NUM> and the storage spool <NUM> are disposed. The housing <NUM> having an opening <NUM> through which the cable <NUM> extends to the first fly rail <NUM>. The housing <NUM> with the spring assembly <NUM> and the cable <NUM> may be attached to a web <NUM> of the first base rail <NUM>, as shown in <FIG>, <FIG> and <FIG>. The cable <NUM> extending from the housing <NUM> to the first fly rail <NUM> along the web <NUM> of the first fly rail <NUM>. The extension ladder <NUM> may include a cable anchor <NUM> attached to the first fly rail <NUM>, as shown in <FIG>, <FIG> and <FIG>. The force applicator <NUM> may also include a housing <NUM> with a spring assembly <NUM> and a cable <NUM> and a cable anchor <NUM> attached to the second base rail <NUM> and second fly rail <NUM> in the same way as described above with respect to the first base rail <NUM> and the first fly rail <NUM>. Preferably the cable anchor <NUM> is attached adjacent the bottom of the first fly rail 22on the inside of the web <NUM> of the first fly rail <NUM>, and the housing <NUM> with the spring assembly <NUM> attached adjacent the top of the first fly rail <NUM> on the inside of the web <NUM> of the first base rail <NUM>. The inside of the first base rail <NUM> and the inside of the first fly rail <NUM> face each other, as shown in <FIG>.

The force applicator <NUM> makes extending the fly section <NUM> easier as well as making retracting the fly section <NUM> much safer. With the force applicator <NUM>, a lower force is required to raise the fly section <NUM> relative to the base section <NUM>, as compared to the absence of a force applicator <NUM>. The force applicator <NUM> provides for a controlled/counter and balanced lowering of the fly section <NUM>. The fly section <NUM> can be safely lowered by releasing the rope <NUM>. The free end of the hoist rope <NUM> is contained and not contacting the ground.

<FIG> shows how the cable <NUM>, after leaving the CTC spring assembly <NUM>, is routed in the space between the first base rail <NUM> and first fly rail <NUM>. <FIG> and <FIG> show the cable 32terminating at a cable anchor 58which is attached to the fly rail. <FIG> shows that the cable anchor 58is riveted to the flange <NUM> of the first fly rail <NUM>. The end of the cable 32passes through a hole in the cable anchor <NUM>. A cable end 130is swaged onto the end of the cable 32to prevent the cable 32from pulling back through the hole in the cable anchor <NUM>. <FIG> shows the fly section <NUM> retracted with the base section <NUM> while <FIG> shows the fly section <NUM> retracted but without the base section <NUM>. <FIG> shows the fly section <NUM> extended with the base section <NUM> while <FIG> shows the fly section <NUM> extended but without the base section <NUM>.

<FIG> show a simplified extension ladder <NUM> in the retracted and extended positions respectively with an alternative embodiment of the force applicator <NUM> having a torque rung <NUM>. A cable <NUM> is shown mounted on the left side of the ladder <NUM>. One end of the cable <NUM> is attached to a torque drum <NUM> of the force applicator <NUM>. The cable <NUM> extends up to and passes around a base pulley <NUM> attached to the upper end of the base section <NUM>. From there the cable <NUM> extends down to a cable anchor <NUM> near the lower end of the first fly rail <NUM>. <FIG> and <FIG> show how the cable <NUM> wraps around the torque drum <NUM>. When the fly section <NUM> is retracted as in <FIG>, the cable <NUM> has been mostly unwound from the torque drum <NUM>. When the fly section <NUM> is extended as in <FIG>, some amount of cable <NUM> has been wrapped around the torque drum <NUM>. The cable <NUM> winds around the torque drum <NUM> because of the action of a torque spring <NUM> contained within the torque rung <NUM>. It is the tension in the cable <NUM> which partially offsets the weight of the fly section <NUM>.

<FIG> show the construction and the function of the torque rung <NUM>. A torque spring <NUM> is mounted around a torque shaft <NUM>. The first end <NUM> of the torque spring <NUM> is fixed to a torque shaft flange <NUM> which is connected to the torque shaft <NUM> and rotates with the torque shaft <NUM>. A second end <NUM> of the torque spring <NUM> is fixed to the torque rung <NUM> body <NUM>. The torque shaft <NUM> extends and is connected to the torque drum <NUM>. As the torque drum <NUM> rotates, the torque shaft <NUM> rotates along with the torque shaft flange <NUM> and thus the torque spring <NUM>, whose first end <NUM> is fixed to the torque shaft flange <NUM>, since the second end <NUM> of the torque spring <NUM> is fixed to the torque rung body <NUM>. A first end <NUM> of the torque rung body <NUM> is attached to a web <NUM> of the first base rail <NUM> and a second end <NUM> of the torque rung body <NUM> is attached to a web <NUM> of the second base rail <NUM> with the web <NUM> of the first base rail <NUM> between the torque shaft flange <NUM> and the torque drum <NUM>. The torque shaft <NUM> extending through the web <NUM> of the first base rail <NUM> from the torque drum <NUM> to the web <NUM> of the first base rail <NUM>.

<FIG> shows the torque rung <NUM> when the fly section <NUM> is fully extended. Several turns of cable <NUM> are wrapped around the torque drum <NUM> and the torque spring <NUM> is exerting some amount of torsion on the torque drum <NUM>. This torsion produces tension in the cable <NUM> which partially offsets the weight of the fly section <NUM>. When the fly section <NUM> is moved to the retracted position, cable <NUM> is pulled from the torque drum <NUM> which causes the torque spring <NUM> to be wound up tighter, as seen in <FIG>. Thus, depending on the spring rate of the torque spring <NUM> and its initial torsion when installed, some amount of the fly section <NUM> weight is offset by the cable <NUM> throughout the fly's range of motion.

With reference to <FIG>, the force applicator <NUM> may include a winch <NUM> attached to the base section <NUM>, and a cable <NUM> attached to the winch <NUM> and the fly section <NUM>. The fly section <NUM> is raised by the action of the winch <NUM> reeling in the cable <NUM>. The winch <NUM> may include a winch frame <NUM> attached to the base rail, and a cable spool <NUM> mounted in the winch frame <NUM>. The cable spool <NUM> has a portion <NUM> around which the cable <NUM> can wrap. Flanges <NUM> of the spool have gear teeth <NUM> which function as driven gears. A driving pinion <NUM> with gear teeth <NUM> is mounted in the winch frame <NUM>. The driving pinion <NUM> engages the driven gears of the cable spool <NUM> so that rotating the driving pinion <NUM> CW causes the cable spool <NUM> to rotate CCW. The cable <NUM> is reeled in on the cable spool <NUM> when the driving pinion <NUM> is rotated CCW. A driving hex <NUM> connected to the driving pinion <NUM> extends up from the winch <NUM>, the driving hex <NUM> engages a hex socket <NUM> which is held in a chuck <NUM> of a power drill <NUM>.

<FIG> and <FIG> show views of the ladder <NUM> with the fly section <NUM> retracted and with the fly section <NUM> extended. The winch <NUM> is attached to the base section <NUM>. The base pulley <NUM> is attached to the upper end of the first base rail <NUM>. A cable <NUM> extends from the winch <NUM>, passes around the base pulley <NUM>, and is anchored to the fly section <NUM> at the fly cable anchor. The fly section <NUM> is raised by the action of the winch <NUM> reeling in the cable <NUM>.

<FIG> shows the components of the winch <NUM>. The winch frame <NUM> is attached to the first base rail <NUM>. The cable spool <NUM> is mounted in the winch frame <NUM>. The cable spool <NUM> has a portion <NUM> around which cable <NUM> can wrap. The flanges <NUM> of the spool have gear teeth <NUM> (not shown) so that they function as driven gears. A driving pinion <NUM> with gear teeth <NUM> (not shown) is mounted in the winch frame <NUM>. The driving pinion <NUM> engages the driven gears of the cable spool <NUM> so that rotating the driving pinion <NUM> CW causes the cable spool <NUM> to rotate CCW. Cable <NUM> is reeled in on the cable spool <NUM> when it is rotated CCW. A driving hex <NUM> connected to the driving pinion <NUM> extends up from the winch <NUM>. This driving hex <NUM> is designed to engage a hex socket <NUM> which is held in the chuck <NUM> of a power drill <NUM>.

<FIG> shows a power drill <NUM> with a hex socket <NUM> in its chuck <NUM> engaged with the driving hex <NUM> of the winch <NUM>. Running the power drill <NUM> in the CW direction would reel in the cable <NUM> and so cause the fly section <NUM> to be extended.

<FIG> are broken views showing the path of the cable <NUM> when the fly section <NUM> is in its retracted position.

<FIG> show the winch <NUM> when the fly section <NUM> is in its extended position. Notice that cable <NUM> has wrapped around the cable spool <NUM>.

Note, it is not intended that the winch <NUM> and cable <NUM> be used to hold the fly section <NUM> in position when the ladder <NUM> is in use. Conventional ladder locks (not shown) would be used. The purpose of the winch <NUM> and cable <NUM> is to enable a user to raise a ladder fly section <NUM> more easily by using a power drill <NUM>. It is intended that when the power drill <NUM> is shut off or removed from the winch <NUM>, the fly section <NUM> will descend by its own weight until its ladder locks properly engage a base rung, or it is fully retracted. Other types of motors to power the winch can be used other than a power drill <NUM>. A power drill <NUM> is very convenient since it is commonly available when a ladder is used. Basically, any type of motor or generator, preferably portable, can be used to lift the fly section which has an interface to transfer the rotational force generated by the motor to the extension ladder to raise and/or lower the fly section <NUM>. The interface can be the hex socket <NUM> attached to a driveshaft of a motor and in turn rotationally connected with the driving hex <NUM> of the ladder <NUM>. Alternatively, there may be no cable but instead a rack on one of the fly rails of the fly section <NUM>, which engages with a pinion on the base section <NUM>, such as one of the base rails adjacent to one of the fly rails that has the rack. The motor effectively turns the pinion which lifts or lowers the fly section through the rack. The motor may be removably attached to the ladder <NUM> to cause the fly section <NUM> be raised or lowered relative to the base section <NUM>, and then completely separated from the ladder <NUM> when the motor is no longer needed so as not to and further weight to the ladder <NUM>. Ideally, the motor is separate and apart from the ladder <NUM> so it does not contribute any weight to the ladder <NUM> and in weight to the ladder <NUM> when it is moved. Only when the ladder <NUM> is in position with the motor the connected with the ladder to lift and/or lower the fly section <NUM> relative to the base section <NUM>.

In another embodiment, the force applicator <NUM> may be a clock-work type power spring <NUM>. A clock-work type power spring <NUM> produces torque on the shaft <NUM> which is connected to the drum <NUM>. When the fly section <NUM> is fully retracted, the power spring <NUM> is wound most tightly. The power spring <NUM> unwinds (relaxes) as the fly section <NUM> moves toward the extended position. The power spring <NUM> is sized to apply torque on the drum <NUM> and so tension in the cable <NUM> and so partially offset the weight of the fly section <NUM> throughout the range of motion of the fly section <NUM>.

<FIG> show a simplified extension ladder <NUM> in the retracted and extended positions. The climbing side is seen in <FIG> and <FIG> and the non-climbing side is in <FIG>. The major components are the power spring unit <NUM> which is connected to the first base rail <NUM> by a bracket <NUM>, a pulley on the first base rail <NUM>, a cable anchor <NUM> on the first fly rail <NUM>, a drum <NUM> on the power spring unit <NUM>, and the cable <NUM>. One end of the cable <NUM> is fixed to and wraps around the drum <NUM>. The cable <NUM> extends from the drum <NUM> to the pulley and then to the cable anchor <NUM> on the first fly rail <NUM>. Tension produced in the cable <NUM> by the power spring unit <NUM> tends to make the fly section <NUM> move from the retracted to the extended position.

<FIG> show how the cable <NUM> wraps around the drum <NUM>. When the fly section <NUM> is extended as in <FIG>, some amount of cable <NUM> is taken up by the drum <NUM>. When the fly section <NUM> is retracted as in <FIG>, nearly all of the cable <NUM> has been unwrapped from the drum <NUM>.

<FIG> show an additional feature. When the ladder <NUM> is in use, the power spring unit <NUM> is in the deployed position of <FIG>, where the power spring unit <NUM> extend essentially perpendicular from the rungs <NUM>. However, for transporting or storing the ladder <NUM>, the power spring unit <NUM> can be moved into the stowed position of <FIG>, where the power spring unit <NUM> is in line and parallel with the rungs <NUM>. (The cable is not shown. ) This stowing action is accomplished by the power spring unit <NUM> pivoting about the end of its bracket <NUM>, as seen in <FIG>. The bracket <NUM> is able to pivot about a pivot pin <NUM> between a deployed position where the drum <NUM> and power spring unit <NUM> extend perpendicularly from the base section <NUM> and a stowed position where the drum <NUM> and power spring unit <NUM> are parallel with the base section <NUM> for transporting or stowing the extension ladder <NUM>.

<FIG> show more details of the power spring unit <NUM> and drum <NUM>. A clock-work type power spring 92attached to the shaft 150produces torque on the shaft <NUM> which is connected to the drum <NUM>. When the fly section <NUM> is fully retracted, the power spring <NUM> is wound most tightly. The power spring <NUM> unwinds (relaxes) as the fly section <NUM> moves toward the extended position. The power spring <NUM> is sized to apply torque on the drum <NUM> and so tension in the cable <NUM> and so partially offset the weight of the fly section <NUM> throughout the range of motion of the fly section <NUM>. The power spring <NUM> is disposed in and protected by a housing <NUM>. One end of the power spring <NUM> is attached to the housing <NUM> and the other end of the power spring <NUM> is attached to the shaft <NUM>. By being attached to the housing <NUM>, it is a fixed point about which the power spring <NUM> tightens or loosens as the shaft <NUM> rotates the power spring <NUM>.

In another embodiment, the force applicator <NUM> is a foot pedal <NUM> which raises the fly section <NUM> a distance of one rung spacing each time the pedal is pressed down fully.

<FIG> shows the ladder <NUM> with the fly section <NUM> retracted. A foot pedal <NUM> slides up and down in a foot pedal track <NUM> attached to the lower end of a base rail. A cable <NUM> is attached to the foot pedal <NUM>. The cable <NUM> extends up to a base pulley <NUM> at the upper end of the base rail. The cable <NUM> passes around the base pulley <NUM> and is attached to a ratchet base <NUM>. This ratchet base <NUM> is constrained to slide up and down the base rail. A tension spring <NUM> biases the ratchet base <NUM> to move down the first base rail <NUM>, and so, also biases the foot pedal <NUM> to move upward in the foot pedal track <NUM> because of tension in the cable <NUM>. The total travel of the ratchet or the foot pedal <NUM> is about <NUM> inches.

A ratchet <NUM> is attached to the ratchet base <NUM>. A ratchet spring <NUM> biases the ratchet <NUM> toward its extended position, as seen in <FIG> and <FIG>.

A ratchet stud <NUM> is attached to the ratchet base <NUM>. When the ratchet base <NUM> is in its lowest position and therefore the foot pedal <NUM> is in its uppermost at-rest position, the ratchet stud <NUM> is in contact with the ratchet <NUM> and so causes it to be in its retracted position. Pushing down on the foot pedal <NUM> a short distance causes the ratchet base <NUM> to move upward and away from contact with the ratchet stud <NUM>. This initial movement allows the ratchet <NUM> to move to its extended position.

Fly studs <NUM> are attached to the first fly rail <NUM> at incremental distances. These increments correspond to the distances between the ladder rungs <NUM>. These fly studs <NUM> are located so as to engage with the ratchet <NUM> when the ratchet <NUM> is extended, but will pass freely over the ratchet <NUM> when it is retracted.

It is assumed that the ladder <NUM> is equipped with conventional ladder locks <NUM> and a standard hoisting rope arrangement. For simplicity, the hoisting rope and its pulley are shown only in <FIG> and <FIG>.

<FIG> shows a side view of the ladder <NUM> shown in <FIG>. The foot pedal <NUM> is in its uppermost position. Contact with the ratchet stud <NUM> is holding the ratchet <NUM> in its retracted position. It should be noted that when the ladder <NUM> is in this condition, the hoisting rope could be used to raise or lower the fly section <NUM> in a conventional manner.

In <FIG>, the user has pushed downward on the foot pedal <NUM> a short distance. This initial motion has allowed the ratchet <NUM> to extend so that it might engage a fly stud.

In <FIG>, the user has pushed the foot pedal <NUM> all the way down. The ratchet base <NUM> and ratchet <NUM> have moved upward a full incremental distance, carrying a fly stud (and the first fly rail <NUM>) with it. <FIG> are seen in perspective in <FIG> and <FIG>.

After the fly section <NUM> has risen one incremental distance, the ladder locks <NUM> would engage the fly section <NUM> as usual. At this point, the user can allow the foot pedal <NUM> to rise to its uppermost position which lowers the ratchet base <NUM> and ratchet <NUM> until they are in a position to engage the next fly stud. By repeating the up and down motion of the foot pedal <NUM>, the fly section <NUM> is easily raised, using leg strength, one rung at a time.

<FIG> shows the ladder <NUM> which has just been fully extended, the foot pedal <NUM> is still down.

<FIG> and <FIG> show the ladder <NUM> fully extended, the foot pedal <NUM> in its uppermost at-rest position, the ratchet <NUM> retracted. At this point the fly section <NUM> may be lowered using the hoisting rope in the conventional way.

Note that when the foot pedal <NUM> is in its uppermost position, the fly section <NUM> may be lowered from any incremental position by using the hoisting rope.

In another embodiment, the force applicator <NUM> includes a tension gas spring <NUM>, a fixed pulley block <NUM> and a moving pulley block <NUM>. <FIG> show views of the ladder <NUM> with the fly section <NUM> retracted and with the fly section <NUM> extended. The tension gas spring <NUM> is attached to the lower end of a first base rail <NUM>. The base pulley <NUM> is attached to the upper end of the first base rail <NUM>. The axle <NUM> of the fixed pulley block <NUM> is attached to the first base rail <NUM>. The moving pulley block <NUM> is attached to the end of the tension gas spring piston rod <NUM>. A cable <NUM> has one end attached to the fixed pulley block <NUM>. The cable <NUM> passes back and forth between the fixed and moving pulley blocks <NUM>, <NUM>. The outgoing cable <NUM> extends to the base pulley <NUM>, passes around it, and is attached to the first fly rail <NUM> at the fly cable attachment.

<FIG> show the operation of the cable <NUM>, pulley blocks, and tension gas spring <NUM>. When the ladder fly section <NUM> is in the retracted position as shown in <FIG>, the tension gas spring piston rod <NUM> is fully extended, which puts the pulley blocks close to each other. In this condition enough cable <NUM> has been extended from the pulley blocks to allow the fly section <NUM> to be in its retracted position. When the ladder fly section <NUM> is in its extended position as shown in <FIG>, the pulley blocks have been moved apart by the retraction of the tension gas spring piston rod <NUM> and cable <NUM> has been drawn into the pulley blocks which results in the fly section <NUM> being in its extended position.

The action of the pulley blocks is that of a conventional block and tackle arrangement. The motion of the moving pulley block <NUM> produces an amplified motion of outgoing cable <NUM> in proportion to the number of times the cable <NUM> passes back and forth between the pulley blocks. The tension in the cable <NUM> as it leaves the pulley blocks is reduced from the tension of the gas spring by that same ratio.

For example, if the cable <NUM> passes back and forth <NUM> times between the pulley blocks, the outgoing cable <NUM> tension will be <NUM>/<NUM> of the gas spring tension. But the outgoing cable <NUM> will extend <NUM> times the motion of the gas spring. So, a <NUM>-pound gas spring with an <NUM>-inch stroke will be able to supply a tension of <NUM> pounds over <NUM> inches of cable extension. This <NUM>-pound tension can serve to counteract some amount of the fly section <NUM> weight, enabling the user to extend and retract the fly section <NUM> easily.

It is assumed that the counterbalance force will always be less than the weight of the fly section <NUM>. Locking the fly section <NUM> at the desired height prior to climbing will be accomplished by conventional ladder locks <NUM> on the fly section <NUM> engaging the appropriate base rung.

In another embodiment, the force applicator <NUM> includes a dual diameter drum <NUM>. <FIG>, <FIG> show views of the ladder <NUM> with the fly section <NUM> retracted. A tension gas spring <NUM> is fixed to the lower end of the first base rail <NUM>. A drum anchor <NUM> is attached to the first fly rail <NUM>. A dual diameter drum <NUM> rotates on an axle <NUM> which is part of the drum anchor <NUM>. There is a cable anchor <NUM> attached to the upper end of the base section <NUM>. The lower cable <NUM> extends from the moving end of the gas spring and wraps around and is attached to the larger diameter portion <NUM> of the dual diameter drum <NUM>. The upper cable <NUM> is attached to the cable anchor <NUM> and wraps around and is fixed to the smaller diameter portion <NUM> of the dual diameter drum <NUM>. (<FIG> show the drum diameters more clearly. ) <FIG> and <FIG> show views of the ladder <NUM> with the fly section <NUM> fully extended.

<FIG> show how the cables wrap around the dual diameter drum <NUM>. When the fly section <NUM> is retracted as in <FIG>, most of the lower cable <NUM> is wrapped around the larger diameter portion <NUM> of the dual diameter drum <NUM> and the upper cable <NUM> is mostly un-wrapped from the smaller diameter portion 170of the dual diameter drum <NUM>. When the fly section <NUM> is extended as in <FIG>, most of the lower cable <NUM> has unwrapped from the larger diameter portion 172of the dual diameter drum <NUM> and most of the upper cable <NUM> has wrapped around the smaller diameter portion 170of the dual diameter drum <NUM>.

<FIG> shows the principle of operation of this dual diameter drum <NUM> design. The upper part of <FIG> shows the drum <NUM> and cables when the fly section <NUM> is retracted. The gas spring applies a tension force to the moveable end of the lower cable <NUM>. The reaction force on the axle <NUM> of the drum <NUM> is a fraction of the applied force on the lower cable <NUM>. This fraction is in proportion to the ratio of the two diameters of the dual diameter drum <NUM>. This reaction force on the axle <NUM> acts on the fly section <NUM> to offset its weight. The lower part of <FIG> shows the dual diameter drum <NUM> and cables when the fly section <NUM> is extended. The dual diameter drum <NUM> will roll toward the fixed end of the upper cable <NUM> (carrying the first fly rail 22with it) a distance which is a multiplication of the applied motion of the end of the cable <NUM>.

For example, the diameters of the dual diameter drum <NUM> can be chosen so that an applied gas spring force of <NUM> pounds on the moveable end of the cable <NUM> will produce a reaction force on the fly section <NUM> (through the axle <NUM>) of <NUM> pounds. Consequently, <NUM> foot of motion at the moveable end of the cable <NUM> will cause the fly section <NUM> to move <NUM> feet. Thus, a short stroke from a gas spring can produce a long travel of the fly section <NUM>.

One other virtue of this embodiment is the fact that gas springs typically have a very low spring rate. So, the force which offsets the weight of the fly section <NUM> will remain nearly constant throughout the travel of the fly section <NUM>.

This explanation and figures have shown a gas spring being used. Gas springs are desirable because of their very low spring rate over the length of their stroke. A low spring rate results in a uniform counterbalance force over the full range of the fly section's motion. However, more conventional springs, such as coil springs, could be used if a varying counterbalance force can be tolerated.

The present disclosure pertains to a method for using an extension ladder <NUM>. The method comprises the steps of extending a fly section <NUM> of the extension ladder <NUM> relative to a base section <NUM> of the extension ladder <NUM>. There is the step of leaning the fly section <NUM> against an object. There is the step of sliding the fly section <NUM> downwards relative to the base section <NUM> while a force applicator <NUM> attached to the fly section <NUM> and the base section <NUM> applies a counterbalancing force to the fly section <NUM> to effectively reduce a weight of the fly section <NUM>. The object can be a wall or a pole.

The present disclosure pertains to a method for manufacturing an extension ladder <NUM>. The method comprises the steps of attaching a cable anchor <NUM> to a first fly rail <NUM> of a fly section <NUM> of the extension ladder <NUM>. There is the step of attaching a spring assembly <NUM> to a first base rail <NUM> of a base section <NUM> of the extension ladder <NUM>, the fly section <NUM> slidingly attached to the base section <NUM>. There is the step of attaching an end of a cable <NUM> which extends from the spring assembly <NUM> to the cable anchor <NUM>.

The step of attaching the spring assembly <NUM> may include the steps of mounting a torque spring <NUM> around a torque shaft <NUM>, fixing a second end <NUM> of a torque spring <NUM> to a torque rung body <NUM>, and fixing a first end <NUM> of the torque spring <NUM> to a torque shaft flange <NUM> which is connected to the torque shaft <NUM>. The torque shaft <NUM> extends and is connected to a torque drum <NUM>.

The present disclosure pertains to a method for using an extension ladder <NUM>. The method comprises the steps of extending a fly section <NUM> of the extension ladder <NUM> relative to a base section <NUM> of the extension ladder <NUM>. There is the step of leaning the fly section <NUM> against an object <NUM>. There is the step of sliding the fly section <NUM> downwards relative to the base section <NUM> while a force applicator <NUM> attached to the fly section <NUM> and the base section <NUM> applies a counterbalancing force from a motor engaged with the force applicator <NUM> to effectively reduce a weight of the fly section <NUM>.

Each base rail having an upper end with a cap, and a lower end with a foot, each fly rail having an upper end with a cap and a lower end with a cap. Each foot may be rotably attached to the lower end of each base rail, and may include a tread on the bottom of the foot to better grab the ground and prevent the ladder from sliding when leaning against an object. The foot may also include a spur plate extending from the foot to dig into the ground to better fix the ladder in place.

Claim 1:
An extension ladder (<NUM>) comprising:
a base section (<NUM>) including a first base rail (<NUM>) and a second base rail (<NUM>) in a spaced relation including a plurality of base rungs (<NUM>) attached to and extending between the first base rail (<NUM>) and the second base rail (<NUM>);
a fly section (<NUM>) including a first fly rail (<NUM>) and a second fly rail in a spaced relation including a plurality of fly rungs (<NUM>) attached to and extending between the first fly rail (<NUM>) and the second fly rail, the fly section (<NUM>) in sliding engagement with the base section (<NUM>); and
a force applicator (<NUM>) which offsets some or all of the weight of the fly section (<NUM>), the force applicator (<NUM>) comprising:
a spring assembly (<NUM>) attached to the first base rail (<NUM>); and
a cable (<NUM>) extending from the spring assembly (<NUM>) and attached to the first fly rail (<NUM>), (<NUM>), characterized in that the spring assembly (<NUM>) includes an output spool (<NUM>), a storage spool (<NUM>) disposed adjacent the output spool (<NUM>), and a power spring (<NUM>), wherein the power spring (<NUM>) is positioned about the output spool (<NUM>) and the storage spool (<NUM>) and extending therebetween .