Patent Application
20190249446
The present invention generally relates to a lifting device including a telescoping mast.
In general, a lifting device including a telescoping mast may be used to elevate a load. As examples, lifting devices including telescoping masts may be configured to elevate communication devices (e.g., antennas), lighting, vehicles (e.g., cars), vehicle components (e.g., transmissions), constructions panels (e.g., drywall, plywood panels, fiberboard panels, etc.), and other loads.
There is a possibility that these lifting devices may fail in use, whereby the telescoping mast will unexpectedly and rapidly collapse, and the load will drop under the collapsing telescoping mast. For example, panel hoists or lifts are lifting devices used to elevate a construction panel into position. Panel lifts are generally comprised of a telescoping mast and a winch. The winch usually has a braking system to prevent the telescoping mast from collapsing under the weight of the panel. However, should the line associated with the winch break or otherwise fail, the braking system will be unable to prevent the telescoping mast from collapsing under the weight of the panel. This can result in the load falling off the lifting device or the lifting device tipping over potentially causing damage or injury.
In addition, the lifting device may include a base. The base may have an opening for removably receiving the telescoping mast to connect the two components to one another. However, the tolerances required to allow the telescoping mast to be detachable from the base often results in the telescoping mast being susceptible to horizontal movement or wiggle when detachably secured to the base. While this movement can be minor close to the base, when the telescoping mast is fully extended, any horizontal movement is magnified at the top of the telescoping mast, which can damage the lifting device and/or result in the load falling off the lifting device or the lifting device tipping over potentially causing damage or injury.
In one aspect, a lifting device for elevating a load is disclosed. The lifting device includes a telescoping mast and a brake. The telescoping mast has opposite upper and lower ends. The telescoping mast includes an outer mast section and an inner mast section telescopically received within the outer mast section. The inner mast section is configured to extend in an upward direction and retract in a downward direction relative to the outer mast section. The emergency brake is secured to the inner mast section. The emergency brake includes first and second eccentrics that are configured to rotate relative to the inner mast section between an unlocked position, in which the first and second eccentrics are free from locking engagement with the outer mast section to allow retraction of the inner mast section within the outer mast section, and a locked position, in which the first and second eccentrics are in locking engagement with the outer mast section to inhibit retraction of the inner mast section within the outer mast section.
In another aspect, a lifting device for elevating a load is disclosed. The lifting device includes a telescoping mast, a head piece and a movable base. The telescoping mast is configured to extend and retract in a heightwise direction and has opposite upper and lower ends. The head piece is secured to the telescoping mast at the upper end thereof and configured to support the load thereon. The movable base is configured to support the telescoping mast in an upright position. The base includes a mast holder sized and shaped to receive a lower end of the telescoping mast therein. The mast holder defines an opening at an upper end thereof and through which the lower end of the telescoping mast enters the mast holder. The mast holder includes opposing interior mast holder surfaces that are configured to engage the lower end of the telescoping mast when the telescoping mast is received in the mast holder. The opposing interior holder surfaces define a transverse distance therebetween that tapers in a downward direction away from the opening.
Corresponding reference characters indicate corresponding parts throughout the drawings.
Referring to
The lift 10 generally includes a base 20, a telescoping mast 40, and a head piece 80, each of which is indicated generally in
Referring to
As can be seen best from
In the illustrated embodiment, a foot 32 is pivotably attached to the mast holder 21 to prevent the base 20 from rolling when the panel lift 10 is in use. When in use, the foot 32 is rotated down to engage the floor to resist movement. When not in use, the foot 32 is rotated upward and clipped to one of the legs 25 for storage. The end of the foot 32 can include a rubber grip 33 to better engage the floor and provide greater resistance to movement.
The mast holder 21 is configured to support the telescoping mast 40 in an upright position. The top plate 22 defines an upper opening 34, and the bottom plate 23 defines a lower opening 35. The upper and lower openings 34, 35 are sized and shaped to receive the telescoping mast 40 therein. In the illustrated embodiment, the upper and lower openings 34 and 35 are rectangular to match the rectangular shape of the telescoping mast 40. It is to be understood that the upper and lower openings 34, 35 may be other shapes, such as circular, corresponding to other cross-sectional shapes of the telescoping mast without necessarily departing from the scope of the present invention. The upper opening 34 is sized to tightly receive the telescoping mast 40 to provide a first point of support against horizontal movement. In a preferred embodiment, the open area of the upper opening 34 is slightly greater than the cross-sectional area of the telescoping mast 40, and preferably no greater than necessary to receive the telescoping mast therein. The open area of the lower opening 35 is greater than the open area of the upper opening 34. The open area of the lower opening 35 is sized to be more than slightly greater than the cross-sectional size of the telescoping mast 40, having an amount of clearance allowing the telescoping mast to easily pass therethrough. The larger lower opening 35 allows the telescoping mast 40 to be more easily inserted into the mast holder 21, and avoids alignment problems when inserting the mast 40 into the openings 34, 35.
A support frame, including frame members 36, is attached to and extends below the bottom plate 23. In the illustrated embodiment, the frame members 36 include cross-wise, U-shaped frame members (e.g., vertical, cross-wise plates). It is understood that the frame and the frame members 36 may be of other designs and configurations, including interconnected panel frame members. The frame members 36 have interior holder surfaces 37 extending downward from the bottom plate 23, and defining a seat 38 generally opposing the lower opening 35. The interior holder surfaces 37 extend inward or toward a vertical imaginary axis passing through the centers of the upper and lower openings 34, 35 from adjacent the bottom plate 23 toward the seat 38. In the illustrated embodiment, the upper and lower openings 34, 35 are square shaped and the interior holder surfaces 37 are positioned on each side of the lower opening 35. As shown in
As shown in
Referring to
A prime mover, generally indicated at 44, is configured to extend and retract the telescoping mast 40. The winch 44 is connected to the outer mast section 41 via an arm 39 and can rotate between a stored position (not shown) in which the winch is positioned alongside the outer mast section and a deployed position in which the winch is angled away from the outer mast section. A locking pin 45 engages an opening 47 on the support bracket 46 to lock the winch 44 in place. The locking pin 45 can be biased in a locked configuration with a spring. The winch 44 includes a spool 48 and crank 50 connected to the spool. A line 49 is operatively connected to (i.e., wound on) the spool 48 of the winch 44. It is understood the line 49 can be any flexible connection member such as a cable, strap, rope or chain without departing from the scope of the present disclosure. The illustrated crank 50 is in the form of handle or wheel secured to the spool 48 to allow an operator to wind or unwind the line 49. The winch 44 includes a spring loaded handbrake or winch brake 51 to prevent the line 49 from unwinding. One end of the line 49 is wrapped around the spool 48 with the other end attached to the second inner mast section 43, and the line 49 engaging a series of pulleys 52 (
As shown in
As shown in
In the illustrated embodiment, each eccentric 110, 120 has a non-uniform radial distance between the axis of rotation of eccentric and engagement surface along the arc length of the engagement surface 116. More specifically, the radial distance between the axis of rotation of the eccentric 110, 120 and the lower end of the engagement surface 116 is greater than the radial distance between the axis of the rotation of the eccentric and the upper end of the engagement surface 116. Thus, as described in more detail below, as each eccentric 110, 120 rotates, the engagement surface 116 will move closer and eventually engage the telescoping mast 40. In the illustrated embodiment, the engagement surface 116 is arc shaped and may have a uniform radius of curvature along its arc length. However, in other embodiments, the engagement surface may have other shapes.
The illustrated emergency brake 100 also includes a torsion spring 140 disposed between the first and second eccentrics 110, 120 along the length of the shaft 130. The shaft 130 extend through a body of the torsion spring 140, and first and second legs of the torsion spring 140 are secured to the respective first and second eccentrics 110, 120 adjacent the engagement surface 116 (i.e., at or adjacent the second end portions). The spring 140 applies opposite spring forces to the eccentrics 110, 120, including a first spring force applied to the first eccentric and a second spring force applied to the second eccentric in a direction opposite the first spring force. Thus, the spring 140 rotates the first and second eccentrics 110, 120 in opposite directions. In the preferred embodiment, the ends of the spring 140 extend through openings 141 in each eccentric 110, 120. However, any suitable attachment method, such as welding or fasteners, is within the scope of the present invention. In other embodiments, the emergency brake 100 may include other ways of applying a biasing force (e.g., resiliently biasing force) to the eccentrics in directions toward the engagement positions. For example, one or more linear springs may be operatively connected to the eccentrics.
The emergency brake 100 is secured to the inner mast section 42 near the lower end thereof. The shaft 130 is attached to the inside of the inner mast section 42 and supports the first and second eccentrics 110, 120 inside the inner mast section. The inner mast section 42 includes first and second openings 61 and 62 corresponding to the first and second eccentrics 110, 120. The first and second openings 61 and 62 are positioned to allow the first and second eccentrics 110, 120 to rotate and extend through the first and second openings to engage the outer mast section 41. A stop 150 is secured to the inner mast section 42 above the emergency brake 100 to prevent the second inner mast section 43 from contacting the brake. The stop 150 can also prevent any over rotation of the first and second eccentrics 110, 120. In the illustrated embodiment, the stop 150 is a second shaft positioned above the shaft 130 of the emergency brake 100; however, any suitable device configured to prevent the second inner mast section from contacting the brake is within the scope of the present invention.
The emergency brake 100 prevents the inner mast section 42 from collapsing by frictionally engaging the outer mast section 41 in the event the inner mast section is subject to a sudden and uncontrollable collapse (e.g., free fall experienced if the line breaks or the telescoping mast's descent is not controlled with the winch 44). The first and second eccentrics 110, 120 each have a center of gravity spaced apart radially from its rotational axis (e.g., the shaft 130). At rest, gravity acting on the offset center of gravity and the reaction force applied at the first end portions of the eccentrics 110, 120 by the shaft 130 imparts a rotational force or torque to the eccentrics in a direction that tends to rotate the eccentrics toward one another about the shaft. In this unlocked position, shown in
Upon a sudden and uncontrollable descent (e.g., free fall), such as when the line 49 breaks or the hand brake 51 is released without manually controlling the descent with the winch 44, the first and second eccentrics 110, 120 move or rotate into a locked position, shown in
The minimum magnitude of downward acceleration of the inner mast section 42 required to rotate the first and second eccentrics 110, 120 into the locked position is called the threshold magnitude. The threshold magnitude lies somewhere between greater than 0 ft/s2 (no acceleration; at rest) and 32.2 ft/s2 (9.81 m/s2; the acceleration due to gravity). If the inner mast section 42 accelerates downward at a magnitude below the threshold magnitude, the spring force is not able to overcome the torque acting on the eccentrics to rotate the first and second eccentrics 110, 120 into the locked position from the unlocked position and the first and second eccentrics remain free from locking engagement with the outer mast section 41. If the inner mast section 42 accelerates downward at a magnitude above the threshold magnitude, which will typically be the acceleration due to gravity during a sudden and uncontrollable decent or when the descent is not controlled with the winch (e.g., free fall), the spring force rotates the first and second eccentrics 110, 120 into the locked position, moving the first and second eccentrics into locking engagement with the outer mast section 41. The value of the threshold magnitude varies depending on, among other parameters, the mass of each eccentric 110, 120, the rotational friction between each eccentric and the shaft 130, and the spring constant k of the spring 140 (strength of the spring). The smaller the threshold magnitude, the quicker the emergency brake 100 will move into the locked position. However, it is preferred that the threshold magnitude is greater than a maximum magnitude of acceleration of the inner mast section 42 when the operator retracts the telescoping mast 40 with the winch 44, to prevent the emergency brake 100 from engaging the outer mast section 41 when the inner mast section is retracted. The emergency brake 100 will remain in the unlocked position as long as the magnitude of acceleration imparted by the operator when retracting the telescoping mast 40 is less than the threshold magnitude, allowing the inner mast section 42 to retract.
When the inner mast section 42 accelerates downward at a magnitude above the threshold magnitude, the spring force imparted by the spring 140 on the first and second eccentrics 110, 120 rotates each eccentric into locking engagement with the outer mast section. The first and second eccentrics 110, 120 rotate in opposite directions from the unlocked position to the locked position. As a result, the first and second eccentrics 110, 120 engage opposite sides of the outer mast section 41. As the spring 140 rotates each eccentric 110, 120 from the unlocked position, the engagement surface 116 on each eccentric engages the outer mast section 41. Once the engagement surface 116 of each eccentric 110, 120 start to engage the outer mast section 41, any continued downward movement of the inner mast section 42 relative to the outer mast section further secures the first and second eccentrics against the outer mast section. Once the engagement surface 116 starts to engage the outer mast section 41, the inner mast section 42 pushes down on the shaft 130 while the engagement surface of each eccentric remains engaged to the outer mast section, further rotating each eccentric. If the eccentrics 110, 120 include a friction-enhancing structure 114, such as teeth, the friction-enhancing structure engages the outer mast section 41 to facilitate the rotation of each eccentric 110, 120 by the outer mast section. Because the distance between the engagement surface 116 and axis of rotation of the shaft 130 increases, as each eccentric 110, 120 rotates, successive portions of the engagement surface 116 engage the outer mast section 41, increasing the locking force applied by each eccentric. At some point along the engagement surface 116, the engagement surface applies a sufficient amount of force against the outer mast section 41 to bring the inner mast section 42 to a stop (i.e. stop the inner mast section from moving relative to the outer mast section). The outer mast section 41 may or may not deflect as a result of the force applied by the eccentrics 110, 120. If the outer mast section 41 does deflect, the increasing distance along the engagement surface 116 will keep the engagement surface in contact with the outer mast section. Once the first and second eccentrics 110, 120 apply enough locking force against the outer mast section 41, the inner mast section 42 comes to a rest, stopping the fall of the inner mast section. In this locked position, the first eccentric 110 extends through the first opening 61 to engage the outer mast section 41 and the second eccentric 120 extends through the second opening 62 to engage the outer mast section, preventing the inner mast section 42 from falling relative to the outer mast section. Thus, it is apparent that the emergency brake 100 operates independent of the line 49 and is able to prevent the inner mast section 42 from falling should the line break or the descent is not controlled with the winch 44. Because the emergency brake 100 operates independent of the lifting or moving system that elongates or retracts the telescoping mast, the emergency brake 100 can be incorporated into any type of telescoping mast. For example, the emergency brake 100 can be incorporated into a telescoping lift, a panel lift, a drywall lift, a transmission lift, a lighting lift, a communications lift, or any other type of telescoping mast supporting a load that can be raised and/or lowered.
To disengage the emergency brake 100 from the locked position, the inner mast section 42 is extended or lifted in the upward direction. As the inner mast section 42 is lifted the first and second eccentrics 110, 120 rotate towards the unlocked position. This rotation gradually disengages the engagement surface 116 on each eccentric 110, 120 from contacting the outer mast section 41. Once each eccentric 110, 120 completely disengages the outer mast section 41, each eccentric rotates, due to gravity, back to the unlocked position. The inner mast section 42 can then be retracted or lowered in the downward direction.
Referring to
The mechanical linkage 260 provides additional mass to facilitate compression of the spring 240 by the first and second eccentrics 210, 220. Thus, when the emergency brakes 100 and 200 are generally similar in size, a stronger spring 240 may be used in the emergency brake 200 of the second embodiment than the emergency brake 100 of the first embodiment to compensate for the additional mass of the mechanical linkage 260. However, it is understood that the springs 140 and 240 are sized according to each emergency brake 100, 200. For example, where the emergency brake 200 has a smaller mass than emergency brake 100, the spring 240 may not be stronger than spring 140. In addition, the mechanical linkage 260 prevents the first and second eccentrics 210, 220 from over rotation when the emergency brake 200 is attached to the telescoping mast 40, when the first and second eccentrics are in the locked position, and when the emergency brake is not yet attached to the telescoping mast during assembly.
In the illustrated embodiment, an emergency brake 100 of the first embodiment is attached to the lower end of the inner mast section 42 and an emergency brake 200 of the second embodiment is attached to the lower end of the second inner mast section 43. It is appreciated that the emergency brake 100 and emergency brake 200 are interchangeable. For example, after accounting for the differences in relative size and placement, the emergency brake 200 can be attached to the inner mast section 42 and the emergency brake 100 can be attached to the second inner mast section 43, or the telescoping mast 40 can only include one type of emergency brake 100 or 200 for each mast section.
The emergency brake 200 of the second embodiment is secured to the second inner mast section 43 and operates in a similar way as described above in reference to emergency brake 100. The second inner mast section 43 includes first and second openings 71, 72 corresponding to the first and second eccentrics 210, 220. The first and second openings 71, 72 are positioned to allow the first and second eccentrics 210, 220 to rotate and extend through the first and second openings to engage the inner mast section 42. In the unlocked position, shown in
It is apparent that more than three mast sections can be included in the telescoping mast 40 and that any mast section telescopically received within another mast section can include an emergency brake 100 or 200 as described herein to prevent the mast section from falling relative to the other mast section. It is also apparent that while the brakes described above include first and second eccentrics 110, 120 or 210, 220, it is possible that the brakes only have one eccentric. In such an arrangement, one end of the spring 140 or 240 would remain attached to the eccentric and the other end would be secured to the shaft or elsewhere on the mast section.
Referring to
Each panel edge support 85 is secured to one end of a movable rail 87. Each rail 87 is a c-shaped channel and fits inside the hollow body of the cross member 82. The end of the rail 87 opposite the panel edge support 85 is positioned inside the hollow body of the cross member 82. Each rail 87 can slide in and out of an open end of the cross member 82. In this manner, each rail 87 slides along the cross member 82 on one side and the other rail 87 on the opposite side. Both rails 87 can slide pass each other as they slide inside the hollow body of the cross member 82. Adjacent to each open end of the cross member 82 is a locking pin 88. The locking pin 88 engages a set of holes (not shown) located on each rail 87 to prevent the rail from sliding. The holes are spaced at set intervals along the length of each rail 87. Each locking pin 88 is connected to the side of the cross member 82 corresponding to the side the rail 87 slides along. As the rail 87 slides in and out of the cross member 82, the locking pin 88 can engage a hole to prevent the rail from further movement. The locking pins 88 can be biased in a locked configuration with a spring. In this manner, the locking pins 88 can be pulled away from the cross member 82 to disengage the pin from the hole in the rail 87 and then snap back into another hole as the rail is sliding. As explained in more detail below, the ability for the panel edge supports 85 to be moved to different locations allows the head piece 80 to support different panels of varying widths.
Referring to
The mounting base 90 has opposite top and bottom surfaces. A pin 96 extends from the bottom surface in a direction away from the top surface of the mounting base 90. The pin 96 is sized and shaped to fit inside a corresponding cylindrical opening in the top of the telescoping mast 40. Two bearing flanges 97 extend from the top surface in a direction away from the bottom surface of the mounting base 90. The two bearing flanges 97 are generally parallel with one another. A bearing 98 is secured to each bearing flange 97. The bearings 98 are aligned and receive a shaft 95 therein. The shaft 95 is longer than the width of the mounting base 90 such that when the shaft is inserted into the bearings 98, each end of the shaft extends pass the side edge margin of the mounting base 90. A hole at the center of the shaft 95 receives a fastener 27 to connect a spring bracket 99 to the shaft. The spring bracket 99 is U-shaped with a hole on either side. The fastener 27 extends through the hole on one side of the spring bracket 99, through the hole in the shaft 95 and then through the opposite side of spring bracket to connect the spring bracket to the shaft. This connection allows the spring bracket 99 to pivot. A spring shaft 79 extends from the spring bracket 99 in an opposite direction from the sides of the spring bracket. A spiral spring 78 surrounds the spring shaft.
Referring to
To load a panel onto the head piece 80, typically the cross arms 83 will be rotated to position the hooks 84 closer to the floor. The panel can also be loaded onto the head piece 80 when the clip 76 locks the cross arms 83 in a horizontal plane. In the illustrated embodiment, the cross arms 83 rotate until the base 91 of the cross member bracket 89 or the spring 78 contacts the mounting base 90. In the preferred embodiment, the cross arms 83 rotate a maximum of about 60 degrees relative to the horizontal plane. However, any rotation between 0 and 90 degrees is within the scope of the present invention. Once the cross arms 83 are rotated, the panel is placed on the cross arms with the hooks 84 engaging the lower edge of the panel to prevent the panel from sliding off. The rails 87 slide in or out of the cross member 82 to position the panel edge supports 85 adjacent to the sides of the panel. Each panel edge support 85 prevents the panel from sliding or tilting off the cross arms 83.
To attach the head piece 80 to the telescoping mast 40, the pin 96 is inserted into the corresponding cylindrical opening in the top of the telescoping mast. To remove the head piece 80, the head piece is lifted until the pin 96 is no longer in the cylindrical opening. The pin 96 also allows the head piece 80 to rotate, 360 degrees, around the telescoping mast 40 to better position the cross arms 83 and/or panel.
To operate the panel lift 10, the operator assembles the panel lift 10 by deploying the legs 25 on the base 20, inserting the lower end of the telescoping mast 40 into the mast holder 21, and inserting the pin 96 of the head piece 80 into the cylindrical opening at the upper end of the telescoping mast. The operator then adjusts the head piece 80 to receive the panel. Once the panel is loaded onto the head piece 80, the operator turns the winch 44 to retract the line 49 and extend the telescoping mast 40 in an upward direction. After the panel is unloaded, the operator turns the winch 44 in the opposite direction to extend the line 49 and retract the telescoping mast 40 in a downward direction. As the telescoping mast 40 retracts, the first and second eccentrics 110, 120 and 210, 220 of each brake remain in an unlocked position, free of locking engagement, allowing the inner mast section 42 to retract within the outer mast section 41 and the second inner mast section 43 to retract within the inner mast section 42. If the line or other flexible connection member 49 breaks while the telescoping mast 40 is in an extended position, the emergency brake 100 on the inner mast section 42 will engage the outer mast section 41, preventing the inner mast section from collapsing relative to the outer mast section. Likewise, the emergency brake 200 on the second inner mast section 43 will engage the inner mast section 42, preventing the second inner mast section from collapsing relative to the inner mast section. If the emergency brakes 100 and 200 engage, the operator can then disengage each brake and retract the telescoping mast 40. Once the operator is done using the panel lift 10, the operator can disassemble the panel lift by detaching the head piece 80, the telescoping mast 40, and the base 20 for each other.
In view of the above, it will be seen that the several features of the invention are achieved and other advantageous results obtained.
The telescoping structure 40 is removably secured to the base 20 in a manner to prevent horizontal movement or wiggle. The upper opening 34 is sized to tightly receive the telescoping mast 40 and the angled interior holder surfaces 37 are able to engage each side of the telescoping mast, as the telescoping mast is lowered into the base 20, to ensure the telescoping mast is firmly secured in the base. In another aspect of the present invention, the telescoping mast 40 does not rely on a braking system connected to the winch to prevent the telescoping mast from falling. The emergency brakes 100 and 200 of the present invention operate independent of any prime mover, such as a line 49, used to extend or retract the telescoping mast. Thus, the emergency brakes 100 and 200 can stop the sections of the telescoping mast 40 from collapsing in the event the prime mover fails.
Having described the invention in detail, it will be apparent that modifications and variations are possible without departing from the scope of the invention defined in the appended claims.
When introducing elements of the present invention or the preferred embodiment(s) thereof, the articles “a”, “an”, “the” and “said” are intended to mean that there are one or more of the elements. The terms “comprising”, “including” and “having” are intended to be inclusive and mean that there may be additional elements other than the listed elements.
As various changes could be made in the above products without departing from the scope of the invention, it is intended that all matter contained in the above description and shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.
