Patent Application
20060032340
The present invention relates to apparatus for tensioning shaft-mounted helical springs, and in particular for tensioning shaft-mounted torsion springs of overhead doors.
Sectional overhead doors for residential and commercial garages typically have a number of hinged horizontal sections with rollers at each end that run inside tracks extending vertically on each side of the door opening. The tracks continue either vertically or, perhaps most commonly, horizontally inward above the door opening to accommodate the door when in its open position. These doors commonly incorporate a counterweighting system to reduce the effective door weight that must be lifted by a manual or motorized door-opening mechanism.
The components of a typical counterweighting system include an elongate round shaft with a pulley at each end, and at least one helical torsion spring mounted generally concentrically on the shaft. The shaft is rotatably mounted to the building structure above and parallel to the door opening. Each pulley has a door-lifting cable attached to the door at a selected point, typically near the bottom of the door. One end of the spring is non-rotatably fixed to the building structure, and the other end is fixed to a spring cone which in turn is lockably mounted onto the shaft (typically by means of set screws). The spring may be tensioned by rotating the spring cone around the shaft and then locking the spring cone on the shaft. The tensioned spring exerts a rotational force on the shaft, inducing tension forces in the cables, which in turn exert upward forces on the door. These upward forces effectively counteract and reduce the weight that needs to be lifted when operating the door.
There are many known types of spring cones, most of which incorporate a number of radial sockets (typically four) into which steel winding rods can be inserted for purposes of winding the spring cone around the shaft to tension the spring. With the spring cone loose on the shaft, a first rod is inserted into one socket and manual force is applied to the rod to rotate the spring cone and one end of the spring a partial turn, thus increasing spring tension. With the first rod being firmly held (to restrain spring tension), a second rod is inserted into another socket and used to turn the cone further. With the second rod being firmly held, the first rod may be withdrawn and moved to a new socket. This alternating process is continued until a desired spring tension has been achieved, whereupon the spring cone is tightened onto the shaft and the rods are removed from the sockets.
This well-known procedure is effective but potentially dangerous. If the rods are accidentally let go of while the spring cone is loose on the shaft, the tensioned spring will quickly unwind, causing the spring cone to spin on the shaft. If one or both rods are still engaged in spring cone sockets, they will spin rapidly with the spring cone and thus may injure a person standing too close. In fact, the rods may even fly out of the spring cone and thus become dangerous projectiles that can seriously injure or even kill a bystander. The danger inherent in such situations is greater for larger and heavier doors, which typically have heavier springs that store greater potential energy when tensioned.
These risks are particularly great when spring tensioning is being attempted by a single worker. Muscle fatigue and momentary inattention or distraction are only two factors that could cause the worker to lose hold of the winding rods. In view of these concerns, it is less dangerous if the spring tensioning procedure is performed by two workers, each operating only one winding rod. Then if one worker becomes unexpectedly tired or inattentive and loses control of one rod, the other worker will in most cases be holding the other rod safely, and preventing the spring from unwinding. An obvious disadvantage of this safer alternative procedure, however, is that the need for two workers results in higher cost for the spring tensioning operation.
For the foregoing reasons, it is desirable to have spring tensioning methods and means that do not use loose winding rods that can cause injury in case of inadvertent and uncontrolled unwinding of a tensioned spring, and, further, that can be safely by only one worker. The prior art discloses a number of attempts to address this problem. U.S. Pat. No. 2,718,282 (Davis), discloses spring tensioning apparatus having a splined cylindrical member with a longitudinal slot to permit mounting of the member over a spring shaft. The slot is then closed off using a secondary member that slides into longitudinal keyways in the cylindrical member on either side of the slot. The secondary member is also splined so as to create an effectively continuous splined perimeter around the cylindrical member when the secondary member has been positioned in the slot. The cylindrical member has means for connecting to a spring cone so that the spring cone will rotate when the cylindrical member is rotated. Also provided is a pair of pawl-equipped ratchet levers, each having a cylindrical inner surface and an opening to allow positioning over the shaft. The levers are placed over the shaft and slid over the splined cylindrical member, whereupon they may be operated in alternating fashion, with the pawls of the levers engaging the splines of the cylindrical member and causing it to rotate, thus rotating the spring cone and tightening the spring. Because the shaft openings in the levers are smaller than the diameter of the cylindrical member, the levers cannot come free of the cylindrical member without sliding them laterally off of the cylindrical member.
Although being a useful device, the Davis apparatus has several disadvantages. For example, it requires precise machining for splining of the cylindrical and secondary members, as well as for the keyways in the cylindrical member and the corresponding keys of the secondary member. Indeed, if the keyways are not machined to close tolerances, the secondary member will either fit too tightly (thus being difficult to install and remove) or it will be too loose (thus being prone to sliding out of the cylindrical member, making the apparatus inoperable. Even when these parts have been machined to provide an optimal fit, their mating surfaces can become damaged or covered with grime, paint, or other contaminants, in each case making insertion and/or removal of the secondary member difficult or impossible. Furthermore, the secondary member is of necessity a loose component that could be accidentally lost, again making the apparatus unusable.
U.S. Pat. No. 3,651,719 (Wessel) discloses another spring tensioning apparatus that operates on the ratchet principle. This apparatus features an hinged split collar assembly releasably mountable around a spring cone, with a rigid pin that goes into one of the spring cone sockets so that rotation of the collar will cause rotation of the spring cone. The split collar has rounded ratchet teeth around its perimeter, the teeth extending across the full width of the inner collar. The apparatus includes a pair of pawled ratchet handles, each with a hinged split collar section approximately half the width of the toothed inner collar. The Wessel apparatus is operated by opening the inner collar and mounting it to the spring cone, closing the inner collar and locking its hinged sections with an anchor pin, opening the ratchet handle collars of the ratchet handles and placing them over the inner collar, closing the ratchet handle collars and locking their hinged sections together with anchor pins, and, finally, operating the handles in alternating fashion to tighten the spring.
The Wessel apparatus also has disadvantages and drawbacks. Its installation requires the use of three anchor pins, and the loss of even one of these loose components may make the apparatus unusable. It also has several hinges that are prone to wear and breakage that could make efficient use of the apparatus difficult or impossible. Furthermore, installation of the Wessel apparatus on the spring shaft involves a number of steps before it is ready to operate, and these steps must also be performed in reverse in order to remove the apparatus from the shaft after the spring has been tensioned. This comparatively labour-intensive procedure increases the cost of spring tensioning.
Another ratchet-type spring tensioning device is found in U.S. Pat. No. 5,605,079 (Way). This apparatus has a split housing, which is separable for installation onto the shaft and the spring cone, with a bore for receiving the shaft and a number of pins for engaging holes in the winding cone. A split sprocket is integrally mounted to the housing and an annular groove on each side of the sprocket receives a ratchet tool. The ratchet tools are locked into the groove using bolts to prevent disengagement, and are operated in alternating fashion to rotate the sprocket, thus rotating the spring cone to adjust the tension in the spring. Disadvantages of this system include the number of loose components and the higher degree of assembly and disassembly required (i.e. assembly of the split housing and sprocket, attachment of the ratchet tools, and the corresponding disassembly once the adjustment is completed).
In view of the disadvantages of the prior art devices described above, there is a need for an improved apparatus for adjusting the tension of a helically wound torsion spring that has minimal or no small loose components prone to being misplaced, that has minimal hinged components prone to wear and disrepair, and that is simple to attach to and remove from a spring shaft, while being safely operable by a single worker. The present invention is directed to these needs.
In general terms, the invention is an apparatus for safely tensioning a torsion spring, without need for spring cone tightening rods that may pose an injury hazard in the event of an inadvertent release of spring tension during the tensioning operation. The apparatus features a central ratchet assembly with cogged ratchet wheels at each end, slotted to allow the assembly to be placed over the spring shaft adjacent to the spring cone. The ratchet assembly includes sub-apparatus connectable to the spring cone so that the spring cone (and therefore the spring) will rotate when the ratchet assembly is rotated. The slots in the ratchet wheels are closed by cogged bridging elements to create a continuously cogged perimeter around the ratchet wheels. The apparatus includes a pair of pawl-equipped operating levers that may be positioned over the ratchet wheels so that the pawls can engage the ratchet wheel cogs. The levers may then be operated in alternating fashion to rotate the ratchet assembly, thus tensioning the spring.
Accordingly, in one aspect the present invention is an apparatus for tensioning a helical spring mounted generally concentrically on an elongate round shaft having a shaft diameter, said spring having a first end fixed to a building support and a second end anchored to a spring cone lockably mounted on the shaft, said apparatus comprising:
In the preferred embodiment, the trunnion is a semi-cylindrical sleeve. In an alternative embodiment, the trunnion may be an elongate member having separate cylindrical outer surfaces for rotatably receiving the levers.
Also in the preferred embodiment, the primary ratchet wheels are mounted at opposite ends of the trunnion. In operation of the apparatus in this embodiment, the levers are mounted onto the trunnion inboard of the primary ratchet wheels. In an alternative embodiment, the primary ratchet wheels are mounted inboard of the ends of the trunnion, such that the levers are mounted onto the trunnion outboard of the primary ratchet wheels. In a variant of this alternative embodiment, the levers may be mounted either inboard or outboard of the primary ratchet wheels.
In the preferred embodiment, each bridging element is an auxiliary ratchet wheel having substantially the same configuration and features of the primary ratchet wheels. Each auxiliary ratchet wheel is rotatably and coaxially mounted to its corresponding primary ratchet wheel, such that it is rotatable relative to the primary ratchet wheel between the open and engaged position. Unlike the primary ratchet wheels, the auxiliary ratchet wheels need not have cogs around their full perimeter, although that might be convenient or advantageous in some situations. What is important is for the auxiliary ratchet wheels to have sufficient cogs positioned so as to provide a substantially continuous series of cogs around the periphery of the combined primary/auxiliary ratchet wheel combination when in the engaged position. The cogs of the two wheels will necessarily lie in closely adjacent parallel planes, such that the cogs of both wheels are readily engageable by the pawl member of one of the levers.
Alternatively, each bridging element may be a cogged element smaller than its corresponding primary ratchet wheel, mountable thereto in either hinged or swivelling fashion so that it can either swing or swivel between the open and engaged positions. Where the bridging element is a cogged element hinged to the primary wheel, it may be adapted such that when in the engaged position its cogs will lie in the same plane as the primary wheel cogs. Alternatively, and in embodiments where the bridging element is a swivelling cogged element, its cogs will typically lie in a plane parallel to and closely adjacent to the plane of the primary wheel cogs, as in the case where the bridging elements are auxiliary ratchet wheels.
In the preferred embodiment, each lever includes pawl biasing means, for biasing the lever's pawl member inwardly toward the primary ratchet wheel on which the lever may be mounted. The pawl biasing means may comprise a spring. Also in the preferred embodiment, each lever includes pawl orientation means, for selectively orienting the cog-engaging surface of the lever's pawl member to accommodate rotation of the ratchet wheel assembly in either direction. The pawl orientation means may be a handle associated with the outer end of the pawl member.
Each lever preferably includes pawl alignment means, to facilitate positioning of the lever on the trunnion with the lever's pawl member in optimal alignment with the cogs of the corresponding primary ratchet wheel and bridging element. The pawl alignment means may comprise a guide member mounted to the hub section of the lever, with the guide member being rotatable against a rub plate mounted to the trunnion.
Embodiments of the invention will now be described with reference to the accompanying figures, in which numerical references denote like parts, and in which:
The preferred embodiment of the invention, generally represented by reference numeral 10, is shown fully assembled in
A pair of primary ratchet wheels 30 are fixedly and coaxially mounted to the trunnion 22 in spaced relation. In the preferred embodiment shown in
As best understood by reference to
In the illustrated embodiments, the portion of centroidal opening 34A farthest from perimeter gap 31A is shown as having a semi-circular portion (which is concentric with the primary ratchet wheel); however, this is not essential. What is important regarding the geometrical configuration of centroidal opening 34A is that it is large enough to enclose a circular shape having a diameter equal to that of inner surface 23 of trunnion 22 (and thus will be at least slightly larger than the cross-section of shaft 90), such that there will be no interference when the assembled apparatus 10 is positioned over shaft 90. It may be preferable or convenient to fashion centroidal opening 34A with a semi-circular portion to facilitate mounting of the primary ratchet wheel 30 onto trunnion 22, particularly in embodiments where one or both of the primary ratchet wheels 30 are mounted inboard of the ends of trunnion 22. It will be appreciated, however, that centroidal opening 34A could take a different shape, subject to suitable adaptation for concentrically mounting trunnion 22 to primary ratchet wheels 30.
As will be appreciated from
Also provided, in association with each primary ratchet wheel 30, is a bridging element with a cogged, arcuate-edged section, for closing off the perimeter gap in the primary ratchet wheel 30. Each bridging element is operable between:
It will be appreciated by persons skilled in the art that it is not necessary for the bridging element or any portion thereof to be disposed within perimeter gap 31A of primary ratchet wheel 30 when the bridging element is in the engaged position. In some embodiments (such as those illustrated in
Accordingly, the term “bridging” and related forms of this term, as used herein in association with a bridging element of the apparatus, are to be construed as denoting that the bridging element spans (i.e., bridges) perimeter gap 31A of its associated primary ratchet wheel 30 when in the engaged position, with the cogs of the bridging element being either in a substantially co-planar relationship with the cogs of the primary ratchet wheel 30, or lying in a plane parallel to and offset from the plane of the primary ratchet wheel 30.
As illustrated in
In the preferred embodiment, as particularly illustrated in
The arcuate slots 46 and stop posts are configured such that when an auxiliary ratchet wheel 40 is rotated in one direction until the stop posts hit the ends of their respective arcuate slots 46, the auxiliary ratchet wheel 40 will be in the open position, and when the auxiliary ratchet wheel 40 is rotated in the other direction until the stop posts hit the other ends of their arcuate slots 46, the auxiliary ratchet wheel 40 will be in the engaged position, with the spacing of the cogs 42 of the auxiliary ratchet wheel 40 conforming as desired with the spacing of the cogs 32 of the corresponding primary ratchet wheel 30.
Although the bridging elements of the embodiments shown in FIGS. 1-A, 2, 3, and 4 (i.e., in the form of auxiliary ratchet wheels) are shown with cogs spaced around their full perimeter, persons skilled in the field will appreciate that this is not essential. Each bridging element need only have enough cogs to span or bridge the perimeter gap 31A of its associated primary ratchet wheel 30 when the bridging element is in the engaged position. Accordingly, a bridging element in the form of an auxiliary ratchet wheel could have un-cogged perimeter except in a cogged region intended to bridge perimeter gap 31A in the engaged position. In fact, a bridging element in the form of an auxiliary ratchet wheel, in alternative embodiments, need not form a complete circular shape, provided that it has an arcuate cogged region adapted to bridge perimeter gap 31A in the corresponding primary ratchet wheel 30.
The apparatus of the invention also includes locking means, for releasably securing each bridging element in the engaged position such that cogs of the bridging element cannot be displaced relative to the cogs of the associated primary ratchet wheel 30. In the preferred embodiment, and as particularly illustrated in
In alternative embodiments, the bridging element may be a comparatively small member with a cogged, arcuate-edged section just large enough to span the perimeter gap of the corresponding primary ratchet wheel 30. In a first alternative embodiment, shown in
In a second alternative embodiment, shown in
In a third alternative embodiment, shown in
In a yet further embodiment, the bridging element could take the form of a segment of an auxiliary ratchet wheel 40 as illustrated in
The invention 10 also includes spring cone engagement means 60, which may take a variety of forms well known in the art of the invention. In the preferred embodiment illustrated in FIGS. 1-A, 5, and 6, the spring cone engagement means 60 has a central hub 62 and at least one outwardly-extending bracket 64 having mounted thereto a radially-oriented sleeve 66 which slidingly receives a cone-engaging pin 68 adapted to be insertable into a socket 96 of a spring cone 94. The pin 68 may be spring-loaded to bias it radially inward, such that it will tend to stay engaged in the socket 96 when engaged therein. Alternatively, and as illustrated in
The spring cone engagement means 60 is mounted to other components of the invention 10 such that it will rotate with the ratchet wheel assembly 20. In the preferred embodiment, and as particularly illustrated in FIGS. 1-A, 5, and 6, this is accomplished by rigidly connecting the spring cone engagement means 60 to one of the auxiliary ratchet wheels 40, such as by welding. In other embodiments, however, such as where the bridging elements are comparatively small and do not cover the entire surface of their associated primary ratchet wheels 30, the spring cone engagement means 60 may be mounted directly to one of the primary ratchet wheels 30.
The invention 10 also comprises a pair of ratchet levers 70, as illustrated in
Each lever 70 also has a pawl assembly 80 comprising a pawl member 82 with an inner end 82A and an outer end 82B, with the inner end 82A defining a cog-engaging surface 83A and a non-engaging surface 83B. The pawl member 82 is mounted to the lever 70 in any suitable fashion such that its inner end 82A can be retractably extended inward toward the hub 74. In the particular embodiment shown in
Preferably, the pawl member 82 is also provided with pawl-orientation means, for orienting the cog-engaging surface 83A as desired, depending on the direction in which the lever 70 is to be operated. As illustrated in the Figures, the pawl-orientation means can be provided by way of a handle 88 associated with the outer end 82B of the pawl member 82. However, this is merely one example, and those skilled in the art of the invention will understand that various other pawl-orientation means could be used without departing from the concept or scope of the invention.
Assembly of the preferred embodiment of the invention 10 may now be readily understood having reference to
In the illustrated embodiment, the levers 70 cannot be readily removed from the ratchet wheel assembly 20 because of the geometry of the assembly, and in particular the fact that the hubs 74 in the illustrated embodiment closely enshroud their corresponding primary ratchet wheels 30. In this arrangement, the invention 10 has no loose components that might be inadvertently misplaced. More significantly, perhaps, this arrangement prevents the levers 70 from flying loosely away from the ratchet wheel assembly in the event of an unexpected unwinding of a torsion spring being tensioned with the apparatus. However, there may be circumstances in which it will be desirable for the levers 70 to be removable, which can be easily accomplished by modifying the configuration of the hubs 74 (e.g., by making them essentially semi-circular or smaller) so that they can be mounted directly over their corresponding primary ratchet wheels 30.
The operation of the present invention may now be easily understood having particular reference to
It will be readily appreciated by those skilled in the art that various modifications of the present invention may be devised without departing from the essential concept of the invention, and all such modifications are intended to be included in the scope of the claims appended hereto.
In this patent document, the word “comprising” is used in its non-limiting sense to mean that items following that word are included, but items not specifically mentioned are not excluded. A reference to an element by the indefinite article “a” does not exclude the possibility that more than one of the element is present, unless the context clearly requires that there be one and only one such element.
This application is a continuation-in-part of application Ser. No. 10/662,366 filed Sep. 16, 2003, and the disclosure of said earlier application is fully incorporated herein by reference.
| Number | Date | Country | |
|---|---|---|---|
| Parent | 10662366 | Sep 2003 | US |
| Child | 11245117 | Oct 2005 | US |
