Patent Application
20090159734
Tension holders are used in a variety of load-lifting applications such as elevated platforms for building maintenance. Such platforms can be used in conjunction with a motorized hoisting device, whereby the hoisting device is attached to the platform of an elevated platform or basket that may then be raised or lowered using the hoisting device. The hoisting device and associated rigging typically comprises a tension holder, whereby a continuous lines such as a cable or rope passes through the tension holder. The tension holder is used to keep tension on the line when it would otherwise be slack.
A tension holder may also be associated with a fairlead, which is a device such as a ring or a block that has a guide opening, typically used to guide a rigging such as a line, such as wire or nylon rope or other cable, around an object, or to stop the rigging from moving laterally.
A tension holder is used in a variety of applications in which riggings are used, including marine vehicles, loading devices, and various hoisting applications such as elevated platforms for building maintenance. A tension holder is typically used on a suspended scaffold work basket or platform to keep tension on the line whenever the unit is not suspend in the air and line has the capability to go slack. In a hoisting application, an elevated platform or basket is typically raised or lowered using a powered hoisting device attached to the platform. The hoisting device utilizes a cable that is guided through a fairlead and then through a tension holder. A tension holder has a wear surface that conforms to the diameter of a line to keep tension on the line. It is used to keep the line taught and in place and also to prevent the lines from entangling with other items or themselves.
Prior art tension holders are made up of a number of parts including rollers with bearings which increase assembly and service time.
In one embodiment, a platform has a hoisting machine mounted thereon. A rigging, operable to raise and lower the platform, passes through a restraint device comprising a tension holder. The tension holder comprising a first body having a substantially planar face surface and a rear portion having a divot disposed therein. A second body, substantially similar to the first body; and having a substantially planar face surface; is disposed in a substantially facing arrangement with the first to permit a line to pass between the substantially planar face surfaces. A lever is disposed in the divot of the first body and is operable to draw together the substantially planar face of the first body and the substantially planar face of the second body whereby friction can be selectively applied to the line when the line is disposed between the substantially planar first surface and said substantially planar second surface.
The foregoing summary, as well as the following detailed description of preferred embodiments, is better understood when read in conjunction with the appended drawings. For the purposes of illustration, there is shown in the drawings exemplary embodiments; however, the present disclosure is not limited to the specific methods and instrumentalities disclosed. In the drawings:
It is to be understood that the embodiments disclosed herein are not limited in application to the details of construction and the arrangement of components set forth in the following description or illustrated in the drawings. The disclosure is capable of other embodiments and of being practiced or being carried out in various ways. Also, it is to be understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting.
The tension holder described herein reduces parts, reduces service and improves production performance. The tension holder incorporates a wear resistant material which is made as two identical halves reducing parts on hand. There are no rollers with bearings to reduce wear, which increase assembly and service time.
The tension holder assembly may be used in conjunction with hoisting devices that are used to elevate platforms or baskets typically associated with large structure service and maintenance, such at buildings, bridges, towers, and the like.
Line 230 may be securely attached to the top of the structure to be traversed. Line 230 is further guided at the top of the hoisting device 200 by a restraint assembly 210. Such a restraint assembly guides the line 230 from the drum 240 to the top of the platform by preventing the line or cable from moving laterally and otherwise prevent the line or cable from snagging. The restraint assembly 230 also prevents the line 230 from vibrating or rubbing on other surfaces.
The restraint device 210 typically comprises a fairlead, which is a member such as a ring or a block that has a guide opening, and a tension holder. The tension holder, as described more fully herein is a device that keeps tension in the line 230 when the hoisting device 200 is in a position that would cause the line 230 to go slack. The restraint assembly 210 operates to restrain movement of a line 230 passing through an opening 306 of the restraint assembly. The line 230 may be any type of rigging operable to elevate or lower a platform to be controlled by the hoisting device, and is typically a wire, rope or cable.
An embodiment of tension holder 303 is further illustrated in
The clamping occurs when the bodies 401a and 401b are drawn together by a combination of hardware. In particular, a cylinder 405 is placed proximate a divot 409 that transverses body 401(a). Strap 409 is secured at one end to body 401b and at another end to cylinder 405. Strap 409 thereby secures the cylinder 405 to the tension holder assembly. A lever 403 is attached to cylinder 405 to provide a rotational moment about an axis 406 when the lever is manually rotated. Rotating the lever 403 upwardly causes the cylinder 405 to rotate in a clockwise direction. Rotating the lever 403 downwardly causes the cylinder to rotate in a counter clockwise direction. The counter-clockwise rotation causes the tension assembly to clamp shut on the line (e.g., 230).
Spring loaded pins 404a and 404b are disposed between the cylinder and the body 401a. The spring loaded pins transfer the rotational force of the cylinder into a pressing force against body 401a. In particular, the rotation of the cylinder 405 forces the spring loaded pins 404a, 404b against body 401a thereby clamping the bodies 401a, 401b together about a line (e.g., 230).
A further feature of the embodiment described above is that tension holder assembly comprised of two bodies 401a and 401b and is designed such that the bodies are substantially similar. As such it provides for ease of manufacturability and a reduction of parts required. The same part may be used for both bodies 401a and 401b.
The various embodiments of the fairlead may be composed of appropriate materials that provide durability, resilience, abrasion resistance and strength. For example, thermoplastic polymers such as nylon and its various embodiments such as Nylatron may be used and can be fabricated using a single injection mold. In other embodiments other types of polymers can be used. However, the materials that may be used to fabricate the disclosure described herein are not limited to polymers. The present disclosure contemplates the use of various materials such as metal, plastic, or wood as may be useful for various applications and embodiments.
It will be understood that each of the elements described above, or two or more together may also find a useful application in other types of methods differing from the type described above. Although the more detailed examples provided above relate to traction sheaves in hoisting devices associated with elevated platforms for building maintenance, it should be apparent to one of ordinary skill in the art that the apparatus and methods described herein will find application to other systems that utilize traction sheaves. Additionally, the foregoing description has set forth various embodiments of the apparatus and methods via the use of diagrams and examples. While the present disclosure has been described in connection with the preferred embodiments of the various figures, it is to be understood that other similar embodiments may be used or modifications and additions may be made to the described embodiment for performing the same function of the present disclosure without deviating there from. Furthermore, it should be emphasized that a variety of applications, including marine and transportation systems, are herein contemplated. Therefore, the present disclosure should not be limited to any single embodiment, but rather construed in breadth and scope in accordance with the appended claims. Additional features of this disclosure are set forth in the following claims.
