Patent Application
20090121069
The present invention relates generally to tools used in tensioning bundle ties and more specifically to a bundle tie tensioning clutch to be used in a bundle tie tensioning tool.
Flexible bundle ties are well known items. Such ties are used to secure wires, cables, tubing and similar items into tight, neat bundles. Typically, flexible bundle ties include a head portion and a tie tail portion extending from the head. In use, the tie tail is looped around the items to be secured and then inserted through the head. A locking or ratcheting mechanism in the head holds the tie tail in the head and secures the tie around the bundle. Preferably, the tie tail is pulled through the head under tension to draw the items to be secured into a tight bundle. Thereafter, the excess portion of the tie tail may be clipped off near the head.
Many flexible ties are economically molded of flexible plastic. For some applications, however, plastic has insufficient strength or other drawbacks, and metal ties are used. Metal ties include a flat strap portion and a locking head portion, each of which is made of a strong, durable metal such as stainless steel. As a rule, metal ties are significantly stronger than plastic ties of the same size and are typically pulled at much higher tensions than plastic ties when they are installed.
A variety of tools have been developed to enable workers to install flexible bundle ties with speed, uniformity and economy. Generally, such tools function to grip the tie tail portion of the tie after the tie has been looped around the items to be bundled. The tool pulls the tie tail until a predetermined desired tension is achieved, after which the tool cuts off the excess portion of the tie tail closely adjacent the head. Such tools greatly simplify the task of properly installing bundle ties.
In a typical tie tensioning tool, a tie is grasped and pulled by a tensioning clutch including a pawl, a pawl link, a shaft, a torsion spring, and tension abutment such as a backing plate. The tensioning clutch is generally slidably situated in a housing. The pawl link usually includes a yoke in which the pawl is rotatably supported on the shaft. The torsion spring includes a substantially stationary leg that cooperates with an aperture in the pawl link, and a biasing leg that cooperates with the pawl, thereby biasing the pawl toward the backing plate.
Various handheld tools have been developed to assist in the installation of flexible ties. In one well known form of such tool, the tool comprises a pistol or gun-like device having a movable trigger or lever that is squeezed by the operator to pull on the tie tail and thereby tension the tie. The operator continues squeezing the trigger until a predetermined tension is achieved after which a cutting blade adjacent the nose of the tool snaps upwardly to clip off the excess portion of the tie tail. A knob at the rear of the tool allows the worker to adjust or set the tension at which cutoff occurs.
Examples of such manually operated handheld tools are shown in the inventors' U.S. Pat. No. 4,997,011, issued Mar. 5, 1991, U.S. Pat. No. 4,793,385 issued Dec. 27, 1998, and U.S. Pat. No. 5,921,290 issued Jul. 13, 1999, commonly owned by the assignee hereof.
The pawls of prior devices were normally cast in hardened steel and had teeth, which gripped a tie when the tie was inserted between the pawl and the cooperating tension abutment or backing plate. The pawl is a wear part of a tensioning tool. That is, eventually and frequently, the teeth on the pawl wear down and the clutch needs to be repaired or the pawl replaced. This is especially true when the tensioning tool is used with metal ties, such as stainless steel ties. Replacing or repairing a damaged or worn pawl is both time and labor intensive. Most prior devices require that the tool be taken out of service for repair, and replacement of the pawl requires disassembly of the tool's housing. As with any industrial teardown repair, care must be taken to ensure that reassembly is properly executed, and the tool must be tested prior to reinstatement of service.
Therefore, the art of tensioning bundle ties may benefit from a bundle tie tensioning clutch having an engagement surface that may be changed when desired, without significant disassembly of the remainder of the tensioning tool.
The present invention provides a bundle tie tensioning clutch having an engagement surface that may be changed when desired, without significant disassembly of the remainder of the tensioning tool.
In one embodiment, a tensioning clutch according to the present invention includes a pawl link, a tension abutment at least partly contemporaneously movable with said pawl link, and a pawl mechanism movably coupled to the pawl link. The pawl mechanism includes a pawl insert that is detachably coupled to a pawl body. The pawl insert includes a tie engagement surface, which is preferably biased towards and movable away from, the tension abutment, which may be a backing plate coupled to the pawl link. While the backing plate and pawl link could be provided separately, the backing plate may, instead, be formed integrally with the pawl link. The pawl mechanism is rotatably supported by the pawl link. The pawl link may form a yoke at least partially in which the pawl mechanism is movably supported. Such movable support may be provided in the form of rotatable support upon a bearing shaft.
The pawl insert is detachably coupled to said pawl body, which may be, for example, by a threaded mounting bolt inserted through said pawl insert and engaging a threaded mounting aperture located in the pawl body. In another embodiment, the pawl insert may be a polygonal insert having a plurality of tie engagement surfaces, such as three tie engagement surfaces. The pawl insert may be formed from, or at least include, a material including a carbide. The insert may include a tool surface, an access surface generally opposed from the tool surface by an insert thickness, at least one side surface extending from the access surface to the tool surface, and a mounting aperture accessible through the insert thickness. The insert tie engagement surface is preferably formed by the junction of the side surface and the access surface. The pawl body preferably includes an insert lip adapted to interface to at least one side surface of the pawl insert. The insert access surface may be a polygonal, planar surface, such as a triangular surface, for example. Similarly, the insert tool surface may be a polygonal, planar surface, such as a triangular surface.
The pawl mechanism of a tensioning clutch according to the invention may be biased towards the tension abutment by a torsion spring exerting a first force against said pawl link and a second force against the pawl mechanism. The second force may be exerted against the pawl body.
In another embodiment, an improvement is provided for a bundle tie tensioning tool having a mechanism for grasping a bundle tie. The improvement includes a pawl mechanism movably coupled to a pawl link. The pawl mechanism includes a pawl insert detachably coupled to a pawl body. Furthermore, the pawl link may be adapted for substantially linear reciprocal sliding movement within a housing of the tool.
Although the disclosure hereof is detailed and exact to enable those skilled in the art to practice the invention, the physical embodiments herein disclosed merely exemplify the invention which may be embodied in other specific structures. While the preferred embodiment has been described, the details may be changed without departing from the invention, which is defined by the claims.
Turning now to the Figures,
A tie 12 is tensioned by means of a tensioning clutch 26, which is slidably disposed at least partially within the barrel portion 22 of the housing 14. The tensioning clutch 26 grips a tail portion 18 of the tie 12 and pulls it rearwardly as the trigger 24 is moved from the initial position to the second position. When the trigger 24 is released, it springs forwardly to the initial position. At the same time, the tensioning clutch 26 releases the tie tail 18 and moves forwardly relative to the tie tail 18. As the trigger 24 is once again squeezed, the tensioning clutch 26 once again grips the tie tail 18 and draws it rearwardly. The process is repeated until a desirable tension is achieved in the tie 12.
With reference more particularly to
A nose guide block 38 may be provided within the housing 14. The guide block 38 includes a surface that engages the gripping pawl 42 when the pawl link 40 is at the leftmost or initial position. Such engagement pivots the gripping pawl 42 away from the backing plate 44 to facilitate insertion of the tie tail 18 into the tool 10. When the pawl link 40 moves toward the right, the tie tail 18 is pinched between the gripping pawl 42 and the backing plate 44. The tie tail 18 is thus pulled along with the pawl link 40. It will be appreciated that, as the pawl links 40 move to the right, the gripping pawl 42 grips the tie tail 18 to pull the tie tail 18 and thereby tension the tie 12. When the pawl link 40 is reciprocated to the left, the gripping pawl 42 loosens its grip on the tie tail 18, thereby permitting the pawl link 40 to return to its initial position without simultaneously moving the tie tail 18.
Turning now to
The foregoing is considered as illustrative only of the principles of the invention. Furthermore, since numerous modifications and changes will readily occur to those skilled in the art, it is not desired to limit the invention to the exact construction and operation shown and described. While the preferred embodiment has been described, the details may be changed without departing from the invention, which is defined by the claims.
