Band Tensioning Device

This invention relates to band-tensioning devices and in particular relates to band-tensioning devices that are compact to fit within a confined space and further that provide a capability of remote actuation of an indicator means to indicate the degree of tension provided by the tensioning device.

Many devices are available to latch and tension band clamps. Most of the current devices are lever action over-center latches requiring a substantial amount of room to operate, particularly when the tension to be applied by the device is in the range of 2000 to 3000 pounds. In certain applications, for example, in the V-band that holds the thrust reverser assembly to the body of a jet aircraft engine, a significant tension is required but only a small space is available in which the tensioning device can be operated.

In certain situations, the band tension can be critical to the proper operation of a device and it is desirable in such instances for an indication of the band tension applied by the tensioning device to be transmitted to a location remote from the band-tensioning device. Again, in the example of a thrust reverser V-band, the V-band must be properly tensioned during operation of the aircraft. Serious mechanical failures or even personal injury could result from a separation of the thrust reverser from the remainder of the engine. During maintenance of the engine, the V-band may be loosened and retightened by different mechanics. The entire engine assembly is surrounded by a cowling that typically is formed of two halves that can be separated to uncover the engine components for maintenance work. If the cowling is closed after maintenance, without proper tension being placed on the thrust reverser V-band, it would be possible that the thrust reverser could separate from the engine during operation and cause severe damage to the aircraft. It is therefore desirable to have some indication of whether or not the proper tension has been applied to the V-band that is easily available to the operator who is closing the engine cowling so that the cowling could not be closed if the V-band was not at the proper tension.

It is, therefore, an object of the present invention to provide a low-profile band-tensioning device that can apply relatively high degrees of tension to a band clamp but that can be operated in a minimal amount of space.

It is a further object of this invention to provide such a tensioning device that includes a remote indicator actuatable to indicate the achievement of a predetermined amount of tension by the tensioning device.

It is an another object of this invention to provide such a band-tensioning device that meets the normal requirements of load capacity and ease of manufacture, installation, and maintenance.

In accordance with the above-stated objects a band-tensioning device is provided for use with a band clamp. The band clamp preferably has means at each end thereof for connection to respective male and female parts of the tensioning device. The tensioning device includes a T-bolt that has a shank portion and a T-head portion that is affixed transversely to a first end of the shank portion. Means are provided for mounting the T-bolt to a first end of the band. A nut is threadably engaged on a second end of the shank portion and is operable to draw the T-bolt T-head portion toward the first end of the band. A keeper means is affixed to a second end of the band and is constructed and arranged to cooperatively receive the T-head portion of the T-bolt so that as the T-head is drawn toward the first end of the band, the second end of the band is drawn along with it. Anti-rotation means associated with the nut is operable to engage the nut to prevent rotation of the nut about the shank. The anti-rotation means is disengageable from the nut upon the placement of a force-applicating tool, such as a wrench, on the nut. In one embodiment of the tensioning device of the present invention, the anti-rotation means includes an arm that is pivotally mounted to the T-bolt mounting means and is movable between a first position in which a first portion of the arm engages the nut and a second position in which the first portion is spaced from the nut. The arm is preferably constructed to include a cam surface that engages the force-applicating tool and operates by way of cam action between the cam surface and the force-applicating tool to move the arm into its second position as the force-applicating tool is placed on the nut.

In a preferred embodiment of the tensioning device of the present invention an indicator assembly is located remotely from the tensioning device and is operable to indicate the achievement of a predetermined tension by the tensioning device. In the aircraft environment, the T-bolt mounting means and keeper means are affixed to first and second ends, respectively, of a V-band clamp used to hold together the subassemblies of the engine. The indicator means preferably includes a stop member that is positionable between the first and second halves of a cowling surrounding the engine to prevent the closure of the cowling prior to the attainment by the tensioning device of a predetermined degree of tension. Upon attainment of such predetermined degree of tension the stop member is operable by the tensioning device to move to a position out of engagement with the cowl halves to permit the closing of the cowl halves.

The objects and advantages of the present invention will be better understood by those of ordinary skill in the art and others upon reading the ensuing specification when taken in conjunction with the appended drawings wherein:

FIG. 1 is an isometric view of one embodiment of a band-tensioning device made in accordance with the principles of the present invention;

FIG. 2 is a side elevational view of the band-tensioning device of FIG. 1 in the tensioned state;

FIG. 3 is a side elevational view in somewhat expanded scale of the band-tensioning device of FIG. 2 in the loosened state; and

FIG. 4 is a side elevational view in partial section of another embodiment of a band-tensioning device made in accordance with the principles of the present invention.

One embodiment of a band-tensioning device made in accordance with the principles of the present invention is illustrated in FIGS. 1, 2, and 3. While the tensioning device of the present invention is useful with any band-type clamp arrangement, the preferred embodiment will be described in the aircraft engine environment in which it is used to apply a predetermined tension to a V-band surrounding the thrust reverser assembly of a typical turbofan jet engine to hold the thrust reverser to the remainder of the engine assembly. A trunnion mount fixture 10 is attached to a first end 11 of the band clamp. The trunnion mount fixture includes a web 12 and two parallel projecting flanges 14 and 16. The flanges 14 and 16 have C-shaped ears 14a and 16a integrally formed at one end thereof. The ears 14a and 16a receive bushings 18 and 20. The male portion of the tensioning device includes a frame assembly 22 having trunnion pins 24 extending from the opposing sides of the frame 22, the trunnion pins being received within the bushings 18 and 20 to trunnion mount the male portion of the tension assembly to the V-band. Preferably, the ends of the trunnion pins 24 are threaded and are threadably engaged by threaded fasteners such as hex nut 26. Preferably, a washer 28 is inserted between the hex nut and its respective bushing 18 or 20 in a conventional manner.

A T-bolt 30 having a shank portion 30a and a T-head portion 30b that is integrally formed with the shank portion 30a at a first end of the shank portion, passes through the frame 22. A second end of the shank portion 30a is threaded and is engaged by a cooperatively threaded, rotatable tension-applying means such as nut 32. Rotation of the nut 32 in a first direction, for example, clockwise, as viewed in FIG. 1, draws the T-head portion of the T-bolt 30 toward the frame 22. A female keeper member 34 substantially identical to the trunnion mount assembly 10 is affixed to a second end 13 of the V-band and cooperates with the T-bolt to receive the T-head portion 30b within C-shaped ears 34a and 34b integrally formed on the keeper member 34. In operation, therefore, rotation of the nut 32 will draw the T-head portion of the T-bolt toward the frame 22 drawing with it the female member 34, which carries along with it the second end of the V-band, thereby drawing the first and second ends of the V-band together. The tension on the band is therefore determined by the number of turns applied to the nut 32 and the distance that the T-bolt head is drawn toward the frame 22. The length of the T-bolt and the pitch of the thread are predetermined for the desired tension to be applied to the band in a given situation. In the aircraft environment the tension applied to the V-band by the tension device of the present invention is typically in the neighborhood of 2000 to 3000 pounds.

To prevent accidental loosening of the V-band, an anti-rotation means is associated with the nut 32. In the embodiment of FIG. 1, the nut 32 includes a ring portion 33 and the anti-rotation means includes an arm 36 pivotally mounted at a first end to the frame 22. The arm 36 has a pin 38 extending from it adjacent its second end. The pin 38 engages one of a plurality of holes formed in the ring portion 33 to prevent rotation of the nut 32. Preferably, the second end of the arm 36 has a cam surface 39 formed thereon that cooperates with a force-applying tool, such as a wrench, to move the arm 36 upwardly as viewed in FIG. 1, thereby removing the pin 38 from engagement with the holes in the ring portion 33 of the nut 32.

An indicator assembly 40 is located remotely from the tensioning device and is operably connected to the tensioning device to provide an indication of whether or not a predetermined amount of tension has been applied to the band clamp by the tensioning means. The remote indicator assembly 40 shown in FIG. 1 includes an indicator tab 42 pivotally mounted to a frame assembly 44. The indicator tab 42 is connected to the tensioning device through a linkage assembly comprised of a first link 43 attached to the tab at a first end thereof and attached to a crank arm 46 at a second end thereof. The crank arm 46 is pivotally attached at a first end thereof to the first link and at a second end thereof to the frame 44. A push-pull cable 48 is attached at a first end thereof to the crank arm at a point intermediate the first and second ends of the crank arm. A second end of the push-pull cable 48 is coupled to a control arm 50 pivotally mounted on the frame 22. Referring now to FIGS. 2 and 3, it can be seen that when the tensioning device is in its fully tensioned state, as shown in FIG. 2, the indicator tab 42 is in a first position withdrawn within the cowling 58 of the aircraft engine. However, when the tension is released from the band by the tensioning device, the T-bolt T-head portion moves in a direction away from the frame 22 and carries with it a collar 52 that is affixed to the bolt so that it moves with the bolt. When the collar 52 is spaced from the frame 22, a bias spring 54 associated with the second end of the push-pull cable 48 expands to move the control arm 50 about pivot pin 51, which moves the push-pull cable to pull the crank arm 46, and, in turn, the first link 43, in such a manner as to pivot the indicator tab 42 about the pivot pin 56 and place an edge 42a of the indicator tab 42 between sections of the cowl 58a and 58b. In the event that a maintenance worker attempts to close the cowl halves 58a and 58b, without applying the proper tension to the V-band having the tensioner of the present invention attached thereto, the indicator tab 42 will prevent the closing of the cowl halves and will provide a reminder to the maintenance personnel to check the tension on the V-band.

FIG. 3 illustrates a force-applicating tool such as a socket wrench 60, in place on the tension-applying nut 32. It can be seen that the wrench 60 cooperates with the cam surface 39 of the arm 36 to force the arm away from the nut 32, thereby permitting rotation of the nut. As the nut is rotated as shown by arrow 62 in FIG. 3, the T-bolt head is drawn toward the frame as indicated by the arrow 64, carrying with it the collar 52. The collar 52 is preset at a particular location on the bolt during manufacture of the tensioning device so that when the T-bolt is drawn sufficiently to provide the predetermined amount of tension, for example, 3000 pounds, the locking collar 52 engages a finger at the first end 50a of the control arm 50, forcing the control arm to pivot clockwise as viewed in FIG. 3 about the pivot pin 51. Pivoting of the control arm 50 moves the push-pull cable 48 in a direction, shown by arrow 65, to pivot the second link 46 of the indicator assembly in such a manner as to rotate the indicator tab 42 counterclockwise as viewed in FIG. 3 to move the edge 42a inside the cowling, permitting closure of the cowl halves 58a and 58b. Preferably, the control arm 50, first and second links 43 and 46, and the bias springs 54 and 63 are designed such that the indicator tab 42 remains in the down position, as viewed in FIG. 3, up to the very time that the predetermined tension is applied to the band by the tensioning device as indicated by the movement of the locking collar 52 and its interaction with the finger 50a. The tab 42 then has a snap action quickly moving it to the up position out of the way of the cowl halves in a rapid manner, not as a gradual rotation. The snap action is preferable so that it will not be possible to close the cowl halves up until the time that the predetermined tension is applied to the V-band to ensure safety and integrity of the engine system.

When the T-bolt T-head portion is engaged in the ears 34a and 34b of the keeper 34, it is preferably locked into position by a stop pin 68 biased by a spring 70 into a position blocking exit of the T-bolt head portion from the ears 34a and 34b. If it is desired to remove the V-band, the pin 68 can be manually withdrawn and the T-head removed from the ears. In order to ensure that upon loosening of the nut 32 the T-bolt head will move away from the frame 22 so as to relieve tension on the V-band, a bias spring 70 is installed surrounding the T-bolt within the frame 22 and acts against the distal end of the nut 32 and a pair of collars 72 and 74 attached to the T-bolt to force the T-bolt head away from the frame.

FIG. 4 illustrates another embodiment of a tensioning device made in accordance with the principles of the present invention. In the embodiment of FIG. 4, a sleeve 76 surrounds a nut 132 threadably engaging a first end of a shank portion of a T-bolt 130. The sleeve 76 has slots 78 formed therein allowing access to a series of holes 80 formed in a barrel portion of the nut 132. An anti-rotation arm 136 is pivotally mounted on a frame 122 and is biased against the sleeve 76 by a bias spring 82. The anti-rotation arm 136 has a pin 137 at a first end thereof that engages the holes 80 in the nut 132 to prevent its rotation. The anti-rotation arm 136 has a cam surface formed therein that cooperates with a cam portion 76a of the sleeve 76 so that when a wrench or other force-applying tool is placed on the nut the wrench will force the sleeve 76 in the direction of the T-bolt head and the cam portion 76a of the sleeve and the cam surface of the anti-rotation arm 136 cooperate to move the anti-rotation arm away from the nut 132 disengaging the pin 137 from the holes in the nut and permitting rotation of the nut to increase or decrease the tension applied by the tensioning device. Upon removal of the wrench from the nut, a bias spring 82 that surrounds the shank of bolt 130 will expand a longitudinal direction and force the sleeve 76 back over the nut, causing the slots 78 to register with the pin 137 on the anti-rotation arm 136 and permit engagement of the pin 137 with the holes 80 in the nut 132, again preventing rotation of the nut 132. The remaining aspects of the tensioning device of FIG. 4 are essentially the same as those described earlier and the tensioning device is again attached by means of control arm 50 and a push-pull cable 48 to a remote indicating device.

It can be seen therefore that a tensioning device for use with a band-type clamp has been provided that is of low profile and that can be adjusted to a predetermined tension within a confined area. A remote indicating device is associated with the tensioning device to provide an indication of whether or not a predetermined amount of tension has been applied to the band clamp by the tensioning device. While two embodiments of the tensioning device of the present invention have been described and illustrated, it will be understood by those of ordinary skill in the art and others that changes can be made to the illustrated and described embodiments while remaining within the spirit and scope of the present invention. For example, the interaction between the anti-rotation means and the force-applicating tool, such as a wrench, used to adjust the tensioning device can be accomplished through means other than either of those illustrated and described as long as the anti-rotation means is disengaged upon placement of a force-applicating tool on the device. Further, while the linkage described and illustrated between the tensioning device and the remote indicator means provides for a quick snap action of the indicator device at the moment that the predetermined tension is reached, certain environments may tolerate or even prefer that the indicator device be moved more slowly as more and more tension is provided. Also, while the present invention has been described and illustrated in an aircraft engine environment, it is useful in any environment in which a band clamp is used and tension must be applied to the band clamp, particularly in situations where remote indication of the achievement of a predetermined degree of tension is desirable. Therefore, the present invention should be defined solely by reference to the appended claims.