Abstract
A system including an annular socket body for tightening a lock ring around a threaded end of a conduit connector extending through an opening in a wall of a junction box is provided. To facilitate capturing of the lock ring by the socket body without interference, the wrench lugs of the socket body each have a circumferential extent that is less than 50% of a circumferential extent between teeth of the lock ring, and there are half as many wrench lugs than teeth. Flat side faces of the wrench lugs are disposed at an angle of between about 15° and 40° relative to sides of the teeth of the lock rings so that the wrench lugs engage the lock ring teeth in a sliding point contact that promotes uniform engagement between the wrench lugs and the lock ring teeth when torque of about 1400 inch-pounds is applied to the socket body.
Claims
1. A system for tightening a lock ring around a threaded end of a conduit connector extending through an opening in a wall of a junction box, the lock ring having a plurality of teeth uniformly spaced around its outer periphery, the peripheral ends of the lock teeth being uniformly angled toward the wall of the junction box when the lock ring is threaded onto the end of the conduit connector preparatory to tightening, comprising: an annular socket body open at one side and closed on an opposite side by an end wall, and including a plurality of wrench lugs radially extending from an inner circumference of the socket body, the wrench lugs each having a circumferential extent that is less than about 50% of a circumferential extent between teeth disposed around the outer periphery of the lock ring, and there being half as many or less wrench lugs than teeth disposed around the lock ring to facilitate capturing of the lock ring by the annular socket body without mechanical interference, and a driver detachably connectable to the end wall of the annular socket body for applying a predetermined torque to the lock ring sufficient to begin dimpling between peripheral ends of the lock ring teeth and the wall of the junction box without the formation of a closed annular groove in the wall of the junction box.
2. The system for tightening a lock ring defined in claim 1, wherein flat side faces on either side of the wrench lugs are disposed at an angle of between about 15° and 40° relative to sides of the teeth of the lock rings such that the wrench lugs engage the lock ring teeth in a sliding point contact that promotes uniform engagement between the wrench lugs and the lock ring teeth when the predetermined torque from the driver is applied.
3. The system for tightening a lock ring defined in claim 1, wherein a radial thickness of the annular wall of the socket body is between about 100% to 150% of a radial length of the teeth of the lock ring.
4. The system for tightening a lock ring defined in claim 1, wherein a radial thickness of the annular wall of the socket body is between about 3%-4% of an inner diameter of the annular socket body.
5. The system for tightening a lock ring defined in claim 1, wherein a radial gap between the distal ends of the lock ring teeth and the inner diameter of the annular socket body is between about 80% to 100% than a radial extent of the lock ring teeth when the lock ring is concentric with annular socket body.
6. The system for tightening a lock ring defined in claim 1, wherein a radial extent of the wrench lugs overlaps between about 33% and 50% of the radial extent of the lock ring teeth when the lock ring is concentric with annular socket body.
7. The system for tightening a lock ring defined in claim 1, wherein a radial length of the wrench lugs is about 133%-150% of a radial length of the teeth.
8. The system for tightening a lock ring defined in claim 1, wherein the circumferential extent of the wrench lugs is greater than about 40% of the circumferential extent of the distances between teeth disposed around the outer periphery of the lock ring.
9. The system for tightening a lock ring defined in claim 1, wherein the driver applies between about 1200 and 1400 inch-pounds of torque to the lock ring.
10. The system for tightening a lock ring defined in claim 1, wherein the driver is a right-angled impact wrench adjustable to the predetermined torque.
11. A method for tightening a lock ring around a threaded end of a conduit connector extending through an opening in a wall of a junction box, the lock ring having a plurality of uniform teeth evenly spaced around its outer periphery, the peripheral ends of the lock teeth being uniformly angled toward one side of the lock ring, comprising the steps of: manually threading the lock ring over the threaded end of the conduit connector; capturing the threaded lock ring with an annular socket body that is open at one side and closed on an opposite side by an end wall, and that includes a plurality of wrench lugs radially extending from an inner circumference of the socket body, the wrench lugs each having a circumferential extent that is less than 50% of a circumferential extent between teeth disposed around the outer periphery of the lock ring, and there being half as many or less wrench lugs than teeth disposed around the lock ring to facilitate capturing of the lock ring by the annular socket body without mechanical interference, and applying a predetermined torque to the lock ring sufficient to begin dimpling between peripheral ends of the lock ring teeth and the wall of the junction box without the formation of a closed annular groove in the wall of the junction box.
12. The method defined in claim 11, wherein a radial gap between the distal ends of the lock ring teeth and the inner diameter of the annular socket body is between about 80% to 100% than a radial extent of the lock ring teeth when the lock ring is concentric with annular socket body.
13. The method defined in claim 11, wherein a radial extent of the wrench lugs overlaps between about 33% and 50% of a radial extent of the lock ring teeth when the lock ring is concentric with annular socket body.
14. The method defined in claim 10, wherein the wrench lugs have flat side faces on either side that engage a side of the teeth of the lock rings, and wherein the flat side faces on either side of the wrench lugs are disposed at an angle of between about 15° and 40° relative to sides of the teeth of the lock rings such that the wrench lugs engage the lock ring teeth in a sliding point contact that promotes uniform engagement between the wrench lugs and the lock ring teeth when the predetermined torque is applied to the annular socket body.
15. The method defined in claim 10, further including the step of detachably connecting a driver to the annular socket body that applies said predetermined torque to the lock ring.
16. The method defined in claim 14, wherein the driver applies between about 1200 and 1400 inch-pounds of torque to the lock ring.
17. The method for tightening a lock ring defined in claim 11, wherein a radial thickness of the annular wall of the socket body is between about 100% to 150% of a radial length of the teeth of the lock ring.
18. The method for tightening a lock ring defined in claim 11, wherein a radial thickness of the annular wall of the socket body is between about 3%-4% of an inner diameter of the annular socket body.
Description
BRIEF DESCRIPTION OF THE SEVERAL DRAWINGS
[0015] FIG. 1 is a perspective view of a junction box with a row of conduit connectors installed therein;
[0016] FIG. 2 is a plan view of a prefabricated module of an electrical power system including a junction box, conduit connectors, and an array of electrical conduits;
[0017] FIG. 3A is an outside perspective view of the annular socket body of the system of the invention;
[0018] FIG. 3B is a top plan view of the socket body illustrated in FIG. 3A;
[0019] FIG. 3C is a side view of the socket body illustrated in FIG. 3A;
[0020] FIG. 3D is a side view of a lock ring, illustrating how the lock ring teeth are bent to one side;
[0021] FIG. 3E is a plan view of the socket body illustrated in FIG. 3A, illustrating the spacing between the inner wall and wrench lugs of the socket body and the teeth of lock ring indicated in phantom, as well as the angle between the sides of the wrench lugs and the sides of the lock ring teeth;
[0022] FIG. 4A is an exploded view of a conduit connector, a section of a junction box wall having a knock-out opening, a lock ring to be threaded over the conduit connector, and the annular socket body of the system of the invention;
[0023] FIG. 4B is a perspective view of a conduit connector extending through the knock-out opening in a wall of a junction box with a lock ring that has been manually threaded over the conduit connector, and the socket body and driver used to tighten the lock ring;
[0024] FIG. 4C is a perspective view of the socket body and driver applying torque to the lock ring shown in FIG. 4B, and
[0025] FIG. 4D is a perspective view of the lock ring of FIG. 4C after being properly torqued by the socket body and driver.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0026] With reference now to FIGS. 1 and 2, the system and method of the invention assembles conduit connectors 1 to electrical junction boxes 3 by tightening lock rings 5 over the threaded end 8 of the connector 1. During assembly, the threaded end 8 is extended through one of the circular openings 10 formed by removing a knock-out in the wall 12 of the junction box 3. An electrician or factory worker then manually screws a lock ring 5 over the threaded end 8 of the connector 1. As described in detail hereinafter, the system of the invention tightens the lock ring 5 to within a predetermined range of torque such that the teeth 14 of the lock ring begin to dimple the wall 12 of the junction box 3. Set screws 16a, 16b are provided on the connector 1 opposite to the threaded end 8. These set screws 16a, 16b are used to clampingly secure one end of a tubular, metallic conduit 18 to the connector end that protrudes out of the junction box 3. As is illustrated in FIG. 2, the system and method of the invention are particularly useful in the assembly of electrical power modules 20, which may comprise a junction box 3 with pre-installed connectors 1, or the combination of a junction box 3, connectors 1, and an array 22 of conduits 18 held together in a parallel arrangement via clamping straps 24.
[0027] As shown in FIGS. 3A-3C, the socket 30 that forms part of the system of the invention includes an annular socket body 32 having an annular wall 33. The socket body 32 has an open end 34 for receiving a lock ring 5, and a closed end covered by a circular wall 36. The circular wall 36 includes a square detent opening for receiving the output shaft of a driver such as a pneumatic or electric torque wrench. The circular wall 36 further includes a diametral bore 40 for housing a spring and detent ball (not shown) for providing a detachable coupling between the socket body 32 and the output shaft of a driver. In order to reduce mechanical interference between the socket body 32 and a lock ring 5 during the tightening operation, the socket body 32 has half as many wrench lugs 44a-c or less than the number of teeth 14 of the lock ring 5. As this embodiment of the socket 30 is directed toward the tightening of lock rings 5 having six equidistantly spaced teeth 14, three wrench lugs 44a-c spaced 120° apart are provided around the inner surface 45 of the socket body 32. The socket body 32v is formed from tool steel, and the wrench lugs 44a-c are integrally formed with the annular wall 33 of the socket body 32 for strength and durability.
[0028] With specific reference to FIGS. 3D and 3E, the lock rings 5 forming part of this exemplary embodiment of the inventive system include six teeth 14 around their outer diameter. The teeth 14 are circumferentially spaced 60° from one another and define annular gaps 46 around the outer diameter of the lock rings 5. The teeth 14 are slightly bent toward a same face of the lock rings 5 as shown in FIG. 3D which defines the inside face 48 of the lock rings 5. The opposite side of the lock rings 5 defines the outside face 50 in this application. During the tightening operation, the lock rings 5 are oriented so that their inside faces 48 face the wall 12 of the junction box 3 so that the outer edges 52 of the teeth 14 bite into the junction box wall 12, as will be scribed in detail hereinafter. The lock rings 5 further have a threaded inner diameter 51 for engaging the threaded end 8 of a conduit connector 1.
[0029] With specific reference to FIG. 3E, the wrench lugs 44a-c each have flat, opposing side walls 54a, b. These walls 54a, b are parallel to the radius of the annular socket body 32. The teeth 14 of the lock rings 5 also have flat, opposing side walls 56a, b. However, the side walls 56a, b of the teeth 14 are each angled away from the radius of the socket body 32 such that the side walls 44a, b of the wrench lugs 44a-c are disposed at an angle θ with respect to the side walls 56a, b of each tooth 14. Consequently, during a tightening operation where the socket body 32 rotates counterclockwise as seen from FIG. 3E, the side wall 54b of one or more of the wrench lugs 44a-c engages the side wall 56b of three of the six the teeth 14 of lock ring 5 at the angle θ in a sliding point contact that promotes uniform engagement between the wrench lugs and the lock ring teeth. If the inner surface 45 of the annular socket body 32 and the lock ring 5 are slightly non-concentric at the beginning of such a tightening operation, only the side wall 54b of only one of the wrench lugs 44a-c may engage the side wall 56b of only one of the teeth 14. However, the sliding point contact provided by the angle θ between the wrench lug walls 54b and tooth walls 56b in combination with the relatively high amount torque applied to the socket 30 advantageously causes the socket 30 to move into concentricity with the lock ring 5, thereby bringing two or three of the wrench lugs 44a-c into contact with the side wall 56b of two or three of the teeth 14. Such a centering movement promotes a uniform application of torque around the lock ring 5 that advantageously suppresses planar misalignment between the teeth 14 of the lock ring 5 as they engage the wall 12 of the junction box 3. The angle θ is between about 15° and 40°. An angle less than 15° may not generate enough sliding point contact to apply a centering force onto the socket body 32. An angle greater than 40° may result in binding between the wrench lugs 44a-c and the teeth 14 that interferes with the removal of the socket 30 from the lock ring 5 after a tightening operation.
[0030] FIG. 3E illustrates four additional structural features of the socket 30 which reduce the probability of mechanical interference when the socket 30 is used to tighten lock rings 5 when assembling electrical power modules 20. First, the circumferential extent C.sub.1 of each of the wrench lugs 44a-c is 50% or less than the circumferential extent C.sub.2 of the annular gaps 46 between the teeth 14 of the lock rings 5. In one preferred embodiment, C.sub.1 is between about 40% to 50% of C.sub.2. Such relative proportioning substantially increases the probability that the wrench lugs 44a-c will be received within the annular gaps 46 of the lock ring 5 without striking the teeth 14 when the socket 30 is positioned over a lock ring 5. Second, the radial thickness R.sub.0 of the annular wall 33 of the socket body 32 is between about 133% to 200% of a radial extent R.sub.1 of the teeth 14 of the lock ring 5. For a socket 30 capable of tightening a lock ring 4″ in diameter, this radial thickness R.sub.0 might be between about ⅛″ and 3/16″, while the radial extent R.sub.1 of the teeth 14 is about 3/32″. In terms confined exclusively to the socket body 32, the radial thickness R.sub.0 of the annular wall 33 of the socket body 32 is only about 3%-4% of the inner diameter D2 of the annular wall 33. Such a relatively thin annular wall 33 reduces the diameter of the socket 30, making it easier to manipulate in the small workspaces provided in the corners of the junction box 3 and between the cut-out openings 10. It also lowers the weight of the socket 30, making it easier for the factory worker to manipulate and less strenuous to support. Third, when the lock ring 5 is concentric with the socket body 32, a radial gap R.sub.3 between about 80% to 100% of a radial extent of the lock ring teeth 14 is provided between the outer edges 52 of the lock ring teeth 14 and the inner surface 45 of the annular wall 33 of the socket body 32. Such relative proportioning not only reduces the probability of interference between the outer edges 2 of the teeth 14 and the annular wall 32 of the socket body 32 when the socket 30 is positioned over the lock ring 5, but also facilitates the centering movement between the socket 30 and the lock ring 5 described earlier. Finally, the radial length R.sub.2 of the wrench lugs 44a-c is only between about 133% to 150% of the radial length R.sub.1 of the teeth 14. Hence, when the when the lock ring 5 is concentric with the socket body 32, the wrench lugs 44a-c overlap only about the outer one-third to one-half of the teeth 14. Such relative proportioning helps to avoid mechanical interference between the inner surfaces of the wrench lugs 44a-c and the outer surfaces of the annular gaps 46 between the teeth 14.
[0031] Turning now to FIGS. 4A and 4B, the system of the invention further includes a driver 60 that is preferably right-angled as shown to allow the factory worker to easily manipulate the socket 30 within the small workspaces present at the corners of the junction box 3 and between the openings 10 along the junction box wall 12. The driver 60 includes a torque control (not shown) that allows the factory worker to set the torque applied by the driver 60 to the lock ring 5 to between about 1200 to 1400 inch-pounds of torque. The driver 60 includes a drive shaft (not shown) which is detachably connectable to the square detent opening 38 of the socket 30 via the spring and detent ball housed within the diametral bore 40. The driver 60 may be one of several commercially available products and forms no part of the invention per se.
[0032] FIGS. 4A-4D illustrate how the previously described system implements the method of the invention. In the first step of the method, one or more connectors 1 is extended through one of the openings 10 present in a side wall 12 of a junction box 3. Next, the factory worker manually threads a lock ring 5 over the threaded end 8 of the connector 1, taking care that the lock ring 5 is oriented so that its inside face 48 faces the junction box wall 12. In such an orientation, the teeth 14 of the lock ring 5 will be bent toward the wall 12 such that the outer teeth edges 52 become the closest points between the wall 12 and the lock ring 5. As illustrated in FIG. 4B, the worker manually threads the lock ring 5 until the teeth edges 52 are either directly adjacent to or in direct contact with the junction box wall 12.
[0033] When the manual threading of the lock ring 5 has been completed, the factory worker positions the interconnected socket 30 and driver 60 over the threaded lock ring 5 as shown in FIG. 4B, and then proceeds to capture the lock ring 5 within the annular socket body 32 as shown in FIG. 4C. A rapid capturing of the lock ring 5 without mechanical interference between the lock ring teeth 14, wrench lugs 44a-c, and annular wall 33 is facilitated by all of the previously-discussed structural features of the socket body 32. The factory worker then actuates the driver 60. At this juncture, the sliding point contact provided by the angle θ between the wrench lug walls 54b and tooth walls 56b in combination with the relatively high amount torque applied to the socket 30 advantageously causes the socket 30 to move into concentricity with the lock ring 5, thereby bringing two or three of the wrench lugs 44a-c into contact with the side wall 56b of two or three of the teeth 14. As previously pointed out, the application of torque to two or three points around the circumference of the lock ring 5 advantageously suppresses planar misalignment between the teeth 14 of the lock ring 5 as they engage the wall 12 of the junction box 3.
[0034] Prior to the actuation of the driver 60, the torque has been pre-adjusted to a level which will cause the teeth 14 of the lock ring 5 to begin dimpling or grooving the wall 12 of the junction box 3 without the formation of a closed annular groove in the wall 12. The applicants have observed that the application of a torque of between about 1220 and 1400 inch-pounds typically achieves this goal for lock rings 5 having a diameter of between 2″ and 4″. As shown in FIG. 4D, if the torque has been adjusted properly, the outer teeth edges 52 will form a pattern of discontinuous dimples or grooves 64 in the wall 12 that trace a “phantom circle” just before the driver 60 de-actuates due to the torque limit being exceeded. These dimples or grooves 64 widen and deepen along their lengths due to the screw thread such that the outer teeth edges 52 are seated at slightly different depths along their lengths, thus providing a positive “bite” into the wall 12. The fact that the teeth 14 are slightly bent toward the wall 12 biases the outer teeth edges 52 into the dimples or grooves 64 in cantilever spring fashion. This spring bias, in combination with the bite between the outer teeth edges 52 and the wall 12 that forms the dimples or grooves 64, securely affixes the lock ring 5 in place such that it will not loosen when subjected to the vibration that accompanies the transportation of the resulting junction box modules 20 from the factory to the building site.
