Patent ID: 12240033

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

With reference now to the drawings, and particularly toFIG.1, there is shown an exploded perspective view of a multi-part conduit bender1. The multi-part conduit bender handle1preferably includes at least a lower tube10and an upper tube12. The lower tube10includes an outer diameter, which includes a ¾ male national pipe tap (NPT)14to be formed on opposing ends thereof. However, other outer diameter sizes may be used to accommodate other national pipe tape sizes, such as ½ NPT or 1″ NPT. One end of the lower tube10is threaded into a female ¾ NPT102in a conduit bender head100. An inner diameter16of the upper tube12is preferably greater than an outer diameter of a ¾ EMT conduit104, such that the ¾ EMT conduit may be inserted into the inner diameter16of the upper tube12. A length of the upper tube12is preferably the same length as the lower tube10. A preferable inner diameter of the upper tube12is at least 0.97 inches.

With reference toFIG.3, a modified ¾ female NPT18is preferably formed in one end of the upper tube12and an opposing end is preferably left open for insertion of the ¾ EMT conduit104. The opposing end of the upper tube12is also preferably chamfered or deburred for safety reasons. The modified ¾ female NPT18provides a threaded connection that includes the locking characteristics of a tapered thread with the thread depth engagement of a straight cut thread. The modified ¾ female NPT18includes a 60-degree thread angle, taper angle, root and crest. However, there are two primary differences between a standard ¾ female NPT thread and the modified ¾ female NPT. The first difference is the inner diameter20of the upper tube is preferably enlarged to about 1.00 inches from 0.97 inches and the second difference is a depth “D” of the modified ¾ NPT female threads18is increased to about 0.85 inches. The increased inner diameter20is enlarged for a depth “D” of the modified ¾ female NPT18. As a result of the increased inner diameter20, the ¾ male NPT14on the lower tube10will fully thread into the modified ¾ female NPT18of the upper tube12. The result is that when torque is applied to the multi-part conduit handle1, there is no flexing in the screw joint between the upper tube12and the lower tube10, which can lead to loosening or mechanical failure.

NPT threads as defined by ANSI B1.20.1 is a general-purpose tapered thread most commonly used to couple pipes for carrying air, water, oil, gas, etc. The pipes are designed to be wrench tightened to create a locking joint that when combined with a sealing agent, provides a liquid or gas tight connection. The characteristics of NPT (also known as ANSI/ASME B1.20.1 Pipe Threads, General Purpose) are as follows: the angle between the taper and the center axis of the pipe is 1o 47′ 24″ (1.7899o) truncation of roots and crests are a flat 60-degree thread angle pitch, which is measured in threads per inch (TPI). If the threads18,20were cut to follow the ANSI B1.20.1 standards, which generally reach the point of tightness, after 4 to 5 turns, there would not be enough thread engagement. In standard use for sealing, 4 to 5 turns provide plenty of thread engagement to provide for desired sealing qualities. In the application of a handle for a conduit bender, the upper tube12and the lower tube10are subjected to a shear force and if a standard taper to taper thread were used, there would not be enough material overlap in the threads to create a joint capable of sustaining the mechanical stresses of a handle for a conduit bender.

With reference toFIG.2, a first tube110is threadably engaged with a second tube112. If a male NPT thread114is formed on the first tube110and a female straight thread116is formed on the second tube112, the result is that the male NPT threads would only be fully supported at the very beginning of the straight female threads116. A gap results at the far end of the thread joint between the lower tube10and the upper tube12, which would allow for flex in the connection, when torque is applied to the conduit bender handle when forming conduit bends. There would not be enough material overlap in the threads to create a joint capable of sustaining the mechanical stresses of a handle for a conduit bender. Further, the resulting flex would result in the threads114,116loosening or a total mechanical failure of the conduit bender handle.

There are other methods of joining the lower tube10to the upper tube12besides that illustrated inFIGS.1-3. With reference toFIG.4, a multi-part conduit bender handle2includes forming straight male threads22on the lower tube10and straight female threads24in the inner diameter16of the upper tube12. The straight male threads22are screwed into the female threads24. A locking compound may be applied to the threads22,24to prevent the lower tube10from unscrewing from the upper tube12. With reference toFIG.5, a multi-part conduit bender handle3includes forming coarse male threads26on the lower tube10and coarse female threads28in the inner diameter16of the upper tube12. The coarse male threads26are screwed into the coarse female threads28. A locking compound may be applied to the threads26,28to prevent the lower tube10from unscrewing from the upper tube12.

With reference toFIG.6, a multi-part conduit bender handle4includes extending a pin projection30from an outer surface of one end of the lower tube10and forming a twist slot32through an end of the upper tube12. The twist slot32includes an entrance portion34and a locking portion36. The locking portion36terminates an end of the entrance portion34and the locking portion36is preferably perpendicular to the entrance portion34. The lower tube10is inserted into the upper tube12, such that the pin projection30enters the entrance portion34and is locked in the locking portion36.

With reference toFIG.7, a multi-part conduit bender handle5includes at least one threaded fastener38, forming at least one lower fastener hole40through one end of the lower tube10and forming at least one upper fastener hole42through an end of the upper tube12. The one end of the lower tube10is inserted into the inner diameter16of the upper tube12, such that the at least one lower fastener hole40aligns with the at least one upper fastener hole42. The at least one threaded fastener38is inserted through the at least one hole40,42. The at least one thread fastener38is preferably secured with at least one washer44and at least one nut46.

With reference toFIG.8, a multi-part conduit bender handle6includes a spring pin48, forming a lower pin hole50through one end of the lower tube10and forming a spring pin hole52through an end of the upper tube12. The spring pin48is secured in the spring pin hole52with any suitable method. The spring pin48is retracted and the one end of the lower tube10is inserted into the inner diameter16of the upper tube12, such that the lower pin hole40aligns with a spring-loaded projection of the spring pin48.

While particular embodiments of the invention have been shown and described, it will be obvious to those skilled in the art that changes and modifications may be made without departing from the invention in its broader aspects, and therefore, the aim in the appended claims is to cover all such changes and modifications as fall within the true spirit and scope of the invention.