It is a joint between two parts allowing movement in one plane only. It is a kind of hinged joint between two rods, often like a ball and socket … Read More
It is a joint between two parts allowing movement in one plane only. It is a kind of hinged joint between two rods, often like a ball and socket joint.
There are many situations where two parts of machines are required to be restrained.
For Example two rods may be joined coaxially and when they are pulled apart they should not Separate i.e. should not have relative motion and continue to transmit force. Similarly if a cylindrical part is fitted on another cylinder (the internal surface of one contacting the External surface of the other) then there should be no slip along the circle of contact. Such situations of no slip or no displacements are achieved through placing a third part or two parts at the jointing regions. Such parts create positive interference with the jointing Parts and thus prevent any relative motion and thus help transmit the force. One should remember that the rivets in a riveted joint had exactly the same role as they prevented the Slipping of one plate over the other (in lap joint) and moving away of one plate from other (in butt joint). The rivets provided positive interference against the relative motion of the plate. Knuckle joint is yet another to join rods to carry axial force. It is named so because of its freedom to move or rotate around the pin which joins two rods, a motion which naturally exists at finger joints or knee. A knuckle joint is understood to be a hinged joint in which projection in one part enters the recess of the other part and two are held together by passing a pin through coaxial holes in two parts. This joint cannot sustain compressive Force because of possible rotation about the pin. In this unit we will study other Interfering parts for geometrically different jointing parts.
Knuckle joints are most common in steering and drive train applications where we need to move something (steering linkage etc) but also need to allow for offset angles. A knuckle joint is used when two or more rods subjected to tensile and compressive forces are fastened together such that their axes are not in alignment but meet in a point. This type of joint allows a small angular movement of one rod relative to another. The joint can be easily connected and disconnected. Knuckle joint is found in valve rods, braced girders, links of suspension chains, elevator chains, etc. The drawing of a knuckle joint is shown in Fig. 4. The end of one of the rods is forged in the form of a fork while the end of the other rod has an eye, which can be inserted in the jaws of the fork. A cylindrical pin is driven through the holes in the forks and the eye. The pin is secured in position by a taper pin, split pin or a thin nut screwed up to shoulder on the end of the pin. The ends of the rods are made octagonal for good hard grip Read Less