Construction of a Tappet

Experiment Name: -Construction of a tappet of one by one plain weave.

Introduction:

Tappets are generally used for heald shedding. Tappet, cam and wipers are names given indiscriminately to those irregular pieces of mechanism to which a rotary motion is given for the purpose of producing, by sliding contact, reciprocating motion in rods and levers. When the rod is to receive a series of lifts, with intervals of rest, the piece is generally called tappet.

Objectives:

    To know the construction of tappet shedding mechanism.

    To identify the different parts shaped this shedding.

    To learn the mechanism of tappet shedding.

Construction of Tappet for plain weave:-

To design a shedding tappet for plain weave, the following particular have been taken into consideration:-

1.     Lift of tappet, 4 inch or 10.16 cm.

2.     Distance from the center of the driving shaft to the nearest point of contact, with the treadle bowl, 2 inches 0r 5.08 cm.

3.     Dwell of tappet, one third of a pick

4.     Diameter of treadle bowl, 2 inches or 5.08 cm,

Fig (left side bottom) shows the design, fig (main) the outline for the plain weave shedding tappet and fig (right side bottom) the picks to the round in one repeat of the design. At a radius of 2 inches or 5.08 cm describe the circle a (fig. main). This circle represents the distance from the center of the driving shaft to the nearest point of contact with the treadle bowl. For plain weave tappet, the bottom shaft is used as the driving shaft, whereas for twill and other weaves a counter shaft is used as the tappet shaft.

At a radius of 3 inches or 7.62 cm (5.08 cm+ 2.54 cm= 7.62 cm) describe the circle B. one inch or 2.54 cm. is added for the radius of treadle bowl.

At a radius of 7 inches or 17.78 cm (7.62 cm +10.16 cm=17.78 cm) describe the circle C. Four inches or 10.16 cm are added for the lift of tappet.

The circle B represents the center of the treadle bowl when the inner circle of the tappet is acting upon the bowl.

The circle C represents the center of the bowl when pressed down by the tappet.

The pattern being a plain one, as shown in Fig (left side bottom), the circles must be divided into two equal parts, and each half-circle will then represent one pick. By the line DE divide the circles into two equal parts fig (main &right side bottom).

Now, as the healds must have a pause or dwell equal to one third of a pick when at the top and the bottom of their stroke, divide each half-circle into three equal parts by lines FK, GH. Divide FH and GK each into six equal parts and divide the space between the circles B and C into six unequal parts, the largest being in the middle, gradually decreasing towards the circles B and C. to find out the six unequal parts, describe a semi-circle L between B and C at a radius of half of the lift of tappet, which is 5.08 cm. Now divide its circumference into six equal parts and then draw perpendicular lines from them on the line GH. This gives six unequal divisions on the lift to obtain the desire eccentric shape of the tappet.

Conclusion:

From this experiment we learn how to make a tappet for plain weave. Tappet shedding mechanism is important for driving loom. It is also important for fabric design. By this experiment we also learn the different parts of this tappet. This would be very helpful in our future life.