[Photo: A pinsetter sets up bowling pins in the configuration shown.]
Originally, pinspotters manually set up pins. However, in 1952, the first automatic pinsetters were commercially produced, greatly speeding up the game and allowing its popularity to blossom.
In bowling, a pinsetter, or pinspotter, was originally a person who would manually reset bowling pins in their correct position, clear fallen pins, and return bowling balls to the players. In 1936 Gottfried Schmidt invented the mechanical pinsetter, which largely did away with pinsetting as a manual profession.
The design of the machines varies, but a common design (the Brunswick Model A, dating from 1955, as well as the developed A2 and JetBack versions of it) works as follows:
First, the balls and pins are pushed off the end of the lane onto a fabric tray the width of the lane. This tray shakes, funneling the ball and pins to the next stage. Two large (≈5 ft; 1.5 m) spinning hoops are situated with their common axis along the bowling lane. The one closer to the bowler is smooth on the inside; the one further from the bowler has a series of pockets in which a pin can rest.
When a ball rolls back to the first hoop, friction lifts the ball up to the side where it catches on two rubberized rails. Still touching the inside of the hoop, the ball is rolled up the rails. When it gets near the top, the rails end, dropping the ball on a track which rolls the ball back to the bowler.
When a pin rolls back, its geometry is such that the first hoop has little effect on it. Still being shaken by the tray, it bounces around until it lands in a pocket on the second hoop which takes it to the top of the hoop and drops it into a metal tray, shaped somewhat like a scoop with the lip of the scoop facing the bowler. The pin is dropped in with the "handle" facing either to the bowler's left or right, but with the body of the pin centered in the scoop. The weight of the pin as it slides through the scoop orients the pin so that its base faces the bowler. From there a conveyor belt lifts the pin up, letting it slide into one of ten spots in a carousel. (This carousel is situated just above the caddy which the bowler can see when the pins are actually set.) When a pin lands in a spot, the carousel rotates so that the next pin will land in another spot. Once the carousel is full, the machine waits until it needs to re-set the pins. At that point, the pins are simultaneously dropped from the carousel into the caddy which lowers them all onto the lane.