Fig. 1004. Feed-motion of Woodworth's planing machine, a smooth supporting roller, and a toothed top roller.

Fig. 1005. Contrivance employed in Russia for shutting doors. One pin is fitted to and turns in socket attached to door, and the other is similarly attached to frame. In opening the door, pins are brought together, and weight is raised. Weight closes door by depressing the joint of the toggle towards a straight line, and so widening the space between the pins.

Fig. 1006. Folding library ladder. It is shown open, partly open, and closed; the rounds are pivoted to the side-pieces, which are fitted together to form a round pole when closed, the rounds shutting up inside.

Fig. 1007. Self-adjusting step-ladder for wharfs at which there are rise and fall of tide. The steps are pivoted at one edge into wooden bars forming string-pieces, and their other edge is supported by rods suspended from bars forming hand-rails. The steps remain horizontal whatever position the ladder assumes.

Fig. 1008. Lifting jack operated by an eccentric, pawl, and ratchet. The upper pawl is a stop.

Fig. 1009. Jig-saw, the lower end connected with a crank which works it, and the upper end connected with a spring which keeps it strained without a gate.

Fig. 1010. Contrivance for polishing lenses and bodies of spherical form. The polishing material is in a cup connected by a ball-and-socket joint and bent piece of metal, with a rotating upright shaft set concentric to the body to be polished. The cup is set eccentric, and by that means is caused to have an independent rotary motion about its axis on the universal joint, as well as to revolve about the common axis of the shaft and the body to be polished. This prevents the parts of the surface of the cup from coming repeatedly in contact with the same parts of surface of the lens or other body.

Fig. 1011. Device for converting oscillating into rotary motion. The semicircular piece A is attached to a lever which works on a fulcrum a, and it has attached to it the ends of 2 bands C and D, which run round 2 pulleys, loose on the shaft of the fly-wheel B. Band C is open, and band D crossed. The pulleys have attached to them pawls winch engage with two ratchet-wheels fast on the fly-wheel shaft. One pawl acts on its ratchet-wheel when the piece A turns one way, and the other when the said piece turns the other way, and thus a continuous rotary motion of the shaft is obtained.

Fig. 1012. Reciprocating into rotary motion. The weighted racks a, a', are pivoted to the end of a piston-rod, an 1 pins at the end of the said racks work in fixed guide-grooves b, h, in such manner that one rack operates upon the cog-wheel in ascending and the other in descending, and so continuous rotary motion is produced. The elbowlever c and spring d are for carrying the pin of the right-band rack over the upper angle in its guide-groove b.

Mechanical Movements Part 16 957Mechanical Movements Part 16 958Mechanical Movements Part 16 959Mechanical Movements Part 16 960Mechanical Movements Part 16 961

Fig. 1013. C. Parsons's device for converting reciprocating motion into rotary, and endless rack provided with grooves on its side gearing with a pinion having 2 concentric flanges of different diameters. A substitute for crank in oscillating cylinder engines.

Fig. 1014. Four-way cock, used many years ago on steam engines to admit and exhaust steam from the cylinder. The 2 positions represented are produced by a quarter turn of the plug. Supposing the steam to enter at the top, in the upper figure the exhaust is from the right end of the cylinder, and in the lower figure the exhaust is from the left - the steam entering, of course, in the opposite port.

Fig. 1015. Continuous circular into intermittent rectilinear reciprocating. A motion used on several sewing machines for driving the shuttle. Same motion applied to 3 revolution cylinder printing-presses.

Fig. 1016. A method of repairing chains, or tightening chains used as guys or braces. Link is made in two parts, one end of each is provided with swivelnut, and other end with screw; the screw of each part fits into nut of other.

Fig. 1017. Continuous circular motion into intermittent circular - the cam C being the driver.

Fig. 1018. A. B. Wilson's 4-motion feed, used in Wheeler and Wilson's, Sloat's, and other sewing machines. The bar A is forked, and has a second bar B, carrying the spur or feeder, pivoted in the said fork. The bar B is lifted by a radial projection on the cam C, at the same time the 2 bars are carried forward. A spring produces the return stroke, and the bar B drops of its own gravity.

Fig. 1019. E. P. Brownell's crank-motion to obviate dead-centres. The pressure on the treadle causes the slotted slide A to move forward with the wrist until the latter has passed the centre, when the spring B forces the slide against the stops until it is again required to move forward.

Fig. 1020. Mechanical means of describing parabolas, the base, altitude, focus, and directrix being given. Lay straight-edge with near side coinciding with directrix, and square with stock against the same, so that the blade is parallel with the axis, and proceed with pencil in bight of thread, as in the preceding.

Fig. 1021. Mechanical means of describing hyperbolas, their foci and vertices being given. Suppose the curves 2 opposite hyperbolas, the points in vertical dotted centre line their foci. One end of thread being looped on pin inserted at the other focus, and other end held to other end of rule, with just enough slack between to permit height to reach vertex when rule coincides with centre line. A pencil held in bight, and kept close to rule, while latter is moved from centre line, describes one half of parabola; the rule is then reversed for the other half.