Lever (mechanism)

“ The mechanism which I have employed consists first of a lever put in motion (in the manner of a metronome) by the alternating action of two fixed electro-magnetic cylinders exerted on a third moveable cylinder connected with the lower arm of the lever, the upper arm of which maintains a metallic wheel, serving in the ordinary way as a regulator, in a continuous gyratory motion. ”

“ The segment disk containing these figures also serves as an interlocking device which prevents moving more than one speed controlling [265] lever at a time, in order to avoid damaging the driving mechanism.
The feeding movement for each head is independent. Lever D controls the engagement or disengagement of the vertical or cross feeds for the head on the cross-rail. The feed for the side-head is controlled by lever E. When this lever is pushed inward, the entire head feeds vertically, but when it is pulled out, the tool-bar feeds horizontally. ”

“ On the back of the operating lever is a friction spring which should overcome the tension of the brake spring, so as to have the left end of the operating lever remain in raised position until returned by the assembling elevator as it returns to normal. ”

“ It has been confounded, under the common name of Mechanics, with the other science, Mechanics Proper, or Machinery, which considers the effect of force transmitted by Mechanism from one part of a material combination to another. For example, the Mechanical Powers, as they are usually termed, (the Lever, the Wheel and Axle, the Inclined Plane, the Wedge, and the Screw,) have almost always been treated with reference to the relation between the Power and the Weight, and not primarily as a mode of changing the velocity and kind of the motion. ”

“ When the assembling elevator is being raised, the lug on the lower right side raises the left end of the operating lever, lowering the right against the adjusting screw in the brake trip which releases the brake, and allows the slide to return to its normal position. ”

“ The stop rod is pulled down below the mold disk dog by the lever until the slide moves downward, the roller follows the runway, when owing to a depression, the roller drops, releasing the lever and permitting the stop rod to come to operating position in front of the dog. As the slide moves to transfer position, the lever pulls the stop rod down below the dog. ”

“ In order that no balancing feats shall be required of the person in charge, there is, on the supporting standard, a quadrant, in the notches of which a lever on the engine frame engages, thus allowing the rigid framework, and therefore the propeller shaft, to be maintained at any angle to the vertical without trouble. ”

“ The head of the borer contains three little cylinders, set at an angle of 120°, to rotate the drill, the valves opening automatically to admit air at very high pressures behind the pistons. Any carpenter can imagine the advantage of a drill which has merely to be forced against its work, the movement of a small lever by the thumb doing the rest! ”

“ If the fusee has been turned to the correct taper, the driving power of the spring will remain constant as it unwinds, for it gets least leverage over the fusee when it is strongest, and most when it is weakest, the intermediate stages being properly proportioned. To test this, a weighted lever is attached to the key spindle, with the weight so adjusted that the fully wound spring has just sufficient power to lift it over the topmost point of a revolution. ”

“ Among the moving elements the first to be considered is the lever, which really forms a broad classification comprising many elements that will hardly be recognized as levers at first blush. Levers in some form are to be found in practically every machine. A wheel, a gear, and a pulley are really levers in disguise, as will be explained presently.
Of course everyone knows that a simple lever consists of a rigid bar that swings on a fulcrum. ”

“ Illustrations may be seen on every hand, as when a workman pries up a stone, or when a housewife pries up a tack with the aid of a hammer. The principle here involved is that of the lever—a principle which in its various practical modifications is everywhere utilized in mechanics. Very seldom indeed is the direct push or pull utilized; since the modified push or pull, as represented by the lever in its various modifications of pulley, ratchet-wheel, and the like, has long been known to meet the needs of practical mechanics. ”

“ The Lever being the simplest of all the mechanic powers, is in general considered the first. It is an inflexible rod or bar of any kind, so disposed as to turn on a pivot or prop, which is always called its fulcrum. It has the weight or resistance to be overcome attached to some one part of its length, and the power which is to overcome that resistance applied to another; and, since the power, resistance, and fulcrum admit of various positions with regard to each other, so is the lever divided into three kinds or modifications, distinguished as the first, second, and third kinds of lever. ”

“ Beneath the bracket to which the knife is fastened are two spiral springs that force the bracket and knob button against the sector screws. Moving the lever operates the sector, and the screw coming in contact with the button on the slide causes the knife to move in or out one point or as many as the lever is moved. When casting a 10-point slug, have the pointer on figure 10. ”

“ The lever is an extremely simple mechanical power; it has only one moving part. Friction produces but little effect upon it, so that the laws which we have given may be actually applied in practice, without making any allowance for friction. In this we notice a marked difference between the lever and the pulley-blocks already described. ”

“ When a lever is applied to raise a weight, or overcome a resistance, the space through which it acts at any one time is small, and the work must be accomplished by a succession of short and intermitting efforts. In fig. 81., after the weight has been raised from W to W′, the lever must again return to its first position, to repeat the action. During this return the motion of the weight is suspended, and it will fall downwards unless some provision be made to sustain it. ”

“ Fig. 205.—"Lever" watch escapement.
In the illustration a tooth has just passed under the "impulse face" b of P1. The lever has been moved upwards at the right end; and its forked end has given an impulse to R, and through it to the balance-wheel. The spring winds up. The pin C prevents the lever dropping, because it no longer has the notch opposite to it, but presses on the circumference of R. As the spring unwinds it strikes the lever at the moment when the notch and C are opposite. ”

“ The extremity of a lever which supports itself on a horizontal axis describes a circle's circumference placed in a vertical plane; the path travelled through by this extremity is therefore not directed in the way of the weight of the load to lift, weight which pulls following a vertical right angle. By it, it results that the resistance that it is necessary to surmount to make to turn from a certain angle the lever arm depends on the initial position from this lever arm. It is so much the greater as the lever is closer to the horizontal position. ”

“ You can lift a ton with [23] an effort of only 100 pounds if your effort arm is twenty times as long as your weight arm but the end of your effort arm would have to move twenty inches to raise the ton weight one inch. We are assuming in all these cases that the lever itself has no weight and that there is no friction at the fulcrum.
Of course levers are not used merely for the purpose of lifting weight, but to overcome any resistance or merely to apply pressure upon an object. In almost every household we may find examples of the three orders of levers. ”

“ In the Aristotelian Mechanica we find a remark on the marvel of a great weight being moved by a small force, and the problems discussed bring in the lever in various forms as a means of doing this. We are told also that practically all movements in mechanics reduce to the lever and the principle of the lever (that the weight and the force are in inverse proportion to the distances from the point of suspension or fulcrum of the points at which they act, it being assumed that they act in directions perpendicular to the lever) . ”

“ As the distances of the power and weight from the fulcrum of a lever may be varied at pleasure, and any assigned proportion given to them, a lever may always be conceived having a power equal to that of any given machine. ”

“ In order, however, to prevent any oscillation of the machine in turning round, the levers are kept in a horizontal position by means of small chains a a, one end of which is fixed to the top of the upright shaft, and the other terminates in a small square piece of wood b, which exactly fills the notch c in the lever. ”

“ Yet, all this time, the great reformer has been left to accomplish his operations without note or comment; and while thundering along the earth or ploughing the sea with giant speed and giant power, men have not endeavored to track his influence upon humanity, nor work out any evidences of those strange changes he is effecting over the whole surface of society. The steam-engine is not merely a power to turn the wheels of mechanism,—it beats and throbs within the heart of a nation, and is felt in every fibre and recognized in every sinew of civilized man. ”

“ At the extremity of a lever, one can cause to act a force of which the direction is different from the vertical; it will suffice
to employ a cord extended in this direction, passing over a pulley and pulled then by a weight. A rule similar to the preceding will help to evaluate the motive power of a similar engine ”

“ We have a system of levers to do our walking with, and they act precisely as do all levers. One leg is a lever to pry the body over the other leg, and the latter becomes a pendulum and swings back by force of gravity. ”

“ Where great resistances have to be overcome, but where the distance through which the resistance must be urged is short, the lever or the screw is generally found to be the most appropriate means of [Pg 150] increasing power. When, however, the resistance has to be moved a considerable distance, the aid of the pulley, or the wheel and axle, or sometimes of both combined, is called in. The wheel and axle is the form of mechanical power which is generally used when the distance is considerable through which a weight must be raised, or through which some resistance must be overcome. ”

“ It is counterbalanced by a powerful lever or beam, having an adjust able weight shaped like an eagle, which raises it automatically. In the bar handle is a screw stop by means of which the length of the lever rod can be adjusted and its pressure, or the pull, per fectly regulated. ”

“ It should, however, be observed that, broadly considered, a hand-wheel and a lever are substantial equivalents in these devices. The wheel is a continuous lever. The rim enables the operator to lay hold at any point desired, and takes the place of a number of levers. But it is denied that momentum hand-wheels are the equivalents of levers. ”

“ If the machine was fixed on the loom for a Norwich tie, or with the cards to hang over the back, then the connections from the levers might all be at the centres of the lifters and the bars D would only be [193] required to steady them. The levers for raising the lifters are shown at F, with their fulcrum at I. G is a spring, one of which is attached to each lever to keep it down, as the tappet has not a positive rising and sinking motion, only raising the levers and allowing their own weight and the draw of the springs to recover them. ”

“ Our draft is to be the most difficult subject in lever escapements; it is to be represented just as if it were working in a watch; it is to represent a good and reliable action in every respect, one which can be applied without special difficulty to a good watch, and is to be “up to date” in every particular and to contain the majority of the best points and conclusions reached in our analysis.
Specifications for Lever Escapement:
The pallets are to be equidistant; the wheel teeth of the “club” form; there are to be two rollers; wheel, pallet, and balance centers are to be in straight line. ”

“ When one end of the lever (A) goes down, the other end goes up, as shown in Fig. 129; and in Fig. 130, when the shaft (C) of one wheel turns in one direction, the shaft of the other wheel turns in the opposite direction.
It is plain that a gear, like a lever, may change direction as well as increase or decrease power. It is the thorough knowledge of these facts, and their application, which enables man to make the wonderful machinery we see on every hand. ”

“ The modern lever is usually somewhat different and partakes more of the nature of a handle. They are seen in sawmills where they manipulate the carriage machinery; on certain agricultural implements where their function is to throw clutches in and out of gear; sometimes they are used as the handle by which the rudder of a small boat is controlled; and occasionally the lever has a place as an adjunct of a wagon or log-car brake. ”

“ While the lifting action of the lever escapement corresponds to that of the cylinder, the fork and roller action corresponds to the impulse action in the chronometer and duplex escapements.
Our experience leads us to believe that the action now under consideration is but imperfectly understood by many workmen. It is a complicated action, and when out of order is the cause of many annoying stoppages, often characterized by the watch starting when taken from the pocket. ”