Air cushion

“ A bag full of air, such as a common air-cushion, can be squeezed till the air in its interior occupies a much smaller volume; and, if you treat a syringe full of air in the same way as the syringe full of water was treated, you will find, if the piston fits well, that it can be driven down some distance and then springs back again. Air in fact is not only a compressible, but it is an elastic fluid or gas. Heat expands air just as it expands water, but the expansion of air for the same degree of heat is much greater.
36. Steam is an Elastic Fluid or Gas. ”

“ Then it grows thicker, till there is enough for one to breathe and live in. But the air is wrapped around the earth like a cushion, or like a peach around its stone; and you know that even a cushion, or a football, or a bicycle tire can be blown up with air so hard that it seems like a rock and would hurt if you struck it. The star struck this cushion. ”

“ High speed gives some advantage. A judicious use of cushion helps condensation somewhat also, because when any gas like steam or air is compressed, it gives off heat, and this heat in the cushion will keep up the temperature of the cylinder. This cannot be carried very far, however, for the back pressure of cushion will reduce the energy of the engine movement. ”

“ It is necessary to have a tell tale connected with the apparatus, which will show when the surface of the glass has been thus adjusted. The shadow of the deep frame is an inexpensive tell-tale, and enables the operator to know when the adjustment is right. I have now described, in detail, the construction of the air-cushion with its back-board, as well as that of the frame which holds the plate glass, and I think it will be evident that the first cost of the materials of which they are made is comparatively little, and that the workmanship required to produce it is reduced to a minimum. ”

“ Connected with the cushion is a pressure gauge, and a tube with a cock, for charging the cushion with air from the lungs. Experience shows what pressure is necessary with any given paper, and the gauge enables one to know that the pressure is neither deficient nor in excess of that which is safe for the glass. ”

“ Air as a cushion is used to prevent the rebound of the springs of an automobile and is also widely employed in machinery to absorb the momentum of moving parts or to slow the action of a spring. In a door check, for instance, a powerful spring is provided which would slam the door shut were it not for the cushioning action of air. A plunger is connected to the door and slides in a cylinder on the door frame. The air compressed by the plunger can escape only very slowly through a small port. ”

“ A pneumatic attachment for trousers, consisting of an inflatable cushion, having a V-shaped recess in the lower portion thereof, thereby forming a crotch, a partition extending from the top of said crotch to the top of the cushion, thereby forming independent reservoirs therein, and an air-supply tube common to said reservoirs. ”

“ At the same time the air-supply through these pipes was so improved that the air in the pipes, by mechanical contrivances, was kept at a considerable pressure; and by means of valves and stopcocks, the act of breathing below water is performed as easily as in the atmosphere; and there is no need to come to the surface at all for purposes of respiration. The breathing apparatus is so constructed that every mouthpiece is connected with two sets of tubes, one of which receives and carries off the expired air, whilst the other supplies the fresh air to be breathed. ”

“ If an independent chest be employed, its closeness to the ground renders it possible for dust easily to pass through the air-holes in the walls at the moment of suction, and even to enter the cylinder, where its presence is particularly harmful, leading, as it does, to the rapid wear of the rubbing surfaces. ”

“ In a system of ventilation it is not only a question of providing a certain volume of air from the outside, but the great problem is to provide a sufficient volume of pure air of proper temperature and of proper humidity. Air that is laden with smoke, dust and suspended matter, or that which contains gas or foul odors, is objectionable and does not meet the requirements. Therefore, the source of the air becomes important. The ventilating system must also keep the air in proper circulation at a proper velocity. ”

“ It 's usually fitted with an air-lock and supplied with compressed air. As if the caisson were a diving-bell sunken in the earth—don't you know? The air in it keeps out the water, and the metal holds up the sand. ”

“ By pulling out one of the buttons of the wind chest, we admit the air through eleven holes at a time, having an angular distance of 30° and directing it against the corresponding circle of holes on the turning disk. If the arrangement of holes is not repeated identically twelve times on the same circle, we cannot, of course, make use of the above arrangements of holes of the wind tube, and we must then employ one of the movable brass tubes, which communicate with the interior of the wind chest by means of rubber tubes and stopcocks. ”

“ In the same way, when you force the air out of a rubber suction cap, such as is used to fasten reading lamps to the head of a bed, the air pressure outside holds the suction cap tightly to the object against which you first pressed it, making it stick there.
We can easily experiment with air pressure because we can get almost entirely rid of it in places and can then watch what happens. A place from which the air is practically all pumped out is called a vacuum. ”

“ It is a decked boat, to go underwater: and several persons have gone under water many leagues. The difficulty is, to provide the persons in the boat with fresh air for respiration; and this is contrived, by having a reservoir of air, of suitable dimensions to the size of the boat, and the number of persons in it. By means of a condensing pump, the air, in this reservoir, is condensed about 400 times; and by a spring, the air is let out at intervals, as circumstances require, the carbonic acid produced by respiration being absorbed by quicklime. ”

“ A tube runs from the left side of this wall to the right wing of the airplane, also from the right side of the wall to the left wing. At the end of each tube there is what we call a 'venturi tube.' This is a kind of suction device operated by the wind. The wind which blows through the left venturi tube sucks the air out of the right-hand side of the mercury tube, and the right venturi tube sucks the air out of the left-hand side of the mercury tube. The stronger the wind, the greater the suction. ”

“ A few air-bricks connecting the inside by a hollow flue formed in the wall, with its outlet as far as possible from the inlet, should be sufficient to ventilate any strong-vault. But if other ventilation is necessary in the room, have a jet of gas always alight; and over the gas place a bell-shaped covering communicating with the outer air, or with a chimney flue in preference, by a two-inch iron pipe. ”

“ Of the more usual mechanical aids at the disposal of the glass-blower, we have already mentioned hand-tools, blocks, and moulds of various kinds. Next in importance to these is the use of compressed air91 for blowing large or heavy articles; the pressure available by the human breath is very limited, and the volume of air that can be thus delivered is not very large, while the constant use of the lungs for such a purpose is trying for the workman. ”

“ To prevent any possibility of back-draught the outlet should be provided with some means of constant suction, and, the more thoroughly to remove the foul air, the more suction the better, provided there is also an ample inlet for fresh air: if not ample, the suction would produce a smoking chimney and draughts from around the windows and doors, and perhaps draw in air from foundation and drains. ”

“ Carnelley, Haldane, and Anderson, the results of which are summarised in the following table:—
The air to be admitted may be warmed by passing it over hot-water or steam-pipes. In large establishments, as in hospitals, theatres, etc., it has been arranged so that the incoming air is passed through a screen of coarse cloth, which is kept wet by water trickling down each cord. The air is thus kept moist and freed from dust.
The great advantage of the plan of propulsion, is its certainty. ”

“ The air is delivered by fan propulsion at the ceiling, and is taken out at the floor, giving a downward system of ventilation.
" The apparatus is powerful enough to change the air in the chamber every six minutes ; but it can only be worked slowly, owing to the draughts produced, and the air vitiated by respiration is brought back to be re-inhaled."—M. Emil Trélat.
" Whilst the air is in the lungs, it acquires so much heat that it becomes specifically lighter than the surrounding air, and rises above our heads. The heated air which passes upwards should pass away. ”

“ As the skin absorbs no moisture, these boats gain no weight by use, and, having no moisture to give off when out of the water, they do not, like wooden boats, show the effect of exposure to the air by leaking. ”

“ These are made to shut air-tight against their frames, so as to prevent the air from taking a short cut back to the upcast, while preserving free access between the different districts without following the whole round of the air-ways. The ventilation of ends is effected by means of brattices or temporary partitions of thin boards placed midway in the drift, and extending to within a few feet of the face. The air passes along one side of the brattice, courses round the free end, and returns on the other side. ”

“ One, the gullet, has only to swallow solid food or drink, so that its walls can remain soft, and indeed fall together, except when it is actually swallowing. The other tube, the air-pipe or windpipe, has to carry air, which neither will fall of its own weight, nor can readily be gulped down or belched up. It is absolutely necessary that its walls should become stiff enough to keep it open constantly and let the air flow backward and for{136}ward. So we find growing up in the walls of this air pipe, cells which turn themselves into rings of gristle, or cartilage. ”

“ It is, therefore, better that the ventilating openings, both for inlet and departure, should altogether make up much more than a hole half an inch across.
It is not possible to have too much fresh air in a room, provided only an uncomfortable and chilling draught is not allowed to blow upon the body of the inhabitant. You may easily prevent any discomfort or mischief from draught, even where a great abundance of air is admitted, by hanging a curtain to catch it and turn it aside. ”

“ This air space, under pressure, produces a vapor barrier such that heat cannot readily escape when it is emitted from the foot. Thus the wearer of the boot supplies his own warmth, which is retained as long as he is active, regardless of prevailing temperatures. ”

“ A single round hole, a little more than half an inch across, would allow as much air to pass through it, as would be sufficient to supply the breathing of one person, provided the air were driven along by the movements of a fan, or by other mechanical contrivance, with the force of a very gentle breeze. ”

“ In each and all of these catastrophes his life would not have been worth ten seconds' purchase, even with his many spiracles, but for the anastomosing branches of his windpipes, the cross-rungs of his air-ladder, which enabled the air received by the unchoked segments to pass in every direction through the whole system. ”

“ Take a small piece of wet linen and lay it upon your forehead, or upon your arm, leaving it freely exposed to the air, and you will find, that as the moisture evaporates from the linen, your skin underneath will feel colder and colder. The heat of the skin is used up in converting the moisture of the linen into steam, exactly as the heat of a fire is used up in converting the water of a kettle into steam when this is made to boil. ”

“ It must necessarily be always very extravagant, as it will constantly require a great amount of air to insure a thorough circulation through all parts of the room. I wish, therefore, most emphatically, to condemn all systems relying upon openings in the ceiling for the escape of the foul air, while depending upon the circulation of warmed air for obtaining the necessary additional warmth. ”

“ Five minutes later, he was back in the airshaft, wielding his broom energetically. He forged on to the front of the group, heading further and further along in the airshaft, until finally he came to the place he was looking for—the tube that led to the heart of the air supply. ”

“ A modern pneumatic conveying plant of the suction type comprises: (1) An exhauster, or an air pump, of either the reciprocating or the rotary type. (2) A suction nozzle. (3) A discharger, whereby the material is extracted from the pipe line at the desired position, without “breaking” or losing the vacuum. (4) One or more appliances for filtering the air and extracting any foreign material which may have been carried over from the discharger and which would damage the cylinder walls of the exhauster if allowed to enter the plant. ”

“ Breathing is done through a mouthpiece of rubber; the teeth close on the rubber tabs and the rubber flange lies between the teeth and the lips. The expired air finds exit through a rubber flutter valve in an angle tube just outside the mask. This arrangement furnishes a double line of protection; if the face piece is punctured or torn, gas-containing air cannot be breathed as long as the noseclip and mouthpiece are in position. ”