페이지 이미지
PDF
ePub

their usefulness. They occupy much room on account of the length of belt required to communicate motion from the crank-shaft to the blower; and the current of air which enters the casing to supply the volume and velocity required must pass the apertures and be deflected by the fans at such high velocities as to produce a humming noise truly distressing to the passengers—particularly to persons of delicate temperament. “It is not deemed necessary, in addition to these objections, to enumerate others; such as the constant difficulty of keeping the belt tight and of retaining it on the pulleys, and the necessity of frequent repairs arising from the breaking of the machinery by the slipping of the belt; the two pointed out above being the most prominent and essential. “To avoid these objections, has been the subject of much reflection amongst engineers and others. The fans have been variously shaped and curved ; wings have been adapted to the apertures in the casing to deflect the entering currents, and thus prevent the humming noise; but all these attempts, whilst they have added greatly to the original cost and repairs, have not proved effectual. “These ends I have attained in the most simple and effective manner by my said improvement, which consist simply in increasing the diameter of the fan-blower, and attaching it to the crank-shaft of the auxiliary engine, so that the required volume and velocity of blast may be acquired by a much less number of revolutions; and the air is admitted and deflected under'velocities which avoid entirely the disagreeable hum and noise of other blowers, at the same time bringing the number of revolutions within the capacity of the crank-shaft of the auxiliary engine, so that the fans can be attached directly to it; thus effecting economy in the room occupied, and in the original cost of construction and repairs, by dispensing with the belt and pulleys heretofore employed in forming the connexion between the crank-shaft and blower, which are so liable to derangement, and which add much to the noise.” One patent has been granted this year for a mode of feeding boilers, in such a manner that the resistance of the steam to the ingress of the water is avoided; and the pressure of the steam is also made to regulate the dampers for increasing and diminishing the draught of the furnace. The devices need not here be described, as they are but slight modifications of those already in use. Two patents have been granted for safety apparatus for steam boilers. The one is for the combination of the alarm whistle with the safety-valve, and the other is for a device to avoid the evils which result from the safety-valve becoming sealed. Further notice of them is unnecessary. One condenser has this year been patented, which operates nearly upon the same principle with others heretofore in use. In this apparatus the steam enters the condenser or hot well, and is condensed by a jet of water; part of the water of condensation is pumped from the well to the boiler, and the rest into a reservoir, from which it passes through a long coil of tube which is surrounded by cold water, directly from the outside of the vessel. By this means the water of condensation becomes cold, and is carried back to the hot well to furnish the jet for condensing the steam, and is then again pumped out into the boiler, or passes again through the refrigerating tubes. Thus it will be perceived that the same water is constantly used for the generation and condensation of steam, and no addition of water is necessary except a small quantity to supply - - * waste. When the water, as in the ocean and some rivers, is such as to injure and produce incrustation in the boiler, it is evident that this mode of economising the water which has been properly prepared for use is of very great importance. Slide valves.—Two patents have been granted this year for improvements in balancing slide valves. When the valve is closed, the steam entering the steam chamber will press it forcibly against the valve-seat, so that great power is required to cause it to slide, and the valve and the valveseat soon become injuriously worn. To balance the valve and avoid these inconveniences has long engaged the attention of engineers, and many devices for that purpose have already been invented. But those patented within the last year sufficiently differ from those previously in use to deserve notice. In one of them, the proper balance is attained by the use of a blind or auxiliary valve, connected with the valve proper, and working against the top of the chest in such a manner as to receive upon its top the pressure of the atmosphere. The device patented is very similar to one already in use. The following claim extracted from the patent will sufficiently set forth the invention: “The described means of neutralizing the effect of the pressure of the steam (or fluid, as the case may be) upon the back of the valves, and equalizing the pressure of the atmosphere on the upper side of the blank valve and on the under side of the valve, thus preventing friction and allowing the valves to move with perfect ease when under a pressure, as set forth, viz.: by attaching or applying the blank valve to the commonly used slide valve, as described, in combination with the false aperture and the aperture to the atmosphere, through the cover and the inverted seat, as described, and all operating as mentioned and set forth.” The other apparatus balances the valve by the manner in which the steam is let on, and will be understood by reference to the following extract from the patent: “In constructing our balanced slide valve, we so arrange the respective parts thereof as to cause the steam to operate equally on opposite sides of the sliding part thereof, allowing the steam to enter into and to escape from the cylinder equally on each side of said valve. In effecting this, we sometimes cause the valve to slide between two stationary check-pieces, in each of which are contained three openings, operating in the ordinary way for the induction and eduction of steam. “Instead of the two stationary check pieces above named, we sometimes employ one stationary valve seat, which is embraced on each of its sides by the slide valve, the stationary valve seat being furnished with three steam openings on each of its sides, so arranged as to produce the same result with that first named, and in a manner substantially the same; the two modes being mere modifications of one principle.” One patent has been granted for improvements in pistons. The patented pistons differ but little from those formerly used, and need not be described. Reciprocating engines.—Three patents have been granted this year for improvements in engines of this variety. One of them is for improvements in the double cylinder or twin cylinder engine, similar to one noticed in my last report, for working steam expansively. The engines, however, differ from each other in important particulars, which will be understood by comparing the following extract with the description given, in my last report, of the engine patented in 1845.

The inventor says he has “invented and made certain new and useful improvements in the mechanical arrangement, construction, application, and combination of the parts of steam engines that are intended to work by the action of steam, admitted into one cylinder at a given pressure, and in the progress of the stroke or half revolution the communication with the boiler is cut off, and the steam is allowed to pass into a second cylinder and work expansively, which has been done before by others, but not in the manner invented by me, the first difference between my hereinafter described invention, and nearly all that have preceded it, being that I use two parallel and equal-sized cylinders set alongside of each other. The second difference is, that with these two cylinders I use only one induction steam pipe from the boiler, and one eduction pipe from both the cylinders to the atmosphere, or a condenser. The third difference is that the steam is admitted, by a proper induction valve, to about the half-length of the first cylinder; the induction valve is then closed, and an expansion valve simultaneously opened from the first to the second cylinder. Thus the operation of the steam commencing at the same end of both cylinders forms the fourth difference between my plans and those of others, and the expansion valve is sustained open, so that the steam shall act expansively during the remainder travel of the first piston, and shall also propel the pistons both in the same direction, during a large portion of the travel or stroke of each, without reacting from one piston upon the other, which constitutes a fifth difference between this invention and others which have preceded it. The exhaust valves operate to exhaust both cylinders to the air, or to a condenser, at the same time, from the same end of each cylinder to the same said pipe, and this constitutes a sixth difference between this and other plañs preceding it, a large portion of these ends being attained by placing the piston rods in connexion with two cranks on one main or driving shaft; which two cranks are to be placed either at right-angles, or at some acute or lessening angle, less than ninety degrees apart, which is believed to be the seventh clear and distinct difference between these arrangements and any that have preceded them. It is well known that double engines have been made to act with either equal or unequal cylinders, upon cranks set at opposite points in the same line, with valves and openings that pass the steam from the top of the first piston to the bottom of the second, and vice versa; and three-fold engines, having cranks more than ninety degrees apart, have been used ; and marine engines with cranks set at ninety degrees apart, each operated by a separate and unconnected cylinder, are in common use; yet. no one of these operates in the manner herein proposed ; the nearest approach to which has been made with two cylinders and pistons operating on a pair of right-angled cranks, the valves set to admit the steam from the boiler only when the first crank had passed upwards or downwards to an angle of forty-five degrees, and at one hundred and thirty-five degrees passing the steam expansively from the first to the second cylinder, to the end of the stroke of the first piston, and thus making the second piston carry the first crank past the dead centres, each piston travelling without steam operating on it during the first quarter of each stroke. All these and many other modifications of steam engines, for the same end, are variant from my invention and improvements, by not acting in so direct concert to produce an expansive, direct, and continuous action of the steam in the same direction, or both pistons through the relative positions of the cylinders and cranks, and the arrangement and combination of the acting parts.”

Another double cylinder engine has been patented which works upon a different principle. The engine is of a very simple variety; but in some particulars, and for some purposes, it seems to possess advantages, and I will therefore present its peculiarities in the following extract from the patent: “In the steam engine as now constructed, the piston must be accurately fitted to the cylinder, and packed; the cylinder is then provided with a head or cover accurately fitted and bolted, and provided with a stuffing box around the piston rod; and then the end of the piston rod, where it receives the connecting rod, is either provided with a sliding head working on ways, or with a parallel motion, which are not only very expensive, but either of these methods occupy much room; for there must be, between the upper end of the cylinder and the beam or other connexion, room sufficient for the length of piston and connecting rods, which, in many instances, is a source of great inconvenience, as, for instance, in steamboats. “Many of these objections I avoid, and render the engine cheaper and less liable to derangement by making the piston a long hollow cylinder, the outer diameter of which fits either accurately or loosely the inside of the steam cylinder, the upper end of which is provided with a stuffing box which surrounds the hollow cylindrical piston : that is, therefore, made of greater length than the steam cylinder within which it works, thus avoiding the necessity of a packed piston. The inner end of this piston cylinder is closed to form the piston head, and to the inner surface of it is attached the connecting rod, which extends to the crank. By this. arrangement, the unequal wear of the piston and cylinder by the vibrations of the connecting rod is avoided. “The steam, of course, in this arrangement can act only in one direction, and therefore will be only single acting; but when it is desired to make a double-acting engine, then two such single acting engines are so arranged as to be connected together by a crank shaft, having two cranks on opposite sides of the axis, so that the moment one ceases to act the other commences, the valves alternately opening and closing the induction and eduction valves.” “It will be obvious that this engine may be single-acting by having but one cylinder and its appendages; double-acting, as above described; threesold acting, by having three cylinders with the cranks, making an angle of 120° with each other, so as to divide the circle into three equal parts, the three sold acting being the best for working the steam expansively by means of cut-off valves, as the steam will at all times be acting with its full force in one, and expansively in another. “By constructing an engine on this plan, but one packing will be required for each cylinder, and that a stuffing box which admits of adjustment much more readily than a piston which can only be repacked by taking the engine apart. . It dispenses with the necessity of a sliding 'head or parallel motion, the cylindrical piston performing that office by having the connecting rod jointed to it within and at the bottom, at the same time saving the room occupied by the piston rod in the common engine; and what is of great importance, the piston can always be kept oiled by simply oiling the stuffing box, which is not the case in engines as heretofore made.” Letters patent have this year been granted for a reciprocating engine, which receives and rejects the steam through the piston rod and piston. The piston rod is a cylindrical tube opening into the interior of the pis

ton; the openings in the piston have two valves in them, with stems extending from them through the upper and lower faces of the piston; as the piston reaches either extremity of the cylinder, the stems strike the ends of the cylinder, and operate the valves in a manner which can be easily understood, so as to admit and discharge the steam at each end of the stroke. - Letters patent have been granted for improvements upon a gas engine which was patented several years ago, and consist principally in devices for retaining and equalizing the temperature of the parts. . There are several points of claim ; but the invention does not possess that striking originality which requires particular description in this place. Rotary engines.—Four patents have this year been granted for improvements in rotary engines. In one of them the mode of operating and timing the valves in such a manner as to be opened in equilibrio is a principal object. In another the valves are made to receive the pressure of the steam upon their faces, and resist it, by resting against a pivot so located that the valve has a slight tendency to rest against the edge of the interior revolving disk which operates them, and against which they press with sufficient force only to prevent the escape of the steam. In another the parts are so arranged that the steam operates by successive impingements and reactions throughout the circumference of the engine. It appears to me unnecessary to extract from either of the patents for rotary engines, or to give the subject of steam engines a more extended

notice.

LUMBER, AND MACsIINERY FOR OPERA riNG THEREIN.

Improvements in this class of machinery have not been numerous. It will be readily understood that machinery for working lumber is mostly of an elementary character, and that for a long series of years a great portion of the inventive talent of this country has been exercised upon it, and has carried it to a high degree of perfection. It is not remarkable, therefore, that but few new inventions should be made in proportion to those which are reinventions, and that as a consequence more applications should be more frequently rejected each succeeding year. Very little has been developed this year in the higher varieties of this branch of machinery; indeed, there is already excellent machinery in use for performing almost every conceivable operation upon lumber of which it is susceptible.

Saw-mills.--About five patents have been granted this year for improvements in saw-mills, some of which I deem it proper to notice.

In ordinary saw-mills the saw usually does not entirely separate the board from the log, but saws it nearly off, and the carriage is then moved back, and the log set for another cut. Sawed in this way, the boards at one end are of course imperfect, and much time is lost in running back the carriage for each successive cut. To remedy these inconveniences and defects, an improved combination of parts has been made and patented within the year—a gang of saws sufficient in number to saw the whole log in boards. The log is placed upon a carriage and moved up towards the saw, much in the usual way. After the sawing has progressed considerably, the log is seized by another apparatus on the back side of the saws, and carried entirely throńgh, while the first carriage returns to receive another log, and present it to the saw as soon as it has finished saw

« 이전계속 »