NEW HYDRAULIC TRANSMISSION.
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A Reinine of Recently, Published Patents.
We have dealt from time to time in these columns with that farm of transmission in which a practically incompressible fluid, such as oil or water, serves as the medium through which the engine power is transmitted to the rear axle. The: idea of an hydraulic transmission is extremely fascinating, and has for king been the subject of experiments and of invention, as it affords not only a noiseless method ot transferring torque, but canalso be made to give an infinite Variety of gear ratios ranging from a direct top gear to a free engine. Many of those forms of hydraulic transmission, which we have described here,. have cmbodied EIT1' engine-driven pump, which forces the liquid into the cylinders of an hydraplic motor. lly varying the amount of 61ip which is permitted in one or ether of these components the gear ratio is altered accordingly.
It will be evident that, if 100 per cent. slip is arranged, or, in other words, if the engine-driven pump merely churns up the fluid, then there will be no transmission of power whatever, and this will correspond to the free-engine or neutral position of the ordinary gearbox. On the other hand, if the passages between a pump and motor are so controlled that no slip is possible and pump and motor will rotate en bloc as one unit, then the transmission will be a directi one. It can readily be understood that this degree of slip can be controlled simply by means of a valve, and will afford every possible gradation between the two extremes which we have enumerated. There is no need for a clutch in the transmission.
We are this week concerned with specification No 151,308, describing a new hydraulic transmission, Which, although, as in other cases, depending
• upon the amount of slip allowed to the fluid for the variation in ratio, has, notwithstanding, several points of novelty. Instead of a pump and a motor, we have an outer casing, which is attached, my, to the engine shaft, and an inner. drum with a couple of projecting vanes, which is coupled to the propeller Shaft. The space between outer ease and drum is fluid filled, andthere are rotating drums
Bla
whieb, with the vanes,farm. enclosures for the Raid. If this were all, the rotation of the outer casing would involve rotation of the inner drum at the same or at' a lower speed than that of the cas ing, according to the degree of sslip of
• the liqdid past the 'projeCting vanes.
This, in fact;-"ffeS-Ciilaes the transmission invented by L. K. -Oheewright arta another. It is necessarily a little !no-re complicated than as described on account of the necessity for making arrangements to vary the slip so as to. alter the gear ratio. -Reference to the drawing which we reproduce will shcpie..that the outer casing contains,!besidee the main drum, 1.:wo smaller drums, which are generally in contact with it. Thesesmaller drums have gaps or grooves cut in them, which allow of the passage of the two vanes on the main drum, In order that there may 'be ne possibility of slip between these drums, and to ensure that the gap always presents itself simultaneously with the appearance of a vane on the drum, the three are connected externally to the main casing -by gearwheele. Actually it is the compression of the fluid betweed these two mall drums or between a vane on the main drum and one of them which effects the power transmission. The liquid in this blocked passage may leak out of the main casing through a email passage controlled by a valve. The calVe is operated through link motion controlled by a, centrifugal governer, in such a manner that an increased engine speed tends to close the passage and decrease the gear ratio. Presumably, this weuld take effect when a car was travelling against a gradient Which had the effect of slowing dawn the engine, to open the passage allowing leakage, thuS increasing the percentage of slip and increasingi the gear ratio. When on the: level or at a down gradient the engine speed is increased, the governor weights fly out,' thus closing the peasage and decreasing the ratio until, with. the governor weights in extreme position, the passage would be closed entirely and the ratio would be one to one, or direct.
A separate chamber is provided with a reservoir Of liquid in communication_ will the Main drum, the object being to prevent any vacuum forming behind the revolving rollers which, transmit the drive.
Other Patents ofrinterest.
No. 151,350, by Girling, con
cerns the control mechanism for :friction.' clutches. It is applicable to all the various types of clutch ascommonly employed in motorcars. Between' driving and driven member groove or wedgeshaped aperture is formed, in which are disposed a nuenber of steel balls. These . rest on an inner sliding wedge. For disengagement the wedge is moved axially, so as to increase the pitch diameter of the circle in which the halls lie, thrusting them in between the wedge-like surfaces. of the main members of the .clutch, time separating them. For engagement of the clutch this wedge is withdrawn, but, owing to the particular angle of repose of the various taper surfaces employed, the balls do not immediately follow the sliding wedge, but fall back upon it gradually, thus ensuring a smooth engagement of the clutch, notwithstanding carelessness of operation by the driver.
A. J. Adams, in No. 151,357, describes an impulse starter for a magneto of the type in which, while the engine is re. volved slowly, the armature is held fox a time, the driving gear merely winding up a coil spring. At a given instant the armature as released and revolves quickly, thus effecting a good spark for ignition.. The advantage of the eonetruotlion described is that it is proof against the ingress of dirt and moisture.
J. G. Schulz removes the engine and transmission gear from a commercial vehicle, so that its design can be evolved without any reference to arrangement of the driving meclumistn, and puts them on a small trailer at the rear of the vehicle. Provision is made for facility of connection between the trailer and the vehicle, and the actual driving wheels of Ilse outfit are not on the trailer, but on The vehicle itself. The specification ie numbered 151,376.
G. F. Wells, in No. 151,439, describes a portable gas producer which, he states, may be used either under pressure OT by suction.,
No. 151,454, by J. Beflienod, refers to an electric starter of the type in which the driving pinion is brought axially into contact with the driven wheel. In this design the engagement is effected by the .
displacement of a s rod by the attraction of the poles of the starting motor.
T. Bradford. 113,68 a D-sizapecl holiest, block made of rubber, which hewould interpose between frame and axle to act as a' shock abeerber, in the oase of excessive spring deflection. The specification
is No.' 151,466. . •
No. 151,425 is a specification in which Jahri Feeder and Co. describe their by now well-known arrangement of gear, by which their anti-balance plough is temporarily put into balance for manceuvring at the headlands.