US 2719000 A
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Sept. 27, 1955 J. THEVENAZ 2,719,000
ADJUSTABLE BLADED IMPELLER Filed May 22, 1952 Q Fig.2
M VENTOR N 729E VENA 2 F BY United States Patent Ofiice 2,719,000 iatented Sept. 27, 1955 ADJUSTABLE BLADED IMPELLER Jean Thevenaz, Les Tuileries de Grandson, Switzerland, assignor to Paillard S. A., Sainte-Croix, Switzerland, a corporation of Switzerland Application May 22, 1952, Serial No. 289,308
Claims priority, application Switzerland May 29, 1951 3 Claims. (Cl. 230-114) Some apparatus require considerable ventilation for difierent speeds of rotation of the fan. This is particularly the case in connection with cinematograph projectors provided with a single motor for driving the film and for ventilation and adapted to operate at different speeds, for example when the apparatus is provided for silent films or sound films, of which the speeds are respectively 16 and 24 images per second. Fans of the normal type have serious disadvantages as they must be dimensioned to provide sufiicient ventilation at low speeds and absorb at high speeds, a force which is often inadmissible whilst providing a uselessly exaggerated ventilation.
The present invention has for its subject a fan, particularly for a cinematograph projector, which tends to remedy the above mentioned disadvantage, by the fact that it comprises a device for adjusting the supply of air, said device being so controlled as to ensure nearly the same supply of air at least at two different speeds of rotation of the fan.
One form of construction of the subject of the invention is shown, by way of example, in the accompanying drawings, wherein:
Fig. 1 is a view parallel to the plane of rotation of a fan according to the invention, with parts partly broken away.
Fig. 2 is a section on the line IIII of Fig. 1.
Figure 3 is a perspective view of one fan blade and its associated spring assembled in accordance with the invention.
A plate 1 is secured to a sleeve 2 adapted to be secured to the shaft of a motor for driving the fan. An annular part 3 is secured parallel to the plate 1 by means of screws 4 and distance pieces 5. The blades of the fan are formed by plates 6 having a stamped portion 7 in the form of a semi-cylinder, of which the ends project from the edges of the said plates and form the pivots 8 of the blades. The pivots engage with the holes 9 provided in the part 3 and the plate 1. The plate 1 has arcuate slots 10 in each of which is located a projection 14 of the blades 6, which results in limiting the possible rotation of the said blades. The latter are subjected to the action of springs 11, each formed by a bent rod of which one end is curved and located in a hole 12 of the plate 1, the other end bearing against the blade 6. The rod is held at an intermediate point by a lug 13.
The center of gravity of the blades is located between the arched portion 7 and the end opposite to that against which the spring 11 bears.
When the fan is not driven in rotation, the blades are subjected to the sole action of springs 11, and occupy the position shown in Fig. l, in connection with blade 6a.
When the fan is driven in rotation, centrifugal force acting of the spring 11. When the speed exceeds a predetermined limit, the action of centrifugal force is greater than that of the spring and the blade pivots and takes up the position of the blade 6b, shown in Fig. 1. In this position, which is determined by the length of the slot 10, the blade displaces a smaller quantity of air than in position 6a.
The two extreme positions of the blades 6 are so determined that the delivery of the fan is the same for at least two different speeds of rotation of the fan. By judicious selection of the constancy of the spring and of the eccentricity of the center of gravity relatively to the pivotal axis of the blade, it is possible to obtain a nearly constant delivery of the fan for all speeds of rotation included between two limit speeds.
Such a fan, applied to a cinematograph projector, enables a correct ventilation to be obtained both during projection of silent films at a speed of 16 images per second and of Sound films at a speed of 24 images per second. This fan enables the avoidance either of the addition of an auxiliary motor of constant speed only driving the fan, or the selection of a single motor of high power, extremely heavy and expensive. Further, a uselessly accentuated noise of ventilation is also avoided during the projection of sound films.
1. A radial fan comprising blades mounted in a pivotal manner between a plate and an annular part, a number of springs equal to that of said blades, each spring cooperating with a blade, each of said springs being formed by a bent rod, one end of said rod being bent and located in a hole of said plate, the other end of said rod bearing against an edge of said blade, the center of gravity of said blade being located opposite to said edge with regard to the axis of rotation of said blade, so that the action of centrifugal force acting on said blades is opposed to the action of said springs, thus ensuring a nearly constant delivery of air for different speeds or rotation of said fan.
2. A fan according to claim 1, wherein each of said blades has a stamped part in the form of a semi-cylinder of which the ends project from the edges of the blades and constitute their pivots of rotation.
3. A fan comprising a plate, an annulus, means spacing said annulus above said plate, a plurality of blades interposed between said plate and annulus and pivotally mounted thereon, each of said blades having a depending extension, said plate having a plurality of apertures, each of said plates having its extension positioned in a respective one of said apertures, a plurality of springs, each of said springs being a rod, one portion of said rod being secured to said plate, another portion of said rod engaging a blade at a distance from the pivotal axis of said blade, said pivotal axis being located between the center of gravity of said blade and the point of engagement of said rod with said blade, whereby when the fan is rotating the centrifugal force acting on each of said blades is opposed by a spring so that at different rotative speeds the blades assume diiferent positions.
References Cited in the file of this patent UNITED STATES PATENTS 2,253,406 Wagner Aug. 19, 1941 2,351,516 Jandasek June 13, 1944 FOREIGN PATENTS 280,189 Germany Nov. 7, 1913