US3263911A - Rotary piston blower with mechanical and pneumatic compression - Google Patents

Description

c. HUBRICH Aug. 2, 1966 ROTARY PISTON BLOWER WITH MECHANICAL AND PNEUMATIC COMPRESSION Filed Nov. 1, 1965 5 Sheets-Sheet 1 INVENTOR. Christoph Hubrich C. HUBRICH Aug. 2, 1966 ROTARY PISTON BLOWER WITH MECHANICAL AND PNEUMATIC COMPRESSION Filed Nov. 1, 1963 3 Sheets-Sheet 2 Fig. 2

INVENTOR. Christoph Hub/id;

C. HUBRICH Aug. 2, 1966 ROTARY PISTON BLOWER WITH MECHANICAL AND PNEUMATIC COMPRESSION Filed NOV.

5 Sheets-Sheet 5 INVENTOR. Chrisfaph l-lu brl'ch United States Patent "ice 3,263,911 ROTARY PISTON BLOWER WITH MECHANICAL AND PNEUMATIC COMPRESSION Christoph Hubrich, Offenbach (Main)-Bieber, Germany, assignor to Polysius G.m.b.H., Neubeckum, Germany Filed Nov. 1, 1963, Ser. No. 320,895 3 Claims. (Cl. 230-138) The present invention relates to a rotary piston blower with interengaging rotary pistons. Blowers of this type have in addition to various advantages one foremost disadvantage, as will presently appear. When the rotary piston during its rotation passes beyond the edge of the outlet so that the conveying chamber containing air at the initial pressure communicates with the pressure chamber, compressed air rushes from the outlet into the conveying chamber and while losing a part of its pressure increases the pressure of the air in said chamber. As a result thereof the degree of efliciency considerably decreases relative to the ideal adiabatic stroke piston degree of efficiency. This drop in efficiency increases with increasing pressure ratio between the air pressure at said outlet and the air pressure in said chamber so that at a certain pressure ratio (in practice about 1.8) the upper limit of economy has been reached. In the past, attempts have been made by various designs, such as the Ljungstrom or Zoller-Wittich blowers, or by the selection of non-symmetric or uneven rotary piston shapes to overcome the above-mentioned drawback of rotary piston blowers. These endeavors have led more and more away from the simple lemniscate shape of the original Roots rotary piston. The thus created rotary piston designs are considerably more diflicult to machine and greatly complicate the heretofore simple structure.

It is, therefore, an object of the present invention to provide a method of improving the efficiency of rotary piston blowers.

It is also an object of this invention to provide a rotary piston blower with inner compression in the fluid conveying chamber while retaining the original lemniscate shape of the original Roots rotary piston.

These and other objects and advantages of the invention will appear more clearly from the following specification in connection with the accompanying drawings, in which FIGS. l to 3 diagrammatically show a rotary piston blower according to the present invention in three consecutive stages of operation.

The method according to the present invention is characterized primarily in that the fluid which with each cycle of the blower is conveyed from an inlet to an outlet has its pressure increased prior to the said fluid reaching said outlet. This method may be carried out by a rotary piston blower in which a plurality of rotatable main pistons cooperate with the housing means of the blower so as to confine delivery chamber means and to convey therein fluid from the inlet to the outlet of the housing, while rotatable auxiliary piston means are provided which are adapted in cooperation with the main pistons to compress fluid in said delivery chamber means prior to said main pistons releasing fluid from the delivery chamber means to said outlet. The said main pistons may have any lemniscate profile while the auxiliary piston means may have the same profile as the main pistons up to their outer radius where their contour rnenges into a circular contour. However, two diagrammatically oppositely located edges of said auxiliary piston means have been rounded off.

Referring now to the drawing in detail and FIG. 1 thereof in particular, the arrangement shown therein comprises a housing 1 having rotatably mounted therein a rotary piston 2 and a rotary piston 3. Pistons 2 and 3 may henceforth be called main rotary pistons. These two main rotary pistons 2 and 3 are so contoured that'at all 3 ,Z63,9l l Patented August 2, 1966 times they sealingly engage each other so as to prevent, in cooperation with other sealing elements to be described further below, the direct flow of fluid within the housing from an inlet 6 to an outlet 7. Each of the pistons 2 and 3 is, furthermore, so contoured as to engage the surface In and 1b respectively of the housing 1 in such a way that at all times one surface portion of the main pistons 2 and 3 sealingly engages the respective housing surfaces 1a, 1b.

The main rotary pistons 2 and 3 are drivin-gly interconnected in any convenient manner, for instance by gears 2a, 2b (indicated by dot-dash lines only).

Cooperating with the main pistons 2 and 3 are two rotatable auxiliary pistons 4 and 5 respectively, which are drivingly connected, for instance by gears, to the main pistons 2 and 3, respectively. The driving connection may be such that the auxiliary pistons 4 and 5 rotate at the same speed as the main pistons 2 and 3.

As to the contour of the auxiliary pistons 4 and 5, it will be seen from the drawing that each tooth 4a, 4b; 5a, 5b has a sharp- edged portion 10, 11; 12, 13 and a rounded portion 10a, 11a; 12a, 13a. The sharp- edged portions 10, 11; 12, 13 serve so-to-speak as scoops, for a purpose which will appear more clearly as the description proceeds. Moreover, the countour sections 22, 21 between portions 10, 10a and 11, 11a of auxiliary piston 4 and, similarly, the contour sections between the portions 12 and 12a, 16 and 13a of auxiliary piston 5 are such that at least a portion thereof will, during each rotation of the respective auxiliary pistons, sealingly engage the respective adjacent housing surfaces lc, 1d. The contour sections 19 between the portions 10a and 11 and also the contour sections 20 between 10 and 10a are such as, during each rotation of auxiliary piston 4, to temporarily sealingly engage the main piston 2 (see, for instance FIGS. 1 and 2). The corresponding portions of auxiliary piston 5 are, of course, similarly designed for temporary sealing engagement with the main piston 3. Sections 19 and 20 of piston 4 which engage piston 2 have a contour shaped in conformity with corresponding sections 18, 1811 on piston 2, the respective length of these sections being indicated by dash lines.

As will be evident from the above, the various pistons form with the housing a plurality of chambers 8, 9, 14, 15 and 1 6 which, during the operation of the blower, vary in shape and location. In addition thereto, the various pistons confine with each other and housing portions a chamber 17 which always communicates with the outlet 7 but which also varies in shape during the operation of the blower. Pistons 2 and 3 rotate about axes 27 and 28 respectively, while pistons 4 and 5 rotate about axes 25 and 26 respectively, the spacing between axes 25, 27; 27, 28; and 28, 26 being the same.

Operation Referring first to the state of operation of the blower as illustrated in FIG. 1, the chamber 8 has just been completely closed off from inlet 6. At this stage, chamber 8 containing air of the same pressure condition as it prevails at the inlet 6, becomes a delivery or conveying chamber since, as will be seen from FIG. 3, it will eventually deliver the air enclosed in chamber 8 into the pressure chamber 17 and to the outlet 7.

In FIG. 1 position, piston 4 has completely closed chamber 16 with regard to chamber 17. No work will be performed for the transport of the air in chamber 16 from FIG. 1 position to FIG. 3 position inasmuch as no compression of the air in chamber 16 takes place.

The air in chamber 14 was previously compressed in a manner which is not illustrated in FIGS. 1 to 3 for pistons 2 and 4 but is shown therein for pistons 3 and 5. Since the operation of pistons 2 and 4 is identical to that of pistons 3 and with the exception that pistons 3 and 5 reach the positions of pistons 2 and 4 at a different time, the compression in chamber 14 may be explained in connection with the operation of pistons 3 and 5 in FIGS. 1 to 3. When piston 4 moves in the direction of the arrow indicated thereon, chamber 16 will communicate with the pressure chamber 17 in a manner similar to that in which chamber 15 in FIGS. 1 and 2 communicates with chamber 17 through chamber 9. Thereupon, chamber 14 will be closed off from pressure chamber 17 in a manner analogous to chamber 15 being closed ofi from chamber 17 in FIG. 3, and the air therein is compressed to a pressure higher than that prevailing in chamber 17.

When the pistons 2 and 4 move into their FIG. 1 positions, the main piston 2 opens up a communication between the chambers 8 and 14. As a result thereof, the air in chamber 14 of higher pressure than in chamber 17 brings about a pneumatic compression of the air in the delivery chamber 8. Since auxiliary piston 4 continues its rotative movement indicated by the arrow thereon, it so-to-speak moves into chamber 8, and since piston 4 still sealingly engages piston 2 and a section of the housing surface 10, piston 2 mechanically compresses the air in chamber 8. The air in chamber 8 is compressed to a pressure which preferably equals or exceeds the pressure in pressure chamber 17.

When pistons 2 and 4 have reached their FIG. 3 position, they have opened a passage therebetween through which the chamber 8 communicates with the pressure chamber 17. In the course of the further rotary movement of piston 2, as indicated by the arrow thereon, and the rotary movement of piston 4 in the direction of the arrow on the latter, communication is established between the chambers 8 and 16, and both pistons now displace air from chambers 8 and 1 6 into pressure chamber 17.

In the course of a rotation of 360 of each piston, the phase of operation of FIGS. 1 to 3 will be repeated four times, in the same sequence.

It will be appreciated that the scoop shape of the sharp-edged portions of piston 4 aids in displacing and entrapping of air from and in the chambers partially formed by piston 4.

While the above description referred only to pistons 2 and 4 of the blower according to the invention, it will be appreciated that the operation of the pistons 3 and 5 is precisely the same as that of pistons 2 and 4.

As will be evident from the above description, by increasing and decreasing the size of the auxiliary pistons 4 and 5 as well as by a super-compression in the chamber 1 4, as described above in connection with FIG. 4, i.e. by an earlier sealing engagement between the pistons 2 and 4, any desired end compression will be obtainable in the delivery chamber 8. Whereas with heretofore known blowers, the isochoric degree of efliciency of the blower will, in comparison to the ideal adiabatic degree of efliciency, drop already at a pressure ratio of 1.7 by 20% and at a pressure ratio of 2.5 by 30%, the present invention obviates this loss to at least a great extent.

While in the preceding description, reference is made to a sealing engagement between the pistons, it is to be understood that, as is well known in connection with rotary piston blowers, an actual contact between the rotors must not take place. Instead, at each socalled position of'sealing engagement, the pistons are spaced from each other by a fraction of a millimeter. This spacing, however, which may be termed play, has been disregarded in the preceding description of the operation.

It is, of course, to be understood that the present invention, is by no means limited to the particular design as described above, but also comprises any modifications within the scope of the appended claims.

What I claim is:

1. In a rotary blower: housing means having fluid inlet means and fluid outlet means, two main piston means rotatable within said housing means, and two auxiliary piston means rotatable withinsaid housing means in axially spaced relationship to said main piston means and at the same speed as the latter for respective cooperation with said main piston means, said main piston means being rotatable in opposite direction with regard to each other, and each auxiliary piston means being rotatable in a direction opposite to the direction of rotation of the respective main piston means cooperating therewith, each of said rotatable main piston means being adapted with a respective first section of said housing means to form main chamber means adapted to receive and entrap fluid from said inlet means, each of said auxiliary piston means being operable in response to a first position thereof relative to the respective main piston means cooperating therewith to form with said main piston means and with a respective adjacent second sectionof said housing means first auxiliary chamber means adapted to receive fluid from said outlet means, each of said auxiliary piston means also being operable with a respective adjacent third section of said housing means to form second auxiliary chamber means adapted to receive and entrap fluid from said out-' let means, each of said auxiliary piston means being operable in response to a second relative position thereof with regard to the respective main piston means cooperating therewith to release fluid from the respective first auxiliary chamber means to the respective main chamber means pertaining thereto to thereby efiect a pneumatic compression of said fluid in said main chamber means and then to enter said main chamber means for mechanically increasing the fluid pressure therein, each of said main and auxiliary piston means having rounded end portions for substantially sliding engagement with respective adjacent sec tions of said housing means, and each of said main and auxiliary piston meanshaving flank sections interconnecting said rounded end portions and being arranged on opposite sides of the axes of rotation thereof, the flank sections of said auxiliary piston means partially corresponding as to their contour to portions of the flank sections of said main piston means and being operable alternately to substantially rollingly engage the rounded end portions of the respective main piston means cooperating therewith, and the flank sections of each of said main piston means being operable alternately to substantially rollingly engage the rounded end portions of the other main piston means.

2. A rotary blower according to claim 1, in which that end of each rounded end portion of each auxiliary piston means which is located in front with regard to the direction of rotation of said auxiliary piston means forms a relatively sharp edge with the adjacent portion of the flank sections of said auxiliary piston means.

3. A rotary blower according to claim 1, in which the distance of the axis of rotation of each auxiliary piston means from the axis of rotation of the respective main piston means cooperating therewith equals the distance between the axes of rotation of said two main piston means.

References Cited by the Examiner UNITED STATES PATENTS 1,746,885 2/1930 Bunge et al. 230141 2,437,658 3/1948 Williams 230-141 2,691,482 10/1954 Ungar 230-141 3,058,652 10/1962 Glamann 230l41 FOREIGN PATENTS 94,751 11/1897 Germany. 958,143 5/ 1964 Great Britain.

MARK NEWMAN, Primary Examiner.

WILBUR J. GOODLIN, Examiner.

Claims (1)

1. IN A ROTARY BLOWER: HOUSING MEANS HAVING FLUID INLET MEANS AND FLUID OUTLET MEANS, TWO MAIN PISTON MEANS ROTATABLE WITHIN SAID HOUSING MEANS, AND TWO AUXILIARY PISTON MEANS ROTATABLE WITHIN SAID HOUSING MEANS IN AXIALLY SPACED RELATIONSHIP TO SAID MAIN PISTON MEANS AND AT THE SAME SPEED AS THE LATTER FOR RESPECTIVE COOPERATION WITH SAID MAIN PISTON MEANS, SAID MAIN PISTON MEANS BEING ROTATABLE IN OPPOSITE DIRECTION WITH REGARD TO EACH OTHER, AND EACH AUXILIARY PISTON MEANS BEING ROTATABLE IN A DIRECTION OPPOSITE TO THE DIRECTION OF ROTATION OF THE RESPECTIVE MAIN PISTON MEANS COOPERATING THEREWITH, EACH OF SAID ROTATABLE MAIN PISTON MEANS BEING ADAPTED WITH A RESPECTIVE FIRST SECTION OF SAID HOUSING MEANS TO FORM MAIN CHAMBER MEANS ADAPTED TO RECEIVE AND ENTRAP FLUID FROM SAID INLET MEANS, EACH OF SAID AUXILIARY PISTON MEANS BEING OPERABLE IN RESPONSE TO A FIRST POSITION THEREOF RELATIVE TO THE RESPECTIVE MAIN PISTON MEANS COOPERATING THEREWITH TO FORM WITH SAID MAIN PISTON MEANS AND WITH A RESPECTIVE ADJACENT SECOND SECTION OF SAID HOUSING MEANS FOR AUXILIARY CHAMBER MEANS ADAPTED TO RECEIVE FLUID FROM SAID OUTLET MEANS, EACH OF AUXILIARY PISTON MEANS ALSO BEING OPERABLE WITH A RESPECTIVE ADJACENT THIRD SECTION OF SAID HOUSING MEANS TO FORM SECOND AUXILIARY CHAMBER MEANS ADAPTED TO RECEIVE AND ENTRAP FLUID FROM SAID OUTLET MEANS, EACH OF SAID AUXILIARY PISTON MEANS BEING OPERABLE IN RESPONSE TO A SECOND RELATIVE POSITION THEREOF WITH REGARD TO THE RESPECTIVE MAIN PISTON MEANS COOPERATIN THEREWITH TO RELEASE FLUID FROM THE RESPECTIVE FIRST AUXILIARY CHAMBER MEANS TO THE RESPECTIVE MAIN CHAMBER MEANS PERTAINING THERETO TO THEREBY EFFECT A PNEUMATIC COMPRESSION OF SAID FLUID IN SAID MAIN CHAMBER MEANS AND THEN TO ENTER SAID MAIN CHAMBER MEANS FOR MECHANICALLY INCREASING THE FLUID PRESSURE THEREIN, EACH OF SAID MAIN AUXILIARY PISTON MEANS HAVING ROUNDED END PORTIONS FOR SUBSTANTIALLY SLIDING ENGAGEMENT WITH RESPECTIVE ADJACENT SECTIONS OF SAID HOUSING MEANS, AND EACH OF SAID MAIN AND AUXILIARY PISTON MEANS HAVING FLANK SECTIONS INTERCONNECTING SAID ROUNDED END PORTIONS AND BEING ARRANGED ON OPPOSITE SIDES OF THE AXES OF ROTATION THEREOF, THE FLANK SECTIONS OF SAID AUXILIARY PISTON MEANS PARTIALLY CORRESPONDING AS TO THEIR CONTOUR TO PORTIONS OF THE FLANK SECTIONS OF SAID MAIN PISTON MEANS AND BEING OPERABLE ALTERNATELY TO SUBSTANTIALLY ROLLINGLY ENGAGE THE ROUNDED END PORTIONS OF THE RESPECTIVE MAIN PISTON MEANS COOPERATING THEREWITH, AND THE FLANK SECTIONS OF EACH OF SAID MAIN PISTON MEANS BEING OPERABLE ALTERNATELY TO SUBSTANTIALLY ROLLINGLY ENGAGE THE ROUNDED END PORTIONS OF THE OTHER MAIN PISTON MEANS.

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