US 3556691 A
Description (OCR text may contain errors)
Jan. 19, 1971 r A. F. BUR! 3,555,691
PUMP HAVING A PISTON WITH A COMBINED ROTARY AND RECIPROCATIITIG ACTION 2 Sheets-Sheet 1 Filed Aug. 4, 1969 FIG I FIG] INVENTOR ALBERT F. BUR I BY ,ardf/ ATTORNEYS Jan. 19, 1971 A. F. BUR! 3,556,691
7 PUMP HAVING A PISTON WITH A COMBINED ROTARY AND RECIPROCATING ACTION Filed Aug. 4, 1969 2 SheetsSh eet z I I 7/ I I l I 6 V l i 3 r %838 H 3 1: 06 v 54 E F164 .LI"T G. 5
F|G.6 j I I 5 INVENTOR ALBERT F. BURI BY "75w! ATTORNEYS United States Patent Oifice 3,556,691 Patented Jan. 19, 1971 3,556,691 PUMP HAVING A PISTON WITH A COMBINED ROTARY AND RECIPROCATING ACTION Albert Friedrich Buri, Eigeuweg 11, Ettingen, Basel-Land, Switzerland Filed Aug. 4, 1969, Ser. No. 847,090
Claims priority, application Switzerland, Aug. 30, 1968, i
13,066/ 68 Int. Cl. F04b 7/ 06' US. Cl. 417-500 6 Claims ABSTRACT OF THE DISCLOSURE This invention relates to a pump having a piston with a combined rotary and reciprocating action.
During the past few years the continuous, largely automated method of manufacture has become characteristic of the chemical processing industry. Such processes call for the accurate control of a very Wide range of throughputs involving media with a great variety of compositions which imposes exacting requirements on the pumping and dosing equipment employed. Dosing pumps in particular have assumed a major significance, and pumps using a piston having a combined reciprocating and rotary action have proved especially suitable.
Existing pumps of the above type are equipped with a rotary and reciprocating piston which is an exact fit in the pump chamber. In order to achieve adequate sealing be tween the inlet and outlet of the pump chamber very tight tolerances are necessary between the pump housing and the piston, such tolerances resulting in a considerable drop in efficiency and in the dosing accuracy. The demands with regard to machining, tolerances and strength limits the choice of materials that can be used. In addition these existing pumps are not very suitable for suspensions or highly corrosive media since irregular operation results which leads to inaccuracies in dosing rates.
In accordance with the present invention, therefore, we provide a pump comprising a housing defining a chamber, an inlet connection to said chamber and an outlet connection therefrom, a piston mounted for reciprocatory movement in said chamber to draw fluid therein through said inlet during an induction stroke of said piston and to expel fluid drawn into said chamber from said outlet during a reciprocal exhaust stroke of said piston, the piston having a duct, one end thereof opening into said chamber and the other end terminating in at least one aperture in the outer surface of said piston, the piston being mounted so that the aperture is aligned with said inlet during said induction stroke and is rotated so that the aperture is aligned with said outlet during the exhaust stroke, said pump further including means for urging the inlet and outlet connections against the outer surface of said piston to provide a fluid tight seal therewith.
A pump in accordance with the invention overcomes the disadvantages mentioned above because the inlet and outlet connections are separate and are urged onto the periphery of the piston to provide a fluid tight seal therewith.
In one form of the invention the inlet and outlet connections are spring-loaded so that the piston no longer has to be a close fit in the pump housing, thus overcoming the problems associated with sealing and the provision of close tolerances. Temperature fluctuations resulting in changes in the dimensions of the housing, piston and inlet and outlet connections are compensated for by the spring loading. The most suitable materials for the pump are glass and the branded product Teflon.
In order that the invention may be fully understood a preferred embodiment thereof will now be described with reference to the accompanying drawings, in which:
FIG. 1 is a cross section of a pump in accordance with the present invention,
FIGS. 2 to 6 show cross sections of a simplified pump at various stages in the operation thereof, and
FIG. 7 shows a cross section of the simplified pump along the line VII-VII in FIG. 4.
The pump shown in FIG. 1 comprises the following main components: a double-walled pump housing 1 having two connections 10 and 11 for circulating heating or cooling media through the housing; a pump cylinder 2; a hollow piston 3 having one end opening into the pump chamber formed by the housing 1 and the other end closed by an insert 12, the piston 3 having a perforated zone 4 including one or more apertures which are accurately defined both with regard to position and dimensions relative to the ends of the piston; a suction input connection 5 and diametrically opposite thereto a pressure output connection 6, the ends of the input and output connections within the chamber are shaped to fit closely to the periphery of the piston 3. The inlet and outlet connections are urged against the piston by compression springs 7 and 8. Other elements such as the sealing and connecting parts are of standard design found in pumps and are therefore not dealt with in detail.
The most suitable material for the housing 1, the cylinder 2 and the piston 3 is instrument glass and for the two connections 5 and 6 Teflon (registered trademark).
The simplified diagrams FIGS. 2 to 7 are used to facilitate understanding of the operation of the pump shown in FIG. 1, the legend for these diagrams being as before i.e., the pump housing 1, piston 3 with perforated zone 4, the suction input connection 5 and the pressure output connection 6. The hollow piston 3 is actuated by a drive mechanism (not shown) so that it is given a rotary movement represented by the arrow r and a reciprocating motion represented by the arrow h. The perforated zone 4 is located so that at the beginning of the suction stroke it faces the suction connection 5 while the pressure connection 6 is urged against the solid wall of the piston 3 closing the output connection (FIG. 2). Axial movement of the piston 3 in the direction of the arrow +h in FIG. 2-
causes liquid or a suspension to be drawn into the interior of the piston 3 and the pump chamber in the direction of the arrow S. The liquid thus enters the pump chamber via the suction connection 5 and the perforations in the piston 4. At the same time or on completion of the axial stroke -|h the piston 3 is rotated in the direction of the arrow r (FIG. 3). As a result the perforated zone 4 is rotated so that during the return stroke of the piston h liquid or suspension in the pump housing and piston is expelled via the perforated zone 4 into the pressure connection 6 in the direction of the arrow D (FIG. 4). During this stage the suction connection 5 is closed by the solid wall of the piston exactly in the same manner as the pressure connection 6 was closed during the inlet stroke (FIGS. 2, 3). On completion or during the return stroke the piston 3 is again rotated in the direction r so that the perforated zone 4 is in a position to draw in liquid or suspension from the suction connection 5, (FIG. 5), as soon as the perforated zone is moved opposite the suction connection upon the piston being moved in the direction +h. The above cycle of operations is repeated (FIG. 6).
For preference the drive should provide infinitely variable reciprocating and rotary motions which would enable, for instance, the stroke to be ,speeded up and shortened or slowed down and lengthened according to requirements.
In the case of the pump as illustrated the piston is not an exact fit in the pump housing. Instead the seal on the inlet and outlet sides is provided by the input and output connections that are spring-loaded onto the outer surface of the piston. Accordingly the dosing accuracy is not affected by tolerance problems nor by the influence of temperature fluctuations on materials so that virtually all the materials such as metal, glass, plastics or ceramics can be used for the construction of these pumps. This advantage combined with the elimination of valves makes it possible for such pumps to handle most of the liquids or suspensions encountered in practice.
Another advantage of these pumps is associated with their dosing capacity: this remains constant and very accurate over a remarkably wide range. An experimental design of pump made of glass and Teflon (registered trademark) achieved dosing accuracies of 0.2 to 2% at a pumping rate of 0.04 to 5.3 litres per hour. Both from the point of view of throughput and dosing accuracy these values exceed those attainable with many of the existing forms of pump by considerable margins.
'1. A pump comprising a housing defining a chamber, an inlet connection to said chamber and an outlet connection therefrom, a piston mounted for reciprocatory movement in said chamber to draw fluid therein through said inlet during an induction stroke of said piston and to expel fluid drawn into said chamber from said outlet during a reciprocal exhaust stroke of said piston, the piston having a duct, one end thereof opening into said chamher and the other end terminating in at least one aperture in the outer surface of said piston, the piston being mounted so that the aperture is aligned with said inlet during said induction stroke and is rotated so that the aperture is aligned with said outlet during the exhaust stroke, said pump further including means for urging the inlet and outlet connections against the outer surface of said piston to provide a fluid tight seal therewith.
2. A pump according to claim 1, in which said piston is hollow and includes a plurality of apertures in the outer 4 surface thereof which communicate with the hollow interior to form said duct.
3. A pump according to claim 2, including a cylinder within which said piston is mounted for reciprocal and rotary motion, said cylinder being secured to said housing and extending into said chamber.
4. A pump according to claim 3, in which at least a portion of said piston extends from that part of the cylinder within said chamber at both extremities of the exhaust and induction stroke and said inlet and outlet connectionsare mounted so as to bear against the outer surface of said portion of said piston to provide a fluid tight seal therewith.
5. A pump according to claim 1, in which said housing includes a jacket surrounding said chamber and an inlet and outlet to said jacket for the admission and extraction of cooling fluid.
6. A pump comprising a housing defining a chamber therein, a cylinder secured to said housing and extending into said chamber, a hollow piston mounted in said cylinder for reciprocatory and rotary motion, said piston having one end opening into said chamber and a plurality of apertures in the outer surface of the piston communicating with the hollow interior thereof, inlet and outlet connections each mounted to said housing and communicating with said chamber, said inlet and outlet connections each having an insert mounted therein and springloaded to urge said inserts onto the outer surface of said piston to provide a fluid tight seal therewith, said piston being so mounted that during a reciprocal induction stroke the apertures in the piston align with said inlet connection and during an exhaust stroke and rotation of said piston the apertures align with said outlet connection.
References Cited UNITED STATES PATENTS 3,136,255 6/1964 Plato 103l57 FOREIGN PATENTS 1,335,784 7/1963 France l03l57 HENRY F. RADUAZO, Primary Examiner