Pump Apparatus

Abstract

Pump apparatus embodying a flexible conduit which is collapsed to effect a pumping action. In one embodiment the flexible pumping conduit forms a priming mechanism for a centrifugal pump and the actuating member for collapsing the conduit is connected to the pump shaft by a drive coupling which prevents operation of the mechanism when the pump is primed. In another embodiment the actuating member is connected to a shaft by a spiral spring which permits the member to shift radially with respect to the shaft.

Description

BACKGROUND OF THE INVENTION

This invention relates generally to the pump art, and more specifically to pumping apparatus embodying a flexible conduit which is collapsed to effect a pumping action. The invention is particularly concerned with new and improved centrifugal pumping apparatus which utilizes a flexible conduit-type pump as priming mechanism.

A typical self-priming centrifugal pump is comprised of a relatively large casing or hopper which has several internal chambers and communicating flow passages. Such a casing is constructed to define a suction chamber connected to a suction inlet pipe, a pressure or discharge chamber connected to an outlet pipe, and an impeller chamber or volute between the suction and discharge chambers. A rotatable impeller is disposed within the volute and is operable to establish a suction flow of liquid into the suction chamber and to force the liquid out of the pump through the discharge chamber at a desired pumping pressure. The operation of the pump requires a reservoir of water in the casing in adequate supply to permit priming and to maintain the prime when the suction flow of liquid into the pump has been established.

Because of its complex construction and the necessity of maintaining an internal supply of liquid, the casing of a self-priming centrifugal pump as described above is large, heavy and expensive to make. The complex internal shape of the casing also is the cause of inefficiencies in the operation of the pump. Since the impeller is the only part of a centrifugal pump that does any work, the other portions of the pump through which the liquid flows, including the casing chambers and the internal ports and passageways, restrict the potential output and cause losses in flow rate and pumping pressure. Another disadvantage of conventional self-priming centrifugal pumps is that they are susceptible to damage resulting from cavitation and from shock loads caused by pressure surges in the connected pipes.

Straight centrifugal pumps do not maintain a residual supply of liquid in the casing and therefore the casing construction is simpler, less expensive and more efficient than that of a self-priming pump. Although advantageous from the standpoint of casing design, conventional straight centrifugal pumps present problems in connection with priming. Such pumps are primed by auxiliary devices which in the past have included exhaust primers utilizing an eductor principle, piston-type hand primers, and vane-type pumps. These devices are expensive and many are relatively inefficient for priming purposes. Another disadvantage is that the priming devices of the prior art are operated independently of the associated pump and require a means of control, such as complex electrical systems, which will permit the devices to be shut off after the pump has been primed.

SUMMARY OF THE INVENTION

The present invention overcomes the limitations and disadvantages of conventional centrifugal pumping apparatus by providing a new and improved construction which is characterized by an efficient priming mechanism. The efficiency and other advantages of the priming mechanism are such that the pump casing can be constructed with the simplicity of design characterizing straight centrifugal pump casings. The pumping apparatus of the present invention is therefore capable of operating at greater flow rates with less loss in head and is less expensive to build than conventional self-priming centrifugal pumps. At the same time, the new pumping apparatus of this invention will prime faster than prior apparatus and has the characteristic of being self-priming in that separate operation and control of an auxiliary priming device, as is conventional with straight centrifugal pumps, is not required.

In accordance with a preferred embodiment of the present invention, a flexible pumping conduit has an inlet connected to the suction area of the pump volute in which an impeller is rotatably mounted. A cam is driven by the same shaft which rotates the pump impeller and is adapted to collapse the tube in such a manner as to create a pumping action. The flexible conduit and the actuating cam are preferably mounted near the pump motor and are protected by being placed between the motor and the impeller on the impeller shaft. As the shaft is rotated, air from the suction or intake side of the pump is sucked into the eye of the impeller and is forced through the conduit to discharge, thereby effecting the desired priming operation in an efficient manner.

A featured aspect of the preferred embodiment of the invention resides in the manner of operatively connecting the cam to the impeller or motor shaft. The cam is connected to the shaft so that rotation of the cam will automatically cease when the pump has been fully primed and is operating at its rated capacity. This preferred arrangement avoids the disadvantages of separately controlled auxiliary priming devices associated with conventional straight centrifugal pumps.

Another feature of this invention resides in the connection of the outlet of the flexible conduit to the discharge side of the pump and the provision of a one-way check valve between the outlet connection of the conduit and the pump impeller. The check valve prevents air from the discharge side of the pump from being pulled into the suction side while the pump is operated. Another advantage of this preferred arrangement, including the provision of the check valve in the discharge line of the pump, is that surge pressures are absorbed in the discharge pipe rather than in the pump casing itself, thereby preventing the casing from being damaged.

An important advantage of the present invention is that it simplifies the problems involved in designing and constructing centrifugal pumps to suit a user's specific requirements. The ability of conventional self-priming pumps to prime efficiently depends upon several factors including the size of the impeller, its rotative speed, and the geometry of the casing in respect to the cutwaters. A change in the impeller size and speed or the casing geometry to adapt the pumping unit to specific pumping needs could result in a complete loss or decrease in efficiency of the priming ability of the pump. As a consequence, a manufacturer of conventional self-priming pumps has been required in connection with pumps of each size to manufacture and stock many constructions having different shapes, impeller sizes and priming operations. The present invention makes it possible to furnish a pump having a standardized construction which can be readily modified by changing its rotative speed, diameter of impeller, etc., to suit specific pumping requirements without regard to the effect of such changes upon the priming ability of the pump.

As will be apparent from the following disclosure, the collapsible chamber, flexible conduit-type pump comprising one aspect of the invention is adapted for independent use as a pumping apparatus capable of handling fluids and semifluids, including liquids, gases, powders, liquids which contain solids, and the like. The efficiency and operating characteristics of the mechanism are enhanced by a preferred construction in which the cam is mounted in a novel manner for radial movement on its actuating shaft. This arrangement avoids pulsating, uneven flow through the flexible conduit as has been a characteristic of conventional pumping mechanisms of a similar type. The preferred manner of mounting the cam on its actuating shaft also avoids sharp increases in pressure and consequent rupture of the conduit such as can occur with many conventional apparatus.

Still other features and advantages and a full understanding of the invention will be had from the following detailed description taken in conjunction with the accompanying drawings.

DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view taken along the line 1--1 of FIG. 2 of a centrifugal pump constructed in accordance with a preferred embodiment of the present invention;

FIG. 2 is a cross-sectional view taken generally along the line 2--2 of FIG. 1;

FIG. 3 is a cross-sectional view on an enlarged scale taken on the line 3--3 of FIG. 1;

FIG. 4 is an elevational view of a flexible pumping conduit embodied in the construction of FIG. 1;

FIG. 5 is a cross-sectional view of another embodiment of the present invention;

FIG. 6 is a cross-sectional view taken generally on the line 6--6 of FIG. 5; and

FIG. 7 is a cross-sectional view showing a modification of the centrifugal pump construction of FIGS. 1-3.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring now to the drawings, and to FIGS. 1-4 in particular, the centrifugal pumping apparatus constructed in accordance with a preferred embodiment of the present invention is generally designated by reference numeral 10. The pumping apparatus 10 includes a casing 11 having a portion 12 which defines an impeller chamber or volute 13, a hub portion 14 extending from the portion 12, and a pedestal 15 which is bolted to the portion 12 around the hub 14.

A member 16 is disposed within the casing portion 12 to define an end wall of the volute or impeller chamber 13. The member 16 has a neck portion 17 which is threaded into the inner end of the hub 14, a radially extending wall 18 and an outer peripheral flange 19 which engages the inner surface of the casing portion 12. A suitable O-ring seal 20 is disposed between the flange 19 and the adjacent wall of the casing portion 12. The radial wall 18 of the member 16 is spaced from the end of the hub 14 to define an annular chamber 25. Passageways 26 (only one of which is shown) through the radial wall 18 communicate the chamber 25 with the central portion of the impeller chamber 13.

The pump volute 13 has a tangentially communicating discharge passage 30 which terminates at a discharge port 31. An outlet pipe 32 is adapted to be connected to the discharge port 31. The casing 11 also includes an inlet port 33 which communicates with the center of the volute 13 on the axis of the casing 11. A suction inlet pipe (not shown) is adapted to be connected to the port 33.

A vaned impeller 35 is disposed within the chamber 13 on the end of a shaft 36 which is adapted to be driven by a motor or other power source (not shown). The shaft 36 extends through and is rotatably supported within the hub 14 of the casing by sets of spaced bearings 37, 38. A sealing assembly 39 is provided around the inner end of the shaft 36 inside the neck portion 17 of the member 16.

When the pump shaft 36 is actuated to rotate the impeller 35, an area of reduced pressure is created in the eye 40 of the impeller adjacent the suction port 33. Assuming that the pump has been primed, atmospheric pressure acting on the liquid to be pumped forces the liquid into the eye of the impeller 35 to establish a suction flow of liquid into the pump. The liquid entering the suction port 33 is entrained in the blades of the impeller 35 and is centrifugally thrown into the surrounding channel of the volute 13, thereby decreasing the velocity of the liquid and increasing the pressure. The liquid in the volute 13 is exhausted from the pump through the passageway 30, the outlet port 31 and the pipe 32.

The mechanism for priming the pump 10 is mounted within the hub 14 between the bearings 37, 38 and is generally designated by reference numeral 45. The priming mechanism 45 is shown as including a pair of adjacent, flexible pumping conduits 46, 47 which may be made of an elastomeric or rubberlike material. Each of the pumping conduits 46, 47 may be of any desired length so as to extend around the inside of the hub 14 any desired number or fractional number of turns. Each of the conduits 46, 47 has a flanged inlet port 48 at one end of the conduit and a flanged outlet port 49 at the other end. The conduits are mounted around the inside of a ring 50 which is fitted within the hub 14. As shown, the ring 50 has openings for receiving the flanges of the inlet and outlet ports 48, 49, respectively.

The inner wall of the hub 14 is formed with a groove or recess 51 which communicates the inlet openings 48 of the conduits 46, 47. A passageway 52 extends longitudinally through the wall of the hub 14 between the chambers 25, 51. A second recess or groove 53 in the inner wall of the hub 14 forms a chamber communicating the outlet openings 49 of the conduits 46, 47. An outlet opening 54 is formed through the wall of the hub 14 into the chamber 53 and is adapted to receive the end of a pipe 55 which extends into connection with the pump discharge pipe 32. It will be understood that the chamber 51 can be ported through an opening in the wall of the hub 14 similar to the opening 54 and that the opening can be connected to the suction area of the volute 13 by an external hose or conduit. An external connection between the chamber 51 and the inlet side of the pump may be desired in applications where the pump is intended to handle materials that might clog the internal passage 52 leading to the priming mechanism 45.

The flexible conduit 46 is wrapped around a pressure ring 60 which has a smaller diameter than the ring 50 and is adapted to oscillate or orbit around the inside of the ring 50 to collapse the conduit 46. The pressure ring 60 is oscillated by a cam 61 which is mounted for rotation with the impeller shaft 36 eccentric to its axis. The cam 61 is rotatable within the pressure ring 60 and any suitable form of bearing structure, such as the illustrated needle bearings 62, roller bearings, ball bearings, sleeve-type bearings or the like, are provided between the outside of the cam and the inner surface of the ring.

The structure for effecting a pumping action of the flexible conduit 47 is identical to that described in connection with the conduit 46 and includes a pressure ring 63, a rotatable cam 64 eccentrically mounted on the shaft 36 and bearing structure 65 between the cam and the ring 63. As shown, the assembly of the adjacent conduits 46, 47, the oscillatable pressure rings 60, 63, and the cams 61, 64 is contained within a retaining member 66.

As will be apparent from FIG. 1, the cams 61, 64 are mounted within the retainer 66 so that the throw of the cam 61 is offset 180.degree. with respect to the throw of the cam 64. The provision of a pair of offset cams 61, 64 eliminates the undesirable vibrations which would occur at high rotative speeds with a single eccentrically mounted cam. Another advantage of the illustrated construction is that the use of two priming conduits 46, 47 increases the priming capacity of the pump while permitting the use of conduits having relatively small flow passages. In another embodiment of the invention (not shown), the pumping conduit 47 and the associated actuating mechanism including the cam 65 is eliminated and the cam 61 is counterbalanced to eliminate vibrations.

In accordance with a preferred embodiment of the invention, each of the cams 61, 64 is operatively coupled to the shaft 36 by torque-limiting structure which prevents operation of the priming mechanism 45 after the pump 10 has been primed and is operating at rated capacity and head. The diagrammatically illustrated, torque-limiting structure is a magnetic, hysteresis drive which utilizes the magnetic field of a rotating permanent magnet to drive the material of a driven member through a hysteresis loop. As shown, a permanent ring magnet 70 is carried by a sleeve 71 which is fixed to the shaft 36. A driven magnet ring 72 formed of a hysteresis alloy is mounted around the permanent magnet 70 and is secured to the cams 61, 64. The two ring magnets 70, 72 are separated by a small radial air gap. The follower magnet 72 is magnetized by the presence of the permanent magnet 70 and is rotatable therewith provided the maximum torque of the magnetic drive is not exceeded. When the maximum torque of the drive is exceeded, the follower magnet 72 and the connected cams 61, 64 are no longer caused to rotate and further operation of the priming mechanism 45 is prevented.

The operation of the pumping apparatus forming one embodiment of this invention will be largely apparent from the foregoing description. At the start of the priming cycle when the pump volute 13 is dry, the cams 61, 64 of the priming mechanism 45 are coupled to the shaft 36 for rotation by the magnetic drive comprising the ring magnets 70, 72. Rotation of the eccentrically mounted cams 61, 64 within the pressure rings 60, 63 serves to oscillate the pressure rings and this oscillating motion results in the walls of each flexible pumping conduit 46, 47 being collapsed and pressed together at a moving location proceeding from one end of the conduit to the other. A vacuum is created in each conduit behind the collapsed portion, whereby the air in the volute 13 is sucked into the inlet openings 48 of the conduits through the openings 26, the chamber 25, the hub passage 52 and the chamber 51. At the same time, a positive pumping pressure is created in the conduits 46, 47 in advance of the collapsed portions, whereby the air in the conduits is forced out through the outlet openings 49 into the chamber 53 and through the pipe 55 to the pump discharge pipe 32. This pumping action of the priming mechanism 45 is continued until the air within the volute 13 has been exhausted and a suction flow of liquid has been established into the volute 13 through the inlet opening 33.

When the pump has been fully primed and a suction flow of liquid into the pump inlet has been established, the resistance of the liquid to be pumped through the conduits 46, 47 and forced through the pipe 55 into the pipe 32 exceeds the maximum torque of the magnetic drive 70, 72. At this point rotation of the magnet ring 72 will stop to effectively uncouple the priming mechanism 45 from the drive shaft 36. The priming mechanism will remain inoperative until such time as the resistance to flow through the pumping conduits falls below the maximum torque of the drive 70, 72, whereupon the ring 72 will again rotate with the ring 70. The provision of the structure for stopping operation of the priming mechanism 45 when priming has been completed has the advantage of improving the all over efficiency of the pumping apparatus 10 by eliminating the torque load on the drive motor which would otherwise be imposed by operation of the priming mechanism during the pumping cycle. In addition, the life of the priming mechanism 45 including the conduits 46, 47 is extended by stopping the pumping action of the conduits during the period that there is a suction flow of liquid into the pump through the impeller.

In accordance with the illustrated embodiment of the invention, a one-way check valve 75 is provided in the discharge pipe 32 between the pump outlet port 31 and the connection of the pipe 55 to the pipe 32. As generally explained above, the check valve 75 prevents air in the discharge pipe from returning to the volute 13 of the pump which would impair the desired suction within the volute necessary for establishing the suction flow of liquid. In addition, the check valve 75 confines surge pressures to the discharge piping and prevents such pressures from damaging the pump casing 11.

Reference is now made to the second preferred embodiment of the invention illustrated in FIGS. 5 and 6 which also comprises a flexible conduit-type pumping arrangement. The illustrated pumping apparatus 80 is comprised of a casing 81 having a generally cylindrical sidewall 82 and end walls 83, 84. A member 86 formed with a pair of externally ported passages 87, 88 is secured to the casing wall 82. The walls 82-84 define a casing chamber 89. A drive shaft 90 extends into the chamber 89 of the casing 81 and is mounted for rotation by sets of roller bearings 91 in the end walls 83, 84.

A pair of eccentrically mounted cams 95, 96 are disposed within the casing chamber 89 and are connected to the shaft 90 for rotation therewith. As shown, the cams 95, 96 are separated by a spacer member 97. Each of the cams 95, 96 is coupled to the shaft 90 by spiral springs 98, 99, respectively. The spring connections 98, 99 permit the cams 95, 96 to shift radially with respect to the shaft 90 under conditions to be more fully explained. In the illustrated embodiment, the cams 95, 96 are mounted on the shaft 90 so that the throw of the cams are offset 180.degree. from each other in order to eliminate vibrations. In another embodiment (not shown), a single cam is mounted on the shaft and the cam is counterbalanced to eliminate vibrations.

Pressure rings 100, 101 are mounted around the cams 95, 96, respectively, by bearing structure 102 which permit the cams to rotate within the pressure rings. As shown, the bearing structure 102 comprises strips of Teflon or the like which extend around the outside of each cam in engagement with the surrounding pressure ring. In other embodiments of the invention, the bearing structure may comprise ball bearings, roller bearings, needle bearings or the like.

A flexible pumping conduit 103 formed of an elastomeric or rubberlike material is engaged between the pressure ring 100 and the inner surface of the casing wall 82. A similar conduit 104 is engaged between the pressure ring 101 and the sidewall of the casing 81. Both pressure rings 100, 101 have a diameter in relation to the inner diameter of the casing wall 82 such that the pumping conduits 103, 104 will be collapsed in one portion and allowed to expand to a maximum size in a diametrically opposed portion as the pressure rings are caused to orbit around the inside of the casing wall by rotation of the cams.

Each of the pumping conduits 103, 104 has a neck portion 105 at one end and a neck portion 106 at the other end which define inlet and outlet openings to the conduit. The neck portions 105 of the pumping conduits are retained within passages 107 which extend through the casing wall 82. The neck portions 106 are similarly retained in passages 108 through the casing wall 82. The casing member 86 is formed to define a chamber 109 at the inner end of the passage 88 which communicates the openings through the conduit necks 105. The casing member 86 is also formed to define a chamber 110 at the inner end of the passage 89 which communicates the openings through the conduit necks 106.

The strength of the springs 98, 99 is sufficient to hold the cams 95, 96 in the illustrated eccentric positions and to cause the cams to rotate with the shaft 90 during normal operation of the pump. During such operation, the cams 95, 96 are rotated within the pressure rings 100, 101 and cause the rings to orbit around the inside of the casing wall 82. As a result, each pumping conduit 103, 104 is progressively collapsed against the sidewall from one end of the conduit to the other. A suction is created in each pumping conduit behind the collapsed area to suck material into the communicating opening of the conduit through the casing passage. A pumping pressure is created in advance of the collapsed portion to force the material through the conduit out of the other outlet and casing passage. It will be apparent that the shaft 90 can be rotated in either direction to suck material into the casing passage 88 and force it from the passage 89 or to suck material into the passage 89 and force it from the passage 88.

The pumping apparatus 80 is suitable for handling liquids, gases, liquids which contain solids, powdered material, and the like. The described manner of connecting the cams 95, 96 to the shaft 90 by the springs 98, 99, respectively, enables such materials to be pumped smoothly through the apparatus at high velocities without pulsations and obtains other important advantages. If a solid piece of material of relatively large size should enter either of the pumping conduits, the associated cam will shift radially of the shaft 90 and so that it can continue to rotate without being damaged and without crushing the piece of material. The ability of the cams to shift radially on the shaft 90 also prevents the creation of undesirably large pressures in the pumping conduits which could result in their being ruptured. The operation of many collapsible chamber pumps of the prior art is such that pressure in the flexible conduit increases exponentially with volume, and this characteristic has limited the useful capacity of the pumps. The apparatus of the present invention can be constructed so that the cams will shift to cause a decrease in pressure as the volume increases. By changing the strength of the springs 98, 99, it is also possible to provide for constant pumping pressure or pressures which will increase with volume. It will thus be seen that the pumping apparatus 80 can be constructed to meet a wide range of pumping requirements.

It is to be understood that the invention is not limited to a flexible conduit-type pumping arrangement embodying pairs of offset cams eccentrically mounted on a drive shaft. As explained above in connection with the mechanisms 45 and 80 respectively illustrated in FIGS. 1-3 and FIGS. 4, 5, the provision of pairs of offset cams eliminates vibrations occurring with a single eccentrically mounted cam at high rotative speeds, for example, speeds in excess of about 400 to 500 r.p.m. The same advantage of eliminating vibrations can be achieved by use of a single cam which is suitably counterbalanced. Another preferred arrangement which incorporates a single pumping conduit and a balanced cam constructed to avoid vibrations is illustrated in FIG. 7.

The construction 10' shown in FIG. 7 is illustrated as a modification of the pumping apparatus 10 of FIGS. 1-3 and includes a priming mechanism 45' mounted around the drive shaft 36 within the hub 14 of the pump casing 11. The priming mechanism 45' is comprised of a single conduit 46 in the form previously described which is mounted within the ring 50. The conduit 46 extends around a pressure ring 120 which has a smaller diameter than the ring 50 and is adapted to oscillate or orbit around the inside of the ring 50 to collapse the conduit 46. As shown, the ring 120 has an inner bearing liner or sleeve 121 formed of Teflon or the like. Other alternative bearing structure such as described in connection with FIGS. 1-3, 5 and 6 can be provided in place of the sleeve 121.

The pressure ring 120 is oscillated to collapse the conduit 46 and effect a pumping action by a cam 125 which is operatively connected to the drive shaft 36 in any suitable manner, such as by the torque limiting, magnetic drive of FIGS. 1-3 or the spiral spring of FIGS. 5, 6. In accordance with this embodiment of the invention, the single cam 125 is constructed to prevent vibrations from occurring during rotation. As shown, the cam 125 is substantially triangular in shape and has portions 126, 127 which are equidistant from the center of rotation and engage the bearing sleeve 121 at spaced locations. The cam 125 has a third portion 128 which has a larger radius than the portions 126, 127 and is adapted to progressively collapse the conduit 46 as the cam is rotated. The outer peripheral portions 129 of the cam 125 between the lands defined by the cam portions 126-128 are spaced from the inside of the bearing sleeve 121.

The described shape of the cam 125 is effective to substantially eliminate vibrations even at high rotative speeds in excess of 500 r.p.m. Since the provision of a single-balanced cam and pumping conduit arrangement significantly reduces the number of operating parts required in the double cam and conduit arrangement as shown in FIGS. 1-3, a construction such as shown in FIG. 7 may be preferred in many applications. It will be apparent that the single-balanced cam construction can also be employed with advantage in place of the double cams in the embodiment of FIGS. 5 and 6.

Many other modifications and variations of the invention will be apparent to those skilled in the art in the light of the foregoing disclosure. Therefore, it is to be understood that, within the scope of the appended claims, the invention can be practiced otherwise than as specifically shown and described.

Claims

What is claimed is:

1. Centrifugal pump apparatus comprising:

a. a casing having an impeller chamber and an inlet and an outlet communicating with said chamber,

b. a rotatable impeller within said chamber, and

c. priming means effective to exhaust air from said chamber,

d. said priming means including:

i. a structure forming a continuous tubular conduit having a flexible wall, an inlet opening in communication with said chamber, and an exhaust opening,

ii. a structure for successively flexing said wall along the length of said conduit from said inlet opening to said exhaust opening and thereby causing a flow of fluid through said conduit, and

iii. means for moving said structures relative to one another to exhaust air from said chamber and prime said pump apparatus.

2. Centrifugal pump apparatus as claimed in claim 1 including an outlet flow line connected to said casing outlet, check valve means in said line for preventing fluid flow into said casing, and means connecting said conduit exhaust opening to said flow line at a location downstream from said valve means.

3. Centrifugal pump apparatus as claimed in claim 1 wherein said casing includes a passageway between said inlet opening of said conduit structure and said impeller chamber.

4. Centrifugal pump apparatus comprising:

a. a casing having an impeller chamber and an inlet and an outlet communicating with said chamber,

b. a rotatable impeller within said chamber,

c. fluid conduit structure having a flexible wall, an inlet opening in communication with said chamber, and an exhaust opening,

d. structure for successively flexing said wall along the length of said conduit structure from said inlet opening to said exhaust opening, thereby causing fluid flow through said conduit structure to prime said pump,

e. a rotatable shaft, and

f. means for coupling one of said structures to said shaft for rotation therewith during priming and for operatively disconnecting said one structure from said shaft when priming has been completed.

5. Centrifugal pump apparatus as claimed in claim 4 wherein said coupling means comprises a first member connected to said one structure and a second member connected to said shaft, said members being cooperable to establish a rotary drive transmission of predetermined maximum torque.

6. Centrifugal pump apparatus as claimed in claim 4 wherein said coupling means comprises means forming a magnetic drive having a predetermined maximum torque.

7. Centrifugal pump apparatus comprising:

a. a casing having an impeller chamber and an inlet and an outlet communicating with said chamber,

b. a rotatable shaft,

c. an impeller mounted on said shaft in said chamber,

d. a conduit,

e. said conduit having a flexible wall, an inlet opening in communication with said chamber, and an exhaust opening,

f. structure including actuating means rotatable eccentrically with said shaft for successively collapsing said conduit along its length, thereby causing fluid flow through said conduit to prime said pump, and

g. magnetic, hysteresis drive means for transmitting rotary motion from said shaft to said actuating means, said drive means having a maximum torque and being operable to allow said shaft to rotate relative to said actuating means when said maximum torque is exceeded.

8. Centrifugal pump apparatus as claimed in claim 7 wherein said actuating means is balanced to prevent vibrations during rotation.

9. Centrifugal pump apparatus as claimed in claim 7 wherein said magnetic drive means comprises a first ring magnet connected to said shaft and a second ring magnet connected to said actuating means and spaced from said first magnet.

10. Centrifugal pump apparatus comprising:

a. a casing having an impeller chamber and an inlet and an outlet communicating with said chamber,

b. a shaft,

c. spaced bearing means in said casing mounting said shaft for rotation,

d. an impeller mounted on said shaft in said chamber,

e. a conduit mounted within said casing against a rigid surface,

f. said conduit having a flexible wall, an inlet opening in communication with said chamber, and an exhaust opening,

g. structure mounted around said shaft in position to collapse a portion of said conduit,

h. said structure including a member positioned eccentrically of said shaft, and

i. means for selectively coupling said member to said shaft for rotation therewith,

j. said coupling means comprising magnetic drive means having a maximum torque, whereby said shaft is free to rotate relative to said member when said maximum torque is exceeded.

11. Centrifugal pump apparatus as claimed in claim 10 wherein said member is balanced to prevent vibrations during rotation.

12. Centrifugal pump apparatus as claimed in claim 11 including an outlet flow line connected to said casing outlet, means forming a fluid flow connection between said conduit exhaust opening and said flow line, and one-way check valve means in said flow line between said casing and said fluid flow connection for preventing fluid from returning to said casing.

13. Centrifugal pump apparatus as claimed in claim 11 wherein said conduit is positioned between said bearing means.

14. Centrifugal pump apparatus comprising:

a. a casing having an impeller chamber and an inlet and an outlet communicating with said chamber,

b. a rotatable shaft,

c. an impeller mounted on said shaft in said casing,

d. a pair of conduits in said casing,

e. each of said conduits having a flexible wall, an inlet opening communicating with said chamber, and an exhaust opening,

f. structure mounted around said shaft for successively collapsing each of said conduits along its length to create a flow of fluid therethrough and thereby prime said pump,

g. said structure including a pair of members positioned eccentrically of said shaft so that the throws of said member are offset 180.degree. relative to each other, and

h. means coupling said structure to said shaft for rotation therewith.

15. Centrifugal pump apparatus as claimed in claim 14 wherein said coupling means comprises magnetic drive means having a maximum torque, whereby said shaft is free to rotate relative to said members when said maximum torque is exceeded.

16. Pump apparatus comprising:

a. first and second fluid conduit structures, each having a flexible wall, an inlet opening and an exhaust opening,

b. a rotatable shaft,

c. means supporting said conduit structures around said shaft, and

d. structure including first and second eccentric means adapted to be rotated by said shaft to successively collapse said conduit structures along their lengths to effect pumping actions,

e. said first and second eccentric means being positioned so that their maximum throws are offset 180.degree..

17. Pump apparatus as claimed in claim 21 including coupling means for connecting said shaft to said structure for collapsing said conduit structures, said coupling means having a maximum torque and being operative to permit said shaft to rotate relative to said eccentric means when said maximum torque is exceeded.

18. Centrifugal pump apparatus comprising:

a. a casing having an impeller chamber and an inlet and an outlet communicating with said chamber,

b. a rotatable impeller within said chamber, and

c. priming means effective to exhaust air from said chamber,

d. said priming means including:

i. fluid conduit structure having a flexible wall, an inlet opening in communication with said chamber, and an exhaust opening,

ii. structure for successively flexing said conduit from said inlet opening to said exhaust opening and thereby causing a flow of fluid through said conduit structure, and

iii. means including a drive shaft for moving said structures relative to one another,

iv. said structure for successively flexing said conduit structure including actuating means eccentrically rotatable with said shaft, said actuating means being balanced to prevent vibration during rotation.

19. Pump apparatus comprising:

a. fluid conduit structure having a flexible wall, an inlet opening, and an exhaust opening,

b. means supporting said conduit structure,

c. a rotatable shaft,

d. structure for successively collapsing said conduit structure along its length to effect a pumping action,

e. said structure for collapsing said conduit structure including means eccentrically positioned relative to said shaft, said eccentrically positioned means being balanced to prevent vibrations during rotation, and

f. means coupling one of said structures to said shaft for rotation,

g. said coupling means being operatively positioned between said shaft and said eccentrically positioned means, and said coupling means having a maximum torque and being operative to disconnect said one structure from said shaft when said maximum torque is exceeded.

20. Pump apparatus comprising:

a. fluid conduit structure including a flexible wall, an inlet opening and an exhaust opening,

b. a rotatable shaft,

c. means mounting said conduit structure around said shaft,

d. structure for successively collapsing said conduit structure along its length to effect a pumping action,

e. said structure for collapsing said conduit structure including means eccentrically positioned with respect to said shaft, said eccentrically positioned means being balanced to prevent vibration during rotation,

f. one of said structures being rotatable with said shaft, and

g. spiral spring means surrounding said shaft and connecting said one structure to said shaft for movement radially thereof, said spiral spring means being located between said eccentrically positioned means and said shaft.

21. Pump apparatus as claimed in claim 20 wherein said eccentrically positioned means comprises first and second eccentric means positioned so that their maximum throws are offset 180.degree. .