US 3310000 A
Description (OCR text may contain errors)
March 1967 T. B. MARTIN DUPLEX PLUNGER METERING PUMP Filed Feb. 28, 1966 2 Sheets-Sheet 1 INVENTOR. M04445 5. Moan/v Filed Feb. 28, 1966 T. B. MARTIN DUPLEX PLUNGER METERING PUMP 2 Sheets-Sheet 2 INVENTOR. 71/0444! 5. 114427741 United States Patent 3,310,000 DUPLEX PLUNGER METERING PUMP Thomas B. Martin, Micro-Pump C0rp., R0. Box 392, Danville, Calif. 94526 Filed Febi 28, 1966, Ser. No. 530,703 Claims. (Cl. 103171) This invention relates to a new and improved duplex plunger metering pump and is a continuation-in-part of co-pending application-s 350,306 filed Mar. 9, 196-4, and 350,503 filed Mar. 9, 1964, now Patents Nos. 3,238,878 and 3,238,883, respectively.
More particularly the present invention comprises a high pressure metering pump having a number of advantages over conventional pumps of this general type.
One of the principal advantages .of the construction hereinafter described in detail is the fact that the drive shaft is hermetically sealed from and magnetically coupled to a rotating driving means such as an electric motor. This arrangement does not require a rotary shaft seal and consequently the likelihood of leaking, wear or sticking is reduced and the imposition of undue loads on the driving motor and generation of destructive amounts of frictional heat are likewise eliminated. The drive for the pump is two concentric magnets, one driven by a motor and the other mounted on the pump shaft. Although the gap between the magnets is small, nevertheless, it is suflicient so that a partition may be interposed between the two magnets to serve as a seal and thus eliminate the conventional rotary pump seal interposed between the pump housing and the shaft which extends exteriorly of the pump housing and which frequently is the cause of leakage and other undesirable features. 1
A further feature of the construction is the fact that the sealed pump assembly may be removed intact from the motor and replaced with another pump of the same or different design without interference with the driving motor. Conversely, the motor may be replaced without interference with the pump and its associated piping.
A still further advantage of the present invention is the fact that the pump is self-priming against a high discharge pressure.
A still further feature of the invention is the fact that the pump can handle liquids with entrained gases at high discharge pressure, thereby differing from conventional pumps of this class.
Still another feature of the invention is that, with proper choice of resistant materials, the pump can handle liquids which are ordinarily corrosive to pumps of this class.
A still further advantage of the invention is the fact that it has a powerful suction and can be used in vacuum pump applications.
A still further advantage of the invention is the low cost of construction of the pump, its simplicity of construction and the ease with which it may be maintained and repaired. Particularly, the pump may be examined and parts replaced without disconnecting the pump casing from piping to which the input and discharge ports are connected.
Still another advantage of the invention is freedom from excessive wear of the moving parts by reason of the construction of the pump as hereinafter set forth.
Other objects of the present invention will become apparent upon reading the following specification and referring to the accompanying drawings in which similar characters of reference represent corresponding parts in each of the several views.
In the drawings:
FIG. 1 is a longitudinal vertical sectional view through the pump.
FIGS. 2 and 3 are, respectively, transverse sectional views taken substantially along the lines 22 and 33 of FIG. 1.
FIG. 4 is a fragmentary sectional view taken substantially along the line 44 of FIG. 1.
FIG. 5 is a view similar to FIG. 3 of a modified construction.
The pump which is the subject of this invention has a body or casing 11 formed with an inlet port 12 and discharge port 13 threaded as indicated at reference numerals 14 and 16, respectively, for attachment to inlet and discharge pipes (not shown). Extending longitudinally centrally of casing 11 is a bore 17 for rotary drive shaft 18. The means whereby shaft 18 is rotated is hereinafter described in detail. At the forward end of Casing 11 is a crankcase chamber 19 which opens into the forward end of the pump and is closed off by a front cover 21 with a gasket 22 interposed between the cover and the front end of the casing. Extending laterally in diametrically opposed directions from crankcase 19 are cylinder bores 23 which are closed off by cylinder heads 24L and 24R held in place by screws 26. The outer end of shaft 18 is provided with an eccentric 27 which is received in slider 28 formed of an antifriction material such as a composition of Teflon, glass fiber and molybdenum disulphide, or equivalent material. Slider 28 has curved opposed circular arcuate edges 29 and, displaced therefrom, flat side edges 31. Slider 28 is re ceived in the rearward recessed face 32 of crosshead 33 which reciprocates laterally in crankcase 19 as eccentric 27 revolves. Crosshead 33 is formed with a transverse bore 34 to receive plunger 36 which is held therein by set screw 37. Accordingly, plunger 36 is provided with a substantially transverse reciprocating motion. To avoid imperfections in alignment, provision is made for a slight rocking of plunger 36 by means hereinafter described.
Mounted in each lateral bore 23 is cylinder 41 having a central bore to receive plunger 36 with an exceedingly close fit. The inner end of cylinder 41 has an outside diameter less than the inside diameter of bore 23 and the cylinder is further formed with radial passageways 42 providing communication between crankcase 19 and bore 23 to the central bore 43 of cylinder 41. The passages a 42 comprise in effect ports for the chamber 43 of cylinder 41. The outer end of cylinder 41 has an enlarged head 44 which seals against an O-ring 46 recessed in body 11 and the outer end of cylinder 41 is formed with a conical surface 47 which seats against the inner end of hole 48 in head 24L or 24 R. By reason of the conical surface 47 engaging the hole 48, the cylinder 41 may rock slightly, this movement being necessary to prevent binding of plunger 36 in bore 43 of cylinder 41 as a result of imperfections in alignment.
In the modification best shown in FIG. 3, hole 48 is provided with a resilient ball 49 biased by means of spring 50 in the bottom of hole 48 against the open end of hole 43 of cylinder 41.
The flow of fluid through the pump is accomplished as follows:
Fluid enters intake port 12 through threaded opening 14 and is delivered into crankcase 19 by means of duct 51 in body 11. From crankcase 19 the fluid flows through the opening between bore 23 and cylinder 41 and through ports 42 into the bore 43. As plunger 36 moves to the left as shown in FIG. 3, the port 42 on the left-hand side is closed and the fluid entrained in the bore 43 is compressed. When the pressure overcomes the force of spring 50, the ball 49 is lifted from its seat at the opening of hole 43 and the fluid flows into hole 48 and thence through a notch 52 into the oval-shaped cavity 53 in the inner face of head 24L. Seal 54 assumes the oval shape 3 of the cavity 53 and seals against the end of body 11, all as best shown in FIG. 4.
Referring now to FIG. 2, fluid from cavity 53 on the left side co'mmuicates by angularly disposed drill hole 561., 56R to the cavity 53 on the right-hand side and thence by duct 55 (see FIG. 1) to discharge port 13 and thence through threaded connection 16 to the discharge pipe (not shown). On the reverse stroke of plunger 36, as soon as the pressure in bore 43 drops below the force of spring the ball 49 seats and closes ofl? cylinder bore 43. Thereafter, an additional quantity of fluid is drawn into bore 43 through port 42 in anticipation of the next leftward movement of plunger 36. Meanwhile, the rightward movement of plunger 36 forces fluid from the right cylinder bore 43 into chamber 53 and thence through duct 55 into the discharge port 13.
Rotation of shaft 18 may be accomplished in various ways. A preferred means is similar to that shown in copending application Ser. No. 350,306. An annular ceramic magnet 71, preferably having two north poles and two south poles, is mounted on the exterior end of shaft 18. Surrounding the exterior of magnet 71 is a nonmagnetic, cup-like partition 73, preferably a poor conductor of electricity. Austenitic stainless steel is satisfactory in most applications, although a conductive material such as brass may be used when speed is not excessive. Thus, shaft 18 and magnet 71 are sealed by means of partition 73 without the use of rotary seals common in other rotary pumps and the disadvantages of rotary seals are eliminated. The fluid being pumped may be circulated throughout partition 73 and around magnet 71. For such purpose, a hole 78 may be formed communicating from inlet port 12 and the cavity 79 in which magnet 71 rotates and a return passage 81 may be formed surrounding shaft 18 and communicating with crankcase 19.
Magnet 71 as well as drive magnet 82 is a barium carbonate material having incorporated therein a considerable mass of magnetic material such as iron oxide. Such magnets are produced, among others, by Stackpole Carbon Company under the trademark Cera Magnet. It is a characteristic of such magnets that a plurality of poles may be substantially permanently magnetically induced therein. The magnets have extreme resistance to demagnetization and high electrical resistivity. Eddy current losses are negligible. The number of poles per magnet is subject to wide variation, but in the form herein illustrated, there are preferably two north and two south poles in each of the magnets. The magnets are concentric about the axis of rotation of shaft 18.
The driving motor 83, especially in small sizes, may be a shaded pole induction motor having the axis of shaft 84 in line with the axis of pump shaft 18. Hub 86 is fixed to shaft 84 by any means and is staked to bell-shaped hub 88 which fits around the outer periphery of magnet 82. An adaptor housing 91 is secured to the outer end of motor 83 by bolts 90. Adaptor 91 may be of a die cast material and dilferent shapes of adaptors may be provided to be substituted with different shapes and sizes of standard motors, thus making the pump interchangeable for such motors. The outer flange 92 of adaptor 91 is connected to annular plate 93 by bolts 94, O-ring 96 sealing the inner end of cup 73 to body 11 and being held in tight engagement by means of ring 93. A spacer ring 97 centers the motor sub-assembly relative to the pump sub-assembly. By removing bolts 94 the motor and pump may be interchanged without displacing the other member. Adaptor 91 may be provided in different shapes to make the pump interchangeable for various styles of motors.
As further simplification of the inspection and maintenance of the pump, the plate 21 and the cylinder heads 24L and 24R may be individually removed and the interior parts of the pump inspected and replaced without disconnecting the piping from fittings 14 and 16.
In FIG. 5, a modification is. shown which is particularly suitable for high pressure gas or suction installations. Because many of the parts are similar, the same reference numerals are employed as in the preceding modification. Ball 49 is, however, replaced in this modification. In lieu thereof, there is substituted a cupshape member 101 faced with a resilient disc 102 which seals against the outer end of cylinder 41. Spring 50 biases cup 101 and facing 102 against the cylinder. In pumps of this type the minimization of the space between the end of the plunger 36 and the check ball 49 is desirable and such result is achieved in the modification of FIG. 3. In FIG. 5, however, the space is all but entirely eliminated in that the stroke of plunger 36 may actually engage face 102 and lift the cup 101 against the force of spring 50. Accordingly, an extremely small clearance volume is achieved and gas bubbles between the plunger and the discharge check valve are more efiectively ejected.
In both of the modifications heretofore described, the pump is self-priming even against a very high discharge pressure in the discharge pipe. Liquids having entrained gasses can be handled because of the minimization of space for air or gas bubbles in the cylinder at the end of the discharge stroke of the pump.
Although the foregoing invention has been described in some detail, by way of illustration .and example for purposes of clarity and understanding, it is understood that certain changes and modifications may be practiced within the spirit of the invention and scope of the appended claims.
What is claimed is:
1. A duplex metering pump comprising a casing formed at one end with a pump crankcase, a shaft, means for rotating said shaft in said casing, a plunger having pistons at opposite ends reciprocable in said crankcase, said plunger being a unitary member, means for transmitting rotary motion of said shaft into reciprocating motion of said plunger, a pair of ported cylinders mounted at opposite sides of said crankcase, each said cylinder receiving one said piston mounted at opposite sides of said crankcase and extending diametrically oppositely transverse to said shaft, cylinder heads on said casing, each forming a discharge chamber adjacent the outer end of said cylinder, check means in each said discharge chamber, resilient means biasing said check means to close off the outer end of said cylinder, means forming an inlet port into said casing, said casing formed to transmit fluid from said inlet port to the port of each said cylinder, said plunger arranged so that alternately each said piston on its discharge stroke first closes the port in its cylinder and then expels fluid in said cylinder past said check means against the force of said resilient means into said discharge chamber and then on its suction stroke releases said check means to closed position and draws fluid from said crankcase into said cylinder and means forming a discharge port to receive the discharge from each said discharge chamber, said pistons on each discharge stroke coming into close proximity with said check means, communication from each said cylinder to its corresponding discharge port being direct with said check means immediately beyond said cylinder, whereby the space between said piston at the end of its discharge stroke and said check means is substantially nil.
2. A pump according to claim 1, in which said check means comprises a ball.
3. A pump according to claim 2, in which said ball is resilient.
4. A pump according to claim 1, in which said check means comprises a flat-surfaced member engaging the outer end of said cylinder, said piston on its discharge stroke extending into close proximity to said flat-surfaced member.
5. A pump according to claim 1, which further comprises a first magnet on said shaft, a second magnet in proximity to said first magnet, means for rotating said second magnet to turn said first magnet and reciprocate said plunger, said first magnet being annular, said second magnet annular and surrounding said first magnet, and a non-magnetic seal sealed to said casing and interposed between said magnets.
References Cited by the Examiner UNITED STATES PATENTS 1,535,643 4/1925 Astrom 103l66.5 2,068,392 1/1937 Acker 103171 2,420,850 5/1947 Yuza 103153 6 2/1959 Kifler et a1. 103171 2/1961 Berner 103103 9/1961 Swenson et al 10387 3/1965 Bennett et a1 103228 FOREIGN PATENTS 12/ 1955 France.
4/ 1963 France.
10 DONLEY J. STOCKING, Primary Examiner.
HENRY F. RADUAZO, Examiner.