Patent Publication Number: US-10760557-B1

Title: High efficiency, high pressure pump suitable for remote installations and solar power sources

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention pertains generally to pumps, and more particularly to very high pressure pumps suitable for use in remote and extreme environments, to pump diverse fluids. 
     2. Description of the Related Art 
     Fluid pumps of many diverse constructions are found in countless devices to move an equally diverse set of fluids. In fact, fluid pumps are ubiquitous with both living things and machinery. 
     The impellers necessary to move fluids can take on such diverse geometries as one or more inclined blades spinning about a hub and either propelling the fluid axially or radially with respect to the spin axis, a piston reciprocating within a sleeve or cylinder, a gear pair that rotates to separate on an intake side and mesh on a discharge side, a screw turning within a cylinder, a rotary vane, a diaphragm that moves to change the volume of a chamber, a collapsible tube pinched in a progressive manner by an external object or roller, gas bubbles rising in a liquid, gravity moving a liquid from a higher point of elevation to a lower elevation, ions driven by an electrical field, magnetic particles or objects driven by a magnetic field, and others. There are, quite plainly, many diverse geometries and constructions of fluid impellers. 
     The fluids that are pumped may be even more diverse, ranging from gases such as air or other gases moved by a fan, to low viscosity liquids such as water, and to viscous liquids such as oils and greases pumped within machinery. In the modern world, many different procedures and chemical compositions have been developed that improve a process, formulation, or operation, and rather than manually carrying out these procedures and delivering these compositions, in most cases a mechanized pump will do the work. 
     There are many different characteristics that can be measured to both define the pump and also determine the suitability of the pump for different applications. A few common characteristics are: flow rate, both with no outlet pressure and at various outlet pressures; inlet suction; maximum outlet pressure; horsepower or equivalent energy consumption; pump complexity; initial pump cost; required pump maintenance; and expected operating life usually measured as Mean Time Between Failure (MTBF). Other characteristics can be estimated or calculated therefrom as well, such as pump efficiency and annual operating cost. Pump efficiency is defined as the ratio of the kinetic power imparted on the fluid by the pump in relation to the power supplied to drive the pump, which can be determined from the energy consumed to generate a flow rate at a pressure head. Other exemplary metrics that may be less common but which may be important or critical for some applications include: compatibility with one or many different fluids, including but not limited to slurries, chemical compositions, and varying viscosities; consistency of output through varying pressure heads; conservation of fluid being pumped; mechanical shear; priming requirements; consistency of output flow rate and pressure; starting current and torque; suitable energy sources for driving the pump; and other factors. 
     For different applications, these characteristics are often times quite divergent from other applications. For exemplary purpose, a washing machine drain pump has very low pressure head required, typically only lifting the drain water from a few inches to a few feet, and will preferably be of simple construction, have low initial fabrication cost, will have a long MTBF, and will require little maintenance. However, the drain water may include somewhat corrosive compositions such as sodium hypochlorite (chlorine bleach) and powerful detergents that will quickly dissolve grease used in many pump seals. Further, there may be relatively large particles that pass through the washing machine drum along with the water, such as small pins, nails, screws, sand, and other solid objects, that must be pumped without consequential harm or stoppage of the pump. As has been known in the art of washing machines, a simple centrifugal or radial vane pump may be used to meet all of these objectives. However, such a pump will be unable to generate much in the way a greater pressure head, and consequently the output and pump efficiency will vary greatly with changes in pressure head. 
     In many fluid applications, such as chemical applications, one or more fluids must be mixed with one or more additional fluids to achieve a desired fluid mixture. Commonly, mixing one fluid with another fluid is performed by measuring out a quantity of a first fluid, measuring out a quantity of a second fluid, and combining the measured amounts in a container where the fluids are mixed together. This process is routinely performed by hand, and thus is subject to inaccuracies attributed to human error. Thus, the fluid mixture achieved may not in fact possess the precise desired proportions of the fluids. Additionally, as fluid mixtures are typically mixed in batches (i.e., discrete quantities of a fluid mixture), inconsistencies in the proportions of the mixed fluids from one batch to the next batch may be experienced. 
     Many artisans over the years have applied various technologies to improve various facets of pumps and to expand the applicability of pumps into industries and applications not previously well addressed. The following patents are incorporated herein by reference as exemplary of the state of the art in a variety of fields, various advances being made therein, and for the teachings and illustrations found therein which provide a foundation and backdrop for the technology of the present invention. The following list is not to be interpreted as determining relevance or analogy, but is instead in some instances provided solely to illustrate levels of skill in various fields to which the present invention pertains: U.S. Pat. No. 1,003,479 by Lucas, entitled “Pump valve”; U.S. Pat. No. 1,632,948 by Cardenas, entitled “Water pump”; U.S. Pat. No. 1,736,593 by Harm, entitled “Circulating device”; U.S. Pat. No. 1,827,811 by Derrick, entitled “Bearing for rotary pumps”; U.S. Pat. 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     In addition to the foregoing patents, Webster&#39;s New Universal Unabridged Dictionary, Second Edition copyright 1983, is incorporated herein by reference in entirety for the definitions of words and terms used herein. 
     A challenging application for a pump is chemical injection. These types of pumps are commonly known as chemical injection pumps. Chemical injection pumps are used to inject relatively small or precise amounts of chemicals into process streams. For exemplary purposes only, these chemicals might include surfactants, solvents, chemical reagents, catalysts, emulsifiers and de-emulsifiers, salinating and desalinating agents, anti-freeze, corrosion and scale inhibitors, biocides, clarifiers, oxidizers, and antioxidants. The process stream may be at very high pressure, or the injector may preferably be supplied with very high pressure to improve the distribution, diffusion, or vaporization of the chemical into the process stream. Either of these requirements of high precision or high pressure will eliminate many types of impellers, and will therefore mandate a much smaller subset of pump types and geometries. 
     One extraordinarily demanding application for chemical injection pumps is in the oil and gas industry. This is because oil and gas pipelines may extend for hundreds or even thousands of miles, meaning the ambient temperatures may be very different at different locations along the pipeline. Further, these pipelines will also commonly run through regions of little or no human population, making them not only remote, but also not provided with nearby electrical transmission lines to power equipment. The pipelines may run at very high pressure, mandating pumps capable of handling the substantial head required to properly supply the pipeline. In addition, there are many different chemicals that may be desired to be injected into the pipeline. 
     One common example of the use of a chemical injection pump is the injection of methanol into a natural gas pipeline to reduce or eliminate the formation of hydrates. Hydrates can freeze at almost thirty degrees Fahrenheit above the freezing point of water. Left untreated, the water content of even “dry” natural gas can cause blockage in the pipeline or seriously interfere with instrumentation or other vital components. As a practical example, gas flowing in a pipeline at relatively higher pressures such as 700 psi at an ambient temperature of 60 degrees Fahrenheit may have no issue with freezing. However, through distribution there may be a pressure regulating station that drops the pressure substantially, and associated with this pressure drop is a temperature drop. If the temperature drop and water vapor content are sufficient, the pressure regulator or adjacent components may freeze. 
     Many other chemicals besides methanol may be injected into the pipeline, including but not limited to de-emulsifiers, solvents, de-salting agents, corrosion inhibitors, biocides, clarifiers, scale inhibitors, paraffin dewaxers, surfactants, oxygen scavengers, and hydrogen sulfide scavengers. Consequently, a chemical injection pump designed for a gas pipeline must not only withstand very high pressure heads and temperature extremes, it must also be extremely chemical resistant. 
     In consideration of the remote nature of these pumps, lack of access to external power sources, and the ready availability of gas that is highly pressurized relative to atmosphere, many of these pumps have historically been pneumatically powered by pressurized fuel gas. There are a number of benefits, including low initial capital outlay, operation in remote locations without a need for electrical infrastructure, ready commercial availability, typically a simple design that allows both a higher MTBF and simpler and lower cost maintenance and repair, and a labor force experienced in the installation and maintenance of pneumatic pumps. However, the operating costs including spent fuel gas are much higher, and the emission of fuel gas is undesirable as a fire hazard, a worker safety hazard, and a greenhouse gas emission. 
     As a result of the drawbacks associated with pneumatic pumps, other pumps have been sought after to overcome the disadvantages. Solar powered chemical injection pumps are one such alternative. However, conversion at larger facilities still requires a large output of capital, infrastructure change, and personnel training. Consequently, a solar powered pump must provide significant economic and environmental advantage to be economically viable. 
     SUMMARY OF THE INVENTION 
     In one manifestation, the invention is a pump head. The pump head has a motor coupler; a motor mount; at least one piston housing; a fluid input; a fluid output; and a reciprocating piston operative within said piston housing and in a fluid flow path between said fluid input and said fluid output to pump a fluid from said fluid input to said fluid output. 
     In a further manifestation of the invention, the manifold has a fluid input bore and a fluid output bore, each extending generally longitudinally parallel to a longitudinal axis of the reciprocating piston, and from adjacent a first longitudinal end of the reciprocating piston to adjacent a second longitudinal end of the reciprocating piston. 
     In another manifestation of the invention, the motor mount has a first mounting flange having at least one coupling to which a fastener may engage and which is configured to couple the first mounting flange to a motor, and having a torsion sleeve coupled with and extending from the at least one coupling on a first end of the torsion sleeve. A torsion bolt extends from within the torsion sleeve and is coupled with and extends from the at least one piston housing on a first end of the bolt distal to the torsion sleeve. An elastomeric sleeve isolates the torsion bolt from torsion sleeve. 
     In an additional manifestation of the invention, the torsion bolt is configured to longitudinally compress the elastomeric sleeve and thereby urge the elastomeric sleeve to radially expand towards and against the torsion sleeve. 
     In another manifestation of the invention, a first seal between the reciprocating piston and the at least one piston housing is in direct fluid communication with a fluid inlet into the piston housing and a fluid output from the piston housing. A second seal is located between the reciprocating piston and the at least one piston housing and is isolated from fluid communication with the fluid inlet into the piston housing and the fluid output from the piston housing by the first seal. The reciprocating piston, at least one piston housing, first seal, and second seal in combination define a fluid collection chamber for fluid that has operatively leaked past the first seal into the fluid collection chamber. A fluid conduit connects the fluid collection chamber to the fluid input. 
     In an even further manifestation of the invention, an over-pressure release valve assembly is coupled on an input thereof with the fluid output and is configured to stay closed until a predetermined maximum pressure is exceeded, and is in fluid communication on an output thereof with at least one of the fluid inlet or a fluid reservoir. 
     OBJECTS OF THE INVENTION 
     The present invention and the preferred and alternative embodiments have been developed with a number of objectives in mind. While not all of these objectives are found in every embodiment, these objectives nevertheless provide a sense of the general intent and the many possible benefits that are available from embodiments of the present invention. 
     A first object of the invention is to provide a high efficiency, high pressure, very chemical resistant, and long Mean Time Between Failure (MTBF) pump. A second object of the invention is the provision of such a pump that is further self-priming and which is tolerant of a wide range of fluid viscosities. Another object of the present invention is the provision of precise displacement for predictable injection flow rate. A further object of the invention is to provide a pump having a modular assembly designed for easy servicing, such as foreseeable in arctic cold when a service person is wearing mittens, with no handling of small parts, other than bolts and a wrench, required. Yet another object of the present invention is the provision of a relatively compact pump head that slides directly onto a standard motor shaft, with a torque arm incorporated directly into the mounting flange. An additional object of the present invention is to provide a pump that exhibits reduced pulsation, relatively low starting torque, and therefore relatively low starting amperage, thereby facilitating off-grid electrical power such as solar photovoltaic power. Yet another object of the present invention is to conserve and not release fluids being pumped, through a return of leaked and over-pressure released fluid back to an inlet fluid source. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The foregoing and other objects, advantages, and novel features of the present invention can be understood and appreciated by reference to the following detailed description of the invention, taken in conjunction with the accompanying drawings, in which: 
         FIG. 1  illustrates a preferred embodiment pump head designed in accord with the teachings of the present invention from a front isometric view. 
         FIG. 2  illustrates the preferred embodiment pump head of  FIG. 1  from a rear isometric view. 
         FIG. 3  illustrates the preferred embodiment pump head of  FIG. 1  from a top view. 
         FIG. 4  illustrates the preferred embodiment pump head of  FIG. 1  from a vertical plane sectional view taken along section line  4 ′ of  FIG. 3 . 
         FIG. 5  illustrates the preferred embodiment pump head of  FIG. 1  from a vertical plane sectional view taken along section line  5 ′ of  FIG. 3 . 
         FIG. 6  illustrates the preferred embodiment pump head of  FIG. 1  from a front view. 
         FIG. 7  illustrates the preferred embodiment pump head of  FIG. 1  from a vertical plane sectional view taken along section line  7 ′ of  FIG. 6 . 
         FIG. 8  illustrates the preferred embodiment pump head of  FIG. 1  from a right side view. 
         FIG. 9  illustrates the preferred embodiment pump head of  FIG. 1  from a horizontal plane sectional view taken along section line  9 ′ of  FIG. 8 . 
         FIG. 10  illustrates the preferred embodiment pump head of  FIG. 1  in further combination with a prior art motor from a front isometric view. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     For the following defined terms, these definitions shall be applied, unless a different definition is given in the claims or elsewhere in this specification. 
     All numeric values are herein assumed to be modified by the term “about”, whether or not explicitly indicated. The term “about” generally refers to a range of numbers that one of skill in the art would consider equivalent to the recited value (i.e., having the same function or result). 
     The recitation of numerical ranges by endpoints includes all numbers within that range (e.g., 1 to 5 includes 1, 1.5, 2, 2.75, 3, 3.80, 4, and 5). 
     Although some suitable dimensions ranges and/or values pertaining to various components, features and/or specifications are disclosed, one of skill in the art, incited by the present disclosure, would understand desired dimensions, ranges and/or values may deviate from those expressly disclosed. 
     As used in this specification and the appended claims, the singular forms “a”, “an”, and “the” include plural referents unless the content clearly dictates otherwise. As used in this specification and the appended claims, the term “or” is generally employed in its sense including “and/or” unless the content clearly dictates otherwise. 
     For the purposes of the present disclosure, a torque arm will be understood to be a member that prevents the pump head assembly from rotating relative to the motor frame, and instead insures that the all applied torque is applied to fluid pumping. 
     The following detailed description should be read with reference to the drawings in which similar elements in different drawings are numbered the same. The detailed description and the drawings, which are not necessarily to scale, depict illustrative embodiments and are not intended to limit the scope of the invention. The illustrative embodiments depicted are intended only as exemplary. Selected features of any illustrative embodiment may be incorporated into an additional embodiment unless clearly stated to the contrary. 
       FIGS. 1-3  illustrate pump head  100  in an assembled state. Pump head  100  has a motor coupler  110 , motor mount  120 , right piston housing  140 , left piston housing  141 , manifold  160 , output  180 , and overflow  190 . 
     Motor coupler  110  is configured to couple through coupling body  111  directly with a standard motor shaft, to transmit rotary power from the motor shaft into pump head  100 . Motor connection sleeve  113  accomplishes this coupling, which as illustrated is a slotted sleeve that may receive a keyed shaft and associated key therein. Nevertheless, the type of motor connection is not critical to the present invention, and so other known motor couplers will be considered to be incorporated herein. Bearings  114  allow motor connection sleeve  113  to rotate freely within coupling body  111 . At the end of motor connection sleeve  113  distal to the motor is a cam coupler  117  that allows motor connection sleeve  113  to engage with and directly drive cam  118 . Cam coupler  117  is not centered on the central axis of cam  118 . Therefore, as the motor shaft and motor connection sleeve  113  rotate cam  118 , the outer periphery of cam  118  does not remain stationary. 
     Cam  118  is engaged with piston  144  at saddle  145  as illustrated in  FIG. 9 . Consequently, when cam  118  is rotated by motor connection sleeve  113 , it will function as an eccentric that in turn will drive piston  144  in a reciprocating motion, in one extreme position locating piston  144  farther into right piston housing  140  and farther out of left piston housing  141 , and in the second extreme position locating piston  144  farther out of right piston housing  140  and farther into left piston housing  141 . As piston  144  reciprocates in a horizontal plane, it is prevented from moving vertically up and down by cylinder  143 . Nevertheless, cam  118  will of course not only drive left and right, but up and down as well. To permit this movement, while not incurring any consequential energy loss, cam drive bearing  119  encircles cam  118  and has an outside diameter slightly less than the width of saddle  145 . Cam drive bearing  119  is thus configured to press against a first side of saddle  145  and climb with respect thereto on a first half rotation, while not contacting the opposite side of saddle  145  during this first half rotation. Bearing  119  will then press against the opposite side of saddle  145  and move downward with respect thereto on a second half rotation, while not contacting the first side of saddle  145 . 
     As described and illustrated, since cam  118  and cam drive bearing  119  are disposed in saddle  145  of piston  144 , rotation of cam  118  results in reciprocating motion of piston  144 . Thus, one revolution of motor connection sleeve  113  rotates cam  118  one revolution, which in turn results in one stroke of piston  144 . A stroke of piston  144  is defined as a single back-and-forth cycle of the piston in which piston  144  travels from its furthest extent in a first direction (e.g., toward left piston housing  141 ) to its furthest extent in the opposite direction (e.g., toward right piston housing  140 ) and back to its furthest extent in the first direction. 
     The volume of fluid output by pump head  100  during one stroke of piston  144  is considered the displacement of pump head  100 . The displacement of pump head  100  is a function of the diameter of piston  144  and the stroke length (e.g., longitudinal movement) of piston  144 . Thus, in some embodiments the displacement of pump head  100  may be changed by changing the diameter of piston  144  and/or the stroke length of piston  144 . In some embodiments, a sleeve may be placed in the piston bore defined by cylinder  143  to accommodate a piston having a smaller diameter. Additionally and/or alternatively, in some embodiments cam  118  may be substituted with another cam having a different eccentricity, such as the opening of the cam being located at a different radial position from the center axis of the cam. 
     When pump head  100  is operating, rotary motion from the rotary motor shaft is directly coupled to motor connection sleeve  113 . Since cam  118  is affixed to motor connection sleeve  113 , this rotation also moves cam  118 . Owing to the eccentricity of cam  118 , movement generates a cantilevered force against motor connection sleeve  113 . This force is counteracted by both of the bearings  114 , while the rollers within bearings  114  act as anti-friction devices. The direction of the force upon bearings  114  is one for which most bearings are designed to exhibit great strength and minimal wear, meaning that such force does not consequentially diminish the life of properly selected bearings. 
     Bearing  119  encircles cam  118 . During rotation of motor connection sleeve  113 , bearing  119  is driven against saddle  145  of piston  144  by cam  118 . Cam  118  is therefore also protected from any frictional energy loss and associated component wear by cam drive bearing  119 , while still controlling the extent of eccentric movement. Once again, the force upon bearing  119  is in the proper direction for great strength and minimal wear. 
     In view of the fixed couplings between drive chain members, with the only exceptions being bearings with properly oriented forces, there are no “weak links” in the preferred embodiment drive chain from motor shaft to piston  144 . As long as the three bearings  114  and  119  are properly selected to withstand the radial loading described immediately herein above, and to have long life, then pump head  100  will be both extremely efficient, and also quite capable of generating extremely high pressures while still operating for a very extended time period (long MTBF). 
     Many prior art reciprocating pumps require the use of a return spring to return the piston. However, in the preferred embodiment, the use of cam  118  in combination with cam drive bearing  119  and saddle  145  in piston  144  eliminates the need for a piston return spring. This not only reduces the parts count, it also further improves efficiency and MTBF. 
     In addition to the drawbacks associated with efficiency and MTBF, a return spring may not always properly return. For exemplary purposes, a highly viscous liquid may delay and ultimately prevent the spring from fully returning the piston. This will alter the amount of fluid actually pumped during a single stroke. In contrast, cam  118  will positively drive piston  144  through the full stroke with each revolution, ensuring that the correct amount of fluid is actually pumped in any given stroke. 
     In the most demanding applications, such as, for exemplary and non-limiting purposes, pipeline chemical injection pumps, both efficiency and MTBF are particularly critical, and even small improvements can translate into substantial cost savings over the life of the pump head. This is in part due to the very nature of the remote installation, making the cost to access and repair or replace a pump very high. Ideally, a preferred embodiment pump head  100  would be permanent for the life of the pipe line, thereby substantially lowering the annual and lifetime cost to operate the preferred embodiment pump head  100 . 
     Piston  144  with saddle  145  as disclosed herein is functionally identical to and structurally very similar to piston 44 illustrated and described in U.S. Pat. No. 9,316,216 by Cook et al, owned by the present assignee, and incorporated by reference herein above. Therefore, further illustration and understanding of the operation of this cam, saddle and piston may be gleaned therefrom. 
     Motor mount  120  replaces and improves upon traditional hat-brim style pump head mounting flanges. These traditional mounting flanges have holes drilled at intervals around the brim region, and through the holes are affixed bolts to secure the pump head to a collar about the motor. Unfortunately, such prior art flanges do not accommodate any dimensional deviations that might, for exemplary purpose, lead to axial mis-alignment between motor connection sleeve  113  and the motor shaft. Furthermore, the prior art rigid coupling also necessitates higher starting torque, greater pulsation of drive, pump, and pumped fluid, and increased vibration transmission between motor and pump head. Higher starting torque is disadvantageous for starting amperage, making the prior art less conducive for use in non-grid applications such as solar powered pumping stations. The high starting torque of the prior art also increases peak forces on the moving components, which accelerates wear and decreases MTBF. 
     In distinct contrast to the prior art brim, the present invention provides a motor mount  120  having a left mounting flange  121  and right mounting flange  122 . The particular number of mounting flanges is not critical to the present invention, though at least two are preferred to better accommodate dimensional tolerances or other mismatches that may arise. Motor mounting bolts  123  are used to rigidly and securely fasten motor mount  120  to a motor, and lock washers  124  or any other method of securing fasteners may be provided to ensure that motor mounting bolts  123  do not unintentionally loosen over time. 
     In the rare event that field service is required, and particularly in remote arctic locations, the service person may be working in extreme sub-zero conditions. In some prior art designs, this will require the service person to handle and precisely place small parts. This may be easily accomplished in the controlled environment of an office building or factory, but in extreme sub-zero conditions even the most manually dextrous persons will find the chore impossible. Most commonly in such a hostile environment, the service person will be wearing thick mittens to protect hands, and small parts simply cannot be manipulated. 
     In contrast, the preferred embodiment is designed so that pump head  100  may be removed as a single unit and replaced with another like pump head. This will only require the removal of the motor mounting bolts  123  and input and output fluid couplers that connect to input connector  162  and output  180  respectively, followed by sliding of motor connection sleeve  113  from the motor shaft, and then installation of the replacement pump head including sliding of motor connection sleeve  113  onto the motor shaft, and subsequent replacement or reinstallation of the removed motor mounting bolts and fluid couplers. This can all be done easily by a service person wearing mittens and outfitted with an allen wrench or the like. While this may seem at first blush to be minor, again, in extreme sub-zero conditions, preferred motor mount  120  can be critical. 
     Torsion sleeve  125  provides an outer rigid sleeve through which torsion bolt  127  will pass. Separating the two is a rubber or otherwise elastomeric torsion sleeve  128  which is configured to reduce vibration from passing through, and allowing peak impulses of torsional energy to be stored and later released. As may best be appreciated from  FIG. 9 , the head of torsion bolt  127  extends at least across a shoulder within elastomeric torsion sleeve  128 . In a contemplated alternative embodiment, the head of torsion bolt  127  may extend partially, but not completely, across the end of elastomeric torsion sleeve  128 . In either case, when torsion bolt  127  is tightened into coupling body  111 , this will cause elastomeric torsion sleeve  128  to compress longitudinally, and in turn expand radially. As may be appreciated then, prior to compression, elastomeric torsion sleeve  128  may fit easily within torsion sleeve  125 . However, when compressed by torsion bolt  127 , elastomeric torsion sleeve  128  will radially expand and compress against torsion sleeve  125 , thereby firming the connection between the associated mounting flange  121 ,  122  and coupling body  111 . 
     While a sleeve geometry is described and illustrated for elastomeric torsion sleeve  128 , it will be appreciated that other geometries that accomplish the intended isolation between torsion sleeve  125  and torsion bolt  127  are also contemplated herein. The elastomeric isolation means that peak rotational forces are dampened, while torsion sleeve  125  still functions as a torsion arm. Reducing peak rotational forces not only helps to increase Mean Time Between Failure (MTBF), it also reduces peak current draw of the motor, making the motor more suitable to use in solar powered and other applications sensitive to peak current draw. This also helps to reduce pulsation within the pumped fluid, by smoothing out the piston drive force. In the event of catastrophic failure of rubber torsion sleeve  128 , which is highly unlikely due to the fact that forces applied thereto are entirely compressive in nature, torsion bolt  127  will still be constrained by and within torsion sleeve  125 . This constrainment helps to ensure that pump head  100  will not be consequentially harmed or destroyed, even if rubber torsion sleeve  128  catastrophically fails. 
     An optional cap  126  may be provided to enclose torsion bolt  127 , thereby reducing the chance that a service person would mistakenly remove torsion bolts  127  rather than removing motor mounting bolts  123 , in the rare event that service is required. Once again, this may at first blush appear to be minor, but in extreme sub-zero conditions, this can be critical. 
       FIGS. 4-9  illustrate the internal fluid passages and piston operation in greater detail. Right piston housing  140  and left piston housing  141  each provide a central bore that defines cylinder  143  through which piston  144  travels in reciprocating motion. Manifold anchor bolts  142  are provided to secure manifold  160  to each of the piston housings  140 ,  141 . As already described herein above with reference to  FIG. 9 , a recess or saddle  145  in piston  144  serves to engage with cam drive bearing  119  and transmit rotary motion from a motor shaft through to piston  144 . Continuing with  FIG. 9 , when piston  144  reciprocates within cylinder  143 , at each end thereof piston housings  140 ,  141  define chambers that are alternately being compressed and being vacuumed. To maintain this alternating compression and vacuum, a pair of high pressure piston outer seals  146 , also visible in  FIG. 9 , are provided. 
     When these high pressure piston outer seals  146  are functioning perfectly, there will be no leakage of the pumped fluid past. However, over time even tiny amounts of leakage may tend to accumulate. Further, and with proper design and construction only with very great aging of components, piston outer seals  146  may begin to or completely fail. In such instances, it is desirable to avoid any accumulation of fluids. 
     A pair of piston inner seals  147  are provided that together with high pressure piston outer seals  146  define a chamber that collects any fluid bypassing high pressure piston outer seals  146 . This fluid is then conducted through piston bypass drain bore  148 , visible in  FIG. 9 , to bypass passages  152 ,  153 . Turning now to  FIG. 5 , one of bypass passages  152 ,  153  connects with bypass bore  154  in manifold  160 , which in turn ultimately connects with input bore  163  and from there to the input supply line and fluid source reservoir. As visible in  FIG. 5 , bypass passage  152  within right piston housing  140  connects to bypass bore  154 , and bypass passage  153  terminates at the face of manifold  160 . Noteworthy here is that right and left piston housings  140 ,  141  are fabricated with identical geometry, and are simply rotated through a half-circle relative to each other at the time of installation. This means that while bypass passage  152  within right piston housing  140  connects to bypass bore  154 , and bypass passage  153  terminates, in left piston housing  141  bypass passage  153  connects to bypass bore  154 , and bypass passage  152  terminates. 
     Turning to  FIG. 4 , input check valve assembly  150  couples piston  144  to input to piston housing bore  164 , which in turn couples to input bore  163 . Input check valve assembly  150  is a one-way check valve, assuring that during movement of piston  144  in a first direction (away as viewed in  FIG. 4 ), fluid is drawn into cylinder  143 . However, when piston  144  changes direction and moves towards the reader in  FIG. 4 , input check valve assembly  150  will close preventing fluid from undesirably being pumped back into the inlet bore  163 . Instead, output check valve assembly  151  will now open, allowing fluid within cylinder  143  to be pumped through output check valve assembly  151  and onward through the output to piston housing bore  166  and then to output bore  165 . The combination of piston  144  with good high pressure piston outer and inner seals  146 ,  147 , along with good high pressure input and output check valve assemblies  150 ,  151  ensures generation of adequate vacuum on the inlet side to be both self priming for nearly all materials, and to be compatible through a wide range of viscosities as well. This in turn helps to ensure that the preferred embodiment will not require human intervention to start fluid flow, even through very diverse ambient temperatures, and with a very wide range of fluid chemical compositions. 
     Manifold  160  supports piston housings  140 ,  141 , through manifold anchor bolts  142  that pass through the piston housings and secure into manifold  160 . In turn, anchor bolts  161  couple manifold  160  and to motor coupler  110 , and in the process sandwich piston housings  140 ,  141  between. 
     Manifold  160  is provided with an input connector  162 , which as illustrated comprises a female threaded connector. Nevertheless, any suitable fluid connector may be used, and the female threaded connector is purely exemplary. Input connector  162  is in fluid communication with input bore  163 , thereby ensuring that fluid arriving from a fluid reservoir through input connector  162  will be passed through to input bore  163 , then to the input to piston housing bore  164 , and then alternately into distal ends of cylinder  143 . 
     A plurality of caps  167  may be used to terminate the main bores in manifold  160 , which are the input bore  163  and output bore  165 , leaving only a single input connector  162  supplying fluid into pump head  100 . As long as input bore  163  runs essentially the entire length of manifold  160 , then input supply fluid will be delivered to both right piston housing  140  and left piston housing  141 , adjacent to opposed ends of piston  144 . This allows pump head  100  to operate as a double acting simplex positive displacement pump, which means that pump head  100  will be pumping in both directions of piston movement, for the entire motor shaft rotation. Some examples of double acting simplex positive displacement plunger pumps are described in U.S. Pat. Nos. 4,978,284, 5,173,039, 5,183,396, 6,257,843 and 6,527,524 owned by the present assignee, the disclosures of which are incorporated herein by reference. 
     Fittings, such as hose fittings, may be coupled to the inlet and outlet bores of the manifold as desired to couple fluid inlet and fluid outlet lines (e.g., hoses, pipes, etc.) to pump head  100 . Such fittings may include elbows, tees, reducers, couplers, caps, ball valves, stopcock valves, or any other suitable or desirable coupling. Further, various instrumentation or other apparatus may also optionally be coupled into pump head  100  either through input connector  162  and output  180 , or at any other suitable location or access point. As but one non-limiting but illustrative example, one or more of caps  167  may be removed to affix instrumentation such as pressure gauges or any other suitable or desired instrumentation. 
     As illustrated in  FIG. 7 , output bore  165  which runs transverse to the motor shaft longitudinal axis is in free fluid communication with output axial bore  168 , which runs parallel to the motor shaft longitudinal axis. Fluid traveling out of pump head  100  through output  180  will first pass through back flow valve  182 , which as the name suggests will simply ensure that fluid only passes out of pump head  100  at output  180 , and not back in. An o-ring seal  184  or the like may be provided to provide a leak-free seal between the output nipple and manifold  160 . 
     While for normal operation, the aforementioned output is adequate, there may be unforeseeable circumstances where a blockage develops in plumbing external to pump head  100 , such as for exemplary purposes a natural gas pipeline, or where blockage develops in the plumbing coupling piston  144  to the external plumbing, such as through failure of back flow valve  182  to open. In such cases, the continued reciprocation of piston  144  will quickly increase pressure from piston  144  through the output bore  165  and to the point of blockage to dangerous levels that can lead to ruptures in the plumbing, or permanent damage to pump head  100  or to a motor such as motor  10  illustrate in  FIG. 10 . To prevent or greatly reduce the likelihood of such damage, an output to over-pressure bore  169  couples output axial bore  168  to over-pressure release valve assembly  170 . Over-pressure valve assembly  170  is configured to stay closed until a predetermined maximum pressure is exceeded. For exemplary purposes, this pressure threshold may be selected to ensure that at no time will the pump head exceed a maximum safe pressure. Over-pressure valve assembly  170  comprises an over-pressure release ball  171 , over-pressure release spring  172 , and over-pressure release end stop  173 . When the pressure threshold of over-pressure valve assembly  170  is exceeded, then over-pressure release ball  171  will be pushed with sufficient force to overcome the opposing force provided by over-pressure release spring  172 , and thereby unseat over-pressure release ball  171 . This permits pressurized fluid within output axial bore  168  to pass through over-pressure valve assembly  170  and within internal bore  175 , thereby lowering the pressure within axial bore  168  to an acceptable level. An over-pressure release end stop  173  is provided that maintains the compression of over-pressure release spring  172 . In a preferred embodiment, over-pressure release end stop  173  is at a fixed distance from over-pressure release ball  171 , and therefore sets a fixed activation pressure for opening over-pressure valve assembly  170 . Nevertheless, in an alternative embodiment contemplated herein, over-pressure release end stop  173  may be adjustable to be either closer to or farther from over-pressure release ball  171 , in which case the activation pressure for opening over-pressure valve assembly  170  may thereby also be adjustable. 
     An o-ring seal  174  may be provided to seal an overflow output nipple  190  to manifold  160 . Most preferably, overflow output nipple  190  will be in fluid communication with at least one of the fluid reservoir, fluid input line, input connector  162 , or input bore  163 . This may, for exemplary and non-limiting purpose, be achieved through external tubes and fittings that affix to overflow output nipple  190 . As may be apparent then, if there is a blockage preventing fluid from being pumped through output  180 , piston  144  will simply draw fluid from the fluid reservoir, and return the fluid back to the reservoir via overflow output nipple  190 . 
       FIG. 10  illustrates preferred embodiment pump head  100  in further combination with a prior art motor  10 . While an electric motor is illustrated and preferred, the present invention is not solely limited thereto, and other types of motors may be used in alternative embodiments. 
     Motor  10  may, for exemplary and non-limiting purposes, be provided with some type of motor mounting bracket, such as motor mounting bracket  12  illustrated. Pump head  100  is securely affixed to motor  10  by sliding motor connection sleeve  113  onto the motor shaft (not visible), and then affixing motor mounting bolts  123  into motor  10 , for exemplary purposes such as at threaded mounting holes provided in the motor collar. As may be apparent, the exact number, spacing, size, and coupler type of motor mounting bolts  123  will vary depending upon the type of coupler provided with motor  10 . 
     As visible in  FIG. 9 , motor connection sleeve  113  may optionally have one or more threaded holes formed therein to accommodate a set screw. If this set screw hole is aligned with access hole  112  visible for example in  FIG. 7 , or a similar optional access hole such as illustrated in  FIG. 9 , then an installer may also secure motor connection sleeve  113  to the motor shaft using such as set screw. 
     In an alternative embodiment contemplated herein, a clutch or transmission maybe connected between electric motor  10  and motor connection sleeve  113  to control or alter the transmission of power from electric motor  10  into pump head  100 . As used herein, a transmission will be understood to be an assembly of associated parts by which rotational power is converted from a first rotational speed or rate at the power input of the transmission to a second possibly different rotational speed or rate at the power output of the transmission. As used herein the terms “speed” or “rate” may refer to a fixed speed or rate or a variable speed or rate unless the content clearly dictates otherwise. 
     In some embodiments, the transmission may include one or more chains and sprockets, one or more belts and pulleys, one or more gears, etc. used to alter the output speed from the input speed. In some embodiments, the transmission may be a speed reduction, such as a gear reduction including one or more gears reducing the rotational rate of the output shaft from the rotational rate of the input shaft, while in other embodiments the transmission may be a speed accelerator, such as a gear accelerator including one or more gears increasing the rotational rate of the output shaft from the rotational rate of the input shaft. 
     In addition to the provision of a transmission, or alternatively thereto, in some embodiments of the invention, motor  10  may be configured to run at more than one speed. The speed may for exemplary purpose be varied by a speed controller or switch. 
     Pump head  100  may be manufactured from a variety of materials, including metals, resins and plastics, ceramics, or even combinations or composites of the above. The specific material used may vary, though special benefits are attainable if several important factors are taken into consideration. First, anticipated chemical exposure associated with a particular application may dictate material choice. There are many chemicals that are corrosive to ordinary carbon steel, and in such instances, various ceramics and stainless steel compositions are preferred. Additionally, there are a variety of polymers that are also relatively chemically inert. However, few polymers have the combination of strength and temperature resistance that most of the components of the present invention demand for most applications. One notable exception is the material used for the various seals described herein above, where there are several known polymers and natural and synthetic rubber compositions that might be selected, again depending upon the specific requirements of an application. In addition to chemical resistance, temperature resistance, strength, abrasion resistance, and other known factors will be considered. As may be apparent then, it is preferable that all materials are sufficiently tough and durable to not fracture, even when great forces are applied thereto. In the case of preferred embodiment pup head  100 , a preferred material for the majority of components is stainless steel, which offers great strength and excellent corrosion resistance against a wide variety of chemicals. While stainless steel might be suitable for some applications as the material used to fabricate piston  144 , various ceramics known in the pump industry may be preferable. Consequently, for application to extreme conditions and a wide range of chemical compositions, particularly such as may be encountered in the demanding application of chemical injection pump connected to a natural gas pipeline, a combination of ceramic piston, chemically inert polymer seals, and the vast majority of remaining components fabricated from stainless steel is preferable. Nevertheless, those skilled in the art will readily understand the requirements in light of the present disclosure for a given application, and so will be able to select a suitable set of compositions. 
     While the foregoing details what is felt to be the preferred embodiment of the invention and many alternatives thereto, no material limitations to the scope of the claimed invention are intended. Further, features and design alternatives that would be obvious to one of ordinary skill in the art are considered to be incorporated herein. The scope of the invention is set forth and particularly described in the claims herein below.