FLUID EJECTION APPARATUS FOR DISCREET PACKET TRANSFER OF FLUID TECHNICAL FIELD [0001] The present disclosure relates to a fluid ejection apparatus and more specifically to a fluid ejection apparatus for discreet packet transfer of a fluid. BACKGROUND [0002] $n inkjet printing apparatus utilizes a fluid such as an ink. To print the ink to a media, a pump is utilized to move ink or other fluid to a print head to print to the media. Ensuring proper movement of the ink through the pump to the media helps to provide a better user experience with the inkjet printing apparatus. If the pump were to allow ink to leak due to changes in atmospheric pressure or due to changes in the orientation of the printer the user experiences would be less than favorable. BRIEF DESCRIPTION OF THE DRAWINGS [0003] FIG.1 is a schematic view of a fluid ejection apparatus; [0004] FIGS.2A and 2B are illustrative examples of a pump for a fluid ejection apparatus; [0005] FIG.3 is an exploded perspective view of the pump of FIG.2; [0006] FIGS.4A-4C are schematic views of the rocker-spring engaging with the diaphragm and pump housing body of the present disclosure; [0007] FIG.5 is a sectioned perspective view of the example pump with one diaphragm in a first position; [0008] FIG.6 is a sectioned perspective view of the pump with the diaphragm in a second position differing from FIG.5; [0009] FIG.7 is a schematic view of an embodiment of a cam according to the present disclosure; [0010] FIG.8 is a bottom view of a fluid interconnect plate, which shows the fluid passages and fluid chambers; [0011] FIGS.9a-9c are schematic views of the sequencing of the fluid chambers in the fluid interconnect; and [0012] FIG.10 is a sequential view of the three diaphragms in operation during a pump cycle. DETAILED DESCRIPTION [0013] Referring now to FIGS.1-10, examples of a progressive pump for a fluid ejection apparatus are shown throughout this disclosure. The examples provide discrete fluid packet movement of the fluid through various positions within the pump between an inlet and an outlet. A fluid packet is a controlled volume of fluid which is being moved from a first position to a second position within a pump. A cam, which may be radially symmetrical, is provided which may be reversed so that the pump may operate in either of two directions. The fluid chambers within the pump are opened and closed simultaneously in pairs with one pair moving fluid at a time. The chambers in the fluid moving pair can either be fluidically connect to the fluid interconnects to move packets of fluid in and out of the pump or to each other to pass a packet of fluid between fluid chambers. Other chambers outside the moving pair are closed for fluid movement, therefore the fluid transfer in, out, and within the pump is controlled and is a discrete fluid packet. Moreover, the fluidic isolation between the inlet and outlet of the pump allow for opposition to large positive and negative heads both while pumping and when the pump is stationary. [0014] Referring now to FIG.1, a schematic view of a fluid ejection apparatus 10 is depicted. The depicted example provides an inkjet printing apparatus, which utilizes a fluid such as, for non-limiting example, an ink. To print the ink to a media, a pump 12 is utilized to move ink or other fluid to a print head 14 to print to the media. In the depicted example, the fluid ejection apparatus 10 schematically depicts the pump 12 fluidly connected to the print head 14, which directs the ink on to a media, such as paper. While an inkjet printer is shown in the instant example, other fluid source and destination structures or mechanisms may be embodied which utilize such pump to move a fluid. Accordingly, the description of the ink jet printing apparatus is merely an example and not to be considered limiting. [0015] Referring now to FIGS.2A and 2B, perspective views of an example pump 12 is depicted. The pump 12 comprises a pump housing body 16 with a plurality of pivot brackets 18. The pump 12 further comprises a fluid interconnect plate 20 having a fluid inlet 22, a fluid outlet 24, and a plurality of fluid passages (76 in FIG.8) connecting the fluid inlet 22 to the fluid outlet 24. The pump 12 also comprises a timing mechanism 26 that allows for the movement of discreet fluid packets through the pump 12. The timing mechanism 26 comprises in some examples a cam 28 and a plurality of rocker-springs 30. These structures allow for timed movement of diaphragms (50 in FIG.3) within the pump 12. [0016] The cam 28 rotates to drive motion of a plurality of the rocker-springs 30 according to some examples. For example, movement of the cam 28 may cause a raising and lowering of arms of the rocker-springs 30. The cam 28 may be rotated by a motor, transmission, or a combination thereof. The cam 28 has a center axle (40 in FIG.3) and guide walls 32 surrounding the center axle to interact with the plurality of rocker-springs 30. The cam 28 is connected to the plurality of rocker-springs 30, where the guide walls 32 have actuator surfaces (48 in FIG.7) that define an eccentric travel path around the center axle. A first end 34 of a first arm 36 of each of the plurality of rocker-springs 30 engages at least one of the actuator surfaces to cause the plurality of rocker-springs 30 to pivot at a pivot shaft 38 as the first end 34 of the first arm 36 of each of the plurality of rocker-springs 30 follows the eccentric travel path of the actuator surfaces. As the plurality of rocker-springs 30 pivot at the pivot shaft 38 there is a raising and lowering of the arms of the rocker-springs 30 that causes a sequentially change in a volume of a plurality of fluid chambers to move a discreet packet of fluid entering the fluid inlet 22 unidirectionally through the plurality of fluid passages to the fluid outlet 24. The rocker- springs 30 drive movement of diaphragms within the pump 12 to displace volume and movement of the discrete fluid packets within the fluid interconnect plate 20. The fluid packets are controlled amounts of fluid, for example ink. In the instant example, each fluid packet may move from one fluid chamber to a second fluid chamber, to a third fluid chamber before exiting the pump 12. The fluid packets are discreet because fluid from one chamber moves to another due to the sequenced movement of pairs of diaphragms (FIG.3) and the opening and closing of valves within the pump 12. [0017] Referring now to FIG.3, an exploded perspective view of the pump 12 is depicted. Starting at the bottom of the figure, the cam 28 and rocker-springs 30 are shown. These structures at least partially define the timing mechanism 26. The cam 28 has a center axle 40 and the guide walls 32 surrounding the center axle 40 to interact with the plurality of rocker-springs 30. Each of the plurality of rocker-springs 30 includes the first arm 36, a second arm 42 and the pivot shaft 38. The first arm 36 includes the first end 34 and a stem retainer portion 44. The second arm 42 includes a second end 46 of the rocker-spring 30. The pivot shaft 38 is positioned between the first arm 36 and the second arm 42, where the pivot shaft 38 is positioned in a corresponding pivot bracket 18 of the plurality of pivot brackets 18 of the pump housing body 16. [0018] As noted, the cam 28 includes the guide walls 32 surrounding the center axle 40, where the guide walls 32 have an inner and an outer actuator surface 48 (the actuator surfaces) that define an eccentric travel path around the center axle 40. The cam 28 is connected to the plurality of rocker-springs 30 such that the first end 34 of the first arm 36 of each of the plurality of rocker-springs 30 engages the actuator surfaces 48 to cause the plurality of rocker-springs 30 to pivot at the pivot shaft 38 as the first end 34 of the first arm 36 of each of the plurality of rocker-springs 30 follows the eccentric travel path of the actuator surfaces 48. This action sequentially changes a volume of the plurality of fluid chambers, as discussed herein, to move a discreet packet of fluid entering the fluid inlet 22 unidirectionally through the plurality of fluid passages to the fluid outlet 24. [0019] The pump 12 further includes a plurality of diaphragms 50 disposed in the pump housing body 16. The pump housing body 16 may be of various shapes and according to one example, the pump housing body 16 may be formed with a side wall 52 and a plurality of chambers 54 within the side wall 52. The chambers 54 may be of various shapes and in some examples may be generally cylindrical in shape, as depicted, to receive either or both of the rocker-springs 30 and the diaphragms 50. However, the shape of the chambers 54 may vary in such a manner as to receive a similarly shaped diaphragm and or the rocker-spring. In some examples however, the shapes may differ and the relationship of the shape of a chamber 54 and the diaphragm 50 is not limiting. [0020] Each of the plurality of diaphragms 50 is disposed in the pump housing body 16 and on the fluid interconnect plate 20 to provide a plurality of fluid chambers each having a volume. The plurality of diaphragms 50 each further include a stem 56 with a link member 58. The diaphragms 50 may be formed of various elastomeric materials. The diaphragms 50 are elastic and may vary in shape with movement of the stems 56. The diaphragms 50 may therefore change volume with movement. In the instant example, there are three diaphragms 50. [0021] A portion of the stem 56 of each of the respective diaphragm 50 seats in the stem retainer 44 of the first arm 36, while the second end 46 of the second arm 42 couples to the link member 58. This configuration allows the diaphragms 50 to flex with movement of the stems 52 and rocker-springs 30 to change the volume of a fluid chamber formed between the fluid interconnect plate 20 and each diaphragm 50. For example, as the first end 34 of the first arm 36 of each of the plurality of rocker-springs 30 follows the eccentric travel path of the actuator surfaces 48 the rocker-spring 30 pivots at the pivot shaft 38 to move the second arm 42 coupled to the portion of the stem 56 and the second end 46 coupled to the link member 58 and thereby the stem 56 of the diaphragm 50 to change the volume of the fluid chamber. [0022] Referring to FIGS.4A-4C, there is shown an example of the portion of the stem 56 of the diaphragm 50 seated in the stem retainer 44 of the first arm 36, while the second end 46 of the second arm 42 couples to the link member 58. As illustrated in FIG. 4A, with the plurality of diaphragms 50 disposed in the pump housing body 16, the stem 56 and the link member 58 are available for attaching to the rocker-spring 30. The second end 46 of the second arm 42 of the rocker-spring 30 is lowered down over the diaphragm 50 so that a portion of the stem 56 feeds into stem retainer 44 of the first arm 36. As illustrated in FIG.4B, the second end 46 of the second arm 42 is then positioned to engage the second end 46 of the second arm 42 with the link member 58 of the diaphragm 50. As illustrated, the second end 46 of the second arm 42 can have a split fork configuration that engages and holds the link member 58 that in this embodiment has a ball configuration. In FIG.4C, the rocker-spring 30 is then rotated and moved to position the pivot shaft 38 of the rocker-spring 30 in a pivot socket 60 in the pivot bracket 18 of the pump housing body 16. [0023] Referring to Figs.2A and 3, the pump 12 further includes a crown retainer 62 that joins the pump housing body 16, the plurality of diaphragms 50 and the fluid interconnect plate 20. Each of the pump housing body 16, fluid interconnect plate 20, cam 28, rocker-spring 30 and crown retainer 62 can be formed of a polymeric material using, for example, injection molding techniques. Examples of suitable polymeric materials include, but are not limited to, polypropylene, copolymers of polypropylene, polyethylene, copolymers of polyethylene, polycarbonates, and acrylonitrile butadiene styrene, among others. [0024] Referring now to FIG.5, there is shown a sectioned perspective view of pump 12 is depicted. The figure reveals the operation of the timing mechanism 26, cam 28 and the subsequent movement of the diaphragm stems 56 and diaphragms 50. The timing mechanism 26 includes the cam 28 near the top of the assembly and the second end 46 of the second arm 42 of rocker-spring 30-1 on the right-hand side of the depicted example is at a high point relative the second ends 46 of the other rocker-springs 30. For example, moving left, a first arm 36 of a second rocker-spring 30-2 is shown at a slightly lower elevation than the first arm 36 at the far right-hand side. A third first arm 36 of a third rocker spring may be located at its lowest elevation of the three. [0025] In the section view, and with reference to the right-hand side of the assembly, the first end 34 of the rocker-spring 30-1 is shown engaging the actuator surfaces 48 of the cam 28 that pivots the rocker-spring 30-1 at the pivot shaft 38 to position second end 46 of the rocker- spring 30-1 at a high point relative the fluid interconnect plate 20. The sectioned rocker-spring 30-1 also reveals the positioning of the diaphragm 50 and the stem 56 within the chamber 54 of the pump housing body 16. In the depicted example, the diaphragm 50 is flexed away from the fluid interconnect plate 20 and sealing surfaces 64 thereon. The fluid chamber 66 is shown defined between the diaphragm 50 and the fluid interconnect plate 20. The rocker-spring 30 depicted in the section view is lifted to a high point in its cycle of upward and downward movement. As a result of the upward positioning, the stem 56 is pulled upwardly and the diaphragm 50 is flexed to maximize the volume of the fluid chamber 66 formed by the diaphragm 50 and fluid interconnect plate 20. Alternatively, the other rocker-springs 30 are in more downward positions and accordingly, those diaphragms 50 (not shown) are flexed downwardly and may be sealed against the sealing surfaces 64. [0026] With reference now to FIG.6, an alternate section view is depicted showing a differing position of the diaphragm 50 shown in FIG.5. The rocker-spring 30 is depicted in the lowest position with the top inner surface of the diaphragm 50 resting on the valve sealing surface 64. Once the rocker-spring 30 and diaphragm 50 have reached this position the cam 28 continues to cause the rocker-spring 30 to push downwardly on the stem 56 adding additional force to seal the diaphragm 50 to the valve sealing surface 64 in the fluid interconnect plate 20. This overtravel by the rocker-spring 30 beyond the point that the underside of the diaphragm 50 contacts the valve sealing surface 64 on the fluid interconnect plate 20 causes the rocker-spring 30 to flex. This distortion of the rocker-spring 30 adds a closing force to the isolation valves, enabling each chamber to hold back higher pressures. [0027] During operation, the actuator surfaces 48 of the cam 28 is formed so that a leading diaphragm 50 opens at the same time as a trailing diaphragm 50 closes, which allows for the sequential movement of fluid. The terms leading and trailing are used from the perspective of the rotational direction of the cam and the direction of flow of the fluid. That is, leading refers to a location the fluid is filling and trailing refers to a location that the fluid is exiting. The fluid movement is described as movement discrete packets because a finite amount of fluid of one fluid chamber 66 and diaphragm 50 can move at a time. Thus, the controlled movement of the fluid occurs in a sequential nature. [0028] With reference to both FIGS.5 and 6, and to summarize, maximum volume is achieved by pulling the stem 56 away from the fluid interconnect plate 20 which un-rolls and straightens the sides of the cup and moves the roof of the diaphragm 50 further away from the fluid interconnect plate 20. Alternatively, volume in the fluid chamber 66 is reduced by moving the stem 56 of the diaphragm 50 towards the fluid interconnect plate 20. This causes the sides of the diaphragm 50 to roll over and the inner roof of the diaphragm to move closer to the fluid interconnect plate 20 reducing the volume that can be contained within. [0029] Referring now to FIG.7 there is shown an embodiment of the cam 28 with the guide walls 32 and the actuator surfaces 48. As discussed herein, the actuator surfaces 48 define an eccentric travel path 68 around the center axle 40 that rotates to open a leading fluid chamber of the plurality of fluid chambers and to close a trailing fluid chamber of the plurality of chambers simultaneously with movement of corresponding pairs of the diaphragms. This movement of the actuator surfaces 48 causes the discreet packet of fluid to move between the leading and trailing fluid chambers. As this occurs, a third fluid chamber is in a closed state, thereby fluidically isolating the fluid inlet 22 and the fluid outlet 24 of the fluid interconnect plate 20. [0030] The first end of the first arms of each of the plurality of rocker-springs are positioned in the eccentric travel path 68, where they engages the actuator surfaces 48 to cause the plurality of rocker-springs to pivot at the pivot shaft as the first end of the first arm of each of the plurality of rocker-springs follows the eccentric travel path 68 of the actuator surfaces 48. As described herein, the plurality of fluid chambers sequentially open and close as the first end of the first arm of each of the plurality of rocker-springs follows the eccentric travel path 68 of the actuator surfaces 48 to move the discreet packet of fluid entering the fluid inlet unidirectionally through the plurality of fluid passages to the fluid outlet. [0031] As illustrated, the guide walls 32 of the cam 28 can be divided into equal sections that provide for sequentially changes in the volume of the fluid chambers to move the discreet packet of fluid entering the fluid inlet unidirectionally through the plurality of fluid passages to the fluid outlet. For example, starting at point 70 in the eccentric travel path 68 and moving the path in a clockwise direction the first end of the first arm of a rocker-spring will be in its closest relative position to the center axle 40 of the cam 28. In this position, the inner actuator surface 48 positions the rocker-spring such that it pushes the stem of the diaphragm towards the fluid interconnect plate. This causes the volume in the fluid chamber to be reduced to the point where the rocker-spring is in the lowest position with the top inner surface of the diaphragm resting on the valve sealing surface to seal the diaphragm to the valve sealing surface in the fluid interconnect plate. In other words, this inner portion of the actuator surface 48 of the guide walls 32 positions and provides compressive force to the rocker-spring to minimize the volume of the diaphragm to the point where the diaphragm contacts the sealing surface to make an effective seal. [0032] As point 72 in the eccentric travel path 68 is reached, the first end of the first arm of the rocker spring transitions to the outer actuator surface 48 which begins to move the first end of the first arm of the rocker-spring away from the center axle 40 of the cam 28 to unseal the diaphragm from the sealing surface, thereby beginning to open the diaphragm and increase the volume of the fluid chamber. The inner actuator surface 48 continues to move the first end of the first arm of the rocker-spring away from the center axle 40 of the cam 28, thereby continuing to increase the volume of the fluid chamber towards its maximum volume, which is achieved at point 74 in the eccentric travel path 68. After point 74, the first end of the first arm of the rocker spring transitions back to the outer actuator surface 48 and begins to move the first end of the first arm of the rocker-spring back towards the center axle 40 of the cam 28, thereby pushing the stem of the diaphragm towards the fluid interconnect plate. This action reduces the volume in the fluid chamber until the rocker-spring reaches its lowest position again at point 70, where at point 70 the top inner surface of the diaphragm rests on the valve sealing surface to seal the diaphragm to the valve sealing surface in the fluid interconnect plate. [0033] So, as discussed, the timing of motion and fluid flow is controlled by the cam 28. In addition to controlling the timing of motion and the fluid flow, the cam 28 can also be used to control the volume of the fluid packet moved via the pump 12. For example, in one embodiment, given the three fluid chambers 66, the guide walls 32 of the cam 28 can be divided into three equal 120 degree sections. In this configuration, one section positions the actuator surfaces closest to the center axle, which as discussed herein positions the rocker-spring 30 to hold a diaphragm 50 at the minimum-volume or a valve closed position for the entire 120 degrees. The next two 120 degree sections form transitions or ramps that start and rise symmetrically to position the actuator surfaces 48 at the furthest position from the center axle 40 of the cam 28, the diaphragm open point. This symmetrical set of ramps causes a set of two chambers to change volume simultaneously with the leading chamber in the set increasing in volume (opening) to accept fluid from the trailing chamber which decreases in volume (closes). The trailing chamber is left in the minimum volume, valve closed position and the chamber pairing advances, so the current leading chamber becomes the trailing chamber in the next chamber pairing. This advancing chamber pairing sequences through all sets of chambers in the pump head before starting the sequence over. [0034] FIG.7 provides for another embodiment in which for the given three fluid chambers 66 the guide walls 32 of the cam 28 can be divided into three equal 100 degree sections, with a 20 degree dwell section linking each subsequent 100 degree section. As discussed herein, the 20 degree dwell section linking each subsequent 100 degree section provide a redundancy feature of the cam 28, where sequential pairs of the fluid chambers 66 are closed, thereby each forming an isolation valve, for any given 20 degree dwell section, while a third fluid chamber 66 remains open. So, as provided by the cam 28 of FIG. 7, sequential pairs of the fluid chambers 66 will both be in a closed state for 20 degrees of rotation of the eccentric travel path 68 of the actuator surfaces 48 relative to the first end of the each of the first arm of the plurality of rocker-springs. As a result, there will be three 20 degree valve pairing, as seen in FIG.7, in which sequential pairs of the three fluid chambers will be in a closed or sealed state while the third of the fluid chambers is in the open state for the 20 degree dwell section. FIG. 7 also illustrates an embodiment in which the discreet packet of fluid is fully contained in a given fluid chamber 66 of the plurality of fluid chambers 66 with 100 degrees of rotation of the eccentric travel path 68 of the actuator surfaces 48 relative to the first end of the each of the first arm of the plurality of rocker-springs. For the present embodiment, the discreet packet of fluid will then be fully contained in one of the plurality of fluid chambers 66 when a sequential pair of the plurality of fluid chambers 66 are both in the closed state. [0035] With reference now to FIG.8, a bottom view of the fluid interconnect plate 20 is depicted. In this view, the fluid interconnect plate 20 is shown having three fluid chambers 66, each corresponding to one of the diaphragms 50. Extending though the fluid interconnect plate 20 are plurality of fluid passages 76 connecting the fluid inlet 22 to the fluid outlet 24. The plurality of fluid passages 76 of the fluid interconnect plate 20 include for each fluid chamber 66 an intra-chamber inlet 78 and an intra-chamber outlet 80. As illustrated, the intra-chamber outlet 80 of a first fluid chamber 66 of the plurality of fluid chambers fluidly connects via the fluid passages 76 to the intra-chamber inlet 78 of a second fluid chamber 66 subsequent to the first fluid chamber 66 of the plurality of fluid chambers. In addition, the intra-chamber inlet 78 for each fluid chamber 66 is within an area 82 defined by the sealing surface 64 on the fluid interconnect plate 20. In an additional embodiment, the intra-chamber inlet 78 for each fluid chamber 66 can be outside the area 82 defined by the sealing surface 64 on the fluid interconnect plate 20, as illustrated in FIG.8. [0036] For the various embodiments, the fluid passages 76 direct fluid in and out of each fluid chamber 66. The intra-chamber inlets 78 are located at the center of each fluid chamber 66 so that flow can be interrupted by the isolation valve formed by diaphragm 50 and valve sealing surface 64. The intra-chamber outlet 80 directs fluid to each chamber 66 outside of the valve sealing surface 64. The fluid interconnect plate 20 also include the fluid inlet 22 and the fluid outlet 24, which are used to connect the pump to a source and destination for fluid being conveyed. [0037] The fluid passages 76 of the interconnect plate 20 direct the movement of fluid through the chambers 66 of the pump in a daisy-chain fashion. For example, the fluid passages 76 direct fluid coming from the inlet 22 into a first chamber 66 to a second fluid chamber 66, out the second fluid chamber 66 and into the third fluid chamber 66, and out the outlet 24 in the third chamber 66. In this example the fluid passages 76 are formed from, but not limited to, channels formed in the interconnect plate 20. In addition, in this example the fluid passage 76 connects the non-valved intra-chamber 80 outlet to the valved intra-chamber inlet 78 in the next fluid chamber 66. The fluid passages 76, however, can connect leading and following fluid chambers 66 in any order. In addition, the relative positions of the fluid inlet 22 and the fluid outlet 24 seen in FIG.8 can be switched if desired. In a similar fashion, the relative positions of the intra-chamber inlets 78 and intra-chamber outlets 80 may also be switched if desired. These are non-limiting because the pump may work in bi-directional manner. [0038] As discussed herein, each fluid chamber 66 can form an isolation valve when the diaphragm 50 and the sealing surface 64 leading to the next fluid chamber 66 in the series closes when the diaphragm 50 is in the lowest volume position. The valve may comprise of the inner flat roof surface of the diaphragm 50 that mates and seals to the upper edge of the valve sealing surface 64 detail surrounding the intra-chamber inlet 78 and, as seen in FIG.8, the fluid inlet 22 in the fluid interconnect plate 20 for each respective fluid chamber 66. The valve closing force is supplied by the rocker-spring 30, as discussed herein, where the actuator surfaces 48 of the cam 28 can provide the inner flat roof surface of the diaphragm 50, if desired, an amount of over- travel towards the fluid interconnect plate 20. The over-travel can be beyond the point where the diaphragm 50 touches the surface of the valve sealing surface 64. The over-travel drives the diaphragm 50 onto the valve sealing surface 64 with a controlled force. As the cam 28 continues to turn past the downward dwell period, the actuator surfaces 48 begin to move away from the center axle 40 of the cam 28, which causes the rocker-spring 30 to lift diaphragm 50 and open the isolation valve allowing fluid to flow into the chamber 66. When a fluid chamber 66 is fully open there is a large space between diaphragm 50 and valve sealing surface 64 that is in the flow of fluid in and out of the fluid chamber 66, which provides a self-cleaning function to the valve seat. There may be at least one or two fluid chambers 66 closed throughout the pump cycle which automatically isolates the fluid inlet 22 and the fluid outlet 24 regardless of whether the pump 12 is running or is stopped. This simplifies the design in that an encoder is not needed on the pump or pump drive to ensure that the pump is stopped in a position where the isolation valves are closed. [0039] Referring now to FIGS.9a-9c, three sequence schematic views are shown to provide teaching of the sequencing of the fluid chambers 66 of the fluid interconnect plate 20 and the movement of packets of fluid through the pump 12. Each of the fluid chambers 66 is provided a subscript for purpose of clarification of description. In each sequence segment view, one pair of fluid chambers 66 is circled with a broken line to indicate the pair of chambers 66 that are changing volume at that moment in the sequence. In addition, the pair of encircled chambers 66 contain up-down arrows to indicate which of the pair of chamber volumes is increasing (up arrow) and which is decreasing (down arrow). Further the third chamber 66 outside of the broken line has a horizontal bar which indicates that it is not changing but is in a closed or a dwell position. As previously described, when a chamber 66 is in dwell, the isolation valve associated with that chamber, is closed so no fluid can pass through that chamber 66. Also, the semi-circular arrow represents the rotational direction in this example of the cam 28. With reference first to FIG. 9a, the sequence shows what occurs during a first segment of the rotation of the cam 28. In the figure, the first fluid chamber 661 and third fluid chamber 663 are circled indicating that the internal volume of these two chambers 66 are changing. As previously described, one pair of fluid chambers 66 are transferring fluid at one time with the leading chamber increasing in volume and the trailing chamber simultaneously decreasing in volume. In FIG.9a the isolation valve 48 in fluid chamber 662 is closed preventing fluid from moving between fluid chambers 661 and 663. This causes a packet of fluid to be drawn in from the fluid inlet (22 in FIG. 2) into fluid chamber 661 and a separate packet of fluid to be expelled out of fluid outlet (24 in FIG.2) from fluid chamber 663. In this starting segment of the pump cycle none of the fluid chambers 66 are fluidically connected to another but rather the first and last chambers are fluidically connected to the fluid inlet and the fluid outlet. [0040] With reference to FIG. 9b, the second segment of the pump cycle, the leading fluid chamber 661 is reducing in volume while the following fluid chamber 662 is simultaneously increasing in volume causing a packet of fluid to be transferred from fluid chamber 661 into fluid chamber 662. At the same time the isolation valve in fluid chamber 663 is closed to prevent fluid from being sucked back into fluid chamber 662 from the fluid outlet which would greatly decrease the efficiency of the pump. [0041] With reference now to FIG.9c, the third and final segment of the pump cycle, the leading fluid chamber 662 is reducing in volume while the following fluid chamber 663 is simultaneously increasing in volume causing a packet of fluid to be transferred from fluid chamber 662 into fluid chamber 663. At the same time the isolation valve in fluid chamber 661 is closed to prevent fluid from being sucked into fluid chamber 661 from the fluid inlet which would greatly decrease the efficiency of the pump. Thus, from these sequences, it is clear that two fluid chambers 66 are transferring fluid at any one time with the leading fluid chambers increasing in volume and the trailing fluid chamber decreasing in volume to move packets of fluid in and out of the pump and between fluid chambers 66. [0042] As has been described briefly and is more clearly shown in FIG.9, the fluid chambers 66 may be isolated in desired manners during operation so that discreet fluid packets are moved from one chamber to another. The valves that control movement of packets of fluid in, out, and around the pump act as isolation valves that fluidically disconnect the inlet from the outlet side of the pump. Regardless of rotational degree, or position, the cam 28 is disposed least one and sometimes two of the isolation valves (e.g., when the 20 degree dwell section is provided in cam 28) are in a closed position whether the pump is running or is stopped. [0043] Referring now to FIG.10, a schematic sequence of the three diaphragms 1, 2, 3 are shown in relation to the cam 28 (FIG.7) rotation positions. The three diaphragms also correspond to the fluid chambers 66 having subscript numbers 1, 2 and 3, as seen in FIGS.9a-9c. Each column represents one of the diaphragms 1, 2, 3 and the rows represent the general position of the cam 28 during a rotation. Looking at the first row, for the 10-110 degree cam rotation diaphragm 1 is opening and filling the first fluid chamber 661. At the same time, diaphragm 2 is in a dwell or closed state to provide the isolation valve thereby closing fluid flow between the second fluid chamber 662 and the third fluid chamber 663. Further, at this time in rotational position of the cam 28, diaphragm 3 is emptying and closing the third fluid chamber 663. [0044] From the 110-130 degree cam rotation, the 20 degree dwell section linking each subsequent 100 degree section is provided, where sequential pairs of the fluid chambers 66 are closed. In the present example, from the 110-130 degree cam rotation both the second fluid chamber 662 and the third fluid chamber 663 are in their closed position to provide two isolation values, while the discreet packet of fluid is fully contained in the first fluid chamber 661. [0045] Moving one row down to the cam positioning of 130-240 degrees, the first fluid chamber 661 is full and diaphragm 1 is closing to transfer fluid to the second fluid chamber 662, where diaphragm 2 opens and accepts fluid from the first fluid chamber 661 through the fluid passage extending therebetween. During this cam positioning, the third fluid chamber 663, is in its closed or dwell state to provide an isolation valve. [0046] From the 240-260 degree cam rotation, the 20 degree dwell section linking each subsequent 100 degree section is provided, where sequential pairs of the fluid chambers 66 are closed. In the present example, from the 240-360 degree cam rotation both the third fluid chamber 663 and the first fluid chamber 661 are in their closed position to provide two isolation values, while the discreet packet of fluid is fully contained in the second fluid chamber 662. [0047] Moving one row down to the cam positioning of 260-350 degrees, the second fluid chamber 662 is full and diaphragm 2 is closing to transfer fluid to the third fluid chamber 663, where diaphragm 3 opens and accepts fluid from the second fluid chamber 662 through the fluid passage extending therebetween. During this cam positioning, the first fluid chamber 661, is in its closed or dwell state to provide an isolation valve. [0048] Finally, from the 350-10 degree cam rotation, the last of the 20 degree dwell section linking each subsequent 100 degree section is provided, where sequential pairs of the fluid chambers 66 are closed. In the present example, from the 350-10 degree cam rotation both the first fluid chamber 661 and the second fluid chamber 662 are in their closed position to provide two isolation values, while the discreet packet of fluid is fully contained in the third fluid chamber 663. [0049] As will be understood with this disclosure, various improved functionalities. The isolation valves allow for movement of discreet packets of fluid through the pump from the fluid inlet 22, through fluid chambers 66, and to the fluid outlet 24. The timing mechanism 26 and the isolation valves allow for isolation of pairs of the fluid chambers 66 regardless of the position of the cam 28. With this isolation, the pump 12 can withstand large positive or negative head pressures and reduce differential metering, for example when a fluid circuit has differing pressure and volume characteristics on either side of the pump. The pump 12 may also comprise a reversible or bi-directional operation. The pump 12 may be reversed by changing direction of the cam 28. [0050] The pump 12 may also provide self-priming functionality. That may be with fluid, air or a combination of fluid and air. [0051] While the foregoing is directed to the various examples described, other and further examples may be devised without departing from the basic scope of the claims that follow. For example, the present examples contemplate that any of the features shown in any of the examples described herein, or incorporated by reference herein, may be incorporated with any of the features shown in any of the other examples described herein, or incorporated by reference herein, and still fall within the scope of the present claims.