Abstract:
The invention provides a pumping system for delivering a plurality of different materials serially at a location at substantially the same flow rate wherein the system has a plurality of diaphragm pumps wherein each diaphragm pump has a first chamber for receiving a hydraulic fluid from a first and/or second hydraulic fluid source and a second chamber for receiving a material to be pumped from one of a plurality of pumpable material sources and wherein the system has a sensor for detecting the pressure of the hydraulic fluid in each of the first chambers of the plurality of diaphragm pumps which sensor is operable connected to a source of hydraulic fluid such that the sensor can activate the source of hydraulic fluid to ensure that the hydraulic fluid in each of the first chambers of the plurality of diaphragm pumps has an equivalent pressure at a time when delivery from one of the diaphragm pumps ceases and delivery from another commences; and a method of delivering a plurality of different materials at a location at substantially the same flow rate.

Description:
RELATED APPLICATION DATA 
       [0001]    This application claims priority from GB Patent Application No. 0707220.0, filed Apr. 14, 2007, which is incorporated herein in its entirety by reference hereto. 
       BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The present invention provides a pump for delivering two different materials serially at a location at substantially the same flow rate and pressure. The pump is useful for consistently filling capsules with two different materials such that the internal pressure of the capsules is substantially uniform. A resin capsule is commonly used for securing a bolt into a rock face to support the rock face, e.g, in a rock tunnel in a mine. A resin capsule generally comprises a tubular sheath of a frangible film, with a longitudinal barrier dividing the capsule into two compartments. The capsule is terminated by clips. Within the capsule, one compartment is filled with a mastic of polyester resin and fillers (usually limestone) and the other compartment is filled with a paste containing activator for the polyester resin, extended with fillers such as further limestone and water. The capsule typically has a diameter of 12-40 mm and a length of 300-3000 mm. Resin capsules are manufactured continuously on “form-fill-seal” machinery. There are many variants of this machinery. Generally, the sheath is first formed by folding a web of film into a tube and continuously forming longitudinal seals and the internal barrier as the tube travels through the machine. At a short distance after the formation of the tube, nozzles inject the resin mastic and activator paste into their respective compartments. At later stages the terminating clips are affixed and the tube is severed between clips to form the discrete capsules. Typical output of such a machine is 12-25 metres of resin capsules per minute. 
         [0004]    Customer requirements are that the capsules should have consistent mass, consistent internal pressure and consistent proportion between resin and activator components. These requirements are met by ensuring constant flow rates and pressures from the nozzles injecting the resin and activator components. 
         [0005]    In resin-grouted rock bolting practice, there is commonly a requirement that two setting times of resin be used: a fast-set resin at the distal end of the rock bolt hole, and a slow-set resin nearer the collar. Use of the fast-slow combination makes installation of the bolt easier in holes more than about 1.5 m deep. 
         [0006]    Various methods are used to place the two setting times of resin in the hole. The simplest is for the operator to separately load discrete capsules, the first-loaded capsule or capsules containing fast-set resin and the later loaded capsule or capsules containing slow-set resin, This method is slow and prone to operator error however. 
         [0007]    A better method is to have the fast and slow resins in the same capsule, which will have one end filled with fast resin mastic and the other with slow resin mastic. Such a capsule is known as a two-speed capsule and is used on a large scale in Australia where capsules are sold under the trade names “TooSpeedie” and “Duospeed”. A two-speed capsule is believed to be manufactured by using parallel resin mastic pumping lines for the fast and slow components with the capsule forming machine switching between the two lines. It will be appreciated that delicate balancing of the two lines is necessary to achieve the switch without fluctuation of pressure or flow, and that this balancing must be regularly adjusted as the pumps wear. 
         [0008]    2. Description of the Prior Art 
         [0009]    Conventionally a pumping system comprising a pair of diaphragm pumps is used to fill normal capsules because it produces a constant flow and pressure. Such a system is described in U.S. Pat. No. 4,543,044. They are generally known as constant-flow diaphragm pumps and will be referred to herein as a CFD pump. The disadvantage of the CFD pump is its high initial cost. Each one is custom-made. The CFD pumping technology cannot be readily applied to the manufacture of two-speed capsules, due to the high capital cost of providing dual parallel CFD pumps. 
         [0010]    An advantage of using a CFD pump is that, unlike a conventional progressing cavity pump (such as made by Mono or Moyno), it can be used to pump a mastic containing coarse particles of a filler. Thus a two-speed capsule is more expensive to manufacture by using a conventional progressing cavity pump because it contains more polyester resin and activator. Furthermore, whilst a progressing cavity pump is more readily available and cheaper than a CFD pump, it suffers from the limitations that the rotors and stators wear and need regular replacement; and that as the components wear there is a drift in flow rate and pressure, which makes long-term automatic control difficult. 
         [0011]    As an alternative, a different method of achieving the two setting times of resin in the same capsule has been found. This method uses direct injection of an accelerator into a portion of the length of the capsule, in synchronisation with capsule formation. When the capsule is broken and the contents mixed during rock bolt installation, the accelerator mixes with the resin and transforms part of the resin from slow to fast. This method can be used in conjunction with the conventional method of manufacturing normal capsules, i.e. by using a CFD pump and including coarse filler in the capsule. Although the production line is relatively low-cost to build, this method has the disadvantages of reduced shelf-life of the capsules as the accelerator migrates inside the capsule; mixing of the accelerator with the resin in the rock bolt hole is not efficient such that the dosage of accelerator is much higher than in pre-blending fast resin mastic prior to injection; and the accelerator normally used (which is di-methyl paratoluidine) is a high-cost material. 
         [0012]    Accordingly improvements in the production of two-speed resin capsules have been sought. 
       SUMMARY OF THE INVENTION 
       [0013]    According to the invention there is provided a pumping system for delivering a plurality of different materials serially at a location at substantially the same flow rate wherein the system has a plurality of diaphragm pumps wherein each diaphragm pump has a first chamber for receiving a hydraulic fluid from a first and/or a second hydraulic fluid source and a second chamber for receiving a material to be pumped from one of a plurality of pumpable material sources and wherein the system has a sensor for detecting the pressure of the hydraulic fluid in each of the first chambers of the plurality of diaphragm pumps which sensor is operably connected to a source of hydraulic fluid such that the sensor can activate a source of hydraulic fluid to ensure that the pressure of the hydraulic fluid in each of the first chambers of the plurality of diaphragm pumps is equivalent at a time when delivery from one of the diaphragm pumps ceases and delivery from another commences. 
         [0014]    According to the invention there is also provided a method of delivering a plurality of different materials at a location at substantially the same flow rate which method comprises the steps of:
       (a) providing a pumping system having a plurality of diaphragm pumps wherein each diaphragm pump has a first chamber for receiving a hydraulic fluid from a first or a second hydraulic fluid source and a second chamber for receiving a material to be pumped from a plurality of pumpable material sources;   (b) filling a second chamber of a first diaphragm pump with a first pumpable material from a first pumpablc material source;   (c) pumping hydraulic fluid front a first hydraulic fluid source to the first chamber of the first diaphragm pump so that the pumping system provides the first pumpable material at the location, whilst:   (1a) filling the second chamber of a second diaphragm pump with a second pumpable material from a second pumpable material source;   (2a) sensing pressure of the hydraulic fluid in the first chamber of the first diaphragm pump and the pressure of the hydraulic fluid in the first chamber of the second diaphragm pump;   (3a) using the second hydraulic fluid source to adjust the pressure of the hydraulic fluid in the first chamber of the second diaphragm pump such that it has an equivalent pressure to the pressure of the hydraulic fluid in the first chamber of the first diaphragm pump;       
 
         [0021]    (d) stopping pumping of the hydraulic fluid from the first hydraulic fluid source to the first chamber of the first diaphragm pump; 
         [0022]    (e) pumping hydraulic fluid from the first hydraulic fluid source to the first chamber of the second diaphragm pump so that the system provides the second pumpable material at the location at substantially the same rate as the first pumpable material, whilst: 
         [0023]    (1b) filling the second chamber of the first diaphragm pump with a first pumpable material from a first pumpable material source; 
         [0024]    (2b) sensing the pressure of the hydraulic fluid in the first chamber of the first diaphragm pump and the pressure of the hydraulic fluid in the first chamber of the second diaphragm pump; 
         [0025]    (3b) using the second hydraulic fluid source to adjust the pressure of the hydraulic fluid in the first chamber of the first diaphragm pump such that it has an equivalent pressure to the pressure of the hydraulic fluid in the first chamber of the second diaphragm pump; and 
         [0026]    (f) ceasing pumping of the hydraulic fluid from the first hydraulic fluid source to the first chamber of the second diaphragm pump. 
         [0027]    The method of the invention optionally additionally includes the step of (g) repeating steps (c) to (f) one or more times. 
         [0028]    A hydraulic fluid source for use in the invention is preferably a hydraulic fluid pump connected to a supply of hydraulic fluid. Preferably the first and second hydraulic fluid sources comprises a first and second hydraulic fluid pump which are each connected to a supply of hydraulic fluid. Preferably the first chamber of a diaphragm pump used in the invention has a hydraulic fluid drain connected to the supply of hydraulic fluid. A pumpable material source is preferably a pump (for example a hydraulic pump or a diaphragm pump, especially a compressed air diaphragm pump) connected to a supply of pumpable material. 
         [0029]    A diaphragm pump generally has a housing divided by a moveable diaphragm into a first variable-volume chamber for hydraulic fluid and a second variable-volume chamber for pumpable material. The first chamber has an inlet for hydraulic fluid and the second chamber has an outlet for pumpable material. Supply of hydraulic fluid to the first chamber causes the diaphragm to move in the direction of the second chamber such that the pumpable material is pumped out of the outlet of the second chamber. 
         [0030]    The system according to the invention preferably has two diaphragm pumps each of which is connected in use to a different source of pumpable material. The system is preferably arranged such that it can be operated continuously. More preferably the system has a controller which in use directs one pump to discharge the pumpable material from its second chamber whilst controlling the filling of the second chamber of the other pump with a different pumpable material. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0031]    The invention is illustrated by way of example with reference to the FIGURE of the accompanying drawings which shows a schematic layout of a pumping system according to the invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0032]    The pumping system  1  shown in the Figure has a first diaphragm pump  5 , a second diaphragm pump  50 , a programmable logic controller (PLC)  100 , and a sensor  110 . The pumping system  1  is shown in the Figure to be connected to a first source of a first pumpable material  300  via first material pump  105  and to a second source of a second pumpable material  320  via second material pump  125 . The pumping system  1  is also shown in the Figure to be connected to a first hydraulic pump  200  and to a second hydraulic pump  250 . The first diaphragm pump  5  has a first chamber · 10  which is filled with hydraulic fluid  15 , a second chamber  20  which is filled with a first pumpable material  22  and a diaphragm  30  which separates the first chamber  10  from the second chamber  20 . The first chamber  10  has a port  11  which is connected to the first hydraulic pump  200  via a valve  35 . Port  11  of the first chamber  10  is also connected to the second hydraulic pump  250  via a valve  40  (as an alternative, the first chamber  10  of the first hydraulic pump  5  may be provided with a further port to which the second hydraulic pump  250  may be connected via the valve  40 ). The first chamber  10  also has a sensor port  12  and a drain port (not shown). The second chamber  20  has a port  21  which is connected to the first material pump via first material valve  45 . Where the pumping system I is used to fill a resin capsule, the volume of the second chamber  20  is sufficient to deliver enough of the first material to fill its respective portion of a resin capsule. Port  21  of the second chamber  20  is also connected to an outlet  48  via outlet valve diaphragm pump  50  has a first chamber  60  which is filled with hydraulic fluid  15 , a second chamber  70  which is filled with a second pumpable material  72  and a diaphragm  80  which separates the first chamber  60  from the second chamber  70 . The first chamber  60  has a port  61  which is connected to the first hydraulic pump  200  via a valve  85 . Port  61  of the first chamber  60  of second diaphragm pump  50  is also connected to the second hydraulic pump  250  via a valve  90  (as an alternative, the first chamber  60  of the second hydraulic pump  50  may be provided with a Further port to which the second hydraulic pump  250  may be connected via the valve  90 ). The first chamber  60  also has a sensor port  62  and a drain port (not shown). The second chamber  70  has a port  71  which is connected to the second material pump  125  via second material valve  95 . Where the pumping system  1  is used to fill a resin capsule, the volume of the second chamber  70  is sufficient to deliver enough of the second material to fill its respective portion of a resin capsule. Port  71  of the second chamber  70  is also connected to an outlet  98  via outlet valve  97 . Like outlet  48 , outlet  98  may be connected to a packaging machine (not shown), e.g. for resin capsules. Again, for convenience, the outlet valve  97  may be located close to the packaging machine (not shown). 
         [0033]    First material pump  105  is connected to a supply  300  of first pumpable material  22 . Second material pump  125  is connected to a supply  320  of second pumpable material  72 . First and second material pumps  105 , 125  are in the form of conventional compressed air operated diaphragm pumps. As an alternative, material pumps  105 , 125  may be close coupled low-pressure diaphragm pumps powered by a pressure accumulator where rapid pumping of first and second pumpable material is required. By close coupled is meant that the length of the connection between diaphragm pumps  5 , 50  and material pumps  105 , 125  is minimised. As a further alternative, the functions of first and second material pumps  105 , 125  may be performed by first hydraulic pump  200 . The advantage of this embodiment is that the PLC  100  does not need to coordinate the activity of the first and second material pumps  105 , 125 , simplifying the PLC  100 . In this embodiment, the first hydraulic pump  200  runs continuously supplying hydraulic fluid to either of the first chambers  10 , 60  and pumpable material  22 , 72  to either of the second chambers  20 , 70 , first and second hydraulic pumps  200 , 250  are connected to a supply  260  of hydraulic fluid  15 . The drain ports (not shown) of the first chambers  10 , 60  of the first and second diaphragm pumps  5 , 50  are connected to the supply  260  of hydraulic fluid  15  via drain valves (not shown). 
         [0034]    The second hydraulic pump  250  is an auxiliary hydraulic pump and is run intermittently. As an alternative, the second hydraulic pump  250  comprises a hydraulic accumulator and the second hydraulic pump  250  is run continuously to pressurise the accumulator. The advantage of such an arrangement is that the accumulator will be faster to operate than the second hydraulic pump  250 . 
         [0035]    Sensor  110  senses the pressure of the hydraulic fluid in first chambers  10 , 60  of the first and second diaphragm pumps  5 , 50  via sensor ports  12 , 62 . Sensor  110  is also operably connected to valves  40 , 90  and to second hydraulic pump  250  (connections not shown). The PLC  100  controls the operation of valves  35 , 40 , 45 , 47 , 85 , 90 , 95 , 97  via PLC control wires (not shown). PLC  100  is also connected to sensor  110 . In operation, to fill the second chamber of a diaphragm pump with pumpable material, the following procedure is needed. Outlet valve  47 , 97  of the diaphragm pump  5 , 50  is closed and the first material valve  45 , 95  is opened. At the same time, valves  35 , 85 , 40 , 90  are closed and drain valves (not shown) are opened. Then second chamber  20 , 70  of the respective diaphragm pump  5 , 50  is fed with pumpable material  22 , 72  from supply  300 , 320  via material pump  105 , 125 . In operation, at the start of a cycle, where the second chamber  20  of the first diaphragm pump  5  has been filled with the first pumpable material  22  (which may be for example fast resin mastic) and outlet valve  47  is open and first material valve  45  is closed, the first diaphragm pump  5  will then deliver the first pumpable material  22  to the packaging machine (not shown) when valve  35  is open, the drain valve (not shown) of the first chamber  10  and valve  40  are closed and first hydraulic pump is operating to deliver hydraulic fluid  15  from source  260  to the first chamber  10  of first diaphragm pump  5 . 
         [0036]    The rate of delivery of the first pumpable material  22  to the packaging machine (not shown) is the same as the rate at which the first hydraulic pump  200  delivers hydraulic fluid  15  to the underside of the diaphragm  30  in first chamber  10  of first diaphragm pump  5 . First hydraulic pump does not simultaneously deliver any hydraulic fluid  15  to the first chamber  60  of second diaphragm pump  50 . 
         [0037]    While the first diaphragm pump  5  is delivering the first pumpable material  22  to the packaging machine (not shown), the second diaphragm pump  50  is being prepared. The second chamber  70  of the second diaphragm pump  50  is refilled with the second pumpable material  72  (which may be for example slow resin mastic) from supply  320  via second material pump  125 . Outlet valve  97  is closed and second material valve  95  is open. At the same time the drain valve (not shown) of the first chamber  60  is open so that the hydraulic fluid  15  drains from the first chamber  60  into supply  260  as the second pumpable material  72  is pumped into the second chamber  70 . 
         [0038]    When the second chamber  70  is full, sensor  110  detects this and then causes the PLC to close second material valve  95  and the drain valve (not shown) of first chamber  60 . The sensor  110  activates the second hydraulic pump  250  to re-pressurise the first chamber  60  until the sensor  110  detects that pressures in first chambers  10  and  60  are equivalent. In this example, the first and second materials  22 , 72  have the same viscosity, and so an equivalent pressure in each of the first chambers  10 , 60  to be detected by the sensor  110  at this stage is an identical pressure. 
         [0039]    Where the first and second materials  22 ,  72  have different viscosities, using an identical pressure will generate different initial flow rates at the outlets  48 , 98 . In order to overcome this problem, two approaches are possible to find an equivalent pressure. Firstly, the pressure in the first chambers  10 , 60  of each diaphragm pump  5 , 50  as each diaphragm pump  5 , 50  is delivering pumpable material  22 , 72  is measured and stored in the PLC  100  for a given cycle. When the first chambers  10 , 60  are being re-pressurised for the next cycle, the sensor  110  increases the pressure in the first chambers  10 , 60  until it is equal to that measured by the sensor  110  and stored in the PLC  100  in the previous cycle. Secondly, a ratio could be used by sensor  110  to calculate the equivalent pressure. The ratio could be set by an operator theoretically, e.g. by basing it on the relative viscosities of the first and second materials  22 , 72 , empirically, e.g. by basing it on the appearance of the packaged first and second materials or by a combined theoretical and empirical approach. As a further alternative, a closed loop control system could he used. 
         [0040]    At the time when delivery of the first material  22  should stop and delivery of the second material  72  should commence, the packaging machine (not shown) generates a signal. In order for the pumping system  1  to function properly, the time taken to fill the second chamber  20 , 70  of a diaphragm pump  5 , 50  with pumpable material  22 , 72  and re-pressurise the first chamber  10 , 60  should be less than the time taken to deliver a sufficient amount of the first or second material  22 , 72  to the packaging machine (not shown). 
         [0041]    When the signal is received, PLC  100  closes valve  35  and outlet valve  47  and opens valve  85  and outlet valve  97  so that the first hydraulic pump  200  switches to delivering hydraulic fluid  15  to the first chamber  60  of the second diaphragm pump  50 . Second pumpable material  72  is then delivered to the packaging machine (not shown). The pre-pressurisation of the first chamber  60  of the second diaphragm pump  50  and the fact that delivery of the second material  72  is driven by the same hydraulic pump  200 , which runs without interruption, ensures that the switch from the delivery of the first material  22  to delivery of the second material  72  occurs without fluctuation in pressure or flow. 
         [0042]    While the second diaphragm pump  50  is delivering the second pumpable material  72  to the packaging machine (not shown), the first diaphragm pump  5  is being prepared in a similar manner to that used for the second diaphragm pump  50 , as described above. The second chamber  20  of the first diaphragm pump  5  is refilled with the first pumpable material  22  from supply  300  via first material pump  105 . Outlet valve  47  is closed and first material valve  45  is open. At the same time the drain valve (not shown) of the first chamber  10  is open so that the hydraulic fluid  15  drains from the first chamber  10  into supply  260  as the first pumpable material  22  is pumped into the second chamber  10 . When the second chamber  10  is full, sensor  110  detects this and then causes first material valve  45  to close. The sensor  110  activates the second hydraulic pump  250  to re-pressurise the first chamber  10  until the sensor  110  detects that pressures in first chambers  10  and  60  are equivalent. 
         [0043]    At the time when delivery of the second pumpable material  72  should stop for delivery of the first pumpable material  22  to re-commence, the packaging machine (not shown) again generates a signal. At this stage a cycle is completed. The cycle may be repeated for as long as is required. 
         [0044]    The invention allows the CFD pump principle to be economically applied to the manufacture of resin capsules containing two speeds of resin mastic. Use of the CFD pump allows the two-speed capsule to utilise coarse filler. The resulting capsule will have the advantages of being produced at a lower cost, having better storage characteristics and being more convenient to use than has been attainable previously.