Peristaltic Pump

Abstract

A peristaltic pump head 4 and a pump drive unit for detachable connection to one another. The pump head comprises a pumping chamber 52, at least one tube within the pumping chamber to receive a fluid,

Description

The present invention relates to a detachable pump head for a peristaltic pump, a pump drive unit for use with the pump head, and a peristaltic pump comprising such a pump head and pump drive unit. In particular, the present invention relates to detachable pump heads and pump drive units having a sensor system capable of detecting component failure within the pump head. Peristaltic pumps are a type of fluid pump in which a fluid medium to be pumped is conveyed within tubes compressed by pressing elements such as rollers. Typically, such pumps comprise a pumping chamber defining a generally circular or semi-circular surface against which one or more compressible tubes are disposed. A rotor comprising a pressing element is used to compress the tubes against the pressing surface to effectively “pinch” a portion of the tube between the pressing element and the pressing surface. By compressing the tube in this manner, the medium is trapped in two portions before and after the pressing element. As the rotor rotates, the pressing element traverses along the pressing surface, causing the portion of the tube in front of the pressing element to collapse and the portion of the tube behind the pressing element to expand back to an uncompressed shape. When the portion of the tube in front of the pressing element collapses the tube “squeezes” the medium, increasing its pressure, so that it moves to move in a forward direction relative to the direction of movement of the pressing element. Likewise, as the portion of the tube behind the pressing element re-expands, this creates a low pressure region which draws the medium behind the pressing element in a forwards direction. Due to the use of internal tubes, peristaltic pumps ensure that the medium being pumped does not make direct contact with the rotor or the pressing element. As such, peristaltic pumps are often used for applications where is it desired to reduce or eliminate contamination of the pumped medium, and are therefore particularly suited for medical and food production purposes. Over time, the tube material may begin to weaken due to cyclical fatigue as the tube is repeatedly pinched against the pressing surface by the pressing element. If the tube weakens beyond a critical point, it will burst allowing the pumped medium to enter the pumping chamber. If the pump continues to run following such a burst event, this could cause damage to the pump and could increase the risk that the medium is contaminated. It is desirable to detect such bust events so that the pump can be deactivated promptly. Accordingly, it is known to provide peristaltic pumps with sensor arrangements that are capable of detecting a burst event. Typically, such sensor arrangements comprise a sensor in fluid communication with the pumping chamber. A suitable sensor arrangement for this purpose is a magnetic float sensor, in which a floating toroidal magnet surrounds a central pole containing a magnetic reed switch. When medium leaks from the burst tube, the medium floods the pumping chamber, causing the magnetic float to rise along the pole. The movement of the magnetic float is detected by the reed switch, and this can be used to alert the user to the presence of a burst event. Typically peristaltic pumps comprise a pump head and a pump drive unit. The pump head incorporates the tubes, rotor and pumping chamber described above, and the pump drive unit comprises a motor configured to supply rotational power to the rotor. Conventionally, pump heads and pump drive units are provided as a single integral unit, in which the two are not designed to be separable. Because the pump head and the pump drive unit are not separable, in such peristaltic pumps it is relatively easy to incorporate sensing circuitry capable of detecting a burst event. However, it is also known to provide a peristaltic pump comprising a pump head and a pump drive unit that are designed so that they are detachable from one another. In such arrangements the pump head may be provided as single consumable cartridge, in which the interior of the pump head is sealed from the surrounding environment and the internal components, such as the tube(s), rotor, and pressing elements, are not removable. Because the pump head is detachable from the pump drive unit, it can be easily replaced. Therefore, when a burst event occurs, it is relatively straightforward to remove the old, broken, pump head and replace it with a new pump head. Nevertheless, it is generally desirable for the detachable pump head to be capable of detecting a burst event. However, this would require that the various sensing components are incorporated into the pump head and therefore detachable pump heads having such burst detection capability would be more expensive to manufacture. This would increase the cost of the consumable portion of the peristaltic pumping system and require additional communications connections that would increase system complexity. It is an object of the present invention to provide a detachable peristaltic pump head and corresponding pump drive unit that is capable of detecting a burst event with reduced manufacturing cost and complexity. It is a further object of the invention to provide an alternative peristaltic pump head and corresponding pump drive unit. Finally, it is an objection of the present invention to obviate or mitigate one or more disadvantaged of the prior art, whether described herein or elsewhere. According to a first aspect of the invention there is provided a peristaltic pump head for detachable connection to a pump drive unit, the peristaltic pump head comprising: a pumping chamber; at least one tube contained within the pumping chamber and configured to receive a medium to be pumped; a rotor contained within the pumping chamber, the rotor being supported for rotation about an axis and having a pressing element configured to exert a peristaltic action on the tube during rotation so as to transport the medium through the tube; and a fluid detection compartment in fluid communication with the pumping chamber, the fluid detection compartment containing a fluid detection element; wherein the fluid detection element is configurable between a first configuration indicative of the absence of fluid in the fluid detection compartment and a second configuration indicative of the presence of fluid in the fluid detection compartment, the configuration of the fluid detection element being detectable by a sensor disposed on the pump drive unit. Because the fluid detection element is configurable between two configurations in response to the presence of fluid in the fluid detection compartment, it is possible to determine using the sensor arrangement whether fluid is present within the fluid detection compartment and, consequently, whether the at least one tube has burst or ruptured (referred to as a “burst event”). It will be appreciated that only the fluid detection element has contact with fluid in the fluid detection compartment, and that it is this contact that causes the fluid detection element to change configuration between the first and second configurations. The chance in configuration of the fluid detection element can be detected remotely by the sensor. Accordingly, the sensor does not need to be incorporated into the pump head. Instead, all of the pump control and sensing electronics may instead be incorporated into the pump drive unit. This provides the benefit that electronic components such as the sensor do not need to be replaced with the pump head each time that a tube bursts. As a result, the cost of manufacturing the pump head and therefore the cost of the consumable portion of the peristaltic pump is reduced. In this context, a fluid detection element encompasses substantially any element configured to change configuration in response to the ingress of fluid into the fluid detection compartment. The “configuration” of the fluid detection element encompasses properties such as the orientation, shape, size, or position of the fluid detection element. A “fluid detection compartment” encompasses substantially any compartment that is in fluid communication with the pumping chamber such that it may receive fluid from the pumping chamber when the at least one hose bursts. The first configuration of the fluid detection element is defined by a first position of the fluid detection element and the second configuration of the fluid detection element is defined by a second position of the fluid detection element. The fluid detection element is movable within the fluid detection compartment from the first position to the second position in response to the presence of fluid within the fluid detection compartment. The fluid detection compartment may comprise a pole. The fluid detection element may be configured to move between the first position and the second position along the pole. It has been found that when the fluid detection element moves along a pole in response to the presence of fluid, this movement is easy to detect by the sensor. Accordingly, a reliable indication of the presence of fluid can be made. The pole may comprise a plurality of longitudinally extending recesses. During use, solid particles of material (otherwise known as spall) will abrade from the hose material due to frictional wear (otherwise known as spallation). These particles will become entrained in any liquids present within the pumping chamber, such as for example any lubricant. During use small amounts of lubricant may enter the fluid detection compartment due to splashing etc. caused by the rotor and the pressing element. Should the lubricant be saturated with spall, the spall may enter any clearance between the pole and the fluid detection element. The presence of spall in the clearance could prevent the fluid detection element from moving when fluid enters the fluid detection compartment in a burst event, and cause the burst event to remain undetected. However, when the pole comprises recesses, the recesses provide channels for the spall to be washed away, thus mitigating the chance that the fluid detection element will become stuck. The fluid detection element may comprise an aperture within which the pole is received. The fluid detection element may define a polygonal cross-section in a plane perpendicular to the pole during use. The fluid detection compartment may be generally prismatic and define a correspondingly polygonal cross-section. For example, the fluid detection element and the fluid detection compartment may define square cross-sections. Because the fluid detection element and the fluid detection compartment define corresponding cross-sections, this prevents the fluid detection element from rotating about the pole. This helps to ensure that the magnet (discussed below) always faces the sensor of the pump drive unit. The fluid detection element may comprise a float portion. For example, the fluid detection element may comprise a portion made from an aerated material, such as aerated injection moulded plastic, which causes the fluid detection element to float upon contact with liquid. The fluid detection element may comprise a magnet. For example, the fluid detection element may comprise a neodymium magnet that is embedded within the float portion. The fluid detection element may be configured to move the magnet in dependence upon the configuration of the fluid detection element. That is to say, the in the first configuration of the fluid detection element the magnet may have a first position and / or orientation, and in the second configuration of the fluid detection element the magnet may have a second position and / or orientation. The fluid detection compartment may comprise an opening in communication with the pumping chamber. The opening of fluid detection compartment may function as a combined inlet and outlet in which fluid can be received from and drained back into the pumping chamber. In particular, the opening may be the only fluidic passage leading to or from the fluid detection compartment to the pumping chamber or the atmosphere during use. The opening may be in the shape of a vertically oriented elongate slot. When the opening is in the shape of a vertically oriented elongate slot, this provides more space to enable spall to pass freely out of the opening. Accordingly, the shape of the opening prevents the opening being blocked by spall. The pumping chamber may comprise a pressing surface against which the at least one tube is pressed by the pressing element during use. The pressing surface may define a diameter .The opening may be spaced apart in a vertical direction during use from the lowermost point of the pressing surface by a distance equal to at least around 40 % of the diameter of the pressing surface. The pressing surface may define the maximum radial extent of the pumping chamber. Accordingly, the opening may be spaced apart from the bottom of the pumping chamber by around 40 % of the diameter of the pumping chamber. Because the opening is spaced apart from the bottom of the pumping chamber by at least around 40 % of the diameter of the pumping chamber, this allows the vertically lowermost portion of the pumping chamber and the at least one tube to by submerged in a bath of lubricant, whilst ensuring that the fluid detection compartment is spaced sufficiently far away from the lubricant to avoid falsely triggering the fluid detection element. Alternatively, the opening may be spaced apart in a vertical direction during use from the vertically lowermost point of the pressing surface by a distance equal to at least around 50 % of the diameter of the pressing surface. In such embodiments, because the opening is spaced apart from the bottom of the pumping chamber by at least around 50 % of the diameter of the pumping chamber, this provides additional spacing between the lubricant and the fluid detection compartment to reduce or avoid lubricant unnecessarily entering the fluid detection compartment due to splashing etc. The fluid detection compartment may comprise a ledge upon which the fluid detection element rests in the first position, such that during use a gap exists between the fluid detection element and a bottom of the fluid detection compartment. The presence of the gap allows spall to settle below the float, and thereby reduces the chance that spall will agglomerate around the fluid detection element preventing it from moving in respond to fluid entering the fluid detection compartment. The pumping chamber may contain a lubricant configured to lubricate the tube during peristaltic action of the pressing element on the tube. The rotor may define a rotor coupling configured to detachably couple to an output shaft of the pump head. The rotor coupling may be a female coupling. In alternative embodiments, the rotor coupling may be a male coupling. The pumping chamber may be substantially sealed from the outside environment so as to prevent ingress of external fluids into the pumping chamber. The pump head may comprise a pressure release valve in communication with the pumping chamber. The pressure release valve may be configured to allow fluid contained within the pumping chamber to be evacuated in response to leakage of the medium contained in the at least one tube into the pumping chamber. According to a second aspect of the invention, there is provided a peristaltic pump comprising: a pump head according to the first aspect of the invention; and a pump drive unit configured for detachable connection to the pump head, the pump drive unit comprising a sensor aligned with the fluid detection compartment and configured to determine whether the fluid detection element is in the first configuration or the second configuration. The sensor may be a magnetic sensor configured to sense the presence of a magnet of the fluid detection element. For example, the magnetic sensor may be a reed switch. The pump drive unit may further comprise: a motor configured to rotate an output shaft; and an output shaft coupling configured to transfer rotation of the output shaft to the rotor of the pump head when the pump head is connected to the pump drive unit. The output shaft coupling may be a male coupling. In alternative embodiments, the output shaft coupling may be a female coupling. The fluid detection element may be movable within the fluid detection compartment from a first position to a second position. The sensor may be aligned with the first position of the fluid detection element. In particular, if the fluid detection element is a magnet and the sensor is a magnetic sensor, the magnetic sensor may be aligned with the magnet when the fluid detection element is in the first position and / or configuration. The pump drive unit may further comprise a display element configured to indicate the detection of fluid in the fluid detection compartment to a user. That is to say, the display element may be configured to display the detection of tube failure and / or leakage. The pump drive unit may further comprise a control signal-connected to the sensor and configured to determine based upon an output of the sensor whether the fluid detection element is in the first configuration or the second configuration. A detailed description of the invention is set out below with reference to the accompanying drawings in which: Figure 1 is a perspective view of a peristaltic pump in accordance with the present invention; Figure 2 is a front perspective view of a pump head of the peristaltic pump according to the invention in isolation; Figure 3 is a rear perspective view of the pump head in isolation; Figure 4 is a front perspective view of a pump drive unit of the peristaltic pump according to the invention in isolation; Figure 5 is a cross-sectional front view of the pump head taken through the line A-A of Figure 6; Figure 6 is a cross-sectional side view of the pump head 4 taken through the line B-B of Figure 5; Figure 7 is a partial cross-sectional plan view of the fluid detection compartment of the pump head taken through the line C-C of Figure 6; and Figure 8 is a partial cross-sectional side view of the pump head and the pump drive unit in an assembled state taken through the line B-B of Figure 5. Figure 1 shows a perspective view of a peristaltic pump 2 according to the present invention. The peristaltic pump 2 comprises a pump head 4 and a pump drive unit 6. The pump drive unit 6 receives electrical power from a power cable 8 and comprises a control panel 10 capable of receiving input commands from a user and displaying information to the user via a screen (not shown). The control panel 10 is positioned on the front of the pump drive unit 6. The pump head 4 is attached to a side of the pump drive unit 6 adjacent to the control panel 10, however in alternative embodiments the pump head 4 may be attached on substantially any side of the pump drive unit 6 to suit any particular ergonomic requirements. The pump drive unit 6 further comprises a pivotable latch member 12 configured to selectively fix the pump head 4 to the pump drive unit 4. Figures 2 and 3 show respective front and rear perspective views of the pump head 4 in isolation. The pump head 4 comprises a pump head housing 14 defining a front face 16, sides 18, and a rear portion 20. The front face 16 is generally flat aside from a pressure release valve 22 that protrudes from its upper portion. The sides 18 define a generally ribbed construction to provide increased mechanical strength and heat dissipation. On a left hand one of the sides 18 (from the perspective of Figure 2) are disposed a pair of tube connector assemblies 24 configured to receive external tubes (not shown) carrying a medium to be pumped. The tube connector assemblies 24 comprise collars 26 that define a rotatable threaded connection with respective bosses 28 of the housing 14. The collars 26 comprise openings 30 at their distal ends that are suitable for receiving the external tubes. The collars 26 define a generally knurled outer surface to assist the user when the collars 26 are gripped. During use, when the external tubes are received by the openings, the collars 26 are rotated by the user. Due to the threaded connection between the collars 26 and the bosses 28, when the collars 26 are rotated the collars 26 translate towards the bottom of the bosses 28, thus compressing the external tubes to hold the tubes in position and form a substantially fluid tight seal therebetween. Although not shown, additional sealing features such as o-rings or the like may be used to ensure leakage from the tube connector assemblies 24 dos not occur. With reference to Figure 3, the rear portion 20 of the pump head 4 comprises a circumferentially extending connection boss 32 having three equally spaced radially extending flanges 34. The connection boss 32 and the flanges 34 together define a bayonet connector. The rear portion 20 further defines a central opening 36 within which a rotor coupling 38 is disposed. Referring to Figure 4, the pump drive unit 6 is shown in isolation. The pump drive unit 6 comprises a drive unit housing 40 and a connection assembly 42 configured to receive the connection boss 32 of the pump head 4. The connection assembly 42 comprises a circumferentially extending lip 44 that is spaced apart from a face 46 of the housing 33 to define an annular gap 47 therebetween. The lip 44 is sized to receive the connection boss 32 of the pump head 4. The lip 44 comprises three inwardly recessed notches 46 that are sized to receive the flanges 34 of the pump head 4. During use, the flanges 34 of the pump head 4 are passed through the notches 46 of the lip 36 and into the annular gap 47. The pump head 4 is then rotated so that the flanges 34 become trapped between the rear face 46 and the lip 44, preventing axial movement between the pump head 4 and the pump drive unit 6 in the manner of a bayonet connection. The latch member 12 is then used to secure the pump head 4 to the pump drive unit 6 so that the two cannot be separated. The pump drive unit 6 further comprises an output shaft 48 that protrudes outwardly from the drive unit housing 40. The output shaft 48 is driven by a motor (not shown) contained within the pump drive unit 6. The output shaft 48 further comprises a coupling portion 50 comprising a male coupling formation having a number of radially extending splines. With reference to Figure 3, the rotor coupling 38 of the pump head 4 defines a correspondingly shaped female coupling formation comprising matching spines configured to transfer rotation from the output shaft 48 to the rotor coupling 38. Figure 5 shows a cross-sectional front view of the pump head 4 taken through the line A-A of Figure 6. The pump head 4 comprises a pumping chamber 52, a rotor 54, and a fluid detection compartment 56. The pumping chamber 52 is defined by a semi-circular wall 58 defining a pressing surface 60 on its inside. The pump head 4 further comprises a pair of internal tube connection assemblies 62. With reference to Figure 6, each internal tube connection assembly 62 comprises a pair of tube connection spigots 64 positioned side-by-side. The connection spigots 64 are in fluid communication with the tube connector assemblies 24. With reference once more to Figure 5, a pair of internal tubes (not shown) are received by the connection spigots 64 at either end. The tubes may be made from any suitable material, but are preferably made from a thermoplastic vulcanisate (TPV) such as for example Santoprene (RTM) or Verderprene. The tubes are laid side-by-side over the pressing surface 60 so that the tubes make generally uniform contact with the pressing surface 60 along the whole extent of the pressing surface 60. The rotor 54 is supported for rotation relative to the pump head housing 14 about an axis 66, and comprises a central portion defining the rotor coupling 38. The rotor 54 further comprises generally cylindrical hub 68 having a pair of oppositely positioned pressing elements 70. The pressing elements 70 are defined by generally arcuate protrusions extending radially outwards from the axis 66. During use, the pressing elements 70 urge the tubes against the pressing surface 60, and in particular act to “pinch” the tubes therebetween. When the rotor 54 rotates about the axis 66, the point at which the tubes are “pinched” translates along the length of the tubes, acting to push medium within the tubes in front of the pinch point and to drag medium behind the pinch point in a forward direction. Accordingly, a medium can be pumped from the upper to the lower tube connection assembly 24. Such action of the pressing elements 70 of the rotor 54 on the tubes may be referred to as a peristaltic action. In order to reduce friction between the pressing elements, the pumping chamber 52 comprises a bath of lubricant (not shown). The lubricant may be any suitable lubricant chosen in dependence upon the materials of the pump head housing 14 and the internal tubes. For example, the lubricant may be a polytetrafluoroethylene (PTFE) lubricant. The amount of lubricant contained within the pumping chamber 52 is relatively small in comparison to the volume of the pumping chamber, and is typically just enough to submerge the tubes at the lowermost part of the pumping chamber 52. During each rotation of the rotor 54, the pressing elements 70 will be repeatedly dipped into the lubricant bath so that they are coated with lubricant ready for the next rotation. Figure 6 shows a cross-sectional side view of the pump head 4 taken through the line B-B of Figure 5, and Figure 7 shows a partial cross-sectional plan view of the fluid detection compartment 56 of the pump head 4 taken through the line C-C of Figure 6, With reference to Figures 5 to 7 in combination, it can be seen that the fluid detection compartment 56 comprises an opening 72 formed on a vertically oriented side wall 74 of the pumping chamber 52. The opening 72 is in the shape of a vertically oriented elongate slot. The slot-like shape of the opening 72 reduces the likelihood that the opening 72 will become blocked by spall generated by frictional contact between the tubes and the pressing elements 70. The fluid detection compartment 56 further comprises a fluid detection element 74 and a pole 76. The fluid detection element 74 comprises a float 78 and a magnet 80 encapsulated within the float 78. The float 78 defines a central aperture 82 through which the pole 76 is received. The float 78 is made from aerated plastic so that it exhibits a low density enabling it to float upon contact with liquid. During use, when the medium-carrying tubes are functioning normally and have not burst, only lubricant will be present in the pumping chamber 52. The opening 72 of the fluid detection compartment 56 is positioned so that is approximately half way up the pumping chamber 52 in a vertical direction. That is to say, the opening 72 is spaced apart from the lowermost part of the pressing surface 60 by a distance equal to around 50 % of the diameter of the pressing surface 60. Because the opening 72 is spaced apart from the bottom of the pressing surface by this distance, this minimises the amount of lubricant that may accidentally enter the fluid detection compartment 56. However, in alternative embodiments the opening 72 may be positioned at a point vertically above or below that shown in the figures. In particular, the opening 72 may be positioned as low as around 40 % of the diameter of the pressing surface 60 from the lowermost part of the pressing surface 60, as this provides sufficient distance from the pool of lubricant to mitigate against accidental ingress of lubricant into the fluid detection compartment 56. When the medium-carrying tubes are functioning normally, the fluid detection element 74 will be positioned at the bottom of the pole 76 due to the action of gravity. This is the position of the fluid detection element 74 shown in Figures 5 and 6. In this position, the fluid detection element 74 can be said to define a first configuration and / or first position. During use, if one of the medium-carrying tubes in the pumping chamber 52 bursts, the medium carried by the tube will begin to enter the pumping chamber 52, causing the pumping chamber 52 to flood. Eventually, the leaked fluid (a mixture of the pumped medium and lubricant) will enter the fluid detection compartment 56 via the opening 72. When the fluid contacts the float 78, the entire fluid detection element 74 will be displaced vertically and carried upwards along the pole 76. The movement of the fluid detection element 74 along the pole 76 and out of the first configuration and / or position may be said to define a second configuration and / or position. In the first position, the fluid detection element 74 rests upon a ledge 84 (see Figure 5) so as to space the fluid detection element 74 apart from the bottom of the fluid detection compartment 56. As a result, the bottom of the fluid detection element 74 is spaced apart from the bottom of the opening 72 by a small amount. This spacing prevents spall from agglomerating underneath the float 78 and therefore reduces the chance that the float 78 will become stuck to the bottom of the fluid detection compartment 56 in the first position. With reference to Figure 7, it can be seen that the pole 76 comprises four longitudinally extending recesses 86 defined between splines 88. The recesses 86 provide channels between the pole 76 and the aperture 82 to enable spall to pass therethrough, thus reducing the likelihood that spall will agglomerate within the aperture and cause the float 78 to become stuck in the first position. Additionally, the splines 88 ensure that only narrow point and / or line contact takes place between the aperture 82 and the pole 76, so as to minimise frictional forces that would resist movement of the float 78 along the pole 76. Although the pole 76 shown in the figures comprises four longitudinally extending recess 86 and splines 88, it will be appreciated that in alternative embodiments the pole 76 may comprise substantially any suitable number of recesses 78 and splines 88. Furthermore, it can be seen from Figure 7 that the float 78 defines a generally square cross-sectional shape in a plane normal to the longitudinal direction of the pole 78. With reference to Figure 6, the pump head housing 14 comprises a generally rectangular arrangement of walls 90 protruding from one of the sides 18 of the pump head 4 in a horizontal direction that define the top, bottom and sides of the fluid detection compartment 56. With reference again to Figure 7, the walls 90 are open at a distal end relative to the opening 72 so as to enable the pole 76 and the fluid detection element 74 to be received therein. The open end of the walls 90 is closed by an end cap 92 that is bonded in position to prevent leakage. The walls 90 are spaced apart from one another by a distance that is wide enough to permit the float 78 to freely move along the pole 76 but that is close enough to prevent the float 78 from rotating about the pole 76. As such, the distance between the walls 90 is wider than the length of a single side of the float 78, but narrower than the widest dimension of the float 78 in the plane normal to the longitudinal axis of the pole 76 (i.e. the walls 90 are spaced apart by an amount narrower than a diagonal defined between diagonally opposite corners of the float 78). It will be appreciated that in alternative embodiments the walls 90 and the fluid detection element 74 may have substantially any shape that prevents rotation of the fluid detection element 74 within the fluid detection compartment 56. For example, the fluid detection element 74 and the fluid detection compartment 56 may define corresponding prismatic cross-sectional shapes. The cross-sectional shaped my in particular by polygonal, however the same result could be achieved with irregular shapes. In a further alternative, the fluid detection element 74 could be splined or keyed to the pole 76 or to the walls 90 to prevent rotation therebetween, or multiple poles 76 and multiple apertures 82 could be employed to prevent rotation of the fluid detection element 74. Figure 8 shows a partial cross-sectional side view of the pump head 4 and the pump drive unit 6 in an assembled state taken through the line B-B of Figure 5. With reference to Figures 7 and 8, the magnet 80 is encapsulated by the float 78 on a side of the float 78 that faces towards the pump drive unit 6. The magnet 80 is a neodymium magnet, however substantially any suitable magnet could be used. The pump drive unit 6 further comprises a magnetic sensor 94 configured to sense the presence, absence or relative position of the magnet 80. The magnetic sensor 94 is, in particular, a reed switch. However, it will be appreciated that in alternative embodiments substantially any suitable sensor may be used that is able to determine the presence, absence or relative position of the magnet 80. The sensor 94 is positioned within a longitudinally extending boss 96 that protrudes from the drive unit housing 40 in a direction towards the pump head 6. The boss 96 is both horizontally and vertically aligned with the position of the magnet 80 when the fluid detection element 74 is in the first position, as shown in the figures. Accordingly, when the fluid detection element 74 is in the first position the distal end of the sensor 94 positioned in close proximity to the magnet 80. This helps to ensure that the sensor 94 is able to detect the presence of the magnet 80 when it is in the first position. During a burst event when the internal tubes burst and the fluid detection compartment 56 is flooded, the float 78 will lift away from the bottom of the fluid detection compartment 56 and float vertically upwards along the pole 76. Accordingly, the distance between the magnet 80 and the sensor 94 will increase. During this movement, the strength of the magnetic field generated by the magnet 80 that is observed by the sensor 94 will decrease according to the inverse square law, and accordingly the sensor 94 can determine that the fluid detection element is no longer in the first position. Because the sensor 94 is a reed switch, this occurs when the sensing members (i.e. the reeds) within the switch separate form one another. Accordingly, the field strength at which the reed switch decouples should be chosen in dependence upon the change in magnetic field strength observed when the fluid detection element 74 moves upwards along the pole 76 and the strength of the magnet 80 itself. In the present embodiment, the reed switch decouples when the float 78 has travelled approximately 50 % of the length of the pole 78. The separation of the sensing members can be detected by a control unit in electrical communication with the sensor 94, for example by measuring the voltage across the sensor 94. However, it will be appreciated that alternative types of magnetic sensor may be employed that can measure the magnetic field strength in across a substantially continuous spectrum. In such embodiments, the control can continuously sense the strength of the magnetic field and use this to determine the relative position of the fluid detection element 74. Accordingly, different field strengths may be used by the control to indicate the presence of a burst event in dependence upon the properties of the pump head 4. Once a burst event has been detected, the control will indicate the presence of the burst event. This may include, for example, the use of a visual message on a display screen of the control panel 10, illuminating or flashing a light positioned somewhere on the pump head 4 or the pump drive unit 6, the sounding of an alarm, or a mixture of any of the above or any other suitable manner of alerting the user to the detection of the burst event. The control may further be configured to automatically deactivate the pump drive unit 6 in response to the detection of the burst event, so as to prevent damage to the drive unit 6 or contamination of the pumped medium. Once the user has been alerted to the presence of the burst event, the user may then remove the broken pump head 4 from the drive unit 6 and replace it with a working pump head 4 so that the pumping operation can continue. The pump head 4 is of a substantially sealed construction such that, during normal use, fluid does not enter into the pumping chamber 52 from the outside environment, and so that lubricant contained within the pumping chamber 52 does not leak out. As previously described, the pump head 4 comprises a pressure release valve 22. The pressure release valve 22 is in fluid communication with the pumping chamber and is positioned at a top end of the pumping chamber 52. During use, when a burst event occurs, the pumping chamber 52 will flood with leaked medium. This will displace the air contained in the remainder of the pumping chamber 52, causing the air to be compressed. The pressure release valve 22 is configured to allow the air within the pumping chamber 52 to escape from the pumping chamber during such a burst event, whilst otherwise preventing external fluids from entering the pumping chamber 52 when a burst event has not occurred. In the present embodiment, the pressure release valve 22 is set to vent trapped air once the pressure inside the pumping chamber 52 reaches 1 bar gauge pressure. Although the peristaltic pump 2 described above uses a sensor 94 aligned with the magnet 80 when the fluid detection element 74 is in the first position, it will be appreciated that in alternative embodiments the sensor 94 may be aligned with the position of the magnet 80 when the fluid detection is in the second position. In such embodiments, when the sensor 94 does not detect the presence of the magnet 80, this will indicate to the control that the fluid detection element is not in the second position, and therefore the internal tubes have not burst. Although the sensor 94 described above is a magnetic sensor and the fluid detection element comprises a magnet 80, it will be appreciated that the invention can be carried out with substantially any sensor that is capable of determining whether or not the fluid detection element 94 is in a configuration that is indicative of the occurrence or a burst event or a configuration which indicates that a burst event has not occurred. For example, the sensor 94 could be a light sensor that it configured to detect the movement of the fluid detection device through a transparent window of the pump head housing 14. Although the fluid detection element 74 is configured to move linearly between two positions in response to the entry of leaked fluid into the fluid detection compartment, it will be appreciated that in alternative embodiments substantially any type of movement may be employed provided that this is detectable by the sensor. This includes changes of shape, size, orientation or the like. For example, the fluid detection element may be a rotatable baffle that is displaced by the presence of leaked fluid, in which the movement of the baffle is detected by the sensor 94, for example due to the movement or orientation of a magnet 80 disposed within the baffle or by viewing the baffle through a window using an optical sensor. Alternatively, the fluid detection element may comprise a deformable membrane, the expansion of which indicates the presence of leaked fluid in the fluid detection compartment, the expansion being determined by the displacement of a magnet on the membrane or by optical inspection of the membrane by an optical sensor. In further embodiments, the fluid detection element may be made from a material that expands upon contact with leaked fluid, the expansion of the material being detectable by a sensor. For example, the material once expanded may protrude from the pump head 4 and actuate a pressure switch positioned on the pump drive unit 6. In general, changes in configuration of the fluid detection element 74 can be detected in a straightforward and reliable manner by using a remote sensor. Although the pumping chamber 52 of the pump head 4 described above comprises a pair of side-by-side medium-carrying tubes, it will be appreciated that in alternative embodiments substantially any number of tubes may be used for pumping the medium. In particular, the pump head 4 may comprise a single tube, or more than two tubes. Additionally, although the rotor 54 comprises a pair of pressing elements 70, it will be appreciated that in alternative embodiments the rotor 54 may comprise any suitable number of pressing elements 70. For example, the rotor 54 may comprise a single pressing element or more than two pressing elements. The pressing elements may be equally or unequally spaced around the axis 66 so as to suit any particular pumping requirements.

Claims

1. A peristaltic pump head for detachable connection to a pump drive unit, the peristaltic pump head comprising:a pumping chamber;at least one tube contained within the pumping chamber and configured to receive a medium to be pumped;a rotor contained within the pumping chamber, the rotor being supported for rotation about an axis and having a pressing element configured to exert a peristaltic action on the tube during rotation so as to transport the medium through the tube; anda fluid detection compartment in fluid communication with the pumping chamber, the fluid detection compartment containing a fluid detection element;wherein the fluid detection element is configurable between a first configuration indicative of the absence of fluid in the fluid detection compartment and a second configuration indicative of the presence of fluid in the fluid detection compartment, the configuration of the fluid detection element being detectable by a sensor disposed on the pump drive unit;wherein the first configuration of the fluid detection element is defined by a first position of the fluid detection element and the second configuration of the fluid detection element is defined by a second position of the fluid detection element, the fluid detection element being movable within the fluid detection compartment from the first position to the second position in response to the presence of fluid within the fluid detection compartment.

2. A peristaltic pump head according to claim 1, wherein the fluid detection compartment comprises a pole, and wherein the fluid detection element is configured to move between the first position and the second position along the pole.

3. A peristaltic pump head according to claim 2, wherein the pole comprises a plurality of longitudinally extending recesses.

4. A peristaltic pump head according to claim 2 or 3 wherein the fluid detection element comprises an aperture within which the pole is received.

5. A peristaltic pump head according to any of claims 2 to 4, wherein the fluid detection element defines a polygonal cross-section in a plane perpendicular to the pole during use, and wherein the fluid detection compartment is generally prismatic and defines a correspondingly polygonal cross-section.

6. A peristaltic pump head according to any preceding claim, wherein the fluid detection element comprises a float portion.

7. A peristaltic pump head according to any preceding claim, wherein the fluid detection element comprises a magnet.

8. A peristaltic pump head according to claim 7, wherein the fluid detection element is configured to move the magnet in dependence upon the configuration of the fluid detection element.

9. A peristaltic pump head according to any preceding claim, wherein the fluid detection compartment comprises an opening in communication with the pumping chamber.

10. A peristaltic pump head according to claim 9, wherein the opening is in the shape of an vertically oriented elongate slot.

11. A peristaltic pump head according to claim 9 or 10, wherein the pumping chamber comprises a pressing surface against which the at least one tube is pressed by the pressing element during use;wherein the pressing surface defines a diameter; andwherein the opening is spaced apart in a vertical direction during use from the lowermost point of the pressing surface by a distance equal to at least 40 % of the diameter of the pressing surface.

12. A peristaltic pump head according to claim 11, wherein the opening is spaced apart in a vertical direction during use from the vertically lowermost point of the pressing surface by a distance equal to at least 50 % of the diameter of the pressing surface.

13. A peristaltic pump head according to any of claims 1 to 12, wherein the fluid detection compartment comprises a ledge upon which the fluid detection element rests in the first position, such that during use a gap exists between the fluid detection element and a bottom of the fluid detection compartment.

14. A peristaltic pump head according to any preceding claim, wherein the pumping chamber contains a lubricant configured to lubricate the tube during peristaltic action of the pressing element on the tube.

15. A peristaltic pump head according to any preceding claim, wherein the rotor defines a rotor coupling configured to detachably couple to an output shaft of the drive unit.

16. A peristaltic pump head according to claim 15, wherein the rotor coupling is a female coupling.

17. A peristaltic pump head according to any preceding claim, wherein the pumping chamber is substantially sealed from the outside environment so as to prevent ingress of external fluids into the pumping chamber.

18. A peristaltic pump head according to claim 17, wherein the pump head comprises a pressure release valve in communication with the pumping chamber.

19. A peristaltic pump comprising:a pump head according to any preceding claim; anda pump drive unit configured for detachable connection to the pump head, the pump drive unit comprising a sensor aligned with the fluid detection compartment and configured to determine whether the fluid detection element is in the first configuration or the second configuration.

20. A peristaltic pump according to claim 19, wherein the sensor is a magnetic sensor configured to sense the presence of a magnet of the fluid detection element.

21. A peristaltic pump according to claim 19 or 20, wherein the pump drive unit further comprises:a motor configured to rotate an output shaft; andan output shaft coupling configured to transfer rotation of the output shaft to the rotor of the pump head when the pump head is connected to the pump drive unit.

22. A peristaltic pump according to claim 21, wherein the output shaft coupling is a male coupling.

23. A peristaltic pump according to any of claims 21 to 22, wherein the fluid detection element is movable within the fluid detection compartment from a first position to a second position and wherein the sensor is aligned with the first position of the fluid detection element.

24. A peristaltic pump according to any of claims 19 to 23, wherein the pump drive unit further comprises a display element configured to indicate the detection of fluid in the fluid detection compartment to a user.

25. A peristaltic pump according to any of claims 19 to 24, wherein the pump drive unit further comprises a control signal-connected to the sensor and configured to determine based upon an output of the sensor whether the fluid detection element is in the first configuration or the second configuration.

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