Patent Publication Number: US-9402789-B2

Title: Pump set having secure loading features

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This patent application is a continuation application of and claims the benefit of priority under 35 U.S.C. §120 to co-pending U.S. patent application Ser. No. 13/430,113, filed Mar. 26, 2012 entitled METHOD FOR USING A PUMP SET HAVING SECURE LOADING FEATURES, which is a continuation of Ser. No. 12/757,187, filed Apr. 9, 2010, titled METHOD FOR USING A PUMP SET HAVING SECURE LOADING FEATURES, which is a continuation application of U.S. patent application Ser. No. 11/366,227, filed Mar. 2, 2006, titled METHOD FOR USING A PUMP SET HAVING SECURE LOADING FEATURES, the entireties of each which is incorporated by reference for all purposes. 
    
    
     BACKGROUND 
     This invention relates generally to pump sets and pumps to deliver fluids to patients by way of a flow control apparatus, and more particularly to a method for using a pump set having a safety interlock device to control operation of a pump. 
     Administering fluids containing medicine or nutrition to a patient is well known in the art. Fluids can be delivered to patients by gravity flow, but often are delivered to the patient by a pump set loaded on a flow control apparatus, such as a peristaltic pump, which delivers fluid to the patient at a controlled rate of delivery. A peristaltic pump usually comprises a housing that includes a rotor or the like operatively engaged to at least one motor through a gearbox. The rotor drives fluid through the tubing of the pump set by the peristaltic action effected by rotation of the rotor by the motor. The motor is operatively connected to a rotatable shaft that drives the rotor, which in turn progressively compresses the tubing and drives the fluid at a controlled rate through the pump set. A controller operates the motor to drive the rotor. Other types of peristaltic pumps not employing rotors are also known. 
     In order for the pump to deliver an accurate amount of fluid corresponding with the flow parameters programmed into the pump, the administration feeding set must be correctly loaded on the pump. If the pump set is misaligned in the pump, the pump may deliver an inaccurate amount of fluid to a patient or the pump generates a low flow alarm requiring the condition to be examined and the set reloaded. Existing pumps have systems to detect whether the pump set is properly loaded. An example of such a pump having a detection system is shown in co-assigned U.S. Pat. No. 4,913,703, entitled SAFETY INTERLOCK SYSTEM FOR MEDICAL FLUID PUMPS, the disclosure of which is incorporated by reference. This system uses a magnet on the pump set which is detected by circuitry in the pump. It would be desirable to provide a pump set that can be detected but which does not require each pump set to have a magnet. 
     SUMMARY OF INVENTION 
     In one aspect, an enteral feeding set for an enteral feeding pump having a control system for controlling operation of the pump to supply nutrient liquid to a patient through the enteral feeding set loaded in the pump, a source of electromagnetic radiation operatively connected to the control system of the pump for emitting electromagnetic radiation, and an electromagnetic radiation detector operatively connected to the control system for receiving the electromagnetic radiation and providing an indication to the control system that the feeding set is properly loaded in the feeding pump generally comprises a conduit for carrying nutrient liquid to a patient. A safety interlock includes a light pipe for providing a passage of the electromagnetic radiation from the source of electromagnetic radiation to the electromagnetic radiation detector only when the safety interlock is loaded in the pump such that nutrient liquid flow to the patient is regulated by the pump. 
     In another aspect, an enteral feeding set for an enteral feeding pump having a control system for controlling operation of the pump to supply nutrient liquid to a patient through the enteral feeding set loaded in the pump, a source of electromagnetic radiation operatively connected to the control system of the pump for emitting electromagnetic radiation, and an electromagnetic radiation detector operatively connected to the control system for receiving the electromagnetic radiation and providing an indication to the control system that the feeding set is properly loaded in the feeding pump generally comprises a conduit for carrying nutrient liquid to a patient. A light pipe is positioned with respect to the conduit for providing a passage of the electromagnetic radiation from the source of electromagnetic radiation to the electromagnetic radiation detector only when the light pipe is loaded in the pump such that nutrient liquid flow to the patient is regulated by the pump. 
     In yet another aspect, a safety interlock adapted for use in a medical device having a control system for controlling operation of the medical device, a source of electromagnetic radiation disposed to emit electromagnetic radiation, and an electromagnetic radiation detector operatively connected to the control system generally comprises a light pipe adapted for providing a passage of the electromagnetic radiation from the source of electromagnetic radiation to the electromagnetic radiation detector only when the light pipe is loaded in the medical device such that nutrient liquid flow to the patient is regulated by the medical device. 
     In one aspect of the present invention, a method of using a feeding set on an enteral feeding pump generally comprises inserting an interlock device of the feeding set into a recess of the enteral feeding pump. Infrared radiation is intermittently emitted in a direction for striking the inserted interlock device and is transmitted and internally reflected within the interlock device to redirect the infrared radiation toward a first detector when the interlock device is properly inserted in the pump recess. The first detector detects the infrared radiation redirected within the interlock device. A visible light emitter is intermittently energized only after infrared radiation has been detected by the first detector. Visible light is filtered with the interlock device to prevent transmission through the interlock device, and a second detector is read to verify that visible light emitted by the visible light emitter has been blocked. Operation of the enteral feeding pump is enabled to pump nutrient liquid in the feeding set in response to detection of infrared radiation by the first detector and the verification that no visible light is detected by the second detector. 
     In another aspect of the present invention, a method of using a feeding set on an enteral feeding pump. The feeding set has an interlock device adapted to be inserted into a recess of the enteral feeding pump. The method generally comprises inserting the interlock device into the recess of the enteral feeding pump. Electromagnetic radiation is emitted in a direction for striking the inserted interlock device and at least a portion of the electromagnetic radiation striking the interlock device is detected when the interlock device is properly inserted in the pump recess. Operation of the enteral feeding pump to pump nutrient liquid in the feeding set is enabled in response to the detected electromagnetic radiation. 
     In yet another aspect of the present invention, a method for controlling a pumping apparatus capable of mounting a pump set having a safety interlock device thereon generally comprises emitting electromagnetic radiation from a first source of electromagnetic radiation in a direction for striking the safety interlock device of the pump set. A first electromagnetic radiation detector is activated to detect electromagnetic radiation striking the first detector. Electromagnetic radiation is emitted from a second source of electromagnetic radiation in a direction for striking the safety interlock device of the pump set. A second electromagnetic radiation detector is activated to detect electromagnetic radiation striking the second detector. The pumping apparatus is controlled to operate for pumping fluid in the pump set only when electromagnetic radiation emitted from the first source is detected by the first detector and when the second detector does not detect electromagnetic radiation. 
     In one aspect of the present invention, a controller for operating a pumping apparatus to supply fluid to a patient through a pump set having a safety interlock loaded in the pumping apparatus generally comprises a first source of electromagnetic radiation operatively connected to the pumping apparatus for emitting electromagnetic radiation. A first electromagnetic radiation detector is operatively connected to the pumping apparatus. A second source of electromagnetic radiation is operatively connected to the pumping apparatus for emitting electromagnetic radiation, and a second electromagnetic radiation detector is operatively connected to the pumping apparatus. A processor is programmed to: (i) instruct the first source of electromagnetic radiation to emit electromagnetic radiation in a direction for striking the safety interlock of the pump set; (ii) activate the first electromagnetic radiation detector to detect the electromagnetic radiation emitted from the first source of electromagnetic radiation; (iii) instruct the second source of electromagnetic radiation to emit electromagnetic radiation in a direction for striking the safety interlock of the pump set; (iv) activate the second electromagnetic radiation detector to detect the electromagnetic radiation emitted from the second source of electromagnetic radiation; and (v) control the pumping apparatus to operate for pumping fluid in the pump set only when electromagnetic radiation emitted from the first source is detected by the first detector and when the electromagnetic radiation emitted from the second source is not detect by the second detector. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic diagram showing a perspective view of an enteral feeding pump showing a portion of a feeding set received on a pump in accordance with one or more aspects of the present invention; 
         FIG. 2  is a schematic diagram showing a perspective view of a pump in accordance with one or more aspects of the present invention; 
         FIG. 3  is a schematic diagram showing an elevation view of an administration feeding set pertinent to one or more aspects of the present invention; 
         FIG. 4  is a block diagram schematically representing a portion of functional elements of a pump in accordance with one or more aspects of the present invention; 
         FIG. 5  is a schematic diagram showing a section of a pump and a safety interlock device of a first embodiment of the present invention; 
         FIG. 6  is a schematic diagram showing a top plan view of a pump and safety interlock device of  FIG. 5 ; 
         FIG. 6A  is a schematic diagram similar to  FIG. 6  showing propagation of a representative light ray in a safety interlock device in accordance with one or more aspects of the present invention; 
         FIG. 7  is a schematic diagram showing a section of a pump and safety interlock device of a second embodiment of the present invention; 
         FIG. 7A  is a schematic diagram showing a section of a pump and a safety interlock device of a third embodiment of the present invention; 
         FIG. 8  is a schematic diagram showing a section of a pump and a safety interlock device of a fourth embodiment of the present invention; 
         FIG. 9  is a schematic diagram showing a section of a pump and a safety interlock device of a fifth embodiment of the present invention; 
         FIG. 10  is a schematic diagram showing a section of a pump and a safety interlock device of a sixth embodiment of the present invention; 
         FIG. 11  is a state diagram of a microprocessor of a pump of the present invention; 
         FIG. 12  is a schematic diagram showing a section of a pump and a safety interlock device of a seventh embodiment of the present invention; 
         FIG. 13  is a schematic diagram showing section of a pump and a safety interlock device of an eighth embodiment of the present invention; 
         FIG. 14  is a schematic diagram showing a top plan view of a pump and a safety interlock device of a ninth embodiment of the present invention; 
         FIG. 15  is a state diagram of a microprocessor of a pump in accordance with one or more embodiments of the present invention; 
         FIG. 16  is a block diagram schematically representing a portion of functional elements of a pump in accordance with one or more aspects of the present invention; 
         FIG. 17  is a flow chart representative of a software subsystem utilizable with a pump that pulses an infrared emitter in accordance with one or more aspects of the present invention; 
         FIG. 18  is a flow chart representative of a software subsystem utilizable with a pump that does not pulse the infrared emitter in accordance with one or more aspects of the present invention; 
         FIG. 19  is a state diagram showing conditions encountered in executing instructions of the software subsystem shown in  FIG. 18 ; 
         FIG. 20  is a schematic diagram showing a top plan view of a pump and a safety interlock device of a tenth embodiment of the present invention; 
         FIG. 21  is a schematic diagram showing a section of the pump and the device along line  21 - 21  of  FIG. 20 ; and 
         FIG. 22  is a schematic diagram showing a section similar to  FIG. 21  but showing a safety interlock device of an eleventh embodiment of the present invention. 
     
    
    
     Corresponding reference characters indicate corresponding parts throughout the several views of the drawings. 
     DETAILED DESCRIPTION 
     Referring now to the drawings, an enteral feeding pump (broadly, “a pumping apparatus”) constructed according to the principles of the present invention is generally indicated at  1 . The feeding pump comprises a housing generally indicated at  3  that is constructed so as to mount an administration feeding set (broadly, a “pump set”) generally indicated at  5  (see  FIGS. 1 and 3 ). It will be appreciated that “housing” as used herein may include many forms of supporting structures (not shown), including without limitation multi-part structures and structures that do not enclose or house the working components of the pump  1 . The pump  1  also has a display screen  9  on the front of the housing  3  that is capable of displaying information about the status and/or operation of the pump. Buttons  11  on the side of the display screen  9  are provided for use in controlling and obtaining information from the pump  1 . It will be understood that although the illustrated pump  1  is an enteral feeding pump, the present invention has application to other types of peristaltic pumps (not shown), including medical infusion pumps. A pump of the same general type as described herein is shown in co-assigned U.S. Pat. No. 4,909,797 entitled ENTERAL DELIVERY SET WITH SHADED DRIP CHAMBER, the disclosure of which is incorporated herein by reference. 
     The enteral feeding pump  1  further includes a pumping unit (indicated generally at  23 ) comprising a pump motor  25  located in the housing  3  and shown schematically in  FIG. 4 . An electrical cord  27  extends from the housing  3  for connection to a source of electrical power for the motor  25 . Alternatively, or in addition, a battery (not shown) may be received in the housing  3  for powering the pump motor  25 . The pumping unit  23  further includes a rotor (generally indicated at  37 ) mounted on a rotor shaft (not shown) of the pumping unit. The rotor  37  includes an inner disk  39 , an outer disk  41  and three rollers  43  (only one is shown) mounted between the inner and outer disks for rotation about their longitudinal axes relative to the disks. In the illustrated embodiment, the pump motor  25 , rotor shaft and rotor  37  may broadly be considered “a pumping device”. The pump housing  3  includes a first lower recess  45  above the rotor  37  and a second lower recess  47  generally adjacent the first lower recess. The housing  3  has an upper recess  49  generally axially aligned with the first lower recess  45  and a shoulder  51  at the bottom of the upper recess for receiving and holding part of the feeding set  5 . A curved recess  53  in the housing  3  above the second lower recess  47  receives and holds another part of the administration feeding set  5  in place. The lower recesses  45 ,  47 , upper recess  49  and curved recess  51  may broadly be considered, individually or as a group, “a receiving portion” of the housing  3  that receives parts of the administration feeding set  5  in a manner that will be described in more detail hereinafter. 
     Referring now to  FIG. 3 , the administration feeding set  5  comprises tubing (broadly, “a conduit”) indicated generally at  55  that provides a fluid pathway between at least one source of fluid and a patient. Tubing  55  can be made of a medical grade, deformable silicone and comprises first tube section  57  connected between a drip chamber  59  and a safety interlock device, generally indicated at  61 . A second tube section  63  is connected to the safety interlock device  61  and at an outlet of the tubing  55  to a connector, such as a barbed connector  65 , suitable for connection to a gastrostomy device (not shown) attached to a patient. Third tube section  67  is connected at an inlet of the tubing  55  to a bag  69  of nutrient liquid and to the drip chamber  59 . As previously stated, pump sets of different constructions may be used, for example a recertification set (not shown) may be used to verify and/or correct the pump accuracy. The pump  1  can be configured to automatically recognize what kind of set is installed and to alter its operation to conform to that called for by the particular pump set. Still further, the pump  1  can be configured to detect with sensors whether the first tube section  57  is properly installed on the pump. 
     As shown in  FIG. 3 , the safety interlock device  61  connects first tube section  57  and the second tube section  63  of the administration feeding set  5 . The safety interlock device  61  has a central axial bore  81  to allow the flow of fluid between the first tube section  57  and the second tube section  63  (see,  FIG. 5 ). The safety interlock device  61  has an upper cylindrical portion  83  that receives a portion of the tube  57 , an electromagnetic radiation propagation affecting member  87  that extends radially outward from the upper cylindrical portion, and a lower cylindrical portion  89  that is received in the second tube section  63  for attaching the second tube section to the safety interlock device. It is to be understood that the safety interlock device  61 , and in particular the member  87  may be separate from the administration feeding set  5 , and/or may be attached to the administration feeding set in such a way that liquid does not pass through the safety interlock device. The electromagnetic radiation propagation affecting member  87  is sized to be received on a seat, indicated generally at  91 , formed at the bottom of the second lower recess  47  in the pump  1  when the administration feeding set  5  is properly loaded on the pump. In the illustrated embodiment, the seat  91  is generally semi-cylindrical to correspond with the shape of the safety interlock device  61  and includes an axially facing surface  95  in the second lower recess  47  and a radially facing surface  99  in the second lower recess  47 . In this first and most other embodiments, proper functioning of the pump  1  is generally achieved when the radiation propagation affecting member  87  is seated in substantially face-to-face relation with the axially facing surface  95  of the seat  91 . However, the rotation orientation of the member  87 , within the seat  91 , about its axis is generally not pertinent to operation. In a few embodiments (noted hereinafter) a particular orientation of the member  87  is useful, in which cases keying structures are provided. Other ways of positioning the propagation affecting member  87  may be used within the scope of the present invention. The safety interlock device  61  and the seat  91  in the housing  3  may be shaped to prevent the administration feeding set  5  from being accidentally dislodged and to prevent the use of non-compliant feeding sets that do not have the safety interlock device. In the illustrated embodiment, the safety interlock device  61  and seat  91  are generally cylindrical in shape but it is understood that other shapes (e.g., hex-shaped) may be used for the safety interlock device and the seat. As will be discussed in more detail below, the safety interlock device  61  is comprised of a material (e.g., a thermoplastic polymer resin such as polysulfone thermoplastic resin or other suitable materials) that is opaque to visible light but easily transmits electromagnetic radiation in the infrared range. 
     Generally speaking, a safety interlock device is able to affect the propagation of electromagnetic radiation by diffusion, diffraction, reflection and/or refraction, or any combination of diffusion, diffraction, reflection and/or refraction. Diffusion is generally understood as the scattering of electromagnetic radiation rays either when reflected from a rough surface or during transmission of electromagnetic radiation through a translucent medium. Diffraction is generally understood as the bending of electromagnetic radiation rays around the edges of opaque objects. Reflection is understood as the return or change in the direction of travel of particles or radiant energy which impinges on a surface but does not enter the substance providing the reflecting surface. Refraction is understood as the change in direction of motion of a ray of radiant energy as it passes obliquely from one medium into another in which the speeds of propagation are different (e.g., media of different densities). The amount of refraction is based on the index of refraction dependent in part on the density of the material facing the medium. 
     The pump  1  can be programmed or otherwise controlled for operation in a desired manner. For instance, the pump  1  can begin operation to provide feeding fluids from bag  69  to the patient. The care giver may select, for example, the amount of fluid to be delivered, the rate at which the fluid is to be delivered and the frequency of fluid delivery. As shown in  FIG. 4 , the pump  1  has a controller  77  (broadly, “a control system”) including a microprocessor  79  that allows it to accept programming and/or to include pre-programmed operational routines that can be initiated by the care giver. The microprocessor  79  controls pump electronics  80  that operate the motor  25 . A software subsystem  82  is used to determine if the feeding set  5  has been positioned properly on the pump  1 . 
     In the first embodiment, the pump includes an infrared (“IR”) emitter  105  (broadly, “a source of electromagnetic radiation”) housed in the second lower recess  47 . Referring to  FIGS. 5 and 6 , the IR emitter  105  is operatively connected to the controller  77  for emitting an electromagnetic signal having a (“first”) wavelength in the infrared range in a direction for striking the safety interlock device  61  of the feeding set  5 . In the illustrated embodiment, the source of electromagnetic radiation is an infrared (IR) emitter  105  but it is understood that other types of sources of electromagnetic radiation may be used without departing from the scope of this invention. An infrared (“IR”) detector  109  located in the second lower recess  47  is operatively connected to the controller  77  for receiving the infrared signal from the IR emitter  105  and providing an indication to the controller that the feeding set  5  is properly positioned in the pump  1 . In the illustrated embodiment, the IR detector  109  (broadly, “a first sensor”) detects infrared radiation but it is understood that electromagnetic radiation sensors that detect other types of electromagnetic radiation may be used without departing from the scope of this invention. The IR detector  109  distinguishes infrared radiation from other types of electromagnetic radiation (e.g., visible or ultraviolet light). A visible light detector  111  (broadly, “a second electromagnetic radiation detector” and “a second sensor”) is housed in the second lower recess  47  generally adjacent the IR detector  109 . The visible light detector  111  provides a signal to the controller  77  when visible light from the surrounding environment (e.g., electromagnetic radiation of a second wavelength) is detected to indicate that the safety interlock device  61  is not mounted in the second lower recess  47  in a position that blocks visible light from reaching the detector. Preferably, the visible light detector  111  is configured to detect electromagnetic radiation in the visible range, but not to detect electromagnetic radiation outside the visible range (e.g., infrared radiation). A second electromagnetic radiation detector could be configured to detect electromagnetic radiation in other ranges, such as in the ultraviolet range. Thus, the visible light detector  111  can distinguish visible light from infrared radiation. As used herein, electromagnetic radiation of a “first” or “second” wavelength is intended in each case to encompass a range of wavelengths, such as wavelengths falling in the infrared range, visible range and/or ultraviolet range. 
     Other sensors (not shown), such as a sensor that determines the type of pump set that has been placed in the pump  1  and a flow monitoring sensor can be in communication with the controller  77  to facilitate accurate operation of the pump. The IR emitter  105  is positioned in an alcove  113  in the second lower recess  47  of the housing  3  so that electromagnetic radiation (indicated by arrows A 1  in  FIG. 6 ) from the emitter is directed to the electromagnetic radiation propagation affecting member  87  of the safety interlock device  61  (see also,  FIG. 5 ). When the safety interlock device  61  is properly located on the seat  91 , the infrared radiation from the IR emitter  105  is diffused through the electromagnetic radiation propagation affecting member  87  and internally reflected so that the infrared radiation is directed to and detected by the IR detector  109 . Diffusion may be enhanced by the addition of particulates to the material of the member  87 . In this first embodiment (and other embodiments) the infrared radiation propagation is affected primarily through internal reflection. Other effects on infrared radiation propagation, such as diffusion, may also assist. However, any infrared radiation that is refracted is minimal and does not contribute to the infrared radiation signal seen by the IR detector  109  (i.e., refraction causes a reduction in signal strength). The IR detector is positioned in an alcove  117  in the radially facing surface  99  of the seat  91  and the visible light detector  111  is positioned in an alcove  119 . The alcoves  113 ,  117 ,  119  recess the IR emitter  105  and the IR and visible light detectors  109 ,  111  to protect them from physical contact with the propagation affecting member  87 . Although not shown, a clear plastic window may enclose each of the emitter  105  and the detectors  109 ,  111  within their corresponding alcoves  113 ,  117 ,  119  for additional protection. Moreover, the alcoves  117  and  119  help to shield the detectors  109  and  111  from ambient electromagnetic radiation (which may include both visible light and infrared radiation). 
     In the illustrated first embodiment, the IR emitter  105  is located approximately 90 degrees from the IR detector  109 . When the feeding set  5  is not loaded in the second lower recess  47  and the electromagnetic radiation propagation affecting member  87  is not received on the seat  91 , the infrared radiation from the IR emitter  105  is not detected by the IR detector  109 . Also when the safety interlock device  61  is not received on the seat  91 , visible light from outside of the pump  1  (i.e., ambient light) may enter the second lower recess  47  and is detected by the visible light detector  111 . The propagation affecting member  87  is preferably constructed of a material that transmits infrared radiation, but is opaque to visible light. The propagation affecting member  87  may be monolithic or may have other constructions such as an outer layer (not shown) that transmits infrared radiation, but does not transmit visible light and an inner layer or core that is transmissive to both infrared radiation and visible electromagnetic radiation. 
     Referring now to  FIG. 6A , movement of infrared radiation within the electromagnetic radiation propagation affecting member  87  is schematically illustrated. The IR emitter  105  emits infrared radiation in a cone toward the side of the member  87 . The IR emitter  105  is arranged generally perpendicular to the immediately adjacent side of the member  87 . The centerline CL of the cone is denoted in the drawing. For simplicity, we will ignore diffusion and look at a ray R 1  of radiation that is a bisector of approximately one half of the cone. The ray R 1  is representative of the nominal path of infrared radiation in this half of the cone. The other half of the cone (i.e., that portion above the centerline CL in  FIG. 6A ) is believed to be of small or no use in providing a light signal capable of being detected by the IR detector  109 . The ray R 1  strikes the side of the propagation affecting member  87  at an angle so that it enters the member rather than being reflected back. The ray R 1  travels generally toward the center of the member  87  until it reaches a boundary B (broadly, “an inner boundary region”) around the axial bore  81  of the member. The ray R 1  is reflected back toward the side of the member  87  where a good percentage of the ray is reflected back toward the center. At the boundary B, the ray R 1  is once more reflected back toward the side of the member  87 . Finally, the ray strikes the interior side of the member  87  at a location that is about 96 degrees away from the location of the IR emitter  105 . It has been found that a particularly high level of intensity of infrared radiation escapes the member  87  at this location. Accordingly, the IR detector  109  is preferably positioned here, or in a range of around 75-105 degrees. Another higher intensity node is found at a location around 49 degrees from the IR emitter  105 , as would be expected from the reflection. 
     The boundary B of the electromagnetic radiation propagation affecting member  87  can be made of the same material as the remainder of the member. The material at the boundary B may be more “polished” (i.e., more specular) than elsewhere to increase its ability to reflect electromagnetic radiation impinging upon the boundary. However, it is also possible that the central part of the member  87  could be formed of a separate material. In that case, the member  87  would be formed of an inner and an outer member, such as described below in regard to  FIG. 22 . In use, the administration feeding set feeding fluid bag  69  can be hung from a suitable support, such as an IV pole (not shown). The drip chamber  59  can be placed in the first lower recess  45  and upper recess  49  in an operating position as shown in  FIG. 1 . The first tube section  57  is placed around the lower part of the rotor  37  and the safety interlock device  61  is placed on the seat  91  at the bottom of the second lower recess  47 . The seat  91  in the second lower recess  47  is generally located so that the safety interlock device  61  can be placed into the second lower recess at a location in which the first tube section  57  is substantially stretched around the rotor  37 . The IR emitter  105  and IR detector  109  may intermittently or continuously check for the presence of the properly loaded feeding set  5 . When the safety interlock device  61  is received in a proper operating position on the seat  91 , the infrared signal from the IR emitter  105  is directed to the electromagnetic radiation propagation affecting member  87 . The electromagnetic radiation propagation affecting member admits the infrared radiation into its interior where the electromagnetic radiation is diffused and internally reflected (see  FIGS. 6 and 6A ). Some of the infrared radiation which is redirected outward and impinges the outer boundary of the electromagnetic radiation propagation affecting member  87  substantially at right angles thereto passes out of the electromagnetic radiation propagation affecting member. Some of the escaping infrared radiation is directed toward the IR detector  109 . The IR detector is periodically operated and detects the presence of infrared radiation when the feeding set  5  has been properly loaded on the pump. It is understood that the IR detector  109  is preferably unable to detect electromagnetic radiation having a wavelength in the visible light region of the electromagnetic spectrum. Upon detection of the infrared signal, the IR detector  109  sends a corresponding signal to the microprocessor  79 . Also, when the safety interlock device  61  is loaded onto the seat  91 , visible light is blocked by the member  87  from reaching the visible light detector  111 . When the set  5  is loaded, the visible light detector  111  sends a signal to the microprocessor  79  to indicate that visible light is blocked and the pump  1  may be operated. 
     In one embodiment, the IR emitter  105  and IR detector  109  are both operated intermittently to detect the presence of the safety interlock device  61  on the seat  91 . The IR emitter  105  is operated to generate a pattern of infrared radiation pulses. The IR detector  109  is operated in a series of detector activations or pulses that check for the presence of electromagnetic radiation from the IR emitter  105 . Typically, the number of activations from the IR detector  109  will be greater than the number of pulses from the IR emitter  105  for a given period of time. For example, the IR detector  109  may have two activations in a three second time period and the IR emitter  105  may be programmed to generate one pulse of infrared radiation during the three second time period. During the three second time period, the pump  1  has a ratio of detector activations to emitter activations of about 2:1. It is understood that the pump  1  may have other ratios and that the IR emitter  105  and IR detector  109  may operate in other predetermined intermittent patterns without departing from the scope of this invention. The IR detector  109  and the controller  77  may be configured for recognizing a particular, and for example irregular, pattern of activations of the IR emitter  105 . 
       FIG. 7  shows a seat  191  and a safety interlock device  121  of a second embodiment of the present invention. The safety interlock device  121  of this embodiment has a electromagnetic radiation propagation affecting member  123  with an angled annular surface  125 . The IR emitter  129  is located in an alcove  131  in a radially facing surface  132  of a seat  191  of housing  143  and is positioned to direct infrared radiation toward the safety interlock device  121  in a similar manner as the first embodiment. In the embodiment of  FIG. 7 , the IR detector  133  and visible light detector  135  are located in respective alcoves  137 ,  139  in an axially facing surface  141  of the seat  191 . The angled annular surface  125  is reflective so that it reflects infrared radiation from the IR emitter  129  downward to the IR detector  133  when the safety interlock device  121  is received on the seat  191  of the housing  143 . When the safety interlock device  121  is not properly received in the seat  191 , visible ambient light can be detected by the visible light detector  135 . 
       FIG. 7A  shows a seat  159  and a safety interlock device  161  of a third embodiment of the present invention. In this embodiment, the safety interlock device  161  includes a reflector  165  on the external radial surface of an electromagnetic radiation propagation affecting member  167 . The reflector  165  may be a layer of reflective tape or a layer of polished metal affixed to the remainder of the electromagnetic radiation propagation affecting member  167 . In the embodiment of  FIG. 7A , the IR emitter  169 , the IR detector  171 , and the visible light detector  173  are arranged in an alcove  175  in a radially facing surface  177  of housing  179  in a manner such that the three devices are generally vertically aligned and parallel to each other. It is understood the IR emitter  169 , IR detector  171 , and visible light detector  173  may be otherwise arranged. When the safety interlock device  161  is received in the seat  159 , the infrared radiation emitted from the IR emitter  169  is reflected off the reflector  165  and transmitted to the IR detector  171  and ambient visible light is blocked from detection by the visible light detector  173 . When the safety interlock device  161  is not loaded in the seat  159 , infrared radiation is not transmitted to the IR detector  171  and ambient visible light can be detected by the visible light detector  173 . 
       FIG. 8  shows a seat  189  and safety interlock device  191  of a fourth embodiment of the present invention. As in the prior embodiments, the safety interlock device  191  can be removably positioned on the seat  191  and thereby releasably attached to the pump by the user or caregiver. In this embodiment, the safety interlock device  191  includes a light pipe  195  (“an electromagnetic radiation propagation affecting member”) received in the seat  189  of the housing  199  when the feeding set  201  is loaded on the pump. The light pipe  195  includes an outer annular portion  205 , an angled annular wall  207 , and a central portion  209  between the angled wall and the upper portion  211  that receives a tube  213  of the feeding set  201 . As shown in  FIG. 8 , the IR emitter  217  and IR detector  219  are both housed below a bottom wall  221  of the seat  189 . The IR emitter  217  directs infrared radiation upward to the outer annular portion  205  of the light pipe  195  that is reflected by the angled annular wall  207  through the central portion  209  of the light pipe (around a central fluid passage  218 ) before being reflected to the IR detector  219  by the angled annular wall  207  on the opposite side of the light pipe. When the safety interlock device  191  is not properly seated on the seat  189  in the loaded position of the feeding set  201 , the IR signal from the IR emitter  217  is not transmitted through the light pipe  195  to the IR detector  219 . A visible light detector (not shown) may be present for use in detecting ambient light as in earlier embodiments of the invention. 
       FIG. 9  shows a seat  231  and a safety interlock device  235  of a fifth embodiment of the present invention. This safety interlock device  235  of this embodiment comprises an infrared radiation transmissive material that also refracts the infrared radiation transmitted through the safety interlock device. The safety interlock device  235  has a generally polygonal shape. Opposite sides  236  of the safety interlock device  235  are angled parallel to each other. The seat  231  is keyed to receive the safety interlock device in the particular orientation illustrated in  FIG. 9  so that electromagnetic radiation is refracted in the desired manner, as will be described. An IR emitter  237 , an upper IR detector  239  (broadly, “a second detector”), and a lower IR detector  241  (broadly, “a first detector”) are positioned for sensing if an administration feeding set  245  has been properly loaded into the pump. The upper and lower IR detectors  239 ,  241  are positioned on the opposite side of the seat  231  from the IR emitter  237  such that the emitter and the detectors are oriented at approximately 180 degrees with respect to each other. Also, the upper IR detector  239  and lower IR detector  241  are spaced apart a distance D so that when infrared radiation is passed through the safety interlock device  235 , the radiation (as indicated at arrow A 5 ) is refracted or bent downward so that the lower IR detector  241  senses the presence of infrared radiation and sends a signal to the microprocessor to enable operation of the pump. The sides of the safety interlock device  25  are angled parallel to each other so that refraction of the infrared radiation is directed by the refraction to the lower IR detector  241 . When the safety interlock device  235  is not loaded in the seat  231  of the pump, the infrared radiation from the IR emitter  237  (as indicated by phantom arrow A 6 ) passes through the seat such that the beam of infrared radiation is directed to only the upper IR detector  239 , which sends a signal to the controller to disable operation of the pump. The density and width of the safety interlock device  235  affects the distance D between the upper detector  239  and the lower detector  241  so that if an feeding set is used having a safety interlock device made of a material having a different density and/or width, the electromagnetic radiation will not be refracted the proper distance to impinge on the lower IR detector  241  even if the feeding set is properly loaded. A visible light detector (not shown) may be present for use in detecting ambient light as in earlier embodiments of the invention. 
       FIG. 10  shows a seat  271  and safety interlock device  273  of a sixth embodiment of the present invention. The safety interlock device  273  of this embodiment is generally similar to the first embodiment but includes a layer  275  of infrared radiation blocking material on the external surface of the safety interlock device. As in the first embodiment, the safety interlock device  273  includes an electromagnetic radiation propagation affecting member  279  that transmits infrared radiation through the safety interlock device. The external radial surface  281  of the electromagnetic radiation propagation affecting member  279  is free from infrared radiation blocking material as this surface is used to receive the infrared signal from the IR emitter  285  so that the IR signal is transmitted through the safety interlock device  273  for detection by the IR detector  287 . It is understood that the IR emitter  285  and IR detector  287  of this embodiment may be positioned at any angle around the radial surface  291  of the seat  271 . The IR blocking layer  275  prevents infrared electromagnetic radiation from outside sources (e.g., sunlight) from reaching the IR detector  287  when the administration feeding set  295  is loaded on the pump. It is envisioned that portions of the radial surface  281  of the electromagnetic radiation propagation affecting member  279  may have IR blocking material thereon. In that event, the electromagnetic radiation propagation affecting member  279  is preferably keyed with structure (not shown) on the seat  271  so that the IR emitter  285  and IR detector  287  are unblocked. A visible light detector (not shown) may be present for use in detecting ambient light as in earlier embodiments of the invention. 
     The safety interlock device  273  of this embodiment may be constructed by a “co-injection molding” process also referred to as a “two-shot injection molding” process. The process includes injection molding the safety interlock device  273  with the electromagnetic radiation propagation affecting member  279  comprising an infrared radiation transmissive material (e.g., light transmissive thermoplastic polymer resin) together with the IR blocking layer  275  (e.g., an opaque thermoplastic polymer resin). Other variations of this embodiment may include the use of a visible light blocking material (e.g., thermoplastic polymer resin mixed with red dye) instead of an IR blocking material to allow infrared electromagnetic radiation to pass through the safety interlock device but prevent visible light from passing through the device. 
       FIG. 11  is a state diagram illustrating the various conditions the controller  77  ( FIG. 4 ) may encounter when operating the software subsystem  82  to determine if the safety interlock device  61  is properly loaded on the pump. The state diagram has application to other embodiments, but will be described in respect to the first embodiment. As shown in  FIG. 11 , for the controller to provide a “SET LOADED” status, the status of the IR emitter  105  and IR detector  109  must be “ON” and the status of the visible light detector  111  must be “OFF”. Any other combination of status indications from the IR emitter  105 , IR detector  109  and visible light detector  111  results in a “FAULT” status being indicated by the controller. The “FAULT” status will prompt the user to check the loading of the safety interlock device  61  and will prevent the pump  1  from operating. Once the feeding set  5  is properly loaded, the controller  77  will sense a “SET LOADED” condition and initiate operation of the pump  1 . During operation of the pump, the IR emitter  105  may operate continuously so that the safety interlock status is continuously monitored and if the status changes from “SET LOADED” to “FAULT”, the controller  77  will stop operating the pump  1  and enter an alarm condition. Optionally, the IR emitter  105  may be operated intermittently with brief pulses of infrared electromagnetic radiation being transmitted at a set time interval to the IR detector  109  so that the safety interlock status is continuously monitored. The visible light detector  111  may continuously check for the presence of visible light so that if the safety interlock  61  is removed from the seat  91  and allows visible light into the recess, the visible light detector  111  immediately senses this condition and signals the controller  77  to enter an alarm condition. The visible light detector  111  may operate intermittently without departing from the scope of this invention. 
       FIG. 12  shows a seat  301  and safety interlock device  303  of a seventh embodiment of the present invention. In this embodiment, the safety interlock device  303  is made of an infrared radiation opaque material and has an opening  307  passing from the top surface  309  to the bottom surface  311  of the device. The opening  307  is configured to break the beam of infrared radiation (indicated at A 7 ) from the IR emitter  313  via diffraction into a series of spaced apart beams (indicated at A 8   a  thru A 8   e ) that are detected by a series of IR detectors  321   a  through  321   e  located below the seat  301  in the housing  327 . In the illustrated embodiment the IR emitter  313  is located in an alcove  331  above the safety interlock device  303  and the IR detectors ( 321   a - 321   e ) are located in an alcove  335  below the safety interlock device  303 . The IR detectors  321   a  through  321   e  are spaced apart a distance such that the infrared radiation that is diffracted by the opening  307  impinges on the IR detectors. It is understood that the IR emitter  313  could be below the safety interlock device  303  and that the IR detectors  321   a - 321   e  could be above the safety interlock device or in some other arrangement without departing from the scope of this invention. A visible light emitter and array of visible light detectors (not shown) could be used in place of the IR emitter  313  and IR detectors  321   a - 321   e.    
     In the embodiment of  FIG. 12 , the infrared radiation from the IR emitter  313  diffracted by the safety interlock device  303  so that the infrared radiation from the IR emitter is detected by the IR detectors  321   a  thru  321   e  when the interlock device  303  is properly located on the seat  301 . The number of detectors  321   a - 321   e  may be other than shown in this embodiment without departing from the scope of the present invention. When the interlock device  303  is not present, infrared radiation from the IR emitter  313  is seen by the middle IR detector  321   c  (broadly, a second detector), but not by the other detectors  321   a ,  321   b ,  321   d ,  321   e . The interlock device  303  is preferably keyed (not shown) to the housing  327  to assure proper positioning. A visible light detector (not shown) may also be used to detect ambient visible light as in earlier embodiments of the invention. 
       FIG. 13  shows a seat  381  and a safety interlock device  385  of an eighth embodiment of the present invention. In this embodiment, the safety interlock device  385  has an electromagnetic radiation propagation affecting member  387  made of a material capable of transmitting infrared radiation. The electromagnetic radiation propagation affecting member  387  has a layer of material  389  on the top surface of the member that is opaque to the transmission of IR. The opaque layer  389  has an opening  391  that breaks the single infrared radiation beam A 9  from the IR emitter  393  via diffraction into a series of spaced apart beams A 10   a  through A 10   e  that are detected by respective IR detectors  395   a  through  395   e  when the safety interlock device  385  is properly seated in the pump. When the propagation affecting member  387  is removed from the seat  381 , only the IR detector  395   c  sees the infrared radiation from the IR emitter  393 . It will be understood that the number of IR detectors  395   a - 395   e  may be other than shown. It is further understood an IR detector other than IR detector  395   c  can see infrared radiation or more than one IR detector can see the infrared radiation when the propagation affecting member  387  is removed from the seat  381 . One can also switch the orientation of the group of IR detectors  395   a - 395   e  to be in the lower portion of seat  381  and the IR emitter or IR emitters in the upper portion of the seat. A visible light emitter and visible light detectors (not shown) could be used in place of the IR emitter  393  and IR detectors  395   a - 395   e . In that event, the electromagnetic radiation propagation member would be capable of transmitting visible light, but have a layer (like layer  389 ) that is opaque to visible light. Moreover, another visible light detector could be used in this eighth embodiment as in prior embodiments. The interlock device  385  is preferably keyed (not shown) to assure proper positioning. 
       FIG. 14  shows a seat  421  and a safety interlock device  461  of a ninth embodiment of the present invention. The seat  421  is part of a pump  401  that is illustrated in block diagram form in  FIG. 16 . The pump  401  mounts a feeding set  405  including tubing  455  and a safety interlock device  461 . The feeding set  405  may be substantially the same as the feeding set  5  shown in  FIG. 3 . A pumping device  423  includes a rotor  437  driven by a motor  425 . The rotor  437  can engage the tubing  455  to pump fluid to a patient, substantially as described in previous embodiments. This embodiment includes an IR emitter  427 , an IR detector  429 , a visible light emitter  433 , and a visible light detector  435  in respective alcoves in the housing  439  ( FIG. 14 ). In this embodiment, the IR emitter  427  and the IR detector  429  are arranged at an approximately 90 degree angle with respect to each other and the visible light emitter  433  and the visible light detector  435  are arranged at an approximately 90 degree angle with respect to each other. Other relative angles are also possible. Generally speaking, the IR detector  429  is located relative to the IR emitter  427  so that in the absence of the safety interlock device  461 , the infrared radiation emitted by the IR emitter will not impinge upon the IR detector. Both the IR emitter  427  and visible light emitter  433  are arranged generally perpendicular to the immediately adjacent side of the safety interlock device  461  when properly mounted on the pump  401 . Moreover in this and other embodiments, the gap between the emitters  427 ,  433  and the safety interlock device  461  is preferably small in relation to the diameter of the safety interlock device (e.g., nominally 0.005 inches or about 0.13 mm). The safety interlock device  461  of this embodiment is transmissive to infrared radiation but is opaque to visible light. In other words, the interlock device  461  filters out visible light but passes infrared radiation. 
     The infrared signal emitted by the IR emitter  427  is diffused and reflected in the safety interlock device  461  such that the signal strikes the IR detector  429  when the feeding set  405  is properly loaded. The seat  421  and safety interlock device  461  of this embodiment are especially useful in operating in a dark room since the visible light emitter  433  provides a second electromagnetic radiation signal (e.g., a blue light) that substitutes for visible light not present in a dark room. The control system of this embodiment first pulses the IR emitter  427  until the IR detector  429  receives a signal recognizing that the safety interlock device  461  is loaded. Next, the visible light emitter  433  is activated to send a light signal that is blocked by the safety interlock device  461  if the safety interlock device is correctly located in the seat  421 . The visible light detector  435  is operated to check for the visible light signal and to detect excess ambient light. If either condition is detected (i.e., light from emitter  433  or excess ambient light), a controller  477  activates an alarm that warns the operator to check the alignment of the feeding set  405  and does not allow the pump  401  to operate until the condition is corrected. The blockage of ambient light by the safety interlock device  461  causes the controller  477  to recognize that the set is loaded and the pump may be operated. The pump  401  detects a fault condition if the visible light detector  435  detects the visible light signal from the visible light emitter  433  after the IR detector  429  detects the presence of the safety interlock device  461 . 
     Referring to  FIG. 16 , the controller  477  has a microprocessor  479  that controls pump electronics  480  that operate the motor  425 . The controller  477  includes at least one software subsystem  482  used in detecting the proper positioning of the feeding set  405  on the pump  401 . Operation of the software subsystem  482  for use in controlling the pump  401  based on whether the feeding set  405 , and in particular the safety interlock device  461 , is properly positioned on the pump, is given in a flowchart illustrated in  FIG. 17 . This particular set of instructions operates so that the IR emitter  427  is turned on and off or “pulsed”. When the pump  401  is powered up at  1396 , the software initializes at block  1398  by setting several items to OFF. For example, the IR emitter  427  and visible light emitter  433  are set to OFF. Similarly, a program feature called Ambient Lock is set to OFF, as are program features InstantOutput and Output. Briefly, Ambient Lock is a feature that is triggered to prevent operation of the pump  401  when it is determined that the IR detector  429  sees infrared radiation from a source other than the IR emitter  427 . The InstantOutput is a temporary or preliminary output of the software (i.e., whether the pump  401  is to be allowed to begin pumping). Output is the final output of the software used for determine whether the pump  401  is permitted to operate for pumping fluid. 
     At the outset as shown in  FIG. 17 , the function of the software subsystem  482  will be described assuming that the safety interlock device  461  has been properly positioned on the pump  401 . After the initialization  1398 , the IR emitter  427  is switched (or “toggled”) ON at block  1400  so that infrared radiation is emitted. If the safety interlock device  461  is positioned so that the infrared radiation strikes the safety interlock device, the propagation of the infrared radiation from the emitter  427  will be affected so that infrared radiation is diffused and reflected within the safety interlock device. Some of the infrared radiation exits the safety interlock device and strikes the IR detector  429 . The software pauses briefly at block  1401  after the IR emitter  427  is toggled on and then reads the IR detector  429  at block  1402  to determine if it is “ON” (i.e., that infrared radiation is detected). The software subsystem  482  then proceeds to a decision block  1404  where it queries whether the IR detector  429  is ON and either the IR emitter  427  is OFF or the Ambient Lock is ON. In the case where the safety interlock device  461  is properly positioned, the IR detector  429  is ON, but the IR emitter  427  is ON and the Ambient Lock is OFF. Therefore, the answer to the query at decision block  1404  is “no”. In other words, the IR detector  429  has seen infrared radiation from the emitter  427 , which is indicative of proper positioning of the safety interlock device. The software then sets the Ambient Lock to OFF at block  1404   a  (which is no change from its initialized condition) and proceeds to another decision block  1406 . 
     In the next decision block  1406 , the software subsystem  482  can operate to bypass evaluation of the visible light detector  435  in a situation where either the Ambient Lock is ON (because infrared radiation was detected by detector  429  when the IR emitter  427  was OFF), or where the IR emitter  427 , IR detector  429  and visible light emitter  433  are all OFF. In the present case, Ambient Lock is OFF and both the IR emitter  427  and IR detector  429  are ON, so the software proceeds to read the visible light detector  435  at block  1408 . The properly located safety interlock device  461  blocks the visible light detector  435  so the reading is OFF. Thus when queried at the next decision block  1410 , the answer is “no” and the program moves to the next decision block  1412 . The visible light emitter  433  has not been turned on yet so the program causes the visible light emitter to be turned on at block  1414  and moves to the end of the program where there is a delay  1415 . The InstantOutput and Output were both initialized to OFF so that the pump  401  is not yet allowed to run. After the delay at  1415 , the program returns to step  1400 . The intermittent operation of the IR emitter  427  and conditional operation of the visible light emitter  433  provides significant power savings in operation of the pump  401 . This feature is helpful when the pump  401  is operated on battery power. 
     Proceeding back to the toggling step  1400 , the IR emitter  427  is now turned OFF and the IR detector  435  reads OFF when it is queried at  1404  after the delay. As a result, the Ambient Lock stays OFF so that when the next decision block  1406  is reached the answer is again in the affirmative and the visible light detector  435  is read once again at  1408 . The safety interlock device  461  still blocks the visible light detector  435  so the visible light detector is OFF. Unlike the first loop through the program steps, the visible light emitter  433  is now on so the program moves on to set the InstantOutput to ON at block  1416 , indicating that the pump  401  should be allowed to operate for pumping fluid. However, the program may not immediately allow the pump  401  to operate. As indicated in the next action block  1418 , output filtering may be used before the final Output is given. For instance, the software may require at block  1418  that there be a number of occurrences of the InstantOutput  1416  being set to ON before the final Output  1418  is set to ON. Various algorithms for establishing confidence in the final output of the program could be employed. On the other hand, output filtering could be omitted in which case the Output  1418  would be equivalent to the InstantOutput  1416  in every instance. In either case, once the Output  1418  is set to ON, the pump  401  is allowed to operate. Once operation of the pump  401  is permitted, a routine for checking to make sure the safety interlock device  461  remains in position can be executed. In the illustrated embodiment, this is accomplished by continued operation of software subsystem  482 . It is also envisioned that the visible light emitter  433  could be turned off again to conserve power. Various ways of operating the IR emitter  427  and visible light emitter  433  intermittently can be employed within the scope of the present invention. 
     It will be appreciated that there are several circumstances in which the software subsystem  482  would prevent operation of the pump  401  by detecting fault conditions indicative of the safety interlock device  461  of the feeding set  405  not being properly positioned on the pump. Reference is also made to  FIG. 15  showing several conditions that can occur from the implementation of the software instructions found in the software subsystem  482 . The conditions shown are not intended to be exhaustive, but representative of likely conditions to occur in the operation of the pump  401 . Until such time as the IR detector  429  detects infrared radiation (IR detector “ON”), the software subsystem  482  will not allow the pump  401  to operate. In other words, Output  1418  will never be set to ON until after the IR detector  429  has at least once detected infrared radiation. If the IR detector  429  has never been ON, when the software reaches decision block  1406 , the answer will be “no” and the program will proceed to the end of the loop with Instant Output  1422  set to OFF. Similarly, the visible emitter  433  will not be turned on at  1414  until a point after infrared radiation from the IR emitter  427  has been detected by the IR detector  429 . In that case, the software subsystem  482  proceeds from decision block  1406  to turn the visible emitter  433  is OFF (block  1420 ) and the InstantOutput is set to OFF (block  1422 ). 
     In the first condition or state of  FIG. 15 , both the IR emitter  427  and IR detector  429  are OFF. This may occur, for example if the IR emitter  427  had been ON, but the IR detector  429  did not detect infrared radiation in a previous loop of the software subsystem  482  shown in  FIG. 17 . This would occur, for example if the feeding set  405  has not been installed. At decision block  1406 , the answer to the query would have been “no”, so the program would have set InstantOutput  1422  to OFF and passed to the end of the loop. In a second loop, the IR emitter  427  is toggled OFF so that now both the IR emitter and IR detector  429  are OFF as shown in condition 1. This is an indication that the feeding set  405  is not in place on the pump  401  (a “fault” condition). We note that the condition XX in the table of  FIG. 15  is meant to indicate not applicable or inactive for the particular component in the specific condition described. 
     The second condition of  FIG. 15  is the first of the conditions in which the feeding set  405  and safety interlock  461  would be detected. Previously, the software subsystem  482  would have cycled through a loop in which the visible light emitter  433  would have been turned on at  1414 . This prior program loop is represented by condition 6 in which the IR emitter  427  and IR detector  429  are ON, but the visible light emitter  433  has not yet been energized so that Output is not yet allowed at block  1418  to be set to ON. In the second loop, the IR emitter  427  and IR detector  429  are OFF, but when the program reaches block  1408  the visible light detector  435  is read. Assuming the feeding set  405  is properly in position, the visible light detector  435  will not be ON so that the software subsystem  482  finds the feeding set properly positioned and sets Output  1418  to ON so that the pump  401  may operate. Condition 8 recognizes that in a later loop of the software subsystem  482  the IR emitter  427 , IR detector  429  and visible light emitter  433  may all be ON, but that a reading of OFF for the visible light detector  435  still allows results in Output  1418  being set to ON. Conditions 3 and 9 are similarly parallel, but in these conditions the visible light detector  435  detects light emitted from the visible light emitter  433 , thus preventing the pump  401  from being activated to pump fluid to a patient. 
     Condition 4 illustrates a situation in which ambient electromagnetic radiation in the environment surrounding the pump  401  is detected by the IR detector  429 . The IR emitter  427  is OFF, so the software subsystem  482  may know that the infrared radiation is not coming from the IR emitter. In that event, the software subsystem  482  receives a “yes” answer to the query at block  1404  and then sets AMBIENT LOCK to ON in block  1404   b . As a result, the software subsystem  482  bypasses at block  1406  any evaluation of the presence of visible light and sets InstantOutput to OFF at  1422 . In condition 5, the safety interlock device  461  is not in place so that the initial reading at block  1402  of the IR detector  429  with the IR emitter  427  ON will be that the IR detector is OFF. The software subsystem  482  will immediately proceed after block  1406  through blocks  1420  and  1422  to set Output (at block  1418 ) to OFF without any further evaluation of visible light. The pump  401  may also be configured to indicate there is a BRIGHT ambient light condition such as might occur if the pump was placed in or near a window in home use. The indication of bright ambient light would instruct the user to move the pump to a lower light location. 
     The software subsystem  482  is also capable of detecting a condition in which there is excessively bright ambient light. As shown in condition 7, the IR emitter  427  and IR detector  429  are both ON, which is indicative of the feeding set  405  being properly positioned on the pump  401 . In fact, the set  405  either has not been properly loaded, or an improper set that does not block visible light has been loaded. However, although the visible light emitter  433  is OFF, the visible light detector  435  detects visible light. The software subsystem  482  proceeds at decision block  1410 , when the visible light detector  435  is ON, to block  1420  and  1422  so InstantOutput is set to OFF and the pump  401  cannot run. 
     Another software subsystem  484  that could be used to operate the controller  477  of the pump  401  is illustrated in  FIG. 18 . In this system for detecting proper placement of the feeding set  405  including the safety interlock device  461 , the IR emitter  427  is not turned off and on (i.e., it is not “pulsed”). Thus after the initialization step  1428 , the IR emitter  427  is turned on at block  1430  and remains on while the pump  401  is powered. As illustrated in condition 1 in the table of  FIG. 19  showing selected operating conditions of the software subsystem  484  of  FIG. 18 , the only time the IR emitter  427  is OFF is when the pump  401  is not yet turned on. Referring again to  FIG. 18 , the software subsystem  484  delays at block  1431  after the IR emitter  427  is turned on before reading the IR detector  429  at block  1432 . The software subsystem  484  conditions any further checks for confirming the feeding set is properly positioned on the detection of infrared radiation by the IR detector  429  at block  1433 . Condition 2 illustrates the situation where the IR emitter  427  is on, but infrared radiation is not detected by the IR detector  429 . Once the IR detector  429  detects infrared radiation, the program proceeds in a first loop to read the visible light detector  435  at block  1434  to make certain the visible light detector is OFF (block  1435 ), and then turns the visible light emitter  433  ON at block  1436 . After a delay at block  1437 , the software subsystem  484  proceeds to a second loop in which the software subsystem  484  confirms that visible light is blocked at  1435  and because the visible light emitter  433  is found to be ON at  1438  sets InstantOutput to ON at block  1440 . Assuming no further output filtering, Output is set to ON at block  1442  and the pump  401  is permitted to operate. However if visible light is detected (i.e., at block  1434 ) prior to activation of the visible light emitter  433 , the visible light emitter is prevented from being turned on. In that case, the software subsystem  484  will proceed to block  1444  to turn the visible light emitter  433  off, and at block  1446  to set InstantOutput to OFF. Detection of visible light by the visible light detector  435  prior to activation of the visible light emitter is shown in condition 3 of  FIG. 19 . 
     Conditions 4 and 6 both result in the software subsystem  484  setting Output  1442  to ON and allowing the pump  401  to operate because the feeding set and safety interlock device  461  are detected. Conditions 5 and 7 illustrate circumstances in which the detection of visible light by the visible light detector  435  prevents operation of the pump even though infrared radiation has been detected by the IR detector  429 . In condition 7, the visible light detector  435  may be detecting either light from the visible light emitter  433  or from ambient. In either case, the pump  401  is not permitted to operate. In  FIGS. 17 and 18  other variations may be described by tracing a path through the flow chart, as shown. 
       FIGS. 20 and 21  show a fragmentary portion of a pump  601  adjacent a seat  602  of the pump, and safety interlock device  603  of a tenth embodiment of the present invention. The safety interlock device  603  comprises a material that transmits both infrared radiation and visible light. The safety interlock device  603  includes a blocking portion  607  that is opaque to the transmission of visible light so that the visible light is not transmitted to the visible light detector  609  when the safety interlock device is loaded on the pump. The safety interlock device  603  includes a key  613  that is received in a corresponding slot  615  in the pump housing so that the safety interlock device  603  must be aligned with the blocking portion  607  generally adjacent the visible light detector. In the illustrated embodiment, the key  613  is a protrusion extending from the safety interlock device  603  but it is understood that the key and the corresponding slot  615  could be other shapes and sizes without departing from this invention. Other structures for keying the position of a safety interlock device in a pump may be used within the scope of the present invention. 
     When the safety interlock device  603  is loaded in the pump  601  infrared electromagnetic radiation from the IR emitter  616  is diffused and reflected through the safety interlock device and detected by the IR detector  617  to verify that the set has been loaded. Next, the visible light detector  609  will check for visible light in the pump  601  will not detect any because of the location of the blocking portion  607  of the safety interlock device  603  that blocks visible light. In the embodiment of  FIG. 20 , the visible light emitter  619  will be emitted, sending a visible light signal into the safety interlock device  603 . The visible light signal will not be transmitted to the visible light detector  609  because of the present of the blocking portion  607  and the control system of the pump  601  will allow the pump to operate. 
       FIG. 22  shows a fragmentary section of a pump  701  including a seat  702 , and safety interlock device  703  of an eleventh embodiment of the present invention. The safety interlock device  703  is made of a material that transmits infrared radiation, but blocks electromagnetic radiation in the visible range so that the visible light is not transmitted to a visible light detector  709  when the safety interlock device is loaded on the pump  701 . Other suitable constructions for passing electromagnetic radiation of one wavelength and blocking electromagnetic radiation of another wavelength may be employed within the scope of the present invention. An arrangement of visible and infrared emitters and detectors like that shown in  FIG. 20  may be employed in the eleventh embodiment, although different arrangements are also possible. 
     The safety interlock device  703  comprises an outer member  704  and an inner member  706 . The outer member includes an upper tubular portion  708 , a lower tubular portion  710  and an annular flange  712 . The annular flange has upper and lower annular channels  714 . In the illustrated embodiment, the channels allow less material to be used, but have no effect on the operation of the safety interlock device  703 . A first tube section  757  of a feeding set is received in the upper portion  708  of the outer member  704  of the safety interlock device  703  and a second tube section  763  is received over the lower portion  710  of the outer member. 
     The outer member  704  is made of the material that selectively blocks visible light and passes infrared radiation. The inner member  706  can be made of the same material as the outer member, or of a different material. However, the inner member  706  is substantially opaque to electromagnetic radiation in the infrared range and also in the visible range, and is also preferably highly reflective. In the illustrated embodiment, the inner member  706  is made of the same material as the outer member  704 , but is white in color. The inner member  706  can be formed as one piece with the outer member  704 , such as by a dual injection or extrusion process. Additionally, the outer and inner members  704 ,  706  could be made as separate pieces and attached to each other in a suitable manner such as bonding or welding. The inner member  706  is positioned in the optical path of the infrared radiation that enters the safety interlock device  703 , and is disposed between the infrared radiation path and first tube section  757 . Accordingly, an outer surface of the inner member  706  defines an “inner boundary region” in this eleventh embodiment for reflecting infrared radiation. The inner member  706  inhibits the loss of internal reflection of infrared radiation that might be caused by the presence of certain liquids (e.g., water) flowing in the tube  757 . Thus, a strong reflection of infrared radiation to the infrared radiation detector (not shown) can be made regardless of the optical characteristics of the fluid flowing through the tube  757 . 
     When introducing elements of the present invention or the preferred embodiment(s) thereof, the articles “a”, “an”, “the” and “said” are intended to mean that there are one or more of the elements. The terms “comprising”, “including” and “having” are intended to be inclusive and mean that there may be additional elements other than the listed elements. Moreover, the use of “up”, “down”, “top” and “bottom” and variations of these terms is made for convenience, but does not require any particular orientation of the components. 
     As various changes could be made in the above without departing from the scope of the invention, it is intended that all matter contained in the above description and shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.