CLAMSHELL PRESSURE SENSOR HOUSING AND METHODS FOR MANUFACTURING SAME

BACKGROUND

Field

[0001] The present invention relates generally to sensor housings, and more particularly, to a clamshell sensor housing and methods for manufacturing sensor housings.

Background

[0002] Generally, pressure sensors consist of three basic elements: a force-gathering element (commonly a flexible diaphragm), which converts pressure into a measurable strain; strain gauge (or force-gathering element measurement circuitry) elements, which transform the strain into a proportional electrical signal; and a housing, which provides the required protection against environmental conditions and incorporates mechanical and electrical interfaces.

[0003] In one application of a pressure sensor, a tube is connected to the pressure sensor. to carry, to the force-gathering element, a medium containing the pressure to be measured. For example, blood pressure can be monitored through a fluid-filled tube or catheter where a diaphragm in the tip of the catheter deflects to transfer pressure to a pressure sensor external to the body. This method is typically used in either canula-based or catheter-based pressure sensors. These sensors are typically Piezoresistive Technology (PRT) sensors. The sensors typically need to send the signals back to a remote device to capture the measured signals, which often subject the sensors to signal degradation in the transmission process.

[0004] Another blood pressure sensing technology is the fiber optic blood pressure sensor. The sensor works through a small cavity embedded in the sensor tip, where the blood pressure is measured by observing the changes in length of the cavity using a measurement based on white light interferometry. Sensing light is transmitted to and

reflected back from the detecting diaphragm and cavity of the sensor tip via a multimode fiber.

[0005] Current pressure sensor construction techniques require the use of manufacturing processes that are both time consuming and expensive. For example, one approach for manufacturing housings for sensors is to create housings that are tubular in shape and then inserting the force-gathering and strain gauge elements into the housing. Typically, both the force-gathering and strain gauge elements are mounted on a carrier. The carrier is then inserted into the housing. It is often difficult to align the carrier with respect to the housing unless precision assembly machines are used. These machines are generally expensive and cannot produce sensors in high volume.

[0006] The current state of the art in pressure sensor construction is limited by the low level of signal output, remote sensing requirement, large physical size, low volume manufacturability or custom fabrication for all designs. It is desirable to be able to address these design issues.

SUMMARY OF THE PREFERRED EMBODIMENTS

[0007] In one preferred embodiment of the present invention, a sensor housing is described. The sensor housing includes a first housing portion and a second housing portion, a supply pressure channel comprising a slot displaced in the first housing portion and a matching protrusion displaced in the second housing portion; and, a cavity in the first housing coupled to the supply pressure channel, the cavity spaced for a pressure sensor module having a sensing element contained therein, the sensing element being in communication with the supply pressure channel.

[0008] In another preferred embodiment of the present invention, a pressure sensor is described having a sensor housing including a first housing portion and a second housing portion; and, a supply pressure channel comprising a slot displaced in the first housing portion and a matching protrusion displaced in the second housing portion; and, a pressure sensor module encapsulated between the first housing portion and the second housing portion, the pressure sensor module having a sensing element contained therein, the sensing element being in communication with the supply pressure channel.

[0009] In yet another preferred embodiment, a method for creating a pressure sensor is described that includes the initial step of providing a sensor housing with a first housing portion and a second housing portion, and a supply pressure channel that includes a slot displaced in the first housing portion and a matching protrusion displaced in the second housing portion. The method also includes the step of encapsulating a pressure sensor module between the first housing portion and the second housing portion, with a sensing element contained therein, the sensing element being placed in communication with the supply pressure channel.

[0010] In still yet another preferred embodiment, a pressure sensor is described, the pressure sensor comprising a pressure sealed housing; and a pressure sensing element

encapsulated in the pressure sealed housing. The pressure sensing element includes an connector integrated with the pressure sensing element; and a plurality of circuits having a plurality of electrical connector mating surface, wherein the electrical connector mating surface is an integral part of the pressure sealed housing.

[0011] Other objects, features and advantages will become apparent to those skilled in the art from the following detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

[0012] The invention may be more readily understood by referring to the accompanying drawings in which:

[0013] FIG. 1 is an exploded perspective view of a board-mounted sensor module and a clamshell sensor housing configured in accordance with one preferred embodiment of the present invention;

[0014] FIG. 2 is a perspective view of the clamshell sensor housing, with the board- mounted sensor module mounted therein, configured in accordance with one preferred embodiment of the present invention;

[0015] FIG. 3 is a top plan view of the clamshell sensor housing, with the board- mounted sensor module mounted therein, of FIG. 2;

[0016] FIG. 4 is a side elevational view of the clamshell sensor housing, with the board-mounted sensor module mounted therein, of FIG. 2;

[0017] FIG. 5 is a bottom plan view of the clamshell sensor housing, with the board- mounted sensor module mounted therein, of FIG. 2;

[0018] FIG. 6 is a cross-sectional view of the clamshell sensor housing, with the board- mounted sensor module mounted therein, of FIG. 2;

[0019] FIG. 7 is a top plan view of the clamshell sensor housing of FIG. 1 ;

[0020] FIG. 8 is a side elevational view of the clamshell sensor housing of FIG. 1;

[0021] FIG. 9 is a bottom plan view of the clamshell sensor housing of FIG. 1;

[0022] FIG. 10 is an edge view of the clamshell sensor housing of FIG. 1;

[0023] FIG. 11 is a top plan view of the board-mounted sensor module of FIG. 1;

[0024] FIG. 12 is a side elevational view of the board-mounted sensor module of FIG.

l;

[0025] FIG. 13 is a bottom plan view of the board-mounted sensor module of FIG. 1 ;

[0026] FIG. 14 is a bottom plan view of a second clamshell sensor housing configured in accordance with a second preferred embodiment of the present invention; [0027] FIG. 15 is a side elevational view of the second clamshell sensor housing;

[0028] FIG. 16 is a perspective view of a third clamshell sensor housing configured in accordance with a third preferred embodiment of the present invention; [0029] FIG. 17 is a side elevational view of the third clamshell sensor housing;

[0030] FIG. 18 is a top plan view of the third clamshell sensor housing;

[0031] FIG. 19 is a front elevational view of the third clamshell sensor housing;

[0032] FIG. 20 is a side elevational view of a clamshell sensor housing with a sealed sensor tip design configured with another embodiment of the present invention; [0033] FIG. 21 is a side elevational view of a clamshell sensor housing with a threaded sensor tip design configured with another embodiment of the present invention; [0034] FIG. 22 is a side elevational view of a clamshell sensor housing with a stubbed sensor tip design configured with another embodiment of the present invention; [0035] FIG. 23 is a side elevational view of a clamshell sensor housing with a stubbed sensor tip design configured with another embodiment of the present invention; [0036] FIG. 24 is a perspective view of a clamshell sensor housing with a flange mount feature configured with one embodiment of the present invention; and,

[0037] FIG. 25 is a perspective view of a clamshell sensor housing with a snap-fit mount feature configured with one embodiment of the present invention. [0038] Like numerals refer to like parts throughout the several views of the drawings.

DETAILED DESCRIPTION

[0039] In one preferred embodiment, a pressure sensor is created using a pressure sensor casing that is comprised of two portions (more preferably halves) of a casing that are folded over to enclose a sensor module. The sensor module contains a pressure sensing element and may also include supporting electronics, such as a signal amplification circuit, to provide signal amplification and/or conditioning of the signals received from the pressure sensing element. The sensor module is placed into the open clamshell casing before the clamshell casing is folded over. In one preferred embodiment, the casing is sealed with an adhesive. The clamshell casing has appropriate inlets and cavities for allowing the medium containing the pressure to be measured to come into contact with the pressure sensing element of the sensor module. The clamshell casing also includes a vent for use where the sensor module is a gauged sensor modules. A gauged sensor eliminates the effects of atmospheric pressure because the vent allows atmospheric pressure to be applied to the back of the pressure sensing element. Preferably, the clamshell housing is unitary with a flexible central hinge potion to facilitate the folding function.

[0040] In one preferred embodiment, the sensor module includes a

Microelectromechanical Systems (MEMS) device implementing a Piezoresistive Transducer (PRT) mounted on a Printed Circuit Board (PCB). The inventive pressure sensor also includes a plurality of connectors on the end of the PCB for connecting to external electronics. In one preferred embodiment, as described further herein, the PCB is sized for insertion into an opening in a plug of a cable conforming to a cable standard, and the plurality of connectors are spaced to match the connectors in the plug.

[0041] FIG. 1 illustrates a sensor housing 102 that is a clamshell housing having two halves 102a, 102b. Two halves 102a, 102b fold over on each other to enclose a sensor assembly 150. A pair of bridges/runners 124 is created during the molding process of

sensor housing 102 and act functionally as a hinge. In one preferred embodiment, sensor housing 102 is created using injection molding. Pair of bridges/runners 124 is used to hold halves 102a, 102b of sensor housing 102 together during the manufacturing process in an injection molding process. Specifically, pair of bridges/runners 124 allow sensor housing 102 to be created as a single piece of plastic in a single cavity of a mold as opposed to using a separate cavity for each portion of two halves 102a, 102b of sensor housing 102. In another preferred embodiment, each portion of two halves 102a, 102b of sensor housing 102 are created in a separate mold. Preferably, pair of bridges/runners 124 are removed after sensor housing 102 is assembled.

[0042] To ensure that two halves 102a, 102b of sensor housing 102 are and remain aligned properly during and after, respectively, the manufacture of sensor 100, several alignment features are presented on housing 102. For example, housing 102 includes a plurality of alignment holes 122 and a plurality of alignment studs 120 that are matched to these alignment holes. Plurality of alignment studs 120 are protrusions that are mated with plurality of alignment holes 122 to align and hold two halves 102a, 102b of sensor housing 102 in place. Plurality of alignment holes 122 and plurality of alignment studs 120 are also shown in FIG. 7 and FIG. 10.

[0043] Sensor housing 102 also includes alignment features that are used to serve additional purposes other than just achieving and maintaining the alignment of two halves 102a, 102b of sensor housing 102. For example, the alignment features can also function as adhesive barriers and/or define passageways through which a medium carrying the pressure to be measured may be passed to sensor assembly 150, as further described herein. In one preferred embodiment, housing 102 includes a pair of alignment guides 140 and a pair of alignment channels 142 matched to pair of alignment guides 140. Specifically, pair of alignment guides 140 are channel alignment protrusions that mate with

channel alignment indentations, i.e., pair of alignment channels 142, when the two halves of sensor housing 102 are secured to each other to align the two halves as well as define a supply pressure channel 130. Supply pressure channel 130 is a passage way through which the medium (e.g., air or liquid) travels having the pressure or other characteristic to be sensed. Also, pair of alignment guides 140 (also seen in FIG. 8) and pair of alignment channels 142 together act as adhesive barriers to prevent adhesives used to seal two halves 102a, 102b from seeping into pressure channel 130 when sensor housing 102 is assembled.

[0044] Sensor assembly 150 is formed using a sensor assembly circuit board 158, which in one preferred embodiment is a circuit board on which a sensor module and accompanying electronics are mounted. A plurality of cavities/core-outs 132, 134, 136, and 138 in sensor housing 102 provide the required clearances for the electronic components on sensor assembly circuit board 158. In one preferred embodiment, electronic components such as a pair of electronic components 152, 154 are used for such purposes as electronic signal conditioning to achieve a desired level and quality of electrical output by sensor assembly 150. Sensor assembly circuit board 158 includes a contact 156 that is an electrical ground contact to connect to external circuitry (not shown). Sensor assembly circuit board 158 also includes a cable strain relief 160, which is a cut-out in sensor assembly circuit board 158 through which wires or cables may pass through. The cut-out acts as a strain relief for these wires or cables. In one preferred embodiment, where sensor 100 is coupled to external circuitry using a cable plugged onto sensor assembly circuit board 158, as further described herein, strain relief 160 is not used.

[0045] In one preferred embodiment, sensor assembly circuit board 158 includes a plurality of sensor assembly alignment tabs 162 that allow sensor assembly circuit board 158 to be aligned with the housing when it is placed in sensor housing 102. Plurality of sensor assembly alignment tabs 162 also prevent significant movement of sensor assembly

circuit board 158 in sensor housing 102 once it is inserted in either of halves 102a, 102b of sensor housing 102. In one preferred embodiment, each alignment tab of plurality of sensor assembly alignment tabs 162 rests in a respective indentation of a plurality of circuit board alignment indentations 166. Sensor assembly circuit board 158 also includes a pressure sensor access port 164, which is an opening in sensor assembly circuit board 158 through which the diaphragm (not shown) of a sensor module 172 is accessed.

[0046] Sensor module 172 includes a sensor based on Piezoresistive Technology

(PRT) in one preferred embodiment. Specifically, sensor module 172 includes a pressure sensitive silicon device that outputs a voltage signal that changes with respect to pressure changes detected in the medium in supply pressure channel 130. Sensor assembly circuit board 158 also includes an Application Specific Integrated Circuit (ASIC) 174 that is coupled to sensor module 172. ASIC 174 amplifies the voltage signal received from sensor module 172 to desire output voltage levels. In one preferred embodiment, ASIC 174 also provides compensation for temperature related changes. Sensor assembly circuit board 158 further includes an electronic component 176 for electronic signal conditioning to achieve desired electrical output from sensor 100.

[0047] FIG. 2 is a perspective view of sensor 100 after it has been assembled, which includes a sensor tip 202, located at the tip of sensor 100. Sensor tip 202 has a pressure source interface connection 210 that is a protrusion on which a pressure tube may be secured. In one preferred embodiment, pressure source interface connection 210 includes a barbed fitting with ridges 212, also as shown in FIG. 3, that assist in securing the pressure tube to sensor 100. For example, the pressure tube may be stretched over pressure source interface connection 210 and be held in place by ridges 212.

[0048] Referring to FIG. 4, which is a side view of sensor 100, a protruded portion 402 is illustrated on half 102b of sensor housing 102. Protruded portion 402 is the external,

surface, manifestation of cavity/core-out 138. As described above, cavity/core-out 138 is used to provide clearance for any electronic components on sensor assembly circuit board 158. Specifically, cavity/core-out 138 is used to provide space to accommodate sensor module 172. In one preferred embodiment, protruded portion 402 is used to provide the space needed for sensor module 172 without having half 102b of sensor housing 102 being sized larger as a whole to accommodate sensor module 172. FIG. 4 also illustrates a side view of sensor assembly circuit board 158.

[0049] FIG. 5 is a bottom plan view of assembled sensor 100 with a secondary pressure source 404 (see also FIG. 9) through which passes a reference pressure for sensor module 172. In one preferred embodiment, secondary pressure source 404 is an opening that provides a pressure based on atmospheric pressure. A plurality of contacts 502 are used for interfacing with the circuitry contained on sensor assembly circuit board 158. In one preferred embodiment, plurality of contacts 502 is spaced so that the contacts will directly interface with a plurality of contacts on a cable configured in accordance with a standard such as the IEEE-1394 ("Firewire") standard, available at http://www.1394ta.org/. For example, sensor assembly circuit board 158 will slide directly into the opening in a connector on a Firewire cable. In another preferred embodiment, plurality of contacts 502 are spaced so that the contacts will directly interface with a plurality of contacts on a Universal Serial Bus (USB) standards-based cable connector. The USB standards is available at http://www.usb.org. In yet another preferred embodiment, plurality of contacts 502 are spaced to interface with another, matching, plurality of contacts on a circuit board.

[0050] Referring to FIG. 6, which is a cross-sectional view taken along line A-A of

FIG. 5, sensor 100 is shown with protruded portion 402 with secondary pressure source 404 that interfaces with sensor module 172 on sensor assembly circuit board 158. Sensor module 172 also includes an input pressure port (not shown) that interfaces with supply

pressure channel 130 through pressure sensor access port 164 (as shown in FIG. 1), on sensor assembly circuit board 158. Sensor assembly circuit board 158 is further shown in: FIG. 11, which is a plan view of sensor assembly circuit board 158 illustrating the location of sensor module 172; FIG. 12, which is a side view of the circuit board; and FIG. 13, which is a plan view of sensor assembly circuit board 158 illustrating the location of pressure sensor access port 164. As discussed previously, the plurality of electronic components 152, 154, and 176, and ASIC 174 are located on sensor assembly circuit board 158 and interface with sensor module 172 to allow the amplifying and conditioning of the signals generated by sensor module 172.

[0051] FIG. 14 illustrates a second preferred embodiment of a sensor housing 1102 comprised of two halves 1102a, 1102b, and which includes a sensor tip 1202. Sensor tip 1202 is located at the tip of sensor housing 1102 and has a pressure source interface connection 1210 that is a protrusion on which a pressure tube may be secured. In one preferred embodiment, pressure source interface connection 1210 includes a barbed fitting with ridges 1212 that assist in securing a pressure tube to the sensor. Sensor housing 1102 also includes a protruded portion 1402 with a secondary pressure source 1404 on sensor housing half 1102b. Similar to sensor housing 1102, two halves 1102a, 1102b of sensor housing 1102 are formed with a pair of bridges/runners 1124 during the molding of sensor housing 1102.

[0052] FIG. 15 illustrates another view of sensor housing 1102 showing an edge view of sensor halves 1102a, 1102b. To ensure that two halves 1102a, 1102b of sensor housing 1102 are and remain aligned properly during and after manufacturing of the sensor, several alignment features are present on sensor housing 1102. For example, sensor housing 1102 includes a plurality of alignment studs 1120 that are matched to a plurality of alignment holes in sensor housing 1102. Plurality of alignment studs 1120 are protrusions that are

mated with plurality of alignment holes to align and hold two halves 1102a, 1102b of sensor housing 1102 in place. Sensor housing 1102 also includes a pair of alignment guides 1140 mated to a pair of alignment channels.

[0053] FIG. 16 illustrates a third preferred embodiment of a sensor housing 2102 comprised of two halves 2102a, 2102b, and which includes a sensor tip 2202. Sensor tip 2202 is located at the tip of sensor housing 2102 and has a pressure source interface connection 2210 that is a protrusion on which a pressure tube may be secured. In one preferred embodiment, pressure source interface connection 2210 includes a barbed fitting with ridges 2212 that assist in securing a pressure tube to the sensor. Sensor housing 2102 also includes a protruded portion 2402 with vent hole 2404 on sensor housing half 2102b. Similar to sensor housing 2102, two halves 2102a, 2102b of sensor housing 2102 are formed with a pair of bridges/runners 2124 during the molding of sensor housing 2102. Similar to pair of bridges 124 in sensor housing 102, pair of bridges/runners 2124 is created during the molding process of sensor housing 2102 and act functionally as a hinge. In one preferred embodiment, sensor housing 2102 is created using injection molding. Pair of bridges/runners 2124 is used to hold halves 2102a, 2102b of sensor housing 2102 together during the manufacturing process in an injection molding process. As shown in FIGs. 16, 18 and 19, sensor housing 2102 includes a pair of interlocking tab portions including a male interlocking tab portion 2502, and a female interlocking tab portion 2504 in sensor tip 2202.

[0054] FIG. 17 illustrates another view of sensor housing 2102 showing a side view of sensor halves 2102a, 2102b. To ensure that two halves 2102a, 2102b of sensor housing 2102 are and remain aligned properly during and after manufacturing of the sensor, several alignment features are present on sensor housing 2102. For example, sensor housing 2102 includes a plurality of alignment studs 2120 that are matched to a plurality of alignment

holes 2122 in sensor housing 2102. Plurality of alignment studs 2120 are protrusions that are mated with plurality of alignment holes 2122 to align and hold two halves 2102a, 2102b of sensor housing 2102 in place. FIGs. 16 and 18 also illustrate a plurality of circuit board alignment indentations 2166 in which a plurality of sensor assembly alignment tabs of a sensor assembly (such as those described for plurality of sensor assembly alignment tabs 162), may rest. FIG. 20 illustrates a sensor assembly 20000 having a sensor housing 20102 showing a side view of sensor housing portions 20102a, 20102b, and which includes a sensor tip 20202. Sensor tip 20202 is located at the tip of sensor housing 20102 and has a pressure source interface connection 20210 that is a protrusion on which a pressure tube may be secured. In one preferred embodiment, pressure source interface connection 20210 includes a seal 20212 that assist in securing a pressure tube to the sensor. In one preferred embodiment, seal 20212 includes an o-ring. Similarly, in FIG. 21, a sensor assembly 21000 includes a sensor housing 21102 with sensor housing portions 21102a, 21102b having a sensor tip 21202. Sensor tip 21202 is located at the tip of sensor housing 21102 and has a pressure source interface connection 21210 that is a protrusion on which a pressure tube may be secured. In one preferred embodiment, pressure source interface connection 21210 includes a threaded attachment interface 21212 that assist in securing a pressure tube to the sensor. In one preferred embodiment, threaded attachment interface 21212 can be screwed into a receptacle with a matching thread, or a pliable receptacle such as tubing that may be comprised of plastic, rubber and/or another suitable material. In FIG. 22, a sensor assembly 22000 having a sensor housing 22102 showing a side view of sensor housing portions 22102a, 22102b that includes a sensor tip 22202. Sensor tip 22202 is located at the tip of sensor housing 22102 and, in one preferred embodiment, has a stubbed pressure source interface connection 22210. In one embodiment, stubbed pressure

source interface connection 22210 is configured to be as short as possible so that the sensor package may be made as small as possible. In another preferred embodiment, stubbed pressure source interface connection 22210 is sized to be long enough to provide a mounting surface for a customized connector (not shown) so that the actual configuration of the pressure source interface connector may be interchangeable. For example, a threaded sensor tip may be placed on stubbed pressure source interface connector 22210 for one operation, and then a sensor tip that accommodates a seal, similar to pressure source interface connection 20210 may be interchanged for the threaded sensor tip for another use of the sensor.

[0056] FIG. 23 is a detailed view of sensor assembly 22200, where a strain relief

23160 in a sensor assembly circuit board 23158 of a sensor assembly 23150 is being used to provide support and strain relief for a plurality of wires 23002. In one preferred embodiment, as illustrated, plurality of wires 23002 are looped through strain relief 23160. In another preferred embodiment, plurality of wires 23002 may simply be inserted through strain relief 23160 without a looping operation.

[0057] FIGs. 24 and 25 demonstrate two preferred embodiments for mounting a sensor assembly. FIG. 24 illustrates a sensor assembly 24000 having a flange 24502 with a mounting hole 24504. In one preferred embodiment, sensor assembly 24000 may be secured to a circuit board via a screw or other fastener inserted though mounting hole 24504. With regard to FIG. 25, a sensor assembly 25000 includes a snap-fit post 25502 with a body 25506 and a header portion 25504. In one preferred embodiment, snap-fit post 25502 may be inserted into a circuit board (not shown) to mount sensor assembly 25000 to the circuit board.

[0058] The embodiments described above are exemplary embodiments. Those skilled in the art may now make numerous uses of, and departures from, the above-described

embodiments without departing from the inventive concepts disclosed herein. Various modifications to these embodiments may be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments, e.g., in a temperature sensor housing or other sensor housing applications, without departing from the spirit or scope of the novel aspects described herein. In addition, the generic principles defined herein may be applied to other enclosure applications, such as enclosures for other types of electronic devices. Thus, the scope of the invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein. The word "exemplary" is used exclusively herein to mean "serving as an example, instance, or illustration." Any embodiment described herein as "exemplary" is not necessarily to be construed as preferred or advantageous over other embodiments. Accordingly, the present invention is to be defined solely by the scope of the following claims.