Accelerometer for implantable medical device

Details Accelerometer for implantable medical device Accelerometer for implantable medical device

1999-03-31

2001-04-17

Kwok, Helen C. (Department: 2856)

Measuring and testing

Speed, velocity, or acceleration

Structural installation or mounting means

C607S017000, C607S018000

Reexamination Certificate

active

06216537

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates generally to accelerometers. More particularly, the present invention relates to structure for mounting accelerometers.
BACKGROUND OF THE INVENTION
Accelerometers are well known in the art. An accelerometer is a device which measures acceleration, or more accurately measures force exerted by a body as a result of a change in the velocity of the body. A moving body possesses an inertia which tends to resist change in velocity. It is this resistance to change in velocity that is the source of the force exerted by the moving body. This force is directly proportional to the acceleration component in the direction of movement when the moving body is accelerated.
Various types of accelerometers are available. Generally, in a micromachined accelerometer formed using silicon, a central (e.g., typically spherical or rectangular shaped) mass is suspended by one or more microbridges. The microbridges are attached to a supporting substrate which surrounds the mass with a gap provided therebetween. The mass is supported within and has free movement relative to the supporting structure.
The movement of the mass is measured in various manners. For example, the movement of the mass may be measured by measuring a corresponding change in the output of a wheatstone bridge incorporating beam piezo resistors formed in the microbridges.
Further, for example, in silicon capacitive accelerometers, such as those available from VTI Hamlin (Finland), the sensing element of the accelerometer consists of three layers of silicon isolated from each by thin glass layers. The middle silicon layer incorporates a cantilevered mass beam structure. The force of gravity or acceleration acting on the silicon mass causes the beam structure to bend. This deflection is detected as a change in the distance between electrodes in capacitors formed on both sides of the mass using metal electrodes.
Generally, such micromachined accelerometers require external circuitry to process the signal output by the accelerometer. For example, such a signal output may be used for triggering an automobile airbag of an airbag deployment system, may be used for triggering medical treatment in an implantable medical device, or may be used as an input for any other application where acceleration is to be detected.
Accelerometers are generally constrained in that typically a micromachined accelerometer as described above has a single axis sensitive to acceleration. That is, the sensing element of an accelerometer can only measure acceleration along a line perpendicular to a particular plane thereof. For example, the plane may be defined by a principle surface of the sensing element from which side during fabrication various fabrication steps are performed, e.g., masking, etching, etc. For example, in an automobile airbag system, the direction of acceleration which must be sensed in the event of a collision is typically along a line lying in a horizontal plane, i.e., parallel to the ground. Further, for example, the direction of acceleration which is to be sensed of a person implanted with an implantable medical device, may be the direction of acceleration along a line lying in a horizontal plane, i.e., a line orthogonal to a plane defined by the patient's chest.
Various accelerometer structures are available such that the accelerometer can be surface mounted on a substrate in one or more orientations. For example, an accelerometer available from EG&G Inc., (Wellesley, Mass.), available under the Model No. 3255 includes an accelerometer wherein the sensitive axis is perpendicular to the bottom plane of the package. The package can be mounted in two orientations, allowing the sensitive axis to be either perpendicular or parallel to the mounting plane defined by the substrate upon which it is mounted. This accelerometer measures acceleration using a wheatstone bridge technique.
Table 1 below lists U.S. Patents showing other transducer, e.g., accelerometer, configurations.
TABLE 1
U.S. Pat. No.
Inventor(s)
Issue Date
4,896,068
Nilsson
23 January 1990
5,044,366
Alt
3 September 1991
5,215,084
Schaldach
1 June 1993
5,425,750
Moberg
20 June 1995
5,674,258
Henschel et al.
7 October 1997
5,373,267
Kaida et al.
13 December 1994
5,318,596
Barreras et al.
7 June 1994
5,031,615
Alt
16 July 1991
4,653,326
Danel et al.
31 March 1987
5,594,172
Shinohara
14 January 1997
4,140,132
Dahl
20 February 1997
4,679,434
Stewart
14 July 1987
4,742,182
Fuchs
3 May 1988
4,891,985
Glenn
9 January 1990
4,987,7810
Reimann
29 January 1991
5,014,702
Alt
14 May 1991
5,031,615
Alt
16 July 1991
5,235,237
Leonhardt
10 August 1993
5,745,347
Miller et al.
28 April 1998
5,616,863
Koen
1 April 1997
5,503,016
Koen
2 April 1996
All references listed in Table 1, and references listed elsewhere herein, are incorporated by reference in their respective entireties. As those of ordinary skill in the art will appreciate readily upon reading the Summary of the Invention, Detailed Description of the Embodiments, and claims set forth below, at least some of the devices and methods disclosed in the references of Table 1, and elsewhere herein, may be modified advantageously by using the teachings of the present invention. However, the listing of any such references in Table 1, or elsewhere herein, is by no means an indication that such references are prior art to the present invention.
SUMMARY OF THE INVENTION
The present invention has certain objects. That is, various embodiments of the present invention provide solutions to one or more problems existing in the prior art with respect to the mounting of accelerometer devices, such as for mounting accelerometers in implantable medical device applications. One of such problems involves the need to rotate the axis of sensitivity of many accelerometer devices 90° when mounted on a substrate as compared to conventional mounting of such devices. Further, for example, other problems include: the need to place the accelerometer device relative to the circuit board in a predetermined orientation, the inability to effectively mass produce such accelerometer devices, the inability to test accelerometer devices after assembly, and the inability to provide a small, compact, and robust package.
In comparison to known techniques for providing surface mountable accelerometer devices and assemblies, such as for implantable medical devices, various embodiments of the present invention may provide one or more of the following advantages. For example, the present invention provides for desired orientation of the axis of sensitivity of the accelerometer device in a desired application. Further, embodiments of the present invention provide for the ability to mount the accelerometer 1800 in two axes while still maintaining functionality. Yet further, the various embodiments of the present invention may provide for the advantages of effective mass production, testability after assembly, and provision of a small, compact, and robust package for use in various applications, such as implantable medical devices.
Some embodiments of the present invention include one or more of the following features: a surface mountable accelerometer device for use in an implantable medical device; an accelerometer sensing element having an axis of sensitivity; at least one interposer, e.g., a multilayer end cap, for use in mounting a transducer element, e.g., an accelerometer sensing element, such that an axis of sensitivity of the transducer element is in a particular orientation; an accelerometer sensing element which includes a device body having a longitudinal axis extending between generally parallel first and second ends thereof, a principal surface that extends between the first and second ends of the device body parallel to the longitudinal axis with the axis of sensitivity being perpendicular to a plane defined by the principle surface, and two or more conductive pad regions on each of the first and second ends of the device body; first and second multilayer end caps for use in mounting an accelerometer sensing element to

Affiliated with

Also associated with

Rating

Accelerometer for implantable medical device does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Accelerometer for implantable medical device, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Accelerometer for implantable medical device will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-2455434