Patent Application
20060082259
Embodiments of the invention relate to controlling bond line thickness in a transducer housing. More specifically, embodiments relate to a transducer housing configured to provide a uniform bond line thickness between the transducer and the housing.
A transducer is a device that converts energy from one form (e.g., electrical) to another (e.g., mechanical). Transducers are used in a variety of automotive, commercial, and industrial applications. Ceramic crystals are used as transducers in ultrasonic devices. The crystals convert an electrical input into sound waves. Ultrasonic devices may be used in medical imaging, non-destructive testing, and distance and level sensing applications among others.
Although a variety of devices that use transducers exist, there are some problems with transducers used in ultrasonic devices. In particular, it was found that the manner in which the transducer ceramic piezoelectric crystals are mounted and fixed in a housing can adversely effect the operation of the device or transducer.
In many ultrasonic devices, adhesive is typically used to bond the transducer to the housing. The methods used to apply the adhesive as well as the adhesive used may vary. This can cause relatively large variations in device performance. Excessive adhesive or bond thickness can adversely affect the characteristics of a transducer. In some applications, the optimum thickness of the adhesive is 0.002″-0.005″. The optimum thickness is based on the specific transducer-to-housing interface. The interface bond and its thickness is a combination of housing and transducer frequency requirements. When what is called the “bond line thickness” of the adhesive is not uniform, sensitivity of the device is significantly degraded. In addition, a non-uniform bond line can impact the radiation of sound waves from the device. This, in turn, can cause non-uniform penetration or reflection of the sound waves in or from a target of interest.
Accordingly, in one embodiment, the invention provides an apparatus and method for producing uniform bond line thickness by utilizing a spacer or a grid pattern in the receptacle of the transducer housing. The bond line thickness is controlled by the height of the spacer or grid pattern. The transducer can be pressed tight to the top of the spacer with an adhesive providing a bond between the transducer and the housing member.
Another embodiment provides a housing configured to retain a transducer. The housing includes a wall and a receptacle positioned adjacent to the wall. The receptacle has a member configured to allow ultrasonic energy to pass through. The member has a first surface and a second surface, whereby the first surface includes at least three spacers defining a uniform planar surface. The spacers are configured to maintain a substantially uniform bond line thickness between the transducer and the member. In further embodiments of this invention, the spacers can be configured in a variety of shapes and may take the form of pyramids, columns, domes, etc. The spacers are configured to be of substantially equal height in order to maintain a uniform bond line thickness.
In a yet another embodiment, the wall is annular and the spacers are configured in a crosshatch, or grid pattern, on the first surface. The grid pattern is configured to maintain uniform spacing between the transducer and the member. The bond line is further controlled by the depth of the spacers, which are configured to maintain a substantially constant bond line. The constant bond line thickness is maintained regardless of the type of adhesive used between the transducer and the member and regardless of the method used to deposit the adhesive between the transducer and the member.
Another embodiment provides a method of providing a uniform bond line in a housing for a transducer. The method includes providing a spacer on a first surface of the housing. A height of the spacer is pre-selected and then a predetermined amount of adhesive is deposited on the housing and the spacer such that passage of ultrasonic energy through the housing is not adversely affected. Further, the spacer is configured to maintain a substantially uniform bond line and spacing between the transducer and the member.
Another embodiment provides a housing configured to retain a transducer and a generally circular component. The housing includes a wall and a receptacle adjacent to the wall. The receptacle has a member configured to allow ultrasonic energy to pass through. The member has a first surface and a second surface. The first surface is planar and configured to receive a generally circular component. The component has a first surface and a second surface. The second surface of the component is bonded with adhesive to the first surface of the member. The first surface of the component includes spacers. The spacers are configured to maintain uniform spacing between the transducer and the component. In a further embodiment of the invention, the spacers are configured in a crosshatch, or a grid pattern, on the first surface of the member.
Additional aspects and features of embodiments will become apparent by reference to the detailed description of the invention taken in combination with the accompanying drawings.
a is a cross-sectional view of the transducer housing shown in
b is a cross-sectional view of a transducer housing of another embodiment of the present invention.
c is a cross-sectional view of a transducer housing of another embodiment of the present invention.
d is a cross-sectional view of a transducer housing of another embodiment of the present invention.
e is a cross-sectional view of a transducer housing of another embodiment of the present invention.
As best seen by reference to
The spacers 38 are configured to maintain uniform spacing between the transducer 14 and the member 26, especially when adhesive 50 is applied as a bonding agent. The grid pattern 46 holds the adhesive and provides additional surface area for the adhesive to bond to help ensure a substantially constant-thickness bond line 42. The type of adhesive used for creating the bond line will vary and is dependent on the specific housing material chosen, although Loctite E120 adhesive has proven to be useful for bonding ceramic ultrasonic transducers to a polyethylene housing. Additionally, the process used to apply the adhesive 50 to the member 26 can vary. However, mechanical dispensing units have proven to increase the accuracy of dispensing.
As best seen by reference to
A cross-section of the embodiment of the invention shown in
b is a cross-section view of another embodiment of the present invention. In this embodiment, a first surface 130 of a member 126 includes three spacers 138, which are configured to maintain a uniform bond line 142 between a transducer 114 and the member 126. The spacers 38 define a uniform planar surface that forms a constant bond line 142 and the bond line 142 is controlled by the height of the spacer 138. The spacers 138 help ensure a substantially constant-thickness bond line 142. Although the spacers 138 shown in
In further embodiments of the present invention, as shown in
Cross-section views of this embodiment of the invention are shown in
The embodiments described above and illustrated in the figures are presented by way of example only and are not intended as a limitation upon the concepts and principles of the invention. As such, it will be appreciated by one having ordinary skill in the art that various changes in the elements and their configuration and arrangement are possible without departing from the spirit and scope of the invention. Although the invention has been described by reference to the drawings and examples contained herein, it is not limited thereby and encompasses everything within the scope of the following claims.
