Rotating dovetail connection for materials testing
A rotating dovetail connection is provided in order to attach jaw faces to grips in materials testing. The connection includes a machined tongue on the jaw face and a corresponding groove on the jaw face holder. A ball plunger within the holder serves to center the jaw face and to retain the jaw face in the holder. The jaw faces can be installed an removed without the use of tools or loose parts. The rotating dovetail facilitates a secure connection between the jaw face and the grip while allowing the jaw faces to rotate.
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This application claims priority under 35 U.S.C. 119(e) from U.S. provisional patent application Ser. No. 61/069,815, filed on Mar. 18, 2008, the contents of which are hereby incorporated by reference.
BACKGROUND OF THE INVENTION1. Field of the Invention
The present invention pertains to a device for use in material testing equipment and accessories. More specifically, the present invention pertains to a mechanism for the connection of removable jaw faces to material testing grips.
2. Description of the Prior Art
In the prior art, materials testing systems are used in a variety of industries and are generally used with some sort of accessory to provide specimen gripping or holding. Many of these tests require that the accessories have specific gripping surfaces or sizes. The size and type of gripping surface needed can vary greatly from test to test, making jaw face changes a frequent event in many labs. Therefore, removable jaw faces with various sizes and surfaces are a common commodity in the materials testing industry.
Many different embodiments of jaw face attachment have developed over the years by various manufacturers. These connection mechanisms include simple pin and aperture connections as well as rigid dovetail connections. Each mechanism has advantages and disadvantages.
Zwick has implemented the use of a rigid dovetail connection as shown in
MTS has implemented an externally accessible pin and a corresponding aperture to connect the jaw faces to the grips as shown in
Instron, the assignee of the present application, has implemented four jaw face to grip connection methods of interest. These method include set screw and groove; internal pin an aperture; internal pin and retaining wire; and hook and fixed pin. All of these methods allow the jaw faces to rotate. This rotation is needed to compensate for both inconsistencies in specimen thickness and elastic deformation of grip bodies during testing. The set screw and groove method as shown in
The internal pin and aperture method as shown in
The internal pin and retention wire method was developed by the present assignee for use on side-acting screw action grips and uses a semi-permanent pin installed in the back of a typical pin and aperture jaw face as shown in
On higher capacity pneumatic side-action grips, the present assignee has implemented the use of a hook and fixed pin connection method as shown in
It is therefore an object of the present invention to provide a connection apparatus for materials testing which is easy to operate, is robust, and provides repeatable jaw face positioning.
It is therefore a further object of the present invention to provide a secure rotating jaw face connection to be used in material testing accessories which substantially eliminates the complexity and difficulty involved in installing and removing jaw faces.
It is therefore a still further object of the present invention to reduce or eliminate the need for tools in the assembly and disassembly of the connection apparatus for materials testing, while maintaining secure operation of the apparatus.
These and other objects are attained by providing a rotating dovetail connection for use on materials testing accessories that use removable jaw faces. This rotating dovetail connection is related to the dovetail joinery connection that allows for a secure sliding connection in carpentry without the use of auxiliary parts. Adapting the tongue and groove of the joint into a rounded edge permits the connection to rotate while still being held securely together. This is particularly useful in jaw face attachment where slight rotation of the jaw faces is desired. The tongue also has a detent machine into the back side to permit a spring loaded ball to hold the jaw face securely and accurately in the holder. The degree of rotation is controlled by the placement of the groove in relation to the back of the jaw face. Another embodiment machines flats and a cross aperture on the jaw face for to allow use in grips that use the pin and aperture connection method.
Further objects and advantages of the invention will become apparent from the following description and from the accompanying drawings and claims, wherein:
Referring now to the drawings in detail wherein like numerals refer to like elements throughout the several views, one sees that
As shown in
The cross-sectional view of the holding device 12 in
The profile of the gripping device 14, which exhibits the male end of the rotating dovetail connection 10, is shown in
When the rotating dovetail connection 10 is not put under any extraneous load, the ball plunger 16 forces the gripping device 14 in the negative Z direction against the transverse circular bore 30 of the holder device 12. When an extraneous load is applied to the gripping device 14 in the positive Z direction, the ball plunger 16 is compressed, the rounded surface 22 mates up with the transverse circular bore 30, and the connection is free to rotate about the X-axis in
Thus the several aforementioned objects and advantages are most effectively attained. Although preferred embodiments of the invention have been disclosed and described in detail herein, it should be understood that this invention is in no sense limited thereby and its scope is to be determined by that of the appended claims.
Claims
1. A connection for materials testing within a material testing accessory compromising:
- a holder including a bore and a latching mechanism; and
- a gripping mechanism having a tongue insertable into said bore in said holder, said tongue being at least partially rotatable within said bore, and a detent configuration for engaging said latching mechanism.
2. The connection as claimed in claim 1, wherein said gripping mechanism is held in place by said latching mechanism.
3. The connection as claimed in claim 1, wherein said bore of said holder is at least partially cylindrical and wherein said gripping mechanism is free to rotate throughout a range within said bore of said holder.
4. The connection as claimed in claim 1, wherein said tongue includes at least one sloped surface to ease installation into said bore of said holder.
5. The connection as claimed in claim 1, wherein said bore includes a cross cut pathway sized to allow said tongue on said gripping mechanism to slide through.
6. The connection as claimed in claim 1, wherein said tongue includes an undercut which is sized to allow said tongue on said gripping mechanism be held securely in said holder.
7. The connection as claimed in claim 1, wherein said latching mechanism is a spring loaded ball plunger passing through a central longitudinal aperture in said holder.
8. The connection as claimed in claim 1, wherein said gripping mechanism is a removable jaw face.
9. The connection as claimed in claim 1, wherein said material testing accessory is a pneumatic, hydraulic, or screw-action grip.
10. The connection as claimed in claim 1 wherein said tongue includes lateral flat surfaces.
Type: Application
Filed: Feb 2, 2009
Publication Date: Sep 24, 2009
Applicant:
Inventor: James Brittain Smallwood (Milton, MA)
Application Number: 12/322,386
International Classification: G01N 3/02 (20060101);