Patent Description:
In a spring-loaded connector which has a tubular housing hosting spring loaded piston with a clip accommodated therein with a plurality of beams, it would be conceived that the clip is inserted into the tubular housing by pushing the beams of the clip. However, this process may damage the beams and reduce a reliability of the connector.

In addition, providing a piston assembly to allow insertion of the clip by pushing it via an end face opposite to the beams requires increased wall thickness to achieve the require press fit resistance. Such increase of thickness leads to an increase of the pitch in a plug having several spring-loaded connectors. The documents <CIT> discloses a spring contact element.

An object of the invention is to provide a reliable compact piston assembly and a spring-loaded contact including the same.

In the above aim, a first aspect of the invention is a piston assembly for a spring-loaded contact, comprising:.

According to the above structure, as the piston assembly is made of separate parts (a piston body and a piston head) and the piston head is configured to be attached to the piston body, the clip can be inserted into the through hole of the piston body from the piston head side, so that clip is not damaged during assembling. In addition, the piston head is ultrasonically welded to the piston body, thus the thickness of the piston assembly can be reduced with still providing enough strength.

wherein the base end is located in the through hole on a piston head side.

According to this structure, damage of the flexible contacting end is prevented when pushing the base end to insert the clip into the though hole from the piston head side.

Advantageously, the base end comprises a tubular wall arranged to withstand a press fit force applied to the clip to insert the clip into the through hole.

Advantageously, the piston head provides an abutment to the clip. According to this structure, the clip is axially supported by the piston head.

Advantageously, the clip comprises a clipping portion opposite to the piston head.

Advantageously, at least one of the piston body, the piston head and the clip is plated before the piston head is ultrasonically welded to the piston body. One embodiment of the invention is applicable to such plated parts.

Advantageously, the welded portion is free of Heat Affected Zone, or wherein the welded portion is comprising a Heat Affected Zone having a thickness lower than <NUM>.

Advantageously, a wall thickness at a position where the piston body and the piston head is welded is less than <NUM>. Ultrasonic welding of the present embodiment can achieve this compact structure.

Advantageously, a mating length along a longitudinal axis of the piston assembly at a position where the piston head is mating with the piston body is less than <NUM>. Ultrasonic welding of the present embodiment can also achieve this compact structure.

Other aspect of the inventions is a spring-loaded contact, comprising;.

Advantageously, the conductive portion comprises a pin portion for mating with the clip. According to this structure, the pin portion can be securely held by the clip.

Advantageously, the conductive portion comprises a base portion for connecting an electronic or electric circuit.

Other features and advantages of the present invention will appear more clearly from the following detailed description of particular non-limitative examples of the invention, illustrated by the appended drawings where:.

It is of course understood that obvious improvements and/or modifications for one skilled in the art may be implemented, still being under the scope of the invention as it is defined by the appended claims.

<FIG> depicts one embodiment of a spring-loaded contact according to the invention and <FIG> depict a piston assembly used in the spring-loaded contact.

The spring-loaded contact <NUM> has a cylindrical housing (guiding cylinder) <NUM> and a piston assembly <NUM> in the form of a short rod, comprising a clip <NUM>, accommodated in the housing <NUM>. The housing <NUM>, piston assembly <NUM> and clip <NUM> may be designed to align concentrically with each other. The piston assembly <NUM> is configured to be movable in an axial direction Ax of the housing <NUM>. In the housing <NUM> a coil spring S and a conductive rod <NUM> are disposed whose configurations and functions will be described later.

The piston assembly <NUM> has a tubular piston body <NUM> and a cap-shaped piston head <NUM> attached to the end of the piston body <NUM> as can be seen in <FIG>. The clip <NUM> is inserted into the inside of the piston body <NUM>. An insertion direction is depicted with a reference character "B" in <FIG>.

The piston body <NUM> and the piston head <NUM> can be typically machined from brass, phosphour-bronze, beryllium-copper or other copper alloy or other conductive metals/alloys, including nickel-silver alloys. The clip <NUM> can be manufactured from a copper alloy, typically beryllium-copper or other high strength conductive copper alloy. The parts are typically post-plated with any one of a variety of coatings, typically a gold plating, for the purpose of enhancing electrical contact and improving wear and corrosion resistance before the piston head <NUM> is attached to the piston body <NUM>.

It is noted that the shape of piston body <NUM> in <FIG> and the shape in <FIG> are different, but they are not essential difference in the invention and the both embodiments can be used
The piston body <NUM> in <FIG> is provided with a tubular wall <NUM> having a through hole <NUM> and a flange <NUM> formed on the outer surface of the tubular wall <NUM>. The flange <NUM> has a greater diameter than the diameter of tubular wall <NUM>. In the embodiment of <FIG>, the tubular wall has a constant diameter at both sides of the flange <NUM>. By contrast, in the embodiment of <FIG>, the tubular wall <NUM> has a greater diameter in a front portion and a smaller diameter in a rear portion.

Inside of the piston body <NUM>, a receiving portion <NUM> is formed into which a tubular part <NUM> of the piston head <NUM> is inserted along the insert direction B. The receiving portion <NUM> is a cylinder-shaped space which may has a constant inner diameter greater than that of the though hole <NUM>. however, in alternative embodiments, the piston body <NUM> might have a constant diameter through-hole. The piston body <NUM> further comprises an annular face <NUM> extending in radial direction at the end of the receiving portion <NUM>.

As shown in <FIG>, the piston assembly <NUM> is disposed in the housing <NUM> such that the flange <NUM> is positioned within the housing <NUM> and a front part of the piston assembly <NUM> is protruding from an end wall <NUM> of the housing <NUM>. The flange <NUM> is pushed by way of the coil spring S so that the flange <NUM> abuts inside of the end wall <NUM>. The piston assembly <NUM> can be pushed into the housing <NUM> as the coil spring S is compressed when it contacts an external component (not shown).

The piston head <NUM> has a cylindrical body <NUM> (<FIG>) which may have a rounded contact end. The cylindrical body <NUM> includes a tubular part <NUM> with an end annular face <NUM>. Outer diameter of the tubular part <NUM> is substantially identical to the inner diameter of the receiving portions <NUM> of the piston body <NUM> so that the surfaces can be welded to each other.

Referring to <FIG>, the clip <NUM> has a base end <NUM> in the form of tubular wall <NUM> and a clipping portion <NUM> positioned opposite to the piston head <NUM>. The base end <NUM> is provided with an end face <NUM>. The base end <NUM> may has an outer diameter substantially identical to the inner diameter of the though hole <NUM> so that the clip <NUM> can be pushed and inserted into the through hole <NUM> (press fit assembly). The clipping portion <NUM> comprises a plurality of flexible beams <NUM> in a form of cantilever extending form the base end <NUM>. As each beam <NUM> is slightly bent radially inwardly, the diameter of the clipping portion <NUM> is becoming smaller toward the tip end.

As shown in <FIG>, the clipping portion <NUM> can hold the end of the conductive rod <NUM>. In particular, the conductive rod <NUM> has a circular base end 205a and a pin portion 205b extending vertically form the inner surface of the base end 205a. The clipping portion <NUM> is configured to support the end of the pin portion 205b. In the embodiment of <FIG>, the circular base end 205a can be mechanically fixed to the inside of the housing <NUM> (by press fit assembly, or welding assembly).

For a person skilled in the art it is understood that a different number of beams <NUM> can be used so long as they can hold a part of the conductive rod 205b.

In the assembled condition, the end face <NUM> of the piston head <NUM> may abut or substantially abut the end face <NUM> of the clip <NUM> so that the clip <NUM> can be axially supported within the piston body <NUM>. Annular face <NUM> of the piston head <NUM> may also abut an end face <NUM> of the piston body <NUM>. A gap between both faces <NUM> and <NUM> can be sealed with a certain material. In a preferable embodiment, the piston head <NUM> and the piston body <NUM> may has substantially identical diameters so that there is no step at the connecting portion of the two parts.

The clip <NUM> is configured to be inserted into the piston body <NUM> along the direction B from the piston head <NUM>, which is in the opposite direction to a standard direction. The advantage of inserting the clip <NUM> in this direction is that the beams <NUM> of the clip <NUM> make contact with the rod deeper into the spring pin assembly, thus providing reliable contact in a shorter height (a length along the front-rear direction in drawings). In addition, inserting and pushing the clip <NUM> from the side where the piston head will be assembled provides the ability to push on end face <NUM>, avoiding any stress on the beams <NUM>.

The reverse insertion has been made possible by the assembly construction. If the piston body <NUM> is not a separate part, the clip <NUM> cannot be inserted without damaging the beams <NUM>. The present embodiment allows the assembler to push on the strong end of the clip <NUM>.

In this embodiment, the outer surface of the tubular part <NUM><NUM> is secured to the inner surface of the receiving portion <NUM> of the piston body <NUM>. Preferably, the tubular part <NUM> is ultrasonic welded to a part of the piston body <NUM> to thereby form a circumferential welded area W. The welded area W is extending along the axial direction. The welded area W preferably presents a length Lm in axial direction less than <NUM>.

In addition, such ultrasonic welded area W is typically free of Heat Affected Zone, or comprises a very limited Heat Affected Zone having a thickness lower than <NUM> as temperature during ultrasonic welding remains low. The welded area W is also typically free of added metal.

Ultrasonic welding permits at least one of the followings: a better gold platting (especially at the bottom of holes) as the temperature does not increase during the ultrasonic welding , a better behavior in respect to the radiofrequencies, a better resistance to heat and aging due to the fact that the connector is monobloc. Further, ultrasonic welding permits that thin parts can be welded to each other. Thus, wall thickness Lw at a position where both parts are ultrasonic welded may be less than <NUM>, preferably less than <NUM>, and more preferably less than <NUM>.

In one embodiment, the annular face <NUM> of the piston head <NUM> (<FIG>) can also be ultrasonically welded to the face <NUM> of the piston body <NUM>.

Other technologies to join two parts includes the followings; press-fitting, crimping, latching, brazing, soldering, conductive adhesives and other welding processes. However, in press-fitting, the problem can be high force and thick walls required. In crimping, the problem can be mechanical deformation and potential plating damage. In brazing, the problem can be expensive, complicated, slow process, heat damaging the plating. In soldering, the problem can be part geometry and size, heat damaging the plating. In conductive adhesives, the problem can be low mechanical strength. In the other welding processes, the problem can be damage to plating.

According to the embodiment, the piston assembly <NUM> consists of separate and simple to manufacture parts; the piston body <NUM> and the piston head180. This enable that the clip <NUM> can be inserted into the piston body <NUM> along the direction B, thus damaging to the beams <NUM> can be prevented. In addition, due to the fact that the piston head <NUM> is ultrasonically welded to the piston body <NUM>, compact welded area W with sufficient reliability can be obtained.

Claim 1:
A piston assembly (<NUM>) for a spring-loaded contact (<NUM>), comprising:
- a piston body (<NUM>), arranged to be received into a guiding cylinder (<NUM>) of the spring loaded contact (<NUM>),
- a piston head (<NUM>), with a contacting surface arranged for contacting an external part,
- a clip (<NUM>) arranged to mate with a conductive portion (<NUM>) of the spring loaded contact, the piston assembly being characterized by that the piston body (<NUM>) comprises a through hole (<NUM>), the clip being arranged into the through hole,
and that the piston head (<NUM>) is attached to the piston body (<NUM>) by an ultrasonic welded portion.