Metal working – Means to assemble or disassemble – Means to drive self-piercing work part
Reexamination Certificate
1999-04-07
2001-07-24
Young, Lee (Department: 3729)
Metal working
Means to assemble or disassemble
Means to drive self-piercing work part
C029S818000, C227S139000, C227S150000, C269S2540DF
Reexamination Certificate
active
06263561
ABSTRACT:
BACKGROUND
The application is a continuation-in-part of U.S. patent application Ser. No. 08/307,849 filed on Sep. 30, 1994 in the name of Heinrich Luckhardt, which claims the benefit of PCT International Application No. PCT/EP93/00836 filed Apr. 2, 1993, and the benefit of German Application No. P4 211276.1 filed on Apr. 3, 1992. This invention relates to installation heads and, in particular, discloses an improved installation head with holding fingers that interact with an improved fastener to ensure proper alignment of the fastener from its entry into the installation head until the fastener is installed in a workpiece. The present invention is suited for use with any type of fastener, particularly pierce-type fasteners.
In the mass production of parts, fastener installation tools are commonly used to simultaneously install fasteners in, for example, a panel, as the panel is being formed in a press. The installation tool is mounted in the press and, as the press closes, the fastener is installed. The installation tool has a housing, a plunger passage, a plunger operatively mounted in the plunger passage, and a fastener feed mechanism that feeds fasteners into the plunger passage. The passage and the fastener have complementary shapes, and the plunger is adapted to drive the fastener through the passage into the panel. To assist in the initial alignment of the fastener with respect to the plunger, catches are used to hold the fastener in the passage as the fastener enters. Once the plunger contacts the fastener, the fastener either drops through to the workpiece or is temporarily held by, for example, spring-loaded detents extending into the passage.
Although the passage and fastener are configured to facilitate the proper alignment of the fastener with respect to the plunger and the panel, the fastener can become misaligned within the passage. For example, if the detents stick or fail, the fastener will cock in the passage and be misaligned when it is driven into the panel. Misalignment problems are exacerbated when the installation tool is not vertically oriented with respect to the workpiece. Non-vertical orientations are very common. As should be appreciated, misalignment can result in faulty installations, damage to the part, and damage to the installation tool.
The installation head illustrated in U.S. patent application Ser. No. 08/307,849 overcomes the above problems. However, it does have disadvantages. First, the fingers which hold the fastener against the plunger do not hold the fastener at the critical point of contact with the workpiece. It has been found by Applicant that it is important to hold the fastener until at least the installation end of the fastener engages the workpiece so that the fastener is being held between the plunger and the workpiece. At this point, the fingers can be removed and proper installation will be ensured. Additionally, Applicant has found that in many applications, it is important that the fingers maintain guiding contact with the fastener until the fastener is completely installed in the panel. Neither of these holding techniques can be achieved by the disclosed invention because the fingers are cammed away from the fastener through contact with the panel surface. By definition, the fingers release the fastener prior to the fastener making installation contact with the panel. Although this distance is slight, it is sufficient to result in misalignment of fasteners. This is particularly true, since the panel surface is required to act as a cam surface when, in fact, it is not designed to be a cam surface. Therefore, any restriction of the fingers can result in the fingers not moving properly and resulting in a cocked fastener at the critical installation point. It should be appreciated that any tilting of the fastener at installation can result in an improper installation of the fastener.
Another disadvantage to the installation head disclaimed in the co-pending application is the potential marring of the panel surface due to the fingers being cammed against the surface at installation. This marring can be unacceptable in many applications, resulting in rejected panels and increased manufacturing costs.
BRIEF SUMMARY OF THE INVENTION
The present invention overcomes the above problems by providing an installation tool having fingers that hold a fastener from the point that the fastener enters the plunger passage until the fastener is either partially or completely installed in, for example, a panel. The term “panel” is used herein to define the workpiece, and panel may include, for example, a plate, sheet metal part, such as a body panel, bracket, or structural member. Further, the present invention includes an improved fastener that has sides that are displaced to mate with the free ends of the fingers in the installation tool so that the fastener can be held and guided throughout its path of travel. Still further, the present invention includes a method for installing a fastener with an installation tool so that the fastener is held throughout its travel to ensure a properly aligned, properly installed fastener. The present invention is described with respect to pierce-type fasteners but would be suited for other types of fasteners, such as rivet-type fasteners, weld nuts, etc.
The installation tool of the present invention has a main body with a nosepiece having a bore or fastener passage and a fastener entry path for inserting fasteners into the passage adjacent the plunger. The nosepiece reciprocates relative to the plunger which has a free end adapted to engage the fastener when the fastener is in the bore for driving the fastener through the main body and into a panel or other workpiece. At least two fingers are operatively connected to and pivotally mounted with respect to the plunger and the fastener. The fingers extend beyond the free end of the plunger for engaging the fastener and, in particular, for engaging a displaced area formed on the fastener. The fingers hold the fastener adjacent the plunger as the plunger drives the fastener to the panel. This ensures that the fastener is positively held in a properly aligned position with respect to the plunger and the panel from the point that the fastener enters the plunger passage to at least engagement of the fastener against the panel.
The fastener of the present invention is specifically designed for installation by the installation head of the present invention. The fastener includes top, bottom, and sides, with the bottom having a configuration that, when pressed into a workpiece, will interlock the bottom of the fastener with the workpiece material to provide a strong connection between the fastener and the workpiece. As will be understood, top, bottom, side, etc., are relative terms used for ease of description; however, the installation head of this invention may be adapted to attach a fastener to a panel in most any attitude and thus such terms are not limiting. The side of the fastener includes a displaced area that is positioned between the top and bottom of the fastener. The displaced area is adapted to receive the fingers in a positive inter-engagement between the fastener and the installation tool fingers to accurately position and align the fastener with respect to the workpiece. The displacement area is defined by a displaced portion in the side of the fastener which mates with the free end of the fingers of the installation tool. The displaced surface can be in the shape of a groove having a generally semi-circular or triangular cross-section; a ridge having a generally semi-circular cross-section; an indent which is adapted to receive a protrusion on the free end of the fingers; a protrusion which is adapted to be received within an indent on the free end of the fingers; a slot which extends perpendicular to the top and bottom surfaces, etc. It should be appreciated by those of ordinary skill in the art that many different types of displaced surfaces will provide the positive engagement between the fingers and the fastener.
The fingers of the present inven
Luckhardt Christof
Luckhardt Heinrich
Luckhardt Wolfgang
Sickels David W.
Howard & Howard
Luckhardt Christof
Luckhardt Wolfgang
Multifastener Corporation
Tugbang A. Dexter
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