Weldable plastic fastener

• US 5,672,036 A
• Filed: 12/07/1995
• Issued: 09/30/1997
• Est. Priority Date: 05/22/1992
• Status: Expired due to Fees

• Current Assignee: Unimation, Inc. (Stäubli Holding AG)
• Original Assignee: Unimation, Inc. (Stäubli Holding AG)
• Inventors: Medal, James
• Primary Examiner(s): Wilson, Neill R.
• Application Number:
  US08/568,638
• Time in Patent Office: 663 Days
• Field of Search: 411/82, 411/238, 411/171, 411/338, 411/339, 411/437, 411/908, 411/930, 29/426.5, 285/21
• US Class Current: 411/82
• CPC Class Codes: B29C 65/08 using ultrasonic vibrations non-plastics element to plastics elements B29C65/645
• CPC Class Codes: B29C 65/562 using extra joining elements, i.e. which are not integral with the parts to be joined using plastic snap elements B29C65/58; using plastic rivets B29C65/601
• CPC Class Codes: B29C 65/645 using friction or ultrasonic vibrations
• CPC Class Codes: B29C 66/05 Particular design of joint configurations
• CPC Class Codes: B29C 66/3022 said melt initiators being integral with at least one of the parts to be joined
• CPC Class Codes: B29C 66/30221 said melt initiators being point-like
• CPC Class Codes: B29C 66/41 Joining substantially flat articles B29C66/47 and subgroups take precedence; Making flat seams in tubular or hollow articles B29C66/51 and subgroups take precedence
• CPC Class Codes: B29C 66/53245 said articles being hollow
• CPC Class Codes: B29C 66/5344 said single elements being substantially annular, i.e. of finite length, e.g. joining flanges to tube ends B29C66/5346 takes precedence
• CPC Class Codes: B29L 2031/463 Grips, handles handgrips as part of the body finishing of the vehicles B29L2031/3029
• CPC Class Codes: B29L 2031/7158 Bottles
• CPC Class Codes: B29L 2031/737 Articles provided with holes, e.g. grids, sieves nets B29L2028/00
• CPC Class Codes: B65D 23/104 Handles formed separately
• CPC Class Codes: B65D 23/106 the gripping region of the handle extending between the neck and the base of the bottle or jar and being located in a radial plane comprising the axis of the bottle or jar
• CPC Class Codes: F16B 33/006 Non-metallic fasteners using screw-thread
• CPC Class Codes: F16B 39/225 by means of a settable material
• CPC Class Codes: F16B 4/004 Press fits, force fits, interference fits, i.e. fits without heat or chemical treatment F16B4/002 takes precedence
• CPC Class Codes: G06T 11/203 Drawing of straight lines or curves
• CPC Class Codes: H05K 7/142 Spacers not being card guides
• CPC Class Codes: Y10S 411/93 Flowing metal or settable material

Abstract

A bolt and nut formed from a plastic material are provided with the bolt having proximate and distal ends and the nut having an interior surface defining a bore. Raised projection members are formed integrally extending from the nut interior surface into the bore and together define a diameter slightly smaller than the shank diameter. In this manner, an interference fit is provided between the shank and projection members. With the bolt shank inserted through aligned holes in parts to be fastened, the nut can be mounted on the distal end of the bolt shank, as by a force fit, and slid thereon by exerting an axial force on the nut until the parts are clamped between the bolt head and nut. At the interface formed by the engaged projection members and the bolt shank at the areas engaged with a force fit, intermixing of the respective plastic materials of the shank and projections can occur which, when solidified, forms a bond at the interface to secure the nut in place on the shank and thereby provide a good and secure clamping force to the fastened parts. To separate the parts, a torque force sufficient to break the bond formed between the projections and shank is applied to the nut. The nut can then be removed from the shank and the shank withdrawn from the aligned part holes, thus allowing the parts to be separated in their original state without any damage thereto.

Claims

1. A plastic nut and bolt combination for fastening panels to each other, the combination comprising:

a bolt having a shank formed from a plastic material and having proximate and distal ends thereof;

a polygonal nut formed from a plastic material and having exterior flats and an interior surface defining a bore;

a plurality of raised projection members formed integrally extending from the nut interior surface into the bore together defining a diameter slightly smaller than the shank diameter so as to provide an interference fit between the shank and projection members; and

a bonded interface being located between the engaged projection members and the bolt shank at the areas engaged with a force fit comprising a solidified intermixture of the respective plastic materials which forms a bond with each other at the bonded interface, application of a torque force allowing removal of the nut from the shank by breaking the bond formed therebetween at the interface.

2. The combination of claim 1 wherein the bolt has an enlarged head formed at the proximate end of the shank and the panels have aligned bores through which the shank is inserted with the nut clamping against the bottom panel to tightly capture the panels between the nut and the bolt head.

3. The combination of claim 1 wherein the bolt shank has its distal end chamfered and the projection members extend axially and have at least one inclined surface to allow the inclined surfaces of the projections to engage and cam against the chamfered bolt distal end as the nut is mounted on the bolt shank.

4. The combination of claim 3 wherein the projection members have oppositely facing inclined surfaces at either end thereof to allow the nut to be mounted on the shank by engagement of either of the oppositely facing inclined surfaces of the projections with the bolt distal end.

5. The combination of claim 1 wherein there are four equally spaced projection members on the nut interior annular surface.

6. The combination of claim 1 wherein the projection members extend axially along the nut interior surface and substantially have the shape of a trapezoid having inclined surfaces facing the bore openings.

7. The combination of claim 6 wherein the inclined surfaces are spaced inwardly within the nut bore from the bore openings.

8. An assembly for maintaining a clamping fastening force on panels, the assembly comprising:

an upper and a lower panel each having top and bottom surfaces and a bore extending through each of the panels from the top to the bottom surface;

a plastic bolt having a head and a shank having a first predetermined diameter with the shank extending from the bolt head;

a plastic nut having a first end and a second end with a central bore wall extending through the nut from the first end to the second end to define a shank receiving bore having a second predetermined diameter;

a plurality of axial plastic projection members on the bore wall with the projection members defining a third predetermined diameter less than the shank first diameter to provide an interference fit with the shank when the nut is mounted on the shank with the nut and shank being bonded upon reducing the regions between the projections and shank to a flowable state which then solidifies to thereby bond the nut on the shank;

the bolt shank being inserted in aligned bores of the panels and the nut is mounted on the end of the bolt shank distal from the bolt head until it engages the lower panel bottom surface to exert a clamping force on the panels by the bolt head on the upper panel top surface and the nut on the lower panel bottom surface; and

a bonded plastic interface between the shank and projections having been defined by their respective plastics having been liquified to a flowable state to intermix and then solidified to maintain the clamping force exerted by the bolt head and nut on the panels.

9. The assembly of claim 8 wherein the axial projections are in the shape of a trapezoid having inclined surfaces spaced inwardly in the nut bore from the nut ends to allow the nut to be mounted on the bolt shank by engagement of either inclined surface with the shank distal end and with either one of the first and second nut ends engaging the lower panel bottom surface.

10. The assembly of claim 8 wherein the projections are circumferentially spaced around the nut bore wall to define spaces therebetween to allow the nut to be removed from the shank by breaking the bonds formed at the interface between the projections and the shank surface upon application of a loosening torque force to either the head or the nut.

11. The assembly of claim 10 wherein the spaces between the projections occupy a greater volume in the nut bore than the volume occupied by the projections.

12. The assembly of claim 8 wherein there are four projections spaced equally at 90 degree intervals on the nut annular wall.

13. The assembly of claim 8 wherein the projections are formed integrally with the nut bore wall and the bolt and nut are formed from the same plastic material comprising one of a polycarbonate, a polypropylene and a nylon plastic material.

14. The assembly of claim 8 further comprising a spacing member on the bolt shank between the upper and lower panel with the clamping force pushing the upper panel bottom surface and the lower panel top surface into engagement with opposite ends of the spacing member.

15. A plastic nut for welding to a plastic bolt having a shank with a predetermined diameter, said plastic nut comprising:

a body of plastic;

exterior flats on the body defining a peripheral surface for the body and to be engaged by a tool to turn the nut;

an interior surface in the plastic body defining a bore with an axis in the body to receive therein the bolt shank;

a plurality of axially-extending projections in the bore projecting radially inwardly toward the axis; and

the interior axially-extending surfaces on the projections being spaced from one another about the interior surface of the bore and defining a diameter smaller than the bolt shank to have an interference fit with the bolt shank and for being liquified and for intermixing with plastic of the bolt and thereby forming a plastic bond with the bolt shank, the axially-extending projections being substantially trapezoidal in cross-section with said interior, axially-extending surfaces being smaller in size than base portions of the projections integrally joined to the interior bore surface.

16. A method of securing two members together with a plastic bolt having a shank and a head with a plastic nut, said method comprising the steps of:

abutting the two members together having bolt receiving openings in the respective members being aligned to receive a bolt;

inserting the bolt shank through the openings and abutting the bolt head against one of the members;

providing a nut with a bore having inwardly-extending projections in the bore defining a diameter less than a diameter of the bolt shank;

forcibly sliding the axial projections on the nut relative to the bolt shank to provide a force fit at an interface between the projections and the bolt shank when the nut is slid onto the bolt shank;

liquefying the plastic of the bolt and nut at the interface to intermix the bolt and nut plastics; and

solidifying the intermixed plastic at the interface to bond the nut to the bolt shank and thereby securing the two members together.

17. A method in accordance with claim 16 including the step of disassembling the nut from the bolt by applying a turning torque to the nut to break the bond at the interface to allow removal of the nut from the bolt shank.