WO2021010891A1

WO2021010891A1 - Locating pin for dimensionally variable parts

Info

Publication number: WO2021010891A1
Application number: PCT/SG2020/050071
Authority: WO
Inventors: Shien Yang LEE; Kok Kit CHEY; Zhong Xin CHEN; Mun Hoon Wayne NG
Original assignee: Akribis Systems Pte Ltd
Priority date: 2019-07-12
Filing date: 2020-02-13
Publication date: 2021-01-21

Abstract

A locating pin (100) for dimensionally variable parts is disclosed. The locating pin (100) comprises: a base (10) having a cylindrical body (12) being extended from the base (10) to form a pin member (20), characterized in that the pin member (20) has a frustro-conical head (22) with a plurality of augmented cylindrical circumferential edges equally distributed around the head (22) thereof, wherein the cross-section of the frustro-conical head (22) is provided with a plurality of cylindrical surfaces (23) with a facet (24) positioned in between two cylindrical surfaces (23).

Description

LOCATING PIN FOR DIMENSIONALLY VARIABLE PARTS

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to locating pin for use in establishing location of a workpiece with respect to the locating pin, and particularly pertains to a locating pin adapted for accommodating a larger amount of dimensional variation in a workpiece locating bore or cavity without introducing unacceptable local stresses.

2. Discussion of Prior Art

It is known that locating pins are being used to precisely secure a plurality of workpieces in a fixed relative condition.

US Patent Publication No. 20100320806 discloses a vehicle glazing having a centring pin bonded thereto, the centring pin comprising a base portion bonded to the vehicle glazing and a centring portion adapted to be inserted into a hole in the bodywork of a vehicle, the centring portion being joined to the base portion, and moveable between a lowered position, in which the glazing may be stored, and a raised position, in which the glazing may be fitted into an aperture in a vehicle.

US Patent Publication No. 20090120922 entitled“Ceramic Body and Steel Post Locating Pin Assembly“ discloses a composite locating pin adapted for interconnection with a welding apparatus, securing a plurality of workpieces in a fixed relative condition, and resisting slag adhesion, deformation and pin failure, during a welding cycle, including, in a preferred embodiment, a removable pin body formed of a technical ceramic, a pin post formed of a steel alloy, and an adhesive layer intermediate the body and post, wherein the body and post are cooperatively configured so as to be removably yet securely interfitted in an assembled condition, and the layer is configured so as to further secure the pin in the assembled condition.

US Patent No. 10081064, entitled“Expanding Locating And Clamping Pin”, discloses an expanding locating and clamping pin assembly configured to locate and clamp a part includes a housing, a locating pin, an actuating mechanism, and a controller. The housing is configured with a plurality of radial jaw guides and a part rest face. The locating pin has a plurality of jaws radially movable in the radial jaw guides, extending past the part rest face, and configured with a part clamping feature. The actuating mechanism is connected to the housing and the jaws and is configured to synchronously move the jaws to a radial position and to apply the clamping force. The controller controls the radial position of the jaws and the clamping force. The part rest face and the jaws of the locating pin are configured to receive the part in a located position and to clamp the part in the located position via the clamping force.

US Patent No. 9,902,048, entitled “Pin Clamp With Multi-Thickness Clamping Feature” discloses a pin clamp for clamping a workpiece, said pin clamp comprising: a housing; a locating pin extending through said housing and having a longitudinal axis, said locating pin being sized to be positioned within an opening of the workpiece; a finger positioned adjacent to said locating pin and movable in a transverse direction relative to said longitudinal axis to retain the workpiece on the locating pin; a linear actuator coaxial with said longitudinal axis and configured to move said locating pin in opposite directions along said longitudinal axis; a sequence bracket attached to said housing; a lock bracket attached to said housing opposite said sequence bracket; and a sequence cam connected with said linear actuator in a manner allowing axial movement of said linear actuator to be converted into transverse movement of said sequence cam perpendicular to said longitudinal axis, said sequence cam including a ledge configured to ride along a top surface of said sequence bracket during a first part of a clamping sequence, said sequence cam further including an engagement surface which engages an angled surface of said lock bracket during a second part of said clamping sequence to lock said locating pin and said finger against the workpiece upon retraction of said linear actuator.

BRIEF SUMMARY OF THE INVENTION

The main object of the present invention is to provide a locating pin for dimensionally variable parts. In other words, the present invention is intended for use with workpieces with a prismatic cavity to be used to establish location with respect to the locating pin. The present invention is further intended for use to locate workpieces with appreciable local compliance in the vicinity of the locating cavity relative to the local compliance of the pin contact surfaces.

The present invention is applicable to workpieces with locating cavities or locating cavities construed of polymeric and/or metallic materials, and the advantage of the present locating pin is its ability to effectively absorb workpiece- to-workpiece dimensional variations in the locating cavity without compromising workpiece location determinism.

Another main object of the present invention is to provide a locating pin (100) for dimensionally variable parts, comprising: a base (10) having a cylindrical body (12) being extended from the base (10) to form a pin member (20), characterized in that the pin member (20) has a frustro-conical head (22) with a plurality of augmented cylindrical circumferential edges around the head (22) thereof, wherein the cross-section of the frustro-conical head (22) is provided with a plurality of cylindrical surfaces (23) with a facet (24) positioned in between two cylindrical surfaces (23).

Yet a further object of the present invention is to provide a locating pin (100) for dimensionally variable parts, wherein a 3- or more concentric partial external cylindrical surfaces are formed along the pin member (20).

Another object of the present invention is to provide a locating pin (100) for dimensionally variable parts , wherein the pin member (20) is provided with a plurality of facets (24).

A further object of the present invention is to provide a locating pin (100) for dimensionally variable parts, wherein the base (10) of the pin (100) is configured to position to a machine.

Another further object of the present invention is to provide a locating pin (100) for dimensionally variable parts, wherein the base (10) is provided with or without an adaptor (?) for mount the locator pin (100) to the machine.

Still yet another object of the present invention is to provide a locating pin (100) for dimensionally variable parts, wherein the pin member (20) is adapted to be inserted through a locating bore cavity provided on a workpiece.

Yet a further object of the present invention is to provide a locating pin (100) for dimensionally variable parts, wherein the width of the pin member (20) is narrower than the width of the base (10).

Another object of the present invention is to provide a locating pin (100) for dimensionally variables parts, wherein the height of the pin member (20) is substantially the same as that of the base (10).

Still yet another object of the present invention is to provide a locating pin (100) for dimensionally variable parts, wherein the cross section (22) of the pin member (20) is much smaller than that of the base (10).

Still another object of the present invention is to provide a locating pin (100) for dimensionally variable parts, wherein cross section (22) of the pin member (20) is longer than that of the base (10). A further object of the present invention is to provide a locating pin (100) for dimensionally variables parts, wherein the pin member (20) is generally a cylindrical portion extending from the base (10) of the locating pin (100) along the axis until the cross section (22) thereof.

BRIEF DESCRIPTION OF THE DRAWINGS

Various features will become apparent to those skilled in the art from the following detailed description of the disclosed non-limiting embodiment. The drawings that accompany the detailed description can be briefly described as follows:

FIG. 1 is a schematic perspective view of a locating pin with three circumferential facets in accordance with the present invention;

FIG. 2 is a cross-section view of the pin member of the locating pin in accordance with the present invention;

FIG. 3 is a graph showing the effect of randomly distributed workpiece locating cavity in accordance with the present invention;

FIG. 4 is a schematic view indicating the radial deformation mechanism in accordance with the present invention; and

FIG. 5 is a schematic view showing isometric radial expansion induced in an undersized part by a conventional locating pin.

DETAILED DESCRIPTION OF THE INVENTION

The present invention concerns a locating pin (100) adapted for use with workpieces with a prismatic cavity or locating hole to be used to establish location with respect to the locating pin. As shown in FIG. 1 , there is shown a schematic perspective view of a locating pin (100) with three circumferential facets (20) in accordance with the present invention.

In accordance with a preferred embodiment of the present invention, the locating pin (100) for dimensionally variable parts has a base (10), which is a cylindrical shape, and has a cylindrical body (12). The cylindrical body (12) is extended from the base (10) along the axis of the body (12) to form the pin member (20). The locating pin (100) is characterized in that the pin member (20) has a conical head (22) as a lead-in chamber with a plurality of augmented cylindrical circumferential edges distributed around the head (22) of the pin member (20). The conical head is functioned to facilitate the insertion of the pin into a locating bore. The diameter of the base (10) is larger than the widest length along the cross section of the pin member (20). The frustro-conical head (22) is provided with a plurality of cylindrical surfaces (23), and between each cylindrical surface (23), a facet (24) is formed. In the present preferred embodiment, three facets (24) are shown and described.

The pin member (20) of the locating pin (100) is provided with a 3- or more concentric partial external cylindrical surfaces, formed along the pin member (20), and the facets (24) are formed on the pin member (20). The frustro-conical head (22) provides a larger amount of radial force generated by a workpiece, and the base (10) of the pin (100) is configured to position to a milling machine or the like. The pin member (20) is generally a cylindrical portion extending from the base (10) of the locating pin (100) along the axis until the cross section (22) thereof.

FIG. 2 is a cross-section view of the pin member (20) of the locating pin (100) in accordance with the present invention. In the preferred embodiment, the workpiece locating cavity is nominally cylindrical. In order to locate the workpiece in relation to the locating pin (100), the pin (100) and the workpiece are mated together such that the locating pin’s (100) contact surfaces are come into contact with the internal surface of the workpiece locating cavity. To ensure deterministic location, the pin contact diameter is chosen to be an interference fit with the workpiece as its least material condition.

In the mated condition, the pin contact surfaces exert outward radial forces on the workpiece locating cavity, deforming the cavity locally to allow the locating pin (100) insertion. The deformed workpiece cavity exerts a number of radial elastic forces on the locating pin (100). This force sytem has an energetic minimum when the workpiece locating cavity stiffness center is coincident with the locating pin center. In this mated condition, the workpiece is positioned with respect to the locating pin (100) to the limit of frictional effects.

The base (10) of the locating pin (100) may be provided with a threaded adaptor or can be damped glued, brazed welded, press fitted or the like for mount the locating pin (100) to the machine, and when in use, the pin member (20) is adapted to be inserted through a locating hole provided on a workpiece, as mentioned earlier.

In the present invention, the cross section of the pin member (20) is narrower than the cross section of the base (10), and the height of the pin member (20) is substantially the same as that of the base (10).

In accordance with the present invention, the larger the number of pin contact surfaces or the larger the number of facets (24), the larger the number of radial locating forces, which improves positional determinism of the workpiece in spite of local cavity geometry aberrations by the elastic averaging effect. As the number of pin contact surfaces tends to infinity, a conventional cylindrical locating pin is approximated.

The discrete pin contact surfaces of the present invention improves the ability to accommodate dimensional variations in the workpiece locating cavity without causing undesirably large mating and unmating forces. For instance, consider the case a workpiece with cylindrical locating cavity with diameters normally distribute around a nominal value. Further consider that the workpiece is required to be deterministically located relative to the locating pin by elastic interference between the locating cavity and locating pin. In addition, consider that no permanent deformation on the workpiece locating cavity is allowed. This set of conditions lead to a design problem where the locating pin diameter is to be chosen to deterministically locate the largest fraction of workpieces without causing plastic deformation due to excessive stresses. A similar situation is encountered when, instead of avoiding plastic deformation, mating or unmating force is to be kept below a required value, thereby limiting the amount of total radial forces that can be generated by the interference fit.

For a given limit of maximal radial force, the present invention permits a larger amount of spatial interference between the workpiece locating cavity and the pin contact diameter. This allows the selection of larger pin contact diameter compared to that allowed by cylindrical locating pines. The net result is that a larger proportion of workpieces are satisfactorily located with deterministic position, acceptable amounts of permanent deformation, and acceptable mating and unmating forces. This is shown in FIG. 3, wherein the x-axis of the graph is the interference in pm. On the graph shown in FIG. 3, the shaded area fZZJ is acceptable fit zone with conventional locating pin, the shaded area

acceptable fit zone with disclosed locating pin.

The mechanism by which the locating pin (100) of the present invention allows a larger amount of radial interference for a given maximum radial force depends on the compliance distribution around the workpiece locating cavity. If the workpiece locating cavity has thin walls, radial deformation primarily occurs in a bulk compressive mode. The radial force is determined by how much material needs to be displaced to accommodate the locating pin. The present invention has a smaller total pin contact area, and therefore, less material has to be displaced, leading to lower radial forces. When the workpiece locating cavity is thin-walled, radial compliance can be describe by the cavity walls acting as a shell. The present invention allows the shell to undergo a cross sectional distortion to conform to the locating pin. It has been found that this transition from in-plane tensile loading on the shell to out of plane bending significantly reduces radial forces and stresses in the locating cavity. In other words, the present invention allows thin walled part to undergo a shape change which causes less force than cylindrical pins which force a size change. FIG. 4 indicates the thin-walled locating cavity in accordance with the present invention.

RECTIFICATION SHEET RULE 91 FIG. 5 is a schematic view showing isometric radial expansion of a conventional locating pin, wherein the conventional cylindrical locating pin forces the shell to expand isometrically outwards

The locating pin 100 facilitates manufacture and eliminates the use of a relatively complicated pivoting clamp, articulated chucks, expanding collets, or the like for machine operations.

Although the different non-limiting embodiments have specific illustrated components, the embodiments of this invention are not limited to those particular combinations. It is possible to use some of the components or features from any of the non-limiting embodiments in combination with features or components from any of the other non-limiting embodiments. It should be understood that like reference numerals identify corresponding or similar elements throughout the several drawings. It should also be understood that although a particular component arrangement is disclosed in the illustrated embodiment, other arrangements will benefit herefrom.

Although particular step sequences are shown, described, and claimed, it should be understood that steps may be performed in any order, separated or combined unless otherwise indicated and will still benefit from the present disclosure.

The preferred forms of the invention described above are to be used as illustration only, and should not be utilized in a limiting sense in interpreting the scope of the general inventive concept. Obvious modifications to the exemplary embodiments and methods of operation, as set forth herein, could be readily made by those skilled in the art without departing from the spirit of the present invention. It is therefore to be understood that within the scope of the appended claims, the disclosure may be practiced other than as specifically described. For that reason the appended claims should be studied to determine true scope and content.

Claims

1. A locating pin (100) for dimensionally variable parts, comprising: a base (10) having a cylindrical body (12) being extended from the base (10) to form a pin member (20), characterized in that the pin member (20) has a conical head (22) facilitating to insert the locating pin into a locating bore, with a plurality of augmented cylindrical circumferential surfaces (23) equally distributed around the head (22) thereof, wherein the cross-section of the conical head (22) is provided with a plurality of cylindrical surfaces (23) with a facet (24) positioned in between two cylindrical surfaces (23).

2. The locating pin (100) as set forth in Claim 1 , wherein a 3- or more concentric partial external cylindrical surfaces (23) are formed along the pin member (20).

3. The locating pin (100) as set forth in Claim 1 , wherein the pin member (20) is provided with a plurality of facets (24).

4. The locating pin (100) as set forth in Claim 1 , wherein the conical head (22) provides a smaller force for a given interference.

5. The locating pin (100) as set forth in Claim 1 , wherein the base (10) of the pin (100) is configured to position to any structure or a stationery/moving machine.

6. The locating pin (100) as set forth in Claim 5, wherein the base (10) includes a threaded adaptor for mount the locator pin (100) to the machine.

7. The locating pin (100) as set forth in Claim 1 , wherein the pin member (20) is adapted to be inserted through a locating bore or cavity provided on a workpiece.

8. The locating pin (100) as set forth in Claim 1 , wherein the locating hole is a prismatic hole.

9. The locating pin (100) as set forth in Claim 1 , wherein the cross section of the pin member (20) is narrower or bigger than that of the base (10).

10. The locating pin (100) as set forth in Claim 1 , wherein the height of the pin member (20) is substantially the same, longer or shorter than that of the base (10).

11. The locating pin (100) as set forth in Claim 1 , wherein the cross section (22) of the pin member (20) is much smaller than that of the base (10).

12. The locating pin (100) as set forth in Claim 1 , wherein the pin member (20) is generally a cylindrical portion extending from the base (10) of the locating pin (100) along the axis until the cross section (22) thereof.