Method of manufacturing a lock follower arm with a press-fitted hub

Abstract

A lock follower, particularly a handle or pressure follower, comprises a hub part consisting of a machined rod-like or tubular material and an arm part consisting of a punched sheet-metal material. The parts are rigidly joined together by flow of material from the arm part to a peripheral groove in the hub part. Preferably the hub part exhibits in the neighborhood of the groove a portion of smaller diameter than the main portion of the hub but of larger diameter than the hole for the hub part in the arm part. Said portion is pressed so far into the hole in the arm part while deforming the material defining the hole that the arm part abuts an abutment in the hub part. Further, the portion of the hub located between the peripheral groove and the abutment preferably has axially extending ridges around the periphery thereof to facilitate flow of material and rigidly securing the two parts together in both axial and circumferential direction.

Description

The present invention relates to followers for locks, and particularly but not exclusively to handle or pressure followers.

Lock followers have previously been die cast as one piece structures. The follower comprises a solid hub with an arm projecting outwardly therefrom, the hub and arm having varying dimensions and shapes, depending upon the type of lock for which the follower is intended. Consequently, the die casting of followers is an expensive method of manufacture, because of the high outlay incurred by the required tools. In addition there is needed an extensive machining of the cast followers.

In U.S. Pat. Nos. 1,715,996, 2,369,873 and 2,470,771 there are described previously known followers comprising two main parts, i.e. one hub part and one arm part. In these followers one part is loosely inserted into or threaded onto the other part, i.e. the parts are not rigidly secured to each other. Such a follower lacks sufficient strength to cope with the torsional and axial strains which at use will be met by a follower of the kind here under concern. Therefore the said previously known followers are of no interest in the present context.

An object of the present invention is to provide a novel type of lock follower which can be manufactured automatically and in which both the hub part and the arm part can be given a varying shape and form whilst using relatively inexpensive tools.

A lock follower according to the invention comprises a hub part and an arm part having a through hole for receiving the hub part, and is mainly characterised in that the hub part consists of a machined rod-like or tubular material and the arm part consists of a punched sheet-metal material, said parts being rigidly joined together by flow of material from the arm part to a peripheral groove in the hub part.

The two portions are joined together by a simple pressing operation, thereby enabling the follower to be manufactured in a much simpler manner.

It is previously known from the British Patent Specification No. 984,819 to provide hermetically sealed housing constructions instead of heat-sealed housing constructions for electromechanical and electronic use, by using two parts of mutually different hardness and plasticity, wherein the softer material is caused to flow into a groove disposed in the harder material. In this instance there is used a forward, laterally directed flange followed by a shoulder having the form of a compression ring on the part of harder material, said shoulder or abutment being adapted to be embedded in the end of the part of softer material. Consequently, in order to achieve the hermetic seal and heat-seal intended, this known arrangement requires the parts to have a comparatively complicated design.

According to the present invention, by means of which another type of joint is obtained between the hub part and the arm part, a housing to be hermetically sealed between the parts is lacking. Therefore said parts can be of much simpler design. The two parts may also comprise a material having the same, or substantially the same degree of hardness, although it is also possible, if desired, to make the parts of mutually different materials.

In practice it is preferred that the hub part, in the region of the groove, exhibits a portion of smaller diameter than the main portion of the hub, although with larger diameter than the through hole in the arm part, which portion is pressed so far into the hole in the arm part while deforming the material defining the hole that the arm part abuts an abutment in the hub part.

The arm part is, in this way, held axially locked to the hub part in an effective manner.

An effective locking of the two parts, both axially and circumferentially, can be obtained if, in accordance with a preferred embodiment of the invention, the part located between the groove and the abutment exhibits axially extending ridges distributed around the periphery.

In this embodiment the migration of materials from the arm part to the groove in the hub part takes place in a particularly simple and effective manner, owing to the fact that the axially extending ridges cut and press material out of the arm part, this material flowing into the groove. At the same time the two parts are reliably fixed together in a circumferential or tangential direction, i.e. in a direction in which the joint between the arm part and the hub part are subjected to the highest stresses, namely torsional stresses as a result of lever action at use.

The invention also relates to a method of manufacturing a lock follower of the aforedescribed type, the method comprising the steps of punching the arm part from a sheet-metal blank and providing it with a through hole for receiving the hub part; providing the hub part with a peripheral groove and pressing the two parts together in a manner such as to lock the parts together by means of flow of material from the arm part to the groove in the hub part.

Thus, it is possible to join the hub part and the arm part already before the arm part is completely punched out of the metal blank. This is of special advantage at manufacture of the follower in an automatic machine.

When applying the method according to the invention, the hub part, prior to being joined to the arm part, can be cut from a tubular or rod-like material of indefinite length.

When using rod-like material, the material, prior to being cut, may be provided, in a lathe, with an axial bore, circumferential grooves and axial ridges. The hub part is then cut from the material at the desired length.

When the hub part is manufactured from a tubular material, there is already provided a centre bore for the follower. In both cases it is comparatively easy to shape this bore into a rectangular hole, conveniently after joining the hub part to the arm part. Then the rectangular hole will be correctly positioned relative to the direction of the arm part. Still more exactness is obtained when according to an embodiment preferred in practice the rectangular hole in the hub part is punched already before the arm part is fully punched from the metal blank.

So that the invention will be more readily understood and further features thereof made apparent, an exemplary embodiment of the invention will now be described with reference to the accompanying schematic drawings, in which

FIG. 1 is a perspective view of a follower according to the invention in which a portion of the arm part is cut away and removed for the sake of clarity,

FIG. 2 is a partly cut away side view of the follower according to FIG. 1, and

FIG. 3 illustrates the arm part threaded onto the hub part but before the two parts have been pressed together.

Referring to FIG. 1 there is illustrated a pressure follower 1 intended for a lock and comprising a hub part 2 manufactured from a tubular material, and an arm part 3 which has been punched from a sheet-metal blank.

The arm part 3 exhibits a circular bore 3a for receiving the hub part.

The hub part 2 has a cylindrical main portion 2a which merges, via an abutment 2e, with a serrated or axially ridged portion 2c. Adjacent the serrated portion 2c is a peripheral groove 2b which is bordered on the side thereof opposite said serrated portion 2c by a portion 2d which has a slightly smaller diameter than that of the serrated portion 2c. The diameter of the portion 2d corresponds--as is evident from FIG. 3--to the inner diameter of the through hole or bore 3a disposed in the arm part 3. At the other end the hub part exhibits a portion 2f which forms an abutment and which, similarly to the opposing end portion 2d, serves as a bearing means for the follower when this is in use.

The hub part 2 is joined to the arm part 3 by bringing the two parts together under pressure. In this connection, the arm part 3, as illustrated in chain lines in FIG. 2, may for instance initially be inserted over the hub part 2d which has the same diameter as the through hole 3a of said arm part. In this way, the two parts are accurately steered relative to one another. The two parts are then pressed together, whereupon the axial ridges on part 2c press material from the portion of the arm part defining the hole 3a, the material pressed out by said ridges flowing into the groove 2b. When one side of the arm part abuts the abutment 2e of the hub part, the hub part and arm part are accurately and positively fixed to one another both in an axial and a circumferential direction.

The hub part may be made from rod material which is provided in a lathe with a centre bore 2g, the bearing portions 2f, 2d, the serrated portion 2c and the groove 2b. The hub part can then be cut into the required length by means of the lathe tool.

When manufacturing the arm part, a strip of sheet-metal is fed into a punching tool and the through hole 3a and optionally also the smaller hole 3b is punched from the strip.

As before mentioned, the centre bore of the hub part is punched to a hole 2g of rectangular shape, optionally after the two parts have been joined together. Thereby the rectangular hole 2g obtains a correct position relative to the arm part.

At a modified method of manufacture suitable for manufacture in an automatic machine the hole 3a for the hub part is firstly punched in a metal blank (not shown). Thereafter the hub part is pressed into the hole, so that it is joined to the blank. Thereafter the rectangular hole 2g is punched in the hub part. When this has been done the arm part is punched from the metal blank. The arm part may possibly initially be partly punched from the blank but it has when the hub part is pressed thereonto some portions which are still being attached to the blank. The complete follower is then removed by means of a final punching operation.

Claims

1. A method of manufacturing a lock follower from one arm part and one hub part, comprising punching said arm part from a sheet-metal blank, providing a through hole in said arm part for receiving said hub part, providing said hub part with a first, larger outer diameter portion adjacent a second, smaller outer diameter portion to thereby define a shoulder, providing axial ridges on said second portion, the outer diameter of said second portion being larger than said through hole, providing said hub part with a peripheral groove adjacent said second portion, and joining said hub part and said arm part together by pressing said second portion of said hub part into said through hole causing a flow of material from said arm part into said peripheral groove and abutting said shoulder against said arm part; wherein said hub part is machined and cut from a length of tubular or rod material prior to joining it to said arm part, and is provided with said peripheral groove and axial ridges prior to being cut from said tubular or rod material.

2. A method according to claim 1, characterised by punching a rectangular bore from a circular centre bore of the hub part subsequent to joining said hub part to said arm part.

3. A method according to claim 1, characterised by punching the rectangular bore before fully punching out the arm part from the sheet-metal blank.